Silane functional stabilizers for extending long-term electrical power cable performance

1. A method for extending the useful life of in-service electrical cable, comprising injecting a dielectric enhancement fluid composition into at least one section of an electrical cable having a stranded conductor encased in a polymeric insulation jacket, and having an average operating temperature T, the composition comprising:

(a) at least one organoalkoxysilane functional additive selected from the group consisting of

(i) a voltage stabilizer-based alkoxysilane compound of Formula 1

wherein:

m is 1-4;

A is a linear or branched alkylene radical containing from 1 to 10 carbon atoms, or one of

where S 3 , S 4 and S 5 are linear or branched alkylene radicals containing a total of between 3 and 10 carbon atoms, and T is oxygen or sulfur;

X is a linear or branched alkyl radical containing from 1 to 5 carbon atoms;

Y is C 1 -C 4 acyloxy, C 1 -C 4 alkyloxy, amino, amino-oxy or silyloxy; and

n is one, two or three,

(ii) a hindered amine light stabilizer (HALS)-based alkoxysilane of formula (XI)

wherein:

m+n is a number from 1 to 40, n varies from zero to 50% of the sum m+n;

A is —O—;

T 1 and T 4 which can be identical or different are methyl, methoxy, ethoxy or OH;

T 2 is trimethylene or is also a direct bond if A is —O— and T 1 and T 4 are methyl;

T 3 is methyl, C 7 -C 9 alkyl or cyclohexyl;

T 5 is C 1 -C 12 alkyl;

X 1 is as defined for T 1 or is a group (CH 3 ) 3 SiO—; and

X 2 is hydrogen, methyl, ethyl, a group (CH 3 ) 3 Si— or, if n is zero and T 1 and X 1 are methyl,

X 2 is also a group of the formula (XIII)

and, if m+n is a number from 3 to 10, X 1 and X 2 together can also be a direct bond, and

(iii) a UV absorber-based alkoxysilane compound of formula (IA) or (IIA)

wherein:

G 1 and G 6 are hydrogen;

G 2 and G 7 are independently H, cyano, CF 3 —, fluoro, —CO—G 3 , or E 3 SO 2 —;

G 3 is straight or branched chain alkyl of 1 to 24 carbon atoms, straight or branched chain alkenyl of 2 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, phenylalkyl of 7 to 15 carbon atoms, phenyl, or said phenyl or said phenylalkyl substituted on the phenyl ring by 1 to 4 alkyl of 1 to 4 carbon atoms;

E 1 is phenylalkyl of 7 to 15 carbon atoms, phenyl, or said phenyl or said phenylalkyl substituted on the phenyl ring by 1 to 4 alkyl groups of 1 to 4 carbon atoms each;

E 2 and E 9 are independently straight or branched alkyl chain of 1 to 24 carbon atoms, straight or branched chain alkenyl of 2 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, phenylalkyl of 7 to 15 carbon atoms, phenyl, or said phenyl or said phenylalkyl substituted on the phenyl ring by 1 to 3 alkyl of 1 to 4 carbon atoms; or E 2 is said alkyl of 1 to 24 carbon atoms or said alkenyl of 2 to 18 carbon atoms substituted by one or more —OH, —OCOE 11 , —OE 4 ,—NCO, —NH 2 , —NHCOE 11 , —NHE 4 or —N(E 4 ) 2 , or mixtures thereof, where E 4 is straight or branched chain alkyl of 1 to 24 carbon atoms; or said alkyl or said alkenyl interrupted by one or more —O—, —NH—, or —NE 4 — groups or mixtures thereof and which can be unsubstituted or substituted by one or more —OH, —OE 4 , or —NH 2 groups or mixtures thereof,

E 11 is hydrogen, straight or branched chain alkyl of 1 to 18 carbon atoms, straight or branched chain alkenyl of 2 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, aryl of 6 to 14 carbon atoms or phenylalkyl of 7 to 15 carbon atoms;

