EP3052527A1 - Method of preparing pregelatinized, partially hydrolyzed starch and related methods and products - Google Patents

Method of preparing pregelatinized, partially hydrolyzed starch and related methods and products

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Publication number
EP3052527A1
EP3052527A1 EP14789654.2A EP14789654A EP3052527A1 EP 3052527 A1 EP3052527 A1 EP 3052527A1 EP 14789654 A EP14789654 A EP 14789654A EP 3052527 A1 EP3052527 A1 EP 3052527A1
Authority
EP
European Patent Office
Prior art keywords
starch
acid
pregelatinized
partially hydrolyzed
wet
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP14789654.2A
Other languages
German (de)
English (en)
French (fr)
Inventor
Yijun SANG
Weixin D. Song
Cesar Chan
Chris C. Lee
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
United States Gypsum Co
Original Assignee
United States Gypsum Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US14/044,582 external-priority patent/US9540810B2/en
Priority claimed from US14/494,547 external-priority patent/US9828441B2/en
Application filed by United States Gypsum Co filed Critical United States Gypsum Co
Publication of EP3052527A1 publication Critical patent/EP3052527A1/en
Pending legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B30/00—Preparation of starch, degraded or non-chemically modified starch, amylose, or amylopectin
    • C08B30/12—Degraded, destructured or non-chemically modified starch, e.g. mechanically, enzymatically or by irradiation; Bleaching of starch
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
    • C04B24/24—Macromolecular compounds
    • C04B24/28—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • C04B24/283—Polyesters
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
    • C04B24/24—Macromolecular compounds
    • C04B24/38—Polysaccharides or derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
    • C04B28/16—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements containing anhydrite, e.g. Keene's cement
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C04B38/10—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by using foaming agents or by using mechanical means, e.g. adding preformed foam
    • C04B38/106—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by using foaming agents or by using mechanical means, e.g. adding preformed foam by adding preformed foams
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B30/00—Preparation of starch, degraded or non-chemically modified starch, amylose, or amylopectin
    • C08B30/12—Degraded, destructured or non-chemically modified starch, e.g. mechanically, enzymatically or by irradiation; Bleaching of starch
    • C08B30/14—Cold water dispersible or pregelatinised starch
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B30/00—Preparation of starch, degraded or non-chemically modified starch, amylose, or amylopectin
    • C08B30/12—Degraded, destructured or non-chemically modified starch, e.g. mechanically, enzymatically or by irradiation; Bleaching of starch
    • C08B30/18—Dextrin, e.g. yellow canari, white dextrin, amylodextrin or maltodextrin; Methods of depolymerisation, e.g. by irradiation or mechanically
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
    • C04B2103/10—Accelerators; Activators
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
    • C04B2103/20—Retarders
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
    • C04B2111/00612—Uses not provided for elsewhere in C04B2111/00 as one or more layers of a layered structure
    • C04B2111/0062—Gypsum-paper board like materials

Definitions

  • Starches generally contain two types of polysaccharides (amylose and
  • amylopectin and are classified as carbohydrates.
  • Some starches are pregelatinized, typically through thermal means. Generally, pregelatinized starches can form dispersions, pastes, or gels with cold water. Pregelatinized starches are generally digestible and have been used in a number of ways, including as an additive to a variety of food products (e.g., in baking, snacks, beverages, confections, dairy, gravies, prepared foods, sauces, and meats) and in pharmaceuticals .
  • gypsum wallboard Another use for pregelatinized starches is in the preparation of gypsum wallboard.
  • stucco i.e., calcined gypsum in the form of calcium sulfate hemihydrate and/or calcium sulfate anhydrite
  • water, starch, and other ingredients as appropriate are mixed, typically in a pin mixer as the term is used in the art.
  • a slurry is formed and discharged from the mixer onto a moving conveyor carrying a cover sheet with one of the skim coats (if present) already applied (often upstream of the mixer). The slurry is spread over the paper (with skim coat optionally included on the paper).
  • Another cover sheet is applied onto the slurry to form the sandwich structure of desired thickness with the aid of, e.g., a forming plate or the like.
  • the mixture is cast and allowed to harden to form set (i.e., rehydrated) gypsum by reaction of the calcined gypsum with water to form a matrix of crystalline hydrated gypsum (i.e., calcium sulfate dihydrate). It is the desired hydration of the calcined gypsum that enables the formation of the interlocking matrix of set gypsum crystals, thereby imparting strength to the gypsum structure in the product. Heat is required (e.g., in a kiln) to drive off the remaining free (i.e., unreacted) water to yield a dry product.
  • set i.e., rehydrated
  • pregelatinized starches add water demand to the process.
  • water content must be added into the stucco slurry. This excess water creates inefficiencies in the manufacture, including increased drying time, slower manufacturing line speeds, and higher energy costs.
  • pregelatinized and partially hydrolyzed starch demands less water.
  • the invention provides a method of making a pregelatinized, partially hydrolyzed starch comprising: (a) mixing at least water, non-pregelatinized starch, and a weak acid that substantially avoids chelating calcium ions to make a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%; (b) feeding the wet starch precursor into an extruder; and (c) pregelatinizing and acid-modifying the wet starch precursor in the extruder at a die temperature of about 150°C (about 300°F) to about 210°C (about 410°F).
  • the invention also provides a starch produced according to this method.
  • the invention provides a method of making a pregelatinized, partially hydro lyzed starch comprising: (a) mixing at least water, non-pregelatinized starch, and a strong acid to make a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%, wherein the strong acid is in an amount of about 0.05 wt.% or less by weight of the starch; (b) feeding the wet starch into an extruder; and (c) pregelatinizing and acid-modifying the wet starch precursor in the extruder at a die temperature of about 150°C (about 300°F) to about 210°C (about 410°F).
  • the invention also provides a starch produced according to this method.
  • the invention provides a method of making board comprising: (a) forming a pregelatinized, partially hydrolyzed starch by (i) mixing at least water, non-pregelatinized starch, and an acid to form a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%, the acid selected from the group consisting of: (1) a weak acid that substantially avoids chelating calcium ions, (2) a strong acid in an amount of about 0.05 wt.% or less by weight of the starch, or (3) any combination thereof; (ii) feeding the wet starch precursor into an extruder; and (iii) pregelatinizing and acid- modifying the wet starch in the extruder having a die at a temperature of about 150°C (about 300°F) to about 210°C (about 410°F); (b) mixing the pregelatinized and partially hydrolyzed starch with at least water and stucco to form a s
  • FIG. 1 is an amylogram plotting viscosity (left y-axis) and temperature (right y-axis) versus time (x-axis) that shows pasting profiles of starches extruded at a moisture content of 16 wt.% with the solid content of testing slurry being 10 wt.% as set forth in Example 2.
  • FIG. 2 is an amylogram plotting viscosity (left y-axis) and temperature (right y-axis) versus time (x-axis) that shows pasting profiles of starches extruded at a moisture content of 13 wt.% with the solid content of testing slurry being 10 wt.% as set forth in Example 2.
  • FIG. 3 is a graph plotting temperature versus time showing the temperature rise set (TRS) hydration rate of two slurries containing pregelatinized, partially hydrolyzed starches treated with alum in an amount of 3 wt.% and retarder in amounts of 0.05 wt.% and 0.0625 wt.%, respectively, and a third slurry containing a conventional pregelatinized corn starch having a viscosity of 773 centipoise and retarder in an amount of 0.05 wt.% as set forth in Example 3.
  • TRS temperature rise set
  • Embodiments of the invention provide methods of making pregelatinized, partially hydrolyzed starches.
  • the invention provides a method of preparing board (e.g., gypsum wallboard).
  • Pregelatinized, partially hydrolyzed starches produced according to the method of the invention can be used in a variety of other ways, such as in foodstuffs (e.g., in baked goods, beverages, confections, dairy, instant puddings, gravies, soup mixes, prepared foods, pie fillings, sauces, and meats), pharmaceuticals, feeds, adhesives, and colorings.
  • Such starches prepared in accordance with some embodiments of the invention are generally digestible and can provide food products with desired viscosity, and can retain most of the functional properties of the original base material.
  • Embodiments of the invention are premised, at least in part, on the surprising and unexpected discovery of pregelatinizing and acid-modifying starch in a single step in an extruder.
  • pregelatinizing and acid-modifying starch in a single step in an extruder has considerable advantages in comparison to pregelatinizing and acid-modifying starch in separate steps.
  • inventive method of making pregelatinized, partially hydrolyzed starch allows for a higher output, faster production, and lower energy costs without sacrificing desired properties (e.g., viscosity, fluidity, cold water solubility, etc.) as described herein.
  • Conventional acid-modification processes include purification and neutralization steps.
  • the use of a weak acid (e.g., alum) and/or a small amount of a strong acid avoids the need for any neutralization step and the subsequent purification step typically required in conventional systems to purify the starch of salts resulting from the neutralization step, in accordance with some embodiments of the invention.
  • the extrusion process in accordance with embodiments of the invention, not only pregelatinizes the starch, but also partially hydrolyzes (i.e., via acid-modification) starch molecules.
  • the extrusion process in one step provides both physical modification (pregelatinization) and chemical modification (acid-modification, partially acid hydrolysis).
  • the pregelatinization provides the ability for the starch to impart strength (e.g., on a final product such as gypsum board).
  • Acid-modification beneficially partially hydrolyzes the starch to provide the starch with the ability to impart strength on a final product, such as gypsum board, and low water demand in product manufacture, such as in the case of gypsum board manufacturing processes.
  • the product of methods of preparing starch in accordance with embodiments of the invention is pregelatinized and partially hydrolyzed starch.
  • the invention provides a highly efficient acid-modification reaction.
  • the pregelatinization and acid-modification in the extruder occurs at elevated temperatures and/or pressures as described herein and can result in an acid hydrolysis rate that can be, e.g., approximately 30,000 times or greater faster than
  • the hydrolysis is designed to convert the starch into smaller molecules within an optimum size range, which is defined herein by the desired viscosity of the pregelatinized, partially hydrolyzed starch. If the starch is over hydrolyzed, it can be converted into unduly small molecules (e.g., oligosaccharides or sugars), which, in the case of gypsum board, can result in less board strength than that provided by the pregelatinized, partially hydrolyzed starch of desired viscosity.
  • unduly small molecules e.g., oligosaccharides or sugars
  • the pregelatinized, partially hydrolyzed starch can be prepared by (i) mixing at least water, non-pregelatinized starch, and an acid to form a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%.
  • the acid can be: (1) a weak acid that substantially avoids chelating calcium ions, (2) a strong acid in an amount of about 0.05 wt.% or less by weight of the starch, or (3) any combination thereof.
  • the wet starch precursor is pregelatinized and acid-modified in one step in an extruder at an elevated die temperature and/or pressure as described herein.
  • the starch is hydrolyzed to a degree that results in a desired viscosity, e.g., as described herein.
