Use of additives in the production of copper (II) hydroxide phosphate

Abstract

The invention relates to a method for preparing copper (II) hydroxide phosphate by adding a chelating agent, to copper (II) hydroxide phosphate obtainable by the method and to use of the chelating agent in producing copper (II) hydroxide phosphate.

Description

Technical Field

[0001] The present invention relates to a method for preparing copper (II) hydroxide phosphate by adding a chelating agent, to the copper (II) hydroxide phosphate obtainable by the method and to the use of the chelating agent in the production of copper (II) hydroxide phosphate. Background Art

[0002] Copper(II) hydroxide phosphate, also referred to in the literature as basic copper phosphate, is used for various purposes, inter alia, as an additive to plastics. For example, according to unexamined German patent applications Nos. 3 917 294 A1 and 4 136 994 A1, it is incorporated into plastics so that the plastics can be marked with a laser beam.

[0003] In the prior art, essentially two methods are known for preparing copper(II) hydroxide phosphate, namely the reaction of an aqueous dispersion of a copper precursor compound with phosphoric acid at normal pressure and the hydrothermal synthesis starting from a copper precursor compound and a phosphate at high pressure.

[0004] The term "hydrothermal synthesis" refers to a predominantly heterogeneous reaction carried out in an aqueous medium at above 100°C and 1 bar in a closed reaction vessel. Under the conditions described, substances that are originally of low solubility dissolve in the form of complexes. In this case, it is known that additives can be added to the aqueous reaction mixture in order to influence the structure of the reaction product, copper(II) hydroxide sulfate.

[0005] For example, Zhao et al. describe in Int. J. Electrochem. 8 (2013) 490-593 a hydrothermal method for the synthesis of copper (II) phosphate hydroxide starting from CuSO4*5H2O and (NH4)2HPO4. The preparation is carried out at a temperature of 160-200°C for 24 hours, with the addition of sodium dodecylbenzenesulfonate as an additive. The resulting Cu2(OH)PO4 superstructure has a walnut-shaped configuration and a size of 3-4 μm.

[0006] Han et al. describe in Materials Letters 166 (2016) 71-74 a hydrothermal synthesis of copper (II) phosphate hydroxide starting from Cu(NO3)2 and Na2HPO4. The preparation was carried out at a temperature of 120°C with the addition of sodium dodecylbenzenesulfonate and polyvinylpyrrolidone. Oval Cu2(OH)PO4 crystals were obtained.

[0007] Hu et al., Journal of Alloys and Compounds 695 (2017) 561-566, reported a hydrothermal synthesis of copper(II) phosphate hydroxide starting from Cu(CH3COO)2 and diammonium hydrogen phosphate. The preparation was carried out at a temperature of 120°C for 6 hours with the addition of polyethylene glycol. Rose-shaped, rod-shaped or brick-shaped Cu2(OH)PO4 crystals were obtained.

[0008] However, as already explained, processes for preparing copper(II) phosphate hydroxide which do not require operation under pressure, i.e. which are carried out in a non-pressurized manner, are also known in the prior art. The advantage of these processes is that the preparation work is low, since no autoclave is required for operation. In addition, these processes are generally much faster and / or can be carried out at lower reaction temperatures.

[0009] For example, the unexamined German patent application No. 3 342 292 describes a process in which basic copper carbonate in aqueous dispersion is treated with at least a stoichiometric amount of phosphoric acid at a temperature below 70° C., the resulting reaction mixture is further mechanically moved in the same temperature range, then briefly heated to boiling point, and the resulting copper(II) phosphate hydroxide is finally separated. However, this process not only has a very long reaction time of more than 10 hours, but also the resulting product has a very different color depth depending on the quality of the starting materials. However, products with an almost colorless, homogeneous color are desired, in particular for the field of application of plastic additives.

[0010] Patent DE 19 543 803 describes a method in which 85% phosphoric acid is added to an aqueous dispersion of copper (II) hydroxide, the reaction mixture is left to stand at 50° C. for about 1 hour, then heated to boiling point for 1 hour, and after cooling, the resulting product is filtered and dried. This method makes it possible to obtain copper (II) hydroxide phosphate in a relatively simple and cost-effective process. However, the morphology of copper (II) hydroxide phosphate cannot be affected using this method. In addition, although the color of the obtained product is relatively bright, copper (II) hydroxide phosphate (hereinafter referred to as: CHP) still has a light green hue.

