Lightweight, mechanical and acoustic plasterboard

Abstract

The present invention relates to a plasterboard having both a low density and good mechanical and acoustic properties. The present invention also relates to a method for manufacturing such a plasterboard.

Description

[0001] LIGHTWEIGHT, MECHANICAL AND ACOUSTIC PLASTERBOARD

[0002] The present invention relates to a plasterboard having both low density and good mechanical and acoustic properties. The present invention also relates to a method for manufacturing such a plasterboard.

[0003] Plasterboard panels consist of a layer of plaster sandwiched between two facing sheets, usually paper-based. Industrially, the plasterboard manufacturing process comprises three main stages: forming, setting, and drying. During the forming stage, a slurry is prepared in a mixer from gypsum in the form of calcium sulfate hemihydrate, water, and other ingredients to adjust the properties of the mixture and / or the final product. For example, foaming agents or foam can be added to the mixture to reduce the density of the plasterboard, water-repellent agents can be added to improve moisture resistance, and dispersants can be used to improve the flowability of the mixture. The slurry is then poured onto a first sheet carried along by a conveyor belt.After folding over the edges of the first sheet, a second facing sheet is inserted. Typically, an extruder is used to flatten the second sheet onto the plasterboard layer, smoothing the surfaces and adjusting the plasterboard thickness to the desired value. During this process, calcium sulfate hemihydrate reacts with water to form calcium sulfate dihydrate. Excess water is removed during a drying stage in a kiln.

[0004] Good mechanical and acoustic performance can be easily achieved by using high-density plasterboard, typically at least 1, as the mass effect is extremely favorable for these properties.

[0005] For buildings open to the public, regulations impose increasingly stringent mechanical and acoustic properties. Currently, the plasterboards used are thick and high-density. However, reducing the weight of plasterboards has become a primary objective, as it offers considerable advantages, including:

[0006] - Easier and therefore faster installation,

[0007] - a reduction in gypsum consumption thanks to the reduced mass effect, and

[0008] - a reduction in the energy used to dry the board. However, the incompatible nature of mechanical and acoustic properties, in the absence of mass effect, makes weight reduction considerably difficult. In particular, stiffer boards, and therefore more mechanically resistant, will propagate sound waves more easily than more flexible boards, and will therefore be less effective from an acoustic point of view. Conversely, flexible boards will have better acoustic performance but will be less mechanically resistant.

[0009] In this context, the inventors demonstrated that it was possible for a low-density plasterboard to achieve both good mechanical and acoustic performance. Specifically, they demonstrated that a low-density plasterboard with the following characteristics met both mechanical and acoustic performance requirements:

[0010] - a surface hardness of 15 mm or less,

[0011] - a deflection under load (in the longitudinal direction) of less than or equal to 1.0 mm, and

[0012] - a Young's modulus less than or equal to 3.0 GPa.

[0013] SUMMARY

[0014] Thus, the present invention relates to a plasterboard comprising a layer of plaster, located between a first and a second facing sheet, said plasterboard having the following characteristics:

[0015] - a density less than or equal to 0.94,

[0016] - a surface hardness of 15 mm or less,

[0017] - a longitudinal deflection under load of less than or equal to 1.0 mm, and

[0018] - a Young's modulus less than or equal to 3.0 GPa.

[0019] In some embodiments, the density of the plasterboard is less than or equal to 0.89, preferably less than or equal to 0.84, or even less than or equal to 0.83.

[0020] In some embodiments, the density of the plasterboard is greater than 0.72, preferably greater than 0.78.

[0021] In some embodiments, the thickness of the plasterboard is 18 mm ± 10%, preferably 18 mm ± 5%.

[0022] In some embodiments, the surface hardness of the plasterboard is less than or equal to 14.5 mm, and preferably greater than 13.8 mm. In some embodiments, the longitudinal deflection of the plasterboard under load is less than or equal to 0.98 mm, or even less than or equal to 0.95 mm.

[0023] In some embodiments, the Young's modulus of the plasterboard is less than or equal to 2.9 GPa, and preferably greater than 2.3 GPa, or even greater than 2.6 GPa.

[0024] In some embodiments, the plasterboard of the invention has a breaking strength, in the longitudinal direction, greater than or equal to 1000 N, preferably greater than or equal to 1100 N.

[0025] In some embodiments, the plasterboard of the invention has a residual deflection of less than or equal to 0.5 mm.

[0026] In some embodiments, the plasterboard of the invention has a shrinkage of less than or equal to 10%, or even less than or equal to 5%, measured at 800°C.

[0027] Preferably, the plaster layer is formed from a mix comprising:

[0028] - plaster,

[0029] - a retardant, preferably an acid retardant,

[0030] - a heat-resistant accelerator,

[0031] - a sulfate-based accelerator (which is not calcium sulfate),

[0032] - a foaming agent, and

[0033] - water.

[0034] In some embodiments, the mix further comprises a fire retardant selected from vermiculite, mineral or metallic fibers (e.g., glass fibers), silicone oil, amorphous silicon dioxide (e.g., microsilica, fumed silica), or a mixture of at least two of these, preferably glass fibers. The fire retardant content is advantageously 1 to 6%, preferably 2 to 4%, by weight of the dry weight of plaster.

[0035] In some embodiments, the retardant is a polycarboxylic acid or a salt thereof. Preferably, the retardant is selected from citric acid, tartaric acid, a salt thereof, and a mixture of at least two of these, or even better, citric acid or a salt thereof.

