Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2001-08-30
2003-06-24
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C524S425000, C524S492000, C524S588000, C528S024000, C428S405000, C525S477000, C174S13700R
Reexamination Certificate
active
06582825
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to silicone rubber compositions. In particular, this invention relates to silicone rubber compositions useful as high voltage insulators (HVI's).
High voltage insulators such as those used in power transmission lines, distribution stations or surge arrestors are typically made of porcelain or glass. Under ordinary working conditions, these high voltage insulators stand long use. A severe contaminate environment such as a seaside or an industrial district can cause insulators to degrade. High electrical stress can cause droplets of water to join together into a larger single drop known as a filament. Water filaments dissolve conductive pollution to form conductive paths that lower surface resistance. As the conductive paths form along the surface of an insulator, ohmic heating, caused by leakage current, causes a decrease in resistance and a corresponding increase in current. The heating can cause evaporation and subsequent drying to form a “dry-band”. The electrical stress across this “band” or gap can be the site for electrical discharge activity (corona, arcing, and/or partial discharges). The discharge activity leads to flashover.
“Hydrophobicity” as used herein refers to a lack of affinity or a repulsion for water or failure to adsorb water. A hydrophobic surface has a low surface energy. Water resides on the surface as discrete droplets. In contrast, a hydrophilic (water-loving) surface has a high free surface energy thereby enabling water to cover the surface as a film. Periods of wetness in a contaminate environment can cause electrical discharge activity on an insulator surface that destroys hydrophobicity. If the hydrophobicity property is not recovered, more water accumulates, accelerating dry band arcing and discharge activity.
Hydrophobicity can be determined by measuring a contact angle (CA) between a substrate surface and a surface of pure water. Silicones without additives typically have a contact angle of about 114°. After corona treatment to destroy hydrophobicity, the contact angle is typically in a range between about 10° C. and about 50° C. Hydrophobicity recovery is measured after a 24-hour rest period. Recovered contact angle (RCA) conventionally, is the contact angle after the recovery period subsequent to corona treatment.
Both hydrophobicity and recovered contact angle are important properties in high voltage insulators, particularly when used in harsh environments. Thus, there is a need for silicone compositions with improved hydrophobicity properties.
SUMMARY OF THE INVENTION
The present invention relates to a particulate material that imparts an improved hydrophobicity and improved recovered contact angle property to a silicone composition. The silicone composition comprises (A) a silicone polymer and (B) an inorganic hydrophobicity imparting particulate (HIP) that imparts improved hydrophobicity properties.
In another aspect, the present invention relates to a silicone composition, comprising (a) a silicone polymer in a range between about 15% and about 50%, by weight of the total composition; (b) a hydrophobicity imparting particulate in a range between about 1% and about 50% by weight of the total composition that imparts a hydrophobicity property to the total composition; (c) an anti-tracking agent and a flame retardant in a range between about 20% and about 70% by weight of the total composition; (d) a coupling agent in a range between about 0.01% and about 1% by weight of the total composition; (e) a curing agent in a range between about 0.1% and about 5% by weight of the total composition; (f) an extending filler up to about 20% by weight of the total composition; and (g) at least one processing fluid in a range between about 0.1% and about 5% by weight of the total composition.
In another aspect, the present invention relates to a silicone composition comprising (A) a silicone polymer and (B) two or more hydrophobicity imparting particulates that impart a hydrophobicity property to the composition or at least one hydrophobicity imparting particulate that imparts a hydrophobicity property to the composition and a filler.
In another aspect, the present invention relates to an insulator comprising a housing portion. The housing portion comprises a cured product of (A) a silicone polymer and (B) an inorganic hydrophobicity imparting particulate.
In still another aspect, the present invention relates to an insulator comprising a housing portion which comprises a cured product of (A) a silicone polymer and (B) two or more hydrophobicity imparting particulates that impart a hydrophobicity property to the composition or a hydrophobicity imparting particulate that imparts a hydrophobicity property to the composition and a filler.
