MXPA97004083A - Filling compounds for optimal fiber cables - Google Patents

Abstract

Hydrophobic compositions useful for filling voids within optical fiber-lined cables are described. The compositions include about 85 to 95 parts by weight of mineral oil, 5 to 15 parts by weight of di-block copolymer (styrene) - (ethylene / propylene), having a styrene: (ethylene / propylene) ratio of 37.5. : 62.5 to 27.5: 72.5 and a specific gravity of approximately 0.90 to 0.95, optional antioxidant and optional metal deactivator

Description

COMPOSTA OT BBTJfff "? ^ TtA C * .VR DK FTBRAS OPTTAS The present invention relates to optical fiber cables that incorporate a unique composition that protects the components that carry signal from the cable against damage during manufacture, installation and use. it relates more particularly to the unique composition which imparts the desirable protective properties described herein to the fiber optic cable In general, in fiber optic cables a plurality of optical fibers (generally about 100) are circumscribed together in an extruded plastic tube. , often referred to as "shock absorber tube." A plurality of these units, generally about 6 to 50, are circumscribed in a common extruded plastic tube-type liner.Even in the most compact of the manufactures, there are usually gaps between the two. Optical fibers within the buffer tube The present invention relates in particular to a composite It can fill up in the gaps inside the shock absorber tube. Fiber optic cables are subject to various stresses and shocks during manufacture, installation and use, any of which poses a risk of damage to the conductors that carry signals within the cable. These events may include stretching or compression of drivers; compression of one or more of the conductors against the lining, fracture of all or a portion of a conductor, and cracking or perforation of the lining, in such a way that water can penetrate and disturb the operation of the conductors. Accordingly, it has been proposed to incorporate a filler material into the cable, to fill the gaps between the conductors and between the conductors and the inner surface of the damper tube. This filler material should conveniently provide protection to the conductors against detachment and physical damage, while remaining sufficiently flexible so that the cable can be used in any conventional manner where it is employed during fabrication, installation and use. This filler material should also protect against the incursion of water in the event that the water is able to penetrate the lining. The identification of a completely satisfactory cable filling composition has not been simple. In particular, this composition must be sufficiently fluid that the inside of the cable can easily be fed during fabrication and must also be sufficiently flexible so that the cable can be coiled or bent so that it can be exposed particularly during fabrication and installation. The filling composition should not be so fluid that it runs off the cable, through the cutting ends or through perforations or cracks in the buffer tube that may occur. In addition, since the filler compositions are usually mixtures of materials, it is highly desirable that the filler composition resist any tendency of the various components to separate from each other, even in the face of exposure to any of the wide range of physical attacks and environmental conditions. to which the cable can be subjected. Examples of cable filler systems that have been described in the past include blends of oil with a colloidal gelling agent such as fumed silica, together with an amount of a copolymer such as a styrene-rubber or styrene-rubber block copolymer. -styrene. Examples are described in U.S. Pat. No. 4,971,419, U.S. Pat. No. 5,285,513 and the U.S. Patent. No. 5,358,664, the latter of which discloses compositions that incorporate a complex aluminum soap. It would be convenient to be able to identify satisfactory filling compositions useful in optical fiber cables, which exhibit the desirable properties described herein better than the existing filling compositions. It would also be useful if this filler composition does not require a different inorganic gelling agent such as those described in the aforementioned patents. The present invention is directed to a composition that is useful as a filler material to substantially fill gaps between fibers in a fiber optic cable, wherein the filling material consists essentially of: (a) 85 to 95 parts by weight of oil selected from the group consisting of: (a) naphtanic mineral oils comprising 45 to 50% by weight of naphthenic and the rest paraffins, exhibiting a viscosity at 40 ° C, from 19 to 66 centistokes, a viscosity at 100 ° C of 3.5 to 7.5 centistokes, a viscosity index of 40 to 65, a specific gravity at 15.6 ° C of 0.87 to 0.90, a defrosting point of -42.8 to -31.8 * C (-45 ° to -25 ° F) and an average molecular weight of 310 to 400; and (a2) poly-alphadefines and their mixtures, which exhibit a viscosity at 40 ° C of 15 to 400 centistokes, a viscosity at 100 ° C of 1 to 40 centistokes, a viscosity index of 120 to 160, specific gravity at 15.6 * C from 0.9 to 0.84 and a defrosting point of -104.1 to -40 ° C (-50 ° F). (b) 5 to 15 parts by weight of a diblock (styrene) - (ethylene / propylene) copolymer, having a styrene: (ethylene / propylene) ratio of 0.55 to 0.65 and an approximate specific gravity of 0.90 to 0.95; (c) Optional antioxidant in an amount, if present, of up to two parts by weight; and (d) Optional metal deactivator in an amount, if present, of up to 0.1 part by weight.

