EP4003914A1

EP4003914A1 - Method for preparing microspherules of an oxygenated zinc compound

Info

Publication number: EP4003914A1
Application number: EP20746222.7A
Authority: EP
Inventors: Olivier Roumache
Original assignee: INDUSTRIELLE LIEGEOISE DES OXYDES S A Ste
Current assignee: INDUSTRIELLE LIEGEOISE DES OXYDES S A Ste
Priority date: 2019-07-31
Filing date: 2020-07-30
Publication date: 2022-06-01
Also published as: CA3145847A1; WO2021019002A1; BE1027472A1; BE1027472B1; CN114423713A

Abstract

The present invention relates to a method for preparing a composition of microspherules of an oxygenated zinc compound, comprising the steps of providing a precipitate of an oxygenated zinc compound, adjusting the conductivity of the precipitate obtained until a conductivity measured using the conductivity measurement method of less than 3000 μS/cm is obtained, and obtaining the composition of microspherules of an oxygenated zinc compound from the precipitate. The present invention also relates to a composition of microspherules of an oxygenated zinc compound having a conductivity measured using the conductivity measurement method of less than 3000 μS/cm, and the use thereof.

Description

“Process for preparing microspherules of an oxygenated zinc compound”

Field of the invention

The present invention relates to the field of inorganic chemistry and more particularly to a composition of microspherules of an oxygen-containing zinc compound which can be easily dispersed in a material and which exhibits a high homogeneity of dispersion when it is dispersed in a material.

State of the art

Zinc oxygenates, such as zinc oxide, zinc hydroxide, zinc carbonate and their derivatives are generally used as additives in many fields. Zinc oxide can for example be used in the field of oils, paints, varistors, ceramics.

Zinc oxygenates are commonly used to be dispersed in a material, such as a nutrient composition (as a feed additive: fodder (hay, straw, grass silage, oilseeds and cereals). )) and manufactured products which are usually made of combined feed mixtures and which may contain additives (https://www.efsa.europa.eu/en/topics/topic/animal-feed) or material polymeric (compound / composite material based on elastomer or plastic).

In the specific field of elastomers, the oxygenated zinc compound is used in particular as an activator during the vulcanization reaction of polymers such as, for example, polyisoprene, polybutadiene, styrene-butadiene rubbers or else EPDM rubbers ( ethylene-propylene-diene monomer). Vulcanization is a crosslinking reaction typically using sulfur as crosslinking agent, an oxygenated zinc compound as activator, an accelerator such as for example CBS (N- Cyclohexyl-2-benzothiazole sulfenamide) or DPG (diphenylguanidine) as well as fatty acids such as steric acid and its derivatives. Since the oxygenated zinc compound is insoluble in the polymer material, stearic acid will help the solubilization of the oxygenated zinc compound in the polymer material (The rubber formulary design Library). It is generally accepted that during the vulcanization reaction, the oxygenated compound of zinc (the activator), a fatty acid (stearic acid) and an accelerator combine in situ in the polymer material so as to form a catalyst which will catalyze the crosslinking of the polymer by reaction between double bonds of the polymer and sulfur.

Zinc oxygenates can also sometimes have the role of filler, which like other products (carbon black, chalk, kaolins, talc, etc.), give the product specific properties (conductivity, improvement resilience, heat transfer, etc.).

When an oxygenated zinc compound is dispersed in a material such as, for example, a polymeric material, obtaining a final dispersion with good dispersion homogeneity is of utmost importance. Indeed, for example when using ZnO as vulcanization activator, an inhomogeneous distribution of ZnO risks generating a vulcanized polymer having an inhomogeneous crosslinking density. As this inhomogeneous distribution of ZnO is uncontrolled, the distribution of crosslinking density is then also uncontrolled. As a result, the vulcanized polymer has an uncontrolled structure and properties, which can have negative consequences on the mechanical properties of the vulcanized polymers and therefore on their final quality.

When the oxygen-containing zinc compound acts as a filler, an inhomogeneous dispersion of the latter in a material such as for example a polymer material, can also have a negative impact on the properties that the oxygenated zinc compound should provide and therefore on the final quality and properties of the final material.

It is therefore important to be able to have a process for preparing microspherules of an oxygen-containing zinc compound, thanks to which the microspherules obtained can be easily dispersed homogeneously in a material such as for example a nutrient composition or a polymer material.

A method of producing a microspherule powder of an oxygenated zinc compound and its use in polymers is disclosed in EP1546039B1. This patent focuses primarily on the drying step that takes place after a "wet process" synthesis of an oxygenated zinc compound. In particular, the drying step is carried out by an atomization process in an atomization chamber. The oxygen-containing zinc compound obtained is in the form of microspherules exhibiting, inter alia, a Flodex number of less than 15, a D 50 of between 50 and 200 μm.

There is therefore a continuing need to develop an improved process for the preparation of a composition of microspherules of an oxygenated zinc compound which can be readily dispersed in materials, in particular in polymeric materials or nutrient compositions and which makes it possible to obtain a homogeneity of dispersion which is improved. In addition, such preparation processes must be sufficiently versatile and economically profitable to meet the needs of industry.

Summary of the invention

The inventors have surprisingly found that it is possible to provide an improved process meeting the aforementioned needs. A subject of the present invention is therefore a process for preparing a composition (C) of microspherules of an oxygenated zinc compound, comprising the steps:

a) providing a precipitate (PR) of an oxygenated zinc compound, preferably a precipitate of an oxygenated zinc compound in the form of a suspension,

b) adjusting the conductivity of said precipitate (PR) obtained in step a) until a conductivity is obtained measured using the conductivity measurement method of less than 3000 pS / cm,

c) obtaining said composition (C) of microspherules of an oxygenated zinc compound from said precipitate (PR).

A subject of the present invention is also a composition (C) of microspherules of an oxygenated zinc compound having a conductivity measured according to the conductivity measurement method of less than 3000 pS / cm.

A subject of the present invention is also said composition (C) according to the invention obtained by said process according to the invention.

A subject of the present invention is also the use of said composition (C) according to the invention or of said process according to the invention in a vulcanization process.

A subject of the present invention is also the use of said composition (C) according to the invention or of a composition obtained by said method according to the invention in a material, preferably a material chosen from the group consisting of nutrient compositions. , polymeric materials and mixtures thereof; more preferably, said material is a polymer.

Description of the drawings

Figure 1 is a diagram showing an atomization device.

FIG. 2 represents the results of rheology measurements on a dispersion of a composition (C) of an oxygenated zinc compound according to one embodiment of the invention dispersed in a polymer material.

Figure 3 shows the results of rheology measurement on a dispersion of a ZnO compound having a conductivity measured by the conductivity measurement method greater than 3000 pS / cm dispersed in a polymer material.

Detailed description of the invention The precipitate (PR)

In the context of the present invention, "oxygenated zinc compound" can be defined as a compound comprising a zinc atom and an oxygen atom. In particular, said oxygenated zinc compound can be chosen from the group consisting of zinc oxide, zinc hydroxide, zinc carbonate, zinc hydroxycarbonate and their mixtures or their derivatives, preferably the oxygenated compound. zinc is a mixture of zinc oxide and zinc hydroxide.

If desired, said oxygenated zinc compound can be obtained by precipitation on a support. In particular, said support can be an amorphous filler, preferably calcium carbonate, silica, waxes and their mixtures.

In particular, said precipitate (PR) of an oxygenated zinc compound provided in step a) has a conductivity, preferably a conductivity measured according to the conductivity measurement method of greater than 3000 pS / cm, more particularly greater than 4000 pS / cm, even more particularly greater than 5000 pS / cm, even more particularly greater than 10,000 pS / cm, even more particularly greater than 20,000 pS / cm, even more particularly greater than 30,000 pS / cm. If desired, said precipitate (PR) may not be in suspension or may be in dry form. In particular, said precipitate (PR) may not be in suspension and may contain less than 50% by weight of moisture, preferably may contain less than 20% by weight of moisture, more preferably may contain less than 10% by weight of moisture, even more preferably may contain less than 1% by weight of moisture.

Preferably, said precipitate (PR) of an oxygenated zinc compound may be in the form of a suspension (S1).

In particular, said suspension (S1) comprises a percentage by weight of said precipitate of an oxygenated zinc compound greater than or equal to 1% by weight, preferably greater than or equal to 5% by weight, more preferably greater than or equal to 8% by weight, even more preferably greater than or equal to 10% by weight relative to the total weight of said suspension (S1).

