Patent Publication Number: US-2019177968-A1

Title: Acoustical sound proofing material with improved fracture characteristics and methods for manufacturing same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/171,315, filed Oct. 25, 2018, which is a continuation of U.S. patent application Ser. No. 13/783,165, filed Mar. 1, 2013, which is a continuation of U.S. patent application Ser. No. 11/697,691, filed Apr. 6, 2007. U.S. patent application Ser. No. 16/171,315 is also a continuation of Ser. No. 13/783,179, filed Mar. 1, 2013, which is a divisional of Ser. No. 11/697,691, filed Apr. 6, 2007. 
    
    
     BACKGROUND 
     Noise control constitutes a rapidly growing economic and public policy concern for the construction industry. Areas with high acoustical isolation (commonly referred to as ‘soundproofed’) are requested and required for a variety of purposes. Apartments, condominiums, hotels, schools and hospitals all require walls, ceilings and floors that are specifically designed to reduce the transmission of sound in order to minimize or eliminate the disruption to people in adjacent rooms. Soundproofing is particularly important in buildings adjacent to public transportation including highways, airports and railroad lines. Additionally, theaters and home theaters, music practice rooms, recording studios and others require increased noise abatement for acceptable listening levels. Likewise, hospitals and general healthcare facilities have begun to recognize acoustical comfort as an important part of a patient&#39;s recovery time. One measure of the severity of multi-party residential and commercial noise control issues is the widespread emergence of model building codes and design guidelines that specify minimum Sound Transmission Class (STC) ratings for specific wall structures within a building. Another measure is the broad emergence of litigation between homeowners and builders over the issue of unacceptable noise levels. To the detriment of the U.S. economy, both problems have resulted in major builders refusing to build homes, condos and apartments in certain municipalities; and in cancellation of liability insurance for builders. 
     Various construction techniques and products have emerged to address the problem of noise control, such as: replacement of wooden framing studs with light gauge steel studs; alternative framing techniques such as staggered-stud and double-stud construction; additional gypsum drywall layers; the addition of resilient channels to offset and isolate drywall panels from framing studs; the addition of mass-loaded vinyl barriers; cellulose-based sound board; and the use of cellulose and fiberglass batt insulation in walls not requiring thermal control. All of these changes help reduce the noise transmission but not to such an extent that certain disturbing noises (e.g., those with significant low frequency content or high sound pressure levels) in a given room are prevented from being transmitted to a room designed for privacy or comfort. The noise may come from rooms above or below the occupied space, or from an outdoor noise source. In fact, several of the above named methods only offer a three to six decibel improvement In acoustical performance over that of standard construction techniques with no regard to acoustical isolation. Such a small improvement represents a just noticeable difference, not a soundproofing solution. A second concern with the above named techniques is that each involves the burden of either additional (sometimes costly) construction materials or extra labor expense due to complicated designs and additional assembly steps. 
     More recently, an alternative building noise control product has been introduced to the market in the form of a laminated, damped drywall panel as disclosed In U.S. Pat. No. 7,181,891. That panel replaces a traditional drywall layer and eliminates the need for additional materials such as resilient channels, mass loaded vinyl barriers, additional stud framing, and additional layers of drywall. The resulting system offers excellent acoustical performance improvements of up to 15 decibels in some cases. However, the panel cannot be cut by scribing and breaking. Rather than using a box cutter or utility knife to score the panel for fracture by hand, the panels must be scored multiple times and broken with great force over the edge of a table or workbench. Often times, the quality of the resulting break (in terms of accuracy of placement and overall straightness) is poor. The reason for the additional force required to fracture the laminated panel is because the component gypsum layers have a liner back paper (or liner fiberglass nonwoven) that has a high tensile strength. Tests have shown that scored panels of this type require approximately 85 pounds of force to fracture versus the 15 pounds required to break scored ½ inch thick standard gypsum wallboard and the 46 pounds of force required to break scored ⅝ inch thick type X gypsum wallboard. This internal layer (or layers, in some cases) must be broken under tension via considerable bending force during a typical score and snap operation. 
     In many cases, the tradesman is forced to cut each panel with a power tool such as a circular saw or a rotary cutting tool to ensure a straight cut and a high quality installation. This adds time and labor costs to the panel installation and generates copious amounts of dust which act as a nuisance to the laborers and adds even more installation expense in the form of jobsite clean up. 
