Novel hydrogen-absorbing composition, process for its preparation and use as composition for filling optical fibre cables

Description

A subject-matter of the invention is novel hydrogen-absorbing compositions comprising dispersing agents and their use in the manufacture of optical fibre cables.

Optical fibres, which make possible the transmission of increasingly large amounts of information, are laid in cables liable to be subjected to significant mechanical and chemical stresses, in particular when they are submarine cables. To restrict the effects of these stresses, the fibres are protected by metal or plastic sheathings and are “immersed” in greases which contribute to cushioning the impacts and to restricting the microcurves which result therefrom and which interfere with the transmission of the signals. These microcurves are also caused by the appearance of hydrogen microbubbles which form inside the grease at the time of the manufacture of the cable, during welding operations or over time as an effect of ageing. This is why some greases currently sold comprise compounds which absorb hydrogen.

Thus, the French patent application published under the number 2 607 311 discloses a hydrophobic thixotropic composition intended for the manufacture of optical fibre cables comprising 100 parts by weight of a lubricating fluid composed of 30% to 100% by weight of polybutene, preferably hydrogenated polybutene, having a number-average molecular mass of between 280 and 800 and of 0% to 70% by weight of at least one liquid lubricant chosen from mineral oils, synthetic oils and silicones and 7 to 20 parts by weight of a hydrophobic thixotropic agent chosen from a hydrophobic silica and a hydrophobic bentonite. The use of a polar agent, such as propylene carbonate, for improving the dispersion of the silicas or bentonites is disclosed in the patent application. The British patent application published under the number 2 144 559 discloses hydrogen-absorbing compositions for optical fibre cables which comprise polybutene, aromatic hydrocarbons, palladium or active charcoal. The United States patent published under the U.S. Pat. No. 4,668,889 discloses hydrogen-absorbing compositions for the filling of optical fibre cables which comprise the mixture of an unsaturated silicone with a catalyst chosen from transition metals, organic salts of transition metals or organometallic compounds of the said metals and more specifically palladium powder, platinum powder, nickel powder, iron pentacarbonyl or chloroplatinic acid, the said metals optionally being supported on inert compounds, such as animal or vegetable carbon black. The United States patent published under the U.S. Pat. No. 4,741,592 discloses hydrogen-absorbing compositions for the filling of optical fibre cables which comprise the mixture of an unsaturated polymer obtained by the polymerization of conjugated dienes with a catalyst chosen from transition metals, organic salts of transition metals or organometallic compounds of the said metals and more specifically palladium powder, platinum powder, nickel powder, iron pentacarbonyl or copper chromite, the said metals optionally being supported on inert compounds, such as animal or vegetable carbon black. The European patent application published under the number EP 0 632 301 discloses hydrogen-absorbing compositions for the filling of optical fibre cables which comprise the mixture of an unsaturated hydrocarbonaceous compound, for example polybutene or propylene-ethylene, propylene-butene and propylene-hexene copolymers, the propylene-butene-ethylene terpolymer, glyceryl ricin-oleate or resin oil, with a catalyst chosen from transition metals, organic salts of transition metals or organometallic compounds of the said metals and more specifically palladium powder, platinum powder, nickel powder or iron pentacarbonyl, the said metals optionally being supported on inert compounds. The French patent application published under the number 2 763 955 discloses a composition for filling optical fibre cables which comprises from 75% to 95% by weight of a propoxylated bisphenol with a molecular weight of less than 3 000, from 5% to 25% by weight of a thixotropic agent and from 0.1% to 1% by weight of an antioxidizing agent.

The palladium-based compounds are provided in the form of very fine powders with a diameter of approximately ten microns and with a high specific surface area. In point of fact, these powders are difficult to disperse homogeneously and have a tendency to form agglomerates in the greases, which reduces the overall specific surface area of the catalyst and thus the effectiveness of the grease in absorbing hydrogen. On the other hand, at equal effectiveness, a good dispersion of the catalyst in the grease makes it possible to use smaller amounts of catalyst and thus to decrease the cost price of these greases. This is why the Applicant Company has sought to develop novel compositions in which the catalyst powders are dispersed more homogeneously than in those of the state of the art.

A subject-matter of the invention is a composition, characterized in that it comprises a hydrocarbonaceous and/or silicone compound or a mixture of hydrocarbonaceous and/or silicone compounds, a nonzero proportion of one or more transition metals and a nonzero proportion of at least one slightly polar dispersing liquid fatty phase, having one or more hydrocarbonaceous chains, with an HLB of between 0.5 and 9, preferably between 4 and 9.