The present invention is further directed to a cable comprising a plurality of conductors contained within a liner, leaving gaps between the conductors and the linings, wherein the filling material present, substantially fills the voids. The cable components apart from the filler composition described in more detail herein, include any of those conventionally employed in the fiber optic cable industry. Generally speaking, the cable comprises several fibers that carry individual signals, circumscribed together in a buffer tube that is preferably composed of thermoplastic polymer and preferably is a unitary, seamless construction, means in this specialty are known for continuous extrusion of these buffer tubes while simultaneously incorporating the desired fiber optic conductors and the fill composition into the buffer tube. The conductors themselves may comprise a plurality of longitudinal filaments, each of which may be single fibers or may be composed of sub-units where a plurality of conductors are linked together or even circumscribed within their own lining within the cable itself.

The filler composition of the present invention exhibits a number of satisfactory properties, including the following: It performs well and remains flexible and homogeneous during the temperature range of -40 ° C to 80 ° C; It is free of syneresis (draining of its oil component) over the same temperature range; It is capable of yielding and recovering under the stresses it experiences when the cable is manufactured and handled; It is thermally stable and oxidatively stable; It is not adversely affected by water, and avoids incursion of water into the cable; It is compatible with the material of the shock absorber tube and any other materials of construction of the cable; It is economical, safe and compatible with existing equipment used in that field. A component of the filler material of the present invention is oil. The preferred oil is present in an amount corresponding to 85-95 parts by weight of the filler material. The oil should have the following characteristics.

Among the preferred oils are naphthenide mineral oils. These are a commercially recognized type of product that generally contains 45 to 50% by weight of naphthenics and the rest paraffinic. In general, the naphthenic mineral oils useful in this invention exhibit the following properties set forth in Table 1: Property Preferred Range Viscosity, 40"c 19 to 66 centistokes (ASTM D-445) (cst) Viscosity, 40 ° C 3.5 to 7.5 cSt (ASTM D-445) Viscosity Index, 40 to 65 (ASTM n-2270) Gravity Specific 0.87 to 0.90 (ASTM D-1298) Defrosting point -42.8 to -31.7 ° C (ASTM D-97) (-45 ° F to -25 ° F) Average molecular weight 310 to 400 Preferred examples of naphthenic mineral oils include those sold by Witco Corp. as "LP 100", "LP 150", "LP 200", "LP 250", "LP 300" and "LP 350".

Other preferred oils useful in the present invention are poly (alpha olefins) having properties that are in the ranges set forth in Table 2: Property Preferred Range Viscosity, 40 ° C 15 to 400 centistokes (ASTM D-445) (CSt) Viscosity, 100 ° C 1 to 40 cSt (ASTM D-445) Viscosity Index, 120 to 100 (ASTM n-2270) Gravity Specific 0.79 to 0.84 (ASTM D-1298) Defrosting point -73.3 to -45.5 ° C (ASTM D-97) (-100 ° F to -50 ° F) The term "poly-alpha-olefins" is used here. it embraces polymers and copolymers of alkenes and mixtures of alkenes, including ethylene, propylene, butene, 1-decene, 1-dodecene and the like. Polymers that have been partially hydrogenated are also included. Numerous commercially available poly-alpha-olefins meet these criteria. Among them are the products known as "Synfluid PAO" (Chevron), particularly those such as grades 2 cSt, 4 cSt, 6 cSt and 8 cSt. Others include those sold by Mobil under the trademark "SHF" such as "SHF-61", a low viscosity hydrogenated poly-alpha-olefin, "SHF-62", "SHF-82", "SHF-401" and " SHF-1001". The filler material of the present invention also includes 5 to 15 parts by weight of a diblock copolymer of (styrene) - (ethylene / propylene). A preferred block copolymer of a molar ratio of styrene to rubber (ethylene / propylene) in the range of about 37.5: 62.5 to about 27.5: 72.5. Preferred block copolymer also exhibits an approximate specific gravity of 0.90 to 0.925 and a Shore A hardness of 70 to 75. A preferred polymer exhibiting these characteristics and useful in the present invention is the product sold by Shell Chemical Corapany under the name commercial "KRATON" G1701", an unplasticized styrene- (ethylene / propylene) block copolymer exhibiting a styrene: (ethylene / propylene) ratio of approximately 37:63, a Shore A hardness of 72, an approximate specific gravity of 0.92 and a breaking strength of 21.09 Kg / cm2 (300 psi) (as determined by the ASTM D-412 test.) Another preferred copolymer is sold by Shell under the trademark "KRATON G1702." It is a block copolymer. of unplasticized styrene- (ethylene / propylene), which exhibits a styrene: (ethylene / propylene) ratio of approximately 28:72, a Shore A hardness of 75, a specific gravity of approximately 0.91 and a breaking strength of 21 .09 Kg / cm2 (300 psi) (ASTM D-422). The filler material does not need to include any additional gelling component or "anti-drip" component. While it provides a very satisfactory performance in the intended environment with a fiber optic cable. If desired, however, any other gelling compound such as fumed silica can be optionally included equally. However, one or more antioxidants may optionally be included and optionally also include a metal deactivator. An antioxidant component, if present, is employed in a small but effective amount, which is generally in the order of up to about two parts by weight. Examples of suitable antioxidants include phenolic-based and phosphite-based antioxidants. Examples are multiple and are well known in the field of polymer formulations. Specific examples include "Irganox 1010", "Irganox 1076", "Irganox 1035" (Ciba-Geigy) and "Mark 2112", "Mark 1500" and "Mark 5004" (Witco). A metal deactivator, if present, is employed in a small but effective amount, generally in the order of up to about 0.1 part by weight of the filler material. Examples of suitable metal deactivators include "Reomel 39 LF" and other commercially available products that are known in the art.

