WO2002032846A1

WO2002032846A1 - Novel concentrated, stable and low-sodium gluconic acid composition

Info

Publication number: WO2002032846A1
Application number: PCT/FR2001/003170
Authority: WO
Inventors: Léon Mentink; Jean-Pierre Graux; Agostino Scaringi; Raphaël LECROART
Original assignee: Roquette Freres
Priority date: 2000-10-18
Filing date: 2001-10-12
Publication date: 2002-04-25
Also published as: AU2001295701A1; FR2815343A1; FR2815343B1

Abstract

The invention concerns a stable aqueous gluconic acid composition, said acid being in the form of at least a salt and optionally in the form of free acid and/or one, at least, of its lactones. Said composition is characterised in that it has: a pH higher than 4.0, a dry matter content at least equal to 50 %, an ion gluconate content at least equal to 50 %, expressed in total dry weight of gluconate ions, derived from gluconic acid in the form of salt(s) and optionally of free acid and/or lactone(s) relative to the dry matter of said composition, a sodium ion content less than 8 %, expressed in total dry weight relative to the dry weight of said composition, and an efficient content of a stabilising agent selected in the group consisting of saccharides other than gluconic acid, its salts and lactones, amino compounds and any mixtures of at least any two of said products.

Description

NEW COMPOSITION OF GLUCONIC ACID, CONCENTRATED, STABLE AND POOR IN SODIUM

The present invention relates to a new composition of gluconic acid, concentrated, stable and low in sodium, said gluconic acid being in the form of at least one of its salts, and optionally free acid and / or d 'one of its lactones. It also relates to the use of a stabilizing agent selected for the preparation of said composition. Finally, it relates to the use of said composition in various application fields and, in particular, for the preparation of compositions of mineral binders or of adjuvants for mineral binders. By "mineral binder" is meant any hydraulic binder, in particular any mineral powder, capable of forming with water a paste which sets and hardens gradually, even in the absence of air. This definition applies, inter alia, to cements, to natural or artificial hydraulic lime, to mixtures such as mortars, grout, plasters and concretes, based on ground cement and / or lime, water and / or aggregates. (sands, gravel, pebbles, ...), with the raw materials used in the manufacture of cements such as pozzolans, clinkers, slag, limestone fillers and silica fumes. By “mineral binder” is also meant any plaster composition and, more broadly, any non-hydraulic binder based on calcium sulphate, gypsum and / or lime. Depending on their end use and conditions of use, it is sometimes necessary to add to the mineral binders adjuvants such as grinding agents or grinding aids, plasticizers, water reducers-plasticizers and superplasticizers . These adjuvants make it possible, for example, to modify the workability, setting, hardening, resistance, durability and / or certain other properties of the mineral binder. Many plasticizing-water reducing or superplasticizing products are already used such as molasses, lignosulfonates, sulfonated naphthalene formaldehyde condensates or sulfonated melamine formaldehyde condensates, polyacrylates.

Among these, oxidized sugars, in particular gluconic acid as well as its salts and / or its lactones, occupy a place of choice because very good plasticizers and water reducers, but also retarders of setting, moreover allowing '' improve the resistance of concrete at 28 days.

They are also described as grinding agents in international patent application WO 98/37970. The notion of grinding improvement agent appears in its broadest sense, relating to clinkers, ores, ceramics, pigments or coal.

The use of gluconic acid, its salts and / or its lactones, in the field of mineral binders must be understood here according to all its variants, including very specific applications such as the cementing of wells in the industry of oil and gas.

The use of these products in plasters is also known from French patent FR 2 707 626, in particular. Associated with an anionic melamine formaldehyde resin, they reduce the amount of mixing water to be added to powdered plaster. Reinforcing the water-reducing power of the resin, they provide a setting retarding function and thus allow a “workability”, or time of use of the paste, suitable despite the reduction in the amount of water.

It is emphasized, in this patent, that interest exists as much for prefabricated plaster panels as for plaster tiles, plaster-based coatings, finishing and molding products which involve significant quantities of plaster . The behavior of gluconic acid and gluconates vis-à-vis plaster, and more generally, calcium sulfate, finds particular applications as described in US Pat. No. 3,688,829. It is also known that the gluconate ion has a certain number of advantages during its use:

- complexing properties, in particular with respect to metals, - the solubility of the complexes formed, the expression of these complexing properties over wide pH ranges,

- a capacity for removing dirt,

- anti-redeposition properties, - respect for colors,

- low acidity,

- the preservation of the environment,...

These many aspects have led to very diverse applications, which are furthermore authorized by its moderate cost.

An article by PFIZER in "American Dyestuff Reporter" of October 1948 underlines the interest of its use in the textile industry, for the scouring, the bleaching or the dyeing of materials as widespread as wool, silk, cotton, regenerated cellulose, as well as for printing cellulosic materials.

