CH624651A5

CH624651A5 - Process for imparting water repellency to plaster structures

Info

Publication number: CH624651A5
Application number: CH1088377A
Authority: CH
Inventors: Raymond Soubirous
Original assignee: Lambert Ind
Priority date: 1976-09-07
Filing date: 1977-09-06
Publication date: 1981-08-14
Also published as: BE858468A; FR2363532A1; IL52829A0; GB1581396A; IT1085699B; GR63625B; AR217445A1; AU2859277A; PT66896B; JPS5363431A; BR7705937A; AU512195B2; DE2740049A1; EG12807A; PT66896A; IL52829A; FR2363532B1

Description

L'invention repose sur ces observations, qui étaient donc tout à fait inattendues, que l'incorporation par mélange dudit polymère dans une proportion de moins de 0,5 partie, de préférence d'environ 0,15 partie de polymère pour 100 parties de poudre de plâtre, constituée principalement de semi-hydrate, d'anhydrite III dit anhydrite soluble et de surcuit, comme il est habituel en matière de plâtre de construction, procure aux ouvrages de bonnes propriétés hydrofuges sans détérioration importante des propriétés de résistance, qu'il n'est pas nécessaire d'ajouter de catalyseur, qu'il n'y a pas lieu à difficulté anormale de mélange de la poudre de plâtre avec l'eau soit au moyen des outils manuels, soit au moyen des machines habituellement utilisées, qu'il n'y a pas d'expansion abondante de la pâte obtenue et que le prix d'hydrofugation est relativement modéré. The invention is based on these observations, which were therefore completely unexpected, that the incorporation by mixing of said polymer in a proportion of less than 0.5 part, preferably about 0.15 part of polymer per 100 parts of plaster powder, consisting mainly of semi-hydrate, of anhydrite III called soluble anhydrite and in addition, as is usual in building plaster, provides works with good water-repellent properties without significant deterioration in resistance properties, which it is not necessary to add a catalyst, since there is no abnormal difficulty in mixing the plaster powder with water either by means of manual tools or by means of the machines usually used, that there is no abundant expansion of the paste obtained and that the water-repellency price is relatively moderate.

A partir d'une poudre de plâtre contenant 94,5% de sulfates de calcium dont 20% environ d'anhydrite soluble, 5% d'impuretés et environ 0,5% de produits de retard et d'épaississeur, par mélange de 1,5 kg de polymère hydrofugeant par tonne de poudre de plâtre, on a obtenu une poudre dont un échantillon de la pâte correspondante obtenue par gâchée mécanique à la machine à projeter a permis d'obtenir, sur prismes moulés de 4 x 4 x 16 cm, après 7 j d'hydratation et séchage, les résultats d'essai suivants : From a plaster powder containing 94.5% of calcium sulphates of which approximately 20% of soluble anhydrite, 5% of impurities and approximately 0.5% of retardants and thickener, by mixing 1 , 5 kg of water-repellent polymer per tonne of plaster powder, a powder was obtained, a sample of the corresponding paste obtained by mechanical mixing with a spraying machine made it possible to obtain, on molded prisms of 4 x 4 x 16 cm , after 7 days of hydration and drying, the following test results:

Résistance à la flexion 56 bars Flexural strength 56 bars

Résistance de compression 212 bars Compressive strength 212 bar

Dureté Brinell 335 bars Brinell hardness 335 bars

Module d'élasticité dynamique 91900 bars Dynamic elastic modulus 91 900 bars

Masse volumique 1260 kg/m3 Density 1260 kg / m3

Absorption d'eau par immersion totale pendant 24 h 1,75% Water absorption by total immersion for 24 h 1.75%

On a observé que la bonne conservation de la poudre de plâtre contenant l'hydrofugeant nécessite la présence d'anhydrite soluble qui est la variété de sulfate de calcium obtenue par déshydratation du gypse à' température modérée au-delà du semi-hydrate et qui se transforme spontanément en semi-hydrate au contact de l'air par absorption de la vapeur d'eau que l'air contient. C'est pourquoi, si on veut assurer la conservation des aptitudes hydrofuges, il faut aussi protéger la poudre contenant l'hydrofugeant contre l'action de la vapeur d'eau de l'air. It has been observed that the good conservation of the plaster powder containing the water repellant requires the presence of soluble anhydrite which is the variety of calcium sulphate obtained by dehydration of the gypsum at moderate temperature above the semi-hydrate and which spontaneously transforms into a semi-hydrate on contact with air by absorption of the water vapor that the air contains. This is why, if we want to ensure the conservation of water repellency, we must also protect the powder containing the water repellant against the action of water vapor from the air.

La poudre de plâtre contenant l'hydrofugeant peut être employée avec une aptitude particulière à la constitution d'enduits extérieurs de bâtiments, particulièrement d'enduits projetés à la machine à projeter, de préférence relativement durs et compacts, dont la masse spécifique après séchage est d'environ 1,26 kg/dm3. The plaster powder containing the water repellant can be used with a particular aptitude for constituting exterior coatings for buildings, particularly coatings sprayed on the spraying machine, preferably relatively hard and compact, the specific mass of which after drying is about 1.26 kg / dm3.

