Electrical-insulating pressure-sensitive adhesive tape having a backing comprising a resin bonded, as opposed to a fiber bonded, web

Claim 1

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° C., remaining essentially unchanged after exposure to 130° 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° C. for months.

Claim 10

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° C., remain essentially unchanged under exposure to 130° 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° 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.

Claim 11

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° C., remain essentially unchanged under exposure to 130° 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° 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.