RU2778487C2 - Method for production of pregelatinized partially hydrolyzed starch and related methods and products - Google Patents

Abstract

FIELD: building materials.

SUBSTANCE: invention relates to the modification of starches. The proposed method for the production of pregelatinized partially hydrolyzed starch includes mixing of at least water, non-pregelatinized starch and strong acid in the amount from 0.0001 wt.% to 0.05 wt.% relatively to non-pregelatinized starch to obtain moist starch-containing precursor substance with a moisture content from 8 wt.% to 25 wt.%, and supply of the specified moist starch-containing precursor substance to an extruder. In the extruder, pre-gelatinization and acid modification of the specified moist starch is carried out at a head temperature ranging from 150°C (300°F) to 210°C (410°F). A method for the manufacture of a gypsum wall plate is also proposed. The method includes mixing of the specified pregelatinized and partially hydrolyzed starch with at least water and construction gypsum to obtain a suspension, placement of the suspension between the first sheathing sheet and the second sheathing sheet to obtain a wet prefabricated structure, cutting of the wet prefabricated structure to obtain a wall plate, and drying of the wall plate.

EFFECT: invention provides low water consumption in the manufacture of products and high strength of the finished product.

7 cl, 3 dwg, 8 tbl, 4 ex

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. Application No. 14/044582, filed October 2, 2013, PCT International Application No. PCT/US2013/064776, filed October 14, 2013, and U.S. Application No. 14/494547, filed September 23, 2014 year, and the contents of all of these prior patent applications are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

[0002] Starches generally contain two types of polysaccharides (amylose and amylopectin) and are classified as carbohydrates. Some starches are subjected to pre-gelatinization (pregelatinization), usually using thermal methods. In general, pregelatinized starches can form dispersions, pastes or gels with cold water. In general, pregelatinized starches are highly digestible and are used in a variety of ways, including as an additive in a variety of food products (e.g., baked goods, snack foods, beverages, confectionery, dairy products, sauces, convenience foods, seasonings, and meat products) and in pharmaceuticals. drugs.

[0003] Another use of pregelatinized starches is in the manufacture of gypsum wallboard. However, in the manufacture of the board, stucco (i.e., calcined gypsum in the form of calcium sulfate hemihydrate and/or calcium sulfate anhydrite), water, starch and other ingredients, if necessary, are mixed, usually in a finger mixer (a term used in this field). technology). The slurry is prepared and discharged from the mixer onto a moving conveyor carrying a skin sheet with one of the cover layers (if present) already applied (often before the mixer). The slurry is spread over the paper (with a cover layer optionally placed on the paper). Another skin sheet, with or without a top coat, is applied to the slurry using, for example, a forming plate or the like. and get a layered structure of the desired thickness.

[0004] The mixture is cast and left to set to form set (ie, rehydrated) gypsum by reacting the calcined gypsum with water to form a matrix of crystalline hydrated gypsum (ie, calcium sulfate dihydrate). It is the required hydration of the calcined gypsum that allows the formation of an interlocking matrix of set gypsum crystals, thereby giving strength to the gypsum structure in the product. To obtain a dry product, heat is required (eg in a kiln) to remove any remaining free (ie, unreacted) water.

[0005] Pregelatinized starches often increase the water demand of said process. To compensate for water consumption and ensure sufficient fluidity during production, water must be added to the plaster suspension. This excess water makes production inefficient, including longer drying times, slower production line speeds, and higher energy costs. The present inventors have found that pregelatinized and partially hydrolyzed starch requires less water.

[0006] The authors of the present invention also found that the methods for obtaining pregelatinized partially hydrolyzed starches were not completely satisfactory. Conventional methods for producing such pregelatinized partially hydrolyzed starches are not efficient, have low yield and low productivity, and high energy costs. Thus, there is a need in the art for an improved process for producing pregelatinized, partially hydrolyzed starch, in particular one exhibiting low water demand.

[0007] It is to be understood that such description of the prior art has been made by the inventors of the present invention to assist the reader and should not be construed as a reference to the prior art nor as an indication that any of the listed problems have been recognized by themselves. in this field of technology. Although in some respects and embodiments of the invention, the principles described may alleviate the problems inherent in other systems, it should be understood that the scope of the protected innovation is determined by the appended claims, and not by the ability of the claimed invention to solve any particular problem mentioned in this document.

BRIEF DESCRIPTION OF THE INVENTION

[0008] According to one aspect, the present invention provides a method for producing pregelatinized partially hydrolyzed starch, comprising: (a) mixing at least water, non-pregelatinized starch and a weak acid that does not substantially chelate with calcium ions, to obtain a wet starch-containing substance - precursor with a moisture content of about 8% wt. up to about 25% wt.; (b) supplying said wet starch precursor to an extruder; and (c) pregelatinizing and acid modifying the wet starch precursor in an extruder at a die temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF). The invention also provides a starch obtained according to said process.

[0009] According to another aspect, the present invention provides a method for producing pregelatinized partially hydrolyzed starch, including: (a) mixing at least water, non-pregelatinized starch and a strong acid to obtain a wet starch-containing precursor substance with a moisture content of from about 8% of the mass. up to about 25% wt., while the strong acid is present in an amount of about 0.05% wt. or less by weight relative to the weight of starch; (b) supplying wet starch to an extruder; and (c) pregelatinizing and acid modifying the wet starch precursor in an extruder at a die temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF). The invention also provides a starch obtained according to said process.

[0010] According to another aspect, the present invention provides a method for making a board, comprising: (a) obtaining a pregelatinized partially hydrolyzed starch by (i) mixing at least water, a non-pregelatinized starch and an acid to obtain a wet starch precursor with a moisture content of from about 8% mass. up to about 25% wt., while the acid is selected from the group consisting of: (1) a weak acid that essentially does not form chelates with calcium ions, (2) a strong acid in an amount of about 0.05% wt. or less by weight relative to the weight of starch or (3) any combination thereof; (ii) supplying the wet starch precursor to the extruder; and (iii) pregelatinization and acid modification of the wet starch in a die extruder at a temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF); (b) mixing the pregelatinized and partially hydrolysed starch with at least water and stucco to form a slurry; (c) placing the slurry between the first skin sheet and the second skin sheet to form a wet assembly; (d) cutting the wet assembly to form a slab; and (e) drying the board. In some embodiments, the set gypsum core has a compressive strength greater than a set gypsum core made using starch prepared according to another process. According to another aspect, the present invention proposes a plate obtained according to the specified method.

BRIEF DESCRIPTION OF MULTIPLE DRAWING TYPES

[0011] FIG. 1 is an amylogram obtained by plotting viscosity (left y-axis) and temperature (right y-axis) versus time (x-axis) showing the bonding profiles of starches extruded at 16 wt. phase in the test suspension is 10% wt., as indicated in example 2.

[0012] FIG. 2 is an amylogram, an amylogram obtained by plotting viscosity (left y-axis) and temperature (right y-axis) versus time (x-axis), showing the bonding profiles of starches extruded at 13 wt% moisture content, where the content of the solid phase in the test suspension is 10% wt., as indicated in example 2.

[0013] FIG. 3 is a temperature versus time graph showing the rate of hydration at a given temperature rise (TRS) of two suspensions containing pregelatinized partially hydrolysed starches treated with alum at 3% wt. and retarder setting in amounts of 0.05% wt. and 0.0625% wt., respectively, and a third suspension containing conventional pregelatinized corn starch with a viscosity of 773 centipoise and a retarder in the amount of 0.05% wt., as indicated in example 3.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Embodiments of the present invention provide methods for producing pregelatinized partially hydrolysed starches. According to one aspect, the present invention provides a method for manufacturing a board (eg, gypsum wallboard). The pregelatinized partially hydrolyzed starches prepared according to the method of the present invention can be used in various other ways, for example, in food products (for example, in baked goods, drinks, confectionery, dairy products, instant puddings, sauces, soup mixes, convenience foods , pie fillings, condiments and meat products), pharmaceuticals, feeds, adhesives and paints. Such starches, produced in accordance with some embodiments of the present invention, are generally highly digestible and produce foodstuffs with the desired viscosity and retain most of the functional properties of the original base material.

[0015] Embodiments of the present invention are based, at least in part, on the surprising and unexpected discovery of the possibility of pregelatinization and acid modification of starch in the extruder in one stage. Surprisingly and unexpectedly, pregelatinization and acid modification of starch in one stage in an extruder has significant advantages over pregelatinization and acid modification of starch in separate stages. For example, the inventive process for producing pregelatinized partially hydrolysed starch provides higher yield, faster production, and lower energy costs while maintaining desired properties (e.g., viscosity, flow, cold water solubility, etc.) as described herein. document.

[0016] In addition, it has been found that extrusion conditions (eg, high temperature and high pressure) can significantly increase the rate of acid hydrolysis of starch. Surprisingly and unexpectedly, such a one-step process makes it possible to use a weak acid such as alum and/or smaller amounts of a strong acid to carry out the acid modification of starch. Both acidic forms provide a mechanism in which protons from the acid catalyze the hydrolysis of starch. Conventional acid modification methods include purification and neutralization steps. In some embodiments of the present invention, the use of a weak acid (e.g., alum) and/or a small amount of a strong acid eliminates the need for any neutralization step and subsequent purification step typically required in conventional starch purification systems to remove salts from the starch step. neutralization.

[0017] According to embodiments of the present invention, the proposed extrusion method allows not only gelatinization of starch, but also partially hydrolyzes (ie, through acid modification) starch molecules. Thus, the one-step extrusion process provides both physical modification (pregelatinization) and chemical modification (acid modification, partial acid hydrolysis). Pregelatinization provides the starch with the ability to impart strength (eg, to an end product such as gypsum board). The acid modification successfully partially hydrolyzes the starch, providing the starch with the ability to impart strength to the final product such as gypsum board, and providing low water consumption in the manufacture of products, for example in the case of gypsum board manufacturing processes. Thus, the product produced according to the starch production methods of the embodiments of the present invention is pregelatinized and partially hydrolysed starch.

[0018] In some embodiments, the present invention provides a highly efficient acid modification reaction. Pregelatinization and acid modification in the extruder occurs at elevated temperatures and/or pressures as described herein and can result in acid hydrolysis rates that can be, for example, about 30,000 times or faster than conventional acid hydrolysis rates at lower temperatures (eg 50 ºC) and/or pressures. The rate of acid hydrolysis is further increased by using low levels of moisture in the starch precursor (from about 8 wt. % to about 25 wt. %) and, therefore, by increasing the concentration of reactants. Due to this high efficiency of acid modification, the inventors have surprisingly and unexpectedly found that a weak acid or a very low level of strong acid can be used in the starch precursor material to provide optimal acid modification and eliminate the need for neutralization and purification, which are costly, time consuming and represent are inefficient requirements of conventional systems.

[0019] According to some embodiments of the invention, hydrolysis serves to convert starch into smaller molecules within an optimal size range, which is defined herein depending on the desired viscosity of the pregelatinized partially hydrolyzed starch. If the starch is over-hydrolysed, it can be reduced to molecules that are too small (eg oligosaccharides or sugars) which, in the case of gypsum board, can result in board strength less than that imparted by pregelatinized partially hydrolyzed starch of the desired viscosity.

[0020] Pregelatinized partially hydrolyzed starch can be obtained by (i) mixing at least water, non-pregelatinized starch and acid to obtain a wet starch-containing precursor substance with a moisture content of from about 8 wt%. up to about 25% wt. The acid may be: (1) a weak acid that does not substantially chelate with calcium ions, (2) a strong acid in an amount of about 0.05% by weight. or less by weight relative to the weight of starch; or (3) any combination thereof. The wet starch precursor is subjected to extruder pregelatinization and acid modification in a single step at elevated die temperature and/or pressure as described herein. The starch is hydrolyzed to the extent that provides the desired viscosity, for example, as described herein.

[0021] Thus, in some embodiments, a pregelatinized partially hydrolysed starch can be made by mixing at least water, a non-pregelatinized starch, and a weak acid that does not substantially chelate calcium ions to form a wet starch precursor with a moisture content of about 8% wt. up to about 25% wt. The wet starch is then fed into the extruder. While in the extruder at a die temperature of about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF), the wet starch undergoes pregelatinization and acid modification such that it is at least partially hydrolyzed.

[0022] According to additional embodiments of the invention, pregelatinized partially hydrolyzed starch can be obtained by mixing at least water, non-pregelatinized starch and a strong acid to obtain a wet starch-containing precursor substance with a moisture content of from about 8% of the mass. up to about 25% wt., while the strong acid is present in an amount of about 0.05% wt. or less by weight relative to the weight of starch. The wet starch is then fed into the extruder. While in the extruder at a die temperature of about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF), the wet starch undergoes pregelatinization and acid modification such that it is at least partially hydrolyzed.

[0023] Advantageously, the resulting pregelatinized, partially hydrolysed starch has low water consumption when incorporated into the stucco slurry and, in some embodiments, can be used to produce board (eg, gypsum board) with good strength. Thus, according to another aspect, the present invention provides a method for the manufacture of gypsum board using starch obtained in one stage in an extruder using the pregelatinization and acid modification methods of the invention. In some embodiments, the pregelatinized partially hydrolysed starches produced according to embodiments of the present invention have low water consumption compared to other pregelatinized starches known in the art.

[0024] As a result, the pregelatinized, partially hydrolysed starches produced according to embodiments of the present invention can be incorporated into a plaster slurry (eg, via a feedline in a finger mixer) with good flowability. In some embodiments, higher amounts of pregelatinized, partially hydrolyzed starches made in accordance with embodiments of the present invention may be included, as no excess water needs to be added to the system, so that even higher strengths and lower board densities can be achieved. The resulting board exhibits good strength properties (eg, good core hardness, nail pull resistance, compressive strength, etc., or any ratio therebetween based on any combination of the values of each parameter described herein). The incorporation of the starch obtained according to the method of the present invention in the production of gypsum board preferably allows the production of an ultra-low density product due to the increase in strength. The gypsum board may be in the form of, for example, gypsum wallboard (often referred to as dry gypsum), which may include such board not only for walls, but also for ceilings and other locations, as is known in the art. However, the starch obtained according to the proposed method may have other applications, for example, in food products.

Pregelatinization and acid modification

[0025] Starches are carbohydrates and contain two types of polysaccharides, namely linear amylose and branched amylopectin. The starch grains are semi-crystalline, eg as seen in polarized light, and are insoluble at room temperatures. Gelatinization is a process in which starch is placed in water and heated ("cooked") so that the crystal structure of the starch grains melts and the starch molecules dissolve in the water to form a good dispersion. It has been found that when the starch grain is converted to a gelled form at the beginning, the starch grain provides little viscosity in water, since the starch grains are insoluble in water. As the temperature rises, the starch grain swells and the crystal structure melts at the pregelatinization temperature. Maximum viscosity is achieved with maximum swelling of the starch grain. Further heating will lead to the destruction of starch grains and the dissolution of starch molecules in water with a sharp drop in viscosity. Upon cooling, the starch molecule will re-associate to form a 3-D gel-like structure, with the viscosity increasing due to the gel-like structure. Some commercial starches are sold in pregelatinized form while others are sold in granular form. According to some variants of implementation of the present invention, in relation to the gypsum board, the granular form is subjected to at least some degree of pregelatinization. To illustrate, with respect to gypsum board, the starch is pregelatinized before it is added to the gypsum slurry, also referred to herein as stucco slurry (usually in a mixer, eg a pin mixer).

[0026] Thus, as used herein, "pregelatinized" means that the starch has any degree of pregelatinization, such as before it is incorporated into a gypsum slurry or when used in other applications. In some gypsum board embodiments, the pregelatinized starch may be partially gelatinized when incorporated into the slurry, but become fully gelatinized when subjected to elevated temperature, such as in a kiln during a drying step to remove excess water. In some gypsum board embodiments, the pregelatinized starch is not fully gelatinized even when exiting the kiln, provided that the starch meets the viscosity profile in the medium range according to some embodiments of the invention under the conditions according to the method based on a viscosity modifying additive (VMA).

[0027] When referring to viscosity herein, the indicated viscosity is measured according to the VMA method, unless otherwise indicated. According to the method described, the viscosity is measured using a Discovery HR-2 Hybrid Rheometer (TA Instruments Ltd) equipped with a concentric cylinder, standard cup (30 mm diameter) with blade geometry (28 mm diameter and 42.05 m long).

[0028] After the starch has been prepared, Differential Scanning Calorimetry (DSC) methods are used to determine if the starch is fully gelatinized. The DSC step can be used to see if the starch is fully gelatinized, for example to confirm the absence of retrogradation. One of two methods is used depending on the temperature required to completely gelatinize the starch, which can also be determined by DSC, as will be appreciated by one of ordinary skill in the art.

[0029] Method 1 is used when the DSC data indicate that the starch is fully gelatinized or has a gelatinization temperature of 90° C. or lower. Method 2 is used when the gelatinization temperature is above 90°C. Since the viscosity is measured when the starch is in water, Method 2 uses pressure cooking in a sealed vessel, which allows superheating to temperatures above 100° C. without appreciable evaporation of the water. Method 1 is intended for starches that are already fully gelatinized, or for starches with a gelatinization temperature of up to 90°C, since, as described below, gelatinization occurs in a rheometer, which is an open system and in which it is impossible to create conditions of increased pressure for gelatinization. Thus, in the case of starches with higher gelatinization temperatures, method 2 is used. In any case, when measuring viscosity, starch (7.5 g on a dry basis) is added to water to give a total mass of 50 g.

