JP2019206710A - Method of preparing pregelatinized, partially hydrolyzed starch and methods of manufacturing board - Google Patents

Abstract

To provide an improved method of producing a pregelatinized, partially hydrolyzed starch.SOLUTION: Disclosed are methods relating to an extruded pregelatinized, partially hydrolyzed starch prepared by mixing at least water, a non-pregelatinized starch and an acid to form a starch precursor. The acid can be a weak acid that substantially avoids chelating calcium ions, or a strong acid in a small amount. In the method, pregelatinization and acid modification of the starch precursor occurs in one step in an extruder. Also disclosed are methods of preparing a board using the starch prepared according to the methods, and starches and boards prepared by various methods of the invention.SELECTED DRAWING: Figure 1

Description

Cross-reference to related applications This application includes US Patent Application No. 14 / 044,582 filed October 2, 2013, International PCT Application No. PCT / US2013 / 064776 filed October 14, 2013, and Claims priority based on US patent application Ser. No. 14 / 494,547, filed Sep. 23, 2014. All of the above patent applications are hereby incorporated by reference in their entirety.

  Starch generally contains two types of polysaccharides (amylose and amylopectin) and is classified as a carbohydrate. Some starches are usually pregelatinized by thermal means. Generally, pregelatinized starch can form a dispersion, paste, or gel with cold water. Pregelatinized starch is generally easy to digest and can be used in a number of ways, such as in various food additives (eg, in baked goods, snacks, beverages, confectionery, dairy products, gravies, processed foods, sauces and meats) and in pharmaceuticals. Have been used.

  Another use of pregelatinized starch is in the preparation of gypsum wallboard. In this case, during the manufacture of the board, stucco (ie calcined gypsum in the form of calcium sulfate hemihydrate and / or calcium sulfate anhydrous gypsum), water, starch, and optionally other ingredients typically Are mixed in a pin mixer. This pin mixer is a pin mixer as that term is used in the art. A slurry is formed and one of the skim coats (if a skim coat is present) is discharged from the mixer onto a moving conveyor that carries the already applied cover sheet (often upstream of the mixer). This slurry is spread on paper (optionally with a skim coat included on the paper). Another cover sheet with or without a skim coat is placed on top of the slurry to form a sandwich structure of the desired thickness using, for example, a forming plate or the like.

  The mixture is shaped and solidified by the reaction of calcined gypsum and water to form a hardened (ie, rehydrated) gypsum and form a matrix of crystalline hydrated gypsum (ie, calcium sulfate dihydrate). It is the desired hydration of calcined gypsum to form a connected crystal matrix of hardened gypsum, thereby imparting strength to the gypsum structure in the product. Heating (eg, in a furnace) is required to evaporate the remaining free (ie unreacted) water to obtain a dry product.

  In many cases, pregelatinized starch increases the water requirements of the process. In order to compensate for the required amount of water and to provide sufficient fluidity during production, water must be added to the stucco slurry. This excess water results in manufacturing inefficiencies such as increased drying time, reduced production line speed, and increased energy costs. The inventors have found that the pregelatinized partially hydrolyzed starch requires less water.

  The inventors have also found that the preparative technique of pregelatinized partially hydrolyzed starch is not fully satisfactory. Conventional methods for preparing such pregelatinized partially hydrolyzed starch are not efficient, produce less, produce slowly, and have high energy costs. Accordingly, there is a need in the art for an improved method of producing pregelatinized partially hydrolyzed starch, particularly with a low water requirement.

  This background description is made by the inventors to assist the reader and should not be regarded as a reference to the prior art, or any of the problems indicated are recognized in the art. It should be understood that this should not be taken as an indication of what is being done. While the described principles may alleviate inherent problems in other systems in some aspects and embodiments, the scope of the innovation to be protected is defined by the appended claims. It should be understood that the claimed invention is not to be defined by the ability to solve any particular problems described herein.

  In one aspect, the present invention provides a method for making pregelatinized partially hydrolyzed starch comprising: (a) at least water, non-pregelatinized starch, and a weak acid that does not substantially chelate calcium ions. To produce a wet starch precursor having a moisture content of about 8% to about 25% by weight; (b) feeding the wet starch precursor to an extruder; and (c) the wettability The starch precursor is pregelatinized and acid modified in the extruder described above at a die temperature of about 150 ° C. (about 300 ° F.) to about 210 ° C. (about 410 ° F.). The present invention also provides starch made according to this method.

  In another aspect, the present invention provides a method of making pregelatinized partially hydrolyzed starch comprising: (a) mixing at least about 8 weight percent of water, non-pregelatinized starch, and strong acid. Creating a wet starch precursor having a moisture content of from about 25% to about 25% by weight, wherein the strong acid is in an amount up to about 0.05% by weight of the weight of the starch; b) feeding the wet starch to an extruder; and (c) feeding the wet starch precursor at a die temperature of about 150 ° C (about 300 ° F) to about 210 ° C (about 410 ° F). Including pregelatinization and acid modification in the above-described extruder. The present invention also provides starch made according to this method.

  In another aspect, the present invention provides a method of making a board, comprising: (a) (i) mixing at least water, non-pregelatinized starch, and an acid from about 8% to about Forming a wet starch precursor having a moisture content of 25% by weight, the acid comprising: (1) a weak acid that does not substantially chelate calcium ions; and (2) about 0% of the weight of the starch. Forming a strong acid in an amount up to .05% by weight, or (3) selected from the group consisting of any combination thereof; (ii) feeding the wet starch precursor to the extruder; and ( iii) alphatizing the wet starch by alphalating and acid modifying the extruder with a die at a temperature of about 150 ° C (about 300 ° F) to about 210 ° C (about 410 ° F). Partial hydrolysis Forming starch; (b) mixing the pregelatinized partially hydrolyzed starch with at least water and stucco to form a slurry; (c) adding the slurry between the first cover sheet and the second cover sheet. Placing the wet assembly into a board; (d) cutting the wet assembly into a board; and (e) drying the board. In some embodiments, the hardened gypsum core has a greater compressive strength than a hardened gypsum core made with starch prepared by a different method. In another aspect, the present invention provides a board made according to this method.

FIG. 1 is an amylogram plotting viscosity (left y-axis) and temperature (right y-axis) against time (x-axis). This figure shows the pasting curve of starch extruded at a solids content of 10% by weight of the test slurry and a moisture content of 16% by weight, as described in Example 2. FIG. 2 is an amylogram plotting viscosity (left y-axis) and temperature (right y-axis) against time (x-axis). This figure shows the pasting curve of starch extruded at a solid content of 10% by weight of the test slurry and a moisture content of 13% by weight as described in Example 2. FIG. 3 is a graph plotting temperature against time, as described in Example 3, 3% by weight of alum and 0.05% and 0.0625% by weight of retarder, respectively. Two slurries containing pregelatinized partially hydrolyzed starch treated with a third slurry containing conventional pregelatinized corn starch having a viscosity of 773 centipoise and a retarder in an amount of 0.05% by weight. Figure 2 shows the temperature rise cure (TRS) hydration rate.

  Embodiments of the present invention provide a method for making pregelatinized partially hydrolyzed starch. In one aspect, the present invention provides a method for preparing a board (eg, gypsum wallboard). The pregelatinized partially hydrolyzed starch made according to the method of the present invention is a food product (eg, baked food, beverage, confectionery, dairy product, instant pudding, gravy, soup mix, processed food, pie filling, sauce, And in meat), can be used in various other ways, such as in pharmaceuticals, feed, adhesives, and colorants. Such starches prepared according to some embodiments of the present invention are generally easy to digest, can give foods the desired viscosity, and can maintain most of the functional properties of the original base material. .

  Embodiments of the present invention are premised at least in part on the surprising and unexpected discovery of pregelatinizing and acid-modifying starch in one step in an extruder. Surprisingly and unexpectedly, pregelatinizing and acid-modifying starch in one step in an extruder has significant advantages compared to pregelatinizing and acid-modifying starch in a separate step. For example, as described herein, the method of the present invention for making pregelatinized partially hydrolyzed starch can be produced without sacrificing the desired properties (eg, viscosity, flowability, solubility in cold water, etc.) Larger quantities, faster production, and lower energy costs.

  Furthermore, it has been found that extrusion conditions (eg high temperature and high pressure) can significantly increase the acid hydrolysis rate of starch. Surprisingly and unexpectedly, this one-step process allows the use of a weak acid, such as alum, and / or a smaller amount of a strong acid for acid modification of starch. Both acid forms provide a mechanism by which protons from the acid catalyze the hydrolysis of starch. Conventional acid modification processes include purification and neutralization steps. By using a weak acid (eg, alum) and / or a small amount of strong acid, according to some embodiments of the present invention, the need for a neutralization step and a subsequent purification step is eliminated. A purification step is required in conventional systems to purify the starch of the salt produced in the neutralization step.

  The extrusion process not only pregelatinizes the starch but also partially hydrolyzes the starch molecules (ie, by acid modification) according to embodiments of the present invention. Thus, the one-step extrusion process provides both physical modification (alphalation) and chemical modification (acid modification, partial acid hydrolysis). By pregelatinization, the starch gains the ability to impart strength (eg to a final product such as gypsum board). By acid modification, starch is advantageously partially hydrolyzed to gain the ability to impart strength to the final product, such as gypsum board, and less water is required in product manufacture, such as in the gypsum board manufacturing process . Therefore, the product of the starch preparation method of the embodiment of the present invention is pregelatinized partially hydrolyzed starch.

  According to some embodiments, the present invention provides a highly efficient acid modification reaction. Pregelatinization and acid modification in the extruder occurs at high temperatures and / or high pressures as described herein so that the acid hydrolysis rate can be reduced at lower temperatures (eg, 50 ° C.) and / or at lower pressures. It can be about 30,000 times greater than the conventional acid hydrolysis rate. The acid hydrolysis rate is further increased by using low moisture (about 8% to about 25% by weight) levels in the starch precursor, thereby increasing the concentration of the reactants. Because of this highly efficient acid modification, it is surprising and unexpected that a weak acid or very low level of strong acid can be used in the starch precursor to achieve optimal acid modification, neutralization and The inventors have found that there is no need for purification. This neutralization and purification is costly, time consuming and an inefficient requirement with conventional systems.

  According to some embodiments, the hydrolysis is designed to turn starch into small molecules within the optimal size range. The optimal size range is defined herein by the desired viscosity of the pregelatinized partially hydrolyzed starch. If the starch is hydrolyzed excessively, it is converted into an excessively small molecule (eg oligosaccharides or saccharides), so that in the case of gypsum board, the board strength afforded by pregelatinized partially hydrolyzed starch with the desired viscosity Rather, the board strength can be smaller.

  The pregelatinized partially hydrolyzed starch comprises (i) mixing at least water, non-pregelatinized starch, and an acid to form a wet starch precursor having a moisture content of about 8 wt% to about 25 wt%. Can be prepared. The acid is (1) a weak acid that does not substantially chelate calcium ions, (2) a strong acid in an amount up to about 0.05% by weight of the starch, or (3) any combination thereof. be able to. The wet starch precursor is pregelatinized and acid modified in one step in an extruder at high die temperatures and / or high pressures as described herein. The starch is hydrolyzed to the desired viscosity, for example as described herein.

  Thus, in some embodiments, the pregelatinized partially hydrolyzed starch is about 8 wt% to about about wt% mixed with at least water, non-pregelatinized starch, and a weak acid that does not substantially chelate calcium ions. It can be made by making a wet starch precursor having a moisture content of 25% by weight. The wet starch is then fed to the extruder. While in an extruder at a die temperature of about 150 ° C. (about 300 ° F.) to about 210 ° C. (about 410 ° F.), the wet starch is pregelatinized and acid-modified so that it is at least partially hydrolyzed. Is done.

  In a further embodiment, the pregelatinized partially hydrolyzed starch comprises at least water, non-pregelatinized starch, and a strong acid to provide a wet starch precursor having a moisture content of about 8 wt% to about 25 wt%. And the strong acid is in an amount up to about 0.05% by weight of the weight of the starch. The wet starch is then fed to the extruder. While in an extruder at a die temperature of about 150 ° C. (about 300 ° F.) to about 210 ° C. (about 410 ° F.), the wet starch is pregelatinized and acid-modified so that it is at least partially hydrolyzed. Is done.

  Desirably, the resulting pregelatinized partially hydrolyzed starch requires less water when incorporated into a stucco slurry, and in some embodiments a board with good strength (eg, gypsum board) May be useful in the manufacture of Thus, in another aspect, the present invention provides a method for making gypsum board using starch prepared using the method of the present invention that is alpha-modified and acid-modified in one step in an extruder. In some embodiments, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention requires less water than other pregelatinized starches known to those skilled in the art.

As a result, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention (e.g., through a feed line to a pin mixer) is incorporated into a stucco slurry with good flowability. In some embodiments, higher amounts of pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can be incorporated so that higher strength and lower board density can be obtained. . This is because it is not necessary to add excess water to the system. The resulting board exhibits good strength properties (eg, good core hardness, nail resistance, compressive strength, etc., or a relationship between them based on any combination of values provided herein. about). Advantageously, the incorporation of starch prepared according to the method of the present invention during the production of gypsum board increases the strength, making it possible to produce very low density products. The gypsum board can be in the form of, for example, gypsum wallboard (often referred to as drywall), and this gypsum wallboard is not only for walls, but also for ceilings and other places, as will be appreciated by those skilled in the art. Can also be used. However, the starch prepared according to this method can also have other uses such as in food.
Alpha and acid denaturation

  Starch is classified as a carbohydrate and contains two types of polysaccharides: linear amylose and branched amylopectin. Starch granules are semicrystalline, for example as seen under polarized light, and are insoluble at room temperature. Gelatinization is a process in which starch is heated in water ("heated") so that starch crystal grains melt and starch molecules dissolve in water and disperse well. Since starch granules are insoluble in water, it has been found that when starch granules change to a gelatinized form, they show little viscosity in water at an early stage. As the temperature rises, the starch granules swell and the crystal structure melts at the gelatinization temperature. Peak viscosity is obtained when the starch granules swell to the maximum. Upon further heating, the starch granules break, starch molecules dissolve in water and the viscosity decreases rapidly. After cooling, the starch molecules reassociate to form a 3-D gel structure, and the viscosity increases due to this gel structure. Some commercially available starches are sold in pregelatinized form and others are sold in fine grain form. In accordance with some embodiments of the present invention, for a gypsum board, the fine grain form undergoes at least some degree of gelatinization. Illustratively, for gypsum board, the starch is pregelatinized before being added (usually in a mixer such as a pin mixer) to a gypsum slurry, also referred to herein as a stucco slurry.