L'invention a ainsi pour objet d'une façon générale un procédé d'hydrofugation d'ouvrages en plâtre, caractérisé par l'incorporation à la gâchée de plâtre de méthylhydrogènepolysiloxane du type indiqué en une proportion inférieure à 0,5 partie, de préférence voisine de 0,15 partie en masse, pour 100 parties de poudre de plâtre. Cependant, elle n'est pas limitée par le mode particulier de mise en jeu de l'hydrofugeant par mélange à la poudre de plâtre, laquelle contient les divers éléments constituant le plâtre. On a observé que l'incorporation de l'hydrofugeant au plâtre peut être effectuée par addition de l'hydrofugeant à l'un quelconque des sulfates de calcium constitutifs de la poudre de plâtre, puis par mélange de ce sulfate de calcium avec les autres éléments constitutifs de la poudre de plâtre. The subject of the invention is therefore generally a process for waterproofing plasterwork, characterized by the incorporation into the batch of methylhydrogenpolysiloxane plaster of the type indicated in a proportion of less than 0.5 part, preferably around 0.15 part by mass, per 100 parts of plaster powder. However, it is not limited by the particular mode of application of the water repellent by mixing with plaster powder, which contains the various elements constituting the plaster. It has been observed that the incorporation of the water repellant into the plaster can be carried out by adding the water repellant to any of the calcium sulphates constituting the plaster powder, then by mixing this calcium sulphate with the other elements. constituents of plaster powder.

On peut aussi incorporer l'élément hydrofugeant lors de la gâchée du plâtre, qu'il s'agisse de gâchée discontinue comme lors de la mise en œuvre manuelle du plâtre ou de gâchée continue comme lors de la mise en œuvre par machine à projeter. It is also possible to incorporate the water-repellent element during the mixing of the plaster, whether it is a batch mixing as during the manual processing of the plaster or a continuous mixing as during the processing by spraying machine.

On pourrait encore, sans sortir du cadre de l'invention, utiliser la dilution intermédiaire de l'hydrofugeant dans un liquide compatible. We could also, without departing from the scope of the invention, use the intermediate dilution of the water repellant in a compatible liquid.

La proportion de l'hydrofugeant indiquée de 0,15 partie en masse d'hydrofugeant pour 100 parties de poudre de plâtre représente une valeur ayant procuré des résultats d'hydrofugation The proportion of the water repellant indicated of 0.15 part by mass of water repellent per 100 parts of plaster powder represents a value which has given water repellency results.

5 5

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convenable pour un prix raisonnablement bas sans présenter les difficultés importantes à la gâchée, l'expansion abondante, la détérioration des propriétés mécaniques dont il a été question au sujet de l'emploi de quantités de l'ordre de 0,5 à 1,5 partie pour 100 parties de poudre de plâtre. Le domaine des concentrations utile s'étend naturellement, conformément à l'invention, aux concentrations inférieures et supérieures à 0,15% tout en restant inférieures à 0,5%. suitable for a reasonably low price without presenting the significant difficulties in tempering, abundant expansion, deterioration of the mechanical properties which have been discussed in connection with the use of quantities of the order of 0.5 to 1.5 part for 100 parts of plaster powder. The useful concentration range naturally extends, in accordance with the invention, to concentrations below and above 0.15% while remaining below 0.5%.

3 624 651 3,624,651

On comprendra que l'agent incorporé indiqué est caractéristique de la classe des polymères linéaires qui, aux doses employées, seraient par eux-mêmes insuffisamment hydrofuges et qui sont susceptibles de former un composé convenablement 5 hydrofuge au cours de la gâchée ou postérieurement; on comprendra aussi que cet agent incorporé est notamment caractéristique de la classe correspondante des dérivés organiques du silicium. It will be understood that the incorporated agent indicated is characteristic of the class of linear polymers which, at the doses employed, would by themselves be insufficiently water-repellent and which are capable of forming a suitably water-repellent compound during mixing or subsequently; it will also be understood that this incorporated agent is in particular characteristic of the corresponding class of organic silicon derivatives.

R R

Claims

624,651

2

1. Process for waterproofing plaster works, which consists in incorporating, in the absence of water, into the plaster powder a linear polymer which is an organic derivative of silicon, namely a liquid polyhydrogenomethylsiloxane having the sequence following:

CH3

I

-Si-O-I

H

itself insufficiently water repellent, but forming a suitably water repellent compound by chemical reaction during mixing, characterized in that an amount less than 0.5 part of said polymer is distributed per 100 parts of plaster powder, said plaster powder comprising calcium sulphate semi-hydrate, anhydrite III and necessarily overcooked plaster, and the water necessary for mixing is subsequently added.

2. Method according to claim 1, characterized in that the quantity of the polymer used is approximately 0.15 part per 100 parts of plaster powder.

3. Method according to claim 1 or 2, characterized in that the said polymer is incorporated into all of the constituent elements of the plaster powder.

4. Method according to claim 1 or 2, characterized in that first distributes said polymer in one of the calcium sulfates constituting the plaster powder, then this calcium sulfate is mixed with the other constituent elements plaster powder.

5. Products obtained by the process according to claim 1.

6. Exterior coatings for buildings, prepared from the products according to claim 5.

We know that plaster works are naturally hydrophilic: liquid water permeates them and is likely to migrate within them.

To date, it has not been disclosed means of waterproofing the mass of said works at relatively low price to be marketable on a large scale in order to avoid the aforementioned drawbacks; the main object of the present invention is to provide such a means.

Various products are known which are used for water repellency of powders. One of them is a polyhydrogenomethylsiloxane composed of units

CH3

I

-If-O-

I

H

which is marketed in particular by Dow Corning S. à r. 1. at Rueil-Malmaison under the name of Dow Corning 1107 fluid, the current price of which is approximately 28,000 French francs per tonne and the indications for use of which consist in distributing it in the proportion by mass of 0.5 to 1, 5 parts of product per 100 parts of powder per mixture in the presence of a suitable catalyst in the powder to be waterproofed. The introduction of this product into plaster powder according to said directions for use corresponds to a relatively high water repellency price and makes said plaster powder unsuitable for the use for which it is usually intended; mixing plaster powder with water is abnormally difficult and the paste obtained expands abundantly, significantly deteriorating the strength properties of the product.