Joint coating composition for construction elements and method for producing a structure

The present invention relates to an adhesive mortar composition for building elements, especially paper-lined gypsum boards, and to the use of the composition for the production of a structure such as a partition, wall cladding or ceiling.

It is well known to use plasterboard panels for partition walls, vertical cladding or sloping construction elements, as well as suspended or non-suspended ceilings.

Such boards usually have a core, essentially made of plaster, covered on both sides with a sheet serving both as reinforcement and cladding, which sheet may be made of paper or of inorganic fibers.

European patent application published under number 496 682 describes a mortar for filling the joints formed between adjacent side edges of two gypsum boards, and for producing a tapeless joint. The mortar contains, as a percentage of dry matter by weight:

• 5-30% semi-water gypsum;

• 7-25% polymer in the form of an aqueous suspension and / or dispersible powder;

• if desired, other additives for adjusting setting time and / or adjusting the quality of the paste and / or the adhesion of the mortar;

• at least one inert filler in an amount to make the mixture up to 100%.

Example 15 of this patent application describes a specific composition containing the composition having the following weight proportions:

• 194 parts alpha plaster;

• 108 parts of a vinyl acetate / ethylene copolymer stabilized with polyvinyl alcohol, the dry matter content being 55%;

• 6.6 parts of vinyl acetate / ethylene copolymer in the form of a dispersible powder;

• 0.67 parts of cellulose ether;

• 669.3 parts of limestone;

• 2.25 parts of polyvinyl alcohol;

• 0.027 parts of polyacrylamide;

• 2.25 parts of clay;

• 0.045 parts of white Portland cement;

• 1.12 parts of gypsum and starch (in a 50/50 ratio); and • 0.125 parts of hydrolytically degraded keratin.

US Patent Application No. 5,653,797 describes a composition for filling joints formed by adjacent edges of panels made of boards, which includes:

a) calcium sulfate hemihydrate;

b) sufficient water to adjust the composition to a viscosity;

c) a setting retarder comprising a polymer composition containing acrylic amide and acrylic acid monomers;

d) a setting accelerator containing a metal salt with acidic cations.

This application mentions the possibility of using a binder such as latex or polyvinyl alcohol.

Table 2 at column 8 of this application shows a composition containing:

• 20 to 30% calcium sulfate hemihydrate;

• 1 to 4% latex type binder;

• 1 to 10% perlite;

• 10 to 50% limestone;

• 0.5 to 4% clay;

• 0.1 to 1% of a thickening agent;

• 0.5 to 3% talc;

• 1 to 4% mica;

• 0.01 to 1% of the delay described above;

• 0.01 to 2% of the above-described accelerator;

• 0.01 to 1% of a preservative;

• 20 to 30% water.

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However, the above composition undergoes excessive shrinkage on hardening.

International patent application published under the number WO 99/48833 discloses a composition that can be used to fill the joints between two adjacent gypsum boards. The said composition is hydraulically bound when mixed with an appropriate amount of a setting accelerator and contains a material such as gypsum and a special retarder based on a polymer or sulfonate copolymer.

Example 11 of this application describes a joint filler composition having the following composition (weight percent):

• 35.9% calcium sulfate half hydrate;

• 4.1% vinyl acetate / ethylene copolymer in 50% aqueous solution;

• 7.1% perlite;

• 0.3% cellulose ether;

• 8.1% limestone;

• 2.6% of wollastonite;

• 2.6% kaolin;

• 0.1% lime;

• 1.0% retarder;

• 38.3% water.

A disadvantage of the above composition is also its excessive shrinkage.

The mortars or compositions described do not meet expectations as they do not have all of the following characteristics:

- good workability;

- a color consistent with the color of the building elements for which they are intended; and

- the ability to form a joint which undergoes little or no shrinkage and has good mechanical properties (hardness, tensile strength, compressive strength, impact resistance, some low formability or elasticity to prevent cracking).

Moreover, the compositions disclosed in the aforementioned US documents No. 5,653,797 and WO 99/48833 have the peculiarity of containing a strong retarder which blocks the hydration of the calcium sulfate hemihydrate. The user is therefore required to add an accelerator to initiate the hydration process. This leads to some inconvenience when the mortar is to be applied on a construction site as there is a risk that the user does not add the correct amount of accelerator.

