Electrical-insulating pressure-sensitive adhesive tape having a backing comprising a resin bonded, as opposed to a fiber bonded, web
AssigneeMinnesota Mining and Manufacturing Company
InventorGaylord L. Groff
Life of this patent
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Abstract
Electrical-insulating pressure-sensitive adhesive tape, the backing of which is a web of oriented polymeric fibers impregnated with a crosslinked polymeric resin to provide a voids-volume of less than 60%.
Claims13
Electrical-insulating pressure-sensitive adhesive tape comprising a flexible backing member and a pressure-sensitive adhesive layer, said flexible backing member comprising a resin-bonded, as opposed to fiber-bonded, web which consists essentially of (a) at least one layer of nonwoven, randomly-intermingled, electrical-insulating oriented polymeric fibers and (b) a binder consisting essentially of a crosslinked polymeric resin, which fibers form a continuous, substantially uniform network extending to both surfaces of the resin-bonded web, the resin-bonded web having a ratio of the fibers to the resin from 1:2 to 6:1, a voids-volume of less than 60%, a thickness of 25-200 micrometers, and a tear strength of at least 2 kN/m at a thickness of 75 micrometers, said fibers
- having a denier of 1 to 8,
- having a softening point of at least 200.degree. C.,
- remaining essentially unchanged after exposure to 130.degree. C. for months, and
- having a tenacity of at least one gram per denier;
- said crosslinked polymeric resin binder would by itself provide a self-sustaining film which
- has a tensile strength of at least 100 psi (0.7 MPa),
- is capable of being folded repeatedly upon itself without cracking,
- has a dielectric strength of at least 25 volts per micrometer, and
- remains essentially unchanged after exposure to 130.degree. C. for months.
The method of making an electrical-insulating pressure-sensitive adhesive tape comprising the steps of
- (1) forming a fluffy web of non-woven, randomly-intermingled, electrical-insulating, oriented polymeric fibers which
- have a denier of 1-8,
- have a softening point of at least 200.degree. C.,
- remain essentially unchanged under exposure to 130.degree. C. for months, and
- have a tenacity of at least one gram per denier;
- (2) simultaneously squeezing and saturating the fluffy web with a dispersion of a crosslinkable polymeric resin in a volatile vehicle, which resin by itself is capable of forming a self-sustaining film which
- has a tensile strength of at least 100 psi (0.7 MPa),
- is capable of being folded repeatedly upon itself without cracking,
- has a dielectric strength of at least 25 volts per micrometer, and
- remains essentially unchanged after exposure to 130.degree. C. for months;
- (3) then heating to drive off the vehicle to provide a dried handleable web having a ratio of the fibers to the resin from 1:2 to 6:1;
- (4) densifying the dried web under heat and pressure to a voids-volume of less than 60% and a thickness of 25-200 micrometers, the heat being sufficient to crosslink the polymeric resin binder to provide a resin-bonded, as opposed to fiber-bonded, web;
- and
- (5) applying a layer of pressure-sensitive adhesive to the resin-bonded web to provide an electrical-insulating pressure-sensitive adhesive tape.
Electrical-insulating pressure-sensitive adhesive tape comprising a flexible backing member and a pressure-sensitive adhesive layer, said flexible backing member comprising a resin-bonded, as opposed to fiber-bonded, web which comprises (a) at least one layer of nonwoven, randomly-intermingled, electrical-insulating, oriented polymeric fibers and (b) a polymeric resin binder, which fibers form a continuous, substantially uniform network extending to both surfaces of the resin-bonded web and
- have a denier of 1 to 8,
- have a softening point of at least 200.degree. C.,
- remain essentially unchanged after exposure to 130.degree. C. for months, and
- have a tenacity of at least one gram per denier;
- characterized in that
- said polymeric resin binder is a crosslinked polymeric resin which would by itself provide a self-sustaining film which
- has a tensile strength of at least 0.7 MPa,
- is capable of being folded repeatedly upon itself without cracking,
- has a dielectric strength of at least 25 volts per micrometer, and
- remains essentially unchanged after exposure to 130.degree. C. for months, and
- said resin-bonded web having
- a ratio of fibers to resin from 1:2 to 6:1,
- a thickness of 25 to 200 micrometers, and
- a tear strength of at least 2 kN/m at a thickness of 75 micrometers.
Dependencies are inferred from the claim text.