HK1117494A - Gypsum-containing product having increased resistance to permanent deformation and method and composition for producing it - Google Patents
Gypsum-containing product having increased resistance to permanent deformation and method and composition for producing it Download PDFInfo
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- HK1117494A HK1117494A HK08107763.2A HK08107763A HK1117494A HK 1117494 A HK1117494 A HK 1117494A HK 08107763 A HK08107763 A HK 08107763A HK 1117494 A HK1117494 A HK 1117494A
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Description
The present application is a divisional application, the parent application of which is application number 98801196.4, filed on 1998 at 8/21, entitled "gypsum articles having improved resistance to permanent deformation and methods and compositions for making the same".
Technical Field
The present invention relates to methods and compositions for making set gypsum products, including, for example, gypsum board, reinforced gypsum composite board, stucco, machinable material, joint treatment material, and acoustical tile, and to methods and compositions for making these products. More particularly, the present invention relates to set gypsum-containing products having improved resistance to permanent deformation (e.g., sag resistance) through the use of one or more reinforcing materials. Some preferred embodiments of the present invention relate to methods of making such articles comprising hydrating calcined gypsum in the presence of a reinforcing material that imparts increased strength, resistance to permanent deformation (e.g., sag resistance) and dimensional stability (e.g., no shrinkage during drying of the set gypsum) to the set gypsum so hydrated. The reinforcing materials also impart other improved properties and advantages to the set gypsum-containing product when it is made. In another embodiment of the invention, the set gypsum is treated with one or more reinforcing materials to provide similar, if not identical, reinforcement, resistance to permanent deformation (e.g., sag resistance), dimensional stability, and other improved properties and advantages to the gypsum-containing product. In some embodiments of the invention, the set gypsum-containing product of the invention contains a relatively large amount of the hydrochloride salt, but the adverse effects of such salt concentrations on the gypsum product are generally avoided.
Background
Many well-known practical articles contain an effective amount, often as the major component, of set gypsum (calcium sulfate dihydrate). Set gypsum, for example, is a major component of gypsum plasterboards used in typical drywall construction of interior walls and in building ceilings (see, for example, U.S. patents 4009062 and 2985219). They are also a major component of gypsum/cellulose fiber composite boards and products, as disclosed in US 5320677. Products that fill joints between gypsum board edges often contain large amounts of gypsum (see, for example, U.S. patent No. US 3297601). For example, acoustical tiles used in suspended ceilings may contain a significant amount of set gypsum, as disclosed in U.S. patents 5395438 and 3246063. Conventional plasters, such as those typically used to create plaster surfaces for internal building walls, generally depend primarily on the formation of set gypsum. Many specialty materials, such as the refinable moulding and moulding materials disclosed in US patent US5534059, contain substantial amounts of gypsum.
Most such gypsum products are prepared by forming a mixture of calcined gypsum (calcium sulfate hemihydrate and/or calcium sulfate anhydrite) and water (and, where appropriate, other components), casting the mixture into a mold or onto a surface of a desired shape, forming a matrix of crystalline hydrated gypsum (calcium sulfate dihydrate) by reacting the calcined gypsum with water, and allowing the mixture to harden to form set (i.e., rehydrated) gypsum. Slight heating is usually also applied to remove the remaining free (unreacted) water and obtain a dry product. Calcined gypsum, which forms an interlocking matrix of set gypsum crystals upon the desired hydration, thereby imparting strength to the gypsum structure in the gypsum product.
All of the gypsum-containing products described above benefit if their constituent set gypsum crystal structures are strengthened in order to make the products more resistant to stresses that may be encountered during use.
Efforts have been made to replace the partially set gypsum matrix with lower density materials, such as expanded perlite or air voids, to produce many of these lighter weight gypsum products. In this case, because the amount of set gypsum that provides the strength of the low density product is small, it is desirable to increase the strength of the set gypsum above the standard level, just to maintain the overall product strength at the level of the higher density products of the prior art.
Furthermore, in many gypsum-made components, high resistance to permanent deformation (e.g., resistance to sagging), especially at high humidity and high temperature, or even under load conditions, is desirable. The human eye typically does not see the sag of a gypsum board below about 0.1 inch per 2 feet of gypsum board. Therefore, there is a need for gypsum articles that resist permanent deformation over the life of such articles. For example, gypsum boards and tiles are often stored or used in a horizontal position. If the set gypsum matrix in these articles is not sufficiently resistant to permanent deformation, especially at high humidity and high temperatures, or even under load, the article begins to sag in the area between the points where the article is secured or supported by the underlying structure. This can make them unsightly and make such articles difficult to put into use. In many applications, the gypsum product must be able to withstand loads, such as insulation or condensation loads, without appreciable sag. Thus, there is a continuing need to form set gypsum with improved resistance to permanent deformation (e.g., sag resistance).
Set gypsum in gypsum products is also required to have good dimensional stability during the manufacture, processing and industrial use of the gypsum product. Set gypsum can shrink or expand, especially under conditions of changing temperature and humidity. For example, when moisture is absorbed by the crystal spaces of the gypsum matrix in a gypsum board or tile exposed to high humidity and temperature, the board expands due to moisture absorption, which can exacerbate sag. In addition, during the manufacture of set gypsum products, there is typically a significant amount of free (unreacted) water that remains in the matrix after the gypsum has set. This free water is typically subsequently removed by mild heating. As the evaporating water leaves the interstitial spaces of the gypsum matrix, the matrix tends to shrink due to the inherent forces of the set gypsum (i.e., the water is held in the matrix in the portion between the interlocking set gypsum crystals, which then move closer together as the water evaporates).
There are many advantages if such dimensional instability can be avoided or reduced. For example, if the gypsum board does not shrink during drying, more products will be produced using existing gypsum board production methods, and gypsum products that rely on maintaining precise shapes and size ratios (such as used in molding and forming) will be better suited for their purposes. For example, some mortars intended for use on interior wall surfaces of buildings have advantages in that they do not shrink during drying, so that thicker layers of mortar can be used without fear of cracking, without the need to apply thin layers multiple times and so that it takes a long time between layers for them to dry sufficiently.
Other particular problems exist with some specialty types of gypsum products. For example, the production of low density gypsum products often uses foaming agents to create water bubbles in the calcined gypsum slurry (flowable aqueous mixture) that, when set gypsum is formed, create corresponding permanent voids in the product. A problem that often arises is that because the aqueous foam used is inherently unstable, many of the water bubbles collect and escape from the thinner slurry (as do the bubbles in the bubble bath) before the set gypsum is formed, so that to obtain a product of the desired density, a large amount of foaming agent must be used to create the desired amount of voids in the set gypsum. This increases the cost and the risk of chemical foaming agents having adverse effects on other components or characteristics of the gypsum product. Accordingly, there is a need to reduce the amount of foaming agent required to create the desired amount of voids in the set gypsum product.
There is also a need for a new and improved composition and method for producing set gypsum-containing products made from mixtures containing high concentrations (i.e., at least 0.015% by weight based on the weight of calcium sulfate material in the mixture) of chloride ions or salts thereof. The chloride ions or salts thereof may be impurities in the calcium sulfate material itself or in the water used in the mixture (e.g., seawater or brackish ground water) that could not have been used to prepare a stable set gypsum product prior to the present invention.
There is also a need for a new and improved composition and method for treating set gypsum to improve its strength, resistance to permanent deformation (e.g., sag resistance), and dimensional stability.
There is a continuing need for new and improved set gypsum products, and compositions and methods for producing the same, which solve, avoid or reduce the above-mentioned problems. The present invention meets these needs.
Summary of the invention
The present inventors have surprisingly discovered set gypsum-containing products and compositions and methods for making them that unexpectedly meet the above-described needs. Each of the embodiments of the present invention satisfies one or more of these needs.
The set gypsum-containing product of the invention having improved resistance to permanent deformation is prepared according to the invention by first forming a mixture of a calcium sulfate material, water and an amount of one or more reinforcing materials selected from the group consisting of condensed phosphoric acids, each containing 2 or more phosphoric acid units; and condensed phosphates or condensed phosphate ions, each containing 2 or more phosphate units.
The mixture is then maintained under conditions sufficient for the calcium sulfate material to form an improved set gypsum material.
As used herein, the term "calcium sulfate material" refers to anhydrous calcium sulfate; calcium sulfate hemihydrate; calcium sulfate dihydrate; calcium and sulfate ions; or a mixture of any or all of them.
In some embodiments of the invention, the calcium sulfate material is primarily calcium sulfate hemihydrate. In this case, all of the above-mentioned reinforcing materials will give the set gypsum formed improved resistance to permanent deformation. However, some reinforcing materials (e.g., sodium trimetaphosphate (also referred to herein as STMP), sodium hexametaphosphate (also referred to herein as SHMP) having 6-27 repeating phosphate units, and ammonium polyphosphate (also referred to herein as APP) having 1000-3000 repeating phosphate units) will provide preferred advantages, such as greater sag resistance. Furthermore, APP provides the same sag resistance as that provided by STMP, even when only one-quarter of the STMP concentration is added.
In some preferred embodiments of the invention, this is accomplished by adding trimetaphosphate ion to the mixture of calcined gypsum and water from which the set gypsum product is to be produced (as used herein, the term "calcined gypsum" refers to alpha calcium sulfate hemihydrate, beta calcium sulfate hemihydrate, water-soluble calcium sulfate anhydrite, or mixtures of any or all of them, and the terms "set gypsum" and "hydrated gypsum" refer to calcium sulfate dihydrate). When the water in the mixture reacts spontaneously with the calcined gypsum to form set gypsum, we have surprisingly found that the set gypsum has improved strength, resistance to permanent deformation (e.g., sag resistance) and dimensional stability compared to set gypsum formed from a mixture that does not contain trimetaphosphate ions. The mechanism by which these properties are improved is not clear.
Furthermore, the present inventors have unexpectedly found that trimetaphosphate ions (like APP) do not retard the rate at which calcined gypsum forms set gypsum. In fact, in the use range of trimetaphosphate ion, the hydration rate of calcined gypsum to set gypsum is actually accelerated when the addition amount is large. This is particularly surprising because of the increased strength of set gypsum, since it is generally believed in gypsum technology that phosphoric acid or phosphate materials retard the formation of set gypsum and reduce the strength of the formed gypsum. This is true for most of these species, but not for the trimetaphosphate ion.
Thus, in general, some preferred embodiments of the present invention provide a method of producing a set gypsum-containing product having improved strength, resistance to permanent deformation (e.g., sag resistance), and dimensional stability, comprising: a mixture of calcined gypsum, water, and trimetaphosphate ion is formed and maintained at conditions sufficient to convert calcined gypsum to set gypsum, e.g., preferably at a temperature of less than about 120F.
In some preferred embodiments of the invention, the method is a method of producing a gypsum board having a core of set gypsum interlayer sandwiched between cover sheets of paper or other material. The panels are prepared by forming a flowable mixture of calcined gypsum, water and trimetaphosphate ions, depositing the mixture between cover plates, and allowing the resulting assembly to set and dry.
