Functionalized starch for gypsum boards

Abstract

The present invention relates to a process for the manufacture of gypsum boards using functionalized starch as adhesive and / or fluidizing agent, gypsum boards obtainable by such a process, and compositions useful in such a process.

Description

[0001] The present invention relates to a method for manufacturing gypsum board using functionalized starch as an adhesive and / or fluidizing agent, gypsum board that can be obtained by such method, and compositions that can be used in such method.

[0002] Gypsum board is a panel consisting of a layer of plaster sandwiched between two facing sheets, typically made of paper backing. Industrially, the manufacture of gypsum board involves three main stages: forming, setting, and drying. In the forming stage, a slurry is continuously prepared in a mixer from calcined plaster powder, water, and other specific ingredients to shape the composition and / or the properties of the final product. The composition is then continuously poured onto a first sheet conveyed by a conveyor belt (usually towards an extruder) to form a board. After the edges of the first sheet have been folded, a second facing sheet is typically introduced at the extruder. When in use, the extruder flattens the second sheet on the composition, smoothing the surface and reducing the thickness of the gypsum board to the desired value.

[0003] A key feature of much research is the adhesion of sheets (typically paper sheets) to the plaster core of boards. To improve adhesion, starch is often added to the slurry, and during the drying process of the board, the starch migrates towards the paper and concentrates at the core / finishing interface. This is achieved by selecting starches with specific rheologies that vary with temperature.

[0004] EP0172773 describes the use of natural or modified starch in the manufacture of paper-faced boards with improved core / paper adhesion. EP0936201 describes the use of starch mixtures modified in relation to the long-term strength of mixtures of cementitious materials, including plaster. The purpose of this document is to control the setting and slump values ​​of the mixed slurry without affecting long-term strength.

[0005] US2004 / 045481 describes a slurry for lightweight boards comprising hemihydrate, starch, foam, and water, wherein the starch comprises 1.5 to 3% by weight of the hemihydrate. The resulting board has a reduced density.

[0006] US2003 / 084980 describes a slurry for lightweight panels comprising a hemihydrate, acid-hydrolyzed starch, a starch crosslinking agent, and water. The starch used has a low gelatinization temperature, promoting its migration to the core / finishing interface, while crosslinking prevents complete migration of the starch out of the core.

[0007] US2005 / 126437 describes the use of modified starch for improving strength, wherein the modified starch is insoluble in the slurry during mixing but dissolves upon increasing temperature. The starch is modified, for example, by hydroxyalkylation or acetylation.

[0008] To improve the fluidity of the slurry, a fluidizing agent must be added. US 2011 / 195241 and EP3393997 describe gypsum panels containing starch and a fluidizing agent, which may be naphthalene sulfonate, phosphate condensate, or polycarboxylate.

[0009] To limit the amount of additives in the slurry and thereby simplify the method of manufacturing gypsum board, it would be advantageous to have compounds that can act as both adhesives and fluidizing agents.

[0010] The inventors have now discovered compounds that satisfy this need. Specifically, these compounds are specific starches that are functionalized by esterification with dicarboxylic acids (or their derivatives) substituted with long aliphatic chains. The inventors have demonstrated that low concentrations of this compound in slurries used to prepare gypsum board result in good adhesion and fluidization properties. Such technical effects are quite surprising for this type of ester-functionalized starch, which is commonly used in the food and pharmaceutical industries but not in the construction industry.

[0011] Therefore, the present invention relates to a method for manufacturing gypsum board, comprising: - A composition comprising water, calcined gypsum powder, and starch functionalized with groups of formula (I) is provided: - - -C(O)-RC(O)O - M + (I), in: R is a C1-C12 aliphatic divalent chain replaced by a C4-C22 aliphatic chain, and M + It is a cation. - The composition is poured onto the first strip to form a wet plaster layer on the first strip. - Provide a second strip on the wet plaster layer, and - To shape plasterboard, an extruder is preferred.

[0012] In some embodiments, R is a C2 or C3 alkylene chain substituted with a C6-C12 alkenyl chain, preferably a C2 alkylene chain substituted with a C8 alkenyl chain.

[0013] In some embodiments, the starch is pregelatinized starch or ungelatinized starch, more particularly ungelatinized acid-hydrolyzed starch, ungelatinized oxidized starch, pregelatinized acid-hydrolyzed starch, or pregelatinized oxidized starch.

[0014] In some implementations, the starch is ungelatinized starch, such as ungelatinized acid-hydrolyzed starch or ungelatinized oxidized starch.

