Plasterboard comprising recyclate of water-repellent plaster

Abstract

The present invention relates to a method for manufacturing a plasterboard from recyclate of water-repellent plaster. It also relates to a plasterboard obtained by such a method.

Description

[0001] PLASTERBOARD COMPRISING WATERPROOF RECYCLED PLASTER

[0002] The present invention relates to a method for manufacturing a plasterboard from water-repellent plaster recyclate. It further relates to a plasterboard obtained by such a method.

[0003] TECHNOLOGICAL BACKGROUND

[0004] Gypsum boards are panels comprising a layer of plaster between two facing sheets, usually made of paper. Industrially, the manufacturing process for gypsum boards involves three main steps: forming, setting, and drying. During the gypsum board forming step, a mix is ​​prepared in a mixer from gypsum in the form of calcium sulfate hemihydrate, water, and other ingredients to adjust the properties of the mix and / or the final product. For example, foaming agents or foam may be added to the mix to reduce the density of the gypsum board, water-repellent agents may be added to improve moisture resistance, and dispersants may be used to improve the flowability of the mix. The mix is ​​then poured onto a first sheet carried by a conveyor belt.After folding the edges of the first sheet, a second facing sheet is introduced. Typically, an extruder is used to flatten the second sheet over the plaster layer, smooth the surfaces, and adjust the plasterboard thickness to the desired value. During the process, calcium sulfate hemihydrate reacts with water to form calcium sulfate dihydrate. Excess water is removed during a drying step of the plasterboard in an oven.

[0005] Given the reversibility of the hydration reaction of calcium sulfate hemihydrate, typically by calcination, plaster is a material of choice from a recycling point of view. While recycling internal plaster waste is a route being developed in plasterboard manufacturing plants as a sustainable alternative to landfilling, difficulties persist in integrating all recyclates into the recycling process. In particular, the presence of water-repellent derivatives, particularly cross-linked polysiloxanes, poses major problems for recycling. These cross-linked compounds have a tendency, even at very low concentrations, to break the foams introduced to reduce the density of plasterboard. The stability of the foam is so sensitive to the presence of cross-linked polysiloxanes that the proportion of such recyclates in plasterboard manufacturing processes does not exceed 1% of the total weight of the plaster.The same applies to external recyclates whose composition is not controlled.

[0006] Various solutions have been proposed to overcome this problem. For example, application FR3O59662 describes the use of specific foaming agents, such as alpha-olefin sulfonate, which are compatible with water-repellent plaster recyclates. However, these foaming agents are stable foaming agents and therefore do not allow the formation of very low-density plasterboards. A delay in setting has also been observed with these foaming agents.

[0007] There is therefore a real need to provide a manufacturing process for very low density plasterboard, which is simple and inexpensive, and which allows the incorporation of an increased proportion of water-repellent plaster recyclates.

[0008] SUMMARY OF THE INVENTION

[0009] In this context, the inventors have demonstrated that the use of superdispersants (or "superfluidifiers") of the polycarboxylate ether or polyaryl ether type makes it possible to overcome the aforementioned problem. Significant quantities of gypsum recyclates could be incorporated into the gypsum mix, while using the foaming agents conventionally used in gypsum boards, in particular an alkyl sulfate. Alkyl sulfate is a so-called "unstable" foaming agent which allows the formation of boards of very low density.

[0010] Thus, the present invention relates to a method of manufacturing a plasterboard, comprising the following steps:

[0011] - the preparation of a foam from a mixture comprising water and a foaming agent,

[0012] - the preparation of a main mix comprising water, plaster, a dispersant, and the foam prepared previously, - the supply of a first facing sheet,

[0013] - pouring the main mix onto the first facing sheet, to form a layer of wet plaster,

[0014] - the provision of a second facing sheet on the wet plaster layer, to obtain a wet plasterboard, and

[0015] - drying the wet plasterboard, to obtain said plasterboard, characterized in that:

[0016] - the foaming agent comprises an alkyl sulfate, an alkyl ether sulfate or a mixture thereof,

[0017] - the plaster includes a water-repellent plaster recycle, and

[0018] - the dispersant comprises a polycarboxylate ether, a polyaryl ether or a combination thereof.

[0019] The plaster may comprise 0.01 to 50% by dry weight, preferably 1 to 20% by dry weight, of water-repellent plaster recyclate, relative to the total dry weight of plaster.

[0020] Waterproof plaster recyclate typically includes crosslinked polysiloxanes.

[0021] The water-repellent plaster recyclate may comprise 5 to 50,000 ppm, for example 10 to 10,000 ppm by weight of crosslinked polysiloxanes relative to the total dry weight of plaster.

[0022] The content of crosslinked polysiloxanes in the main mix is ​​advantageously from 5 to 50,000 ppm, preferably from 10 to 10,000 ppm, better still from 50 to 5,000 ppm, for example from 500 to 2,000 ppm, relative to the total dry weight of plaster.

[0023] The main mix may further include a water-repellent agent.

[0024] The water repellent agent is preferably a siloxane, a polysiloxane or a wax.

[0025] The weight content (in dry extract) of water-repellent agent is advantageously from 0.01 to 2%, for example from 0.01 to 1.7%, in particular from 0.02 to 1%, preferably from 0.03 to 0.8%, or even from 0.1 to 0.8%, or even from 0.4 to 0.6%, relative to the total dry weight of plaster.

[0026] The main mix may also include glass fibers, preferably in a weight content (in dry extract) of 0.01 to 2% relative to the total dry weight of plaster.