  Thus, as used herein, “pregelatinized” means that the starch has been gelatinized to any degree, for example, before being incorporated into a gypsum slurry or for other uses. means. In some embodiments related to gypsum board, pregelatinized starch can be partially gelatinized when incorporated into the slurry, but has been exposed to high temperatures, for example, in an oven during the process of removing excess water. When fully gelatinized. In some embodiments related to gypsum board, pregelatinized starch is used in the oven if the starch meets the moderate viscosity characteristics of some embodiments under conditions according to the viscosity modified blending (VMA) method. Even when leaving, it is not completely gelatinized.

  In the present specification, when referring to viscosity, unless otherwise specified, the viscosity is in accordance with the VMA method. According to this method, viscosity is measured using a Discovery HR-2 hybrid rheometer (TA Instruments Ltd) with a concentric cylinder, a standard cup (diameter 30 mm) with a blade shape (28 mm diameter, 42.05 mm length). .

  Once the starch is obtained, a differential scanning calorimetry (DSC) technique is used to determine whether the starch is fully gelatinized. A DSC process can be used to observe whether the starch is fully gelatinized, for example to ensure that no aging has occurred. Depending on the temperature required to fully gelatinize the starch, one of two procedures is applied. As will be appreciated by those skilled in the art, the temperature can also be determined by DSC.

  If DSC reveals that the starch is fully gelatinized or has a gelatinization temperature of 90 ° C. or less, use Procedure 1. If the gelatinization temperature is higher than 90 ° C., use procedure 2. Since the viscosity is measured while the starch is in water, procedure 2 uses a pressure heat treatment in a sealed container to overheat to temperatures above 100 ° C. and does not cause obvious water evaporation. As discussed below, step 1 is already fully gelatinized starch or gelatinization below 90 ° C. because gelatinization occurs in an open rheometer that cannot create pressure conditions for gelatinization. For starch with temperature. Procedure 2 is thus performed with starch having a higher gelatinization temperature. In both methods, when measuring the viscosity, starch (7.5 g, dry basis) is added to water for a total weight of 50 g.

In procedure 1, starch is dispersed in water (starch and starch 15% of the total weight of water) and the sample is immediately transferred to a cylinder cell. Cover the cell with aluminum foil. The sample is heated from 25 ° C. to 90 ° C. at 5 ° C./min with a shear rate of 200 s ⁻¹ . The sample is held at 90 ° C. for 10 minutes at a shear rate of 200 s ⁻¹ . The sample is cooled from 90 ° C. to 80 ° C. at 5 ° C./min at a shear rate of 200 s ⁻¹ . The sample is held at 80 ° C. for 10 minutes at a shear rate of ^{0 s −1} . The viscosity of the sample is measured at 80 ° C. and a shear rate of 100 s ⁻¹ for 2 minutes. Viscosity is the average of measurements from 30 seconds to 60 seconds.

Procedure 2 is used with starches having a gelatinization temperature higher than 90 ° C. The starch is gelatinized according to methods well known in the starch industry (eg, by pressure heat treatment). The aqueous gelatinized starch solution (15% of the total weight) is immediately transferred into a rheometer measuring cup and allowed to equilibrate at 80 ° C. for 10 minutes. The viscosity of the sample is measured at 80 ° C. and a shear rate of 100 s ⁻¹ for 2 minutes. Viscosity is the average of measurements from 30 seconds to 60 seconds.

  Viscograph and DSC are two different ways of representing starch gelatinization. The degree of starch gelatinization can be determined, for example, from a thermogram from DSC, using, for example, the peak area (crystal melting). Viscograms (from Viscograph) are less desirable for determining the degree of partial gelatinization, but for example, starch viscosity change, gelatinization maximum, gelatinization temperature, aging, viscosity at holding, cooling completed It is an excellent tool for obtaining data such as viscosity at time. To determine the degree of gelatinization, DSC measurement is performed in the presence of excess water, particularly in the presence of 67% or more excess water by weight. If the moisture content of the starch / water mixture is less than 67%, the gelatinization temperature will increase as the moisture content decreases. If the available water is limited, it is difficult to melt the starch crystals. If the moisture 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 start temperature indicates the temperature at which gelatinization starts. The gelatinization end temperature indicates the temperature at which gelatinization ends. The enthalpy of gelatinization represents the amount of crystal structure that has melted during gelatinization. By using the enthalpy from the starch DSC thermogram, the degree of gelatinization can be indicated.

  Different starches have different gelatinization start temperatures, finish temperatures and gelatinization enthalpies. Accordingly, different starches may be fully gelatinized at different temperatures. It will be appreciated that starch is fully gelatinized when heated above excess gelatinization temperature in excess water. Furthermore, for any particular starch, if the starch is heated at a temperature below the gelatinization end temperature, the starch will partially gelatinize. Thus, partial gelatinization and incomplete gelatinization will occur when the starch is heated below the gelatinization end temperature in the presence of excess water, as measured, for example, by DSC. Full gelatinization will occur when starch is heated above the gelatinization end temperature in the presence of excess water, as measured, for example, by DSC. The degree of gelatinization can be adjusted in different ways, for example by adjusting the starch at a temperature below the gelatinization end temperature to form a partial gelatinization. For example, if the enthalpy to fully gelatinize the starch is 4 J / g, if DSC indicates that the starch has a gelatinization enthalpy of only 2 J / g, this means that 50% of the starch is gelatinized. . Fully gelatinized starch will not have a DSC thermogram gelatinization peak (enthalpy = 0 J / g) as measured by DSC.

  As stated, the degree of gelatinization can be any suitable amount, for example about 70% or more. However, a lower degree of gelatinization is closer to fine starch and maximizes the benefits of increased strength, better (more complete) dispersion, and / or reduced water requirements in some embodiments of the invention. May not be available to the limit. Thus, in some embodiments, a higher degree of gelatinization is preferred, such as about 75% or more, about 80% or more, about 85% or more, about 90% or more, about 95% or more, about 97%. As described above, gelatinization of about 99% or more or complete (100%) is preferable. In the case of gypsum board, starch with a lower degree of gelatinization can be added to the slurry to cause further gelatinization (eg up to 100%) in the oven. For purposes of addition to the slurry, “complete gelatinization” means that the starch is fully heat treated above the gelatinization temperature, or the starch is fully heat treated and can be seen by DSC technology. It will be understood that this is achieved in other ways. The starch may be expected to have some slight aging due to cooling, but in some embodiments as recognized by those skilled in the art, starch may be added to the gypsum slurry or otherwise used. Will be understood as being "completely gelatinized". In contrast, such aging is not acceptable in making viscosity measurements with the VMA method discussed herein.

  Starch molecules can be acid modified to hydrolyze, for example, glycosidic bonds between glucose units to obtain the desired molecular weight. One advantage of acid-modifying starch to reduce molecular weight would be to reduce water requirements. The water requirement of conventional pregelatinized starch that has not been acid-modified is very high, with high energy costs. It has traditionally been thought that denaturation is generally preferred to occur prior to gelatinization because it tends to be more efficient and less costly. Surprisingly and unexpectedly, however, the inventors have found that pregelatinization and acid modification can be combined in one step so that they occur simultaneously rather than sequentially.

Starch Preparation Method According to some embodiments of the present invention, a wet starch precursor is prepared prior to entering the extruder. The wet starch precursor can be prepared by any suitable method. For example, in some embodiments, the wet starch precursor is prepared by combining starch raw material, water and acid. The acid is (a) a weak acid that does not substantially chelate calcium ions, and / or (b) a small amount of strong acid.

  Any suitable starch material can be used so long as the starch material can be used to make a pregelatinized partially hydrolyzed starch, such as one that meets the moderate viscosity characteristics of some embodiments of the present invention. Can be selected to prepare a wet starch precursor. As used herein, “starch” refers to a composition that includes a starch component. Thus, the starch can be 100% pure starch, or other ingredients such as those commonly found in flour, such as protein and fiber, if the starch component constitutes about 75% or more by weight of the starch composition. You may have a component. The starch can be in the form of starch-containing flour (eg, corn flour), such as greater than about 75% by weight of the flour, such as greater than about 80%, greater than about 85%, greater than about 90%, greater than about 95%, etc. Or flour with a starch. Any suitable unmodified starch or flour can be used to prepare the pregelatinized partially hydrolyzed starch precursor of the present invention. For example, the starch can be CCM260 yellow corn meal, CCF600 yellow corn flour (Bunge North America), Clinton 106 (ADM), and / or Midsol 50 (MGP Ingredients).

  The wet starch precursor can be prepared to have any suitable moisture content so that the desired level of pregelatinization and modification is obtained in the extruder. In some embodiments, for example, the wet starch precursor desirably has a moisture content of from about 8% to about 25% by weight of the total starch precursor weight, such as from about 8% to about 23%, For example, about 8% to about 21%, about 8% to about 20%, about 8% to about 19%, about 8% to about 18%, about 8% to about 17% by weight. About 8% to about 16%, about 8% to about 15%, about 9% to about 25%, about 9% to about 23%, about 9% to about 21% by weight About 9 wt% to about 20 wt%, about 9 wt% to about 19 wt%, about 9 wt% to about 18 wt%, about 9 wt% to about 17 wt%, about 9 wt% to about 16 wt% About 9% to about 15%, about 10% to about 25%, about 10% to about 23%, about 10% to about 21% %, About 10% to about 20%, about 10% to about 19%, about 10% to about 18%, about 10% to about 17%, about 10% to about 16%. %, About 10% to about 15%, about 11% to about 25%, about 11% to about 23%, about 11% to about 21%, about 11% to about 20%. %, About 11% to about 19%, about 11% to about 18%, about 11% to about 17%, about 11% to about 16%, about 11% to about 15%. %, About 12% to about 25%, about 12% to about 23%, about 12% to about 21%, about 12% to about 20%, about 12% to about 19%. %, About 12% to about 18%, about 12% to about 17%, about 12% to about 16%, about 12% to about 15 wt%, about 13 wt% to about 25 wt%, about 13 wt% to about 23 wt%, about 13 wt% to about 21 wt%, about 13 wt% to about 20 wt%, about 13 wt% to about 19%, about 13% to about 18%, about 13% to about 17%, about 13% to about 16%, about 13% to about 15%, about 14% to about 25%, about 14% to about 23%, about 14% to about 21%, about 14% to about 20%, about 14% to about 19%, about 14% to about 18% by weight, about 14% to about 17% by weight, about 14% to about 16% by weight, or about 14% to about 15% by weight, all based on the total weight of the wet starch precursor . When preparing wet starch, it will be understood that the moisture content described herein includes ambient moisture and added water.

  While not wishing to be bound by any particular theory, it is believed that lower moisture content results in greater friction in the extruder. In some embodiments, wet starch is loaded with sufficient mechanical energy when fed through the extruder so that friction prevents the wet starch from easily passing through the extruder. It can be prepared to have a moisture content. As friction increases, the breaking of hydrogen bonds in starch can increase.

  Any suitable weak acid that does not substantially chelate calcium ions may be mixed into the wet starch. While not wishing to be bound by any particular theory, chelation prevents, for example, the weak acid from forming a coordination complex with calcium or otherwise preventing the formation of gypsum crystals in the gypsum slurry. Including that. Such hindrance can result in a decrease in the number of gypsum crystals produced, a delay in crystal formation (decrease in speed), and a decrease in interactions between gypsum crystals. With respect to not chelating calcium ions, the term “substantially” refers to 90% or more of available calcium ions (eg, 92% or more, 95% or more, 96% or more, 97% or more, 98% or more, or 99% %) Generally does not form a chelate with the acid.

  Weak acids of embodiments of the present invention have a pKa value of about 1 to about 6, such as about 1 to about 5, about 1-4, about 1-3, about 1-2, about 1.2 to about 6, about 1. About 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, about 2 to about 5, about 2 to about 4, about 2 To about 3, about 3 to about 6, about 3 to about 5, about 3 to about 4, about 4 to about 6, or about 4 to about 5. As will be appreciated by those skilled in the art, the pKa value is a measure of the strength of the acid; the lower the pKa value, the stronger the acid.

  Weak acids that do not substantially chelate calcium ions are characterized by the absence of multiple binding sites such as multiple carboxyl functional groups (COO-) that tend to bind calcium ions. In some embodiments, gypsum crystal formation is substantially affected, for example, such that chelation is minimized (ie substantially free) or compared to gypsum crystal formation in the absence of weak acids. As such, the weak acid has a minimal amount of binding sites, such as multiple —COO— groups, or is substantially free of multiple binding sites, such as —COO— groups. In some embodiments, for example, aluminum sulfate (alum) is a weak acid suitable for use in preparing wet starch because it does not substantially chelate calcium ions. Alum does not have multiple binding sites.

  In some embodiments, alum is added to the wet starch precursor in any suitable form, eg, as an alum-containing liquid with a 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 as well.