[0015] In some embodiments, the content of fluidizing agent other than the starch functionalized with the group of formula (I) is less than 0.1 wt%, preferably less than 0.05 wt%, more preferably less than 0.04 wt%, and even more preferably less than 0.03 wt% relative to the dry weight of gypsum powder.

[0016] In some embodiments, the composition does not contain any fluidizing agent other than starch functionalized with the group of formula (I).

[0017] In some embodiments, the content of calcined gypsum powder is at least 60% by weight relative to the total solids content of the composition.

[0018] In some embodiments, the starch functionalized with the group of formula (I) is at least 0.1% by weight, preferably at least 0.5% by weight, and at most 10% by weight, preferably at most 7% by weight, for example at most 5% by weight, relative to the dry weight of gypsum powder.

[0019] In some embodiments, the weight ratio of water to calcined gypsum powder in the composition is: - At least 0.19, and - Up to 0.85, preferably up to 0.80, more preferably up to 0.65, and even more preferably up to 0.55.

[0020] In some embodiments, the composition further comprises at least one reinforcing agent, such as glass fiber or polyvinyl acetate.

[0021] In some embodiments, the composition further comprises additives, preferably selected from accelerators, retarders, flame retardants, anti-sagging agents, flame retardants, anti-shrinkage agents, biocides, and waterproofing agents.

[0022] In some implementations, the first and second strips are paper or cardboard strips.

[0023] In some implementations, the method further includes a solidification step and a drying step.

[0024] The present invention also relates to gypsum boards that can be obtained by methods as defined herein.

[0025] Another object of the present invention is a composition comprising: - Calcined gypsum powder, - Starch functionalized with the group of formula (I): - - -C(O)-RC(O)O - M + (I), in: R is a C1-C12 aliphatic divalent chain substituted with a C4-C22 aliphatic chain (preferably: R is a C2 or C3 alkylene chain substituted with a C6-C12 alkenyl chain, more preferably R is a C2 alkylene chain substituted with a C8 alkenyl chain), and M + It is a cation, and - water.

[0026] In some embodiments, the composition comprises one or more of the following features: - The content of calcined gypsum powder is at least 60% by weight relative to the total solids content of the composition, and / or - The content of starch functionalized with the group of formula (I) is at least 0.1% by weight, preferably at least 0.5% by weight, and at most 10% by weight, preferably at most 7% by weight, for example at most 5% by weight, relative to the dry weight of gypsum powder, and / or - The weight ratio of water to calcined gypsum powder in the composition is at least 0.19 and at most 0.80, preferably at most 0.65, and more preferably at most 0.55.

[0027] Detailed description This invention is based on the use of a specific starch in a composition (or "slurry") for the manufacture of gypsum board. More specifically, this invention provides a composition comprising water, calcined gypsum powder, and starch functionalized with groups of formula (I): - - -C(O)-RC(O)O - M + (I), in: R is a C1-C12 aliphatic divalent chain that has been replaced by a C4-C22 aliphatic chain. M + It is a cation.

[0028] As used in this article, the term "gypsum" encompasses: - Calcium sulfate dihydrate (CaSO4·2H2O), which corresponds to solidified gypsum. - Calcium sulfate hemihydrate (CaSO4·1 / 2H2O), which corresponds to uncured gypsum (also known as "hemihydrate gypsum" or "calcined gypsum"), and / or - Its mixture, which specifically corresponds to plaster that has not fully hardened.

[0029] As used herein, the term "calcined gypsum powder" refers to any natural or synthetic calcined gypsum powder that is composed of or substantially composed of calcium sulfate hemihydrate (CaSO4·1 / 2H2O).

[0030] The term "gypsum board" (or equivalently, "gypsum-based panel," "gypsum board," or "drywall") refers to, for example, a finished product formed from solidified gypsum, as well as gypsum boards where the gypsum has not fully solidified during the manufacturing process.

[0031] Advantageously, the content of calcined gypsum powder in the composition is at least 60% by weight (e.g., at least 65% by weight, at least 70% by weight, at least 75% by weight, or at least 80% by weight) relative to the total solids content of the composition.

[0032] In some embodiments, the weight ratio of water to calcined gypsum powder in the composition is at least 0.19, for example at least 0.25, at least 0.3, at least 0.4, or at least 0.5.

[0033] In some embodiments, the weight ratio of water to calcined gypsum powder in the composition is at most 0.85, preferably at most 0.80, for example at most 0.65, or at most 0.55.