     A figure of merit for the sound reducing qualities of a material or method of construction is the material or wall assembly&#39;s Sound Transmission Class (STC). The STC rating is a classification which is used in the architectural field to rate partitions, doors and windows for their effectiveness in blocking sound. The rating assigned to a particular partition design as a result of acoustical testing represents a best fit type of approach to a curve that establishes the STC value. The test is conducted in such a way as to make it independent of the test environment and yields a number for the partition only and not its surrounding structure or environment. The measurement methods that determine an STC rating are defined by the American Society of Testing and Materials (ASTM). They are ASTM E 90, “Standard Test Method Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements,” and ASTM E413 “Classification for Sound Insulation,” used to calculate STC ratings from the sound transmission loss data for a given structure. These standards are available on the Internet at http://www.astm.org. 
     A second figure of merit for the physical characteristics of construction panels is the material&#39;s flexural strength. This refers to the panel&#39;s ability to resist breaking when a force is applied to the center of a simply supported panel. Values of flexural strength are given in pounds of force (lbf) or Newtons (N). The measurement technique used to establish the flexural strength of gypsum wallboard or similar construction panels is ASTM C 473 “Standard Test Methods for the Physical Testing of Gypsum Panel Products”. This standard is available on the Internet at http://www.astm.org. 
     The desired flexural strength of a panel is dependant upon the situation. For a pristine panel, a high flexural strength is desirable since It allows for easy transportation and handling without panel breakage. However, when the panel is scored by the tradesman (for example, with a utility knife) for fitting and installation, a low flexural strength is desirable. In that case, a low value indicates that the scored panel may be easily fractured by hand without excessive force. 
     Accordingly, what is needed is a new material and a new method of construction to reduce the transmission of sound from a given room to an adjacent area while simultaneously minimizing the materials required and the cost of installation labor during construction. 
     SUMMARY 
     In accordance with the present invention, a new laminar structure and associated manufacturing process are disclosed which significantly improve both the material&#39;s installation efficiency and the ability of a wall, ceiling, floor or door to reduce the transmission of sound from one architectural space (e.g. room) to an adjacent architectural space, or from the exterior to the interior of an architectural space (e.g. room), or from the interior to the exterior of an architectural space. 
     The material comprises a lamination of several different materials. In accordance with one embodiment, a laminar substitute for drywall comprises a sandwich of two outer layers of selected thickness gypsum board, each lacking the standard liner back paper, which are glued to each other using a sound dissipating adhesive wherein the sound dissipating adhesive is applied over all of the interior surfaces of the two outer layers. In one embodiment, the glue layer is a specially formulated QuietGlue™, which is a viscoelastic material, of a specific thickness. Formed on the interior surfaces of the two gypsum boards, the glue layer is about 1/32 inch thick. In one instance, a 4 foot×8 foot panel constructed using a 1/32 inch thick layer of glue has a total thickness of approximately ½ inches and has a scored flexural strength of 22 pounds force and an STC value of approximately 38. A double-sided wall structure constructed using single wood studs, R13 fiberglass batts in the stud cavity, and the laminated panel screwed to each side provides an STC value of approximately 49. The result is a reduction in noise transmitted through the wall structure of approximately 15 decibels compared to the same structure using common (untreated) gypsum boards of equivalent mass and thickness. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This invention will be more fully understood in light of the following drawings taken together with the following detailed description. 
         FIG. 1  shows a laminar structure fabricated In accordance with this invention for reducing the transmission of sound through the material while providing superior fracture characteristics. 
         FIG. 2  shows a second embodiment of a laminated structure containing five (5) layers of material capable of significantly reducing the transmission of sound through the material while providing superior fracture characteristics. 
         FIG. 3  shows flexural strength results for one sample embodiment of a laminar material constructed in accordance with the present Invention. 
         FIG. 4  shows flexural strength results for several examples of drywall materials including typical drywall, laminated panels in current use, and the present invention. 
         FIG. 5  shows a wall structure wherein one element of the structure comprises a laminar panel constructed in accordance with the present invention. 
         FIG. 6  graphically shows detailed results data of sound attenuation tests for an example embodiment of this invention and a typical wall of similar weight and physical dimensions. 
     
