EP2802546A1

EP2802546A1 - Binder for interior wall coating

Info

Publication number: EP2802546A1
Application number: EP13702319.8A
Authority: EP
Inventors: Philippe Dumont
Original assignee: New Lime Development Sprl
Current assignee: New Lime Development Sprl
Priority date: 2012-01-11
Filing date: 2013-01-10
Publication date: 2014-11-19
Also published as: BE1020340A3; WO2013104031A1

Abstract

The invention relates to a binder composition comprising an intimate mixture of: hydrated lime powder having a weight-average particle size of less than 100 μm, and plaster (calcium sulphate hemihydrate) powder having a weight-average particle size of less than 100 μm, the weight ratio of hydrated lime having a particle size of less than 100 μm/plaster powder having a particle size of less than100 μm being between 1:0.90 and 1:0.1.

Description

Binder for interior wall coating

The present invention relates to a composition for the preparation of an interior wall coating (not exposed to rain) comprising as binder an intimate mixture of hydrated lime and plaster.

State of the art The slaked lime or calcium hydroxide is prepared by extinction of quicklime or calcium oxide. Depending on the reactivity of the calcium oxide or its degree of sintering, depending on the quenching reaction conditions and on the drying conditions, the hydrated lime obtained will have very variable properties. Thus, for example, the BET specific surface area of the hydrated lime may vary between 7 and 70 m ² / g, while the size of the micelles may vary for example from a few microns to 100 microns or more.

Calcium hydroxide has a lamellar structure, which gives it a high degree of plasticity, thus making it possible to obtain very water-rich and very creamy calcium hydroxide mortars, in which a large quantity of aggregates (for example sand) can be incorporated, while maintaining great maneuverability for the mortar.

This plasticity and maneuverability were very appreciated for the realization of mortars of plaster and masonry obtained by extinction of quicklime with a high proportion of water. This reaction product was decanted into pits to remove supernatant water. After a few weeks, a lime paste was obtained with a free water content of approximately 50%. This type of mortar is well known for the realization of interior plastering plaster. Despite the intrinsic qualities of lime (ie good plasticity, good handling, slow setting, alkaline pH anti-corrosion and biocide, good air permeability, good degree of whiteness, total absence of radioactive elements) compared to plaster the use of lime has declined in favor of plaster. One reason for this abandonment of lime in favor of plaster is that the powdered powdered dry conventional hydrated lime has a much lower plasticity than that obtained for a paste lime, so that the maximum amount of sand that can be incorporated in a conventional hydrated water-lime mixture while maintaining acceptable plasticity is greatly reduced, thereby greatly increasing the cost per unit volume of the plaster prepared from conventional hydrated lime and sand.

It has also been proposed by US3057742 to mix hydrated lime with plaster in dry form, to prepare a ready-to-use dry mixture after addition of water. However, according to this document, the mixture of hydrated lime and plaster has many disadvantages, following insufficient maturation of the hydrated lime. The plaster composition thus obtained has problems of consistency, fluidity, and crack formation. In an attempt to avoid these problems, the document US3057742 proposes to add to the mixture a small amount of finely divided additives capable of giving a certain viscosity when mixed with water at a rate of 2% by weight. Even using hydroxyethyl cellulose or methyl cellulose at 1% by weight based on the weight of hydrated lime and plaster, the composition does not form a binder having both a standard consistency greater than or equal to 0.88 and a plasticity greater than 20 according to standard NBN B13-206.

By GB 1390098 (whose inventor is the inventor of the present invention), it has been proposed to prepare mortars based on hydrated lime and plaster, rich in plaster (1 to 9 parts by weight of plaster per part). by weight of hydrated lime), prepared by mixing together quicklime and gypsum. Such a mortar does not have both a high consistency and sufficient plasticity. Much research has been conducted to improve the plasticity of a coating prepared from conventional hydrated lime, as well as its ability to receive a large volume of sand, while maintaining acceptable plasticity. All of these studies (sometimes known as "Sand Carrying Capacity - SCC" - Plasticity of Lime Mortars - Dr. Rune Hedin - 1962) on coatings made from conventional hydrated lime have not been successful. Given the low capacity of conventional hydrated lime-based coatings to be mixed with sand while maintaining good plasticity, ready-to-use plaster, despite all its disadvantages and shortcomings, has gradually replaced lime-based coatings. hydrated conventional. Plaster, as such, is a by-product or more exactly a waste of phosphoric acid production plants. The cost of plaster, although lower than the cost of a traditional hydrated lime is however not non-zero. Due to its low plasticity and low water retention, the plaster does not allow the incorporation of large amounts of mineral fillers, so that it is not possible to reduce the cost of plaster-based plaster. by incorporating a large amount of inexpensive mineral filler (eg sand, etc.), but also to give particular properties to the gypsum plaster coating by incorporating a large amount of particular mineral filler.