[0034] In one particular embodiment, the weight ratio of water to calcined gypsum powder in the composition is 0.5 to 0.8.

[0035] The composition comprises starch functionalized with groups of formula (I) as defined herein (hereinafter, "functionalized starch"). Such functionalization can be carried out by esterification of the starch with a diacid compound of formula (II): HO(O)CRC(O)OH, wherein R is as defined in formula (I), or by any ester, anhydride, or salt of such diacid. This type of starch functionalization is well known to those skilled in the art and is specifically described in Ackar et al., Molecules 2015, 20, 10, 19554-19570.

[0036] The functionalized starch in the composition can be obtained from starch of any source, such as corn (e.g., waxy corn, dent corn), potato, sorghum, arrowroot, wheat, cassava, or rice, especially corn (e.g., waxy corn) or cassava.

[0037] In some embodiments, the functionalized starch of the composition is natural starch functionalized with groups of formula (I) as defined herein.

[0038] In some embodiments, the functionalized starch of the composition is ungelatinized (or equivalently "unpregelatinized") or pregelatinized starch functionalized with groups of formula (I) as defined herein. Preferably, the functionalized starch of the composition is ungelatinized (or equivalently "unpregelatinized") starch functionalized with groups of formula (I) as defined herein.

[0039] In some embodiments, the functionalized starch of the composition is a modified starch functionalized with groups of formula (I) as defined herein. “Modified starch” refers to starch that has undergone at least one modification reaction (different from a functionalization reaction), such as acid hydrolysis, oxidation, or pregelatinization. Modified starch may, in particular, be ungelatinized acid-hydrolyzed starch, ungelatinized oxidized starch, pregelatinized acid-hydrolyzed starch, or pregelatinized oxidized starch. One or more modification reactions may be carried out before or after functionalization.

[0040] The functionalized starch of the composition may have 10 4 Up to 10 9 g / mol, preferably 10 5 Up to 10 7 g / mol, more preferably 10 g / mol 5 Up to 10 6 The weight-average molecular weight (g / mol) can be determined by asymmetric flow field separation (AF4), multi-angle light scattering, and / or refractive index detection.

[0041] The functionalized starch in the composition advantageously has a gelatinization temperature (Tgel) of up to 45°C, preferably up to 40°C, more preferably up to 35°C, for example, from 15°C to 45°C. The gelatinization temperature can be determined by viscometry, particularly by a rapid viscometer. Typical viscometry methods for determining gelatinization temperature have the following characteristics: - Temperature profile: (i) Hold at 35°C for 5 minutes, (ii) Increase temperature between 35°C and 90°C for 10 minutes, (iii) Hold at 90°C for 10 minutes, (iv) Cool between 90°C and 35°C for 5 minutes; - Functionalized starch concentration: 14% by weight dry weight based on water.

[0042] In this paper, the gelatinization temperature is defined as the temperature at which the viscosity changes by 4 cP / s over time.

[0043] Preferably, the functionalized starch has a solubility in distilled water at 25°C of 90% or higher, more preferably 95% or higher, even more preferably 98% or higher, and particularly 99% or higher.

[0044] Functionalized starch contains unfunctionalized hydroxyl groups (i.e., -OH groups) and hydroxyl groups functionalized with the group of formula (I).

[0045] The content of hydroxyl groups functionalized using formula (I) can be: - At least 0.01%, such as at least 0.05%, at least 0.1%, at least 0.5%, at least 1%, at least 2%, at least 5%, at least 10%, or at least 20%, and - Preferably up to 70%, for example up to 60%, up to 50%, up to 40%, up to 30%, up to 20%, or up to 10%. Such content is defined as: (number of hydroxyl groups functionalized with the group of formula (I)) / (number of unfunctionalized hydroxyl groups + number of hydroxyl groups functionalized with the group of formula (I)).

[0046] Advantageously, the amount of groups of formula (I) in the functionalized starch is such that: - The functionalized starch has a solubility in distilled water at 25°C of 90% or higher, more preferably 95% or higher, even more preferably 98% or higher, and particularly 99% or higher; and - The slump of the compositions of the present invention is at least 5% higher, preferably at least 10% higher, and more preferably at least 15% higher than that of similar compositions without starch.

[0047] Slump can be determined by mixing the components of the composition (e.g., gypsum powder, water, additives, etc.) and vigorously agitating them in a mixer (e.g., a Waring Blender LB20E*, at speed 12 for 20 seconds) to form a slurry, and then immediately pouring the resulting slurry into a slump ring. The slump ring is then quickly lifted, and the liquid slurry forms a cake. The diameter of the cake is measured using a ruler.