On a neighboring track, but later, the article "Mechanism of Magnesium Retardation of Cellulose Dégradation During Oxygen Bleaching" (TAPPI

- June 1973), uses the same properties for the bleaching of paper pulp.

The properties of the gluconate ion thus highlighted (and the essential of which appears in an article by D.T. Sa yer - April 1964 - Chemical Review, 633-

643), have led to a gradual but significant widening of its fields of application.

This is the case for cleaning textile materials, as described in patent EP 0 425 369 in the name of Applicant, or dishes, as described in German patent 1,915,056, in particular in the context of the (partial) replacement of the phosphates in the washing compositions used. Gluconic acid and gluconates are commonly used as sequestering agents in washing bottles and glassware in general. Their use has a number of advantages such as the removal of haze and rust spots on the glass, the elimination of scale and rust deposits on the washing equipment.

This field of use, particularly interesting for washing bottles of milk or beer, can find an extension in modern technologies, for example the cleaning of membranes after ultrafiltration of milk (Journal of Dairy Research - (1992) 59, pp 29-38).

The intervention of the gluconate ion has also been claimed for the cleaning of metal surfaces, in particular chemical or electrolytic degreasing, stripping eliminating rust and old paints, or also for the deposit, or "plating", of metals on d 'other.

It is, more generally, useful for the preparation of metallic surfaces comprising moreover, in particular, chemical or electrolytic activation phases, or electrolytic deposits, such as the zinc plating described in French patent FR 2 350 409, in the name of the plaintiff. It can also be of interest to polishing or polishing, chemical or electrolytic.

The use of the gluconate ion also concerns the surface conversion of aluminum or satin-finishing, or more generally, the chemical conversion of metallic surfaces such as steel, described in patent EP 0 102 284 in the name of the applicant.

The intervention of the gluconate ion also relates to the inhibition of corrosion by water and, in particular, by the oxygen dissolved therein, metallic substrates such as those based on iron, copper, nickel, aluminum and others, industrial installations, in particular, cooling, whether in open or closed circuits, as described in French patent FR 2,512 072 in the name of the plaintiff.

This property relating to the annihilation of the corrosive nature of dissolved oxygen can also be exploited in very specific fields such as the enhanced recovery of petroleum as described in patent EP 0 272 887.

The intervention of the gluconate ion is still recommended in the context of applications as diverse as the elimination of splashes and deposits of cement, the manufacture of calcium chloride or chlorine, photography, the paint industry, the polycarbonate industry, the stabilization of sodium aluminate solutions or even stable xanthan gum solutions. However, it was quickly noticed that, due to the ease of formation of lactone (s), it was difficult to prepare anhydrous gluconic acid compositions. This has resulted in a practice of marketing aqueous solutions of this acid having a dry matter ("MS") of about 50%. Such solutions have insufficient stability and require in particular to be stored above 15-20 ° C to avoid any risk of crystallization. In the event of partial solidification, reheating to 50-60 ° C. then makes it possible to dissolve the crystals present and to obtain a transparent solution without modifying the characteristics of the product.

Beyond this drawback, those skilled in the art have realized that, given the extremely low pH of said solutions (generally of the order of 2.0), neutralization with sodium hydroxide is, in many cases case, necessary for their implementation in various applications (admixtures for concrete or plaster, detergent compositions among others). However, for mineral binders for example, there are setting problems due to the excessive presence of sodium, as well as undesirable phenomena such as swelling and / or accelerated aging of concrete, or the appearance of efflorescence on the works .

Partially neutralized qualities of sodium gluconate then appeared, having a DM of the order of 60% and improved stability.

Such products have advantages such as being more concentrated, being less prone to crystallization. However, their pH remains low (always below 3.9) and their high sodium level (-10.5 - 11%), after neutralization at pH 7.0, remains unacceptable vis-à-vis current criteria, in particular those used for the admixture of concrete, for example.

In addition, gluconic acid solutions with 50% DM or partially neutralized and marketed at around 60% DM remain at a relatively high cost price.

In parallel, and in particular on the basis of this last criterion, so-called “technical” sodium gluconate solutions have been developed, obtained by fermentation or by chemical oxidation of sugar (s).

Although very popular, they have the disadvantage of necessarily low DM (generally of the order of 45%) to avoid any risk of crystallization, as well as high sodium levels, hardly compatible with current requirements.

It follows from the above that, to the knowledge of the Applicant, there is no aqueous gluconic acid composition available which simultaneously has the following advantages: - good physical stability, - a sufficiently high pH to require, for neutralization, only reduced quantities of alkali and not to be corrosive, a content of sodium ions nevertheless sufficiently low to avoid the manifestation of the negative effects of this ion, a sufficiently high dry matter and advantageous for significantly reducing the costs of transport and storage, or even the microbiological risks associated with these operations,

- a content of gluconate ions sufficient to guarantee the full manifestation of the properties offered by this entity.