From an environmental point of view, plaster presents in addition to its residual radioactivity problem (due to the radioactivity of the calcium phosphate ore used for the production of phosphoric acid, with phosphogypsum as a byproduct, which after dehydration gives the plaster ), a greenhouse gas emission budget less favorable than that for a lime - sand mixture. Given the quantities of plaster consumed annually (for example, we are talking about an annual consumption of 8 to 10 million tons of plaster only for France), the impact "greenhouse gas" of the plaster is far from negligible . Brief description of the invention

The subject of the invention is a composition suitable for the preparation of a suitable binder after the addition of water to the interior wall coating preparation, in particular to the plastering, said coating comprising, on the one hand, (a) as a binding an intimate mixture of hydrated lime and plaster, and secondly (b) a filler, said composition thus comprising hydrated lime, plaster and optionally a filler. Said coating prepared from a composition according to the invention has excellent plasticity and is capable of receiving large amounts of aggregates (for example sand), while maintaining excellent handling and ensuring a gradual grip. The coating thus obtained has good durability and can have a good degree of whiteness. The color of the coating depends, for example fillers and / or dyes added to the coating. The composition according to the invention is a composition advantageously ready for use after mixing with water and advantageous incorporation of aggregate (s) and / or fillers (for example sand), the incorporation of aggregate (s). ) being operated before, during and / or after mixing with water. The composition may optionally comprise one or more aggregates, solid particles, fibers or inert fillers.

The composition according to the invention makes it possible to produce monolayer ceilings, the application of the coating being easy (good adhesion to the substrate, adequate setting time and hardening allowing a good smoothing of the wall, etc.). The composition according to the invention allows the incorporation of a high quantity of non-reactive materials or fillers, such as sand, while obtaining a coating. good plastic. The coating according to the invention therefore has a high "sand carrying capacity", ie a high capacity to receive sand while ensuring a good plastic coating, this capacity being defined by the ratio volume mortar / amount of binder (in liter per kg) while maintaining a plasticity as high as possible.

The invention therefore particularly relates to a suitable composition after adding water or mixture with a quantity of water for the preparation of a binder in the form of an intimate mixture of hydrated lime and plaster, particularly for the preparation of an interior wall coating, more specifically a plaster coating, said composition comprising an intimate mixture of powdered hydrated lime of average particle size by weight less than ΙΟΟμηι and plaster (calcium sulfate hemihydrate) powder of average particle size by weight less than ΙΟΟμπι; the weight ratio hydrated lime of particle size less than ΙΟΟμιη / plaster powder having a particle size less than ΙΟΟμιη being between 1: 0.90 and 1: 0.1, advantageously between 6: 4 and 8: 2, preferably between 6, 5: 3.5 and 7.5: 2.5, the intimate mixture of hydrated lime powder

mean particle size by weight less than ΙΟΟμπι and plaster (calcium sulphate hemihydrate) powder of average particle size by weight less than ΙΟΟμπι without charge being able to form after addition of water a binder having a standard consistency (E / C) higher or equal to 0.88, advantageously greater than 0.90 and a plasticity greater than 20, but advantageously greater than 23, said standard consistency and said plasticity being measured according to the standard NBN B 13-206. This ratio by weight is determined in dry form. The composition according to the invention is therefore rich in hydrated lime with respect to the amount of plaster.

