CA1268583A

CA1268583A - Optical glass fibre having a synthetic resin coating and curable elastomer forming material

Info

Publication number: CA1268583A
Application number: CA000514015A
Authority: CA
Inventors: Dirk J. Broer; Petrus C.P. Bouten; Cornelis M.G. Jochem
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Plasma Optical Fibre BV
Priority date: 1985-07-23
Filing date: 1986-07-17
Publication date: 1990-05-01
Anticipated expiration: 2007-05-01
Also published as: DE3687933D1; JPS6227710A; JP2529671B2; EP0212706B1; NL8502106A; EP0212706A1

Abstract

ABSTRACT:
Optical glass fibre having a synthetic resin coating and curable elastomer forming material.
The invention relates to an optical glass fibre 1 having a synthetic resin coating which consists of at least two layers 2 and 3 in which the first layer 2 is formed from an elastomer forming material which can be cured by exposure to actinic radiation, and in which the optical glass fibre exhibits a great tensile strength, a small risk of static fatigue fracture and a low ageing rate, owing to the fact that the synthetic resin compo-sition comprises between 0.1 and 5 % by weight of one or more phosphorus compounds of the following structural formula:

Description

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 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 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 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 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 H O l-- O O O cr~ O ~O o ~ I
r~ I
H O I-- O C~O O O t O O
X , H ~ C~
HO ~O O O O O O -~ O O
XO~

H 1-- 0 0 0 0 0 (~ t O O t X
O U~ ~
Xr- o o o ~ o -t O O U~ I
O
o h X ~ O O )1~~\1 0 0 ~1 0o ~ I
O H ~ ` ~:

H ~ O O ~ O O O t O O ~ ~
H
H tr~
H ~D O O O C O O ::t O O
H a~
H ~ O O ~ O O O ~ O ~I I I I

a) ~ ~ O
~ ~ O O ~ O O ~ ~ ~ ~ O
I
a~
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;: t O O~ O ~ O O ~ I ~ O tY~ 0~ 0 ~ n ~1 :u ~ a ~o o o o o o o c~
h o `, t--o t~
C) ~
V
O O ~ O O O t t\~ O
,~

c) a~ ~1 a ~2 h P. ~
3 0 ~ ~ o rl ,!4 h o rl O 0 ~ h X P~
~ X n~
~1 a) o o ~1 ,~
3 ~1 UJ h ~
O o o h :1 o X o o ~ ~ 0 U~ o o O h ~ o rl rl o ~ ~o u~ ~ ~ o ,~
O ~ ~ 1 0~D
~ E E
E ~I h ~ o I ~1 ~a o ~ h o4D H
H~ ~ ~ E ~ O

^ 10-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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An optical glass fibre having a synthetic resin coating, which comprises a glass fibre, a first layer of a synthetic rubber having a modulus of elasticity of from 1 to 10 MPa and a second layer of a synthetic resin having a modulus of elasticity exceed-ing 100 MPa, at least the first layer of synthetic rubber being formed from an elastomer forming material which can be cured by actinic radiation, characterized in that the elastomer forming material comprises a total amount of 0.1 to 5% by weight of one or more compounds selected from phosphorus compounds of the following structural formula:

wherein n has a value of 1 or 2 and wherein R is an organic group.

2. An optical glass fibre as claimed in Claim 1 character-ized in that R is an organic group which co-reacts during curing of the curable synthetic resin composition and is built into the polymeric network thus formed.

3. An optical glass fibre as claimed in Claim 2, character-ized in that the curable synthetic resin composition comprises a polyurethane acrylate and that R is an organic group which comprises at least one acrylate ester group.

4. An optical glass fibre as claimed in Claim 3, character-ized in that R is a 2-acryloxy ethylate group.

5. An optical glass fibre as claimed in Claim 1, character-ized in that the curable elastomer forming material comprises up to 2% by weight of a poly(dimethyl siloxane-co-ethyleneoxide) acrylate.

6. A curable elastomer forming material which can be made to cure by actinic radiation to form a hydrophobic synthetic rubber, characterized in that the curable elastomer forming mat-erial comprises a total amount of 0.1 to 5% by weight of one or more compounds selected from phosphorus compounds of the following structural formula:
wherein n has a value of l or 2 and wherein R is an organic group.

7. A curable elastomer forming material as claimed in Claim 6, characterized in that R is an organic group which co-reacts during curing of the curable elastomer forming material and is built into the polymeric network thus formed.

8. A curable elastomer forming material as claimed in Claim 7, characterized in that the curable elastomer forming material comprises a polyurethane acrylate and that R is an organic group which comprises at least one acrylate ester group.

9. A curable elastomer forming material as claimed in Claim 8, characterized in that R is a 2-acryloxy ethylate group.

10. A curable elastomer forming material as claimed in Claim 6, characterized in that the curable elastomer forming material comprises up to 2% by weight of a poly(dimethyl siloxane co-ethy-leneoxide) acrylate.