If desired, said suspension (S1) comprises a percentage by weight of said precipitate of an oxygenated zinc compound of less than 90% by weight, preferably less than 80% by weight, more preferably less than 50% by weight, of even more preferably less than 30% by weight, even more preferably less than 20% by weight, even more preferably less than 15% by weight, even more preferably less than 12% by weight relative to the weight total of said suspension (S1).

If desired, said suspension (S1) comprises a percentage by weight of a precipitate of an oxygenated zinc compound of between 1% and 90% by weight, preferably between 5 and 50% by weight, more preferably between 8 % and 30% by weight, even more preferably between 8% and 20% by weight, even more preferably between 8% and 15%, even more preferably between 8% and 12% by weight relative to the total weight of said suspension (S1).

More preferably, said suspension (S1) is a suspension in an aqueous medium. Preferably, said aqueous medium can be selected from the group consisting of a reaction medium, pure water, salt water. By the term salt water is meant water comprising at least one salt. The term reaction medium can refer to the aqueous medium resulting directly from the process of precipitating the precipitate of an oxygenated zinc compound.

In particular, when said suspension (S1) is a suspension in an aqueous medium, said suspension (S1) may comprise a percentage by weight of water greater than or equal to 50% by weight, preferably greater than or equal to 60% by weight , more preferably greater than or equal to 70%, even more preferably greater than or equal to 80% by weight, even more preferably greater than or equal to 85% by weight even more preferably greater than or equal to 90% by weight relative to the total weight of said suspension (S1).

If desired, when said suspension (S1) is an aqueous suspension, said suspension (S1) comprises a percentage by weight of water less than 99% by weight, preferably less than 95% by weight, preferably less than 93% by weight. weight relative to the total weight of said suspension (S1).

If desired, when said suspension (S1) is an aqueous suspension, said suspension (S1) comprises a percentage by weight of water of between 99 and 50% by weight, preferably between 95 and 60% by weight, more preferably between 95 and 70%, even more preferably between 95 and 80% by weight, even more preferably between 95 and 85%, even more preferably between 93 and 85% relative to the total weight of said suspension (S1 ). According to the process of the present invention, step a) of providing a precipitate (PR) of an oxygenated zinc compound can be carried out by any means known to those skilled in the art.

Preferably, said step a) of providing a precipitate

(PR) of an oxygenated zinc compound comprises a process of precipitation in a solvent, preferably in water.

Such precipitation methods are known to those skilled in the art. For example, from a precursor (a zinc compound), it is possible by adding either an acid or a base to form said precipitate (PR) of an oxygenated zinc compound. The choice of acid or base will depend on the zinc compound.

Preferably, said precipitation process comprises a step a1) of reaction between a zinc compound, preferably a zinc compound selected from the group consisting of ZnS204, Zn (NO3) 2, ZnCL, ZnSU4 and their mixtures and at least an inorganic base.

The reaction between the zinc compound and the said at least one inorganic base is in fact a precipitation reaction which allows the creation of an oxygenated zinc compound, such as for example Zn (OH) 2 and / or ZnO.

More preferably, said zinc compound is ZnS2C> 4. Processes for obtaining ZnS204 are known in the art, for example, said ZnS204 can be obtained by reaction between metallic Zn and SO2 in the presence of water.

If desired, said at least one inorganic base comprises at least one alkaline or alkaline-earth cation M, preferably chosen from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and their combinations and at least one anion A, preferably selected from the group consisting of O ^2- , OH, CO3 ² , HCO3 and combinations thereof.

Preferably, said at least one inorganic base has the formula [M] _x [A] _y in which M is an alkaline or alkaline-earth cation, preferably selected from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and their combinations and A is an anion, preferably selected from the group consisting of O ² OH, CO3 ² , HCO3 and their combinations. The x and y coefficients can take the values 1 or 2 or a value between 1 and 2. The value of the x and y coefficients depends on the cation and the anion.

More preferably, said at least one inorganic base is chosen from the group consisting of LiOH, NaOH, KOH, Ca (OH), Mg (OH), MgO U2CO3, Na ₂ C0 ₃ , K2CO3, CaCOs, CaO MgCOs UHCO3, NaHCOs, KHCOs, Ca (HC0 ₃ ) 2, Mg (HC0 ₃ ) 2, MgO.CaO and their mixtures and / or combinations. Even more preferably, said at least one base is NaOH or KOH or CaO or MgO or CaO.MgO, even more preferably, said at least one base is NaOH.

In general, said precipitation process can generate inorganic salts as side products which in particular can become trapped in said precipitate (PR) and / or crystallize around said precipitate (PR) when the latter is not in the form of a precipitate. suspension, for example, in dry form. Alternatively, in particular when said precipitate (PR) is in the form of a suspension, these inorganic salts are included in said suspension. In particular, the inorganic salts included in said suspension can be at least partially or totally dissolved, for example in dissociated form in said suspension. If, for example, said suspension is an aqueous suspension, the inorganic salts can be at least partially or totally dissolved, for example in dissociated form in water.

In particular, in said precipitation process, during step a1), if the zinc compound is ZnS2C> 4, hydrosulfite salts are then generated by reaction between ZnS2Ü4 and said at least one inorganic base, these salts of 'hydrosulphites can then be degraded by less partially in various other sulphate and / or hydrogen sulphate and / or sulphite and / or hydrogen sulphite and / or thiosulphate salts.

In particular, in said precipitation process, during step a1), if the zinc compound is ZnN03, then nitrate salts are generated by reaction between ZnN03 and said at least one inorganic base. In particular, in said precipitation process, during step a1), if the zinc compound is ZnCl2, chloride salts are then generated by reaction between ZnCl2 and said at least one inorganic base. In particular, in said precipitation process, during step a1), if the zinc compound is ZnSO4, then sulfate salts are generated by reaction between ZnSO4 and said at least one inorganic base. In particular, in said precipitation process, during step a1), if said zinc compound is a mixture of at least two compounds each independently selected from the group consisting of ZnS2Ü4, Zn (NÜ3) 2, ZnCl2, ZnSÜ4 , a mixture of at least two inorganic salts each independently selected from the group consisting of hydrosulfites, sulfates, hydrogen sulfates, sulfites, hydrogen sulfites, thiosulfates, nitrates, chlorides.

Consequently, said precipitate (PR) provided in said step a) can comprise at least one inorganic salt, in particular at least one inorganic salt resulting from said precipitation process, in particular when said precipitate (PR) is not in the form of suspension or is in dry form. Preferably, if said precipitate (PR) is in the form of a suspension (S1), said suspension (S1) may further comprise at least one inorganic salt, in particular at least one inorganic salt resulting from said precipitation process. In particular when said precipitate (PR) is not in the form of a suspension or is in dry form, said precipitate may comprise said at least one inorganic salt in a concentration such that the conductivity of said precipitate (PR) measured according to the method of measuring conductivity, greater than 3000 pS / cm, more particularly greater than 4000 pS / cm, even more particularly greater than 5000 pS / cm, even more particularly greater than 10,000 pS / cm, even more particularly greater than 20,000 pS / cm, even more particularly greater than 30,000 pS / cm. In particular if said precipitate (PR) is in the form of a suspension (S1), said suspension (S1) may further comprise at least one inorganic salt in a concentration such that the conductivity of said precipitate (PR) measured according to the method of conductivity measurement, is greater than 3000 pS / cm, more particularly greater than 4000 pS / cm, even more particularly greater than 5000 pS / cm, even more particularly greater than 10,000 pS / cm, so even more particularly greater than 20,000 pS / cm, even more particularly greater than 30,000 pS / cm.

In particular, said at least one inorganic salt is chosen from the group consisting of nitrate salts, chloride salts, sulphate salts, hydrosulphite salts, hydrogen sulphate salts, sulphite salts, salts of hydrogen sulfite, thiosulfate salts and mixtures thereof. More particularly, said at least one inorganic salt is chosen from the group consisting of sulphate salts, hydrosulphite salts, hydrogen sulphate salts, sulphite salts, hydrogen sulphite salts, thiosulphate salts and of their mixtures.