[0030] In Method 1, starch is dispersed in water (15% starch based on the total weight of starch and water) and the sample is immediately transferred to a cylindrical cell. The cell is covered with aluminum foil. The sample is heated from 25°C to 90°C at a rate of 5°C/min and a shear rate of 200 sec ^-1 . The sample is kept at 90°C for 10 min at a shear rate of 200 sec ^-1 . The sample is cooled from 90°C to 80°C at a rate of 5°C/min and a shear rate of 200 sec ^-1 . The sample is kept at 80°C for 10 min at a shear rate of 0 sec ^-1 . The viscosity of the sample is measured at 80° C. and a shear rate of 100 sec ^-1 for 2 minutes. Viscosity is the average value of a measurement from 30 seconds to 60 seconds.

[0031] Method 2 is used for starches with a gelatinization temperature greater than 90°C. The starch is gelatinized according to methods well known in the manufacture of starch (eg by pressure cooking). An aqueous solution of gelatinized starch (15% of the total mass) is immediately transferred to the measuring cup of the rheometer and brought to equilibrium at 80°C for 10 minutes. The viscosity of the sample is measured at 80°C and a shear rate of 100 sec ^-1 for 2 minutes. Viscosity is the average value of a measurement from 30 seconds to 60 seconds.

[0032] Viscograph and DSC are two other ways of describing starch gelatinization. The degree of starch gelatinization can be determined using, for example, a DSC thermogram, for example, using peak area (crystal melting) for calculation. The viscograph (obtained on a viscograph) is less desirable for determining the degree of partial gelatinization, but is a good tool for obtaining data such as starch viscosity change, maximum gelatinization, gelatinization temperature, retrogradation, aging viscosity, viscosity at the end of cooling, etc. . To determine the degree of gelatinization, DSC measurements are performed in the presence of excess water, in particular at 67% by weight or higher. When the water content of the starch/water mixture is less than 67%, the gelatinization temperature will increase as the water content decreases. Starch crystals are difficult to melt when the amount of available water is limited. When the water content of the starch/water mixture reaches 67%, the gelatinization temperature will remain constant no matter how much more water is added to the starch/water mixture. The gelatinization onset temperature indicates the initial gelatinization temperature. The end gelatinization temperature indicates the end gelatinization temperature. The enthalpy of gelation reflects the amount of crystal structure melted during gelation. Using the enthalpy obtained from the starch DSC thermogram, the degree of gelatinization can be determined.

[0033] Other starches have different gelatinization start temperatures, gelatinization end temperatures, and gelatinization enthalpies. Therefore, other starches may become fully gelatinized at different temperatures. It should be understood that the starch is fully gelatinized when it is heated above the final temperature of gelatinization with an excess of water. In addition, for any particular starch, when the starch is heated below its end gelatinization temperature, the starch will partially gelatinize. Thus, partial and incomplete gelatinization will occur in the presence of excess water when the starch is heated below the gelatinization end temperature, for example, as determined by DSC. Full gelatinization will occur in the presence of excess water when the starch is heated above the end gelatinization temperature, for example, as determined by DSC. The degree of gelatinization can be controlled in various ways, such as, for example, by heating the starch below the gelatinization end temperature, which results in partial gelatinization. For example, if the enthalpy required to completely gelatinize the starch is 4 J/g, while the DSC data show that the enthalpy of starch gelation is only 2 J/g, this means that 50% of the starch has been gelled. Fully gelatinized starch will not have a gelatinization peak on the DSC thermogram (enthalpy = 0 J/g) when measured by DSC.

[0034] As noted, the degree of gelatinization may be any suitable value, such as about 70% or more, and the like. However, lower degrees of gelatinization will be more consistent with granular starch and will not allow the full benefits of increased strength, better (more complete) dispersion, and/or reduced water consumption, according to some embodiments of the present invention. Thus, according to some embodiments of the invention, it is preferable that there is a higher degree of gelatinization, for example, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 97%, at least about 99%, or complete (100%) gelatinization. Starch with a lower degree of gelatinization can be added to the suspension, while in the case of gypsum board in the kiln, additional gelatinization occurs (for example, up to 100%). In terms of addition to the suspension, "fully gelled" should be understood to mean that the starch is sufficiently digested at or above its gelling temperature, or otherwise fully gelled as can be seen from the DSC data. While some small degree of retrogradation can be expected on cooling, in some embodiments the starch should still be considered "fully gelled" in terms of addition to gypsum slurry or use in other products, as one of ordinary skill in the art will appreciate. On the contrary, from the point of view of the VMA method discussed in this document, such retrogradation is unacceptable when measuring viscosity.

[0035] The starch molecule can be subjected to acid modification, for example, to hydrolyze the glycosidic bonds between glucose units and provide the desired molecular weight. One of the advantages of acid modification of starch, which provides a reduction in molecular weight, is that water consumption will be reduced. Conventional pregelatinized starches, which have also not been acid modified, have a very high water demand, which is accompanied by a higher energy cost. It has generally been thought that it is generally preferred that such modification occur prior to gelation, as it is generally more efficient and less expensive. However, surprisingly and unexpectedly, the inventors have found that gelatinization and acid modification can be combined in one stage in such a way that these processes can occur simultaneously, and not sequentially.

Method for obtaining starch

[0036] According to some embodiments of the present invention, the wet starch precursor is obtained prior to entering the extruder. The wet starch precursor may be prepared by any suitable method. For example, in some embodiments, a wet starch precursor is prepared by adding raw water and an acid to starch, which is (a) a weak acid that is substantially non-chelating with calcium ions and/or (b) a strong acid in a small amount. quantity.

[0037] Any suitable starch-containing raw material may be selected to form the wet starch precursor, provided that it can be used to form a pregelatinized partially hydrolyzed starch, such as a mid-range viscosity starch according to some embodiments of the present invention. As used herein, "starch" refers to a composition containing a starch component. As such, the starch may be 100% pure starch, or may contain other components such as those normally found in flour, such as protein and fiber, provided that the starch component is at least about 75% by weight based on the mass of the starch. compositions. The starch may be in the form of flour (e.g., cornmeal) containing starch, e.g., flour containing at least about 75% starch by weight relative to the flour, e.g., at least about 80%, at least about 85%, at least about 90%, at least about 95%, and the like). Any suitable unmodified starch or flour can be used to prepare the precursor of the pregelatinized partially hydrolysed starches of the invention. For example, the starch may be CCM260 yellow corn meal, CCF600 yellow corn meal (Bunge North America), Clinton 106 (ADM), and/or Midsol 50 (MGP Ingredients).

[0038] A wet starch precursor can be made having any suitable moisture content so that the desired levels of pregelatinization and acid modification can be achieved in the extruder. According to some embodiments of the invention, for example, it is desirable that the wet starch precursor has a moisture content of from about 8% by weight. up to about 25% wt. by weight relative to the total weight of the starch-containing precursor substance, for example, from about 8% of the mass. up to about 23% wt., for example, from about 8% wt. up to about 21% wt., from about 8% wt. up to about 20% wt., from about 8% wt. to about 19% wt., from about 8% wt. up to about 18% wt., from about 8% wt. up to about 17% wt., from about 8% wt. up to about 16% wt., from about 8% wt. up to about 15% wt., from about 9% wt. up to about 25% wt., from about 9% wt. up to about 23% wt., from about 9% wt. up to about 21% wt., from about 9% wt. up to about 20% wt., from about 9% wt. up to about 19% wt., from about 9% wt. up to about 18% wt., from about 9% wt. up to about 17% wt., from about 9% wt. up to about 16% wt., from about 9% wt. up to about 15% wt., from about 10% wt. up to about 25% wt., from about 10% wt. up to about 23% wt., from about 10% wt. up to about 21% wt., from about 10% wt. up to about 20% wt., from about 10% wt. up to about 19% wt., from about 10% wt. up to about 18% wt., from about 10% wt. up to about 17% wt., from about 10% wt. up to about 16% wt., from about 10% wt. up to about 15% wt., from about 11% wt. up to about 25% wt., from about 11% wt. up to about 23% wt., from about 11% wt. up to about 21% wt., from about 11% wt. up to about 20% wt., from about 11% wt. up to about 19% wt., from about 11% wt. up to about 18% wt., from about 11% wt. to about 17% wt., from about 11% wt. up to about 16% wt., from about 11% wt. up to about 15% wt., from about 12% wt. up to about 25% wt., from about 12% wt. up to about 23% wt., from about 12% wt. up to about 21% wt., from about 12% wt. up to about 20% wt., from about 12% wt. up to about 19% wt., from about 12% wt. up to about 18% wt., from about 12% wt. up to about 17% wt., from about 12% wt. up to about 16% wt., from about 12% wt. up to about 15% wt., from about 13% wt. up to about 25% wt., from about 13% wt. up to about 23% wt., from about 13% wt. up to about 21% wt., from about 13% wt. up to about 20% wt., from about 13% wt. to about 19% wt., from about 13% wt. up to about 18% wt., from about 13% wt. up to about 17% wt., from about 13% wt. up to about 16% wt., from about 13% wt. up to about 15% wt., from about 14% wt. up to about 25% wt., from about 14% wt. up to about 23% wt., from about 14% wt. up to about 21% wt., from about 14% wt. up to about 20% wt., from about 14% wt. to about 19% wt., from about 14% wt. up to about 18% wt., from about 14% wt. to about 17% wt., from about 14% wt. up to about 16% wt. or from about 14% of the mass. up to about 15% wt. based on the total weight of the wet starch precursor. It should be understood that when making wet starch, the moisture content given herein includes ambient moisture as well as added water.

[0039] While not wishing to be bound by any particular theory, it is believed that lower moisture content results in more friction in the extruder. In some embodiments, wet starch can be produced having a moisture content that provides sufficient mechanical energy input when loading the wet starch through the extruder such that friction prevents the wet starch from moving too easily through the extruder. Increased friction can increase the breakdown of hydrogen bonds in starch.

[0040] Any suitable weak acid that does not substantially chelate with calcium ions can be mixed into the wet starch. Without wishing to be bound by any particular theory, chelation involves a weak acid, such as one that forms a coordination complex with calcium or otherwise prevents the formation of gypsum crystals within the gypsum slurry. Such interference may be a decrease in the amount of gypsum crystals formed, a slowdown (decrease in rate) of crystal formation, a decrease in interactions between gypsum crystals, and the like. The term "substantially" in relation to the absence of calcium ion chelation generally means that at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least at least 98% or at least 99%) of the available calcium ions do not chelate with the acid.

[0041] Weak acids according to embodiments of the present invention can be defined as acids having a pKa value of from about 1 to about 6, for example, from about 1 to about 5, from about 1 to 4, from about 1 to 3, from about 1 to 2, about 1.2 to about 6, about 1.2 to about 5, about 1.2 to about 4, about 1.2 to about 3, about 1.2 to about 2, about 2 to about 6, from about 2 to about 5, from about 2 to about 4, from about 2 to about 3, from about 3 to about 6, from about 3 to about 5, from about 3 to about 4, from about 4 to about 6, or about 4 to about 5. As is known in the art, the pKa value is a measure of the strength of an acid; the lower the pKa value, the stronger the acid.

[0042] Weak acids that do not substantially chelate calcium ions are characterized, for example, by the absence of multi-binding sites, such as multiple carboxyl functional groups (COO-), that normally bind calcium ions. In some embodiments, the weak acid has a minimal amount of multi-binding sites, such as multi-COO groups, or substantially no multi-binding sites, such as multi-COO groups, such that, for example, chelation is minimal (i.e. , essentially eliminated) or the formation of gypsum crystals is essentially not affected compared to the formation of crystals in the absence of a weak acid. In some embodiments, for example, aluminum sulfate (alum) is a weak acid suitable for use in making wet starch because said aluminum sulfate does not substantially chelate with calcium ions. Alums do not have multibinding sites.

[0043] In some embodiments, the alum is added to the wet starch precursor in any suitable form, such as a liquid containing alum at the desired solids content. For example, liquid alum can be included in an aqueous solution in which alum is present in any suitable amount. Other weak acids can be added in a similar manner.

[0044] Wet starch can be mixed to include any suitable amount of a weak acid that does not substantially chelate with calcium ions, so that a pregelatinized partially hydrolyzed starch with the desired viscosity and low water consumption is obtained, while said starch does not undergo excessive hydrolysis and does not convert into sugar. For example, according to some embodiments of the invention, the specified weak acid is added in an amount of from about 0.5% of the mass. up to about 5% wt. based on the mass of starch, for example, from about 0.5 wt%. up to about 4.5% wt., for example, from about 0.5% wt. up to about 4% wt., from about 0.5% wt. up to about 3.5% wt., from about 0.5% wt. up to about 3% wt., from about 1% wt. up to about 5% wt., from about 1% wt. up to about 4.5% wt., from about 1% wt. up to about 4% wt., from about 1% wt. up to about 3.5% wt., from about 1% wt. up to about 3% wt., from about 1.5% wt. up to about 5% wt., from about 1.5% wt. up to about 4.5% wt., from about 1.5% wt. up to about 4% wt., from about 1.5% wt. up to about 3.5% wt., from about 1.5% wt. up to about 3% wt., from about 2% wt. up to about 5% wt., from about 2% wt. up to about 4.5% wt., from about 2% wt. up to about 4% wt., from about 2% wt. up to about 3.5% wt., from about 2% wt. up to about 3% wt., from about 2.5% wt. up to about 5% wt., from about 2.5% wt. up to about 4.5% wt., from about 2.5% wt. up to about 4% wt., from about 2.5% wt. up to about 3.5 wt%. or from about 2.5% of the mass. up to about 3% wt. It should be understood that the amounts listed include the weak acid component, and when the weak acid is in solution, do not include water or other components of the solution.

[0045] A wet starch precursor can be prepared, optionally further containing pseudoacids that can chelate calcium ion, such as tartaric acid. Thus, in some embodiments, a pseudo-acid, such as tartaric acid, can be combined with any suitable weak acid that does not chelate with calcium ions. As you know, tartaric acid slows down the crystallization of gypsum. However, in combination with a weak non-chelating acid, tartaric acid prevents the crystallization of gypsum from being significantly slowed down, so that the hydrolysis reaction is optimized by acid modification. In addition to tartaric acid, other pseudo-acids such as succinic acid or malic acid may be useful, provided they do not overpower the accelerating effect of alum. In some embodiments, the wet starch precursor comprises both alum and tartaric acid.

[0046] When included, pseudoacids (eg, tartaric acid) may be present in any suitable amount. For example, tartaric acid may be present in an amount of from about 0.1% wt. up to about 0.6% wt. based on the mass of starch, for example, from about 0.1% of the mass. to about 0.4% wt., from about 0.2% wt. up to about 0.3% wt.

[0047] In some embodiments, oil may be added to the wet starch, although not necessarily, to improve the movement of the starch within the extruder. In some embodiments, possible oils include canola oil, vegetable oil, corn oil, soybean oil, or any combination thereof. For example, according to some embodiments of the invention, canola oil or one of the substitutes listed above can, although not necessarily, be added in an amount of from about 0 wt%. up to about 0.25% wt. by weight relative to the mass of starch, for example, from about 0.1% of the mass. to about 0.2% wt., from about 0.1% wt. to about 0.15% wt., from about 0.15% wt. to about 0.25% wt., from about 0.15% wt. up to about 0.2% wt. or from about 0.2% of the mass. up to about 0.25% wt.

[0048] In some embodiments, the wet starch precursor is prepared by mixing water, unpregelatinized starch, and a small amount of strong acid. In some embodiments, the pKa of a strong acid is about -1.7 or less. Any such strong acid may be used, wherein in some embodiments the strong acid comprises sulfuric acid, nitric acid, hydrochloric acid, or any combination thereof. In some embodiments, sulfuric acid, alone or in combination with other acids, is preferred because the sulfate ion can accelerate gypsum crystallization in gypsum board embodiments.

[0049] The amount of strong acid is relatively small, such as about 0.05 wt%. or less by weight relative to the mass of starch, for example, about 0.045% of the mass. or less, about 0.04% of the mass. or less, about 0.035% of the mass. or less, about 0.03% of the mass. or less, about 0.025% of the mass. or less, about 0.02% of the mass. or less, about 0.015% of the mass. or less, about 0.01% of the mass. or less, about 0.005% of the mass. or less, about 0.001% of the mass. or less, about 0.0005% of the mass. or less, for example, from about 0.0001% of the mass. to about 0.05% wt., from about 0.0001% wt. to about 0.045% wt., from about 0.0001% wt. to about 0.04% wt., from about 0.0001% wt. to about 0.035% wt., from about 0.0001% wt. to about 0.03% wt., from about 0.0001% wt. to about 0.025% wt., from about from about 0.0001% wt. to about 0.02% wt., from about 0.0001% wt. to about 0.015% wt., from about 0.0001% wt. to about 0.01% wt., from about 0.0001% wt. to about 0.005% wt., from about 0.0001% wt. to about 0.001% wt., from about 0.0001% wt. up to about 0.0005% wt. by weight relative to the weight of starch. It should be understood that these amounts include the strong acid component, and when the strong acid is in solution, do not include water or other components of the solution. For example, a typical strong acid modification uses a 2% sulfuric acid solution with ~35% starch solids (2 g of sulfuric acid per 35 g of starch). The percentage is based on the pure sulfuric acid components. This content is calculated as the weight of the sulfuric acid component divided by the weight of the wet starch. For example, if the purity of sulfuric acid is 50% (meaning that half the mass of the solution is pure sulfuric acid), then the mass of the sulfuric acid solution is doubled. For illustration, to ensure a concentration of 0.1% wt. 0.1 g of pure sulfuric acid is added per 100 g of starch. If the concentration of the sulfuric acid solution is 50%, to ensure a concentration of 0.1% wt. add 0.2 g of 50% sulfuric acid solution.

