BR102017004434A2 - tannin derivative for use as a coagulant in the treatment of water and aqueous effluents, coagulant mixture, and process for preparing tannin derivative for use as a coagulant in the treatment of water and aqueous effluents. - Google Patents

Abstract

The present invention relates to a tannin derivative for use as a coagulant in the treatment of water and aqueous effluents, providing a product with a tannin content of at least 65% on a dry basis and free formaldehyde content below 1000 ppm. coagulant and the process for preparing the tannin derivative.

Description

(54) Title: TANIN DERIVATIVE FOR USE AS COAGULANT IN THE TREATMENT OF WATER AND WATER EFFLUENTS, COAGULANT MIXTURE, AND, PROCESS FOR THE PREPARATION OF TANIN DERIVATIVE FOR USE AS COAGULANT IN THE TREATMENT OF WATER EFFLUENT WATERS.

(51) Int. Cl .: C02F 1/54; B01D 21/01 (57) Abstract: The present invention relates to a tannin derivative for use as a coagulant in the treatment of water and aqueous effluents, providing a product with a tannin content of at least 65% on a dry basis and formaldehyde content free below 1000 ppm, to a coagulant mixture and to the process to prepare the tannin derivative.

(73) Holder (s): TANAC S.A.

(72) Inventor (s): ANDRÉ FRIDERICHS; CÉSAR AUGUSTO SEVERO RODRIGUES; CARLOS RODOLFO WOLF; OTÁVIO GUIMARÃES DECUSATI (85) Date of the Beginning of the National Phase:

3/6/2017

1/16 “TANIN DERIVATIVE FOR USE AS COAGULANT IN THE TREATMENT OF WATER AND WATER EFFLUENTS, COAGULANT MIXTURE, AND, PROCESS FOR THE PREPARATION OF TANIN DERIVATIVE FOR USE AS COAGULANT IN THE TREATMENT OF WATER AND WATER EFFLUENTS”

FIELD OF APPLICATION [001] The present invention relates to a tannin derivative for use as a coagulant in the treatment of water and aqueous effluents and in coagulant mixtures and their preparation process.

BACKGROUND OF THE INVENTION [002] Conventional cationic flocculants derived from tannins are known to be effective in removing colloids and / or particles suspended in water and aqueous effluents, in addition to forming relatively more concentrated iodines. However, liquid products of this type synthesized via Mannich's aminomethylation reaction have a free formaldehyde content, expressed on a dry basis, greater than 2000 ppm.

[003] Although in the European Community, in the context of

REACH Regulation, formaldehyde is not yet considered as a restricted substance classified as SVHC (substances of very high concerri), products containing formaldehyde or capable of emitting formaldehyde are subject to special controls and specific labeling. Thus, coagulants / flocculants containing reduced content of free formaldehyde are highly desirable.

[004] The formaldehyde content can be reduced in part by improving the conversion of the reactants, employing more energetic reaction conditions, but the stability of the coagulants, both during synthesis and / or in storage, ends up being compromised. Alternatively, the formaldehyde content of an aqueous solution of a cationic polymer can be reduced by converting the product to a powder, in a process called

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2/16 atomization, in a spray dryer. However, the reduction is not sufficient to guarantee a dry powder formaldehyde content of less than 1000 ppm.

[005] Attempts to obtain, via Mannich reaction, cationic products derived from tannin and free of formaldehyde, using amines and monoaldehydes alternative to formaldehyde, such as acetaldehyde, usually result in products with low water solubility, with a tendency to phase separation already in the reactor itself, most likely due to the lower reactivity of the aldehydes. Increasing the amine content to improve solubility requires a greater load of aldehydes in the formula, which ends up generating products with high levels of aldehydes and free amines.

[006] The alternative employing glyoxal, as dialdehyde, comes up against its strong tendency to form cyclic by-products (imidazoles) in contact with amines, even in the presence of tannin. This imposes limits on the molecular weight of the product and compromises its efficiency as a flocculant for the reduction of particles and clarification of water and effluents.