The binder prepared after adding water to a composition according to the invention, but in the absence of filler or additives or after removal of fillers and additives

optionally present in the composition according to the invention, that is to say consisting essentially of hydrated lime, plaster and water present both standard consistency (E / C) greater than or equal to 0.88, in particular greater than 0.90, and a plasticity greater than 20, in particular greater than 23, measured according to standard NBN B 13-206. By Standard NBN B 13-206, we mean the Belgian standard established for building lime, test methods, Standard Consistency and Plasticity of hydrated lime, by the "Building Lime" Commission of the Belgian Institute for Standardization ( IBN), publication authorized February 6, 1980. The composition may include one or more inert fillers. However, advantageously at least 75% by weight, preferably at least 80% by weight, for example 85% by weight to 99% by weight (for example 90%, 95%, etc.) of the composition according to the invention (% by weight expressed in dry form) consists of an intimate mixture of hydrated lime and plaster. This then allows the ceiling to incorporate, at the place of use of the binder, large amounts of various fillers depending on the desired effect or properties.

According to an advantageous characteristic of the composition according to the invention, the composition comprises, relative to its dry weight, less than 20% by weight, advantageously less than 15% by weight, preferably less than 10% by weight, in particular less than 5% by weight of hydrated lime with a particle size greater than ΙΟΟμιη, as well as less than 20% by weight, advantageously less than 15% by weight, preferably less than 10% by weight, in particular less than 5% by weight of plaster of particle size greater than ΙΟΟμπι.

According to one particular characteristic of compositions according to the invention, with respect to its dry weight, at least 90% by weight, advantageously at least 95% by weight, preferably at least 97% by weight of hydrated lime and plaster present in said composition consists of hydrated lime powder of average particle size by weight less than 50μπι intimately mixed with powdered plaster of average particle size by weight less than 50μπι. According to an advantageous detail of the composition according to the invention, said composition is advantageously prepared by mixing quicklime, gypsum (CaSO ₄ .2H ₂ O) in the presence of water, followed, if appropriate, by a drying step. This extinction step is for example carried out in a mixer-grinder.

In the composition according to the invention, the intimate mixture of powdered hydrated lime with a mean particle size by weight of less than ΙΟΟμπι and plaster (calcium sulphate hemihydrate) with a powder of average particle size by weight less than ΙΟΟμπι without charge is advantageously adapted to form after addition of water, a binder having a standard consistency (E / C) greater than 0.90 and a plasticity greater than 23 measured according to the standard NBN B 13-206.

According to preferred embodiments, the intimate mixture of hydrated lime powder having a mean particle size by weight of less than ΙΟΟμηι and plaster (calcium sulphate hemihydrate) powder having a mean particle size by weight of less than ΙΟΟμπι without charge is adapted to form after adding of water a binder having a standard consistency (W / C) greater than or equal to 0.90, for example equal to or greater than 0.91 and a plasticity greater than 24, for example 25, 26, 27, 28 or more , said standard consistency and said plasticity being measured according to the standard NBN B 13-206.

Advantageous embodiments of the composition according to the invention comprise one or more of the following details and / or characteristics,

advantageously a combination of the following details and / or characteristics:

the composition, before being mixed with water to form the binder or the coating, has a moisture content of less than 2% by weight, advantageously less than 1% by weight, for example between 0.degree. , 1% and 0.7% by weight; and or

the composition is substantially free of particles having a particle size of less than 3μιη, in particular with a particle size of less than 6μιη; and or the composition comprises at least 5% by weight, advantageously at least 10% by weight of inert filler particles having a fineness modulus of between 2 and 5, advantageously between 2 and 4; and or

the composition comprises, as inert particles for filling fine sand or a mixture of inert particles comprising more than 50% by weight of fine sand, the fine sand advantageously having a mean particle size by weight of less than 2 mm, preferably of between 200 μm. and 1mm; and or

the composition comprises a quantity of inert particles of fineness filling of between 2 and 5, advantageously between 2 and 4, adapted so that the volume ratio of binder / volume of inert filler particles is between 1: 7 and 1: 2, advantageously between 1: 6 and 1: 3; and or

the composition comprises a quantity of inert or non-reactive fibers in a basic medium. The invention also relates to a process for preparing a composition according to the invention. According to this process, quicklime is mixed with gypsum (CaSO 4-2H ₂ O) in the presence of water; the ratio by weight quicklime / gypsum being between 1: 1.5 and 1: 0.16, said mixing step being carried out so that the mixture is substantially homogeneous and so as to maintain the temperature between about 100 ° C. and 200 ° C., advantageously between 105 ° C. and