[0027] The weight content (in dry extract) of foaming agent is advantageously 0.02 to 0.5%, preferably 0.05 to 0.3%, or even 0.1 to 0.15%, relative to the total dry weight of plaster.

[0028] The weight content (in dry extract) of dispersant is advantageously from 0.005 to 0.6%, preferably from 0.01 to 0.1%, relative to the total dry weight of plaster. The weight content (dry content) of plaster is advantageously at least 70%, preferably at least 80%, or even at least 90%, relative to the total dry weight of the main mix.

[0029] The mass ratio of water to plaster in the main mix is ​​advantageously:

[0030] - at least 0.3, preferably at least 0.5; and

[0031] - of at most 1, preferably of at most 0.85, or even of at most 0.8, or even of at most 0.7.

[0032] The main mix may further comprise one or more ingredients selected from adhesion promoters, setting accelerators, setting retarders, anti-sag agents, flame retardants, anti-shrinkage agents, and biocidal agents.

[0033] Preferably, each of the first and second facing sheets is independently a paper sheet, a cardboard sheet or a glass mat.

[0034] The present invention also relates to a plasterboard obtained by the method as defined in the present application.

[0035] FIGURES

[0036] [Fig 1] shows an image of a plaster layer obtained from a composition comprising PNS as a dispersant.

[0037] [Fig 2] shows an image of a plaster layer obtained from a composition including PAE as a dispersant (scale 5 mm).

[0038] [Fig 3] shows an image of a plaster layer obtained from a composition comprising a combination of PAE and PNS as dispersants (scale 5 mm).

[0039] [Fig 4] shows images of plaster layers obtained from compositions including PAE as a dispersant (scale 5 mm).

[0040] DETAILED DESCRIPTION

[0041] The term "plaster" within the meaning of the present invention generally designates both set plaster, i.e. calcium sulfate dihydrate (CaSO4, 2 H2O), and unset plaster, i.e. calcium sulfate hemihydrate (CaSO4, 1 / 2 H2O). The expression "plasterboard" designates, for example, the finished product formed by set plaster but also a plasterboard during manufacture in which the plaster is not entirely set. In certain cases, the term "plaster" will however be understood in the strict sense, i.e. designating calcium sulfate hemihydrate. This is evident, for example, when the term "plaster" is used in reference to the raw material for the preparation of the mixes. Similarly, when reference is made to a quantity relative to the dry weight of plaster, the latter is considered in its calcium sulfate hemihydrate form.

[0042] The term "waterproof plaster recyclate" for the purposes of the present invention means plaster recycled from waterproof plaster-based products or comprising waterproof plaster products, in particular waterproof plaster, waterproof plasterboard, waterproof plaster tiles, waterproof joint fillers, or waterproof finishing fillers. Such a waterproof recyclate means in particular recycled plaster comprising crosslinked polysiloxanes. The quantity of crosslinked polysiloxanes may vary depending on the origin of the recycled plaster. It may typically contain:

[0043] - at least 5 ppm, or even at least 10 ppm, or even at least 50 ppm, for example at least 500 ppm, and

[0044] - preferably up to 50,000 ppm, or even up to 10,000 ppm, or even up to 5,000 ppm, for example up to 2,000 ppm, or up to 1,000 ppm, by weight of crosslinked polysiloxanes relative to the total dry weight of plaster.

[0045] The plaster used in the process according to the invention advantageously comprises:

[0046] - at least 5 ppm, or even at least 10 ppm, or even at least 50 ppm, for example at least 500 ppm, and

[0047] - preferably up to 50,000 ppm, or even up to 10,000 ppm, or even up to 5,000 ppm, for example up to 2,000 ppm, or up to 1,000 ppm, by weight of crosslinked polysiloxanes relative to the total dry weight of plaster, said crosslinked polysiloxanes typically originating from said water-repellent plaster recyclate.

[0048] The main mix of the method according to the invention comprises water, plaster, a dispersant, and a foam.

[0049] The plaster used in the process according to the invention generally comprises: - at least 0.01%, preferably at least 0.2%, more preferably at least 1%, better still at least 2%, or even at least 5%, or even at least 10%, for example at least 15% by dry weight of water-repellent plaster recyclate (relative to the total dry weight of plaster); and

[0050] - at most 60%, preferably at most 50%, better still at most 40%, or even at most 30%, or even at most 20%, by dry weight of water-repellent plaster recyclate (relative to the total dry weight of plaster).

[0051] For example, the plaster may comprise 0.01 to 50% by dry weight, preferably 1 to 20% by dry weight, of water-repellent plaster recyclate, relative to the total dry weight of plaster.

[0052] The plaster used in the method according to the invention may further comprise non-water-repellent plaster recyclates. In such a case, the total dry weight content of plaster recyclates (i.e. water-repellent and non-water-repellent) may be, for example, at least 0.01%, at least 1%, at least 5%, at least 10%, at least 20%, at least 40%, or at least 50%, relative to the total dry weight of plaster. More particularly, the total dry weight content of plaster recyclates (i.e. water-repellent and non-water-repellent) may be from 0.01 to 100%, from 0.01 to 80%, from 1 to 80%, from 0.01 to 50%, from 0.2 to 40%, from 1 to 30%, or from 2 to 20%, relative to the total dry weight of plaster.

[0053] The dry weight content of plaster is at least 70%, preferably at least 80%, or even at least 90%, relative to the total dry weight of the main mix.

