Water-soluble container containing dye and method for producing a colored aqueous alkaline metal cyanide solution

Description

[0001] The invention relates to a water-soluble container filled with at least one dye or at least one dye composition. The water-soluble container according to the invention can be used in a process for producing colored, aqueous alkali metal cyanide solutions. The invention also relates to a process for producing a pre-application composition, comprising at least one water-soluble container according to the invention and at least one water-soluble alkali metal cyanide compound, as well as the aqueous application composition obtainable therefrom by dissolution. State of the art

[0002] Alkali metal cyanide compounds, especially sodium cyanide, are used as leaching agents in the mining industry, particularly in gold and silver extraction. Solid alkali metal cyanide is usually delivered to the mine and dissolved on-site in a dissolution station in water or an aqueous solvent to produce an aqueous alkali metal cyanide solution. This aqueous alkali metal cyanide solution is then brought into contact with the ore, dissolving the accessible metal through the formation of a corresponding metal-cyanide complex. Depending on the mine's geographical location, the water used for dissolution may have low temperatures, often ≤ 15 °C, high hardness, or high salinity.

[0003] The alkali metal cyanide compounds used are problematic for humans and the environment. Alkali metal cyanide solutions are colorless and indistinguishable from water to the naked eye. Therefore, especially in the case of leaks, it is impossible to tell with the naked eye whether the substance is just water or an alkali metal cyanide solution. To make alkali metal cyanide solutions distinguishable from water, they can be dyed. For stronger alkali metal cyanide solutions, this is required by the International Cyanide Management Institute.

[0004] If one wants to produce weak and stronger alkali metal cyanide solutions from the same batch of delivered solid alkali metal cyanide, and to be able to distinguish the weak alkali metal cyanide solutions from the stronger alkali metal cyanide solutions, the coloring takes place at the dissolving station when the need for coloring actually exists.

[0005] Alternatively, one could keep two batches of solid alkali metal cyanide on hand: one uncolored for the weak alkali metal cyanide solutions and one colored for the stronger alkali metal cyanide solutions. However, this would entail a correspondingly larger storage requirement and additional capital commitment.

[0006] Water-soluble containers based on polyvinyl alcohols, suitable for holding additives, are known from the prior art and are described, for example, in US 6,124,036, WO 02 / 16205, EP 0 457 715 and CH 579 667. However, the disclosed water-soluble containers are not suitable for use in aqueous solvents, which are often found in mines (aqueous solvents with low temperature, high hardness, or salinity), and under these conditions, the containers cannot dissolve quickly enough or can only dissolve incompletely.

[0007] US 6,124,036 discloses an article comprising (a) an aqueous composition of 70 to 95 parts of a poly(oxyalkylene)-substituted chromogen and 5 to 30 parts of water; and (b) a water-soluble film containing the composition. The water-soluble film preferably consists of poly(vinyl alcohol).

[0008] The present invention is based on the objective of providing a means by which a dye or dye composition contained in a water-soluble container can be added to water or aqueous solvent at the dissolution station in the simplest possible manner and within a reasonable timeframe. In particular, almost complete dissolution within a reasonable timeframe should be ensured even under the conditions prevailing in some mines (low ambient and water temperatures, water with a high content of salts and minerals (especially NaOH, NaCl, CaCO₃, Ca(OH)₂, and MgCO₃)). Description

[0009] The object is achieved according to the invention with a water-soluble container suitable for receiving an additive or additive composition and filled with an additive or additive composition comprising at least one dye or at least one dye composition. wherein the water-soluble container has a wall thickness in the range of 5 to 50 µm, and wherein the water-soluble container comprises or consists of a water-soluble polymer composition, wherein the polymer composition comprises: a) at least one polyvinyl alcohol copolymer P1 with a degree of hydrolysis in the range of 75 to 95 mol%, wherein the polyvinyl alcohol copolymer P1 is a copolymer comprising vinyl alcohol repeat units, vinyl ester repeat units and repeat units of at least one comonomer, wherein the at least one comonomer is selected from pentaerythritol acrylate and optionally acrylic acid;or b) at least one polyvinyl alcohol copolymer P1 with a degree of hydrolysis in the range of 75 to 95 mol%, wherein the polyvinyl alcohol copolymer P1 is a copolymer comprising vinyl alcohol repeat units, vinyl ester repeat units, and repeat units of at least one comonomer, wherein the at least one comonomer is selected from pentaerythritol acrylate and optionally acrylic acid; and at least one polyvinyl alcohol P2 with a degree of hydrolysis in the range of 87 to 95 mol%; wherein, in addition to a) the at least one polyvinyl alcohol copolymer P1 or b) the at least one polyvinyl alcohol copolymer P1 and the at least one polyvinyl alcohol P2, the polymer composition may optionally contain additives;wherein the polymer composition, in the case that it comprises at least one polyvinyl alcohol copolymer P1 and no polyvinyl alcohol P2, has a content of repeating units of the at least one comonomer in the range of 10 to 20 wt%, based on the total weight of polyvinyl alcohol copolymer P1; and wherein the polymer composition, in the case that it comprises at least one polyvinyl alcohol copolymer P1 and at least one polyvinyl alcohol P2, has a content of repeating units of the at least one comonomer in the range of 10 to 20 wt%, based on the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2.

