High density para-aramid papers
AssigneeE. I. Du Pont de Nemours and Company
InventorEdward W. Tokarsky
Life of this patent
Estimating the term…
Abstract
High density para-aramid papers comprising 5 to 25 percent, by weight, binder and an amount of para-aramid fibers selected from the group consisting of para-aramid pulp, para-aramid floc and mixtures thereof, compacted to provide a volume percent para-aramid fiber of at least 53 minus 0.13 times the volume percent floc in the paper are useful in the preparation of circuit board substrates having a low coefficient of thermal expansion.
Claims10
Process for preparing high density para-aramid paper for use in electrical circuit board laminates having low coefficient of thermal expansion comprising the steps of (1) preparing a 0.01 to 3 percent, by weight, aqueous slurry of para-aramid fibers made up of 0-50 volume percent para-aramid pulp and 50-100 volume percent para-aramid floc having lengths of 0.8 to 12.7 mm, (2) forming a sheet from the slurry using known papermaking methods, (3) drying the thusly formed sheet and (4) calendering the sheet in one or more steps between rigid rolls heated to 125.degree. to 400.degree. C. at a pressure of 1500 to 5000 lbs/inch (268 to 894 kg/cm) nip pressure.
Dependencies are inferred from the claim text.