Improved roofing membrane and method of making same

Abstract: A roofing membrane having a reinforcing fabric saturated with a bituminous material. The reinforcing fabric having a first fiberglass scrim layer to which is stitched a non-woven polyester mat.

Description: The invention relates to a new and improved substrate for bituminous roofing membranes which are readily manufactured, flexible, capable of being impregnated by bituminous material and having sufficient strength to be useful in reinforcing roofing membranes. Prior to this invention a single ply fiberglass scrim fabric laminated to a porous non-woven fiberglass mat (or a synthetic fibre and a mineral fibre as disclosed in EP-A-0 242 524 and EP-A-0 208 918) was used as a substrate for a bituminous roofing member but was found to be lacking in directionally uniform strength and integrity. To overcome this problem and provide a membrane which can be readily manufactured with a minimum of processing steps and handling, the herein-disclosed bituminous roofing membrane was developed. Therefore, it is an object of the invention to provide a two-ply substrate for bituminous roofing membrane which can be readily manufactured, is structurally strong and provides increased service life. Other objects and advantages of the invention will become readily apparent as the specification proceeds to describe the invention. In the manufacture of roofing membranes, a reinforcing sheet is saturated with bituminous material by leading the sheet through a tank or vat of bituminous material heated to about 135° to 220°F (275° to 425°F) using methods which are known in the art. This invention may also be utilized with cold mastics, i.e., materials which will not come into contact with hot coatings either in the coating process or during application to a roof. The resulting roofing membranes are rolled up for later installation, principally on flat roofs using additional bituminous material or a torch or other source of heat to seal the membrane and the joints. The bituminous material used in making these membranes is often a "modified bituminous" such as asphalt combined with about 20% by weight of static polypropylene or 5 to 15% styrene butadiene block copolymer rubber. This invention relates to a new form of composite sheet for use in reinforcing such membranes. The reinforcing sheet of the new roofing substrate consists of a first layer of a fiberglass scrim fabric to which is stitched or knitted a second layer of non-woven polyester staple fibers on a Malimo or weft insertion machine with stitch through capability. The first layer of this invention is an open network structure made of continuous filament fiberglass preferably a network which is neither woven together, nor knit together, nor held together by adhesive. It consists of a non-woven fiberglass scrim prepared for example as described in U.S. Patent No. 3,728,195 of about 3.4 to 34 grams per square metre (0.1 to 1 ounces per square yard). Most preferably the fiberglass network weighs about 17 grams per square metre (.5 ounces per square yard.) The fiberglass yarn is in the range of 1800 - 2400 denier. The non-woven layer of polyester staple fibers has a weight of approximately 17 grams per square metre (.5 ounces per square yard) with the fibers having a length of 3.81 to 7.62 centimetres (1½" to 3") and is wet laid to form the mat. The stitch or knit yarn secures the second layer to the scrim fabric on a Malimo or weft insertion machine with stitch through capability and provides 12 stitches per inch in the machine or warp direction of the reinforcing sheet. The stitch yarn, in the preferred form of the invention is, 150 denier, 64 filament textured polyester yarn knit in a tricot stitch of 1-0/1-2. The second layer of this invention is a mat or network which, by providing partial or full coverage in the openings or "windows" between the yarns of the first layer, enables the bituminous material to form a continuous sheet on the composite. The second layer is a mat which consists of polyester filaments. ("Mat" as used herein refers to an entangled mass of filaments, preferably structures which are wet laid or spun bond.) The mat is preformed, preferably wet laid, and lightweight relative to mats used in the prior art without reinforcement in bituminous roofing membranes. More specifically, "lightweight" means a mat weighing about 3.4 to 136 grams per square metre (0.1 to 4 ounces per square yard), most preferably about 17 g/m 2 (0.5 ounces per square yard). By "preformed" is meant a mat which has been fabricated into the mat form before it is combined with the scrim fabric. As described above, the reinforcing fabric after it has been run through the Malimo or weft insertion machine to stitch the non-woven mat to the scrim fabric, is either taken up on a roll and supplied or supplied in a continuous manner to a tank of bituminous material to form the roofing membrane as described above. Obviously the herein described roofing member is lightweight, flexible, easily manufactured at a minimal cost and can be easily handled after formation for application to a roof.

Claims: A method of manufacturing a roofing membrane having a fiberglass web and a second layer secured together with a bituminous coating, characterized in that said fiberglass web is a fiberglass scrim having openings between yarns forming the scrim, said second layer is non-woven polyester staple fibers having a network of a size to partially or fully cover the openings of the scrim, and the membrane is formed by securing the fiberglass web and the second layer by stitching or knitting the second layer to the fiberglass web with a yarn, and coating the secured fiberglass web and second layer with the bituminous material. The method according to Claims 1 wherein the securing step is performed with a tricot stitch. The method according to Claim 2 wherein the number of stitches is 4.8 per cm (12 per inch). The method according to any of the preceding claims wherein said fiberglass scrim is a non-woven fiberglass scrim material. The method according to Claim 2 wherein the tricot stitching is 1-0/1-2. The method according to any one of the previous claims wherein the yarn used to secure the fiberglass yarn to the second layer is a 150 denier, 64 filament textured yarn. The method according to any one of the previous claims wherein the yarn used to secure the second layer to the fiberglass web is polyester. The method according to any of the preceding claims wherein the step of coating is performed by saturating the secured fiberglass web and second layer with the bituminous material. The method according to any of the preceding claims wherein the bituminous material includes polypropylene. The method according to Claim 9 wherein the amount of polypropylene in the bituminous material is 20% by weight. The method according to any of Claims 1 to 10 wherein the bituminous material includes styrene butadiene block copolymer. The method according to Claim 11, wherein the amount of styrene butadiene block copolymer in the bituminous material is 5 to 15% by weight.

Inventors: CALLAWAY BRIAN, MORRIS DAVID MOORE III, CALLAWAY, BRIAN, MORRIS, DAVID MOORE III
Applicants: MILLIKEN & CO, MILLIKEN & COMPANY
Application year: 1995
Main classification: D06N5
IPC codes: B32B5, D06N5, B32B7, E04D5