[007] Formaldehyde-free, stable and high molecular weight products prepared by tannin reaction with cationic unsaturated monomers can be efficient, but the tannin content in the compositions, expressed on dry basis, does not exceed 50%. The preparation process is usually very long, lasting more than 24 hours, which, associated with the high levels of cationic monomers, greatly increases the cost of the formula. [008] US 4,558,080 describes a process for obtaining a stable flocculant based on tannin prepared by polymerization, via Mannich reaction, of tannin, formaldehyde and an amine, such as monoethanolamine, with strict monitoring of viscosity, in order to ensure that the product has stability for at least 3 months at room temperature. Although it is not clearly mentioned in the report, products prepared according to the teachings of this patent document

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3/16 have relatively high free formaldehyde content, above 2000 ppm on a dry basis.

[009] The documents US 5,643,462, US 5,684,109 and US 5,916,991 describe water-soluble compositions, capable of removing color and turbidity from water, based on products of radical reaction between tannin and aminofunctional monomers, especially salt quaternary methyl chloride and dimethylaminoethyl acrylate (AETAC). The compositions are free of aldehydes, however the preparation process is relatively complex and very time consuming. The raw material cost of the formulas, which contain at least 50% of aminofunctional acrylic monomer, is quite high.

[0010] US patent 6,478,986 describes a quaternary ammonium tannate used as a coagulant or flocculant in water treatment, obtained by the Mannich reaction between tannin, a mixture of primary and secondary amines and formaldehyde, catalyzed by a strong mineral acid. The product presents stability to the environment for more than 6 months, but the residual formaldehyde content exceeds 2000 ppm on a dry basis.

[0011] The patent document US 2008/0135492 presents a coagulant based on tannin, glyoxal and dimethylaminopropylamine used in levels of 5 to 50 ppm for treatment of industrial effluents contaminated with oils. The preparation is done, preferably, by reaction of aqueous condensed tannin extract, a dialdehyde, preferably glyoxal, and a diamine, preferably dimethylamino propylamine. The synthesis is carried out in an acid medium with the addition of hydrochloric acid. The final product is free of formaldehyde, however the flakes formed in an aqueous medium are very thin and the ability to clarify waters containing higher levels of suspended solids is limited. The product contains low tannin content and the cost of raw material is quite high.

[0012] US patent 7,998,351 discloses a coagulant for aqueous effluents contaminated with oil based on reaction products of

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4/16 tannins and unsaturated monomers. Dimethylaminoethyl methacrylate (MADAME), reacted as a hydrochloride, and 2-methacryloxyethyltrimethylammonium chloride are mentioned. The tannin used is preferably a condensed tannin. The product is free of formaldehyde, but the tannin content is relatively low, not exceeding 40% of solids, which makes the cost of raw material quite high.

[0013] German patent DE 42 19 343 describes a reaction product of tannin and formaldehyde with cationizing agents, such as trimethylglycidylammonium chloride (GTAC), used as a flocculant for water treatment. The preparation process is quite long and the cationizing agent, of high cost, constitutes at least 50% of the solids weight. In the document, it is emphasized that tannin derivatives with high molecular weight have a greater flocculation efficiency. The aminomethylation of tannins with formaldehyde and dimethylamine as an alternative to obtain cationic flocculants is mentioned briefly in the text, without providing further details.

[0014] Cationic polymers of high molecular weight, exemplified by polyamines prepared by reaction of epichloridine and primary and / or secondary amines, such as ethylenediamine and dimethylamine, and by polymerization products of diallyldimethylammonium chloride (DADMAC) and their combinations with other unsaturated monomers , present high efficiency as flocculants. However, the products are not very efficient to eliminate color in effluents with a high content of suspended solids. Polyamines are typified, for example, by US 3,738,945, US 3,975,347, US 4,054,542 and EP 2 463 324, while poly (DADMAC) and its copolymers are prepared as described in US 4,673,511, US 4,715,962, US 5,207,924 and US 5,750,781, among others.