[0050] It should be understood that there are different grades of acids (>95%, 98%, 99.99%). These differences are taken into account by the term "about" in relation to the amount of strong acid in the starch precursor. One of ordinary skill in the art will readily be able to determine the wt % described herein used to include other grades of acids. The amounts of strong acid used in some embodiments of the present invention are significantly less than the amounts that have been added to conventional systems used, eg, at least about 2 grams of sulfuric acid per 35 grams of starch. In some embodiments, a small amount of a strong acid, as described above, can be used in combination with a weak acid that does not chelate calcium ions, such as the alum described herein.

[0051] Embodiments of the present invention feed the wet starch precursor through the extruder such that the wet starch precursor undergoes pregelatinization and acid modification in the extruder in a single step. It should be understood that an extruder is a machine tool commonly used to melt and process polymers into the desired shape by melting the polymer and pumping it through a die. The extruder also allows the polymer to be mixed with other ingredients such as dye, reinforcing fibres, mineral fillers, and the like. The purpose of the extruder is to disperse and distribute all ingredients loaded into it and melt said ingredients at a constant temperature and pressure.

[0052] Configurations and devices for extruders are known in the art. In general, an extruder comprises a feed hopper for delivering feed material, a preconditioner containing heating jackets for conditioning the polymer with a plasticizer (eg, water), an extrusion modular die containing a heating zone, and a die assembly. Extruders generally comprise a feed screw, knife and screw(s). The feed screw is used to convey the wet starch precursor to the extruder. A knife is used to cut the stringy pregelatinized partially hydrolyzed starch into small tablets so that they can be crushed. The screw(s) assist in mixing the wet starch precursor, transport the wet starch precursor through the extruder, and provide mechanical shear. The extruder may be single screw or twin screw, as will be appreciated by one of ordinary skill in the art. See, for example, Leszek Moscicki, Extrusion-Cooking Techniques, WILEY-VCH Verlag & Co. KGaA, 2011.

[0053] In single screw extruders, the screw typically comprises a deep channel feed zone for transporting solids out of the feeder opening and compressing it, a compression zone in which the screw channels become progressively shallower and the polymer melts, and a shallow channel dosing zone that moves molten polymer into the head. Some screws are designed with the possibility of adding mixing devices (for example, pins extending from the screw).

[0054] Twin screw extruders typically have two screws that rotate either in the same direction (i.e., rotating in the same direction) or in opposite directions (i.e., counter-rotating). The two augers can be rotated with non-engaged or fully engaged screws. Whereas in the case of single screw extruders the feed material fills the entire extruder port, in the case of twin screw extruders only part of the port is filled so that the feed or inlet openings below can be used to add some ingredients.

[0055] The head assembly typically includes a plate, a gasket, and a worm press head. When extruding materials, the process may be either continuous, where the material is extruded to an indeterminate length, or semi-continuous, where the material is extruded piecemeal. The materials to be extruded may be hot or cold.

[0056] The present invention provides a method for producing pregelatinized partially hydrolysed starch in an extruder. Any suitable extruder may be used, such as a single screw extruder (for example, the Advantage 50 extruder, available from American International, located in South Beloit, Illinois) or a twin screw extruder (for example, the Wenger TX52 extruder, available from Wenger, located in in Sabet, Kansas).

[0057] As described herein, a non-pregelatinized starch, an acid in the form of a weak acid that does not substantially chelate with calcium ions, and/or a small amount of a strong acid and water are mixed and fed into an extruder. In some embodiments, additional water may be introduced into the extruder. While in the extruder the combination of heating elements and mechanical shear results in melting and pregelatinization of the starch, the weak acid partially hydrolyzes the starch to the desired molecular weight, indicative of the desired viscosity, as described herein. The conditions in the extruder, due to the mechanical energy, will also cause the starch molecules to break down, which has somewhat the same effect as the acid modification. It is believed that since, in some embodiments, conditions in the extruder (eg, high temperature and high reaction pressure) favor such a chemical reaction, a weak acid and/or low amounts of a strong acid can be used. Thus, the method according to the invention improves the efficiency of the acid modification of starch.

[0058] The main screw(s) can be operated at any suitable speed so as to provide the required mixing and mechanical shear. For example, according to some embodiments of the invention, the main screw may operate at a speed of about 350 rpm (± about 100 rpm). The loading auger may be operated at any suitable speed to provide the desired feed rate. For example, according to some embodiments of the invention, the loading auger may operate at a speed of about 14 rpm (± about 5 rpm).

[0059] The knife can be operated at any suitable speed. For example, according to various embodiments of the invention, the knife can operate at a speed of from about 400 rpm to about 1000 rpm, for example, from about 400 rpm to about 900 rpm, from about 400 rpm to about 800 rpm /min, from about 400 rpm to about 700 rpm, from about 400 rpm to about 600 rpm, from about 400 rpm to about 500 rpm, from about 500 rpm to about 1000 rpm, from about 500 rpm to about 900 rpm, from about 500 rpm to about 800 rpm, from about 500 rpm to about 700 rpm, from about 500 rpm up to about 600 rpm, from about 600 rpm to about 1000 rpm, from about 600 rpm to about 900 rpm, from about 600 rpm to about 800 rpm, from about 600 rpm to about 700 rpm, from about 700 rpm to about 1000 rpm, from about 700 rpm to about 900 rpm, from about 700 rpm to about 800 rpm, from about 800 rpm to approx. 1000 rpm , from about 800 rpm to about 900 rpm, or from about 900 rpm to about 1000 rpm.

[0060] Wet starch can be gelled and acid modified in a die extruder at any suitable temperature such that the wet starch becomes sufficiently gelled without burning the materials. For example, wet starch can be gelatinized and acid modified in a die extruder at a temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF), for example, according to various embodiments of the invention from about 150 ºC to about 205 ºC ( 400 ºF), approx. 150 ºC to approx. 199 ºC (approx. 390 ºF), approx. 150 ºC to approx. 193 ºC (approx. 380 ºF), approx. ºC to approx. 182 ºC (approx. 360 ºF), approx. 154 ºC (approx. 310 ºF) to approx. 210 ºC, approx. 154 ºC to approx. 205 ºC (approx. 400 ºF), approx. 154 ºC to about 193 ºC, about 154 ºC to about 188 ºC, from about 154 ºC to about 182 ºC, from about 160 ºC (about 320 ºF) to about 210 ºC, from about 160 ºC to about 205 ºC (about 400 ºF), from about 160 ºC to about 199 ºC, from about 160 ºC to about 193 ºC, from about 160 ºC to about 188 ºC, from about 160 ºC to about 182 ºC, from about 166 ºC (about 330 ºF) to about 210 ºC, from about 166 ºC to about 205 ºC, from about 166 ºC to about 199 ºC, from about 166 ºC to about 193 ºC, about 166 ºC to about 188 ºC, from about 166 ºC to about 182 ºC, from about 171 ºC (about 340 ºF) to about 210 ºC, from about 171 ºC to about 205 ºC, from about 171 ºC to about 199 ºC, from about 171 ºC to about 193 ºC, from about 171 ºC to about 188 ºC, from about 171 ºC to about 182 ºC, from about 177 ºC (about 350 ºF) to about 210 ºC, from about 177 ºC to about 205 ºC, from about 177 ºC to about 199 ºC, from about 177 ºC to about 193 ºC, from about 177 ºC to about 188 ºC, or from about 177 ºC to about 182 ºC. Although the die may be at any sufficient temperature as described herein, the temperature of the die is generally above the melting point of the starch crystals.

[0061] The degree of gelatinization can be any suitable value, for example, at least about 70% or more, for example, at least about 75%, at least about 80%, at least about 85%, at least about 90 %, at least about 95%, at least about 97%, at least about 99%, or complete (100%) gelatinization may occur. In the case of wallboard production as described below, starch with such lower degrees of gelatinization can be added to the plaster slurry, whereby, for example, additional gelatinization (eg up to 100%) takes place in the kiln.

[0062] The pressure in the extruder may be at any suitable level so as to provide suitable conditions for pregelatinization and acid modification. The pressure inside the extruder is determined by the raw material being extruded, moisture content, die temperature and screw speed, which will be taken into account by one of ordinary skill in the art. For example, the pressure in the extruder may be at least about 2000 psi (about 13800 kPa), for example, at least about 2250 psi (about 15500 kPa), at least about 2500 psi (about 17200 kPa), at least about 2750 psi (about 19000 kPa), at least about 3000 psi (about 20700 kPa), at least about 3500 psi (about 24100 kPa), at least about 4000 psi (about 27600 kPa), or at least about 4500 psi ( about 31000 kPa). In some embodiments, the pressure may be from about 2000 psi (about 13800 kPa) to about 5000 psi (about 34500 kPa), for example, from about 2000 psi (about 13800 kPa) to about 4500 psi (about 31000 kPa), from about 2000 psi (about 13800 kPa) to about 4000 psi (about 27600 kPa), from about 2000 psi (about 13800 kPa) to about 3500 psi (about 24100 kPa), from about 2000 psi (about 13800 kPa) to about 3000 psi ( about 20700 kPa), from about 2000 psi (about 13800 kPa) to about 2500 psi (about 17200 kPa), from about 2500 psi (about 17200 kPa) to about 5000 psi (about 34500 kPa), from about 2500 psi (about 17200 kPa) to about 4500 psi (about 31000 kPa), from about 2500 psi (about 17200 kPa) to about 4000 psi (about 27600 kPa), from about 2500 psi (about 17200 kPa) to about 3500 psi (about 24100 kPa), from about 2500 psi (about 17200 kPa) to about 3000 psi (about 20700 kPa), from about 3000 psi (about 20700 kPa) to about 5000 psi (about 34500 kPa), from about 3000 psi (about 20700 kPa) to about 4500 psi (about 31000 kPa), from about 3000 psi (about 20700 kPa) to about 4000 psi (about 27600 kPa), from about 3000 psi (about 20700 kPa) to about 3500 psi (about 24100 kPa), from about 3500 psi (about 24100 kPa) to about 5000 psi (about 34500 kPa) , from about 4000 psi (about 27600 kPa) to about 5000 psi (about 34500 kPa), from about 4000 psi (about 27600 kPa) to about 4500 psi (about 31000 kPa) or from about 4500 psi (about 31000 kPa) to about 5000 psi (approximately 34500 kPa).

[0063] Surprisingly and unexpectedly, it has been found that the method according to the invention for producing pregelatinized partially hydrolyzed starch in an extruder in one step is significantly faster than pregelatinization and acid modification of starch in two stages, carried out sequentially. Significantly higher amounts of pregelatinized partially hydrolysed starch can be obtained using the method proposed in the invention than starch obtained by any other method. The higher production volume and faster production rate are due to the high reaction rate at high temperature and/or high pressure. In some embodiments, pregelatinization and acid modification occur in less than about 5 minutes, such as less than about 4 minutes, such as less than about 3 minutes, less than about 2 minutes, less than about 90 seconds, less than about 75 seconds, less than about 1 minute. , less than about 45 seconds, less than about 30 seconds, less than about 25 seconds, less than about 20 seconds, less than about 15 seconds, or less than about 10 seconds. In addition, according to some variants of the invention, pregelatinization and acid modification occur in the extruder at a rate limited by any two of the above values. For example, the rate of pregelatinization and acid modification can be from about 10 seconds to 5 minutes, for example, from about 10 seconds to about 4 minutes, from about 10 seconds to about 3 minutes, from about 10 seconds to about 2 minutes, from about 10 seconds up to about 90 seconds, from about 10 seconds to about 75 seconds, from about 10 seconds to about 1 minute, from about 10 seconds to about 45 seconds, from about 10 seconds to about 30 seconds, from about 10 seconds to about 25 seconds, from about 10 seconds to about 20 seconds, or from about 10 seconds to about 15 seconds.

[0064] Proposed in the invention, the method of obtaining pregelatinized partially hydrolyzed starch can be a continuous process flowing at any sufficient speed. In some embodiments, the starch is subjected to pregelatinization and acid modification at an extruder output rate of at least about 100 kg/hour, such as at least about 150 kg/hour, at least about 200 kg/hour, at least at least about 250 kg/hour, at least about 300 kg/hour, at least about 350 kg/hour, at least about 400 kg/hour, at least about 450 kg/hour, 500 kg/hour, at least at least about 550 kg/hour, for example, at least about 600 kg/hour, at least about 650 kg/hour, at least about 700 kg/hour, at least about 750 kg/hour, at least about 800 kg/h, at least about 850 kg/h, at least about 900 kg/h, at least about 950 kg/h, at least about 1000 kg/h, at least about 1050 kg/h, at least about 1100 kg/h, at least about 1150 kg/h, at least n about 1200 kg/hour, at least about 1250 kg/hour, at least about 1300 kg/hour, at least about 1350 kg/hour, at least about 1400 kg/hour, at least about 1450 kg/hour or at least about 1500 kg/hour. In addition, according to some variants of the invention, the rate of output in the extruder may be limited to any two of the above values. For example, the output rate may be from about 100 kg/hour to about 1500 kg/hour (for example, from about 100 kg/hour to about 1500 kg/hour, from about 100 kg/hour to 1000 kg/hour, from about 250 kg/hour to about 1500 kg/hour, from about 250 kg/hour to about 1000 kg/hour, from about 600 kg/hour to about 1250 kg/hour, from about 650 kg/hour to about 1200 kg/hour, from about 700 kg/hour to about 1100 kg/hour, from about 750 kg/hour to about 1000 kg/hour, etc.).

[0065] The inventors have found that, in some embodiments, conditions in the extruder (eg, high temperature and high pressure) are particularly conducive to efficient and sufficient pregelatinization and acid modification of starch in one step. When wet starch is stirred in the extruder, it creates very high friction, which thereby generates heat. The action of the screw creates a shear force in the extruder because the distance between the screw and the chamber in the extruder is very small. Specific mechanical energy (SME) describes the mechanical energy of an object per unit mass. SME will depend on moisture content. Higher moisture content (eg for flow purposes) will result in low viscosity and low friction and thus lower SME. If more moisture is present, the SME will be less important due to the low viscosity and low friction. The moisture content of the wet starch precursor of the invention described herein provides an effective SME.

[0066] In the extruder, due to the conditions provided by the embodiments of the present invention described herein, the starch is gelatinized with high efficiency. Without wishing to be bound by any particular theory, it is believed that good mixing in the extruder according to some embodiments of the present invention requires less water to proceed with the reaction in the extruder. Very low moisture content contributes to a high concentration of the reactant, which can accelerate the rate of a chemical reaction. The high temperature of the extruder also greatly increases the reaction rate. When the starch exits the extruder, the reaction has already taken place, so that the starch is pregelatinized and partially hydrolysed.

[0067] In conventional acid modification, starch is added to a strong acid solution. This conventional process uses significantly more water and acid than the surprising and unexpected process involving simultaneous, rather than sequential, pregelatinization and acid modification of starch in a single extruder step as described herein. Conventional acid modification takes several hours. After the reaction has taken place, the acid must be neutralized, purified and washed. These neutralization and purification steps are time consuming and expensive.

[0068] Until the surprising and unexpected discovery made by the inventors, it was considered undesirable in conventional acid modification to use a weak acid that does not substantially chelate with calcium ions, or a strong acid in a small amount. This is because, in the conventional method, the weaker the acid or the smaller the amount of strong acid, the longer the acid modification takes. Thus, in conventional acid modification, it has been desirable to use a strong acid (eg, with a pKa below about -1.7) in large amounts. Surprisingly and unexpectedly, when preparing pregelatinized partially hydrolyzed starch in an extruder according to embodiments of the present invention using a weak acid or a small amount of strong acid, as described herein, there is no need for neutralization and purification steps due to slightly acidic conditions and less interfering effect on gypsum crystallization, respectively. In some embodiments, the acid may still be present in the pregelatinized, partially hydrolyzed starch.

Properties of starch and benefits of using starch in gypsum board

[0069] The starch produced in the extruder according to embodiments of the present invention may be any pregelatinized, partially hydrolysed starch. In some embodiments, starch can be prepared having different properties as desired (eg, mid-range viscosity, cold water solubility, cold water viscosity, and the like) as described herein.