[0010] In one embodiment, the invention relates to a water-soluble container suitable for receiving an additive or additive composition and filled with an additive or additive composition comprising at least one dye or at least one dye composition. wherein the water-soluble container has a wall thickness in the range of 5 to 50 µm, and wherein the water-soluble container consists of a polymer composition, the polymer composition comprising at least one polyvinyl alcohol copolymer P1, wherein the comonomer content is in the range of 10 to 20 wt.%, based on the total weight of polyvinyl alcohol copolymer P1. In this embodiment, the polymer composition does not include any polyvinyl alcohol P2 according to this invention.

[0011] In a further embodiment, the invention relates to a water-soluble container suitable for receiving an additive or additive composition and filled with an additive or additive composition comprising at least one dye or at least one dye composition, wherein the water-soluble container has a wall thickness in the range of 5 to 50 µm, and wherein the water-soluble container comprises or consists of a water-soluble polymer composition, wherein the polymer composition comprises at least one polyvinyl alcohol copolymer P1 and at least one polyvinyl alcohol P2, wherein the comonomer content is in the range of a total of 10 to 20 wt.%, based on the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2.In this embodiment, the polymer composition comprises a mixture of at least one polyvinyl alcohol copolymer P1 and at least one polyvinyl alcohol P2 according to this invention.

[0012] The container with the additive or additive composition can be placed in the dissolving station and immersed in the water or aqueous solvent. It dissolves, thereby releasing the additive or additive composition along with the dye or dye composition.

[0013] Thus, it is possible to produce both colorless alkali metal cyanide solutions (i.e., the container with the additive or additive composition is not added to the water or aqueous solvent) and colored alkali metal cyanide solutions (i.e., the container with the additive or additive composition is added to the water or aqueous solvent) from the same batch of solid alkali metal cyanide.

[0014] Alternatively, it is also possible to supply solid alkali metal cyanide with an accompanying container according to the invention containing the additive or additive composition, e.g., in a single container. With such a supplied combination of solid alkali metal cyanide on the one hand and the container with the additive or additive composition on the other, it is not necessary to change the established procedures at the dissolution station in the mine. The aforementioned combination can simply be mixed with water or aqueous solvent, thereby releasing the additive or additive composition.

[0015] It was found that the polyvinyl alcohol copolymer P1 according to the invention exhibits particularly good water solubility at a degree of hydrolysis in the range of 75 to 95 mol%, even when the liquid aqueous solvent has a temperature of approximately ≤ 15°C, in particular approximately 1 to 10°C, and / or a pH value in the range of 6 to 14. This means that even in mines containing water or aqueous solvents at low temperatures (≤ 15°C, in particular approximately 1 to 10°C) or a pH value in the range of 6 to 14, the material of the container according to the invention dissolves at a good rate. Good water solubility is also achieved with the container according to the invention in liquid aqueous solvents with a comparatively high content of salts and / or minerals (in particular NaCl, CaCO₃, and MgCO₃), such as seawater.

[0016] Likewise, the polyvinyl alcohol P2 according to the invention, with a degree of hydrolysis in the range of 87 to 95 mol%, exhibits particularly good water solubility, even when the liquid aqueous solvent has a temperature of approximately ≤ 15 °C, in particular approximately 1 to 10 °C, and / or the liquid aqueous solvent has a pH value in the range of 6 to 14.

[0017] Likewise, the mixture of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2 exhibits particularly good water solubility, provided that the comonomer content is in the range of 10 to 20 wt.%, based on the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2, even when the liquid aqueous solvent has a temperature of approximately ≤ 15 °C, in particular approximately 1 to 10 °C, and / or the liquid aqueous solvent has a pH value in the range of 6 to 14.