    
    
     DESCRIPTION OF SOME EMBODIMENTS 
     The following detailed description Is meant to be exemplary only and not limiting. Other embodiments of this invention, such as the number, type, thickness, dimensions, area, shape, and placement order of both external and internal layer materials, will be obvious to those skilled In the art in view of this description. 
     The process for creating laminar panels in accordance with the present invention takes into account many factors: exact chemical composition of the glue; glue application process; pressing process; and drying and dehumidification process. 
       FIG. 1  shows the laminar structure of one embodiment of this invention. In  FIG. 1 , the layers in the structure will be described from top to bottom with the structure oriented horizontally as shown. It should be understood, however, that the laminar structure of this invention will be oriented vertically when placed on vertical walls, doors or other vertical partitions, as well as horizontally or even at an angle when placed on ceilings and floors. Therefore, the reference to top and bottom layers is to be understood to refer only to these layers as oriented in  FIG. 1  and not in the context of the vertical use of this structure. In  FIG. 1 , the assembly numerated as  100  refers to an entire laminated panel constructed in accordance with this invention. A top layer  101  is made up of a paper or fiberglass-faced gypsum material and in one embodiment is ¼ inch thick, in one embodiment sixty (60) pound paper eighteen (18) mils thick is used. The resulting panel is ¼ inch plus eighteen (18) mils thick. Of course, many other combinations and thicknesses can be used for any of the layers as desired. The thicknesses are limited only by the acoustical attenuation (i.e., STC rating) desired for the resulting laminar structure and by the weight of the resulting structure which will limit the ability of workers to install the laminated panel on walls, ceilings, floors and doors for its intended use. 
     The gypsum board In top layer  101  typically is fabricated using standard well-known techniques and thus the method for fabricating the gypsum board will not be described. Next, the bottom face of gypsum layer  101  is an unfaced (without paper or fiberglass liner) interior surface  104 . In other embodiments, surface  104  may be faced with a thin film or veil with a very low tensile strength. In one embodiment this thin film or veil can be a single use healthcare fabric as described more completely below in paragraph 21. Applied to surface  104  is a layer of glue  102  called “QuietGlue™. Glue  102 , made of a viscoelastic polymer, has the property that the kinetic energy in the sound which interacts with the glue, when constrained by surrounding layers, will be significantly dissipated by the glue thereby reducing the sound&#39;s total energy across a broad frequency spectrum, and thus the sound energy which will transmit through the resulting laminar structure. Typically, this glue  102  is made of the materials as set forth in TABLE 1, although other glues having similar characteristics to those set forth directly below TABLE 1 can also be used in this invention. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Fire-Enhanced (FE) Quiet Glue ™ Chemical Makeup 
               
            
           
           
               
               
            
               
                   
                 WEIGHT % 
               
            
           
           
               
               
               
               
               
            
               
                   
                 COMPONENTS 
                 Min 
                 Max 
                 Preferred 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 acrylate polymer 
                 30 
                 70 
                 41 
               
               
                   
                 ethyl acrylate, 
                 0 
                 3.0 
                 0.3 
               
               
                   
                 methacrylic acid, 
               
               
                   
                 polymer with ethyl-2- 
               
               
                   
                 propenoate 
               
               
                   
                 hydrophobic silica 
                 0 
                 1.0 
                 0.2 
               
               
                   
                 paraffin oil 
                 0 
                 3.0 
                 1.5 
               
               
                   
                 silicon dioxide 
                 0 
                 1.0 
                 0.1 
               
               
                   
                 sodium carbonate 
                 0 
                 3.0 
                 0.6 
               
               
                   
                 stearic acid, aluminum 
                 0 
                 1.0 
                 0.1 
               
               
                   
                 salt 
               
               
                   
                 surfactant 
                 0 
                 2.0 
                 0.6 
               
               
                   
                 rosin ester 
                 0 
                 20 
                 7 
               
               
                   
                 Zinc Borate 
                 0 
                 25 
                 12 
               
               
                   
                 Melamine Phosphate 
                 0 
                 10 
                 6 
               
               
                   
                 Ammonium 
                 0 
                 10 
                 6 
               
               
                   
                 Polyphosphate 
               
               
                   
                 Hexahydroxy methyl 
                 0 
                 5.0 
                 1.5 
               
               
                   
                 ethane 
               
               
                   
                 CI Pigment Red 
                 0 
                 1.0 
                 0.02 
               
               
                   
                 Dispersion 
               
               
                   
                 Water 
                 10 
                 40 
                 23 
               
               
                   
                 2-Pyridinethiol, 1-oxide, 
                 0 
                 3.0 
                 1 
               
               
                   
                 sodium salt 
               
               
                   
                   
               
            
           
         
       
     
     The preferred formulation is but one example of a viscoelastic glue. Other formulations may be used to achieve similar results and the range given is an example of successful formulations investigated here. 
     The physical solid-state characteristics of QuietGlue™ include:
         1) a broad glass transition temperature below room temperature;   2) mechanical response typical of a rubber (i.e., elongation at break, low elastic modulus);   3) strong peel strength at room temperature;   4) weak shear strength at room temperature;   5) does not dissolve in water (swells poorly); and   6) peels off the substrate easily at temperature of dry ice.
 
