ES2718130A1 - Dry additive for plasters (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Improved dry additive for plaster characterized by the fact that it is composed of a base of polycarboxylic acid, more specifically citric acid, to which is added colloidal silicon dioxide in a proportion of between 0.8% and 1.2% of the weight referred to acid, where the proposed additive is presented as a dry powder, the amount by weight of additive to add to dry gypsum for use comprises from 0.06 grams to 2 grams for each 1000 grams of dry gypsum, so that the mixture with the gypsum whose properties are to be improved is carried out before mixing with water, and the additive can be incorporated in the dry mass of gypsum during its manufacture. (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

Dry additive for plasters.

Object of the invention

The present invention, as expressed in the description of the descriptive report that is written, refers to the formulation of an additive that considerably improves the properties of gypsum, lime and plaster, commonly used in construction, as well as to the method to obtain said additive, and that has the particularity that it is used as an additive in the dry phase. This type of additive is also formulated for the manufacture of prefabricated and hollow bricks, whose method of elaboration of the latter, differs from its traditional form to a plaster-based elaboration using the recommended additive.

In addition, the plaster additive has a considerable advantage in terms of energy savings, for the manufacture of ceramic elements, such as hollow or solid bricks, it has been shown that the amount of energy supplied for cooking them is 800-1400 ° C, through the use of calcium sulfate we can obtain a significant reduction of it around 160-400 °. The energy saving already represents an unprecedented punctual event in the sector of the construction of prefabricated elements made in continuous, using, if desired, the traditional extrusion systems of the ceramic industry.

More specifically, the plaster additive that is recommended is presented in the form of dry powder, and its transformation into a liquid state is also possible as required, so that the mixing of the additive with the plaster is carried out in dry or dry phase, achieving with it numerous advantages, such as an easy to use and transport product with a solid final composition.

Another important advantage derived from the use of this additive is the improvement in the characteristics of calcium sulfate, substantially increasing properties such as the setting time control, improvement of plasticity and fluidity, mechanical resistance, Shore C hardness, absorption of water and durability: in addition to confer other benefits such as the possibility of manufacturing all types of prefabricated products without the use of castings, using extrusion methods as in the manufacture of ceramic bricks.

The most relevant properties of the resulting plaster mortar with respect to other rigid mortars of cement, ceramics or clay, being a mortar more plastic than these, improves the insulation: acoustic, thermal, thermohygrometic, fire, deformability before an earthquake v an absorption of pressure waves.

Scope

The scope of the present invention is within the sector dedicated to the manufacture of construction materials, as well as the civil and industrial construction and building sector or in any field where mortars and prefabricated materials are used.

Its use as wall coverings, mortar between construction elements, as well as prefabricated solid or perforated means a significant reduction in energy production costs.

It is also possible to apply this additive for use in the compartmentalization of spaces, trasdosados, medianeras, facades, plasters, plasters, of any home or building.

Background

As is known, very different types of mortars of all types of plaster are known in the sector. The main lack of these mortars, however, is the lack of mechanical resistance, so they tend to deteriorate very easily in the face of friction and require subsequent finishes with fire cladding panels. Likewise, they will need periodic maintenance to correct the damage that will occur in the mortar over time. As for acoustic and thermal insulation, these plaster mortars must also be accompanied by certain finishes or insulating plates. In addition, for all these types of finishes they require the execution of additional works such as sealing of joints, installation of metal periphery, etc., being therefore desirable the existence of a mortar that fulfills all the functions outlined in a single direct application and without treatments later.

Another particularity presented by the plaster mortar obtained is the use and the possibility of being able to use it in solid phase, this implies the possibility of mixing or premixing for later use in bulk, or packaging. It is therefore that it can be mixed with the plaster directly at the factory, including said additive in the plaster bag itself with all quantifiable guarantees by quality control systems, thus minimizing the possibilities of dosing errors and facilitating the work of the operators who They will give the final use on site. This will mean that by having a dosage control, other additions that confer even higher mechanical properties can be incorporated, such as: beads. arlites, silica, calcium carbonate, marble dust, all kinds of fibers (carbon, polypropylene, polyamide-type polyamides, terephthalamide, glass fibers), foaming, aerating or even insulating materials such as polystyrenes, polyurethanes. etc.