[0018] In particular, water-soluble containers according to the invention, comprising the polyvinyl alcohol copolymer P1, are characterized by the fact that aging processes which negatively affect the solubility and mechanical properties (such as deformability, flexibility, brittleness) of the container in aqueous solvents are suppressed or occur only at a low rate. Without being bound to this theory, it is assumed that the crystallization of the polymer during storage, chemical reactions with surrounding media, especially cyanide compounds, during storage, and the water content of the polymer composition play a role in these aging processes.

[0019] The total content of repeat units of the at least one comonomer, selected from pentaerythritol acrylate and optionally acrylic acid, is, according to the invention, in the range of 10 to 20 wt.%, based on the total weight of polyvinyl alcohol copolymer P1 and optionally polyvinyl alcohol P2. If no polyvinyl alcohol P2 is present, the comonomer content refers to the weight of polyvinyl alcohol copolymer P1 alone. It has been observed that a comonomer content of at least 10 wt.% is required to achieve sufficient inhomogeneity in the polymer chains of the polymer composition in order to suppress crystallization of the polymers and to ensure solubility even after prolonged storage. Even after storage in chemically aggressive environments (e.g., in the presence of cyanide compounds), polyvinyl alcohol copolymers P1 with a total comonomer content of 10 to 20 wt.% have been found to retain their solubility.-% shows good solubility. However, a comonomer content of more than 20 wt% has a negative impact on the solubility of the polymer composition and is therefore disadvantageous.

[0020] With a container wall thickness in the range of 5 to 50 µm, the container walls have a good surface area to volume ratio. This means that the material thickness through which the liquid water or liquid aqueous solvent has to penetrate is relatively small. This also contributes to the container dissolving at a good rate. Furthermore, containers with a wall thickness in the range of 5 to 50 µm exhibit sufficiently good mechanical stability.

[0021] The polyvinyl alcohol copolymer P1, like the polyvinyl alcohol P2, has thermoplastic properties. Therefore, material produced from this polymer composition can be thermoplastically deformed and joined by fusion welding. Accordingly, the walls of the container can be joined together by fusion welding.

[0022] A "container" within the meaning of this invention is a three-dimensional structure used to hold substances and at least partially enclosing them. It can, for example, be designed as a dimensionally stable container or as a bag. Film bags are particularly preferred. Film bags can be obtained, for example, by welding two layers of film together, by folding a film and welding the open sides, or preferably from film tubes by welding both ends together.

[0023] Within the scope of this invention, "water-soluble" or "soluble" means, with regard to the container, that the container dissolves in a sufficient quantity of an aqueous solvent to at least 50% by weight, preferably at least 75% by weight, and in particular at least 95% by weight, based on the total weight of the water-soluble container. Any non-water-soluble components of the polymer composition are accordingly "released" by the dissolution of the water-soluble components.

[0024] The dissolution rate of the water-soluble container can be determined, for example, by dissolving the water-soluble container, which contains a predetermined amount of at least one water-soluble dye or at least one water-soluble dye composition, in an aqueous solvent at a predetermined temperature, in particular a temperature specified by the intended application (e.g., a temperature ≤ 15 °C), while stirring, and then determining the time until the maximum dye concentration in the solution is reached. To determine when the maximum dye concentration is reached, the absorbance of the solution can be measured at regular intervals, for example, by UV / Vis spectroscopy or photometry. A method for determining the dissolution rate of the water-soluble container is described in the examples.The expert can adapt the procedure described there to the respective requirements.

[0025] The completeness of dissolution of the water-soluble container can be determined, for example, optically. Large polymer residues are visually detectable if dissolution is incomplete (possibly after filtration). Smaller polymer residues can be detected using suitable optical methods, such as nephelometry, due to the Tyndall effect. Suitable methods are familiar to those skilled in the art.

[0026] A polymer composition that dissolves completely without residue is particularly preferred; that is, the water-soluble container dissolves 100% by weight in the aqueous solvent. This avoids residues of the polymer composition that could clog filter systems and / or pumps when used in a mine.