When the board thus formed has all the desired improved properties-increased strength, resistance to permanent deformation (e.g. sagging) and dimensional stability, it has been observed that for unknown reasons the bond strength between the gypsum core and the cover board (which usually contains paper) is lost or even lost when the board for some reason becomes wet or does not completely dry during production, even when the board contains typical non-pregelatinized starches (e.g. acid-modified starches) which usually give better integrity of the paper-to-core bond. The cover sheet can peel away from the gypsum board, which is unacceptable. The inventors fortunately have also discovered a solution to this potential problem. It has been found that this problem can be avoided by adding pregelatinized starch to the produced slurry. The starch is then distributed throughout the formed gypsum core and it has been surprisingly found that doing so avoids weakening the bond between the core and the cover sheet.
Thus, in some embodiments of the present invention, compositions and methods are provided for producing further improved gypsum boards. The composition contains a mixture of water, calcined gypsum, trimetaphosphate ion, and pregelatinized starch. The method includes forming such mixtures, depositing them between cover plates, and allowing the resulting assembly to set and dry.
In the event that it is desired to produce lightweight gypsum board, the present invention provides compositions and methods for producing such lightweight gypsum board. The composition contains a mixture of water, calcined gypsum, trimetaphosphate ion, and water foam, and the method comprises forming such a mixture, depositing them between cover plates, and allowing the resulting assembly to set and dry. The composition and method provide lightweight panels because the bubbles of the water foam create corresponding air voids in the set gypsum core forming the panel. The overall strength of the panel is higher than panels produced with water foam in the prior art mix because the trimetaphosphate ions in the mix used to form the panels of the present invention provide increased strength. For example, a ceiling tile of 1/2 inches thick made according to the present invention has better resistance to permanent deformation (e.g., sag resistance) than a ceiling tile of 5/8 inches thick made using the prior art compositions and methods. Therefore, the present invention can significantly save the cost of producing the ceiling.
The inventors have surprisingly found that the mixture contains trimetaphosphate in addition to the aqueous foam, which also has other advantages. That is, it has been found that when trimetaphosphate ions are present in the mixture, proportionately higher voids (more total void volume) are produced per unit amount of aqueous foam used in the formed gypsum product. The reason for this is not clear, but it is advantageous to produce the desired amount of void volume in the set gypsum product, provided that a small amount of foaming agent is used. This in turn reduces the cost of production and the risk of detrimental effects of the chemical foaming agent on other components or characteristics of the gypsum product.
In some embodiments of the present invention, there are provided composite boards comprising set gypsum and a reinforcing material, prepared as follows: forming or depositing a mixture on a surface, wherein the mixture contains a reinforcing material, a calcium sulfate material, water, and an amount of one or more reinforcing materials selected from the group consisting of: condensed phosphoric acids, each containing 2 or more phosphoric acid units; and condensed phosphates or condensed phosphate ions, each containing 2 or more phosphate units. The mixture is then maintained under conditions sufficient for the calcium sulfate material to form a set gypsum material.
The present invention also provides a composite board comprising set gypsum and matrix particles, at least a portion of the set gypsum being located at and near the interstices of the matrix particles that are readily accessible. The plate is prepared by forming or depositing a mixture on the surface, wherein the mixture comprises: a matrix particle; calcium sulfate hemihydrate, at least a portion of which is in crystalline form, at and near the interstices of the matrix particles; water and an amount of one or more reinforcing materials selected from the group consisting of: condensed phosphoric acids, each containing 2 or more phosphoric acid units; and condensed phosphates or condensed phosphate ions, each containing 2 or more phosphate units. The mixture is then maintained under conditions sufficient for the calcium sulfate hemihydrate to form set gypsum, whereby the set gypsum portion at and near the readily accessible voids of the matrix particles is formed by in situ hydration of the calcium sulfate hemihydrate crystals in and near the voids of the matrix particles.
The present invention also provides set gypsum-containing machinable articles prepared by forming a mixture containing starch, water-redispersible polymer particles, a calcium sulfate material, water, and an amount of one or more reinforcing materials selected from the group consisting of: condensed phosphoric acids, each containing 2 or more phosphoric acid units; and condensed phosphates or condensed phosphate ions, each containing 2 or more phosphate units. The mixture is then maintained under conditions sufficient for the calcium sulfate material to form a set gypsum material.
The present invention also provides a set gypsum product for modifying a joint between edges of gypsum board, the product being prepared by filling a joint with a mixture comprising a binder, a thickener, a non-homogenizing agent, a calcium sulfate material, water and an amount of one or more reinforcing materials selected from the group consisting of: condensed phosphoric acids, each containing 2 or more phosphoric acid units; and condensed phosphates or condensed phosphate ions, each containing 2 or more phosphate units. The mixture is then maintained under conditions sufficient for the calcium sulfate material to form a set gypsum material.
The present invention also provides a set gypsum acoustical tile prepared by forming or depositing in a tray trough a mixture comprising gelatinized starch, mineral wool, a calcium sulfate material, water, and an amount of one or more reinforcing materials selected from the group consisting of: condensed phosphoric acids, each containing 2 or more phosphoric acid units; and condensed phosphates or condensed phosphate ions, each containing 2 or more phosphate units. The mixture is then maintained under conditions sufficient for the calcium sulfate material to form a set gypsum material.
The present invention also provides another type of set gypsum acoustical tile prepared by forming or depositing in a tray trough a mixture comprising gelatinized starch, expanded perlite particles, a fibrous reinforcing agent, a calcium sulfate material, water, and an amount of one or more reinforcing materials selected from the group consisting of: condensed phosphoric acids, each containing 2 or more phosphoric acid units; and condensed phosphates or condensed phosphate ions, each containing 2 or more phosphate units. The mixture is then maintained under conditions sufficient for the calcium sulfate material to form a set gypsum material.
The present invention also provides a set gypsum product prepared by forming a mixture of a reinforcing material, calcium sulfate dihydrate, and water. More specifically, these embodiments include treating the gypsum cast with a reinforcing material. It has been found that the resulting mixture of reinforcing material, water and calcium sulfate dihydrate provides a set gypsum product having improved strength, resistance to permanent deformation (e.g., sag resistance), and dimensional stability. This post-solidification treatment can be achieved by adding a reinforcing material, by spraying or soaking the calcium sulphate dihydrate cast body with the reinforcing material.
In some embodiments of the invention, compositions and methods are provided for producing set gypsum-containing products from mixtures containing high concentrations of chloride ions or salts thereof (i.e., at least 0.015% by weight based on the calcium sulfate material in the mixture). The chloride ions or salts can be impurities in the calcium sulfate material itself or in the water used in the mixture (e.g., seawater or brackish ground water) that could not have been used to prepare a stable set gypsum product prior to the present invention.
Description of the drawings
FIG. 1 is a chart depicting the weight of a gypsum board article including the gypsum board of the present invention.
FIG. 2 is a graph comparing the sag resistance of gypsum boards made according to the present invention with commercially available gypsum boards, wherein all test boards were assembled using conventional staple fastening and screw-down ceiling connectors.
Fig. 3 is a graph comparing the sag resistance of gypsum boards made according to the present invention to commercially available gypsum boards, wherein all test boards were assembled using a conventional F2100 ceiling connector (i.e., adhesive).
FIG. 4 is a graph comparing the sag deflection effect of gypsum boards made according to the present invention with commercially available gypsum boards.
FIG. 5 is a graph depicting the effect of sag deviation on gypsum board treated in accordance with the present invention, which has been made using gypsum board including pre-set and dried gypsum (i.e., calcium sulfate dihydrate).
Description of the preferred embodiments
The present invention can be practiced with compositions and methods similar to those used in the art for making various set gypsum products. The compositions and methods of some preferred embodiments of the present invention differ from the prior art methods of making various set gypsum-containing products primarily by the inclusion of trimetaphosphate salt such that in the methods of the present invention, the rehydration of calcined gypsum to form set gypsum occurs in the presence of trimetaphosphate ion, thereby demonstrating the advantages of the present invention. In other aspects, the compositions and methods of the invention can be the same as the corresponding compositions and methods of the prior art.
The trimetaphosphate salt contained in the composition of the present invention may include any water-soluble trimetaphosphate salt that does not adversely interact with the other components of the composition. Examples of some practical salts are sodium trimetaphosphate, potassium trimetaphosphate, ammonium trimetaphosphate, lithium trimetaphosphate, aluminum trimetaphosphate and mixtures of these salts. Sodium trimetaphosphate is preferred. It is readily commercially available, for example, from Solutia corporation of St.Louis, Missouri, a unit formerly Monsanto corporation of St.Louis, Missouri.
For use in a preferred method of practicing the invention, trimetaphosphate salt can be dissolved in an aqueous mixture of calcined gypsum to a concentration of from about 0.004 to about 2.0% by weight trimetaphosphate ion based on the weight of calcined gypsum. The preferred concentration of trimetaphosphate ion is from about 0.04 to about 0.16% by weight. A more preferred concentration is about 0.08% by weight. If ease of storage and transport is required in the practice of some embodiments of the invention, the trimetaphosphate salt can be pre-dissolved in water and mixed into the mixture as an aqueous solution.
According to a preferred embodiment of the present invention, the trimetaphosphate ion need only be present in the aqueous mixture of calcined gypsum during hydration of calcined gypsum to form set gypsum. Thus, while it is generally more convenient, and thus preferred, to mix trimetaphosphate ions into the mixture at an early stage, trimetaphosphate ions can also be mixed into the mixture of calcined gypsum and water at a later stage. For example, in the preparation of a typical gypsum board, water and calcined gypsum are added together in a mixing apparatus, thoroughly mixed, and then typically deposited onto a cover sheet on a conveyor belt, and a second cover sheet is placed over the deposited mixture before a quantity of calcined gypsum is rehydrated to form set gypsum. Although it is more convenient to add the trimetaphosphate ion to the mixture in a mixing device during its preparation, the trimetaphosphate ion can also be added at a later stage, for example by spraying an aqueous solution of trimetaphosphate ions into the aqueous mixture of calcined gypsum that has been deposited just prior to placing the second plate over the deposit so that the aqueous solution of trimetaphosphate ions wets out into the deposited mixture and they are present as bulk hydration occurs to form set gypsum.
Other methods of adding trimetaphosphate ion to the mixture will be apparent to those of ordinary skill in the art and are, of course, within the scope of the present invention. For example, one or both cover sheets may be pre-coated with a trimetaphosphate salt so that when the deposited aqueous calcined gypsum mixture contacts the cover sheets, the trimetaphosphate salt dissolves and causes the trimetaphosphate ions to migrate into the mixture. Another method is to mix the trimetaphosphate salt with the gypsum even before heating to form calcined gypsum so that when the calcined gypsum is mixed with water and rehydration occurs, the salt is already present.
Other methods of adding trimetaphosphate ion to the mixture are by adding trimetaphosphate ion to set gypsum by any suitable means, such as spraying or wetting the set gypsum with a solution containing trimetaphosphate. It has been found that the trimetaphosphate ions can migrate into the set gypsum through conventional paperboard used in processing set gypsum.
The calcined gypsum used in the present invention may be present in the forms and concentrations typical for those used in the corresponding embodiments of the prior art. It may be natural or synthetic alpha calcium sulfate hemihydrate, beta calcium sulfate hemihydrate, water soluble calcium sulfate anhydrite or a mixture of any or all of them. In some preferred embodiments, calcium sulfate alpha hemihydrate is used because it produces set gypsum with higher strength. In other preferred embodiments, beta calcium sulfate hemihydrate or a mixture of beta calcium sulfate hemihydrate and water soluble calcium sulfate anhydrite is used.
