Electrically conductive foam and method of preparation and use
AssigneeCharleswater Products, Inc.
InventorGeorge R. Berbeco
Life of this patent
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Abstract
An article of manufacture which comprises a urethane foam characterized by electrically conductive properties to prevent the accumulation of static charge on electronic components or devices which are placed on or wrapped in the foam or alternatively electronic devices in which the electronic leads, themselves, are inserted in an electrically conductive relationship into the foam. The urethane foam contains a binding agent and is impregnated generally uniformly therethrough with an electrically conductive amount of an electrically conductive particulate material.
Claims27
An electrically conductive foam adapted for use with electronic components sensitive to static charges, which foam consists essentially of:
- an open-cell polymeric foam uniformly impregnated with electrically conductive particulate material in an amount of from about 2% to 40% by weight of the impregnated foam and sufficient to provide for a surface resistance of the foam of less than about 30,000 ohms per square inch, the particulate material having a particle size of less than 40 millimicrons, and from about 1% to 60% by weight of the impregnated foam of a film-forming polymeric-binding material securing the conductive particulate material to the foam.
An electrically conductive foam adapted for use with electronic components sensitive to static charges, which foam consists essentially of:
- an open-cell, polymeric, urethane foam having a foam density ranging from about 0.5 to 10 pounds per cubic foot and uniformly impregnated with electrically conductive, carbon-black particulate material having a particle size of less than about 40 millimicrons and a nitrogen surface area ranging from about 100 to 1200 m.sup.2 /gram, the carbon-black particulate material comprising from about 10% to 30% by weight of the foam and in an amount sufficient to provide for a surface resistance of the foam of less than about 10,000 ohms per square inch, and a film-forming polymeric-binding material comprising a styrene-containing polymer and a polystyrene polymer, present in an amount of from 25% to 60% by weight of the impregnated foam, securing the conductive particulate material to the foam.
A process for preparing an electrically conductive foam adapted for use with electronic components sensitive to static charges, which process consists essentially of:
- (a) providing an aqueous dispersion which comprises
- (i) electrically conductive carbon black having a particle size of less than 40 millimicrons,
- (ii) a dispersing agent for the carbon black, and
- (iii) a styrene-butadiene copolymer and a polystyrene-polymer latex having over about 60% of styrene
- (b) immersing an open-cell, porous urethane foam into the aqueous dispersion to impregnate uniformly the foam with the carbon-black particles;
- and
- (c) drying the impregnated foam to remove water and to bind the carbon-black particles to the foam with the copolymer, to provide an impregnated foam having from about 25% to 60% by weight of the styrene-butadiene copolymer and about 10% to 30% by weight of carbon-black particles, the foam having a surface resistance of less than about 10,000 ohms per square inch.
A process for preparing electrically conductive foam adapted for use with electronic components sensitive to static charges, which process consists essentially of:
- (a) impregnating a substantially open-cell, porous foam with an aqueous dispersion consisting essentially of from about 2% to 40% by weight of electrically conductive particulate material in an amount sufficient to provide for the surface resistance of the dried foam of less than about 30,000 ohms per square inch, the particulate material having a particle size of less than 40 millimicrons, the dispersion containing from about 1% to 60% by weight of the impregnated foam of a film-forming polymeric-binding material to secure the conductive particulate material to the foam, and a dispersant agent for the dispersion of said particulate material in the aqueous dispersion;
- (b) removing excess water from the foam;
- and, thereafter,
- (c) heating the uniformly impregnated foam at a temperature sufficient to dry the foam and to bind the particulate material in the foam by the film-forming polymer, and to provide a surface resistance of the impregnated, bound, dried foam of less than about 30,000 ohms per square inch.
Dependencies are inferred from the claim text.