[0036] In some embodiments, the retardant content by weight is 0.01 to 0.1%, preferably 0.03 to 0.06%, or even 0.03 to 0.04%, relative to the dry weight of plaster.

[0037] In some embodiments, said heat-resistant accelerator comprises ground gypsum coated with sugar.

[0038] In some embodiments, the weight content of heat-resistant accelerator is 0.5 to 3%, preferably 2 to 2.5%, relative to the dry weight of plaster.

[0039] In some embodiments, the sulfate-based accelerator is potassium sulfate. In some embodiments, the weight content of the sulfate-based accelerator is 0.1 to 1%, preferably 0.4 to 0.8%, relative to the dry weight of plaster.

[0040] In some embodiments, the foaming agent is an alkyl sulfate, an alkyl ether sulfate, an alpha-olefin sulfonate or a mixture of at least two of these, preferably an alkyl ether sulfate.

[0041] In some embodiments, the weight content of foaming agent is 0.01 to 0.1%, preferably 0.03 to 0.07%, relative to the dry weight of plaster.

[0042] In some embodiments, the mix further comprises a plasticizer, preferably selected from a polynaphthalene sulfonate, a polycarboxylate ether, a polyaryl ether, and a mixture of at least two of these. The plasticizer content by weight is advantageously 0.05 to 0.4%, preferably 0.1 to 0.3%, relative to the dry weight of plaster.

[0043] In some embodiments, the plaster content by weight is at least 70%, preferably at least 80%, or even at least 90%, relative to the total dry weight of the mix.

[0044] In some embodiments, the mass ratio of water to plaster in the mix is:

[0045] - of at least 0.5, preferably at least 0.6, or even at least 0.7; and

[0046] - at most 0.95, preferably at most 0.85, or even at most 0.8.

[0047] The present invention also relates to a method for manufacturing a plasterboard as defined in this application, comprising the following steps:

[0048] - the supply of a batch of plaster,

[0049] - the supply of a first facing sheet,

[0050] - pouring the mixed plaster onto the first facing sheet to form a layer of wet plaster,

[0051] - the supply of a second facing sheet on the wet plaster layer, to obtain a wet plasterboard, and

[0052] - the drying of the wet plasterboard, to obtain said plasterboard.

[0053] DETAILED DESCRIPTION

[0054] In this application, unless otherwise stated, a weight content of a component (or a weight ratio of components) is based on the weight of the component itself, and therefore, on its weight in dry extract when used, for example, diluted in a dispersion or a solution.

[0055] The term "plaster" in the context of the present invention generally refers to 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," for example, refers to the finished product made from set plaster, but also to a plasterboard in the process of being manufactured in which the plaster has not yet fully set. In certain cases, however, the term "plaster" will be understood in its strict sense, i.e., referring to calcium sulfate hemihydrate. This is evident, for example, when the term "plaster" is used to refer to the raw material for preparing mixes. Similarly, when referring to a quantity relative to the dry weight of plaster, the latter is considered to be in its calcium sulfate hemihydrate form.

[0056] The plasterboard according to the invention is a low-density plasterboard. Thus, it has a density less than or equal to 0.94. Said density is preferably less than or equal to 0.89, or even less than or equal to 0.83.

[0057] Advantageously, said density is greater than 0.72, preferably greater than 0.78.

[0058] In this application, density is defined conventionally, i.e., in relation to the density of water, taken as 1000 kg / m3. The density of the plasterboard is measured by weighing a known volume (length x width x thickness) of a plasterboard sample.

[0059] The thickness of the plasterboard according to the invention is advantageously 18 mm ± 10%, preferably 18 mm ± 5%, better still 18 mm ± 2%.

[0060] The thickness of the plasterboard is measured with a precision micrometer (e.g., Palmer) and according to the standard NF EN 520+A1 (version November 2009: paragraph 5.4).

[0061] The plasterboard according to the invention has a surface hardness of less than or equal to 15 mm, preferably less than or equal to 14.5 mm, or even less than or equal to 14.3 mm. In general, said surface hardness is greater than 13.8 mm.

[0062] The surface hardness of the plasterboard is measured according to the standard NF EN 520+A1 (November 2009 version: paragraph 5.12).

[0063] The plasterboard according to the invention has a deflection under load, in the longitudinal direction, of less than or equal to 1.0 mm. Preferably, said deflection under load in the longitudinal direction is less than or equal to 0.98 mm, or even less than or equal to 0.95 mm.

[0064] The longitudinal deflection of the plasterboard under load is measured according to standard NF EN 520+A1 (November 2009 version: paragraph 5.8). The plasterboard according to the invention has a Young's modulus less than or equal to 2.9 GPa, or even less than or equal to 2.8 GPa.

[0065] Preferably, the Young's modulus is greater than 2.3 GPa, or even greater than 2.6 GPa.

[0066] The Young's modulus of the plasterboard is measured according to the ISO / PAS 16940 standard.

[0067] Advantageously, the plasterboard according to the invention has a breaking strength, in the longitudinal direction, greater than or equal to 1000 N, preferably greater than or equal to 1100 N.

[0068] The breaking strength of the plasterboard, in the longitudinal direction, is measured according to standard NF EN 520+A1 (November 2009 version: paragraph 5.7).

[0069] Advantageously, the plasterboard according to the invention has a residual deflection of less than or equal to 0.5 mm.

