DD258859B5 - Optical fiber for the transmission of light waves - Google Patents

Description

Isophthalsäuredi methyl ester mitder1,1 to 1,6 molar amount of butanediol -1,4 with the addition of an esterification catalyst, eg. Example, a titanium compound in amounts of 1 10 ~ ^{4 to} 5 1CT ⁴ MoI per mole of ester, first transesterified and then polycondensed under a vacuum of 0.1-5Torr.

Surprisingly, it has been found that an isophthalic acid-modified polybutylene terephthalate copolyester enables the production of optical fibers with high mechanical strength, which are characterized by a constant damping over a wide temperature range in their transmission properties. Obviously, due to the slight shrinkage or shrinkage of the polybutylene terephthalate-isophthalate copolyester used according to the invention, only slight contraction forces are exerted on the fiber core material such that virtually no microbending occurs.

embodiment

The invention will be explained in more detail below on some embodiments.

I.Beispiel:

A mixture of terephthalic acid dimethyl ester and isophthalic acid dimethyl ester prepared according to the desired copolymer fraction in the range of 5-22 Ma .-% is mixed with the 1.1-1.6 molar amount of 1,4-butanediol with addition of an esterification catalyst, for. As a titanium compound, in amounts of 1 x 10 " ^{4 to} 5 10" ⁴ MoI per mole ester first transesterified and then polycondensed under a vacuum of 0.1-5Torr. The viscous melt thus obtained is poured into a strand and then comminuted.

The mold temperature during injection molding was in all cases 6O ⁰ C. Both in the mold shrinkage and in the Nachschwindung the best values are measured on a polybutylene terephthalate copolyester containing 20Ma .-% isophthalic acid; the Ε-modulus is only slightly influenced by the copolymerization. The following example describes the preparation of a polybutylene terephthalate copolyester containing 20% by weight of isophthalic acid.

2nd example:

A mixture of 3481 g (17.6 mol) of terephthalic acid dimethyl ester and 854 g (4,4 mol) of dimethyl isopthalate with 30 mol of 1,4-butanediol is stirred in a stirred, stirred reactor of 12 liters, 2.25 g of titanium tetrabutoxide (2.7 × 10 ⁴ mol / Mol ester) was added and transesterifed in the course of 3 hours at 130-190 ⁰ C without pressure. Subsequently, the excess butanediol is distilled off at a temperature of 210-215 ⁰ C and a vacuum of 20 Torr and finally polycondensed at 245-250 ⁰ C and a vacuum below 1 Torr over 2 hours. The melt is left from the reactor, cooled as a strand, crushed and dried before further processing for 12 hours at 120 ⁰ C in a vacuum of 1-5Torr. The relative solution viscosity in phenol / tetrachloroethane methane 1/1 at 20 ⁰ C is at a concentration of 0.5g / dl 1725th

3rd example:

A dumbbell-shaped test specimen of a polybutylene terephthalate-isophthalate copolyester according to Example 2 is stored in a filling compound based on polyisobutylene and paraffinic hydrocarbons at 80 ⁰ C. Even after several weeks of storage time, elongation at break and tensile strength of the copolyester remain unchanged.

4th example:

A step index fiber according to FIG. 1 (quartz glass core 1 with a diameter of 200 kt, buffer layer and simultaneously optical jacket 2 of addition-crosslinked silicone rubber with a wall thickness of 90% and a refractive index n _D = 1.408) was produced by extrusion using a polybutylene terephthalate-isophthalate copolyester according to Example 2 coated. The resulting solid core has a smooth surface and excellent dimensional stability. The diameter is 1.0mm and the diameter variations are in the range of ± 15μιη. The ovality is = 4μιη.

The coating was carried out with the following technological data:

Screw length of the extruder: 2OD

Screw diameter: 25 mm

Withdrawal speed: 20 m / min

Hose tool with vacuum

Melt Temperature: 203 ⁰ C

Cooling of the extrudate: Combined air / water cooling

The copolyester used for the coating has the following properties:

Melting point DTA: 194 ° C

Water absorption at 2O ⁰ C and 65% rel. Humidity: 0.19%

Tensile strength: 50.5 N / mm ²

Tear strength: 15.7 N / mm ²

Elongation at break: 1312%

Modulus of elasticity: 1900 N / mm ²

Bending stress: 61 N / mm ²

Mold shrinkage ": 0.91%

Nachschwindung ^x after 168 h b. 80 ^° C: 0.13%

Nachschwindung ⁴ after 168 hb. 110 ° C: 0.22%

x) on injection standard test bars, mold temperature during injection 60 ⁰ C.