  • a pregelatinized, partially hydrolyzed starch can be made by mixing at least water, non-pregelatinized starch, and a weak acid that substantially avoids chelating calcium ions to make a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%.
  • the wet starch is then fed into an extruder. While in the 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, such that it is at least partially hydrolyzed.
  • a pregelatinized, partially hydrolyzed starch can be made by mixing at least water, non-pregelatinized starch, and a strong acid to make a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%, wherein the strong acid is in an amount of about 0.05 wt.% or less by weight of the starch.
  • the wet starch is then fed into an extruder. While in the 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, such that it is at least partially hydrolyzed.
  • the resulting pregelatinized, partially hydrolyzed starch has low water demand when included in a stucco slurry and can be useful in the manufacture of board (e.g., gypsum board) with good strength, in some embodiments.
  • the invention provides a method of making gypsum board using starch prepared with the inventive methods of pregelatinizing and acid-modifying in a single step in an extruder.
  • the pregelatinized, partially hydrolyzed starches prepared in accordance with embodiments of the invention have low water demand relative to other pregelatinized starches known in the art.
  • pregelatinized, partially hydrolyzed starches prepared in accordance with embodiments of the invention can be included in a stucco slurry (e.g., by a feed line into a pin mixer) with good fluidity.
  • higher amounts of the pregelatinized, partially hydrolyzed starches prepared in accordance with embodiments of the invention can be included since excess water is not needed to be added to the system, such that even higher strengths and lower board densities can be achieved.
  • the resulting board exhibits good strength properties (e.g., having good core hardness, nail pull resistance, compressive strength, etc., or any relationship therebetween, based on any combination of values for each provided herein).
  • gypsum board can be in the form of, e.g., gypsum wallboard (often referred to as drywall), which can encompass such board used not only for walls but also for ceilings and other locations as understood in the art.
  • gypsum wallboard often referred to as drywall
  • starch prepared according to the method can have other applications, such as in food products.
  • Starches are classified as carbohydrates and contain two types of polysaccharides, namely linear amylose, and branched amylopectin.
  • Starch granules are semi-crystalline, e.g., as seen under polarized light, and are insoluble at room temperatures. Gelatinization is the process by which the starch is placed in water and heated ("cooked"), such that the crystalline structure of the starch granules is melted, and the starch molecules are dissolved in water, resulting in good dispersion. It has been found that, when transforming a starch granule to gelatinized form, initially, the starch granule provides little viscosity in water because starch granules are water insoluble.
  • the starch granule As the temperature increases, the starch granule swells and the crystalline structure melts at the gelatinization temperature. Peak viscosity is achieved when the starch granule has maximum swelling. Further heating will break the starch granules and dissolve the starch molecules in water, with a precipitous drop-off in viscosity. After cooling, the starch molecule will re-associate to form a 3-D gel structure, with the viscosity increasing due to the gel structure.
  • Some commercial starches are sold in a pregelatinized form, while others are sold in the granular form.
  • the granular form undergoes at least some degree of gelatinization. To illustrate, in relation to gypsum board, the starch is
  • stucco slurry typically in a mixer, e.g., a pin mixer.
  • pregelatinized means that the starch has any degree of gelatinization, e.g., before it is included in the gypsum slurry or for use in other applications.
  • the pregelatinized starch can be partially gelatinized when included in the slurry, but becomes fully gelatinized when exposed to elevated temperature, e.g., in the kiln during the drying step to remove excess water.
  • the pregelatinized starch is not fully gelatinized, even upon exiting the kiln so long as the starch meets the mid-range viscosity characteristic of some embodiments when under the conditions according to the Viscosity Modifying
  • VMA Admixture
  • viscosity is referred to herein, it is in accordance with the VMA method, unless otherwise indicated. According to this method, viscosity is measured using a
  • DSC differential scanning calorimetry
  • Procedure 1 is utilized where the DSC reveals that the starch is fully gelatinized or has a gelatinization temperature at or below 90°C.
  • Procedure 2 is utilized where the gelatinization temperature is above 90°C. Since the viscosity is measured while the starch is in water, procedure 2 uses pressure cooking in a sealed vessel to allow for superheating to temperatures above 100°C without causing the water to appreciably evaporate.
  • Procedure 1 is reserved for starches already fully gelatinized or for starches having gelatinization temperature up to 90°C, because, as discussed below, the gelatinization takes place in the rheometer which is an open system and cannot create pressurized conditions for
  • the starch is dispersed in the water (15% starch of the total weight of starch and water) and the sample is immediately transferred to a cylinder cell.
  • the cell is covered with aluminum foil.
  • the sample is heated from 25°C to 90°C at 5°C/min and a shear rate of 200 s "1 .
  • the sample is held at 90°C for 10 min at a shear rate of 200 s "1 .
  • the sample is cooled from 90°C to 80°C at 5°C/min and a shear rate of 200 s "1 .
  • the sample is held at 80°C for 10 min 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 min.
  • the viscosity is the average of the measurement from 30 seconds to 60 seconds.
  • Procedure 2 is used for starches having gelatinization temperature greater than 90°C.
  • the starch is gelatinized according to the methods well-known in the starch industry (e.g., by pressure cooking).
  • the gelatinized starch water solution (15% of total weight) is immediately transferred into the rheometer measuring cup and equilibrated 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.
  • the viscosity is the average of the measurement from 30 seconds to 60 seconds.
  • Viscograph and DSC are two different methods to describe starch gelatinization.
  • Degree of starch gelatinization can be determined by, for example, thermogram from DSC, e.g., using peak area (melting of crystal) for calculation.
  • a viscogram (from viscograph) is less desirable to determine degree of partial gelatinization but is a good tool to obtain data such as the viscosity change of starch, gelatinization maximum, gelatinization temperature, retrogradation, viscosity during holding, viscosity at the end of cooling, etc.
  • the DSC measurements are done in the presence of excess water, particularly at or above 67% by weight. If water content of starch/water mixture is less than 67%, gelatinization temperature will increase as water content decreases.
  • gelatinization temperature When water content of starch/water mixture reaches 67%, gelatinization temperature will keep constant no matter how much more water is added into the starch/water mixture.
  • Gelatinization onset temperature indicates the starting temperature of gelatimzation.
  • Gelatimzation end temperature indicates the end temperature of gelatimzation.
  • Enthalpy of gelatimzation represents the amount of crystalline structure melted during gelatimzation. By using the enthalpy from a starch DSC thermogram, the degree of gelatimzation can be indicated.
  • the degree of gelatimzation can be any suitable amount, such as about 70% or more, etc.
  • smaller degrees of gelatimzation will more closely approximate granular starch and may not take full advantage of the strength enhancement, better (more complete) dispersion, and/or water demand reduction of some embodiments of the invention.
  • it is preferred that there is a higher degree of gelatimzation e.g., at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%), at least about 97%, at least about 99%, or full (100%) gelatimzation.
  • Starch with lower degree of gelatimzation can be added to slurry with additional gelatimzation (e.g., to 100%) taking place in the kiln in the case of gypsum board.
  • additional gelatimzation e.g., to 100%
  • the starch is sufficiently cooked at or above its gelatimzation temperature or to otherwise achieve full gelatimzation as can be seen from DSC techniques.
  • the starch will still be understood as “fully gelatinized” for addition to gypsum slurry, or for use in other applications, in some embodiments as one of ordinary skill in the art will recognize.
  • such retrogradation is not accepted in making the viscosity measurement.
  • the starch molecule can be acid-modified, e.g., to hydrolyze glycosidic bonds between glucose units to achieve desired molecular weight.
  • acid-modifying starch such that a reduction in molecular weight is achieved is that the water demand will decrease.
  • Conventional pregelatinized starches that were not also acid-modified had a very high water demand, which is associated with higher energy costs. It has been conventionally believed that it is generally preferred that the modification take place before gelatinization because it tends to be more efficient and less cost intensive.
  • pregelatinization and acid-modification can be incorporated into a single step, such that they can occur simultaneously rather than in series.
  • a wet starch precursor prior to entry into the extruder, is prepared.
  • the wet starch precursor can be prepared by any suitable method.
  • the wet starch precursor is prepared by adding to a starch raw material water and an acid that is (a) a weak acid that substantially avoids chelating calcium ions, and/or (b) a strong acid in a small amount.
  • starch raw material can be selected to prepare the wet starch precursor so long as it can be used to make pregelatinized, partially hydrolyzed starch, such as one meeting the mid-range viscosity characteristic of some embodiments of the invention.
  • starch refers to a composition that includes a starch component.
  • the starch can be 100% pure starch or may have other components such as those commonly found in flours such as protein and fiber, so long as the starch component makes up at least about 75% by weight of the starch composition.
  • the starch can be in the form of a flour (e.g., corn flour) containing starch, such as flour having at least about 75% starch by weight of the flour, e.g., at least about 80%, at least about 85%, at least about 90%, at least about 95%), etc.).
  • a flour e.g., corn flour
  • Any suitable unmodified starch or flour can be used to prepare the precursor of the pregelatinized, partially hydrolyzed starches of the invention.
  • 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, such that desired levels of pregelatinization and acid-modification are achieved in an extruder.
  • the wet starch can be prepared to have a moisture content that allows for sufficient mechanical energy input when the wet starch is fed through the extruder, such that friction prevents the wet starch from moving through the extruder too easily.
  • the increased friction can increase the disruption of hydrogen bonding in the starch.
  • any suitable weak acid that substantially avoids chelating calcium ions may be mixed into the wet starch.
  • chelation includes the weak acid, for example, forming a coordination complex with calcium or otherwise interfering with the formation of gypsum crystals within the gypsum slurry. Such interference may be the reduction in number of gypsum crystals formed, retardation
  • substantially with respect to not chelating calcium ions generally means that at least 90% (e.g., at least 92%, at least 95%>, at least 96%>, at least 97%>, at least 98%, or at least 99%) of the available calcium ions are not chelated to the acid.
  • Weak acids in accordance with embodiments of the invention can be defined as those having a pKa value from about 1 to about 6, e.g., from about 1 to about 5, from about 1 to 4, from about 1 to 3, from about 1 to 2, from about 1.2 to about 6, from about 1.2 to about 5, from about 1.2 to about 4, from about 1.2 to about 3, from about 1.2 to about 2, from about 2 to about 6, from about 2 to about 5, from about 2 to about 4, from about 2 to about 3, from about 3 to about 6, from about 3 to about 5, from about 3 to about 4, from about 4 to about 6, or from about 4 to about 5.
  • the pKa value is a measure of the strength of an acid; the lower the pKa value, the stronger the acid.
  • Weak acids that substantially avoid chelating calcium ions are characterized, for example, by a lack of multi-binding sites, such as multiple carboxyl functional groups (COO-), which tend to bind calcium ions.
  • the weak acid has a minimal amount of multi-binding sites, such as multi-COO- groups, or is substantially free of multi-binding sites, such as multi-COO- groups, such that, for example, chelation is minimal (i.e., substantially avoided) or gypsum crystal formation is not substantially impacted relative to the crystal formation in the absence of the weak acid.