[0015] The Chinese patent document CN 104311812 describes the preparation of a coagulant through the reaction of vegetable tannin,

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5/16 formaldehyde, dimethylamine and epichlorohydrin, in solvent using dimethylformamide. At the end of the process, it is necessary to apply a vacuum to remove dimethylformamide, a restricted substance classified as SVHC in the context of the European Union's REACH Regulation.

[0016] Thus, the technique still needs a method to prepare coagulants that have high water solubility and very good storage stability as an aqueous solution, with the tannin content over the high product solid fraction and reduced free formaldehyde content. SUMMARY OF THE INVENTION [0017] The present invention relates to a tannin derivative, with a high tannin content and reduced free formaldehyde content, for use as a coagulant in the treatment of water and aqueous effluents, to a coagulant mixture using the tannin derivative and to a process that allows to prepare the tannin derivative, quickly and at a lower cost. DETAILED DESCRIPTION OF THE INVENTION [0018] Tannin derivatives for use as aqueous coagulants prepared according to the process described in the present invention are distinguished by their high water solubility and high efficiency in the removal of suspended materials in the treatment of water and aqueous effluents. The coagulant efficiency of the new products prepared according to the invention can be optimized by combining them with cationic polymers of high molecular mass, such as polyamine derivatives obtained from epichloridine and amines and homo- or copolymers of DADMAC, in a wide range, covered by proportions from 10: 1 to 1:10.

[0019] The high coagulant / flocculant efficiency of the product of the invention is obtained thanks to a two-step process for reaction between tannin, amine compounds, primary and / or secondary amines or their respective salts, and formaldehyde. The sequenced process guarantees the fixation of the amino functionality, allows an adequate control of the molecular mass and

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6/16 ensures an almost complete conversion of formaldehyde. The final product has high molecular weight, good storage stability, can be atomized to a powder without forming agglomerates, and still has free formaldehyde content below 1000 ppm on dry basis, typically below 500 ppm.

[0020] According to the process described in the present invention, the total polymerization process time does not exceed 8 hours, which contributes to a relatively low process cost compared to alternative tannin cationization processes, which can last up to 24 hours.

[0021] Tannin derivatives for use as coagulants prepared according to the invention have high solubility in water and very good storage stability as an aqueous solution, which is particularly surprising, since the tannin content on the solid fraction of the tannin derivative is quite high, ranging between 65% and 80%. The particularly high content of tannin contributes to a lower raw material cost and accentuates the environmentally friendly character of the final product.

[0022] Another advantage of the invention is the possibility of reducing the chloride content in relation to usual products on the market, exemplified by materials prepared according to US patents 4,558,080 and US 6,478,986. [0023] In the process described in the present invention, condensed tannins present, among others, in acacia, quebracho and eucalyptus are used. Condensed tannins include 70 to 80% of active polyphenolic compounds, the remainder being a mixture of carbohydrates, gums and fractions of amino and / or imino acids.

[0024] Condensed tannins can be classified into two categories: those that contain mostly resorcinol units, exemplified by the acacia and quebracho tannins, and those that contain mostly floroglucinol units, more reactive, represented by the eucalyptus and pecan tannins . The structures of the flavonoid unit of

Petition 870170014300, dated 03/06/2017, p. 16/30 / 16 condensed tannin are shown below.

[0025] Preferably tannin derived from black wattle is used, both in the form of an aqueous extract with solids in the range of 42-52%, and in the form of powder, obtained by drying the aqueous extract in a spray dryer. The equivalent weight of the black wattle tannin repetitive unit is approximately 300g.

[0026] The second ingredient used in the reaction is an aldehyde.

