TW201332933A - High starch light weight gypsum wallboard - Google Patents

Abstract

The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1% - 3.0% by weight based on the weight of dry stucco. The pregelatinized starch is present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, gypsum wallboard, and a method of making gypsum wallboard.

Description

High starch light weight gypsum wallboard

The present invention relates to a method of producing a gypsum slurry containing a pregelatinized starch and a naphthalenesulfonate dispersant, and a product made therefrom. The present invention is also directed to a method of enhancing the drying strength of such gypsum-containing products including wallboard by using a naphthalenesulfonate dispersant in combination with a pregelatinized starch in a slurry for producing a gypsum-containing product.

Certain properties of gypsum (calcium sulfate dihydrate) make it very common for the manufacture of industrial and architectural products, such as gypsum wallboard. Gypsum is an abundant and often inexpensive raw material that can be cast, molded or otherwise formed into useful shapes by dehydration and rehydration processes. The basic material for the manufacture of gypsum wallboard and other gypsum products is calcium sulfate in the form of a hemihydrate (CaSO ₄ .1/2H ₂ O), commonly referred to as "stucco", which is thermally converted to sulfuric acid in the form of a dihydrate. Calcium (CaSO ₄ .2H ₂ O) from CaSO ₄ . 2H ₂ O is produced by removing 1-1/2 water molecules.

While conventional gypsum-containing products such as gypsum wallboard can produce large amounts of gypsum dust during cutting or drilling, such gypsum products have many advantages, such as low cost and ease of use. In the manufacture of gypsum-containing products, the use of starch as a component in the slurry for the manufacture of such products has resulted in a number of improvements. Starch can increase the flexural strength and compressive strength of gypsum-containing products including gypsum wallboard. Gypsum wallboard is known to contain sheet starch in an amount of less than about 10 lbs/MSF.

It is also necessary to use a large amount of water in the gypsum slurry containing the pregelatinized starch to ensure proper fluidity of the slurry. Unfortunately, most of the water must eventually be removed by heating, which is expensive due to the high cost of the fuel used in the heating process. The heating step is also time consuming. The use of naphthalene sulfonate dispersants has been found The fluidity of the slurry can be increased, thus overcoming the problem of water requirements. In addition, it has also been found that if the level of use is sufficiently high, the naphthalenesulfonate dispersant can be crosslinked to the pregelatinized starch to adhere the gypsum crystals after drying, thereby increasing the dry strength of the gypsum composite. In the past, it was not recognized that tri-phosphates affect the water requirements of gypsum slurries. However, the inventors have found that increasing the trimetaphosphate content in the presence of a particular dispersant to a level that has hitherto been unknown makes it possible to achieve moderate slurry fluidity at high starch content and unexpectedly reduce the amount of water. Of course, this is highly desirable as it in turn reduces the amount of fuel used and the processing time associated with subsequent water removal process steps. Therefore, the inventors have also found that the dry strength of the gypsum board can be increased by using a naphthalenesulfonate dispersant in combination with the pregelatinized starch in the slurry for making the wallboard.

The present invention generally comprises a slurry comprising a stucco, a naphthalene sulfonate dispersant, and a pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount from about 0.1% to about 3.0% by weight, based on the weight of the dry stucco. The pregelatinized starch is present in an amount of from at least about 0.5% by weight up to about 10% by weight, based on the weight of dry stucco in the formulation. Other slurry additives may include accelerators, binders, paper fibers or fiberglass, and other known components. The invention also encompasses gypsum-containing products made from such slurries.

The present invention also encompasses a slurry comprising stucco, a trimetaphosphate, a naphthalenesulfonate dispersant, and a pregelatinized starch. The sodium trimetaphosphate is present in an amount of at least about 0.12% by weight based on the weight of the stucco. In a preferred embodiment, the trimetaphosphate is present in an amount of from about 0.12 to about 0.4% by weight, based on the weight of the dry stucco. The naphthalenesulfonate dispersant is present in an amount from about 0.1% to about 3.0% by weight, based on the weight of the dry stucco. The pregelatinized starch is present in an amount of from at least about 0.5% by weight up to about 10% by weight, based on the weight of dry stucco in the formulation. Other slurry additives may include accelerators, binders, paper fibers or fiberglass, and other known components. The invention also encompasses gypsum-containing products made from such slurries.