  • aluminum sulfate (alum) is an appropriate weak acid to use in preparing the wet starch since it substantially avoids chelating calcium ions. Alum does not have multi-binding sites.
  • alum is added into the wet starch precursor in any suitable form, such as in liquid containing alum of desired solids content.
  • the liquid alum can be included in an aqueous solution where the alum is present in any suitable amount.
  • Other weak acids can be added similarly.
  • the wet starch can be mixed to include any suitable amount of a weak acid that substantially avoids chelating calcium ions, such that the pregelatinized, partially hydrolyzed starch is prepared with desired viscosity and low water demand and is not over hydrolyzed into sugar.
  • such weak acid is included in an amount of from about 0.5 wt.% to about 5 wt.% based on the weight of the starch, such as from about 0.5 wt.%) to about 4.5 wt.%, e.g., from about 0.5 wt.% to about 4 wt.%, from about 0.5 wt.% to about 3.5 wt.%, from about 0.5 wt.% to about 3 wt.%, from about 1 wt.% to about 5 wt.%, from about 1 wt.% to about 4.5 wt.%, from about 1 wt.% to about 4 wt.%, from about 1 wt.% to about 3.5 wt.%, from about 1 wt.% to about 3 wt.%, from about 1.5 wt.% to about 5 wt.%, from about 1.5 wt.% to about 4.5 wt.%, from about 1.5 wt.
  • the wet starch precursor can be prepared to optionally further comprise secondary acids that can chelate calcium ion, such as tartaric acid.
  • a secondary acid such as tartaric acid
  • a secondary acid can be combined with any suitable weak acid that does not chelate calcium ions.
  • Tartaric acid is known to retard gypsum crystallization.
  • tartaric acid avoids substantial retarding of gypsum crystallization, such that the hydrolysis reaction via acid-modification is optimized.
  • other secondary acids such as succinic acid or malic acid, may be beneficial so long as they do not surpass the accelerating effect of alum.
  • succinic acid or malic acid may be beneficial so long as they do not surpass the accelerating effect of alum.
  • the wet starch precursor includes both alum and tartaric acid.
  • secondary acids e.g., tartaric acid
  • tartaric acid can be present in any suitable amount.
  • tartaric acid can be present in an amount of from about 0.1 wt.% to about 0.6 wt.%) based on the weight of the starch, e.g., from about 0.1 wt.% to about
  • oil can optionally be added to the wet starch to improve the conveyability of starch inside the extruder.
  • Possible oils include canola oil, vegetable oil, corn oil, soybean oil, or any combination thereof, in some embodiments.
  • canola oil or one of the aforementioned substitutes can optionally be added in an amount of from about 0 wt.%> to about 0.25 wt.%> by weight of the starch, e.g., from about 0.1 wt.% to about 0.2 wt.%, from about 0.1 wt.% to about 0.15 wt.%, from about 0.15 wt.%) to about 0.25 wt.%>, from about 0.15 wt.%> to about 0.2 wt.%>, or from about 0.2 wt.% to about 0.25 wt.%.
  • the wet starch precursor is prepared by mixing water, non-pregelatinized starch, and a small amount of a strong acid.
  • the strong acid has a pKa of about -1.7 or less. Any such strong acid can be used and, in some embodiments, the strong acid comprises sulfuric acid, nitric acid, hydrochloric acid, or any combination thereof. Sulfuric acid, alone or in combination with other acids, is preferred in some embodiments because sulfate ion can accelerate gypsum crystallization in gypsum board embodiments.
  • the amount of strong acid is relatively small, such as about 0.05 wt.%> or less by weight of the starch, e.g., about 0.045 wt.%> or less, about 0.04 wt.%> or less, about
  • 0.035 wt.%) or less about 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 wt.%) or less, about 0.0005 wt.%> or less, such as from about 0.0001 wt.%> to about 0.05 wt.%, from about 0.0001 wt.% to about 0.045 wt.%, from about 0.0001 wt.% to about 0.04 wt.%, from about 0.0001 wt.% to about 0.035 wt.%, from about 0.0001 wt.% to about 0.03 wt.%, from about 0.0001 wt.% to about 0.025 wt.%, from about from about 0.0001 wt.% to about 0.02 w
  • Embodiments of the invention provide feeding the wet starch precursor through an extruder, such that the wet starch precursor is pregelatinized and acid-modified in a single step in the extruder.
  • an extruder is a machine generally used to melt and process polymers into a desired shape by melting the polymer and pumping it through a die.
  • the extruder can also mix the polymer with other ingredients, such as color, reinforcing fibers, mineral fillers, etc.
  • the purpose of the extruder is to disperse and distribute all of the ingredients fed into it and to melt the ingredients with a constant temperature and pressure.
  • Configurations and arrangements for extruders are known in the art.
  • an extruder comprises a feed hopper to deliver the feed material, a preconditioner comprising heat jackets for conditioning polymer with plasticizer (e.g., water), an extruder modular head comprising heating zones, and a die assembly.
  • Extruders generally include a feed auger, a knife, and screw(s).
  • the feed auger is present to help convey the wet starch precursor into the extruder.
  • the knife is present to cut the string-like pregelatinized, partially hydrolyzed starch into small pellets, such that they can be ground.
  • the screw(s) help mix the wet starch precursor, convey the wet starch precursor through the extruder, and provide mechanical shearing.
  • An extruder can be of the single-screw or twin-screw varieties as will be understood by one of ordinary skill in the art. See, e.g., Leszek Moscicki, Extrusion-Cooking Techniques, WILEY-VCH Verlag & Co. KGaA, 2011.
  • the screw In single-screw extruders, the screw generally comprises a feed section with deep channels for transporting the solids from the throat of the feeder and compressing them, a compression section at which point the screw's channels become progressively less deep and the polymer is melted, and a metering section with shallow channels that conveys the melted polymer to the die.
  • Some screws are designed to include mixing devices (e.g., pins extending from the screw).
  • Twin-screw extruders generally have two screws that rotate either in the same direction (i.e., co-rotating) or in opposite directions (i.e., counter-rotating). The two screws may rotate with non-intermeshing or fully intermeshing flights. Whereas in the case of single-screw extruders, the material being fed fills the entire screw channel, in the case of twin-screw extruders, only part of the screw channel is filled, such that downstream feedports or vents can be utilized for the addition of certain ingredients.
  • the die assembly generally comprises a plate, spacer, and die head.
  • the process can be either continuous, such that the material is extruded in an indefinite length, or semi-continuous, such that the material is extruded in pieces.
  • Materials being extruded may be hot or cold.
  • the invention provides a method of preparing pregelatinized, partially hydrolyzed starch in an extruder.
  • Any suitable extruder can be used, such as a single-screw extruder (e.g., the Advantage 50 available from American Extrusion International, located in South Beloit, IL) or a twin-screw extruder (e.g., the Wenger TX52 available from Wenger located in Sabetha, KS).
  • non-pregelatinized starch an acid in the form of a weak acid that substantially avoids chelating calcium ions and/or a strong acid in a small amount, and water are mixed and fed into the extruder.
  • additional water may be added to the extruder.
  • a combination of heating elements and mechanical shearing melts and pregelatinizes the starch, the weak acid partially hydrolyzes the starch to a desired molecular weight indicated by viscosity as desirable as described herein.
  • the conditions in the extruder because of the mechanical energy, will also cause the starch molecules to degrade, which partially produces the same effect of acid-modification.
  • the main screw(s) can be operated at any suitable speed, such that desired mixing and mechanical shearing are achieved.
  • 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 achieve desired feeding rate.
  • 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.
  • the knife can be operated at a speed of from about 400 RPM to about 1,000 RPM, e.g., from about 400 RPM to about 900 RPM, from about 400 RPM to about 800 RPM, from about 400 RPM to about 700 RPM, from about 400 RPM to about 600 RPM, from about 400 RPM to about 500 RPM, from about 500 RPM to about 1,000 RPM, from about 500 RPM to about 900 RPM, from about 500 RPM to about 800 RPM, from about 500 RPM to about 700 RPM, from about 500 RPM to about 600 RPM, from about 600 RPM to about 1,000 RPM, from about 600 RPM to about 900 RPM, from about 600 RPM to about 800 RPM, from about 600 RPM to about 700 RPM, from about 700 RPM to about 1,000 RPM, from about 700 RPM to about 900 RPM, from about 700 RPM to about 800 RPM, from about 800 RPM to about 1,000 RPM, from about 700 RPM to about 900 RPM, from
  • the wet starch can be pregelatinized and acid-modified in an extruder having a die at any suitable temperature, such that the wet starch becomes sufficiently pregelatinized without burning the materials.
  • the wet starch can be pregelatinized and acid- modified the wet starch in an extruder having a die at a temperature of from about 150°C (about 300°F) to about 210°C (about 410°F), e.g., in various embodiments, from about 150°C to about 205°C (about 400°F), from about 150°C to about 199°C (about 390°F), from about 150°C to about 193°C (about 380°F), from about 150°C to about 188°C (about 370°F), from about 150°C to about 182°C (about 360°F), from about 154°C (about 310°F) to about 210°C, from about 154°C to about 205°C (about 400°F), from about 154°C
  • the degree of gelatinization can be any suitable amount, such as at least about 70% or more, e.g., at least about 75%, at least about 80%>, at least about 85%>, at least about 90%, at least about 95%, at least about 97%, at least about 99%, or full (100%)
  • gelatinization In the case of making wallboard as described below, starch with such lower degrees of gelatinization can be added to stucco slurry, e.g., with additional gelatinization (for example, to 100%) taking place in the kiln.
  • the pressure in the extruder can be at any suitable level, such that appropriate conditions for pregelatinization and acid-modification are achieved. Pressure inside the extruder is determined by the raw material being extruded, moisture content, die temperature, and screw speed, which will be recognized by one of ordinary skill in the art.
  • the pressure in the extruder can be at least about 2,000 psi (about 13,800 kPa), such as at least about 2,250 psi (about 15,500 kPa), at least about 2,500 psi (about 17,200 kPa), at least about 2,750 psi (about 19,000 kPa), at least about 3,000 psi (about 20,650 kPa), at least about 3,500 psi (about 24,100 kPa), at least about 4,000 psi (about 27,600 kPa), or at least about 4,500 psi (about 31,000 kPa).
  • the pressure can be from about 2,000 psi (about 13,800 kPa), such as at least about 2,250 psi (about 15,500 kPa), at least about 2,500 psi (about 17,200 kPa), at least about 2,750 psi (about 19,000 kPa), at least about 3,000 psi (about 20,650 kPa), at
  • 2,000 psi to about 5,000 psi 34,500 kPa
  • the inventive method of preparing pregelatinized, partially hydrolyzed starch in a single step in an extruder is considerably faster than pregelatinizing and acid-modifying starch in two steps in series.
  • Significantly greater amounts of pregelatinized, partially hydrolyzed starch can be prepared with the inventive method than starch prepared with any other method.
