The present invention relates to a bulky asphalt-impregnated sheet having different properties on both surfaces thereof and a method and a system for manufacturing such bulky asphalt-impregnated sheet.
Recently, we have developed an asphalt roofing which comprises a base material of a bulky sheet of non-woven fabric made of filaments intertwisted with each other and an asphalt with which said base material is uniformly and completely saturated and which also covers both sides of said base material. This asphalt roofing can be produced by feeding said bulky sheet along a vertical path into a bath of molten asphalt, thereby permitting the air contained within the bulky sheet to successively escape vertically through the bulky sheet itself into the atmosphere while permitting the bulky sheet to be uniformly and completely saturated with said molten asphalt, and then withdrawing said sheet into the atmosphere and drying the same. The present invention utilizes an intermediate product of such asphalt roofing, namely, a bulky sheet which is impregnated with and covered, on its both sides, by asphalt which is still in a fluid or semi-solidified state, to produce a novel product, that is a bulky asphalt-impregnated sheet having materials of different properties and different functions on both sides thereof. This novel product can be produced by dipping a bulky sheet of non-woven fabric into a bath of molten asphalt to saturate said bulky sheet with the asphalt, withdrawing said sheet upward from said bath of molten asphalt, scraping off the asphalt on one surface, either front or rear surface, of said sheet while the sheet is being pulled upward and the asphalt is held in a fluidized or semi-solidified state, and then supplying and firmly adhering a material of different property onto said sheet.
The conventional asphalt roofing is produced by preparing a felt-like base material mixed with paper or asbesto fibers or a base material made of non-woven fabric of synthetic fibers, impregnating said base material with molten asphalt and then forming asphalt coating layers on both sides of said base material. In case of the felt-like base material made of paper or asbesto fibers, the base material has a thickness of about 1.4 mm, including base material having a thickness of about 0.6 mm and a surface asphalt layer having a thickness of about 0.4 mm. Therefore, the scraping off of the thin surface layer of the asphalt under fluidized or semi-solidified state will necessarily result in breaking or tearing of the base material made of the fragile fibers.
Also, in the case of a base material made of non-woven fabric, the base material has a thickness below 2 mm and the surface asphalt layer has a thickness to below 0.5 mm. The base material has a sufficiently high strength to allow the surface asphalt layer to be scraped off, but the exposed surface is hard and smooth so that the adhering ability is decreased. Furthermore, since the base material has a small thickness, it tends to soften and deform if the material of different property is supplied at high temperature. Accordingly, a roofing having materials of different properties on both side surfaces cannot be obtained, except a combined structure including two sheets adhered together.