The term “hydrocarbonaceous and/or silicone compound or mixture of hydrocarbonaceous and/or silicone compounds” denotes in particular hydrocarbons, hydrocarbonaceous polymers, silicone oils and/or polyol derivatives.

The composition which is a subject-matter of the present invention generally comprises from 50% to 90% by weight of hydrocarbonaceous and/or silicone compound or of mixture of hydrocarbonaceous and/or silicone compounds.

Hydrocarbons or hydrocarbonaceous polymers include, for example, poly-alpha-olefins (PAO) or copolymers of alpha-olefins comprising from 8 to 12 carbon atoms, polyisobutene (PIB) or polybutene, obtained by polymerization of isobutene, of 1-butene and/or of 2-butene, propylene-ethylene, propylene-butene and propylene-hexene copolymers, propylene-butene-ethylene terpolymers or polybutadienes. The silicone oils can be chosen from poly(alkylsiloxanes), in particular poly(dimethylsiloxanes), with high molecular weights having a viscosity of the order of 10 000 to 30 000 cSt at ambient temperature. The polyol derivatives are obtained by etherification or esterification of a compound having several hydroxyl functional groups, such as, for example, glycerol, TMP or bisphenol, by means of hydrocarbonaceous fatty chains or alkoxide chains, such as polyethylene glycol, polypropylene glycol or polybutylene glycol.

The composition which is a subject-matter of the present invention also comprises one or more metal catalysts in a proportion by weight ranging up to 5% by weight of the said composition. Examples of metal compounds appropriate to the present invention include, for example, transition metals, organic salts of transition metals or organometallic compounds of the said metals and more specifically palladium powder, platinum powder, nickel powder, iron pentacarbonyl, chloroplatinic acid, copper chromite, Raney nickel, palladium supported on active charcoal, palladium supported on alumina, platinum supported on alumina or platinum supported on active charcoal.

According to a specific alternative form of the present invention, the composition comprises up to 1% by weight of palladium supported on alumina or on active charcoal.

The composition which is a subject-matter of the present invention also comprises up to 15% by weight of silica. Hydrophobic treated silica, such as, for example, Aerosil™ R974, can be used but the preferred silica is hydrophilic silica, for example hydrophilic pyrogenic silica, such as that sold under the name of Aerosil™ 200, or hydrophilic colloidal silica, such as that sold under the name of Cab-O-Sil™ TS 720.

The composition which is a subject-matter of the present invention optionally comprises up to approximately 5% of a viscosifying polymer. Examples of viscosifying polymer include styrene, ethylene, propylene, butylene or butadiene polymers or diblock copolymers of these monomers, such as polystyrene-polyethylene, polystyrene-[polyethylene+polypropylene], polystyrene-polyisoprene or polystyrene-polybutene, or triblock polymers, such as polystyrene-polyethylene-polystyrene, polystyrene-[polyethylene+polypropylene]-polystyrene, polystyrene-polyisoprene-polystyrene or polystyrene-polybutadiene-polystyrene. Polymers of this type are sold under the trade names Kraton™ G or Kraton D, Septon™ or Shellvis™.

The composition which is a subject-matter of the present invention optionally comprises up to approximately 2% of an antioxidizing agent chosen, for example, from compounds with a sterically hindered phenolic structure, such as polymeric 2,2,4-trimethyl-1,2-dihydroquinoline, phenothiazine, octyl (3,5-di-tert-butyl-4-hydroxyphenyl)propionate, hydroquinone monomethyl ether or triethylene glycol bis[3-(3′-tert-butyl-4′-hydroxy-5′-methylphenyl)propionate], sold under the name of Irganox™ 245, or ethylenebis-(oxyethylene) bis(3-tert-butyl-4-hydroxy-5-methylhydro-cinnamate), Irganox™ 1076, or Irganox™ 1010.

The term “slightly polar dispersing liquid fatty phase having one or more hydrocarbonaceous chains, with an HLB of between 0.5 and 9, preferably between 4 and 9″ is preferably understood to mean fatty phases which are liquid at ambient temperature.

The HLB number, or hydrophilic-lipophilic balance, and its method of determination are known to a person skilled in the art. This parameter makes it possible to assess the hydrophobic and hydrophilic natures of a given surface-active agent. In the context of the present invention, for surface-active agents comprising an ester functional group, it is determined by the following formula:
HLB=20×[1−(SN/AN)
in which SN represents the saponification number of the product, measured according to NFT Standard 60206, and AN represents the acid number of the precursor acids, measured according to NFT Standard 60204.

