Abstract:
A bituminous water vapor retarder is disclosed of the type which can be used under concrete slabs in contact with soil or granular fill. The vapor barrier is a multi-ply weather coated permanently bonded semi-flexible bituminous core board composed of the homogeneous high melt point bituminous material in combination with an exclusive core suspended midpoint in the board. This core is sealed under heat and pressure between liners of asphalt and impregnated felt and a glass mat liner. An asphalt weather coat is applied to the glass mat liner and covered with a polyethylene anti-stick sheet.

Description:
[0001]     This disclosure relates to a vapor barrier and more specifically to a bituminous water vapor retarder of the type which can be used under concrete slabs in contact with soil or granular fill.  
       BACKGROUND  
       [0002]     ASTM Specification E1993-98 is the standard specification for bituminous water vapor retarders used in contact with soil or granular fill under concrete slabs. That specification deals with a bituminous membrane water vapor retarder consisting of asphaltic materials reinforced with multiple plies of a suitable fabric. The property requirements of ASTM E1993-98 are with respect to water vapor permeance under certain conditions, tensile strength, and puncture resistance. A considerable amount of work has been undertaken in order to develop a membrane which will meet the requirements of ASTM E1993-98. This work has resulted in the development of the present disclosure which meets or exceeds that specification.  
       SUMMARY OF THE DISCLOSURE  
       [0003]     In accordance with the disclosure, the bituminous water vapor retarder membrane has a multi-layer core comprising an aluminum sheet, laminated between a pair of thermoplastic sheets. The thermoplastic sheets are preferably polyester and the aluminum sheet is laminated to the polyester sheets with a low density polyethylene adhesive.  
         [0004]     This laminated aluminum foil-polyester core is in turn laminated between a pair of fabrics at least one of which is impregnated with asphalt. It is preferred that one of the fabrics be an asphalt saturated felt and that the other fabric be a non woven fiberglass scrim which provides improved strength to the membrane. The asphalt saturated felt fabric layer is adhesively secured to the core by an asphalt coating and it has been found that superior results in the adhesion of the asphalt coating to the core are achieved if the core itself has an acrylic coating.  
         [0005]     In like manner, the fiberglass scrim is adhesively secured to the core by means of an asphalt coating, with the surface of the polyester sheets adjacent the asphalt coating being covered with an adhesion promoter, preferably in the form of an acrylic coating. It is preferred that the acrylic coating on the outer surfaces of the polyester core sheets be selected from the group consisting of a methacrylic acid ester, or glycidyl acrylate, or methalacrylate or a copolymer of acrylonitrile and styrene. Although an acrylic coating is the preferred adhesion promoter, as an alternative adhesion could be promoted by treating the outside surface of each polyester film by a well-known plasma or corona surface treatment in order to facilitate adhesion of the asphalt coating to the core. A number of other well known adhesion promoters may also be used.  
         [0006]     The polyester sheet is preferably a polyethylene terapthalate (PET).  
         [0007]     Thus, the migration of water vapor from an underlying support surface such as the ground or gravel to an overlying porous slab such as a concrete slab, can be substantially inhibited by a method which comprises placing a multi-layer bituminous membrane on the supporting surface, the bituminous membrane comprising an aluminum sheet laminated between a pair of polyester sheets to form a multi-layer core with the core being laminated to at least one fabric sheet impregnated with asphalt, and placing the concrete slab on top of the bituminous membrane. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is an enlarged cross sectional view of a vapor barrier constructed in accordance with the disclosure showing core sandwiched between a pair of fabric sheets; and  
         [0009]      FIG. 2  is a further enlarged cross sectional view of the multi-layer core of the vapor barrier of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION  
       [0010]     The vapor retarder of this disclosure is a semi-flexible bituminous core board  10 .  FIG. 1  is an enlarged cross section of this board. The board  10  consists of a unique core  12  which has an asphalt coating  14  and  15  on either side. The asphalt coating  14  on one side bonds the core  12  to an asphalt saturated felt fabric sheet  16 . On the other side the asphalt coating  15  bonds the core  12  to a fiberglass fabric or scrim  18 . On the top of the fiberglass scrim it is preferred that there be a 1-mil polyethylene sheet  20  primarily for purposes of preventing the boards from sticking to one another when they are stacked one on top of the other.  