170 ° C, preferably between 110 ° C and 160 ° C. The stage of extinction of quicklime is advantageously in the presence of a liquid additive at room temperature (20 ° C) and soluble or dispersible (able to be dispersed) in water, for example a silicone compound and / or diethylene glycol. In this process, an intimate mixture of powdered hydrated lime having a particle size of less than 1 μm and powdered plaster having a particle size of less than ΙΟΟμπι is recovered, the mixing step being, if necessary, carried out in a mill and / or followed by a step. grinding and or followed by a classification step. Advantageously, at least a quantity of quicklime is premixed in a first step with inert particles), the gypsum and a quantity of water (advantageously containing one or more additives adapted to increase the specific surface area of the lime) are then added and mixed. hydrated) with quicklime premixed with inert particles. Thereafter, the mixture obtained is optionally dried, optionally after adding a quantity of quicklime to the mixture resulting from the quicklime / water / gypsum reaction.

Preferably, the step or steps of mixing are carried out in a mill, so as to subject the mixture to grinding. This mill is advantageously provided with means for controlling the temperature.

According to an advantageous feature, water is added in a controlled manner to the reactive mixture containing quicklime and gypsum to maintain the temperature between about 100 ° C and 200 ° C, preferably between 105 ° C and 170 ° C, preferably between 110 ° C and 160 ° C.

According to a characteristic of the process, the quicklime / gypsum mixture is sieved in order to remove particles having a particle size of less than 3 μm, in particular with a particle size of less than 5 μπι. This sieving operation is advantageously carried out after a drying step.

According to an advantageous feature, at least a quantity of inert particles of fineness filling of between 2 and 5, advantageously between 2 and 4, is added to the lime / gypsum mixture.

According to another advantageous feature, in a first step quicklime is premixed with a quantity of inert particles of fineness filling of between 2 and 5, advantageously between 2 and 4, before adding and mixing gypsum, advantageously premixed with a quantity of inert particles of fineness filling of between 2 and 5, advantageously between 2 and 4. According to other advantageous features of examples of the process according to the invention, quicklime and gypsum are mixed in the presence of a quantity of water of between 10% and 30%, advantageously between 11% and 20% by weight. quick lime.

Preferably, it controls and / or adjusts the moisture content of the gypsum or a part thereof and / or load or inert or part thereof, before its / their mixing with quicklime.

In particular, it controls and / or adjusts the moisture content of the gypsum or part thereof and / or load or part thereof so that the gypsum and possibly mixed load (s) with quicklime contain) a a quantity of water of between 10% and 30%, advantageously between 11% and 20% by weight of quicklime.

The invention finally relates to the use of a composition according to the invention for the preparation of a coating for an inner wall of a building, wall or ceiling. The invention has many advantages, including:

- Easy production in the same heaters, a composition based lime performance and adapted to prepare binders for interior plaster coatings, without or substantially without energy input;

- composition easy to use by the ceiling, because requiring only the addition of mixing water in a mechanical mixer;

- Binder composition allowing the incorporation of large amounts of various fillers, mineral, vegetable, synthetic, in order to achieve any type of coating and thus to produce special function coatings, such as insulation, significant thickness, decorative appearance, color, biocides, permeable to water vapor, etc.

- composition with a lower ecological footprint, because it can use the heat released during the extinction of quicklime to obtain the hydraulicity of the hydrated lime, and because having a SCC (sand carrying capacity) high to reduce the amount of calcined product per unit volume.

Although features of the invention are given in the appended claims, features and details of the invention will become apparent from the following description of preferred embodiments, given by way of example only, as well as from the description of Figure 1 which schematically shows a production facility composition according to the invention. Examples

In the present paper, the measurement of the plasticity of hydrated lime is carried out according to the Belgian standard B 13-206. This plasticity measured according to this standard characterizes the ease with which the material or a mixture containing hydrated lime is used. This method can be applied to lime and plaster mortars mixed or not with an aggregate or mineral or organic filler.

The method consists in causing, by standardized shocks, a determined spreading of a fixed volume of hydrated lime paste, plaster, water, and possibly an aggregate of standard initial consistency. The adjustment of the standard consistency (defined by the mass ratio of the water on the binders and possible aggregates "E / C") is to obtain a spread of the paste to a determined diameter on a glass plate after a single shake from the shaking table. Plasticity is conventionally defined as the number of shakes necessary to obtain a spread of the dough to a determined diameter.

