Use of an additive in the production of copper(II) hydroxide phosphate

Abstract

The invention relates to a process for producing copper(II) hydroxide phosphate from a copper(II) compound and phosphoric acid, to a copper(II) hydroxide phosphate obtainable by this process and to the use of an additive in the production of copper(II) hydroxide phosphate.

Description

[0001] Use of an additive in the production of copper(II) hydroxide phosphate

[0002] SUBJECT OF THE INVENTION

[0003] The invention relates to a process for producing copper(II) hydroxide phosphate by adding a chelating agent, a copper(II) hydroxide phosphate obtainable by this process, and the use of a chelating agent in the production of copper(II) hydroxide phosphate.

[0004] BACKGROUND OF THE INVENTION

[0005] Copper(II) hydroxide phosphate, also referred to in the literature as basic copper phosphate, is used, among other things, as a plastic additive for various purposes. For example, according to German patent applications Nos. 3 917 294 A1 and 4 136 994 A1, it is added to plastics to make them etchable using laser beams.

[0006] Two processes for the production of copper(II) hydroxide phosphate are known from the prior art: the reaction of an aqueous dispersion of a copper precursor compound with phosphoric acid under normal pressure and the hydrothermal synthesis, in which the reaction takes place under increased pressure starting from a copper precursor compound and a phosphate salt.

[0007] Hydrothermal synthesis is a largely heterogeneous reaction in aqueous medium above 100°C and 1 bar in a closed reaction vessel. Under these conditions, otherwise sparingly soluble substances dissolve as complexes. In this context, it is known to add additives to the aqueous reaction mixture to influence the structure of the reaction product, copper(II) hydroxide phosphate.

[0008] For example, Zhao et al., Int J. Electrochem. Sci. 8 (2013) 490-593, describe the hydrothermal synthesis of copper(II) hydroxide phosphate starting from CuSCVS H₂O and (NH₄)₂HP₄. The Herste II process is carried out at a temperature of 160-200°C with the addition of the additive sodium dodecylbenzenesulfonate for 24 h. Cu₂(OH)PC>₄ superstructures with a walnut shape and a size of 3-4 pm are obtained.

[0009] Han et al., Materials Letters 166 (2016) 71-74, describe the hydrothermal synthesis of copper(II) hydroxide phosphate starting from Cu(NOs)₂ and Na₂HP₄. The preparation process is carried out at a temperature of 120°C with the addition of sodium dodecylbenzenesulfonate and polyvinylpyrrolidone. Elliptically shaped Cu₂(OH)PC>₄ crystals are obtained.

[0010] Hu et al., Journal of Alloys and Compounds 695 (2017) 561-566, describes the hydrothermal synthesis of copper(II) hydroxide phosphate starting from Cu(CH3COO)2 and diammonium hydrogen phosphate. The synthesis is carried out at a temperature of 120°C with the addition of polyethylene glycol for 6 h. Rose-, rod-, or brick-shaped Cu2(OH)PC>4 crystals are obtained.

[0011] As already explained, processes for the production of copper(II) hydroxide phosphate are also known from the prior art that do not require working under pressure, i.e., they proceed without pressure. These have the advantage of less preparative effort, since work in autoclaves is not necessary. Furthermore, these are generally significantly faster and / or can be carried out at lower reaction temperatures.

[0012] For example, German patent DE OS 3342 292 describes a process in which basic copper carbonate in aqueous dispersion is treated with at least stoichiometric amounts of phosphoric acid at temperatures below 70°C, the resulting reaction mixture is mechanically agitated at the same temperature, then briefly heated to boiling point, and finally the resulting copper(II) hydroxide phosphate is separated. However, this process not only has very long reaction times of > 10 h, but depending on the raw material quality, products with significant color variations are obtained. A nearly colorless product with a uniform color is desirable, especially for applications as a plastic additive.

[0013] German patent DE 19543803 describes a process in which 85% phosphoric acid is added to an aqueous dispersion of copper(II) hydroxide, the reaction mixture is allowed to stand for approximately 1 hour at 50°C, and then heated to boiling for 1 hour. After cooling, the resulting product is filtered and dried. This process enables the production of copper(II) hydroxide phosphate in a relatively simple and cost-effective manner. However, the morphology of the copper(II) hydroxide phosphate cannot be influenced by this process. Furthermore, while the color of the product obtained is relatively light, the copper(II) hydroxide phosphate (hereinafter referred to as "KHP") still exhibits a slightly greenish tint. For some applications of copper(II) hydroxide phosphate, it may be advantageous to selectively control its morphology and specific surface area.For example, the biological and / or catalytic properties of a compound regularly depend on its structure and / or specific surface area. Furthermore, it is desirable to obtain copper(II) hydroxide phosphate with specific color properties, particularly low inherent color and high brightness. This is especially advantageous when copper(II) hydroxide phosphate is added as an additive to a composition, particularly a plastic composition.