If desired, said at least one inorganic salt may be selected from the group consisting of alkali or alkaline earth salts of nitrate, alkali or alkaline earth salts of chloride, alkali or alkaline earth salts of sulphate, alkali or alkaline earth salts of hydrosulphite, alkali or alkaline earth salts of hydrogen sulphate, alkali or alkaline earth salts of sulphite, alkali or alkaline earth salts of hydrogen sulfite, alkali or alkaline earth salts of thiosulfate and mixtures thereof. Preferably said at least one inorganic salt may be chosen from the group consisting of alkali salts or alkaline earth salts of sulphate, alkali or alkaline earth salts of hydrosulphite, alkali or alkaline earth salts of hydrogen sulphate, alkali or alkaline earth salts of sulphite, alkali salts or alkaline earth metals of hydrogensulfite, alkali or alkaline earth salts of thiosulfate and mixtures thereof.

In particular, said at least one inorganic salt may comprise at least one cation, preferably chosen from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and their combinations and at least one anion, of preferably selected from the group consisting of HSO4, HSO3, SO3 ² , S2O3 ² , S2O4 ² , NO3, Cl and SO4 ^2_ and combinations thereof.

Preferably, said at least one inorganic salt is chosen from the group consisting of UHSO4, UHSO3, U2SO3, U2S2O3, U2S2O4, LiNOs, LiCl, U2SO4, NaHSC, NaHSOs, Na ₂ S0 ₃ , Na ₂ S ₂ 03, [\ la2S2O4 , NaNOs, NaCI, NaS0 ₄ , KHS0 ₄ , KHSO3, K2SO3, K2S2O3, K2S2O4, KNOs, KCI, KSO4, Ca (HS04) 2, Ca (HS03) 2, CaS03, CaS203, CaS204, Ca (N03) 2, CaCl204, Ca (N03) 2 , CaS04, Mg (HS04) 2, Mg (HS03) 2, MgS03, MgS203, MgS204, Mg (NC> 3) 2, MgCl2, MgS04 and mixtures thereof, preferably said at least one inorganic salt can be chosen from the group consisting of U2S2O4, UHS04, LiHSOs, U2SO4, U2SO3, U2S2O3, Na ₂ S ₂ 04, NaHS0 ₄ , NaHSOs, Na ₂ S0 ₄ , Na ₂ S0 ₃ , Na ₂ S ₂ 03, K2S2O4, KHS0 ₄ , KHSO3, K2SO4, K2SO3, K2S2O3, CaS204, Ca (HS04) 2, Ca (HS03) 2, CaS04, CaS03, CaS203, MgS204, Mg (HS04) 2, Mg (HS03) 2, MgS04, MgSC> 3, MgS203 and mixtures thereof, of more preferably said at least one inorganic salt can be chosen from the group consisting of Na2S2C> 4, NaHSC> 4, NaHSC> 3, Na2SC> 4, Na2SC> 3, Na2S203, and mixtures thereof.

In particular, in said precipitation process, in step a1), if the zinc compound is ZnNO3, said at least one inorganic salt is a nitrate salt.

In particular, in said precipitation process, during step a1), if the zinc compound is ZnCl2, said at least one inorganic salt is a chloride salt. In particular, in said precipitation process, in step a1), if the zinc compound is ZnSO4, said at least one inorganic salt is a sulfate salt. In particular, in said precipitation process, during step a1), if the zinc compound is ZnS2Ü4, said at least one inorganic salt is chosen from the group consisting of hydrosulfite salts, sulfate salts, hydrogen sulphate, sulphite salts, hydrogen sulphite salts, thiosulphate salts and mixtures thereof.

In particular, in said precipitation process, during step a1), if the zinc compound is a mixture of at least two compounds each independently selected from the group consisting of ZnS2Ü4, Zn (NÜ3) 2, ZnCl2, ZnSÜ4 , said precipitate (PR) provided in said step a) may comprise at least two inorganic salts each independently selected from the group consisting of hydrosulphites, sulphates, hydrogen sulphates, sulphites, hydrogen sulphites, thiosulphates, nitrates, chlorides.

More particularly, in said step a1) if the zinc compound is ZnS204 and if said at least one inorganic base has the formula [M] _x [A] _y in which M is a cation selected from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and their combinations and A is an anion selected from the group consisting of O ² , OH, CO3 ² , HCO3 and their combinations and the coefficients x and y can take the values 1 or 2 or a value between 1 and 2, the value of the x and y coefficients depends on the cation and the anion or when said at least one inorganic base is chosen from the group consisting of LiOH, NaOH, KOH, Ca (OH ), Mg (0H) 2, Li C0 ₃ , Na ₂ C0 ₃ , K2CO3, CaCOs, MgCOs LiHCOs, NaHCC> 3, KHCO3, Ca (HCC> 3) 2, Mg (HCC> 3) 2, CaO, MgO, CaO.MgO and mixtures thereof, said at least one inorganic salt may be selected from the group consisting of U2S2O4, UHSO4, UHSO3, U2SO4, U2SO3, U2S2O3, Na ₂ S ₂₀ 04, NaHSC, NaHSOs, Na ₂ S0 ₄ , [\ la2SO3, [\ la2S2O3, K2S2O4, KHS0 ₄ , KHSOs, K2SO4, K2SO3, K2S2O3, CaS ₂ 04, Ca (HS0 ₄ ) 2, Ca (HS0 ₃ ) 2, CaS0 ₄ , CaS03, CaS203, MgS204, Mg (HS04) 2, Mg (HS03) 2, MgSC, MgS03, MgS203 and mixtures thereof.

Even more particularly, in said step a1), if the zinc compound is ZnS2Ü4 and if said at least one inorganic base is NaOH, said at least one inorganic salt can be chosen from the group consisting of Na2S2C> 4, NaHSC NaHSC > 3, Na2SC> 4, Na2SÜ3, Na2S2Ü3 and mixtures thereof.

More particularly, in said step a1) if the zinc compound is Zn (NÜ3) 2, and if said at least one inorganic base has the formula [M] _x [A] _y in which M is a cation selected from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and their combinations and A is an anion selected from the group consisting of O ^2- , OH, CO3 ² , HCO3 and their combinations and the x coefficients and y can take the values 1 or 2 or a value between 1 and 2, the value of the coefficients x and y depends on the cation and the anion, said at least one inorganic salt can have the formula MNO3 if M is Li ⁺ or Na ⁺ or K ⁺ or M (N03) 2 if M is Ca ²⁺ or Mg ²⁺ .

Even more particularly, in said step a1) if the zinc compound is Zn (NÜ3) 2 and if said at least one inorganic base has the formula [M] _x [A] _y in which M is a cation selected from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and their combinations and A is an anion selected from the group consisting of O ^2- , OH, CO3 ² , HCO3 and their combinations and the x coefficients and y can take the values 1 or 2 or a value between 1 and 2, the value of the coefficients x and y depending on the cation and the anion; or when said at least one inorganic base is selected from the group consisting of CaO, MgO, CaO.MgO, LiOH, NaOH, KOH, Ca (OH), Mg (0H) 2, Li C0 ₃ , Na ₂ C0 ₃ , K2CO3 , CaCOs, MgCOs LiHCOs, NaHCOs, KHCOs, Ca (HC0 ₃ ) 2, Mg (HC0 ₃ ) 2 and mixtures thereof, said at least one inorganic salt may be selected from the group consisting of L1NO3, NaN03, KNO3, Ca (N03 ) 2, Mg (NO3) 2 and mixtures thereof. Even more particularly, in said step a1), if the zinc compound is Zn (NÜ3) 2 and if said at least one inorganic base is NaOH, said at least one inorganic salt may be NaNOa.

More particularly, in said step a1) if the zinc compound is ZnCl2, and if said at least one inorganic base has the formula [M] _x [A] _y in which M is a cation selected from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and their combinations and A is an anion selected from the group consisting of O ² , OH, CO3 ² , HCO3 and their combinations and the coefficients x and y can take the values 1 or 2 or a value between 1 and 2, the value of the coefficients x and y depends on the cation and the anion, said at least one inorganic salt can have the formula MCI if M is Li ⁺ or Na ⁺ or K ⁺ or MCI2 if M is Ca ²⁺ or Mg ²⁺ .