[0070] The residual deflection of the plasterboard is measured according to standard NF EN 520+A1 (November 2009 version: paragraph 5.4).

[0071] Advantageously, the plasterboard exhibits good fire resistance. In particular, the plasterboard according to the invention can exhibit shrinkage of 10% or less, or even 5% or less, measured at 800°C.

[0072] For a shrinkage measurement at 800°C, the temperature 800°C is reached after heating according to the ISO 834 curve.

[0073] The shrinkage of the plasterboard is measured by the following equation (1):

[0074] [Eq 1]

[0075] Withdrawal (%) = ((Initial Volume - Final Volume) Initial Volume) x 100 (1)

[0076] In certain embodiments, the plasterboard according to the invention has the following characteristics:

[0077] - a density less than or equal to 0.94 (preferably less than or equal to 0.89, or even less than or equal to 0.83) and greater than 0.72 (preferably greater than 0.78);

[0078] - a surface hardness of less than or equal to 15 mm (preferably less than or equal to 14.5 mm, or even less than or equal to 14.3 mm) and greater than 13.8 mm;

[0079] - a deflection under load in the longitudinal direction less than or equal to 1.0 mm (preferably less than or equal to 0.98 mm, or even less than or equal to 0.95 mm);

[0080] - a Young's modulus less than or equal to 3.0 GPa (preferably less than or equal to 2.9 GPa) and greater than 2.3 GPa (preferably greater than 2.6 GPa); - optionally, a breaking strength, in the longitudinal direction, greater than or equal to 1000 N, preferably greater than or equal to 1100 N;

[0081] - optionally, a residual deflection of 0.5 mm or less; and

[0082] - optionally, a shrinkage of 10% or less, or even 5% or less, measured at 800°C

[0083] In certain embodiments, the plasterboard according to the invention has the following characteristics:

[0084] - a density less than or equal to 0.89 (preferably less than or equal to 0.83) and greater than 0.78;

[0085] - a surface hardness of less than or equal to 14.5 mm (or even less than or equal to 14.3 mm) and greater than 13.8 mm;

[0086] - a longitudinal deflection under load of less than or equal to 1.0 mm (preferably less than or equal to 0.98 mm, or even less than or equal to 0.95 mm);

[0087] - a Young's modulus less than or equal to 3.0 GPa and greater than 2.6 GPa;

[0088] - optionally, a breaking force, in the longitudinal direction, greater than or equal to 1100 N;

[0089] - optionally, a residual deflection of 0.5 mm or less; and

[0090] - optionally, a shrinkage of less than or equal to 5%, measured at 800°C.

[0091] The plasterboard according to the invention comprises a layer of plaster, located between a first and a second facing sheet.

[0092] The said plaster layer is advantageously formed from a mix (which can also be called a "composition") comprising:

[0093] - plaster,

[0094] - a retardant, preferably an acid retardant,

[0095] - a heat-resistant accelerator,

[0096] - a sulfate-based accelerator,

[0097] - a foaming agent, and

[0098] - water.

[0099] In said mix, the weight content of plaster (dry content) is advantageously at least 70%, preferably at least 80%, or even at least 90%, relative to the total dry weight of the mix.

[0100] Typically, the mass ratio of water to plaster in the mix is:

[0101] - at least 0.3, for example at least 0.5, preferably at least 0.6, or even at least 0.7; and

[0102] - at most 0.95, preferably at most 0.85, or even at most 0.8. The retarder slows the setting of the plaster and typically produces smaller calcium sulfate dihydrate crystals. Preferably, the retarder is an organic acid or a salt thereof, and more particularly a mono- or polycarboxylic acid (for example, dicarboxylic or tricarboxylic) or a salt thereof.

[0103] Preferably, the retardant is chosen from citric acid, tartaric acid, a salt of these, and a mixture of at least two of these.

[0104] Better still, the retardant is citric acid (or a salt thereof).

[0105] Examples of acid salts include salts of alkalis (e.g. lithium, sodium, or potassium), alkaline earths (e.g. calcium or magnesium), transition metals (e.g. copper, iron, or zinc), or ammonium.

[0106] Other examples of retardants include proteins, phosphates, or sugars.

[0107] The weight of the retarder is adjusted to optimize the mechanical and acoustic properties of the plasterboard. A high retarder content is beneficial for acoustic properties but results in slower plaster setting, which is detrimental to mechanical properties. Conversely, a low retarder content is detrimental to acoustic properties but results in faster plaster setting, which is beneficial to mechanical properties.

[0108] Advantageously, the retardant content by weight is 0.01 to 0.1%, preferably 0.03 to 0.06%, or even 0.03 to 0.04%, relative to the dry weight of plaster.

[0109] The heat-resistant accelerator's role is to speed up the setting of the plaster, and typically increases the number of nucleation sites to which the calcium sulfate dihydrate binds to grow. The heat-resistant accelerator is also known by the acronym "HRA" (an English acronym for "heat-resistant accelerator").

[0110] Preferably, the heat-resistant accelerator comprises (preferably, is made of) ground gypsum, which is advantageously coated with a hygroscopic agent such as: a sugar (said sugar typically being a monosaccharide, such as dextrose or fructose; a disaccharide such as sucrose; or a polysaccharide such as starch), a sodium C10-13 alkylbenzene sulfonate, or a stearate (e.g., magnesium or calcium stearate). Better still, the heat-resistant accelerator comprises (preferably, is made of) ground gypsum coated with a sugar. In such an ingredient, the mass ratio of the hygroscopic agent (e.g., sugar) to the ground gypsum is generally from 1 / 100 to 10 / 100, more particularly from 3 / 100 to 7 / 100. The median diameter (Dv(0.5)), determined by laser granulometry, is generally 15 to 40 pm, preferably 20 to 30 pm.