[0011] However, for some areas of application of copper(II) hydroxide phosphate, it may be advantageous to control its morphology and specific surface area in a targeted manner. For example, the biological and / or catalytic properties of a compound often depend on its structure and / or specific surface area. It is also desirable to obtain copper(II) hydroxide phosphate with specific color values, in particular a low intrinsic color and a high brightness. This is particularly advantageous if copper(II) hydroxide phosphate is added as an additive to a composition, in particular a plastic composition.

[0012] Although, as mentioned above, specific forms of copper(II) phosphate hydroxide can be obtained by hydrothermal synthesis, this requires operation at temperatures greater than 100° C. and in pressure vessels (autoclaves), in most cases even above the critical point of water.

[0013] Purpose

[0014] Against this background, the object of the present invention is to provide a non-pressurized process for preparing copper(II) hydroxide phosphate, by means of which the morphology and / or the specific surface area of ​​the product can be influenced and it is possible to prepare copper(II) hydroxide phosphate having a higher brightness and / or a lower intrinsic color compared with the processes known in the prior art. Summary of the invention

[0015] According to the invention, this object is achieved by a process for preparing copper(II) hydroxide phosphate, which comprises the following process steps:

[0016] a) producing a reaction mixture from an aqueous solution or dispersion of phosphoric acid and a copper(II) compound in preferably at least stoichiometric amounts, wherein "at least stoichiometric" means that the amount of copper(II) ions of the copper(II) compound relative to the amount of phosphoric acid in the reaction mixture is at most 2.

[0017] b) converting a copper(II) compound with phosphoric acid in a reaction mixture, and

[0018] c) separating copper(II) hydroxide phosphate from the reaction mixture,

[0019] The conversion in step b) is carried out in a non-pressurized manner, and the method

[0020] Features

[0021] In process step a) and / or b) a chelating agent is added to the reaction mixture.

[0022] 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, even more preferably at most 2.5 and most preferably at most 2. A ratio of 2, which corresponds to the stoichiometric amount of phosphoric acid, means that the ratio of phosphate ions to copper (II) ions in the reaction mixture is the same as in the product CHP (Cu2(OH)PO4). In the case of such a ratio, the product can be formed particularly quickly and efficiently. Since phosphoric acid is more cost-effective 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 have observed that the generation rate of CHP can be increased even more by making the phosphoric acid, which is cost-effective, excessive.

[0023] According to the present invention, the term "chelating agent" refers to a substance that can form a chelate. A chelate is a cyclic coordination compound having at least one central metal atom or ion and a multidentate ligand, i.e., a "chelate ligand". A ligand is an ion or molecule that can be bound by a coordination bond, i.e., coordinated to a central metal atom or ion. The difference between a coordination bond and a conventional covalent bond is that the ligand in the coordination bond provides a double bonding electron, and is therefore referred to as a "Lewis base". In this case, "multidentate" means that the ligand has two or more coordination sites, and is thereby coordinated to a metal atom or ion. In other words, a chelate ligand must therefore have two or more atomic groups that can act as electron donors.

[0024] In a preferred embodiment of the present invention, the chelating ligand has three or more, more preferably four or more, particularly preferably five or more, most preferably six or more coordination sites.

[0025] When dissolved or dispersed in an aqueous solvent or dispersion medium, the chelating agent at least partially generates a chelating ligand. The chelating ligand may be charged or uncharged.

[0026] The central metal atom or ion has an electron hole, so that the ligand can coordinate with it with its free electron pair; it is therefore called a "Lewis acid". In the context of the present invention, the central atom or ion is copper, which is provided in step a) of the reaction by adding a copper (II) compound in an aqueous solution or dispersion.

[0027] Without being bound by this theory, the inventors assume that by adding a chelating agent in step a) of the reaction, the copper (II) of the copper (II) compound is better stabilized in solution or suspension. Depending on the binding strength of the various chelating agents, the stability of the copper (II) may be affected to varying degrees. Thus, the conversion of the copper (II) in step b) is affected, so is the crystallization of the product. This makes it possible to prepare crystals with a specific morphology and / or a specific surface area.

[0028] The bond strength of a chelating agent depends essentially on the number of coordination sites and their "hardness".