Even more particularly, in said step a1) if the zinc compound is ZnCl2 and if said at least one inorganic base has the formula [M] _x [A] _y in which M is a cation chosen from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and their combinations and A is an anion selected from the group consisting of O ^2- , OH, CO3 ² , HCO3 and their combinations and the coefficients x and y can take the values 1 or 2 or a value between 1 and 2, the value of the x and y coefficients depends on the cation and the anion; or when said at least one inorganic base is selected from the group consisting of CaO, MgO, CaO.MgO, LiOH, NaOH, KOH, Ca (OH), Mg (0H) 2, Li ₂ C0 ₃ , Na ₂ C0 ₃ , K ₂ C0 ₃ , CaCOs, MgCOs LiHCOs, NaHCOs, KHCOs, Ca (HC0 ₃ ) 2, Mg (HC0 ₃ ) 2 and their mixtures, said at least one inorganic salt selected from the group consisting of LiCl, NaCl, KCI, CaCl ₂ , MgCl ₂ and their mixtures.

Even more particularly, in said step a1), if the zinc compound is ZnCl ₂ and if said at least one inorganic base is NaOH, said at least one inorganic salt may be NaCl.

More particularly, in said step a1) if the zinc compound is ZnSO4, and if said at least one inorganic base has the formula [M] _x [A] _y wherein M is a cation selected from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and combinations thereof and A is an anion selected from the group consisting of O ² , OH, CO3 ² , HCO3 and their combinations and the x and y coefficients can take the values 1 or 2 or a value between 1 and 2, the value of the x and y coefficients depends on the cation and the anion, said at least one inorganic salt may have the formula M2SO4 if M is Li ⁺ or Na ⁺ or K ⁺ or MSO4 if M is Ca ²⁺ or Mg ²⁺ .

Even more particularly, in said step a1) if the zinc compound is ZnSC ^ and if said at least one inorganic base has the formula [M] _x [A] _y in which M is a cation chosen from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and their combinations and A is an anion selected from the group consisting of O ² , OH, CO3 ² , HCO3 and their combinations and the coefficients x and y can take the values 1 or 2 or a value between 1 and 2, the value of the x and y coefficients depends on the cation and the anion; or when said at least one inorganic base is selected from the group consisting of CaO, MgO, CaO.MgO, LiOH, NaOH, KOH, Ca (OH), Mg (0H) 2, Li ₂ C0 ₃ , Na ₂ C0 ₃ , K2CO3, CaCOs, MgCOs LiHCOs, NaHCOs, KHCOs, Ca (HC0 ₃ ) 2, Mg (HC0 ₃ ) 2 and their mixtures, said at least one inorganic salt may be selected from the group consisting of U2SO4, Na2SÜ4, K2SO4, CaSC> 4, MgSO4 and mixtures thereof.

Even more particularly, in said step a1), if the zinc compound is ZnSO4 and if said at least one inorganic base is NaOH, said at least one inorganic salt may be NaSO4.

In particular said at least one inorganic salt will depend on said at least one inorganic base and on said zinc compound. For example, if said at least one inorganic base comprising Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ or Mg ²⁺ is used, then said at least one inorganic salt which is generated respectively comprises Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ or Mg ²⁺ . In another example, if said zinc compound comprises an S2O4 ² anion, Cl, SO4 ² or NO3, then said at least one inorganic salt which is generated comprises respectively S2O4 ² (which can decompose at least partially into HSCP, HSO3, SO4 ² , SO3 ² , S2O3 ² ), Cl, SO4 ² or NO3.

For the purposes of the present invention, said at least one inorganic salt, when it is included in said suspension, can be dissolved, for example in dissociated form.

In another particular embodiment, said precipitation process may comprise a step a1) of reaction between a zinc compound, preferably a zinc compound chosen from the group consisting of Zn (NH3) 4 (OH) 2, Zn ( NH3) 4 CO3, Zn (NH3) 4Cl2 and mixtures thereof and at least one inorganic acid, preferably an inorganic acid selected from the group consisting of HCl, H2SO4, CO2 and mixtures thereof.

The conductivity adjustment

The inventors have found that when the conductivity of said precipitate (PR) is less than 3000 pS / cm, it is possible to obtain compositions of microspherules of an oxygen-containing zinc compound which can be easily dispersed in a material. The dispersions obtained then exhibit improved dispersion homogeneity compared to the state of the art. In addition, it has been observed that the materials obtained by these dispersions exhibit improved and particularly reproducible properties compared to the state of the art.

If desired, the conductivity of said precipitate (PR) of said oxygen-containing zinc compound obtained in step a) is adjusted until a conductivity is obtained measured according to the conductivity measurement method of less than 2500 pS / cm, preferably less than 2000 pS / cm.

If desired, the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) can be adjusted until a conductivity is obtained measured according to the conductivity measurement method of less than 1500 pS / cm, in in particular less than 1000 pS / cm, even more particularly less than 700 pS / cm. Advantageously, the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) is adjusted until a conductivity is obtained, measured according to the conductivity measurement method, greater than 100 pS / cm, preferably greater than at 200 pS / cm, preferably greater than 300 pS / cm, more preferably greater than 400 pS / cm. Surprisingly, it has been observed that such an adjustment of the conductivity of the precipitate (PR) makes it possible to obtain a composition of microspherules of an oxygen-containing zinc compound having the aforementioned advantages while allowing said process according to the invention to be economically profitable. If desired, the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) can be adjusted until a conductivity is obtained, measured according to the conductivity measurement method, of between 3000 and 100 pS / cm , preferably between 2500 and 400 pS / cm, more preferably between 2000 and 400 pS / cm, even more preferably between 1500 and 400 pS / cm, even more preferably between 1000 and 400 pS / cm , even more preferably between 700 and 400 pS / cm.

In the context of the present invention, said step b) of adjusting the conductivity of said precipitate (PR) of said oxygen-containing zinc compound can be carried out by any technique known to those skilled in the art making it possible to adjust said conductivity of said precipitate (PR).

Said step b) of adjusting the conductivity of said precipitate (PR) can be carried out by washing, dialysis, or by a centrifugation or filtration process or a combination of these techniques.

If desired, said step b) of adjusting the conductivity of said precipitate (PR) can be carried out by filtration and washing, preferably by filtration and washing simultaneously, more preferably by washing and filtration simultaneously carried out in a filter press.

Advantageously, said step b) of adjusting the conductivity of said precipitate (PR) is carried out by filtration and washing. simultaneously, said washing being carried out with a solvent. Advantageously, said solvent is an organic solvent, an aqueous solution or their mixtures. Preferably, said organic solvent can be chosen from the group consisting of methanol, ethanol, acetonitrile, DMF, DMSO and their mixtures. Preferably, said aqueous solution can be a solution of demineralized water or a solution of salt water.

Advantageously, said washing solvent is at a temperature greater than 20 ° C, preferably greater than 25 ° C, more preferably greater than 30 ° C. It is understood that preferably, the temperature of said solvent may be less than 50 ° C, more preferably less than 45 ° C, even more preferably less than 40 ° C.

Advantageously, said solvent is at a temperature between 20 ° C and 50 ° C, preferably between 30 ° C and 40 ° C.

It has surprisingly been observed that if the solvent is added to said precipitate (PR) at a temperature between 20 ° C and 50 ° C, preferably between 30 ° C and 40 ° C, the temperature is high enough to possibly allow rapid (compatible with an industrial process) and efficient dissolution of said inorganic salts included in said precipitate (PR) of an oxygenated zinc compound and sufficiently short for said process according to the invention to be economically profitable. In addition, in the case where the salts are soluble, washing at this temperature is optimal to avoid the precipitation of inorganic salts.

Advantageously, said solvent has a pH between 6 and 12, preferably between 7 and 11.

In the context of the present invention, said washing can be carried out by any technique known to those skilled in the art.

Advantageously, said washing is carried out by filtration, by repulping or dilution, preferably by filtration in a filter press.

In particular, the washing step can involve the addition of said solvent and removal of said added solvent, in particular so as to decrease the conductivity of said precipitate (PR); the solvent which is removed thus comprising said at least one inorganic salt.

The method of measuring the conductivity In the context of the present invention, said method of measuring the conductivity comprises:

a step m1) of forming a mixture M1 consisting of said precipitate (PR) and demineralized water having a conductivity less than or equal to 3.5 pS / cm, said precipitate (PR) having a concentration of 100 g / L and said mixture (M1) having a total weight P1,

- a step m2) of heating to boiling for a period sufficient to dissolve in demineralized water of said mixture (M1) at least partially said inorganic salts included in said precipitate (PR), preferably said period is 10 minutes.

