Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1999-02-16
2000-11-28
Szekely, Peter A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 4, 106823, C04B 2426
Patent
active
061536733
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a novel phosphomagnesium cement composition.
Phosphomagnesium cements are hydraulic binders, i.e. binders which solidify in the presence of water. They are characterized by a binding phase based on at least one phosphorus compound and at least one magnesium compound.
Phosphomagnesium cements are particularly advantageous for their rapid setting and their high mechanical properties. In addition, they can be used in contact with acid media.
However, these cements lack flexibility: their modulus of elasticity is often high. This is a drawback when, for example, the cement is used to cover a support which, when subjected to various stresses, moves and undergoes deformations. If the coating based on phosphomagnesium cement lacks flexibility, it cracks and splits.
It has also been observed that, under conditions of high humidity, these cements can have poor durability, in particular poor resistance to dry/wet or frost/thaw cycles.
The object of the present invention is thus to propose a phosphomagnesium cement which has a low modulus of elasticity, while at the same time retaining its advantageous properties, such as high mechanical properties or use in acid media.
The aim of the invention is also to propose a water-repellent phosphomagnesium cement which is thus relatively insensitive to wet conditions.
With this aim, the invention relates to a phosphomagnesium cement which can be obtained by placing a binding phase, based on at least one phosphorus compound and on at least one magnesium compound, in contact with at least one polymer in the form of water-insoluble particles, and water.
The invention also relates to the process for preparing this phosphomagnesium cement, which consists in placing in contact the phosphorus and magnesium compounds, at least one polymer in the form of water-insoluble particles, and water.
Other advantages of the invention will become more apparent on reading the description and the examples.
The invention relates firstly to a phosphomagnesium cement which can be obtained by placing a binding phase, based on at least one phosphorus compound and on at least one magnesium compound, in contact with at least one polymer in the form of water-insoluble particles, and water.
Conventionally, cements consist of a binding phase comprising, where appropriate, the usual additives in the field. Although a different term is used to define cements comprising granulates, besides the said binding phase and any additives, the single term "cement" will be used for greater convenience in the description, to refer to these two types of compositions.
The cement according to the invention is a phosphomagnesium cement. The binding phase of such a cement thus comprises a phosphorus-based first constituent and a magnesium-based second constituent.
As regards the phosphorus-based first constituent, any phosphorus compound can be used provided that it comprises phosphorus pentoxide, which is available directly or in the form of a precursor.
Thus, as phosphorus-based compound, mention may be made, without wishing to be limiting, of phosphorus pentoxide, phosphoric acid or derivatives such as orthophosphoric acid, pyrophosphoric acid or polyphosphoric acid, or alternatively salts of such acids, such as the phosphates, hydrogenphosphates, orthophosphates, pyrophosphates, polyphosphates, tripolyphosphates or tetrapolyphosphates of aluminium, of calcium, of potassium, of magnesium or of ammonium, or of mixtures thereof.
It should be noted that phosphorus-containing rejects in the fertilizer manufacturing industries, or alternatively in steel works (stripping of steel, anticorrosion treatment), can be used as phosphorus-based constituents.
According to one specific embodiment of the invention, salts of the phosphorus-based acids mentioned above are used.
Preferably, phosphates or hydrogenphosphates of potassium, of magnesium or of ammonium, or mixtures thereof, are used. Even more preferably, the phosphorus-based constituent is ammonium dihydrogenphosphate, optionally mixed with ammo
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Colombet Jean-Francois
Lemos Dominique
Orange Gilles
Rhodia Chimie
Szekely Peter A.
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