Patent Publication Number: US-2006009100-A1

Title: Waterproofing membrane

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to composite waterproofing sheets which include multiple layers with one or more layers of bentonite.  
      Bentonite (sodium monmorillonite) particles swell and gel in the present of water and are used in waterproofing sheets. Current bentonite containing waterproofing sheets are relatively heavy. In order to secure a waterproofing sheet to a vertical wall, it must be installed using concrete nails. The heavy weight of such sheets also requires significant manpower for installation. One reason for the heavy weight of such sheets is the large amount of granular bentonite material needed in order to attain sufficient internal pressure to effect a water seal. A typical roll of 96 square feet of bentonite sheeting averages 96 pounds. Such rolls are difficult to move around in construction job sites. Furthermore, shipping costs due to weight per square foot for such materials are also a consideration.  
      There are a number of patents which describe the use of bentonite in sheet material intended for waterproofing. These patents include the following: White U.S. Pat. Nos. 5,389,166, 5,237,945, 5,174,231, 5,346,565 and 5,346,566; Alexander U.S. Pat. Nos. 5,063,100, 5,053,265, 5,180,255, 5,187,915 and 5,112,665; Heerten U.S. Pat. Nos. Re 37,295 and 5,221,568; Starita et al. U.S. Pat. No. 5,725,942; Byrd U.S. Pat. No. 5,580,630; Kangas U.S. Pat. No. 5,473,848; Clem U.S. Pat. Nos. 4,467,015 and 4,501,788; Blaze U.S. Pat. No. 4,344,722; Crawford U.S. Pat. No. 4,565,468; Harriett U.S. Pat. Nos. 4,656,062 and 4,787,780; Shbakhman et al. U.S. Pat. No. 4,581,868; Randall U.S. Pat. No. 4,879,173; Klatt et al. U.S. Pat. No. 6,342,088; Weaver U.S. Pat. No. 3,943,032; McGroarty et al., U.S. Pat. Nos. 4,693,923, 5,079,088 and 5,091,234; McGroarty U.S. Pat. No. 4,837,085; and McGroarty U.S. Pat. No. 5,376,429.  
     SUMMARY OF THE INVENTION  
      The present invention includes a waterproofing sheet comprising a scrim and two layers of bentonite particles with one layer being attached to the scrim and a water permeable layer disposed between the first and second layers of bentonite. In another aspect of the present invention, the layers of bentonite particles are compacted under a force of at least 25 pounds per square inch, and preferably 100 pounds per square inch. In another aspect of the present invention, the bentonite particles are held together with an adhesive and compacted such that the waterproofing sheet can be bent at least about 360° on a 0.5 inch radius. In a further aspect of the present invention, the waterproofing sheet is attached to a thermal insulating board providing waterproofing between itself and any adjacent board or between the board and whatever it is attached to. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a waterproofing membrane of the present invention.  
       FIG. 2  is perspective view of the waterproofing membrane attached to an insulating board.  
       FIG. 3  is a sectional view of a plurality of insulating boards and membranes secured to a wall.  
       FIG. 4  is a sectional view illustrating a method of joining two insulating boards of the present invention and securing them to a substrate.  
       FIG. 5  is a sectional view of a joint of  FIG. 4  completed.  
       FIG. 6  is a sectional view illustrating an alternative embodiment of a joint of the present invention.  
       FIG. 7  is a perspective view of a method of attaching the waterproofing membrane to a corner of an insulating board.  
       FIG. 8  is a perspective view illustrating a plurality of insulating boards providing the waterproofing membrane in the joint between the insulating boards and in an overlapping relationship. 
    
    
     DETAILED DESCRIPTION  
      The present invention includes a four layer waterproofing membrane generally indicated at  10  in  FIG. 1 . Like reference characters will be used to indicate like elements throughout the drawings. The four layer waterproofing membrane  10  is approximately one half the weight of previous bentonite waterproofing membranes. In addition the membrane  10  of the present invention is flexible. The reduced weight of the waterproofing  10  membrane permits installation of the membrane without the use of dangerous nail guns or concrete nails since the membrane can be installed on vertical walls using adhesives instead of nails.  
      The four layers of the membrane include a porous woven layer  12 , two flexible compressed bentonite layers  14  and  16 , and a water permeable thin flexible membrane  18  disposed between the two bentonite layers  14  and  16 . The membrane  18  may also be water impermeable membrane. Although each of the layers are distinct, the layers are integrated with each other to form an indivisible membrane  10 .  