Said heating step m2) generally causes the evaporation of part of the water from said mixture (M1). In this case, a step m3) of adding a sufficient quantity of demineralized water to said mixture (M1) to obtain said total weight P1 is carried out.

After said step m3), said method of measuring the conductivity further comprises:

- a step m4) of decanting said mixture (M1) to obtain a decanted mixture (M2),

a step m5) of measuring the conductivity of said decanted mixture (M2). Said step m5) is repeated five times and is carried out using a conductivity meter with internal temperature correction. The conductivity is expressed at 25 ° C and is an average of the five measurements.

Said method for measuring the conductivity further comprises a calibration step with KCl solutions of known concentration and conductivity. The conductivity measurement method will be described in detail in the examples. In the context of the present invention, it is therefore of course understood that the “conductivity of said precipitate (PR)” in fact means the “conductivity of said precipitate (PR) measured according to the conductivity measurement method”. In fact, step m2) of heating to boiling makes it possible to dissolve at least in part said inorganic salts included in said precipitate (PR). At least part of said inorganic salts is therefore found dissolved in the water of said mixture (M1). During step m5), the conductivity is in fact measured in solution in said decanted mixture (M2) and therefore represents the concentration of said inorganic salts dissolved in the water of said decanted mixture (M2). In particular, in said step a1), when said at least one inorganic base is NaOH, a step of adjusting the conductivity of said precipitate (PR) of said oxygen-containing zinc compound obtained in step a) until obtaining a conductivity measured according to the conductivity measurement method of less than 3000 pS / cm, may correspond to a step of adjusting the salt concentration of said precipitate (PR) obtained in step a) until a salt concentration of less than 2.95% by weight relative to the total weight of said precipitate (PR).

In another example, in said step a1), when said at least one inorganic base is NaOH, a step of adjusting the conductivity of said precipitate (PR) obtained in step a) until a measured conductivity is obtained according to the method of measuring the conductivity less than 2500 pS / cm, in particular less than 2000 pS / cm, more particularly less than 1500 pS / cm, even more particularly less than 1000 pS / cm, even more so more particularly less than 700 pS / cm can correspond respectively to a step of adjusting the salt concentration of said precipitate (PR) obtained in step a) until a salt concentration of less than 2.4% is obtained , in particular less than 1.85%, in particular less than 1.3%, more particularly less than 0.75%, even more particular less than 0.42% by weight relative to the total weight of said precipitate (PR).

Alternatively, a step of adjusting the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) is adjusted until a conductivity measured according to the conductivity measurement method is obtained greater than 100 pS / cm, preferably greater than 200 pS / cm, preferably greater than 300 pS / cm, more preferably greater than 400 pS / cm may correspond respectively to a step of adjusting the concentration of salts of said precipitate (PR) obtained in step a) until a salt concentration greater than 0.1% by weight relative to the total weight of said precipitate is obtained.

Composition (C) of microspherules of an oxygenated zinc compound

Said composition (C) of microspherules of an oxygenated zinc compound is obtained from said precipitate, the conductivity of which has been adjusted in step b).

In the context of the present invention, said composition

(C) microspherules of an oxygenated zinc compound being obtained from said precipitate can be obtained by any technique known from the state of the art. For example, said composition, said composition (C) of microspherules of an oxygenated zinc compound being obtained from said precipitate can be obtained by means of a step c1) of drying and / or calcination.

Consequently, advantageously, said step of obtaining said composition (C) of microspherules of an oxygenated zinc compound can comprise a step c1) of drying and / or calcining of said precipitate (PR) of oxygenated zinc compound. Preferably, said step c1) of drying and / or calcination is carried out by:

• an atomization process or

• heating in a rotary kiln or

• filtration by forming a filter cake with said precipitate (PR) of an oxygenated zinc compound and by sucking said filter cake in a stream of hot air, preferably a stream of hot air at a temperature between 20 ° C and 100 ° C, even more preferably between 30 ° C and 70 ° C.

More preferably, said step c1) of drying and / or calcination is carried out by an atomization process.

If desired, said drying step c1) is carried out until a precipitate (PR) is obtained comprising less than 5% by weight of water, preferably less than 2% by weight of water, more preferably less of 1% by weight of water relative to the total weight of said precipitate (PR).

Even more preferably, said step b) of adjusting the conductivity of said precipitate (PR) is carried out before said step c) for obtaining said composition of microspherules of an oxygen-containing zinc compound comprising a step c1) of drying and / or calcination.

The advantage is linked to the fact that if said step b) were carried out after said step c1), then an additional drying step would be necessary after step b) for adjusting the conductivity of said precipitate (PR), which would generate a cost. It is therefore economically more profitable for said step b) of adjusting the conductivity to take place before said step c1) of drying and / or calcination.

Even more advantageously, said atomization process comprises injection by means of a nozzle of an aqueous suspension of said precipitate (PR) of the oxygenated zinc compound obtained in step b), having a solid matter content of 25 to 70% by weight relative to the total weight of said aqueous suspension, under a pressure of 10 to 100 bars, preferably 10 to 50 bars inside an atomization chamber, in a stream of gas entering at a temperature of 150 ° C to 800 ° C and exiting at a temperature of 50 to 300 ° C. It has been observed that when such an atomization process is used, the process according to the invention makes it possible to obtain a composition of microspherules of an oxygenated zinc compound which exhibits, among other things, improved flowability and whose dispersion. in a material, exhibits a further improved homogeneity of dispersion compared to a powder of an oxygenated zinc compound which is not in the form of microspherules.

Since said composition (C) of microspherules of an oxygenated zinc compound is obtained from said precipitate whose conductivity has been adjusted in step b), said composition (C) of microspherules of an oxygenated zinc compound exhibits a conductivity measured using the conductivity measurement method less than 3000 pS / cm.

Advantageously, said composition (C) of microspherules of an oxygenated zinc compound can have a conductivity measured according to the conductivity measurement method of less than 2500 pS / cm, preferably less than 2000 pS / cm.

If desired, said composition (C) of microspherules of an oxygenated zinc compound can exhibit a conductivity measured according to the conductivity measurement method preferably less than 1500 pS / cm, more preferably less than 1400 pS / cm, so more preferably less than 1300 pS / cm, even more preferably less than 1250 pS / cm, even more preferably less than 1000 pS / cm, even more preferably less than 900 pS / cm, even more preferably less than 800pS / cm, even more particularly less than 700pS / cm. Advantageously, said composition (C) of microspherules of an oxygenated zinc compound can have a conductivity measured according to the conductivity measurement method of greater than 100 pS / cm, preferably greater than 200 pS / cm, preferably greater than 300 pS / cm, more preferably greater than 400 pS / cm.

Advantageously, said composition (C) of microspherules of an oxygenated zinc compound can exhibit a conductivity measured according to the conductivity measurement method of between 3000 and 100 pS / cm, preferably between 2500 and 400 pS / cm, so more preferably, between 2000 and 400 pS / cm, even more preferably between 1500 and 400 pS / cm, even more preferably between 1000 and 400 pS / cm, even more preferably between 700 and 400 pS / cm .

If desired, said composition (C) of microspherules of an oxygenated zinc compound can comprise at least one inorganic salt, preferably, said at least one inorganic salt is chosen from the group consisting of nitrate salts, chloride salts, sulfate salts, hydrosulfite salts, hydrogensulfate salts, sulfite salts, hydrogensulfite salts, thiosulfate salts, and mixtures thereof. More particularly, said at least one inorganic salt is chosen from the group consisting of sulphate salts, hydrosulphite salts, hydrogen sulphate salts, sulphite salts, hydrogen sulphite salts, thiosulphate salts and of their mixtures.

If desired, said at least one inorganic salt may be selected from the group consisting of alkali or alkaline earth salts of nitrate, alkali or alkaline earth salts of chloride, alkali or alkaline earth salts of sulphate, alkali or alkaline earth salts of hydrosulphite, alkali or alkaline earth salts of hydrogen sulphate, alkali or alkaline earth salts of sulphite, alkali or alkaline earth salts of hydrogen sulfite, alkali or alkaline earth salts thiosulfate and mixtures thereof. Preferably, said at least one inorganic salt can be chosen from the group consisting of alkali or alkaline earth salts of sulphate, alkali or alkaline earth salts of hydrosulphite, alkali or alkaline earth salts of hydrogensulfate, alkali or alkaline earth salts of sulfite, alkali or alkaline earth salts of hydrogensulfite, alkali or alkaline earth salts of thiosulfate and mixtures thereof.