  Wet starch is suitable for weak acids that do not substantially chelate calcium ions so that pregelatinized partially hydrolyzed starch is prepared with the desired viscosity and low water requirements and is not excessively hydrolyzed to sugar. Can be mixed to include any amount. For example, in some embodiments, such weak acids are included in an amount of about 0.5 wt% to about 5 wt% based on the weight of starch, such as about 0.5 wt% to about 4.5 wt%. % By weight, such as from about 0.5% to about 4%, from about 0.5% to about 3.5%, from about 0.5% to about 3%, from about 1% to about 5%. %, About 1% to about 4.5%, about 1% to about 4%, about 1% to about 3.5%, about 1% to about 3%, about 1.5% % To about 5%, about 1.5% to about 4.5%, about 1.5% to about 4%, about 1.5% to about 3.5%, about 1% .5% to about 3%, about 2% to about 5%, about 2% to about 4.5%, about 2% to about 4%, about 2% to about 3%. 5 wt%, about 2 wt% to about 3 wt%, about 2.5 wt% To about 5 wt%, about 2.5 wt% to about 4.5 wt%, about 2.5 wt% to about 4 wt%, about 2.5 wt% to about 3.5 wt%, or about 2. It is included in an amount of 5% to about 3% by weight. It will be understood that these amounts include a weak acid component and, when the acid is in solution, does not include water or other components of the solution.

  The wet starch precursor can optionally be prepared to further comprise a second acid capable of chelating calcium ions such as tartaric acid. Thus, in some embodiments, a second acid, such as tartaric acid, can be combined with any suitable weak acid that does not chelate calcium ions. Tartaric acid is known to delay gypsum crystallization. However, tartaric acid does not substantially delay gypsum crystallization when combined with a weak acid that does not chelate so that the hydrolysis reaction by acid modification is optimized. In addition to tartaric acid, other second acids such as succinic acid or malic acid may be advantageous as long as the acceleration effect of alum is not exceeded. In some embodiments, the wet starch precursor comprises both alum and tartaric acid.

  The second acid (eg, tartaric acid), if included, can be present in any suitable amount. For example, tartaric acid can be present in an amount from about 0.1% to about 0.6% by weight based on the weight of the starch, such as from about 0.1% to about 0.4% by weight, about 0.00%. It can be present in an amount from 2% to about 0.3% by weight.

  In some embodiments, oil can optionally be added to the wet starch to improve starch transport in the extruder. In some embodiments, possible oils include canola oil, vegetable oil, corn oil, soybean oil, or any combination thereof. For example, in some embodiments, canola oil or one of the foregoing alternatives can optionally be added in an amount from about 0% to about 0.25% by weight of the starch weight, for example about 0%. 0.1 wt% to about 0.2 wt%, about 0.1 wt% to about 0.15 wt%, about 0.15 wt% to about 0.25 wt%, about 0.15 wt% to about 0. It can be added in an amount of 2% by weight, or from about 0.2% to about 0.25% by weight.

  According to some embodiments, the wet starch precursor is prepared by mixing water, non-pregelatinized starch, and a small amount of strong acid. In some embodiments, the strong acid has a pKa of about −1.7 or less. Any such acid can be used, and in some embodiments, the strong acid comprises sulfuric acid, nitric acid, hydrochloric acid, or any combination thereof. Since sulfate ions can accelerate gypsum crystallization in gypsum board embodiments, in some embodiments, sulfuric acid alone or a combination of sulfuric acid and other acids is preferred.

  The amount of strong acid is relatively small, for example about 0.05% or less by weight of the starch, such as about 0.045% or less, about 0.04% or less, about 0.035% or less, about 0%. 0.03 wt% or less, about 0.025 wt% or less, about 0.02 wt% or less, about 0.015 wt% or less, about 0.01 wt% or less, about 0.005 wt% or less, about 0.001 % By weight or less, about 0.0005% by weight or less, for example, about 0.0001% to about 0.05% by weight of starch, about 0.0001% to about 0.045% by weight, about 0.005%. 0001% to about 0.04%, about 0.0001% to about 0.035%, about 0.0001% to about 0.03%, about 0.0001% to about 0.025% % By weight, about 0.0001% to about 0.02% by weight, about 0.0001 % To about 0.015%, about 0.0001% to about 0.01%, about 0.0001% to about 0.005%, about 0.0001% to about 0.001% %, From about 0.0001% to about 0.0005% by weight. It will be understood that these amounts include a strong acid component and when the strong acid is in solution, it does not include water or other components of the solution. For example, conventional strong acid modification uses a 2% sulfuric acid solution at ˜35% starch solids (2 g sulfuric acid for 35 g starch). Percentages are based on pure sulfuric acid component. Calculated as the weight of the sulfuric acid component divided by the weight of wet starch. For example, if the sulfuric acid is 50% pure (meaning that half the weight of the solution is pure sulfuric acid), the weight of the sulfuric acid solution is doubled. Illustratively, 0.1 g pure sulfuric acid is added to 100 g starch for 0.1 wt%. When the sulfuric acid solution concentration is 50%, 0.2 g of 50% sulfuric acid solution is added to obtain 0.1% by weight.

  It will be appreciated that the acids have different grades (> 95%, 98%, 99.99%). These differences are encompassed by the term “about” with respect to the amount of strong acid in the starch precursor. One skilled in the art will readily be able to determine the weight percentages described herein to include different grades. The amount of strong acid used in accordance with some embodiments of the present invention is significantly less than the amount of strong acid contained in conventional systems, such as about 2 g or more sulfuric acid for 35 g starch. used. 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 alum, as described herein.

  Embodiments of the present invention provide that the wet starch precursor is fed through the extruder such that the wet starch precursor is pregelatinized and acid modified in one step in the extruder. It will be understood that an extruder is a machine generally used to melt and process a polymer into the desired shape by melting the polymer and extruding it through a die. The extruder can also mix the polymer with other ingredients such as pigments, reinforcing fibers, mineral fillers and the like. The purpose of the extruder is to disperse and distribute all the components fed to the extruder and to melt the components at a constant temperature and pressure.

  The construction and arrangement of the extruder is known to those skilled in the art. In general, an extruder includes a feed hopper for feeding feed, a preconditioner with a heating jacket for conditioning a plasticizer (eg, water) and a polymer, an extruder module head with a heating zone, a die assembly, Is provided. The extruder generally comprises a feed auger, a knife, and screw (s). A feed auger is present to help carry the wet starch precursor to the extruder. A knife is present to cut the string of pregelatinized partially hydrolyzed starch into small pellets so that the pregelatinized partially hydrolyzed starch can be ground. The screw assists in mixing the wet starch precursor, transports the wet starch precursor through the extruder, and provides mechanical shear. The extruder can be a single screw or twin screw type of extruder as will be understood by those skilled in the art. Leszek Mosicki, Extension-Cooking Technologies, WILEY-VCH Verlag & Co. See KGaA, 2011.

  In a single screw extruder, the screw is generally provided with a deep groove, which carries solids from the mouth of the feeder and compresses them, a screw groove which becomes progressively shallower, a compression part where the polymer melts, and a shallow groove And a metering section for transporting the molten polymer to the die. Some screws are designed to include a mixing device (eg, a pin extending from the screw).

  Twin screw extruders generally have two screws that either rotate in the same direction (ie, co-rotate) or rotate in the opposite direction (ie, counter-rotate). The two screws may rotate with a non-meshing screw type or with a fully meshing screw type. In the case of a single screw extruder, the material being supplied fills the entire screw groove, but in the case of a twin screw extruder, a downstream feed port or feed hole can be used for the addition of specific components. As such, only a portion of the screw groove is filled.

  The die assembly generally includes a plate, a spacer, and a die head. When extruding material, the process can be either continuous, where the material is extruded at infinite length, or semi-continuous, where the material is extruded at a specific length. The material being extruded may be hot or cold.

  The present invention provides a method for preparing pregelatinized partially hydrolyzed starch in an extruder. Any suitable extruder can be used, such as a single screw extruder (eg, Advantage 50 available from American Extension International, South Bellot, Ill.), Or a twin screw extruder (eg, in Sabetha, Kansas). Wenger TX52) available from a certain Wenger.

  As described herein, non-pregelatinized starch, a weak acid that does not substantially chelate calcium ions and / or a small amount of an acid in the form of a strong acid, and water are mixed and fed to the extruder. In some embodiments, additional water may be added to the extruder. In the extruder, the weak acid partially hydrolyzes the starch to the desired molecular weight while the starch is melted and alphalated with a combination of heating elements and mechanical shear. Its molecular weight is indicated by the desired viscosity as described herein. Depending on the conditions in the extruder, starch molecules also deteriorate due to mechanical energy, and in part have the same effect as acid modification. It is believed that weak acids and / or small amounts of strong acids can be used because conditions in the extruder of some embodiments (eg, high reaction temperature and high pressure) facilitate this chemical reaction. The method of the present invention thus improves the efficiency of starch acid modification.

  The main screw (s) can be operated at any suitable speed to achieve the desired mixing and mechanical shear. For example, in some embodiments, the main screw can be operated at a speed of about 350 RPM (± about 100 RPM). The feed auger can be operated at any suitable speed to obtain the desired feed rate. For example, in some embodiments, the feed auger can be operated at a speed of about 14 RPM (± about 5 RPM).

  The knife can be operated at any suitable speed. For example, in various embodiments, the knife can be operated at a speed of about 400 RPM to about 1,000 RPM, such as about 400 RPM to about 900 RPM, about 400 RPM to about 800 RPM, about 400 RPM to about 700 RPM, about 400 RPM to about 600 RPM, About 400 RPM to about 500 RPM, about 500 RPM to about 1,000 RPM, about 500 RPM to about 900 RPM, about 500 RPM to about 800 RPM, about 500 RPM to about 700 RPM, about 500 RPM to about 600 RPM, about 600 RPM to about 1,000 RPM, about 600 RPM to about 900 RPM, about 600 RPM to about 800 RPM, about 600 RPM to about 700 RPM, about 700 RPM to about 1,000 RPM, about 700 RPM to about 900 RPM, about 700 RPM to about 800 RPM, about 00RPM~ about 1,000 RPM for, can be operated at about 800RPM~ about 900 RPM, or from about 900RPM~ about 1,000 RPM for the speed of.

  The wet starch can be pregelatinized and acid modified in an extruder with a suitable arbitrary temperature die such that the wet starch is fully pregelatinized without carbonizing the material. For example, wet starch can be pregelatinized and acid modified in an extruder having a die at a temperature of about 150 ° C. (about 300 ° F.) to about 210 ° C. (about 410 ° F.), for example, in various embodiments. About 150 ° C to about 205 ° C (about 400 ° F), about 150 ° C to about 199 ° C (about 390 ° F), about 150 ° C to about 193 ° C (about 380 ° F), about 150 ° C to about 188 ° C. (About 370 ° F), about 150 ° C to about 182 ° C (about 360 ° F), about 154 ° C (about 310 ° F) to about 210 ° C, about 154 ° C to about 205 ° C (about 400 ° F), about 154 ° C to about 199 ° C, about 154 ° C to about 193 ° C, about 154 ° C to about 188 ° C, about 154 ° C to about 182 ° C, about 160 ° C (about 320 ° F) to about 210 ° C, about 160 ° C to about 205 ° C (about 400 ° F), about 160 ° C to about 199 ° C, about 160 ° C to about 193 ° C About 160 ° C to about 188 ° C, about 160 ° C to about 182 ° C, about 166 ° C (about 330 ° F) to about 210 ° C, about 166 ° C to about 205 ° C, about 166 ° C to about 199 ° C, about 166 ° C To about 193 ° C, about 166 ° C to about 188 ° C, about 166 ° C to about 182 ° C, about 171 ° C (about 340 ° F) to about 210 ° C, about 171 ° C to about 205 ° C, about 171 ° C to about 199 ° C. About 171 ° C to about 193 ° C, about 171 ° C to about 188 ° C, about 171 ° C to about 182 ° C, about 177 ° C (about 350 ° F) to about 210 ° C, about 177 ° C to about 205 ° C, about 177 ° C It can be pregelatinized and acid modified in an extruder having a temperature die of from about 199 ° C, from about 177 ° C to about 193 ° C, from about 177 ° C to about 188 ° C, or from about 177 ° C to about 182 ° C. The extruder die can be at any sufficient temperature, as described herein, but the die temperature generally exceeds the melting temperature of the starch crystals.

  The degree of gelatinization can be any suitable amount, for example about 70% or more, such as about 75% or more, about 80% or more, about 85% or more, about 90% or more, about 95% or more, about 97%. Above, it can be about 99% or more or complete (100%) gelatinization. In the case of making wallboard as described below, starch with such a lower degree of gelatinization is added to the stucco slurry to cause further gelatinization (eg up to 100%) in an oven, for example. Can do.

  The pressure in the extruder can be at any suitable level that will provide the appropriate 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 and will be recognized by those skilled in the art. For example, the pressure in the extruder can be about 2,000 psi (about 13,800 kPa) or more, such as about 2,250 psi (about 15,500 kPa) or more, about 2,500 psi (about 17,200 kPa) or more, about 2,750 psi (about 19,000 kPa) or more, about 3,000 psi (about 20,650 kPa) or more, about 3,500 psi (about 24,100 kPa) or more, about 4,000 psi (about 27,600 kPa) or more, or about 4 , 500 psi (about 31,000 kPa) or more. In some embodiments, the pressure can be from about 2,000 psi to about 5,000 psi (34,500 kPa), such as from about 2,000 psi to about 4,500 psi, from about 2,000 psi to about 4,4. 000 psi, about 2,000 psi to about 3,500 psi, about 2,000 psi to about 3,000 psi, about 2,000 psi to about 2,500 psi, about 2,500 psi to about 5,000 psi, about 2,500 psi to about 4, 500 psi, about 2,500 psi to about 4,000 psi, about 2,500 psi to about 3,500 psi, about 2,500 psi to about 3,000 psi, about 3,000 psi to about 5,000 psi, about 3,000 psi to about 4,500 500 psi, about 3,000 psi to about 4,000 psi, about 3,000 psi to about 3 500 psi, about 3,500psi~ about 5,000 psi, about 4,000psi~ about 5,000 psi, it is possible about 4,000psi~ about 4,500 psi, or from about 4,500psi~ about 5,000 psi.