[0054] Typically, the mass ratio of the total amount of water to the plaster in the main mix is:

[0055] - at least 0.3, preferably at least 0.5; and

[0056] - at most 1, preferably at most 0.85, or even at most 0.8, or even at most 0.7, for example at most 0.65.

[0057] In some embodiments, the mass ratio of the total amount of water to plaster in the main mix is ​​from 0.25 to 0.65, for example from 0.25 to 0.5.

[0058] The foam for the main batch is prepared before incorporation into the main batch, from a mixture comprising water and a foaming agent. The foaming agent comprises an alkyl sulfate, an alkyl ether sulfate or a mixture thereof.

[0059] Preferably, the foaming agent comprises at least 50%, or even at least 60%, more preferably at least 70%, or even at least 80%, in particular at least 90%, for example at least 95%, by weight of alkyl sulfate, alkyl ether sulfate or mixture thereof.

[0060] Preferably, the foaming agent consists of an alkyl sulfate, an alkyl ether sulfate or a mixture thereof.

[0061] Advantageously, the foam is obtained from a mixture comprising (preferably consisting of):

[0062] - from 0.1 to 10%, preferably from 0.2 to 5%, or from 0.5 to 2% by weight of foaming agent, and

[0063] - from 90 to 99.9%, preferably from 95 to 99.8%, or from 98 to 99.5% by weight of water, relative to the total weight of the mixture.

[0064] The foam is generally formed from the above mixture and by adding air, typically in a static or dynamic foam generator. The amount of air introduced is determined according to the desired foam density. The foam generally has a density of 50 to 300 g / L, for example 80 to 250 g / L or 100 to 200 g / L.

[0065] In the main mix, the weight content (in dry extract) of foaming agent is advantageously 0.02 to 0.5%, preferably 0.05 to 0.3%, or even 0.1 to 0.15%, relative to the total dry weight of plaster.

[0066] The dispersant comprises a polycarboxylate ether, a polyaryl ether, or a combination thereof.

[0067] A “polycarboxylate ether” (PCE) means a copolymer comprising (or even consisting of) a first and a second repeating unit, where: - the first repeating unit is a repeating unit of olefinic unsaturated monocarboxylic acid type, or an ester or salt thereof, or a repeating unit of olefinic unsaturated sulfonic acid type, or an ester or salt thereof, and

[0068] - the second repeating unit is a repeating unit of olefinic unsaturated alcohol type substituted by a polyalkylene glycol group.

[0069] Typically, the first repeating unit represents 30 to 99 mol% of the total molar amount of first and second repeating units.

[0070] The olefinically unsaturated monocarboxylic acid repeating unit (or an ester or salt thereof) is preferably selected from acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, and their esters or salts.

[0071] The olefinically unsaturated sulfonic acid repeating unit (or an ester or salt thereof) is preferably selected from α-lylsulfonic acid, vinylsulfonic acid and their esters or salts.

[0072] Preferably, the first repeating unit is preferably chosen from acrylic acid, methacrylic acid and their esters or salts.

[0073] Preferably, the second repeating unit is a repeating unit of formula (I):

[0074] [Chem 1] in which:

[0075] - p is an integer from 0 to 3,

[0076] - R 2 is hydrogen or a C1-C5 aliphatic group (e.g. C1-C5 alkyl),

[0077] - R 1 is of formula (II):

[0078] [Chem 2]

[0079] (H), where:

[0080] - each of m and n is, independently, an integer from 2 to 4,

[0081] - each of x and y is, independently, an integer from 55 to 350,

[0082] - w is 0 or 1,

[0083] - when w is 1, z is an integer from 55 to 350,

[0084] - when w is 1, R 3 is a substituted or unsubstituted aryl (eg phenyl), and

[0085] - R 4 is hydrogen, a C1-C20 aliphatic group, a C5-C8 cycloaliphatic group, a substituted or unsubstituted aryl, or one of the following groups:

[0086] [Chem 3] Or :

[0087] - R5 is an alkyl (eg C1-C12 alkyl), aryl, aralkyl (eg aryl-(C1-C12 alkyl)) or alkylaryl (eg (C1-C12 alkyl)-aryl) group,

[0088] - R 6 is a divalent alkyl (eg C1-C12 alkyl), aryl, aralkyl (eg aryl-(C1-C12 alkyl)) or alkylaryl (eg (C1-C12 alkyl)-aryl) group, and

[0089] - R 7 is an alkyl (eg C1-C12 alkyl), aryl, aralkyl (eg aryl-(C1-C12 alkyl)) or alkylaryl (eg (C1-C12 alkyl)-aryl) group.

[0090] Advantageously, at least one of m and n is 2. Preferably, each of m and n is, independently, 2 or 3.

[0091] When m or n is 2, then the corresponding group is -(C2H4O)-, that is: -(CH2- CH2-O)-.

[0092] When m or n is 3, then the corresponding group is -(C3H6O)-, which includes in particular: -(CH2-CH2-CH2-O)-, -(CH2-CH(CH3)-O)-, or -(CH(CH3)-CH2-O)-.

[0093] When m or n is 4, then the corresponding group is -(C4H8O)-, which includes in particular: -(CH2-CH2-CH2-CH2-O)-, -(CH2-CH2-CH(CH3)-O)-, -(CH(CH3)-CH2-CH2-O)- or - (CH(CH3)-CH(CH3)-O)-.