[0014] Although, as shown above, certain morphologies of copper(II) hydroxide phosphate can be obtained by production via hydrothermal synthesis, this requires working in pressure vessels (autoclaves) and at temperatures > 100°C, usually even working above the critical point of water.

[0015] TASK

[0016] Against this background, the object of the present invention was therefore to provide a pressureless process for the production of copper(II) hydroxide phosphate, with which the morphology and / or specific surface area of ​​the product can be influenced and which enables the production of copper(II) hydroxide phosphate with higher brightness and / or lower inherent coloration than the processes known from the prior art.

[0017] DESCRIPTION OF THE INVENTION

[0018] This problem is solved according to the invention by a process for the production of copper(II) hydroxide phosphate comprising the following process steps: a) generation of a reaction mixture from an aqueous solution or dispersion of a copper(II) compound and a preferably at least stoichiometric amount of phosphoric acid, wherein at least stoichiometric means that the amount of copper(II) ions of the copper(II) compound to the amount of phosphoric acid in the reaction mixture is at most 2, b) reaction of the copper(II) compound with the phosphoric acid in the reaction mixture, and c) separation of copper(II) hydroxide phosphate from the reaction mixture, wherein the reaction in step b) is carried out without pressure, and the process is characterized in that a chelating agent is added to the reaction mixture in process step a) and / or b).

[0019] In a preferred embodiment of the invention, the ratio of the amount of copper(II) ions of the copper(II) compound to the amount of phosphoric acid in the reaction mixture is at most 5, preferably at most 3, more preferably at most 2.5, and most preferably at most 2. A ratio of 2 corresponds to a stoichiometric amount of phosphoric acid, meaning that phosphate ions are present in the reaction mixture in a ratio to copper(II) ions as in the product KHP (Cu₂(OH)PC>4). Such a ratio allows for particularly rapid and efficient product formation. Since phosphoric acid is less expensive than copper(II) compounds, in an advantageous embodiment the ratio of the amount of copper(II) ions of the copper(II) compound to the amount of phosphoric acid is at most 2, preferably at most 1.8, more preferably at most 1.5, even more preferably at most 1, and most preferably at most 0.5.The inventors observed that an excess of the inexpensive phosphoric acid could further increase the formation rate of KHP.

[0020] According to the invention, chelating agents are substances capable of forming chelates. Chelates are cyclic coordination compounds that have at least one central metal atom or ion and a polydentate ligand, the so-called chelating ligand. A ligand is an ion or molecule that can bind, i.e., coordinate, to a central metal atom or ion via a coordinate bond. The distinction between a coordinate bond and a classical covalent bond lies in the fact that, in a coordinate bond, the ligand provides both bonding electrons; it is therefore a "Lewis base." In this context, polydentate means that the ligand has two or more coordination sites through which it coordinates to the metal atom or ion. In other words, the chelating ligand must have two or more atomic groups that can act as electron donors.

[0021] In a preferred embodiment of the invention, the chelating ligand has three or more, more preferably four or more, particularly preferably five or more and most preferably six or more coordination sites.

[0022] When dissolved or dispersed in the aqueous solvent or dispersing medium, the chelating agent at least partially transforms into a chelating ligand. This ligand can be charged or uncharged.

[0023] The central metal atom or ion has electron vacancies to which the ligands can coordinate with their lone pairs of electrons; it is therefore a "Lewis acid". In the context of the invention, the central atom or ion is copper, which is provided in step a) of the reaction in the aqueous solution or dispersion by adding the copper(II) compound.

[0024] Without being bound to this theory, the inventors assume that the addition of the chelating agent in step a) of the reaction better stabilizes the copper(II) of the copper(II) compound in the solution or suspension. The stability of the copper(II) is affected to varying degrees depending on the binding strength of the different chelating agents. This, in turn, influences the conversion of the copper(II) in step b) of the reaction and thus also the crystallization of the product. This enables the production of crystals with a specific morphology and / or surface area.

[0025] The binding strength of the chelating agent depends essentially on the number of coordination sites and its "hardness".

[0026] Generally, the bond strength increases with the number of coordination sites. Chelate complexes are more stable than comparable complexes with monodentate, unlinked ligands. This "chelate effect" has two main causes. First, the formation of chelate complexes is entropically advantageous because the number of molecules increases, or at least decreases less, during the formation of the chelate complex than in the formation of comparable complexes with monodentate ligands. Therefore, the number of degrees of freedom of the system is higher during the formation of chelate complexes.