  • the higher production amount and faster output rate are because of high reaction rate at high temperature and/or high pressure.
  • pregelatinization and acid-modification occur in less than about 5 minutes, such as less than about 4 minutes, e.g., less than about 3 minutes, less than about 2 minutes, less than about 90 seconds, less than about 75 seconds, less than about 1 minute, less than about 45 seconds, less than about 30 seconds, less than about 25 seconds, less than about 20 seconds, less than about 15 seconds, or less than about 10 seconds.
  • the pregelatinization and acid-modification occur at a rate in the extruder bound by any two of the foregoing points.
  • the pregelatinization and acid-modification rate can be between about 10 seconds and 5 minutes, e.g., between about 10 seconds and about 4 minutes, between about 10 seconds and about 3 minutes, between about 10 seconds and about 2 minutes, between about 10 seconds and about 90 seconds, between about 10 seconds and about 75 seconds, between about 10 seconds and about 1 minute, between about 10 seconds and about 45 seconds, between about 10 seconds and about 30 seconds, between about 10 seconds and about 25 seconds, between about 10 seconds and about 20 seconds, or between about 10 seconds and about 15 seconds.
  • starch is pregelatinized and acid-modified at a production output rate in an extruder of at least about 100 kg/hr, such as at least about 150 kg/hr, at least about 200 kg/hr, at least about 250 kg/hr, at least about 300 kg/hr, at least about 350 kg/hr, at least about 400 kg/hr, at least about 450 kg/hr, 500 kg/hr, at least about 550 kg/hr, e.g., at least about 600 kg/hr, at least about 650 kg/hr, at least about 700 kg/hr, at least about 750 kg/hr, at least about 800 kg/hr, at least about 850 kg/hr, at least about 900 kg/hr, at least about 950 kg/hr, at least about 1,000 kg/hr, at least about 1,050 kg/h
  • the production output rate in an extruder can be bound by any two of the foregoing points.
  • the production output rate can be between about 100 kg/hr and about 1,500 kg/hr (e.g., between about 100 kg/hr and about 1,500 kg/hr, between about 100 kg/hr and 1,000 kg/hr, between about 250 kg/hr and about 1,500 kg/hr, between about 250 kg/hr and about 1,000 kg/hr, between about 600 kg/hr and about
  • the conditions in an extruder are particularly conducive to efficiently and sufficiently pregelatinizing and acid-modifying starch in a single step.
  • the extruder mixes the wet starch, it creates very high friction, thereby generating heat.
  • the shear force is created by the screw in the extruder because the space between the screw and chamber in the extruder is very small.
  • Specific mechanical energy (SME) describes mechanical energy of an object per unit of mass. SME will depend on the moisture content. Higher moisture content (e.g., for purposes of fluidity) will result in low viscosity and low friction and, thus, a smaller SME. If more moisture is present, a smaller SME will result because of low viscosity and low friction.
  • the moisture contents in the wet starch precursor of the invention as described herein provide effective SME.
  • the starch is pregelatinized highly efficiently. While not wishing to be bound by any particular theory, it is believed that the good mixing in the extruder in accordance with some embodiments of the invention requires less water for reaction in an extruder. Very low moisture content facilitates a high concentration of reactant, which can accelerate the chemical reaction rate. The high temperature of the extruder also significantly accelerates the reaction rate. When the starch leaves the extruder, the reaction has occurred, such that it is pregelatinized and partially hydrolyzed.
  • pregelatinized, partially hydrolyzed starch is prepared in an extruder according to embodiments of the invention using a weak acid or a strong acid in a small amount as described herein, there is no need for neutralization and purification steps, due to the mild acidic condition and less interference with gypsum crystallization, respectively. In some embodiments, there can still be acid present in the pregelatinized, partially hydrolyzed starch.
  • the starch prepared in an extruder in accordance with embodiments of the invention can be any pregelatinized, partially hydrolyzed starch.
  • the starch can be prepared to have various properties as desired (e.g., mid-range viscosity, cold water solubility, cold water viscosity, etc.) as described herein.
  • Pregelatinized, partially hydrolyzed starches prepared in an extruder in accordance with embodiments of the invention can be suitable for use in gypsum board.
  • pregelatinization and acid-modification are beneficial, e.g., for strength purposes by achieving a desired viscosity (and, hence, molecular weight range) in accordance with embodiments of the invention as described herein.
  • the starch that is introduced into the stucco slurry can be at least about 70% gelatinized, e.g., at least about 75% gelatinized, at least about 80% gelatinized, at least about 85% gelatinized, at least about 90% gelatinized, at least about 95% gelatinized, at least about 97% gelatinized, or 100% gelatinized (i.e., fully gelatinized).
  • a wet starch comprising a weak acid that substantially avoids chelating calcium ions as described herein into an extruder, in accordance with embodiments of the invention, hydrolyzes the starch, such that a desired viscosity is achieved, thus indicating a desired molecular weight range is achieved. Viscosity thereby indicates the molecular weight of the pregelatinized, partially hydrolyzed starch, as will be appreciated by one of ordinary skill in the art.
  • pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention can be prepared to have any suitable viscosity.
  • the viscosity is characterized as having a "mid-range" viscosity (i.e., having a viscosity from about 20 centipoise to about 700 centipoise) when the pregelatinized, partially hydrolyzed starch is subjected to conditions according to the VMA method with the pregelatinized, partially hydrolyzed starch in water in an amount of 15% by weight of the total weight of the pregelatinized, partially hydrolyzed starch and water.
  • the VMA method is used to determine whether the pregelatinized, partially hydrolyzed starch exhibits the mid-range viscosity characteristic when subjected to the conditions of the VMA method. This does not mean that the pregelatinized, partially hydrolyzed starch must be added to the gypsum slurry under these conditions. Rather, when adding the pregelatinized, partially hydrolyzed starch to slurry, it can be in wet (in various concentrations of starch in the water) or dry forms, and it need not be fully gelatinized as described herein or otherwise under the conditions set forth in the VMA method.
  • the mid-range viscosity of the pregelatimzed 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 from about 100 centipoise to about 700 centipoise.
  • the viscosity of the pregelatimzed starch when tested under the VMA method can be, e.g., as listed in Tables 1 A, IB and 1C below.
  • an “X” represents the range “from about [corresponding value in top row] to about [corresponding value in left-most column].”
  • the indicated values represent viscosity of the pregelatimzed starch in centipoise. For ease of presentation, it will be understood that each value represents “about” that value. For example, the first "X” in Table 1 A is the range “about 20 centipoise to about 25 centipoise.”
  • the viscosity of the pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention can have a range between and including any of the aforementioned endpoints set forth in Tables 1A, IB or 1C.
  • the pregelatinized, partially hydrolyzed starch has a viscosity (10% solids, 93°C) of from about 5 Brabender Units (BU) to about 33 BU, measured according to the Brabender method described herein, e.g., from about 10 BU to about 30 BU, from about 12 BU to about 25 BU, or from about 15 BU to about 20 BU.
  • pregelatinized, partially hydrolyzed starches prepared in accordance with embodiments of the invention can provide significant benefits to the strength of the product (e.g., wallboard) to which they are applied. Since starch contains glucose monomers containing three hydroxyl groups, starch provides many sites for hydrogen bonding to gypsum crystals.
  • the molecular size of pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention allows for optimal mobility of starch molecules to align starch molecules with the gypsum crystals to facilitate good binding of starch to gypsum crystals to strengthen the resulting crystalline gypsum matrix, e.g., via hydrogen bonding.
  • the strength of the crystalline gypsum matrix is enhanced, and less starch is required to promote that strength compared with conventional starches.
  • the inventors have found dissolved starch molecules with, for example, mid-range viscosity (representing mid range molecular weight of starch) allows for optimal mobility of starch molecules to align starch molecules with gypsum crystals to facilitate good starch and gypsum hydrogen-bonding and core strength in some embodiments.
  • Pregelatinized, partially hydrolyzed starch prepared in accordance with some embodiments of the invention also provides advantages with respect to water demand, in some embodiments. Adding conventional pregelatinized starch to gypsum slurry requires that additional water be added to the gypsum slurry in order to maintain a desired degree of slurry fluidity. This is because conventional pregelatinized starch increases the viscosity and reduces the fluidity of the gypsum slurry. Thus, the use of pregelatinized starch in conventional systems has resulted in an increase in water demand such that even more excess water would be required in the gypsum slurry.
  • pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention demands less water so that the effect on water demand in the gypsum slurry is reduced, especially in comparison to conventional starches.
  • the positive impact on water demand can be even more significant in accordance with some embodiments of the invention.
  • This lower water demand provides considerable efficiencies during manufacture. For example, excess water requires energy input for drying. The speed of the line must be slowed to accommodate the drying. Thus, by reducing the water load in the gypsum slurry, less energy resources and cost can be seen, as well as faster production rates.
  • the increase in water demand in a gypsum slurry is less than the increase in water demand required by other starches such as pregelatinized starches having viscosity above 700 centipoise (e.g., about 773 centipoise), e.g., prepared by a different method.
  • Any suitable non-pregelatinized starch can be selected in preparing a
  • starch refers to a composition that includes a starch component.
  • the starch can be 100% pure starch or may have other components such as those commonly found in flours such as protein and fiber, so long as the starch component makes up at least about 75% by weight of the starch composition.
  • the starch can be in the form of a flour (e.g., corn flour) containing starch, such as flour having at least about 75% starch by weight of the flour, e.g., at least about 80%, at least about 85%, at least about 90%, at least about 95%, etc.).
  • the starch can be in the form of a corn flour containing starch.
  • the pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention can be prepared to have desired cold water solubility.
  • Conventional pregelatinization techniques involve making starch cold water soluble and generally require cooking starch in an excess amount of water. However, these conventional techniques are not efficient.
  • Extrusion, in accordance with embodiments of the invention, which allows for a combination of heating and mechanical shearing, is surprisingly and unexpectedly an energy efficient method that can be used to produce pregelatinized, partially hydrolyzed starch in a one step process having a low moisture content with cold water solubility.
  • Cold water solubility is defined as having any amount of solubility in water at room temperature (about 25°C).
  • starches exhibiting solubility in cold water can provide significant benefits to the strength of gypsum products (e.g., wallboard).
  • Cold water soluble starches of the present invention have a cold water solubility greater than about 30% and, when added to a set gypsum core, can increase the strength of the gypsum core.
  • the solubility of the pregelatimzed starch in water is defined as the amount of starch that dissolves in room temperature water divided by the total amount of starch.
  • the cold water solubility of the pregelatimzed, partially hydrolyzed starch prepared in accordance with embodiments of the invention is from about 30% to about 100%). In other embodiments, the cold water solubility of the extruded pregelatimzed, partially hydrolyzed starch is from about 50% to about 100%. In other embodiments, the cold water solubility of the extruded pregelatimzed, partially hydrolyzed starch is from about 50% to about 100%.