[0094] The mass average molecular weight, generally determined by light scattering, is advantageously from 20,000 to 60,000 Da. Polycarboxylate ethers are well known and in particular described in applications US 2006 / 281885 and US 2006 / 281886, which are incorporated herein by reference.

[0095] A “polyaryl ether” (PAE) means a polymer comprising aromatic groups and ether groups (preferably aromatic ether groups) within its backbone. Polyaryl ethers are well known and are notably described in application EP 2 627 708, which is incorporated herein by reference.

[0096] In a particular embodiment, the polyaryl ether is a polycondensation product comprising (or based on): i) at least one aromatic or heteroaromatic unit comprising a polyether side chain, and ii) at least one aromatic or heteroaromatic phosphate unit.

[0097] Preferably, the aromatic or heteroaromatic unit comprising a polyether side chain comprises one or more polyalkylene glycol side chains, more preferably one or more polyethylene glycol side chains. In particular, it is preferred that the aromatic or heteroaromatic unit comprising a polyether side chain (preferably one or more polyalkylene glycol side chains) is selected from the group consisting of alkoxylated (preferably ethoxylated) aromatic or heteroaromatic units functionalized with a hydroxyl. For example, said alkoxylated aromatic or heteroaromatic compounds functionalized with a hydroxyl are selected from phenoxyethanol, phenoxypropanol, 2-alkoxyphenoxyethanol, 4-alkoxyphenoxyethanol, 2-alkylphenoxyethanol, 4-alkylphenoxyethanol or mixtures thereof.

[0098] Other aromatic or heteroaromatic units comprising a polyether side chain (preferably one or more polyalkylene glycol side chains) are amino-functionalized alkoxylated (preferably ethoxylated) aromatic or heteroaromatic units, such as N,N-(dihydroxyethyl)aniline, N-(hydroxyethyl)aniline, (dihydroxypropyl)aniline, N-(hydroxypropyl)aniline or mixtures thereof. Even more preferred are alkoxylated phenol derivatives such as phenoxyethanol and / or phenoxypropanol. Particularly preferred are alkoxylated, more preferably ethoxylated, phenol derivatives having a mass average molecular weight of 300 to 10,000 Daltons, for example polyethylene glycol monophenyl ether.

[0099] The phosphate aromatic or heteroaromatic unit may be obtained by phosphating the corresponding alcohol with polyphosphoric acid and / or phosphorus pentoxide according to methods known in the art. Preferably, the phosphate aromatic or heteroaromatic unit is selected from the group of hydroxyl-functionalized alkoxylated (preferably ethoxylated) aromatic or heteroaromatic units comprising at least one phosphoric ester group, such as phenoxyethanolphosphate and / or poly(ethylene glycol)monophenyl ether phosphate and / or amino-functionalized alkoxylated (preferably ethoxylated) aromatic or heteroaromatic units comprising at least one phosphoric ester group, such as N,N-(dihydroxyethyl)aniline diphosphate, N,N-(dihydroxyethyl)aniline phosphate, N-(hydroxypropyl)aniline phosphate, or mixtures thereof.Even more preferred are alkoxylated, more preferably ethoxylated, phenol derivatives comprising at least one phosphoric ester group such as polyethylene glycol monophenyl ether phosphate.

[0100] Preferably, the aromatic or heteroaromatic unit comprising a polyether side chain is represented by formula (III):

[0101] AB-[(CH(R 8 )-CH(R 9 )-O)aX] q (III), in which:

[0102] A is a substituted or unsubstituted C5-C10 aryl or heteroaryl;

[0103] B is N, NH or O; q=2 if B is N and q=1 if B is NH or O; each of R 8 and R 9 is, independently, hydrogen, C1-C10 alkyl, C5-C8 cycloalkyl, aryl or heteroaryl; a is an integer from 1 to 300, preferably from 10 to 60, more preferably from 20 to 50; and

[0104] X is hydrogen, C1-C10 alkyl, C5-C8 cycloalkyl, aryl or heteroaryl.

[0105] Preferably, the aromatic or heteroaromatic phosphate unit is represented by the formula (IV):

[0106] OF-[(CH(R 10 )-CH(R 11 )-O) b -P(O)(OM)2]r (IV), in which:

[0107] D is substituted or unsubstituted C5-C10 aryl or heteroaryl;

[0108] E is N, NH or O; r=2 if E is N and r=1 if E is NH or O; each of R 10 and R 11 is, independently, hydrogen, C1-C10 alkyl, C5-C8 cycloalkyl, aryl, or heteroaryl; each M is, independently, hydrogen, an alkali metal (eg Na, Li, K), or ammonium, and b is an integer from 0 to 300.

[0109] Said polycondensation product may further comprise (or be based on) at least one unit represented by the formula (V):

[0110] OF-[(CH(R 10 )-CH(R n )-O)bH] r (V), in which D, E, r, R 10 , R 11, and b are as defined in formula (IV).

[0111] Said polycondensation product may further comprise (or be based on) at least one unit represented by the formula (VI):

[0112] (Y 1 )(Y 2 )C(R 12 )(R 13 ) (VI), in which: each of Y 1 and Y 2 represents, independently, formula (III) or (IV) as described above, and each of R 12 and R 13 represents, independently, hydrogen, methyl, -COOH or substituted or unsubstituted aryl or heteroaryl having 5 to 10 ring carbon atoms (e.g. phenyl), preferably hydrogen.

[0113] The polycondensation product may comprise (or be based on) units of formula (III) which may be identical to or different from each other.