In the practice of the present invention, other conventional additives may be used in conventional amounts to impart desired characteristics and to facilitate manufacturing operations, such as water foams, set accelerators, set retarders, re-calcination inhibitors, binders, adhesives, dispersion aids, leveling or non-leveling agents, thickeners, bactericides, fungicides, pH adjusters, colorants, reinforcing materials, flame retardants, water repellents, fillers, and mixtures thereof.
In some preferred embodiments of the invention, the methods and compositions are used to make gypsum board comprising a core of set gypsum material sandwiched between cover sheets, with trimetaphosphate ion being used in the amounts and manners described above. On the other hand, the compositions and methods can be carried out with the same components and in the same manner as corresponding compositions and methods of the prior art for making gypsum board, for example, as disclosed in U.S. Pat. Nos. 4009062 and 2985219, which are incorporated herein by reference. The boards made using this preferred inventive composition and method have improved strength, resistance to permanent deformation, and dimensional stability.
In a preferred method and composition for making gypsum board, the facing sheets of the board contain paper, and pregelatinized starch is also used, to avoid an otherwise somewhat increased risk of paper delamination under extremely humid conditions. The pre-gelatinization of the raw starch is achieved by cooking in water at a temperature of at least 185F or by other well-known methods.
Some examples of readily available gellable starches which serve the purpose of the present invention are (identified by their trade names): PCF1000 starch, sold by Lauhoff Grain company; AMERIKOR818 and HQM PREGEL starches, both sold by Archer Daniels Midland.
In order to use pregelatinized starches in the preferred embodiment of the invention, they are present in the aqueous mixture of calcined gypsum in an amount of from about 0.08 to about 0.5% by weight based on the weight of calcined gypsum. Preferably, the pregelatinized starch is present in an amount of about 0.16 to about 0.4% by weight. More preferably about 0.3% by weight. The pregelatinized starch of the embodiments of the present invention can also be used to replace all or part of the starch conventionally used in the prior art, if the corresponding embodiments of the prior art also contain starch that has not been pregelatinized, as is done in many cases.
In embodiments of the present invention where a foaming agent is used to create voids in the set gypsum product to provide a lightweight product, any of the conventional foaming agents known to be useful in preparing foamed set gypsum products can be used. Many such blowing agents are well known and readily available, for example from GEO Specialty Chemicals of Ambler, Pennsylvania. Further descriptions of useful blowing agents are found, for example, in: US patent US 4676835; 5158612, respectively; 5240639 and 5643510; and PCT International publication WO95/16515, published on 22.6.1995.
In many cases, it is preferable to create a larger number of voids in the gypsum product to maintain its strength. This can be achieved by using a foaming agent that produces a foam that is less stable when contacted with the calcined gypsum slurry. Preferably, this is achieved by incorporating a large amount of a blowing agent known to produce less stable foams with a small amount of a blowing agent known to produce more stable foams.
Such foaming agent mixtures may be premixed "off-line", i.e., separately from the process of preparing the foamed gypsum product. However, it is preferred to mix such blowing agents both simultaneously and continuously, as an integral "in-line" part of the process. This can be done, for example, by pumping separate streams of different foaming agents and conveying the streams together or just before into a foam generator, the function of which is to produce a stream of aqueous foam that is subsequently injected and mixed with the calcined gypsum slurry. By mixing in this manner, the ratio of foaming agent in the mix can be simply and efficiently adjusted (e.g., by varying the flow rate of one or both of the separate streams) to produce the desired void characteristics in the foamed set gypsum product. Such adjustments will be made based on testing of the final article to determine if such adjustments are needed. This "in-line" mixing and conditioning is further described in U.S. patent No. 5643510 and co-pending U.S. patent application 08/577367, filed on 12/22 of 1995.
An example of a class of blowing agents useful for producing unstable foams has the formula
ROSO3ΘM⊕ (Q)
Wherein R represents an alkyl group having 2 to 20 carbon atoms and M represents a cation. Preferably, R represents an alkyl group having 8 to 12 carbon atoms.
An example of a class of blowing agents useful for producing stable foams has the formula
CH3(CH2)xCH2(OCH2CH2)YOSO3ΘM⊕ (J)
Wherein X represents a number from 2 to 20, Y represents a number from 0 to 10 and the value is greater than 0 in at least 50% by weight of the blowing agent, and M represents a cation.
In some preferred embodiments of the present invention, blowing agents having the above formulas (Q) and (J) are mixed together such that the blowing agent portion of formula (Q) and the blowing agent portion of formula (J) (Y is 0) together comprise from 86 to 99 weight percent of the formed blowing agent mixture.
In some preferred embodiments of the invention, the aqueous foam has been produced from a premixed blowing agent having the formula
CH3(CH2)xCH2(OCH2CH2)YOSO3ΘM⊕ (Z)
Wherein X represents a number from 2 to 20, Y represents a number from 0 to 10 and the value is 0 in at least 50% by weight of the blowing agent, and M represents a cation. Preferably, the blowing agent of formula (Z) has from 86 to 99% by weight of Y being O.
In some preferred embodiments of the invention, the methods and compositions are used to prepare composite boards comprising set gypsum and particles of reinforcing material, using trimetaphosphate ion in the concentrations and manners described above. It is particularly preferred that the composite article comprises set gypsum and matrix particles, at least a portion of the set gypsum being located in and adjacent to the voids of the readily accessible matrix particles. The composition of the invention comprises a mixture of: a matrix particle having an easily accessible void therein; calcined gypsum at least partially in crystalline form at and near the interstices of the matrix particles; and a water-soluble trimetaphosphate salt. The composition may be mixed with water to form a mixture of water of the present invention, matrix particles having readily accessible voids therein, calcined gypsum (at least a portion of which is in crystalline form at and near the voids of the matrix particles), and trimetaphosphate ions. The method includes forming such a mixture, depositing the mixture on a surface or injecting into a mold, allowing them to set and dry. Alternatively, the compositions and methods can be practiced with the same components and embodiments as the corresponding compositions and methods of the prior art for making composite panels, for example, as disclosed in U.S. patent No. 5320677, which is incorporated herein by reference.
In some preferred embodiments of the present invention, the methods and compositions are used to prepare machinable materials using trimetaphosphate ion in the concentrations and manners described above. In some preferred forms of these embodiments, the composition contains a mixture of calcined gypsum, water-soluble trimetaphosphate salt, starch, and water-redispersible polymer particles. The composition is mixed with water to form a mixture of water, calcined gypsum, trimetaphosphate ion, starch, and water-redispersible polymer particles of the present invention. The method includes forming such a mixture, depositing the mixture on a surface or injecting into a mold, allowing them to set and dry. In other respects, the compositions and methods can be practiced with the same components and embodiments as the corresponding compositions and methods of the prior art for preparing machinable stucco materials, except for the incorporation of trimetaphosphate and trimetaphosphate ions, as disclosed, for example, in U.S. patent No. 5534059, which is incorporated herein by reference.
In some preferred embodiments of the invention, the methods and compositions are used to prepare materials for use in modifying the joint between the edges of gypsum boards using trimetaphosphate or trimetaphosphate ion at the concentrations described above. For other aspects, the compositions and methods can be carried out using the same components and embodiments as corresponding compositions and methods used in the prior art for preparing joint-modifying materials, except for the incorporation of trimetaphosphate and trimetaphosphate ions, for example, as disclosed in U.S. patent No. US3297601, which is incorporated herein by reference. In some preferred forms of this embodiment, the composition contains a mixture of calcined gypsum, a water-soluble trimetaphosphate salt, a binder, a thickener, and a non-homogenizing agent. The composition may be mixed with water to form a mixture of calcined gypsum, trimetaphosphate ion, binder, thickener, and non-homogenizing agent of the present invention. The method includes forming such a mixture, injecting the mixture into the joint between the edges of the gypsum board, allowing them to set and dry.
In this preferred joint modification embodiment, the binder, thickener and non-leveling agent are selected from components well known to those skilled in the joint compound art. For example, the binder may be a conventional latex binder, with poly (vinyl acetate) and poly (ethylene-co-vinyl acetate) being preferred, and their content in the composition is about 1-15% by weight. Examples of useful thickeners are cellulosic thickeners such as ethylhydroxyethyl cellulose, hydroxypropyl methylcellulose, methylhydroxypropyl cellulose or hydroxyethyl cellulose, which are present in the composition in an amount of about 0.1 to 2% by weight. Examples of suitable non-homogenizing agents are attapulgite, sepiolite, bentonite and montmorillonite clays, which are present in the composition in an amount of about 1 to 10% by weight.
In some preferred embodiments of the present invention, the methods and compositions are used to prepare acoustical tiles using the above concentrations of trimetaphosphate ion. In some preferred forms of this embodiment, the composition contains water, calcined gypsum, trimetaphosphate ion, a mixture of gelatinized starch and mineral wool, or a mixture of water, calcined gypsum, trimetaphosphate ion, gelatinized starch, expanded perlite particles, and a fiber reinforcement. The method includes forming such a mixture, casting the mixture into a tray trough, allowing them to set and dry. In other respects, the compositions and methods can be practiced with the same components and in the same manner as the corresponding compositions and methods of the prior art for making acoustical tiles, except for the incorporation of trimetaphosphate ion, as disclosed, for example, in U.S. patent nos. 5395438 and 3246063, which are incorporated herein by reference.
The following examples further illustrate some preferred embodiments of the present invention and compare them to methods and compositions outside the scope of the present invention. Unless otherwise indicated, the concentrations of the materials in the compositions and mixtures are in percent by weight based on the weight of calcined gypsum. The abbreviation "STMP" means sodium trimetaphosphate and the abbreviation "TMP" means trimetaphosphate.
Example 1
Cubic compressive strength of laboratory
Samples of gypsum articles were prepared according to the present invention and compared to the compressive strength of samples prepared using different methods and compositions. The test was performed according to ASTM C472-93.
Preparation of test specimens with the dry mix: 500g beta calcium sulfate hemihydrate; 0.6g of an accelerator, known as CSA (weather stability Accelerator), purchased from the American Gypsum company, containing finely ground particles of calcium sulfate dihydrate coated to maintain effectiveness; and 0g of additive (control), 0.5-2g of STMP (preferred inventive sample) or 0.5-2g of other phosphate additives (comparative sample). The samples were then mixed with 700ml tap water at a temperature of 70F in a 2 litre WARING mixer, allowed to wet for 5 seconds and mixed at low speed for 10 seconds. The slurry thus formed was cast into a mold to make cubes (2 inches per side). After the calcium sulfate hemihydrate sets to form gypsum (calcium sulfate dihydrate), the cubes are removed from the mold and dried in a 112F air oven for at least 72 hours, or until their weight ceases to change. The dried cubes had a density of about 44 pounds per foot3(pcf)。
The compressive strength of each cube was determined on a SATEC tester. The average of the three samples is shown as the result in table 1 below. The strength values of the control samples varied because various sources of beta calcium sulfate hemihydrate and/or different batches of beta calcium sulfate hemihydrate were used. The results in the table show the pounds per inch2(psi) measured compressive strength and% change in strength (% Δ) from the relevant control. The evaluation measurements had a trial error of about +/-5% (thus showing a 10% increase in intensity compared to the control, virtually anywhere between 5-15%).