[0048] In equation (I), R is a C1-C12 aliphatic divalent chain that has been replaced by a C4-C22 aliphatic chain.

[0049] As used herein, the term "aliphatic [divalent] chain" refers to a straight or branched (preferably straight) hydrocarbon [divalent] chain, saturated or unsaturated.

[0050] In one particular embodiment, the aliphatic chain is an alkyl or alkenyl chain.

[0051] In one particular embodiment, the aliphatic divalent chain is an alkylene or alkenylene chain.

[0052] As used herein, the term "alkyl" refers to a straight-chain or branched (preferably straight-chain) saturated hydrocarbon chain.

[0053] As used herein, the term "alkylene" refers to a straight-chain or branched (preferably straight-chain) divalent chain of a saturated hydrocarbon.

[0054] As used herein, the term "alkenyl" refers to a straight-chain or branched (preferably straight-chain) unsaturated hydrocarbon chain having at least one carbon-carbon double bond.

[0055] As used herein, the term "alkenyl" refers to a straight-chain or branched (preferably straight-chain) unsaturated hydrocarbon divalent chain having at least one carbon-carbon double bond.

[0056] In one particular embodiment, R is a C1-C6 aliphatic divalent chain (preferably C1-C6 alkylene, more preferably C2 or C3 alkylene) substituted with a C4-C22 aliphatic chain.

[0057] In a more particular embodiment, R is a C1-C6 aliphatic divalent chain (preferably C1-C6 alkylene, more preferably C2 or C3 alkylene) substituted with a C6-C12 aliphatic chain.

[0058] In one or even more particular embodiment, R is a C1-C6 aliphatic divalent chain substituted with a C6-C12 alkenyl group (preferably a C1-C6 alkylene chain, more preferably a C2 or C3 alkylene chain).

[0059] Preferably, R is a C2 or C3 alkylene chain substituted with a C6-C12 alkenyl chain.

[0060] More preferably, R is a C2 alkylene chain substituted with a C8 alkenyl chain.

[0061] M + It is a cation. M+ can be any cation generated by the neutralization of a -COOH group by a base. In a preferred embodiment, M... + It is an alkali metal cation, such as lithium, sodium, or potassium cation. Preferably, M + It is a sodium cation.

[0062] In formula (I), the symbol "---" represents the following bond, through which the group of formula (I) is connected to the rest of the molecule, more specifically to the oxygen of the hydroxyl group derived from starch, thereby forming an ester bond.

[0063] In a preferred embodiment, the groups of formula (I) are represented as follows: .

[0064] In some embodiments, the starch functionalized with the group of formula (I) is at least 0.1% by weight, preferably at least 0.5% by weight, and more preferably at least 1% by weight relative to the dry weight of gypsum powder.

[0065] In some embodiments, the content of starch functionalized with the group of formula (I) is at most 10% by weight, preferably at most 7% by weight, for example at most 5% by weight, relative to the dry weight of gypsum powder.

[0066] In one particular embodiment, the content of starch functionalized with the group of formula (I) is 0.5% to 7% by weight, preferably 1% to 5% by weight, relative to the dry weight of calcined gypsum powder.

[0067] The compositions described herein may contain other components, particularly those used to adjust the physicochemical properties of such compositions.

[0068] In some embodiments, in addition to starch functionalized with the group of formula (I), the composition further comprises one or more fluidizing agents. Fluidizing agents are also known as "fluidizers," "dispersants," "plasticizers," or "water-reducing agents."

[0069] Such fluidizing agents can be specifically selected from polycarboxylates, especially polyether polycarboxylates, sulfonated polynaphthalene (e.g., salts of sulfonated condensates of naphthalene and formaldehyde), lignin sulfonates, sulfonated melamine resins (salts of sulfonated condensates of melamine and formaldehyde), and polyacrylates commonly used in the manufacture of gypsum boards.

[0070] As an example of a fluidizing agent, one could mention GLENIUM produced by BASF. ® Bozzoto named FLUBE ® Chryso named CHRYSOFLUID ® Sika under the name VISCOCRETE ® BASF under the name MELMENT ® Or by Mapei under the name MAPEFLUID ® Those for sale. Fluidizing agents may be more specifically selected from sulfonated polynaphthalene and sulfonated melamine-formaldehyde resins, and more preferably from sulfonated polynaphthalene.