E 3 is alkyl of 1 to 20 carbon atoms, hydroxyalkyl of 2 to 20 carbon atoms, alkenyl of 3 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, phenylalkyl of 7 to 15 carbon atoms, aryl of 6 to 10 carbon atoms or said aryl substituted by one or two alkyls of 1 to 4 carbon atoms or 1,1,2,2-tetrahydroperfluoroalkyl where the perfluoroalkyl moiety is of 6 to 16 carbon atoms;

L is methylene; and

with the proviso that at least one of E 1 , E 2 and E 9 contains a group —T 1 —Si(OR 2 ) n (R 1 ) 3-n , —T 1 —X—CO—X—T 2 —Si(OR 2 ) n (R 1 ) 3-n , T 1 —CO—X—T 2 —Si(OR 2 ) n (R 1 ) 3-n , —X—T 1 —Si(OR 2 ) n (R 1 ) 3-n or —X—T 1 —X—CO—X—T 2 —Si(OR 2 ) n (R 1 ) 3-n ,

where, for E 1 , E 2 and E 9 , T 1 and T 2 are independently alkylene of 2 or 3 carbon atoms, and R 1 and R 2 are independently alkyl of 1 to 6 carbon atoms or phenyl, and n is 1, 2, or 3, and X is —O—, —NE 4 — or —NH—; and

(b) at least one catalyst suitable to catalyze hydrolysis and condensation of the at least one functional additive of (a),

wherein the at least one organoalkoxysilane functional additive of (a) comprises:

at least one of the voltage stabilizer-based alkoxysilane compounds of Formula (1) of (i) and at least one of the HALS-based alkoxysilane of formula (XI) of (ii); and/or

at least one of the voltage stabilizer-based alkoxysilane compounds of Formula (1) of (i) and at least one of the UV absorber-based alkoxysilane compounds of formula (IA) or (IIA) of (iii); and/or

at least one of the HALS-based alkoxysilane of formula (XI) of (ii) and at least one of the UV absorber-based alkoxysilane compounds of formula (IA) or (IIA) of (iii), and

wherein the injected composition provides for both initial permeation of the at least one functional additive into the polymeric insulation, and extended retention of subsequent condensation products of the at least one functional additive in the cable insulation.

2. The method of claim 1 , wherein the cable section has a stranded conductor surrounded by a conductor shield encased in a polymeric insulation jacket with an outer insulation shield, and having an interstitial void volume in the region of the conductor, and wherein injecting comprises injecting the dielectric enhancement fluid composition into the interstitial void volume, and/or into the space between the polymeric insulation jacket and the outer insulation shield.

3. The method of claim 1 , wherein the dielectric enhancement fluid composition further comprises

(c) at least one water-reactive organosilane material selected from

(i) an organosilane monomer having at least two water-reactive groups,

(ii) the organosilane monomer (i) where at least one of the water-reactive groups is substituted with a condensable silanol group,

(iii) an oligomer of the above organosilane monomer (i), and/or

(iv) a co-oligomer of the above organosilane monomer (i) with a different organosilane monomer, and wherein the catalyst provides for covalent binding of the at least one functional additive of (a) to the at least one water-reactive material (c) upon hydrolysis and condensation thereof.

4. The method of claim 3 , wherein the organosilane monomer of (i) has a diffusion coefficient at least about 15 times greater than the diffusion coefficient of a tetramer thereof, the diffusion coefficient being determined at the average operating temperature T of the at least one section of the in-service electrical cable.

5. The method of claim 3 , wherein the dielectric enhancement fluid composition further comprises:

(d) a non-water-reactive organic material which has a diffusion coefficient of less than about 10 −9 cm 2 /sec and an equilibrium concentration of at least about 0.005 gm/cm 3 in said polymeric insulation, the diffusion coefficient and the equilibrium concentration being determined at the average operating temperature T; and/or

(e) an organic compound having an equilibrium concentration in the polymeric insulation at 55° C. which is less than 2.25 times the equilibrium concentration at 22° C.