[0027] Secondly, a chelating ligand can only detach from the central atom after all bonds have been broken, meaning that the chelating ligand is significantly more difficult to dissociate from the metal atom or ion. Furthermore, the probability of immediate recombination after cleavage is also increased. Thus, chelate complexes are not only thermodynamically but also kinetically more stable than comparable complexes with monodentate ligands. The effects mentioned above are more pronounced the more coordination sites the chelating ligand has through which it binds to the copper(II) center.

[0028] However, the bond strength also depends on the "hardness" of the chelating ligand. According to the HSAB principle ("principle of hard and soft acids and bases," R.G. Pearson), the bond strength of a Lewis acid-base complex depends on the polarizability of the central atom and the donor atom of the ligand. Generally, combinations of "hard" acids with "hard" bases, i.e., compounds with poorly polarizable molecules or ions, exhibit higher complex formation constants than combinations of "hard" acids or bases with "soft" acids or bases. This is because these "hard"-"hard" bonds have a strongly ionic character. Similarly, "soft"-"soft" combinations, i.e., combinations of easily polarizable molecules or ions with low charge density, are also usually more stable than "mixed" combinations, as these bonds have a strongly covalent character.

[0029] Lewis acids can be systematically classified according to their hardness. This is essentially determined by the charge density, i.e., (partial) charge divided per unit volume of the ion / molecule. Soft acids are, for example, the singly charged transition metals of higher periods, such as Au. + or Ag + .

[0030] The hardness of Lewis bases essentially results from the hardness of the donor atoms. This hardness is higher the smaller, more electronegative, and more highly oxidized the donor atom is. In this context, a hard Lewis base is, for example, F\

[0031] The smaller transition metals with double charge, such as Fe 2+ or Cu 2+ are considered borderline cases between the classic hard Lewis acids (e.g. Ti) 4+ , Al 3+ ) and the soft Lewis acids (e.g., Ag + , Hg 2+ ) to classify.

[0032] From the fact shown above that bonds between molecules / ions of similar polarizability are preferred, it follows that copper(II) preferentially forms complexes with Lewis bases with medium-hard donor atoms (N, CI).

[0033] Stabilizing the copper(II) in the copper(II) compound allows for better dispersal in the solvent or dispersion medium. Impurities adhering to the copper(II) compound are also suspended or dissolved during this process. Consequently, these impurities are precipitated to a lesser extent during the reaction in step b) than would be the case if no complexing agent were added to the reaction mixture. Therefore, products of higher purity are obtained. The copper(II) hydroxide phosphate from the process according to the invention thus exhibits less inherent color and greater brightness.

[0034] In a preferred embodiment of the invention, at least two, preferably three or more, and particularly preferably five chelating agents are added to the reaction mixture. The inventors have found that a combination of chelating agents from different classes of substances leads to a synergistic effect. The combination of carboxylic and phosphoric acids or their derivatives is particularly advantageous.

[0035] In the context of the invention, "pressureless" means that the pressure in the reaction vessel in step b) does not significantly exceed the normal pressure of 1 bar, or only for a maximum of 50% of the reaction time of the copper(II) compound with the phosphoric acid in the reaction mixture, preferably for a maximum of 30% of the reaction time, more preferably for a maximum of 20% of the reaction time, and most preferably for a maximum of 10% of the reaction time, i.e., by no more than 0.5 bar. The reaction time is understood to be the time until the copper(II) hydroxide phosphate is obtained, which is separated from the reaction mixture in step c). Furthermore, the reaction temperature in step b) does not significantly exceed, i.e., by no more than 10°C, the boiling point of the solvent or dispersion agent. Therefore, in contrast to solvo- or hydrothermal synthesis, it is not necessary to work in a pressure vessel.

[0036] Step a)

[0037] In step a) of the process, a reaction mixture is prepared from an aqueous solution or dispersion of a copper(II) compound and a preferably at least stoichiometric amount of phosphoric acid. This can be achieved by first dispersing the copper(II) compound in an aqueous solvent or dispersion medium. The aqueous solvent or dispersion medium contains at least 20% water by weight, preferably at least 40%, particularly preferably at least 50%, even more preferably at least 70%, and most preferably at least 90%. In a further embodiment, the aqueous solvent or dispersion medium consists of water. The solvent or dispersion medium may also contain polar organic solvents such as (polyhydric) alcohols or amines. Polyhydric alcohols are particularly preferred as further components.

[0038] In a preferred embodiment of the invention, the copper(II) compound is first dissolved or suspended in the aqueous solvent or dispersion medium, and only then is the preferably at least stoichiometric amount of phosphoric acid added, so that the reaction mixture is formed.

[0039] In this context, it is particularly preferred if the chelating agent is added to the aqueous solvent or dispersion medium before the phosphoric acid is added. This ensures that the copper(II) compound is completely stabilized before the reaction with phosphoric acid in step b). The beneficial effects associated with the stabilization can thus be maximized.