Preferably, formaldehyde is used in the form of an aqueous solution, varying between 20 and 55% of active, preferably with 37% of active, stabilized with contents of 2 to 12% of methanol. Other equally usable forms of formaldehyde comprise paraformaldehyde supplied with formaldehyde contents between 90 and 96%. If paraformaldehyde is used, attention must be paid to the complete depolymerization of the material before mixing and reacting with the tannin.

[0027] The third ingredient used in the reaction is an amino compound capable of reacting with aldehydes. The amino compound can be an aliphatic monoamine, such as monomethylamine, dimethylamine, diethylamine, monoethanolamine, monomethylethanolamine, diethanolamine and / or their respective inorganic salts, an aliphatic monoamine with amino groups

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8/16 tertiary, such as dimethylamino propylamine, and / or their respective hydrochlorides, an aliphatic diamine, such as ethylene diamine, aminoethylethanolamine, a cycloaliphatic diamine, such as piperazine, a cycloaliphatic diamine with secondary amino group, such as aminoethylpiperazine, and polyamines more functional, such as tris (2-aminoethyl) amine.

[0028] Combinations of the different types of amine are also usable. The preferred materials are dimethylamine and its hydrochloride, which have high reactivity with formaldehyde, contributing to the reduction of the free formaldehyde content, and which due to its monofunctional character, allow an easier control of the development of the molecular mass of the product during the process. Dimethylaminopropylamine, which gives a high cationic character, is also very useful for the purposes of the invention.

[0029] The three ingredients are combined in such proportions that the process can be carried out safely, without risk of gelatination or the formation of insoluble fractions, resulting in a product that has a high molecular mass, high solubility in water and has a charge enough cationic to function as a coagulant or flocculant.

[0030] Within the scope of the present invention, these requirements of the tannin derivative are met when for each repetitive unit of the tannin 0.7 to 2.0 mol of amine compound and an amount of aldehyde sufficient for the molar relationship between aldehyde and amine compound remains in the range of 0.75: 1 to 1.40: 1.

[0031] While lower levels of amine compounds are associated with unsatisfactory solubility in water, higher levels of amine compounds imply a reduction in the tannin content and increase the hydrophilicity of the product, which manifests itself in the formation of very small flakes in the final application. If the molar ratio of formaldehyde to the amine compound is less than 0.75: 1, it is not possible to obtain a

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9/16 adequate molecular weight. A molar excess of formaldehyde greater than 40% makes the process less stable and leads to end products with free formaldehyde contents greater than 1000 ppm.

[0032] A fourth ingredient that influences the reaction speed of the three ingredients and the final characteristics of the product is the acid used to neutralize the amine compound and to adjust the pH of the reaction mixture and, eventually, the final product. When commercial salts, usually hydrochlorides, of the amine compounds defined in the invention are used, the acidic component is used only when necessary to adjust the pH of the mixture and adjust the pH of the final product. In this case, inorganic acids, such as hydrochloric acid and sulfuric acid, or organic acids such as formic, acetic or lactic acids or mixtures thereof, are used. Preferably hydrochloric or sulfuric acid, or a mixture of both, is used. If non-neutralized amine compounds are used, it is necessary to add an extra amount of acids to neutralize the amine and adjust the pH of the reaction mixture, in order to avoid precipitation of the tannin. In this case, inorganic acids are also preferred, preferably hydrochloric, sulfuric acids or a mixture of both. The use of sulfuric acid to neutralize the amine compound and to adjust the pH is particularly interesting to reduce the chloride content. Chloride-free or low-chloride coagulants are desirable as they do not significantly contribute to the increase in the conductivity of water or treated effluent and are less corrosive to metals.

[0033] The process of preparing the tannin derivative can be conducted in different ways, depending on the type of amine compound used.

