Classifications

• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04D—ROOF COVERINGS; SKY-LIGHTS; GUTTERS; ROOF-WORKING TOOLS
  • E04D5/00—Roof covering by making use of flexible material, e.g. supplied in roll form
  • E04D5/12—Roof covering by making use of flexible material, e.g. supplied in roll form specially modified, e.g. perforated, with granulated surface, with attached pads

Definitions

• This invention relates to the sealing of overlapped rubbery olefinic polymer (i.e., homopolymer, copolymer, terpolymer, etc.) sheets to each other, to spliceable sheets, to a method of making such sheets, and to a transfer tape having particular utility in the manufacture of the heat-sealable sheets.
• overlapped rubbery olefinic polymer i.e., homopolymer, copolymer, terpolymer, etc.
• Rubbery olefinic polymer sheet material finds widespread industrial use in applications where it is necessary to contain or exclude liquids. Compared to vinyl sheet material, the rubbery olefinic polymer sheet materials have longer life, greater flexibility and resilience at low temperatures, ability to withstand high temperatures without stretching or softening unduly, and superior resistance to ultraviolet light.
• the most widely used rubbers for. formulating these sheets are polymers of ethylene, propylene, and diene monomers (commonly known as EPDM), butyl rubber, and blends of the two.
• EPDM polymers of ethylene, propylene, and diene monomers
• butyl rubber butyl rubber
• the olefinic polymers are commonly blended with desired fillers, coloring agents, extenders, vulcanizing or crosslinking agents, antioxidants, etc.
• membranes typically on the order of 1.5 millimeters thick and 2 to 6 meters wide. These membranes are then heated to perhaps 150°C. for 2 hours to effect vulcanization.
• spliced rubbery membranes are laid over new or existing roofs and typically either fastened down (e.g., at 40-centimeter intervals) with metal battens or ballasted with round river-washed stones.
• roof temperatures may approach the boiling point of water when exposed to the summer sun, and they may sink to -30°C. -- or even lower -- during the winter.
• the present invention provides an easy, simple, rapid, and effective technique for splicing rubbery membranes to form larger membranes.
• the resultant splices are strong, resistant to temperature extremes, and able to withstand the expansion and contraction that results from exposure to summer and winter conditions, all the while maintaining a water-tight seal.
• One aspect of the invention relates to spliceable sheet material having particular utility in the fabricatic.. of lapped-seam membrane roofing, comprising in combination a rubbery water-impermeable membrane consisting essentially of thermoset olefinic polymer having on one side, at least in a border area along one edge, a thin layer of firmly bonded heat-sealable adhesive of a type that wets the membrane.
• a presently preferred material for the rubbery olefin polymer membrane is EPDM
• a presently preferred adhesive is linear low density polyethylene having a softening point (as defined in ASTM Test D-16, Procedure 19) of at least 80°C., preferably 100°C., and most preferably at least 120°C.
• polyethylene may include the normally employed stabilizers, filers, extenders, processing aids, pigments, and the like.
• suitable adhesives can be formulated from thermoplastic blends of polyethylene and polypropylene, homopolymers of olefin monomers, polymers of two or more olefin monomers, etc., provided that-the softening point meets the stated temperature requirement.
• the melt index of the adhesive is desirably at least 0.5 dl/g, a melt index of about 1 being presently preferred.
• the softening point of the heat-sealable adhesive should not exceed 250°C., and preferably is significantly lower, to minimize the possibility of degrading the rubbery membrane.
• a presently preferred spliceable sheet material of the type described in the preceding paragraph is one in which linear low density polyethylene is adhered to the border area on one side of the rubbery sheet material adjacent a lateral edge and also on the border area on the other side adjacent the opposite lateral edge, this arrangement lending itself to a natural shingling type of overlapping.
• a simple but unique transfer tape having particular utility in making the spliceable border areas of the sheet material just described comprises a release liner having strippably adhered to one face a thin layer of heat-sealable adhesive.
• a preferred transfer tape construction comprises a polyester film release liner, e.g., biaxially oriented polyethylene terephthalate, carrying a heat-sealable thermoplastic polyolefin layer, e.g., linear low density polyethylene.