TABLE 1
Compressive strength
| Additive agent | 0% additive (psi) | 0.1% of additive (psi;% Delta) | 0.2% of additive (psi;% Delta) | 0.4% of additive (psi;% Delta) | 0.8% of additive (psi;% Delta) |
| STMP | 987 | 1054；6.8 | 1075；8.9 | 1072；8.6 | - |
| STMP | 724 | 843；16.4 | 957；32.2 | 865；19.5 | 783；8.1 |
| STMP | 742 | 819；10.4 | 850；14.6 | - | - |
| STMP | 714 | 800；12.0 | 834；16.8 | - | - |
| STMP | 842 | 985；17.0 | 1005；19.4 | 1053；25.1 | 611；-27.4 |
| STMP | 682 | 803；17.7 | 826；21.1 | 887；30.1 | - |
| Sodium phosphate | 950 | 951；0.1 | 929；-2.2 | - | - |
| Sodium tripolyphosphate | 950 | 993；4.5 | 873；-8.1 | - | - |
| Sodium hexametaphosphate | 950 | 845；-11.1 | 552；-41.9 | - | - |
| Dicalcium phosphate | 763 | 769；0.8 | 775；1.6 | 761；-0.3 | - |
| Disodium phosphate | 763 | 757；-0.8 | 728；-4.6 | 700；-8.3 | - |
| Phosphoric acid-calcium hydrate | 763 | 786；3.0 | 766；0.4 | 824；8.0 | - |
The data in Table 1 illustrate that the strength of the inventive Sample (STMP) is generally significantly increased as compared to the control, while the strength of the comparative sample is generally increased little, or not increased, or even significantly decreased.
Example 2
Permanent deformation resistance (sag resistance of plasterboard laboratory)
In the laboratory, gypsum board samples were prepared according to the present invention and compared to the resistance to permanent deformation of sample boards prepared using methods and compositions outside the scope of the present invention.
The samples were prepared by mixing the mix in a 5 liter WARING mixer at low speed for 10 seconds: 1.5kg beta calcium sulfate hemihydrate; 2g of CSA accelerator; 2 liters of tap water; and 0g of additive (control), 3g of STMP (inventive) or 3g of further additive (comparative). The slurry thus formed was cast into a tray tank to prepare gypsum flat plate samples, each having a size of about 6X 24X 1/2 inches. After the calcium sulfate hemihydrate sets to form gypsum (calcium sulfate dihydrate), the boards are dried in a 112F oven until their weight stops changing. The final weight of each panel was recorded. To avoid the effect of the cover paper on the sag performance of the gypsum board under wet conditions, no paper overlay was applied to the boards.
Each drying panel was then laid flat on two horizontal positions of 1/2 inch wide supports, the length of which extended to support the full width of the panel, one at each end of the panel. The panel was held in this position for a specified period of time (4 days in this example) under continuous ambient conditions of 90F temperature and 90% relative humidity. The degree of sag of the panel is then determined by measuring the distance (in inches) between the center of the top surface of the panel and an imaginary horizontal plane between the top surface end edges of the panel. It is believed that the resistance of the set gypsum matrix of the board to permanent deformation is inversely proportional to the degree of sag of the board. Thus, the greater the degree of sag, the lower the relative permanent set resistance of the set gypsum matrix-containing board.
The test for resistance to permanent deformation, including the composition and concentration of the additives (% by weight based on calcium sulfate hemihydrate), the final weight of the board and the measured degree of sag, is shown in table 2. The additives used in the comparative examples (outside the scope of the invention) represent other materials that were intended to improve the sag resistance of gypsum board under high temperature conditions.
TABLE 2
Degree of gypsum board sag
| Additive agent | Additive (weight%) | Plate weight (g) | Plate droop (inch) |
| None (control group) | 0 | 830 | 0.519 |
| STMP | 0.2 | 838 | 0.015 |
| Boric acid | 0.2 | 829 | 0.160 |
| Sodium aluminium phosphate | 0.2 | 835 | 0.550 |
| Wax emulsion | 7.5 | 718 | 0.411 |
| Glass fiber | 0.2 | 838 | 0.549 |
| Glass fiber and boric acid | 0.2+0.2 | 825 | 0.161 |
The data in table 2 show that the panels prepared according to the invention (STMP) are more resistant to sagging (and therefore also to permanent deformation) than the panels of the control group and the panels of the comparative example not according to the invention. In addition, the sag rate of the panels made according to the present invention is much less than 0.1 inch per 2 feet of panel sag, and thus is not readily observable to the human eye.
Example 3
Permanent deformation resistance (sag resistance of gypsum board production line)
Fig. 1 shows a comparison of the weight of the articles, and fig. 2 and 3 show the sag resistance of such articles. The product weight of the 1/2 inch indoor ceiling tile of the invention (i.e., mixing trimetaphosphate salt with calcined Gypsum and water) was the same as the weight of 1/2 inch SHEETROCK ® conventional Gypsum board for an indoor tile made by United States Gypsum Company. The average 1/2 inch indoor ceiling shown in fig. 1 is a Gold Bond ® high strength ceiling made by National Gypsum Company (National Gypsum Company). The average 5/8 inch gypsum board shown in FIG. 1 is SHEETROCK ® 5/8 inch Firecode type X gypsum board manufactured by American Gypsum.
FIG. 2 is a graph comparing the sag resistance of gypsum boards made according to the present invention with the sag resistance of the above-described commercially available gypsum boards, all of which were installed using conventional staple and screw-down ceiling connectors.
FIG. 3 is a graph comparing the sag resistance of gypsum boards made according to the present invention to the sag resistance of the above-described commercially available gypsum boards, all of which were installed using a conventional F2100 two-part polyurethane bonded ceiling joint.
The following are descriptions of gypsum board and other detailed constructions for making ceiling tiles for use in sag comparisons as depicted in fig. 2 and 3:
A. gypsum board
1.1/2 inch by 48 inch by 96 inch, prepared according to the invention.
2.1/2 inch by 48 inch by 96 inch, national gypsum company Gold Bond ® high strength ceiling.
3.1/2 inch by 48 inch by 96 inch, conventional SHEETROCK ® gypsum board manufactured by American Gypsum company.
4.5/8 inch by 48 inch by 96 inch, SHEETROCK ® FIRECode type X gypsum board manufactured by American Gypsum company.
B. Framework-18 inches high by 102 inches long, made of nominally 2 inches by 3 inches wood joined by r.j.cole joint compound-USG tuff setting HES joint compound. Seam tape-USG fiberglass mesh self-adhesive attachment seam tape.
C. Vapor barrier coating- #4512 silver vapor barrier, entry: 246900.
D. and blowing glass wool and rock wool mineral fibers on the insulator-Delta blowing insulator.
E. Spray Texture (Texture) -USG SHEETROCK ® ceiling spray Texture Q T homopolymer.
F. Fasteners-1 inch crown (c.) x 1.25 inch long (lg.) x ga.u-type nails, and #6 x 1.25 long drywall screw nails. Foamseal company's F2100 two-part polyurethane adhesive. Ceiling structure
A. 2 x 4s are attached to both ends of the frame to make a frame.
B. A 12(12) block of gypsum board was attached to the framing frame with F2100 adhesive. Gypsum board having an average curl (bead) width of 1 inch was measured.
C. The ceilings were carefully raised and placed on top of the pre-constructed four walls to make an 8 feet by 48 feet house.
D. The ceiling assembly was attached to the ceiling of the wall and secured around the wall with #8 x 3.5 inch screws. The gypsum panels are attached to the frame using screws and staples to form a second ceiling panel. The ceiling is also raised and attached to the four (4) walls.
In each ceiling, 3(3) gypsum boards of various types are used to form 2(2) ceiling boards. One ceiling was mechanically fixed (see fig. 2) while the other ceiling was fixed with only F2100 urethane adhesive (see fig. 3). Gypsum boards of different gypsum board types are laid alternately flat along the ceiling. The frames used were 8 feet 5 inches long by 18 inches high, and spaced 24 inches apart ("o.c.") on center.
The ceiling was mechanically secured at 12 inches along the center of the area frame using 1 inch crown by 1.25 inch long by 16Ga. staples at 7 inch center to center distance along the joint and #6 by 1.25 inch long drywall screws.
Adhesively attached ceilings use a bead (bead) of about 1.25 inches along the frame. The hems are used on one side of the area frame and along the hems on both sides of the gypsum joint frame.
The plasterboard is attached so that its paper-wrapped edge is aligned parallel to the frame chord.
After taping the plaster joint, the starting position was determined. Next, the ceiling tile is coated with a vapor barrier coating and then painted with a texture (textured). Immediately after texturing, a second reading was taken. Rock wool insulation is then blown to the top of the frame. A third reading is then taken. The temperature and humidity are increased while blowing the insulating material to the top of the frame. The target temperature and humidity were 90 ° F and 90% relative humidity. These conditions were maintained for 7 days while measuring deviations every morning and afternoon. After 7 days, the houses were opened and they were allowed to cool to room temperature. The measurement of sag was read for another 3(3) days and the test was terminated.
As shown in fig. 2 and 3, the gypsum board made according to the present invention has significantly better sag resistance than other gypsum boards and below the visual limit of about 0.1 inch per 2 foot length of board sag.
Example 4
Nail pull resistance of laboratory gypsum board
The nail pull resistance of a typical paper-faced gypsum board sample produced in accordance with the present invention and prepared in the laboratory was compared to a control board. Nail pull resistance is a composite measure of the strength of the gypsum board core, its paper facing strength, and the bond between the paper and the gypsum. This test measures the maximum force required to pull a headed nail through the board until a major fracture occurs in the board and is performed according to ASTM C473-95.
Slurry was prepared in a HOBART mixer with medium speed mixing for 40 seconds: 3.0kg beta calcium sulfate hemihydrate; 5g of CSA coagulant; 10g of LC-211 starch (dry milled acid modified non-pregelatinized wheat starch for gypsum board formation, commonly included in prior art formulations, sold by Archer Daniels Midland Milling, Inc.); 20g of hammer-milled paper fibers; 3 liters of tap water; 0-6g STMP; and 0-30g of PCF1000 pregelatinized corn starch, sold by the company Lauhoff Grain.
The slurry thus formed was cast on top of paper in a tray tank and then coated on top of it to prepare flat gypsum board samples each having dimensions of 14 x 24 x 1/2 inches. The paper on one side is a multi-ply paper with manila outer folds (ply) and the paper on the other side is a multi-ply newsprint strip (newstone), both of which are typical papers used in the gypsum board industry for making paper-faced gypsum board. Each panel was then held in a 350F oven until they lost 25% by weight, and then transferred and held in a 112F oven until they reached a constant weight.
The final panel weight and nail pull resistance were determined. The results are shown in Table 3.
TABLE 3
Nail pull resistance
| STMP concentration (% by weight) | PCF1000 starch (% by weight) | Plate weight (lbs/1000 ft)2) | Nail pull resistance (1bs) |
| 0 | 0 | 2465 | 150 |
| 0.1 | 0 | 2454 | 155 |
| 0.2 | 0 | 2326 | 158 |
| 0.1 | 0.5 | 2458 | 168 |
| 0.2 | 1.0 | 2495 | 176 |
The results in table 3 show that the panels prepared according to the invention have a very high overall strength (nail pull resistance) compared to the control panels.