[0029] Basically, the bond strength increases with the number of coordination sites. Chelates are more stable than similar complexes with monodentate ligands that are not linked together. There are basically two reasons for this "chelation effect".

[0030] First, the formation of chelates is entropically favorable, since during the formation of chelates the number of molecules increases, or at least decreases to a smaller number than during the formation of similar complexes with monodentate ligands. Thus, during the formation of chelates the number of degrees of freedom of the system is greater.

[0031] Secondly, the chelating ligand can be eliminated only after all bonds have been cut from the central atom, which means that the difficulty of dissociating the chelating ligand from the metal atom or ion is greatly increased. In addition, the probability of recombination immediately after the splitting is also increased. Therefore, chelates are not only thermodynamically but also kinetically more stable than similar complexes with monodentate ligands. The more coordination sites the chelating ligand has for binding to the copper(II) center, the greater the above effects.

[0032] However, the bond strength also depends on the "hardness" of the chelating ligand. According to the HSAB principle (hard and soft acid-base principle, RGPearson), the bond strength of the Lewis acid-base complex depends on the polarizability of the central atom and the donor atom of the ligand. Basically, the combination of a "hard" acid with a "hard" base, i.e. a compound with poor molecular or ionic polarizability, has a higher complex formation constant than the combination of a "hard" acid or base with a "soft" acid or base. This is because these "hard"-"hard" bonds have highly ionic bonding characteristics.

[0033] "Soft"-"soft" combinations, i.e. combinations of easily polarizable molecules or ions with low charge density, are also generally more stable than "mixed" combinations because the bonds are highly covalent.

[0034] Lewis acids can be systematically classified according to their hardness, which is basically determined by the charge density, i.e. the (partial) charge of the ion / molecule divided by the unit volume. For example, soft acids are singly charged, high-period subgroup elements such as Au.+ or Ag + .

[0035] The hardness of a Lewis base is essentially determined by the hardness of the donor atom. The smaller the donor atom, the more electronegative it is, the higher the degree of oxidation, and the higher the hardness. In this context, a hard Lewis base is, for example, F - .

[0036] Doubly charged lower transition metals, such as Fe 2+ Cu 2+ , will be classified as a typical hard Lewis acid (such as Ti 4+ 、Al 3+ ) and soft Lewis acids (such as Ag + , Hg 2+ )

[0037] In view of the above facts, bonding between molecules / ions with similar polarizability is preferred, and therefore copper(II) preferably forms complexes with Lewis bases having semi-hard donor atoms (N, Cl).

[0038] By stabilizing the copper (II) of the copper (II) compound, the compound can be better dispersed in the solvent or dispersion medium. Impurities attached to the copper (II) compound are also suspended or dissolved in this process. Therefore, in the conversion of step b), these impurities are coprecipitated to a lesser extent than if no complexing agent is added to the reaction mixture. For this reason, a product with higher purity can be obtained. Therefore, the copper (II) phosphate hydroxide obtained according to the method of the present invention has a lower inherent color and a higher brightness.

[0039] In a preferred embodiment of the present invention, at least two, preferably three or more, particularly preferably five chelating agents are added to the reaction mixture. The inventors have found that the combination of chelating agents of different material classes can lead to a synergistic effect. The combination of carboxylic acid and phosphoric acid or its derivatives is particularly advantageous.

[0040] According to the present invention, "non-pressurized" means that the pressure in the reaction vessel in step b) does not significantly exceed the normal pressure by 1 bar, i.e., does not exceed 0.5 bar, or is only so for at most 50% of the conversion time of the copper (II) compound and phosphoric acid in the reaction mixture, preferably at most 30% of the conversion time, even more preferably at most 20% of the conversion time, and most preferably at most 10% of the conversion time. The term "conversion time" refers to the time until copper (II) phosphate hydroxide separated from the reaction mixture in step c) is obtained. In addition, the conversion temperature in step b) will not significantly exceed the boiling point of the solvent or dispersion medium, i.e., not more than 10°C. Therefore, compared with solvothermal or hydrothermal synthesis, the operation does not need to be carried out in a pressure vessel.