[0040] Alternatively, the preferably at least stoichiometric amount of phosphoric acid can be dissolved or suspended in the aqueous solvent or dispersant, and the copper(II) compound can then be added. In a further embodiment of the invention, the phosphoric acid and the copper(II) compound are added simultaneously to the solvent or dispersant to obtain the reaction mixture.

[0041] In a further embodiment of the invention, the phosphoric acid and the copper(II) compound are added to the solvent or dispersion medium in partial amounts, alternating periodically or aperiodically, in order to obtain the reaction mixture.

[0042] Step b)

[0043] In step b), the copper(II) compound reacts with the phosphoric acid in the reaction mixture. Steps a) and b) are not necessarily separated in time, but can also overlap. The reaction of the copper(II) compound with the phosphoric acid can begin upon the addition of a partial amount of the copper(II) compound and / or the phosphoric acid.

[0044] In an advantageous embodiment of the invention, however, steps a) and b) are separated in time, so that step b), i.e., the reaction of the copper(II) compound with the phosphoric acid, only takes place when the copper(II) compound and the phosphoric acid are completely dissolved or dispersed in the solvent or dispersion medium. This can be achieved, in particular, by keeping the reaction mixture below the temperature required to initiate the reaction of the copper(II) compound and the phosphoric acid.

[0045] Separating steps a) and b) has the advantage that the implementation can be better tracked and controlled.

[0046] Step c)

[0047] In the final step, the copper(II) hydroxide phosphate is separated from the reaction mixture. This can be done using conventional separation methods. The separation method selected from the group consisting of filtration, evaporation, centrifugation, sedimentation, and flotation is particularly preferred.

[0048] The preferred separation method is filtration. This allows for the particularly efficient removal of any impurities that are dissolved or finely dispersed in the solvent or dispersion medium.

[0049] In a preferred embodiment of the invention, the chelating agent is selected from the group consisting of amino, carboxylic, phosphoric, sulfuric and sulfonic acids and their salts, esters and amides; polyhydric alcohols; nitriles; bipyridines; phenanthrolines; polyhydric phenols; polyhydric amines; polyhydric ethers; lactams; oximes; urea derivatives; polyhydric ketones and aldehydes such as acetylacetonate (acac); thiols such as dimercaptosuccinic acid (DMSA); and combinations of the aforementioned.

[0050] Since copper(II) preferentially forms stable complexes with Lewis bases with moderately hard donor atoms such as N or CI, the chelating agents are preferably those that have nitrogen as one or more donor atoms. Therefore, the chelating agents are preferably selected from the group consisting of amino acids, carboxylic acid amides, nitriles, bipyridines, phenanthrolines, polyhydric amines, urea derivatives, lactams, and oximes.

[0051] The chelating agent selected from the group consisting of ethylenediamine (en), 2-(2-aminoethylamino)ethanol (AEEA), diethylenetriamine (dien), iminodiacetate (ida), triethylenetetramine (trien, TETA), triaminotriethylamine (tren), nitrilotriacetate (nta), bis(salicylidene)ethylenediamine (salen), ethylenediaminotriacetate (ted), ethylenediaminetetraacetate (EDTA), diethylenetriaminepentaacetate (DTPA), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA), dimethylglyoxime (dmg), 8-hydroxyquinoline (oxin), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), tetrasodium iminodisuccinate (IDHA), methylglycine diacetic acid and combinations thereof is particularly preferred. the aforementioned.

[0052] The addition of Lewis bases with medium-hard donor atoms such as N stabilizes the copper(II) of the copper(II) compound particularly well in aqueous solvents or dispersion media.

[0053] This allows impurities to be separated particularly efficiently, since the particularly pronounced stabilization of the copper(II) results in the copper(II) compound being better distributed in the solvent or dispersion medium, and in step b) impurities are precipitated to a lesser extent.

[0054] In a preferred embodiment of the invention, the copper(II) compound is selected from the group consisting of copper(II) hydroxide, copper(II) sulfate, copper(II) carbonate, basic copper(II) carbonate, copper(II) halides, and combinations thereof. Particularly preferred is the copper(II) compound selected from copper(II) fluoride, copper(II) chloride, copper(II) bromide, copper(II) hydroxide, or copper(II) iodide, and combinations thereof. Most preferred is the copper(II) compound copper(II) chloride or copper(II) hydroxide.

[0055] Copper(II) hydroxide and copper(II) halides, especially copper(II) chloride, have the advantage of very good availability at comparatively low purchase prices. Even if the copper(II) compound contains a component, in particular an anion, that falls under the definition of a chelating ligand, the addition of such a copper(II) compound in step a) is not to be understood as the addition of a chelating agent according to the invention. In other words, this means that the chelating agent is an additional component of the reaction mixture that must be separated from the copper(II) compound.