Example 5
Production line gypsum board dimensional stability and permanent deformation resistance
In a typical large-scale production line, paper-faced foamed gypsum board is produced in an industrial gypsum board production facility. Gypsum boards were prepared with various concentrations of trimetaphosphate ion and compared to the dimensional stability and permanent set resistance of control boards (prepared without the addition of trimetaphosphate ion). In the preparation of some gypsum boards, the gypsum boards are prepared using methods and components typical of those used in the prior art to produce gypsum boards, except for the use of trimetaphosphate ions. The components and their approximate weight percentages (expressed in narrower ranges by weight of calcined gypsum used) are shown in Table 4.
TABLE 4
Components for producing gypsum boards
| Components | By weight% |
| Beta calcium sulfate hemihydrate | 100 |
| Water (W) | 94-98 |
| Setting accelerator | 1.1-1.6 |
| Starch | 0.5-0.7 |
| Dispersing agent | 0.20-0.22 |
| Paper fiber | 0.5-0.7 |
| Retarder | 0.07-0.09 |
| Foaming agent | 0.02-0.03 |
| Sodium trimetaphosphate ("STMP") | 0-0.16 |
| Re-calcination inhibitor | 0.13-0.14 |
In table 4: the setting accelerator comprises particles of a finely ground sugar coating of calcium sulphate dihydrate, manufactured by the american gypsum company, and is known as "HRA" (denoting heat resistant setting accelerators); the starch was dry milled acid modified HI-BOND starch available from LauhoffGrain corporation; the dispersant was DILOFLO, a naphthalenesulfonate salt available from GEO Specialty Chemicals, Ambler, Peng; the paper fiber is hammer-broken fine paper fiber; the retarder was VERSENEX 80, a chelating agent available from Rogers of Van Walters & Kirkland, Washington; the blowing agent was WITCOLATE1276 available from Witco corporation of Greenwich, Connecticut; sodium trimetaphosphate was purchased from Monsanto corporation of st.louis, Missouri; the recalcination inhibitor was CERELOSE2001, which was used to reduce the dextrose recalcification of the final board product during drying.
Gypsum board was produced on a 4 foot wide continuous line: continuously adding the components to a mixer and mixing to form an aqueous slurry (in a separate foam generating system, a foaming agent is used to generate a water foam; the foam is fed into the slurry through the mixer); continuously depositing the slurry on a paper face sheet (overlay paper) on a conveyor belt; another paper face sheet (bottom paper) was laid over the deposited slurry to form an 1/2 inch thick gypsum board; cutting the moving gypsum board so that the size of the panels is about 12 x 4 feet and 1/2 inches thick when the calcium sulfate hemihydrate hydrates to form calcium sulfate dihydrate to a degree sufficient to harden the slurry enough to be cut accurately; the gypsum board is dried in a heated multi-tier oven.
The resistance of the panels to permanent deformation was then determined by measuring sag as described in example 2, except that the produced panels were cut into test panels of approximately 1 foot by 4 feet (the 1 foot being in the direction of the production line, i.e. parallel). Sag measurements were performed after subjecting the test panels to a temperature of 90F and a relative humidity of 90% for 24, 48 and 96 hours. Table 5 shows the results for the inventive samples produced with various concentrations of trimetaphosphate ion and the control sample (0% sodium trimetaphosphate) produced immediately before and after the inventive samples were produced.
TABLE 5
Droop of gypsum board in production line
(1 ft. times.4 foot board)
| STMP concentration (% by weight) | Plate sag after 24 hours (inches) | Plate sag after 48 hours (inches) | Plate sag after 96 hours (inches) |
| 0 (front) | 3.45 | 3.95 | 5.27 |
| 0.004 | 3.23 | 3.71 | 5.19 |
| 0.008 | 2.81 | 3.31 | 4.58 |
| 0.016 | 1.72 | 1.91 | 2.58 |
| 0.024 | 0.96 | 1.12 | 1.61 |
| 0.04 | 0.49 | 0.68 | 0.82 |
| 0.08 | 0.21 | 0.24 | 0.29 |
| 0 (rear) | 3.65 | 4.58 | 6.75 |
The data in Table 5 show that as the concentration of STMP is increased, the gypsum boards made according to the invention have progressively increased sag resistance (and thus progressively increased permanent set resistance) as compared to the control boards.
Table 5A further illustrates the sag resistance provided by the compositions and methods of the present invention. More specifically, Table 5A shows the moisture deflection of gypsum boards having sag, i.e., 1 foot by 2 foot dimensions as measured according to ASTM C473-95, on a production line having the same formulation as set forth above in Table 4. Table 5A shows that the sag resistance trend measured according to ASTM C473-95 is the same as the sag resistance trend of feldspathic plasterboard (1 foot x 4 foot) shown in fig. 5.
TABLE 5A
ASTM C473-95 for production line gypsum boards
Results of humidification deviation test
| Test number | STMP additive (% by weight) | Dry plate weight lb/MSF | Humidification deflection (inches) for 48 hours | |
| In parallel | Crossing | |||
| Before control group | 0 | 1590 | -0.306 | -0.247 |
| 1 | 0.04 | 1583 | -0.042 | -0.034 |
| 2 | 0.08 | 1609 | -0.027 | -0.021 |
| 3 | 0.16 | 1583 | -0.015 | -0.014 |
| After the control group | 0 | 1585 | -0.409 | -0.145 |
Wet 12X 4 foot line gypsum board and final dried 12X 4 foot line gypsum board (as determined according to ASTM C473-95) were also determined to determine their shrinkage in width and length after drying. The more the plates shrink, the poorer their dimensional stability. The results are shown in Table 6.
TABLE 6
Shrinkage rate of gypsum board in production line
| STMP concentration (% by weight) | Plate Width shrinkage (inch/4 foot) | Plate length shrinkage (inch/12 foot) |
| 0 (control group) | 0.13 | 0.38 |
| 0.004 | 0.06 | 0.38 |
| 0.008 | 0 | 0.31 |
| 0.016 | 0 | 0.25 |
| 0.024 | 0 | 0.25 |
| 0.040 | 0 | 0 |
| 0.080 | 0 | 0 |
| 0.16 | 0 | 0 |
The data in table 6 shows that the plates prepared according to the invention have better dimensional stability than the control plates. When the amount of the STMP added was 0.04% or more, no shrinkage in length and width was observed.
Example 6
Sag resistance under humidified and condensed conditions (production line plasterboard)
Additional tests illustrate the sag resistance provided by the compositions and methods of the present invention. More specifically, production line ceilings were tested where controlled condensation was performed at a vapor barrier placed between the ceiling and the joist. The procedure for this test is as follows. Small-scale shelving and indoor enclosing walls are built. The top and side spaces of the small joist are insulated and kept cool to obtain controlled condensation at the ceiling. The ceiling area is 8 feet by 8 feet, the door frame dimensions are 2 feet by 8 feet, and the center-to-center spacing is 24 inches. The top and sides of the indoor space are surrounded by a 6 mil polymer (poly) vapor barrier, increasing the humidity of the indoor space to achieve controlled condensation at the ceiling.
Two 4 foot by 8 foot panels of test material (one test article and one control article) were attached side by side to the frame with a 6 mil polyethylene vapor barrier layer directly on top of the panels. The ends of the plates are not fixed. The indoor humidity is improved by the steam humidifier, and the temperature in the rest buildings is reduced by the window type air conditioning device. The steam output of the warmer is adjusted until constant condensation occurs at the steam barrier above the ceiling. Constant temperature and constant humidity were not necessarily maintained throughout the test. Thus, the results should be considered as a relative measure of sag resistance between the test article and the control article, with no attempt to predict the amount of sag under defined conditions.
The sag of the ceiling at three locations (midspan between each pair of frames) was then measured periodically along the panel, giving a total of 6 readings of deflection per article per test. In each sag measurement, the temperature within the range of the skulls and the room enclosure was recorded.
For background information, theoretical dew point conditions (assuming constant indoor temperature at 70F.) are shown below.
| At room temperature | Relative humidity of room | Temperature of the rest of the building |
| 70℉70℉70℉70℉70℉ | 50％60％70％80％90％ | 51℉56℉60℉63℉68℉ |
The tests were carried out over a period of 19 days using the following materials: 1/2 inches of a production line gypsum board according to the invention; and 5/8 inch Firecode type X gypsum board as described previously. The results are shown in FIG. 4 below and show that gypsum boards made according to the invention consistently have less sag than the control (i.e., the aforementioned 5/8 inch Firecode type X gypsum board).
In this test, the distributed load applied to the midspan between each frame immediately after the 8 th day reading was 1.0 lb/linear foot. This applied load significantly increased the sag of the control panel, but had little effect on the inventive panel. As shown in fig. 4, the gypsum boards made in accordance with the present invention exhibited sag deviations significantly below the human visual range, i.e., less than 0.1 inch per 2 feet of length.
Example 7
Nail pulling resistance of gypsum board of production line
In a typical large-scale production line, another set of paper-faced foamed gypsum boards is prepared in a gypsum board preparation plant. The gypsum boards were prepared with three concentrations of trimetaphosphate ion and compared to the nail pull resistance of a control board (prepared without the addition of trimetaphosphate ion).
Gypsum board is made using methods and components typical of prior art gypsum board manufacturing methods and components, except that trimetaphosphate ions are used in the manufacture of some boards. The composition and weight percent thereof were the same as those listed in table 4 above. The preparation of the plate is described in example 5.
Nail pull resistance was determined according to ASTM C473-95. The results of the inventive samples prepared with various concentrations of trimetaphosphate ion and the control sample (0% sodium trimetaphosphate) prepared immediately before and after the inventive sample preparation are shown in table 7.
TABLE 7
Nail pulling resistance of gypsum board of production line
| STMP concentration (% by weight) | Nail pull resistance (lbs) |
| 0 (front) | 89 |
| 0.04 | 93 |
| 0.08 | 96 |
| 0.16 | 99 |
| 0 (rear) | 90 |
The results in Table 7 show that gypsum boards made according to the invention have higher overall strength (nail pull resistance) than the control boards.
Example 8
Production line gypsum board paper combines wholeness
In a typical large-scale production line, another set of paper-faced foamed gypsum boards is prepared in a gypsum board preparation plant. The boards were prepared with various concentrations of trimetaphosphate ion, pregelatinized starch, and non-pregelatinized starch, and compared to the integrity of the bond between the gypsum board core and its overlay paper of a control board (without either trimetaphosphate ion or pregelatinized starch added) after conditioning to extreme humidity and humidity conditions.
Gypsum board is made using methods and components typical of prior art gypsum board manufacturing methods and components, except that in some board preparations the trimetaphosphate ion and pregelatinized starch are introduced and the concentration of the non-pregelatinized starch is changed. The composition and weight percent thereof were the same as those listed in table 4 above. The preparation of the plate is described in example 5.
The pregelatinized starch used in the experiments was PCF1000, available from Lauhoff Grain. The non-pregelatinized starch was HI-BOND, a dry-milled acid-modified non-pregelatinized starch available from Lauhoff Grain, Inc.