[0111] The weight content of heat-resistant accelerator is adjusted to optimize the mechanical and acoustic properties of the plasterboard. A high HRA content promotes mechanical properties, while a low HRA content promotes acoustic properties.

[0112] Advantageously, the weight content of heat-resistant accelerator is 0.5 to 3%, in particular 1 to 2.8%, preferably 1.5 to 2.6%, or even 2 to 2.5%, relative to the dry weight of plaster.

[0113] The sulfate-based accelerator's role is to speed up the setting of the plaster, and it works advantageously by releasing sulfate ions into the mix. These released sulfate ions typically increase the solubility of the plaster and thus accelerate the crystallization of the gypsum. It is understood that the heat-resistant accelerator and the sulfate-based accelerator are two distinct components in the mix described in this application. In this application, the term "sulfate-based accelerator" does not refer to calcium sulfate.

[0114] The sulfate-based accelerator is typically a mineral salt comprising sulfate ions, for example a mono-sulfate salt or a bisulfate salt, preferably mono-sulfate.

[0115] It is advantageous that the solubility of the sulfate-based accelerator, measured at 20°C in distilled water, is at least 80 g / L, or even at least 100 g / L.

[0116] Preferably, the sulfate-based accelerator is selected from sodium sulfate, potassium sulfate, ammonium sulfate, magnesium sulfate, copper sulfate, zinc sulfate, manganese sulfate, iron sulfate, and a mixture of at least two of these.

[0117] Even better, the sulfate-based accelerator is potassium sulfate.

[0118] The weight content of sulfate-based accelerator is adjusted to optimize the mechanical and acoustic properties of the plasterboard. A high sulfate-based accelerator content is beneficial for mechanical properties because it improves the board's rigidity, but this rigidity is detrimental to acoustic properties. Conversely, a low sulfate-based accelerator content is detrimental to mechanical properties because the resulting board will be more flexible, but this flexibility will be beneficial to acoustic properties.

[0119] Advantageously, the weight content of the sulfate-based accelerator is 0.1 to 1%, preferably 0.2 to 0.9%, and even better 0.4 to 0.8%, relative to the dry weight of the plaster. The foaming agent advantageously allows the formation of foam, and therefore air bubbles, within the plasterboard, which in turn lowers the density of the plasterboard.

[0120] Foaming agents are well known in the field of plasterboard. A foaming agent can be, in particular, an alkyl sulfate, an alkyl ether sulfate, an alpha-olefin sulfonate, or a mixture of at least two of these. Preferably, the foaming agent is an alkyl ether sulfate.

[0121] In the mix, the weight content of foaming agent is advantageously 0.01 to 0.1%, preferably 0.03 to 0.08% (for example 0.05 to 0.08%), or even 0.03 to 0.07%, relative to the dry weight of plaster.

[0122] In one particular method, the foaming agent is added as is to the mix at the time of its preparation.

[0123] In another particular method, a foam is first formed from a mixture comprising water and the foaming agent before being incorporated into the mix. In such a particular method, the foam is generally obtained from a mixture comprising (preferably, consisting of):

[0124] - from 0.1 to 10%, preferably from 0.2 to 5%, or even from 0.5 to 2% by weight of foaming agent, and

[0125] - from 90 to 99.9%, preferably from 95 to 99.8%, or even from 98 to 99.5% by weight of water, relative to the total weight of the mixture.

[0126] The foam is generally formed from the aforementioned 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.

[0127] Preferably, the mix also includes a fire retardant. Such a fire retardant is advantageously chosen from vermiculite, mineral or metallic fibers (e.g., glass fibers), silicone oil, amorphous silicon dioxide (e.g., microsilica, fumed silica), or a mixture of at least two of these, preferably glass fibers.

[0128] Advantageously, the weight content of fire retardant is 1 to 6%, preferably 2 to 4%, relative to the dry weight of plaster.

[0129] Preferably, the mix also includes mineral (e.g., glass or basalt fibers) or metallic fibers. Even more preferably, the mix includes glass fibers.

[0130] Advantageously, the mineral or metallic fiber content is 1 to 6%, preferably 2 to 4%, by weight of the dry weight of plaster. Mineral or metallic fibers can act as fire retardants and also influence the mechanical properties of the plasterboard. In particular, mineral or metallic fibers can increase the plasterboard's breaking strength.

[0131] The mix may further include a fluidifier, preferably selected from a polynaphthalene sulfonate, a polycarboxylate ether, a polyaryl ether, and a mixture of at least two of these.

[0132] The fluidizers are well known and are described in particular in the following applications: EP 2 627 708, US 2006 / 281885 and US 2006 / 281886.

[0133] The weight content of fluidifier is advantageously 0.05 to 0.4%, preferably 0.1 to 0.3%, relative to the dry weight of plaster.

[0134] The mix may also include a water-repellent agent.

[0135] The water-repellent agent is advantageously chosen from a siloxane, a polysiloxane, or a wax. More preferably, the water-repellent agent is chosen from polyalkylhydrogenosiloxanes, particularly polymethylhydrogenosiloxanes (PM HS).