[0041] Step a)

[0042] In step a) of the method, a reaction mixture consisting of an aqueous solution or dispersion of phosphoric acid and a copper(II) compound in preferably at least stoichiometric amounts is prepared. This can be accomplished by first dispersing the copper(II) compound in an aqueous solvent or dispersion medium. The aqueous solvent or dispersion medium contains, relative to its total weight, at least 20%, preferably at least 40%, particularly preferably at least 50%, even more preferably at least 70%, most preferably at least 90% water. In another embodiment, the aqueous solvent or dispersion medium consists of water. As a further component, the solvent or dispersion medium may contain a polar organic solvent, such as a (polyvalent) alcohol or an amine. Polyvalent alcohols are particularly preferred as further components.

[0043] In a preferred embodiment of the invention, the reaction mixture is produced in such a way that the copper(II) compound is firstly dissolved or suspended in an aqueous solvent or dispersion medium and then phosphoric acid is added in a preferably at least stoichiometric amount.

[0044] In this case, it is particularly preferred to add the chelating agent to the aqueous solvent or dispersion medium before the addition of phosphoric acid. This ensures that the copper(II) compound is fully stabilized before the conversion with phosphoric acid occurs in step b). Thus, the beneficial effects associated with stabilization can be maximized.

[0045] Alternatively, a preferably at least stoichiometric amount of phosphoric acid can be dissolved or suspended in an aqueous solvent or dispersion medium and the copper(II) compound can subsequently be added thereto.

[0046] In another embodiment of the present invention, phosphoric acid and the copper (II) compound are added simultaneously to the solvent or dispersion medium to obtain a reaction mixture.

[0047] In another embodiment of the present invention, phosphoric acid and the copper (II) compound are added alternately in partial amounts to the solvent or dispersion medium in a periodic or aperiodic manner to obtain a reaction mixture.

[0048] Step b)

[0049] In step b), the copper (II) compound reacts with phosphoric acid in the reaction mixture. Steps a) and b) are not necessarily separated in time and may overlap. That is, the conversion of the copper (II) compound with phosphoric acid may start as early as when part of the copper (II) compound and / or phosphoric acid is added.

[0050] However, in an advantageous embodiment of the invention, steps a) and b) are separated in time, whereby step b), i.e. the conversion of the copper(II) compound with phosphoric acid, is only carried out 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 temperature of the reaction mixture below the temperature required to initiate the reaction of the copper(II) compound and the phosphoric acid.

[0051] The benefit of separating steps a) and b) is that the conversion process can be better tracked and controlled.

[0052] Step c)

[0053] In the last step, the copper(II) phosphate hydroxide is separated from the reaction mixture. This can be done by common separation methods. Particularly preferably, the separation method is selected from the group consisting of filtration, evaporation, centrifugation, precipitation and flotation.

[0054] Most preferably, the separation method is filtration. Thus, any impurities present in dissolved or finely dispersed form in the solvent or dispersion medium can be removed particularly effectively.

[0055] In a preferred embodiment of the present invention, the chelating agent is selected from the following group: amino acids, carboxylic acids, phosphoric acid, sulfuric acid and sulfonic acids and their salts, esters and amides; polyvalent alcohols; nitriles; bipyridines; phenanthrolines; polyvalent phenols; polyvalent amines; polyvalent ethers; lactams; oximes; urea derivatives; polyvalent ketones and aldehydes, such as acetylacetonate (acac); thiols, such as dimercaptosuccinic acid (DMSA); and combinations thereof.

[0056] Since copper(II) particularly preferably forms stable complexes with Lewis bases having semi-hard donor atoms such as N or Cl, chelating agents are preferably those which contain nitrogen as one or more donor atoms. Preferably, the chelating agent is selected from the group consisting of amino acids, carboxylic acid amides, nitriles, bipyridines, phenanthrolines, polyvalent amines, urea derivatives, lactams and oximes.

[0057] Particularly preferably, the chelating agent is selected from the group consisting of ethylenediamine (EN), 2-(2-aminoethylamino)ethanol (AEEA), diethylenetriamine (DIEN), iminodiacetate (IDA), triethylenetetramine (TRIEN, TETA), triaminotriethylamine (TRENE), nitrilotriacetate (NTA), bis(salicylidene)ethylenediamine (SALENE), ethylenediaminetriacetate (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.

[0058] The copper(II) in the copper(II) compound is particularly well stabilized in aqueous solvents or dispersion media by the addition of a Lewis base having a semi-hard donor atom (eg N).

[0059] Impurities can therefore be separated off particularly effectively, since the particularly strong stability of copper(II) means that the copper(II) compound can be dispersed better in the solvent or dispersion medium and impurities coprecipitate to a lower extent in step b).

