RU2651684C1 - Fire-resistant gypsum panel with low weight and density - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: group of inventions relates to gypsum panels with low mass and density, with good thermal insulating properties, good resistance to heat shrinkage, good fire resistance and, in some aspects of the present invention, good water resistance. Gypsum panel contains a solified gypsum middle layer, located between the two facing sheets, formed from a slurry containing at least water, gypsum building plaster and pregelatinized starch. Starch is present in an amount of from about 0.5 % to about 10 % by weight of the weight of the construction gypsum and effective to increase the hardness of the hardened gypsum middle layer as compared to the gypsum middle layer formed from the slurry, not containing pregelatinized starch. Gypsum building plaster is contained in an amount of approximately 700 lb/kt. f. feet (about 3.4 kg/m²), wherein the gypsum building plaster and water are contained in at least amounts, effective to create a crystalline matrix essentially consisting of calcium sulfate dihydrate. Panel has a density in a range of about 27 to 32 pounds/foot³ (from about 430 to about 513 kg/m³), an average hardness of the middle layer of at least about 11 pounds (about 5 kg) determined in accordance with ASTM C473-09, and a thermal insulation coefficient of at least about 17 minutes. Thickness of the panel is approximately 0.625 inches (about 1.6 cm).

EFFECT: technical result is a decrease in mass and density, an increase in thermal insulation properties, resistance to heat shrinkage, fire resistance, water resistance.

23 cl, 11 ex, 4 dwg, 15 tbl

Description

CROSS REFERENCES TO RELATED APPLICATIONS FOR PATENTS

[001] This partially continuing application claims priority according to an earlier application for US Patent No. 12/795125, filed June 7, 2010, which is a continuation of the application for US Patent No. 11/449177, filed June 7, 2006, according to which U.S. Patent No. 7731794 was issued on June 8, 2010, which claims priority according to provisional application for US Patent No. 60/688839, filed June 9, 2005, the entire contents of which are incorporated herein by reference.

BACKGROUND

[002] The earlier claims mentioned above relate to a method for producing gypsum suspensions containing a phosphate component, pregelatinized starch and a naphthalene sulfonate dispersant, and to products made from these suspensions. Earlier applications also relate to methods for increasing the dry strength of gypsum panels with low weight and density by introducing into the slurry used for the manufacture of panels, a phosphate-containing component, pregelatinized starch and a naphthalene sulfonate dispersant.

[003] Traditional gypsum-containing products, such as gypsum panels, have many advantages, such as low cost and easy machinability, however, significant amounts of gypsum dust can be generated when cutting or drilling the product. In earlier applications, various improvements have been achieved in the manufacture of gypsum-containing products by introducing starches and other ingredients into the suspensions used to make these products. Starch can increase bending strength and compressive strength of gypsum-containing products, including gypsum panels.

[004] In General, it is necessary to apply significant amounts of water in gypsum suspensions containing pregelatinized starch, to ensure appropriate fluidity of the suspension. Unfortunately, most of this water must subsequently be removed by heating, which is expensive due to the high cost of the fuel used for heating. The heating step also takes time. As described in earlier applications, it was found that the use of naphthalenesulfonate dispersants can increase the fluidity of suspensions, thereby solving the problem of water demand. In addition, it was also found that naphthalenesulfonate dispersants used in sufficiently high concentrations can crosslink with pregelatinized starch, binding gypsum crystals after drying, which increases the strength of the gypsum composite in the dry state.

[005] It was previously believed that phosphate-containing components did not affect the water requirement of the gypsum slurry. However, as described in earlier applications, the inventors of the present invention found that increasing the concentration of the phosphate-containing component to previously unknown concentrations in the presence of a particular dispersant makes it possible to achieve the corresponding fluidity of the suspension with an unexpectedly reduced water content, even in the presence of high concentrations of starch. This, of course, is highly desirable, because, in turn, it reduces fuel consumption and time costs associated with subsequent stages of the water removal process. The inventors have also found that the dry strength of gypsum panels can be increased by using a naphthalenesulfonate dispersant in combination with pregelatinized starch in a slurry used to make said panels.

[006] The inventions described in earlier applications included gypsum panels containing a cured gypsum composition formed between two substantially parallel cladding sheets, said cured gypsum composition made using a gypsum-containing suspension of water, building gypsum, pregelatinized starch, naphthalene sulfonate sulfonate and optionally water soluble phosphate, preferably sodium trimetaphosphate. Said gypsum panel has high strength and significantly lower weight than conventional gypsum panels. In addition, when cutting, sawing, breaking or drilling panels made according to the indicated embodiment, much less dust is generated.

[007] Another embodiment of the invention according to earlier applications includes a method for manufacturing gypsum panels comprising mixing a gypsum-containing slurry containing water, gypsum, pregelatinized starch and a naphthalene sulfonate dispersant, the pregelatinized starch being in an amount of at least about 0.5% by weight weight up to about 10% by weight of the weight of the gypsum.

The resulting gypsum-containing suspension is applied to the first sheet of facing paper, and a second sheet of facing paper is placed on the applied suspension to form a gypsum board. The gypsum board is cut after the gypsum-containing suspension has solidified sufficiently to be cut, and the resulting gypsum board is dried. The gypsum-containing suspension may optionally contain a phosphate-containing component, for example sodium trimetaphosphate. Other conventional ingredients may also be used in the suspension, including, where appropriate, accelerators, binders, paper fiber, fiberglass, and other known ingredients. Soap foam is usually added to reduce the density of the finished gypsum panel product.

[008] The present invention generally relates to gypsum panels with low mass and density, with good thermal insulation properties, good heat shrink resistance, good fire resistance, and, in some aspects of the present invention, good water resistance.

[009] Gypsum panels used in buildings and other construction applications (such as gypsum wall panels or ceiling panels) typically comprise a gypsum middle layer with cladding sheets made of paper, fiberglass or other suitable materials. Gypsum panels are usually made by mixing “building gypsum” with water and other ingredients to form a slurry that is used to form the middle layer of the panels.

. Обожженный гипс может содержать бета-полугидрат сульфата кальция, альфа-полугидрат сульфата кальция, водорастворимый безводный сульфат кальция, или смеси любых или всех из указанных веществ, природного или синтетического происхождения. При введении в суспензию, применяемую для формирования среднего слоя панелей, обожженный гипс подвергается процессу гидратации, который завершается во время формирования гипсовых панелей. Указанный процесс гидратации, завершенный соответствующим образом, дает в целом непрерывную кристаллическую основу отвержденного двуводного гипса в различных кристаллических формах (т.е. формах CaSO₄⋅2H₂O).[010] As is commonly understood in the art, gypsum contains predominantly one or more forms of calcined gypsum, i.e. gypsum subjected to dehydration (usually by heating) to form anhydrous gypsum or semi-aquatic gypsum

. Calcined gypsum may contain beta calcium sulfate hemihydrate, alpha calcium sulfate hemihydrate, water soluble anhydrous calcium sulfate, or mixtures of any or all of these substances, of natural or synthetic origin. When introduced into the suspension used to form the middle layer of the panels, the calcined gypsum undergoes a hydration process, which is completed during the formation of the gypsum panels. Said hydration process, appropriately completed, gives a generally continuous crystalline base of the cured gypsum in various crystalline forms (i.e., CaSO ₄ ⋅ 2H ₂ O).

[011] During the formation of the panels, the facing sheets are usually provided in the form of continuous tapes. The gypsum slurry is applied in the form of a stream or strip on the first of the facing sheets. The suspension is distributed over the width of the first facing sheet with a predetermined approximate thickness to form the middle layer of the panel. Then the second facing sheet is placed on top, placing the gypsum middle layer between the facing sheets and forming a continuous panel.

[012] The continuous panel is usually moved along the conveyor to ensure that the hydration of the middle layer continues. When the middle layer is sufficiently hydrated and hardened, it is cut into one or more required sizes to obtain separate gypsum panels. The resulting panels are then passed through a drying oven at a temperature sufficient to complete the hydration process and the panels are dried to the desired level of free moisture (usually a relatively low free moisture content).

[013] Depending on the method used, the intended use of the panels and other conditions, additional layers, strips or tapes of a suspension containing gypsum and other additives can be applied to the first and / or second cladding sheets to provide certain properties of the finished panels, such as hardened edges or hardened surface of the panel. Similarly, the foam can be introduced into the slurry for the gypsum middle layer and / or other strips or strips of the suspension in one or more places of the method to ensure the distribution of voids in the gypsum middle layer or parts of the middle layer of the finished panels.

[014] The resulting panels can be cut and processed for use in various applications, depending on the required panel size, composition of the facing layer, composition of the middle layer, etc. Gypsum panels typically vary in thickness from about 14 inches to about one inch, depending on the intended use and application of the panels. The panels can be used in a wide range of structural elements used to create walls, flows and other similar systems using one or more fasteners, such as screws, nails and / or adhesives.

[015] If the finished gypsum panels are exposed to relatively high temperatures, for example, when exposed to a high temperature flame or gases, part of the gypsum core layer can absorb enough heat to cause water to form from the two-water gypsum crystals in the middle layer. The absorption of heat and the release of water from two-water gypsum may be sufficient to slow down the transfer of heat through or inside the panels for a period of time. At a certain level of high temperatures, a high-temperature flame or gases can also cause phase changes in the gypsum middle layer and rearrangement of crystalline structures. Such temperatures can additionally cause melting or other complexation of salts and impurities in the crystalline structures of the gypsum middle layer. The heat absorbed by the gypsum middle layer as a result of such exposure to a high-temperature flame or gases may also be sufficient to re-burn part of the middle layer, depending on the temperature of the heat source and the exposure time.

[016] More specifically, when heated to 212 ° F (100 ° C), the gypsum middle layer undergoes a decomposition reaction in which 75% of the crystallization water is discharged as steam and the gypsum turns into hemihydrate, according to Equation 1 below:

Upon further heating to 250 ° F (120 ° C), the remaining crystallization water is removed and the hemihydrate turns into anhydrite, i.e. calcium sulfate (Equation 2):

When the middle layer reaches 392 ° F (200 ° C), all the gypsum turns into the anhydrite phase. The indicated transition temperature is approximate and may vary depending on impurities or additives in gypsum. The heat of dehydration required for reactions [1] and [2] together is 390 BTU / lb (906 kJ / kg). The indicated energy absorbed by the phase change reactions and the heat removed with the generated steam act as a significant heat sink and are responsible for most of the unique quality of gypsum as a fire retardant material. For example, it takes seven times more energy to heat gypsum from 75 ° F to 400 ° F (24 to 204 ° C) than is necessary to heat an equal mass of concrete.

[017] When gypsum is fired, absorption and dissipation of thermal energy in the specified process, the volume of the crystalline matrix is reduced. The amount of reduction depends on the initial composition of the gypsum, which will contain various impurities from the mineral deposit from which the gypsum was extracted, or additives from the production method. It is generally believed that the bulk of shrinkage occurs during the dehydration reactions [1] and [2] during the conversion of gypsum to anhydrite.

[018] The shrinkage of the gypsum middle layer affects the performance of the gypsum panels in the presence of a high temperature flame or gases. The higher the shrinkage, the more difficult it will be to achieve a given level of fire resistance characteristics. This can be strengthened or reduced depending on the design of the building itself.

[019] Cracks during shrinkage are observed due to the fact that the gypsum panel is limited in movement in the plane of the panel due to its attachment in the building structure to the supporting structures or other supporting structures. If the building structure bends away from the fire, the panel on the side of the fire falls into the compression zone, since it is deformed into a concave surface. Shrink effects are minimized if the panel is squeezed laterally and longitudinally in length and width. This is observed in the case of walls with wooden racks, when the racks are charred and weakened from the side of the fire, so that they deviate from the fire under the vertical load applied to the structure.

[020] On the contrary, if the building structure deviates toward the fire, the side of the panel exposed to the fire will form a convex surface subject to stretching. Susceptibility to cracks during shrinkage increases as the movement of the structure pulls the panel. This is observed in the case of walls with a light steel frame, when metal racks are heated and expand to a greater extent from the side of the fire, as well as roof-ceiling and floor-ceiling structures, where the load due to gravity causes the structure to deviate downward, since the structure weakens under the action fire underneath. The overall effect on the fire resistance of a structure depends on the relative rates of shrinkage and deviation.

[021] Gypsum panels may experience shrinkage of the dimensions of the panels in one or more directions as a result of some or all of the above effects of high temperature heating, and the shrinkage may cause a violation of the integrity of the panel structure. If the panels are attached to a wall, ceiling, or other supporting structures, shrinkage of the panel may cause the panels to separate from other panels attached to the same structures and their supports, and, in some cases, cause the panels or supports (or both of these elements) to collapse. construction). As a result, hot air at high temperatures can pass through or into wall or ceiling structures.

[022] As described above, gypsum panels withstand the effects of relatively high temperatures for a period of time that is capable of itself delaying the passage of high temperatures through the panels or between the panels and inward (or through) the systems in which the said panels are used. Gypsum panels, referred to as fire resistant or “with an established degree of fire resistance”, are usually formulated to improve the ability of panels to delay the passage of heat through wall or ceiling structures and play an important role in controlling the rate of spread of fire in buildings. As a result, building code authorities and other interested public and private enterprises usually set the most stringent standards for the fire resistance characteristics of gypsum panels with a specified degree of fire resistance.

[023] The ability of gypsum panels to withstand fire and the associated intense heat can be assessed by appropriate testing. Examples of these tests commonly used in the construction industry include tests published by Underwriters Laboratories (UL) certified safety laboratories, such as the UL U305, U419, and U423 test protocols and protocols, as well as the procedures described in E119 specification published American Society for Testing and Materials (ASTM). These tests may include the construction of pilot structures using gypsum panels, usually using one layer of panels on each side of the wall frame formed by wooden or steel struts. Depending on the test, the structure may or may not be subjected to loading forces. The surface of one of the sides of the structure is subjected to increasing temperatures for a period of time corresponding to the heating curve, as it is called in the test methods UL U305, U419 and U423 and in the methods ASTM E119.

[024] During the tests, temperatures are monitored directly near the heated side and temperatures on the surface of the unheated side of the structure in order to evaluate the temperatures to which the gypsum panels under test are exposed and the heat transferred through the structure to unexposed panels. The tests are completed when one or more violations of the structural integrity of the panels occur, and / or when the temperature on the unaffected side of the structure exceeds a predetermined threshold. Typically, these threshold temperatures are based on the maximum temperature at any of these sensors and / or average temperatures recorded by the sensors on the surface of gypsum panels not exposed to temperature.