[0070] Pregelatinized partially hydrolysed starches produced in an extruder according to embodiments of the present invention may be suitable for use in gypsum board. In the case of gypsum board applications, for example, pregelatinization and acid modification are valuable, for example, to impart strength by providing the desired viscosity (and hence molecular weight range) according to embodiments of the present invention, as described herein. In the proposed method for producing wallboard described herein, the degree of gelatinization of the starch added to the plaster slurry may be at least about 70%, for example, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 97%, or 100% (i.e., the starch is fully gelatinized).

[0071] In addition, according to embodiments of the present invention, feeding into the extruder a wet starch containing a weak acid that does not substantially form chelates with calcium ions, as described herein, allows the starch to be hydrolyzed in such a way as to provide the desired viscosity, which, respectively, indicates that the desired molecular weight range has been reached. Viscosity is thus an indication of the molecular weight of the pregelatinized partially hydrolyzed starch, as will be appreciated by one of ordinary skill in the art.

[0072] According to some embodiments of the invention, it is possible to obtain a pregelatinized partially hydrolyzed starch obtained according to embodiments of the present invention, having any suitable viscosity. In some embodiments, said viscosity is characterized as "mid-range" viscosity (i.e., a viscosity in the range of about 20 centipoise to about 700 centipoise) when the pregelatinized partially hydrolysed starch is subjected to the conditions of the VMA method using the pregelatinized partially hydrolyzed starch in water in an amount of 15% by weight relative to the total weight of pregelatinized partially hydrolyzed starch and water. Thus, the VMA method is used to determine whether the pregelatinized partially hydrolysed starch has a mid-range viscosity characteristic when exposed to the conditions according to the VMA method. This does not mean that pregelatinized partially hydrolysed starch should be added to the gypsum slurry under these conditions. Rather, when the pregelatinized partially hydrolysed starch is added to the slurry, it may be in wet (at various concentrations of starch in water) or dry form and need not be fully gelled as described herein or otherwise be under the conditions described in the method. VMA.

[0073] According to some embodiments of the invention, the viscosity in the middle range of pregelatinized starch can be from about 20 centipoise to about 700 centipoise, for example, from about 20 centipoise to about 500 centipoise, from about 30 centipoise to about 200 centipoise, or from about 100 centipoise to approximately 700 centipoise. According to embodiments of the present invention, the viscosity of the pregelatinized starch when tested according to the VMA method may have the values, for example, listed below in tables 1A, 1B and 1C. In these tables, "X" represents a range "from about [corresponding value in top row] to about [corresponding value in leftmost column]". The values indicated are the viscosity of the pregelatinized starch in centipoise. For ease of presentation, it should be understood that each value is "about" the specified value. For example, the first "X" in Table 1A is in the range "from about 20 centipoise to about 25 centipoise".

Table 1A

Viscosity range start value (centipoise) Viscosity range end value (centipoise) twenty 25 thirty 35 40 45 fifty 55 60 65 70 75 25 X thirty X X 35 X X X 40 X X X X 45 X X X X X fifty X X X X X X 55 X X X X X X X 60 X X X X X X X X 65 X X X X X X X X X 70 X X X X X X X X X X 75 X X X X X X X X X X X 100 X X X X X X X X X X X X 125 X X X X X X X X X X X X 150 X X X X X X X X X X X X 175 X X X X X X X X X X X X 200 X X X X X X X X X X X X 225 X X X X X X X X X X X X 250 X X X X X X X X X X X X 275 X X X X X X X X X X X X 300 X X X X X X X X X X X X 325 X X X X X X X X X X X X 350 X X X X X X X X X X X X 375 X X X X X X X X X X X X 400 X X X X X X X X X X X X 425 X X X X X X X X X X X X 450 X X X X X X X X X X X X 475 X X X X X X X X X X X X 500 X X X X X X X X X X X X 525 X X X X X X X X X X X X 550 X X X X X X X X X X X X 575 X X X X X X X X X X X X 600 X X X X X X X X X X X X 625 X X X X X X X X X X X X 650 X X X X X X X X X X X X 675 X X X X X X X X X X X X 700 X X X X X X X X X X X X

Table 1B

Viscosity range start value (centipoise) Viscosity range end value (centipoise) 100 125 150 175 200 225 250 275 300 325 350 375 125 X 150 X X 175 X X X 200 X X X X 225 X X X X X 250 X X X X X X 275 X X X X X X X 300 X X X X X X X X 325 X X X X X X X X X 350 X X X X X X X X X X 375 X X X X X X X X X X X 400 X X X X X X X X X X X X 425 X X X X X X X X X X X X 450 X X X X X X X X X X X X 475 X X X X X X X X X X X X 500 X X X X X X X X X X X X 525 X X X X X X X X X X X X 550 X X X X X X X X X X X X 575 X X X X X X X X X X X X 600 X X X X X X X X X X X X 625 X X X X X X X X X X X X 650 X X X X X X X X X X X X 675 X X X X X X X X X X X X 700 X X X X X X X X X X X X

Table 1C

Viscosity range start value (centipoise) Viscosity range end value (centipoise) 400 425 450 475 500 525 550 575 600 625 650 675 425 X 450 X X 475 X X X 500 X X X X 525 X X X X X 550 X X X X X X 575 X X X X X X X 600 X X X X X X X X 625 X X X X X X X X X 650 X X X X X X X X X X 675 X X X X X X X X X X X 700 X X X X X X X X X X X X

[0074] Thus, the viscosity of the pregelatinized partially hydrolyzed starch obtained according to embodiments of the present invention may range between and include any of the above endpoints listed in Tables 1A, 1B or 1C. Alternatively, in some embodiments, the pregelatinized partially hydrolysed starch has a viscosity (10% solids, 93°C) of about 5 Brabender Units (BU) to about 33 BU, as measured according to the Brabender method described herein, for example, from about 10 BU to about 30 BU, from about 12 BU to about 25 BU, or from about 15 BU to about 20 BU.

[0075] In some embodiments, the pregelatinized, partially hydrolyzed starches made in accordance with embodiments of the present invention can provide significant strength advantages to the product (eg, wallboard) in which they are used. Because starch contains glucose monomers containing three hydroxyl groups, starch provides many sites for hydrogen bonding with gypsum crystals. Without wishing to be bound by any particular theory, it is believed that the molecular size of the pregelatinized, partially hydrolysed starch produced according to embodiments of the present invention provides optimal mobility of the starch molecules and allows the starch molecules to cluster around the gypsum crystals, which promotes good binding of the starch to the gypsum crystals and strengthens the resulting crystalline gypsum matrix, for example, through the formation of hydrogen bonds.

[0076] Conventional pregelatinized starches prepared according to a method other than the method described herein, for example, having viscosities outside the average range, which will either have longer chains and a higher molecular weight (viscosity that is too high) , or shorter chains and lower molecular weights (viscosities that are too low), respectively, do not provide the same combination of benefits. In addition, it is believed that in terms of starch effectiveness, when the starch molecules are sufficiently bound to the gypsum crystals, the additional amount of starch does not add a significant advantage, since the crystals are already bound, so that there are no additional sites in the gypsum crystals with which starch can stick together or bind. Accordingly, due to the optimal binding of gypsum crystals and pregelatinized partially hydrolyzed starch molecules produced according to embodiments of the present invention, the strength of the crystalline gypsum matrix is increased, while less starch is required to provide such strength compared to conventional starches. The inventors have found that dissolved starch molecules, for example, with a medium range viscosity (meaning a medium range starch molecular weight) provide optimal mobility of the starch molecules, which allows the starch molecules to cluster with gypsum crystals and promotes good hydrogen bonding of starch and gypsum and strength core according to some embodiments of the invention.

[0077] In some embodiments, the pregelatinized partially hydrolysed starch produced in some embodiments also provides water consumption benefits. The addition of conventional pregelatinized starch to a gypsum slurry requires the addition of additional water to the gypsum slurry to maintain the required fluidity of the slurry. This is because conventional pregelatinized starch increases the viscosity and reduces the fluidity of the gypsum slurry. Thus, the use of pregelatinized starch in conventional systems would lead to an increase in water consumption such that an even greater excess of water would be required in the gypsum slurry.

[0078] Surprisingly and unexpectedly, the pregelatinized partially hydrolyzed starch produced according to the embodiments of the present invention, in particular with the desired viscosity in the middle range, requires less water, so that the impact on water consumption in the gypsum slurry is reduced, especially compared to conventional starches. In addition, due to the effectiveness of the pregelatinized partially hydrolysed starch produced according to the embodiments of the present invention so that less starch can be used, the positive effect on water consumption may be even greater according to some embodiments of the present invention. This lower water consumption provides significant efficiency in production. For example, excess water requires energy input for drying. When drying, the speed of the production line must be reduced. Thus, by reducing the amount of water in the gypsum slurry, it is possible to use less energy and reduce costs, as well as provide greater productivity. In some embodiments, the increase in water demand of the gypsum slurry is less than the increase in water demand required when using other starches, such as pregelatinized starches with a viscosity greater than 700 centipoise (e.g., about 773 centipoise), for example, prepared by a different process.

[0079] Any suitable non-pregelatinized starch can be selected to make the pregelatinized partially hydrolysed starch, as long as it is sufficient for pregelatinization and acid modification in the extruder. As used herein, "starch" refers to a composition containing a starch component. As such, the starch may be 100% pure starch or may contain other components, for example, components normally found in flour such as protein and fiber, provided that the starch component is at least about 75% by weight based on the mass of the starch. compositions. The starch may be in the form of flour (e.g., cornmeal) containing starch, e.g., flour containing at least about 75% starch by weight based on the weight of the flour, e.g., at least about 80%, at least about 85%, at least about 90%, at least about 95%, and the like). By way of example, and not limitation, the starch may be in the form of starch-containing cornmeal.

[0080] According to some embodiments of the invention, it is possible to obtain a pregelatinized partially hydrolyzed starch obtained according to embodiments of the present invention having the desired cold water solubility. Conventional pregelatinization methods involve making starch soluble in cold water and generally require cooking the starch in excess water. However, these conventional methods are not effective. Extrusion according to embodiments of the present invention, providing a combination of heat and mechanical shear, is surprisingly and unexpectedly an energy-saving method that can be used to produce, in a one-step process, pregelatinized partially hydrolyzed starch having a low moisture content with cold water solubility. Solubility in cold water is defined as having any degree of solubility in water at room temperature (about 25°C). It has been found that starches exhibiting cold water solubility can provide significant strength advantages to gypsum products (eg wallboard). The cold water soluble starches of the present invention have a cold water solubility greater than about 30% and, when added to a set gypsum core, can increase the strength of the gypsum core. The solubility of pregelatinized starch in water is defined as the amount of starch that dissolves in room temperature water divided by the total amount of starch.

[0081] According to some embodiments of the invention, the cold water solubility of the pregelatinized partially hydrolyzed starch obtained according to embodiments of the present invention is from about 30% to about 100%. In other embodiments, the cold water solubility of the extruded pregelatinized partially hydrolyzed starch is from about 50% to about 100%. According to embodiments of the present invention, the cold water solubility of the extruded pregelatinized partially hydrolyzed starch may have the values shown in Table 2, for example. leftmost column]. These values represent the cold water solubility of the extruded pregelatinized partially hydrolysed starch prepared according to the embodiments of the present invention (Table 2). For ease of presentation, it should be understood that each value is "about" the specified value. For example, the first "X" in Table 2 is in the range "about 30% to about 35%." The ranges shown in the table are between the start and end points and include the specified points.

table 2

Initial value of cold water solubility range (%) Final value of cold water solubility range (%) thirty 35 40 45 fifty 55 60 65 70 75 80 85 90 95 35 X 40 X X 45 X X X fifty X X X X 55 X X X X X 60 X X X X X X 65 X X X X X X X 70 X X X X X X X X 75 X X X X X X X X X 80 X X X X X X X X X X 85 X X X X X X X X X X X 90 X X X X X X X X X X X X 95 X X X X X X X X X X X X X 100 X X X X X X X X X X X X X X

[0082] While not wishing to be bound by any particular theory, it is believed that a combination of mechanical and thermal energy during the extrusion process is responsible for the cold water solubility of the pregelatinized partially hydrolysed starch produced according to embodiments of the present invention. It is believed that when starch is extruded, the hydrogen bonds between starch molecules are broken. When extruded starch is dissolved in water, starch forms hydrogen bonds with water molecules. After the pregelatinization process, the molecules of the extruded pregelatinized partially hydrolyzed starch can form hydrogen bonds with the gypsum crystals, thus imparting greater strength to the gypsum product. Accordingly, since starches exhibiting cold water solubility improve the strength of the gypsum wallboard, less starch is required compared to conventional starches.

[0083] According to some embodiments, the cold water viscosity (10% solids, 25°C) of the pregelatinized partially hydrolyzed starch, measured according to the Brabender method described herein, is from about 10 BU to about 120 BU, for example, from about 20 BU to about 110 BU, about 30 BU to about 100 BU, about 40 BU to about 90 BU, about 50 BU to about 80 BU, or about 60 BU to about 70 BU.

The use of starch obtained according to the proposed method in the manufacture of boards

[0084] In some embodiments, a board (e.g., gypsum wallboard) can be made by preparing pregelatinized, partially hydrolyzed starch by mixing at least water, non-pregelatinized starch, and acid to form a wet starch precursor with a moisture content of about 8 wt. up to about 25% wt., while the acid is selected from: a weak acid, which essentially does not form chelates with calcium ions, a strong acid in an amount of about 0.01% wt. or less by weight relative to the weight of starch, or any combination thereof.

[0085] The wet starch precursor is then fed into an extruder in which the die temperature is from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF), where the wet starch is pregelatinized and acid modified so that it at least partially hydrolyzed. The pregelatinized partially hydrolysed starch can then be mixed with at least water and stucco to form a slurry which can then be placed between the first skin sheet and the second skin sheet to form a wet assembly. The wet precast can then be cut to form a slab which is then dried. The seized gypsum core of the board preferably has a compressive strength greater than a gypsum core made using starch prepared according to another method.

[0086] Surprisingly and unexpectedly, the pregelatinized partially hydrolyzed starch produced according to embodiments of the present invention can be included in a slurry in a relatively low amount (solid/solid basis) and still provide a significant increase in board strength. Accordingly, the pregelatinized, partially hydrolyzed starch produced in accordance with embodiments of the present invention may be included in the gypsum slurry in an amount of from about 0.1% to about 10% by weight based on the weight of the plaster, for example, from about 0.5% to approximately 10%.

[0087] It has been found that increasing the amount of pregelatinized partially hydrolysed starch produced according to embodiments of the present invention in slurry above the above limits does not improve strength as effectively, as strength levels may somewhat stop rising when even more starch is added according to some embodiments of the invention . However, if necessary, higher amounts of starch can be used, especially when diminishing returns on strength are allowed.

[0088] In embodiments of the present invention, the pregelatinized partially hydrolysed starch may be added to the gypsum slurry in an amount such as those shown in Tables 3A and 3B below. In said table, "X" is a range "from about [corresponding value in top row] to about [corresponding value in leftmost column]". The indicated values are the amount of starch as a percentage by weight relative to the weight of the plaster. For ease of presentation, it should be understood that each value is "about" the specified value. For example, the first "X" is in the range "from about 0.1% starch by weight based on the weight of the plaster to about 0.25% starch by weight based on the weight of the plaster."

Table 3A

0.1 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5 2.75 3.0 3.5 0.25 X 0.5 X X 0.75 X X X 1.0 X X X X 1.25 X X X X X 1.5 X X X X X X 1.75 X X X X X X X 2.0 X X X X X X X X 2.25 X X X X X X X X X 2.5 X X X X X X X X X X 2.75 X X X X X X X X X X X 3.0 X X X X X X X X X X X X 3.5 X X X X X X X X X X X X X 4.0 X X X X X X X X X X X X X X 4.5 X X X X X X X X X X X X X X 5.0 X X X X X X X X X X X X X X 5.5 X X X X X X X X X X X X X X 6.0 X X X X X X X X X X X X X X 6.5 X X X X X X X X X X X X X X 7.0 X X X X X X X X X X X X X X 7.5 X X X X X X X X X X X X X X 8.0 X X X X X X X X X X X X X X 8.5 X X X X X X X X X X X X X X 9.0 X X X X X X X X X X X X X X 9.5 X X X X X X X X X X X X X X 10.0 X X X X X X X X X X X X X X

Table 3B

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 4.5 X 5.0 X X 5.5 X X X 6.0 X X X X 6.5 X X X X X 7.0 X X X X X X 7.5 X X X X X X X 8.0 X X X X X X X X 8.5 X X X X X X X X X 9.0 X X X X X X X X X X 9.5 X X X X X X X X X X X 10.0 X X X X X X X X X X X X

[0089] Thus, the amount of pregelatinized partially hydrolyzed starch added to the slurry, obtained according to embodiments of the present invention, may range between and include any of the above endpoints given in Tables 3A or 3B.

[0090] According to some embodiments of the invention, the pregelatinized partially hydrolyzed starch obtained according to the embodiments of the present invention can be added to the suspension in combination with other starches for various applications. For example, in the case of the gypsum wallboard described below, the pregelatinized partially hydrolyzed starch made according to embodiments of the present invention can be combined with other starches to enhance both core strength and paper-core bond, particularly if some increase in water consumption is to be tolerated.

