LU82392A1 - IMPROVED JOINING CEMENT - Google Patents

Description

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The present invention relates to jointing cements suitable for filling the empty spaces forming in the surfaces of building structures and, more particularly, for filling the joints formed between adjacent plates in the structure of a wall or a ceiling, 'while forming a smooth finished surface.

Conventional jointing compositions consist of a mineral filler, for example, crushed lime stone, as well as a binder, usually an organic polymer, together with additives intended for

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improve or adjust the working properties of the composition; moreover, these compositions are mixed with the amount of water necessary to obtain the desired working consistency. These compositions can be sold dry in a ready-to-use mixture but, in any case, after application, these compositions dry by the evaporation of the added water. In a damp or wet environment, the drying time can be excessively long (for example, it can reach six weeks), thus delaying the completion of the construction concerned.

An object of the present invention is to provide a relatively fast setting jointing composition which is less dependent on atmospheric conditions than conventional compositions, at least of which, however, they retain the working properties and smooth finish.

According to the present invention, a jointing cement intended to be mixed with water is provided, comprising 35 to 95% by weight of gypsum plaster in particles with a granularity of less than Λ • 150 yun, 0 h 64 # by weight of an inert mineral filler in particles with a granularity of less than 100 dm .; as well as 1 to 10 # by weight of an organic polymeric binder.

Additives such as a conventional filler, a setting retardant for gypsum plaster, a coloring agent and a foam inhibitor can be incorporated.

Thanks to the incorporation of a quick setting hydraulic material such as gypsum plaster, the setting of the cement of the present invention does not depend on the evaporation of water, while the empty spaces or the joints filled with this cement can be ready to undergo additional finishing operations in a short foreseeable period whatever the atmospheric conditions. The setting times can be adjusted using conventional setting agents for the cementitious material concerned. Appropriate setting times for cements of this type can range from 30 minutes to 6 hours at the discretion of the user. For example, with a cement with a setting time of 2 hours, a joint can be filled (including the application of a tape) in four hours.

The preferred gypsum plasters for the subject of the present invention are plasters of hemihydrates in particles with a granularity of less than 10% which are produced by conventional methods. Plasters of this type naturally have setting times of the order of a few minutes and these setting times must be extended so that the user of the cement has sufficient time to apply and smooth.

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t For this purpose, conventional retarders can be used, for example, citric acid.

The inert fillers falling within the context of the present invention must be chemically inert and they must be chosen to ensure desirable characteristics of impregnation and of work. Calcium carbonate, for example, in the form of ground limestone, is a well-known filler in conventional jointing compositions, as well as talc. The gypsum plaster itself provides a filling function and the amount of inert fillers can be reduced accordingly. The preferred granularity for the crushed limestone particles is less than 100 yum. For talc, it is less than 40 ^ im. It is optionally possible to add a clay such as kaolinite or montmorillonite, preferably in an amount of 0 to 2% by weight.

The polymeric binder serves to reinforce the cement after it has set, but it also helps to ensure the working properties of the cement.

. The binder must be soluble or dispersible in water and the preferred polymer is polyvinyl alcohol.

Starch can also be added, which helps to ensure the working properties of the cement.

Other additives can be incorporated such as a foam inhibitor to prevent the formation of bubbles, as well as a coloring agent in order to impart the desired shade of color to the cement after setting, for example for '' match the ivory color of the covering paper with a drywall.

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The table below gives preferred formulations according to the invention:

Material% by weight

Minimum Maximum

Hemihydrate plaster 35 95

Crushed lime stone 0 64

Talc 0 10

Clay 0 2

Polyvinyl alcohol 1 10 ♦

Starch 0 5

Foam inhibitor 0 3

Coloring agent 0 1

Self-timer as required.