[025] Test procedures, such as those described in UL U305, U419 and U423, and ASTM E119, are aimed at the stability of the structure to heat transfer through the structure as a whole. The tests also provide, in one aspect, a measure of the resistance of the gypsum panels used in the structure to shrink in the x-y direction (width and length) when the structure is subjected to high temperature heating. These tests also provide a measure of the stability of the panels against loss of structural integrity, which leads to the opening of gaps or the space between the panels in the wall structure, which ultimately leads to the passage of high temperatures into the internal cavity of the structure. In another aspect, the tests provide a measure of the ability of the gypsum panels to withstand heat transfer through the panels and structure. It is believed that such tests reflect the ability of this system to provide building residents and fire / fire control systems with a window of opportunity to take action in a fire or to avoid a fire condition.

[026] In the past, various strategies have been applied to improve the fire resistance of gypsum panels with a specified degree of fire resistance. For example, thicker, denser middle layers of the panels were used to increase the presence of both water and gypsum in the panels, which improved the ability of the panels to act as a heat sink, to reduce panel shrinkage and to increase the structural stability and strength of the panels. Alternatively or additionally, to increase the density of the middle layers of the panels, glass and other fibers were included in the gypsum middle layers to improve the fire resistance of the gypsum panels by increasing the tensile strength of the middle layers of the panels and by distributing shrink stresses over the middle layer matrices. Similarly, in the past, certain amounts of certain types of clay, such as clays with a particle size of less than about one micron, and additives of colloidal silicon oxide or alumina, such as additives with a particle size of less than about one micron, have been used in the middle layers of gypsum panels to provide improved fire resistance (and resistance to high temperature shrinkage).

[027] However, it was believed in the art that reducing the weight and / or density of gypsum panels by reducing the amount of gypsum in the middle layer would adversely affect the structural integrity of the panels and the resistance of the panels to fire and high temperature conditions.

дюйма с массой от 2 до 2,3 фунта на квадратный фут (от 2000 до 2300 фунтов на тысячу квадратных футов («фунт/тыс.кв.футов»)) и плотностями от примерно 50 фунтов на кубический фут («фунтов/фут³») или выше. Патент '022, кроме того, направлен на увеличение содержания гипса (и следовательно плотности и массы) панелей, описанных в патенте '066, и уменьшения содержания минеральных/стеклянных волокон в указанных панелях, для обеспечения еще большей емкости гипсового теплоотвода. В таких источниках, как патент '022, дополнительно учитывают, что свойства вермикулита расширяться, если нет ограничения, привели бы к выкрашиванию (то есть раздроблению, отслаиванию или шелушению) среднего слоя и разрушению конструкции стены, изготовленной с использованием указанных панелей, содержащих вермикулит, в течение относительно короткого времени в условиях высоких температур.[028] Another approach used in the past to improve the fire resistance of gypsum panels with a defined degree of fire resistance was to introduce expanded vermiculite (also called vermiculite ore) and mineral or glass fibers into the middle layer of the gypsum panels. These approaches suggest that vermiculite swells when heated to compensate for the shrinkage of the gypsum components of the middle layer. Mineral / glass fibers were believed to hold portions of dried gypsum together. This approach is discussed in US Patent Nos. 2526066 and 2744022. However, both of these references refer to a high density middle layer providing enough gypsum to act as a heat sink. These patents describe the production of gypsum panels with a thickness of

inches with a mass of 2 to 2.3 pounds per square foot (2,000 to 2,300 pounds per thousand square feet (“pounds / thousand square feet”) and densities of about 50 pounds per cubic foot (“pounds / foot ³ ") or higher. The '022 patent also aims to increase the gypsum content (and hence the density and mass) of the panels described in the' 066 patent and reduce the content of mineral / glass fibers in these panels to provide even greater gypsum heat sink capacity. Sources such as the '022 patent additionally take into account that the properties of vermiculite expand if there is no restriction, would lead to chipping (i.e. crushing, peeling or peeling) of the middle layer and the destruction of the wall structure made using these panels containing vermiculite, for a relatively short time at high temperatures.

дюйма с минимальной массой примерно 1925 фунтов/тыс. кв.футов и плотностью примерно 46 фунтов/фут³. Указанная плотность сравнима с более толстыми и гораздо более тяжелыми гипсовыми панелями толщиной 5/8 дюйма (от примерно 2175 до 2300 фунтов/тыс. кв.футов), в настоящее время предлагаемых коммерчески для применений с установленной степенью огнестойкости.[029] In another example, US Pat. No. 3,454,456 describes the introduction of unexpanded vermiculite into the middle layer of gypsum panels with a defined fire resistance to resist shrinkage of the panels. The '456 patent is also based on a relatively high gypsum content and density to provide the required heat sink capacity. The '456 patent describes panel weights for finished gypsum panels with a thickness of

inches with a minimum weight of approximately 1925 pounds / thousand. sq. ft. and a density of approximately 46 lb / ft ³ . The indicated density is comparable to the thicker and much heavier 5/8 inch thick gypsum panels (from about 2,175 to 2,300 psi) currently offered commercially for fire rated applications.

[030] Patent 456 also discloses that the use of vermiculite in the middle layer of a gypsum panel to increase the degree of fire resistance of the panel has significant limitations. For example, in patent 456 it is noted (as in the patent '022) that the expansion of vermiculite in the middle layer can cause destruction of the middle layer due to spalling and other destructive effects. The '456 patent also describes that particles of unexpanded vermiculite can weaken the structure of the middle layer so that the middle layer becomes weak, soft and brittle. The '456 patent overcomes such significant internal restrictions on the use of vermiculite in gypsum panels by applying a “unique” unexpanded vermiculite with a relatively narrow particle size distribution (more than 90% of unexpanded particles are smaller than the size of the openings in No. 50 sieve (approximately 0.117 inches (0.297 mm )), and less than 10% is slightly larger than the size of the holes in the No. 50 sieve). This approach supposedly suppresses the adverse effects of vermiculite expansion on the panel, as described in column 2, lines 52-72, of the '456 patent.

[031] In another approach, US Pat. No. 3,616,173 is directed to / 4 inch thick fireproof gypsum panels with a gypsum middle layer described in the '173 patent as being lighter or less dense. In the '173 patent, said panels are distinguished from prototype panels with a thickness of 1/2 inch and a weight of about 2000 pounds / thousand. sq. feet or more, and having densities of the middle layer greater than about 48 pounds / ft ³ Thus, the '173 patent describes panels with a density of about 35 lb / ft ³ or higher, and preferably from about 40 lb / ft ³ to about 50 lb / ft ³ . According to the '173 patent, the described densities of the middle layer are achieved by incorporating significant amounts of finely dispersed inorganic material - clay, colloidal silicon oxide or colloidal alumina - into the gypsum middle layer, as well as glass fibers in the amount necessary to prevent the shrinkage of gypsum panels in high temperature conditions.

[032] Other attempts have also been made to increase the strength and structural integrity of gypsum panels and to reduce the weight of panels by various means. See, for example, US Pat. Nos. 7,731,794 and 7736720 and published patent applications US No. 2007/0048490 A1, 2008/0090068 A1 and 2010/0139528 A1. However, such attempts alone were not considered sufficient for the manufacture of panels with low mass, sufficiently resistant to fire and high temperature conditions.

[033] In many applications, providing such low-mass gypsum panels capable of withstanding the effects of a relatively high temperature or fire in order to delay the passage of heating levels through said panels for at least half an hour would be an important contribution to the art. Nevertheless, it was generally believed that a significant decrease in the density of the middle layer of gypsum panels would also reduce the strength properties and structural integrity of these panels, as well as reduce the ability of the panels to delay the passage of heat through the panels for at least half an hour. More specifically, panels with the expected low strength and structural integrity and intentionally low gypsum content are of particular interest in these applications, since these panels are expected to be extremely susceptible to shrink forces and other stresses caused by contact with relatively high temperatures or fire, and are ineffective for absorption and retention of heat associated with these conditions.

[034] However, it is generally recognized that the reduction in the weight of gypsum panels makes them more convenient and more economical to transport, and more convenient to process and install. Therefore, if gypsum panels could be obtained with a low mass, and therefore with a low density, effective in applications requiring fire resistance and high heat, not based on additives such as vermiculite, clay, colloidal silicon oxide or colloidal alumina, Significant progress in the field of fireproof gypsum panels would be presented.

[035] Finally, note that without water-resistant additives, cured gypsum absorbs up to 50% of the mass of gypsum when immersed in water. And when gypsum panels, including fireproof gypsum panels, absorb water, they swell, begin to deform and lose strength, which can destroy their fire retardant properties. Fire-resistant panels with low mass and density contain much more voids filled with air and / or water than conventional heavier fire-resistant panels. It is believed that these voids increase the speed and degree of absorption of water, which makes such fire-resistant panels with a low mass more capable of absorbing water than conventional heavier fire-resistant panels.

[036] In the past, many attempts have been made to improve the water resistance of gypsum panels in general. Various hydrocarbons, including wax, resins and asphalt, were added to the slurry used to make the panels, to give the hardened panels water resistance. It is also well known to use siloxanes for this purpose.

[037] Although the use of siloxanes in gypsum slurries is a useful tool for waterproofing finished panels by creating silicone resins in situ, siloxanes are not expected to sufficiently protect panels of low weight and density. Thus, in the art there is a need for a method for producing fire-resistant gypsum panels with low weight and density, with improved water resistance, at a reasonable cost, by improving the water resistance usually imparted by siloxanes.

SUMMARY OF THE INVENTION

[038] The gypsum panels with low mass and low density according to the present invention are an improvement on the idea of the earlier, pending, application for US patent No. 12/795125, the contents of which are incorporated into this application by reference. The invention according to the '125 application includes a suspension for creating low density gypsum panels, which may contain gypsum, dispersant, a phosphate-containing component and pregelatinized starch. The dispersant may be present in an amount of about 0.1% -3.0% by weight of the weight of dry gypsum. Pregelatinized starch may be present in an amount of at least about 0.5% by weight to about 10% by weight of the weight of dry gypsum in the composition. The phosphate-containing component may be present in an amount of at least about 0.12% by weight of the weight of dry gypsum. Other suspension additives may include accelerators, binders, paper or glass fibers and other known constituents. The invention also includes gypsum panels with low mass and low density, made using these suspensions.

[039] In some aspects, the present invention includes gypsum panels with a nominal thickness of 5/8 inches, low weight and low density, which is much lighter and less dense than gypsum panels with a nominal thickness of 5/8 inches, commonly used in construction, with the ability delay the passage of high levels of heating through the panel for more than half an hour, and methods of manufacturing these panels. In some of these aspects, the panel according to the present invention (middle layer plus facing sheets) has a density of from about 27 to about 37 pounds per cubic foot (“pounds / foot ³ ”), preferably from about 29 to about 34 pounds / foot ³ , and more preferably from about 30 to about 32 pounds / ft ³ , is located between two essentially parallel facing sheets. In these aspects, the weight of the panel of the present invention with a thickness of about 5/8 inches is less than about 1900 pounds / thousand sq. feet, preferably less than about 1740 pounds / thousand. sq. feet and more preferably less than about 1640 pounds / thousand. sq. feet.

[040] In other aspects, the composition for the low weight and density panels of the present invention, and the methods for manufacturing said panels, provide gypsum panels with the above flame retardant properties, a density of less than about 37 lb / ft ³ , preferably less than about 34 lb / ft ³ and more preferably less than about 32 lb / ft ³ , and a nail pull resistance that complies with ASTM C 1396 / C 1396 / M-09. More specifically, in embodiments of the present invention, said panels have a nail pull resistance of at least 87 pounds.

[041] In other aspects of the present invention, the cured gypsum middle layer composition for a panel with an installed fire resistance rating of 5/8 inch nominal thickness is prepared using a gypsum-containing slurry containing at least water, gypsum and other gypsum components listed below. In one of these embodiments, the cured gypsum middle layer has a density of from about 25 to about 36 pounds / ft ³ , and said middle layer contains gypsum in an amount of from about 1040 pounds / thousand. sq. feet to about 1,490 pounds / thousand sq. feet; pregelatinized starch in an amount of from about 0.3% to about 4% by weight of gypsum; mineral, glass or carbon fiber in an amount of from about 0.1% to about 0.3% by weight of gypsum, and phosphate in an amount of from about 0.15% to about 0.5% by weight of gypsum. (Unless otherwise indicated, the percentages of the gypsum middle layer components are indicated by weight based on the mass of gypsum used to form the middle layer suspension).

[042] In other aspects, the gypsum middle layer of the panel of the present invention has a density of from about 27 to about 33 pounds per cubic foot, and the weight of the cured gypsum middle layer is from about 1315 to about 1610 pounds / thousand. sq. feet. In these aspects, the gypsum middle layer also contains from about 0.5% to about 2.0% pregelatinized starch; from about 0.1% to about 0.3% mineral, glass, or carbon fiber; gypsum, and from about 0.01% to about 0.15% phosphate.

дюйма. Такие панели будут иметь содержание составляющих панелей примерно 120% от указанных выше величин. Также, способность указанных панелей противостоять огню и условиям высокой температуры будет находиться на уровне по меньшей мере примерно 120% от соответствующих показателей для панелей номинальной толщиной 5/8 дюйма. Другие аспекты и варианты панелей согласно настоящему изобретению и составов среднего слоя рассмотрены ниже в настоящей заявке.[043] The present invention also includes the preparation and use of gypsum panels having a nominal thickness.

inches. Such panels will have a content of constituent panels of approximately 120% of the above values. Also, the ability of these panels to withstand fire and high temperature conditions will be at least about 120% of the corresponding values for panels with a nominal thickness of 5/8 inches. Other aspects and variations of the panels of the present invention and middle layer compositions are discussed below in this application.

[044] Other conventional additives can also be used in each aspect of the middle layer suspensions and gypsum middle layer compositions according to the present description, in the required amount, to impart the desired properties to the middle layer and to facilitate the manufacture of panels. Examples of such additives include setting agents, setting agents, dehydration inhibitors, binders, adhesives, dispersing agents, leveling or non-leveling agents, thickeners, bactericidal agents, fungicides, pH adjusters, colorants, water-repellent agents, fillers and mixtures of these additives.

[045] In the above aspects and other aspects of the panels of the present invention described in this application, and methods for manufacturing said panels, an aqueous foam is added to the suspension of the middle layer in an amount effective to provide the required densities of the gypsum middle layer using methods additionally discussed below. The introduction of the foam component into the suspension of the middle layer leads to the distribution of voids and the size of the voids, which contribute to one or more strength properties of the panel and / or middle layer. Similarly, additional suspension layers, strips or tapes containing gypsum or other additives (which may have an increased density compared to other parts of the middle layer) can be applied to the first or second cladding sheets to provide certain properties of the finished panel, such as hardened edges or hardened surface of the panel.