And the merit of the Applicant Company is to have found, after numerous researches, that it was now possible to propose such compositions, for example compositions whose gluconic acid is mainly in the form of salt (s), since said compositions contained a sufficient amount of stabilizing agent (s) of selected nature.

More specifically, the subject of the present invention is a stable aqueous composition of gluconic acid, said acid being in the form of at least one salt and optionally in the form of free acid and / or one of its lactones, said composition being characterized in that it has:

- a pH greater than 4.0,

- a dry matter at least equal to 50%, - a content of gluconate ions at least equal to

50%, expressed in total dry weight of gluconate ions, coming from gluconic acid in the form of salt (s) and optionally free acid and / or lactone (s), relative to the dry matter of said composition , a content of sodium ions of less than 8%, expressed in total dry weight relative to the dry matter of said composition, and an effective content of a stabilizing agent chosen from the group comprising: saccharides other than gluconic acid, - its salts and lactones, amino compounds and any mixtures of at least any two of these products. By “stable composition” within the meaning of the present invention is meant any composition of the genus in question which, if it is subjected to storage for 1 month at 20 ° C., does not generally change in appearance and in particular does not show, during such storage: - no formation of crystals, visible to the naked eye,

- no significant variation in apparent viscosity. By “effective amount” within the meaning of the present invention is meant an amount of stabilizing agent (s) at least equal to that sufficient for the gluconic acid composition to be stable in accordance with the definition given above. Depending on the nature of the stabilizing agent, this sufficient amount may be more or less low, including less than 3%, expressed relative to the dry matter of said composition. In the context of the invention, however, effective quantities are generally situated between 3 and 50%.

As a result of which, according to a preferred variant, the gluconic acid composition according to the invention as described above is characterized in that it has a total content of saccharides other than gluconic acid, its salts and lactones , and in amino compounds at least equal to 3% and at most equal to 50%, expressed in total dry weight relative to the dry matter of said composition.

The Applicant Company has found that the presence, in the proportions indicated above, of particular products constituted by saccharides other than gluconic acid (in whatever form), amino compounds and mixtures of these products, gave the gluconic acid compositions containing them, not only good stability, and in particular a non-crystallizable character, at room temperature (20 ° C) but also: - good stability, and in particular a non-crystallizable nature, at low temperature (5 ° C), the ability to be able, if necessary, to be advantageously concentrated and then stored, transported and / or used with relatively high dry matter (MS), for example between 52 and 75%,

- the capacity to contain in parallel, if necessary, only limited levels of alkali or alkaline-earth metals, and in particular sodium ion levels of less than 8% (dry / dry), without detriment to the application efficiency of said compositions

- Improved efficiency in various industrial fields such as in particular the preparation of mineral binder compositions or adjuvants intended for said compositions.

According to a variant, the gluconic acid composition according to the invention is characterized in that it has a total content of saccharides other than gluconic acid, its salts and lactones, of between 3 and 47%, preferably between between 10 and 45%, said content being expressed in total dry weight of said saccharides relative to the dry matter of said composition.

This total content may advantageously be between 15 and 40%, in particular between 25 and 40%, it being understood that this total content may result from the presence only of a single saccharide other than gluconic acid, its salts and lactones or conversely result from the combined presence of several saccharides other than gluconic acid, its salts and lactones.

By “saccharides other than gluconic acid, its salts and lactones” within the meaning of the present invention, is understood in particular the set: - monosaccharides, disaccharides, trisaccharides, oligosaccharides and polysaccharides, of linear, cyclic or branched structure, n '' having undergone no particular oxidation or reduction reaction such as, for example, glucose, fructose, mannose, xylose, ribose, arabinose, maltose, maltotriose, galactose, lactose, sucrose, glucose syrups, maltodextrins, pyrodextrins, cyclodextrins, starches, modified starches physically, inulin and any mixtures of at least any two of these products,

saccharides of linear, cyclic or branched structure such as those mentioned above and their mixtures, having undergone a reduction reaction, in particular a catalytic hydrogenation reaction, whatever it is and at any time whatsoever, such as for example sorbitol, mannitol, xylitol, ribitol, arabitol, maltitol, maltotriitol, galactitol, lactitol, glucosido-1-6 mannitol, isomaltitol, palatinitol, erythritol, syrups hydrogenated glucose, hydrogenated maltodextrins and pyrodextrins and any mixture of at least any two of these products. - saccharides resulting from internal dehydration, in one or more stages, reduced products such as those mentioned above and in particular from internal dehydration of sorbitol or mannitol such as for example sorbitan, isosorbide, mannitan and isomannide.

