Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
685~3
20104-~093
The invention relates to an optical glass fibre hav.Lng a
synthetic resin coating, which comprlses a glass fibre, a ~irst
layer of a synthetic rubher having a modulus of elasticity of from
1 to 10 MPa and a second layer of a synthetic resin having a
modulus of elasticity exceeding 100 MPa, at least the first layer
of synthetic rubber being formed from a synthakic resin
composition which can be cured by actinic radiation.
The invention further relates to a curable elastomer
forming material which can be made to cure by actinic radiation
thereby forming a hydrophobic synthetic rubber.
An optical glass fibre is to be understood to mean
herein a fibre of glass or quartz glass such as, for exampler the
fibres used for telecommunication purposes. Actinic radiation is
to be understood to mean herein UV-ligh~ or high energy radiation,
such as lrradiatlon with electrons or ions.
Such an optical glass fibre and curable synthetic resin
composi~ion are described in U.S. Patent 4,741,596 which issued to
U.S. Phillps Corp., on May 3, 1988. The synthetic resin coatiny
of the glass fibre, comprising a first soft layer and a second
hard layer, serves to prov:Lde a glass fibre with a larye strength
and a low susceptibllity to mlcrobending. In this way,
transmission losses caused by mechanical deformation of the glass
fibre are kept low in the widest possible temperature range. The
optical glass fibre may be further protected by enveloping it in
additional layers of a thermoplastic synthetic resin or metal, in
the form of a cladding or in the form of a tube in which the fibre
~' ~
~L268~3
20104-8093
can move freely. The use of a synthetic resin composi~lon which
can be cured by actinic radiation, makes it
la
'~1
9L~ 83
Pl~ ll.LI~l 2 15.5.1986
possible to envelop the glass fi.bre immedia-tely after it
has been formed, for example, by drawing from a preform,
which drawing and coating processes can be carried out at
a high ra-te.
In order to reduce the risk of breakage of the
glass fibre in the cabling process and during arranging the
cables in a telecomuunications network, the aim is to
manufacture glass fibres having a great tensile strength
when used under dynamic circumstances. In order to improve
10 the operational reliability of glass fibres used in
telecommunications networks, the aim is to produce
glass fibres whose properties depend -to the smallest
possible degree on varying ambient conditions, and which
exhibit a very low ageing rate.
15 If the glass fibre is constantly subjected to a mechanical
load, the risk of fatigue fracture must be minimal. It has
been found that the presence of water adversely affects all
the said properties.
It is an object ofthe invention to improve
20 optical fibres and curable syn-thetic resin compositions as
described in the opening paragraph, -to such an extent tha-t
the coated glass fibre exhibi-ts a greater tensile s-trength,
a reduced risk of static fatigue fracture and a lower
ageing rate, particularly in the presence of water.
Thls object is achievecl in accorclance wit:h the
invention by an optical glass fibre and a curable
elastomer forming material as describod inthe opening para-
graph, which are further characterized in that the curable
elastomer f`orming material comprlses a total amount of 0.1
30 to 5 % by weight of one or more compounds selected from
phosphorus compounds of the following structural formula;
R - P - (OH)3_n
35 wherein _ has a value of1 or 2 and wherein R is an organic
group The organic group R may, for example via an oxygen
atom or via a carbon atom, be chemically bound to the
phosphorus atom, the structural formula representing a
~ 3
PHN 11.4~1 3 15,5,1986
phosphate ester or a phosphonate 9 r0SpeCtively~
The addition of the phosphorus compound in
accordance with the inven-tion resu~s in an improved
adhesion between -the first layer of synthetic rubber and
the glass fibre. Unlike customary adhesion primers such
as, for e~ample, silanes, the addition of the phosphorous
compound does not result in a reduction of the curing rate
and conversion degree a-t the outer surface of the syn-
thetic rubber. The phosphorus compound in accordance wi-th
the invention has the particular advantage that an acid
medium develops near the interface of the glass fibre ancd
the first layer of synthetic rubber~ as a result of which
ageing of the glass or quar-tz glass is counteracted. In
this way, the desired greater strength and prolonged service
lS life of the optical glass fibre coated with synthetic resin
is obtained. However, for the purpose of making connections
it remains possible to rerDove the synthetic resin coating
at the end of the fibre in a simple way by stripping.