[0136] Polyalkylhydrogenosiloxanes are well known and described in particular in US 5,135,805, US 5,624,418 or WO 99 / 50200. Polyalkylhydrogenosiloxanes can notably have the repeating motif -[SiH(R')-O]- where R' is a C1-C4 alkyl, such as a methyl.

[0137] In the mix, the weight content of water-repellent agent is advantageously from 0.01 to 2%, for example from 0.01 to 1.7%, especially 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.

[0138] The mix may also include ingredients other than those mentioned above, particularly to adjust the physico-chemical properties of the mix and / or the plasterboard.

[0139] For example, the mix may also include one or more ingredients chosen from among the adhesion agents, anti-sagging agents, and biocidal agents.

[0140] Examples of adhesion agents include starch, polyvinyl acetate, polyvinyl alcohol, dextrin, or vegetable flour.

[0141] One example of an anti-sagging agent is sodium trimetaphosphate.

[0142] Examples of biocidal agents include carbamates, such as 3-iodoprop-2-yn-l-yl butylcarbamate, or pyrithione complexes.

[0143] In certain embodiments, the plaster layer of the plasterboard according to the invention is formed from a mix comprising: - plaster,

[0144] - 0.01 to 0.1% (preferably 0.03 to 0.06%, or even 0.03 to 0.04%) of retardant, preferably acidic,

[0145] - 0.5 to 3% (in particular 1 to 2.8%, preferably 1.5 to 2.6%, or even 2 to 2.5%) of heat-resistant accelerator,

[0146] - 0.1 to 1% (preferably 0.2 to 0.9%, even better 0.4 to 0.8%) of sulfate-based accelerator,

[0147] - 0.01 to 0.1% (preferably 0.03 to 0.07%) of foaming agent,

[0148] - optionally 1 to 6% (for example 2 to 4%) of mineral or metallic fibers (preferably glass fibers), and

[0149] - water, the contents of retardant, heat-resistant accelerator, sulfate-based accelerator, foaming agent, and mineral or metallic fibers being weight contents expressed in relation to the dry weight of plaster.

[0150] In certain embodiments, the plaster layer of the plasterboard according to the invention is formed from a mix comprising:

[0151] - plaster,

[0152] - 0.01 to 0.1% (preferably 0.03 to 0.06%, or even 0.03 to 0.04%) of retardant chosen from citric acid, tartaric acid, a salt of these, and a mixture of at least two of these;

[0153] - 0.5 to 3% (in particular 1 to 2.8%, preferably 1.5 to 2.6%, or even 2 to 2.5%) of heat-resistant accelerator comprising ground gypsum coated with a sugar such as dextrose,

[0154] - 0.1 to 1% (preferably 0.2 to 0.9%, better still 0.4 to 0.8%) of sulfate-based accelerator chosen from sodium sulfate, potassium sulfate, ammonium sulfate, magnesium sulfate, copper sulfate, zinc sulfate, manganese sulfate, iron sulfate, and a mixture of at least two of these (preferably potassium sulfate);

[0155] - 0.01 to 0.1% (preferably 0.03 to 0.07%) of foaming agent which is an alkyl sulfate, an alkyl ether sulfate, an alpha-olefin sulfonate or a mixture of at least two of these (preferably an alkyl ether sulfate),

[0156] - optionally 1 to 6% (for example, 2 to 4%) of glass fibers, and

[0157] - water, with the levels of retarder, heat-resistant accelerator, sulfate-based accelerator, foaming agent, and glass fibers being weight-based amounts expressed relative to the dry weight of plaster. In certain embodiments, the plasterboard according to the invention comprises a layer of plaster, located between a first and a second facing sheet, and has the following characteristics:

[0158] - a density less than or equal to 0.94 (preferably less than or equal to 0.89, or even less than or equal to 0.83) and greater than 0.72 (preferably greater than 0.78);

[0159] - a surface hardness of less than or equal to 15 mm (preferably less than or equal to 14.5 mm, or even less than or equal to 14.3 mm) and greater than 13.8 mm;

[0160] - a deflection under load in the longitudinal direction less than or equal to 1.0 mm (preferably less than or equal to 0.98 mm, or even less than or equal to 0.95 mm);

[0161] - a Young's modulus less than or equal to 3.0 GPa (preferably less than or equal to 2.9 GPa) and greater than 2.3 GPa (preferably greater than 2.6 GPa);

[0162] - optionally, a breaking strength, in the longitudinal direction, greater than or equal to 1000 N, preferably greater than or equal to 1100 N;

[0163] - optionally, a residual deflection of 0.5 mm or less; and

[0164] - optionally, a shrinkage of 10% or less, or even 5% or less, measured at 800°C; and

[0165] - the plaster layer being formed from a mix comprising:

[0166] - plaster,

[0167] - 0.01 to 0.1% (preferably 0.03 to 0.06%, or even 0.03 to 0.04%) of retardant, preferably acidic,

[0168] - 0.5 to 3% (in particular 1 to 2.8%, preferably 1.5 to 2.6%, or even 2 to 2.5%) of heat-resistant accelerator,

[0169] - 0.1 to 1% (preferably 0.2 to 0.9%, even better 0.4 to 0.8%) of sulfate-based accelerator,

[0170] - 0.01 to 0.1% (preferably 0.03 to 0.07%) of foaming agent,

[0171] - optionally 1 to 6% (for example 2 to 4%) of mineral or metallic fibers (preferably glass fibers), and

[0172] - water, the contents of retardant, heat-resistant accelerator, sulfate-based accelerator, foaming agent, and mineral or metallic fibers being weight contents expressed in relation to the dry weight of plaster.