saccharides of linear, cyclic or branched structure such as those mentioned above and their mixtures, having undergone an oxidation reaction, including catalytic oxidation, whatever it is and at any time whatsoever, partial or total and in the form of free acid and / or salt (s) and / or lactone (s) with the exception of gluconic acid, its salts and lactones, such oxidized saccharides may consist, for example, into glucaric acid, glucuronic acid, glucoheptonic acid, arabinonic acid, arabinaric acid, xylonic acid, xylaric acid., "- acid lactobionic, maltobionic acid, maltotriionic acid, acid erythorbic, oxidized glucose syrups, oxidized maltodextrins and pyrodextrins and any mixtures of at least any two of these products. derivatives derived from the chemical transformation of any of the saccharides, hydrogenated or not, oxidized or not, described above such as, for example, those obtained by etherification, esterification, crosslinking, boration, sulfation or sulfonation of one any of said saccharides. derivatives derived from biological transformation, in particular by fermentation, of any of the saccharides, hydrogenated or not, oxidized or not, described above, in particular the low molecular weight derivatives having at least two hydroxyl or carboxyl functions such as for example glycerol and (salts of) oxalic, tartaric, lactic, citric, malic, fumaric or succinic acids. As indicated, the stabilizing agent contained in the compositions according to the invention can also consist, in whole or in part, of at least one amino compound.

According to a variant, the gluconic acid composition according to the invention is characterized in that it has a total content of amines of between 6 and 50%, preferably between 8 and 40%, said content being expressed by weight total dryness of said amines relative to the dry matter of said composition.

By “amino compound” within the meaning of the present invention is meant in particular simple amines, whether primary, secondary or tertiary, such as, for example, monoethanolamine, diethanolamine or triethanolamine but also more complex amino derivatives such as 2-amino-2methyl 1 propanol (hereinafter "AMP"), tetraethylene pentamine or those corresponding to the general formula: RI OH | |

HC - C - C - B - A

I I

R2 R3 in which :

- RI, R2 and R3, which may be the same or different, represent the hydrogen atom or an alkyl, substituted alkyl, alkene, aryl or aralkyl group,

B represents a hydrocarbon chain comprising at least one unit - CH2 - and the number of carbons located on the chain is less than or equal to 10, ^' - A represents the groups: y R5 y R5 / R5

- NOT ; - N ⁺ - R6, X ^" ; N ⁺ - R6, X ^"

\ R6 \ „H ^ \ R7 in which: - X represents a halogen,

- R5, R6 and R7, which may be the same or different, represent alkyl, substituted alkyl, alkene, aryl or aralkyl radicals.

The term “amino compound” also means, in particular:

- natural proteins of animal or vegetable origin as well as all the products capable of being obtained, in any way, from these proteins such as poly-, oligo- and dipeptides and amino acids,

- synthetic polymers of amino acids, for example aspartic acid, and their derivatives,

- amino derivatives of acids or acid polymers such as, for example, amino derivatives of di-, tri-, tetra- or pentaacetic, mono- or disuccinic, tartaric, citric or phosphonic acids such as derivatives known to man of art under the abbreviations of NTA, EDTA, DTPA, EDTMP, MGDA, EDMS and EDDS. The inventive concept of the present invention is therefore also based on the use of at least one saccharide other than gluconic acid, its salts and lactones and / or at least one amino compound to improve the stability of a composition d gluconic acid having a DM at least equal to 50%, said gluconic acid being in the form of salt (s) and optionally in the form of free acid and / or lactone (s).

As indicated, the presence of such a stabilizing agent in the gluconic acid composition according to the invention has, inter alia, the advantage of being associated, if desired, with a limited presence of sodium ions within the same composition.

According to a preferred variant of the present invention, said composition is characterized in that it has a content of sodium ions at most equal to 7%, preferably at most equal to 6%, expressed in total dry weight relative to the material said composition.

This sodium ion content can in particular be between 2 and 5% approximately.

According to another very advantageous variant, the composition according to the invention has a weight ratio between respectively its total content of sodium ions and its total content of stabilizing agent (s), less than 40%, preferably less than 35%, expressed in sec / sec. This ratio can, for example, be between 0 and 25% approximately.

The presence of a stabilizing agent also makes it possible, as already pointed out, to advantageously propose gluconic acid compositions which are stable while exhibiting a high MS, said

MS being moreover relatively rich in gluconate ions, as well as a relatively high pH and close to the pH at which said compositions are, ultimately, implemented application.

In particular, the composition according to the invention can be characterized in that it has:

- a dry matter at least equal to 52%, preferably between 52 and 65%, and - a pH at least equal to 4.5, preferably at least equal to 5.0.