[0091] Thus, according to some embodiments of the present invention, the gypsum slurry may include one or more pregelatinized, partially hydrolysed starch obtained according to embodiments of the present invention, as well as one or more other types of starches. Other starches may include, for example, pregelatinized starches with viscosities below 20 centipoise and/or above 700 centipoise. One example is pregelatinized corn starch (eg, with a viscosity greater than 700 centipoise, eg, about 773 centipoise). Other starches may also be in the form of, for example, non-pregelatinized starches, such as acid-modified starches, as well as alkylated starches, for example, ethylated starches, which are not gelled, and the like. Before being added to the gypsum slurry, the combination of starches may be premixed (e.g., in a dry mix, optionally with other components such as plaster, etc., or wet mixed with other wet ingredients), or they may be added to the gypsum slurry one at a time. once or in any of their variations. You can use any suitable proportion of pregelatinized partially hydrolyzed starch, obtained according to variants of implementation of the present invention, and other starch.

[0092] For example, the starch content of the pregelatinized partially hydrolyzed starch produced according to embodiments of the present invention, as a percentage of the total starch content added to the gypsum slurry, may be, for example, at least about 10% by weight, for example, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, at least about 99%, at least about 100%, or any range between the indicated values. According to some embodiments of the invention, the ratio of pregelatinized partially hydrolyzed starch obtained according to embodiments of the present invention to other starch can be about 25:75, about 30:70, about 35:65, about 50:50, about 65:35, about 70 :30, approximately 75:25, etc.

[0093] In some embodiments, along with the starch component, the slurry is formulated to include water, plaster, foaming agent (sometimes referred to simply as "foam"), and other additives as needed. Surprisingly and unexpectedly, according to some embodiments of the invention, in particular those exhibiting a viscosity in the middle range, it was found that the amount of water that must be added to maintain the fluidity of the suspension at the same level that would be without the use of pregelatinized partially hydrolyzed starch obtained in the extruder according to embodiments of the present invention is less than the increase in the amount of water required when using starch obtained according to another method. The stucco may be in the form of calcium sulfate alpha hemihydrate, calcium sulfate beta hemihydrate and/or calcium sulfate anhydrite. The plaster may be fibrous or non-fibrous. A blowing agent may be included to form an air pore distribution within the continuous crystalline matrix of the set gypsum. According to some embodiments of the invention, the blowing agent contains a major mass fraction of an unstable component and a minor mass fraction of a stable component (for example, when combining an unstable component and a mixture of a stable component/unstable component). Such a weight ratio, the ratio of the unstable component to the stable component, is effective in forming an air void distribution within the set gypsum core. See, for example, US Pat. Nos. 5,643,510; 6342284; and 6632550.

[0094] It has been found that suitable pore distribution and wall thickness (independently) can be effective in terms of increasing strength, especially boards with lower density (for example, below about 35 lb/cu. ft. (about 561 kg/m ³ ) ). See, for example, US 2007/0048490 and US 2008/0090068. Water evaporation pores, which are generally about 5 µm in diameter or less, also contribute to the overall pore distribution along with the air pores (foam) mentioned above. In some embodiments, the volume ratio of pores larger than about 5 microns to pores larger than about 5 microns or less is from about 0.5:1 to about 9:1, for example, from about 0.7:1 to about 9: 1, about 0.8:1 to about 9:1, about 1.4:1 to about 9:1, about 1.8:1 to about 9:1, about 2.3:1 to about 9:1, about 0.7:1 to about 6:1, about 1.4:1 to about 6:1, about 1.8:1 to about 6:1, from about 0.7:1 to about 4:1, from about 1.4:1 to about 4:1, from about 1.8:1 to about 4:1, from about 0.5:1 to about 2.3:1, from about 0 .7:1 to about 2.3:1, about 0.8:1 to about 2.3:1, about 1.4:1 to about 2.3:1, about 1.8:1 to about 2.3:1, etc. In some embodiments, the foaming agent is present in the slurry, for example, in an amount of less than about 0.5% by weight based on the weight of the plaster, for example, from about 0.01% to about 0.5%, from about 0.01% to about 0.4%, from about 0.01% to about 0.3%, from about 0.01% to about 0.2%, from about 0.01% to about 0.1%, from about 0.02% up to about 0.4%, from about 0.02% to about 0.3%, from about 0.02% to about 0.2%, and the like, by weight relative to the weight of the plaster.

[0095] Additives such as set accelerator (e.g., wet gypsum set accelerator, heat-resistant set accelerator, stabilized set accelerator for various climatic conditions) and set retarder are well known and can be used according to some embodiments of the invention. See, for example, US Pat. about 0% to about 10% by weight based on the weight of the plaster (e.g., from about 0.1% to about 10%), for example, from about 0% to about 5% by weight, based on the weight of the plaster (for example, from about % to about 5%). Other additives may be included in the present invention, if necessary, for example, to impart strength, which will allow a product with a lower mass and sufficient strength to avoid permanent deformation, ensure the strength of the raw material, for example, when placing the product on a conveyor moving along the production line, flame retardant, waterproof, etc.

[0096] For example, according to some embodiments of the invention, the suspension may optionally contain at least one dispersant to increase fluidity. Like the pregelatinized partially hydrolysed starch prepared according to embodiments of the present invention and other ingredients, dispersants may be included in the core slurry in dry form with other dry ingredients and/or in liquid form with other liquid ingredients. Examples of dispersants include naphthalenesulfonates such as polynaphthalenesulfonic acid and its salts (polynaphthalenesulfonates) and derivatives, which are condensation products of naphthalenesulfonic acids and formaldehyde; as well as polycarboxylate dispersants such as polycarboxylic ethers such as PCE211, PCE111, 1641, 1641F or PCE type 2641 dispersants such as (BASF) MELFLUX 2641F, MELFLUX 2651F, MELFLUX 1641F, MELFLUX 2500L and COATEX Ethacryl M dispersants, which are available at Coatex, Inc.; and/or lignosulfonates or sulfonated lignin. Lignosulfonates are water-soluble anionic polyelectrolyte polymers, by-products of wood pulp production using sulphite pulping. One example of a lignin that can be used in the practice of the principles of the embodiments of the present invention is Marasperse C-21, which is available from Reed Lignin Inc.

[0097] In general, lower molecular weight dispersants are preferred. Lower molecular weight naphthalenesulfonate dispersants are preferred because they generally have lower water consumption than higher molecular weight, higher viscosity dispersants. Thus, molecular weights from about 3,000 to about 10,000 (eg, from about 8,000 to about 10,000) are preferred. As another example, according to some embodiments of the invention, in the case of dispersants of the PCE211 type, the molecular weight can be from about 20,000 to about 60,000, while these dispersants show less retarding than dispersants with a molecular weight above 60,000.

[0098] One example of a naphthalenesulfonate is DILOFLO, which is available from GEO Specialty Chemicals. DILOFLO is a 45% solution of naphthalenesulfonate in water, although other aqueous solutions are also readily available, for example, with a solids content ranging from about 35% to about 55% by weight. The naphthalenesulfonates can be used in dry solid or powder form, such as LOMAR D, which is available from, for example, GEO Specialty Chemicals. Another typical naphthalene sulfonate is DAXAD, available from Hampshire Chemical Corp.

[0099] When used, the dispersant may be included in any suitable (solid phase/solid phase) amount, such as, for example, from about 0.1% to about 5% by weight based on the weight of the plaster, for example, from about 0, 1% to about 4%, about 0.1% to about 3%, about 0.2% to about 3%, about 0.5% to about 3%, about 0.5% to about 2, 5%, about 0.5% to about 2%, about 0.5% to about 1.5%, and the like.

[0100] According to some embodiments of the invention, if necessary, one or more phosphate-containing compounds can also optionally be included in the suspension. For example, phosphate-containing components useful according to some embodiments of the invention include water-soluble components and may be in the form of an ion, salt or acid, namely, condensed phosphoric acids, each of which contains two or more units of phosphoric acid; salts or condensed phosphate ions, each containing two or more phosphate units; and monobasic salts or monovalent orthophosphate ions, as well as a water-soluble acyclic polyphosphate salt. See, for example, US Pat. Nos. 6,342,284; 6632550; 6815049; and 6822033.

[0101]According to some embodiments of the invention, phosphate compositions, when added, can increase the strength of the raw material, resistance to permanent deformation (eg, deflection), dimensional stability, and the like. Trimetaphosphate compounds may be used, including, for example, sodium trimetaphosphate, potassium trimetaphosphate, lithium trimetaphosphate, and ammonium trimetaphosphate. Sodium trimetaphosphate (STMP) is preferred, although other phosphates may be suitable, including, for example, sodium tetrametaphosphate, sodium hexametaphosphate containing from about 6 to about 27 repeating phosphate units and having the molecular formula Na_n+2P_nO_3n+1 where n=6-27, potassium tetrapyrophosphate having the molecular formula K_fourP₂O₇, trisodium dipotassium tripolyphosphate having the molecular formula Na₃K₂P₃O_ten, sodium tripolyphosphate having the molecular formula Na₅P₃O_ten, sodium tetrapyrophosphate having the molecular formula Na_fourP₂O₇, aluminum trimetaphosphate having the molecular formula Al(PO₃)₃, sodium acid pyrophosphate having the molecular formula Na₂H₂P₂O₇, an ammonium polyphosphate containing 1000 to 3000 repeating phosphate units and having the molecular formula (NH_four)_n+2P_nO_3n+1, where n=1000-3000, or polyphosphoric acid containing two or more repeating phosphoric acid units and having the molecular formula H_n+2P_nO_3n+1where n is two or more.

[0102] In some embodiments, the present invention may include phosphate in dry form or in water form (eg, about 5% to about 20% phosphate solution, eg, about 10% solution). When included in the present invention, the phosphate may be in any suitable amount (solid/solid basis), for example, from about 0.01% to about 0.5% by weight, based on the weight of the plaster, for example, from about 0 03% to about 0.4%, about 0.1% to about 0.3%, or about 0.12% to about 0.4% by weight based on the weight of the plaster.

[0103] Suitable additives may also optionally be included in the present invention to provide a flame retardant and/or water resistant product, including, for example, siloxanes (water resistant); fibers; heat sink additives such as aluminum trihydrite (ATH), magnesium hydroxide or the like; and/or high thermal expansion particles (eg, expanding to about 300% or more of their original volume when heated for about one hour at 1560°F ( ^about 850°C)). See, for example, co-pending, same-grant application US Patent Application No. 13/400010 (filed Feb. 17, 2012) for a description of these and other ingredients. In some embodiments, high thermal expansion vermiculite is included in the invention, although other fire resistant materials may be used. A board of any fire related product of the invention may have a Thermal Insulation Index (TI) of about 17 minutes or more, e.g., about 20 minutes or more, about 30 minutes or more, about 45 minutes or more, about 60 minutes or more etc.; and/or have high temperature shrinkage (at temperatures of about 1560°F (850°C)) of less than about 10% in the xy directions and expansion in the z direction of more than about 20%. If necessary, flame retardant or water resistant additives can be included in the present invention in any suitable amount depending on, for example, the degree of fire hazard and the like. For example, when applied, the amount of fire retardant or water resistant additives may be from about 0.5% to about 10% by weight based on the weight of the plaster, for example, from about 1% to about 10%, from about 1% to about 8%, from about 2 % to about 10%, from about 2% to about 8% by weight relative to the weight of the plaster, and the like.

[0104] In some embodiments, when included in the present invention, the siloxane is preferably added in the form of an emulsion. The slurries are then shaped and dried under conditions conducive to polymerization of the siloxane to form a highly cross-linked silicone resin. A catalyst can be added to the gypsum slurry to help polymerize the siloxane and produce a highly cross-linked silicone resin. In some embodiments, the solvent-free poly(methylhydrosiloxane) solution sold under the name SILRES BS 94 by Wacker-Chemie GmbH (Munich, Germany) can be used as the siloxane. This product is a siloxane solution containing no water or solvents. It is contemplated that, in some embodiments, from about 0.3% to about 1.0% BS 94 siloxane, based on the weight of dry ingredients, can be used. For example, according to some variants of the invention, it is preferable to use from about 0.4% to about 0.8% siloxane, based on the weight of dry plaster.

[0105] The composition of the suspension can be obtained at any suitable ratio of water/plaster, for example, from about 0.4 to about 1.3. However, since the pregelatinized partially hydrolysed starches made according to the embodiments of the present invention make it possible to reduce the amount of water that must be added to the suspension for the introduction of these starches, compared with other starches (for example, conventional pregelatinized starch obtained according to another method), the suspension can be prepared at an input water/plaster ratio that is lower, in some embodiments, than that commonly used for other starchy gypsum slurries, especially at low weight/density. For example, in some embodiments, the water/plaster ratio may be from about 0.4 to about 1.1, from about 0.4 to about 0.9, from about 0.4 to about 0.85, from about 0. 45 to about 0.85, about 0.55 to about 0.85, about 0.55 to about 0.8, about 0.6 to about 0.9, about 0.6 to about 0.85 , from about 0.6 to about 0.8, and the like.

[0106] Sheathing sheets can be made from any suitable material and at any basis weight. A board core made from a slurry containing a pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention preferably provides sufficient board strength even with skin sheets with a lower basis weight, such as, for example, less than 45 lb/1000 sq. ft (about 220 g/m ² (for example, from about 33 lb/1000 sq. ft (about 161 g/m ² ) to 45 lb/1000 sq. ft (about 220 g/m ² )) according to some embodiments of the invention even in the case of a board with a lower mass (for example, with a density of about 35 lb/cu. ft (about 561 kg/m ³ ) or less.) However, if necessary, according to some embodiments of the invention, heavier base masses can be used, for example , to further enhance the resistance to pulling nails or to improve the processing, for example, to give the desired "tactile" characteristics suitable for end users.

[0107] According to some embodiments of the invention, to enhance strength (e.g., nail pull strength), especially in the case of a lower density board, one or both skin sheets can be made of paper and have a basis weight of, for example, at least about 45 pounds/1000 sq. ft (about 220 g/m ² ) (for example, from about 45 lb/1000 sq. ft (about 220 g/m ² ) to about 65 lb/1000 sq. ft (about 317 g/m ² ), from about 45 lb/1000 sq. ft (about 220 g/m ² ) to about 60 lb/1000 sq. ft (about 293 g/m ² ), from about 45 lb/1000 sq. ft (about 220 g/m ² ) to about 55 lb/1000 sq. ft (about 269 g/m ² ), from about 50 lb/1000 sq. ft (about 244 g/m ² ) to about 65 lb/1000 sq. ft (about 317 g/m ² ), from about 50 lb/1000 sq. ft (about 244 g/m ² ) to about 60 lb/1000 sq. ft (about 293 g/m ² ), and the like). Optionally, according to some embodiments of the invention, one cover sheet (for example, the "right" side of the paper when installed) may have the higher basis weight mentioned above, for example, to increase resistance to nail pulling and improve processing, while the other cover sheet (for example, "back" sheet when the board is installed) may have a slightly lower basis weight, if necessary (for example, a basis weight of less than about 45 lb/1000 sq. ft (about 220 g/m ² ), for example, from about 33 lb/1000 sq. ft (about 161 g/m ² ) to about 45 lb/1000 sq. ft (about 220 g/m ² ) or from about 33 lb/1000 sq. ft (about 161 g/m ² ) to about 40 lb ( about 18 kg)/1000 sq. ft (about 195 g/m ² )).

[0108] The mass of the slab is a function of the thickness. Since boards are typically manufactured in varying thicknesses, the density of the board is used in the present invention as a measure of the mass of the board. The benefits of the pregelatinized partially hydrolysed starch produced in accordance with embodiments of the present invention can be appreciated with regard to different board densities, for example, about 40 lb/cu. ft (about 641 kg/m ³ ) or less, for example, from about 20 lb/cu. ft (about 320 kg/m ³ ) to about 40 lb/cu. ft (about 641 kg/m ³ ), from about 24 lb/cu. ft (about 384 kg/m ³ ) to about 37 lb/cu. ft (about 593 kg/m ³ ) and the like. However, the preferred embodiments of the present invention have a particular benefit at lower densities, where the increased strength provided by the pregelatinized partially hydrolysed starch produced according to the embodiments of the present invention preferably allows a lower weight board with good strength and lower water consumption than in the case of a board made from other starches obtained according to a different method.