Preferably, said at least one inorganic salt is chosen from the group consisting of UHSO4, UHSO3, U2SO3, U2S2O3, U2S2O4, LiNOs, LiCl, U2SO4, NaHSC, NaHSOs, Na ₂ S0 ₃ , Na ₂ S ₂ 03, [\ la2S2O4 , NaNOs, NaCl, NaS0 ₄ , KHS0 ₄ , KHSOs, K2SO3, K2S2O3, K2S2O4, KNOs, KCI, KSO4, Ca (HS04) 2, Ca (HS03) 2, CaS03, CaS203, CaS204, Ca (N03) 2, CaCl204, Ca (N03) 2 , CaS04, Mg (HS04) 2, Mg (HS03) 2, MgS03, MgS203, MgS204, Mg (NC> 3) 2, MgCl2, MgS04 and mixtures thereof, preferably said at least one inorganic salt can be chosen from the group consisting of U2S2O4, UHS04, LiHSOs, U2SO4, U2SO3, U2S2O3, Na ₂ S ₂ 04, NaHS0 ₄ , NaHSOs, Na ₂ S0 ₄ , Na ₂ S0 ₃ , Na ₂ S ₂ 03, K2S2O4, KHS0 ₄ , KHSO3, K2SO4, K2SO3, K2S2O3, CaS204, Ca (HS04) 2, Ca (HS03) 2, CaS04, CaS03, CaS203, MgS204, Mg (HS04) 2, Mg (HS03) 2, MgS04, MgSC> 3, MgS203 and mixtures thereof, of more preferably said at least one inorganic salt can be chosen from the group consisting of Na2S2C> 4, NaHSC> 4, NaHSC> 3, Na2SC> 4, Na2SC> 3, Na2S203, and mixtures thereof.

Advantageously, said composition (C) of microspherules of an oxygenated zinc compound can comprise said at least one inorganic salt in a concentration of less than 2.95%, in particular less than 2.4%, in particular less than 1.85 %, especially lower at 1.3%, more particularly less than 0.75%, even more particularly less than 0.42% by weight relative to the total weight of said composition (C). Advantageously, said composition (C) of microspherules of an oxygenated zinc compound may comprise said at least one inorganic salt in a concentration greater than 0.01% by weight relative to the total weight of said composition (C), preferably in a concentration greater than 0.05% by weight relative to the total weight of said composition (C), more preferably greater than 0.1% by weight relative to the total weight of said composition (C). Advantageously, said composition (C) of microspherules of an oxygenated compound of zinc may comprise said at least one inorganic salt in a concentration of between 0.01% and 2.95% by weight relative to the total weight of said composition (C), preferably between 0.1% by weight and 2, 4% by weight relative to the total weight of said composition ( C), more preferably between 0.1% by weight and 1.85% by weight relative to the total weight of said composition (C), more preferably between 0.1% by weight and 1.3% by weight. weight relative to the total weight of said composition (C), more preferably between 0.1% by weight and 0.75% by weight relative to the total weight of said composition (C), more preferably between 0, 1% by weight and 0.42% by weight relative to the total weight of said composition (C).

If desired, said composition (C) of microspherules of an oxygenated zinc compound may comprise less than 5% by weight of water, preferably less than 2% by weight of water, more preferably less than 1% by weight of water. weight of water relative to the total weight of said composition (C).

In the context of the present invention, the term “microspherules” can be defined as being particles each consisting of aggregated particles. It has been observed that when microspherules are composed of smaller aggregated particles, the microspherules disintegrate when they are dispersed in a material or in powders or when they are placed in aqueous suspension.

Advantageously, said microspherules have a D50 measured by laser particle size distribution in aqueous solution of between 50 μm and 200 μm, preferably between 80 and 170 μm. Advantageously, said microspherules have a D10 measured by laser particle size distribution in aqueous solution of between 1 μm and 80 μm, preferably between 8 and 70 μm. Advantageously, said microspherules have a D90 measured by laser particle size distribution in aqueous solution of between 200 μm and 300 μm, preferably between 210 and 260 μm. In the context of the present invention, the notation D _x represents a diameter, expressed in μm, relative to which X% by volume of the total volume of the particles measured is composed of smaller particles. It has been observed that when said microspherules have D50, D10 and D90 as specified above, the size distribution of microspherules is narrow. This has the consequence that the properties of the composition of microspherules of an oxygenated zinc compound are even better controlled, which also allows better control over the properties of the dispersions of said composition in materials, such as for example in polymer materials. or animal nutrient compositions.

Advantageously, said microspherules each consist of aggregated particles each having a D50 of between 1 and 20 μm, more preferably between 1 and 10 μm, even more preferably between 1 and 5 μm or even between 1 and 3 μm.

Advantageously, said microspherules have a Flodex index of less than 15, preferably less than 10. The Flodex index is a test making it possible to measure the ease of flow of the powders. The apparatus used is a receptacle in which the powder to be tested is placed and whose base consists of a diaphragm with a calibrated opening through from which it is observed whether there is flow of said powder. By successive tests, the minimum diameter through which this powder flows freely is determined. This diameter (in millimeters) corresponds to the Flodex index.

In general, the characteristics of D10 and / or Dso and / or Dgo and / or of Flodex index can be obtained by any means known to those skilled in the art, for example by virtue of said drying step and / or calcining said precipitate (PR).

Said microspherules may also have a BET specific surface area of less than 150 m ² / g, advantageously less than 100 m ² / g, and preferably less than 50 m ² / g. The BET specific surface is measured by measured by adsorption manometry with a helium / nitrogen mixture (70/30) and calculated according to the BET method (Brunauer-Emmett-Taylor), after degassing at 150 ° C. for at least 1 hour.

In a particular embodiment, said precipitate (PR) of an oxygenated zinc compound provided in step a) has a conductivity, preferably a conductivity measured according to the conductivity measurement method of greater than 3000 pS / cm. In this particular embodiment, said precipitate (PR) of an oxygenated zinc compound is in the form of a suspension (S1) in an aqueous medium and the latter comprises a percentage by weight of a precipitate of a oxygenated zinc compound of between 8% and 15% by weight relative to the total weight of said suspension (S1).

In this particular embodiment, said step a) of providing a precipitate (PR) of an oxygen-containing zinc compound comprises a method of precipitation in water, said precipitation method comprises a step a1) of reaction between a compound of ZnS204 and an inorganic base, NaOFI. This precipitation process allows the creation of an oxygenated zinc compound consisting of Zn (OFI) 2 and ZnO. Inorganic salts are generated during this precipitation process, so that said suspension (S1) also comprises at least one inorganic salt may be selected from the group consisting of Na2S204, NaHSC, NaHS03, Na2S04, Na2S03, Na2S203 and mixtures thereof. The conductivity of said precipitate (PR), measured according to the conductivity measurement method, is greater than 3000 pS / cm.

In this embodiment, the conductivity of said precipitate (PR) obtained in step a) is then adjusted in step b) until a conductivity is obtained measured according to the conductivity measurement method of less than 3000 pS / cm. Said step b) of adjusting the conductivity of said precipitate (PR) is carried out by washing and filtration simultaneously carried out in a filter press with an aqueous solution.

In this embodiment, then said method comprises a step of obtaining said composition (C) of microspherules of an oxygenated zinc compound comprising a step c1) of drying and calcining said precipitate (PR) of oxygenated zinc compound carried out by an atomization process. In this embodiment, said atomization process comprises injection by means of a nozzle of an aqueous suspension of said precipitate (PR) of the oxygen-containing zinc compound obtained in step b), having a solid matter content of 25 to 70% by weight relative to the total weight of said aqueous suspension, under a pressure of 10 to 100 bars, preferably 10 to 50 bars inside an atomization chamber, in an incoming gas stream at a temperature of 150 ° C to 800 ° C and exiting at a temperature of 50 to 300 ° C. After the atomization process, a composition (C) of microspherules of an oxygenated zinc compound having a conductivity measured according to the conductivity measurement method of between 3000 and 100 pS / cm is obtained. In this embodiment, said composition (C) of microspherules of an oxygenated zinc compound comprises less than 1% by weight of water relative to the total weight of said composition (C). In this embodiment, said composition (C) comprises an inorganic salt selected from the group consisting of Na2S2C> 4, NaHSC> 4, NaHSC> 3, Na2SC> 4, Na2SO3, Na2S2O3, and mixtures thereof. Said inorganic salt being present in a concentration of between 0.01% and 2.95% by weight relative to the total weight of said composition (C). In this embodiment, it is observed that the microspherules of said composition (C) are composed of smaller aggregated particles, the microspherules disintegrate when they are dispersed in a material or in powders or when they are suspended. watery.