  Surprisingly and unexpectedly, the process of the present invention for preparing pregelatinized partially hydrolyzed starch in one step in an extruder is considerably faster than pregelatinizing and partially hydrolyzing starch in two successive steps. Has been found. By using the present invention, significantly higher amounts of pregelatinized partially hydrolyzed starch can be prepared than starch prepared using any other method. Higher production and higher production rates are due to high reaction rates at high temperatures and / or high pressures. 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, Occurs in less than 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. Further, in some embodiments, pregelatinization and acid modification occur in the extruder at a rate limited by any two of the aforementioned time points. For example, the pregelatinization and acid modification rate can be from about 10 seconds to about 5 minutes, such as 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 to about 90 seconds, about 10 seconds to about 75 seconds, about 10 seconds to about 1 minute, about 10 seconds to about 45 seconds, about 10 seconds to about 30 seconds, about 10 seconds to about 25 seconds, about 10 seconds to about 20 seconds Or about 10 seconds to about 15 seconds.

  The process of the present invention for preparing pregelatinized partially hydrolyzed starch can be a continuous process occurring at any sufficient rate. In some embodiments, the starch is pregelatinized and acid-modified in the extruder at a production rate of about 100 kg / hour or more, such as about 150 kg / hour or more, about 200 kg / hour or more, about 250 kg / hour or more. About 300 kg / hour or more, about 350 kg / hour or more, about 400 kg / hour or more, about 450 kg / hour or more, 500 kg / hour, about 550 kg / hour or more, for example, about 600 kg / hour or more, about 650 kg / hour or more, about 700 kg / Hour or more, about 750 kg / hour or more, about 800 kg / hour or more, about 850 kg / hour or more, about 900 kg / hour or more, about 950 kg / hour or more, about 1,000 kg / hour or more, about 1,050 kg / hour or more, About 1,100 kg / hour or more, about 1,150 kg / hour or more, about 1,200 kg / hour or more, about 1,250 kg / hour or more, about 1,300 k / Hour or more, about 1,350Kg / hour or more, about 1,400 kg / hour or more, about 1,450Kg / hour or more, or gelatinized and acid modified with from about 1,500 kg / hr or more production speed. Further, in some embodiments, the production rate can be limited by any two of the aforementioned speed points. For example, the production rate is about 100 kg / hour to about 1,500 kg / hour (eg, about 100 kg / hour to about 1,500 kg / hour, about 100 kg / hour to about 1,000 kg / hour, about 250 kg / hour to about 1 500 kg / hour, about 250 kg / hour to about 1,000 kg / hour, about 600 kg / hour to about 1,250 kg / hour, about 650 kg / hour to about 1,200 kg / hour, about 700 kg / hour to about 1,100 kg / Hour, such as about 750 kg / hour to about 1,000 kg / hour).

  In some embodiments, the inventors have found that the conditions in the extruder (eg, high temperature and high pressure) make a particular contribution to the efficient and sufficient starch alphalation and acid modification in one step. . Mixing wet starch in an extruder creates very high friction, which generates heat. Since the space between the screw and the chamber in the extruder is very small, shear force is created by the screw in the extruder. Specific mechanical energy (SME) represents the mechanical energy per unit mass of an object. SME will depend on water content. As the moisture content increases (eg due to fluidity), the viscosity and friction will decrease, and thus the SME will decrease. If more moisture is present, the SME will be smaller due to lower viscosity and friction. The moisture content in the wet starch precursor of the present invention described herein provides an efficient SME.

  Within the extruder, starch is pregelatinized with high efficiency due to the conditions provided by the embodiments of the invention described herein. While not wishing to be bound by any particular theory, good mixing in an extruder according to some embodiments of the present invention requires the water required for the reaction in the extruder. Is considered to be smaller. Since the water content is very low, the concentration of reactants tends to increase, and the chemical reaction rate can be accelerated. The high temperature of the extruder also significantly accelerates the reaction rate. As the starch exits the extruder, the reaction occurs so that the starch is pregelatinized and partially hydrolyzed.

  In conventional acid modification, starch is added into a strong acid solution. This conventional method, as described herein, is significantly more water than the surprising and unexpected method of simultaneously starch pregelatinization and acid modification in one step rather than continuously. And acid. Conventional acid modification takes several hours. After the reaction takes place, it is necessary to neutralize the acid, purify and wash away. The neutralization and purification steps are time consuming and costly.

  Until the inventors' surprising and unexpected discovery, it was considered undesirable in conventional acid modifications to use weak acids or small amounts of strong acids that do not substantially chelate calcium ions. This is because, in the conventional method, if the acid becomes weak or the amount of strong acid decreases, it takes a long time for the acid modification. Thus, conventional acid modifications have shown large amounts of strong acids (eg, having a pKa of less than about -1.7). Surprisingly and unexpectedly, when preparing pregelatinized partially hydrolyzed starch in an extruder using a weak acid or a small amount of strong acid as described herein in accordance with an embodiment of the present invention, a neutralization step and There is no need for a purification step. This is due to the mild acidic conditions and less interference with gypsum crystallization, respectively. In some embodiments, the acid can still be present in the pregelatinized partially hydrolyzed starch.

Starch Properties and Advantages of Using Starch in Gypsum Board Starch prepared in an extruder according to embodiments of the present invention can be any pregelatinized partially hydrolyzed starch. In some embodiments, the starch can be prepared to have a variety of desired properties as described herein (eg, moderate viscosity, cold water solubility, cold water viscosity, etc.).

  Pregelatinized partially hydrolyzed starch prepared in an extruder according to embodiments of the present invention can be suitable for use in gypsum board. For use in gypsum board, for example, pregelatinization and acid modification are advantageous, for example for strength purposes, by obtaining the desired viscosity (and hence molecular weight range) according to the embodiments of the invention described herein. is there. In the method of making wallboard discussed herein, the starch placed in the stucco slurry can be gelatinized by about 70% or more, such as about 75% or more gelatinization, about 80% or more gelatinization, about It can be 85% or more gelatinized, about 90% or more gelatinized, about 95% or more gelatinized, about 97% or more gelatinized, or about 100% gelatinized (ie, fully gelatinized).

  Further, in accordance with an embodiment of the present invention, as described herein, a wet starch containing a weak acid that does not substantially chelate calcium ions is fed to the extruder so that the desired viscosity is obtained, ie The starch is hydrolyzed to show that the desired molecular weight range has been obtained. Therefore, as will be appreciated by those skilled in the art, viscosity indicates the molecular weight of pregelatinized partially hydrolyzed starch.

  In some embodiments, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can be prepared to have any suitable viscosity. In some embodiments, the pregelatinized partially hydrolyzed starch is a condition of the VMA process when the pregelatinized partially hydrolyzed starch is in water in an amount of 15% by weight of the total weight of the pregelatinized partially hydrolyzed starch and water. The viscosity is characterized as having a “moderate” viscosity (ie, having a viscosity of about 20 centipoise to about 700 centipoise). Therefore, the VMA method is used to determine whether pregelatinized partially hydrolyzed starch exhibits moderate viscosity characteristics when subjected to VMA method conditions. This does not mean that the pregelatinized partially hydrolyzed starch must be added to the gypsum slurry under these conditions. Rather, when the pregelatinized partially hydrolyzed starch is added to the slurry, the starch can be in wet form (various concentrations of starch in water) or dry form, and as described herein, completely It need not be gelatinized or otherwise need not be under the conditions described in the VMA method.

  In some embodiments, the moderate viscosity of pregelatinized starch can be from about 20 centipoise to about 700 centipoise, such as from about 20 centipoise to about 500 centipoise, from about 30 centipoise to about 200 centipoise, or about It can be from 100 centipoise to about 700 centipoise. In embodiments of the present invention, the viscosity of pregelatinized starch when tested under the VMA method can be, for example, as listed in Tables 1A, 1B and 1C below. In the table, “X” represents a range from “about [corresponding value in the top row] to about [corresponding value in the leftmost column]”. The value shown represents the viscosity of pregelatinized starch in centipoise units. It will be understood that each value is represented by “about” for ease of presentation. For example, the first “X” in Table 1A ranges from “about 20 centipoise to about 25 centipoise”.

  Thus, the viscosity of pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can have a range that includes between and includes any of the aforementioned endpoints listed in Tables 1A, 1B, or 1C. Alternatively, in some embodiments, the pregelatinized partially hydrolyzed starch has a viscosity (10% solids, 93%) of from about 5 Brabender Units (BU) to about 33 BU, measured according to the Brabender method described herein. ° C), for example, having a viscosity of about 10 BU to about 30 BU, about 12 BU to about 25 BU, or about 15 BU to about 20 BU.

  In some embodiments, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention provides an advantageous advantage to the strength of products (eg, wallboard) in which pregelatinized partially hydrolyzed starch is used. be able to. Starch contains a glucose monomer containing three hydroxyl groups, thus providing multiple sites for hydrogen bonding to gypsum crystals. While not wishing to be bound by any particular theory, the molecular size of pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention provides optimal starch molecule mobility and Are aligned with gypsum crystals, promoting good bonding of starch molecules and gypsum crystals, and the resulting crystalline gypsum matrix is believed to be hardened, for example, by hydrogen bonding.

  Conventional pregelatinized starches prepared according to methods other than those described herein, for example, having moderate viscosity, have longer chain lengths and higher molecular weights (too high viscosity) and shorter chain lengths. And low molecular weight (viscosity too low), each not providing the same combination of benefits. In terms of starch efficiency, if the starch molecule is sufficiently bound to the gypsum crystals, the additional starch has a significant advantage because the gypsum crystals are already bound so that there are no additional gypsum crystal sites to which the starch molecules adhere or bind. It is also thought that it will not help. Thus, the optimal bond between pregelatinized partially hydrolyzed starch molecules and gypsum crystals prepared according to embodiments of the present invention improves the strength of the crystalline gypsum matrix and the starch required to enhance this strength is conventionally Less compared to starch. In some embodiments, for example, dissolved starch molecules having moderate viscosity (indicating moderate starch molecular weight) provide optimal mobility of the starch molecules, and the starch molecules align with the gypsum crystals; The inventors have found that good hydrogen bonding between starch molecules and gypsum crystals is promoted and core strength is promoted.

  The pregelatinized partially hydrolyzed starch prepared according to some embodiments of the present invention also provides advantages with respect to water requirements in some embodiments. Adding conventional pregelatinized starch to the gypsum slurry requires that additional water be added to the gypsum slurry in order to maintain the desired degree of slurry fluidity. This is because conventional pregelatinized starch increases the viscosity of the gypsum slurry and decreases flowability. Thus, the use of starch in conventional systems resulted in an increase in water requirements such that more excess water was needed in the gypsum slurry.

  Surprisingly and unexpectedly, pregelatinized partially hydrolyzed starches that are prepared according to embodiments of the present invention, particularly with the desired moderate viscosity, require less water, especially compared to conventional starches. Thus, the impact on the water requirement in the gypsum slurry is reduced. Furthermore, due to the efficiency of pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention such that less starch can be used, according to some embodiments of the present invention, The positive effect can be even more significant. This smaller water requirement provides considerable efficiency during manufacture. For example, excess water requires energy input to dry. The speed of the line must be slow to accommodate the drying. Therefore, reducing the amount of water input in the gypsum slurry not only increases production speed, but also reduces energy resources and costs. In some embodiments, the increase in water requirement in the gypsum slurry is required by other starches, such as pregelatinized starch with a viscosity greater than 700 centipoise (eg, about 773 centipoise) prepared by different methods, for example. Less than the required increase in water requirements.

  In the preparation of pregelatinized partially hydrolyzed starch, any suitable non-pregelatinized starch can be selected provided it is fully pregelatinized and acid modified in the extruder. As used herein, “starch” refers to a composition that includes a starch component. Thus, the starch can be 100% pure starch, or other ingredients such as those commonly found in flour, such as protein and fiber, if the starch component constitutes about 75% or more by weight of the starch composition. You may have a component. The starch can be in the form of starch-containing flour (eg, corn flour), such as greater than about 75% by weight of the flour, such as greater than about 80%, greater than about 85%, greater than about 90%, greater than about 95%, etc. Or flour with a starch. For example, but not limited to, starch can be in the form of corn flour containing starch.

  In some embodiments, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can be prepared to have a desired cold water solubility. Conventional pregelatinization techniques involve making the starch soluble in cold water and generally require heat treating the starch in an excess amount of water. However, these prior art techniques are not efficient. Extrusion combines heating and mechanical shearing, but surprisingly and unexpectedly produces pregelatinized partially hydrolyzed starch with low water content and cold water solubility in accordance with embodiments of the present invention. It is an energy efficient method that can be used to do. Cold water solubility is defined as having an arbitrary amount of solubility in water at room temperature (about 25 ° C.). It has been discovered that starch that exhibits solubility in cold water can provide significant benefits to the strength of gypsum products (eg, wallboard). The cold water soluble starch of the present invention has a cold water solubility greater than about 30% and can increase the strength of the gypsum core when added to a hardened gypsum core. The solubility of pregelatinized starch in water is defined as the amount of starch soluble in room temperature water divided by the total amount of starch.

  In some embodiments, the cold water solubility of pregelatinized partially hydrolyzed starch prepared 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%. In embodiments of the invention, the cold water solubility of the extruded pregelatinized partially hydrolyzed starch can be, for example, as listed in Table 2. In the table, “X” represents a range from “about [corresponding value in the top row] to about [corresponding value in the leftmost column]”. The values shown represent the cold water solubility of extruded pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention (Table 2). It will be understood that each value is represented by “about” for ease of presentation. For example, the first “X” in Table 2 ranges from “about 30% to about 35%”. The range of the table includes the start point and the end point, and the start point and the end point.

  While not wishing to be bound by any particular theory, the combination of mechanical and thermal energy during extrusion is a measure of the cold water solubility of pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention. It is thought to be the cause. When starch undergoes extrusion, hydrogen bonds between starch molecules are believed to break. When the extruded starch dissolves in water, the starch forms hydrogen bonds with water molecules. After the pregelatinization process, the extruded pregelatinized partially hydrolyzed starch can freely hydrogen bond with the gypsum crystals, thus giving the gypsum product a higher strength. Therefore, less starch is required compared to conventional starch because starch showing solubility in cold water improves the strength of gypsum wallboard.