Stripping can be carried out mechanically as well as by
20 means of a solvent.
The curable elastomer forming material may
adclitionally comprise other customary additions such as
reactive monomers, light sensitive and light absorbing compo-
nents, catalysts, initiators~ lubrican-ts, ~0tting agen-ts,
25 antioxidants and stabilizers.
European Patent Sp0ciation EP 0 101 OC~l
describes curable synthetic resin composit:ions comprising
phosphate esters, but the said synthetic resin corllpo sitions
are not usecl for the rnanufacture of a synthe-tic resin
30coa-ting which is to be applied to an optical glass flbre.
Moreover, the said synthetic resin compositions are not
cured by ac-tinic radiation, but by the phosphate ester
acting as a curing agent.
In order to preclude migration of the phosphorus
35compound in the synthetic resin coating, which would adver-
sely affect the service life of the optical glass fibre,
it is advantageous for R in the above-d0scribed optical glass
fibre and curable elastomer forming material in accordance
5~3
20104-8093
with the invention to he an organic group which co-reacts dur:ing
curing of the curable synthetic resin composition and i5 built
into the polymeric network thus formed.
The phosphorus compouncl may be used in accordance with
~he invention together with curable synthetic resin compositions
which are commonly used in the art and whose chief constituent is,
for example, polysiloxane, polybutadiene, polyether urethane
acrylate, pol~ester urethane acrylate, polysiloxane acrylate, a
polymer formed by reactions between monomers comprising vinyl
groups and silyl groups, or a mixture of such polymers or a
copolymer.
In a preferred embodiment of the optical glass fibre and
the curable elastomer forming material in accordance with the
invention, the curable elastomer forming material comprises a
polyurethane acrylate and R is an organic group which comprises at
least one acrylate ester group. Preferably, the group /R further
consists of a short alkyl chain, such as an ethyl- or propyl-
group. The group R may also contain other unsaturated groups such
as vinyl groups or vinyl groups attached ko aromatic groups.
Suitable curable elastomer ~ormlng materials of this type are
described in, for example, U.S. Patent 4,741,596. In the said
U.S. Patent, very good results are obtained with a phosphorus
compound in which R is a 2-acryloxy ethylate group.
To further improve wetting of the glass fibre by the
curable elastomer forming materlal and to facilitate curing at the
~8~;~3
20104-8093
outer surface of tile synthetic rubber, lt is efficient ~or the
curable elastomer forming material to comprise up to 2~ by weight
of a poly~dimethyl siloxane-co-ethyleneoxide) acrylate.
Dependent upon the composition o~ the selected curable
elastomer forming material, other suitable co-reacting groups,
such as methacrylate groups and vinyl groups, may also be used in
the phosphorus compound.
The invention will now be explained in more
4a
~'~
35~
Pl~ 11,451 5 15.5.1986
detail with reference to examples of embodiments and
examples for comparison and with reference to a drawing,
in which
Fig. 1 is a cross-sectional view o~ an optical
glass fibre in accordance with the inven-tion,
Fig 2 shows the structural formula of mono-2-
acryloxy e-thylphosphate and di-2-acryloxy ethylphosphate
(in which _=1 and n=2, respectively) and in which
Fig. 3 is the structural ~ormula o~ a polyether
urethane acrylate.
Example 1.
In known manner, a glass fibre is formed by
d~awing from a preform. The fibre cornprises a core glass
and a cladding glass having different refractive indices,
Instead, a fibre may be used whose refractive index
changes gradually from the cen-tre outwards and instead of
a fibre drawn from a preform, a fibre may be used which is
formed by means of the double~crucible method. The glass
fibre 1 shown in Figure 1 is of circular cross-section
(diameter 1Z5/um) but may be of any other cross-section,
for example ellip-tical.
Immediately af-ter -the glass fibre has been
formed, a layer of a cura-ble elastomer forming ma-terial is
applied -to said fibre and subsequently the elastomer
forming material is cured -to form a layer of a syn-the-tic
rubber 2 having a thickness of 30/um, The layer is made
-to cure by exposing it to radia-tion for, a-t -the mos-t,
0.5 s using a high-pressure mercury -vapour lamp which
produces W-light having wavelengths between 200 and l~oo
nm and an intens:Lty of 0.6W/cm , measurecl on the layer of
elas-tomer forming material. The elastorner forming material
may also be cured otherwise, for example, by exposing it
to electrons using an Electrocurtain apparatus (marketed
by Energy Sciences Inc., Woburn, Massachussetts).