дюйма). В целом непрерывную гипсовую панель разрезают на отдельные панели требуемой длины после того, как суспензия, содержащая обожженный гипс, затвердела (благодаря гидратации обожженного гипса с образованием непрерывной матрицы отвержденного гипса) достаточно для разрезания, и высушивают полученные гипсовые панели.[046] Another aspect of the present invention includes a method for producing gypsum panels that are capable of delaying the passage of heating levels through panels for about half an hour or more, in which a component of the cured gypsum core layer is formed from an aqueous suspension containing calcined gypsum. In this aspect, the suspension contains pregelatinized starch, dispersants, phosphates, mineral / glass / carbon fibers, foam and other additives, gypsum and water in a mass ratio of water / gypsum from about 0.6 to about 1.2, preferably from about 0 8 to about 1.0, and more preferably about 0.9. The suspension of the middle layer is then applied in the form of a continuous tape and distributed on a continuous tape of the first facing sheet. The continuous tape of the second cladding sheet is then placed on top of the distributed slurry to form a generally continuous gypsum panel of the required approximate thickness of 5/8 inch (or

inch). In general, a continuous gypsum panel is cut into separate panels of a desired length after the suspension containing calcined gypsum has solidified (due to hydration of the calcined gypsum to form a continuous matrix of set gypsum) is sufficient to cut, and the resulting gypsum panels are dried.

[047] The need for a catalyst and method for producing fire-resistant gypsum panels with improved water resistance at a reasonable cost is met or blocked by embodiments of the present invention in which polymerization of siloxane is accelerated, and in some cases, the amount of siloxane required to meet ASTM 1398 specifications may to be reduced.

[048] More specifically, the polymerization of siloxane is improved using a slurry containing gypsum, class C fly ash, magnesium oxide, siloxane emulsion and water, and more than 2.0% by weight of the gypsum of pregelatinized starch. The specified suspension is used in a method of manufacturing a waterproof / fire-resistant gypsum panels, which includes obtaining a suspension from an emulsion of siloxane, pregelatinized starch and water, then combining the specified suspension with a dry mixture of gypsum, magnesium oxide and class C fly ash. Then the resulting suspension is used to obtain gypsum panels as previously described. The resulting product is suitable for the manufacture of a fire-resistant waterproof gypsum panel having a middle layer comprising interwoven matrices of calcium sulfate dihydrate crystals and silicone resin, and a catalyst containing magnesium oxide and class C fly ash components is dispersed in the volume of these interwoven matrices.

[049] A mixture of magnesium oxide and Class C fly ash catalyzes the polymerization of siloxane to accelerate the development of water resistance in a product made from this suspension. Fire-resistant / water-resistant gypsum panels made in this way do not need to be stored for a long time in anticipation of the completion of the siloxane polymerization reactions.

[050] the Use of a catalyst also increases the degree of completion of the reaction, leading to improved water resistance. Through the use of a combination of fly ash and magnesium oxide, water absorption of less than 5% by weight is achievable. Thus, in addition to the fact that the specified catalyst accelerates the polymerization reaction, the specified catalyst also provides the possibility of more complete polymerization of siloxane, which in some cases can reduce the amount of siloxane. Since siloxane is one of the most expensive additives in the panel, reducing the amount used leads to savings in the cost of raw materials.

[051] Another advantage of the present invention is the dimensional stability of the panels. Some compounds used as catalysts for this reaction lead to significant expansion upon drying of the panel. As the inside of the panel expands, it causes cracking of the outside surface, damaging it. The use of fly ash and magnesium oxide leads to very little expansion and very little cracking of the finished panels. It has also been unexpectedly discovered that polymerized silicone resins reduce panel shrinkage under high temperature conditions.

[052] Said combined fly ash and magnesium oxide catalyst also provides satisfactory polymerisation using a wide range of different grades of magnesium oxide. While it is described in the prior art that only deadburned magnesia is suitable as a catalyst for the polymerization of siloxane, even strongly burned or slightly burned magnesium oxide can be used when combined with fly ash. This feature provides gypsum panel manufacturers with additional freedom in choosing sources of magnesium oxide used in suspension.

[053] Finally, more than 2.0% by weight of pregelatinized starch acts in conjunction with siloxane to obtain good water resistance. Although it is believed that the combination of siloxane / high content of pregelatinized starch slows the penetration of water through micropores at the edges of the panel, primarily blocking the absorption of water, and then, when water is absorbed by starch, by forming a highly viscous starch / water combination, we do not intend to limit ourselves to this theory.

[054] The above brief description of the present invention is not intended to limit the scope of the present invention, as is understood by one of ordinary skill in the art. Other aspects and embodiments of the present invention are discussed below and in the accompanying Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[055] The following and further discussed below figures, unless expressly stated otherwise, are examples not limiting the invention as described herein.

[056] FIGURE 1 is a graph of the maximum temperatures for one sensor and a graph of average temperatures from the sensors on the unaffected, unheated surface of the test structure using the panels of the present invention subjected to a fire test in accordance with U419, as described in Example 8 of the present description, and also a graph of the ASTM 119 temperature curve used for furnace temperatures on the exposed, heated side of the test structure.

[057] FIGURE 2 is an expanded graph of maximum temperature data for a single sensor and average temperatures from the sensors shown in Figure 1.

[058] FIGURE 3 is a graph of maximum temperatures for a single sensor and a graph of average temperatures from sensors on an unaffected, unheated surface of a test structure using panels of the present invention subjected to a fire test under conditions according to U305, as described in Example 9 of the present description, and also a graph of the ASTM 119 temperature curve used for furnace temperatures on the exposed, heated side of the test structure.

[059] FIGURE 4 is an expanded graph of maximum temperature data for a single sensor and average temperatures from the sensors shown in Figure 3.

DETAILED DESCRIPTION

[060] Some embodiments of the invention, according to pending applications, provide finished gypsum-containing products made from gypsum-containing suspensions containing gypsum, pregelatinized starch and a naphthalene sulfonate dispersant. The naphthalenesulfonate dispersant is present in an amount of about 0.1% -3.0% by weight of the weight of dry gypsum. Pregelatinized starch is present in an amount of at least about 0.5% by weight to about 10% by weight of the weight of dry gypsum in the composition. Other ingredients that can be used in suspension include binders, paper fibers, glass fibers, and accelerators. Soap foam is usually added to freshly prepared gypsum-containing suspensions to reduce the density of the finished gypsum-containing product, such as gypsum panels.

[061] A combination of from about 0.5% by weight to about 10% by weight of pregelatinized starch, from about 0.1% by weight to about 3.0% by weight of a naphthalenesulfonate dispersant, and at least at least about 0, 12% by weight to about 0.4% by weight of a phosphate-containing component (all percentages are based on the weight of dry gypsum used in gypsum slurry) unexpectedly and significantly increase the fluidity of the gypsum slurry. This significantly reduces the amount of water required to obtain a gypsum slurry with sufficient fluidity for use in the manufacture of gypsum-containing products, such as gypsum panels. It is believed that the amount of the trimetaphosphate salt, at least twice as compared to standard formulations (in the form of sodium trimetaphosphate), stimulates the dispersing activity of the naphthalenesulfonate dispersant.

[062] Naphthalenesulfonate dispersants used in pending applications include polynaphthalenesulfonate acid and salts of the specified acid (polynaphthalenesulfonates), and derivatives representing the condensation products of naphthalenesulfonate acids and formaldehyde. Particularly preferred polynaphthalenesulfonates include sodium and calcium naphthalenesulfonate. The average molecular weight of naphthalenesulfonates can vary from about 3000 to 27000, although it is preferable that the molecular weight is from about 8000 to 10000. For a given% solids content in an aqueous solution, a dispersant with a higher molecular weight has a higher viscosity and causes a greater consumption of water in composition than a dispersant with a lower molecular weight. Suitable naphthalenesulfonates include DILOFLO, available from GEO Specialty Chemicals, Cleveland, Ohio; DAXAD, available from Hampshire Chemical Corp., Lexington, Massachusetts; and LOMAR D, available from GEO Specialty Chemicals, Lafayette, Indiana. Naphthalenesulfonates are preferably used in the form of aqueous solutions with a dry matter content, for example, in the range of 35-55% by weight. Most preferably, the use of naphthalenesulfonates in the form of an aqueous solution with a dry matter content, for example, in the range of 40-45% by weight. Alternatively, if possible, naphthalenesulfonates can be used in dry solid or powder form, for example, such as LOMAR D.

[063] The polynaphthalene sulfonates used according to the present invention have the general structure (I):

where n> 2, and where M represents sodium, potassium, calcium, etc.

[064] A naphthalenesulfonate dispersant, preferably in the form of about 45% by weight of the solution in water, can be used in the range of from about 0.5% to about 3.0% by weight of the dry gypsum used in the gypsum composite. A more preferred range of use of the naphthalenesulfonate dispersant is from about 0.5% to about 2.0% by weight of the weight of dry building gypsum, and a most preferred range is from about 0.7% to about 2.0% by weight of the weight of dry building gypsum. In contrast, known gypsum panels contain the specified dispersant in an amount of about 0.4% by weight or less, by weight of dry gypsum.

[065] In other words, a naphthalene sulfonate dispersant, based on dry weight, can be used in the range of about 0.1% to about 1.5% by weight of the weight of dry gypsum used in the gypsum composite. A more preferred range of use of the naphthalenesulfonate dispersant, based on dry weight, is from about 0.25% to about 0.7% by weight of the weight of dry gypsum, and the most preferred range (based on dry weight) is from about 0, 3% to about 0.7% by weight of the weight of dry gypsum.

[066] The gypsum-containing suspension according to pending applications may contain a phosphate-containing component, such as a salt of a trimetaphosphate, for example, sodium trimetaphosphate. Any suitable water soluble metaphosphates or polyphosphates may be used as the phosphate component of the present invention. It is preferable to use a salt of trimetaphosphate, including double salts, that is, salts of trimetaphosphate containing two cations. Particularly preferred salts of trimetaphosphate include sodium trimetaphosphate, potassium trimetaphosphate, lithium trimetaphosphate, ammonium trimetaphosphate and the like, or combinations of these salts. A preferred salt of trimetaphosphate is sodium trimetaphosphate. It is preferable to use a salt of trimetaphosphate in an aqueous solution, for example, with a dry matter content in the range of about 10-15% by weight. Other cyclic or acyclic polyphosphates may also be used, as described in US Pat. No. 6,409,825 to Yu et al., The contents of which are incorporated herein by reference.

[067] Sodium trimetaphosphate is a known additive in gypsum-containing compositions, although it is usually used in the range of about 0.05% to about 0.08% by weight of the dry gypsum used in the gypsum slurry. In embodiments of the present invention, sodium trimetaphosphate (or other water-soluble metaphosphate or polyphosphate) may be present in the range of about 0.12% to about 0.4% by weight of the dry gypsum used in the gypsum composite. The preferred range of use for sodium trimetaphosphate (or other water-soluble metaphosphate or polyphosphate) is from about 0.12% to about 0.3% by weight of the weight of dry gypsum used in the gypsum composite.

[068] There are two forms of gypsum, alpha and beta. These two types of gypsum are obtained using various means of firing. The beta form or alpha form of gypsum can be used in the present inventions.

[069] Starches, including in particular pregelatinized starch, must be used in gypsum-containing suspensions prepared in accordance with pending applications. Preferred pregelatinized starch is pregelatinized corn starch, for example pregelatinized corn flour, available from Bunge Milling, St. Louis, Missouri, having the following typical analysis: humidity 7.5%, protein 8.0%, oil 0.5%, crude fiber 0.5%, ash 0.3%; having a raw material strength of 0.48 psi; and having a free bulk density of 35.0 pounds / ft ³ . Pregelatinized corn starch should be used in an amount of at least about 0.5% by weight to about 10% by weight of the weight of dry gypsum used in the gypsum-containing slurry.

[070] The authors of the present invention further describe an unexpected increase in dry strength (in particular for gypsum panels), which can be obtained by using at least about 0.5% by weight to about 10% by weight of pregelatinized starch (preferably pregelatinized corn starch) in the presence of from about 0.1% by weight to about 3.0% by weight of a naphthalenesulfonate dispersant (amounts of starch and naphthalenesulfonate are indicated by weight by weight of dry gypsum, p present in the composition). The indicated unexpected result can be obtained regardless of whether a water-soluble metaphosphate or polyphosphate is present or absent.

[071] In addition, it was unexpectedly discovered that pregelatinized starch can be used in an amount of at least about 10 pounds / thousand. sq. feet, or more, in the dried gypsum panels according to the present invention, and you can get even higher strength and even lower weight. The efficiency of the content of 35-45 pounds / thousand was shown sq. feet of pregelatinized starch in gypsum panels.

[072] Other suitable starches include acid-modified starches, such as acid-modified corn flour, available as HI-BOND from Bunge Milling, St. Louis, Missouri. Said starch has the following typical analysis: humidity 10.0%, oil 1.4%, soluble substances 17.0%, alkaline fluidity 98.0%, free bulk density 30 pounds / ft ³ , and in the form of a 20% solution gives a pH 4.3. Another suitable starch is non-gelatinized wheat starch, such as ECOSOL-45, available from ADM / Ogilvie, Montreal, Quebec, Canada.

[073] An additional unexpected result can be obtained according to the present invention if a combination of a naphthalenesulfonate dispersant and a salt of trimethaphosphate is combined with pregelatinized corn starch and, optionally, paper fiber or fiberglass. Gypsum panels made from compositions containing these three ingredients have increased strength and reduced weight, and are more economically desirable due to reduced water requirements in the manufacture of these panels.

[074] Accelerators can be used in the gypsum-containing compositions of the present invention, as described in US Pat. No. 6,409,825 to Yu et al., The contents of which are incorporated herein by reference. One of the desirable heat-resistant accelerators (HRAs) can be made by dry grinding natural gypsum (calcium sulfate dihydrate). Small amounts of additives (typically about 5% by weight), such as sugar, dextrose, boric acid and starch, can be used to produce this HRA. To date, sugar or dextrose is preferred. Another suitable accelerator is a “climate stabilized accelerator” or “climate stable accelerator” (CSA), as described in US Pat. No. 3,573,947, the contents of which are incorporated herein by reference.

[075] The aspects of the present invention described below are not intended to exhaust or limit the invention to the specific compositions, structures, methods and operations described in this application. Rather, the described aspects and embodiments of the present invention have been selected to explain the ideas of the present invention and its application, action and use to enable those skilled in the art to best follow the ideas of the present invention.

[076] The present invention provides combinations of gypsum and other specified ingredients, examples of which are shown in Table I below. These compositions provide fire-resistant gypsum panels with low mass and density, with the required fire-resistant properties, which were previously considered unattainable for gypsum panels with such low masses and densities. The panels of the present invention also provide resistance to nail pulling, suitable for a number of construction purposes, and, in some aspects, such properties are comparable to significantly heavier, denser commercial panels with an established degree of fire resistance. In other aspects, when applied to walls or other structures, these structures have fire test characteristics comparable to structures made from significantly heavier, denser commercial panels with a defined degree of fire resistance.