[0109] For example, according to some embodiments of the invention, the density of the plate can be from about 20 lb/cu. ft (about 320 kg/m ³ ) to about 35 lb/cu. ft (about 561 kg/m ³ ), for example, from about 20 lb/cu. ft (about 320 kg/m ³ ) to about 34 lb/cu. ft (about 545 kg/m ³ ), from about 20 lb/cu. ft (about 320 kg/m ³ ) to about 33 lb/cu. ft (about 529 kg/m ³ ), from about 20 lb/cu. ft (about 320 kg/m ³ ) to about 32 lb/cu. ft (about 513 kg/m ³ ), from about 20 lb/cu. ft (about 320 kg/m ³ ) to about 31 lb/cu. ft (about 497 kg/m ³ ), from about 20 lb/cu. ft (about 320 kg/m ³ ) to about 30 lb/cu. ft (about 481 kg/m ³ ), from about 20 lb/cu. ft (about 320 kg/m ³ ) to about 29 lb/cu. ft (about 465 kg/m ³ ), from about 21 lb/cu. ft (about 336 kg/m ³ ) to about 35 lb/cu. ft (about 561 kg/m ³ ), from about 21 lb/cu. ft (about 336 kg/m ³ ) to about 34 lb/cu. ft (about 545 kg/m ³ ), from about 21 lb/cu. ft (about 336 kg/m ³ ) to about 33 lb/cu. ft (about 529 kg/m ³ ), from about 21 lb/cu. ft (about 336 kg/m ³ ) to about 32 lb/cu. ft (about 513 kg/m ³ ), from about 21 lb/cu. ft (about 336 kg/m ³ ) to about 31 lb/cu. ft (about 497 kg/m ³ ), from about 21 lb/cu. ft (about 336 kg/m ³ ) to about 30 lb/cu. ft (about 481 kg/m ³ ), from about 21 lb/cu. ft (about 336 kg/m ³ ) to about 29 lb/cu. ft (about 465 kg/m ³ ), from about 24 lb/cu. ft (about 384 kg/m ³ ) to about 35 lb/cu. ft (about 561 kg/m ³ ), from about 24 lb/cu. ft (about 384 kg/m ³ ) to about 34 lb/cu. ft (about 545 kg/m ³ ), from about 24 lb/cu. ft (about 384 kg/m ³ ) to about 33 lb/cu. ft (about 529 kg/m ³ ), from about 24 lb/cu. ft (about 384 kg/m ³ ) to about 32 lb/cu. ft (about 513 kg/m ³ ), from about 24 lb/cu. ft (about 384 kg/m ³ ) to about 31 lb/cu. ft (about 497 kg/m ³ ), from about 24 lb/cu. ft (about 384 kg/m ³ ) to about 30 lb/cu. ft (about 481 kg/m ³ ) or from about 24 lb/cu. ft (about 384 kg/m ³ ) to about 29 lb/cu. foot (approximately 465 kg/m ³ ).

[0110] Pregelatinized partially hydrolyzed starches made according to embodiments of the present invention can be added to the slurry to provide a strength enhancement to the product of the invention, which may be particularly useful at lower weight/density. For example, in some embodiments, a board made according to embodiments of the present invention has a compressive strength of at least about 400 psi (about 2750 kPa) at a density of 29 lb/cu. ft (about 465 kg/m ³ ), as determined according to the method described in example 4. Preferably, according to various embodiments of the invention at various board densities given herein, a board made according to the proposed invention method can be obtained, strength which is at least about 400 psi (about 2760 kPa), for example, at least about 450 psi (about 3100 kPa), at least about 500 psi (about 3450 kPa), at least about 550 psi (about 3800 kPa), at least about 600 psi (about 4100 kPa), at least about 650 psi (about 4500 kPa), at least about 700 psi (about 4800 kPa), at least about 750 psi (about 5200 kPa ), at least about 800 psi (about 5500 kPa), at least about 850 psi (about 5850 kPa), at least about 900 psi (about 6200 kPa), at least about 950 psi (6550 kPa), or at least about 1000 psi (about 6900 kPa). In addition, according to some embodiments of the invention, the compressive strength may be limited to any two of the values listed above. For example, the compressive strength may be from about 450 psi (about 3100 kPa) to about 1000 psi (for example, from about 500 psi (about 3450 kPa) to about 900 psi (about 6200 kPa), from about 600 psi (about 4100 kPa ) up to about 800 psi (about 5500 kPa), etc.).

[0111] In some embodiments, a plate made according to the invention complies with the test protocols set forth in ASTM C473-10. For example, in some embodiments of the invention, when casting a ½ inch (1.27 cm) thick board, said board has a nail pull resistance of at least about 65 pounds (about 30 kg) as determined according to ASTM C473-10, e.g. at least about 68 pounds (about 30 kg), at least about 70 pounds (about 32 kg), at least about 72 pounds (about 33 kg), at least about 75 pounds (about 34 kg), at least about 77 pounds (about 35 kg), etc. According to various embodiments of the invention, the resistance to pulling out nails can be from about 68 pounds (about 30 kg) to about 100 pounds (about 45 kg), for example, from about 68 pounds (about 30 kg) to about 95 pounds (about 43 kg), about 68 pounds (about 30 kg) to about 90 pounds (about 41 kg), from about 68 pounds (about 30 kg) to about 85 pounds (about 39 kg), from about 68 pounds (about 30 kg) to about 80 lb (about 36 kg), from about 68 lb (about 30 kg) to about 77 lb (about 35 kg), from about 68 lb (about 30 kg) to 75 lb (about 34 kg), from about 68 lb (about 30 kg) to about 72 pounds (about 33 kg), from about 68 pounds (about 30 kg) to about 70 pounds (about 32 kg), from about 70 pounds (about 32 kg) to about 100 pounds (about 45 kg) , from about 70 pounds (about 32 kg) to about 95 pounds (about 43 kg), from about 70 pounds (n about 32 kg) to about 90 pounds (about 41 kg), from about 70 pounds (about 32 kg) to about 85 pounds (about 39 kg), from about 70 pounds (about 32 kg) to about 80 pounds (about 36 kg ), from about 70 pounds (about 32 kg) to about 77 pounds (about 35 kg), from about 70 pounds (about 32 kg) to 75 pounds (about 34 kg), from about 70 pounds (about 32 kg) to about 72 pounds (about 33 kg), about 72 pounds (about 33 kg) to about 100 pounds (about 45 kg), about 72 pounds (about 33 kg) to about 95 pounds (about 43 kg), from about 72 pounds (about 33 kg) to about 90 pounds (about 41 kg), from about 72 pounds (about 33 kg) to about 85 pounds (about 39 kg), from about 72 pounds (about 33 kg) to about 80 pounds (about 36 kg), from about 72 pounds (about 33 kg) to about 77 pounds (about 35 kg), from about 72 pounds (about 33 kg) to 75 pounds (about 34 kg), from 75 pounds ( 34 kg) to about 100 pounds (about 45 kg), 75 pounds (about 34 kg) to about 95 pounds (about 43 kg), 75 pounds (about 34 kg) to about 90 pounds (about 41 kg), 75 pounds (about 34 kg) to about 85 pounds (about 39 kg), 75 pounds (about 34 kg) to about 80 pounds (about 36 kg), 75 pounds (about 34 kg) to about 77 pounds (about 35 kg), from about 77 pounds (about 35 kg) to about 100 pounds (about 45 kg), from about 77 pounds (about 35 kg) to about 95 pounds (about 43 kg), from about 77 pounds (about 35 kg) ) to about 90 pounds (about 41 kg), from about 77 pounds (about 35 kg) to about 85 pounds (about 39 kg), or from about 77 pounds (about 35 kg) to about 80 pounds (about 36 kg).

[0112] With regard to flexural strength, according to some embodiments of the invention, when casting a ½ inch (1.27 cm) thick plate, the flexural strength of said plate leaves at least about 36 pounds (about 16 kg) in the machine direction (for example , at least about 38 pounds (about 17 kg), at least about 40 pounds (about 18 kg), etc.) and/or at least about 107 pounds (about 49 kg) (for example, at least about 110 pounds (about 50 kg), at least about 112 pounds (about 51 kg), etc.) in the transverse direction, as defined according to ASTM C473. According to various embodiments of the invention, the board may have a bending strength in the machine direction from about 36 pounds (about 16 kg) to about 60 pounds (about 27 kg), for example, from about 36 pounds (about 16 kg) to about 55 pounds ( about 25 kg), from about 36 pounds (about 16 kg) to about 50 pounds (about 23 kg), from about 36 pounds (about 16 kg) to about 45 pounds (about 20 kg), from about 36 pounds (about 16 kg) to about 40 pounds (about 18 kg), from about 36 pounds (about 16 kg) to about 38 pounds (about 17 kg), from about 38 pounds (about 17 kg) to about 60 pounds (about 27 kg), about 38 pounds (about 17 kg) to about 55 pounds (about 25 kg), from about 38 pounds (about 17 kg) to about 50 pounds (about 23 kg), from about 38 pounds (about 17 kg) to about 45 lb (about 20 kg), from about 38 lb (about 17 kg) to about 40 lb (about 18 kg), about t about 40 pounds (about 18 kg) to about 60 pounds (about 27 kg), from about 40 pounds (about 18 kg) to about 55 pounds (about 25 kg), from about 40 pounds (about 18 kg) to about 50 pounds (about 23 kg) or from about 40 pounds (about 18 kg) to about 45 pounds (about 20 kg). According to various embodiments of the invention, the flexural strength in the transverse direction of the plate can be from about 107 pounds (about 49 kg) to about 130 pounds (about 59 kg), for example, from about 107 pounds (about 49 kg) to about 125 pounds ( about 57 kg), from about 107 pounds (about 49 kg) to about 120 pounds (about 54 kg), from about 107 pounds (about 49 kg) to about 115 pounds (about 52 kg), from about 107 pounds (about 49 kg) to about 112 pounds (about 51 kg), from about 107 pounds (about 49 kg) to about 110 pounds (about 50 kg), from about 110 pounds (about 50 kg) to about 130 pounds (about 59 kg), about 110 pounds (about 50 kg) to about 125 pounds (about 57 kg), from about 110 pounds (about 50 kg) to about 120 pounds (about 54 kg), from about 110 pounds (about 50 kg) to about 115 pounds (about 52 kg), from about 110 pounds (about 50 kg) to about 11 2 pounds (about 51 kg), from about 112 pounds (about 51 kg) to about 130 pounds (about 59 kg), from about 112 pounds (about 51 kg) to about 125 pounds (about 57 kg), from about 112 pounds (about 51 kg) to about 120 pounds (about 54 kg) or from about 112 pounds (about 51 kg) to about 115 pounds (about 52 kg).

[0113] In addition, according to some embodiments of the invention, the average hardness of the core of the plate can be at least about 11 pounds (about 5 kg), for example, at least about 12 pounds (about 5.4 kg), at least about 13 lb (about 5.9 kg), at least about 14 lb (about 6.4 kg), at least about 15 lb (about 6.8 kg), at least about 16 lb (about 7.3 kg) , at least about 17 pounds (about 7.7 kg), at least about 18 pounds (about 8.2 kg), at least about 19 pounds (about 8.6 kg), at least about 20 pounds ( about 9.1 kg), at least about 21 pounds (about 9.5 kg), or at least about 22 pounds (about 10.0 kg), as determined according to ASTM C473-10. According to some embodiments of the invention, the hardness of the board core can be from about 11 pounds (about 5 kg) to about 25 pounds (about 11.3 kg), for example, from about 11 pounds (about 5 kg) to about 22 pounds (about 10. 0 kg), from about 11 lb (about 5 kg) to about 21 lb (about 9.5 kg), from about 11 lb (about 5 kg) to about 20 lb (about 9.1 kg), from about 11 lb (about 5 kg) to about 19 pounds (about 8.6 kg), from about 11 pounds (about 5 kg) to about 18 pounds (about 8.2 kg), from about 11 pounds (about 5 kg) to about 17 lb (about 7.7 kg), from about 11 lb (about 5 kg) to about 16 lb (about 7.3 kg), from about 11 lb (about 5 kg) to about 15 lb (about 6.8 kg) , from about 11 pounds (about 5 kg) to about 14 pounds (about 6.4 kg), from about 11 pounds (about 5 kg) to about 13 pounds (about 5.9 kg), from about 11 pounds (n about 5 kg) to about 12 pounds (about 5.4 kg), from about 12 pounds (about 5.4 kg) to about 25 pounds (about 11.3 kg), from about 12 pounds (about 5.4 kg) up to about 22 pounds (about 10.0 kg), from about 12 pounds (about 5.4 kg) to about 21 pounds (about 9.5 kg), from about 12 pounds (about 5.4 kg) to about 20 pounds (about 9.1 kg), from about 12 pounds (about 5.4 kg) to about 19 pounds (about 8.6 kg), from about 12 pounds (about 5.4 kg) to about 18 pounds (about 8, 2 kg), from about 12 pounds (about 5.4 kg) to about 17 pounds (about 7.7 kg), from about 12 pounds (about 5.4 kg) to about 16 pounds (about 7.3 kg), from about 12 pounds (about 5.4 kg) to about 15 pounds (about 6.8 kg), from about 12 pounds (about 5.4 kg) to about 14 pounds (about 6.4 kg), from about 12 pounds (about 5.4 kg) to about 13 pounds (about 5.9 kg), from about 13 pounds (about 5.9 kg) to about 2 5 pounds (about 11.3 kg), from about 13 pounds (about 5.9 kg) to about 22 pounds (about 10.0 kg), from about 13 pounds (about 5.9 kg) to about 21 pounds (about 9.5 kg), from about 13 pounds (about 5.9 kg) to about 20 pounds (about 9.1 kg), from about 13 pounds (about 5.9 kg) to about 19 pounds (about 8.6 kg) ), from about 13 pounds (about 5.9 kg) to about 18 pounds (about 8.2 kg), from about 13 pounds (about 5.9 kg) to about 17 pounds (about 7.7 kg), from about 13 pounds (about 5.9 kg) to about 16 pounds (about 7.3 kg), from about 13 pounds (about 5.9 kg) to about 15 pounds (about 6.8 kg), from about 13 pounds (about 5.9 kg) to about 14 pounds (about 6.4 kg), from about 14 pounds (about 6.4 kg) to about 25 pounds (about 11.3 kg), from about 14 pounds (about 6.4 kg ) to about 22 pounds (about 10.0 kg), from about 14 pounds (about 6.4 kg) to about 21 pounds (about 9.5 kg) , from about 14 pounds (about 6.4 kg) to about 20 pounds (about 9.1 kg), from about 14 pounds (about 6.4 kg) to about 19 pounds (about 8.6 kg), from about 14 lb (about 6.4 kg) to about 18 lb (about 8.2 kg), from about 14 lb (about 6.4 kg) to about 17 lb (about 7.7 kg), from about 14 lb (about 6 .4 kg) to about 16 pounds (about 7.3 kg), from about 14 pounds (about 6.4 kg) to about 15 pounds (about 6.8 kg), from about 15 pounds (about 6.8 kg) up to about 25 pounds (about 11.3 kg), from about 15 pounds (about 6.8 kg) to about 22 pounds (about 10.0 kg), from about 15 pounds (about 6.8 kg) to about 21 pounds (about 9.5 kg), from about 15 pounds (about 6.8 kg) to about 20 pounds (about 9.1 kg), from about 15 pounds (about 6.8 kg) to about 19 pounds (about 8, 6 kg), from about 15 pounds (about 6.8 kg) to about 18 pounds (about 8.2 kg), from about 15 pounds (approx. about 6.8 kg) to about 17 pounds (about 7.7 kg), from about 15 pounds (about 6.8 kg) to about 16 pounds (about 7.3 kg), from about 16 pounds (about 7.3 kg) to about 25 pounds (about 11.3 kg), from about 16 pounds (about 7.3 kg) to about 22 pounds (about 10.0 kg), from about 16 pounds (about 7.3 kg) to about 21 pounds (about 9.5 kg), from about 16 pounds (about 7.3 kg) to about 20 pounds (about 9.1 kg), from about 16 pounds (about 7.3 kg) to about 19 pounds (about 8.6 kg), about 16 lb (about 7.3 kg) to about 18 lb (about 8.2 kg), about 16 lb (about 7.3 kg) to about 17 lb (about 7.7 kg) ), from about 17 pounds (about 7.7 kg) to about 25 pounds (about 11.3 kg), from about 17 pounds (about 7.7 kg) to about 22 pounds (about 10.0 kg), from about 17 pounds (about 7.7 kg) to about 21 pounds (about 9.5 kg), from about 17 pounds (about 7.7 kg) to about 20 pounds (about 9.1 kg), from about 17 pounds (about 7.7 kg) to about 19 pounds (about 8.6 kg), from about 17 pounds (about 7.7 kg) to about 18 pounds (about 8.2 kg), from about 18 lb (about 8.2 kg) to about 25 lb (about 11.3 kg), from about 18 lb (about 8.2 kg) to about 22 lb (about 10.0 kg) ), from about 18 pounds (about 8.2 kg) to about 21 pounds (about 9.5 kg), from about 18 pounds (about 8.2 kg) to about 20 pounds (about 9.1 kg), from about 18 pounds (about 8.2 kg) to about 19 pounds (about 8.6 kg), from about 19 pounds (about 8.6 kg) to about 25 pounds (about 11.3 kg), from about 19 pounds (about 8.6 kg) to about 22 pounds (about 10.0 kg), from about 19 pounds (about 8.6 kg) to about 21 pounds (about 9.5 kg), from about 19 pounds (about 8.6 kg ) to about 20 pounds (about 9.1 kg), from about 21 pounds (about 9.5 kg) to about 25 pounds (about 11.3 kg d), from about 21 pounds (about 9.5 kg) to about 22 pounds (about 10.0 kg) or from about 22 pounds (about 10.0 kg) to about 25 pounds (about 11.3 kg).

[0114] Due at least in part to the viscosity characteristic in the middle range, which allows some embodiments of the present invention, these standards (for example, nail pull resistance, flexural strength and core hardness) can be met even with an ultra small board. density (eg, about 31 lb/cu. ft. (about 497 kg/m ³ ) or less) as described herein.

