Homogeneous thermal insulation board and method of making same

Abstract: An insulating board is provided in which the capacity to absorb the moisture exemplified by wood fiber based board, cellulose fiber based board and perlite based board is coupled with the high permeability of fiberglass insulation to provide a board having a balance between the capacity to hold moisture and sufficient permeance to allow the board to give up the moisture as the board is passed through a cycle of absorption and desorption, whether it be on a daily or seasonable cycle.

Description: Field of the Invention This invention relates to a homogeneous thermal insulation board and a method of making same. In particular the present invention deals with an improved insulating sheathing board primarily directed to residential home construction and more particularly to a sheathing board with improved insulating and breathability properties. Background of the Invention As a result of steadily rising energy costs construction practices in residential housing have changed considerably inasmuch as residential dwellings are now more heavily insulated and usually contain high "R" value sheathing wherein the "R" value is a measure for thermal resistance and is the inverse of thermal conductivity. The application of high "R" value sheathing which usually has low permeance has caused concern as a result of the changing moisture patterns that may occur in the wall. Excessive moisture in wall cavities can produce detrimental/destructive effects. The moisture may decrease the effectiveness of the cavity insulation and if a wall cavity remains wet for extended periods may result in the decaying and rotting of wood components of the wall. Under winter conditions condensation tends to accumulate on the insulation/sheathing or siding. The outdoor temperature and indoor humidity are the critical values. Indoor moisture moves toward the drier outdoors and will condense if the sheathing or siding are below the dew point temperature. This condensation may result in the buckling or warping of the siding or the blistering or peeling of the paint on the siding. Walls having higher "R" values have colder outside surfaces with greater condensation potential. The lower permeance values of these walls also results in less moisture movement and consequently less opportunity for moisture to dissipate through vapor diffusion. Where the source of moisture is external, rain water or surface condensation (dew) penetrates the siding under the influence of the wind and capillary action which can pull surface water on the siding exterior up between the horizontal laps of thc siding. The moisture can then migrate from between the laps of the siding and the siding/building paper interface both towards the exterior (into the wood siding towards the paint/finish siding interface) when a relatively low impermeable sheathing is used and towards the interior (into the sheathing material) when a relatively high permeable sheathing is used. Absorption of water into sheathing material of wood fiber based board, cellulose fiber board and perlite based board not only lowers the "R" value but causes dimensional instability in the board as well. Dimensional instability in the board in turn causes the sheathing to warp, buckle and pull away from the nails holding it in place and in many instances may result in the total failure of the product. Condensation occurs typically at a marked change of permeance such as at the interface of two different materials where these materials are below the dew point temperature. It is not significant that the two materials may be both highly permeable to water vapor, only that they are each of differing permeability. An example of this is when a spun bound olefin film covers fiber glass insulation on the cold side of a wall. The film is "permeable" however the fiber glass insulation is more permeable and condensation occurs at the film/insulation interface. How much moisture accumulates is dependent on the potential for evaporation at that interface. Consequently, at cold temperatures considerable moisture may collect with resulting damage to components of the wall if the moisture is allowed to remain there for extended periods of time. A difficulty with sheathing such as asphalt coated wood fiber based board, cellulose fiber based board, and asphalt coated perlite board, is their relatively low permeance. While these materials have a relatively large capacitance to accumulate moisture their relatively low permeability prevents them from giving up the moisture as the wall passes through its climatic cycle whether it be daily or seasonal and as a result the wall never has the opportunity to completely dry. An example of an asphalt coated perlite board is found in CH-A-467912, which discloses an insulation board comprised of at least 40% by weight perlite, 15% cellulose fiber, 10% mineral wool fiber, starch binder and asphalt. As is typical of such boards, the perlite is employed for its thermal insulating and rapid dewatering properties and the fibers and binder are employed for the strength they impart to the board. The effect of the ingredients on the permeability of the board or on the capacity of the board to retain or store moisture is not recognized. Thus, there has existed a definite need for an insulating board which in addition to having sufficient capacity to accumulate moisture has sufficiently high permeance to permit the moisture to escape the board under proper conditions. It