[077] In one of the preferred aspects, the composition and method according to the present invention allows to obtain gypsum panels with a thickness of 5/8 inches, with a panel density (middle layer plus facing sheets) of from about 27 to about 37 pounds / ft ³ . In other preferred aspects, the panel densities are from about 29 lb / ft ³ to about 34 lb / ft ³ or from about 30 to about 32 lb / ft ³ . Such panels according to the present invention provide fire-resistant properties comparable to much heavier and denser gypsum panels.

[078] In another aspect of the present invention, a method for producing fire-resistant gypsum panels by preparing an aqueous suspension containing calcined gypsum with the components discussed herein is provided, wherein calcined gypsum (also called gypsum gypsum) and the water used to form the aqueous suspension are taken in a preferred water / gypsum mass ratio, from about 0.6 to about 1.2 in one aspect, from about 0.8 to about 1.0 in another aspect, and about 0.9 in another aspect. The suspension is applied in the form of a continuous tape to a continuous tape of a facing sheet of paper, non-woven fiberglass or other fibrous material, or a combination of fibrous materials. A second such continuous facing sheet is then placed on top of the tape of the applied slurry to obtain a continuous gypsum panel of the required thickness and width. The continuous gypsum board is cut to the required length after the suspension containing the calcined gypsum has solidified (by hydrating the calcined gypsum with the formation of a continuous matrix of approved gypsum) is sufficient to cut, and the resulting gypsum panels are dried. The dried panels, in addition, can be subjected to additional stages of cutting, molding and cutting.

[079] In other aspects of the present invention, a higher density gypsum layer may be formed on or near the first cladding sheet and / or along the outer edges of the cladding sheet. A layer with a higher density usually provides the panel surfaces with advantageous properties such as increased hardness, improved nail pulling strength, etc. higher density along the outer edges of the cladding sheet usually provides improved edge strength and other advantageous properties. In other aspects, a higher density layer is applied to either the cladding sheets or equivalent parts of the structure of the middle layer / cladding sheet.

[080] Generally, higher density layers are applied using conventional techniques, such as coating one or both of the facing sheets in front of or in the immediate vicinity of applying the middle layer to the first facing sheet, or applying a second facing sheet over a suspension of the middle layer. Similarly, an outer layer with a higher density can be applied in the form of a strip or a narrow strip of gypsum slurry (with a density different from the density of the suspension of the middle layer) on the outer edges of the first facing sheet before or in the immediate vicinity of applying the middle layer on the first facing sheet. In some of these aspects, higher density layers comprise from about 3% to about 4% by weight of the board.

[081] In one aspect of the present invention, there is provided a fire resistant gypsum board with low weight and density, 5/8 inch thick, suitable for use as a wall plate, ceiling plate, or other building applications (such as cladding, roofing, etc.) .d.). Cladding sheets may also be coated with waterproof or resistant to unwanted effects coatings or, in some applications, gypsum, binders, acrylic materials or other coatings suitable for specific building needs. Panels can also be given a range of sizes suitable for standard, custom, or individual applications. Examples of these panels are panels with a nominal width of four feet, having a nominal length of eight feet, ten and twelve feet, common for panels used for building purposes.

дюйма, масса панели составляла бы примерно 120% от массы панелей толщиной 5/8 дюйма.[082] The density of the middle layer and the overall density of low-weight fire-retardant panels contribute significantly to the total weight of the panels compared to conventional panels with similar widths. So, for panels with a thickness of 5/8 inches, the weight of the panel would be from about 1380 pounds / thousand. sq. feet to about pounds / thousand sq. feet, preferably from about 1490 pounds / thousand. sq. feet to about 1,740 pounds / thousand. sq. feet, and most preferably from about 1,540 pounds / thousand. sq. feet to about 1,640 pounds / thousand. sq. feet. For panels thick

inches, the weight of the panel would be approximately 120% of the weight of the panels 5/8 inch thick.

[083] The following table shows examples of compositions for fire-resistant gypsum panels with a low weight and density, a nominal thickness of 5/8 inches, according to the present invention.

[084] Other conventional additives can be used in the practical implementation of the present invention in standard quantities to impart the desired properties and to facilitate manufacture. Examples of such additives are water foams, setting agents, setting agents, dehydration inhibitors, binders, adhesives, dispersing agents, leveling or non-leveling agents, thickeners, bactericidal agents, fungicides, pH adjusters, colorants, water-repellent agents, fillers and mixtures of these additives.

[085] In one aspect, using one or more of the compositions described in Table I, the present invention provides panels and methods for manufacturing panels made with low weight and density, with a nominal thickness of 5/8 inches, for gypsum panels satisfying or superior 30-minute fire resistance, in accordance with the requirements for preventing the spread of fire and structural integrity of buildings in accordance with relevant test protocols Similar results can be obtained using other formulations corresponding to the approach described in this application.

[086] The combination of low weight, fire resistance, and strength and structural characteristics is believed to be due to unexpected results from a combination of the above components, each of which is discussed in more detail below.

[087] Building plaster. In each aspect of the present invention, the gypsum component (or calcined gypsum) used to create the crystalline matrix of the middle layer of gypsum panels typically contains calcium sulfate beta-hemihydrate, water-soluble calcium sulfate anhydride, calcium sulfate alpha-hemihydrate, or any or all of these substances of natural or synthetic origin. In some aspects, gypsum may contain non-gypsum minerals, such as small amounts of clay or other components that are associated with the gypsum source or introduced during roasting, processing and / or delivery of gypsum to the mixer.

[088] As an example, the amounts of gypsum listed in Table I suggest that the gypsum source has a purity of at least 95%. Therefore, the components and their relative amounts, such as the amounts shown in Table I above, used to obtain a suspension of the middle layer, can be changed or modified depending on the source, purity and content of gypsum. For example, the composition of the suspension for the gypsum middle layer can be modified for different compositions of gypsum, depending on the purity of the gypsum, the natural or synthetic source of gypsum, the water content in the gypsum, the clay content in the gypsum, etc.

[089] Starch. In one important aspect of the panels of the present invention and methods for manufacturing said panels, the composition of the suspension of the middle layer, as shown in Table I above, includes pregelatinized starch. Crude starch is pregelatinized by boiling starch in water at a temperature of at least 185 ° F. or using other well-known methods to cause gelation in starch used in the middle layer of the panel. Starch can be included in the suspension of the middle layer in dry form, previously dispersed in liquid form, or as a combination of both of these methods. In dry form, starch can be introduced into the mixer for suspension of the middle layer together with other dry ingredients, or as a separate procedure, stage or stage of introduction. In a pre-dispersed form, mono starch is administered with other liquid ingredients, such as mixing water, or as a separate procedure, step or step for administration.

[090] Some examples of readily available pregelatinized starches that can be used in the practice of the present invention are (commercial names indicated): PCF1000 starch, available from Lauhoff Grain Co .; and AMERIKOR 818 and HQM PREGEL starches, both available from Archer Daniels Midland Co. In one important aspect, the starch component includes at least pregelatinized corn starch, such as pregelatinized corn flour, available from Bunge Milling, St. Louis, Missouri. Such pregelatinized starches have the following typical characteristics: humidity 7.5%, protein 8.0%, oil 0.5%, crude fiber 0.5%, ash 0.3%; have a raw strength of 0.48 psi; and have a free bulk density of 35.0 lb / ft ³ .

[091] Fibers. In aspects of the present invention, including fibers, such as those indicated in Table I above, and methods for manufacturing said panels, the fibers may include mineral fibers, glass and / or carbon fibers, and mixtures of these fibers, as well as other comparable fibers, providing the panels comparable advantages . In one important aspect, glass fiber is introduced into the gypsum slurry of the middle layer and the resulting crystalline structure of the middle layer. Glass fibers in these aspects may have an average length of from about 0.5 to about 0.75 inches and a diameter of from about 11 to about 17 microns. In other aspects, such glass fibers may have an average length of from about 0.5 to about 0.675 inches and a diameter of from about 13 to about 16 microns. In other aspects, E-glass fibers having a softening temperature above about 800 ° C are used, and some of the fibers of this type are Advantex® glass fibers (available from Owens Coming) having a softening temperature above at least about 900 ° C. Instead of or in combination with glass fibers such as the above fibers, mineral wool or carbon fibers such as those known to those of ordinary skill in the art can be used.

[092] Phosphate. In one important aspect of the panels of the present invention and methods for manufacturing said panels, a phosphate-containing component comprising a phosphate salt or other source of phosphate ions is introduced into the gypsum slurry used to form the gypsum middle layer of the panels. The use of these phosphates contributes to providing a gypsum middle layer with increased strength, resistance to permanent deformation (e.g., sag resistance), dimensional stability and increased wet strength of panels, compared to hardened gypsum made from a mixture that does not contain phosphate. In many of these aspects, the phosphate source is introduced in amounts sufficient to ensure dimensional stability of the panel and the middle layer of the panel while the semi-aquatic gypsum in the middle layer is hydrated and forms the crystalline structure of the middle layer of the two-gypsum gypsum (for example, in the time interval between the formation of the plate and firing in the manufacturing process). In addition, we note that since the introduced phosphate acts as a setting retarder, the appropriate accelerator can be added in the required amount to overcome any undesirable inhibitory effects of phosphate.

[093] The phosphate-containing components suitable for use in the present invention are soluble in water and are in the form of an ion, salt or acid, namely, condensed phosphoric acids, each of which contains 2 or more units of phosphoric acid; salts or ions of condensed phosphates, each of which contains 2 or more units of phosphate; and monobasic salts or monovalent orthophosphate ions, for example, such as those described in US Pat. Nos. 6,342,284; 6,632,550; and 6815049, the contents of all of which are incorporated into this application by reference. Suitable examples of such classes of phosphates will be apparent to those skilled in the art. For example, any suitable monobasic orthophosphate-containing compound can be used in the practical implementation of the present invention, including, without limitation, ammonium monophosphate, sodium monophosphate, potassium monophosphate, and combinations thereof. A preferred monobasic phosphate salt is potassium monophosphate.

[094] Similarly, any suitable water soluble polyphosphate salt can be used according to the present invention. The polyphosphate may be cyclic or acyclic. Typical cyclic polyphosphates include, for example, trimetaphosphate salts and tetramephosphate salts. The trimetaphosphate salt may be selected, for example, from sodium trimetaphosphate (also referred to as TMPN in this application), potassium trimetaphosphate, lithium trimetaphosphate, ammonium trimetaphosphate and the like, or combinations of these salts.

[095] Also, any suitable acyclic water-soluble polyphosphate salt may be used according to the present invention. The acyclic polyphosphate salt contains at least two phosphate units. As an example, suitable acyclic polyphosphate salts according to the present invention include, without limitation, pyrophosphates, tripolyphosphates, sodium hexametaphosphate containing from about 6 to about 27 repeating phosphate units, potassium hexametaphosphate containing from about 6 to about 27 repeating phosphate units, ammonium hexametaphosphate containing from about 6 to about 27 repeating phosphate units, and combinations of these compounds. A preferred acyclic polyphosphate salt of the present invention is a salt commercially available as CALGON.RTM. from ICL performance Products LP, St. Louis, Missouri, which is sodium hexametaphosphate containing from about 6 to about 27 repeating phosphate units.

[096] Preferably, the phosphate-containing compound is selected from the group consisting of sodium trimetaphosphate having the molecular formula (NaPO ₃ ) ₃ , sodium hexametaphosphate containing 6-27 repeating phosphate units and having the molecular formula Na _{n + 2} P _n O _{3n + 1} where n = 6-27, tetrakalium pyrophosphate having the molecular formula Na ₃ K ₂ P ₃ O ₁₀ , sodium tripolyphosphate having the molecular formula Na ₅ P ₃ O ₁₀ , tetrasodium pyrophosphate having the molecular formula Na ₄ P ₂ O ₇ , aluminum trimetaphosphate, having the molecular formula Al (PO _{3) 3,} acid pyrophosphate sodium having the molecular formula Na ₂ H ₂ P ₂ O _7, ammonium polyphosphate having 1000-3000 repeating phosphate units and having the molecular formula (NH _{4) n + 2} P _n O _{3n + 1} wherein n = 1000-3000, and polyphosphoric an acid containing 2 or more repeating units of phosphoric acid and having the molecular formula H _{n + 2} P _n O _{3n + 1} where n is 2 or more. Most preferred is sodium trimetaphosphate, commercially available from ICL performance Products LP, St. Louis, Missouri.

[097] Phosphates are usually added in dry form and / or in liquid form in an aqueous solution, the dry ingredients being introduced into the mixer to suspend the middle layer, the liquid ingredients being introduced into the mixer, or at other stages or methods.

[098] Dispersants. In another aspect of the fire-resistant panels of low weight and density, according to the present invention, and methods for manufacturing these panels, dispersants may be included in the gypsum core suspension. Dispersants can be administered dry together with other dry ingredients and / or in an aqueous solution in liquid form, together with other liquid ingredients in the mixing operation of the suspension of the middle layer, or at other stages or procedures.

[099] In one important aspect, said dispersants may include naphthalenesulfonates, such as polynaphthalene sulfonic acid and salts of the indicated acid (polynaphthalene sulfonates), and derivatives which are condensation products of naphthalenesulfonic acids and formaldehyde. Specified desired polynaphthalenesulfonates include sodium and calcium naphthalenesulfonate. The average molecular weight of naphthalenesulfonates can vary from about 3000 to 27000, although it is preferable that the molecular weight is from about 8000 to 10000. For a given percentage of dry matter in an aqueous solution, a dispersant with a higher molecular weight has a higher viscosity and generates more water consumption in composition than a dispersant with a lower molecular weight.

[0100] Suitable naphthalenesulfonates include DILOFLO, available from GEO Specialty Chemicals, Cleveland, Ohio; DAXAD, available from Hampshire Chemical Corp., Lexington, Massachusetts; and LOMAR D, available from GEO Specialty Chemicals, Lafayette, Indiana. Naphthalenesulfonates are preferably used in the form of aqueous solutions with a dry matter content, for example, in the range of 35-55% by weight. Most preferably, the use of naphthalenesulfonates in the form of an aqueous solution with a dry matter content, for example, in the range of 40-45% by weight. Alternatively, if possible, naphthalenesulfonates can be used in dry, solid or powder form, for example, such as LOMAR D.

[0101] Alternatively, in other aspects of the present invention, polycarboxylate dispersants suitable for improving the flowability of gypsum suspensions may be used. A number of polycarboxylate dispersants, especially polycarboxyl ethers, are preferred types of dispersants. One of the preferred classes of dispersants used in suspensions includes two repeating units. Said dispersant is further described in US Pat. No. 7,767,019, entitled "Gypsum Products Utilizing a Two-Repeating Unit System and Process for Making Them", the contents of which are incorporated herein by reference. These dispersants are products of BASF Construction Polymers, GmbH (Trostberg Germany) and are supplied by BASF Construction Polymers, Inc. (Kennesaw, GA) (hereinafter “BASF”) and are referred to hereinafter as “PCE211 type dispersants”. A particularly suitable dispersant of dispersants of the PCE211 type is designated PCE211 (hereinafter “211”). Other polymers from this series suitable for the present invention include PCE111. Dispersants of the PCE211 type are more fully described in US patent application No. 11/827,722 (Publication number US 2007/0255032 A1), filed July 13, 2007, entitled "Polyether-Containing Copolymer", the contents of which are incorporated into this application by reference.