[0060] In a preferred embodiment of the present 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) halide and combinations thereof. Particularly preferably, the copper (II) compound is selected from the group consisting of copper (II) fluoride, copper (II) chloride, copper (II) bromide, copper (II) hydroxide, copper (II) iodide and combinations thereof. Most preferably, the copper (II) compound is copper (II) chloride or copper (II) hydroxide.

[0061] Copper(II) hydroxide and copper(II) halides, in particular copper(II) chloride, have the advantage of being very widely available and at a relatively low purchase price.

[0062] Even if the copper(II) compound has a component, in particular an anion, which falls within the definition of a chelating ligand, the provision of this 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 reaction mixture component which has to be separated from the copper(II) compound.

[0063] In a preferred embodiment of the present invention, the chelating agent is an amino acid or an ester, amide or salt thereof. Particularly preferably, the chelating agent is a sodium salt of an amino acid. The advantage is that the sodium salt of an amino acid is usually particularly easy to dissolve in an aqueous solvent or a dispersion medium. The advantage of amino acids is that the copper (II) of the copper (II) compound can be stabilized by the carboxylic acid group and the amino group. Due to the particularly strong stabilization effect, very bright copper (II) phosphate hydroxide with low intrinsic color can be obtained.

[0064] In a preferred embodiment of the present invention, the amino acid is added before the addition of phosphoric acid, wherein the pH value of the reaction mixture before the addition of phosphoric acid is less than 7, preferably less than 5, even more preferably less than 4, most preferably less than 3. This can prevent the amino group of the amino acid from being present in a protonated form, thereby preventing coordination through the amino group.

[0065] In a particularly preferred embodiment of the present invention, the amino acid is a proteinogenic amino acid. Proteinogenic amino acids are amino acids that are used as protein building blocks in an organism during translation according to the specifications of genetic information. Particularly preferably, the proteinogenic amino acid is selected from the group consisting of alanine, asparagine, cysteine, glutamine, glycine, histidine, leucine, lysine, methionine, proline, serine, valine, and combinations thereof.

[0066] Protein amino acids of particularly high purity are available on the market. Therefore, contamination of copper (II) hydroxide phosphate with foreign matter attached to the chelating agent can be kept at a low level. As a result, particularly pure and bright copper (II) hydroxide phosphate with low inherent color can be obtained.

[0067] By using amino acids as chelating agents, it is possible to obtain copper(II) phosphate hydroxide crystals in the form of elongated prisms that have aggregated to form larger elongated structures.

[0068] In another preferred embodiment of the present invention, the chelating agent is selected from aminosulfonic acid, preferably from taurine and p-aminobenzenesulfonic acid and salts and esters thereof.

[0069] In a preferred embodiment of the invention, the chelating agent is a carboxylic acid or an ester, amide or salt thereof. In a preferred embodiment, the carboxylic acid is a polyvalent carboxylic acid, i.e. a carboxylic acid having a plurality of carboxylic acid groups. Particularly preferably, the carboxylic acid is a hydroxycarboxylic acid, in particular a fruit acid. Particularly preferably, the carboxylic acid, hydroxycarboxylic acid or a salt thereof 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, alkali metal citrates, in particular monosodium citrate, isocitric acid and trimesic acid.

[0070] The advantage of hydroxycarboxylic acids is that they can stabilize the copper(II) compound in the solvent or dispersion medium by both the carboxylic acid group and the hydroxyl group. Therefore, the advantages associated with stabilization are particularly significant.

[0071] In another preferred embodiment of the present invention, the chelating agent is selected from sugars, in particular from monosaccharides, oligosaccharides and polysaccharides, including cyclodextrins.

[0072] Preferably, the carbohydrate is 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-cyclodextrin), or polysaccharides (such as alginate).

[0073] It is particularly preferred that the chelating agent is selected from the group consisting of sucrose, fructose and galactose; the most preferred chelating agent is sucrose.

[0074] The sugars coordinate to the copper(II) via the free electron pairs of the OH groups. Since sugars contain a plurality of OH groups and therefore a plurality of coordination sites, they can stabilize the copper(II) of the copper(II) compound particularly well.