Moreover, the properties of the composition change over time. Depending on the time elapsed since the preparation of the composition, the same amount of accelerator added at the time of use may produce different effects. This leads to uncertainty about hydraulic binding as it is not possible to know exactly when binding will occur.

In addition, the following problems arise in the case where the building element is a plasterboard covered with paper:

- firstly, it is necessary that the plaster has good adhesion to the lining paper, and secondly, this adhesion should not be too high, so that the wallpaper can be torn off one or more times without tearing or damaging the bonding mortar; and

- the bonding mortar must have the water and / or paint absorption capacity as close as possible to the water absorption capacity of the lining paper, so as to avoid the need to use a primer before wallpapering or painting.

It is an object of the invention to provide a tapeless adhesive mortar composition which, when mixed with water, forms a mortar having the above-mentioned properties and advantages. The invention is based on the finding that in order to obtain a satisfactory mortar it is necessary that it contains calcium sulphate, a binder and a waterproofing agent in appropriately selected proportions.

Accordingly, the present invention relates to an adhesive mortar composition comprising:

a) 50 to 60% calcium sulfate hemihydrate;

b) 5 to 15% powdered organic binder;

c) 0.05 to 0.2% of a water sealant, which agent is selected from the group consisting of oleic acid, stearic acid and their alkali metal or alkaline earth metal salts;

d) 1 to 10% of a weight reduction agent, the remainder up to 100% consisting of one or more fillers and optionally one or more additives selected from among the agents

Water-retaining agents, thickeners, workability regulating agents, dyes or pigments, setting retarders and setting accelerators. This composition, when mixed with water, produces a hydraulically setting bonding mortar which can be used alone, i.e. both as joint filler and finish bonding mortar, and allows for bonding without the use of tape.

The invention also relates to the use of the composition defined above for the production of a structure consisting of:

- placing building elements side by side,

- mixing the composition of the bonding mortar with water,

- filling the spaces between the building elements with the bonding mortar obtained without the use of tape, and

- leaving the bonding mortar to harden.

Further features and advantages of the invention are set forth in the following description.

Detailed description of the embodiments of the invention

Composition according to the invention

The main composition of the composition has been presented above.

According to a preferred embodiment of the invention, the composition further comprises: c) from 1 to 10% of a weight reduction agent.

According to a particularly preferred embodiment of the invention, the composition comprises:

a) 50 to 60% calcium sulfate hemihydrate;

b) 5 to 10% organic binder;

c) 0.07 to 0.15% of a water sealant;

d) from 3 to 7% of a weight reduction agent.

Of course, to make up to 100%, the composition comprises one or more fillers, and optionally one or more additives selected from water-retaining agents, thickeners, workability control agents, dyes or pigments, set retarders and set accelerators.

It is preferable to use alpha calcium sulfate hemihydrate as this allows the amount of water needed to be reduced for mixing with the composition.

The organic binder is designed to soften the calcium sulphate in the joint and obtain good mechanical properties. The binder can be copolymers of vinyl esters and ethylene monomers, such as ethylene / vinyl acetate (EVA) copolymers, softened or softened, ethylene / vinyl edetate copolymers and vinyl acetate / vinyl edetate copolymers, polyacrylics, vinyl acetate / acrylic copolymers, styrene copolymers. / acrylic and styrene / butadiene, terpolymers vinyl acetate / vinyl edetate / acrylic and vinyl acetate / edetate / vinyl maleate, acrylic terpolymers and mixtures thereof.

The vinyl copolymers may be stabilized with polyvinyl alcohol.

The organic binder can also advantageously be used in the form of a dispersible powder.

As water-sealing agent, in particular, fatty acid, fatty acid salts, wax or silicone derivatives can be used.

Preferably, oleic acid or stearic acid can be used as the fatty acid.

As the fatty acid salt, the alkali or alkaline earth metal salts are preferred, especially the sodium, potassium, magnesium or calcium salts.

As the silicone derivative, silicates, silicates, hydrated silicone oils, silicone emulsions, amino silicone emulsions, alkyl siloxane resins such as hydrogen methyl polysiloxane and polydimethylaminosiloxane, and mixtures thereof can be used.

The most preferred water sealant is a material selected from oleic acid, stearic acid, sodium oleate and sodium stearate.