[0102] The molecular weight of one of the types of said dispersants of the PCE211 type may be from about 20,000 to about 60,000 Daltons. It has been found that dispersants with a lower molecular weight cause a slower setting time than dispersants having a molecular weight above 60,000 Daltons. In general, the large length of the side chain, which leads to an increase in the total molecular weight, provides dispersibility. However, tests with gypsum have shown that the effectiveness of the dispersant is reduced if the molecular weight exceeds 50,000 Daltons.

[0103] Another class of polycarboxylate compounds suitable as dispersants according to the present invention is described in US Pat. Dispersants type PCE211 and type 2641 are manufactured by BASF Construction Polymers, GmbH (Trostberg, Germany) and sold in the USA by BASF Construction Polymers, Inc. (Kennesaw, Ga.). Preferred type 2641 dispersants are sold by BASF as the MELFLUX 264IF, MELFLUX 265IF and MELFLUX 2500L dispersants.

[0104] Another preferred group of dispersants is sold by BASF and is designated as “Type 1641 Dispersants”. These dispersants are more fully described in US Patent No. 5798425, the contents of which are incorporated into this application by reference. One such type 1641 dispersant is a dispersant sold by BASF under the name MELFLUX 1641F dispersant. Other dispersants that can be used include other polycarboxylate ethers, such as SOATEH Ethacryl M, available from Coatex, Inc. of Chester, SC and lignosulfonates or sulfonated lignin. Lignosulfonates are water-soluble anionic polyelectrolyte polymers, by-products of cellulose production using sulfite technology. One example of a lignin suitable for the present invention is Marasperse C-21, available from Reed Lignin, Greenwich, Conn.

[0105] Moderators / Accelerator. Setting retarders (up to about 2 pounds per thousand square feet (9.8 g / m ² )) or dry accelerators (up to about 35 pounds per thousand square feet (170 g / m ² )) can be introduced into some aspects suspension of the middle layer to change the rate at which the hydration reactions of gypsum occur. "CSA" is a setting accelerator comprising 95% calcium sulfate dihydrate, milled together with 5% sugar, and then heated to 250 ° F (121 ° C) to caramelize sugar. CSA is available from USG Corporation, Southard, Okla. plant, and obtained according to US patent No. 3573947, the contents of which are incorporated into this application by reference. Potassium sulfate is another preferred accelerator. HRA, which is the preferred accelerator, is calcium sulfate dihydrate freshly ground with sugar in a ratio of about 5 to 25 pounds of sugar per 100 pounds of calcium sulfate dihydrate. The specified accelerator is further described in US Patent No. 2078199, the contents of which are incorporated into this application by reference. Both of these accelerators are preferred.

[0106] Another accelerator, known as a wet gypsum accelerator or WGA, is also a preferred accelerator. A description of the application and method of producing a wet gypsum accelerator is presented in US Pat. No. 6,409,825, the contents of which are incorporated herein by reference. The specified accelerator includes at least one additive selected from the group consisting of an organic phosphonic compound, a phosphate-containing compound or mixtures of these compounds. This particular accelerator has significant durability and remains effective for such a time that the wet gypsum accelerator can be produced, stored and even transported over long distances before use. A wet gypsum accelerator is used in amounts ranging from about 5 to about 80 pounds per thousand square feet (24.3 to 390 g / m ² ) of gypsum board.

[0107] The foam. In one important aspect, foam can be added to the suspension of the middle layer in amounts that provide the aforementioned reduced density of the middle layer and the weight of the panel. The introduction of foam into the suspension of the middle layer in appropriate quantities, compositions and methods will provide the desired network and the distribution of voids in the middle layer of the finished dried panels. The indicated structure of voids allows to reduce the amount of gypsum and other components of the middle layer, and the mass and density of the middle layer, while maintaining the required structural and strength properties of the panels. Examples of the use of blowing agents to obtain the desired void structures include those discussed in US Pat. No. 5,643,510, the contents of which are incorporated herein by reference. Approaches for introducing foam into the middle layer slurry are known in the art, and one example of these approaches is discussed in US Pat. No. 5,683,635, the contents of which are incorporated herein by reference.

[0108] The facing sheets. In some aspects of the present invention, the first cladding sheet comprises a low porosity manila paper onto which a gypsum slurry is applied (said sheet is typically the exposed surface of the panel when used in construction applications). Newspaper paper can be used as a second cladding sheet to be placed on the middle layer slurry during the molding process (this sheet usually represents the back hidden surface of the panel when used in construction applications). In other applications, nonwoven fiberglass mats, sheet materials or other fibrous or non-fibrous materials, or combinations of paper with other fibrous materials can be used as one or both of the facing sheets.

[0109] In aspects using paper or similar cladding sheets, the first cladding sheet has a higher density and bulk than the second cladding sheet. For example, in some aspects, the first cladding sheet has a bulk of from about 40 to 60 pounds / thousand. sq. feet, and the second cladding sheet has a bulk of from about 35 to 45 pounds / thousand. sq. feet. The use of such heavy manila paper for the first cladding sheet is preferable because it improves the properties of the panel when pulling a nail and bending in all applications, and especially in ceiling applications.

[0110] The cladding sheets may be included, or surfaces of the cladding sheets may be coated with materials that provide surfaces suitable for particular building applications, such as cladding, roofing, tile base, etc.

[0111] Siloxane. Surprisingly, it was found that a combination of more than 2% by weight of the gypsum pregelatinized starch and at least about 0.4%, and preferably at least about 0.7% by weight of the siloxane gypsum, will provide gypsum panels with water absorption less than 5%. This is especially unexpected since panels with reduced mass and density contain much more voids for air and / or water than conventional panels, and it would be expected that these voids would make panels with low mass much more water-absorbing. It has also been unexpectedly discovered that polymerized silicone resins reduce panel shrinkage under high temperature heating conditions.

[0112] The present invention generally includes improving the water resistance of gypsum-based products by incorporating a polymerizable siloxane into the suspension used to make gypsum-based products. Preferably, siloxane is administered as an emulsion. The suspensions are then shaped and dried under conditions conducive to the polymerization of siloxane to form a highly crosslinked silicone resin. Preferably, a catalyst is added to the gypsum slurry to facilitate the polymerization of the siloxane to form a highly crosslinked silicone resin.

[0113] Preferably, the siloxane as a whole is a linear linear hydrogen-modified siloxane, but may also be a cyclic hydrogen-modified siloxane. Such siloxanes are capable of forming highly crosslinked silicone resins. Such liquids are well known to those of ordinary skill in the art, are commercially available and are described in the patent literature. Typically, the linear hydrogen-modified siloxane used in the practical implementation of the present invention includes a siloxane containing a repeating unit of the general formula:

where R represents a saturated or unsaturated monovalent hydrocarbon radical. In preferred embodiments, R is an alkyl group, and most preferably R is a methyl group. During polymerization, the end groups are removed by condensation and the siloxane groups are bonded together to form a silicone resin. Cross-linking of chains is also observed. The obtained silicone resin imparts water resistance to the gypsum matrix during its formation.

[0114] Preferably, solvent free liquid methyl hydrogen siloxane sold under the name SILRES BS 94 from Wacker-Chemie GmbH (Munich, Germany) will be used as the siloxane. The manufacturer indicates that this product is a liquid siloxane that does not contain water or solvents. It is believed that from about 0.3 to 1.0% siloxane BS 94 can be used, based on the weight of dry ingredients. It is preferable to apply from about 0.4 to about 0.8% siloxane by weight of dry gypsum.

[0115] Siloxane is prepared as an emulsion or stable suspension in water. A number of siloxane emulsions are contemplated for use in said suspension. Siloxane emulsions in water are also commercially available, but they may include emulsifying agents that tend to modify the properties of gypsum products, such as bond paper with gypsum panel products. Therefore, emulsions or stable suspensions obtained without the use of an emulsifier are preferred. Preferably, the suspension will be prepared in situ by mixing liquid siloxane with water. It is essential that the siloxane suspension is stable until use and remains well dispersed under suspension conditions. The siloxane suspension or emulsion should remain well dispersed in the presence of possible additives, such as setting accelerators, which may be present in the suspension. The siloxane emulsion or suspension should also remain stable throughout the stages of gypsum panel formation. Preferably, the suspension remains stable for more than 40 minutes. More preferably, the suspension remains stable for at least one hour. Further, in the discussion and the claims, the term "emulsion" is intended to include stable emulsions and suspensions, which are stable at least until hardening of gypsum by 50%.

[0116] Without wishing to be limited by theory, it is believed that water resistance develops upon curing of siloxane inside the formed panels, and that at least 2.0% by weight of pregelatinized starch acts together with siloxane, slowing the flow of water through micropores at the edges of the panel, primarily , blocking the flow of water, and then, after absorbing water with starch, by forming a highly viscous starch / water combination.

[0117] The siloxane polymerization reaction itself proceeds slowly, and it is necessary to store the panels for sufficient time to develop water resistance before transportation. It is known that catalysts accelerate the polymerization reaction, reducing or eliminating the time required to store gypsum panels during the development of water resistance. The use of tightly calcined magnesium oxide for the polymerization of siloxane is described in co-pending US Patent Application No. 10/917177, entitled “Method of Making Water-Resistant Gypsum-Based Article”, the contents of which are incorporated herein by reference. Deadly calcined magnesium oxide is insoluble in water and interacts less with other components of the suspension. It accelerates the cure of siloxane and, in some cases, causes a more complete cure of siloxane. It is commercially available with a permanent composition. An especially preferred source of deadburned magnesium oxide is BAYMAG 96. It has a BET surface area of at least 0.3 m ² / g. Loss on ignition less than 0.1% by weight. Magnesium oxide is preferably used in amounts of from about 0.1 to about 0.5% by weight of dry gypsum.

[0118] There are at least three types of magnesium oxide on sale, depending on the firing temperature. The “dead burned” magnesium oxide is fired between 1500 ° C and 2000 ° C, eliminating most, if not all, of the activity. The MagChem P98-PV (Martin Marietta Magnesia Specialties, Bethesda, Md.) Is an example of “deadburned” magnesium oxide. BayMag 96 (Baymag, Inc. of Calgary, Alberta, Canada) and MagChem 10 (Martin Marietta Magnesia Specialties, Bethesda, Md.) Are examples of “heavily burned” magnesium oxide. Highly calcined magnesium oxide is calcined between 1000 ° C and 1500 ° C. It has a narrow range of activity, high density, and is commonly used in applications requiring slow decomposition or chemical activity, such as animal feed and fertilizer. The third type is “lightly burnt” or “caustic” magnesium oxide obtained by calcination at temperatures from about 700 ° C to about 1000 ° C. This type of magnesium oxide is used in a wide range of applications, including the processing of plastic, rubber, paper and cellulose, additives in steel steam boilers, adhesives and acid neutralization. Examples of lightly calcined magnesium oxide include BayMag 30, BayMag 40 and BayMag 30 (-325 Mesh) (BayMag, Inc. of Calgary, Alberta, Canada).

[0119] It has been found that the preferred catalysts are obtained from a mixture of magnesium oxide and Class C fly ash. When combined in this manner, any kind of magnesium oxide is suitable. Nevertheless, tightly fired and heavily fired magnesium oxides are preferred due to reduced activity. The relatively high activity of magnesium oxides can lead to cracking reactions with possible hydrogen evolution. When hydrogen is released, the product expands, causing cracks where the gypsum has set. The expansion also causes the destruction of the forms in which the gypsum is poured, leading to loss of parts and deformation of the product in one or more dimensions. Preferably, BayMag 96, MagChem P98-PV and MagChem 10 are preferred sources of magnesium oxide. Preferably, magnesium oxide and fly ash are added to the gypsum before the mixture is introduced into the mixing water. Dry components, such as those indicated, are often injected into the gypsum while it is moving along the conveyor to the mixer.

[0120] The preferred fly ash is Class C fly ash. Class C hydraulic fly ash is the most preferred fly ash component. A typical composition of Class C fly ash is shown in Table 1. Fly ash with a high lime content, more than 20% by weight of lime, is obtained from certain types of coal. ASTM Standard C-618, incorporated herein by reference, describes the characteristics of Class C fly ash. Preferred Class C fly ash is provided by Bayou Ash Inc., Big Cajun, II, L A. Preferably, fly ash is used. in an amount of from about 0.1% to about 5% by weight of dry gypsum. More preferably, fly ash is used in an amount of from about 0.2% to about 1.5% by weight of dry gypsum.

[0121] Catalysis of siloxane leads to faster and more complete polymerization and crosslinking of the siloxane to form a silicone resin. Hydration of building gypsum forms an interwoven matrix of calcium sulfate dihydrate crystals. During the formation of the gypsum matrix, the siloxane molecules also form a silicone resin matrix. Since these matrices are formed simultaneously, at least partially, these two matrices are intertwined. Excess water and slurry additives, including fly ash, magnesium oxide and the additives described below, which were dispersed in the volume of the suspension, are dispersed in the matrices between the particles to achieve water resistance throughout the middle layer of the panel. The high content of pregelatinized starch acts together with siloxane to slow the penetration of water along the most vulnerable edges of the panel.

[0122] In some embodiments, the gypsum panel includes a cured gypsum middle layer between the upper and lower facing sheets. The panel has a density of the middle layer from about 27 to about 37 pounds per cubic foot and a thermal insulation index of more than about 17 minutes. In other embodiments, the gypsum board has a nominal thickness of about 0.625 inches. In other embodiments, the gypsum board has a nominal thickness of about 0.625 inches and a thermal insulation index of at least about 18 minutes.

[0123] In some embodiments, the fire resistant gypsum board comprises a cured gypsum core layer between the upper and lower facing sheets. The panel has a mid-layer density of from about 27 to about 37 pounds per cubic foot. The panel effectively slows down heat transfer through a structure prepared and tested by fire according to UL U419 methods, with one surface being exposed to a heat source and the opposite surface not being heated, so that the maximum temperature at one point on an unheated surface is less than about 415 ° F within 30 minutes when measured according to UL U419. In other embodiments, the fire resistant gypsum board effectively slows down heat transfer through the structure, so that the average temperature on an unheated surface is less than about 340 ° F for about 30 minutes when measured according to UL U419.