      The two bentonite layers  14  and  16  are almost solid, but yet flexible layers of bentonite formed by the compression of bentonite particles. Because of the bentonite compression, a relatively small amount of bentonite is needed to effect a water seal. Prior bentonite products are made of loosely adhered particles which required deep penetration of the intruding water before producing a water seal. Membrane  10  includes closely packed bentonite particles which do not require either deep penetration by water or large amounts of water to effect a water seal.  
      The primary reason for the reduction in the amount of bentonite in the present invention is that the bentonite particles are compressed (closely packed) in a manner heretofore not known before. The closely packed nature of the bentonite particles reduces the water permeability of the bentonite layer. The bentonite particles are compacted from an original size approximately no larger than 30 mesh and smaller than 50 mesh and reduced to a size ranging between 50 mesh and 100 mesh. Described in alternate fashion, the bentonite particles once compacted, occupy ½ to ⅔ of their original space. Such compaction requires less water to expand the bentonite sufficiently to form a water seal. Also less bentonite is needed to form the water seal since the bentonite does not have to expand as much to fill the voids between the bentonite particles.  
      The initial layer  14  of bentonite is placed on the porous woven layer  12 . The porous woven layer  12  is a flexible woven fabric made of natural or synthetic material that is readily permeable by water and dimensionally stable in at least two directions. The porous woven layer acts as a reinforcing layer for the initial layer  14  of bentonite. The layer  12  is porous enough to allow bentonite to be embedded into the fabric but tight enough to retain the bentonite particles. In one example, the fabric comprises at least 90% of the total surface area of the layer with the remainder being holes for bentonite embedment.  
      The layer  12  also serves as the adhering layer for the membrane  10 . The membrane  10  is secured with adhesive to a surface to be protected. The porous woven fabric should be strong enough to support the weight of the bentonite when the membrane of the present invention is secured vertically or to an overhead application. One example of a suitable fabric is a scrim or cheesecloth fabric with openings of 30 to 80 mesh with 40 mesh openings (United States standard mesh) as one preferred example. By scrim is meant any fabric having openings for bentonite particles to be embedded.  
      An ultra thin elastomeric film  18  is positioned between the two bentonite layers  14  and  16 . The film  18  may be woven, braided or perforated to allow water to penetrate, thereby providing water access to both bentonite layers  14  and  16  and must be efficiently flexible or elastic to permit the membrane to be folded upon itself, in other words to be able to be bent virtually 360° about approximately a 0.5 inch radius. In another aspect of the present invention film  18  may be impermeable.  
      The bentonite that is preferred is sodium montmorillonite. The bentonite should have a low free silica content and preferably contain no material having a particle size larger than 20 mesh or smaller than 50 mesh. The moisture of the bentonite should not exceed 5% by weight and have less than 1% fines (particles smaller than 200 mesh).  
      A fifth layer  20  may be applied to the second layer  16  of bentonite. The composition of the fifth layer  20  depends on the final use of the membrane  10 . The fifth layer  20  may be a protective water impermeable layer made of a solid plastic film such as polyethylene, polypropylene, polyvinyledene, EPDM, polyvinylchloride chloride butyl, flakes of polyethylene/propylene made from recycled material or glass, cellulosic or permeable polymer fiber adhered to the bentonite layer  16 . The fifth layer when permeable is preferable when pre-adhering to sheets of insulation. This permeable layer would provide a good base for the subsequent adhesion to a wall. Such fifth layers are useful in an environment that includes long exposure to the elements or a damaging environment. The fifth layer may also be a water-repellent spray to prevent hydration when temporarily exposed to the elements.  
      In the fifth layer configuration, and when both outer layers include a scrim, the membrane  10  of the present invention the scrim provides a better bonding surface to the insulating board and the other side of the membrane then provides a better bonding surface to the surface to which the insulating board and the membrane is to be attached.  
      The membrane  10  is made by initially wetting the porous woven layer  12  with water. A layer  14  of bentonite particles is then applied to the porous woven layer  12 . The bentonite particles positioned next to the porous layer  12  adhere to the layer  12  due to the wetness of the layer and the water absorbing properties of the bentonite. As the bentonite particles are deposited on the porous woven layer, the particles are sprayed with an adhesive in an amount sufficient to form fine adhesive filaments. Approximately 10 to 30% adhesive by weight in relation to the bentonite has been found to be a suitable amount of adhesive.  