is an object of this invention to provide a new and improved insulation board that will meet these needs of capacitance and high permeance and yet provide improved R values. It is another object of this invention to provide an insulating board having greater dimensional stability than comparable insulating hoards. Still another object of the present invention is to provide an insulating board having superior flame and smoke life safety characteristics. Yet another object of the present invention is to provide an insulating board that possesses lower thermal conductivity (or higher "R"/inch) than previously attainable in insulation boards of comparable density. Additional objects and advantages of the invention will be set forth in part in the description, or may be evident by the practice of the invention. Brief Summary of the Invention The present invention is a composite material insulating board in which the capacity to absorb the moisture exemplified by wood fiber based board, cellulose fiber based board and perlite based board is coupled with the high permeability of fiberglass insulation to provide a board having a balance between the capacity to hold moisture and sufficient permeance to allow the board to give up the moisture as the board is passed through a cycle of absorption and desorption, whether it be on a daily or seasonable cycle. The board which has a nominal density of 160-560 kg/m³ (10-35 pcf.) is produced from a homogeneous slurry of less than 40 percent by weight of perlite; 25-50 percent cellulose fiber; 5-60 percent glass fiber; 1-10 percent binder (starch or phenolic resin) and 1-8 percent asphalt. With the Fourdrinier process, the product is made by utilizing a continuously moving foraminous surface which comprises mixing a homogeneous aqueous slurry of pourable consistency containing about 2-5 percent by weight solids of the constituents noted above, forming the slurry into a mat on said foraminous surface, dewatering the same and then drying the mat into a board form. Detailed Description of the Invention As noted above, insulating board in accordance with the present invention has not only the capacity to absorb moisture as exemplified by wood fiber based board, cellulose fiber based board and perlite based board but the high permeability of fiberglass insulation contained therein provides the board with the ability to give up moisture as the board is passed through a cycle of absorption and desorption, whether it be on a daily or seasonable cycle. The balance between the capacity to hold moisture and the ability to give up moisture can be varied by increasing and/or decreasing the amount of fiberglass and the permeance and the permeance of the board relative to the amount of wood fiber or cellulose and the moisture capacitance of the board within the percentage limitations set forth. A glass composite board made in accordance with the present invention is produced by a wet slurry process and preferably the Fourdrinier process, the same process employed to produce perlite based sheathing board with glass fiber added as a partial or full replacement for the expanded perlite. The board is made from a homogeneous mixture containing the ingredients listed in Table I at the indicated rate percentage levels, based upon the total weight of the mixture. By Weight % Ingredient General Example 1 Example 2 Example 3 Perlite 0-40% 15% - - Cellulose 25-50% 47% 47% 29% Glass Fiber 5-60% 25% 42% 60% Binder (Starch or Phenolic Resin) 1-10% 8% 8% 8% Asphalt 1-8% Asphalt Emulsion 3% Asphalt Emulsion 3% Asphalt Emulsion 3% Asphalt Hot Melt 2% The cellulose fiber in the product is customarily provided by using either wood pulp or recycled newsprint fiber and the glass fiber utilized can either be newly produced glass fiber or preferably recycled or scrap fiber which may usually be obtained at a savings since such fiber would ordinarily be destined for a landfill. All of the constituents of the board with the exception of the glass fiber are mixed into a homogeneous aqueous slurry of pourable consistency, the glass fiber is added through a hydrapulper and a stock storage tank with agitating action. For example, the glass fiber may be added to a whirlpool or vortex of the fiber stock which feeds into the head box containing the conventional agitator and feeder. The slurry is formed into a mat on the continuously moving foraminous surface of the Fourdrinier, the mat is dewatered, and then the mat is dried into a board form. The aqueous slurry forming the mat has a solid consistency of about 2-8% by weight and preferably 3 1/2% by weight. Increasing the glass fiber in the formulation provides a board having increased permeance. The partial or full replacement of glass fiber for expanded perlite results in insulating board with improved thermal properties and equivalent flexural strength when compared to perlite based sheathing board. In Table II below are typical properties for samples produced in which there is no glass fiber and those produced in accordance with the compositions Examples 1, 2 and 3 of Table I. Thermal conductivity W/m/K K BTUs Btu in/hr ft² °F Thermal resistance R/cm R/inch Flex strength kg/cm² Flex strength psi Perlite Based Board 0,0577 0.4 1.12 2.5 14.35-14.70 205-210 Example 1 0,0473 0.328 1.36 3.05 14.70 210-210 Example 2 0,0440 0.305 1.47 3.28 14.35-14.70 205-210 Example 3 0,0418 0.290 1.54 3.45 14.35-14.70 205-210 As noted by the data above, the addition of glass fiber in the composition board not only improves the