Preferably, the gypsum-containing product is a gypsum wallboard. In this embodiment, the present invention comprises a set of set gypsum formed between two substantially parallel cover sheets Gypsum wallboard of the composition, which is produced using a gypsum slurry of water, plaster, pregelatinized starch and a naphthalenesulfonate dispersant. The gypsum-containing slurry may optionally contain a trimetaphosphate such as sodium trimetaphosphate. The gypsum wallboard manufactured in accordance with the present invention has high strength but is much lighter than conventional panels. In addition, the dust produced is much less when cutting, sawing, breaking or drilling a wall panel manufactured according to this embodiment.

In another embodiment, the present invention constructs a method of making a gypsum wallboard by mixing a gypsum-containing slurry comprising water, mortar, pregelatinized starch, and a naphthalenesulfonate dispersant, wherein the pre-gelling The starch is present in an amount of from at least about 0.5% by weight up to about 10% by weight, based on the weight of the stucco. The resulting gypsum-containing slurry is deposited on a first paper cover sheet, and a second paper cover sheet is placed on the deposited slurry to form a gypsum wallboard. After the gypsum-containing slurry has hardened enough to be cut, the gypsum wallboard is cut and the resulting gypsum wallboard is dried. The gypsum-containing slurry may optionally contain a trimetaphosphate such as sodium trimetaphosphate. If appropriate, other conventional ingredients including accelerators, binders, paper fibers, fiberglass and other known ingredients are also used in the slurry. Soap bubbles are usually added to reduce the density of the final gypsum wallboard product.

According to an embodiment of the present invention, a gypsum-containing finished product produced from a gypsum-containing slurry containing a stucco, a pregelatinized starch, and a naphthalenesulfonate dispersant is provided. The naphthalenesulfonate dispersant is present in an amount from about 0.1% to about 3.0% by weight, based on the weight of the dry stucco. The pregelatinized starch is present in an amount of from at least about 0.5% by weight to about 10% by weight, based on the weight of dry stucco in the formulation. Other ingredients that can be used in the slurry include binders, paper fibers, fiberglass, and accelerators. Soap bubbles are typically added to the newly formulated gypsum-containing slurry to reduce the density of the final gypsum-containing product, such as gypsum wallboard.

If desired, from about 0.5% by weight up to about 10% by weight of pregelatinized starch, from about 0.1% by weight up to about 3.0% by weight of naphthalene sulfonate dispersion And a combination of a minimum amount of at least about 0.12% by weight up to about 0.4% by weight of trimetaphosphate (both based on the weight of dry stucco used in the gypsum slurry) unexpectedly and significantly enhances the flow of the gypsum slurry . This substantially reduces the amount of water required to produce a gypsum slurry of sufficient fluidity for the manufacture of gypsum-containing products such as gypsum wallboard. The tri-metaphosphate content of at least twice the standard formulation of trimellitic phosphate (such as sodium trimetaphosphate) promotes the dispersing activity of the naphthalenesulfonate dispersant.

The naphthalenesulfonate dispersant used in the present invention includes polynaphthalenesulfonic acid and salts thereof (polynaphthalenesulfonate) and derivatives thereof, which are condensation products of naphthalenesulfonic acid and formaldehyde. Particularly desirable polynaphthalene sulfonates include sodium naphthalene sulfonate and calcium naphthalene sulfonate. While the preferred molecular weight of the naphthalene sulfonate is from about 8,000 to 10,000, the average molecular weight of the naphthalene sulfonate can vary from about 3,000 to about 27,000. In a particular solid % aqueous solution, the higher molecular weight dispersant has a higher viscosity and produces a higher water requirement in the formulation than a lower molecular weight dispersant. Useful naphthalene sulfonates 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. . For example, the naphthalenesulfonate is preferably used in the form of an aqueous solution having a solid content in the range of from 35 to 55% by weight. For example, the naphthalene sulfonate is most preferably used in the form of an aqueous solution having a solids content in the range of from about 40% to about 45% by weight. Alternatively, if appropriate, the naphthalene sulfonate can be used in dry solid or powder form, such as LOMAR D.

The polynaphthalene sulfonate suitable for use in the present invention has the general formula (I):

Wherein n>2, and wherein M is sodium, potassium, calcium and the like.