Advantageously, said microspherules have a D50 measured by laser particle size distribution in aqueous solution of between 80 and 170 μm. Said microspherules also have a D10 measured by laser particle size distribution in aqueous solution of between 8 and 70 μm and a Dgo measured by laser particle size distribution in aqueous solution of between 200 μm and 300 μm. In addition, said microspherules each consist of aggregated particles each having a D 50 of between 1 and 5 µm. Said microspherules have a Flodex index of less than 10. Said microspherules also have a BET specific surface area of less than 50 m ² / g.

Each preferred, advantageous or particular variant of each embodiment can be combined with each preferred, advantageous or particular variant of each embodiment.

It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made thereto without departing from the scope of the appended claims.

Example 1

Synthesis of ZnO

SO2 is reacted with metallic zinc in a container in the presence of water to produce ZnS2C> 4. Metallic zinc and SO2 are added in stoichiometric amounts. Then, NaOH is added to the vessel so as to produce a precipitate (PR) comprising ZnO and Zn (OH) 2. Na2S2O4 is also formed as a side product and remains in the aqueous phase. Na2S204 can also degrade and form other species such as: NaHSC> 4, NaHSC> 3, Na2SC> 4, Na2S03, Na2S2C> 3.

The precipitate (PR) is then filtered in a filter press to form a filter cake which is recovered.

After filtration, the filter cake is washed by adding water and filtered in the filter press so as to obtain a conductivity of the precipitate (PR) in the filter cake, measured by the conductivity measurement method, of 1130 pS / cm.

The method of measuring the conductivity is as follows: 10 g of the precipitate (PR) comprising ZnO and Zn (OH) 2 and forming the filter cake are mixed with 90 g of demineralized water and the resulting mixture is then stirred . At the same time, the resulting mixture is brought to a boil for 10 minutes and then allowed to cool. Demineralized water is added to the resulting mixture so that it has a weight of 100g. The mixture thus obtained is then left to settle.

The temperature of the mixture is then measured and the conductivity meter is set at this temperature. The measured conductivity is expressed at 25 ° C, the average is calculated over five measurements.

Each series of conductivity measurements is preceded by a calibration in order to prevent drift due, for example, to aging of the electrode.

For calibration, the conductivity of a KCI solution is measured at 25 ° C (0.1 N or 1 N depending on the measurement range to be used). If necessary, the cell parameter potentiometer is set to adjust the conductivity value as follows:

• KCI 0.1 N: 12.88 millisiemens / cm,

• KC1 1 N: 1 1 1 .8 millisiemens / cm. The conductivity meter used for the conductivity measurement is a conductivity meter with internal temperature correction (correction factor 2.2% / ° C).

The percentage of salts of the precipitate (PR) comprising ZnO and Zn (OH) 2 of the filter cake is 0.42% by weight relative to the total weight of the precipitate (PR) of the filter cake and is then measured by the method of measuring the percentage by weight of salts as follows: 10.00 g of the precipitate (PR) comprising ZnO and Zn (OH) 2 from the filter cake are mixed with 100 ml of deionized water and the mixture obtained is heated to boiling for 10 minutes. After cooling, the volume of the mixture is brought to 200 ml by adding demineralized water at 20 ° C. The mixture thus obtained is homogenized and filtered through 2 dry pleated filters.

The filtration is repeated as many times as necessary until a clear filtrate is obtained. Then 50 ml of the clear filtrate is transferred to a capsule which has been tared. Everything is evaporated to dryness at 105 ° C until a dry residue is obtained in the capsule and cooled to a constant weight.

Then the capsule is weighed again to the nearest 1 mg. The hot-soluble salts are expressed according to the formula: salts (%) = 400 ^* R / P, with P (g) being the test portion and R (g) the weight of dry residue contained in the capsule.

The precipitate (PR) comprising ZnO and Zn (OH) 2 from the washed filter cake is then injected into an atomization device described in Figure 1.

The atomization device comprises a cylindrical atomization chamber 1 with a conical bottom in which a stream of hot air circulates. The incoming air passes through a filter 2 and a burner 3 beforehand allowing it to be preheated, and penetrates, at a temperature of 550 ° C, into the upper part of the atomization chamber 1 through a finned distributor 4. The air flow rate was of the order of 700 N m ³ / h. The supply of precipitate (PR) comprising ZnO and Zn (OH) 2 is carried out through line 5 by means of a pump, in the form of an aqueous suspension containing 40 to 45% by weight of precipitate (PR) relative to the total weight of the suspension, prepared in a mixer-disperser 12. Said suspension is introduced, at a flow rate of about 80-100 liters per hour and at a pressure of 20 to 30 bars, by the intermediary of a nozzle 6 arranged in the center of the chamber 1. Said suspension is pulverized (atomized) and dried in a few seconds in the stream of hot air.

The ZnO particles obtained fall into the lower part of the chamber where they are collected and discharged through valve 7 so as to be, for example, immediately bagged. At this level, between 85 and 90% of the zinc oxide (Free Flowing) is collected in the form of microspherules comprising less than 0.5% of residual water. The finest particles are evacuated into the air leaving the chamber through line 8 under the suction action of a fan 9. They are then separated from the air leaving, for example in a cyclone 10 and recovered by valve 11 to be optionally recycled at the level of the preparation of the suspension in the disperser 12. About 10 to 15% by weight of fines (non-agglomerated powder in the form of microspherules) are thus immediately separated from the microspherules of an oxygenated compound zinc of the invention, and recycled. The oxygenated zinc compound obtained is a mixture of ZnO and Zn (OH) 2.

The air is filtered by means of a bag filter 13 before leaving the circuit. The particles possibly recovered at this stage are collected at the level of the valve 14 and can also be recycled to the disperser 12 (following the dotted line).

The nozzle 6 used can be a nozzle of the type having a swirl chamber (type Delavan SDX) with an outlet diameter of 1.62 mm in the example presented, or a two-fluid nozzle in the example presented. which the energy is provided by compressed air which makes it possible to obtain very high degrees of atomization and therefore finer powders.

Characteristics of the microspherules of an oxygenated zinc compound obtained

TABLE 1

Microspherules are actually made up of smaller aggregated particles. In order to be able to disaggregate the microspherules, they have undergone ultrasound treatment. The smaller particles that made up the microspherules have a D 50 of 2.6 µm.

Conductivity was measured by the conductivity measurement method.

The salt concentration was measured by the weight percent salt measurement method.

D10, Dso and Dgo were measured by laser granulometry in the aqueous phase.

The specific surface area according to the present invention is measured by adsorption manometry of a He-N2 mixture (70/30) and calculated according to the BET method, after degassing under vacuum at 150 ° C. for at least 1 hour. The Flodex index is a test to measure the ease of flow of powders. The apparatus used is a receptacle in which the powder to be tested is placed and the base of which consists of a diaphragm with a calibrated opening through which it is observed whether there is flow of said powder. By successive tests, the minimum diameter through which this powder flows freely is determined. This diameter (in millimeters) corresponds to the Flodex index.

Dispersion in a polymer

In a roller mixer, a compound based on natural rubber is first heated for 2 minutes, then simultaneously introduced the zinc oxide compound according to the invention and having the characteristics of Table 1 and stearic acid. Mixing is continued for 5 minutes during which the other ingredients listed in Table 2 will be added.

The constituents and quantities used were as follows:

With TSR10 = technically Specified Rubbers (TSR) (Natural rubber),

BR 1220L = High Cis Polybutadiene Rubber,

N347 = Carbon black N347,

S Napht oil = Naphthenic oil,

6ppd = N- (1, 3-Dimethylbutyl) -N'-phenyl-p-phenylenediamine (antioxidant and antiozonant),

TMQ = 2,2,4-Trimethyl-1, 2-Dihydroquinoline polymer

(antioxidant).

• CBS = N-Cyclohexyl-2-benzothiazole sulfonamide (accelerator).

The dispersion obtained had a very great homogeneity. Dispersion homogeneity means uniform zinc density in the final mixture. In the case of vulcanization, this results in rheological control curves which are very close or being superimposed or quasi-superimposed.