thermal performance of the insulating board as compared to the perlite based board, but also improves its "R" value while having minimal effect on the flexural strength of the board. The fiber glass in the formulation of the insulating board also greatly improves the dimensional stability of the board. Test data has shown that the use of 25% glass fiber in the formulation (Example 1) improves the dimensional stability of the board over perlite based board not having fiber glass contained therein by 54%. Utilization of 42% glass fiber in the formulation (Example 2) increases the dimensional stability of the board produced over perlite based board having no glass fiber by 70%, and in the case of the formulation containing 60% glass fiber (Example 3) there is an 85% improvement of dimensional stability over perlite based board not containing glass fiber. The glass composite board of the present invention, also compares very favorably to other sheathing materials as indicated in Table III below. Thermal conductivity W/m/K K BTUs in/hr ft² °F Thermal resistance R/cm R/Inch Composite Board Example 2 0,0440 0.305 1.467 3.28 Perlite Based Board 0,0577 0.40 1.118 2.50 Wood Fiber Based Board 0,0577 0.40 1.118 2.50 Cellulose Fiber Based Board 0,0793 0.55 0.813 1.82 In addition to other favorable properties of the glass composite board, tests reveal that when exposed to flame under controlled conditions, the spread of flame for the boards of Examples 1, 2 and 3 was more than three times less than for a typical asphalt coated wood fiber based board and the development of smoke was at least 30 times less than for the asphalt coated wood fiber based board. Listed in Table IV are the Perm values of the formulations of Examples 1, 2 and 3 asphalt coated perlite based board with fiber based board and cellulose based board with a facer. The term "perm" is a unit of measure used in the industry in connection with the permeability of a material, denoting its ability to transmit water vapor. A perm is equivalent to the transmission of 0,0648 g (1 grain) of water vapor per hour per square feet of the material in question, and is measured in accordance with known standard procedures, set forth, for example, in ASTM E 96 WVT. Any material with a Perm value of less than 5 is normally classified as being impermeable. PERM (grains/sqft) PERM (g/m²) Example 1 36 25.08 Example 2 42 29.29 Example 3 67 46.66 Asphalt Coated Perlite Based Board 0.05 0.035 Wood Fiber Based Board < 5 < 3.50 Cellulose Fiber Based Board with Facer > 5 > 3.50 In Table V below there is illustrated the moisture storage capacitance of Examples 1, 2 and 3 formulations. Moisture Storage Capacitance where relative humidity is 100% Examples 1 and 2 24.8 kg water vapor per m³ (1.55 lbs. water vapor per cu.ft.) Example 3 13.2 kg water vapor per m³ (0.825 lbs. water vapor per cu.ft.) While in the illustrations above the use of the glass composite board is directed to use as sheathing, obviously this board in view of its inherent properties can be used for various other purposes.

Claims: A homogeneous thermal insulation board having a density of 160-560 kg/m3, molded from an aqueous slurry and consisting essentially of less than 40% by weight perlite, 25-50% cellulose fiber, 5-60% glass fiber, 1-10% binder and 1-8% asphalt, the amount of perlite and cellulose fiber present in the board being such that the board has a permeance greater than 322 perms, as based on the transmission of water vapor through a square meter of the board, and a moisture storage capacity of at least 12.8 kg of water vapor per cubic meter when the relative humidity is 100%. A homogeneous thermal insulation board as defined in claim 1, having a density of approximately 208 kg/m3 and consisting essentially of approximately 15% perlite, 47% cellulose fiber, 25% glass fiber, 8% binder and 5% asphalt. A homogeneous thermal insulation board as defined in claim 1, having a density of approximately 208 kg/m3 and consisting essentially of approximately 47% cellulose fiber, 42% glass fiber, 8% binder and 3% asphalt. A homogeneous thermal insulation board as defined in claim 1, having a density of approximately 208 kg/m3 and consisting essentially of approximately 29% cellulose fiber, 60% glass fiber, 8% starch binder and 3% asphalt. A thermal insulation board as defined in claim 1 wherein the binder is selected from the group consisting of starch and phenolic resin. A method of making a homogeneous thermal insulation board, which comprises making an aqueous slurry having a solids content consisting essentially of less than 40% by weight perlite, 25-50% cellulose fiber, 5-60% glass fiber, 1-10% binder, and 1-8% asphalt, forming a mat on a foraminous support from said slurry, dewatering the mat, and then drying the mat to form a board having a density of 160-560 kg/m3, the amount of perlite and cellulose fiber present in the board being such that the board has a permeance greater than 322 perms, as based on the transmission of water vapor through a square meter of the board, and a moisture storage capacity of at least 12.8 kg of water vapor per cubic meter when the relative humidity is 100%.

Inventors: FORTE DON AUGUST, MARTINEZ STEVEN RICHARD, MCCAMPBELL FRANK ALLEN, SANDOVAL CHRISTOPHER PAUL, STEINLE DONALD RALPH, FORTE, DON AUGUST, MARTINEZ, STEVEN RICHARD, MCCAMPBELL, FRANK ALLEN, SANDOVAL, CHRISTOPHER PAUL, STEINLE, DONALD RALPH
Applicants: MANVILLE CORP, MANVILLE CORPORATION
Application year: 1992
Main classification: E04C2
IPC codes: C04B30