[0071] Other examples of fluidizing agents are polymers selected from the following lists: polycarboxylic acid ethers (PCEs), such as polyoxyethylene polycarboxylate; and polyphosphonate polyoxyethylene. Salts of such polymers, such as sodium salts, may be used. In a particular embodiment, the fluidizing agent is or comprises a member of the list consisting of polycarboxylic acid poly(ethylene glycol) and polyphosphonate poly(ethylene glycol).

[0072] The content of such fluidizing agents (other than starch functionalized with the group of formula (I)) may be from 0.05% to 1.2% by weight, preferably from 0.1% to 0.8% by weight, relative to the dry weight of calcined gypsum powder.

[0073] Preferably, the content of one or more fluidizing agents other than the starch functionalized with the group of formula (I) is less than 0.1 wt%, preferably less than 0.05 wt%, more preferably less than 0.04 wt%, and even more preferably less than 0.03 wt% relative to the dry weight of gypsum powder.

[0074] More preferably, the composition does not contain any fluidizing agent other than starch functionalized with the group of formula (I).

[0075] In some embodiments, in addition to starch functionalized with the group of formula (I), the composition further comprises one or more adhesives (or equivalently "glue").

[0076] Such adhesives can be specifically selected from starch (different from starch functionalized with the group of formula (I)), especially acid-hydrolyzed or pregelatinized starch, polyvinyl acetate, polyvinyl alcohol, dextrin, flour, especially corn or wheat or sorghum flour.

[0077] The content of the adhesive other than starch functionalized with the group of formula (I) may include, for example, 0.1 to 8 wt%, such as 0.5 to 6 wt%, or even 1 to 5 wt%, relative to the dry weight of calcined gypsum powder.

[0078] Preferably, the content of the adhesive other than the starch functionalized with the group of formula (I) is less than 2% by weight, more preferably less than 1% by weight, or even more preferably less than 0.5% by weight, for example less than 0.2% by weight, relative to the dry weight of the gypsum powder.

[0079] More preferably, the composition does not contain any adhesives other than starch functionalized with the group of formula (I).

[0080] In some embodiments, the composition further comprises additives (in addition to those previously mentioned). Such additives can be used to adjust the properties of the composition or the properties of the gypsum board. In particular, such additives may be selected from accelerators, retarders, flame retardants, foaming agents, anti-sagging agents, flame retardants, anti-shrinkage agents, biocides, and waterproofing agents.

[0081] Examples of accelerators include heat-resistant accelerators, such as abrasive plaster encapsulated in glucose monohydrate.

[0082] Examples of retarders include, in particular, natural proteins.

[0083] Examples of fire retardants include glucose monohydrate in particular.

[0084] Examples of anti-sagging agents include sodium trimetaphosphate or tartaric acid.

[0085] Examples of flame retardants include vermiculite, clay, glass fiber, or mineral wool (e.g., glass wool).

[0086] Examples of anti-shrinkage agents include vermiculite, clay, or microsilica.

[0087] Examples of biocides include carbamates, such as 3-iodoprop-2-yn-1-ylbutylcarbamate, or pyrothion complexes.

[0088] Examples of waterproofing agents include siloxanes, polysiloxanes, or waxes.

[0089] The content of the other additives may be from 0.2% to 10% by weight, preferably from 1% to 3% by weight, relative to the dry weight of the calcined gypsum powder.

[0090] In some embodiments, the composition further comprises at least one reinforcing agent. The reinforcing agent may be based on a polymeric material (particularly an organic polymeric material) or a mineral material (particularly mineral fibers). When the reinforcing agent is an organic polymeric material, it may be added to the composition in the form of an emulsion. For example, the reinforcing agent may be glass fiber or polyvinyl acetate.

[0091] When present in the composition, one or more reinforcing agents preferably account for at least 1% by weight (or even at least 2% by weight) relative to the dry weight of calcined gypsum powder.

[0092] The density of the composition is typically from 0.6 to 2.5, for example: - Versions 1.0 to 2.3, more specifically 1.3 to 2.0, or - 0.6 to 1.5, and more specifically 0.8 to 1.3.

[0093] The compositions described herein are particularly suitable for use as mixing batches in methods for manufacturing gypsum board (or equivalently: "gypsum-based panel" or "gypsum board").

[0094] Therefore, the object of the present invention is a method for manufacturing gypsum board, the method comprising: - Provide compositions as defined herein, - The composition is poured onto the first strip to form a wet plaster layer on the first strip. - Provide a second strip on the wet plaster layer, and - Preferably, the gypsum board is formed by using an extruder.