  In some embodiments, the pregelatinized partially hydrolyzed starch has a cold water viscosity (10% solids, 25 ° C.) of about 10 BU to about 120 BU, measured according to the Brabender method described herein, For example, it has a viscosity of 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.

Use of starch prepared according to the method in board making In some embodiments, the board (e.g., gypsum board) comprises at least about 8 wt% to about about wt. It can be made by forming a pregelatinized partially hydrolyzed starch by making a wet starch precursor having a water content of 25% by weight, where the acid is: a weak acid, starch that does not substantially chelate calcium ions Selected from strong acids in an amount up to about 0.01% by weight, or combinations thereof.

  The wet starch precursor is then fed to an extruder at a die temperature of about 150 ° C. (about 300 ° F.) to about 210 ° C. (about 410 ° F.) to alphalyze the wet starch and be at least partially hydrolyzed. Acid-modified. The pregelatinized partially hydrolyzed starch is then mixed with at least water and stucco to form a slurry and then disposed between the first cover sheet and the second cover sheet to form a wet assembly. The wet assembly is then cut into boards and dried. The hardened gypsum core of the board preferably has a higher compressive strength than the hardened gypsum core made with starch prepared in a different way.

  The pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can be surprisingly and unexpectedly contained in a relatively small amount (solid / solid basis) in the slurry and still board. A significant improvement in strength can be obtained. Thus, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention is an amount of about 0.1 wt% to about 10 wt%, such as about 0.5 wt% to about 10 wt%, based on the weight of stucco. In gypsum slurry.

  Increasing the amount of pregelatinized partially hydrolyzed starch according to embodiments of the present invention beyond these ranges in the slurry does not effectively improve strength. This is because, in some embodiments, the strength level can reach a certain degree to some extent as more starch is added. However, higher starch levels can be used if necessary, especially where diminishing returns in strength are allowed.

  In embodiments of the present invention, pregelatinized partially hydrolyzed starch can be added to the gypsum slurry in amounts such as those listed in Tables 3A and 3B below. In the table, “X” represents a range from “about [corresponding value in the top row] to about [corresponding value in the leftmost column]”. The value shown represents the amount of starch as a weight percent of stucco. It will be understood that each value is represented by “about” for ease of presentation. For example, the first “X” ranges from “about 0.1 wt% starch of stucco to about 0.25 wt% starch of stucco”.

  Accordingly, the amount of pregelatinized partially hydrolyzed starch added in accordance with an embodiment of the present invention added to the slurry has a range that includes between and includes any of the aforementioned endpoints listed in Tables 3A or 3B. Can do.

  The pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can be added to the slurry in combination with other starches in some embodiments of various applications. For example, in the case of the gypsum wallboard described below, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can be compared to other starches, especially if some increase in water requirements is acceptable. In combination, core strength and paper-core coupling can be improved.

  Thus, in some embodiments of the present invention, the gypsum slurry includes one or more pregelatinized partially hydrolyzed starches prepared according to embodiments of the present invention and one or more other types of starch. But you can. Other starches can include, for example, pregelatinized starch having a viscosity of less than 20 centipoise and / or greater than 700 centipoise. One example is pregelatinized corn starch (eg, having a viscosity of greater than 700 centipoise, about 773 centipoise). Other starches may be in the form of non-pregelatinized starch such as acid-modified starch and in the form of non-gelatinized alkylated starch such as ethylated starch. The starch combination may be pre-mixed (eg, in dry mix, optionally with other ingredients such as stucco, or other wet ingredients in wet mix) before adding to the gypsum slurry, or one of them. Each may be incorporated into the gypsum slurry, or any variation thereof. Pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention, and other starches may be included in any suitable ratio.

  For example, the starch content of pregelatinized partially hydrolyzed starch prepared in accordance with embodiments of the present invention can be a percentage of the total starch content added to the gypsum slurry, for example about 10% or more by weight, for example about 20% or more, about 30% or more, about 40% or more, about 50% or more, about 60% or more, about 70% or more, about 80% or more, about 90% or more, about 95% or more, about 99% or more, about It can be 100% or more, or any intermediate range. In some embodiments, the ratio of pregelatinized partially hydrolyzed starch to other starches prepared according to embodiments of the present invention is about 25:75, about 30:70, about 35:65, about 50:50. About 65:35, about 70:30, about 75:25, and the like.

  In some embodiments, in addition to the starch component, the slurry is formulated to include water, stucco, a foaming agent (sometimes simply referred to as “foam”), and other additives if desired. Is done. Surprisingly and unexpectedly, the same as in the case of no pregelatinized partially hydrolyzed starch prepared in an extruder according to embodiments of the present invention, according to some embodiments, particularly according to embodiments exhibiting moderate viscosity It has been found that the amount of water that needs to be added to maintain a level of slurry fluidity is less than the incremental amount of water required when using starch prepared according to different methods. Yes. The stucco can be in the form of alpha-type calcium sulfate hemihydrate, beta-type calcium sulfate hemihydrate and / or calcium sulfate anhydrate. The stucco can be fibrous or non-fibrous. A blowing agent can be incorporated to form a void distribution within the continuous crystalline matrix of hardened gypsum. In some embodiments, the blowing agent includes a major part of an unstable component and a minor part of a stable component (eg, a blend of unstable and stable / unstable). If). The weight ratio of the unstable component to the stable component is effective for forming a void distribution inside the hardened gypsum core. See, e.g., U.S. Patent Nos. 5,643,510, 6,342,284, and 6,632,550.

  It has been found that suitable gap distribution and wall thickness (independently) can be effective in increasing strength, particularly in lower density boards (eg, less than about 35 pcf). See, for example, US Patent Application Publication Nos. 2007/0048490 and 2008/0090068. The evaporating water gap generally has a gap of about 5 μm or less in diameter, and contributes to the total gap distribution together with the aforementioned gaps (bubbles). In some embodiments, the volume ratio of a gap having a pore size greater than about 5 microns to a gap having a pore size of about 5 microns or less is about 0.5: 1 to about 9: 1. For example, 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, about 0.7: 1 to about 4: 1, about 1.4: 1 to about 4: 1, about 1.8: 1 to about 4: 1, about 0.5: 1 to about 2.3: 1, 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 blowing agent is present in the slurry, for example, in an amount less than about 0.5% by weight of the stucco, such as from about 0.01% to about 0.5% by weight of the stucco, about 0%. 0.01 wt% to about 0.4 wt%, about 0.01 wt% to about 0.3 wt%, about 0.01 wt% to about 0.2 wt%, about 0.01 wt% to about 0.0 wt%. 1% by weight, about 0.02% to about 0.4%, about 0.02% to about 0.3%, about 0.02% to about 0.2%, etc. To do.

  Additives such as accelerators (eg, wet gypsum accelerators, heat resistance accelerators, environmental stability accelerators) and retarders are well known and can be included in some embodiments. See, for example, U.S. Pat. Nos. 3,573,947 and 6,409,825. In some embodiments where accelerators and / or retarders are included, the accelerators and / or retarders are each on a solids basis, for example, from about 0% to about 10% (eg, about 0.1% by weight of stucco). % To about 10%) in the gypsum slurry, for example from about 0% to about 5% (eg about 0.1% to about 5%) of the stucco in the gypsum slurry. Can exist. If desired, other additives may be incorporated, for example to give strength and allow for low weight products with sufficient strength, to prevent permanent distortion, eg products on a conveyor down the production line The green strength may be increased when there is water, fire resistance may be improved, water resistance may be improved, and the like.

  For example, the slurry can optionally include one or more dispersants in some embodiments to improve fluidity. The dispersant may be in dry form with other dry ingredients and / or in liquid form with other liquid ingredients, such as pregelatinized partially hydrolyzed starch and other ingredients prepared according to embodiments of the present invention. May be included. Examples of dispersants include, for example, naphthalene sulfonic acids such as polynaphthalene sulfonic acid and its salts (polynaphthalene sulfonate) and derivatives that are condensation products of naphthalene sulfonic acid and formaldehyde; and polycarboxylic acid ethers and the like. Carboxylate dispersants such as PCE211, PCE111, 1641, 1641F, or PCE2641 type dispersants such as MELFLUX 2641F, MELFLUX 2651F, MELFLUX 1641F, MELFLUX 2500L dispersant (BASF), and Coatex, Inc. COATEX Ethacryl M available from: and / or lignosulfonates or sulfonated lignins. Lignosulfonate is a water-soluble anionic polyelectrolyte polymer that is a by-product from wood pulp production using sulfite pulping. One example of a lignin useful in practicing the principles of embodiments of the present invention is Marasperse C-21, available from Reed Lignin Inc.

  Lower molecular weight dispersants are generally preferred. Lower molecular weight naphthalene sulfonic acid dispersants are preferred because they tend to require less water than higher viscosity, higher molecular weight dispersants. Accordingly, a molecular weight of about 3,000 to about 10,000 (eg, about 8,000 to about 10,000) is preferred. As another example for a PCE 211 type dispersant, in some embodiments, the molecular weight can be from about 20,000 to about 60,000, less than a dispersant having a molecular weight greater than 60,000. Indicates delay.

  One example of naphthalene sulfonate is DILOFLO, available from GEO Specialty Chemicals. DILOFLO is a 45% aqueous solution of naphthalene sulfonate, but other aqueous solutions with a solid content ranging from, for example, about 35% to about 55% by weight are readily available. The naphthalene sulfonate can be used in dry solid or powder form, such as LOMAL D available from GEO Specialty Chemicals. Another preferred naphthalene sulfonate salt is Hampshire Chemical Corp. DAXAD available from

  If a dispersant is included, the dispersant can be included in any suitable (solid / solid) amount, for example, in an amount of about 0.1 wt% to about 5 wt% based on the weight of the stucco. For example, 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.

  In some embodiments, if desired, one or more phosphoric acid-containing compounds may optionally be included in the slurry. For example, a phosphate-containing component useful in some embodiments includes a water-soluble component, and the phosphate-containing component is an ion, salt, or acid, i.e., a condensed phosphorus, each containing two or more phosphate units. Acid; in the form of condensed phosphate salts or ions each containing two or more phosphate units; and orthophosphate monobasic or monovalent ions, and water-soluble acyclic polyphosphates Can be. See, for example, U.S. Patent Nos. 6,342,284, 6,632,550, 6,815,049, and 6,822,033.

If a phosphate composition is added in some embodiments, the phosphate composition can improve green strength, resistance to permanent set (eg, sagging), dimensional stability, and the like. For example, trimetaphosphate compounds including sodium trimetaphosphate, potassium trimetaphosphate, lithium trimetaphosphate, and ammonium trimetaphosphate can be used. Sodium trimetaphosphate (STMP) is preferred, for example sodium tetrametaphosphate, having about 6 to about 27 phosphate repeating units and the molecular formula Na _{n + 2} P _n O _{3n + 1} where n = 6 to 27 Sodium hexametaphosphate having, tetrapotassium pyrophosphate having molecular formula K ₄ P ₂ O ₇ , tripotassium tripolyphosphate having molecular formula Na ₃ K ₂ P ₃ O ₁₀ , sodium tripolyphosphate having molecular formula Na ₅ P ₃ O ₁₀ , Tetrasodium pyrophosphate having molecular formula Na ₄ P ₂ O ₇ , aluminum trimetaphosphate having molecular formula Al (PO ₃ ) ₃ , acidic sodium pyrophosphate having molecular formula Na ₂ H ₂ P ₂ O ₇ , 1,000 to 3,000 and molecular formula has a number of phosphate repeating units _{(NH 4) n + 2 P} n O _{n + 1} in (wherein, n = 1,000 to 3,000) ammonium polyphosphate having, or and molecular formula has two or more phosphate repeating units _{H n + 2 P n O 3n} + 1 ( wherein, n is 2 Other phosphates including polyphosphoric acid having the above may be suitable.

  In some embodiments, the phosphate can be included in a dry form or in water (eg, from about 5% to about 20% phosphate solution, such as about a 10% solution). When phosphate is included, the phosphate can 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 stucco. For example, from about 0.03% to about 0.4%, from about 0.1% to about 0.3%, or from about 0.12% to about 0.4%, based on the weight of the stucco % By weight.

  Additives suitable for fire-rated products and / or water-resistant products may optionally be included, such as siloxane (water resistant); fiber; aluminum trihydrate ( Endothermic additives such as ATH), magnesium hydroxide or the like; and / or highly expandable particles (eg, expandable to about 300% or more of original volume when heated at 1560 ° F. for about 1 hour). Can be mentioned. For a description of these and other components, see, for example, co-pending U.S. Application No. 13 / 400,010 (filed February 17, 2012) by the same applicant. In some embodiments, high expansion vermiculite is included, but other refractory materials can be included. Some fire-rated product boards of the present invention have a thermal insulation index (TI) of about 17 minutes or more, such as about 20 minutes or more, about 30 minutes or more, about 45 minutes or more, about 60 minutes or more; and It may have a high temperature shrinkage in the xy direction of less than about 10% (at a temperature of about 1560 ° F. (850 ° C.)) and an expansion in the z direction of greater than about 20%. The fire-resistant or water-resistant additive can be contained in any suitable amount if desired, for example, depending on fire resistance evaluation. For example, when a fire or water resistant additive is included, the fire or water resistant additive can be in an amount of about 0.5% to about 10% by weight of the stucco, such as from about 1% to about 10 wt%, about 1 wt% to about 8 wt%, about 2 wt% to about 10 wt%, about 2 wt% to about 8 wt%, and the like.

  In some embodiments, when siloxane is included, it is preferred to add the siloxane in the form of an emulsion. The slurry is then shaped and dried under conditions that promote siloxane polymerization to form a highly crosslinked silicone resin. A catalyst can be added to the gypsum slurry that promotes the polymerization of the siloxane to form a highly crosslinked silicone resin. In some embodiments, a solvent-free methylhydrogen siloxane 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 liquid containing no water or solvent. In some embodiments, it is contemplated that from about 0.3% to about 1.0% BS 94 siloxane may be used, based on the weight of the dry ingredients. For example, in some embodiments, it is preferred to use about 0.4% to about 0.8% siloxane based on dry stucco weight.