The dispersion obtained is checked on an MDR2000 rheometer at 150 ° C. according to the method ASTM D2084 - 17 Standard Test Method for Rubber Property - Vulcanization Using Oscillating Disk Cure Meter. Rheology measurements under identical conditions were carried out on dispersions obtained according to the method of "Example 1". The three measurements are shown in Figure 2 and represent the torque S ’(dNm) measured as a function of time (in minutes). The rheology curves are very close to each other, which shows that with each measurement identical or very similar properties. The composition (C) of an oxygenated zinc compound according to the invention can therefore be easily dispersed in polymeric materials, making it possible to obtain a dispersion homogeneity which is improved.

Comparative example 1

In a roller mixer, a natural rubber compound is first heated for 2 minutes, then are simultaneously introduced the zinc oxide compound having a conductivity measured according to the conductivity measurement method greater than 3000 pS / cm and stearic acid. Mixing is continued for 5 minutes during which the other ingredients listed in Table 2 will be added.

The constituents and quantities used were as follows:

The dispersion obtained had a very low homogeneity, which results in rheological control curves which are very distant from each other.

The dispersion obtained is checked on an MDR2000 rheometer at 150 ° C. according to the "ASTM D2084 - 17 Standard Test Method for Rubber Property - Vulcanization Using Oscillating Disk Cure Meter" method. Rheology measurements under identical conditions were carried out on dispersions obtained according to the method of “Comparative Example 1”. The three measurements are shown in figure 3 and represent the torque S '(dNm) measured as a function of time (in minutes). The rheology curves are very distant from each other, which shows that each measurement different properties are obtained. This is the result of a fairly low homogeneity.

Claims

1. Process for preparing a composition (C) of microspherules of an oxygenated zinc compound, comprising the steps:

c) obtaining said composition (C) of microspherules of an oxygenated zinc compound from said precipitate (PR); said microspherules being particles each consisting of smaller aggregated particles.

2. The method of claim 1, wherein the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) is adjusted until a conductivity is obtained measured according to the conductivity measurement method of less than 2500 pS / cm.

3. Method according to any one of the preceding claims, wherein the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) is adjusted until a conductivity is obtained measured according to the method of measurement of conductivity less than 2000 pS / cm.

4. Method according to any one of the preceding claims, wherein the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) is adjusted until a conductivity is obtained measured according to the method of measurement of conductivity less than 1500 pS / cm.

5. Method according to any one of the preceding claims, wherein the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) is adjusted up to obtaining a conductivity measured by the conductivity measurement method of less than 1000 pS / cm.

6. Method according to any one of the preceding claims, wherein the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) is adjusted until a conductivity is obtained measured according to the method of measurement of conductivity less than 700 pS / cm.

7. Method according to any one of the preceding claims, wherein the conductivity of said precipitate (PR) of said oxygenated zinc compound obtained in step a) is adjusted until a conductivity is obtained measured according to the method of measurement of conductivity greater than 400 pS / cm.

8. A method according to any preceding claim, wherein said precipitate (PR) provided in said step a) comprises at least one inorganic salt.

9. The method of claim 8, wherein said at least one inorganic salt is selected from the group consisting of nitrate salts, chloride salts, sulfate salts, hydrosulfite salts, hydrogen sulfate salts, sulfite salts, hydrogen sulfite salts, thiosulfate salts and mixtures thereof.

10. A method according to any one of the preceding claims, in said step b) of adjusting the conductivity of said precipitate (PR) is carried out by washing, dialysis, or by a centrifugation or filtration process or a combination of these techniques.

1 1. A method according to any preceding claim, wherein said step a) of providing a precipitate (PR) of an oxygenated zinc compound comprises a method of precipitation in a solvent, preferably in water.

12. The method of claim 11, wherein said precipitation process comprises a step a1) of reaction between a zinc compound, preferably a zinc compound selected from the group consisting of ZnS2C> 4, Zn (N03) 2, ZnCl2, ZnSCP and their mixtures and at least one inorganic base.

13. The method of claim 12, wherein said at least one inorganic base comprises at least one alkali or alkaline earth cation M chosen from the group consisting of Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , Mg ²⁺ and combinations thereof and at least one anion A selected from the group consisting of O ² , OH, CO3 ² , HCO3 and combinations thereof.

14. A method according to any one of the preceding claims, wherein said step of obtaining said composition (C) of microspherules of an oxygenated zinc compound may comprise a step c1) of drying and / or calcining said precipitate ( PR) of oxygenated zinc compound.

15. The method of claim 14, wherein said step c1) of drying and / or calcination is carried out by:

• an atomization process or

• heating in a rotary kiln or

filtration by forming a filter cake with said precipitate (PR) of an oxygenated zinc compound and by sucking said filter cake in a stream of hot air, preferably a stream of hot air at a temperature between 20 ° C and 100 ° C, even more preferably between 30 ° C and 70 ° C.

16. Composition (C) of microspherules of an oxygenated zinc compound exhibiting a conductivity measured by the conductivity measurement method of less than 3000 pS / cm; said microspherules being particles each consisting of smaller aggregated particles.

17. Composition (C) according to claim 16, exhibiting a conductivity measured according to the conductivity measurement method of less than 2500 pS / cm.

18. Composition (C) according to claim 16 or claim 17, having a conductivity measured according to the conductivity measurement method of less than 2000 pS / cm.

19. Composition (C) according to any one of claims 16 to 18, exhibiting a conductivity measured by the conductivity measurement method of less than 1500 pS / cm.

20. Composition (C) according to any one of claims 16 to 19, exhibiting a conductivity measured by the conductivity measurement method of less than 1000 pS / cm.

21. Composition (C) according to any one of claims 16 to 20, having a conductivity measured by the conductivity measurement method of less than 700 pS / cm.

22. Composition (C) according to any one of claims 16 to 21, having a conductivity measured according to the conductivity measurement method greater than 100 pS / cm, preferably greater than 200 pS / cm, more preferably greater than. at 300 pS / cm, more preferably greater than 400 pS / cm.

23. Composition (C) according to any one of claims 16 to 22, exhibiting a conductivity measured by the conductivity measurement method of greater than 100 pS / cm.

24. Composition (C) according to any one of claims 16 to 23, comprising at least one inorganic salt.

25. Composition (C) according to claim 24, wherein said at least one inorganic salt is selected from the group consisting of nitrate salts, chloride salts, sulfate salts, hydrosulfite salts, hydrogen sulfate salts. , sulfite salts, hydrogen sulfite salts, thiosulfate salts and mixtures thereof.

26. Composition (C) according to any one of claims 16 to 25, comprising said at least one inorganic salt in a concentration of less than 2.95%, in particular less than 2.4%, in in particular less than 1. 85%, in particular less than 1.3%, more particularly less than 0.75%, even more particularly less than 0.42% by weight, relative to the total weight of said composition (VS).

27. Composition (C) according to any one of claims 16 to 26, wherein said microspherules have a D50 measured by laser particle size distribution in aqueous solution of between 50 μm and 200 μm, preferably between 80 and 170 μm.

28. Composition (C) according to any one of claims 16 to 27, wherein said microspherules have a D-io measured by laser particle size distribution in aqueous solution of between 1 µm and 80 µm, preferably between 8 and 70 µm.

29. Composition (C) according to any one of claims 16 to 28, said microspherules have a D90 measured by laser particle size distribution in aqueous solution of between 200 μm and 300 μm, preferably between 210 and 260 μm.

30. Composition (C) according to any one of claims 16 to 29, wherein said microspherules each consist of aggregated particles each having an D50 of between 1 and 20 µm, more preferably between 1 and 10 µm, so even more preferably between 1 and 5 µm or even between 1 and 3 µm.

31. Composition (C) according to any one of claims 16 to 30, in which said microspherules have a BET specific surface area of less than 150 m ² / g, advantageously less than 100 m ² / g, and preferably less than 50 m ² / g.

32. Composition (C) according to any one of claims 16 to 31, obtained by said process according to any one of claims 1 to 15.

33. Use of a composition (C) according to any one of claims 16 to 31 or of a composition obtained by the process according to any one of claims 1 to 15, in a vulcanization process.

34. Use of a composition (C) according to any one of claims 16 to 31 or of a composition obtained by the process according to any one of claims 1 to 15, in a material chosen from the group consisting of compositions nutrients, polymeric materials, and mixtures thereof.