  • the cold water solubility of the extruded pregelatimzed, partially hydrolyzed starch can be, e.g., as listed in Table 2.
  • Table 2 an "X” represents the range “from about [corresponding value in top row] to about [corresponding value in leftmost column].”
  • the indicated values represent the cold water solubility of a extruded pregelatimzed, partially hydrolyzed starch prepared in accordance with embodiments of the invention (Table 2).
  • Table 2 For ease of presentation, it will be understood that each value represents “about” that value.
  • the first "X” in Table 2 is the range "from about 30% to about 35%.”
  • the ranges of the table are between and including the starting and endpoints.
  • the pregelatimzed, partially hydrolyzed starch has a cold water viscosity (10% solids, 25°C) of from about 10 BU to about 120 BU, measured according to the Brabender method described herein, e.g., from about 20 BU to about 110 BU, from about 30 BU to about 100 BU, from about 40 BU to about 90 BU, from about 50 BU to about 80 BU, or from about 60 BU to about 70 BU.
  • a board e.g., gypsum wallboard
  • a board can be made by forming a pregelatinized, partially hydrolyzed starch by) mixing at least water, non-pregelatinized starch, and an acid to form a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%, the acid selected from: a weak acid that substantially avoids chelating calcium ions, a strong acid in an amount of about 0.01 wt.% or less by weight of the starch, or any combination thereof.
  • the wet starch precursor is then fed into an extruder in which the temperature of the die of about 150°C (about 300°F) to about 210°C (about 410°F) where the wet starch is pregelatinized and acid-modified, such that it is at least partially hydrolyzed.
  • preglelatinized, partially hydrolyzed starch can then be mixed with at least water and stucco to form a slurry, which can then be disposed between a first cover sheet and a second cover sheet to form a wet assembly.
  • the wet assembly can then be cut into a board, which is then dried.
  • the set gypsum core of the board has a compressive strength greater than a set gypsum core made with a starch prepared under a different method.
  • the pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention surprisingly and unexpectedly can be included in the slurry in a relatively low amount (solids/solids basis) and still achieve significant strength enhancement in the board. Accordingly, the pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention can be included in the gypsum slurry in an amount that is from about 0.1% to about 10% by weight based on the weight of the stucco, e.g., from about 0.5%> to about 10%>.
  • pregelatinized, partially hydrolyzed starch can be added to the gypsum slurry in an amount, for example, as listed in Tables 3A and 3B below.
  • an "X” represents the range “from about [corresponding value in top row] to about [corresponding value in left-most column].”
  • the indicated values represent the amount of starch as a percentage by weight of the stucco. For ease of presentation, it will be understood that each value represents “about” that value.
  • the first "X” is the range "from about 0.1% of the starch by weight of the stucco, to about 0.25% of the starch by weight of the stucco.”
  • the amount of the pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention added to the slurry can have a range between and including any of the aforementioned endpoints set forth in Tables 3 A or 3B.
  • Pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention can be added to the slurry in combination with other starches, in some embodiments for various applications.
  • pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention can be combined with other starches to enhance both core strength and paper-core bond, particularly if some increase in water demand is accepted.
  • gypsum slurry may include one or more pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention, as well as one or more other types of starches.
  • Other starches can include, for example, pregelatinized starches having viscosity below 20 centipoise and/or above 700 centipoise.
  • pregelatinized corn starch e.g., having a viscosity over 700 centipoise such as about 773 centipoise).
  • the other starches may also be in the form of, e.g., non-pregelatinized starches, such as acid-modified starches, as well as alkylated starches, e.g., ethylated starches, that are not gelatinized, etc.
  • the combination of starches may be pre- mixed (e.g, in a dry mix, optionally with other components such as stucco, etc., or in a wet mix with other wet ingredients) before addition to the gypsum slurry, or they can be included in the gypsum slurry one at a time, or any variation thereof. Any suitable proportion of pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention and other starch may be included.
  • the starch content of pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention as a percentage of total starch content to be added to gypsum slurry can be, e.g., at least about 10% by weight, such as at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%), at least about 70%>, at least about 80%>, at least about 90%>, at least about 95%, at least about 99%, at least about 100%, or any range in between).
  • the ratio of pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention to other starch can be about 25:75, about 30:70, about 35:65, about 50:50, about 65:35, about 70:30, about 75:25, etc.
  • the slurry is formulated to include water, stucco, foaming agent (sometimes referred to simply as "foam”), and other additives as desired, in some embodiments.
  • foaming agent sometimes referred to simply as "foam”
  • other additives as desired, in some embodiments.
  • the amount of water needed to be added to maintain the slurry fluidity at the same level it would be without the pregelatinized, partially hydrolyzed starch prepared in an extruder in accordance with embodiments of the invention is less than the increase in the amount of water needed when using a starch prepared according to a different method.
  • the stucco can be in the form of calcium sulfate alpha hemihydrate, calcium sulfate beta hemihydrate, and/or calcium sulfate anhydrite.
  • the stucco can be fibrous or non-fibrous.
  • Foaming agent can be included to form an air void distribution within the continuous crystalline matrix of set gypsum.
  • the foaming agent comprises a major weight portion of unstable component, and a minor weight portion of stable component (e.g., where unstable and blend of stable/unstable are combined).
  • the weight ratio of unstable component to stable component is effective to form an air void distribution within the set gypsum core. See, e.g., U.S. Patents 5,643,510; 6,342,284; and 6,632,550.
  • Evaporative water voids generally having voids of about 5 ⁇ or less in diameter, also contribute to the total void distribution along with the aforementioned air (foam) voids.
  • the volume ratio of voids with a pore size greater than about 5 microns to the voids with a pore size of about 5 microns or less is from about 0.5: 1 to about 9: 1, such as, for example, from about 0.7: 1 to about 9: 1, from about 0.8: 1 to about 9: 1, from about 1.4: 1 to about 9:1, from about 1.8: 1 to about 9: 1, from about 2.3: 1 to about 9:1, from about 0.7: 1 to about 6: 1, from about 1.4: 1 to about 6: 1, from about 1.8: 1 to about 6:1, from about 0.7: 1 to about 4: 1, from about 1.4: 1 to about 4: 1, from about 1.8: 1 to about 4: 1, from about 0.5: 1 to about 2.3: 1, from about 0.7: 1 to about 2.3: 1, from about 0.8: 1 to about 2.3: 1, from about 1.4:1 to about 2.3: 1, from about 1.8: 1 to about 2.3: 1, etc.
  • the foaming agent is present in the slurry, e.g., in an amount of less than about 0.5% by weight of the stucco such as about 0.01% to about 0.5%, about 0.01% to about 0.4%, about 0.01% to about 0.3%, about 0.01% to about 0.2%, about 0.01% to about 0.1%, about 0.02% to about 0.4%, about 0.02% to about 0.3%), about 0.02%) to about 0.2%>, etc., all by weight of the stucco.
  • additives such as accelerator (e.g., wet gypsum accelerator, heat resistant accelerator, climate stabilized accelerator) and retarder are well known and can be included, in some embodiments. See, e.g., U.S. Patents 3,573,947 and 6,409,825. In some
  • the accelerator and/or retarder each can be in the gypsum slurry in an amount on a solid basis of, e.g, from about 0%> to about 10%) by weight of the stucco (e.g., about 0.1%> to about 10%>), such as, for example, from about 0%> to about 5% by weight of the stucco (e.g., about 0.1 % to about 5%).
  • Other additives as desired may be included, e.g., to impart strength to enable lower weight product with sufficient strength, to avoid permanent deformation, to promote green strength, for example, as the product is setting on the conveyor traveling down a manufacturing line, to promote fire resistance, to promote water resistance, etc.
  • the slurry can optionally include at least one dispersant to enhance fluidity in some embodiments.
  • the dispersants may be included in a dry form with other dry ingredients and/or in a liquid form with other liquid ingredients in the core slurry.
  • dispersants include naphthalenesulfonates, such as polynaphthalenesulfonic acid and its salts (polynaphthalenesulfonates) and derivatives, which are condensation products of naphthalenesulfonic acids and formaldehyde; as well as polycarboxylate dispersants, such as polycarboxylic ethers, for example, PCE21 1 , PCE1 1 1 , 1641 , 1641F, or PCE 2641-Type Dispersants, e.g., MELFLUX 2641F, MELFLUX 2651F, MELFLUX 1641F, MELFLUX 2500L dispersants (BASF), and COATEX Ethacryl M, available from Coatex, Inc.; and/or lignosulfonates or sulfonated lignin.
  • naphthalenesulfonates such as polynaphthalenesulfonic acid and its salts (polynaphthalene
  • Lignosulfonates are water-soluble anionic polyelectrolyte polymers, byproducts from the production of wood pulp using sulfite pulping.
  • a lignin useful in the practice of 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 naphthalenesulfonate dispersants are favored because they trend to a lower water demand than the higher viscosity, higher molecular weight dispersants. Thus, molecular weights from about 3,000 to about 10,000 (e.g., about 8,000 to about 10,000) are preferred. As another illustration, for PCE21 1 type dispersants, in some embodiments, the molecular weight can be from about 20,000 to about 60,000, which exhibit less retardation than dispersants having molecular weight above 60,000.
  • DILOFLO naphthalenesulfonate
  • GEO Specialty Chemicals a 45% naphthalenesulfonate solution in water, although other aqueous solutions, for example, in the range of about 35 > to about 55 > by weight solids content, are also readily available.
  • Naphthalenesulfonates can be used in dry solid or powder form, such as LOMAR D, available from GEO Specialty Chemicals, for example.
  • LOMAR D available from GEO Specialty Chemicals, for example.
  • Another exemplary naphthalenesulfonate is DAXAD, available from Hampshire Chemical Corp.
  • the dispersant can be included in any suitable (solids/solids) amount, such as, for example, from about 0.1%> to about 5% by weight based on the weight of the stucco, e.g., from about 0.1%> to about 4%>, from about 0.1%> to about 3%>, from about 0.2%> to about 3%, from about 0.5% to about 3%, from about 0.5%> to about 2.5%, from about 0.5% to about 2%), from about 0.5% to about 1.5%, etc.
  • suitable (solids/solids) amount such as, for example, from about 0.1%> to about 5% by weight based on the weight of the stucco, e.g., from about 0.1%> to about 4%>, from about 0.1%> to about 3%>, from about 0.2%> to about 3%, from about 0.5% to about 3%, from about 0.5%> to about 2.5%, from about 0.5% to about 2%), from about 0.5% to about 1.5%, etc.
  • one or more phosphate-containing compounds can also be optionally included in the slurry, if desired.
  • phosphate-containing components useful in some embodiments include water-soluble components and can be in the form of an ion, a salt, or an acid, namely, condensed phosphoric acids, each of which comprises two or more phosphoric acid units; salts or ions of condensed phosphates, each of which comprises two or more phosphate units; and monobasic salts or monovalent ions of orthophosphates as well as water-soluble acyclic polyphosphate salt. See, e.g., U.S. Patents 6,342,284;
  • Phosphate compositions if added in some embodiments can enhance green strength, resistance to permanent deformation (e.g., sag), dimensional stability, etc.