  The slurry formulation can be made at any suitable water / stucco ratio, such as at a ratio of about 0.4 to about 1.3. However, pregelatinized partially hydrolyzed starches prepared according to embodiments of the present invention reduce the amount of water that needs to be added to the slurry in which they are placed, so in some embodiments other starches (e.g., different Compared to conventional pregelatinized starches prepared according to the process), this slurry has a particularly low weight with a lower water / stucco ratio input than the conventional ratio in gypsum slurries containing other starches. / The density can be blended. For example, in some embodiments, the water / stucco ratio is about 0.4 to about 1.1, about 0.4 to about 0.9, about 0.4 to about 0.85, 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, about 0.6 ~ 0.8 and so on.

  The cover sheet can be formed of any suitable material and basis weight. Advantageously, board cores formed from slurries containing pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention, in some embodiments, for example, less than 45 lbs / MSF (eg, about 33 lbs / MSF to 45 lbs / MSF) provides sufficient strength even in boards with lower basis weight cover sheets such as MSF) and is sufficient even for lower weight boards (eg having a density of about 35 pcf or less) I will provide a. However, in some embodiments, a heavier basis weight is used if desired, for example, to further improve nail pull resistance, or to improve hand feel, for example, desirable “feel” characteristics for the end user. Can be promoted.

  In some embodiments, one or both cover sheets can be formed from paper and, for example, about 45 lbs / in order to improve strength (eg, nail pull strength), especially with lower density boards. MSF or higher (eg, about 45 lbs / MSF to about 65 lbs / MSF, about 45 lbs / MSF to about 60 lbs / MSF, about 45 lbs / MSF to about 55 lbs / MSF, about 50 lbs / MSF to about 65 lbs / MSF, about 50 lbs / MSF to about 60 lbs / MSF, etc.). If desired, in some embodiments, a single cover sheet (eg, the “front” paper side when installed) has a higher basis weight as described above, eg, nail resistance and The touch can be improved and other cover sheets (eg, “back” sheets when the board is installed) can have a somewhat lower basis weight if desired (eg, less than about 45 lbs / MSF). Basis weight, such as about 33 lbs / MSF to 45 lbs / MSF, or about 33 lbs / MSF to about 40 lbs / MSF).

  Board weight is a function of thickness. Board density is used herein as a measure of board weight because boards are typically made with various thicknesses. The benefits of pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can be seen over a variety of board densities, such as about 40 pcf or less, such as from about 20 pcf to about 40 pcf, about 24 pcf to About 37 pcf. However, preferred embodiments of the present invention have particular utility at low density and are prepared according to different methods due to the enhanced strength provided by pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention. This advantageously allows the use of lower weight boards that have superior strength and less water requirements than boards made from other starches.

  For example, in some embodiments, the board density can be about 20 pcf to about 35 pcf, such as about 20 pcf to about 34 pcf, about 20 pcf to about 33 pcf, about 20 pcf to about 32 pcf, about 20 pcf to about 31 pcf, About 20 pcf to about 30 pcf, about 20 pcf to about 29 pcf, about 21 pcf to about 35 pcf, about 21 pcf to about 34 pcf, about 21 pcf to about 33 pcf, about 21 pcf to about 32 pcf, about 21 pcf to about 31 pcf, about 21 pcf to about 30 pcf, about 21 pcf About 29 pcf, about 24 pcf to about 35 pcf, about 24 pcf to about 34 pcf, about 24 pcf to about 33 pcf, about 24 pcf to about 32 pcf, about 24 pcf to about 31 pcf, about 24 pcf to about 30 pcf, or about 24 pcf to about 29 pcf Rukoto can.

  Pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can be added to the slurry to enhance the strength of the product of the present invention, which can be particularly advantageous at lower weight / density. . For example, in some embodiments, a board made in accordance with an embodiment of the present invention has a compressive strength of about 400 psi (2,750 kPa) or greater at a density of 29 pcf when tested according to the method described in Example 4. Have Advantageously, in various embodiments at various board densities described herein, a board made by the method of the present invention is about 400 psi or more, such as about 450 psi (3,100 kPa) or more, about 500 psi ( 3,450 kPa) or more, about 550 psi (3,800 kPa) or more, about 600 psi (4,100 kPa) or more, about 650 psi (4,500 kPa) or more, about 700 psi (4,800 kPa) or more, about 750 psi (5,200 kPa) or more Compression of about 800 psi (5,500 kPa), about 850 psi (5,850 kPa), about 900 psi (6,200 kPa), about 950 psi (6,550 kPa), or about 1,000 psi (6,900 kPa) Can be prepared to have strength Kill. Further, in some embodiments, the compressive strength can be limited by any two of the aforementioned strength points. For example, the compressive strength can be about 450 psi to about 1,000 psi (eg, about 500 psi to about 900 psi, about 600 psi to about 800 psi, etc.).

  In some embodiments, a board made in accordance with the present invention meets ASTM standard C473-10 test protocol. For example, in some embodiments, if the board is molded with a thickness of 1/2 inch, the board has a nail pull resistance of greater than about 65 lb, as measured according to ASTM C473-10, such as about 68 lb. As described above, it has nail pulling resistance such as about 70 lb or more, about 72 lb or more, about 75 lb or more, about 77 lb or more. In various embodiments, the nail pull resistance can be about 68 lb to about 100 lb, such as about 68 lb to about 95 lb, about 68 lb to about 90 lb, about 68 lb to about 85 lb, about 68 lb to about 80 lb, about 68 lb. To about 77 lb, about 68 lb to about 75 lb, about 68 lb to about 72 lb, about 68 lb to about 70 lb, about 70 lb to about 100 lb, about 70 lb to about 95 lb, about 70 lb to about 90 lb, about 70 lb to about 85 lb, about 70 lb to about 80 lb, about 70 lb to about 77 lb, about 70 lb to about 75 lb, about 70 lb to about 72 lb, about 72 lb to about 100 lb, about 72 lb to about 95 lb, about 72 lb to about 90 lb, about 72 lb to about 85 lb, about 72 lb to about 80 lb, About 72 lb to about 77 lb, about 72 lb to about 75 lb, about 75 lb to about 100 b, about 75 lb to about 95 lb, about 75 lb to about 90 lb, about 75 lb to about 85 lb, about 75 lb to about 80 lb, about 75 lb to about 77 lb, about 77 lb to about 100 lb, about 77 lb to about 95 lb, about 77 lb to about 90 lb, It can be from about 77 lb to about 85 lb, or from about 77 lb to about 80 lb.

  With respect to flexural strength, in some embodiments, when molded with a 1/2 inch thick board, the board is about 36 lb or more in length (e.g., about 38 lb or more, as measured according to ASTM standard C473). , And / or a bending strength of about 107 lb or more (for example, about 110 lb or more, about 112 lb or more) in the width direction. In various embodiments, the board can have a bending strength in the longitudinal direction of about 36 lb to about 60 lb, such as about 36 lb to about 55 lb, about 36 lb to about 50 lb, about 36 lb to about 45 lb, about 36 lb. About 40 lb, about 36 lb to about 38 lb, about 38 lb to about 60 lb, about 38 lb to about 55 lb, about 38 lb to about 50 lb, about 38 lb to about 45 lb, about 38 lb to about 40 lb, about 40 lb to about 60 lb, about 40 lb to about It can have a bending strength in the longitudinal direction of 55 lb, about 40 lb to about 50 lb, or about 40 lb to about 45 lb. In various embodiments, the board can have a bending strength in the width direction of about 107 lb to about 130 lb, such as about 107 lb to about 125 lb, about 107 lb to about 120 lb, about 107 lb to about 115 lb, about 107 lb to about 107 lb. About 112 lb, about 107 lb to about 110 lb, about 110 lb to about 130 lb, about 110 lb to about 125 lb, about 110 lb to about 120 lb, about 110 lb to about 115 lb, about 110 lb to about 112 lb, about 112 lb to about 130 lb, about 112 lb to about 125 lb , About 112 lb to about 120 lb, or about 112 lb to about 115 lb in the width direction.

  Further, in some embodiments, the board can have an average core hardness of greater than or equal to about 11 lb when measured in accordance with ASTM C473-10, such as greater than or equal to about 12 lb, greater than or equal to about 13 lb, greater than or equal to about 14 lb, about 15 lb. The average core hardness may be about 16 lb or more, about 17 lb or more, about 18 lb or more, about 19 lb or more, about 20 lb or more, about 21 lb or more, or about 22 lb or more. In some embodiments, the board can have a core hardness of about 11 lb to about 25 lb, such as about 11 lb to about 22 lb, about 11 lb to about 21 lb, about 11 lb to about 20 lb, about 11 lb to about 19 lb, About 11 lb to about 18 lb, about 11 lb to about 17 lb, about 11 lb to about 16 lb, about 11 lb to about 15 lb, about 11 lb to about 14 lb, about 11 lb to about 13 lb, about 11 lb to about 12 lb, about 12 lb to about 25 lb, about 12 lb To about 22 lb, about 12 lb to about 21 lb, about 12 lb to about 20 lb, about 12 lb to about 19 lb, about 12 lb to about 18 lb, about 12 lb to about 17 lb, about 12 lb to about 16 lb, about 12 lb to about 15 lb, about 12 lb to about 14 lb, about 12 lb to about 13 lb, about 13 lb to about 25 lb, about 13 lb to about 22 b, about 13 lb to about 21 lb, about 13 lb to about 20 lb, about 13 lb to about 19 lb, about 13 lb to about 18 lb, about 13 lb to about 17 lb, about 13 lb to about 16 lb, about 13 lb to about 15 lb, about 13 lb to about 14 lb, About 14 lb to about 25 lb, about 14 lb to about 22 lb, about 14 lb to about 21 lb, about 14 lb to about 20 lb, about 14 lb to about 19 lb, about 14 lb to about 18 lb, about 14 lb to about 17 lb, about 14 lb to about 16 lb, about 14 lb About 15 lb, about 15 lb to about 25 lb, about 15 lb to about 22 lb, about 15 lb to about 21 lb, about 15 lb to about 20 lb, about 15 lb to about 19 lb, about 15 lb to about 18 lb, about 15 lb to about 17 lb, about 15 lb to about 16 lb, about 16 lb to about 25 lb, about 16 lb to about 22 lb, about 16 lb to 21 lb, about 16 lb to about 20 lb, about 16 lb to about 19 lb, about 16 lb to about 18 lb, about 16 lb to about 17 lb, about 17 lb to about 25 lb, about 17 lb to about 22 lb, about 17 lb to about 21 lb, about 17 lb to about 20 lb, About 17 lb to about 19 lb, about 17 lb to about 18 lb, about 18 lb to about 25 lb, about 18 lb to about 22 lb, about 18 lb to about 21 lb, about 18 lb to about 20 lb, about 18 lb to about 19 lb, about 19 lb to about 25 lb, about 19 lb The core can have a core hardness of about 22 lb, about 19 lb to about 21 lb, about 19 lb to about 20 lb, about 21 lb to about 25 lb, about 21 lb to about 22 lb, or about 22 lb to about 25 lb.

  Due at least in part to the moderate viscosity characteristics obtained in some embodiments of the present invention, these criteria (eg, nail pull resistance, flexural strength and core strength) are very low as described herein. Density boards (eg about 31 pcf or less) can also be adapted.

  Pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention has a temperature rising cure comparable to or exceeding the temperature rising cure (TRS) hydration rate of conventional pregelatinized starch prepared according to different methods. It has been found by the inventors that it exhibits a (TRS) hydration rate. The desired cure time may vary depending on the formulation, and the desired cure time can be determined by one skilled in the art depending on plant conditions and available raw materials.

  Products of embodiments of the present invention can be made on a typical production line. For example, board manufacturing techniques are described, for example, in US Pat. No. 7,364,676 and US Patent Application Publication No. 2010/0247937. Briefly, in the case of gypsum board, the process usually involves discharging the cover sheet onto a moving conveyor. Since the gypsum board is usually formed “front down”, in such an embodiment, the cover sheet is a “front” cover sheet.

  The dry component and / or wet component of the gypsum slurry is supplied to a mixer (eg, a pin mixer) and stirred to form a gypsum slurry. The mixer includes a body and a discharge conduit (eg, a gate-canister-boot arrangement known to those skilled in the art, or the arrangement described in US Pat. Nos. 6,494,609 and 6,874,930). . In some embodiments, the discharge conduit can include a slurry distributor with either one supply port or a plurality of supply ports, eg, US 2012/0168527 (A1) ( The slurry distributor etc. which are described in application number 13 / 341,016) and 2012/0170403 (A1) (application number 13 / 341,209) can be included. In those embodiments that use slurry distributors with multiple feed ports, the discharge conduit can include a suitable flow splitter, as described, for example, in US 2012/0170403 (A1). A flow splitter or the like. The blowing agent can be added to the mixer discharge conduit (eg, at the gate described in US Pat. Nos. 5,683,635 and 6,494,609) or to the body, if desired. The slurry containing the blowing agent that is discharged from the discharge conduit after all the ingredients have been added is the main gypsum slurry and forms the gypsum core. This board core slurry is discharged onto the moving front cover sheet.

  The front cover sheet may have a thin skim coat in the form of a relatively dense slurry layer. Also, as known to those skilled in the art, the hard edge can be formed from the same slurry stream that forms the front skim coat. In embodiments where the foam enters the discharge conduit, the second gypsum slurry stream can be removed from the mixer body to form a dense skim coat slurry, which can then be used as known to those skilled in the art. A surface skim coat and a hard edge can be formed. If a front skim coat and hard edge are included, the front skim coat and hard edge are usually placed before moving the core slurry onto the moving front cover sheet, usually upstream of the mixer. After being discharged from the discharge conduit, the core slurry is spread on a front cover sheet (optionally with a skim coat) as needed and covered with a second cover sheet (usually a “back” cover sheet) to form a sandwich structure Forming a wet assembly. This is the board precursor of the final product. The second cover sheet may optionally have a second skim coat, the second skim coat being formed from a second (dense) gypsum slurry that is the same as or different from the front skim coat, if present. Can be made. The cover sheet may be formed from paper, fiber mat, or other types of materials (eg, foil, plastic, glass mat, non-woven material such as a blend of cellulose filler and inorganic filler, etc.).