[0173] In some embodiments, the plasterboard according to the invention comprises a layer of plaster, located between a first and a second facing sheet, and has the following characteristics: - a density less than or equal to 0.94 (preferably less than or equal to 0.89, or even less than or equal to 0.83) and greater than 0.72 (preferably greater than 0.78);

[0174] - a surface hardness of less than or equal to 15 mm (preferably less than or equal to 14.5 mm, or even less than or equal to 14.3 mm) and greater than 13.8 mm;

[0175] - a deflection under load in the longitudinal direction less than or equal to 1.0 mm (preferably less than or equal to 0.98 mm, or even less than or equal to 0.95 mm);

[0176] - a Young's modulus less than or equal to 3.0 GPa (preferably less than or equal to 2.9 GPa) and greater than 2.3 GPa (preferably greater than 2.6 GPa);

[0177] - optionally, a breaking strength, in the longitudinal direction, greater than or equal to 1000 N, preferably greater than or equal to 1100 N;

[0178] - optionally, a residual deflection of 0.5 mm or less; and

[0179] - optionally, a shrinkage of 10% or less, or even 5% or less, measured at 800°C; and

[0180] - the plaster layer being formed from a mix comprising:

[0181] - plaster,

[0182] - 0.01 to 0.1% (preferably 0.03 to 0.06%, or even 0.03 to 0.04%) of retardant chosen from citric acid, tartaric acid, a salt of these and a mixture of at least two of these,

[0183] - 0.5 to 3% (in particular 1 to 2.8%, preferably 1.5 to 2.6%, or even 2 to 2.5%) of heat-resistant accelerator comprising ground gypsum coated with a sugar such as dextrose,

[0184] - 0.1 to 1% (preferably 0.2 to 0.9%, better still 0.4 to 0.8%) of sulfate-based accelerator chosen from sodium sulfate, potassium sulfate, ammonium sulfate, magnesium sulfate, copper sulfate, zinc sulfate, manganese sulfate, iron sulfate, and a mixture of at least two of these (preferably potassium sulfate);

[0185] - 0.01 to 0.1% (preferably 0.03 to 0.07%) of foaming agent which is an alkyl sulfate, an alkyl ether sulfate, an alpha-olefin sulfonate or a mixture of at least two of these (preferably an alkyl ether sulfate),

[0186] - optionally 1 to 6%, (for example 2 to 4%) of glass fibers, and

[0187] - water, the levels of retardant, heat-resistant accelerator, sulfate-based accelerator, foaming agent, and glass fibers being weight-based levels expressed in relation to the dry weight of plaster.

[0188] In some embodiments, the plasterboard according to the invention has the following characteristics: - a density less than or equal to 0.89 (preferably less than or equal to 0.83) and greater than 0.78;

[0189] - a surface hardness of less than or equal to 14.5 mm (or even less than or equal to 14.3 mm) and greater than 13.8 mm;

[0190] - a longitudinal deflection under load of less than or equal to 1.0 mm (preferably less than or equal to 0.98 mm, or even less than or equal to 0.95 mm);

[0191] - a Young's modulus less than or equal to 3.0 GPa and greater than 2.6 GPa;

[0192] - optionally, a breaking force, in the longitudinal direction, greater than or equal to 1100 N;

[0193] - optionally, a residual deflection less than or equal to 0.5 mm;

[0194] - optionally, a shrinkage of 5% or less, measured at 800°C; and

[0195] - the plaster layer being formed from a mix comprising:

[0196] - plaster,

[0197] - 0.01 to 0.1% (preferably 0.03 to 0.06%, or even 0.03 to 0.04%) of retardant chosen from citric acid, tartaric acid, a salt of these, and a mixture of at least two of these,

[0198] - 0.5 to 3% (in particular 1 to 2.8%, preferably 1.5 to 2.6%, or even 2 to 2.5%) of heat-resistant accelerator comprising ground gypsum coated with a sugar such as dextrose,

[0199] - 0.1 to 1% (preferably 0.2 to 0.9%, better still 0.4 to 0.8%) of sulfate-based accelerator chosen from sodium sulfate, potassium sulfate, ammonium sulfate, magnesium sulfate, copper sulfate, zinc sulfate, manganese sulfate, iron sulfate, and a mixture of at least two of these (preferably potassium sulfate);

[0200] - 0.01 to 0.1% (preferably 0.03 to 0.07%) of foaming agent which is an alkyl sulfate, an alkyl ether sulfate, an alpha-olefin sulfonate or a mixture of at least two of these (preferably an alkyl ether sulfate),

[0201] - optionally 1 to 6% (for example, 2 to 4%) of glass fibers, and

[0202] - water, the levels of retardant, heat-resistant accelerator, sulfate-based accelerator, foaming agent, and glass fibers being weight-based levels expressed in relation to the dry weight of plaster.

[0203] The plasterboard according to the invention comprises a layer of plaster situated between a first and a second facing sheet. Typically, each of the first and second facing sheets is independently a sheet of paper, a sheet of cardboard, or a fiberglass mat. Preferably, each of the first and second facing sheets is a sheet of paper. 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, or at least 250 pm). Said pores advantageously have a d50 of less than 500 pm, preferably less than 400 pm. Preferably, said pores have a d50 of at least 100 pm and less than 300 pm.