[0056] In a preferred embodiment of the invention, the chelating agent is an amino acid, its ester, amide, or salt. Particularly preferred is the sodium salt of an amino acid. This is advantageous because sodium salts of amino acids are generally very soluble in aqueous solvents or dispersants. Amino acids have the advantage that they can stabilize the copper(II) of the copper(II) compound via both the carboxylic acid and the amino group. This particularly pronounced stabilization allows for the obtaining of very light-colored copper(II) hydroxide phosphate with low inherent color.

[0057] In a preferred embodiment of the invention, the amino acid is added before the phosphoric acid is added, wherein the pH of the reaction mixture before the addition of the phosphoric acid is less than pH 7, preferably less than 5, more preferably less than 4, and most preferably less than 3. This prevents the amino group of the amino acid from being present in protonated form and thus prevents coordination via the amino group.

[0058] In a particularly preferred embodiment of the invention, the amino acid is a proteinogenic amino acid. Proteinogenic amino acids are those that are used in living organisms as building blocks of proteins during translation according to genetic information. Particularly preferred are the proteinogenic amino acids selected from the group consisting of alanine, asparagine, cysteine, glutamine, glycine, histidine, leucine, lysine, methionine, proline, serine, valine, and combinations thereof.

[0059] Proteinogenic amino acids are commercially available in particularly high purity. This minimizes contamination of the copper(II) hydroxide phosphate by foreign substances adhering to the chelating agent. Therefore, a particularly pure and light-colored copper(II) hydroxide phosphate with low inherent color is obtained.

[0060] By using amino acids as chelating agents, copper(II) hydroxide phosphate crystals in elongated prism shape are obtained. These are fused together to form larger elongated structures. In a further preferred embodiment of the invention, the chelating agent is selected from the group of aminosulfonic acids, preferably from the group consisting of taurine and sulfanilic acid, as well as their salts and esters.

[0061] In a preferred embodiment of the invention, the chelating agent is a carboxylic acid, its ester, amide, or salt. In a preferred embodiment, the carboxylic acid is a polyhydric acid, i.e., a carboxylic acid with several carboxylic acid groups. Particularly preferred is the carboxylic acid a hydroxycarboxylic acid, especially a fruit acid. Particularly preferred is the carboxylic acid, hydroxycarboxylic acid, or its salt selected from the group consisting of formic acid, acetic acid, glycolic acid, lactic acid, benzoic acid, oxalic acid, tartaric acid, malic acid, citric acid, alkali metal citrates, in particular monosodium citrate, isocitric acid, and trimesic acid.

[0062] Hydroxycarboxylic acids have the advantage that they can stabilize the copper(II) compound in the solvent or dispersion medium via both the carboxylic acid and the hydroxyl groups. This makes the benefits associated with stabilization particularly pronounced.

[0063] In a further preferred embodiment of the invention, the chelating agent is selected from the group of saccharides, in particular from the group of mono-, oligo- and polysaccharides, including cyclodextrins.

[0064] Preferably, the saccharides are selected from the group consisting of hexoses such as glucose, fructose, mannose, galactose, pentoses such as ribose, xylose, lactose, maltose, sucrose, oligosaccharides, including cyclic oligosaccharides such as α-, β-, γ- or δ-cyclodextrins or polysaccharides such as alginates.

[0065] The chelating agent selected from the group consisting of sucrose, fructose and galactose is particularly preferred; sucrose is the most preferred chelating agent.

[0066] Saccharides coordinate to copper(II) via the lone pairs of electrons in the OH groups. Since saccharides possess a large number of OH groups and thus coordination sites, they are particularly effective at stabilizing the copper(II) in copper(II) compounds.

[0067] Furthermore, saccharides generally lack aromatic molecular components and heteroatoms such as sulfur and phosphorus. The inherent color of saccharides is therefore extremely low. Residual saccharides remaining in the product after the reaction thus do not cause any significant coloration, resulting in a particularly light-colored copper(II) hydroxide phosphate with low inherent color. In another embodiment of the invention, the chelating agent is a polyol, in particular an alditol, i.e., a reduced form of a saccharide such as mannitol, lactitol, sorbitol, xylitol, threitol, erythritol, or arabitol.

[0068] By using saccharides as chelating agents, copper(II) hydroxide phosphate crystals in rod form are obtained.

[0069] The inventors discovered that adding chelating agents with a large number of coordination sites, i.e., more than 15 coordination sites, results in "broccoli"-like crystal structures. Examples of such chelating agents include polyphosphates, polyethers such as polyethylene glycols, polyethylene oxides and polypropylene glycols, polyvinylpyrrolidone, and alginates.