[0027] An "aqueous solvent" within the meaning of this invention is a solvent that consists of at least 50% by weight, and in particular at least 60% by weight, water based on the total weight of the solvent. Furthermore, the aqueous solvent may comprise dissolved additives, in particular basic additives (for example, hydroxide salts such as NaOH and KOH), salts (such as NaCl, CaCO₃, Ca(OH)₂, MgCO₃), and at least one cyanide compound. Suitable cyanide compounds are in particular alkali metal cyanide compounds, for example, sodium cyanide (NaCN) and potassium cyanide (KCN).

[0028] The water used can be of any origin. It can be drinking water, demineralized water, groundwater, river water, seawater, or treated water, such as process water, particularly from the mining industry (e.g., a processed leaching solution). The solvent composition refers to the solvents themselves and the substances dissolved in them. Solids, such as sediments from river water, are not considered.

[0029] Generally, polyvinyl alcohols are produced on an industrial scale by first synthesizing a polyvinyl ester using suitable polymerization processes. The resulting polyvinyl ester is then converted to polyvinyl alcohol in a polymer-analogous hydrolysis reaction, whereby the proportion of vinyl ester repeat units remaining in the polymer can vary depending on the reaction conditions. The proportion of vinyl alcohol repeat units in the polymer is usually expressed in mol% and is referred to as the degree of hydrolysis of the polyvinyl alcohol.

[0030] The polyvinyl alcohol copolymers P1 and the polyvinyl alcohols P2 according to the invention cannot therefore be obtained by the direct copolymerization of the monomers constituting them, but are obtained by polymerization followed by hydrolysis of the polymer obtained.

[0031] The composition of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2 can be determined using known analytical methods. IR and NMR spectroscopy are particularly suitable.

[0032] NMR analysis of the polyvinyl alcohol copolymer P1 or the polyvinyl alcohol P2 is carried out, for example, using 1< H-NMR and 13< C-NMR in solution (with a suitable solvent such as deuterated dimethyl sulfoxide, DMSO-D6) or in the solid state.

[0033] IR analysis of the polyvinyl alcohol copolymer P1 or the polyvinyl alcohol P2 is carried out, for example, using ATR infrared spectroscopy (ATR = attenuated total reflection) on polymer films.

[0034] The degree of hydrolysis of the polyvinyl alcohol copolymer P1 or the polyvinyl alcohol P2 can be determined by quantitative <1H NMR spectroscopy. To avoid proton exchange of the polyvinyl alcohol, a <1H NMR solid-state spectrum is recorded using a suitable internal standard. The degree of hydrolysis can then be quantitatively determined by evaluating the areas of the individual signals in the <1H NMR spectrum that can be assigned to the protons in the polymer.

[0035] The polymer composition contains a) at least one polyvinyl alcohol copolymer P1 with a degree of hydrolysis in the range of 75 to 95 mol% or b) at least one polyvinyl alcohol copolymer P1 with a degree of hydrolysis in the range of 75 to 95 mol% and at least one polyvinyl alcohol P2 with a degree of hydrolysis in the range of 87 to 95 mol%.

[0036] The polyvinyl alcohol copolymers P1 according to the invention can be obtained by hydrolysis of poly(vinyl ester-co-pentaerythritol acrylate), in particular by hydrolysis of poly(vinyl acetate-co-pentaerythritol acrylate). If the hydrolysis of a poly(vinyl ester-co-pentaerythritol acrylate) is stopped before the reaction of all vinyl acetate repeat units, the poly(vinyl alcohol-co-vinyl ester-co-pentaerythritol acrylate) is obtained. Complete hydrolysis of the vinyl ester repeat units of poly(vinyl ester-co-pentaerythritol acrylate) enables the preparation of poly(vinyl alcohol-co-pentaerythritol acrylate). Poly(vinyl alcohol-co-vinyl ester-co-pentaerythritol acrylate) and poly(vinyl alcohol-co-vinyl ester-co-pentaerythritol acrylate-co-acrylic acid) can be obtained selectively under suitable reaction conditions.

[0037] Preferred polyvinyl alcohol copolymers P1 according to this invention are polymer compounds comprising or consisting of repeating units, in particular of the following structures (I), (II) and (III): wherein R1 is a linear or branched alkyl group with 1 to 8 carbon atoms, preferably a linear alkyl group with 1 to 5 carbon atoms, and particularly preferably a methyl group or an ethyl group.

[0038] Optionally, the polyvinyl alcohol copolymers P1 according to the invention can further comprise repeating units of the following structure (IV):

[0039] Vinyl alcohol repeat units of structure (I) are typically obtained by hydrolysis of vinyl ester repeat units of structure (II). Acrylic acid repeat units of structure (IV) are typically obtained by hydrolysis of pentaerythritol acrylate repeat units of structure (III).