The standard consistency of a mortar (hydrated lime and / or plaster) possibly mixed with a filler or an aggregate or an additive is measured by applying the methodology of the standard NBN B 13-206, namely to mix 500g of mortar (measured under dry form) to 500 g of water in a planetary mixer whose substantially cylindrical container has a volume of 5 liters and an internal diameter of about 30 cm and whose axis of rotation of the mixer (rotational movement on itself for the drummer accompanied by a planetary movement about the axis of the container) is about 3 cm away from the axis of the container. The speed of rotation of the beater about its axis is about 140 revolutions per minute, while the number of planetary revolution of the beater is about 65 per minute. Once mortar mixture - homogeneous water, the mixture is poured into a flat plastic container with wide opening of 21 liters. This flat container is hermetically sealed by means of a lid and this paste or mortar is thus preserved for 24 hours. After additional mixing of the dough with a trowel for 3 minutes, fill a frustoconical mold without bottom (10cm diameter at the base, height 5cm, diameter of the upper opening 7cm) placed on a vibrating table with the dough to analyze. We then remove the mold

vertically. The dough is vertically shaken by a movement of the table and the diameter of the wafer formed by the spreading of the dough on the table is measured. In fact one measures three diameters of the slab (diameters making between them an angle of 60 °).

This test is repeated by varying the amount of water (E) until an average diameter of about 110 mm (average of the three measurements of diameters forming an angle of 60 ° between them). If the diameter obtained is greater than 110 mm, the test must be repeated with a smaller quantity of water, whereas if the diameter is less than 110 mm, the test must be repeated, but with the addition of a small amount of water to the dough. The standard consistency is given by the report mass between the amount of water (E) and the amount of dry binder (C) corresponding to a spread of the dough 110mm in diameter after a shake.

After adjusting the standard consistency for the analyzed pulp, the table carrying the wafer with a mean diameter of 110 mm is subjected to a series of shaking by a vertical movement of the table (jerks spaced 15 seconds apart) until obtaining a spread slab having an average diameter of about 190 mm (average diameters measured at an angle of 60 ° between them). The number of shakes required to obtain an average diameter of 190 mm is thus determined. Three attempts are made.

In this paper, sand carrying capacity or SCC

of sand incorporation) is a measure of the capacity of a binder to be mixed with sand and water to make a plastic and handy mortar, this property being related to the plasticity of the binder (lime, plaster, cement ).

It has been proposed to measure the SCC by a plastometer (Voss Extrusion Energy Machine), this machine extruding a mortar under specified conditions in a cylinder and measuring the pressure required for the extrusion of the cylinder. If the extrusion of the mortar is at low pressure, it is easy to implement and has a high capacity for incorporation of sand.

This machine makes it possible in particular to make comparisons between different mortars under specified conditions.

However, a standardized test has been developed to estimate SCC or a function parameter of SCC. This standardized test NBN B13-206 (February 1980) measures the standard consistency of binders and mortars, as well as their plasticity. Table I follows the standard consistency and plasticity of standard binders (three measurements being made for plasticity).

N: Number of shocks to the shaking table to obtain the standard diameter of the mortar slab.

The mixture of 70% by weight of plaster C and 30% by weight of hydrated lime has a plasticity substantially equivalent to that of plaster, but still insufficient for a plaster coating. Indeed, for the skilled person plasticity greater than 2 IN is considered necessary to ensure ease of implementation.

From documents US1967959, US 2127952, US3827897 and US3945841 (equivalent to GB 1390098), there are known processes for preparing a mixture containing more than 50% by weight of plaster and less than 50% by weight of hydrated lime, said mixture being prepared by mixing natural gypsum and / or synthetic with quicklime, with or without external heat input. The mixtures obtained by the processes according to these documents are plaster-rich and lack plasticity (plasticity of 16 to 18), their implementation is therefore. difficult.