[0095] The first strip and the second strip can be referred to as the first veneer sheet and the second veneer sheet, respectively. The first strip and the second strip are typically paper or paperboard strips, preferably paper strips.

[0096] The method of the present invention typically further includes a setting step and a drying step. Following such a step, a dry gypsum layer is obtained, defined as a gypsum layer in which the gypsum consists of dry-set gypsum. During the setting step, the hemihydrated calcium sulfate and water contained in the composition react with each other to form calcium sulfate dihydrate. Such a reaction is a hydration reaction. The setting step is also called the “hardening step.” The setting step typically occurs immediately upon forming the composition and pouring (or equivalently “pouring”) it onto the first strip. Typically, in a “wet gypsum layer,” the gypsum is not fully set (i.e., the wet gypsum layer contains calcium sulfate dihydrate and a mixture of calcium sulfate hemihydrate and water).

[0097] The solidification step is usually completed before the drying step.

[0098] The setting process is advantageously carried out without external heating. Typically, this process takes place at room temperature, which is generally defined as a temperature ranging from 15°C to 40°C. Since the reaction between hemihydrated calcium sulfate and water is exothermic, the temperature of the wet gypsum layer during setting is typically 35°C ± 3°C.

[0099] During the drying step, excess water (or "unreacted water") is removed. The drying step is advantageously carried out at temperatures ranging from 85°C to 97°C, and more particularly from 90°C to 95°C.

[0100] Preferably, the method of the present invention is carried out under continuous conditions. Under such continuous conditions, the method of the present invention generally includes the following steps: - Continuously prepare compositions as defined herein in a mixer; - The composition is continuously poured from the mixer onto a first strip (or "first veneer sheet") to form a wet plaster layer on the first strip, wherein the first strip is conveyed by a conveyor belt (typically toward the extruder). - Typically, a second strip (or "second facing sheet") is provided on the wet plaster layer at the extruder, and - To shape the plasterboard.

[0101] When in use, the extruder flattens the second strip on the composition, making the surface smooth and reducing the thickness of the plasterboard to the desired value.

[0102] Under continuous conditions, the method typically further includes solidification and drying steps as defined above.

[0103] The present invention also relates to a gypsum board comprising a gypsum core (more particularly, a dry gypsum layer comprising solidified gypsum), the gypsum core being based on a composition as defined herein, the gypsum layer (or gypsum core) being located between a first strip and a second strip.

[0104] The plaster core based on the composition as defined herein typically comprises: - Hardened plaster (more specifically, dry-hardened plaster), and - Starch functionalized with groups as defined in formula (I) herein, The starch is preferably ungelatinized starch (e.g., ungelatinized acid-hydrolyzed starch or ungelatinized oxidized starch).

[0105] In the gypsum core, the content of starch functionalized with the group of formula (I) may be at least 0.1% by weight (preferably at least 0.5% by weight) relative to the dry weight of gypsum, and at most 10% by weight (preferably at most 7% by weight, for example at most 5% by weight) relative to the dry weight of gypsum.

[0106] In the gypsum core, the content of fluidizing agent other than the starch functionalized with the group of formula (I) is preferably less than 0.1 wt%, preferably less than 0.05 wt%, more preferably less than 0.04 wt%, and even more preferably less than 0.03 wt% relative to the dry weight of the gypsum.

[0107] In the plaster core, the content of the adhesive other than starch functionalized with the group of formula (I) may, for example, include 0.1 to 8 wt%, such as 0.5 to 6 wt%, or even 1 to 5 wt%, relative to the dry weight of the plaster.

[0108] In the plaster core, the content of the adhesive other than the starch functionalized with the group of formula (I) is preferably less than 2% by weight, more preferably less than 1% by weight, or even more preferably less than 0.5% by weight, for example less than 0.2% by weight, relative to the dry weight of the plaster.

[0109] More particularly, the present invention relates to gypsum board that can be obtained by methods as defined herein.

[0110] The gypsum layer in gypsum board is usually referred to as the "gypsum core". Gypsum board typically has a thickness of 6 to 25 mm, preferably 10 to 15 mm.

[0111] The density of a dry plaster layer (or core) is typically 0.4 to 1.5, for example: - 0.8 to 1.5, more specifically 1.0 to 1.2, or - 0.6 to 1.0.

[0112] In this invention, the density of the composition or layer is conventionally defined, that is, the ratio of the density of such a composition or layer to the density of water (equal to 1000 kg / m3).

[0113] As used in this article, "wt%" means "weight %" (e.g., weight content).