[0114] The polycondensation product may comprise (or be based on) units of formula (IV) which may be identical or different from each other.

[0115] The polycondensation product may comprise (or be based on) units of formula (V) which may be the same or different from each other. The polycondensation product may comprise (or be based on) units of formula (VI) which may be the same or different from each other.

[0116] Typically, the molar ratio of (III):(IV) units within the polyaryl ether is from 1:15 to 15:1, preferably from 1:10 to 10:1, more preferably from 1:5 to 3:1.

[0117] When the (V) unit is present, the molar ratio between the (III) : [(IV) + (V)] units within the polyaryl ether is preferably from 1:15 to 15:1, more preferably from 1:10 to 10:1.

[0118] When the (VI) unit is present, the molar ratio between the [(III) + (IV)] : (VI) units within the polyaryl ether is preferably 1:0.8 to 3.

[0119] When both (V) and (VI) units are present, the molar ratio between [(III) + (IV) + (V)] : (VI) units within the polyaryl ether is preferably 1:0.8 to 3.

[0120] The mass average molecular weight of the polyaryl ether may be between 4,000 and 150,000 Da, preferably between 10,000 and 100,000, more preferably between 15,000 and 75,000 Da.

[0121] As used herein, the term "aliphatic" refers to an acyclic, linear or branched, saturated or unsaturated hydrocarbon group.

[0122] As used herein, the term "cycloaliphatic" refers to a mono- or polycyclic, saturated or unsaturated hydrocarbon group.

[0123] As used herein, the term "alkyl" refers to a saturated, straight or branched hydrocarbon group. Examples of alkyl include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, or decyl.

[0124] As used herein, the term "cycloalkyl" refers to a mono- or polycyclic saturated hydrocarbon group. Examples of cycloalkyl include, but are not limited to, cyclopentyl, cyclohexyl, cycloheptyl, or cyclooctyl.

[0125] As used herein, the term "aryl" means a mono- or polycyclic aromatic hydrocarbon preferably having from 5 to 12 (or from 5 to 10) ring carbon atoms. An example of aryl is phenyl.

[0126] As used herein, the term "heteroaryl" refers to a mono- or polycyclic aromatic hydrocarbon, preferably having from 5 to 12 (or from 5 to 10) ring carbon atoms, further comprising at least one heteroatom in the aromatic ring. As used herein, the term "aralkyl" refers to an alkyl as defined herein, substituted with at least one aryl as defined herein (e.g., benzyl).

[0127] As used herein, the term "alkylaryl" refers to aryl as defined herein, substituted with at least one alkyl as defined herein (e.g., methylphenyl).

[0128] Preferably, the dispersant comprises at least 50%, or even at least 60%, more preferably at least 70%, or even at least 80%, in particular at least 90%, for example at least 95%, by weight of polycarboxylate ether, polyaryl ether or a combination thereof.

[0129] In a particular embodiment, the dispersant is comprised of polycarboxylate ether, polyaryl ether, or a combination thereof.

[0130] In another particular embodiment, the dispersant consists of a mixture of:

[0131] - a first dispersant which is a polycarboxylate ether, a polyaryl ether or a combination thereof (typically representing at least 50%, or even at least 60%, better still at least 70%, or even at least 80%, in particular at least 90%, for example at least 95% of the total weight of the dispersant), and

[0132] - a second dispersant, which is for example a polynaphthalene sulfonate, a lignosulfonate, or a combination thereof. Preferably, the second dispersant is a polynaphthalene sulfonate.

[0133] “Lignosulfonate” refers to the product obtained by introducing sulfonic groups into the lignin molecule, i.e., sulfonated lignins as well as sulfite lignins. Lignin can be sulfonated by reaction with sulfite or bisulfite compounds via the well-known sulfonation or sulfoalkylation processes such as high-temperature sulfonation, room-temperature oxidative sulfonation, or sulfoalkylation involving a reaction of lignin with sodium sulfite and an aldehyde. Sulfite lignin, inherently obtained during the sulfite pulping of wood, straw, corn stalks, bagasse, and other similar materials, is also included in the term “lignosulfonate.”

[0134] Lignosulfonate may include ammonium (NH4+), alkali metal (e.g., Na+, K+, Li+), or alkaline earth metal (e.g., Ca2+, Mg2+) salts of lignosulfonic acid. Lignosulfonate may have a very wide range of molecular weights, e.g., molecular weights of 10,000 to 200,000 Daltons. Lignosulfonate is generally polydisperse.

[0135] Polynaphthalene sulfonate (PNS) is well known to those skilled in the art. The weight average molecular weight of PNS is generally between 8,000 and 50,000, although it is preferred in this invention to use PNS having a weight average molecular weight between 8,000 and 20,000, and more preferably between 8,000 and 14,000. The weight average molecular weight of a polymer can be determined by light scattering.

[0136] In the main mix, the weight content (in dry extract) of dispersant is advantageously from 0.005 to 0.6% (for example from 0.01 to 0.5%, or from 0.02 to 0.1%, or from 0.03 to 0.06%), preferably from 0.01 to 0.1%, relative to the total dry weight of plaster.