Perlite, glass microspheres or polymer microspheres can be mentioned as suitable weight reduction agent.

Preferably, the weight reduction agent is expanded, expanded perlite, not waterproofed.

It is also possible to use at least one filler such as, for example, limestone, magnesium carbonate, calcium magnesium carbonate (dolomite), magnesium hydroxide, silica, natural or synthetic gypsum, or natural or synthetic anhydrite.

Limestone is preferably used.

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The adhesive composition of the invention may also contain one or more water-retaining agents which may be selected from cellulose ethers, in particular methyl cellulose (MC), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), ethyl hydroxyethyl cellulose (EHEC), ethyl hydroxyethyl cellulose (EHEC), ethyl hydroxypropyl cellulose (MHC) and methyl hydroxypropyl cellulose (MH) and methyl cellulose (MH). (MHEC).

Water-retaining agents can also increase the viscosity and therefore have a positive effect on the quality of the paste.

Optionally, the cellulose ethers can be partially replaced or accompanied by naturally occurring polycarbonate hydrate derivatives that affect the rheology of the paste, such as galactomans, polysaccharides, xanthan, guar derivatives and the like. Commercially available "modified" cellulose ethers are often the above-mentioned molecules with added wetting agents or thickening agents; they are suitable for use according to the invention. It is, however, possible to use other water-retaining or viscosity-increasing agents, such as starch ethers, which, in addition to their basic function, have a high water-holding capacity, such as polyvinyl alcohol.

The adhesive composition according to the invention may further comprise one or more thickeners which may be polyacrylamides, CMC, starch or clay derivatives such as attapulgite, sepiolite, montmorillonite and bentonite.

Preferably, the thickening agent is polyacrylamide.

The adhesive mortar composition according to the invention may also contain one or more workability regulating agents. The workability adjusting agent may be a fluidizing agent, a wetting agent or a lubricant.

The fluidizing agent suitable for the invention may be sulfonate polymers, preferably melamine formaldehyde sulphate based agents.

As a wetting agent suitable for the invention, mention should be made of alkyl sulfates such as sodium lauryl sulfates, alkylaryl sulfonates or phosphate derivatives.

As a slip agent suitable for the present invention, talc or mica should be mentioned. Due to their lamellar morphology, these agents render the applied surface slippery and help to reduce shrinkage.

The composition according to the invention may also contain one or more dyes, which may, for example, be selected from titanium dioxide and optical brighteners.

The composition of the invention may also contain additives for regulating setting time such as setting accelerators and retarding.

In general, a couple of agents are added, one of which is an accelerator and the other is a retarder.

Among the setting accelerators useful for the invention, sulfates can be mentioned. In the preferred case, gypsum is used in the form of a powdered mixture and starch, the gypsum always has the same setting accelerating ability due to starch, which prevents its aging process. As a result, the bonding of the bonding mortar is insensitive to external plaster contamination, especially those that may become bonding seeds in the tank or plasterer's applicator.

The setting retarders include those based on hydrolytically degraded keratin, hydroxycarboxylic acids such as tartaric acid and citric acid, their salts, and calcium monophosphate. These agents can be used in proportions that vary depending on the ratio of hemihydrate gypsum and accelerator.

Preferably, the proportions of accelerator and retarder are selected such that the setting time is short enough and the joint can be made in one day.

Various other additives may optionally be added to the compositions according to the invention. It is therefore possible to add an agent to the composition which will give it an alkaline pH. The alkaline agent facilitates the dissolution of the water-retaining agent, especially when it is a cellulose ether, and consequently contributes to an increase in viscosity. The basic agent used is an inorganic additive, preferably "white" Portland cement, i.e. iron oxide-free Portland cement, or lime. Preferably, a sufficient amount of the basic agent is added to the blend in an amount necessary to achieve a pH equal to or greater than 8.

Preparation of the composition according to the invention

The adhesive coating mortar composition of the present invention is prepared by mixing the ingredients in any order, preferably until a homogeneous powder is obtained.

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Although the components of the compositions of the invention do not need to be in powdered form, when mixed, the compositions of the invention as a whole are typically in the form of a powder.

In general, the particles making up the powder have a diameter of at most 200 microns.

A method for making a structure according to the invention

According to the invention, to make the structure, the panels or construction elements are placed side by side, the coating mixture is mixed with water to obtain a mortar, and the space between the construction elements is filled with the mortar obtained, without the use of tape, and the joint is allowed to harden. .