[0075] In addition, sugars generally do not contain aromatic molecular components or heteroatoms (such as S and P), so the intrinsic color of sugars is extremely low. Therefore, the sugar substances remaining in the product after the reaction will not cause obvious discoloration of the product, which means that particularly bright copper (II) phosphate hydroxide with low intrinsic color can be obtained.

[0076] In another embodiment of the invention, the chelating agent is a polyol, in particular an alditol, ie a reduced form of a sugar, such as mannitol, lactitol, sorbitol, xylitol, threitol, erythritol or arabitol.

[0077] By using sugars as chelating agents, rod-shaped copper (II) phosphate hydroxide crystals can be obtained.

[0078] The inventors have shown that by adding a chelating agent with multiple coordination sites, i.e. more than 15 coordination sites, a "broccoli"-like crystal structure can be obtained. Such chelating agents are, for example, polyphosphates, polyethers (such as polyethylene glycol, polyethylene oxide and polypropylene glycol, polyvinyl pyrrolidone and alginates).

[0079] In another preferred embodiment, the chelating agent is selected from diphosphoric acid or polyphosphoric acid, or a salt thereof. Preferably, the chelating agent is selected from the group consisting of basic phosphates, basic metaphosphates and basic polyphosphates, with K5P3O being quite particularly preferred. 10 .

[0080] In another preferred embodiment of the present invention, the chelating agent is ascorbic acid. The inventors have found that by adding ascorbic acid, copper (II) phosphate hydroxide with a particularly high specific surface area can be prepared. Its specific surface area> 10m 2 / g, preferably>15m 2 / g, particularly preferably>20m 2 / g, even more preferably>30m 2 / g, most preferably>40m 2 / g.

[0081] Without being bound by this theory, the inventors believe that this is due to the fact that ascorbic acid is easily oxidized, thereby generating a semi-stable complex of ascorbic acid and copper (II) in step a) and / or b), resulting in a highly porous final product. Similar results can be obtained with citric acid and / or its salts, especially in combination with phosphates as a further chelating agent.

[0082] However, it should be borne in mind in this connection that the amount of ascorbic acid and / or citric acid or their salts added should not exceed 3 wt %, preferably not exceed 2 wt %, particularly preferably not exceed 1.5 wt %, and most preferably not exceed 1 wt %, relative to the amount of copper(II) compound. Otherwise, the phase purity of the copper(II) hydroxide may be significantly less than 100%.

[0083] In a preferred embodiment of the present invention, the chelating agent is a surfactant, ie a surface-active substance, which contains both a hydrophobic molecular part consisting of an organic group and a hydrophilic molecular part containing a polar group, wherein the polar group is preferably charged.

[0084] In a preferred embodiment, the surfactant is a nonionic surfactant or an anionic surfactant. Preferably, the hydrophilic molecular part comprises a carboxylate, sulfonate, hydroxyl, ether or ethoxy group.

[0085] In another preferred embodiment of the present invention, the surfactant is selected from the group consisting of cationic surfactants, such as tetraalkylammonium salts (such as hexadecyltrimethylammonium bromide or hexadecyltrimethylammonium chloride), anionic surfactants (such as alkyl carboxylates) and amphoteric surfactants (such as betaine).

[0086] By using amino acids as chelating agents, it is possible to obtain copper(II) phosphate hydroxide crystals in the form of elongated prisms that have aggregated to form a star-shaped structure.

[0087] Chelating agents are added to the reaction mixture to stabilize the copper(II) compounds. For this purpose, only low concentrations of chelating agents are generally required.

[0088] Because generally speaking, at least a portion of the chelating agent remains in the product after the reaction, which may cause discoloration of the product. In addition, for cost considerations, excessive chelating agent should also be avoided. Therefore, in steps a) and / or b), the total amount of chelating agent added to the reaction mixture is preferably no more than 5.0 wt%.

[0089] However, too little chelating agent has the disadvantage that only a slight stabilizing effect may be obtained.

[0090] Therefore, in a preferred embodiment of the present invention, 0.1 to 5.0 wt % of chelating agent, relative to the amount of copper(II) compound, is added to the reaction mixture in process steps a) and / or b).

[0091] Particularly preferably, the chelating agent is 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 %.

[0092] By the process according to the invention, particularly pure copper(II) hydroxide phosphate can be obtained. This means that the phase purity of the copper(II) hydroxide phosphate is greater than 90%, preferably greater than 95%, more preferably greater than 98%, particularly preferably greater than 99%, and most preferably greater than 99.5%.