According to another variant, the gluconic acid composition according to the invention is characterized in that it has a content of gluconate ions at least equal to 55%, preferably at least equal to 60%, and at most equal to 75%, expressed in total dry weight of gluconate ions originating from gluconic acid in the form of salt (s) and, optionally, of free acid and / or lactone (s).

As mentioned above, the compositions of gluconic acid, its salts and / or lactones have been used industrially and commercially for several decades. However, to the knowledge of the Applicant, it had hitherto never been designed, a fortiori prepared and implemented, such compositions in liquid form which are non-crystallizable at 20 ° C, a fortiori also non-crystallizable at 5 ° C and this, while having high characteristics of pH, MS and content of gluconate ions.

This observation is particularly valid for sodium gluconate compositions, in particular those with low contents of sodium ions. By "not crystallizable" is meant that the composition not only does not generate crystals visible to the naked eye, gluconic acid (in free form, salt (s) and / or lactone (s)) after a storage for 1 month at the temperature in question (20 ° C or 5 ° C), but still that the same composition, if it is seeded with 1% by weight (dry / dry) of sodium gluconate crystals and mixed (5 minutes at 100 revolutions / minute), does not show a significant increase in the dry weight of crystals after storage for 1 month at the temperature in question (20 ° C or 5 ° C).

As a result of which, the present invention relates to an aqueous composition of the genus in question characterized a) in that it has: - a pH greater than 4.0,

- a dry matter at least equal to 50%,

- a content of gluconate ions at least equal to 50%, expressed in total dry weight of gluconate ions from gluconic acid in the form of salt (s) and optionally free acid and / or lactones, and b) in that it is non-crystallizable at 20 ° C, preferably non-crystallizable at 20 ° C and at 5 ° C. According to a very advantageous variant, said composition is characterized in that it has:

- a pH at least equal to 4.5, preferably at least equal to 5.0,

- a dry matter at least equal to 52%, preferably between 52 and 65%,

- a gluconate ion content of at least 55%, said ions from predominantly (ie to 50% ^at least by weight) of salt (s) of gluconic acid, and - a sodium content of not more than 8% , preferably at most equal to 7%, expressed in total dry weight relative to the dry matter of said composition.

As a result, new compositions of gluconic acid are now available in the form, exclusive or not, of salt (s), in particular new compositions of sodium gluconate, the conditions of transport and storage of which are improved, in particular with a view to reducing the cost thereof and achieving the best possible compromise between resistance to crystallization and resistance to microbial attack.

These compositions, concentrated and stable, also have the advantage of being able to exhibit particularly low concentrations of sodium ions and thereby significantly increased possibilities of application in industrial fields such as, for example, the preparation of mineral binders, in particular of cement, mortar, concrete, grout, plaster or plaster compositions or of adjuvant compositions intended for said mineral binder compositions.

Finally, these compositions have the advantage of being generally at least as effective, or even more effective than the compositions of the prior art. This is particularly the case in the aforementioned field of mineral binders as will be exemplified elsewhere. In this field, the compositions according to the invention allow in particular:

- to improve the plasticity and / or the mechanical properties of mineral binders based on cement or hydraulic lime,

- to improve the chemical stability of adjuvants, for example setting retarders, stored and used in hot countries,

to improve the workability of plaster compositions, in particular in the context of formulations intended to reduce the amount of water to be used, to better control overall the amount of water added during the preparation and / or the use of an admixture for mineral binder.

Furthermore, because of the numerous advantages which they demonstrate and which have been mentioned above, the compositions according to the invention can be advantageously used in all types of industries and in particular for the preparation of compositions intended for the industries of detergency, metallurgy, chemistry, oil and gas extraction, water treatment, stationery, corrugated or flat cardboard, plastics, textiles, leather, paints, photography, fertilizers and phytosanitary products. Gluconic acid salt compositions containing sorbitol as a stabilizing agent can, for example, be used favorably in the areas of detergency or satin-finishing of aluminum. The present invention will be described in more detail with the aid of the examples which follow and which are in no way limiting. EXAMPLE 1

In the context of this example, the storage behavior at 20 ° C. and 5 ° C. respectively, in particular in terms of resistance to crystallization, of two gluconic acid compositions according to the invention (hereinafter designated respectively) is compared. "COMPOSITIONS A and B") to that of two gluconic acid compositions, representative of products on the market and not in accordance with the present invention (hereinafter respectively designated "COMPOSITIONS T1 and T2").

The compositions tested have the following characteristics in terms of dry matter ("MS" in%), pH value ("pH"), total content of gluconate ions ("GLUCONATE" in% dry / dry), total content of saccharides other than gluconic acid, its salts and lactones (“SACCHARIDES” in% dry / dry) as well as total sodium ion content (“SODIUM” in% ^' dry / dry).