After the production line made the gypsum board, the board was cut into test specimens measuring 4 x 6 x 1/2 inches (the 4 inches being in the direction of the production line). Each of these small panel samples was then conditioned by maintaining the front side covering the total area of the outer surface of the paper in contact with a cloth completely saturated with water at an ambient temperature of 90F and a relative humidity of 90% for about 6 hours, and the panel samples were then slowly dried under the same environment, removing the cloth, until they reached a constant weight (typically about 3 days). A straight score 1/8 inches deep was then made on the back of the panel specimen 2.5 inches from and parallel to a 6 inch edge. The core was then broken along the score without breaking or stressing the paper on the front side of the board, and the larger piece (2.5 x 6 inches) of the board sample was then rotated to apply a force downward while keeping its back side of the small piece upward static and horizontal in order to apply a force to peel the overlay paper on the front side of the lower board from the large board. The force is increased until the two plates are completely separated. The front side of the large panel was then examined to determine the percent surface area where the overlay paper was completely peeled from the core surface (also referred to as "complete peel"). The percentages are shown in table 8, expressed as "% binding failure".
TABLE 8
Gypsum board paper combination failure of production line
| HI-BOND concentration (% by weight) | STMP concentration (% by weight) | PCF1000 concentration (% by weight) | Binding failure (%) |
| 0.60 | 0 | 0 | 87 |
| 0.60 | 0.08 | 0 | 97 |
| 0.96 | 0.08 | 0 | 97 |
| 0.60 | 0.08 | 0.16 | 42 |
| 0.60 | 0.08 | 0.32 | 0 |
| 0.28 | 0.08 | 0.32 | 20 |
| 0.60 | 0 | 0 | 83 |
The data in table 8 shows the problem of paper-to-core bond failure under extremely humid conditions: STMP makes the problem worse; increasing the concentration of typical non-pregelatinized starch (HI-BOND) did not alleviate the problem; the addition of some pregelatinized starch (PCF1000) reduces or eliminates this problem.
Example 9
Post-treatment of calcium sulfate dihydrate
In some other preferred embodiments of the present invention, the cast calcium sulfate dihydrate body is treated with an aqueous solution of trimetaphosphate ions in a manner sufficient to uniformly disperse the aqueous solution of trimetaphosphate ions in the cast calcium sulfate dihydrate body to improve the strength, resistance to permanent deformation (e.g., sag resistance), and dimensional stability of the set gypsum product after re-drying. More specifically, it has been found that treatment of calcium sulfate dihydrate cast bodies with trimetaphosphate ion improves strength, resistance to permanent deformation (e.g., sag resistance) and dimensional stability to a similar degree as achieved by the embodiment in which trimetaphosphate ion is added to calcined gypsum. Thus, embodiments in which trimetaphosphate ions are added to set gypsum provide novel compositions and methods for preparing improved gypsum products, including (but not limited to) boards, fences, stucco, tile, gypsum/cellulose fiber composites, and the like. Thus, any gypsum-based product requiring tight control of sag resistance will be advantageously obtained from embodiments of the present invention. The treatment may also increase the strength of the gypsum cast by about 15%. The gypsum cast body can be impregnated with 0.04 to 2.0% by weight of trimetaphosphate ions (based on the weight of gypsum) by spraying or soaking with an aqueous solution containing the trimetaphosphate ions, and then dried.
The following are two methods of post-treating set gypsum:
1) mixing stucco and other additives (dry basis) 2) mixing stucco and other additives (dry basis)
Preparing slurry from water and preparing slurry from water
↓ ↓
Foaming (weight or density reduction) mixing/stirring (wet process)
↓ ↓
Gypsum casting/final set gypsum casting/final set
And drying ↓
↓ post-processing with STMP
Post-treatment with STMP (spray surface)
(spray or soak) ↓
↓ dry gypsum product
Redried gypsum casting body ↓
↓' improved plaster product
Improved gypsum product
In both of the above methods, the aqueous trimetaphosphate ion solution is provided in a preferred amount and manner sufficient to achieve a concentration of trimetaphosphate ion (based on the weight of calcium sulfate dihydrate) in the cast calcium sulfate dihydrate body of about 0.04 to about 0.16% by weight.
The beneficial effect of reducing sag variation (i.e., sag resistance) using the first method described above is shown in fig. 5. The results of preparing 5 boards and testing the sag deviation are shown in fig. 5. The dry weight of the panel was 750-785 g. The control board was not applied with any solution after the gypsum was cast/final set and dried. Marking of the board with Water only application means that only the set and dried gypsum casting is sprayed with water and then dried. The board marked with the STMP solution was prepared by spraying a 1% by weight aqueous solution of trimetaphosphate ion onto the set and dried gypsum casting, and then dried. The panels marked with a gypsum-STMP solution are produced by spraying the set and dried gypsum casting with an aqueous mixture saturated with gypsum and containing 1% by weight of trimetaphosphate ions and then drying. In general, it is preferable to spray an aqueous solution containing trimetaphosphate ion at a concentration of 0.5 to 2%. The final content of trimetaphosphate ion in the STMP solution boards and the gypsum-STMP solution boards was 0.2% by weight of the mortar used to prepare the gypsum cast and 0.17% by weight of the set gypsum board formed.
Example 10
Treatment of high salt materials
Other embodiments of the present invention relate to the preparation of set gypsum products from a mixture containing a high concentration of chloride ions or salts thereof (i.e., at least 0.015% by weight based on the weight of calcium sulfate material in the mixture) of a calcium sulfate material and water. The chloride ions or salts thereof can be impurities in the calcium sulfate material itself and in the water used in the mixture (e.g., seawater or brackish ground water) that could not be used to prepare a stable set gypsum product prior to the present invention because of attendant problems such as voids, paper bond failure, end burning, poor resistance to permanent deformation, low strength and low dimensional stability.
The tests in Table 9 relate to gypsum boards prepared and treated in the same manner as described in example 2, except that various levels of chloride and trimetaphosphate ions were added to the mixture. Sag deviations were tested in the same manner as described in example 2.
TABLE 9
With mortars containing different amounts of STMP and sodium chloride
Preparation of Gypsum cube (2X 2)/Board core
Laboratory test results for (24X 6X 0.5) castings
| Sodium chloride additive (% by weight) | STMP additive (% by weight) | Dry plate weight (g) | Water absorbed in 90/90 Room (% by weight) | Deflection of 48 hours humidification sag in inches | Compressive Strength of Dry cube (psi) |
| 0 | 0 | 534 | 0.17 | 0.445 | 675 |
| 0.2 | 0 | 535 | 0.88 | 2.086 | 697 |
| 0.5 | 0 | 528 | 1.91 | 4.086 | 603 |
| 1.0 | 0 | 500 | 4.74 | ＞6 | 448 |
| 2.0 | 0 | 481 | 6.94 | ＞6 | 304 |
| 0.5 | 0 | 530 | 1.90 | 3.752 | 613 |
| 0.5 | 0.1 | 526 | 1.94 | 0.006 | 678 |
| 0.5 | 0.2 | 527 | 1.92 | 0.007 | 684 |
| 0.5 | 0.3 | 51 8 | 1.95 | 0.005 | 662 |
| 0.5 | 0.5 | 508 | 1.89 | 0.003 | 668 |
| 0.8 | 0 | 509 | 2.93 | 5.786 | 477 |
| 0.8 | 0.1 | 509 | 3.07 | 0.014 | 540 |
| 0.8 | 0.2 | 505 | 2.91 | 0.007 | 543 |
| 0.8 | 0.4 | 501 | 2.99 | 0.010 | 538 |
| 0.8 | 0.8 | 500 | 2.96 | 0.005 | 554 |
The tests in table 10 show that mixtures containing high concentrations of chloride ions or salts thereof can be used by treatment with trimetaphosphate ions. The panels were prepared and treated in the same manner as in example 4, except that various amounts of chloride ion and trimetaphosphate ion were added to the mixture. The bond integrity between the gypsum board core and its facing paper was tested in the same manner as in example 8.
Watch 10
Laboratory cast plasterboard (24X 14X 0.5) prepared from mortar
Starch and salts in various STMP, PCF1000 and LC-211
Test results for paper to board core bonding under additives
| Salt additive (wt.%) | STMP additive (wt.%) | PCF1000&LC-211 additive (wt.%) | Dry plate weight (g) | Water uptake after 5 days in 90/90 Room (wt.%) | 5 day binding failure (%) | 3 hours humidification binding failure (%) | 3 days humidification binding failure (%) | Combined moisture and humidification failure (%) |
| 0 | 0 | 0.2&0.2 | 2271 | 0.29 | 0 | 5 | 0 | 2 |
| 0.2 | 0 | 0.2&0.2 | 2290 | 0.81 | 1 | 0 | 0 | 0 |
| 0.6 | 0 | 0.2&0.2 | 2284 | 2.12 | 2 | 8 | 0 | 0 |
| 0.2 | 0.1 | 0.2&0.2 | 2269 | 0.87 | 0 | 1 | 2 | 1 |
| 0.6 | 0.1 | 0.2&0.2 | 2267 | 1.95 | 2 | 3 | 0 | 0 |
| 0.6 | 0.2 | 0.2&0.2 | 2271 | 2.07 | 3 | 0 | 3 | 2 |
| 1.0 | 0.2 | 0.2&0.2 | 2285 | 3.61 | 9 | 14 | 3 | 10 |
Table 11 shows the treatment of panels with a PFC1000 starch of trimetaphosphate ion and high hydrochloride salt material (sodium chloride content in mortar 0.08-0.16% by weight), which were otherwise prepared and treated in the same manner as in example 5 above. As shown in table 11, the treatment resulted in an increase in nail pull strength (measured in the same manner as in example 4, astm c 473-95) and provided similar bonding performance (measured in the same manner as in example 8) as compared to the control panel without the addition of sodium chloride. Furthermore, the treatment with trimetaphosphate ion significantly improved the wet droop even with the addition of up to 0.3% of hydrochloride.