  • Trimetaphosphate compounds can be used, including, for example, sodium trimetaphosphate, potassium trimetaphosphate, lithium trimetaphosphate, and ammonium trimetaphosphate.
  • the phosphate can be included in some embodiments in a dry form or in a form in water (e.g., a phosphate solution from about 5% to about 20%, such as about a 10% solution). If included, the phosphate can be in any suitable amount (solids/solids basis), such as from about 0.01%) to about 0.5% by weight based on the weight of stucco, e.g., 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%> by weight based on the weight of stucco.
  • Suitable additives for fire -rated and/or water resistant product can also optionally be included, including e.g., siloxanes (water resistance); fiber; heat sink additives such as aluminum trihydrite (ATH), magnesium hydroxide or the like; and/or high expansion particles (e.g., expandable to about 300% or more of original volume when heated for about one hour at 1560°F). See, e.g., co-pending, commonly assigned U.S. Application No.
  • the board of some fire-related product according to the invention can have a Thermal Insulation Index (TI) of about 17 minutes or greater, e.g., about 20 minutes or greater, about 30 minutes or greater, about 45 minutes or greater, about 60 minutes or greater, etc.; and/or a High Temperature Shrinkage (at temperatures of about 1560°F (850 °C)) of less than about 10% in the x-y directions and expansion in the z-direction of greater than about 20%.
  • TI Thermal Insulation Index
  • the fire or water resistance additives can be included in any suitable amount as desired depending, e.g., on fire rating, etc.
  • the fire or water resistance additives can be in an amount from about 0.5%> to about 10%> by weight of the stucco, such as from about 1% to about 10%>, about 1% to about 8%, about 2% to about 10%, about 2% to about 8%) by weight of the stucco, etc.
  • the siloxane preferably is added in the form of an emulsion.
  • the slurry is then shaped and dried under conditions which promote the polymerization of the siloxane to form a highly cross-linked silicone resin.
  • a catalyst which promotes the polymerization of the siloxane to form a highly cross-linked silicone resin can be added to the gypsum slurry.
  • solventless methyl hydrogen siloxane fluid sold under the name SILRES BS 94 by Wacker-Chemie GmbH (Munich, Germany) can be used as the siloxane.
  • This product is a siloxane fluid containing no water or solvents. It is contemplated that about 0.3% to about 1.0% of the BS 94 siloxane may be used in some embodiments, based on the weight of the dry ingredients. For example, in some
  • the slurry formulation can be made with any suitable water/stucco ratio, e.g., from about 0.4 to about 1.3.
  • the pregelatinized, partially hydrolyzed starches prepared in accordance with embodiments of the invention reduce the amount of water required to be added to the slurry to accommodate them, as compared with other starches (e.g., conventional pregelatinized starch prepared according to a different method), the slurry can be formulated with a water/stucco ratio input that is lower in some
  • the water/stucco ratio can be from about 0.4 to about 1.1, from about 0.4 to about 0.9, from about 0.4 to about 0.85, from about 0.45 to about 0.85, from about 0.55 to about 0.85, from about 0.55 to about 0.8, from about 0.6 to about 0.9, from about 0.6 to about 0.85, from about 0.6 to about 0.8, etc.
  • cover sheets can be formed of any suitable material and basis weight.
  • board core formed from slurry comprising pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention provides sufficient strength in board even with lower basis weight cover sheets such as, for example, less than 45 Ibs/MSF (e.g., about 33 Ibs/MSF to 45 Ibs/MSF) even for lower weight board (e.g., having a density of about 35 pcf or below) in some embodiments.
  • lower basis weight cover sheets such as, for example, less than 45 Ibs/MSF (e.g., about 33 Ibs/MSF to 45 Ibs/MSF) even for lower weight board (e.g., having a density of about 35 pcf or below) in some embodiments.
  • heavier basis weights can be used, e.g., to further enhance nail pull resistance or to enhance handling, e.g., to facilitate desirable "feel" characteristics for end- users.
  • one or both of the cover sheets can be formed from paper and have a basis weight of, for example, at least about 45 Ibs/MSF (e.g., from about 45 Ibs/MSF to about 65 Ibs/MSF, from about 45 Ibs/MSF to about 60 Ibs/MSF, from about 45 Ibs/MSF to about 55 Ibs/MSF, from about 50 Ibs/MSF to about 65 Ibs/MSF, from about 50 Ibs/MSF to about 60 Ibs/MSF, etc.).
  • at least about 45 Ibs/MSF e.g., from about 45 Ibs/MSF to about 65 Ibs/MSF, from about 45 Ibs/MSF to about 60 Ibs/MSF, from about 45 Ibs/MSF to about 55 Ibs/MSF, from about 50 Ibs/MSF to about 65 Ibs/MSF, from about 50 Ibs/MSF to about 60 Ibs/MSF, etc.
  • one cover sheet e.g., the "face” paper side when installed
  • the other cover sheet e.g., the "back” sheet when the board is installed
  • weight basis e.g., weight basis of less than about 45 Ibs/MSF, e.g., from about 33 Ibs/MSF to about 45 Ibs/MSF or from about
  • Board weight is a function of thickness. Since boards are commonly made at varying thicknesses, board density is used herein as a measure of board weight. The advantages of the pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention can be seen across various board densities, e.g., about 40 pcf or less, such as from about 20 pcf to about 40 pcf, from about 24 pcf to about 37 pcf, etc.
  • preferred embodiments of the invention have particular utility at lower densities where the enhanced strength provided by the pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention advantageously enables the use of lower weight board with good strength and lower water demand than board made from other starches prepared according to a different method.
  • board density can be from about 20 pcf to about 35 pcf, e.g., from about 20 pcf to about 34 pcf, from about 20 pcf to about 33 pcf, from about 20 pcf to about 32 pcf, from about 20 pcf to about 31 pcf, from about 20 pcf to about
  • 21 pcf to about 34 pcf from about 21 pcf to about 33 pcf, from about 21 pcf to about 32 pcf, from about 21 pcf to about 31 pcf, from about 21 pcf to about 30 pcf, from about 21 pcf to about 29 pcf, from about 24 pcf to about 35 pcf, from about 24 pcf to about 34 pcf, from about 24 pcf to about 33 pcf, from about 24 pcf to about 32 pcf, from about 24 pcf to about
  • pregelatinized, partially hydrolyzed starches prepared in accordance with embodiments of the invention can be added to slurry to provide strength enhancement to product according to the invention, which can be especially beneficial at lower
  • the board made according to
  • embodiments of the invention has a compressive strength of at least about 400 psi
  • the board produced by the inventive method can be prepared to have a compressive strength of at least about 400 psi, e.g., at least about 450 psi (3,100 kPa), at least about 500 psi (3,450 kPa), at least about 550 psi (3,800 kPa), at least about 600 psi (4,100 kPa), at least about 650 psi (4,500 kPa), at least about 700 psi (4,800 kPa), at least about 750 psi (5,200 kPa), at least about 800 psi (5,500 kPa), at least about 850 psi (5,850 kPa), at least about 900 psi (6,200 kPa), at least about 950 psi
  • the compressive strength can be bound by any two of the foregoing points.
  • the compressive strength can be between about 450 psi and about 1,000 psi (e.g., between about 500 psi and about 900 psi, between about 600 psi and about 800 psi, etc.).
  • board made according to the invention meets test protocols according to ASTM Standard C473-10.
  • the board when the board is cast at a thickness of 1 ⁇ 2 inch, the board has a nail pull resistance of at least about 65 lb as determined according to ASTM C473-10, e.g., at least about 68 lb, at least about 70 lb, at least about 72 lb, at least about 75 lb, at least about 77 lb, etc.
  • the nail pull resistance can be from about 68 lb to about 100 lb, e.g., from about 68 lb to about 95 lb, from about 68 lb to about 90 lb, from about 68 lb to about 85 lb, from about 68 lb to about 80 lb, from about 68 lb to about 77 lb, from about 68 lb to about 75 lb, from about 68 lb to about 72 lb, from about 68 lb to about 70 lb, from about 70 lb to about 100 lb, from about 70 lb to about 95 lb, from about 70 lb to about 90 lb, from about 70 lb to about 85 lb, from about 70 lb to about 80 lb, from about 70 lb to about 77 lb, from about 70 lb to about 75 lb, from about 70 lb to about 72 lb, from about 72 lb
  • the board when cast in a board of 1 ⁇ 2 inch thickness, the board has a flexural strength of at least about 36 lb in a machine direction (e.g., at least about 38 lb, at least about 40 lb, etc) and/or at least about 107 lb (e.g., at least about 110 lb, at least about 112 lb, etc) in a cross-machine direction as determined according to the ASTM standard C473.
  • a machine direction e.g., at least about 38 lb, at least about 40 lb, etc
  • at least about 107 lb e.g., at least about 110 lb, at least about 112 lb, etc
  • the board can have a flexural strength in a machine direction of from about 36 lb to about 60 lb, e.g., from about 36 lb to about 55 lb, from about 36 lb to about 50 lb, from about 36 lb to about 45 lb, from about 36 lb to about 40 lb, from about 36 lb to about 38 lb, from about 38 lb to about 60 lb, from about 38 lb to about 55 lb, from about 38 lb to about 50 lb, from about 38 lb to about 45 lb, from about 38 lb to about 40 lb, from about 40 lb to about 60 lb, from about 40 lb to about 55 lb, from about 40 lb to about 50 lb, or from about 40 lb to about 45 lb.
  • the board can have a flexural strength in a cross-machine direction of from about 107 lb to about 130 lb, e.g., from about 107 lb to about 125 lb, from about 107 lb to about 120 lb, from about 107 lb to about 115 lb, from about 107 lb to about 112 lb, from about 107 lb to about 110 lb, from about 110 lb to about 130 lb, from about 110 lb to about 125 lb, from about 110 lb to about 120 lb, from about 110 lb to about 115 lb, from about 110 lb to about 112 lb, from about 112 lb to about 130 lb, from about 112 lb to about 125 lb, from about 112 lb to about 120 lb, or from about 112 lb to about 115 lb.
  • board can have an average core hardness of at least about 11 lb, e.g., at least about 12 lb, at least about 13 lb, at least about 14 lb, at least about 15 lb, at least about 16 lb, at least about 17 lb, at least about 18 lb, at least about 19 lb, at least about 20 lb, at least about 21 lb, or at least about 22 lb, as determined according to ASTM C473-10.