  The wet assembly provided thereby is transported to the molding site where the product is sized to the desired thickness (eg, by a molding plate) and transported to one or more knife cutting areas where the product is Cut to length. The wet assembly is cured to form a connected crystal matrix of hardened gypsum, and excess water is removed using a drying process (eg, by moving the assembly through a furnace). Surprisingly and unexpectedly, boards prepared according to the present invention using pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention are required in the drying process due to the low water requirement characteristics of starch. It has been found that the time to be significantly less. This is advantageous because energy costs are reduced.

  It is also common to use vibration in the production of gypsum board to remove large gaps or air pockets from the placed slurry. Each of the above steps, as well as processes and apparatus for performing such steps, are known to those skilled in the art.

  The pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention is, for example, gypsum wallboard, acoustic (eg ceiling) tiles, joint compounds, gypsum-cellulose fiber products such as gypsum-xylem fiber wallboard, and the like It can be used in formulating various products such as In some embodiments, such products can be formed from the slurry of embodiments of the present invention.

  Thus, pregelatinized partially hydrolyzed starch prepared in an extruder according to embodiments of the present invention is advantageous in products other than paper surface gypsum board in embodiments of the present invention, as described herein. Can have an effect. For example, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention can be used in mat surface products (eg, textiles) where the board cover sheet is in the form of a fiber mat. The mat can optionally have a topcoat to reduce water permeability. Other ingredients that can be included in the preparation of such matte surface products, as well as fiber mat materials and manufacturing methods are discussed, for example, in US Pat. No. 8,070,895, and US Patent Application Publication No. 2009/0247937. ing.

  In addition, gypsum-cellulose products include cellulose host particles (eg, wood fibers), gypsum, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention, and other ingredients (eg, siloxanes, etc.) if desired. Water-resistant additives). Other components and production methods are described in, for example, U.S. Pat. Nos. 4,328,178, 4,239,716, 4,392,896, 4,645,548, 5, 320, 677, 5,817,262, and 7,413,603.

Illustrative Embodiments In one embodiment, a method of making pregelatinized partially hydrolyzed starch comprises: (a) mixing at least water, non-pregelatinized starch, and a weak acid that does not substantially chelate calcium ions; Making a wet starch precursor having a moisture content of about 8 wt% to about 25 wt%; (b) feeding the wet starch precursor to an extruder; and (c) the wet starch precursor. Alphating and acid modification in the above extruder at a die temperature of about 150 ° C. (about 300 ° F.) to about 210 ° C. (about 410 ° F.).

  In another embodiment, the pressure inside the extruder is about 2,000 psi or greater.

  In another embodiment, the pregelatinized partially hydrolyzed starch has a cold water solubility greater than about 50%.

  In another embodiment, the pregelatinized partially hydrolyzed starch has a cold water viscosity (10% solids, 25 ° C.) of about 10 Brabender Units (BU) to about 120 BU.

  In another embodiment, the pregelatinized partially hydrolyzed starch has a viscosity characteristic of about 20 centipoise to about 700 centipoise when the viscosity is measured while subjecting the starch to the conditions of the VMA method.

  In another embodiment, the pregelatinized partially hydrolyzed starch has a viscosity (10% solids, 93 ° C.) of about 5 BU to about 33 BU.

  In another embodiment, the weak acid that does not substantially chelate calcium ions comprises alum.

  In another embodiment, tartaric acid is included during mixing to form a wet starch precursor.

  In another embodiment, the weak acid that does not substantially chelate calcium ions is in an amount of about 0.5% to about 5% by weight of the starch.

  In another embodiment, the wet starch has a moisture content of about 10% to about 20% by weight of the weight of the starch precursor.

  In another embodiment, pregelatinization and acid modification occur in the extruder at a die temperature of about 175 ° C. (about 350 ° F.) or higher to about 205 ° C. (about 400 ° F.).

  In another embodiment, the production of pregelatinized partially hydrolyzed starch in the extruder is about 100 kg / hr or more.

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

  In another embodiment, pregelatinization and acid modification occur in less than about 1 minute.

  In another embodiment, the method does not include a purification step for pregelatinized partially hydrolyzed starch.

  In another embodiment, the method does not include a neutralization step for pregelatinized partially hydrolyzed starch.

  In another embodiment, the pregelatinized partially hydrolyzed starch is about 70% or more gelatinized.

  In another embodiment, pregelatinized partially hydrolyzed starch is prepared according to an embodiment of the present invention.

  In another embodiment, the method of making pregelatinized partially hydrolyzed starch comprises: (a) mixing at least water, non-pregelatinized starch, and strong acid to a moisture content of about 8 wt% to about 25 wt%. Producing a wet starch precursor having the strong acid in an amount of about 0.05% by weight or less of the weight of the starch; (b) an extruder for the wet starch And (c) pregelatinizing and acidifying the wet starch at a die temperature of about 150 ° C. (about 300 ° F.) to about 210 ° C. (about 410 ° F.). Including denaturation.

  In another embodiment, the method of making pregelatinized partially hydrolyzed starch comprises: (a) mixing at least water, non-pregelatinized starch, and strong acid to a moisture content of about 8 wt% to about 25 wt%. Making a wet starch precursor having the strong acid in an amount of about 0.01 wt% or less of the weight of the starch; (b) an extruder for the wet starch And (c) pregelatinizing and acidifying the wet starch at a die temperature of about 150 ° C. (about 300 ° F.) to about 210 ° C. (about 410 ° F.). Including denaturation.

  In another embodiment, the strong acid has a pKa of about −1.7 or less.

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

  In another embodiment, the method of making a board has a moisture content of about 8% to about 25% by weight of (a) (i) mixing at least water, non-pregelatinized starch, and acid. Forming a wet starch precursor, the acid comprising: (1) a weak acid that does not substantially chelate calcium ions; and (2) in an amount up to about 0.05% by weight of the weight of the starch. Forming a strong acid, or (3) selected from the group consisting of any combination thereof; (ii) feeding the wet starch precursor to the extruder; and (iii) the wet starch The pregelatinized partially hydrolyzed starch can be formed by alphalation and acid modification in the extruder described above having a die at a temperature of about 150 ° C (about 300 ° F) to about 210 ° C (about 410 ° F). And (b) mixing the pregelatinized 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. Forming a wet assembly; (d) cutting the wet assembly into a board; and (e) drying the board.

  In another embodiment, the strong acid is in an amount up to about 0.01% by weight of the starch.

  In another embodiment, the method of making the board comprises: (a) (i) mixing at least water, non-pregelatinized starch, and an acid that does not substantially chelate calcium ions to about 8 wt% to Making a wet starch precursor having a moisture content of about 25% by weight; (ii) feeding the wet starch precursor to an extruder; and (iii) adding the wet starch to about 150 ° C. (about Forming a pregelatinized partially hydrolyzed starch by pregelatinizing and acid-modifying with an extruder as described above having a die at a temperature of from 300 ° F to about 210 ° C (about 410 ° F); (b) Mixing pregelatinized partially hydrolyzed starch with at least water and stucco to form a slurry; (c) adding the slurry between the first cover sheet and the second cover sheet; Placing the wet assembly into a board; (d) cutting the wet assembly into a board; and (e) drying the board.

  In another embodiment, the board making method has a moisture content of about 8% to about 25% by weight of (a) (i) mixing at least water, non-pregelatinized starch, and strong acid. Making a wet starch precursor, wherein the strong acid is in an amount of about 0.05% or less by weight of the starch; (ii) the wet starch precursor is an extruder And (iii) pregelatinizing the wet starch with the extruder having a die at a temperature of about 150 ° C. (about 300 ° F.) to about 210 ° C. (about 410 ° F.); Acid modifying; (b) mixing pregelatinized 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. do it Forming a wet assembly; (d) cutting the wet assembly into a board; and (e) drying the board.

  In another embodiment, the strong acid is in an amount up to about 0.01% by weight of the starch.

  In another embodiment, the hardened gypsum core has a greater compressive strength than a hardened gypsum core made with starch prepared by a different method.

  In another embodiment, the pregelatinized partially hydrolyzed starch is about 70% or more gelatinized when added to the slurry, and further gelatinization occurs during the drying process.

  In another embodiment, the pregelatinized partially hydrolyzed starch is fully gelatinized when added to the slurry.

  In another embodiment, the board has a compressive strength of at least about 400 psi (2,800 kPa) at a density of 29 pcf.

  In another embodiment, the board has a core hardness of about 11 or greater when measured according to ASTM C473-10.

  In another embodiment, the board has a density of about 21 pcf to about 35 pcf.

  In another embodiment, the slurry further comprises sodium trimetaphosphate.

  In another embodiment, the amount of water that needs to be added to maintain the same level of slurry fluidity as without the pregelatinized partially hydrolyzed starch is the pregelatinized partially hydrolyzed starch prepared according to a different method. Less than the incremental amount of water required when used.

  In another embodiment, the starch is in an amount of about 0.5% to about 10% by weight based on the weight of the stucco.

  In another embodiment, the wallboard is prepared according to an embodiment of the present invention.

  It should be noted that the foregoing is merely an example of an embodiment. Other preferred embodiments will be apparent from the entire description herein. It will also be appreciated by those skilled in the art that each of these embodiments may be used in various combinations with the other embodiments provided herein.

  The following examples are further illustrative of the present invention, but, of course, should not be construed as limiting its scope in any way.

Example 1
This example illustrates the preparation of pregelatinized partially hydrolyzed starch according to an embodiment of the present invention.

  Nine pregelatinized partially hydrolyzed starches prepared according to embodiments of the present invention were prepared for various tests of specific properties (eg, viscosity, flowability, strength). These nine starches of the present invention were tested with three commercially available starches.

  In accordance with the method of the present invention for preparing pregelatinized partially hydrolyzed starch, a wet starch precursor is obtained from Bunge North America (St. Louis, Mo.) as a CCM 260 yellow corn meal in an amount of 100 kg of germ-free corn flour, Prepared by mixing different amounts of aluminum sulfate (alum), weak acid and / or tartaric acid (less than 20% by weight of total weak acid) that does not substantially chelate calcium ions, and different amounts of water. The wet starch precursor was fed into a single screw extruder, commercially available as Advantage 50 from American Extension International (South Beloit, Ill.). In the extruder, the wet starch precursor was alpha and acid modified in one step so that alpha and acid modification occur simultaneously.

  Table 4 below lists the extrusion parameters for corn flour in the presence of acid. Extrusion residence time (ie time for pregelatinization and acid modification) was less than 30 seconds. All percentages are based on the total weight of the starch, while moisture is based on the total wet weight expressed as the sum of water, starch and other additives.

  The resulting pregelatinized partially hydrolyzed starch is a conventional pregelatinized corn starch having a viscosity of 773 centipoise (referred to as composition 1A (for comparison)), and Clinton 277 (ADM, Chicago, Ill.) And Caliber 159 (Cargill) As a control, two low water requirement starches (referred to as Composition 1B (comparative) and Composition 1C (comparative), respectively) prepared by extrusion of acid-modified corn starch commercially available as Weisata, Minnesota) evaluated.

  Pregelatinized partially hydrolyzed starch, referred to as Compositions 1D-1L, was made by an extrusion process.

  Table 5 below details the various moisture contents during extrusion and the acid contents during extrusion for compositions 1D-1L. Compositions 1D-1H and 1L were prepared with a moisture content of 16% by weight, and compositions 1I and 1K were prepared with a moisture content of 13% by weight. Compositions 1D to 1G and Compositions 1I to 1L were prepared using an alum solution in an amount of 1% to 4% by weight, and composition 1H contained an alum solution and tartaric acid. Compositions 1F and 1L were prepared using the same moisture content and the same amount of acid, but in Example 3 have different amounts of retarder.

  Examples 2-4 below test the compositions described in Table 5 for various properties. In Example 2, Compositions 1B-1L were evaluated for viscosity in an amylograph test. Example 3 was tested for the fluidity of slurries prepared using one of Compositions 1A, 1D-1I and 1K-1L and evaluated by a slump test. This data was then further validated by measuring the 50% hydration time of the slurry. This reveals how long it takes for the slurry to cure. Example 4 was tested for the strength of slurries prepared using compositions 1A, 1D-1I and 1K and evaluated by the compressive strength test described herein.

Example 2
This example illustrates the viscosity of pregelatinized partially hydrolyzed starch prepared in an extruder according to an embodiment of the present invention. Compositions 1D-1K were tested with respect to how the viscosity changes, especially based on the amount of acid (eg, alum) and moisture content, compared to the extruded commercial acid-modified starch (Compositions 1B-1C). . The moisture content is defined by the moisture level of the wet starch fed through the extruder.

  In the test preparation, the composition was mixed with water to form a starch slurry such that the starch slurry contained the composition in an amount of 10% by weight. The term “solution” is used when the starch is fully gelatinized and completely dissolved, and the term “slurry” is used when the starch is not completely dissolved. Each composition was then tested for viscosity at different temperatures by the amylographic technique described herein. The test results are plotted in FIG. 1 and FIG. Figures 1 and 2 evaluate the viscosity at different temperatures of pregelatinized partially hydrolyzed starch by plotting viscosity (left y-axis) and temperature (right y-axis) against time (x-axis). It is an amylogram. A temperature curve is written over each sample. The same temperature profile was used for each sample. The other curve shows the viscosity of the starch.

  The initial viscosity at 25 ° C. was an indicator of the fluidity of the slurry system containing any one of the compositions 1B to 1K. 25 ° C. is the temperature at which starch is mixed with stucco and other ingredients to make a board. Furthermore, at this temperature, the viscosity of the starch has a negative correlation with the flowability of the stucco slurry.