The first lay0r of synthetic rubber 2 is formed
from a curable elastomer forming material whose main
constituent ( 760/o by weight) is a polyether urethane
~2~5~33
20104-8093
acrylate as described ln U.S. Patent ~,741,596 and depicted in
Figure 3. The curable synthetic resin composition furtller
comprises the reactive monomers 2-phenoxy-ethyl acrylate t14% by
weight) and hexane diol dlacrylate (2% by weight) and the li~ht
sensitive initia~ors 2,2-dimethoxy-2-phenyl-acetophenone (2% hy
weight), 2,2-dimethyl-2-hydroxy-acetophenone (2~ by weight) and 2-
oxygenzophenone-2-ethoxy-ethyl-acetophenone (2% by weight). The
curable synthetic resin composition finally comprises 2~ by weight
of a mixture of mono-2-acryloxy ethylphosphate and di-2-acryloxy
ethylphosphate, see Fig. 2 (n=l and n=2, respectively), the mole
ratio being 1:1.
Subsequently, a second 30 ~m thick synthetic resin layer
3 ls applied to the fibre, ~or exampla by coating the ~ibre with a
curable synthetic resin composition which is made to cure by
exposure to UV-light. A commercially available synthetic resin
composition which is suitable for the second layer is DeSolite 04
marketed by DeSoto Inc.; the said composition comprises a light-
sensitive initiator. A~ter it has been cured, the said material
has a modulus of elasticity of approximately ~00 MPa.
If desired, a cladding of a thermoplastic synthetic
resin, for example nylon, may be provlded around the optical fibre
(cladding is not shown in Fig. 1). The claddiny which envelops
the synthetlc resin coated optlcal flbre may be ln direct contact
with the said fibre. However, ~he cladding may also have the form
of a tube in whlch the optlcal fibre can move freely, for example
~6~
20~04-~09
in silicone oil.
The fibre thus foxmed is subjected to a number of tesks.
The dynamic breaking strength is measured by means of a bending
fracture apparatus. The strength is indicated by t.he risk orf
breakage, as desf~ribed by P.W. France et. al, J. ~ater. Sci. 15,
825-830 (1980). The outcome is listed in Table 1 in which the
fibre of the
~ , 6a
PHN 1 1.451 7 15.5. 1986
invention is compared with a fibre which is produced
in the same way, but which does not comprise the phosphorous
compound and the other constituents are present in propor
tionally larger amounts.
Table 1.
. _
risk of breakagein accordance with for compari-
~t an elongation of: the invention son
5 . 8 % ~ O . 1 % 1 o/o
o 6 . 2 % ~ 0.1 % 99 o/O
6 . 8 % 3 % ~ 99 . 9 %
7~2 % 99 o/O ~ 99 9 o
Table 1 shows that the fibre in accordance with the
invention is stronger than the fibre for comparison.
The fibre in accordance with the invention and
the fibre for comparison are subjected to an accelerated
ageing process by immersing the f`ibres ~or a precletermined
time in water of 60c, after which the dynamic breaking
strength is measured. Subsequently, the fibres are
dried and conditioned at a relative humidity of` 65 %
after which the dynamic breaking strength is measured
again. The results are listed in Table 2 which tabulates
-the elonga-tion at which the risk o:~ breakage is 63 %.
as a function of the time cluring which the fibres are
immersed in water of 60c.
Table 2.
~in accordance with :E`or comparison
the i.nvention
O days 7 . ~) % 6 . 1 %
2 days,wet 6.5 % s.3 %
2 days, dry 6 9 % 5 . 5 /
7 days, wet 6 . 5 % 4 . 9 %
7 days, dry 6. 9 % 5.1 %
38 days, wet 6 . 4 % 4 . 8 %
3 8 days, dry 6.9 % 4 . 9 %
?5~3~
PHN 110451 -8 15.5.1986
in accordance with for comparison
the invention
305 days, wet 6.2 yO L~ . L~ o %
305 days, dry 6.5 % 4.5 o/o
Also after ageing, in water, the fibre in accordance
with the invention proves to be stronger than the
fibre which does not comprise the phosph~r compound~
Moreover, it has been found that in contrast to the
fibre for comparison the fibre ofthe invention almost
completely regains its original strength. after drying.