After the protective sleeve was extruded, the optical transmission loss of the thus obtained optical waveguide with step index light guide was determined. An attenuation of 10.0 dB / km was found. This value corresponds to the previously measured initial value for the optical fiber core material, i. H. the transmission loss was not increased by the thermoplastic coating.

The same results are obtained when a step index fiber according to FIG. 2 is coated, consisting of quartz glass core 1, optical cladding 3 of quartz glass with a lower refractive index and a buffer layer 4.

5th example:

A Gradientenindexfaser according to Figure 3 (quartz glass core 5 with decreasing in the radial direction refractive index, optical cladding 3 of quartz glass with a lower refractive index fiber diameter 125μη% buffer layer 4 of addition-crosslinked silicone rubber with a wall thickness of 60 μιτι) was in the extrusion process with a polybutylene terephthalate copolyester according to Example 2 coated. The outer diameter of the solid core is 1.0mm

 The coating was carried out with the following technological data: Screw length of the extruder: 2OD

Screw diameter. · 32 mm

Withdrawal speed: 22 m / min

Hose tool with vacuum

Melt temperature: 207 ⁰ C

Cooling of the extrudate: Combined air / cold water cooling

After fabrication, the optical transmission loss of the optical waveguide thus obtained was determined with gradient index light guide. An attenuation of 2.5dB / km was found.

This value corresponds to the previously measured initial value for the optical fiber core material, ie the transmission loss was not increased by the thermoplastic coating. The attenuation behavior of this fiber optic cable is almost constant in the temperature range from -50 ° C to +70 ⁰ C. The individual measurements are listed below: Temperature a = f (T); Aa [dB / km]

23 ⁰ C Output value: 2.5dB / km

0 ⁰ C -0,1

-10 ⁰ C +0,1

-20 ° C +0.1

-3O ⁰ C ± 0

-40 ° C +0.1

-50 ° C +0.1

+ 24 ° C +0

+ 50 ⁰ C ± 0

+70 "C ± 0

6th example:

Four individual light waveguides with gradient index light waveguide produced according to example 5 are stranded on a stranding machine, wrapped with 2 layers of polyester film and processed into a TGL 55144 optical waveguide cable with a PVC-soft sheath, a strain relief and a soft PVC protective cover.

After production, the optical transmission losses of the individual wires were determined on the optical fiber cable thus obtained. It was found that all four individual wires had continuity and the attenuation values of the individual wires have not changed, ie the transmission losses of the individual wires have not changed after the operations stranding, Folienbewicklung, Mantelextrusion, traps and protective sleeve extrusion. The temperature dependence of the damping of the 4 single cores corresponds to the requirements. In the range of + 7O ⁰ C to -25 ⁰ C Δα is in the range of -0.1 to +0.1 dB / km.

Similar results are obtained when a TGL 55143 fiber optic cable based on step index light waveguide optical fiber conductors of Example 4 is produced.

7. Example:

A gradient index fiber according to Figure 3 (fiber diameter 125μιη; buffer layer of addition-crosslinked silicone rubber with a wall thickness of 60μΐη) was coated in the extrusion process with a polybutylene terephthalate-isophthalate copolyester according to Example 2 such that the plastic sheath 9 surrounds the optical fiber 8 as a loose tube. The arrangement is shown in FIG. 5. The outer diameter of the wire is 1.9 mm and the wall thickness is 0.4 mm.

The coating took place under the following conditions:

Screw length of the extruder: 2OD

Screw diameter: 25 mm

Withdrawal speed: 18 m / min

tube tool

Melt temperature: 205 ⁰ C

Cooling of the extrudate: Combined air / water cooling

After fabrication, the optical transmission loss of the optical waveguide thus obtained was determined with gradient index light guide. An attenuation of 3.0 dB / km was found. This value corresponds to the previously measured output value for the transmission loss for the optical fiber core material, i. H. the transmission loss was due to the

thermoplastic coating not increased. The damping behavior of this optical fiber is in the temperature range of

-40 ° C to +70 ⁰ C almost constant.

Similar results are obtained when a step index fiber of FIG. 4, consisting of quartz glass core 6 with in radial

Direction decreasing refractive index, Lackprimärschicht 7 and buffer layer 4, is coated.