      When the bentonite layer is compacted the adhesive binds the particles in a fibrous adhesive matrix to form an amalgamate in structure. The fibrous adhesive matrix provides flexibility to the bentonite layer such that the membrane is malleable and may be flexed for storing in roll form or the membrane conforms to non flat surfaces or has the ability to be folded upon itself or bent at least approximately 360° about an approximate 0.5 inch radius and preferably approximately 90° to conform to corners. Suitable adhesives need to be flexible and preferably elastomeric when cured or dried. The adhesives should also not affect the water absorbing properties of the bentonite to any great degree. A nonexhaustive list of suitable adhesives includes styrene butadiene, urea/formaldehyde, acrylics, nitriles, asphalts, butyl and natural rubbers or mixtures thereof. Suitable solvents for delivering the adhesives include aliphatic compounds, ketones, aldehydes, carbon/halides, toluene and other ring compounds and alcohols. Suitable water-soluble adhesives include saccharides, gums, tars, proteins and cellulosics.  
      The water permeable film  18  ( FIG. 1 ) is then positioned over the bentonite layer  14 . The adhesive used to hold the bentonite layer  14  secures the water permeable film  18  in place. The bentonite layer  14  is now compressed through a set of nip rollers.  
      A second layer  16  of bentonite particles is then placed on the water permeable film  18  and sprayed with adhesive in a manner similar to the formation of layer  14 . The bentonite layer  16  is then compacted between a set of nip rollers.  
      The force used to compress is between about 1 pounds per square inch and 200 pounds per square inch and preferably between about 20 pounds per square inch and 100 pounds per square inch with the higher compressions providing the best results. When compacted the bentonite particles are actually crushed to a fine powder. The adhesive filaments hold the particles together making a dense particulate layer that has flexibility.  
      The membrane  10  of the present invention may also be used with a solid insulation board  22  to form a waterproofing/insulating composite as illustrated in  FIG. 2 . The solid board  22  of insulation must be waterproof such as extruded or sealed polystyrene or polyurethane. The insulating board must be impermeable to water and waterproof. By waterproof is meant impervious to or unaffected by water. The membrane  10  is secured using a suitable adhesive to the insulation board  22 . In this situation the fifth layer  20  may be a loose mesh cheesecloth of approximately 60 mesh or an impermeable sheet adhered to the bentonite layer  16  or the expanded polystyrene insulation may be secured directly to the bentonite layer  16  with no fifth layer  20  in between.  
      Conventional dimensions for extruded polystyrene insulating board are 8 feet by 4 feet by ½ to 2 inches thick. Polystyrene board is also made in other thickness less than ½ inch and greater than 2 inches. For purposes of an example, the membrane of the present invention is adhesively secured 8 feet by 4 feet by 2 inch thick to the extruded polystyrene board  22  in a 8 feet 4 inch by 4 feet 4 inch sheet so that in both the length and width directions, the membrane is not only secured to one major side surface of the polystyrene board but is also sufficiently large to cover the 2 inch thick side edges of the polystyrene board when folded upward during installation next to another board. Other thickness widths and lengths of extruded board are similarly accommodated by the thickness A of the board being substantially equal to the width B of the portions of the membrane that extend beyond the board. When the composite waterproofing/insulating board is secured to a wall  26 , as illustrated in  FIG. 3 , the waterproofing/insulating board both insulates and provides waterproofing in one application.  
      The membrane  10   a  and  10   b  may also be pre-attached to both the major surface and the sides  23   a  and  23   b  of the insulating boards  22   a  and  22   b  as illustrated in  FIG. 6 . Therefore when the insulating boards  22   a  and  22   b  are side by side, there will be two layers  11   a  and  11   b  of membranes  10   a  and  10   b  between adjacent insulating board sides  23   a  and  23   b.    
      A plurality of composite insulating/waterproofing boards  21  are secured to the wall  26  as best illustrated in  FIG. 3 . Since the membrane  10  is secured to the side of the insulating board  22 , the joint between insulating boards  22  includes at least one section of the membrane  10  overlying a side surface  23  of the insulating board  22  as best illustrated in  FIGS. 4 and 5 .  