[0034] The present invention deals with a process of preparing a tannin derivative for use as a coagulant in the treatment of water and

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10/16 effluents reacting, in aqueous medium, via Mannich reaction, a condensed tannin extract, particularly black wattle, formaldehyde and one or more aliphatic amines or their inorganic salts, preferably dimethylamine hydrochloride and / or dimethylaminopropylamine. Preferably, the reaction is conducted at temperatures between 30 and 90 ° C, working at atmospheric pressure, with pH of the reaction medium in the range 3 to 6, reacting, for each structural unit of tannin, 0.7 to 2.0 mol of amines and / or its hydrochlorides and, in relation to amino compounds, an amount of formaldehyde approximately equimolar. Usually, for each mole of amine, 0.75 to 1.40 moles of formaldehyde are used. In order to obtain a product with high molecular weight, good process and storage stability, preferably the reaction between tannin, formaldehyde and amine compounds (amine or mixture of amines and / or their respective salts) is carried out in two stages. The first stage is carried out at low temperature, between 30-55 ° C for a period of 30 minutes to 2 hours, and serves to fix the amino function to the tannin. After this operation is completed, the reaction mixture is heated to a temperature between 60 and 90 ° C and maintained for 1 to 6 hours for further reaction, with viscosity monitoring, for reaction between the excess formaldehyde and the tannin. The total process time, operating under the stoichiometries and conditions described, is relatively short, not exceeding 8 hours.

[0035] The sequencing of the process in two distinct reaction steps contributes to obtaining a conversion of formaldehyde greater than 99%, resulting in a stable product, of high molecular mass and with a content of free formaldehyde, expressed on a dry basis, lower at 1000 ppm, typically less than 500 ppm.

[0036] The obtained tannin derivative, which contains at least 65% and a maximum of 80% tannin on a dry basis, has a high capacity for clarifying water containing suspended particulate materials.

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11/16 [0037] The tannin derivative is highly compatible with cationic polyelectrolytes, such as polyamines and DADMAC homo- or copolymers, mentioned above, which can be combined with them in various proportions, forming a coagulant mixture, aiming at synergy of performance and / or cost reduction in specific applications.

[0038] Compatibility with inorganic salts, such as aluminum chloride or sulfate, polyaluminium chloride (PAC) typically used in water and wastewater treatment is limited. However, combinations of 100 parts of the tannin derivative of the present invention with up to 25% inorganic salts are still stable as a solution and can be used as coagulant mixtures for different types of effluents.

[0039] In a preferred process, starting from an aqueous solution of dimethylamine not neutralized with acids, the first step consists of the preparation of the amine salt with acid, particularly inorganic acids. For this purpose, an aqueous solution of the amine is diluted with an extra amount of water and then neutralized by slowly adding an amount of acid, maintaining a temperature below 60 ° C, sufficient to reach a pH in the range of 1.5 to 4.5.

[0040] In the second reaction step, the intermediate thus prepared is loaded into a reactor together with aqueous extract of tannin, and eventually an extra amount of deionized water, properly mixed and heated to 45-50 ° C. At this temperature, the aqueous formaldehyde solution is added and the exotherm is controlled so that the temperature does not exceed 55 ° C, maintaining for 1 hour. The mixture is heated to 80-85 ° C and maintained for up to 6 hours until a product totally soluble in water with viscosity is obtained, measured in the Zahn 1 cup, greater than 65 seconds, considering a solids content of 40%. The reaction mixture is cooled and, eventually, its pH is adjusted to a range of 1.5-4.0, by adding an extra amount of acid.

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12/16 [0041] In another process alternative, starting from a commercial amine already in the form of salt, usually hydrochloride, the initial charge consists of a mixture of the amine salt, deionized water and aqueous tannin extract. Once stirred and properly homogenized, the mixture is heated to 4550 ° C, when the aqueous formaldehyde solution is added. From this point on, the process is carried out as described in the previous paragraph, keeping the load for 1 hour at 50-55 ° C and heating to 80-85 ° C with the same controls and final adjustments as the previous process.