MS pH GLUCONATE SACCHARIDES SODIUM

COMPOSITION A 58 6.0 61.6 31.5 5.8 COMPOSITION B 55 6.0 62.5 29.8 6.5 COMPOSITION Tl 45 5.5 72.0 11.3 10.1 COMPOSITION T2 41 5, 9 69.6 20.2 8.8

For each of these COMPOSITIONS A, B, T1 and T2, the gluconate ions are mainly present in the form of sodium gluconate, the other significant source of said ions being constituted by free gluconic acid.

According to the tests defined previously in the general description, it is checked whether each of these

COMPOSITIONS is stable, in particular non-crystallizable, after 1 month of storage at 20 ° C or

5 ° C.

For each COMPOSITION which thus proves to be stable, it is checked whether, in addition, it is also non-crystallizable (1 month at 20 ° C or 5 ° C) despite a seeding of 1%, by weight (dry / dry), of sodium gluconate crystals, crystals potentially capable of playing the role of primers of crystallization.

More generally, for each COMPOSITION, the maximum dry matter (“MSM” in%) is determined for which the composition in question, as the case may be concentrated or diluted in demineralized water but with respective richness in gluconate ions, sodium ions and saccharides (dry / dry) unmodified, is non-crystallizable, and this:

- at 20 ° C or 5 ° C, without or with seeded crystals

(variants hereinafter designated respectively

"WITHOUT" and "WITH"). Depending on the COMPOSITION, the storage temperature (20 ° C or 5 ° C) and the possible presence of crystallization primers (“WITHOUT” or “WITH”), the MSM values (%) are obtained. -after:

20 ° C 20 ° C 5 ° C 5 ° C

WITHOUT WITHOUT WITH

COMPOSITION A 65% 64% 60% 58% COMPOSITION B 65% * 65% 60% 55% COMPOSITION Tl 46% 44% 44% 42% COMPOSITION T2 55% 52% 50% 48%

* at 70% formation of rare visible crystals.

These results show overall that compositions having MS significantly greater than 50% such as COMPOSITIONS A and B according to the invention can be stable not only at room temperature but also at low temperature (5 ° C) and in particular be non-crystallizable at these temperatures, including therefore at 5 ° C., despite the use of exogenous crystals capable of promoting a phenomenon of crystallization of sodium gluconate.

It is remarkable to note that in the absence of such exogenous crystals, these COMPOSITIONS A and B can be concentrated, if desired, at least up to 60% DM and this, without the appearance, even at 5 ° C, of crystallization phenomenon.

Conversely, the COMPOSITIONS T1 and T2, not in accordance with the invention, cannot validly be concentrated in such MS. COMPOSITION Tl, even if not concentrated, turns out to be intrinsically unstable since it is prone to easily crystallize, despite its relatively low DM (45%). COMPOSITION T2, overall more stable than

COMPOSITION Tl could not, for its part, be concentrated to a higher MS 50% without exhibiting at 5 ° C, ^a crystallization phenomenon, including in the absence of exogenous crystals. In addition, COMPOSITIONS A and B according to the invention have the advantage of a lower content of sodium ions than COMPOSITIONS T1 and T2 and therefore of increased applicability, for example in the field of mineral binders. These COMPOSITIONS A and B also have a weight ratio (dry / dry) SODIUM / SACCHARIDES which is respectively 18.4% and 21.8%, much lower than that of COMPOSITIONS T1 (89.4%) and T2 (43 , 6%).

EXAMPLE 2

We proceed to the preparation of a control mortar (hereinafter designated "MORTAR TO") according to standard CEN 196-1, by mixing 450 g of CPA 52.5 HP cement with 1350 g of standardized sand and 225 g of water. Similarly, we prepare different mortars as before except that we add in addition, respectively:

- MORTAR A: 0.08% of COMPOSITION A according to the invention described in EXAMPLE 1, quantity expressed relative to the weight of cement (dry / dry),

- MORTAR Tl: 0.08% (dry / dry) of COMPOSITION Tl not in accordance with the invention, described in EXAMPLE 1, - MORTAR T2: 0.08% (dry / dry) of COMPOSITION T2 not in accordance with the invention, described in EXAMPLE 1. For each of MORTARS TO, Tl, T2 and A, the spread is measured "E" in mm, the start of setting "DP" and the end of setting "FP" in hours and minutes as well as the mechanical resistances at 17 hours ("R17H" in megapascals or Mpa) and 28 days ("R28J" in Mpa). The following results are obtained:

MORTAR T0 Tl T2 A

E (mm) 235.5 264.2 264.8 260

DP (H + MIN) 4H15 9H50 11H 11H

FP (H + MIN) 5:20 a.m. 12:45 p.m. 1:00 p.m.