[0115] The inventors have also found that pregelatinized partially hydrolysed starches made according to embodiments of the present invention exhibit hydration rates at a given temperature rise (TRS) comparable to or superior to those of conventional pregelatinized starches made according to another process. The required setting time may depend on the formulation, and the required setting time may be determined by one of ordinary skill in the art depending on the manufacturing conditions and available raw materials.

[0116] The product according to embodiments of the present invention can be obtained on conventional production lines. For example, board manufacturing techniques are described in, for example, US Pat. No. 7,364,676 and US Patent Application Publication 2010/0247937. In short, in the case of gypsum board, the method employed typically involves unloading the sheathing sheet onto a moving conveyor. Since gypsum board is usually produced "face down", said skin sheet is the "face" skin sheet according to such embodiments of the invention.

[0117] The dry and/or wet components of the gypsum slurry are loaded into a mixer (eg, a pin mixer) where they are mixed to form a gypsum slurry. The mixer comprises a main unit and an injection pipeline (for example, an inlet-container-funnel device known in the art, or a device described in US Pat. Nos. 6,494,609 and 6,874,930). In some embodiments, the injection conduit may include a slurry distributor with either a single feed opening or multiple feed openings, such as the distributors described in U.S. Patent Application Publication 2012/0168527 A1 (Application No. 13/341016) and Application Publication No. for US patent 2012/0170403 A1 (application No. 13/341209), for example. In these embodiments, when using a multi-port slurry distributor, the discharge line may include a suitable flow splitter, such as the splitters described in US Patent Application Publication 2012/0170403 A1. If necessary, a blowing agent can be added to the mixer discharge line (eg, inlet, as described, for example, in US Pat. Nos. 5,683,635 and 6,494,609) or in the main unit. The slurry discharged from the discharge line after adding all the ingredients, including the blowing agent, is the primary gypsum slurry that will form the core of the board. Such a slurry for forming a board core is discharged onto a moving face skin sheet.

[0118] The face skin sheet may have a thin coating layer in the form of a relatively dense slurry layer. In addition, hard edges, as is known in the art, can be formed, for example, from the same slurry stream from which the top coat is obtained. In embodiments of the invention, when foam is introduced into the injection line, the secondary gypsum slurry stream can be removed from the mixer block to produce a dense slurry to form a skim coat, which can then be used to produce a face skim coat and hard edges, as is known in the art. In use, the top coat and hard edges are typically placed on the moving top cover sheet prior to application of the core slurry, typically prior to the mixer. After being discharged from the injection line, the core-forming slurry is spread, if necessary, over a face skin sheet (optionally having a top layer) and covered with a second skin sheet (usually a "back" skin sheet) to form a wet assembly in the form of a sandwich structure, which is plate blank to obtain the final product. The second skin sheet may optionally have a second cover layer, which may be formed from the same or different recycled (dense) gypsum slurry as the face cover layer, if present. The skin sheets can be made from paper, fibrous mat, or other type of material (eg, foil, plastic, glass mat, non-woven material such as a mixture of cellulose and inorganic filler, etc.).

[0119] The thus obtained wet assembly is transferred to a shaping section where the product is brought to the desired thickness (eg using a forming plate) and to one or more knife sections where it is cut to the desired length. The wet precast is allowed to set to form an intertwining crystalline matrix of set gypsum, with excess water removed through a drying process (eg, by moving the precast through a kiln). Surprisingly and unexpectedly, it has been found that the board produced according to the invention using the pregelatinized partially hydrolysed starch obtained according to the embodiments of the present invention requires significantly less time in the drying process due to the low starch water consumption. This is an advantage as it reduces energy costs.

[0120] In addition, in the manufacture of gypsum board, vibration is often used to remove large pores or air pockets from the deposited slurry. All of the steps described above are known in the art, as well as processes and equipment for carrying out said steps.

[0121] The pregelatinized partially hydrolyzed starch produced according to embodiments of the present invention can be used in the preparation of various products such as, for example, gypsum wallboard, acoustic (e.g., ceiling) tiles, joint sealant, gypsum and cellulose fiber products, such as as gypsum and wood fiber wallboard, etc. According to some embodiments of the invention, the specified product can be made from a suspension according to embodiments of the present invention.

[0122] As such, the pregelatinized partially hydrolysed starch produced in the extruder according to the embodiments of the present invention can have a beneficial effect as described herein in a non-papered gypsum board product according to the embodiments of the present invention. For example, the pregelatinized partially hydrolyzed starch produced according to embodiments of the present invention can be used in mat-covered products (eg, fabrics) in which board skin sheets are in the form of fibrous mats. Such mats may optionally have a top layer to reduce water permeability. Other ingredients that can be used to make such a mat-covered product, as well as fibrous mat materials and manufacturing methods, are discussed in, for example, US Pat.

[0123] In addition, the product made from gypsum and cellulose may be in the form of cellulose particles (e.g., wood fibers), gypsum, pregelatinized partially hydrolyzed starch obtained according to embodiments of the present invention, and other ingredients (e.g., water-resistant additives, such as siloxanes), if necessary. Other ingredients and methods of manufacture are discussed in, for example, US Pat. Nos. 4,328,178; 4239716; 4392896; 4645548; 5320677; 5817262; and 7413603.

Illustrative examples of embodiments of the invention

[0124] According to one embodiment of the invention, the proposed method of obtaining pregelatinized partially hydrolyzed starch includes: (a) mixing at least water, non-pregelatinized starch and a weak acid that does not substantially form chelates with calcium ions, to obtain a wet starch-containing substance - precursor with a moisture content of about 8% of the mass. up to about 25% wt.; (b) feeding said wet starch precursor into an extruder; and (c) pregelatinizing and acid modifying the wet starch precursor in an extruder at a die temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF).

[0125] According to another embodiment of the invention, the pressure inside the extruder is at least about 2000 psi (about 13800 kPa).

[0126] In another embodiment, the cold water solubility of the pregelatinized partially hydrolyzed starch is greater than about 50%.

[0127] In another embodiment, the cold water (10% solids, 25°C) viscosity of the pregelatinized partially hydrolysed starch is from about 10 Brabender units (BU) to about 120 BU.

[0128] According to another embodiment of the invention, the viscosity characteristic of the pregelatinized partially hydrolyzed starch is from about 20 centipoise to about 700 centipoise when measuring the viscosity when exposed to starch conditions according to the VMA method.

[0129] According to another embodiment of the invention, the viscosity (10% solids, 93 ºC) of the pregelatinized partially hydrolyzed starch is from about 5 BU to about 33 BU.

[0130] According to another embodiment of the invention, a weak acid that does not substantially form chelates with calcium ions contains alum.

[0131] According to another embodiment of the invention, tartaric acid is added to the mixture to form a wet starch precursor.

[0132] According to other embodiments of the invention, the amount of a weak acid, which essentially does not form chelates with calcium ions, is from about 0.5% of the mass. up to about 5% of the mass. by weight relative to the weight of starch.

[0133] According to another embodiment of the invention, the moisture content of wet starch is from about 10% of the mass. up to about 20% of the mass. by weight relative to the weight of the starch-containing precursor substance.

[0134] According to another embodiment of the invention, pregelatinization and acid modification occurs in the extruder at a die temperature of at least about 175 ºC (about 350 ºF) to about 205 ºC (about 400 ºF).

[0135] According to another embodiment of the invention, the output of pregelatinized partially hydrolyzed starch is at least about 100 kg/hour in the extruder.

[0136] In another embodiment, pregelatinization and acid modification occur in less than about 5 minutes.

[0137] According to another embodiment of the invention, pregelatinization and acid modification occur within less than about 1 minute.

[0138] According to another embodiment of the invention, the proposed method does not include the stage of purification of pregelatinized partially hydrolyzed starch.

[0139] According to another embodiment of the invention, the proposed method does not include the step of neutralizing the pregelatinized partially hydrolyzed starch.

[0140] According to another embodiment of the invention, the degree of gelatinization of the pregelatinized partially hydrolyzed starch is at least about 70%.

[0141] According to another embodiment of the invention, pregelatinized partially hydrolyzed starch is obtained according to embodiments of the present invention.

[0142] According to another embodiment of the invention, the proposed method for obtaining pregelatinized partially hydrolyzed starch includes: (a) mixing at least water, non-pregelatinized starch and a strong acid to obtain a wet starch-containing precursor substance with a moisture content of from about 8% of the mass. up to about 25% wt., while the strong acid is present in an amount of about 0.05% wt. or less by weight relative to the weight of starch; (b) feeding said wet starch precursor into an extruder; and (c) pregelatinization and acid modification of the wet starch in an extruder at a die temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF).

[0143] According to another embodiment of the invention, the proposed method for obtaining pregelatinized partially hydrolyzed starch includes: (a) mixing at least water, non-pregelatinized starch and a strong acid to obtain a wet starch-containing precursor substance with a moisture content of from about 8% of the mass. up to about 25% wt., while the strong acid is present in an amount of about 0.01% wt. or less by weight relative to the weight of starch; (b) feeding said wet starch precursor into an extruder; and (c) pregelatinization and acid modification of the wet starch in an extruder at a die temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF).

[0144] According to another embodiment of the invention, the pKa of a strong acid is about -1.7 or less.

[0145] In another embodiment, the strong acid is sulfuric acid, nitric acid, hydrochloric acid, or any combination thereof.

[0146] According to another embodiment of the invention, the proposed method of manufacturing board includes: (a) obtaining pregelatinized partially hydrolyzed starch by (i) mixing at least water, non-pregelatinized starch and acid to obtain a wet starch-containing precursor substance with a moisture content of about 8% of the mass . up to about 25% wt., while the acid is selected from the group consisting of: (1) a weak acid that essentially does not form chelates with calcium ions, (2) a strong acid in an amount of about 0.05% of the mass. or less by weight relative to the weight of starch or (3) any combination thereof; (ii) supplying the wet starch precursor to the extruder; and (iii) pregelatinization and acid modification of the wet starch in a die extruder at a temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF); (b) mixing the gelled and partially hydrolyzed starch with at least water and stucco to form a slurry; (c) placing the slurry between the first cover sheet and the second cover sheet to form a wet assembly; (d) cutting the wet assembly to form a slab; and (e) drying the board.

[0147] According to another embodiment of the invention, a strong acid is present in an amount of about 0.01% of the mass. or less by weight relative to the weight of starch.

[0148] According to another embodiment of the invention, the proposed method for making board includes (a) obtaining pregelatinized partially hydrolyzed starch by (i) mixing at least water, non-pregelatinized starch and a weak acid that does not substantially chelate with calcium ions, to obtain a wet starch-containing substance precursor with a moisture content of about 8% of the mass. up to about 25% wt.; (ii) feeding wet starch to an extruder; and (iii) pregelatinization and acid modification of the wet starch in a die extruder at a temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF); (b) mixing the pregelatinized and partially hydrolysed starch with at least water and stucco to form a slurry; (c) placing the slurry between the first cover sheet and the second cover sheet to form a wet assembly; (d) cutting the wet assembly to form a slab; and (e) drying the board.

[0149] According to another embodiment of the invention, the proposed method for manufacturing a plate includes: (a) mixing at least water, non-pregelatinized starch and a strong acid to obtain a wet starch-containing precursor substance with a moisture content of from about 8% of the mass. up to about 25% wt., while a strong acid is present in an amount of about 0.05% wt. or less by weight relative to the weight of starch; (ii) feeding said wet starch precursor into an extruder; and (iii) pregelatinization and acid modification of the wet starch in a die extruder at a temperature of from about 150 ºC (about 300 ºF) to about 210 ºC (about 410 ºF); (b) mixing the pregelatinized and partially hydrolysed starch with at least water and stucco to form a slurry; (c) placing the slurry between the first cover sheet and the second cover sheet to form a wet assembly; (d) cutting the wet assembly to form a slab; and (e) drying the board.

[0150] According to another embodiment of the invention, the strong acid is present in an amount of about 0.01% of the mass. or less by weight relative to the weight of starch.

[0151] According to another embodiment of the invention, the set gypsum core has a compressive strength greater than a set gypsum core made using starch obtained according to another method.

[0152] According to another embodiment of the invention, when added to the suspension, the degree of gelatinization of the pregelatinized partially hydrolyzed starch is at least about 70%, with additional gelatinization occurring during the drying stage.

[0153] According to another embodiment of the invention, the pregelatinized partially hydrolysed starch is fully gelatinized when added to the suspension.

[0154] According to another embodiment of the invention, the compressive strength of the board is at least about 400 psi (about 2760 kPa) (2800 kPa) at a density of 29 lb/cu. foot (approximately 465 kg/m ³ ).

[0155] In another embodiment, the board core hardness is at least about 11, as determined according to ASTM C473-10.

[0156] According to another embodiment of the invention, the density of the plate is from about 21 lb/cu. ft (about 336 kg/m ³ ) to about 35 lb/cu. ft (about 561 kg/m ³ ).

[0157] According to another embodiment of the invention, the suspension further comprises sodium trimetaphosphate.

[0158] According to another embodiment of the invention, the amount of water that must be added to maintain the fluidity of the suspension at the same level that would be without the use of pregelatinized partially hydrolyzed starch is less than the increase in the amount of water required when using pregelatinized partially hydrolyzed starch obtained according to another way.

[0159] According to another embodiment of the invention, the amount of starch is from about 0.5% to about 10% by weight, based on the weight of the plaster.

[0160] According to another embodiment of the invention, a wallboard is produced according to embodiments of the present invention.

[0161] It should be noted that the previous description is merely examples of embodiments of the invention. Due to the completeness of the description given in this document, other typical embodiments of the invention are obvious. One of ordinary skill in the art will also appreciate that each of these embodiments may be used in various combinations with the other embodiments presented herein.

[0162] The following examples further illustrate the invention, but, of course, should not be construed as limiting its scope in any way.

EXAMPLE 1

[0163] This example illustrates the preparation of pregelatinized partially hydrolysed starches according to embodiments of the present invention.

[0164] Nine pregelatinized partially hydrolyzed starches prepared according to embodiments of the present invention were prepared for various tests for certain properties (eg, viscosity, flow, strength). These nine inventive starches were tested along with three commercially available starches.

[0165] According to the inventive process for preparing pregelatinized partially hydrolyzed starch, wet starch precursors were obtained by mixing germless cornmeal, which is available as CCM 260 yellow cornmeal from Bunge North America (St. Louis, MO), in an amount of 100 kg, varying amounts of aluminum sulfate (alum), a weak acid that essentially does not form chelates with calcium ions, and/or tartaric acid (less than 20% by weight of the total weak acids) and varying amounts of water. The wet starch precursors were loaded into a single screw extruder, which is available as an Advantage 50 from American International (South Beloit, IL). In the extruder, the wet starch precursors were subjected to pregelatinization and acid modification in one step so that these processes occurred simultaneously.

[0166] Table 4 below shows the extrusion parameters of cornmeal in the presence of acid. The extrusion time (ie, pregelatinization and acid modification time) was less than 30 seconds. All percentages are calculated based on the total weight of starch, except for moisture, which is calculated based on the total wet weight, expressed as the sum of the weight of water, starch and other additives.

[0167] The resulting pregelatinized partially hydrolyzed starches were compared to a conventional 773 centipoise pregelatinized corn starch, designated composition 1A (comparative), as well as two low water consumption starches obtained by extrusion of acid-modified corn starches, which can be purchase as Clinton 277 (ADM, Chicago, Illinois) and Caliber 159 (Cargill, Wiseta, MN), designated composition 1B (comparative) and composition 1C (comparative), respectively.

Table 4

Substance Corn flour canola oil 0.25% wt. liquid alum 1% wt. - 4% of the mass. Wine acid 0% wt. - 0.3% of the mass. Moisture in starch during extrusion 10% wt. - 20% of the mass. Main auger (rpm) 350 Loading auger speed (rpm) fourteen Head temperature (ºF) 350-370
(approximately 177-188 ^about C) Knife speed (r/min) 400-1000

[0168] During the extrusion process, pregelatinized partially hydrolyzed starches were obtained, designated as compositions 1D-1L.

[0169] Table 5 below provides details of various extrusion moisture content and extrusion acid content for compositions 1D-1L. Compositions 1D-1H and 1L were obtained at a moisture content of 16 wt. -%, while compositions 1I-1K were obtained at a moisture content of 13% of the mass. Compositions 1D-1G and compositions 1I-1L were obtained using liquid alum in an amount ranging from 1% wt. up to 4% wt., while composition 1H contained liquid alum and tartaric acid. Compositions 1F and 1L were prepared using the same moisture content and amount of acid, but in example 3, these compositions contained different amounts of retarder.

Table 5

Composition Moisture Acid Composition 1A 16% wt. No data Composition 1B 19% wt. No data Composition 1C 19% wt. No data Composition 1D 16% wt. 1% wt. alum Composition 1E 16% wt. 2% wt. alum Composition 1F 16% wt. 3% wt. alum Composition 1G 16% wt. 4% wt. alum Composition 1H 16% wt. 2% wt. alum;
0.3% wt. tartaric acid Composition 1I 13% wt. 1% wt. alum Composition 1J 13% wt. 2% wt. Composition 1K 13% wt. 3% wt. alum Composition 1L 16% wt. 3% wt. alum

[0170] In examples 2-4 below, the compositions shown in Table 5 were tested for various properties. In Example 2, compositions 1B-1L were evaluated for viscosity in amylographic tests. In Example 3, the slurries prepared using one of the formulations 1A, 1D-1I and 1K-1L were tested for flowability, which was evaluated by a slump flow test. The data obtained were then further confirmed by measuring the time to reach 50% hydration of the suspensions. Such measurements showed how long it took for the suspensions to set. In Example 4, the slurries prepared using Compositions 1A, 1D-1I and 1K were tested for strength, which was evaluated by the compression test described herein.