[0070] In a further preferred embodiment, the chelating agent is selected from the group consisting of di- or polyphosphoric acid or their salts. Preferably, the chelating agent is selected from the group consisting of alkali phosphates, alkali metaphosphates, and alkali polyphosphates, most preferably K₅P₃O₁₀.

[0071] In another preferred embodiment of the invention, the chelating agent is ascorbic acid. The inventors have discovered that the addition of ascorbic acid allows the production of copper(II) hydroxide phosphates with a particularly high specific surface area. These exhibit a specific surface area of ​​> 10 m². 2 / g, preferably > 15 m 2 / g, especially preferred > 20 m 2 / g, even more preferred > 30 m 2 / g and preferably > 40 m 2 / g on.

[0072] Without being bound to this theory, the inventors assume that this is due to the easy oxidizability of ascorbic acid, resulting in the formation of semi-stable complexes of ascorbic acid and copper(II) in steps a) and / or b), leading to highly porous end products. Comparable results are also obtained with citric acid and / or its salts, especially in combination with phosphates as an additional chelating agent.

[0073] In this context, it should be noted that the addition of ascorbic and / or citric acid or their salts should not exceed 3 wt%, preferably not exceeding 2 wt%, particularly preferably not exceeding 1.5 wt%, and most preferably not exceeding 1 wt% based on the amount of copper(II) compound. Otherwise, the phase purity of the copper(II) hydroxide phosphate may be significantly below 100%.

[0074] In a preferred embodiment of the invention, the chelating agent is a surfactant, i.e., a surface-active substance, which has both a hydrophobic molecular part consisting of an organic residue and a hydrophilic molecular part having a polar group, which is preferably charged.

[0075] In a preferred embodiment, the surfactant is a nonionic surfactant or an anionic surfactant. Particularly preferably, the hydrophilic molecular portion comprises a carboxylate, sulfonate, hydroxy, ether, or ethoxylate group.

[0076] In a further preferred embodiment of the invention, the surfactant is selected from the group consisting of cationic surfactants such as tetraalkylammonium salts such as cetyltrimethylammonium bromide or cetyltrimethylammonium chloride, anionic surfactants such as alkylcarboxylates and amphoteric surfactants such as betaine.

[0077] The use of amino acids as chelating agents yields copper(II) hydroxide phosphate crystals in elongated prism shape. These are fused together to form star-shaped structures.

[0078] The chelating agent is added to the reaction mixture to stabilize the copper(II) compound. Usually, only a low concentration of chelating agent is required for this purpose.

[0079] Since at least some of the chelating agent usually remains in the product after the reaction, this can lead to discoloration of the product. Furthermore, an excessive amount of chelating agent should be avoided for cost reasons. Therefore, preferably, the total amount of chelating agent added to the reaction mixture in steps a) and / or b) should not exceed 5.0 wt%.

[0080] However, an insufficient amount of chelating agent has the disadvantage that the stabilizing effect is only weakly pronounced.

[0081] In a preferred embodiment of the invention, 0.1 to 5.0 wt.% of the chelating agent is therefore added to the reaction mixture in process step a) and / or b) based on the amount of copper(II) compound.

[0082] The chelating agent is preferably added in an amount of 0.5 to 3.0 wt.%, more preferably in an amount of 1 to 3.0 wt.%, and most preferably in an amount of 1 to 2.0 wt.%. Particularly pure copper(II) hydroxide phosphate can be obtained using the process according to the invention. This means copper(II) hydroxide phosphate with a phase purity > 90%, preferably > 95%, more preferably > 98%, particularly preferably > 99%, and most preferably > 99.5%.

[0083] Phase purity can be determined using X-ray structure analysis as follows.

[0084] Quantitative phase determination is performed using the Rietveld method, as described in detail in "Quantitative phase analysis using the Rietveld method," DL Bish and SA Howard, J. Appl. Cryst. (1988). 21, 86-91, or in the textbook "The Rietveld Method," Chapter 1, "Introduction to the Rietveld method," RA Young, ed., Oxford University Press (1995). Preferably, the analysis is performed using pattern analysis software such as the Topas program from Bruker.

[0085] In a further preferred embodiment of the invention, the copper(II) hydroxide phosphate obtained in process step c) has in the L * a * b * -Color space (CIELAB) has an L value of > 78, preferably > 80, especially preferred > 82, even more preferred > 85 and most preferred > 87.

[0086] The L * a * b * The color space according to DIN EN ISO 11664-4 is used to characterize all perceptible colors. In the three-dimensional L* a * b * -Color space is the brightness value L * perpendicular to the planar color plane (a * , b * ) arranged.