QuietGlue may be obtained from Serious Materials, 1259 Elko Drive, Sunnyvale, Calif. 94089.
       

     Gypsum board layer  103  is placed on the bottom of the structure and carefully pressed in a controlled manner with respect to uniform pressure (pounds per square inch), temperature and time. The top face of gypsum layer  103  is an unfaced (without paper or fiberglass liner) interior surface  105 . In other embodiments, surface  105  may be faced with a thin film or veil with a very low tensile strength. The maximum very low tensile strength for the thin film or veil is approximately six (6) psi but the preferred very low tensile strength for this material is as low as approximately one (1) psi. In one embodiment this thin film can be a fabric such as a single use healthcare fabric as described more completely In paragraph 21. Such fabrics are typically used for surgical drapes and gowns. 
     Finally, the assembly is subjected to dehumidification and drying to allow the panels to dry, typically for forty-eight (48) hours. 
     In one embodiment of this invention, the glue  102 , when spread over the bottom of top layer  101 , is subject to a gas flow for about forty-five seconds to partially dry the glue. The gas can be heated, in which case the flow time may be reduced. The glue  102 , when originally spread out over any material to which it is being applied, is liquid. By partially drying out the glue  102 , either by air drying for a selected time or by providing a gas flow over the surface of the glue, the glue  102  becomes a pressure sensitive adhesive, much like the glue on a tape. The second panel, for example the bottom layer  103 , is then placed over the glue  102  and pressed against the material beneath the glue  102  (as in the example of  FIG. 1 , top layer  101 ) for a selected time at a selected pressure. The gas flowing over the glue  102  can be, for example, air or dry nitrogen. The gas dehumidifies the glue  102 , improving manufacturing throughput compared to the pressing process described previously wherein the glue  102  is not dried for an appreciable time prior to placing layer  103  in place. 
     In  FIG. 2 , two external layers of gypsum board  201  and  203  have on their interior faces unfaced surfaces  206  and  207 , respectively. Attached to these are glue layers  204  and  205  respectively. Between the two glue layers  204  and  205  is a constraining layer  202  made up of polyester, non-woven fiber, or another low tensile strength material suitable for the application. The tensile strength of this constraining layer can be a maximum of approximately ten (10) psi but preferably is from approximately one (1) to three (3) psi. 
     Examples of materials for the constraining layer  202  include polyester nonwovens, fiberglass non-woven sheets, cellulosic nonwovens, or similar products. The tensile strength of these materials varies with the length of the constituent fibers and the strength of the fiber/binder bond. Those with shorter fibers and weaker bond strengths have lower tensile strengths. A good example of such materials are the plastic-coated cellulosic nonwoven materials commonly used as single use healthcare fabrics, known for their poor tensile strengths. Single use healthcare fabrics are available from the 3M Corporation of St. Paul, Minn., DuPont of Wilmington, Del. and Ahlstrom of Helsinki, Finland. The preferred maximum very low tensile strength for these materials is approximately six (6) psi but the preferred very low tensile strength for these materials is approximately one (1) psi. The weight of these materials can vary from a high of approximately four (4) ounces per square yard down to a preferred weight of approximately eight tenths (0.8) of an ounce per square yard. Alternate materials can be of any type and any appropriate thickness with the condition that they have acceptably low tensile strength properties in the example of  FIG. 2 , the constraining material  202  approximate covers the same area as the glue  204  and  205  to which it is applied. 
       FIG. 3  shows flexural strength test results for an embodiment wherein the interior surfaces ( 104  and  105 ) the gypsum sheets  101 ,  103  do not have an additional facing material such as paper. The sample tested was constructed consistent with  FIG. 1 , and had dimensions of 0.3 m by 0.41 m (12 inches by 16 inches) and a total thickness of 13 mm (0.5 inch). A three point bending load was applied to the sample according to ASTM test method C 473, bending test method B. The measured flexural strength was 22 pounds force. 
     The flexural strength value of the finished laminate  100  significantly decreases with the elimination of the paper facings at surfaces  104  and  105 .  FIG. 4  illustrates the relationship of two laminate embodiments and typical gypsum wallboard materials. As seen in  FIG. 4 , the currently available laminated panels G 1  to G 4  (QuietRock 510) have an average flexural strength of 85 pounds force when scored. 