[0114] It should be understood that the various aspects, particular embodiments, and preferred embodiments described above with respect to the compositions of the present invention are applicable to the method of manufacturing gypsum board as described herein and to the gypsum board as described herein.

[0115] The invention is illustrated by the following non-limiting embodiments. Example

[0116] Example 1: Fluidization effect of ungelatinized octenyl succinate starch Slump is used to evaluate the flowability of gypsum slurry containing ungelatinized octenyl succinate starch.

[0117] method: The components of the composition were mixed and vigorously stirred in a mixer (a Waring Blender LB20E*, at speed 12 for 25 seconds) to form a slurry, and the resulting slurry was then immediately poured into a slump ring. The slump ring was quickly lifted, allowing the liquid slurry to form a cake. The diameter of the cake was measured using a ruler.

[0118] The diameter of the disc is an estimate of the fluidity of the gypsum slurry.

[0119] Slump test was performed using the following composition (A): - Calcined gypsum powder (CaSO4·½H2O). - Water, wherein the weight ratio of water to calcined gypsum powder is 0.7. - 0.4% by weight of heat-resistant setting accelerator based on dry weight of calcined gypsum powder. - 0.027% by weight of retarder based on the dry weight of calcined gypsum powder, and - 0.5% by weight (composition A1) or 2% by weight (composition A2) of ungelatinized octenyl succinate waxy corn starch based on the dry weight of calcined gypsum powder.

[0120] The amount of calcined gypsum powder used for the test was 300 g.

[0121] The slump of the above composition and the slump of the following comparative compositions were measured: - The corresponding starch-free composition (B). - The corresponding compositions (C1, C2) using ungelatinized acid-hydrolyzed corn starch instead of ungelatinized octenyl succinate waxy corn starch. - The corresponding compositions (D1, D2) use pregelatinized oxidized corn starch instead of ungelatinized octenyl succinate waxy corn starch. - The corresponding compositions (E1, E2) use pregelatinized oxidized wheat starch instead of ungelatinized octenyl succinate waxy corn starch.

[0122] The same batch of calcined gypsum powder was used in the compositions of the present invention and the comparative compositions.

[0123] The results are shown in Table 1 below (standard deviation of starch-free formulation B = 1.2 cm).

[0124] Table 1 .

[0125] Table 1 shows that the compositions (A1, A2) according to the invention require slump values ​​higher than the starch-free reference range (B), and thus cause fluidization effects: A1 has a slump of +3 cm (+16%) and A2 has a slump of +4.5 cm (+28%) relative to the starch-free composition (B).

[0126] Conversely, the slump of compositions containing ungelatinized bound starch (C1, C2) is within the starch-free range (B). The slump of compositions containing 0.5% pregelatinized bound starch (D1, E1) is also within the starch-free range.

[0127] Compositions containing 2% pregelatinized bound starch (D2, E2) even cause a thickening effect (slump reduction of 25-30%, -4 cm).

[0128] Example 2: Fluidization effect of pregelatinized octenyl succinate starch Slump test was also used to evaluate the flowability of gypsum slurries containing pregelatinized octenyl succinate starch. The method described in Example 1 was used.

[0129] Slump test was performed using the following composition (A3): - Calcined gypsum powder (CaSO4·½H2O). - Water, with a water / calcined gypsum powder weight ratio of 0.7. - 0.4% by weight of heat-resistant setting accelerator based on dry weight of calcined gypsum powder. - 0.027% by weight of retarder based on the dry weight of calcined gypsum powder, and - 2% by weight of pregelatinized octenyl succinate tapioca starch based on dry weight of calcined gypsum powder.

[0130] The amount of calcined gypsum powder used for the test was 300 g.

[0131] The slump of the above composition and the slump of the following comparative compositions were measured: - Composition B' (starch-free composition). - Composition C3 (2% by weight of ungelatinized acid-hydrolyzed corn starch). - Composition D3 (2% by weight of pregelatinized oxidized corn starch).

[0132] The same batch of calcined gypsum powder (different from the batch of Example 1) was used in the compositions of the present invention and the comparative compositions.

[0133] The results are shown in Table 2 below (the standard deviation of the starch-free formulation B' is 0.5 cm).

[0134] Table 2 .

[0135] Table 2 shows that the composition (A3) according to the invention has a slump value higher than the starch-free reference range (B'), and thus causes a fluidizing effect: the slump is +1 cm relative to the starch-free composition (B'). Conversely, the slump of the composition containing ungelatinized bound starch (C3) is within the starch-free range (B'). The composition containing pregelatinized bound starch (D3) even causes a thickening effect (slump reduction of 26%, -3 cm).