[0042] In a third version of the preparation process, adopted when the tannin derivative or coagulant mixture is subjected to drying in a spray dryer for supply in powder form, it operates in the same manner as described in the previous paragraphs, but at the end the reaction is not diluted with water. The material thus obtained has a higher solids content and a higher viscosity, making it more suitable for drying in the spray dryer.

[0043] The invention is best illustrated from the following examples.

Example 1: Preparation of dimethylamine hydrochloride [0044] In a 100 liter vitrified reactor with mechanical stirring, total condenser and equipped with a cooling system, 20 kg of deionized water and 20 kg of 60% dimethylamine in water are loaded. The mixture is well homogenized, slowly add about 25 kg of 37% hydrochloric acid, until the pH of the solution reaches the value of 2.5. During the entire addition of the acid, the process exotherm is controlled by turning on the cooling, so that the temperature does not exceed 60 ° C.

Example 2 [0045] In a 100 liter vitrified reactor with mechanical agitation, total condenser and equipped with a cooling system, 16 kg of the material prepared in Example 1 and 32 kg of aqueous extract of acacia tannin are loaded, 50% of solids. The mixture is heated to 48 ° C and then added

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13/16

4.3 kg of 37% formalin and the temperature is allowed to rise by exotherm to 53-55 ° C. The mixture is kept at 50-55 ° C for 1 hour. After this period, the mixture is heated to 80 ° C. When this temperature is reached, a viscosity sample is taken in the Zahn No. 1 cup and the water solubility is tested. At this point in the process, water solubility is still limited and the viscosity, measured at 80 ° C, is below 50 seconds. The process is continued at 80 ° C with sampling every hour until a product completely soluble in water with Zahn 1 viscosity above 65 seconds is obtained. The cooling is activated and 25 kg of deionized water are added. When the temperature reaches below 50 ° C, the product is discharged. The material has solids of 28.0%, 70% of which on the dry basis are tannins, pH 3.5, Ford N ° 4 viscosity at 25 ° C for 15 seconds and formaldehyde content, determined by spectroscopy of fluorescence using the acetylacetone method, 48 ppm expressed on solution.

Example 3 [0046] Using the same procedures and weighings as Example 2, after dilution with water and the temperature reaches about 50 ° C, 500 g of 37% hydrochloric acid are added to the product, in order to put the pH in the range from 1.5 to 2.3. When the temperature reaches less than 40 ° C, the product is discharged. The material has solids of 28.0%, of which 69% on the dry basis are tannins, pH 1.8, Ford N ° 4 viscosity at 25 ° C for 13 seconds and formaldehyde content of 46 ppm in solution .

Example 4 [0047] A product prepared using the same process and weighing as Example 2, but without the final dilution with water, is acidified at 50 ° C with 500 g of 37% hydrochloric acid, placing the pH in the range of 1.5 to 2.3. When the temperature reaches less than 40 ° C, the liquid obtained is sent to a spray dryer, where it is converted to a powder with a moisture content in the range of 4.5 to 6.5% and a free formaldehyde content of 50 ppm.

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14/16

Example 5 [0048] In a 100 liter vitrified reactor with mechanical agitation, total condenser and equipped with a cooling system, 3.5 kg of solid dimethylamine hydrochloride and 32 kg of aqueous 50% acacia tannin are loaded of solids. The mixture is heated to 48 ° C and 4.7 kg of 37% formalin is added and the temperature is allowed to rise by exotherm to 5355 ° C. The mixture is kept at 50-55 ° C for 1 hour. After this period, the mixture is heated to 80 ° C. When this temperature is reached, a viscosity sample is taken in the Zahn No. 1 cup and the water solubility is tested. If at this point in the process the water solubility is still limited and the viscosity, measured at 80 ° C, is below 50 seconds, then the process is continued at 80 ° C with sampling every 30 minutes until a fully soluble product is obtained in water with Zahn 1 viscosity above 65 seconds. Then, the cooling is activated and 36 kg of deionized water are added. After dilution with water and the temperature around 50 ° C, 500 g of 37% hydrochloric acid are added to the product, in order to put the pH in the range of 1.5 to 2.3. When the temperature reaches below 50 ° C, the product is discharged. The material has solids of 28.0%, 75% of which on the dry basis are tannins, pH 1.8, Ford N ° 4 viscosity at 25 ° C for 16 seconds. The free formaldehyde content of the powdered product, atomized in a spray dryer, is 440 ppm.