[0204] The d50 corresponds to the median pore diameter weighted by area, and means that the cumulative area of ​​pores with a diameter from 0 to d50 represents 50% of the total pore area, and the cumulative 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).

[0205] The pores formed can have various shapes. Various methods can be used to determine the diameter of a pore with a non-circular shape, as a person skilled in the art will understand. For example, in some embodiments, an area calculation algorithm can be used to determine the area of ​​a pore with a complex shape, and then an effective pore diameter can be calculated based on the calculated pore area. The diameter can then be used to analyze pore sets.

[0206] The particle size distribution of pores in the gypsum core can be unimodal, bimodal, or multimodal.

[0207] In some embodiments, the plasterboard comprises:

[0208] - a main layer of plaster, located between a first and a second facing sheet,

[0209] - a first layer of plaster, known as "roller coating," sandwiched between the first facing sheet and the main plaster layer; and

[0210] - possibly a second layer of plaster called "roller coating" sandwiched between the main plaster layer and the second facing sheet, where the density of each of the first and optional second roller coating layers is greater than that of the main plaster layer.

[0211] The plasterboard according to the invention can be used for interior fitting in buildings, in particular for mounting or cladding interior partitions, counter-partitions, or ceilings.

[0212] Another object of the present invention is a method for manufacturing a plasterboard as defined in this application, said method comprising the following steps: - supplying a batch of plaster,

[0213] - the supply of a first facing sheet,

[0214] - pouring the mixed plaster onto the first facing sheet to form a layer of wet plaster,

[0215] - the supply of a second facing sheet on the wet plaster layer, to obtain a wet plasterboard, and

[0216] - the drying of the wet plasterboard, to obtain said plasterboard.

[0217] In such a process, the plaster mix is ​​preferably the plaster mix as defined above. It is understood that the particular and preferred methods described above for the plaster mix from which the plasterboard according to the invention can be formed, therefore apply to the plaster mix of the process according to the invention.

[0218] In the process of the invention, the setting of the plaster generally begins as soon as the mix is ​​formed and poured onto the first facing sheet.

[0219] 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, calcium sulfate hemihydrate, and water). During setting, the calcium sulfate hemihydrate and the water in the mix react to form calcium sulfate dihydrate.

[0220] Setting typically occurs in the absence of external heating, specifically 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 can be higher than room temperature.

[0221] The setting process is usually complete just before the drying stage. Typically, wet plasterboard consists of a set plaster layer and excess water (i.e., water that has not reacted).

[0222] During the drying stage of the process, excess water is removed. This drying stage is advantageously carried out at a temperature between 85°C and 97°C, more specifically between 90°C and 95°C. This temperature during the drying stage refers to the temperature measured within the plaster layer of the board. A dry plaster layer, comprising a dry set plaster, is obtained after this stage.

[0223] Preferably, the process of the invention is carried out under continuous conditions. Under such continuous conditions, the process of the invention typically comprises the following steps: - the continuous preparation of a plaster mix (e.g., a plaster mix as described above) in a mixer;

[0224] - the continuous pouring of the 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);

[0225] - the application of a second facing sheet on the wet plaster layer (for example, at the extruder), thus forming a continuous wet plasterboard; and

[0226] - the cutting and drying of the wet plasterboard continues, so as to obtain a plasterboard.

[0227] 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.

[0228] In a particular embodiment, the process according to the invention further includes the formation of a denser layer of plaster (also called a "roller coating layer") on one or both faces of the plasterboard, and optionally on its edges.

[0229] In such an embodiment, the process according to the invention may comprise the following steps:

[0230] - the preparation of a plaster mix (e.g., a plaster mix as described above), referred to as the "main mix",

[0231] - the supply of a secondary batch,

[0232] - optionally the supply of a tertiary batch,

[0233] - the supply of a first facing sheet,

[0234] - the pouring of the secondary mix onto the first facing sheet, to form a first layer known as "wet roller coating",

[0235] - pouring the main batch onto the first layer of wet roller coating, to form a wet plaster layer known as the "main" layer,

[0236] - optionally, pouring the tertiary mix onto the main layer to form a second layer known as a wet "roller coating",

[0237] - the supply 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

[0238] - the drying of the wet plasterboard, to obtain said plasterboard.

[0239] The following examples illustrate the present invention, in a non-limiting manner.

[0240] EXAMPLES Plasterboards 18 mm thick were prepared from different compositions detailed in Table 1 below.

[0241] - The density of plasterboard is measured by weighing a known volume (length x width x thickness) of a sample of plasterboard.

[0242] - The surface hardness of the plasterboard is measured according to standard NF EN 520+A1 (November 2009 version: paragraph 5.12).

[0243] The longitudinal deflection of the plasterboard under load is measured according to standard NF EN 520+A1 (November 2009 version: paragraph 5.7).

[0244] - The Young's modulus of the plasterboard is measured according to the ISO / PAS 16940 standard.

[0245] - The breaking strength of the plasterboard, in the longitudinal direction, is measured according to standard NF EN 520+A1 (November 2009 version: paragraph 5.7).

[0246] - The residual deflection of the plasterboard is measured according to standard NF EN 520+A1 (November 2009 version: paragraph 5.4).