The mixing is carried out in a ratio of the weight of water to the weight of the joint mortar composition of 40-50%.

The method according to the invention is used in particular for the production of structures using gypsum boards covered with a layer of paper. Gypsum boards have edges of various shapes, in particular thinned, rounded or both thinned and rounded at the same time.

The combination according to the invention

The use of the method according to the invention makes it possible to obtain a joint with satisfactory properties. This combination also has the advantage that it allows the paint to be applied by any of the painting techniques used, in particular by roller, brush or airless spraying.

Examples

The following examples illustrate the invention without, however, limiting its scope.

Example 1

A bonding mortar composition E according to the invention and three bonding mortar compositions in powder form were prepared. A, B and C which do not fall within the scope of the invention and are provided herein for comparative purposes.

The individual compositions are presented in the table below, in which the values ​​presented are expressed in parts by weight.

<td colspan="2" rowspan="2">Composition</td><td colspan="4">Adhesive mortars</td>

<td>E (according to the invention)</td><td>A (comparative)</td><td>B (comparative)</td><td>C (comparative)</td>

<td>Gypsum</td><td>Alpha hemihydrate</td><td> 500,0</td><td> 500,0</td><td> 500,0</td><td> 500,0</td>

<td>Organic binder</td><td>Vinyl acetate / ethylene copolymer⁽¹⁾</td><td> -</td><td> 40,0</td><td> 40,0</td><td> 40,0</td>

<td></td><td>Vinyl acetate / vinyl edetate copolymer⁽²⁾</td><td> 60,0</td><td></td><td></td><td></td>

<td>Water sealant</td><td>Powdered silicone</td><td> -</td><td> -</td><td> 2,0</td><td> -</td>

<td></td><td>Sodium stearate</td><td> 1,0</td><td> -</td><td> -</td><td> 1,0</td>

<td></td><td>White cement⁽³⁾</td><td> -</td><td> 100,0</td><td> -</td><td> -</td>

<td>Weight reduction agent</td><td>Perlite⁽⁴⁾</td><td> 40,0</td><td> 40,0</td><td> 40,0</td><td> 40,0</td>

<td>Water-retaining agent</td><td>MHPC</td><td> 3,0</td><td> 3,0</td><td> 3,0</td><td> 3,0</td>

<td>Filler</td><td>Limestone</td><td> 370,9</td><td> 291,9</td><td> 389,9</td><td> 390,9</td>

<td>Machinability regulating agent</td><td>Talc</td><td> 20,0</td><td> 20,0</td><td> 20,0</td><td> 20,0</td>

<td>Additives</td><td>Thickener, retarder, accelerator, dye</td><td>In addition to 1000</td><td>In addition to 1000</td><td>In addition to 1000</td><td>In addition to 1000</td>

⁽¹⁾ stabilized with polyvinyl alcohol ⁽²⁾ stabilized with polyvinyl alcohol ⁽³⁾ white portland cement ⁽⁴⁾ foamed, not sealed against water

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Example 2

Adhesive mortars were prepared by adding 42 g of water per 100 g of mixture to mixtures E, A, B and C of Example 1. The bonding mortars thus obtained were tested by forming a bond between two paper-lined gypsum boards.

Composition A did not give satisfactory results, primarily because the use of cement gave the paste a high pH, ​​which caused hydrolysis in the starch-based wallpaper glue, which in turn caused the wallpaper not to stick to the joint.

Composition B provided good paint application to the joint and good wallpaper adhesion. However, mixing the composition was very difficult, possibly because the silicone wets very poorly. Such mixing cannot therefore take place on the construction site.

Composition C was good to mix. However, after the application of the paint, the joint absorbed too much paint too quickly and the adhesion of the wallpaper to the joint mortar was insufficient due to the joint being too porous, which absorbed too much adhesive.

Composition E, which fulfilled all the criteria of the invention, was good to mix and provided good adhesion, and the binder formed a sufficiently thick layer on which to apply paint or to which wallpaper could be glued. The use of alpha plaster made it possible to reduce the amount of water required and, as a result, to reduce shrinkage during drying. Perlite made the mortar easy to apply and additionally reduced shrinkage. Such a mortar was therefore satisfactory from all points of view.