To carry out a static fatigue test, the
fibres are wo~md on a mandrel having a diameter of 3.4
mm and, subsequently, while being subjected to a
mechanical stress (elongation 3.L~2 /0) they are immersed
in water. In the fibre for comparison, the first
fracture occurs after 10 to 18 minutes and after
85 to 93 minutes 63 % of the fibre windings are broken.
In the fibre in accordance with the invention, the first
fracture does not occur until after more than 1000
minutes.
Additional experiments have shown that
adding the phosphorus compo~md has a positive effect
when used in an amount of at leas-t 0.1 % weight.
Amounts in excess of 5 /0 by weight adversely affect the
properties oE` the synthe-tic rubber.
:[n orcler to further improve the wetting of
the glass fibre and the curing at the surface, poly
(dimethyl siloxane co-ethyleneoxide) acrylate may be
added, for example, in an amoun-t of` 1 % by weigh-t. In the
case of synthe-tic resin composi-tlons in accordance with
the invent:ion~ the surface curing-time is thereby
accelerated by approximately a factor of lO.
Embodiments 2-5 ancl exam le~r comparison VI-XV.
The curable synthetic resin compositions used
in the present examples comprise polypropyleneoxide
urethane acrylates of differen-t molecular weight as the
main constituent (Table 3 lists the number-averaged
358~
Pl~ 11.451 9 15.5.l986
molecular weight). Other sui-table polymers are,
for example, DeSolite O3 ~ and DeSolite O7 ~ marketed
by DeSoto Inc.
Reactive monomers are used to influence the
viscosity and the curing rate. The curable elastomer
forming materials are applied to the glass fibre~ in
accordance with the present examples, at a temperature o~
45 C at which the viscosity amounts to approximately 2 PaOs.
The reactive monomers used are 2-phenoxy-ethyl acryla-te
l0 (PEA), 1,6-hexane dioldiacrylate (HDDA), 2-(2-ethoxy ethoxy)
e-thyl acrylate (EEEA) and tripropylene glycol diacrylate
(TPGDA). Trimethylol propane triacrylate can also suitably
be used in curable synthetic resin compositions in accor-
dance with the invention.
lS In the present examples 2,2-dimethoxy-2-
phenyl acetophenone is used as a light sensitive initiator.
The phosphorous compound used is a mix-ture
in the ra-tio of 1:1 of mono-2-acryloxy ethylphospha-te
and di-2-acryloxy ethylphosphate. An adhesive which is
20 alternatively used by way of example is ~ methacryloxy-
propyl trimethyoxysilane.
Curable synthetic resin compositions as listed
in Table 3 are used, as indicated in example 1, for the
manufacture o~ optical fibres. The examples listed in Table
25 3 can be divided into examples in accordance with the
invention: 2 up to and inclucling 5, and examples for
comparison: V:[ up -to and inclucling XV.
~2~ 33
O O ~ O O 0 3 0 0 ~
PHN 1 1.541' x 0~ ~ 15 . 5. 1986
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583
PHN 11.54'1 11 15.5~l986
Table 3 lists the modulus of elasticit~
at 25 C in MPa, the glass transition ternperature Tg in
C and the elongation at breakage in /0 (bending fracture
test, see example I) of the synthetic rubber which is
formed i~y curing the synthetic resin composition.
Comparing the examples 2 and VI shows that the
use of the silane compound as an adhesive results in
an improved adhesion between the first synthetic resin
coating and the (quartz) glass fibre; this is also true ~or
10 the use of the phosphorus compound in accordance with the
invention. However, the silane compound adversely affects
the curing process particularly at the outer surface of the
synthetic rubber; nor does it have the required ef`fect on
the service life of the optical f`ibre.
The fibres manufactured by means of the
synthetic resin comp~itions in accordance with examples
3 up to and including 5 have proved to be stronger and to
be better resistant to ageing than the fibres of the
examples for comparison VI up -to and including XV.