[0124] In some embodiments, the fire resistant gypsum board comprises a cured gypsum core layer between the upper and lower facing sheets. The panel has a mid-layer density of from about 27 to about 37 pounds per cubic foot. The panel effectively slows down heat transfer through a structure prepared and tested by fire according to UL U305 methods, with one surface being exposed to a heat source and the opposite surface not being heated, so that the maximum temperature at one point on an unheated surface is less than about 415 ° F within 45 minutes when measured according to UL U305.

[0125] In other embodiments, the fireproof gypsum board effectively slows down heat transfer through the structure, so that the maximum temperature at one point on an unheated surface is less than about 270 ° F for about 45 minutes when measured according to UL U305. In other embodiments, the fireproof gypsum board effectively slows down heat transfer through the structure, so that the average temperature on an unheated surface is less than about 340 ° F for about 45 minutes when measured according to UL U305. In other embodiments, the fire resistant gypsum board effectively slows down heat transfer through the structure, so that the average temperature on an unheated surface is less than about 245 ° F for about 45 minutes when measured according to UL U305.

[0126] In some embodiments, the panel has a middle layer density of from about 27 to about 37 pounds per cubic meter and a thermal insulation index above about 17.0 minutes. The gypsum panel contains: (a) approximately 1220-1750 pounds / thousand. sq. feet of set gypsum; (b) about 0.3-4.0% by weight of pregelatinized starch; (c) about 0.15-0.50% by weight of a phosphate-containing component; (d) about 0.3-1.5% by weight of a dispersant; (e) about 0.1-0.3% by weight of mineral, glass or carbon fiber; and (f) the cavity of the foam in an amount effective to provide a certain density of the panel. Percentages by weight are calculated from the weight of the set gypsum, and pounds / thousand. sq. ft. are for a panel with a nominal thickness of 0.625 inches. In other embodiments, sales of pounds / thousand. square feet of set gypsum is proportionally corrected for a panel with a nominal thickness of from about 0.625 to about 0.75 inches.

[0127] In other embodiments, the gypsum board comprises: (a) about 1315-1610 pounds / thousand. sq. feet of set gypsum; (b) about 0.5-2.0% by weight of pregelatinized starch; (c) about 0.10-0.15% by weight of phosphate; (d) about 0.5-1.2% by weight of a dispersant; (e) about 0.1-0.3% by weight of mineral, glass or carbon fiber; and (f) the cavity of the foam in an amount effective to provide a certain density of the panel. Percentages by weight calculated from the weight of the set gypsum, pounds / thousand square feet are given for panels with a nominal thickness of 5/8 inches and are proportionally adjustable for thicker or thinner panels.

[0128] In other embodiments, the gypsum board comprises: (a) about 1360-1460 pounds / thousand. sq. feet of set gypsum; (b) about 1.5-1.8% by weight of pregelatinized starch; (c) about 0.10-0.15% by weight of phosphate; (d) about 0.75-1.0% by weight of a dispersant; (e) about 0.1-0.3% by weight of mineral, glass or carbon fiber; and (f) the cavity of the foam in an amount effective to provide a certain density of the panel. Percentages by weight calculated from the weight of the set gypsum, pounds / thousand square feet are given for panels with a nominal thickness of 5/8 inches and are proportionally adjustable for thicker or thinner panels.

[0129] In other embodiments, the gypsum panel comprises paper cladding sheets, the first cladding sheet having a mass of about 40-60 pounds / thousand. sq. feet. In other embodiments, the panel density is from about 29 to about 34 pounds per cubic foot. In other embodiments, the density of the panel is from about 30 to about 32 pounds per cubic foot.

[0130] In other embodiments, the gypsum panel contains at least 0.4% by weight of siloxane by weight of the set gypsum. In some embodiments, the high-temperature shrinkage of the panel is less than the high-temperature shrinkage of the panel of the same amounts of components without siloxane. In some embodiments, the gypsum board contains more than 2% by weight of pregelatinized starch. In some embodiments, the high-temperature shrinkage of the panel is less than the high-temperature shrinkage of the panel of the same amounts of components without siloxane. In some embodiments, the high-temperature shrinkage of the panel is about 50% of the high-temperature shrinkage of the panel of the same amounts of components without siloxane.

[0131] In other embodiments, the phosphate-containing component is soluble in water and selected from the group consisting of condensed phosphoric acid containing two or more phosphoric acid units, a salt or condensed phosphate ion containing two or more phosphate units, a monobasic salt or a monovalent orthophosphate ion and combinations of these compounds. In some embodiments, the phosphate-containing component comprises cyclic polyphosphate.

[0132] In some embodiments, the construction of the gypsum panels is mounted on metal supports. Gypsum panels comprise a middle layer of hardened gypsum between the upper and lower facing sheets. The middle layer has a density of from about 27 to about 37 pounds per cubic foot and provides a design with an established fire resistance of at least 30 minutes in a test according to UL U419 methods. In some embodiments, gypsum panels are mounted in the structure, and gypsum panels provide an installed fire resistance of at least 30 minutes in a test according to UL 305 procedures.

[0133] In some embodiments, a method of manufacturing a fire resistant gypsum board having a thermal insulation index of at least 17.0 minutes comprises providing a slurry. The suspension contains: (a) approximately 1040-1490 pounds / thousand sq. feet of gypsum, (b) about 0.3-4.0% by weight of pregelatinized starch, (c) about 0.15-0.50% by weight of phosphate, (d) about 0.3-1.5 % by weight of dispersant, (e) about 0.1-0.3% by weight of mineral, glass or carbon fiber; and (f) an amount of foam effective to provide a middle layer density of from about 25 to about 36 pounds per cubic foot. The suspension is applied to the first facing sheet. The suspension is covered with a second facing sheet to form a panel. A predetermined nominal panel thickness is maintained while the middle layer slurry is hydrated. The panel is cut into the required dimensions. The panel is dried. Percentages by weight calculated on the weight of gypsum, and pounds / thousand. sq. ft. are for a panel with a nominal thickness of 0.625 inches.

[0134] In other embodiments, pounds / thousand values. square feet of gypsum are proportionally adjustable for panels with a nominal thickness of from about 0.625 to about 0.75 inches. In other embodiments, the construction of gypsum panels made by the method of the present invention is mounted on metal supports. This design provides an installed fire resistance of at least 30 minutes in a test according to UL U419 methods.

EXAMPLES

[0135] The following examples further illustrate aspects of the invention described herein, but are not intended to limit the scope of the present invention in any way. All values specified in the present description (for example, masses, percentages, temperatures, sizes, times, etc.) are established as a result of measurements and include measurement deviations and error limits reflected in the data, as well as those with which usually one of ordinary skill in the art will encounter a particular component, test, property, or observation to which the values relate.

Example 1

[0136] the Composition of samples of gypsum suspension.

[0137] The compositions of the gypsum slurry are shown in Table 1 below. All values in Table 1 are expressed as mass percentages of the weight of dry gypsum. The values in parentheses represent the dry weight in pounds (pounds / thousand square feet for a panel with a nominal thickness of 1/2 inch).

Example 2

[0138] The manufacture of panels.

дюйма) изготавливали согласно Патентам США №№6342284, выданному Yu et al. и 6632550 выданному Yu et al., содержание которых включено в настоящую заявку посредством ссылок. Способ включал отдельное получение пены и введение пены в суспензию из других ингредиентов, как описано в Примере 5 указанных патентов.[0139] Samples of gypsum panels (nominal thickness approximately

inches) were made according to US Patent No. 6342284 issued by Yu et al. and 6,632,550 to Yu et al., the contents of which are incorporated herein by reference. The method included separately preparing the foam and introducing the foam into the suspension from other ingredients, as described in Example 5 of these patents.

дюйма толщиной и имела массу между примерно 1600 и 1800 фунтов на 1000 квадратных футов материала или фунтов/тыс. кв.футов. («тыс. кв.футов» представляет собой стандартное сокращение в данной области техники для тысячи квадратных футов; это единица измерения площади для коробок, гофрированного материала и стеновых панелей).[0140] The test results of gypsum panels made using Compounds A and B from Example 1 and a control sample are shown in Table 2 below. In the present example and in the other examples below, tests for resistance to pulling a nail, hardness of the middle layer and bending strength were carried out according to ASTM C-473. Additionally, a typical gypsum panel was approximately

inches thick and had a mass between about 1,600 and 1,800 pounds per 1,000 square feet of material or pounds / thousand. sq. feet. (“Thousand square feet” is the standard abbreviation for thousands of square feet in the art; this is a unit of area for boxes, corrugated material, and wall panels).

[0141] As shown in Table 2, gypsum panels made from suspensions of Compounds A and B had a significant reduction in weight compared to a control plate. Referring again to Table 1, the comparison of a plate of Composition A with a plate of Composition B is most convincing. Water / gypsum (w / g) ratios are similar for Composition A and Composition B. A significantly higher content of naphthalenesulfonate dispersant was also used in Composition B. Also, significantly more pregelatinized starch was used in Composition B, about 6% by weight, more than 100% more than in Composition A, which was accompanied by a noticeable increase in strength. Even though the water flow rate to obtain the desired flow rate remained low for the suspension of Composition B, the difference was approximately 10% compared to Composition A. The low water consumption in both compositions is attributed to the synergistic effect of the combination of naphthalenesulfonate dispersant and sodium trimethaphosphate in the gypsum suspension, which increases the fluidity of the gypsum slurry, even in the presence of a significantly higher amount of pregelatinized starch.

[0142] As shown in Table 2, gypsum panels made from a suspension of Composition B had significantly increased strength compared to panels made from a suspension of Composition A. Due to the inclusion of increased amounts of pregelatinized starch in combination with increased amounts of naphthalenesulfonate dispersant and sodium trimethaphosphate, the resistance to pulling a nail for a plate of Composition B increased by 45% compared with a plate of Composition A. A significant increase in bending strength was also observed for the plate Compost Ava B compared to a slab of Composition A.

Example 3

[0143] Tests for weight reduction of a gypsum board 1/2 inch thick.

[0144] Additional examples of gypsum panels (boards C, D, and E), including suspension formulations and test results, are shown in Table 3 below. The composition of the suspensions in Table 3 include the main components of the suspensions. The values in parentheses are expressed in mass percent by weight of dry gypsum.

[0145] As shown in Table 3, boards C, D, and E were made from a suspension containing significantly increased amounts of starch, DILOFLO dispersant, and sodium trimetaphosphate, compared to control panels (approximately a twofold increase in the percentage of starch and dispersant, and two - - a three-fold increase in the content of trimetaphosphate), while maintaining a constant ratio in / g. However, the strength, measured as resistance to pulling a nail, was not significantly affected, while the weight of the panels was significantly reduced. Therefore, in the indicated example of an embodiment of the present invention, a new composition (such as, for example, plate D) with an increased starch content in a suitable fluid suspension can be provided, while maintaining a suitable strength.

Example 4

[0146] Strength test of wet gypsum cube

[0147] Wet gypsum cube strength tests were carried out using Southard CKS slab gypsum available from the United States Gypsum Corp., Chicago, Illinois and tap water in a laboratory to determine wet compressive strength. The following laboratory test procedure was used.

[0148] Building gypsum (1000 g), CSA (2 g), and tap water (1200 cm ³ ) at about 70 ° F were used to cast each wet gypsum cube. Pregelatinized corn starch (20 g, 2.0% by weight of building gypsum) and CSA (2 g, 0.2% by weight of building gypsum) were thoroughly mixed in dry form, first in a plastic bag with building gypsum before mixing with the solution in tap water water containing both naphthalenesulfonate dispersant and sodium trimetaphosphate. The dispersant used was a DILOFLO dispersant (1.0-2.0%, as indicated in Table 4). Used various amounts of sodium trimetaphosphate, also shown in Table 4.

[0149] The dry ingredients and the aqueous solution were first combined in a Warning laboratory mixer, the resulting mixture was allowed to swell for 10 seconds, and then the resulting mixture was stirred at low speed for 10 seconds to obtain a suspension. Then, the resulting suspension was cast in three cubic forms 2``X2''X2 ''. The molded cubes were then removed from the molds, weighed, and sealed in plastic bags to prevent moisture loss prior to the compressive strength test. The compressive strength of wet cubes was measured using an ATS apparatus and recorded as the average value in pounds per square inch (psi). Got the following results:

[0150] As shown in Table 4, samples 4-5, 10-11, and 17 having sodium trimetaphosphate in the range of about 0.12-0.4% according to the present invention generally provided superior wet cube compressive strength compared to with samples in which the content of sodium trimetaphosphate was outside the specified range.

Example 5

[0151] Pilot production of gypsum board with low weight, 1/2 inch thickness.

[0152] Additional tests were performed (test boards 1 and 2), including suspension compositions and test results shown in Table 5 below. The composition of the suspensions in Table 5 include the main components of the suspensions. The values in parentheses are expressed in mass percent by weight of dry gypsum.

[0153] As shown in Table 5, the test boards 1 and 2 were made from a suspension containing significantly increased amounts of starch, a DILOFLO dispersant and sodium trimetaphosphate, with a slightly reduced W / g ratio compared to control panels. However, the strength, measured by the resistance of pulling the nail and bending test, was maintained or improved, and the weight of the panel was significantly reduced. Therefore, in the indicated example of an embodiment of the present invention, a new composition can be provided (such as, for example, test boards 1 and 2) with an increased content of sodium trimetaphosphate and starch in a suitable fluid suspension, while maintaining the required strength.

Example 6

[0154] Pilot production of gypsum board with very low weight, 1/2 inch thickness.

[0155] Additional tests were performed (test boards 3 and 4), including Composition B (Example 1) as in Example 2, except that pregelatinized corn starch was prepared with water at a concentration of 10% (wet starch preparation) and a mixture was used HYONIC PFM Soaps (available from GEO Specialty Chemicals, Lafayette, Indiana). For example, the test plate 3 was obtained using a mixture of HYONIC PFM 10 / HYONIC PFM 33 in the range of 65-70% wt./35-30% of the mass. For example, the test plate 4 was obtained using a mixture of 70/30 wt./mass. HYONIC PFM 10 / HYONIC PFM 33. The results of the experiments are shown in Table 6 below

[0156] As shown in Table 6, the strength characteristics, measured as the resistance to pulling the nail and the hardness of the middle layer, exceeded the ASTM standard. The bending strength according to the measurement results also exceeded the ASTM standard. Again, in the indicated example of an embodiment of the present invention, a new composition can be provided (such as, for example, test plates 3 and 4) with an increased content of sodium trimetaphosphate and starch in a suitable fluid suspension, while maintaining the required strength.

Example 7

[0157] Conducted a test for high temperature insulation according to the methodology described in ASTM Pub. WK25392 for studying the characteristics of high temperature thermal insulation of 5/8 inch thick gypsum panels made according to the present invention.