Example 6 [0049] In a 100 liter vitrified reactor with mechanical agitation, total condenser and equipped with a cooling system, 16 kg of the material prepared in Example 1 and 26 kg of aqueous extract of acacia tannin at 50% solids are loaded. . The mixture is heated to 48 ° C and 5.0 kg of 37% formalin is added and the temperature is allowed to rise by exotherm to 53-55 ° C. The mixture is kept at 50-55 ° C for 1 hour. After this period, the mixture is heated to 80 ° C. Once the temperature is reached, a sample is taken to

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15/16 viscosity in Zahn No. 1 cup and water solubility is tested. If at this point in the process the water solubility is still limited and the viscosity measured at 80 ° C, below 50 seconds, then the process is continued at 80 ° C with sampling every hour until a product that is totally soluble in water is obtained with Zahn 1 viscosity above 65 seconds. Cooling is started and 25 kg of deionized water are added. When the temperature reaches below 50 ° C, the product is discharged. The material has solids of 28.0%, 65% of which on the dry basis are tannins, pH 3.5, Ford N ° 4 viscosity at 25 ° C for 12 seconds and a free formaldehyde content of 177 ppm on solution.

Example 7: Mixing 100 parts of tannin derivative with 18 parts of a polyamine [0050] In a 100 liter vitrified reactor with mechanical stirring, total condenser and equipped with a cooling system, 16 kg of the material prepared in Example 2 are loaded and 4 kg of a polyamine, reaction product of epichlorohydrin, dimethylamine and ethylene diamine, at 20% solids in water. The mixture is kept under stirring for one hour at room temperature. The product is discharged after complete mixing. The coagulant mixture has solids of 26.5%, pH of 3.5, viscosity Ford No. 4 at 25 ° C for 14 seconds and free formaldehyde content of 40 ppm in solution.

Example 8: Mixture of tannin derivative with aluminum sulfate [0051] In a 100 liter vitrified reactor with mechanical stirring, total condenser and equipped with a cooling system, 16 kg of the material prepared in Example 2 and 6.4 are loaded kg of water. Then, 2.24 kg of aluminum sulphate containing at least 8.0% aluminum oxide are added. The mixture is kept under stirring for one hour at room temperature and then 0.5 kg of 85% formic acid is added. The product is discharged after complete mixing. The coagulant mixture has 22.5% solids, pH 1.7, Ford No. 4 cup viscosity at 25 ° C

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16/16 seconds and free formaldehyde content of 35 ppm in solution.

Example 9: Comparative following example 1 of US 4,558,080 [0052] 130.8 g of deionized water is loaded into a reactor and heated to 65 ° C. 125.8 g of tannin dry extract are gradually added with stirring, maintaining a temperature between 54-60 ° C. When the powder is completely dissolved, cool to 43 ° C. Then, 47.7 g of monoethanolamine are added, with good stirring, allowing the temperature to rise to 54 ° C. Add 77.6g of 33% hydrochloric acid, in order to adjust the pH to the range of 6.4-6.7, making sure the temperature does not exceed 60 ° C. Afterwards, cool the mixture to 49 ° C and add 62.7 g of 37% formaldehyde, maintaining a temperature in the range of 50 to 55 ° C. Heat gradually and maintain the temperature around 80-82 ° C, taking samples from the viscosity until a value of 38-40 cps is reached. Cool quickly, dilute with 45.2 g of deionized water and adjust the pH to 2.4 with about 7.8 g of 33% hydrochloric acid. The content of free formaldehyde in the product is 3,125 ppm in solution.