     In comparison, scored typical prior art gypsum sheets (F 1  to F 4  and E 1  to E 4 ) with interior paper faced surfaces, have an average flexural strength of 15 pounds force for ½ inch thick and 46 pounds force for ⅝ inch thick respectively. These prior art laminated panels can be scored and fractured in the standard manner used in construction but lack the acoustic properties of the structures described herein. The other prior art structures shown in  FIG. 4  (A 1 -A 4  to D 1 -D 4  and G 1 -G 4 ) have an average peak load at fracture above fifty pounds force and thus are unacceptable materials for traditional fracture methods during installation. Of these prior art materials, QuietRock® (G 1 -G 4 ) has improved sound attenuation properties but can not be scored and fractured using traditional scoring and breaking methods. The present invention (represented by H 1  to H 4 ) has a scored flexural strength of 22 pounds force as shown in  FIGS. 3 and 4 , and thus can be scored and fractured in the standard manner used in construction while at the same time providing an enhanced acoustical attenuation of sound compared to the prior art structures (except QuietRock). 
       FIG. 5  is an example of a wall structure comprising a laminated panel  508  constructed in accordance with the present invention (i.e., laminate  100  as shown in  FIG. 1 ); wood studs  502 ,  504 , and  506 ; batt-type insulation  512 ; and a ⅝ inch sheet of standard gypsum drywall  510 , with their relationship shown in Section A-A.  FIG. 6  shows the results of sound testing for a structure as in  FIG. 5 , wherein the panel  508  is constructed as shown in  FIG. 1 . Sound attenuation value (STC number) of the structure is an STC of 49. It is known to those practicing in this field that a similar configuration with standard ⅝ inch drywall on both sides of standard 2×4 construction yields an STC of approximately 34. Accordingly, this invention yields a 15 STC point improvement over standard drywall in this particular construction. 
     In fabricating the structure of  FIG. 1 , the glue  104  is first applied in a prescribed manner in a selected pattern, typically to 1/32 inch thickness, although other thicknesses can be used if desired, onto the top layer  101 . The bottom layer  103  is placed over the top layer  101 . Depending on the drying and dehumidification techniques deployed, anywhere from five minutes to thirty hours are required to totally dry the glue in the case that the glue is water-based. A solvent-based viscoelastic glue can be substituted for the water-based glue. The solvent-based glue requires a drying time of about five (5) minutes in air at room temperature. 
     In fabricating the structure of  FIG. 2 , the method is similar to that described for the structure of  FIG. 1 . However, before the bottom layer  203  is applied (bottom layer  203  corresponds to bottom layer  103  in  FIG. 1 ) the constraining material  202  is placed over the glue  204 . A second layer of glue  205  is applied to the surface of the constraining material  202  on the side of the constraining material  202  that is facing away from the top layer  201 . In one embodiment the glue layer  205  is applied to the interior side of bottom layer  203  instead of being applied to layer  202 . The bottom layer  203  is placed over the stack of layers  201 ,  204 ,  202  and  205 . The resulting structure is dried in a prescribed manner under a pressure of approximately two to five pounds per square inch, depending on the exact requirements of each assembly, although other pressures may be used as desired. 
     Accordingly, the laminated structures of this invention provide a significant improvement in the sound transmission class number associated with the structures and thus reduce significantly the sound transmitted from one room to adjacent rooms while simultaneously providing for traditional scoring and hand fracture during installation. 
     The dimensions given for each material in the laminated structures of this invention can be varied as desired to control cost, overall thickness, weight, anticipated moisture and temperature control requirements, and STC results. The described embodiments and their dimensions are illustrative only and not limiting. Other materials than gypsum can be used for one or both of the external layers of the laminated structures shown in  FIGS. 1 and 2 . For example, the layer  103  of the laminated structure  100  shown in  FIG. 1  and the layer  203  of the laminated structure  200  shown in  FIG. 2  can be formed of cement or of a cement-based material in a well known manner. The cement-based material can include calcium silicate, magnesium oxide and/or phosphate or combinations thereof. 
     Other embodiments of this invention will be obvious in view of the above description.