         [0011]     In  FIG. 2  there is shown an enlarged cross sectional view of the core  12  of the vapor barrier board  10 . In the center of this core is an aluminum foil sheet  22  which preferably has a minimum thickness of 0.00028 inches. This aluminum sheet  22  is laminated between a pair of polyester sheets  24  and  25  which have been chemically or physically surface treated, and to the outside of each polyester sheet  24  and  25  is bonded acrylic coatings  26  and  27  respectively. The acrylic coatings  26  and  27  are in turn in contact with and bonded to the asphalt coatings  14  and  15  respectively which in turn bond the core to the asphalt saturated felt fabric sheet  16  on one side and the fiberglass scrim  18  on the other. The acrylic coating on the polyester sheets  24  and  25  helps to create a strong bond between the polyester sheets  24  and  25  and the asphalt coatings  14  and  15 . The strong bond between either polyester sheet  24  or  25  and asphalt coating  14  or  15  resists delamination due to the cold temperature and a sudden impact during transportation.  
         [0012]     While the aluminum foil sheet  22  may be between 0.0001 to 0.0025 inches, it is preferred that the thickness be on the order of 0.00028 minimum. An aluminum foil sheet by itself in an underlayment would exhibit the desired perm ratings and other properties, but under certain conditions, it might exhibit corrosion and delamination. It has been found that such corrosion is reduced or eliminated by laminating the aluminum foil sheet between the polyester sheets in the manner herein described. The best adhesion between the aluminum foil sheet  22  and the two polyester sheets  24  and  25  is achieved by means of a coating of a low density polyethylene adhesive  28  and  30 .  
         [0013]     It is preferred that the polyester sheets  24  and  25  be a polyethylene terapthalate (PET). Applied to the outer surfaces of the polyester core sheets are acrylic coatings  26  and  27 . These acrylic coatings  26  and  27  act as chemical adhesion promoters for promoting adhesion between the outer surfaces of the polyester core sheets  24  and  25  and asphalt layers  14  and  15  which secure the core to the overlying fabric sheets  16  and  18  and are preferred to other well known adhesion promoters. The acrylic coatings are preferably selected from the group consisting of a cross linked copolymer of methacrylic acid ester and glycidyl acrylate, or methacrylate, or a copolymer of acrylonitrile and styrene. Adhesion may also be promoted by means of a physical surface treatment of the polyester film. This can, for example, be satisfactorily done by means of a corona treatment in which a high frequency voltage is applied to the surface of the sheet, which results in a change in the chemistry of the surface of the polyester, enhancing the bonding to the asphalt coating. In the plasma surface treatment, reactive gas molecules are defused toward the surface of the polyester under the influence of electric and/or magnetic fields, and again the chemistry of the substrate surface is changed to impart the desired functionality.  
         [0014]     The felt sheet  16  may be of organic or inorganic material and different gauges of felt may be used depending upon the desired thickness, strength and flexability of the final product. The felt is impregnated with asphalt. The asphalt could be soft, hard or a mixture of the two. The vapor barrier also includes a glass fiber scrim  18  and different gauges of glass fiber scrim may be used. The layers of asphalt  14  and  15  in the vapor barrier bind the core  12  to the fiberglass scrim  18  on one side and to the asphalt saturated felt  16  on the other. The asphalt in these layers  14  and  15  is preferably type III asphalt which is a petroleum based homogeneous high melt point bituminous material meeting ASTM D 132 specifications. The felt in the preferred embodiment is a virgin wood paper and recycled corrugated paper. The glass fiber scrim  18  is preferably a white glass non-woven sheet of fiberglass fibers which are bonded together by formaldehyde binder. It is uniformly smooth and free from delamination, wrinkles, voids and the like.  
         [0015]     The coating asphalt in molten form is added to the saturated felt using a conventional manufacturing process. The coating is spread to achieve the desired uniform thickness. Next, the core  12  is laminated under heat and pressure between a layer of asphalt and the saturated felt  16  on one side and a layer of asphalt and the saturated glass fiber scrim  18 . Then a 1-ml polyethylene sheet  20  is applied to the surface of the glass fiber scrim. The vapor barrier is then cooled, cut and trimmed to proper length and width. The polyethylene sheet  20  serves as an anti-stick sheet to prevent the boards from sticking to one another when they are stacked one on top of the other.  
         [0016]     The vapor barrier constructed in accordance with the foregoing offers a virtually impermeable vapor proofing system with a perm rating of less than 0.002 perms, and it is used primarily for horizontal applications providing excellent tensile strength and puncture resistance. It helps to prevent warping, buckling or delamination of subsequent floor systems reducing fungus, mildew and mold as well as helping to prevent radon gas from entering the structure. The vapor retarder can be used under concrete slabs in contact with soil or granular fill and it helps to maintain the maximum slab moisture transfer rate to no more than 3 pounds per 1,000 square feet per twenty four hours, the amount allowed by the flooring industry&#39;s specifications.  
         [0017]     Although the disclosed vapor barrier has been described with particularity, it will be readily apparent to those skilled in the art that many modifications can be made without departing from the spirit and broad scope of the disclosure.