Claims

1. A method for manufacturing gypsum board, including: - A composition comprising water, calcined gypsum powder, and starch functionalized with groups of formula (I) is provided: - - -C(O)-R-C(O)O - M + (I), in: R is a C1-C12 aliphatic divalent chain replaced by a C4-C22 aliphatic chain, and M + It is a cation. - The composition is poured onto the first strip to form a wet plaster layer on the first strip. - Provide a second strip on the wet plaster layer, and - To form the plasterboard, preferably using an extruder.

2. The method according to claim 1, wherein R is a C2 or C3 alkylene chain substituted with a C6-C12 alkenyl chain, preferably a C2 alkylene chain substituted with a C8 alkenyl chain.

3. The method according to claim 1 or 2, wherein the starch is pregelatinized starch or ungelatinized starch, more particularly ungelatinized acid-hydrolyzed starch, ungelatinized oxidized starch, pregelatinized acid-hydrolyzed starch or pregelatinized oxidized starch.

4. The method according to any one of the preceding claims, wherein the starch is ungelatinized starch, such as ungelatinized acid-hydrolyzed starch or ungelatinized oxidized starch.

5. The method according to any one of the preceding claims, wherein the content of the fluidizing agent other than the starch functionalized with the group of formula (I) is less than 0.1% by weight, preferably less than 0.05% by weight, more preferably less than 0.04% by weight, and even more preferably less than 0.03% by weight relative to the dry weight of the gypsum powder.

6. The method according to any one of the preceding claims, wherein the composition does not contain any fluidizing agent other than the starch functionalized with the group of formula (I).

7. The method according to any one of the preceding claims, wherein the content of calcined gypsum powder is at least 60% by weight relative to the total solids content of the composition.

8. The method according to any one of the preceding claims, wherein the content of starch functionalized with the group of formula (I) is at least 0.1% by weight, preferably at least 0.5% by weight, and at most 10% by weight, preferably at most 7% by weight, for example at most 5% by weight, relative to the dry weight of gypsum powder.

9. The method according to any one of the preceding claims, wherein the weight ratio of water to calcined gypsum powder in the composition is: - At least 0.19, and - Up to 0.85, preferably up to 0.80, more preferably up to 0.65, and even more preferably up to 0.

55.

10. The method according to any one of the preceding claims, wherein the composition further comprises at least one reinforcing agent, such as glass fiber or polyvinyl acetate.

11. The method according to any one of the preceding claims, wherein the composition further comprises an additive, preferably selected from accelerators, retarders, flame retardants, anti-sagging agents, flame retardants, anti-shrinkage agents, biocides, and waterproofing agents.

12. The method according to any one of the preceding claims, wherein the first strip and the second strip are paper or paperboard strips.

13. The method according to any one of the preceding claims further includes a solidification step and a drying step.

14. A gypsum board that can be obtained by the method defined in any one of claims 1 to 13.

15. A composition comprising: - Calcined gypsum powder, - Starch functionalized with the group of formula (I): - - -C(O)-R-C(O)O - M + (I), in: R is a C1-C12 aliphatic divalent chain replaced by a C4-C22 aliphatic chain, and M + It is a cation, and - water.

16. The composition according to claim 15, wherein it has one or more of the following characteristics: - The content of calcined gypsum powder is at least 60% by weight relative to the total solids content of the composition, and / or - The content of starch functionalized with the group of formula (I) is at least 0.1% by weight, preferably at least 0.5% by weight, and at most 10% by weight, preferably at most 7% by weight, for example at most 5% by weight, relative to the dry weight of gypsum powder, and / or - The weight ratio of water to calcined gypsum powder in the composition is at least 0.19 and at most 0.80, preferably at most 0.65, and more preferably at most 0.

55.

17. The composition according to claim 15 or 16, wherein R is a C2 or C3 alkylene chain substituted with a C6-C12 alkenyl chain, preferably a C2 alkylene chain substituted with a C8 alkenyl chain.

18. The composition according to any one of claims 15 to 17, wherein the starch is ungelatinized starch, such as ungelatinized acid-hydrolyzed starch or ungelatinized oxidized starch.

19. The composition according to any one of claims 15 to 18, wherein the content of the fluidizing agent other than the starch functionalized with the group of formula (I) is less than 0.1% by weight, preferably less than 0.05% by weight, more preferably less than 0.04% by weight, and even more preferably less than 0.03% by weight relative to the dry weight of the gypsum powder.