[0087] On the a * -axis the colors green and red are opposite each other, whereas b * The axis separates blue and yellow. Complementary colors are therefore 180° opposite each other. The L * The -axis defines the brightness of the color and includes values ​​from 0 to 100, where 100 represents the highest brightness.

[0088] Among the most important properties of L * a * b * Color models emphasize device independence and perceptual accuracy. In other words, colors are defined as they are perceived by a normal observer under standard lighting conditions, regardless of how they are generated or reproduced.

[0089] Within the scope of the present invention, the L * a *b * -Values ​​determined as follows.

[0090] Determining the L * a * b * The values ​​were determined using an UltraScan VIS spectrophotometer from HunterLab. For this purpose, the samples were placed in a glass cuvette, and a homogeneous surface was created on the side of the cuvette facing the measuring aperture by tapping the cuvette or compacting the sample. In a further preferred embodiment of the invention, the copper(II) hydroxide phosphate obtained in process step c) consists of particles which, according to laser scattering analysis according to DIN-ISO 13320-1, have a median particle size in the range of 2 to 10 pm, preferably 2 to 8 pm, particularly preferably 2 to 7 pm, even more preferably 2 to 6 pm, and most preferably 2 to 5 pm.

[0091] Within the scope of the present invention, the particle sizes were determined according to the currently valid DIN-ISO 13320-1. For this purpose, a sample of the manufactured product is dispersed in a dispersion medium (2-propanol or a solution of tetrasodium pyrophosphate in demineralized water, 14 mmol / L) and wet-measured with a Horiba LA-950V in a measuring range of 0.01 pm to 3000 pm.

[0092] In another preferred embodiment of the invention, the copper(II) hydroxide phosphate obtained in process step c) consists of rod-shaped particles, wherein the aspect ratio is in the range of 1 :3 to 1 :10.

[0093] According to the invention, aspect ratio is understood to be the ratio of the largest elongated dimension of the particle to its smallest dimension.

[0094] The invention further relates to copper(II) hydroxide phosphate, which is obtainable by the process according to the invention, wherein the copper(II) hydroxide phosphate is in the L * a * b * -Color space (CIELAB) has an L value of > 78, preferably > 80, particularly preferably > 82, even more preferably > 85 and most preferably > 87.

[0095] The invention further relates to the use of a chelating agent in the production of copper(II) hydroxide phosphate by reacting a copper(II) compound with phosphoric acid to change the crystal properties of the produced copper(II) hydroxide phosphate.

[0096] EXAMPLES

[0097] The invention will now be explained using specific embodiments of manufacturing examples according to the invention.

[0098] Raw materials: Measurement methods:

[0099] Particle size determination Media, D10, D90: The particle size distributions were determined both volume-based and particle size-based using dynamic light scattering on a Horiba Partica LA-950V (Horiba, Ltd.; Kyoto; Japan). For this purpose, a sample of the manufactured product is dispersed in a dispersion medium (2-propanol or a solution of tetrasodium pyrophosphate in demineralized water, 14 mmol / L) and measured wet with a Horiba LA-950V in a measuring range of 0.01 pm to 3000 gm.

[0100] Phase purity

[0101] Phase purity is determined by X-ray structure analysis. X-ray diffraction (XRD) measurements were performed on a Bruker D8 Advance A25 diffractometer using CuK of the products manufactured according to the following examples. c-Radiation- performed. Quantitative phase determination is carried out using the Rietveld method (see “Quantitative phase analysis using the Rietveld method”, DL Bish and SA Howard, J. Appl. Cryst. (1988). 21, 86-91 or the textbook “The Rietveld Method”, Chapter 1, “Introduction to the Rietveld method”, RA Young, ed., Oxford University Press (1995)) with the aid of the pattern analysis program Topas 4.2 from Bruker.

[0102] L * a * b * -Values

[0103] Determining the L * a * b *The values ​​were determined using an UltraScan VIS-2 spectrophotometer equipped with the HunterLab Ultra Sensor VIS sensor. Samples were placed in a glass cuvette, and a homogeneous surface was created on the cuvette side facing the measuring aperture by tapping the cuvette or compacting the sample. The associated software, Easy Match QC 4.64, used the settings "USVIS 1145" sensor and "RSIN Mode" to calculate the LAB values.

[0104] The method is carried out in accordance with the currently valid version of EN ISO 11664-4.

[0105] Specific surface

[0106] The specific surface area was determined according to the BET method by N2 absorption (DIN ISO 9277) using a BELSORP-mini instrument from BEL. Nitrogen with a purity of 99.999% was used.