EXAMPLE 2

[0171] This example illustrates the viscosity of pregelatinized partially hydrolysed starches produced in an extruder according to embodiments of the present invention. Compositions 1D-1K were compared with extruded commercially available acid-modified starches (compositions 1B-1C), in particular in relation to the change in viscosity depending on the amount of acid (for example, alum) and moisture content, determined by the level of moisture in wet starch, loaded through the extruder.

[0172] In preparation for the test, the test compositions were mixed together with water into the starch suspension so that the starch suspensions contained these compositions in an amount of 10 wt%. It should be noted that the term "solution" is used when the starch is completely gelatinized and completely dissolved, and the term "suspension" is used when the starch is not completely dissolved. Each composition was then tested for viscosity at various temperatures using the amylographic method described herein. The test results are graphically depicted in FIG. 1 and 2, which are amylograms to evaluate the viscosity of pregelatinized partially hydrolysed starches at different temperatures by plotting viscosity (left y-axis) and temperature (right y-axis) versus time (x-axis). The temperature curve passes over the curve of each sample. The same temperature profile was used for each sample. Other curves show the viscosity of starches.

[0173] the Initial viscosity at 25ºC was an indicator of the fluidity of the suspension system containing any of the compositions 1B-1K. 25ºC is the temperature at which the starch will mix with the stucco and other ingredients to make the board. In addition, at this temperature, the viscosity of starch correlates negatively with the fluidity of the plaster slurry.

[0174] Viscosity at the minimum (93ºC) was an indication of the molecular weight of any of the compositions 1B-1K. At a temperature of 93ºC, starch molecules completely dissolve in water. The viscosity of starch solutions at 93ºC correlates positively with starch molecular weight, which is the result of partial hydrolysis.

[0175] FIG. 1 is an amylogram obtained by plotting viscosity (left y-axis) and temperature (right y-axis) against a fifty minute time period (x-axis). Comparative compositions 1B and 1C and inventive compositions 1D-1H described herein were mixed into starch solutions in an amount of 10% by weight based on the weight of the solution. To avoid clumping, the starch was added to the water in the mixing cup of the Waring mixer while mixing at low speed for 20 seconds. The starch solutions were then evaluated using Viscograf-E (CW Brabender® (Brabender) Instruments, Inc., South Hackensack, NJ). According to the Brabender viscosity measurement procedure described herein, viscosity is measured using a CW Brabender viscograph, such as Viscograph-E, which uses reactive torque for dynamic measurements. It should be noted that, as defined herein, Brabender units are measured using a 16 fl oz (about 500 cm ³ ) sample cup with a 700 cmg cartridge at 75 rpm. One of ordinary skill in the art will also readily appreciate that Brabender units can be converted to other viscosity units such as centipoise (e.g. cps = BU × 2.1 when using a 700 cmg measuring cartridge) or Krebs units as described herein. . Bonding profiles of compositions 1D-1H extruded at 16% wt. moisture content are shown in Fig. 1 together with comparative compositions 1B and 1C.

[0176] Considering the compositions 1D-1H proposed in the invention, it can be seen that with an increase in the content of alum from 1% of the mass. up to 4% wt. the initial viscosity decreased from 70 Brabender units (BU) to 10 BU, while the molecular weight also decreased. The initial and 93°C viscosities of compositions 1D-1H decreased to the viscosities of compositions 1B and 1C. Compositions 1B and 1C exhibited the usual limiting viscosities of low water consumption starches.

[0177] The results of the study of compositions 1D-1H shown in FIG. 1 demonstrate that optimum acid modification can be achieved during the extrusion process. The results also show that the inventive process for producing pregelatinized partially hydrolyzed starch has successfully reduced the viscosity (molecular weight) of the starch. No maximum viscosity was observed between 70°C and 90°C, indicating that the compositions 1D-1H were fully gelatinized. If compositions 1D-1H were not fully gelled, there would be an increase in viscosity. Complete gelatinization of the starch compositions was confirmed by differential scanning calorimetry (DSC).

[0178] FIG. 2 is a second amylogram obtained by plotting viscosity (left y-axis) and temperature (right y-axis) against a fifty minute time period (x-axis). Comparative Compositions 1B and 1C and Inventive Compositions 1I-1K described herein were all mixed into starch solutions in an amount of 10% by weight based on the weight of the solution. To avoid clumping, the starch was added to the water in the mixing cup of the Waring mixer while mixing at low speed for 20 seconds. The starch solutions were then evaluated using viscograph E. Bonding profiles of formulations 1I-1K extruded at 13% wt. moisture content shown in Fig. 2 along with comparative compositions 1B and 1C.

[0179] Similar trends observed in the case of compositions 1D-1H were observed with compositions 1I-1K. In particular, the process for preparing pregelatinized partially hydrolysed starch in an extruder described herein has successfully reduced the viscosity of compositions 1I-1K.

[0180] With an increase in the content of alum from 1% wt. up to 3% wt. the initial viscosity decreased from 75 BU to 14 BU, while the molecular weight also decreased. The initial viscosities and viscosities at 93°C of compositions 1I - 1K decreased to the viscosities of compositions 1B and 1C.

[0181] In addition, the results of the study of compositions 1I-1K shown in FIG. 2 demonstrate that optimum acid modification can be achieved during the extrusion process. No peak viscosity was observed between 70ºC and 90ºC, indicating that compositions 1I-1K were fully gelatinized.

[0182] In addition, the results showed that at a lower moisture content, more starch can be hydrolyzed at a given acid level than at a higher moisture content, since at a low moisture content there is more mechanical energy and, thus, more starch is decomposed, so there will be less starch with the same level of acid.

EXAMPLE 3

[0183] This example illustrates the flowability of gypsum slurries containing compositions 1A (comparative), 1D-1I and 1K-1L. The compositions were evaluated for flow by a slump flow test, as will be understood by one of ordinary skill in the art.

[0184] In preparation for the test, suspensions were obtained with each of compositions 1A (comparative), 1D-1I and 1K-1L in an amount of 2 wt. %, the parameters are given below in table 6, the water to plaster ratio (WSR) used was 100 .

Table 6

Ingredient Weight (g) Plaster 400 Heat resistant set accelerator four Starch eight 10% sodium trimetaphosphate solution eight Dispersant 2 1% retarder solution twenty Mixing water 357 Foam PFM-33 (0.5% solution) 25

[0185] Starch was weighed and added to a dry mix containing plaster with a purity greater than 95% and a heat-resistant setting accelerator. Water, sodium trimetaphosphate (10% by weight solution), dispersant and retarder were weighed into the mixing bowl of a Hobart mixer. The dry mix was poured into the mixing bowl of a mixer, available as an N50 5-Quart mixer from Hobart (Troy, Ohio), soaked for 10 seconds, and mixed at speed II for 30 seconds. A 0.5% solution of Hyonic® PFM-33 soap (which is available from GEO® Specialty Chemicals, Ambler, PA) was prepared to produce foam and then mixed with air to form an air foam. Said air foam was added to the slurry using a foam generator.

[0186] Then each suspension was placed in a cylinder with a diameter of 4.92 cm (1.95 inches) and a height of 10 cm (3.94 inches). Next, the cylinder was raised, allowing the suspension to drain freely. The diameters of the formed cone precipitates were then measured to demonstrate the fluidity of the slurries and the values recorded in Table 7 below. Table 8 also shows the results of the time determination in the 50% hydration test, described in more detail below.

Table 7

Composition Retarder Cone draft (cm) Time to 50% hydration (minutes) Composition 1A 0.05% wt. 13.7 cm (5 3/8 inches) four Composition 1D 0.05% wt. 16.5 cm (6 1/2 inches) 3.8 Composition 1E 0.05% wt. 15.2 cm (6 inches) 3.6 Composition 1F 0.05% wt. 16.2 cm (6 3/8 inches) 3.7 Composition 1G 0.05% wt. 16.2 cm (6 3/8 inches) 3.3 Composition 1H 0.05% wt. 17.8 cm (7 inches) 3.7 Composition 1I 0.05% wt. 15.9 cm (6 1/4 inches) 3.6 Composition 1K 0.05% wt. 18.4 cm (7 1/4 inches) 3.4 Composition 1L 0.0625% wt. 18.4 cm (7 1/4 inches) four

[0187] As can be seen from Table 7, slurries made using compositions 1D-1I and 1K exhibit larger cone sizes than slurry made using composition 1A (comparative). They also set more quickly than composition 1A (comparative), indicating that the suspensions containing compositions 1D-1I and 1K had better fluidity than the suspension containing composition 1A.

[0188] In addition, in order to compare the size of the sediment cone for these suspensions, the time to reach 50% hydration was measured when setting the suspensions at the same speed. The temperature profiles of the slurry were measured using software, as will be appreciated by one of ordinary skill in the art.

[0189] This additional study was carried out to confirm that the slump tests were correct, in particular to illustrate that the large slump observed in the case of suspensions containing pregelatinized partially hydrolyzed starches, obtained according to embodiments of the present invention, was a consequence of improved fluidity compared to composition 1A (comparative), and not slow hydration.

[0190] Composition 1H, obtained using 2% of the mass. alum and 0.3% of the mass. tartaric acid effectively hydrolyzed starch to low viscosity and had less effect on hydration rate, since tartaric acid and alum have opposite effects on hydration rate.

[0191] FIG. 3 is a temperature versus time plot showing the rate of hydration at a given temperature rise (TRS). Compositions 1F containing 0.05% and 0.0625% retarder, respectively, hydrate faster or at the same rate as composition 1A (comparative).

[0192] As shown in FIG. 3, composition 1L containing 0.0625% wt. retarder, had the same hydration rate as composition 1A (comparative). The size of the draft of the cone when using the composition 1L containing 0.065% of the mass. retarder, was 18.415 cm (7 1/4 inches) and was significantly more than in the case of composition 1A.

[0193] The results suggest that the large slump sizes observed with the suspensions containing pregelatinized partially hydrolysed starches obtained according to the embodiments of the present invention were due to high fluidity, and not slower setting. In addition, the pregelatinized partially hydrolyzed starches made according to embodiments of the present invention will allow wallboard to be made using less water without compromising flowability.

EXAMPLE 4

[0194] This example illustrates the strength of gypsum discs obtained using suspensions containing compositions 1A (comparative), 1D-1I and 1K. Strength was evaluated based on the compression test described herein.

[0195] To prepare for the test, suspensions were obtained with each of the compositions 1A (comparative), 1D-1I and 1K-1L in an amount of 2% wt., The parameters are shown above in table 4.

[0196] To obtain gypsum discs with a final density of 29 lb/cu. ft (about 465 kg/m ³ ) a water/plaster ratio (WSR) of 100 and air foam was used. The starch was weighed and added to the dry mix containing the plaster and heat resistant set accelerator. Water, 10% sodium trimetaphosphate solution, dispersant and retarder were weighed into the mixing bowl of a Hobart mixer. The dry mix was poured into the mixing bowl of a mixer, available as an N50 5-Quart mixer from Hobart (Troy, Ohio), soaked for 10 seconds, and mixed at speed II for 30 seconds. A 0.5% solution of Hyonic® PFM-33 soap (which is available from GEO® Specialty Chemicals, Ambler, PA) was prepared to produce foam and then mixed with air to form an air foam. Said air foam was added to the slurry using a foam generator. The foam generator was operated at a speed sufficient to provide the required board density of 29 lb/cu. foot (approximately 465 kg/m ³ ). After adding the foam, the slurry was immediately poured into a location just above the top holes of the molds. The excess was scraped off immediately after the plaster had set. The molds were sprayed with mold release agent (WD-40™). The discs obtained were 10.16 cm (4 inches) in diameter and 1.27 cm (0.5 inches) thick.

[0197] After hardening of the discs, they were removed from the mold and then dried at 110°F (43°C) for 48 hours. After removal from the oven, the discs were allowed to cool at room temperature for 1 hour. The compressive strength was measured using a materials testing system, which is available as a SATEC™ E/M system from MTS Systems Corporation (Eden Prairie, MN). The load was applied continuously and without shock at a speed of 0.04 inches/min (about 0.1 cm/min) (at a constant speed in the range from 15 to 40 psi/sec (from about 103 to about 276 kPa/sec)). The results are shown below in Table 8.

Table 8

Composition Compressive Strength (PSI@29lb/cu.ft.)
(kPa@465 kg/m ³ ) Composition 1A 396
(about 2730) Composition 1D 439
(about 3030) Composition 1E 388
(about 2680) Composition 1F 476
(about 3280) Composition 1G 419
(about 2890) Composition 1H 417
(about 2880) Composition 1I 455
(about 3140) Composition 1K 426
(about 2940)

[0198] As can be seen from Table 8, foam discs containing Compositions 1D-1I and 1K had comparable compressive strengths to discs containing Composition 1A (comparative), indicating that the pregelatinized, partially hydrolyzed starches allow reduce water consumption while maintaining its ability to enhance strength. The required compressive strength of sample discs is approximately 400 psi (approximately 2760 kPa). Such strength is necessary so that the slab can be processed properly without it falling apart into pieces.

[0199] The use of the terms in the singular, the term "at least one" and similar terms in the context of the description of the present invention (especially in the context of the following claims) (for example, in relation to acids, starting starches or other components or elements) ) includes both plural and singular nouns unless otherwise specified herein or clearly contradicted by the context. The use of the term "at least one" followed by a list of one or more elements (e.g., "at least one of A and B") is intended to mean one element selected from the listed elements (A or B) or any combination of two or more more than the listed elements (A and B), unless otherwise indicated in this document or clearly inconsistent with the context. The terms "consisting of", "having", "including", and "comprising" are intended to be non-limiting terms (i.e., mean "including but not limited to"), unless otherwise indicated. In this document, the listing of ranges of values simply serves as a shortcut way of listing separately each individual value falling within a given range, unless otherwise indicated herein, with each individual value included in the description of the invention, as if it were individually given in this document. All methods described herein can be performed in any suitable order, unless otherwise indicated or otherwise clearly contradicts the context. In this document, the use of any and all examples or exemplary expression (eg, "such as") is merely intended to better illustrate the invention and does not limit the scope of the invention unless otherwise stated. No expression in the description of the invention should be construed as an indication that any unclaimed element is essential to the practice of the present invention.

[0200] The present document describes the preferred embodiments of the invention, including the best method known to the inventors for carrying out the proposed invention. Variations on these preferred embodiments of the invention may become apparent to those of ordinary skill in the art upon reading the above description. The inventors expect those skilled in the art to make use of such variations as needed, and the inventors expect the present invention to be practiced in a manner other than specifically described herein. Accordingly, the present invention includes all modifications and equivalents of the subject matter set forth in the claims appended herein in accordance with applicable law. In addition, the invention includes any combination of the elements described above in all their possible variations, unless otherwise indicated herein or otherwise clearly contrary to the context.

Claims (18)

1. A method for producing pregelatinized partially hydrolyzed starch, including: (a) mixing at least water, non-pregelatinized starch and a strong acid in an amount of from 0.0001 wt.% to 0.05 wt.% relative to non-pregelatinized starch to obtain a wet starch precursor with a moisture content of from 8 wt.% to 25 wt. .%; (b) supplying said wet starch precursor to an extruder; and (c) pregelatinization and acid modification of said wet starch in an extruder at a die temperature of 150°C (300°F) to 210°C (410°F). 2. The method of claim 1, wherein said strong acid has a pKa value of -1.7 or lower. 3. The method of claim 1, wherein said strong acid is sulfuric acid, nitric acid, hydrochloric acid, or any combination thereof. 4. The method of claim 3, wherein said strong acid is sulfuric acid. 5. The method according to any one of paragraphs. 1-4, which is free from purification and neutralization steps to obtain pregelatinized acid-modified starch. 6. The method according to any one of paragraphs. 1-4, in which the suspension additionally contains sodium trimetaphosphate. 7. A method for manufacturing a gypsum wallboard, including: (a) obtaining pregelatinized partially hydrolyzed starch by i) mixing at least water, non-pregelatinized starch and a strong acid in an amount of from 0.0001 wt.% to 0.05 wt.% relative to non-pregelatinized starch to obtain a wet starch precursor with a moisture content of from 8 wt.% to 25 wt. %; ii) supplying said wet starch precursor to an extruder; and iii) pregelatinization and acid modification of the wet starch in a die extruder at 150°C (300°F) to 210°C (410°F), the pregelatinized, partially hydrolysed starch having a gelatinization degree of at least 70%; (b) mixing said pregelatinized and partially hydrolysed starch with at least water and stucco to form a slurry; (c) placing the slurry between the first cover sheet and the second cover sheet to form a wet assembly; (d) cutting the wet precast to form a wallboard; and (e) drying the wallboard.

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