On the other hand, other advantages offered by the additive that is recommended, derived from the composition that will be described later are:

- Reduction of the amount of mixing water necessary, making it possible to make additive gypsum water ratios of 0.28: that is, it is possible to manufacture compositions of 280 grams of water per 1000 grams of calcium sulfate, provided that it is additive.

- Improved workability and fluidity of the mixture, being more plastic and easy to work even for subsequent moldings. As water increases, fluidity increases, being able to reach a consistent pseudo-solid mass in proportions of 280-320 grams of water per kilogram of plaster.

- Significant and significant increase in the setting time, which can range from a few minutes, to several hours: being linear in the proportion that as the dosage of the additive is increased, the setting time increases.

- Possibility of contribution, as indicated, of other materials or substances such as pounds or elements that provide inertia (silica, carbonates, marble, granite ...), improvement of plasticity, lightening, etc., due to the high compactness mix.

- Obtaining a matrix.

- Obtaining a final matrix of low capillarity with low water absorption.

- Once set, improves resistance to sudden changes in temperature.

- High mechanical resistance.

- High surface hardness and mechanical flexural compression.

- High fire resistance.

- High isolation rate to pressure waves to support.

- High resistance to explosions.

- High ductility before deformations caused by earthquake.

- Possibility of manufacturing perforated bricks, and all kinds of parts \ prefabricated by mechanical extrusion.

The following documents are known by the holder of the present specification that have a certain relationship with the invention that is recommended herein:

- Patent P201200897. It describes a dry additive for mixing in gypsum composed of a base of polycarboxylic acid to which colloidal silicon dioxide is added, lacking these elements in any allotropic way, therefore, its stoichiometry is null, thus invalidating any chemical property thereof, which unlike the patent that is recommended, the element used is colloidal silicon dioxide that provides the characteristics previously described. In addition, the compound P201200897 has an amount by weight of additive to be added to the dry plaster for use, which ranges from 0.025 grams up to 1 gram for every 1000 grams of dry plaster and the compound herein has a composition of 0.06 grams up to 2 grams per 1000 grams of dry plaster. The object of the invention differs from that of the invention which is recommended herein, since both compounds and amounts used are different and therefore the characteristics and uses that are obtained therewith.

- Patent P200800891 additive for mixing with common plaster, which consists of a modified calcium sulfate mortar that has the particularity of incorporating expanded vermiculite and in addition to the mixture of calcium sulfate and water, additive mixing with tartaric acid, citric acid, sulfate of copper and potassium or sodium citrate, which must be administered on the liquid phase of the mixture, prior to the pouring of said phase onto the plaster. It is an excessively complex retardant. Different from the one proposed and with another object of invention. - US2011056409 patent that discloses a plaster additive that contains a setting retardant from a citric acid, and where the use of silicon oxide is exposed, not as a previous element in the mixture, but as an assistant in the drying process and that it is supplied independently to citric acid, and also where the addiction of this retardant is carried out after the addiction of water.

- Patent WO2014037602, which could be considered as the closest in the state of the art since it intends to solve a similar technical problem, where a type of plaster is disclosed that does not have silica dioxide in its formulation, but incorporates silicone, being silicone It is known within this technical sector that both products are completely different, and where the disclosed plaster cannot be used in the dry phase, nor can it be pre-mixed with a citric-type or similar polycarboxylic acid.

In view of the known background within the state of the art, it is stated that the existence of any plaster additive with the composition described in the additive described is not known by the holder of the present specification, which can be used in dry phase and that can be pre-mixed with the other components of the composition of the gypsum, as well as none that offer an improvement of the properties of the final mixture being added in solid phase.

Description of the invention

The invention that is recommended consists of a plaster additive, in the form of dry powder, which is applied on the dry plaster before mixing with water and which differs from the additives known in the state of the art in that it can be Used in dry phase.