Preferably, the naphthalenesulfonate dispersant in the form of an aqueous solution of about 45% by weight can be used in the range of from about 0.5% by weight to about 3.0% by weight based on the weight of the dry stucco in the gypsum composite formulation. A more preferred range of naphthalenesulfonate dispersant is from about 0.5% to about 2.0% by weight, based on the weight of dry stucco, and most preferably from about 0.7% to about 2.0% by weight, based on the weight of dry stucco. In contrast, gypsum wallboard is known to contain the dispersant in an amount of about 0.4% by weight or less based on the weight of the dry stucco.

Stated another way, the naphthalenesulfonate dispersant can be used in a range from about 0.1% to about 1.5% by weight, based on the weight of dry stucco used in the gypsum composite formulation. A more preferred range of naphthalenesulfonate dispersant is from about 0.25 wt% to about 0.7 wt%, based on dry weight, and the optimum range (by dry solids weight) is on dry grout weight From about 0.3% by weight to about 0.7% by weight.

The gypsum-containing slurry may optionally contain a trimetaphosphate such as sodium trimetaphosphate. Any suitable water soluble metaphosphate or polyphosphate can be used in accordance with the present invention. It is preferred to use a trimetaphosphate which comprises a double salt, i.e., a trimetaphosphate having two cations. Particularly useful trimetaphosphates include sodium trimetaphosphate, potassium trimetaphosphate, calcium trimetaphosphate, sodium trimetaphosphate, lithium trimetaphosphate, ammonium trimetaphosphate, and the like, or combinations thereof. Preferably, the trimetaphosphate is sodium trimetaphosphate. The trimetaphosphate is preferably, for example, a solid content of from about 10% to about 15% by weight. It is used in the form of an aqueous solution. Other cyclic or acyclic polyphosphates may also be used as described in U.S. Patent No. 6,409,825, the disclosure of which is incorporated herein by reference.

While sodium trimetaphosphate is typically used in the range of from about 0.05% by weight to about 0.08% by weight based on the weight of dry stucco used in the gypsum slurry, sodium trimetaphosphate is a known additive in the gypsum-containing composition. In an embodiment of the invention, sodium trimetaphosphate (or other water soluble metaphosphate or polyphosphate) may be from about 0.12% to about 0.4 weight by weight of dry stucco used in the gypsum composite formulation. There is a range of %. The preferred range of sodium trimetaphosphate (or other water soluble metaphosphate or polyphosphate) is from about 0.12% to about 0.3% by weight based on the weight of dry stucco used in the gypsum composite formulation.

There are two forms of stucco: alpha and beta. These two types of stucco are produced by different calcination methods. In the present invention, stucco in the form of β or α can be used.

Starch, especially comprising pregelatinized starch, must be used in the gypsum-containing slurry prepared in accordance with the present invention. Preferred pregelatinized starch is pregelatinized corn starch, such as pregelatinized corn flour commercially available from Bunge Milling, St. Louis, Missouri, having the following typical analysis: moisture 7.5%, protein 8.0%, oil 0.5%, coarse fiber 0.5%, ash 0.3%; green strength 0.48 psi; and bulk bulk density 35.0 lb/ft ³ . The pregelatinized starch should be used in an amount of at least about 0.5% by weight up to about 10% by weight, based on the weight of dry stucco in the gypsum-containing slurry.

The inventors have further discovered that by using at least about 0.5% by weight up to about 10% by weight of pregelatinized starch in the presence of from about 0.1% to about 3.0% by weight of a naphthalene sulfonate dispersant (preferred Gelatinized corn starch) can achieve an unexpected increase in dry strength (especially in wallboard) (starch and naphthalene sulfonate content is based on the weight of dry stucco present in the formulation). This unexpected result can be obtained regardless of the presence or absence of water-soluble metaphosphate or polyphosphate.

Additionally, it has been surprisingly found that high strength and light weight can still be achieved by using pregelatinized starch in an amount of at least about 10 lb/MSF or more in the dried gypsum wallboard manufactured in accordance with the present invention. Has been described in gypsum wallboard Pregelatinized starch in an amount of 35-45 lb/MSF is effective. As an example, Formulation B illustrated in Tables 1 and 2 below includes 45 lb/MSF pregelatinized starch which still produces a plate having an excellent strength plate weight of 1042 lb/MSF. In this example (Formulation B), a naphthalenesulfonate dispersant as a 45% by weight aqueous solution was used at a content of 1.28 wt%.