Moreover, binders having a plasticity lower than 20 according to the standard NBN Bl 3-206 do not allow the addition of mineral filler (for example sand), because such an addition would only further reduce the plasticity and therefore of still make it more difficult to implement. Preferred mixtures according to the invention comprise, as binder, the product resulting from the mixture of gypsum and quicklime in the presence of water or of moisture, the weight ratio of quicklime / gypsum being between 1: 1.5 and 1: 0.16. The applicant has noticed that by preparing a mixture according to the invention with a step of hydration of quicklime in the presence of gypsum in proportions by weight quicklime / gypsum of 1: 1.5 to 1: 0.16, binders having a standard consistency and / or improved plasticity were obtained with respect to a binder derived from the simple mixture of hydrated lime and plaster containing more than 50% by weight of hydrated lime, for example 70% by weight of hydrated lime. Example 1 Preparation of Binder No. 1

A standard hydrated lime (Lime B) with a moisture content of less than 2% by weight and a mean particle size by weight of less than ΙΟΟμπι was mixed in a Hobart planetary mixer with fine plaster of average particle size by weight of less than 2%. in weight. The binder thus prepared contained, expressed in dry form, 70% by weight of hydrated lime and 30% by weight of plaster. Example 2 Preparation of Binder No. 2 (Invention)

Quicklime was extinguished in the presence of gypsum in a Hobart planetary mixer with a capacity of 10 liters. In this mixer, 5500 g of quicklime powder and 4200 g of natural gypsum containing about 20% by weight of moisture are introduced.

During this mixing, the temperature of the mixture rises rapidly above 100 ° C., by the reaction of the quicklime with the free water contained in the gypsum.

At this temperature, the mixture is boiled, forming a kind of fluidized bed. Water is then added to maintain the temperature of the reaction mixture between 140 ° C and 160 ° C.

The reaction time was about 10 minutes. The product obtained was a dry solids containing mixture of about 70% by weight of hydrated lime and about 30% by weight of plaster (calcium sulfate hemihydrate).

Example 3 Preparation of Binder No. 3

Example 2 was repeated except that about 2360 g of quicklime was mixed with 4200 g of natural gypsum.

The product obtained was a dry-containing containing mixture of about 50% by weight of hydrated lime and about 50% by weight of plaster (calcium sulfate hemihydrate). Comparative Example 4: Preparation of Binder No. 4

Example 2 was repeated except that a reduced amount of quicklime was mixed with natural gypsum, to prepare a dry-form containing mixture of about 30% by weight of hydrated lime and about 70% by weight of plaster (calcium sulphate hemihydrate).

The quicklime used in Examples 2 to 4 was advantageously a quicklime coked.

The characteristics of these various binders are given in Table II below:

*: NBN B 13-206

As can be seen binder No. 2 has both good standard consistency and good plasticity. Such a binder is capable of being mixed with large quantities of inert fillers, in particular sand, to prepare mortars with sufficient plasticity, thus to prepare ceiling mortars rich in sand or other solids. The mortar prepared by means of binder No. 2 has a hardness and adhesion of greater than 0.1 μm / mm ^{2 by} virtue of its hydraulicity.

Tests were carried out to determine mortar characteristics comprising approximately 1 volume of binder for respectively 3 and 6 volumes of sand (sand having a modulus of fineness of 2.38 - fine sand with rounded grains of average particle size by weight less than 1mm)

All mortars were prepared in a Hobart planetary mixer of 10 liters beginning with the preparation of the hydrated lime / plaster binder, either by simple mixing of hydrated lime and plaster, or by hydration of quicklime in the presence of natural gypsum. Once the binder prepared in the Hobart mixer is added, the fine-grained and rounded dry sand is added with a fineness modulus of 2.38.

After homogenization, water is added to reach the consistency (E / C) required for the mortar. The mortars are then left to rest for 1 hour, before being remixed for 10 minutes before measuring their plasticity according to standard NBN B 13-206.

The results of these tests are given in the following tables (Tables III and IV).

\ TABLE III

The lime mortars made from pulp correspond to the old mortars used, for example, for the ceilings of the Sistine Chapel, these mortars having good durability in spite of very low mechanical resistance and poor adhesion. Despite their very high plasticity values, the application of these lime-based mortars is painful and requires a lot of manpower.

Mortars based on lime A have a great plasticity. This type of lime is very expensive (preparation requiring a very expensive drying step), so that lime A is used only for very specific applications, such as the treatment of fumes.

Mortars based on normal hydrated lime (Lime B) lose their plasticity as soon as the amount of sand added is too great. For example, as soon as the volume ratio lime B / sand is about 1: 3, or even less (for example 1: 6), the plasticity of the mortar is less than 20.

Mortars prepared from binder No. 3 (hydration of quicklime in the presence of plaster, with a weight ratio hydrated lime / plaster of 1: 1, do not allow, after addition of 2, 3 or more than 3 volumes sand by volume of binder, to keep enough plasticity to perform a ceiling.