Claims (1)

Optical fiber for transmission of light having a primary coating and a protective cover made of thermoplastic material, characterized in that the thermoplastic protective cover consists of a polybutylene terephthalate-isophthalate copolyester in an amount of 5-30% by weight, preferably 20% by weight of isophthalic acid. For this 1 page drawings Field of application of the invention The present invention relates to an optical fiber for transmitting light waves having excellent transmission characteristics and high mechanical strength over wide temperature ranges. Characteristic of the known technical solutions Optical fibers, for their protection against chemical and mechanical influences, are given a so-called primary coating of thermally or UV-curable polymers usually applied by dipping. For better handling and further protection against mechanical stress, the primary-coated fibers are provided with a further protective cover. According to the prior art, this, also referred to as a secondary coating, second protective sleeve made of thermoplastically processable polymers is prepared by being extruded onto the primary coated fiber. This protective cover can be applied directly to the primary coating and you get then so-called hard veins. In the case of the hollow wires, the protective sleeve surrounds the primary-coated fiber as a loose hose. Thermoplastics such as polyamide 12, polyamide 11, polyamide 6,10, polyamide 6, polyamide copolymers, high density polyethylene, polycarbonate, ionomer, PETP, polystyrene, PBTP, polyurethane, polypropylene, poly-tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride are suitable for the outer protective cover , Ethylene tetrafluoroethylene copolymer and ethylene-chlorotrifluoroethylene copolymer is known, when the fiber is first provided with a layer of a phenylgruppenhaltigen, curable organopolysiloxane and above a second layer of a curable organopolysiloxane, which contains a trifluoroalkyl group is arranged (DE-OS 2944947). Currently, polyamide 12 can be considered as the most widely used wrapping material. Corresponding information is i.a. contained in: US-PS 3980390, Japanese OS 17649/75, company publications HKE-0445 G.7 "Optical Fiber Cord" and HKE-0035 H.6 "Optical Fiber System" of FURUKAWA ELECTRIC CO., LTD. Systemtechnik "- Company publication of the standard electrics Lorenz AG, Stuttgart, from March 1985. Because of the after extrusion on cooling the o.g. Materials occurring radial and axial contraction forces that lead to an increase in attenuation in the optical fiber, layer thicknesses greater than 0.1 mm are not considered feasible for the outer protective cover. Due to the small wall thickness of max. 0.1 mm, the outer sheaths mentioned even with the use of relatively strong and rigid materials, such as polyamide 12, PETP, PBTP, PA 6 etc. for the fiber not sufficient mechanical protection, so that all occurring mechanical stresses of the wires during further processing to the cable can be withstood without damage and the cable can withstand high tensile and compressive stresses during installation and use. Unmodified polybutylene terephthalates, which have already been described as coating materials for optical fibers, show, due to their crystalline structure, the known problems with regard to an increase in the attenuation of the fiber after the extrusion of the protective cover (DE-OS 2944947). As with other semi-crystalline materials, eg. As PE, PP, PETP, polyamide 12, polyamide 6, etc. lead during solidification of the melt caused by shrinkage and Nachschwindungsvorgänge contraction forces in the axial and radial direction of the fiber to a damping increase by Mikrobending or even to break the fiber. Upon heating above the glass transition temperature, these polymers experience more or less high shrinkage due to orientation relaxation of the molecules. The shrinking forces occurring in this case can, for. B. caused by heat in the jacket extrusion processes or by acting on the cable from the outside thermal stress. Object of the invention The solution according to the invention should make it possible to find a cost-effective and readily procurable coating material for extruded protective sheaths of optical fibers, which offers sufficient mechanical protection. Explanation of the essence of the invention The invention has for its object to use a wire with optical fiber cores, which have low attenuation changes in the temperature range from -50 ° C to +70 ⁰ C, resistant to fillers, can be processed easily to Aderverseilverbänden and these Aderverseilverbände then to Lichtleitkabeln mitextrudierten inside - And outer shells can be further processed. According to the invention the object is achieved in that the extruded, secondary protective sheath of optical fibers of a polybutylene terephthalate-isophthalate copolyester in a proportion of 5-30Ma .-%, preferably 20Ma .-% isophthalic acid. The coating materials according to the invention are obtained when a mixture of terephthalic acid dimethyl ester prepared according to the desired copolymer content in the range from 5 to for example 22% by mass