[0137] Advantageously, the main batch of the process according to the invention further comprises a water-repellent agent. It is known that the combined use of a water-repellent agent and water-repellent plaster recyclate has a negative effect on the stability of foams obtained from foaming agents of the alkyl sulfate or alkyl ether type. The process according to the invention using a foaming agent of the alkyl sulfate or alkyl ether type and a particular dispersant of the PCE or PAE type is, on the contrary, not affected by the simultaneous presence of a water-repellent agent and water-repellent plaster recyclate. The process according to the invention is therefore particularly advantageous for the manufacture of water-repellent plasterboards from water-repellent plaster recyclate.

[0138] The waterproofing agent can be added either to the foam before it is introduced into the main batch, or to the main batch at the time of its preparation.

[0139] The water-repellent agent is advantageously chosen from a siloxane, a polysiloxane or a wax. More preferably, the water-repellent agent is chosen from polyalkylhydrogensiloxanes, in particular from polymethylhydrogensiloxanes (PMHS). Polyalkylhydrogensiloxanes are well known to those skilled in the art and are described in particular in US 5,135,805, US 5,624,418 or WO 99 / 50200. The polyalkylhydrogensiloxanes may in particular have the repeating unit — [SiH(R')- O]- where R' is a C1-C4 alkyl, such as a methyl.

[0140] In the main mix, when present, the weight content (in dry extract) of water-repellent agent is advantageously from 0.01 to 2%, for example from 0.01 to 1.7%, in particular from 0.02 to 1%, preferably from 0.03 to 0.8%, or even from 0.1 to 0.8%, or even from 0.4 to 0.6%, relative to the total dry weight of plaster. It is understood that the water-repellent agent is distinct from the water-repellent plaster recyclate and components thereof.

[0141] Advantageously, the main batch of the method according to the invention further comprises glass fibers.

[0142] In the main mix, when present, the weight content (in dry extract) of glass fibers is advantageously 0.01 to 2%, preferably 0.1 to 1.8%, for example 0.2 to 1.5% relative to the total dry weight of plaster.

[0143] The main mix may include other ingredients, in particular to adjust the physicochemical properties of the mix and / or the plasterboard.

[0144] For example, the main mix may further comprise one or more ingredients selected from adhesion promoters, set accelerators, set retarders, anti-sag agents, flame retardants, anti-shrinkage agents, and biocidal agents.

[0145] Examples of adhesion agents include starch, polyvinyl acetate, polyvinyl alcohol, dextrin, or vegetable flour.

[0146] Examples of setting accelerators include ground gypsum encapsulated in dextrose monohydrate, hydrated calcium sulfate, or potassium sulfate.

[0147] Examples of setting retardants include natural proteins.

[0148] Examples of anti-sagging agents include sodium trimetaphosphate or tartaric acid.

[0149] Examples of flame retardants include vermiculite, clay, or mineral wool (e.g., glass wool).

[0150] Examples of anti-shrinkage agents include vermiculite, clay, or microsilica. Examples of biocidal agents include carbamates, such as 3-iodoprop-2-yn-l-yl butylcarbamate, or pyrithione complexes.

[0151] The method according to the invention comprises:

[0152] - the supply of a first facing sheet,

[0153] - pouring the main mix described above onto the first facing sheet, to form a layer of wet plaster,

[0154] - the provision of a second facing sheet on the wet plaster layer, to obtain a wet plasterboard, and

[0155] - drying the wet plasterboard, to obtain said plasterboard.

[0156] Typically, each of the first and second facing sheets is, independently, a sheet of paper, a sheet of cardboard, or a glass mat. Preferably, each of the first and second facing sheets is a sheet of paper.

[0157] In the method of the invention, the setting of the plaster generally begins as soon as the main mix is ​​formed and poured onto the first facing sheet.

[0158] Typically, during the formation of the "wet plaster layer", the plaster is not completely set (i.e., the wet plaster layer comprises a mixture of calcium sulfate dihydrate and calcium sulfate hemihydrate and water). During setting, the calcium sulfate hemihydrate and water in the mix react with each other to form calcium sulfate dihydrate.

[0159] Setting typically occurs in the absence of external heating, particularly at room temperature. Room temperature generally refers to a temperature between 15°C and 35°C. Since the reaction between calcium sulfate hemihydrate and water is exothermic, the temperature of the wet gypsum layer during setting may be higher than room temperature.

[0160] Setting is generally completed just before the drying step. Typically, the wet plasterboard comprises a layer of set plaster and excess water (i.e., unreacted water). During the drying step of the process, the excess water is removed. The drying step is advantageously carried out at a temperature between 85°C and 97°C, more particularly between 90°C and 95°C. This temperature during the drying step refers to the temperature measured in the plaster layer of the board. A dry plaster layer, comprising dry set plaster, is obtained after such a step.

[0161] Preferably, the method of the invention is carried out under continuous conditions. Under such continuous conditions, the method of the invention typically comprises the following steps:

[0162] - the continuous preparation of a main batch as described above in a mixer;

[0163] - continuously pouring the main mix onto a first facing sheet, to form a layer of wet plaster on the first facing sheet, the first facing sheet being driven by a conveyor belt (for example towards an extruder);

[0164] - providing a second facing sheet over the wet plaster layer (e.g. at the extruder), thereby forming a continuous wet plasterboard; and

[0165] - the cutting and drying of the wet plasterboard continues, so as to obtain a plasterboard.

[0166] When used, the extruder allows the second facing sheet to be flattened onto the wet plaster layer, smoothing the surfaces and adjusting the thickness of the plasterboards to the desired value.

[0167] In a particular embodiment, the method according to the invention further comprises the formation of a denser plaster layer (also called a “roller coating layer”) on one or both faces of the plasterboard, and possibly on its edges.