  The viscosity in the trough (93 ° C.) is an index of the molecular weight of any one of the compositions 1B to 1K. At a temperature of 93 ° C., the starch molecules are completely soluble in water. The viscosity of the starch solution at 93 ° C. has a positive correlation with the molecular weight of the starch obtained by partial hydrolysis.

  FIG. 1 is an amylogram plotting viscosity (left y-axis) and temperature (right y-axis) over 50 minutes (x-axis). Comparative compositions 1B and 1C and inventive compositions 1D, 1H described herein were mixed into a starch solution in an amount of 10% by weight based on the weight of the solution. To prevent lump formation, the starch was added to the water in the mixing cup of the Waring blender with low speed mixing for 20 seconds. The starch solution was then evaluated using Viscograph-E (CW Brabender® Instruments, Inc., South Hackensack, NJ). According to the Brabender Viscosity Measurement Procedure described herein, for example, C.I. Viscograph-E et al. W. Viscosity is measured using a Brabender Viscograph. Note that as defined herein, Brabender units are measured at 75 RPM using a 16 fluid ounce size sample cup with a 700 cmg cartridge. As described herein, Brabender units may be converted to centipoise (eg, cP = BU × 2.1 if the measurement cartridge is 700 cmg) or other viscosity measurements such as Krebs units. Those skilled in the art will also readily recognize that this is possible. The pasting profiles of compositions 1D-1H extruded at a moisture content of 16% by weight are shown in FIG. 1 along with comparative compositions 1B and 1C.

  Considering compositions 1D-1H of the present invention, as the alum increased from 1% to 4% by weight, the initial viscosity decreased from 70 Brabender units (BU) to 10 BU and the molecular weight also decreased. The initial viscosities of compositions 1D-1H and 93 ° C. decreased to the same extent as the initial viscosities of compositions 1B and 1C and 93 ° C. Compositions 1B and 1C represent the conventional viscosity limits of low water requirement starch.

  The results of compositions 1D-1H shown in FIG. 1 demonstrate that optimal acid modification can be obtained during extrusion. These results further suggest that the inventive method of preparing pregelatinized partially hydrolyzed starch successfully reduced the viscosity (molecular weight) of the starch. No viscosity peak was observed at 70 ° C. to 90 ° C., indicating that compositions 1D to 1H were completely gelatinized. If compositions 1D-1H were not fully gelatinized, there would have been an increase in viscosity. Complete gelatinization of the starch composition was confirmed by differential scanning calorimetry (DSC).

  FIG. 2 is a second amylogram plotting viscosity (left y-axis) and temperature (right y-axis) over 50 minutes (x-axis). Comparative compositions 1B and 1C and inventive compositions 1I-1K described herein were mixed into a starch solution in an amount of 10% by weight based on the weight of the solution. To prevent lump formation, the starch was added to the water in the mixing cup of the Waring blender with low speed mixing for 20 seconds. The starch solution was then evaluated using Viscograph-E. The pasting profiles of compositions 1I-1K extruded at a moisture content of 13% by weight are shown in FIG. 2 along with comparative compositions 1B and 1C.

  A trend similar to that observed with compositions 1D-1H was observed with compositions 1I-1K. In particular, the method of preparing pregelatinized partially hydrolyzed starch described herein in an extruder successfully reduced the viscosity of compositions 1I-1K.

  As the alum increased from 1% to 3% by weight, the initial viscosity decreased from 75BU to 14BU and the molecular weight also decreased. The initial viscosities of compositions 1I-1K and 93 ° C. decreased to the same extent as the initial viscosities of compositions 1B and 1C and 93 ° C.

  Furthermore, the results of compositions 1I-1K shown in FIG. 2 demonstrate that optimum acid modification can be obtained during extrusion. No viscosity peak was observed between 70 ° C. and 90 ° C., indicating that compositions 1I-1K were fully gelatinized.

  Furthermore, these results show that for a given acid level, more starch hydrolysis can be done at a lower moisture content than is done at a higher moisture content. This is because at low moisture content there is more mechanical energy and therefore more starch degradation such that starch is smaller with the same acid level.

Example 3
This example illustrates the flowability of a gypsum slurry containing composition 1A (for comparison), 1D-1I, and 1K-1L. The composition was evaluated for fluidity using a slump test. The slump test will be understood by those skilled in the art.

  In the test preparation, the slurry was each of compositions 1A (for comparison), 1D-1I, and 1K-1L in amounts of 2% by weight, using the parameters listed in Table 6 below, It was prepared with a stucco ratio (WSR) of 100.

  Starch was weighed into a dry mixture containing stucco having a purity greater than 95% and a heat resistance promoter. Water, sodium trimetaphosphate (10 wt% solution), dispersant, and retarder were weighed into the mixing bowl of the Hobart mixer. The dried mixture was placed in a 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. For foam preparation, a 0.5% solution of Hyonic® PFM-33 soap (available from GEO® Specialty Chemicals, Ambler, Pa.) Was made and then mixed with air to create bubbles. . Bubbles were added to the slurry using a foam generator.

  Each slurry was then placed in a cylinder having a diameter of 4.92 cm (1.95 inches) and a height of 10 cm (3.94 inches). The cylinder was then pulled up and the slurry was allowed to flow freely. Next, the diameter of the slump formed was measured to illustrate the fluidity of the slurry. They are listed in Table 7 below. Table 8 also includes the results of the 50% hydration time test described in more detail below.

  As can be observed from Table 7, the slurries prepared using Compositions 1D-1I and 1K showed a larger slump size than the slurries prepared using Composition 1A (for comparison). Slurries prepared using compositions 1D-1I and 1K cure faster than composition 1A (for comparison), and slurries containing compositions 1D-1I and 1K are better than slurries containing composition 1A. It showed that it has a good fluidity.

  In addition, the 50% hydration time of the slurry was measured to compare the slump size when the slurry was cured at the same rate. The temperature profile of the slurry was measured using software as understood by those skilled in the art.

  This further test was performed to confirm that the slump test was correct, especially the large slumps observed with slurries containing pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention were caused by slow hydration. Instead, it was exemplified as a result of improved flowability compared to Composition 1A (for comparison).

  Composition 1H prepared with 2 wt% alum and 0.3 wt% tartaric acid effectively hydrolyzed starch until low viscosity and had little effect on hydration rate. This is because tartaric acid and alum have opposite effects on the rate of hydration.

  FIG. 3 is a graph plotting temperature against time and shows the temperature rising cure (TRS) hydration rate. Composition 1F with 0.05% and 0.0625% retarder each hydrates faster than composition 1A (comparative) or hydrates at the same rate.

  As can be seen in FIG. 3, composition 1L with 0.0625 wt% retarder had the same hydration rate as composition 1A (for comparison). The slump size of composition 1L with 0.065 wt% retarder was 18.415 cm (71/4 inch), significantly larger than composition 1A.

  This result indicates that the large slump size observed in slurries containing pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention was not due to slow cure but to high flowability. Suggest. Furthermore, pregelatinized partially hydrolyzed starch prepared according to embodiments of the present invention will allow wallboards using less water without sacrificing flowability.

Example 4
This example illustrates the strength of a gypsum disc prepared using a slurry containing composition 1A (for comparison), 1D-1I, and 1K. Strength was evaluated using the compressive strength test described herein.

  To prepare for testing, the slurry was prepared using the parameters listed in Table 4 above, using 2% by weight of each of compositions 1A (for comparison), 1D-1I, and 1K-1L. did.

  A gypsum disc with a final density of 29 pcf was made using a water stucco ratio (WSR) of 100 and bubbles. Starch was weighed into a dry mixture containing stucco and a heat resistance promoter. Water, 10% sodium trimetaphosphate solution, dispersant, and retarder were weighed into the mixing bowl of the Hobart mixer. The dried mixture was placed in a 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. For foam preparation, a 0.5% solution of Hyonic® PFM-33 soap (available from GEO® Specialty Chemicals, Ambler, Pa.) Was made and then mixed with air to create bubbles. . Bubbles were added to the slurry using a foam generator. The foam generator was run at a speed sufficient to obtain the desired board density of 29 pcf. After the foam was added, the slurry was poured immediately to a point slightly above the top of the mold. As soon as the plaster was cured, the excess was scraped off. The mold was sprayed with a release agent (WD-40 (trademark)). The disk was 10.16 cm (4 inches) in diameter and 1.27 cm (0.5 inches) thick.

After the disk set, the disk was removed from the mold and then dried at 110 ° F. (43 ° C.) for 48 hours. After removal from the oven, the disc was allowed to cool at room temperature for 1 hour. Compressive strength was measured using a material testing system commercially available as SATEC ^™ E / M Systems from MTS Systems Corporation (Eden Prairie, MN). The load was applied continuously at a speed of 0.04 in / min (using a constant speed of 15-40 psi / sec) without impact. The results are shown in Table 8 below.

  As can be seen in Table 8, the foam disk containing compositions 1D-1I and 1K has a compressive strength comparable to the foam disk containing composition 1A (for comparison), and pregelatinized partially hydrolyzed starch is It showed that the properties could be improved and the water requirement could be reduced without sacrificing strength. The desired compressive strength of the disk sample is about 400 psi. Strength is necessary so that the board can be handled properly without collapsing.

  In the context of describing the present invention (especially in the context of the following claims) (eg in terms of acids, raw starch, or other ingredients or items), “one (a)” and “one (an) ) "And" the "and" at least one "and the use of similar indicators are not clearly inconsistent unless otherwise specified herein or in context. As far as it should be construed as covering both singular and plural. The use of the term “at least one” followed by an enumeration of one or more items (eg, “one or more of A and B”) is specifically defined herein. Means one item (A or B) selected from the listed items, or any combination of two or more of the listed items (A and B) unless otherwise indicated or clearly contradicted by context Then it needs to be interpreted. The terms “comprising”, “having”, “including” and “containing”, unless otherwise noted, are non-limiting terms (ie, “including, Meaning “but not limited to”). The recitation of value ranges herein is merely intended to be treated as an abbreviated way of referring individually to each distinct value within that range, unless otherwise specified herein. Each distinct value is incorporated herein as if it were individually described herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples provided herein or exemplary words (eg, “such as”) is merely intended to better illustrate the present invention. Unless otherwise requested, no limitation is imposed on the scope of the present invention. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

  Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations on those preferred embodiments may become apparent to those skilled in the art upon reading the foregoing description. The inventors anticipate that those skilled in the art will use such variations as necessary, and that the invention is practiced in ways other than those specifically described herein. I intend to. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise defined herein or otherwise clearly contradicted by context.

[Appendix]
[Appendix 1]
A method of making pregelatinized partially hydrolyzed starch comprising: (a) mixing at least water, non-pregelatinized starch, and a weak acid that does not substantially chelate calcium ions to about 8 wt% to Making a wet starch precursor having a moisture content of about 25% by weight;
(B) feeding the wet starch precursor to an extruder; and (c) the wet starch at a die temperature of about 150 ° C (about 300 ° F) to about 210 ° C (about 410 ° F). A process comprising pregelatinizing and acid-modifying in an extruder.

[Appendix 2]
The method according to claim 1, wherein the weak acid that does not substantially chelate calcium ions comprises alum.

[Appendix 3]
The method according to appendix 1 or 2, wherein tartaric acid is contained in the mixture for producing the wet starch precursor.

[Appendix 4]
The method according to any one of appendices 1 to 3, wherein the method does not include a purification step and a neutralization step of the pregelatinized partially hydrolyzed starch.

[Appendix 5]
A method for making pregelatinized partially hydrolyzed starch, the method comprising: (a) mixing at least water, non-pregelatinized starch and a strong acid and having a moisture content of about 8 wt% to about 25 wt%. Making a wet starch precursor, wherein the strong acid is in an amount up to about 0.05% by weight of the weight of the starch;
(B) feeding the wet starch precursor to an extruder; and (c) the wet starch at a die temperature of about 150 ° C (about 300 ° F) to about 210 ° C (about 410 ° F). A process comprising pregelatinizing and acid-modifying in an extruder.

[Appendix 6]
The method of claim 5, wherein the strong acid has a pKa of about -1.7 or less.

[Appendix 7]
The method according to appendix 5 or 6, wherein the strong acid is sulfuric acid, nitric acid, hydrochloric acid, or any combination thereof.

[Appendix 8]
(A) (i) mixing at least water, non-pregelatinized starch, and acid to form a wet starch precursor having a moisture content of about 8 wt% to about 25 wt%, comprising: Acid
(1) a weak acid that does not substantially chelate calcium ions;
(2) a strong acid in an amount of about 0.05% or less by weight of the starch, or (3) a formation selected from the group consisting of any combination thereof;
(Ii) feeding the wet starch precursor to an extruder; and (iii) the wet starch has a die at a temperature of about 150 ° C (about 300 ° F) to about 210 ° C (about 410 ° F). Forming pregelatinized partially hydrolyzed starch by pregelatinization and acid modification in the extruder;
(B) mixing the pregelatinized partially hydrolyzed starch with at least water and stucco to form a slurry;
(C) placing the slurry between a first cover sheet and a second cover sheet to form a wet assembly;
(D) cutting the wet assembly into a board; and (e) drying the board.

[Appendix 9]
The method according to appendix 8, wherein the slurry further comprises sodium trimetaphosphate.

[Appendix 10]
When using pregelatinized partially hydrolyzed starch, the amount of water that needs to be added to maintain the fluidity of the slurry at the same level as the slurry without pregelatinized partially hydrolyzed starch 10. The method of appendix 8 or 9, wherein less than the amount of water required for the process.

Claims (1)

A method of making pregelatinized partially hydrolyzed starch comprising: (a) mixing at least water, non-pregelatinized starch, and a weak acid that does not substantially chelate calcium ions to about 8 wt% to Making a wet starch precursor having a moisture content of about 25% by weight;
(B) feeding the wet starch precursor to an extruder; and (c) the wet starch at a die temperature of about 150 ° C (about 300 ° F) to about 210 ° C (about 410 ° F). A process comprising pregelatinizing and acid-modifying in an extruder.