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Claims (20)

1. Tannin derivative for use as a coagulant in the treatment of water and aqueous effluents, characterized by the fact that it comprises: 65% to 80% tannin on the dry basis; less than 1000 ppm of a free aldehyde; viscosity measured by Ford No. 4 cup viscometer of less than 20 seconds, with solids content between 22 and 28%; and pH in the range of 1.5 to 4. 2. Tannin derivative according to claim 1, characterized by the fact that it comprises less than 500 ppm of free aldehyde. 3. Tannin derivative according to claim 1 or 2, characterized by the fact that the aldehyde is formaldehyde. 4. Tannin derivative according to claim 1, characterized by the fact that the tannin is derived from Acacia (black wattle). 5. Tannin derivative according to any one of claims 1 to 4, characterized in that it is presented in powder form. 6. Coagulant mixture, characterized by the fact that 100 parts of the tannin derivative as defined in any one of claims 1 to 5 are combined with: a) up to 100 parts, on solids, of a cationic polymer; or b) up to 25 parts, on solids, of an inorganic salt. 7. Coagulant mixture according to claim 6, characterized by the fact that the cationic polymer is a polyamine derived from epichlorohydrin. 8. Coagulant mixture according to claim 6, characterized by the fact that the cationic polymer is a polymer of diallyldimethylammonium chloride (DADMAC). 9. Coagulant mixture according to claim 6, Petition 870170014300, dated 03/06/2017, p. 27/30 2/3 characterized by the fact that the inorganic salt is an aluminum sulfate, aluminum chloride or polyaluminium chloride (PAC). Coagulant mixture according to any one of claims 6 to 9, characterized in that it is in powder form. 11. Process for the preparation of tannin derivatives for use as a coagulant in the treatment of water and aqueous effluents as defined in any one of claims 1 to 5, characterized by the fact that a tannin and an amine compound in a proportion of 0.7 to 2, The mole of amine compound for each structural unit of tannin is reacted with an amount of aldehyde in a proportion of 0.75 to 1.40 mole of aldehyde for each mole of amine compound, in two consecutive steps, namely: a) at low temperature, between 30 and 55 ° C, for a period of 30 minutes to 2 hours; followed by b) heating to a temperature between 60 and 90 ° C and additional reaction for 1 to 6 hours. 12. Process according to claim 11, characterized by the fact that the tannin used is derived from Acacia (black wattle). 13. Process according to claim 12, characterized by the fact that the tannin used is derived from black wattle with solids in the range of 42 to 52%. 14. Process according to claim 11, characterized by the fact that the aldehyde used is formaldehyde ranging from 20 to 55% active. Process according to claim 11, characterized by the fact that the amino compounds employed are aliphatic monoamines and / or an aliphatic monoamines with tertiary amino groups. 16. Process according to claim 15, characterized by the fact that the amino compounds are dimethylamine, monomethylamine, monomethylethanolamine, dimethylaminopropylamine. Petition 870170014300, dated 03/06/2017, p. 28/30 3/3 17. Process according to claim 15 or 16, characterized by the fact that inorganic acid is added to neutralize the amines, preferably hydrochloric, sulfuric acids or a mixture of both. 18. Process according to claim 11, characterized in that the amine compound is an amine compound salt, preferably hydrochloride. 19. Process according to any one of claims 11 to 18, characterized by the fact that acid is added to the final product for pH adjustment. 20. Process according to claim 19, characterized in that the added acid is hydrochloric acid, sulfuric acid, formic acid, acetic acid or lactic acid, or a mixture of these acids. Petition 870170014300, dated 03/06/2017, p. 29/30 1/1