The person skilled in the art could not have expected that it would be possible to obtain a sufficiently plastic coating, even in the presence of a large amount of filler, by using a composition according to the invention, in particular with the binder. ° 2 of Table II.

Figure 1 is a schematic view of a preferred installation for the preparation of compositions according to the invention.

This installation advantageously comprises:

a hopper 1 receiving the wet gypsum,

a dosing system 2 for the wet gypsum,

means 3 for bringing the wet gypsum dosed to a dryer 4; a dryer 4 (used herein to designate an apparatus for drying gypsum), for example of the screw type, to produce hot dry gypsum containing essentially CaSO ₄ . ½ H ₂ O;

a burner 5 for generating hot gases in the chamber of the dryer 4,

a means 6 for measuring the humidity level of the gypsum leaving the dryer 4,

an outlet 7 for evacuating hot humid gases from the dryer 4,

a control means 8 controlling the residence time of the gypsum in the dryer 4 (rotational speed of the motor 40 driving the screw), as well as the operation of the burner 5 and / or the feed 3 of gypsum into the dryer and / or the evacuation of the gases 7 out of the dryer 4 and / or the internal temperature in the chamber of the dryer 4 (for example, a temperature greater than 100 ° C., such as an average temperature of between 110 ° C. and 150 ° C., or even more) ,

means 9 for controlling the supply of dried gypsum into a hydrator or mill 10;

- A hydrator or mill 10 (by hydrator is meant herein an apparatus adapted to ensure hydration of quicklime hydrated lime), the hydrator is advantageously a screw hydrator to generate movement and mixing between the dried gypsum and quicklime;

a supply 11 of CaO;

one or more feeds 12 for additives or for water, for example for solid additives, such as pigments, fibers, non-reactive particles, etc., liquid additives, such as retarder and / or setting regulator, etc., and mixtures of such additives,

an outlet 13 for bringing the mix of hydrated lime + lime + additive (s), if any, to a conditioning unit 14, for example for packaging a composition according to the invention in a bag, in a pot, etc.

Claims

claims

1. Suitable composition after adding water for the preparation of a binder in the form of an intimate mixture of hydrated lime and plaster, in particular for the preparation of an interior wall coating, more specifically a plaster said composition comprising an intimate mixture of hydrated lime powder having a mean particle size by weight of less than ΙΟΟμπι and plaster (calcium sulphate hemihydrate) powder having a mean particle size by weight of less than ΙΟΟμπι; the weight ratio hydrated lime of particle size less than ΙΟΟμητ / plaster powder having a particle size of less than ΙΟΟμπι being between 1: 0.90 and 1: 0.1, the intimate mixture of powdered hydrated lime with a mean particle size by weight less than ΙΟΟμπι and gypsum (calcium sulfate hemihydrate) powder of average particle size by weight less than ΙΟΟμιη without charge being able to form after addition of water a binder having a standard consistency (E / C) greater than or equal to 0.88 and plasticity greater than 20 measured according to NBN B 13-206.

2. Composition according to claim 1, wherein the weight ratio hydrated lime particle size less than ΙΟΟμπι / plaster powder of particle size less than ΙΟΟμιη is between 6: 4 and 8: 2, preferably between 6.5: 3.5 and 7.5: 2.5.

3. Composition according to claim 1 or 2, characterized in that the composition expressed in the dry state comprises less than 20% by weight,

advantageously less than 15% by weight, preferably less than 10% by weight, in particular less than 5% by weight of hydrated lime with a particle size greater than ΙΟΟμπι, as well as less than 20% by weight, advantageously less than 15% by weight preferably less than 10% by weight, in particular less than 5% by weight of plaster with a particle size greater than 1 μm.

4. Composition according to any one of the preceding claims, characterized in that, expressed in dry form, at least 90% by weight, advantageously at least 95% by weight, preferably at least 97% by weight of hydrated lime and of plaster present in said composition consists of powdered hydrated lime of average particle size by weight of less than 50μπι intimately mixed with powdered plaster of average particle size by weight of less than 50μπι.

5. Composition according to any one of the preceding claims, characterized in that the intimate mixture of hydrated lime powder of average particle size by weight less than ΙΟΟμπι and plaster (calcium sulfate hemihydrate) powder of average particle size by weight less than ΙΟΟμιη without charge is capable of forming, after addition of water, a binder having a standard consistency (W / C) greater than or equal to 0.90, and a plasticity greater than 23, said standard consistency and said plasticity being measured according to the NBN Standard B13-206.