[0093] Phase purity can be determined by X-ray structural analysis in the following manner.

[0094] Quantitative phase determination is achieved by the Rietveld method, as described in detail in "Quantitative phase analysis using the Rietveld method", DLBish and SA Howard, J. Appl. Cryst. (1988) 21, 86-91, or in the textbook "Rietveld method", Chapter 1, "Introduction to the Rietveld method", RA Young, ed., Oxford University Press (1995). The analysis is preferably performed by image analysis software, such as the Topas program from Bruker.

[0095] In another preferred embodiment of the present invention, the copper(II) phosphate hydroxide obtained in process step c) has an L value in the L*a*b* color space (CIELAB) of >78, preferably >80, particularly preferably >82, even more preferably >85, most preferably >87.

[0096] The L*a*b* color space according to DIN EN ISO 11664-4 is used to describe all perceptible colors. In the three-dimensional L*a*b* color space, the lightness values ​​L* are arranged vertically on a flat color plane (a*, b*).

[0097] On the a* axis, green and red are opposite each other, while the b* axis separates blue and yellow. Therefore, complementary colors are 180° opposite each other. The L* axis defines the brightness of the color, covering values ​​from 0 to 100, with 100 representing the highest brightness.

[0098] Some of the most important properties of the L*a*b* color model are that it is device-independent and based on perception. In other words, color is defined as it is perceived by a normal observer under standard lighting conditions, regardless of how it is produced or the technology used to display it.

[0099] In the case of the present invention, the method of determining the L*a*b* value is as follows.

[0100] The L*a*b* values ​​were determined using an UltraScan VIS spectrophotometer from HunterLab. To this end, the sample was poured into a glass cuvette and a uniform surface was created on the side of the cuvette opposite the measurement opening by tapping the cuvette or compacting the sample.

[0101] In another preferred embodiment of the present invention, the copper(II) hydroxide phosphate obtained in process step c) consists of particles whose median particle size, after determination by laser diffraction analysis in accordance with DIN-ISO 13320-1, is from 2 to 10 μm, preferably from 2 to 8 μm, particularly preferably from 2 to 7 μm, even more preferably from 2 to 6 μm and most preferably from 2 to 5 μm.

[0102] In the present case, the particle size is determined according to the currently valid DIN-ISO 13320-1. For this purpose, the prepared product sample is dispersed in a dispersion medium (2-propanol or tetrasodium pyrophosphate in deionized water, 14 mmol / L) and wet measured using a Horiba LA-950V in a measuring range of 0.01 μm to 3000 μm.

[0103] In a further preferred embodiment of the present invention, the copper(II) hydroxide phosphate obtained in process step c) consists of rod-shaped particles with an aspect ratio of 1:3 to 1:10.

[0104] According to the present invention, the term "aspect ratio" refers to the ratio of the largest extension to the smallest extension of a particle.

[0105] The present invention further relates to copper(II) hydroxide phosphate obtainable by the process according to the invention, wherein the copper(II) hydroxide phosphate has an L value in the L*a*b* color space (CIELAB) of >78, preferably >80, particularly preferably >82, even more preferably >85, most preferably >87.

[0106] The invention further relates to the use of a chelating agent in the production of copper (II) hydroxide phosphate, by converting a copper (II) compound with phosphoric acid to change the crystal properties of the produced copper (II) hydroxide phosphate. Example

[0107] The present invention will now be explained on the basis of specific embodiments according to preparation examples of the present invention.

[0108] Raw materials:

[0109]

[0110] Measurement method

[0111] Particle size measurement media, D10, D90

[0112] The particle size distribution was determined by dynamic light diffraction using a Horiba Partica LA-950V (Horiba Co., Ltd.; Tokyo; Japan) in terms of both volume and particle size. To this end, the prepared product samples were dispersed in a dispersion medium (2-propanol or tetrasodium pyrophosphate in deionized water, 14 mmol / L) and wet measured using a Horiba LA-950V in the measurement range of 0.01 μm to 3000 μm.