R17H (Mpa) 9.7 1.7 1.2 1.5

R28J (Mpa) 50.6 56 60 61.1

These results show that the use of a gluconic acid composition in accordance with the invention such as COMPOSITION A makes it possible to impart to the mortar (MORTAR A) not only good plasticity characteristics (spreading value increased by 24 , 5 mm compared to MORTAR T0) and setting delay (start of postponement postponed by 6H45 additional compared to MORTAR T0), but still a particularly high resistance to 28 days (> 60 Mpa) which cannot otherwise be achieved with COMPOSITIONS T1 and T2 not in accordance with the invention.

As already indicated, the latter also have a higher content of sodium ions than that of said COMPOSITION A and therefore, overall, less applicability in the field of mineral binders.

EXAMPLE 3

In the context of this example, we study the interest, in mineral binders, of COMPOSITIONS C, D, E and F according to the invention containing an amino compound as stabilizing agent, said compound amine (hereinafter referred to as "AMINE") being provided in the form of monoethanolamine (COMPOSITION C), diethanolamine (COMPOSITION D), triethanolamine (COMPOSITION E) or AMP (COMPOSITION F) respectively.

The general characteristics of the said

COMPOSITIONS are listed below, including their maximum dry matter ("MSM" in%), at 20 ° C or

5 ° C, with or without sowing of 1%, by weight (dry / dry), of sodium gluconate crystals

(variants "WITH" or "WITHOUT").

COMPOSITION C D E F

MS (%) 52 52 52 52

PH 7.0 6.0 5.0 5.3 5.3

GLUCONATE * (%) 85 79, 4 75, 5 82.1

SODIUM * (%) 4 3, 6 3, 5 3.6

AMINE ** (%) 11 17 21 14.3

MSM / 20 ° C (WITHOUT) 61 56 55 60

MSM / 20 ° C (WITH) 61 56 55 60

MSM / 5 ° C (WITHOUT) 56 52 53 59

MSM / 5 ° C (WITH) 56 52 53 59

* total ion content in dry / dry

** total content of amino compound in dry / dry

COMPOSITIONS C, D, E and F according to the invention prove to be particularly stable. They can in particular be presented to an MS at least equal to

52%, even 59% (COMPOSITION F) without presenting any risk of crystallization, even at 5 ° C.

It is moreover remarkable that, in addition, the maximum dry matter (“MSM”) of these COMPOSITIONS, which is therefore high, does not decrease when these COMPOSITIONS are seeded with crystals which must promote any phenomenon of crystallization, both 20 ° C than 5 ° C.

These COMPOSITIONS have, among other advantages, a low content of sodium ions, significantly less than 6% (dry / dry). Each of COMPOSITIONS C, D and E is tested in a control mortar, in accordance with the protocol described in EXAMPLE 2, except that in the present case: - another batch of CPA 52.5 cement is used

HTS, and - each COMPOSITION is introduced into the mortar at a rate of 0.05% instead of 0.08%, expressed in dry weight relative to the dry weight of cement.

MORTARS C, D and E are respectively obtained, the main characteristics of which, measured as

1 EXAMPLE 2 are repeated below, compared with those obtained in the absence of. any additive (“MORTAR T0”).

MORTAR T0 C D E

E (mm) 222 253 244.5 244.5

DP (H + MIN) 4H15 7H10 7H45 7H10

DF (H + MIN) 6:30 a.m. 8:50 a.m. 9:00 a.m.

R17H (Mpa) 8.8 5.9 6.0 6.0

R28J (Mpa) 52.0 55.8 54.6 55.8

These results confirm overall that the gluconic acid compositions according to the invention, of high MS and stability, make it possible to confer on mineral binders not only good characteristics of plasticity and retardation of setting but also resistance to 28 days very significantly higher than that obtained in the absence of any adjuvant.

In addition, the above-described COMPOSITIONS C to E have, among others, the advantages of: giving these binders resistance "at a young age", in this case after 5 pm, much greater than that generally recognized as necessary to be able to perform a quick formwork, namely 5 Mpa. to present sodium ion contents significantly less than 8% and even 6% (dry / dry). It has also been verified that COMPOSITION F, which has all of the above advantages, also makes it possible to obtain the same performance, including resistance, as crystallized sodium gluconate, despite a dosage reduced by 20 %.

EXAMPLE 4

In the context of this example, the interest of the above-described COMPOSITIONS A and E, in accordance with the invention, is studied in the field of plaster adjuvant and more particularly as setting retarders.