The filler material of the present invention is easily prepared by combining the mineral oil and the diblock copolymer in the indicated amounts, together with a metal deactivator and / or antioxidant if desired, and agitating the materials together completely until a liquid homogeneous is formed. If desired, slight heating may be applied to assist in the formation of the desired completely homogeneous composition. In a preferred process, the components are mixed together at low shear at 25 '* C. The mixture is then heated to 120 to 130 ° C, until the polymer completely dissolves in the oil, the mixture is then cooled to 25 ° C under vacuum to remove any trapped air bubbles. The resulting composition is then fed into the buffer tube, preferably at the point where the cable is manufactured, all by procedures well known in the art. The superior benefits and performance of the present invention are further described in the following examples. These examples include for purposes of illustration and are not intended to limit the scope of what is considered the invention.

Formulations were prepared by combining styrene- (ethylene / propylene) di-block copolymer oil and copolymer ("Kraton G 1701") in a mixer, for several hours at 130 ° C. The samples were then cooled and centrifuged at moderate speed to remove any entrapped air.The rheological properties of the resulting gels were studied with a Brookfield viscometer Model RVF with a spindle # 7 at 23 ° C and 55% humidity according to ASTM D1824 (which recommends 23 + - 1 ° C and 50 plus 5% humidity.) Each sample was sheared for two minutes at four different rotations (2, 4 , 10 and 20 rpm corresponding to shear rates of 0.1, 0.05, 0.02 and 0.01 sec "1, respectively). In order to evaluate the handling characteristics of the samples, the apparent viscosities were measured and the following criteria were calculated: shear thinning index, degree of thixotropy, and thixotropy index. These criteria that are defined below were calculated as recommended by ASTM 2196 with one modification. The apparent viscosities measured in consideration for evaluation of shear thinning index were performed at 2 and 10 rpm while the specific method combinations of typical speeds of 2 and 20 rpm. As defined by ASTM D2196, the shear thinning index is the ratio between the viscosity at 12 rpm at the viscosity at 10 rpm. The degree of thixotropy is a proportion of the viscosity at 12 rpm that is taken with increased speed versus decreasing speed. The index of thixotropy is the proportion of the viscosity at 12 rpm that is taken after a period of rest of 30 minutes to that before the resting period. The volatility test is carried out at 80 ° C and aged for 48 hours. Volatilities were measured by comparing the weight loss of the filler compound before and after aging. The oil separation test was performed in accordance with FED 791 at 80"c for 48 hours.The cone penetration values were determined by ASTM D937, weighing 150 grams.The oils used are described in Table 3: P aities Ac i e ,, .A B C P B F Viscosity, 19.5 37.5 16.9 22.9 47 400 40"C (CSt) Viscosity, 3.6 8.4 3.9 5.1 7.8 40 100 * C (CSt) index of 40 53.9 123 145 135 152 Viscosity TaMa 3 (Cont.) Properties Acei e Point of 40 -37 -73 -48 -54 -40 defrosting Point of 170 190 219 238 246 275 release of explosive gases Color +30 +30 +30 +30 +30 +30 Saybolt Oils A and B were commercial naphthenic mineral oils , which are sold under the names "" LP 100"and" LP 200"(Witco) respectively, oils C, D, E and F were commercial psi-alpha olefin oils, Table 4 illustrates for each sample, the identity of the oil, the amount of the di-block copolymer gelling agent present and the physical properties of the resulting gel In all cases, the gels exhibited properties that show that they were very satisfactory cable fillers.