TABLE 11
| Plant test results of high salt experiments in gypsum control devices | |||||||||
| Experiment of | NaCl | STMP | Hi-binding | PCF 1000 | Plate weight | Nail pulling device | Paper to core bond | 24 hours humidification sag | |
| Period of time | Salt additive | Additive agent | Starch | Starch | Strength of | Load(s) | % failure | (1’×4’) | |
| (wt.％) | (wt.％) | (wt.％) | (wt.％) | (lb/MSF) | (pound) | (pound) | (％) | (inch/4 foot spacing) | |
| 1 (control) | 0 | 0 | 0.52 | 0 | 1581 | 88.7 | 14.8 | 13.6 | 3.25 |
| 2 | 0 | 0 | 0.28 | 0.24 | 1586 | 92.1 | 13.30 | 15.3 | 2.45 |
| 3 | 0.08 | 0 | 0.28 | 0.24 | 1577 | 89.3 | 11.20 | 13.7 | 5.25 |
| 4 | 0.16 | 0 | 0.28 | 0.24 | 1580 | 87.7 | 11.50 | 22.4 | 11.5 |
| 5 | 0.3 | 0 | 0.28 | 0.24 | 1574 | 89.6 | 9.00 | 31.8 | ＞12.5 |
| 6 | 0.3 | 0.08 | 0.28 | 0.24 | 1577 | 89.2 | 8.10 | 30.3 | 0.25 |
| 7 | 0.16 | 0.08 | 0.28 | 0.24 | 1567 | 95.5 | 11.40 | 32.8 | 0.25 |
| 8 | 0.08 | 0.08 | 0.28 | 0.24 | 1592 | 94.5 | 12.20 | 19.5 | 0.25 |
| 9 | 0 | 0 | 0.28 | 0.24 | 1609 | 93.6 | 12.40 | 15.1 | 2.85 |
| 10 (control) | 0 | 0 | 0.52 | 0 | 1561 | 83.9 | 14.90 | 11.5 | 2.25 |
| 11 | 0.3 | 0 | 0.52 | 0 | 1619 | 93.4 | 10.10 | 25.4 | ＞12.5 |
Table 12 shows treated panels with trimetaphosphate ion and PFC1000 starch with higher hydrochloride salt species (higher than in Table 11) (0.368% by weight hydrochloride in mortar) were additionally prepared and treated in the same manner as in example 5 above. As shown in Table 12, the treatment resulted in an increase in nail pull strength (measured in the same manner as in example 4, i.e., ASTM C473-95) and provided better bonding performance (measured in the same manner as in example 8) as compared to the control board.
TABLE 12
| Factory test results of high salt experiments in a plate mill | ||||||||
| Experiment of | % high chlorine | Hydrochloride salt | STMP | Hi bonding | PCF-1000 | Nail pulling strength | Paper to core bond | |
| Period of time | Synthetic gypsum | Concentration of | Additive agent | Starch | Starch | Load(s) | % failure | |
| (wt.％) | (wt.％) | (wt.％) | (wt.％) | (wt.％) | (pound) | (pound) | (％) | |
| 1 (control) | 0 | 0.032 | 0 | 0.4 | 0 | 73 | 14.10 | 49.0 |
| 2 | 50 | 0.12 | 0.16 | 0.15 | 0.25 | 85 | 16.70 | 0.0 |
| 3 | 100 | 0.368 | 0.16 | 0.15 | 0.25 | 86 | 14.40 | 0.0 |
| 4 | 100 | 0.368 | 0.16 | 0.4 | 0 | 89 | 10.90 | 34.0 |
| 5 | 100 | 0.368 | 0 | 0.4 | 0 | 77 | 19.70 | 0.0 |
| 6 (control) | 0 | 0.032 | 0 | 0.4 | 0 | 75 | 19.5 | 10.0 |
Example 11
Treating calcined gypsum with various reinforcing materials
In the examples of the preferred embodiments described above, the reinforcing material is trimetaphosphate ion. However, any reinforcing material that generally falls within the general definition of reinforcing material set forth above will have a positive effect (e.g., improved resistance to permanent deformation) in the treatment of calcined gypsum. Commonly used reinforcing materials are condensed phosphoric acids, each containing 2 or more phosphoric acid units; condensed phosphates or condensed phosphate ions, each containing 2 or more phosphate units.
Specific examples of such reinforcing materials include, for example, the following acids or salts, or their anionic moieties: the molecular formula is (NaPO)3)3Sodium trimetaphosphate having 6-27 repeating phosphate units and having the formula Nan+2PnO3n+1The sodium hexametaphosphate (wherein n is 6-27) has a molecular formula of K4P2O7Tetrapotassium pyrophosphate of formula Na3K2P3O10The molecular formula of the trisodium dipotassium triphosphate is Na5P3O10Sodium triphosphate of formula Na4P2O7Tetrasodium pyrophosphate of formula Al (PO)3)3The molecular formula of the aluminum trimetaphosphate is Na2H2P2O7Sodium acid pyrophosphate of (i) having 1000-3000 repeating phosphate units and having the formula (NH)4)n+2PnO3n+1Or ammonium polyphosphate (wherein n is 1000-3000), or having 2 or more repeating phosphoric acid units and having the formula Hn+2PnO3n+1Wherein n is 2 or more.
The results of treating calcined gypsum with this type of reinforcement material are shown in tables 13, 14 and 15.
In table 13, calcined gypsum was treated with various reinforcing materials during the preparation of gypsum boards and cubes. The panels were prepared and treated in the same manner as in example 2 above. Cubes were prepared and processed in the same manner as in example 1 above. Except that in both cases, various different reinforcing materials were used, rather than only the trimetaphosphate ion. The deflection of the humidified film was measured in the same manner as in example 2. The compressive strength was measured in the same manner as in example 1 above.
In Table 14, calcined gypsum was treated with polyphosphoric acid during the preparation of gypsum boards and cubes. A panel was prepared and treated in the same manner as in example 2. Cubes were prepared and processed in the same manner as in example 1 above. Except that in both cases, various different reinforcing materials were used, rather than only the trimetaphosphate ion. The deflection of the humidified film was measured in the same manner as in example 2. The compressive strength was measured in the same manner as in example 1 above.
In table 15, calcined gypsum was treated with ammonium polyphosphate ("APP") during the preparation of gypsum boards and cubes. The panels were prepared and treated in the same manner as in example 2 above. Cubes were prepared and processed in the same manner as in example 1 above. Except that in both cases, various different reinforcing materials were used, rather than only the trimetaphosphate ion. The deflection of the humidified film was measured in the same manner as in example 2. The compressive strength was measured in the same manner as in example 1 above.
The results of tables 13, 14 and 15 show that all materials tested within the definition of the reinforcing material described above give a product with a significant resistance to permanent deformation when calcined gypsum is treated with the reinforcing material in the production of set gypsum products, compared to the control group.
Watch 13
Laboratory test results for gypsum cubes (2X 2) and panels (24X 6X 0.5) prepared with mortars having various phosphate and hydrochloride additives
| Phosphates or other specialty chemicals | Additive content(wt.％) | Dry plate weight (g) | Delay (-) neutral (0) or Accelerator (+) | Water uptake from 90/90 cell (wt.%) | Sag bias (wt.%) of 10 days humidification | Compressive Strength of Dry cube (psi) |
| Sodium trimetaphosphate | 0.1 | 537.0 | 0/+ | 0.06 | 0.016 | 745 |
| Sodium hexametaphosphate | 0.1 | 538.2 | 0.09 | 0.019 | 552 | |
| Sodium chloride and sodium trimetaphosphate | 0.5&0.1 | 527.5 | + | 1.93 | 0.008 | 621 |
| Sodium chloride and sodium hexametaphosphate | 0.5&0.1 | 539.6 | -/0 | 2.08 | 0.021 | 498 |
| Tetrapotassium pyrophosphate | 0.1 | 538.7 | -/0 | 0.11 | 0.137 | 560 |
| Trisodium dipotassium triphosphate | 0.1 | 538.8 | -/0 | 0.07 | 0.201 | 552 |
| Sodium tripolyphosphate | 0.1 | 535.1 | -/0 | 0.09 | 0.286 | 531 |
| Tetrasodium pyrophosphate | 0.1 | 556.2 | -/0 | 0.18 | 0.436 | 544 |
| Aluminum trimetaphosphate | 0.1 | 536.2 | 0/0 | 0.02 | 0.521 | 673 |
| Phosphoric acid monopotassium salt | 0.1 | 540.9 | 0/+ | 0.11 | 0.595 | 657 |
| Acid sodium pyrophosphate | 0.1 | 547.7 | 0/0 | 0.16 | 1.385 | 637 |
| Boric acid | 0.1 | 539.4 | 0/0 | 0.15 | 1.425 | 624 |
| Trisodium phosphate | 0.1 | 537.0 | 0.13 | 1.641 | 537 | |
| Control | 0.0 | 546.2 | 0/0 | 0.13 | 1.734 | 635 |
| Phosphoric acid | 0.1 | 534.0 | + | 0.22 | 1.796 | 673 |
| Phosphoric acid monosodium salt | 0.1 | 540.9 | + | 0.19 | 2.219 | 679 |
| Magnesium chloride | 0.1 | 528.2 | 0/+ | 0.23 | 2.875 | 521 |
| Phosphoric acid monohydrogen disodium salt | 0.1 | 536.6 | 0/0 | 0.13 | 3.126 | 629 |
| Sodium aluminum sulfate | 0.1 | 543.0 | ++ | 0.24 | 3.867 | 686 |
| Zinc chloride | 0.1 | 536.2 | 0/+ | 0.67 | ＞6.0 | 470 |
| Aluminium chloride | 0.1 | 536.8 | +++ | 0.53 | ＞6.0 | 464 |
| Sodium chloride | 0.1 | 542.6 | + | 0.63 | ＞6.0 | 596 |
TABLE 14
Laboratory test results for gypsum cubes (2X 2)/board (24X 6X 0.5) prepared with mortar with polyphosphoric acid additive
| Polyphosphoric acid | Content of additives (wt.%) | Dry plate weight (g) | Delay (-) neutral (0) or Accelerator (+) | Water uptake from 90/90 cell (wt.%) | Sag deflection (in inches) for 2 weeks humidification | Compressive Strength of Dry cube (psi) |
| No phosphoric acid (control) | 0.0 | 536.5 | 0/0 | 0.06 | 0.683 | 767 |
| Polyphosphoric acid (first mixed with water) | 0.02 | 539.6 | 0/0 | 0.13 | 0.042 | 781 |
| Polyphosphoric acid (first mixed with water) | 0.05 | 535.1 | 0/0 | 0.09 | 0.025 | 842 |
| Polyphosphoric acid (first mixed with water) | 0.1 | 542.3 | -/0 | 0.15 | 0.046 | 708 |
Watch 15
Laboratory test results for gypsum cubes (2X 2)/board (24X 6X 0.5) prepared with mortar with ammonium polyphosphate additive
| Ammonium polyphosphate | Content of additives (wt. -%)) | Dry plate weight (g) | Delayed (-), neutral (0) or procoagulant (+) | Water uptake from 90/90 cell (wt.%) | Sag deflection (in inches) for 2 weeks humidification | Compressive Strength of Dry cube (psi) |
| Control | 0.0 | 540.7 | 0/0 | 0.35 | 0.694 | 912 |
| APP powder (first mixed with water) | 0.01 | 532.5 | 0/0 | 0.35 | 0.045 | 937 |
| APP powder (first mixed with water) | 0.03 | 536.3 | 0/0 | 0.37 | 0.020 | 924 |
| APP powder (first mixed with water) | 0.05 | 539.7 | 0/0 | 0.37 | 0.005 | 901 |
| APP powder (first mixed with water) | 0.1 | 541.3 | 0/0 | 0.28 | 0.005 | 956 |
| APP powder (first mixed with water) | 0.2 | 546.7 | 0/0 | 0.30 | 0.003 | 967 |
| APP powder (first mixed with water) | 0.4 | 538.2 | 0/0 | 0.33 | 0.005 | 998 |
| APP powder (mixing with mortar first) | 0.05 | 533.5 | 0/0 | 0.35 | 0.005 | 907 |
| APP powder (first with Ash)Slurry mixing) | 0.1 | 546.9 | 0/0 | 0.30 | 0.006 | 948 |
| APP powder (mixing with mortar first) | 0.2 | 538.3 | 0/0 | 0.31 | 0.006 | 998 |
| APP powder (mixing with mortar first) | 0.4 | 537.4 | 0/0 | 0.35 | 0.002 | 1017 |
Example 12
Treatment of calcium sulphate dihydrate castings with various reinforcing materials
In general, any reinforcing material falling within the general definition of reinforcing material set forth above will have a positive effect (e.g., increased resistance to permanent deformation and increased strength) during the processing of the cast calcium sulfate dihydrate body. Commonly used reinforcing materials are condensed phosphoric acids, each containing 2 or more phosphoric acid units; condensed phosphates or condensed phosphate ions, each containing 2 or more phosphate units.