[0247] - The R index is measured according to the ISO 717 / 1 standard.

[0248] - For the measurement of shrinkage, the temperature 800°C is reached after heating according to the ISO 834 curve.

[0249] The shrinkage of the plasterboard is measured by the following equation:

[0250] [Eq 2]

[0251] Deduction (%) = ((Initial Volume - Final Volume) Initial Volume) x 100

[0252] [Table 1]

[0253] *weight content relative to the dry weight of plaster; SL = longitudinal direction

[0254] The examples in Table 1 show that it is possible, for a low-density plasterboard, to achieve both good mechanical and acoustic performance by adjusting the surface hardness, the longitudinal deflection under load, and the Young's modulus. It should be noted in particular that:

[0255] - the plasterboard obtained from comparative composition 1 has degraded acoustic performance (higher Young's modulus and lower R);

[0256] - the plasterboard obtained from comparative composition 2 has good acoustic performance but degraded mechanical performance (deflection under load greater than 1 mm);

[0257] - The plasterboard from comparative composition 3 exhibits good mechanical and acoustic performance, but a high density.

Claims

DEMANDS 1. Plasterboard comprising a layer of plaster, situated between a first and a second facing sheet, said plasterboard having the following characteristics: - a density less than or equal to 0.94, - a surface hardness of 15 mm or less, - a longitudinal deflection under load of less than or equal to 1.0 mm, and - a Young's modulus less than or equal to 3.0 GPa.

2. Plasterboard according to claim 1, characterized in that said density is: - less than or equal to 0.89, preferably less than or equal to 0.84; and - greater than 0.72, preferably greater than 0.

78.

3. Plasterboard according to claim 1 or 2, characterized in that the thickness of the board is 18 mm ± 10%, preferably 18 mm ± 5%.

4. Plasterboard according to any one of claims 1 to 3, characterized in that it has one or more of the following characteristics: - a surface hardness of less than or equal to 14.5 mm, and preferably greater than 13.8 mm; - a deflection under load in the longitudinal direction of less than or equal to 0.98 mm, or even less than or equal to 0.95 mm; - a Young's modulus less than or equal to 2.9 GPa, and preferably greater than 2.3 GPa, or even greater than 2.6 GPa.

5. Plasterboard according to any one of claims 1 to 4, characterized in that it has: - a breaking strength, in the longitudinal direction, greater than or equal to 1000 N, preferably greater than or equal to 1100 N; and / or - a residual deflection less than or equal to 0.5 mm.

6. Plasterboard according to any one of claims 1 to 5, characterized in that it has a shrinkage of less than or equal to 10%, or even less than or equal to 5%, measured at 800°C.

7. Plasterboard according to any one of claims 1 to 6, characterized in that the plaster layer is formed from a mix comprising: - plaster, - a retardant, preferably an acid retardant, - a heat-resistant accelerator, - a sulfate-based accelerator, which is not calcium sulfate, - a foaming agent, and - water.

8. Plasterboard according to claim 7, characterized in that the mix further comprises a fire retardant selected from vermiculite, mineral or metallic fibers, silicone oil, amorphous silicon dioxide, or a mixture of at least two of these, preferably glass fibers, the weight content of the fire retardant preferably being 1 to 6%, or even 2 to 4%, relative to the dry weight of plaster.

9. Plasterboard according to claim 7 or 8, characterized in that said retardant is a polycarboxylic acid or a salt thereof, preferably selected from citric acid, tartaric acid, a salt thereof, and a mixture of at least two of these, preferably citric acid.

10. Plasterboard according to any one of claims 7 to 9, characterized in that the retardant content by weight is 0.01 to 0.1%, preferably 0.03 to 0.06%, or even 0.03 to 0.04%, relative to the dry weight of plaster.

11. Plasterboard according to any one of claims 7 to 10, characterized in that said heat-resistant accelerator comprises ground gypsum coated with sugar.

12. Plasterboard according to any one of claims 7 to 11, characterized in that the weight content of heat-resistant accelerator is 0.5 to 3%, preferably 2 to 2.5%, relative to the dry weight of plaster.

13. Plasterboard according to any one of claims 7 to 12, characterized in that said sulfate-based accelerator is potassium sulfate.

14. Plasterboard according to any one of claims 7 to 13, characterized in that the weight content of sulfate-based accelerator is from 0.1 to 1%, preferably from 0.4 to 0.8%, relative to the dry weight of plaster.

15. Plasterboard according to any one of claims 7 to 14, characterized in that the foaming agent is an alkyl sulfate, an alkyl ether sulfate, an alpha-olefin sulfonate or a mixture of at least two of these, the weight content of the foaming agent preferably being 0.01 to 0.1%, or even 0.03 to 0.07%, relative to the dry weight of plaster.

16. Plasterboard according to any one of claims 7 to 15, characterized in that the mix further comprises a fluidifier, the weight content of the fluidifier being preferably 0.05 to 0.4%, preferably 0.1 to 0.3%, relative to the dry weight of plaster.

17. A method for manufacturing a plasterboard as defined in any one of claims 1 to 16, comprising the following steps: - the supply of a batch of plaster, - the supply of a first facing sheet, - pouring the mixed plaster onto the first facing sheet to form a layer of wet plaster, - the supply of a second facing sheet on the wet plaster layer, to obtain a wet plasterboard, and - the drying of the wet plasterboard, to obtain said plasterboard.

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