In the case of surface-active agents comprising an ether functional group, the HLB is calculated by the equation:
HLB=20×(M_h/M)
in which M_h is the mass of the hydrophilic part of the molecule and M is its overall molecular mass.

The composition which is a subject-matter of the present invention comprises from 1% to 20% and preferably between 5% and 10% by weight of dispersing fatty phase.

According to another specific aspect of the present invention, the ratio by weight of the metal catalyst or catalysts to the dispersing fatty phase in the composition is between approximately 0.01 and 0.20.

Slightly polar dispersing fatty phase appropriate to the present invention includes vegetable oils, such as, for example, sunflower oil, rapeseed oil, maize oil, soybean oil, castor oil, linseed oil, coconut oil, groundnut oil, olive oil, palm oil or hydrogenated palm oil, or modified vegetable oils, such as methyl esters of vegetable oils, monoglycerides or diglycerides obtained by controlled hydrolysis of vegetable oils, weakly alkoxylated vegetable oils, in particular weakly ethoxylated and/or propoxylated vegetable oils, more particularly ethoxylated vegetable oils comprising from 1 to 10 ethylene oxide units, or weakly alkoxylated methyl esters of vegetable oils, in particular weakly ethoxylated and/or propoxylated methyl esters of vegetable oils and more particularly methyl esters of vegetable oils ethoxylated with 1 to 4 ethylene oxides. The preparation of these modified vegetable oils is disclosed in the international patent applications published under the numbers WO 96/22109 and WO 00/01233.

The term “weakly alkoxylated” indicates, in the preceding and in the following, that the alkoxylation number and in particular the ethoxylation and propoxylation numbers, which represent respectively the number of ethoxyl units (EO number) and the number of propoxyl units (PO number) per molecule, is less than or equal to approximately 15 [EO number=15 or PO number=15 or (EO number+PO number)=approximately 15].

Other slightly polar liquid dispersing fatty phase appropriate to the present invention includes surface-active agents having an HLB number of between 1 and 9, preferably between 4 and 9, which are miscible with the oils which participate in the composition of the greases. Examples include linear or branched fatty alcohols or fatty acids comprising from 5 to 30 carbon atoms and more particularly from 12 to 22 carbon atoms or the esters of the said acids, the said alcohols, acids or esters optionally being weakly alkoxylated. Preference is given, among these, to surface-active agents which are liquid at ambient temperature, such as those comprising an oleyl, oleyl/cetyl, linoleyl or behenyl chain. These compounds are optionally weakly alkoxylated. Examples of surface-active agents of this nature include sorbitan oleic esters, oleyl alcohols comprising from 1 to 5 ethylene oxide units (EO=5), polyethylene glycol (PEG) oleates comprising from 1 to 5 ethylene oxide units (1≦EO≦5), liquid glucose ethers or oleic acid comprising from 1 to 5 ethylene oxide units.

According to another aspect of the present invention, a subject-matter of the latter is a process for producing the composition as defined above comprising a stage of dispersing the catalyst in the dispersing agent as defined above, followed by mixing the dispersion in the other constituents of the composition which is a subject-matter of the present invention.

The process as defined above is a preferred route but it is possible to mix the dispersing phase with the oils of the grease, to add the palladium powder and then to add the other components.

According to a final aspect of the present invention, a subject-matter of the latter is the use of the composition as defined above as composition for filling optical fibre cables.

The following examples illustrate the invention without, however, limiting it.

A) Demonstration of the Influence of the Dispersing Fatty Phase on the Amount of Hydrogen Absorbed by the Composition

The examples in Tables 1a to 1e are obtained from a model grease composed of:

• • 5 or 10% by weight of a dispersing fatty phase (referred to as DFP)
  • 3.8% by weight of a viscosifying polymer (Shellvis™ 40),
  • 6.5% by weight of hydrophilic silica (Cab-O-Sil™ TS 720),
  • 0.4% of an antioxidant (Irganox™ 1076),
  • 0.6% of palladium supported on alumina catalyst,
  • q.s. for 100% of poly-alpha-olefin (PAO).

The measured characteristics of the compositions are as follows:

• • the volatility, after residence in an oven at 150° C. for 24 h,
  • the release of oil (exsudation) , after residence in an oven at 150° C. for 24 hours,
  • the viscosity at a high shear gradient (approximately 2 500 Pa·s), measured on a Carrimed viscometer with a cone with a diameter of 2 cm and an angle of 2°,
  • the hydrogen absorption per gram of grease at 24 hours and at 48 hours, in a cell under an initial hydrogen pressure of 400 mm of mercury at ambient temperature.