  • board can have a core hardness of from about 11 lb to about 25 lb, e.g., from about 11 lb to about 22 lb, from about 11 lb to about 21 lb, from about 11 lb to about 20 lb, from about 11 lb to about 19 lb, from about 11 lb to about 18 lb, from about 11 lb to about 17 lb, from about 11 lb to about 16 lb, from about 11 lb to about 15 lb, from about 11 lb to about 14 lb, from about 11 lb to about 13 lb, from about 11 lb to about 12 lb, from about 12 lb to about 25 lb, from about 12 lb to about 22 lb, from about
  • these standards e.g., nail pull resistance, flexural strength, and core hardness
  • ultra light density board e.g., about 31 pcf or less
  • pregelatinized, partially hydro lyzed starches prepared in accordance with embodiments of the invention demonstrate temperature rise set (TRS) hydration rates that are comparable to or surpass those of conventional pregelatinized starches prepared according to a different method.
  • TRS temperature rise set
  • the desired setting time may depend on the formulation, and the desired setting time can be determined by one of ordinary skill in the art depending on plant conditions and available raw materials.
  • Product according to embodiments of the invention can be made on typical manufacturing lines.
  • board manufacturing techniques are described in, for example, U.S. Patent 7,364,676 and U.S. Patent Application Publication 2010/0247937.
  • the process typically involves discharging a cover sheet onto a moving conveyor. Since gypsum board is normally formed “face down,” this cover sheet is the “face” cover sheet in such embodiments.
  • Dry and/or wet components of the gypsum slurry are fed to a mixer (e.g., pin mixer), where they are agitated to form the gypsum slurry.
  • the mixer comprises a main body and a discharge conduit (e.g., a gate-canister-boot arrangement as known in the art, or an arrangement as described in U.S. Patents 6,494,609 and 6,874,930).
  • the discharge conduit can include a slurry distributor with either a single feed inlet or multiple feed inlets, such as those described in U.S. Patent Application Publication
  • the discharge conduit can include a suitable flow splitter, such as those described in U.S. Patent Application Publication 2012/0170403 Al .
  • Foaming agent can be added in the discharge conduit of the mixer (e.g., in the gate as described, for example, in U.S. Patents 5,683,635 and 6,494,609) or in the main body if desired. Slurry discharged from the discharge conduit after all ingredients have been added, including foaming agent, is the primary gypsum slurry and will form the board core. This board core slurry is discharged onto the moving face cover sheet.
  • the face cover sheet may bear a thin skim coat in the form of a relatively dense layer of slurry.
  • hard edges as known in the art, can be formed, e.g., from the same slurry stream forming the face skim coat.
  • a stream of secondary gypsum slurry can be removed from the mixer body to form the dense skim coat slurry, which can then be used to form the face skim coat and hard edges as known in the art.
  • the face skim coat and hard edges are deposited onto the moving face cover sheet before the core slurry is deposited, usually upstream of the mixer.
  • the core slurry is spread, as necessary, over the face cover sheet (optionally bearing skim coat) and covered with a second cover sheet (typically the "back" cover sheet) to form a wet assembly in the form of a sandwich structure that is a board precursor to the final product.
  • the second cover sheet may optionally bear a second skim coat, which can be formed from the same or different secondary (dense) gypsum slurry as for the face skim coat, if present.
  • the cover sheets may be formed from paper, fibrous mat or other type of material (e.g., foil, plastic, glass mat, non- woven material such as blend of cellulosic and inorganic filler, etc.).
  • the wet assembly thereby provided is conveyed to a forming station where the product is sized to a desired thickness (e.g., via forming plate), and to one or more knife sections where it is cut to a desired length.
  • the wet assembly is allowed to harden to form the interlocking crystalline matrix of set gypsum, and excess water is removed using a drying process (e.g., by transporting the assembly through a kiln).
  • the pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention can be used in formulating various products, such as, for example, gypsum wallboard, acoustical (e.g., ceiling) tile, joint compound, gypsum-cellulosic fiber products, such as gypsum-wood fiber wallboard, and the like.
  • products such as, for example, gypsum wallboard, acoustical (e.g., ceiling) tile, joint compound, gypsum-cellulosic fiber products, such as gypsum-wood fiber wallboard, and the like.
  • such product can be formed from slurry according to embodiments of the invention.
  • pregelatinized, partially hydrolyzed starch prepared in an extruder in accordance with embodiments of the invention can have beneficial effect, as described herein, in product besides paper-faced gypsum board in embodiments of the invention.
  • embodiments of the invention can be used in mat-faced products (e.g., woven) where board cover sheets are in the form of fibrous mats.
  • the mats can optionally bear a finish to reduce water permeability.
  • Other ingredients that can be included in making such mat- faced product, as well as materials for the fibrous mats and methods of manufacture, are discussed in, e.g., U.S. Patent 8,070,895, as well as U.S. Patent Application Publication 2009/0247937.
  • gypsum-cellulosic product can be in the form of cellulosic host particles (e.g., wood fibers), gypsum, pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention, and other ingredients (e.g., water resistant additives such as siloxanes) as desired.
  • cellulosic host particles e.g., wood fibers
  • gypsum e.g., pregelatinized, partially hydrolyzed starch prepared in accordance with embodiments of the invention
  • other ingredients e.g., water resistant additives such as siloxanes
  • Other ingredients and methods of manufacture are discussed in, e.g., U.S. Patents 4,328,178; 4,239,716; 4,392,896; 4,645,548; 5,320,677;
  • a method of making a pregelatinized, partially hydrolyzed starch comprises: (a) mixing at least water, non-pregelatinized starch, and a weak acid that substantially avoids chelating calcium ions to make a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%; (b) feeding the wet starch precursor into an extruder; and (c) pregelatinizing and acid-modifying the wet starch precursor in the extruder at a die temperature of about 150°C (about 300°F) to about 210°C (about 410°F).
  • the pressure inside the extruder is at least about 2,000 psi.
  • the pregelatinized, partially hydrolyzed starch has a cold water solubility greater than about 50%.
  • the pregelatinized, partially hydrolyzed starch has a cold water viscosity (10%> solids, 25°C) of from about 10 Brabender Unit (BU) to about 120 BU.
  • BU Brabender Unit
  • the pregelatinized, partially hydrolyzed starch has a viscosity characteristic of from about 20 centipoise to about 700 centipoise when the viscosity is measured while the starch is subjected to the conditions according to the VMA method.
  • the pregelatinized, partially hydrolyzed starch has a viscosity (10% solids, 93°C) of from about 5 BU to about 33 BU.
  • the weak acid that substantially avoids chelating calcium ions comprises alum.
  • tartaric acid is included in the mixing to form the wet starch precursor.
  • the weak acid that substantially avoids chelating calcium ions is in an amount of from about 0.5 wt.% to about 5 wt.% by weight of the starch.
  • the wet starch has a moisture content of from about 10 wt.%) to about 20 wt.%> by weight of the starch precursor.
  • the pregelatinizing and acid-modifying occurs at a die temperature of from at least about 175°C (about 350°F) to about 205°C (about 400°F) in the extruder.
  • the output of the pregelatinized, partially hydrolyzed starch is at least about 100 kg/hr in the extruder.
  • the pregelatinizing and acid-modifying occurs in less than about 5 minutes.
  • the pregelatinizing and acid-modifying occurs in less than about 1 minute.
  • the method is free of a purification step for the pregelatinized, partially hydrolyzed starch.
  • the method is free of a neutralization step for the pregelatinized, partially hydrolyzed starch.
  • the pregelatinized, partially hydrolyzed starch is at least about 70% gelatinized.
  • a pregelatinized, partially hydrolyzed starch is prepared according to embodiments of the invention.
  • a method of making a pregelatinized, partially hydrolyzed starch comprises: (a) mixing at least water, non-pregelatinized starch, and a strong acid to make a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%), wherein the strong acid is in an amount of about 0.05 wt.% or less by weight of the starch; (b) feeding the wet starch precursor into an extruder; and (c) pregelatinizing and acid- modifying the wet starch in the extruder at a die temperature of about 150°C (about 300°F) to about 210°C (about 410°F).
  • a method of making a pregelatinized, partially hydrolyzed starch comprises: (a) mixing at least water, non-pregelatinized starch, and a strong acid to make a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%), wherein the strong acid is in an amount of about 0.01 wt.% or less by weight of the starch; (b) feeding the wet starch precursor into an extruder; and (c) pregelatinizing and acid- modifying the wet starch in the extruder at a die temperature of about 150°C (about 300°F) to about 210°C (about 410°F).
  • the strong acid has a pKa of about -1.7 or less.
  • the strong acid is sulfuric acid, nitric acid, hydrochloric acid, or any combination thereof.
  • the method of making board comprises: (a) forming a pregelatinized, partially hydrolyzed starch by (i) mixing at least water, non-pregelatinized starch, and an acid to form a wet starch precursor having a moisture content of from about 8 wt.%) to about 25 wt.%, the acid selected from the group consisting of: (1) a weak acid that substantially avoids chelating calcium ions, (2) a strong acid in an amount of about 0.05 wt.% or less by weight of the starch, or (3) any combination thereof; (ii) feeding the wet starch precursor into an extruder; and (iii) pregelatinizing and acid-modifying the wet starch in the extruder having a die at a temperature of about 150°C (about 300°F) to about 210°C (about 410°F); (b) mixing the pregelatinized and partially hydrolyzed starch with at least water and stucco to form a slurry; (c) dispos
  • the strong acid is in an amount of about 0.01 wt.% or less by weight of the starch.
  • a method of making board comprises (a) forming a pregelatinized, partially hydrolyzed starch by (i) mixing at least water, non-pregelatinized starch, and a weak acid that substantially avoids chelating calcium ions to make a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%; (ii) feeding the wet starch into an extruder; and (iii) pregelatinizing and acid-modifying the wet starch in an extruder having a die at a temperature of about 150°C (about 300°F) to about 210°C (about 410°F); (b) mixing the pregelatinized and partially hydrolyzed starch with at least water and stucco to form a slurry; (c) disposing 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.
  • the method of making board comprises: (a) mixing at least water, non-pregelatinized starch, and a strong acid to make a wet starch precursor having a moisture content of from about 8 wt.% to about 25 wt.%, wherein the strong acid is in an amount of about 0.05 wt.% or less by weight of the starch; (ii) feeding the wet starch precursor into an extruder; and (iii) pregelatinizing and acid-modifying the wet starch in the extruder having a die at a temperature of about 150°C (about 300°F) to about 210°C (about 410°F); (b) mixing the pregelatinized and partially hydrolyzed starch with at least water and stucco to form a slurry; (c) disposing 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.
  • the strong acid is in an amount of about 0.01 wt.% or less by weight of the starch.
  • the set gypsum core has a compressive strength greater than a set gypsum core made with a starch prepared under a different method.
  • the pregelatinized, partially hydrolyzed starch is at least about 70% gelatinized when added to the slurry, with additional gelatinization taking place in the drying step.
  • the pregelatinized, partially hydrolyzed starch is fully gelatinized when added to the slurry.
  • the board has a compressive strength of at least about 400 psi (2,800 kPa) at a density of 29 pcf
  • the board has a core hardness of at least about 11, as determined according to ASTM C473-10.
  • the board has a density of from about 21 pcf to about 35 pcf.