More specifically, the additive has the following composition: on a base of polycarboxylic acid (citric, acetic, malic acid, among others), ground with a fine sieve grade below 2.5mm, a weight ratio of between 0.8% and 1.2% of colloidal silicon dioxide, on the basis of plaster: the exact percentage being used depending on the tolerances established within the manufacturing process of the dry additive. The greater the amount of silicon dioxide used, the greater the dispersion effect caused on the acid particles. Another of the technical advantages obtained with the present additive is that it is used in the dry phase and can be pre-mixed with a citric type polycarboxylic acid or the like.

After the investigations, it has been concluded that the effect of colloidal silicon dioxide begins to be significant from the addition by weight of 0.8% while from 1.2%, a surplus thereof does not cause changes we mean in the performance of this component on the final behavior of the dry additive.

The application of citric acid in its anhydrous form (in the form of crystals), mixed together with the dry mass, does not produce acceptable results since the hygroscopy of the acid causes lumps to be formed that do not dissolve properly, which prevents proper control of the amount of additive that is finally necessary to incorporate into the plaster. It is for this reason that it is necessary to add some element that prevents the formation of these lumps, allowing an adequate dissolution of the additive. Said element must possess very certain qualities, such as high thermostability so that it does not suffer alterations in its structure during setting, impermeability that prevents its interaction with the setting water and that has a high selective absorption on the hydrated crystals of citric acid, finding that the colloidal silicon dioxide meets these requirements in addition to offering other added properties that reinforce the advantageous characteristics of the additive.

The mixture of colloidal silicon dioxide with the base of the ground solid-phase polycarboxylic acid, gives the dry additive the property of being an effective dispersant in addition to protecting it against the hygroscopy of the acid, giving it the necessary capacity to absorb moisture avoiding the formation of moisture. lumps or precipitates. In addition, another of the characteristics that confer it is the dispersibility of the particles keeping them apart for a long period of time thanks to the difference in surface tension of colloidal silicon dioxide.

The strong adsorption that the dry additive confers is caused by the large number of surface points to which the dispersant binds at the same time, this process is established by the adsorption of the polar group towards the acid surface. The rest of the polymeric skeleton is large enough to create an effect known as aesthetic stabilization, by which a physical barrier is created that keeps the acid particles apart. Permanent defloculation is achieved with a minimum separation distance between particles of 200 A. It also produces a decrease in the viscosity of the mixture.

In addition, the formulation process previously described can additionally also be used in its liquid phase, so that polycarboxylic acid (citric, acetic, malic acid, etc.) can be used, plus the dispersant, in aqueous solution or even in a alcohol solution (ethylene glycol, polypropylene glycol, etc.) so that it can be used in the manufacturing process of bricks, prefabricated, or all kinds of pieces in continuous adding the dispersion to the water.

The dosage of the additive on the basis of dry plaster, is established in the following order of magnitude for the following percentages ranging from 0.06 grams to 1 grams per 1000 grams of plaster. That is, for every 1000 kilograms of plaster, they can be added from 0.06 kilograms to 2 kilograms of additive.

The subsequent solid phase dosing of the resulting mixture of plaster additive once the formulation is achieved is for every 1000 kg of dry plaster between 0.06 kilograms to 1 kilogram of additive. On the other hand, if we want to improve the setting time by more than 240 minutes, the percentage should be increased by around 2 kilograms of additive.

Returning to the composition of the mixture in the dry phase, to obtain a greater inertia and plasticity of said mixture, it can be added to a silica sand or an equivalent mineral, resulting in a kneading percentage that can range from 0% 50% silica sand over the proportion of plaster. It is therefore convenient to clarify that the addition of silica sand to the gypsum and additive mixture is carried out in the dry phase and according to that relationship, and its objective is to improve the performance of the mixture, as detailed below.

As indicated above, the increase in the amount of additive in the plaster will cause a proportional increase in the setting time of the plaster once it is mixed with water. For the kneading of the plaster mixture with water, with the percentages indicated previously of additive, a ratio of 1 kilogram of plaster per 0.28 kilograms of water is sufficient, at a minimum and for an optimal mixing with mechanical and energetic means, depending of the end use; In the same way, if on the contrary, we do not want to increase the amount of additive, we can use a quantity of silica around 25%, but we will need to add more water for kneading.