The results of treating the calcium sulfate dihydrate cast bodies with these reinforcing materials are shown in table 16.
In table 16, the coagulated and dried calcium sulfate dihydrate in plate and cube form was treated with various materials. A panel was prepared in the same manner as in example 2 above, and was further processed in the same manner as in example 9. Cubes were prepared in the same manner as in example 1 above and further processed in a similar manner to example 9. Except that in both cases, various different reinforcing materials were used, rather than only the trimetaphosphate ion. The deflection of the humidified film was measured in the same manner as in example 2. The compressive strength was measured in the same manner as in example 1 above.
The results in Table 16 show that all materials tested within the above definition of reinforcing material provide articles with significant resistance to permanent deformation and significantly improved strength when the solidified and dried cast calcium sulfate dihydrate is treated with the reinforcing material as compared to the control.
TABLE 16
Laboratory test results for post-treated gypsum cubes (2X 2)/boards (24X 6X 0.5) prepared with mortar with various phosphate and hydrochloride additives
| Phosphates or other special chemicals | Additive content (wt.%) | Dry plate weight (g) | Water uptake from 90/90 cell (wt.%) | Sag deflection (in inches) for 10 days humidification | Compressive Strength of Dry cube (psi) |
| Sodium trimetaphosphate | 0.4 | 537.0 | 0.5 | 0.016 | 725 |
| Sodium hexametaphosphate | 0.4 | 538.2 | 0.9 | 0.019 | 697 |
| Tetrapotassium pyrophosphate | 0.4 | 538.7 | 0.3 | 0.017 | |
| Tetrasodium pyrophosphate | 0.4 | 556.2 | 0.6 | 0.011 | |
| Acid sodium pyrophosphate | 0.4 | 542.1 | 0.4 | 0.012 | |
| Phosphoric acid monosodium salt | 0.4 | 545.6 | 1.5 | 0.025 | 710 |
| Phosphoric acid monopotassium salt | 0.4 | 487.5 | 0.2 | 0.029 | 708 |
| Phosphoric acid | 0.4 | 534.7 | 0.4 | 0.065 | 624 |
| Sodium tripolyphosphate | 0.4 | 540.5 | 0.6 | 0.123 | 657 |
| Boric acid | 0.4 | 486.6 | 0.1 | 0.345 | 611 |
| Time light | 0.0 | 543.9 | 0.2 | 0.393 | 576 |
| Phosphoric acid monohydrogen disodium salt | 0.4 | 541.3 | 0.7 | 0.674 | 724 |
| Trisodium phosphate | 0.4 | 532.8 | 0.6 | 1.082 | 754 |
| Magnesium chloride | 0.4 | 559.9 | 2.3 | 1.385 | 567 |
| Sodium chloride | 0.4 | 539.4 | 7.7 | 6.385 | 521 |
The invention has been described in detail hereinabove, particularly with reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
Claims (44)
1. A composition comprising a mixture comprising a calcium sulfate material, water, and one or more reinforcing materials selected from the group consisting of: trimetaphosphate, sodium hexametaphosphate having 6-27 repeating phosphate units, tetrapotassium pyrophosphate, trisodium tripolyphosphate dipotassium pyrophosphate, sodium acid pyrophosphate and ammonium polyphosphate having 1000-3000 repeating phosphate units or an anionic portion thereof, wherein the amount of said reinforcing material is from 0.004 to 2.0% by weight based on the weight of said calcium sulfate material, and wherein said product has increased resistance to permanent deformation when said composition is in the form of a set gypsum-containing product.
2. The composition of claim 1, wherein the composition further comprises a blowing agent.
3. The composition according to claim 1 or 2, wherein the composition further comprises a pregelatinized starch.
4. A composition according to claim 1, 2 or 3, further comprising particles of starch and a water-dispersible polymer, and wherein the calcium sulphate material is calcium sulphate hemihydrate.
5. The composition of claim 1, 2, 3 or 4 further comprising a binder, a thickener and a non-leveling agent, and wherein the calcium sulfate material is calcium sulfate hemihydrate.
6. The composition according to claim 1, 2, 3 or 4, further comprising pregelatinized starch and mineral wool.
7. The composition of claim 1, 2, 3 or 4 further comprising pregelatinized starch, expanded perlite particles, and fiber reinforcement.
8. The composition according to any one of claims 1 to 7, further comprising a coagulant.
9. The composition according to any one of claims 1 to 8, wherein the reinforcing material is trimetaphosphate.
10. A set gypsum-containing product made using the composition of any one of claims 1-9.
11. The set gypsum-containing product of claim 10, wherein the set gypsum-containing product is a gypsum board.
12. The set gypsum-containing article of claim 11, wherein the gypsum board comprises a trimetaphosphate compound.
13. The set gypsum-containing product of claim 12, wherein the set gypsum and trimetaphosphate compound are in the form of a core material sandwiched between cover sheets.
14. The set gypsum-containing product of claim 13, wherein the cover sheet comprises paper.
15. The set gypsum-containing article of claim 11, wherein the calcium sulfate material is calcined gypsum, the reinforcing material is at least one trimetaphosphate compound, and the gypsum board has a sag resistance of less than 0.1 inch per two feet of the gypsum board as determined by ASTM C473-95, wherein the concentration of trimetaphosphate ion is from 0.004 to 2.0% by weight based on the weight of the calcined gypsum.
16. The set gypsum-containing product of any one of claims 12 to 15, wherein the trimetaphosphate salt is selected from the group consisting of sodium trimetaphosphate, lithium trimetaphosphate, potassium trimetaphosphate, ammonium trimetaphosphate and aluminum trimetaphosphate or anionic portions thereof or mixtures thereof.
17. The set gypsum-containing product of claim 16, wherein the trimetaphosphate salt is sodium trimetaphosphate.
18. The set gypsum-containing article of any one of claims 10-17, wherein the shrinkage of the gypsum board is less than 0.06 inches per 4 feet of width and less than 0.38 inches per 12 feet of length.
19. The set gypsum-containing product of claims 11, 12, 16 or 17, the gypsum board further comprising pregelatinized starch.
20. A set gypsum-containing product according to claim 19, the pregelatinized starch being in an amount of from 0.08 to 0.5% by weight of the calcined gypsum.
21. A set gypsum-containing product according to claim 20, the pregelatinized starch being in an amount of from 0.16 to 0.4% by weight of the calcined gypsum.
22. A set gypsum-containing product according to claim 20, the pregelatinized starch being in an amount of 0.3% by weight of the calcined gypsum.
23. The set gypsum-containing product of claim 11, 12 or 15, wherein the set gypsum has voids uniformly distributed therein.
24. The set gypsum-containing product of claim 11, 12, 15, or 16, wherein the set gypsum is further formed from at least one foaming agent having the formula
CH3(CH2)xCH2(OCH2CH2)YOSO3ΘM⊕
Wherein X represents a number from 2 to 20, Y represents a number from 0 to 10 and the value is 0 in at least 50% by weight of the blowing agent or mixture of blowing agents, and M represents a cation.
25. A set gypsum-containing product according to claim 24, wherein the foaming agent with Y being 0 is present in an amount of 86 to 99% by weight.
26. A gypsum board comprising a core material sandwiched between cover sheets, wherein the core material comprises set gypsum, said board being prepared by a process comprising:
forming or depositing a mixture between superstrates, wherein the mixture comprises the composition of any one of claims 1 to 9, and
the mixture is maintained under conditions sufficient for the calcium sulfate material to form set gypsum,
the amount of reinforcing material contained in the mixture is from 0.004 to 2.0% by weight based on the weight of the calcium sulfate material, thereby providing the gypsum board with improved resistance to permanent deformation.
27. A method of making a set gypsum-containing article having increased resistance to permanent deformation comprising:
forming the composition of claim 1, further comprising a coagulant,
the composition is maintained under conditions sufficient for the calcium sulfate material to form set gypsum,
the reinforcing material or materials are included in the composition in an amount of 0.004 to 2.0% by weight, based on the weight of the calcium sulphate material, such that the set gypsum-containing product has a greater resistance to permanent deformation than if the composition did not include the reinforcing material.
28. The method according to claim 27, wherein the concentration of the reinforcing material in the composition is from 0.04 to 0.16% by weight based on the weight of the calcium sulfate material.
29. A method according to claim 27 or 28, wherein the concentration of the reinforcing material in the composition is 0.08% by weight based on the weight of the calcium sulphate material.
30. A method according to claim 27 or 28, wherein the reinforcing material is selected from one or more of the following salts or anionic portions thereof: sodium trimetaphosphate and ammonium polyphosphate having 1000-3000 repeating phosphate units.
31. The method according to claim 30, wherein the concentration of the reinforcing material in the composition is 0.08% by weight based on the weight of the calcium sulfate material.
32. The method according to claim 30, wherein the composition further comprises a pregelatinized starch.
33. The method of claim 27, wherein the composition further comprises at least 0.015% by weight of chloride ions or salts thereof, based on the weight of the calcium sulfate material in the mixture.
33. The method of claim 27, wherein the composition further comprises at least 0.015% by weight of chloride ions or salts thereof, based on the weight of the calcium sulfate material in the composition.
34. The method of claim 27, wherein the composition contains 0.02 to 1.5% by weight chloride ion or hydrochloride salt based on the weight of calcium sulfate material in the mixture.
35. The method of claim 33, wherein the enhancing material comprises one or more trimetaphosphate salts or root ions thereof or sodium hexametaphosphate salts or root ions thereof.
36. The method according to claim 33, wherein the composition further comprises a pregelatinized starch.
37. The method of claim 27, wherein: the set gypsum-containing article is a gypsum board comprising a core sandwiched between cover sheets, wherein the core comprises set gypsum; and the board is formed by depositing a mixture of calcined gypsum, water and a trimetaphosphate compound between cover plates to form an assembly, and allowing the resulting assembly to set and dry.
38. The method of claim 37, wherein the set gypsum-containing product contains a reinforcing material.
39. The method of claim 37, wherein the set gypsum-containing article contains matrix particles and at least a portion of the set gypsum is located at and near the voids of the readily accessible matrix particles.
40. The method of claim 37, wherein the set gypsum-containing article is a gypsum board, the board having increased sag resistance.
41. The method of claim 37, wherein the composition further comprises 0.015 to 1.5% by weight of chloride ions or salts thereof, based on the weight of the calcium sulfate material in the composition.
42. The method of claim 41, wherein the composition contains 0.02 to 1.5% by weight chloride ion or hydrochloride salt based on the weight of the calcium sulfate material in the composition.
43. A set gypsum-containing product made by the process of claim 27, 30, 33 or 35.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/916,058 | 1997-08-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| HK1117494A true HK1117494A (en) | 2009-01-16 |
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