6. Composition according to any one of the preceding claims, characterized in that it has a moisture content of less than 2% by weight, preferably less than 1% by weight.

7. Composition according to any one of the preceding claims, characterized in that it is substantially free of particles of particle size less than 3 μιη.

8. Composition according to any one of the preceding claims, characterized in that it comprises at least 10% by weight of inert filler particles having a fineness module of between 2 and 5,

advantageously between 2 and 4.

9. Composition according to the preceding claim, characterized in that the inert filling particles comprise fine sand of average particle size by weight less than 2 mm, preferably between 200μιη and 1mm.

10. Composition according to any one of the preceding claims, characterized in that it comprises a quantity of inert fineness filling particles of between 2 and 5, advantageously between 2 and 4, adapted so that the ratio between the mixing volume. intimate hydrated lime powder of average particle size by weight less than ΙΟΟμπι and plaster (calcium sulphate hemihydrate) powder of average particle size by weight less than ΙΟΟμιη, and the volume of inert filler particles is between 1: 7 and 1 : 2, advantageously between 1: 6 and 1: 3.

11. Composition according to any one of the preceding claims, characterized in that it comprises at least one filler in solid form suitable for the preparation of a coating for an interior wall, in particular a ceiling.

12. Process for the preparation of a composition according to any one of the preceding claims, in which quicklime is mixed with gypsum (CaSO ₄ .2H ₂ O) in the presence of water; the ratio by weight quicklime / gypsum being between 1: 1.5 and 1: 0.16, said mixing step being carried out so that the mixture is substantially homogeneous and so as to maintain the temperature between about 100 ° C. and 200.degree. C., advantageously between 105.degree. C. and 170.degree. C., preferably between 110.degree. C. and 160.degree. C., and an intimate mixture of powdered hydrated lime having a particle size of less than ΙΟΟμπι and plaster powder granulometry is recovered. less than ΙΟΟμηι, the mixing step being so necessary carried out in a mill and / or followed by a grinding step and / or followed by a classification step.

13. Process according to the preceding claim, in which at least a quantity of quicklime is premixed in a first step with a quantity of inert particles, in that gypsum is then added and mixed with premixed quicklime to inert particles. , and then if required add and mix quicklime with quicklime and gypsum mixture.

14. A method according to one of claims 12 and 13, characterized in that the step or steps of mixing in a mill to ensure at least a grinding of quicklime and gypsum during the operation of the mixed.

15. A method according to any one of claims 12 to 14, characterized in that water is added to the reactive mixture containing quicklime and gypsum to maintain the temperature between about 100 ° C and 200 ° C, advantageously enter

105 ° C and 170 ° C, preferably between 110 ° C and 160 ° C.

16. A method according to any one of claims 12 to 15, characterized in that sieves the quicklime / gypsum mixture to remove particles of less than 3μπι.

17. Process according to any one of Claims 12 to 16, characterized in that quicklime and gypsum are mixed in the presence of a quantity of water of between 10% and 30% by weight of quicklime, advantageously between 11% and 20% of the weight of quicklime.

18. A method according to the preceding claim, characterized in that controls and / or adjusts the moisture content of the gypsum or part thereof and / or load or inert or part thereof, before its / their mixture with quicklime.

19. A method according to the preceding claim, characterized in that controls and / or adjusts the moisture content of the gypsum or part thereof and / or load or part thereof for the gypsum and possibly mixed charge (s) with lime live contain) a quantity of water of between 10% and 30%,

advantageously between 11% and 20% of the weight of quicklime.

20. A method according to any one of claims 12 to 19, characterized in that is added to the mixture lime / gypsum at least a quantity of inert fineness of filling particles of between 2 and 5, preferably between 2 and 4.

21. A method according to any one of claims 12 to 20, characterized in that premix in a first step of quicklime with a quantity of inert fineness filling particles of between 2 and 5, advantageously between 2 and 4. , before adding and mixing gypsum, advantageously premixed with a quantity of inert fineness filling particles of between 2 and 5, advantageously between 2 and 4.

22. Use of a composition according to any one of claims 1 to 11, for the preparation of a coating for an interior wall of a building, wall or ceiling.