[0113] Phase purity

[0114] Phase purity was determined by X-ray structural analysis. The products prepared according to the following examples were subjected to X-ray diffraction measurements (XRD) on a diffractometer, model D8 Advance A25 (Bruker), using CuKα radiation. Quantitative phase determination was carried out by the Rietveld method (see "Quantitative Phase Analysis Using the Rietveld Method", DLBish and SA Howard, J. Appl. Cryst. (1988) 21, 86-91, or the textbook "Ritveld Method", Chapter 1, "Introduction to the Rietveld Method", RA Young, ed., Oxford University Press (1995)) using the image analysis program Topas 4.2 of Bruker.

[0115] L*a*b* value

[0116] The L*a*b* values ​​were determined using an UltraScan VIS-2 spectrophotometer equipped with the HunterLab sensor Ultra Sensor VIS. To do this, the sample was poured into a glass cuvette and a uniform surface was created on the side of the cuvette opposite the measurement opening by tapping the cuvette or compacting the sample. The associated software Easy Match QC4.64 used the "USVIS 1145" sensor and the "RSIN mode" settings and calculated the LAB values.

[0117] The method is carried out in accordance with the currently valid version of EN ISO 11664-4.

[0118] Specific surface area

[0119] The specific surface area was determined according to the BET method using a nitrogen absorption method (DIN ISO 9277) on a BELSORP-mini machine from BEL. The nitrogen used had a purity of 99.999%.

[0120] Scanning electron microscopy

[0121] For scanning electron microscopy (SEM) images, a Sigma EVOSEM spectrometer from Zeiss and an INCA Energy 350EDX detector from Oxford were used.

[0122] General description of the experiment

[0123] 150 g Cu(OH)2 (1.54 mol) was suspended in 2250 ml distilled water to produce a blue suspension. This was heated to 90°C, 120 g phosphoric acid (75 wt%, 0.92 mol) and one or more additives in the amounts specified in Table 1 were added, and the reaction mixture was heated to boiling point. After 15 minutes, the crude product was filtered out, resuspended in 1000 ml water, filtered again, and dried overnight in a drying oven at 105°C.

[0124] Table 1:

[0125]

[0126]

[0127] [1] Hexadecyltrimethylammonium bromide

[0128] [2] EFP = elongated prismatic, highly fragmented (composed of many longitudinally clustered crystals), partially agglomerated

[0129] [3]EP = elongated prism, partially agglomerated

[0130] [4] ST = Star shape from longitudinally aggregated crystals

[0131] [5] nd = not determined

Claims

1. A method for preparing copper (II) hydroxide phosphate, comprising the following steps: a) producing a reaction mixture from an aqueous solution or dispersion of phosphoric acid and a copper(II) compound, b) converting a copper(II) compound with phosphoric acid in a reaction mixture, and c) separating copper(II) hydroxide phosphate from the reaction mixture, wherein the conversion in step b) is carried out in a non-pressurized manner, Features In process steps a) and / or b), at least one chelating agent is added to the reaction mixture.

2. The method according to claim 1, characterized in that The amount of phosphoric acid is at least stoichiometric, wherein "at least stoichiometric" means that the amount of copper (II) ions of the copper (II) compound relative to the amount of phosphoric acid in the reaction mixture is at most 2.

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

4. The method according to claim 1, 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) halide, and combinations thereof.

5. The method according to claim 1, characterized in that The at least one chelating agent is an amino acid or a salt thereof, wherein the amino acid is selected from proteinogenic amino acids.

6. The method according to claim 1, characterized in that The at least one chelating agent is a carboxylic acid, a hydroxycarboxylic acid or a salt thereof.

7. The method according to claim 6, characterized in that 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 thereof.

8. The method according to claim 1, characterized in that The at least one chelating agent is a saccharide selected from monosaccharides and oligosaccharides.

9. The method according to claim 1, characterized in that The at least one chelating agent is ascorbic acid.

10. The method according to claim 1, characterized in that The at least one chelating agent is a surfactant.

11. The method according to claim 10, characterized in that The surfactant is selected from anionic surfactants and nonionic surfactants.

12. The method according to claim 1, characterized in that The at least one chelating agent is added in a total amount of 0.1 to 5.0 wt % relative to the amount of the copper (II) compound.

13. Copper (II) phosphate hydroxide obtained by the method according to any one of claims 1 to 12, characterized in that The copper(II) hydroxide phosphate has an L* value of >78 in the L*a*b* color space.

14. Use of a chelating agent in the production of copper (II) hydroxide phosphate obtained by the process according to any one of claims 1 to 12, in order to change the crystal properties of the produced copper (II) hydroxide phosphate.

Images