[0168] In such an embodiment, the method according to the invention may comprise the following steps:

[0169] - the preparation of a main batch as defined above,

[0170] - the supply of a secondary batch,

[0171] - optionally the supply of a tertiary mix,

[0172] - the supply of a first facing sheet, - the pouring of the secondary mix onto the first facing sheet, to form a first layer called wet “roller coating”,

[0173] - pouring the main mix onto the first layer of wet roller coating, to form a layer of wet plaster called “main”,

[0174] - optionally, pouring the tertiary mix onto the main layer, to form a second layer called wet “roller coating”,

[0175] - the provision of a second facing sheet on the main layer (or on the second layer of roller coating where applicable), to obtain a wet plasterboard, and

[0176] - drying the wet plasterboard, to obtain said plasterboard.

[0177] The present invention also relates to a plasterboard obtained by a process as defined in the present application.

[0178] Such a plasterboard typically comprises a plaster layer (called "main") formed from the main mix as defined above, said plaster layer being sandwiched between a first and a second facing sheet.

[0179] More particularly, the plasterboard according to the invention comprises a plaster layer (called "main") sandwiched between a first and a second facing sheet, in which the plaster layer comprises:

[0180] - plaster including a water-repellent plaster recycle,

[0181] - a foaming agent comprising an alkyl sulfate, an alkyl ether sulfate, or a mixture thereof, and

[0182] - a dispersant comprising a polycarboxylate ether, a polyaryl ether or a combination thereof.

[0183] The plaster layer of the plasterboard of the invention comprises pores (or equivalently "bubbles" or "air bubbles"). Such pores advantageously have a d50 of at least 80 pm, for example at least 100 pm, preferably at least 200 pm (in particular at least 220 pm, at least 240 pm, at least 250 pm, or at least 300 pm). Said pores advantageously have a d50 of less than 500 pm. The d50 corresponds to the surface area-weighted median pore diameter, and means that the cumulative surface area of ​​pores with a diameter from 0 to d50 represents 50% of the total pore surface area, and the cumulative surface area of ​​pores with a diameter from d50 to the maximum diameter represents the other 50%. Previous work has shown that this d50 is independent of the imaging technique used (scanning electron microscopy or optical microscopy). The pores formed can have various shapes.Various methods may be used to determine the diameter of a pore having a non-circular shape, as will be understood by those skilled in the art. For example, in some embodiments, a surface area calculation algorithm may be used to determine the surface area of ​​a pore having a complex shape, and then an effective diameter of the pore may be calculated based on the calculated surface area of ​​the pore. The diameter may then be used to analyze sets of pores.

[0184] The pore size distribution in the gypsum core can be monomodal, bimodal or multimodal.

[0185] The density of the plaster layer in the plasterboard is usually 0.4 to 1.5, for example 0.4 to 1.2, preferably 0.4 to 0.8, or even 0.5 to 0.7.

[0186] In the present invention, the density is defined conventionally, that is to say in relation to the density of water, taken equal to 1000 kg / m3.

[0187] In some embodiments, the plasterboard further comprises:

[0188] - a first layer of plaster called “roller coating” sandwiched between the first facing sheet and the main layer of plaster; and

[0189] - possibly a second layer of plaster called “roller coating” sandwiched between the main layer of plaster and the second facing sheet, where the density of each of the first and optional second layer of roller coating is greater than that of the main layer of plaster.

[0190] Plasterboard is usually 6-25mm thick, preferably 10-18mm.

[0191] The plasterboards according to the invention can be used for interior design in buildings, in particular for mounting or covering interior partitions or ceilings. It is understood that the various aspects, particular embodiments, preferred embodiments, described above for the method of the invention apply to the plasterboard of the invention.

[0192] The following examples illustrate the present invention in a non-limiting manner.

[0193] EXAMPLES

[0194] Plasterboards were manufactured from compositions of the same fluidity, comprising water, plaster partly made from water-repellent plaster recyclates, a dispersant, a silicone-type water-repellent agent, and a foaming agent.

[0195] The influence of the nature of the dispersant, the concentration of the dispersant, the nature of the foaming agent, as well as the amount of recyclates was studied. The results are shown in Tables 1 and 2.

[0196] To determine the foam efficiency (FEF), the following equation 1 is used:

[0197] [Eq 1] (Eq. 1)

[0198] Foam volume in the plate)

[0199] F EF (% = T , ,

[0200] Volume (foam introduced) where:

[0201] - Volume (foam introduced) corresponds to the volume of foam introduced into the batch,

[0202] - Volume (foam in the plate) corresponds to the volume remaining in the plasterboard and is determined with the following equation 2:

[0203] (Eq. 2) Volume (foam in the plate) = Volume(mixed) - volume(plaster+water) - volume(foaming solution) where:

[0204] - Volume(plaster+water) corresponds to the volume of plaster and water used to form the mix;

[0205] - Volume(foaming solution) corresponds to the volume of the solution based on water and foaming agent, before foam formation; - Volume(mixture) corresponds to the volume of the mixture after introduction of the foam and is determined with the following equation 3:

[0206] (Eq. 3) Volume(mixture) = Mass (plaster + water + foam) / Density(sample) where:

[0207] - Density(sample) is the density of a sample of mix after introduction of the foam and before drying of the sample,

[0208] - Mass (plaster + water + foam) is the sum of the masses of plaster, water and foam used to form the mix.