The present invention also relates to a method of imparting a hydrophobicity recovery property to a silicone polymer composition. In the method, a target hydrophobicity recovery property is determined for a silicone polymer composition. An inorganic hydrophobicity imparting particulate is selected to impart a hydrophobicity recovery property to a silicone polymer composition. The inorganic hydrophobicity imparting particulate is then added into the silicone polymer composition in an amount to impart the hydrophobicity recovery property.
In another aspect, the present invention relates to a method of improving a hydrophobicity property of a cured silicone polymer composition. In the method, a target hydrophobicity property is determined for a cured silicone polymer composition. An inorganic hydrophobicity imparting particulate is selected that imparts a hydrophobicity property to a silicone polymer composition. A blend of (A) a silicone polymer and (B) the selected inorganic filler is then compounded and cured by heating.
REFERENCES:
patent: 3965065 (1976-06-01), Elliott
patent: 4039503 (1977-08-01), Itoh
patent: 4144222 (1979-03-01), Shinmi et al.
patent: 4279783 (1981-07-01), Kehrer et al.
patent: 4405425 (1983-09-01), Schiller et al.
patent: 4897027 (1990-01-01), Szaplonczay et al.
patent: 5244958 (1993-09-01), Goodman
patent: 5254657 (1993-10-01), Inoue
patent: 5326804 (1994-07-01), Mistry et al.
patent: 5369161 (1994-11-01), Kunieda et al.
patent: 5514741 (1996-05-01), Arai et al.
patent: 5548038 (1996-08-01), Enami et al.
patent: 5668205 (1997-09-01), Yoshida et al.
patent: 5922799 (1999-07-01), Sollradl et al.
patent: 5928778 (1999-07-01), Takahashi et al.
patent: 5958389 (1999-09-01), Le Bras-Roulier et al.
patent: 6015629 (2000-01-01), Heyer et al.
patent: 6043309 (2000-03-01), Nakamura et al.
patent: 6074672 (2000-06-01), Dobkowski et al.
patent: 6162854 (2000-12-01), Meguriya et al.
patent: 2900162 (1978-10-01), None
patent: 0050798 (1982-04-01), None
patent: 0316696 (1989-05-01), None
patent: 0470745 (1992-02-01), None
patent: 09033263 (1998-08-01), None
patent: 0902440 (1999-03-01), None
patent: 0928008 (1999-07-01), None
patent: 1052655 (2000-11-01), None
“Polymer Outdoor Insulating Materials Part 1: Comparison of Porcelain and Polymer Electrical Insulation” by J. Mackevich and M. Shah, Raychem Corp.,—IEEE Electrical Insulation Magazine—May/Jun. 1997—vol. 13, No. 3, pp. 5-12.
“Polymers for High-Voltage Insulators”—Rubber World—Dec. 1997—pp. 42-44.
“Surface Recovery of Silicone Rubber Used for HV Outdoor Insulation” by J.W. Chang and R.S. Gorur—IEEE Transactions on Dielectrics and Electdrical Insulation, vol. 1, No. 6, Dec. 1994, pp. 1039-1046.
“Hydrophobicity of Silicone Rubber Used for Outdoor Insulation”, Proceeds of the 4th Int. Conf. on Properties and Application of Dielectric Materials—Jul. 3-8, 1994.
“Laboratory Analysis of Naturally Aged Silicone Rubber Polymer Insulators From Contaminated Environments, 138 to 765 kV” by R.J. Hill, Proceedings of IEEEE Power Engineering Society Transmission and Distribution Conf.—Apr. 1994, pp. 488-493.
“Molecular Dynamic Phenomena at Polymer Surfaces and Their Relevance to Polymer Adhesion Behavior” by R. Morra, E. Occhiello, F. Garbassi, Metallized Plastics—1991, pp. 363-369.
“Performance and Ageing of Polymeric
Amarasekera Jayantha
Krahn John Raymond
Bennett Bernadette M.
Dawson Robert
General Electric Company
Johnson Noreen C.
Peng Kuo-Liang
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