As an example, in the case of castings of prefabricated solid or hollow molds, water can be increased to 0.7-0.9 kilograms per 1 kilogram of plaster: and for extrusion, we can reach quantities of 0.28-0.3 kg per 1 kg of plaster.

For its liquid form, in dispersion in water or in an aqueous medium, alcohol type, will depend on the concentration of the solution. For its correct formulation of solid phase to liquid phase, it can be established with a maximum concentration of 35% and a variable concentration of 20-25% is ideal: using a volume of 200-250gr of additive until 1000 gr of water is filled with water total mix On the contrary, the use of higher proportions of the aforementioned concentrations causes very dense mixtures, and their use is not practical, although it is not a major problem.

The following is a case of a formulation previously tested and by way of example for informational purposes and not limiting; for a concentration of 25% of solute or additive, this compound is understood as the mixture of the polycarboxylic acid base and colloidal silicon dioxide, with a Ph-1.58 approximate handling times of 35 minutes have been obtained, depending on the type of plaster used and of the time that the plaster is manufactured as well as its degree of purity for quantities of 0.3 kilograms of water per 1 kilogram of plaster, an additive dosage of 2.4 grams can be used.

Therefore, the variation of percentage that oscillates for a concentration of 25% in matter of additive, for its later spill in a liquid substance like water varies between 0.5-5 grams of additive for every 1 kilogram of water.

Another possible mode of application of the mortar is the addiction to the previous mixture of fine silica sand. The object of component addiction focuses mainly on pursuing improvements in the mix. In this case, and as previously anticipated, silica sand has an extra objective. First, it provides more inertia to the mixture, increasing its coefficient of friction, and despite its rigidity, the mortar gives it some handling ductility. Especially suitable for spray mortars, plasters, plasters. But the most important contribution in this regard is the possibility of using it in desert countries, where sand is an environmental problem. It is, therefore, that we speak of a sustainable material compared to any other material on the market. The possibility of making bricks with silica sand, solid or hollow, in sand percentages per 1 kg of plaster up to 50% keeping the dosages already described.

The procedure for the preparation of the proposed additive will consist of a series of steps described below:

- Arrangement of the polycarboxylic acid base (citric, formic, acetic, malic acid, among others), which can be obtained by any of the traditional methods, providing it in an anhydrous form (fine crystalline powder).

- On said base of polycarboxylic acid or citric acid, colloidal silicon dioxide will be added, in the proportion of 0.8-1.2% per 1000 gr of acid.

- Both components will be mechanically mixed with an energetic agitator or for example a paddle mixer, stirring the mixture until it adapts a homogeneous color and texture, performing this act at room temperature, not less than 5 ° C or greater than 30 ° C.

- Finally, the mixture must be properly packaged so as to avoid contact with the outside air, which could vary the humidity parameters of the final product. Thus the packaging wrapper must be opaque and tight.

The additive obtained also has the advantage of being inert with respect to the materials usually used in modified plasters, so that it is possible to include in the mixture in addition to the aforementioned fibers, aggregates of all types of granulometries, carbonates, marble powders, polyurethane, polystyrene, perlite, arlite, etc .: and even elements for recycling, such as greenhouse plastics, ground pieces of tires, shells, rice, straw, sawdust, cellulose, etc., without the possibility of causing a reaction unexpected that degraded the quality of the final product. The versatility offered by the described additive, therefore, causes it to be configured as a novel element that solves important problems associated with this type of product, also providing an easy application and the use for its manufacture of economic components and easily acquired in the market.

In the case of passing the formulation to liquid due to the ease of continuous element manufacturing, the following order is established:

- Arrangement of the polycarboxylic acid base (citric acid, acetic acid, malic acid, among others), which can be obtained by any of the traditional methods, providing it in an anhydrous form (crystalline powder).

- On said base of polycarboxylic acid or citric acid, colloidal silicon dioxide is added, in the proportion of 0.8-1.2% per 1000 gr of acid. The use of dispersants is not necessary, in this process it is possible to obviate and use the base directly, since the use of the same significantly reduces the properties.