• Spliceable rubbery sheet material may then conveniently be fabricated by placing the adhesive surface of the transfer tape in contact with the appropriate area or areas of the rubbery membrane and applying sufficient heat and pressure to melt the adhesive and bond it to the membrane.
• a particularly preferred method is to place the transfer tape in contact with the unvulcanized sheet material, apply sufficient pressure to maintain intimate contact between the tape material and heat the assembly to a temperature high enough to vulcanize (i.e., crosslink, or thermoset) the olefin polymer and, at the same time, soften the adhesive, thereby permitting it to wet and upon cooling, bond firmly to the olefinic polymer sheet.
• the release liner may then remain in place to protect the adhesive from contamination and be removed at the time a splice is to be made.
• T-Peel Test In this test, two 2.54-cm wide x 15-cm long x 1.14-mm thick strips of commercially available EPDM-based membrane, each provided with a 38-micrometer layer of heat-activatable adhesive, are superposed in coextensive adhesive-to-adhesive contact and approximately 5 cm at one end laminated for one minute in a press at 160° C . and 20 k P a. Conventional T-peel tests are then performed in tensile testing equipment in which the jaws are separated at a rate of 30.5 cm/minute. For roofing applications, initial values should be at least 8.8 N/cm when tested at room temperature. After being subjected to any one of the conditions described below and then re-tested, T-peel values should be at least 17.5 N/cm.
• a linear, low density polyethylene (Union Carbide " G -Resin 7047 Natural 7"), having a melt index of 1.0, was extruded through a slot die having an opening of 0.56 mm at a die head temperature of 250°C.
• the extruded polyethylene film was contacted by a 38-micrometer polyester film; the resulting laminate was pulled between a rubber roll and metal roll, located approximately 75 mm from the die opening. The rolls were driven at a considerably faster surface speed than the rate at which the polyethylene was extruded, so that the polyethylene thickness was reduced to approximately 90 micrometers. Samples approximately 75 mm x 100 mm were then cut from the laminate and used for further testing.
• the polyethylene was tack-free at room temperature.
• a sample of the laminate was positioned with the polyethylene layer against a smooth sheet of 1.5-mm cured EPDM rubber, and placed for 30 seconds in a press heated to 218°C. under a pressure of approximately 35 kPa. The sample was then removed from the press and allowed to cool to room temperature, after which the polyester release liner was stripped away, exposing the heat-sealable polyethylene surface.
• the stripping force required was about 0.03 N/cm width. Values of at least about 0.02 N/cm are desirable for ease in processing, values somewhat in excess of 0.1 N/cm being satisfactory but not preferred. Significantly higher stripping values make the product more difficult for the end user to remove the release liner.
• a polyethylene-polypropylene blend (Eastman Chemical Company "Tenite” 5321E polyallomer) was extruded through a 0.38-mm 240°C. die head and processed as in
• one entire side of the rubber membrane may be coated with heat-sealable coating.
• rolls of the membrane may be slit to any desired width, e.g., to fit narrow portions of a roof, while still maintaining heat-sealable coating adjacent each edge.
• Another advantage achieved by overall coating with heat-sealable adhesive is the ability to seal directly to the upper surface of batten strips that have been nailed or otherwise affixed to the roof substrate, thereby permitting completely imperforate roofing membrane construction.
• batten strips made of polyethylene which are not only moisture- and rust-resistant but also inherently possess heat-sealable properties and are compatible with the thermoplastic olefinic heat-sealable coating on the roofing membrane. If, of course, the polyethylene batten strips are used only in the spliced areas, it is adequate to have heat-sealable adhesive only in the border area of the lower membrane, where it will contact the batten strip.

Landscapes

• Engineering & Computer Science (AREA)
• Architecture (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Laminated Bodies (AREA)
• Lining Or Joining Of Plastics Or The Like (AREA)

Applications Claiming Priority (4)

Publications (3)

Family

ID=27081497

Family Applications (1)

Country Status (2)

Cited By (1)

Families Citing this family (7)

Citations (7)

• 1985
  • 1985-03-01 EP EP85301438A patent/EP0156536B1/de not_active Expired - Lifetime
  • 1985-03-01 DE DE8585301438T patent/DE3578504D1/de not_active Expired - Fee Related

Patent Citations (7)

Also Published As

Similar Documents

Legal Events