[0107] Scanning electron microscopy

[0108] For scanning electron microscope (SEM) images, a Zeiss Sigma EVO SEM spectrometer was used in combination with an Oxford INCA Energy 350 EDX detector. General experiment description

[0109] 150 g of Cu(OH)₂ (1.54 mol) are suspended in 2250 ml of distilled water, resulting in a blue-colored suspension. This is heated to 90°C, 120 g of phosphoric acid (75 wt%, 0.92 mol) and the amount of one or more additives according to Table 1 are added, and the reaction mixture is heated to boiling. After 15 minutes, the crude product is filtered off, resuspended in 1000 ml of water, filtered again, and dried overnight at 105°C in a drying oven. Table 1:

[0110] [1] Cetyltrimethyl ammonium bromide

[0111] [2] LFP = elongated prisms, highly fragmented (consisting of many longitudinally fused crystals), partially fused

[0112] [3] LP = elongated prisms, partially fused

[0113] [4] ST = Stars made of elongated, intergrown crystals

[0114] [5] nb = not determined

Claims

Patent claims 1. A process for the production of copper(II) hydroxide phosphate comprising the following process steps: a) generation of a reaction mixture from an aqueous solution or dispersion of a copper(II) compound and a preferably at least stoichiometric amount of phosphoric acid, wherein at least stoichiometric means that the amount of copper(II) ions of the copper(II) compound to the amount of phosphoric acid in the reaction mixture is at most 2, b) reaction of the copper(II) compound with the phosphoric acid in the reaction mixture and c) separation of copper(II) hydroxide phosphate from the reaction mixture, wherein the reaction in step b) is carried out without pressure, characterized in that at least one chelating agent is added to the reaction mixture in process step a) and / or b).

2. The method according to claim 1, characterized in that the at least one chelating agent is selected from the group consisting of amino, carboxylic, phosphoric, sulfuric and sulfonic acids and their salts, esters and amides; polyhydric alcohols; nitriles; bipyridines; phenanthrolines; polyhydric phenols; polyhydric amines; polyhydric ethers; lactams; oximes; urea derivatives; polyhydric ketones and aldehydes such as acetylacetonate, thiols; and combinations of the aforementioned.

3. A method according to one of the preceding claims, characterized in that the copper(II) compound is selected from the group consisting of copper(II) hydroxide, copper(II) sulfate, copper(II) carbonate, basic copper(II) carbonate, copper(II) halides, preferably copper(II) chloride and copper(II) bromide and combinations thereof.

4. Method according to one of the preceding claims, characterized in that the at least one chelating agent is an amino acid or its salt, preferably its sodium salt, wherein the amino acid is selected from the group of proteinogenic amino acids.

5. A method according to any of the preceding claims, characterized in that the at least one chelating agent is a carboxylic acid, hydroxycarboxylic acid or its salt, wherein the carboxylic acid or hydroxycarboxylic acid is selected from the group consisting of formic acid, acetic acid, glycolic acid, lactic acid, benzoic acid, oxalic acid, tartaric acid, malic acid, citric acid, isocitric acid, trimesic acid and combinations of the aforementioned.

6. Method according to one of the preceding claims, characterized in that the at least one chelating agent is a saccharide selected from the group consisting of mono- and oligosaccharides.

7. Method according to one of the preceding claims, characterized in that the at least one chelating agent is ascorbic acid.

8. Method according to one of the preceding claims, characterized in that the at least one chelating agent is a surfactant, preferably selected from the group consisting of anionic surfactants and nonionic surfactants.

9. Method according to one of the preceding claims, characterized in that the at least one chelating agent is added in a total amount of chelating agents of 0.1 to 5.0 wt.% based on the amount of the copper(II) compound.

10. A method according to one of the preceding claims, characterized in that the copper(II) hydroxide phosphate obtained in process step c) has a phase purity > 95%.

11. Method according to one of the preceding claims, characterized in that the copper(II) hydroxide phosphate obtained in process step c) is in CIELAB L * a * b * - Color space according to DIN EN ISO 11664-4, one L * -value of > 80, > 85 or > 87.

12. A method according to one of the preceding claims, characterized in that the copper(II) hydroxide phosphate obtained in process step c) consists of particles, which, according to the determination by laser scattering analysis according to DIN-ISO 3320-1, have a median grain size in the range of 2 to 10 gm.

13. Method according to one of the preceding claims, characterized in that the copper(II) hydroxide phosphate obtained in process step c) consists of rod-shaped particles, wherein the aspect ratio is in the range of 1 :3 to 1 :

10.

14. Copper(II) hydroxide phosphate obtainable by a process according to claims 1-13, characterized in that the copper(II) hydroxide phosphate in the L * a * b * -color space has an L- value of > 78.

15. Use of a chelating agent in the production of copper(II) hydroxide phosphate by reacting a copper(II) compound with phosphoric acid to modify the crystal properties of the produced copper(II) hydroxide phosphate.