A control plaster composition (“PLASTER TO”) is prepared using a semi-hydrated plaster sold by the company LAFARGE and a water / plaster weight ratio of 0.7. Similarly, different plaster compositions are prepared as above except that an additional 0.2% (dry / dry) of, respectively, the

COMPOSITION A (“PLASTER A”), COMPOSITION E

("PLASTER E") or the COMPOSITION Tl described above, not in accordance with the invention.

For each of the PLASTERS T0, Tl, A and E, the start of setting "DP", the end of setting "FP" and the setting time "TP" (= FP-DP) are measured, these values being expressed in minutes .

The following results are obtained: PLASTER T0 Tl A E

DP (mm) 4 35 30 46

FP (MIN) 7 67 62 98 TP (MIN) 3 32 32 52

These results show overall that in the field of plaster compositions, the compositions according to the invention are also very good agents setting retarders, at least as effective as the control COMPOSITION Tl.

It is remarkable to note that in addition, the

COMPOSITION E according to the invention makes it possible, with regard to said COMPOSITION Tl, to further significantly improve the workability of the mineral binder and in particular to increase:

- 11 minutes the value of PD and therefore the time during which the plaster can be used between its preparation and its placement on its support, and

- 20 minutes the value of TP and therefore the time during which the plaster, put in place, can be the subject of finishing operations such as smoothing.

Claims

1 - Stable aqueous composition of gluconic acid, said acid being in the form of at least one salt and optionally in the form of free acid and / or one, at least, of its lactones, said composition being characterized in that that it presents:

- a pH greater than 4.0, - a dry matter at least equal to 50%,

- a content of gluconate ions at least equal to 50%, expressed in total dry weight of gluconate ions, coming from gluconic acid in the form of salt (s) and optionally free acid and / or lactone (s) , relative to the dry matter of said composition,

a content of sodium ions of less than 8%, expressed in total dry weight relative to the dry matter of said composition, and an effective content of a stabilizing agent chosen from the group comprising saccharides other than gluconic acid, its salts and lactones, amino compounds and any mixture of at least any two of these products. 2 Composition according to Claim 1, characterized in that it has a total content of saccharides other than gluconic acid, its salts and lactones and of amino compounds, at least equal to 3% and at most equal to 50%, expressed in total dry weight relative to the dry matter of said composition.

3 - Composition according to claim 2 characterized in that it has a total content of saccharides other than gluconic acid, its salts and lactones, between 3 and 47%, preferably between 10 and 45%, expressed by weight total dry with respect to the dry matter of said composition.

4 - Composition according to claim 2 characterized in that it has a total content of amino compounds between 6 and 50%, preferably between 8 and 40%, expressed as total dry weight relative to the dry matter of said composition.

5 - Composition according to any one of claims 1 to 4, characterized in that it has a content of sodium ions at most equal to 7%, preferably at most equal to 6%, expressed in total dry weight relative to the dry matter of said composition. 6 - Composition according to any one of claims 1 to 5 characterized in that it has:

7 - Composition according to any one of claims 1 to 6 characterized in that it has a content of gluconate ions at least equal to 55%, preferably at least equal to 60%, and at most equal to 75%, expressed by total dry weight of gluconate ions originating from gluconic acid in the form of salt (s) and, optionally, free acid and / or lactone (s). 8 - An aqueous composition of gluconic acid, said acid being in the form of at least one salt and optionally in the form of free acid and / or of at least one of its lactones, said composition being characterized a) in what it has: - a pH greater than 4.0,

- a dry matter at least equal to 50%,

a content of gluconate ions at least equal to 50%, expressed in total dry weight of gluconate ions originating from gluconic acid in the form of salt (s) and optionally free acid and / or lactones, and b) in that it is non-crystallizable at

20 ° C, preferably non-crystallizable at 20 ° C and 5 ° C. 9 - Composition according to claim 8 characterized in that it has: - a pH at least equal to 4.5, preferably at least equal to 5.0,

- a dry matter at least equal to 52%, preferably between 52 and 65%, - a content of gluconate ions at least equal to

55%, said ions coming mainly from gluconic acid salt (s), and

a sodium content at most equal to 8%, preferably at most equal to 7%, expressed in total dry weight relative to the dry matter of said composition.

10 - Composition according to any one of claims 1 to 9, characterized in that it has a weight ratio (dry / dry) between its total content of sodium ions on the one hand and its total content of agent (s) stabilization on the other hand, less than 40%, preferably less than 35%.

11 - Use of a composition according to any one of claims 1 to 10 for the preparation of compositions of mineral binders, in particular of compositions of cements, mortars, concretes, grout, coatings or plasters, for the preparation of adjuvant compositions intended the said compositions of mineral binders or for the preparation of compositions intended for the detergency, metallurgy, chemistry, oil and gas extraction, water treatment, stationery, corrugated or flat cardboard industries , plastics, textiles, leather, paints, photography, fertilizers and phytosanitary products.