[0158] The heat transfer conditions reflected in this test can be described by the energy equation for one-dimensional non-stationary thermal conductivity through the thickness of the panel:

[0159] Where T is the temperature at a given time t at a depth x in the panel. The thermal conductivity coefficient (k), density (ρ), and specific heat (c _p ) at elevated temperatures are nonlinear temperature-dependent functions. The heat release rate q represents a series of endothermic and exothermic reactions, for example, phase transitions of gypsum and burning paper on the surface, which are observed at different temperatures and, accordingly, at different points in time.

[0160] In order to evaluate the overall thermal conductivity through the gypsum panel, and therefore the thermal insulation properties of the panel, it is usually not necessary to measure and describe each variable individually. It is enough to evaluate their cumulative cumulative effect on heat transfer.

[0161] For this purpose, a high temperature thermal insulation test was developed in which samples consisting of two 4 inch (100 mm) diameter discs fastened together by type G horn head screws were tested.

[0162] Samples for testing were obtained from gypsum panels made using the middle layer containing:

[0163] A thermocouple was placed in the center of the sample between the disks. The sample was then mounted on a rib in a rack designed to provide uniform heating over the entire surface of the sample, and placed in a furnace preheated to 930 ° F (500 ° C).

[0164] The temperature rise in the center of the test sample was recorded and the thermal insulation index, TI, was calculated as the time, in minutes, needed to heat the test sample from about 105 ° F (40 ° C) to about 390 ° F (200 ° C). The thermal insulation index of the sample was calculated as:

[0165] The temperature profile, based on data collected by this methodology, often shows the transition from gypsum to hemihydrate at a temperature of about 212 ° F (100 ° C) and the transformation of the hemihydrate into the first phase of anhydrite at about 285 ° F (140 ° C) ) Such data also often show that these phase transitions are complete, the temperature rises rapidly in a linear fashion, and no additional chemical or phase reactions are usually observed at an oven temperature below about 930 ° F (500 ° C). Repeatability and reproducibility of the results were achieved by waiting until the temperature of the middle layer of the sample reached approximately 105 ° F (40 ° C), to start the timing.

[0166] The above thermal insulation test was carried out on disks cut from 5/8 inch thick gypsum panels made according to the present invention having a panel weight of 1,545 pounds / thousand. sq. feet. These samples had an average thermal insulation of 18.6 minutes. In comparison, the average thermal insulation value for a commercially available panel weighing approximately 1,500 pounds / thousand. sq. feet, with a nominal thickness of 1/2 inch, for interior ceilings was 17.0 minutes. It was unexpected that the panel according to the present invention (with a density of the middle layer of about 30 pounds / ft ³ ) had a greater thermal insulation index than a panel of approximately the same mass, but with a higher density of the middle layer (about 35 pounds / ft ³ ).

Example 8

[0167] The panel samples of the present invention were tested according to UL U419 method using gypsum panels with a nominal thickness of 5/8 inches according to the present invention, having a panel weight of about 1546 pounds / thousand. sq. feet containing:

[0168] The physical characteristics of the 4 ′ × 10 ′ gypsum panels were as follows:

'' дюйма толщиной. Стальные стойки малого сечения размещали через 24 дюйма в конструкции согласно U419.[0169] In a test according to U419, wall structures of 10 feet by 10 feet were assembled. The racks were commercially available steel racks of small cross section made of steel from about 0.015 inches thick to about 0.032 inches thick and measuring about 3 5/8 '' or 3 1/2 '' inches wide and about 1

'' inches thick. Small steel struts were placed after 24 inches in the structure according to U419.

[0170] The tests according to U419 are considered one of the most stringent types of UL tests, since steel racks of small cross section often experience thermal deformation (usually bringing exposed panels closer to the flame of a gas burner furnace) due to heat transfer through the panels and into the structural cavity between the exposed and not exposed by panels. Said deformation often causes a divergence of the panel joints, or other disturbances, on the heated, exposed side of the structure, allowing the flame of the gas burner and / or high temperature to penetrate into the cavity of the structure and into the unaffected side of the structure. It is expected that the lighter the size of the steel posts, the higher the likelihood of thermal deformation of the posts and structure.

[0171] Gypsum panels were attached horizontally, i. perpendicular to the uprights on each side of the structure. Usually on each side of the frame two panels of 10 feet by 4 feet and one panel of 10 feet by 2 feet were used. The panels were attached to the frame using one-inch type S double-threaded screws on each side of the assembly, eight inches from the center. The panels were positioned so that the seams between the panels on each side of the frame coincided. Then the seams were sealed with paper connecting adhesive tape and suture sealant. In tests according to U419, the steel used for the steel racks of small cross-section had a thickness of 0.015 inches or 0.018 inches, and the assembly was not subjected to external loading.

[0172] In each of the tests, the finished panel and frame structure was positioned so that one side of the structure, the exposed side, was exposed to a flame jet from a gas burner furnace that heated the exposed side to temperatures and at a speed determined by ASTM 119. According to U419, a set of approximately 14 sensors was placed at a certain distance between the heated exposed side of the structure and each of the gas burners for The temperature used to heat the exposed side of the structure. Also, according to these methods, a set of sensors was placed at a certain distance on the opposite side of the structure, unheated, not exposed. Typically, 12 sensors were used on the non-impacted side of the circuit according to UL methodology. According to the indicated methods, each sensor was covered with an insulating gasket.

[0173] In the test methods, the temperatures of the gas burner furnace were used according to the heating curve of ASTM-119, starting from room temperature and raising the temperature on the exposed side of the structure to temperatures above 1600 ° F, for approximately one hour, while rapid temperature changes were observed at the beginning of the test and near the end of the test. The test was terminated either when a catastrophic failure occurred under load on the exposed side of the structure, or when the average temperatures from the sensors on the exposed side of the structure exceeded a pre-selected temperature (250 ° F above room temperature), or when the temperature from a single sensor on the non-exposed side of the structure, exceeded the second pre-selected temperature (325 ° F above room temperature).

[0174] The data obtained during the U419 test are plotted in Figures 1 and 2. Figure 1 is a graph of temperatures recorded by a single sensor at which the temperature reached its maximum when the test was terminated, and a graph of average temperatures recorded by sensors from the start of the test until the test is terminated. Figure 1 also shows a graph of the temperature curve of ASTM 119 used for furnace temperatures on the heated, exposed side of the structure. Figure 2 is an extended graph of data recorded by a single sensor at which the temperature has reached a maximum and average temperatures recorded by the sensors shown in Figure 1.

[0175] As shown in Figures 1 and 2, both the maximum temperatures recorded by a single sensor and the average temperatures recorded by sensors on the non-exposed side of the structure gradually increased during the test compared to furnace temperatures, with a faster increase observed for temperatures recorded by a single sensor near the end of the test. For example, after about 20 minutes, the maximum temperature from the sensor and the average temperature from the sensors on the non-exposed side of the structure were less than about 180 ° F and about 175 ° F, respectively. After approximately 25 minutes, the maximum temperature from the sensor and the average temperature from the sensors on the non-exposed side of the structure were less than about 195 ° F and about 190 ° F, respectively. After approximately 30 minutes, the maximum temperature from the sensor and the average temperature from the sensors on the non-exposed side of the structure were less than about 230 ° F and about 215 ° F, respectively. The maximum temperature recorded by a single sensor did not exceed 300 ° F, for approximately 30 minutes from the start of the test, at a temperature of less than about 410 ° F after about 35 minutes. The average temperature recorded by the sensors did not exceed 300 ° F until the end of the test after more than about 35 minutes, at a temperature of less than about 290 ° F after about 35 minutes.

[0176] The panels of the present invention also met criteria such as the criteria used to establish the UL degrees of fire resistance, as evidenced by the data shown in Figures 1 and 2. The panels of the present invention met the criteria for granting them a degree of fire resistance of “30 minutes” . Among other requirements, these criteria require that the average temperature from the sensors on the non-exposed side of the structure does not exceed room temperature at the start of the test plus 250 ° F and the maximum temperature from a separate sensor does not exceed room temperature at the time of the test plus 325 ° F (typically, the room temperature in this test is about 90 ° F or less). The temperatures from the test according to U419 according to the specified criteria are given below.

[0177] Therefore, this test showed that the panels according to the present invention have the ability to significantly delay the passage of heat through the wall or ceiling structures by more than 30 minutes according to the very rigid test flow U419. Thus, despite the low density of the middle layer of the panels and the low weight of the panels relative to the thickness of the panels, the panels of the present invention can play an important role in controlling the spread of fire inside buildings.

Example 9

[0178] The panels of the present invention were also tested according to the UL U305 protocol procedures using gypsum panels with a nominal thickness of 5/8 inches, made in accordance with the middle layer and liner formulations described in Example 8 above and having a panel weight of about 1580 pounds / thousand sq. feet.

[0179] The physical characteristics of the gypsum panels according to the present invention used in this test were as follows:

[0180] In this example, the test method according to the U305 protocol required load-bearing structures made of gypsum panels with a nominal thickness of 5/8 inches and a frame with wooden racks. According to U305 test methods, the panels of the present invention were attached to a frame, such as the frame discussed in Example 8 above, made of 2 # 4 Douglas fir racks (approximately 3.5 inches wide and 1.5 inches thick) spaced apart about 16 inches apart, and between the Douglass fir racks 2 × 4 base and roof plates. The panels were attached horizontally, with matching seams on opposite sides of the system, using nails 6d, the seams were glued with duct tape and sealed with a joint sealant. A load of approximately 17,800 pounds was placed on top of the structure.

[0181] The data obtained during the U305 test are shown in Figures 3 and 4. Figure 3 is a graph of temperatures recorded by a single sensor at which the temperature reached its maximum upon termination of the test, and a graph of average temperatures recorded by sensors from the start of the test to the termination tests. Figure 3 also shows a graph of the temperature curve of ASTM 119 used for furnace temperatures on the heated, exposed side of the structure. Figure 4 is an expanded graph of the data recorded by a single sensor at which the temperature reached a maximum and the average temperatures recorded by the sensors shown in Figure 3. The test was terminated due to structural failure under load after about 46 minutes.

[0182] As shown in Figures 3 and 4, both the maximum temperatures recorded by a single sensor and the average temperatures recorded by sensors on the non-exposed side of the structure gradually increased during the test compared to furnace temperatures on the heated side of the structure. For example, after about 20 minutes, the maximum temperature from the sensor and the average temperature from the sensors were less than about 175 ° F and about 165 ° F, respectively. After approximately 25 minutes, the maximum temperature from the sensor and the average temperature from the sensors were less than about 190 ° F and about 180 ° F, respectively. After approximately 30 minutes, the maximum temperature from the sensor and the average temperature from the sensors were less than about 205 ° F and about 190 ° F, respectively. The maximum temperature recorded by a single sensor did not exceed 300 ° F, even after about 45 minutes from the start of the test, at a temperature of less than about 225 ° F after about 35 minutes; less than about 245 ° F after about 40 minutes; and less than about 275 ° F after about 45 minutes. The average temperature recorded by the sensors did not exceed 300 ° F until the end of the test, at a temperature of less than about 205 ° F after about 35 minutes; less than about 230 ° F after about 40 minutes; and less than about 250 ° C after about 45 minutes.

[0183] the Panels according to the present invention also met criteria such as criteria giving the right to assign them a degree of fire resistance of "30 minutes", which is confirmed by the data shown in Figures 3 and 4. As discussed in Example 8, these criteria require that the average temperature from sensors on the side of the non-impacted structure did not exceed room temperature at the time of the start of the test plus 250 ° F and the maximum temperature from a separate sensor did not exceed room temperature at the time of the start of the test pole of 325 ° F (usually room temperature in this test is approximately 90 ° F or less). The temperatures from the test according to U305 according to the specified criteria are given below, where the result "does not exceed" indicates that the maximum temperature limits on the side of the structure not exposed are not reached until the test is terminated due to failure under load.

[0184] This test additionally showed that the panels according to the present invention are capable of providing significant fire resistance and protection, despite the low density of the middle layer of the panels and the low weight of the panels relative to the thickness of the panels. As shown in the above tests of U305, even under significant load, structures made using the panels of the present invention significantly delay the passage of heat through wall or ceiling structures for more than 30 minutes and at least 45 minutes under U305 test conditions.

Example 10

[0185] In this example, the panel of Example 8 was tested for resistance to pulling a nail to determine the strength properties of the panel according to the specified widely used criterion. The test for resistance to pulling a nail is a measure of the combination of strengths of the middle layer of the gypsum board, the facing sheets of the panel and the adhesion between the facing sheets and gypsum. In this test, the maximum force required to pull the nail with the cap through the panel was measured until a large crack in the panel was formed. In this Example, nail pull resistance tests were performed according to ASTM C 473-09.

[0186] Briefly summarizing, the test sample was tested at about 70 ° F and relative humidity of about 50% for 24 hours before testing. A 7/64 inch drill was used to drill guide holes over the entire thickness of the samples. Then, the sample was placed on the sample support panel with a hole in the center of a diameter of three inches, located perpendicular to the path of pulling the nail. A guide hole was mounted in line with the tip of the nail. A load was applied at a loading rate of one inch per minute until the maximum load was reached. At 90% of the peak load, after overcoming the peak load, the test was stopped and the peak load was recorded as resistance to pulling the nail.

[0187] The results of the nail pull resistance test are shown in Table 7 below.

[0188] The average nail pull resistance values for these examples of low weight and low density panels of the present invention averaged 87.4 lbf. This indicates that despite the low density of the panels according to the present invention, the panels according to the present invention can achieve values of resistance to pulling the nail, comparable to much heavier and denser gypsum panels with a set degree of fire resistance.

Example 11

[0189] Laboratory samples were prepared to evaluate the effect of introducing siloxane and siloxane together with pregelatinized starch into the gypsum slurry, and panels according to the present invention were made using this slurry. The compositions used in this test are shown in Table 8 below.

[0190] To obtain a siloxane emulsion, a mixer with high shear rates was used at a speed of about 7500 rpm for 2.5 minutes. The siloxane emulsion was mixed with building gypsum and slurry additives for 10 seconds swelling plus 10 seconds mixing at high speed in a Waring mixer. To assess the water resistance provided by the above compositions of the suspensions of the middle layer, 2 ″ × 2 ″ × 2 ″ cubes were cast from the suspension and dried at about 116 ° F. overnight for water absorption tests. Middle layer slurry formulations were also used to form panels of approximately one foot per one foot, 5/8 inch nominal thickness, by laboratory casting between paper cladding sheets, for the high temperature shrinkage and thermal insulation tests discussed in this example.

[0191] Using molten cubes, a water absorption test was carried out according to ASTM Method C1396 by placing dry cubes in water at 70 ° F for 2 hours and determining the weight gain in percent. This test showed water absorption levels of about 22% for a siloxane-only formulation, and a significantly improved water absorption level of about 3.4% and about 2.1% for 1% siloxane / 2% pregelatinized starch (20 grams) and 1% siloxane / 4% pregelatinized starch (40 grams), respectively.