The dry cement composition according to the present invention and formulated as indicated above has remarkable preservation properties when it is enclosed in a sealed container. In order to ensure the best shelf life, the composition must be sealed in a bag made of a practically impermeable plastic material such as polyethylene. The composition can easily be mixed with the prescribed amount of water immediately before use.

The present invention makes it possible to prepare jointing cements which, apart from the advantage of a predictable and rapid setting which has already been mentioned, have the following qualities: they can be easily mixed with water to form a creamy paste smooth, they form a good "wet edge", they have good bevelling properties, good adhesion and excellent 4 / -Λ - 6 - • filling properties of empty spaces with minimum shrinkage. The hardened cement layer can optionally be sanded. Given these remarkable properties, t • the cements of the present invention are useful for various purposes, in particular for application by hand or machine tools but, in particular, when it comes to filling joints, more particularly, in the surfaces of building structures and wall plates, as already mentioned above.

Consequently, the present invention also provides a method for filling voids or joints formed in structures, this method consisting in applying, to these voids or joints, a cement of the type defined above in admixture with the water, smooth the cement surface as required, then allow the cement to set or harden in the voids or joints.

* Example

An example of implementation of the invention will be given below.

A dry cement formulation has the following composition:

Material% by weight

Hemihydrate plaster (see below) 43 d48

Crushed lime stone (100% of 48330 particles with a granularity of less than 100 µm)

Talc (99.9% of particles with a granularity 4 * 83 less than 40 ^ im). - 7 -

Material% by weight. Polyvinyl alcohol (see below) '1.93' 1

Starch (100% of particles with a granularity 0.14 less than, 150yom)

Citric acid 0.06

Foam inhibitor 0.19

Coloring agent 0.10 The particle size analysis of hemihydrate plaster particles is as follows: 100% of particles with a granularity of less than 150 ytun, 84% of particles with a granularity of less than 75 ynn and 40% of particles granularity less than 45 yuxn; setting time not set: 8 minutes. Polyvinyl alcohol has a hydrolysis index of 87-89% and a viscosity of 27-33 centipoise in a 4% aqueous solution at 20 ° C.

The above formulation has excellent storage properties when sealed in polyethylene bags.

For use, a creamy paste is formed by mixing 100 g of the dry formulation with 47 g of water. * The cement thus obtained has all the desirable working properties mentioned above with a setting time of approximately 2 hours.

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Claims (7)

1. Grouting cement intended to be mixed with water and consisting of a mineral filler, as well as 1 · of an organic polymer binder, characterized in that it comprises 35 to, $ 95 by weight of gypsum plaster in particles with a granularity of less than 150 µm, 0 to 64% by weight of one; inert mineral filler in particles with a granularity of less than 100 µm, as well as $ 1 to $ 10 by weight of an organic polymer binder. 2. Jointing cement according to claim 1, characterized in that it comprises 35 to 95% by weight of gypsum plaster, 0 to 64 $ by weight of calcium carbonate, 0 to 10 $ by weight of talc, 1 to $ 10 by weight of a hydrophilic organic polymer binder and $ 0 to 5 by weight of starch. 3. Jointing cement according to claim 2, characterized in that the binder is polyvinyl alcohol. 4. Jointing cement according to any one of claims 2 and 3, characterized in that it additionally contains 0 to 2 $ of montmorillonite clay. * 5. Grouting cement according to any one. that of claims 2 and 3> characterized in that it contains, in addition, 0 to 2 $ of kaolinite clay. * 6. Jointing cement according to any one of claims 2 to 4, characterized in that it additionally contains 0 to 3 $ by weight of a foam inhibitor and 0 to 1 $ by weight of an agent dye in conjunction with a setting retardant ensuring a setting time ranging from 30 minutes to 6 hours. - 9 -% ρ 7. Method for filling the empty spaces or joints formed in structures by applying a cement to these empty spaces or joints, then letting the cement set or harden, characterized in that a cement is used according to any one of claims 1 to 6, in admixture with water. I ^ · χ Λ t * *