Other useful starches include acid modified starches, such as acid modified corn flour, which are commercially available as HI-BOND from Bunge Milling, St. Louis, Missouri. The starch has the following typical analysis: moisture 10.0%, oil 1.4%, soluble material 17.0%, alkali flow 98.0%, bulk bulk density 30 lb/ft ³ and 20% slurry with a pH of 4.3. Another useful starch is non-pregelatinized wheat starch, such as ECOSOL-45, which is commercially available from ADM/Ogilvie, Montreal, Quebec, Canada.

Another unexpected result can be achieved by the present invention when a combination of a naphthalene sulfonate dispersant, a trimetaphosphate, and a pregelatinized corn starch is combined with paper fibers or glass fibers as needed. Gypsum wallboards made from formulations containing these three ingredients have increased strength and reduced weight, and are more economically desirable due to reduced water requirements in their manufacture.

An accelerator may be used in the gypsum-containing composition of the present invention as described in U.S. Patent No. 6,409,825, the disclosure of which is incorporated herein by reference. A desirable heat resistant accelerator (HRA) can be made from dry ground gypsum powder (calcium sulfate dihydrate). The HRA can be made using small amounts (typically about 5% by weight) of additives such as sugar, dextrose, boric acid, and starch. Currently preferred is sugar or dextrose. Another useful accelerator is described as "climate stabilized accelerator" (CSA) as described in U.S. Patent No. 3,573,947, incorporated herein by reference.

The following examples further illustrate the invention. It is not intended to limit the scope of the invention in any way.

Example 1

Sample gypsum slurry formula

The gypsum slurry formulation is shown in Table 1 below. All values in Table 1 are The dry stucco weight is expressed as % by weight. The value in parentheses is the dry weight in pounds (lb/MSF).

Example 2

Preparation of wallboard

A sample gypsum wallboard is prepared in accordance with U.S. Patent No. 6,342, 284 to Yu et al., and U.S. Patent No. 6,632,550, the disclosure of which is incorporated herein by reference. As described in Example 5 of the patents, this includes separately producing a foam and directing the foam to a slurry of other ingredients.

The results of testing the gypsum wallboard and controls made with Formulations A and B of Example 1 are shown in Table 2 below. As in this example and other examples below, nail pull resistance, core hardness and flexural strength tests were performed in accordance with ASTM C-473. In addition, it should be noted that typical gypsum wallboard thicknesses are about 1⁄2 inch and the weight per 1,000 square feet of material is between about 1600 and 1800 pounds (or lb/MSF). ("MSF" is the standard for 1000 square feet in this technology. Written; it is a measurement method for the area of boxes, corrugated media and wallboard. )

As shown in Table 2, gypsum wallboard prepared with Formulations A and B slurry was significantly less weight-reduced than the control panels. Referring again to Table 1, the comparison between the Formula A plate and the Formula B plate is very significant. The water/stucco (w/s) ratios in Formulation A and Formulation B are similar. A significantly higher level of naphthalenesulfonate dispersant is also used in Formulation B. Substantially more pregelatinized starch is also used in Formulation B, about 6% by weight, which is a 100% increase over Formulation A with a significant increase in strength. Even so, the requirement for water to produce the required fluidity remains low in Formulation B slurry, compared to Formulation A, with a difference of about 10%. The low water requirement in both formulations is due to the synergistic effect of the combination of naphthalene sulfonate dispersant and sodium trimetaphosphate in the gypsum slurry, even if there is a substantially higher level of pregelatinized starch. Increase the fluidity of the gypsum slurry.

As shown in Table 2, the wallboard prepared with the Formulation B slurry had substantially increased strength compared to the wallboard prepared with the Formulation A slurry. By introducing an increased amount of pregelatinized starch in combination with an increased amount of naphthalenesulfonate dispersant and sodium trimetaphosphate, the nail pull resistance of the Formula B plate was improved by 45% compared to the nail resistance of the Formula A plate. Deflection was also observed in the Formula B plate compared to the Formula A plate. Significant increase in strength.

Example 3

1⁄2吋 gypsum wallboard weight reduction test

Additional gypsum wallboard examples (boards C, D, and E) including slurry formulations and test results are shown in Table 3 below. The slurry formulation of Table 3 includes the major components of the slurry. The values in parentheses are expressed as % by weight of dry stucco.