[0192] The high temperature shrink test was carried out according to the methods developed and described in ASTM Pub. WK25392 for providing a quantitative determination of the shrinkage characteristics of gypsum panels according to the present invention at high temperatures. The thermal insulation test was carried out according to the methods discussed in Example 7. For the high-temperature shrinkage test and the thermal insulation test, ten disks with a diameter of 4 inches (100 mm) were cut from two samples of gypsum boards using a vertical drilling machine with a hole saw blade . Six of these disks were used for high temperature shrinkage tests and four disks were used for thermal insulation tests.

[0193] The high temperature shrinkage test methodology reflects the fact that the high temperature shrinkage that gypsum panels can undergo during a fire is influenced by several factors, in addition to the firing reactions that can occur in the middle layer of panels at high temperatures. The test report therefore used a non-ventilated furnace so that no air flow from outside the furnace could cool the test samples. The oven temperature was approximately 1560 ° F (850 ° C) to take into account the fact that shrinkage can occur in the anhydrite phases of the gypsum middle layer structures, as well as firing other high temperature effects acting under high temperature flame conditions.

[0194] To prevent thermal cracking of test samples, which may provide unreliable test results due to cracking and cracking, the test report was modified by placing test samples in an oven before heating to about 1560 ° F (850 ° C). Samples were kept at the indicated temperature for at least 20 minutes before turning off the oven. The oven door was closed until the oven cooled. Samples were not taken for measurements until the temperature dropped to a temperature close to room temperature.

[0195] Since the gypsum board is anisotropic, the amount of shrinkage will vary somewhat in length and width directions. Therefore, we performed two measurements at a right angle and took the average value to calculate the average diameter of the disk. In these tests, two measurements were performed at an angle of 90 ° and found that this approach provides a stable measurement of the average diameter for various samples. Typically, if two measurements for a disc differed by more than 0.01 inch (0.25 mm), the disc was rejected and measurements were excluded from the results. Shrinkage was calculated as the percentage change in average diameter after exposure to temperature and was designated “S,” the values were usually very close, about 0.1% for a group of six test samples.

[0196] As can be seen in Table 7, in addition to providing improved moisture resistance, the introduction of siloxane without the introduction of pregelatinized starch unexpectedly improved the shrink properties of the panel sample, reducing shrink from about 6% to about 3%. The introduction of pregelatinized starch increased the shrinkage of the samples compared to samples without the introduction of pregelatinized starch and to samples into which only siloxane was introduced. Said shrinkage increased with an increase in the amount of pregelatinized starch added. However, the combination of siloxane added and pregelatinized starch unexpectedly significantly improved the high temperature shrinkage of test samples. For example, the introduction of siloxane reduced the shrinkage of samples containing 20 grams of pregelatinized starch from more than 7% to less than 3.5%. Similarly, introducing siloxane into samples with 40 grams of pregelatinized starch reduced high temperature shrinkage from more than 8% to more than 6%. Therefore, the introduction of siloxane into the gypsum panels according to the present invention provides additional resistance to high temperature shrinkage, which should additionally and unexpectedly increase the flame retardant properties of the panels according to the present invention.

[0197] the Use of the terms in the singular and similar indicators in the context of the description of the present invention (especially in the context of the following claims) is intended to include both singular and plural, unless otherwise indicated or clearly prescribed by the context. Indication of ranges of values in the present description is intended to serve only as a brief way of indicating separately for each individual value falling into the specified range, unless otherwise indicated, and each individual value is included in the description, as if it were separately indicated in the description. All methods according to the present description can be carried out in any suitable order, unless otherwise indicated or clearly prescribed by the context. The use of any and all examples, or the language of examples (for example, “such as”) in the present description is intended only to better illustrate the invention and does not impose restrictions on the scope of the present invention, unless otherwise indicated in the claims. The description language should not be construed as indicating any non-claimed element as essential for the practical implementation of the present invention.

[0198] Preferred aspects and embodiments of the present invention are described herein, including the best known to the authors method of implementing the present invention. It should be understood that illustrative embodiments are only examples, and should not be taken as limiting the scope of the present invention.

Claims (45)

1. Gypsum panel containing: a cured gypsum middle layer located between the two cladding sheets, formed from a suspension containing at least water, gypsum and pregelatinized starch; wherein starch is contained in an amount of from about 0.5% to about 10% by weight of the mass of gypsum and is effective for increasing the hardness of the hardened gypsum middle layer compared to the gypsum middle layer formed from a suspension not containing pregelatinized starch; building gypsum is contained in an amount of about 700 pounds / thousand square feet (about 3.4 kg / m ² ), and building gypsum and water are contained in at least amounts effective to create a crystalline matrix essentially consisting of ^two- water gypsum; and wherein the panel has a density in the range of from about 27 to 32 lb / ft ³ (from about 430 to about 513 kg / m ³ ), an average hardness of the middle layer of at least about 11 pounds (about 5 kg), determined in accordance with ASTM C473 -09, and a thermal insulation coefficient of at least about 17 minutes, with a panel thickness of about 0.625 inches (about 1.6 cm). 2. Gypsum panel containing: a cured gypsum middle layer located between the two cladding sheets, formed from a suspension containing at least water, gypsum and pregelatinized starch; wherein starch is contained in an amount of from about 0.5% to about 10% by weight of the mass of building gypsum, effective to increase the hardness of the hardened gypsum middle layer compared to the gypsum middle layer formed from a suspension not containing pregelatinized starch; building gypsum is contained in an amount of about 700 pounds / thousand square feet (about 3.4 kg / m ² ), and building gypsum and water are contained in at least amounts effective to create a crystalline matrix essentially consisting of ^two- water gypsum; wherein said panel has a density in the range of from about 27 to 32 pounds / ft ³ (from about 430 to about 513 kg / m ³ ) and an average hardness of the middle layer of at least about 11 pounds (about 5 kg), determined according to ASTM C473 -09, while said panel having a thickness of about 0.625 inches (about 1.6 cm) is effective for slowing down at least one of: (a) heat transfer through a structure of said panels manufactured according to UL U419, in which one surface is exposed to a heat source and the opposite unheated surface has a plurality of sensors deposited on said surface, so that the maximum temperature from one sensor on the unheated surface is less than about 415 ° F (about 213 ° C) after about 30 minutes when measured according to UL U419, with the heat source following a time-temperature curve according to the standard ASTM E119-09a, and the sensors are arranged according to the scheme according to UL U419, (b) heat transfer through a structure of said panels manufactured according to UL U305 methods, in which one surface is exposed to a heat source and the opposite unheated surface carries a plurality of sensors deposited on said surface, so that the maximum temperature from one sensor on the unheated surface is less than about 415 ° F (about 213 ° C) after about 30 minutes when measured according to UL U305, with the heat source following a time-temperature curve according to standard ASTM E119-09a, and the sensors are arranged according to the scheme according to UL U305. 3. Gypsum panel containing: a cured gypsum middle layer located between the two cladding sheets, formed from a suspension containing at least water, gypsum and starch; wherein starch is contained in an amount of from about 0.3% to about 10% by weight of the mass of gypsum and is effective for increasing the hardness of the hardened gypsum middle layer compared to the gypsum middle layer formed from a suspension containing no starch; building gypsum is contained in an amount of about 700 pounds / thousand square feet (about 3.4 kg / m ² ), and building gypsum and water are contained in at least amounts effective to create a crystalline matrix essentially consisting of ^two- water gypsum; and wherein the panel has a density in the range of from about 27 to 34 lb / ft ³ (from about 430 to about 545 kg / m ³ ), an average hardness of the middle layer of at least about 11 pounds (about 5 kg), determined in accordance with ASTM C473 -09, and a thermal insulation coefficient of at least about 17 minutes. 4. A gypsum panel containing: a cured gypsum middle layer located between the two cladding sheets, formed from a suspension containing at least water, gypsum and starch; wherein starch is contained in an amount of from about 0.3% to about 10% by weight of the mass of building gypsum, effective to increase the hardness of the hardened gypsum middle layer compared to the gypsum middle layer formed from a suspension containing no starch; building gypsum is contained in an amount of about 700 pounds / thousand square feet (about 3.4 kg / m ² ), and building gypsum and water are contained in at least amounts effective to create a crystalline matrix essentially consisting of ^two- water gypsum; moreover, the specified panel has a density in the range from about 27 to 34 pounds / ft ³ (from about 430 to about 545 kg / m ³ ) and an average hardness of the middle layer of at least about 11 pounds (about 5 kg), determined according to ASTMC473- 09, while said panel having a thickness of about 0.625 inches (about 1.6 cm) is effective for slowing down at least one of: (a) heat transfer through a structure of said panels manufactured according to UL U419, in which one surface is exposed to a heat source and the opposite unheated surface has a plurality of sensors deposited on said surface, so that the maximum temperature from one sensor on the unheated surface is less than about 415 ° F (about 213 ° C) after about 30 minutes when measured according to UL U419, with the heat source following a time-temperature curve according to the standard ASTM E119-09a, and the sensors are arranged in accordance with UL U419, and (b) heat transfer through a structure of said panels manufactured according to UL U305 methods, in which one surface is exposed to a heat source and the opposite unheated surface carries a plurality of sensors deposited on said surface, so that the maximum temperature from one sensor on the unheated surface is less than about 415 ° F (about 213 ° C) after about 30 minutes when measured according to UL U305, with the heat source following a time-temperature curve according to standard ASTM E119-09a, and the sensors are arranged according to the scheme according to UL U305. 5. The gypsum panel according to claim 3 or 4, characterized in that it has a density in the range of from about 27 to 32 pounds / ft ³ (from about 430 to about 513 kg / m ³ ). 6. The gypsum panel according to claim 3 or 4, characterized in that it has a density in the range of from about 27 to 31 pounds / ft ³ (from about 430 to about 497 kg / m ³ ). 7. Gypsum panel according to any one of paragraphs. 2 or 4, characterized in that the panel with a thickness of about 0.625 inches (about 1.6 cm) has a thermal insulation coefficient of at least about 17 minutes. 8. Gypsum panel according to any one of paragraphs. 1-4, characterized in that the said panel with a thickness of about 0.625 inches (about 1.6 cm) has a thermal insulation coefficient of at least about 25 minutes. 9. Gypsum panel according to any one of paragraphs. 1-4, characterized in that the said panel has a high temperature shrink in the x-y direction of about 10% or less. 10. Gypsum panel according to any one of paragraphs. 1-4, characterized in that the said panel has a water absorption of about 5% by mass or less, determined according to ASTM C473-09. 11. Gypsum panel according to any one of paragraphs. 1-4, characterized in that the suspension additionally contains at least one of mineral, glass or carbon fibers or a combination of these fibers in an amount of from about 0.1% to about 0.3% by weight of the weight of building gypsum. 12. The gypsum panel according to claim 1 or 2, characterized in that said panel contains from about 1% to about 10% pregelatinized starch by weight of the weight of the building gypsum. 13. The gypsum panel according to claim 3 or 4, characterized in that said starch contains pregelatinized starch, while pregelatinized starch is contained in an amount of from about 0.5% to about 10% by weight of the mass of building gypsum. 14. Gypsum panel according to any one of paragraphs. 1-4, characterized in that the suspension further comprises from about 0.12% to about 0.4% sodium trimetaphosphate by weight of the weight of building gypsum. 15. Gypsum panel according to any one of paragraphs. 1-4, characterized in that at least one of the facing sheets contains a paper facing sheet having a mass of from about 48 pounds / thousand square feet to about 60 pounds / thousand square feet. 16. Gypsum panel according to any one of paragraphs. 1-4, characterized in that the said panel with a thickness of about 0.625 inches (about 1.6 cm) is effective for slowing down the transfer of heat through the structure of these panels, made according to the UL U419 method, in which one surface is exposed to a heat source and the opposite an unheated surface has a plurality of sensors applied to said surface, so that the maximum temperature from one sensor on an unheated surface is less than about 415 ° F (about 213 ° C) after about 30 minutes When measured according to the method of UL U419, wherein the heat source must be time-temperature curve according to ASTM Standard E119-09a, and the sensors are arranged at the arrangement according to UL U419 procedure. 17. Gypsum panel according to any one of paragraphs. 1-4, characterized in that the said panel with a thickness of about 0.625 inches (about 1.6 cm) is effective for slowing down heat transfer through a structure of these panels made according to UL U305 methods, in which one surface is exposed to a heat source and the opposite an unheated surface carries a plurality of sensors deposited on said surface, so that the maximum temperature from one sensor on an unheated surface is less than about 415 ° F (about 213 ° C) after about 30 minutes when measured according to UL U305, the heat source following the time-temperature curve according to ASTM E119-09a, and the sensors are arranged according to the scheme according to UL U305. 18. Gypsum panel according to any one of paragraphs. 1-4, characterized in that said panel is effective for slowing down heat transfer through a structure of said panels made according to UL U419 method, in which one surface is exposed to a heat source and the opposite unheated surface has a plurality of sensors applied to said surface, that the maximum temperature from one sensor on an unheated surface is less than about 415 ° F (about 213 ° C) after about 30 minutes when measured according to UL U419, and heat Tocnik be time-temperature curve according to the standard ASTM E119-09a, and the sensors are located at the arrangement according to UL U419 procedure. 19. Gypsum panel according to any one of paragraphs. 1-4, characterized in that said panel is effective for slowing down heat transfer through a structure of said panels made according to UL U305 methods, in which one surface is exposed to a heat source and the opposite unheated surface carries a plurality of sensors applied to said surface, that the maximum temperature from one sensor on an unheated surface is less than about 415 ° F (about 213 ° C) after about 30 minutes when measured according to UL U305, Heat Source follows the time-temperature curve according to the standard ASTM E119-09a, and the sensors are located at the arrangement according to UL U305 procedure. 20. The gypsum panel of Claim 16, wherein said panel, with a thickness of about 0.625 inches (about 1.6 cm), is effective in slowing down heat transfer through the structure, so that the average temperature from the sensors on an unheated surface is less than about 340 ° F (approx. 171 ° C) after approx. 30 minutes when measured according to UL U419. 21. The gypsum panel according to claim 17, characterized in that said panel with a thickness of about 0.625 inches (about 1.6 cm) is effective in slowing down the transfer of heat through the structure, so that the average temperature from the sensor on an unheated surface is less than about 340 ° F (approx. 171 ° C) after approx. 30 minutes when measured according to UL U305. 22. The gypsum panel of claim 18, wherein said panel is effective in slowing down heat transfer through the structure, so that the average temperature from the sensors on an unheated surface is less than about 340 ° F (about 171 ° C) after about 30 minutes at measurement according to UL U419. 23. The gypsum panel according to claim 19, characterized in that said panel is effective in slowing down the transfer of heat through the structure, so that the average temperature from the sensor on an unheated surface is less than about 340 ° F (about 171 ° C) after about 30 minutes at measurement according to UL U305.

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