TABLE 4 Sample 1 2 3 4 5 6 Oil C D 3 F B S % of Kraton G1-70L 9 9 12 15 9 11 Appearance liger. liger turbid cloudy turbid cloudy clear Cone Penetrations idm) -60C 253 77 120 77 93 82 -40C 295 297 221 196 202 185 -20C 333 333 276 250 272 263 3C 349 336 305 335 133 233 + 21C 359 357 329 270 340 354 Oil separation 48 hrs. 80 C.% 3.0 0.1 0.2 0.4 0.2 0.7 Volatility, 48 hrs. 80 ° C. % 3.1 0.2 0.2 0.3 0.2 0.2 weight loss index 3.4 3.3 3.0 2.3 2.3 Degree of thixotropy 1.0 2.0 1.0 0.5 1.0 1.0 Thixotropy index 1.0 1.0 1.0 1.0 1-0 ._! * TO.

TABLE 4 (Cont.) Sample 1 2 3 4 5 6 Viscosity, cps (2 rpm) 200000 200000 131567 425000 205000370000 Viscosity, cps (10 rpm) 58500 60500 125500 178500 81500 143233 TABLE 4 (Cont.) Sample 7 8 9 10 11 EAAAA% of Kraton G1-70L 12 9.3 12 13 15 Light appearance clear light clear light Cone Penetrations (dmm) - 60C 77 159 142 139 108 -40C 186 229 200 195 173 -20C 231 310 258 161 225 3C 376 349 324 320 293 + 21C 349 363 340 346 313 Oil Separation 48 hrs. 80 ° C,% 0 ^ 2- 12.8 2.2 0, 0.2 Volatility, 48 hrs, go'C,% C _2 0.5 0.4 4.3 Q-2 TABLE 4 (Cont.) Sample 7 8 9 10 11 shear thinning index 2.3 • j ¿. 2.4 2.4 Degree of thixotropy 0.9 0.9 0.9 1.0 0.9 index of thixotropy 1.0 1.0 1.0 1.0 1.0 Viscosity, cps (2 rpm) 436667 175000 256667 521667 758300 Viscosity, cps (10 rpi) 19200 76090 112500 209000 3160Q0

Claims (1)

1. CLAIMS 1.- A composition useful as filling material, for filling substantially hollows between optical fiber conductors in an optical fiber cable, characterized in that the filling material consists essentially of: a) 85 to 95 parts by weight of oils selected from the group consisting of: (a) naphthenic mineral oils comprising 45 to 50% by weight of naphthenics and the rest paraffins, which exhibit a viscosity at 40 ° C, from 19 to 66 centistokes, a viscosity at 100 ° C of 3.5 a 7.5 centistokes, a viscosity index of 40 to 65, a specific gravity of 15.6 ° C from 0.87 to 0.90, a de-icing point of -42.8 to -31.7 ° C (-45 ° F to -25"F) and a average molecular weight of 310 to 400, and (a2) poly-alpha-olefins and their mixtures, which exhibit a viscosity at 40 ° C of 15 to 400 centistokes, a viscosity at 100 ° C of 1 to 40 centistokes, a viscosity index 120 to 160, specific gravity at 15.6 ° C from 0.79 to 0.84 and a thawing point of -73.3 at 45 ° C (-100 to -50 ° F); (b) 5 to 15 parts by weight of a block copolymer (styrene) - (ethylene / propylene) having a styrene: ethylene / propylene ratio (from 37.5: 62.5 to 27.5: 72.5, and a shore A hardness of 70 at 75 and an approximate specific gravity of 0.90 to 0.95, (c) an optional antioxidant component in an amount, if present, of up to two parts by weight, and (d) Optional metal de-activator in an amount, if present, up to 0.1 part by weight 2. Cable comprising a plurality of conductors contained within a liner that leaves gaps between the conductors and the linings, and a filling material according to claim 1, which substantially fills the voids. IflBfjy? JiflEiN PBi LA IWVKt? CXOW Useful hydrophobic compositions are described for filling the gaps within lined optical fiber cables. The compositions include from about 85 to 95 parts by weight of mineral oil, 5 to 15 parts by weight of diblock copolymer (styrene) - (ethylene / propylene), having a styrene ratio: (ethylene / propylene) of 37.5: 62.5 at 27.5: 72.5 and a specific gravity of about 0.90 to 0.95, optional antioxidant and optional metal quencher. R3 / frp / 18/9857? Fi3 20