As shown in Table 3, panels C, D, and E were made from a slurry having a substantially increased amount of starch, DILOFLO dispersant, and sodium trimetaphosphate compared to the control panel (by percentage, starch and dispersant) In this case, it is increased by about two times and is increased by two to three times for the trimetaphosphate, while maintaining the w/s ratio constant. However, the strength measured by the nail pull resistance was not significantly affected and the board weight was significantly reduced. Thus, in this example of an embodiment of the invention, the new formulation, such as panel D, can provide increased starch formulated in a suitable, flowable slurry while maintaining sufficient strength.

Example 4

Wet gypsum block strength test

By using Southard CKS board stucco (available from United Tap water from the State Gypsum Corp., Chicago, Illinois, and the laboratory were tested for wet square strength to determine its wet compressive strength. Use the following laboratory measurements.

For each wet gypsum block casting, stucco (1000 g), CSA (2 g) and tap water (1200 cc) were used at about 70 °F. First pre-gelatinized cornstarch (20 g, 2.0% by weight of stucco) and CSA (2 g, 0.2% by weight of stucco) are thoroughly dry mixed with stucco in a plastic bag, then It is mixed with a tap water solution containing a naphthalenesulfonate dispersant and sodium trimetaphosphate. The dispersant used was a DILOFLO dispersant (1.0-2.0%, as shown in Table 4). As shown in Table 4, different amounts of sodium trimetaphosphate were also used.

The dry ingredients and aqueous solutions were initially combined in a laboratory early warning blender, the resulting mixture was soaked for 10 seconds, and then the mixture was mixed at low speed for 10 seconds to produce a slurry. The resulting slurry was cast into three 2"X2"X2" square molds. The cast squares were then removed from the mold, weighed and sealed in a plastic bag to prevent moisture loss prior to compressive strength testing. The ATS machine measures the compressive strength of the wet square and records the average of pounds per square inch (psi). The results are as follows:

As shown in Table 4, samples 4-5, 10-11, and 17 having sodium trimetaphosphate content within this range were compared to samples having sodium trimetaphosphate outside the range of about 0.12 to 0.4% of the present invention. Higher wet square compressive strength is usually provided.

Example 5

1⁄2吋 light weight gypsum wallboard factory production test

Additional tests (test plates 1 and 2), including slurry formulations and test results, are shown in Table 5 below. The slurry formulation of Table 5 includes the major components of the slurry. The values in parentheses are expressed as % by weight of dry stucco.

^† ASTM Standard: 77 lb MD: Longitudinal XMD: Transverse ¹ DILOFLO is 45% naphthalene sulfonate ^{2 2} 90 °F / 90% relative humidity ³ Fully understood that under these test conditions, the percent failure rate is less than 50% acceptable.

As shown in Table 5, the test panels 1 and 2 were made from a slurry having a substantially increased amount of starch, DILOFLO dispersant, and sodium trimetaphosphate, while slightly reducing the w/s ratio, as compared to the control panel. However, the strength measured by the nail pull resistance and flexural test was maintained or improved, and the board weight was significantly reduced. Thus, in this example of an embodiment of the invention, the new formulation, such as test panels 1 and 2, provides increased trimetaphosphate and starch formulated in a suitable, flowable slurry while maintaining sufficient strength.

Example 6

1⁄2吋 ultra light weight gypsum wallboard factory production test

Formula B was used as in Example 2 except that pre-gelatinized corn starch (wet starch preparation) was prepared at a concentration of 10% with water and a HYONIC PFM soap blend (available from GEO Specialty Chemicals, Lafayette, Indiana) was used. 1) Perform more tests (test plates 3 and 4). For example, test plate 3 was prepared with a HYONIC PFM 10/HYONIC PFM 33 blend varying from 65-70 wt% / 35-30 wt%. For example, test plate 4 was prepared with a 70/30 wt./wt. HYONIC PFM 10/HYONIC PFM 33 blend. The test results are shown in Table 6 below.

As shown in Table 6, the strength characteristics measured by nail pull and core hardness are above the ASTM standard. The flexural strength was also measured to be higher than the ASTM standard. Moreover, in this example of an embodiment of the invention, new formulations, such as test panels 3 and 4, can provide increased trimetaphosphate and starch formulated in a suitable, flowable slurry while maintaining sufficient strength.

The use of the terms "a", "an" and "the" The detailed description of the range of values herein is merely intended to serve as an abbreviated method of individually referring to individual values within the range, and if the individual values are individually recited herein, they are incorporated herein. In the manual. All methods described herein can be performed in any suitable sequence unless otherwise indicated herein or clearly contradicted by context. The use of any and all examples or exemplary terms (such as "such as") In the present specification, any term is not intended to indicate any non-claimed element that is necessary to practice the invention.