The results reveal that all the greases formulated with 5 to 10% of a polar fatty phase have viscosities, exsudations and volatilities close to those of the control formula but that the hydrogen absorption is, on the other hand, markedly improved, in particular when the dispersing fatty phase has an HLB number in the region of 4 or greater than 4. Additives not possessing a long hydrocarbonaceous fatty chain, such as oxypropylated bisphenol A (comparative example), give results which are only slightly better than those of the control.

TABLE 1a
Examples	Control	Ex. 1

DFP (nature; amount as %; HLB)	None	Methyl ester of
		rapeseed oil; 5%
		HLB = 0.5
Volatility	1.17%	4.16%
Exsudation	0%	0%
Plastic viscosity	0.90 Pa · s at	0.78 Pa · s at
	2534 Pa	2445 Pa

H2 pressure	at T = 0 h	405 mmHg (0)	401 mmHg (0)
in mmHg,	at T = 24 h	322 mmHg (1.08)	204 mmHg (3.27)
H2 absorption	at T = 48 h	321 mmHg (1.39)	174 mmHg (3.76)
in ml/g

TABLE 1b
Examples	Ex. 2	Ex. 3

DFP (nature; amount as %; HLB)	Ethoxylated (2	Rapeseed oil;
	EO) oleyl/cetyl	5%;
	alcohol; 5%;	HLB = 0.5
	HLB = 6
Volatility	2.67%	1.81%
Exsudation	0%	0%
Plastic viscosity	0.81 Pa · s at	0.83 Pa · s at
	2093 Pa	2394 Pa

H2 pressure	at T = 0 h	406 mmHg (0)	400 mmHg
in mmHg,	at T = 24 h	277 mmHg (2.14)	304 mmHg (1.59)
H2 absorption	at T = 48 h	246 mmHg (2.65)	277 mmHg (2.04)
in ml/g

TABLE 1c
Examples	Ex. 4	Ex. 5

DFP (nature; amount as	Ethoxylated (4	Alkoxylated (5
%; HLB)	EO) maize oil; 5%;	EO 4 PO 5 EO)
	HLB = 5	oleic acid; 5%;
		HLB = 3
Volatility	1.6%	2.01%
Exsudation	0%	0%
Plastic viscosity	0.90 Pa · s at	0.88 Pa · s at
	2125 Pa	2494 Pa

H2 pressure	at T = 0 h	400 mmHg	405 mmHg
in mmHg,	at T = 24 h	304 mmHg (1.7)	299 mmHg (1.76)
H2 absorption	at T = 48 h	277 mmHg (2.24)	291 mmHg (1.89)
in ml/g

TABLE 1d
Examples	Ex. 6	Comparative

DFP (nature; amount as	Ethoxylated (5	Oxypropylated
%; HLB)	EO) oleic acid; 5%;	bisphenol A 10%;
	HLB = 8.7	HLB = 1
Volatility	1.43%	1.71%
Exsudation	0%	0.06%
Plastic viscosity	0.90 Pa · s at	0.91 Pa · s at
	2344 Pa	2394 Pa

H2 pressure	at T = 0 h	402 mmHg	403 mmHg
in mmHg,	at T = 24 h	279 mmHg (2.03)	315 mmHg (1.45)
H2 absorption	at T = 48 h	249 mmHg (2.53)	309 mmHg (1.55)
in ml/g

TABLE 1e
Examples	Ex. 7	Ex. 8

DFP (nature; amount as %; HLB)	Sorbitan	Ethoxylated (10
	oleate; 10%;	EO) oleic acid;
	HLB = 4.3	HLB = 8.7
Volatility	2.22%	2.0%
Exsudation	1.94%	0%
Plastic viscosity	0.85 Pa · s at	0.89 Pa · s
	1994 Pa

H2 pressure	at T = 0 h	403 mmHg	401 mmHg
in mmHg,	at T = 24 h	284 mmHg (1.97)	255 mmHg (2.4)
H2 absorption	at T = 48 h	249 mmHg (2.54)	221 mmHg (2.97)
in ml/g

B) Demonstration of the Influence of the Catalyst/Dispersing Fatty Phase Ratio by Weight on the Amount of Hydrogen Absorbed by the Composition

The examples in Tables 2a to 2c are obtained from a model grease composed of:

• • 5% by weight of ethoxylated (5 EO) oleic acid with an HLB of 8.7,
  • 3.8% by weight of a viscosifying polymer (Shellvis™ 40),
  • 6.5% by weight of hydrophilic silica (Cab-O-Sil™ TS720),
  • 0% to 0.6% of palladium supported on alumina catalyst,
  • q.s. for 100% of poly-alpha-olefin (PAO).