-Preparation of water or solvent alcohol for subsequent pouring of the polycarboxylic acid base defined the proportion of solution between 10% to 35% if needed. - Premixed for dispersion and subsequent filling until the 1 liter unit is achieved.

- Both components are mixed with an agitator or for example a paddle mixer, stirring the mixture until it adapts a homogeneous color and texture, leaving no remains of suspended solids: performing this act at room temperature, although the mixture can be heated to facilitate dispersion at a temperature not exceeding 60 ° C.

- Finally, the mixture is adequately packaged so as to avoid contact with the outside air, with an opaque and tight container.

Description of the preferred embodiment

As explained above, an embodiment of the present invention is described, which is merely descriptive, not intended to limit the scope of the invention described herein. In the present example, in addition to the manufacture of the additive that is recommended, the mixture to be made for its final application in conjunction with the plaster is described, intended to be used for a manufacturing process of the additive with high levels of quality control.

Generic polycarboxylic acid, or dehydrated or dihydrated citric acid in crystallized form, is milled, with sieve pitch less than 2.5 millimeters. A quantity of 100 kilograms of acid is completed (extrapolated to other proportions). Then, the colloidal silicon dioxide is added, depositing it on the base of citric acid indicated above.

The special mixer with strong turbulence injects 1 kilogram of colloidal silicon dioxide at 100 kilograms (1% by weight percentage of the total additive mass). Mix for 5 to 10 minutes.

Next, the mixture is packaged by means of a barrier and opaque plastic that conveniently protects the product obtained, in a dry atmosphere.

The next step consists in mixing the dry additive obtained with the dry gypsum matrix. To make a 20 kilogram bag of plaster, 12 grams of dry phase additive is added for the present example: and in the case of liquid phase (always at the end of kneading) at 25% concentration, 48 grams of liquid.

If the object is the manufacture in mechanical extruder, in the case of ceramic brick, a minimum amount of water is added. 0.28-0.30 kilograms per 1 kilogram of plaster. If it is intended to pour into mold, the amount of water reaches 0.5-0.7 kilograms.

In case of contribution of silica sand, in a percentage for example of 25%, it is simply added to the dry phase mixture, before pouring the water, we will add said sand: 5 kilograms.

These components, once deposited in a rectangular plastic bucket, or mechanical kneader, are mixed with the help of a rod (any mechanical mixer can also be used as indicated) for about 2-5 minutes, until the assembly has a homogeneous appearance .

The setting process is delayed by the proportion of the additive used that is measured in the operator's working time. For the defined mixture, a time of about 35 minutes is maintained. The more additive is used, the longer and vice versa.

Describing sufficiently the nature of the present invention, as well as the way of putting it into practice, it is not considered necessary to extend its explanation so that any expert in the field understands its scope and the advantages that derive from it, stating that, within its essentiality, it may be carried out in other embodiments that differ in detail from that indicated by way of example, and to which it will also achieve the protection that is sought provided that it does not alter, change or modify its fundamental principle .

Claims (5)

1. DRY ADDITIVE FOR PLASTERS, which is used to be added to the dry phase plaster, in which the formulation of the additive is composed of a polycarboxylic acid base in crystallized form, more specifically citric, acetic, formic or malic acid and which characterized in that said base is added colloidal silicon dioxide, in a proportion between 0.8% and 1.2% of the weight referred to polycarboxylic acid. 2. DRY ADDITIVE FOR PLASTERS, according to claim 1, characterized in that the amount of additive to be added to the dry phase plaster comprises from 0.06 grams to 2 grams per 1000 grams of plaster. 3. DRY ADDITIVE FOR PLASTERS, according to claims 1 and 2, characterized in that the composition of the mixture also comprises silica sand in a proportion of up to 50% with respect to the total gypsum. 4. DRY ADDITIVE FOR PLASTERS, according to claim 1, characterized in that the amount to be used of additive in water is between 0.5 and 5 grams of additive per 1 kg of water. 5. DRY ADDITIVE FOR PLASTERS, according to any of the preceding claims, characterized in that the proportion between water and plaster varies between 0.28 and 0.9 kg of water for 1 kg of plaster.