The preferred embodiments of the invention are described herein, including the best mode known to the inventors to practice the invention. It should be understood that the illustrated embodiment It is merely exemplary and should not be taken to limit the scope of the invention.

Claims (20)

A light weight gypsum board comprising: a set gypsum composition placed between two cover sheets, the set gypsum composition being formed of at least water, mortar, starch and a foaming agent; the amount of the starch is calculated by weight of stucco From about 0.5% by weight to about 10% by weight; the blowing agent comprises an unstable component as a major weight portion and a stable component as a minor weight portion, the amount of the foaming agent and the weight of the unstable component and the stable component The specific energy acts to form a void distribution in the set gypsum composition; the starch and the void distribution provide a plate density of about 34 lb/ft ³ (about 540 kg/m ³ ) or less. And a core hardness of at least about 11 lb (about 5 kg) as determined by ASTM Standard C473. A light weight gypsum board according to claim 1, wherein the blowing agent comprises a mixture of an unstable component and a stabilizing component. The lightweight gypsum board of claim 1 wherein the blowing agent comprises at least about 65% by weight of an unstable component. A light weight gypsum board according to claim 1, wherein the amount of the blowing agent is 0.1% by weight or less based on the weight of the plaster. A light weight gypsum board according to any one of claims 1 to 4, wherein the starch acts to increase the core hardness of the set gypsum composition as compared to a gypsum composition without starch. A light weight gypsum board according to claim 5, wherein the starch comprises pregelatinized starch in an amount of from about 0.5% by weight to about 6% by weight based on the weight of the stucco. The lightweight gypsum board of claim 1, wherein the plate is (a) maintained in an environment sufficient to produce 90% relative humidity and a temperature of 90 °F (about 32 ° C) for about 6 hours, and (b) after drying to constant weight , having at least about 15 lb (about 6.8 kg) Moisture bonded load. The lightweight gypsum board of claim 1, wherein: the starch acts to increase the core hardness of the set gypsum composition compared to the gypsum composition without starch; the plate is maintained at (a) sufficient to produce 90% relative humidity and an environment of 90 °F (about 32 ° C) for about 6 hours, and (b) after drying to constant weight, having a wet bonding load of at least about 15 lb (about 6.8 kg); when the thickness of the plate is About 1⁄2 inch (about 1.3 cm), the plate has a nail pull resistance of at least about 65 lb (about 29 kg) as determined according to ASTM Standard C473. A light weight gypsum board according to claim 8, wherein: the amount of the foaming agent is 0.1% by weight or less based on the weight of the stucco; and when the thickness of the sheet is about 1⁄2 inch (about 1.3 cm), the plate has a C473 according to the ASTM standard. The nail pull resistance of at least about 72 lb (about 33 kg) was determined. A lightweight gypsum board according to claim 1, wherein: the plate is maintained in an environment sufficient to produce a temperature of 90% relative humidity and 90 °F (about 32 ° C) for about 6 hours, and (b) dried to constant weight. Thereafter, having a wet bond loading of at least about 17 lb (about 7.7 kg); and when the plate thickness is about 1⁄2 吋 (about 1.3 cm), the plate has at least about 77 lb (about 35 kg) as determined according to ASTM Standard C473. It is resistant to nails. The lightweight gypsum board of claim 9 wherein the plate has a thickness of about 1⁄2 吋 (about 1.3 cm) and the plate has an average flexural strength of at least about 36 lb (about 16 kg) in the longitudinal direction as measured by ASTM Standard C473 and An average flexural strength of at least about 107 lb (about 48.5 kg) in the transverse direction. The light weight gypsum board of claim 11, wherein: the set gypsum composition is further formed of a dispersant, the amount of the dispersant being from about 0.2% by weight to about 3.0% by weight based on the weight of the stucco; the set gypsum composition is a water to mortar weight ratio of from about 0.7 to about 1.2; The sheet has at least about 17 lb (about 7.7 kg) after (a) is maintained in an environment sufficient to produce 90% relative humidity and 90 °F (about 32 ° C) for about 6 hours, and (b) dried to constant weight. Wet bonded load. A lightweight gypsum board comprising: a set gypsum composition disposed between two cover sheets, the set gypsum composition being formed of