In all cases, the amounts of hydrogen absorbed in 48 h are greater than those absorbed by the control not comprising dispersing phase while comprising 0.6% of catalyst.

TABLE 2a
Examples	Control	Ex. 9

Catalyst/DFP ratio by weight	0	0.04
Catalyst (% by weight)	0%	Pd/Al2O3; 0.20%
Volatility	1.3%	1.3%
Exsudation	0%	0%
Plastic viscosity	0.90 Pa · s at	0.90 Pa · s at
	2344 Pa	2344 Pa

H2 pressure	at T = 0 h	403 mmHg (0)	402 mmHg (0)
in mmHg,	at T = 48 h	402 mmHg (0)	295 mmHg (1.78)
H2 absorption
in ml/g

TABLE 2b
Examples	Ex. 10	Ex. 11

Catalyst/DFP ratio by weight	0.08	0.12
Catalyst (% by weight)	Pd/Al2O3; 0.40%	Pd/Al2O3; 0.60%
Volatility	1.9%	1.9%
Exsudation	0%	0%
Plastic viscosity	0.90 Pa · s at	0.90 Pa · s at
	2344 Pa	2344 Pa

H2 pressure	at T = 0 h	403 mmHg (0)	402 mmHg (0)
in mmHg,	at T = 48 h	244 mmHg (2.59)	173 mmHg (3.78)
H2 absorption
in ml/g

TABLE 2c
		DFP-free
Examples	Ex. 12	control

Catalyst/DFP ratio by weight	0.06%	8
Catalyst (% by weight)	Pd/Al2O3; 0.30%	Pd/Al2O3; 0.60%
Volatility	1.43%	1.17%
Exsudation	0%	0%
Plastic viscosity	0.90 Pa · s · at	0.90 Pa · s at
	2344 Pa	2344 Pa

H2 pressure	at T = 0 h	401 mmHg (0)	405 mmHg (0)
in mmHg,	at T = 48 h	221 mmHg (2.97)	321 mmHg (1.39)
H2 absorption
in ml/g

The examples in Tables 3a to 3c are obtained from a model grease composed of:

• • 10% by weight of vegetable oil (HLB 0.5),
  • 3.8% by weight of a viscosifying polymer (Shellvis™ 40),
  • 6.5% by weight of hydrophilic silica (Cab-O-Sil™ TS720),
  • 0% to 0.3% of palladium supported on alumina catalyst,
  • q.s. for 100% of poly-alpha-olefin (PAO).

In all cases where the catalyst/DFP ratio by weight is greater than 0.01, the amounts of hydrogen absorbed in 48 h are greater than those absorbed by the control not comprising dispersing phase while comprising 0.6% of catalyst.

TABLE 3a
Examples	Control	Ex. 13

Catalyst/DFP ratio by weight	0	0.01
Catalyst (% by weight)	0%	Pd/Al2O3; 0.10%
Volatility	1.8%	1.8%
Exsudation	0%	0%
Plastic viscosity	0.87 Pa · s at	0.89 Pa · s at
	2550 Pa	2556 Pa

H2 absorption	at T = 0 h	0	0
in ml/g	at T = 48 h	0.05	0.98

TABLE 3b
Examples	Ex. 14	Ex. 15

Catalyst/DFP ratio by weight	0.02	0.03
Catalyst (% by weight)	Pd/Al2O3; 0.20%	Pd/Al2O3; 0.30%
Volatility	1.8%	1.8%
Exsudation	0%	0%
Plastic viscosity	0.88 Pa · s at	0.87 Pa · s at
	2550 Pa	2560 Pa

H2 absorption	at T = 0 h	0	0
in ml/g	at T = 48 h	1.9	2.3

TABLE 3c
		DFP-free
Examples	Ex. 16	control

Catalyst/DFP ratio by weight	0.06%	8
Catalyst (% by weight)	Pd/Al2O3; 0.60%	Pd/Al2O3; 0.60%
Volatility	1.8%	1.17%
Exsudation	0%	0%
Plastic viscosity	0.83 Pa · s at	0.90 Pa · s at
	2394 Pa	2344 Pa

H2 absorption	at T = 0 h	0	0
in ml/g	at T = 48 h	2	1.4