      As illustrated in  FIG. 4  and  5 , in abutting insulating boards  22   c  and  22   d , side section  11   d  of membrane  10   d  lies between the two side surfaces  23   c  and  23   d  of the insulating boards  22   c  and  22   d . Section  11   c  of the membrane  10   c  is positioned to lie flat along the wall  26  to be protected overlapping the membrane  10   d  that is attached to the insulating board  22   d . The side section  11   d  provides a swelling waterproofing layer between each insulating board thereby preventing water from seeping between the two boards. Furthermore, the overlapping section  11 C of the membrane  10 C provides a further seal between the boards  22 C and  22 D.  
      A method for covering side surfaces  23 e and  23 f proximate a corner  25  of the insulating board  22  is illustrated in  FIG. 7 . The membrane  10  is cut along broken lines  30  which lies along the plane of the side surface  23   f  and broken line  32  which lies along the plane of side surface  23   e . The portion  11   g  of the membrane  10  after cuts are made along the broken lines is removed. Section  11   e  of the membrane  10  is then moved as indicated by arrow  34  abut against the side surface  23   e  of the board  22 . Similarly, section  11   f  of the membrane  10  is moved as indicated by arrow  36  to abut against the side surface  23   f  of the board  22 . The sections  11   e  and  11   f  may be adhesively secured to the respective side surfaces  23   e  and  23   f  of the insulating board  22 .  
      A method is illustrated in  FIG. 8  for insulating a wall structure  26 . A plurality of insulating boards  22   g ,  22   h  and  22   i  having membranes  10   g ,  10   h  and  10   i  adhesively secured thereto and are positioned in an abutting relationship. The membranes  10   g ,  10   h  and  10   i  extend beyond side surfaces of each of the boards. Specifically illustrated are sections  11   g ,  11   h  and  11   i  which extend beyond the side surfaces  23   g ,  23   h  and  23   i , respectively of the boards  22   g ,  22   h  and  22   i  whose side surfaces  23   g ,  23   h  and  23   i  are positioned along the same plane. Positioned between the insulating boards  22   g  and  22   h  is membrane section  11   g ′ which is positioned between side surfaces  23   g  and  23   h ′ of board  22   h . Section  11   g  of the membrane  10   g  extends beyond side surface  23   g  and has a portion  11   g ′ which lies flat along a portion of side surface  23   h  in an overlapping relationship with portion  10   h ′ of section  10   h  by being cut along line  40 . It will be understood that the portion  10   h ′ of section  10   h  is disposed underneath portion  11   g ′ of section  11   g  and such overlapping relationship between membranes  10   g  and  10   h  continues on beneath the entire length of the boards  22   h  and  22   g.    
      Similarly, section  11   h ′ of the membrane  10   h  is positioned between side surface  23   h ″ and side surface  22   i ′ of boards  22   h  and  22   i , respectively. The membrane  10   h  is cut along the line  41  so that portion  11   h ″ lies in an overlapping relationship with portion  11   i ′ of membrane  10   i . Similarly, the portion  11   i  of membrane  10   i  that extends beyond the side surface  22   i ′ of the insulating board  22   i  lies in an overlapping relationship along the entire length of the membrane  10   h . As indicated by arrows  42  the sections  11   g ,  11   h  and  11   i  along with their overlapping portions are moved to be adjacent the side surfaces  23   g ,  23   h  and  23   i , respectively and are adhered thereto by suitable adhesive.  
      The corner  41  of the board  22   g  is attached to the membrane  10   g  in the same manner as described in  FIG. 6 . Sections  11   g  and  11   g ′″ are cut to produce corner portion  11   g ″ which is discarded. Section  11   g ′″ is moved in the direction of arrow  44  to position portion  11   g ′″ adjacent to the side surface  23   g ″ to which it can be adhesively secured.  
      The method described above provides a complete water seal with insulating capabilities to a wall or overhead structure. A section of waterproofing membrane is disposed between each insulating board and the membranes overlap each other along the entire length of the membranes. The method permits subsequent placement of insulating board along with membrane in any direction resulting in the membrane overlapping the insulating boards and a section of the membrane being positioned between the boards. Thus a waterproofing seal is affected along the perimeter of each insulting board and also between the board and the wall to be protected. The membrane provides a waterproof seal on both surfaces of the membrane. Each insulating board (and the surface to be protected) is therefore protected from water intrusion along its sides and between insulating boards.  
      The present invention has water protected insulation that truly insulates since the insulation is waterproofed by the bentonite membrane under and around each insulating board. If water were to pass under or around the insulating board, it would negate the insulating effect of the board.  
      Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.