  • the slurry further comprises sodium trimetaphosphate.
  • the amount of water needed to be added to maintain the slurry fluidity at the same level it would be without the pregelatinized, partially hydrolyzed starch is less than the increase in the amount of water needed when using a pregelatinized, partially hydrolyzed starch prepared according to a different method.
  • the starch is in an amount of from about 0.5% to about 10%) by weight based on the weight of the stucco.
  • a wallboard is prepared according to embodiments of the invention.
  • This Example illustrates the preparation of pregelatinized, partially hydrolyzed starches in accordance with embodiments of the invention.
  • wet starch precursors were prepared by mixing a degerminated corn flour commercially available as CCM 260 Yellow Corn Meal from Bunge North America (St. Louis, MO) in an amount of 100 kg, varying amounts of aluminum sulfate (alum), a weak acid that substantially avoids chelating with calcium ions, and/or tartaric acid (less than 20 wt.% of the total of weak acids), and varying amounts of water.
  • the wet starch precursors were fed into a single screw extruder commercially available as Advantage 50 from
  • Table 4 describes the parameters of the extrusion of the corn flour in the presence of acid.
  • the residence time of extrusion i.e., the time for pregelatinization and acid-modification
  • composition 1 A comparative
  • Composition 1 B two low water-demand starches prepared by extrusion of acid-modified corn starches, commercially available as Clinton 277 (ADM, Chicago, IL) and Caliber 159 (Cargill, Wayzata, MN), designated Composition IB
  • Compositions 1D-1L Pregelatinized, partially hydrolyzed starches, designated Compositions 1D-1L, were produced in the extrusion process.
  • compositions 1D-1H and IL were prepared with a moisture content of 16 wt.%, while Compositions 1I-1K were prepared with a moisture content of 13 wt.%.
  • Compositions 1D-1G and Compositions 1I-1L were prepared with liquid alum in an amount of ranging from 1 wt.% to 4 wt.%, while Composition 1H included liquid alum and tartaric acid.
  • Compositions IF and IL were prepared using the same moisture content and amount of acid, but in Example 3 had different amounts of retarder.
  • Examples 2-4 below test the Compositions described in Table 5 for various properties.
  • Compositions 1B-1L were evaluated with regards to viscosity in amylograph tests.
  • Example 3 tested slurries prepared with one of Compositions 1 A, 1D-1I, and 1K-1L for fluidity, which was evaluated by means of a slump test. This data was then further corroborated by measuring the time to 50% hydration for the slurries. This illustrated how much time it took for the slurries to set.
  • Example 4 tested slurries prepared with Compositions 1 A, ID- II, and IK for strength, which was evaluated by means of a compressive strength test described herein.
  • This example illustrates the viscosity of pregelatinized, partially hydrolyzed starches prepared in an extruder in accordance with embodiments of the invention.
  • compositions ID- IK were tested in comparison to extruded commercially available acid- modified starches (Compositions 1B-1C), specifically with regards to how viscosity changes based on the amount of acid (e.g., alum) and moisture content, defined by the level of moisture of the wet starch that is fed through the extruder.
  • acid e.g., alum
  • moisture content defined by the level of moisture of the wet starch that is fed through the extruder.
  • the Compositions were mixed with water into a starch slurry, such that the starch slurries contained the Compositions in an amount of 10 wt.%. It will be noted that 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 Amylograph technique described herein. The results of the tests were plotted in FIGS.
  • the initial viscosity at 25°C was an indicator of the fluidity of a slurry system containing any one of Compositions 1B-1K.
  • 25°C is the temperature at which the starch will be mixed with stucco and other ingredients to make board. At this temperature, furthermore, the viscosity of the starch is negatively correlated with the fluidity of the stucco slurry.
  • the viscosity at trough was an indicator of the molecular weight of any one of Compositions IB- IK.
  • the viscosity of the starch solutions at 93°C is positively correlated with the molecular weight of the starch, which results from partial hydrolysis.
  • FIG. 1 is an amylogram plotting viscosity (left y-axis) and temperature (right y-axis) over a fifty minute period (x-axis).
  • Comparative Compositions IB and 1C and inventive Compositions 1D-1H, as described herein, were mixed into starch solutions in an amount of 10% by weight based on the weight of the solution.
  • starch was added into the water in a mixing cup of a Waring blender while mixed at low speed for 20 seconds.
  • the starch solutions were then evaluated using a Viscograph-E (C.W. Brabender® Instruments, Inc., South hackensack, NJ).
  • viscosity is measured using a C.W. Brabender Viscograph, e.g., a Viscograph-E that uses reaction torque for dynamic measurement.
  • the Brabender units are measured using a sample cup size of 16 fl. oz (about 500 cc), with a 700 cmg cartridge at an RPM of 75.
  • Krebs units as described therein.
  • compositions IB and 1C Compositions IB and 1C.
  • compositions 1D-1H As alum increased from 1 wt.% to 4 wt.%, the initial viscosity decreased from 70 Brabender Unit (BU) to 10 BU, while the molecular weight decreased as well.
  • the initial viscosities and viscosities at 93°C of Compositions 1D-1H were reduced as low as those of Compositions IB and 1C.
  • Compositions IB and 1C represent conventional viscosity limits of low water demand starches.
  • compositions 1D-1H shown in FIG. 1 demonstrate that optimal acid-modification can be achieved 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 between 70°C to 90°C, indicating that Compositions 1D-1H were fully gelatinized. Had Compositions 1D-1H not been fully gelatinized, there would have been an increase in viscosity. The full gelatinization of the starch Compositions were confirmed by differential scanning calorimetry (DSC).
  • DSC differential scanning calorimetry
  • FIG. 2 is a second amylogram plotting viscosity (left y-axis) and temperature (right y-axis) over a fifty minute period (x-axis).
  • Comparative Compositions IB and 1C and inventive Compositions II- IK, all as described herein, were mixed into starch solutions in an amount of 10%> by weight based on the weight of the solution.
  • starch was added into the water in a mixing cup of a Waring blender while mixed at low speed for 20 seconds.
  • the starch solutions were then evaluated using a Viscograph-E.
  • the pasting profiles of Compositions 1I-1K extruded at 13 wt.% moisture content are shown in FIG. 2 along with comparative Compositions IB and 1C.
  • compositions II- IK Compositions II- IK.
  • the method of preparing pregelatinized, partially hydrolyzed starch in an extruder as described herein successfully reduced the viscosity of Compositions II- IK.
  • compositions 1I-1K shown in FIG. 2 demonstrate that optimal acid-modification can be achieved during extrusion. No viscosity peak was observed between 70°C to 90°C, indicating that Compositions II- IK were fully gelatinized.
  • This Example illustrates the fluidity of gypsum slurries containing Compositions 1A (comparative), 1D-1I, and 1K-1L.
  • the Compositions were evaluated with regards to fluidity using a slump test that will be appreciated by one of ordinary skill in the art.
  • PFM-33 foam (0.5% solution) 25 [0185]
  • the starch was weighed into a dry mix comprising stucco having over 95% purity and heat resistance accelerator. Water, sodium trimetaphosphate (10 wt.% solution), dispersant, and retarder were weighed into the mixing bowl of a Hobart Mixer. The dry mix was poured into the mixing bowl of a mixer available as N50 5 -Quart Mixer from Hobart (Troy, OH), soaked for 10 seconds, and mixed at speed II for 30 seconds.
  • a 0.5% solution of Hyonic® PFM-33 soap available from GEO® Specialty Chemicals, Ambler, PA
  • the air foam was added to the slurry using a foam generator.
  • Composition 1A 0.05 wt.% 13.7 cm (5 3/8 in) 4
  • Composition ID 0.05 wt.% 16.5 cm (6 1/2 in) 3.8
  • Composition 1G 0.05 wt.% 16.2 cm (6 3/8 in) 3.3
  • composition 11 0.05 wt.% 15.9 cm (6 1/4 in) 3.6
  • Composition IK 0.05 wt.% 18.4 cm (7 1/4 in) 3.4
  • composition 1L 0.0625 wt.% 18.4 cm (7 1/4 in) 4
  • Composition 1H prepared with 2 wt.% alum and 0.3 wt.% tartaric acid, effectively hydrolyzed starch to a low viscosity and had less impact on the hydration rate, because tartaric acid and alum had opposite effect on hydration rate.
  • FIG. 3 is a graph plotting temperature versus time, showing the temperature rise set (TRS) hydration rate.
  • composition 1 A hydrate faster or at the same rate as Composition 1 A (comparative).
  • Composition 1L As seen in FIG. 3, Composition 1L, with 0.0625 wt.% of retarder, had the same hydration rate as Composition 1A (comparative).
  • the slump size of Composition 1L with 0.065 wt.% retarder was 18.415 cm (7 1/4 in), was significantly larger than Composite 1A.
  • This Example illustrates the strength of gypsum disks prepared with slurries containing Compositions 1A (comparative), 1D-1I, and IK. Strength was evaluated using a compressive strength test described herein.
  • a water stucco ratio (WSR) of 100 and air foam were used to make gypsum disks with a final density of 29 pcf.
  • the starch was weighed into a dry mix comprising stucco and heat resistance accelerator.
  • Water, sodium trimetaphosphate 10% solution, dispersant, and retarder were weighed into the mixing bowl of a Hobart Mixer.
  • the dry mix was poured into the mixing bowl of a mixer available as N50 5-Quart Mixer from Hobart (Troy, OH), soaked for 10 seconds, and mixed at speed II for 30 seconds.
  • Hyonic® PFM-33 soap available from GEO® Specialty Chemicals, Ambler, PA
  • the air foam was added to the slurry using a foam generator.
  • the foam generator was run at a rate sufficient to obtain the desired board density of 29 pcf.
  • the slurry was immediately poured to a point slightly above the tops of the molds. The excess was scraped as soon as the plaster set.
  • the molds had been sprayed with mold release (WD-40TM).
  • the disks had a diameter of 10.16 cm (4 in) and a thickness of 1.27 cm (0.5 in).
  • the disks were removed from the mold, and then dried at 110°F (43°C) for 48 hours. After removing from the oven, the disks were allowed to cool at room temperature for 1 hour.
  • the compressive strength was measured using a materials testing system commercially available as SATECTM E/M Systems from MTS Systems Corporation (Eden Prairie, Minnesota). The load was applied continuously and without a shock at speed of 0.04 inch/min (with a constant rate between 15 to 40 psi/s). The results are shown in Table 8 below.
  • the foam disks containing Compositions ID- II and IK had compressive strengths comparable to that which contained Composition 1 A (comparative), indicating pregelatinized, partially hydrolyzed starches could reduce water demand without sacrificing their strength enhancing property.
  • the desirable compressive strength of the disk samples is approximate 400 psi. The strength is required so that the board can be properly handled without falling apart.

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US14/494,547 US9828441B2 (en) 2012-10-23 2014-09-23 Method of preparing pregelatinized, partially hydrolyzed starch and related methods and products
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