[0209] The density of a component (sample, mix, foam) is determined by weighing a known volume of said component.

[0210] - The mechanical properties were determined according to the NF081 standard (in 3-point bending), on samples measuring 40 x 30 cm and 12.5 ± 0.5 mm thick.

[0211] - Water uptake was determined according to standard NF081 with samples of 30 x 30 cm plates and 12.5 ± 0.5 mm thick, previously conditioned at 23°C and 50% relative humidity, and immersed in water for 2 hours.

[0212] Water uptake (%) = ((weight after immersion - initial weight) / initial weight) *100

[0213] - The d50 of the bubbles was determined by microscopy and image processing (Celestron USB Magnifier).

[0214] [Table 1]

[0215] * % by weight relative to the total dry weight of plaster; a 32% solution by weight of active ingredient; b 40% solution by weight of active ingredient; c 40% solution by weight of active ingredient; d36% solution by weight of active ingredient

[0216] SL: longitudinal direction

[0217] Table 1 shows that, unlike the conventional dispersant PNS, a superfluidifier of the PCE or PAE type achieves good foam efficiency when the plaster includes water-repellent plaster recyclates. Good foam efficiency was achieved when the superfluidifier was combined with PNS. Table 1 also shows that by increasing the PAE concentration, foam efficiency is improved.

[0218] Finally, Table 1 shows the physical properties of the formed plates comply with the values ​​required by the standard (Breaking force > 60 daN; Deflection under load < 2.4 mm; Residual deflection < 0.5 mm).

[0219] [Table 2]

[0220] * % by weight relative to the total dry weight of plaster Solution at 32% by weight of active ingredient; b40% solution by weight of active ingredient; c 30% solution by weight of active ingredient; d 36% solution by weight of active ingredient

[0221] SL: longitudinal direction

[0222] Table 2 shows that in the presence of water-repellent plaster recyclate, the superfluidifier / alkyl ether sulfate combination (composition 11) provides better foam efficiency than the superfluidifier / alpha-olefin sulfonate (comparison 10) and PNS / alpha-olefin sulfonate (comparison 9) combinations.

Claims

CLAIMS 1. Method of manufacturing a plasterboard, comprising the following steps: - the preparation of a foam from a mixture comprising water and a foaming agent, - the preparation of a main mix comprising water, plaster, a dispersant, and the foam prepared previously, - the supply of a first facing sheet, - pouring the main mix onto the first facing sheet, to form a layer of wet plaster, - the provision of a second facing sheet on the wet plaster layer, to obtain a wet plasterboard, and - drying the wet plasterboard, to obtain said plasterboard, characterized in that: - the foaming agent comprises an alkyl sulfate, an alkyl ether sulfate or a mixture thereof, - the plaster includes a water-repellent plaster recycle, and - the dispersant comprises a polycarboxylate ether, a polyaryl ether or a combination thereof.

2. Method according to claim 1, characterized in that the plaster comprises 0.01 to 50% by dry weight, preferably 1 to 20% by dry weight, of water-repellent plaster recyclate, relative to the total dry weight of plaster.

3. Method according to claim 1 or 2, characterized in that the water-repellent plaster recyclate comprises crosslinked polysiloxanes.

4. Method according to one of claims 1 to 3, characterized in that the content of crosslinked polysiloxanes in the main mix is ​​from 5 to 50,000 ppm, preferably from 10 to 10,000 ppm, better still from 50 to 5,000 ppm, for example from 500 to 2,000 ppm, relative to the total dry weight of plaster.

5. Method according to one of claims 1 to 4, characterized in that the main mix further comprises a water-repellent agent, which is preferably a siloxane, a polysiloxane or a wax.

6. Method according to claim 5, characterized in that the weight content of water-repellent agent is from 0.01 to 2%, for example from 0.01 to 1.7%, in particular from 0.02 to 1%, preferably from 0.03 to 0.8%, or even from 0.1 to 0.8%, or even from 0.4 to 0.6%, relative to the total dry weight of plaster.

7. Method according to one of claims 1 to 6, characterized in that the main mix further comprises glass fibers, preferably in a weight content of 0.01 to 2% relative to the total dry weight of plaster.

8. Method according to one of claims 1 to 7, characterized in that the weight content of foaming agent is 0.02 to 0.5%, preferably 0.05 to 0.3%, or even 0.1 to 0.15%, relative to the total dry weight of plaster.

9. Method according to one of claims 1 to 8, characterized in that the weight content of dispersant is from 0.005 to 0.6%, preferably from 0.01 to 0.1%, relative to the total dry weight of plaster.

10. Method according to one of claims 1 to 9, characterized in that the plaster weight content is at least 70%, preferably at least 80%, or even at least 90%, relative to the total dry weight of the main mix.

11. Method according to one of claims 1 to 10, characterized in that the mass ratio of water to plaster in the main mix is: - at least 0.3, preferably at least 0.5; and - of at most 1, preferably of at most 0.85, or even of at most 0.8, or even of at most 0.

7.

12. Method according to one of claims 1 to 11, characterized in that the main mix further comprises one or more ingredients chosen from adhesion agents, setting accelerators, setting retarders, anti-sag agents, flame retardants, anti-shrinkage agents, and biocidal agents.

13. Method according to one of claims 1 to 12, characterized in that each of the first and second facing sheets is, independently, a sheet of paper, a sheet of cardboard or a glass veil.

14. Plasterboard obtained by the process as defined in any one of claims 1 to 13. Tl

Images