6. The method of claim 4 , wherein the dielectric enhancement fluid composition further comprises:

(d) a non-water-reactive organic material which has a diffusion coefficient of less than about 10 −9 cm 2 /sec and an equilibrium concentration of at least about 0.005 gm/cm 3 in said polymeric insulation, the diffusion coefficient and the equilibrium concentration being determined at the average operating temperature T; and/or

(e) an organic compound having an equilibrium concentration in the polymeric insulation at 55° C. which is less than 2.25 times the equilibrium concentration at 22° C.

7. The method of claim 3 , wherein the at least one water-reactive organosilane material is/are organoalkoxysilanes.

8. The method of claim 7 , wherein the organoalkoxysilanes are selected from:

(3-methylphenyl)methyldimethoxysilane,

di(4-methylphenyl)dimethoxysilane,

dimethyldi-n-butoxysilane

(4-methylphenyl)methyldimethoxysilane,

3-cyanopropylmethyldimethoxysilane

3-cyanobutylmethyldimethoxysilane

phenethyltrimethoxysilane,

p-tolylethyl)methyldimethoxysilane,

(p-styrylethyl)trimethoxysilane,

phenylmethyldimethoxysilane

3-(2,4-dinitrophenylamino)propyltriethoxysilane, or

3-(triethoxysilylpropyl) p-nitrobenzamide.

9. The method of claim 8 , wherein the organoalkoxysilanes are (p-tolylethyl)methyldimethoxysilane, 3-cyanopropylmethyldimethoxysilane, dimethyldi-n-butoxysilane, or 3-cyanobutylmethyldimethoxysilane.

10. The method of claim 4 , wherein the at least one water-reactive organosilane material is/are organoalkoxysilanes.

11. The method of claim 10 , wherein the organoalkoxysilanes are selected from:

(3-methylphenyl)methyldimethoxysilane,

di(4-methylphenyl)dimethoxysilane,

dimethyldi-n-butoxysilane

(4-methylphenyl)methyldimethoxysilane,

3-cyanopropylmethyldimethoxysilane

3-cyanobutylmethyldimethoxysilane

phenethyltrimethoxysilane,

p-tolylethyl)methyldimethoxysilane,

(p-styrylethyl)trimethoxysilane,

phenylmethyldimethoxysilane

3-(2,4-dinitrophenylamino)propyltriethoxysilane, or

3-(triethoxysilylpropyl) p-nitrobenzamide.

12. The method of claim 11 , wherein the organoalkoxysilanes are (p-tolylethyl)methyldimethoxysilane, 3-cyanopropylmethyldimethoxysilane, dimethyldi-n-butoxysilane, or 3-cyanobutylmethyldimethoxysilane.

13. The method of claim 1 , wherein the organoalkoxysilane functional additives are derived from at least one of the following stabilizing functionalities;

hydroxyphenyl benzotriazole chromophores,

N-Alkoxy 2,2,6,6-tetramethyl piperidine light stabilizers, and/or

ferrocene backbones.

14. The method of claim 1 , wherein the composition further comprises an organoalkoxysilane functional additive derived from a hindered phenolic antioxidant backbone.

15. The method of claim 1 , where the at least one organoalkoxysilane functional additive has a PE retention of at least 0.2%.

16. The method of claim 1 , where the at least one organoalkoxysilane functional additive permeates into the cable insulation reaching at least 90% of saturation in less than 500 hours at 55° C.

17. The method of claim 1 , where the at least one organoalkoxysilane functional additive has a diffusivity in PE greater than 5.0×10 −9 cm 2 /s at 55° C. and a PE retention of at least 0.40 wt % at 5,000 hours at 55° C.

18. The method of claim 1 , wherein the compound of formula (IA) is

19. The method of claim 1 , wherein the voltage stabilizer-based alkoxysilane compound of Formula 1 is an organoalkoxysilane compound selected from the group consisting of

or a combination thereof.