at least water, mortar, starch, a dispersant, and a polyphosphate; the amount of the stucco is at least About 700 lb/MSF (about 3.4 kg/SQM); the amount of starch is from about 0.5% by weight to about 10% by weight based on the weight of the stucco, and the starch acts to increase the solidification compared to the gypsum composition without starch. The effect of the core hardness of the gypsum composition; the amount of the dispersant is from about 0.1% by weight to about 3.0% by weight based on the weight of the stucco; and the amount of the polyphosphate is from about 0.12% by weight to about 0.4% by weight based on the weight of the stucco. The panel has a density of about 34 lb/ft ³ (about 540 kg/m ³ ) or less; the panel has a core hardness of at least about 11 lb (about 5 kg), the core hardness being according to ASTM standard C473 Determination. The light weight gypsum board of claim 13 wherein the amount of stucco is about 700 lb/MSF (about 3.4 kg/SQM) to about 1300 lb/MSF (about 6.3 kg/SQM). The lightweight gypsum board of claim 13 further comprising paper fibers and/or glass fibers in an amount of from about 0.20% by weight to about 1.30% by weight based on the weight of the dry stucco. The lightweight gypsum board of claim 13 further comprising an accelerator in an amount of from about 0.2% by weight to about 0.9% by weight based on the weight of the dry stucco. A light weight gypsum board according to claim 13 wherein: the set gypsum composition is formed at least further by a blowing agent and an accelerator; the amount of the stucco is about 700 lb/MSF (about 3.4 kg/SQM) to about 1300 lb. /MSF (about 6.3 kg / SQM); the amount of the starch is from about 0.5% by weight to about 6% by weight based on the weight of the stucco; the amount of the dispersing agent is from about 0.2% by weight to about 3.0% by weight based on the weight of the stucco; The foaming agent comprises an unstable component as a main weight portion and a stable component as a minor weight portion, and the amount of the foaming agent and the weight ratio of the unstable component to the stable component can be played in the set gypsum composition. Forming a void distribution wherein the amount of blowing agent is 0.1% by weight or less based on the weight of the stucco; the starch and the void distribution serve to provide about 24 lb/ft ³ (about 380 kg/m ³ ) a plate density of up to about 34 lb/ft ³ (about 540 kg/m ³ ) and a core hardness of at least about 11 lb (about 5 kg) at a plate thickness of about 1⁄2 吋 (about 1.3 cm), At least about 65 lb (about 29 kg) of tack resistance, and a flexural strength of at least about 36 lb (about 16 kg) in the machine direction and a flexural strength of at least about 107 lb (about 48.5 kg) in the transverse direction. The effect of the nail pull resistance and flexural strength is determined in accordance with ASTM Standard C473; and the sheet is maintained in an environment sufficient to produce a 90% relative humidity and a temperature of 90 °F (about 32 ° C) for about 6 hours. And (b) having a wet bonded loading of at least about 15 lb (about 6.8 kg) after drying to constant weight. A light weight gypsum board according to claim 17, wherein the amount of the blowing agent is from about 0.02% by weight to about 0.03% by weight based on the weight of the stucco. The lightweight gypsum board of claim 17, wherein: the set gypsum composition is at least further formed from paper fibers and/or glass fibers; the set gypsum composition is formed from a weight ratio of water to stucco of from about 0.7 to about 1.2. The starch comprises pregelatinized starch; The dispersing agent comprises a naphthalene sulfonate; the polyphosphate comprises sodium trimetaphosphate; the amount of the paper fibers and/or glass fibers is from about 0.20% by weight to about 1.30% by weight based on the weight of the stucco; the accelerator comprises heat resistant An accelerator, and the amount thereof is from about 0.2% by weight to about 0.9% by weight based on the weight of the stucco; and the sheet is maintained at (a) in an environment sufficient to produce a temperature of 90% relative humidity and a temperature of 90 °F (about 32 ° C) of about 6 Hours, and (b) after drying to constant weight, have a wet bond loading of at least about 17 lb (about 7.7 kg). The light weight gypsum board according to any one of claims 13 to 19, wherein the set gypsum composition is at least further formed by a foaming agent comprising an unstable component as a main weight portion and a stable component The weight portion, the amount of the blowing agent and the weight ratio of the unstable component to the stabilizing component can function to form a void distribution in the set gypsum composition.