[0040] Repeating units of structure (I) are also referred to herein as vinyl alcohol repeating units. Repeating units of structure (II) are also referred to herein as vinyl ester repeating units. Repeating units of structure (III) are also referred to herein as pentaerythritol acrylate repeating units. Repeating units of structure (IV) are also referred to herein as acrylic acid repeating units.

[0041] In a further preferred embodiment, the polyvinyl alcohol copolymer P1 according to the invention comprises repeating units of the following structures (I), (II.1), (III) and optionally (IV) or consists of these:

[0042] The repeating units of structure (II.1) are also referred to herein as vinyl acetate repeating units.

[0043] The polyvinyl alcohol copolymers P1 according to the invention are produced by the copolymerization of monomers with hydrolyzable functional groups (in particular vinyl esters) and pentaerythritol acrylate, followed by polymer-analogous hydrolysis of at least a portion of the hydrolyzable functional groups of the resulting polymer. The degree of hydrolysis of a polyvinyl alcohol copolymer P1 specified herein indicates the molar fraction of vinyl alcohol repeat units of structure (I), based on the sum of the vinyl alcohol repeat units of structure (I) and the repeat units obtained from the polymerization of the monomers with hydrolyzable functional groups (in particular repeat units of structure (II) or (II.1)). Further comonomers, in particular repeat units of structures (III) and (VI), are not taken into account when determining the degree of hydrolysis of the polyvinyl alcohol copolymer P1 according to the invention.Nevertheless, the other comonomers, especially repeating units of structure (III), can also undergo hydrolysis reactions. Hydrolysis of the repeating units of structure (III) yields, in particular, repeating units of structure (IV) in a polymer-analogous hydrolysis reaction.

[0044] The polyvinyl alcohol copolymers P1 according to the invention have a degree of hydrolysis in the range of 75 to 95 mol%, preferably 80 to 90 mol%, more preferably 85 to 90 mol%. This means that the polyvinyl alcohol content of these polyvinyl alcohol copolymers P1 consists of 75 to 95 mol% repeat units of structure (I) and 5 to 25 mol% repeat units of structure (II), where the percentages refer to the sum of the repeat units of structure (I) and the repeat units of structure (II). Additionally, the polyvinyl alcohol copolymers P1 comprise repeat units of structure (III) and optionally repeat units of structure (IV), which do not contribute to the degree of hydrolysis or are not taken into account in the calculation of the degree of hydrolysis.

[0045] In a preferred embodiment of the invention, the polymer composition comprises at least one polyvinyl alcohol copolymer P1, with at least one vinyl alcohol repeating unit, at least one vinyl acetate repeating unit, and at least one pentaerythritol acrylate repeating unit. In one embodiment, the polyvinyl alcohol copolymer P1 further comprises acrylic acid repeating units. The polyvinyl alcohol copolymer P1 can thus preferably be selected from a poly(vinyl alcohol-co-vinyl acetate-co-pentaerythritol acrylate), a poly(vinyl alcohol-co-vinyl acetate-co-pentaerythritol acrylate-co-acrylic acid), or a mixture of the aforementioned. Preferably, the polyvinyl alcohol copolymer P1 is a poly(vinyl alcohol-co-vinyl acetate-co-pentaerythritol acrylate), a poly(vinyl alcohol-co-vinyl acetate-co-pentaerythritol acrylate-co-acrylic acid), or a mixture of the aforementioned.

[0046] In one embodiment, the polyvinyl alcohol copolymer P1 is a polyvinyl alcohol copolymer P1.1 comprising 10 to 20 wt.% repeat units derived from pentaerythritol acrylate (repeat units of formula (III)) and optionally from acrylic acid (repeat units of formula (IV)), based on the total weight of polyvinyl alcohol copolymer P1. More preferably, the polyvinyl alcohol copolymer P1.1 comprises repeat units derived from pentaerythritol acrylate (repeat units of formula (III)) and optionally from acrylic acid (repeat units of formula (IV)) in a range of 10.5 to 17.5 wt.%, in particular 11 to 15 wt.%, based on the total weight of polyvinyl alcohol copolymer P1.1.The proportion of repeat units derived from vinyl alcohol (repeat units of formula (I)) and from vinyl ester (repeat units of formula (II)) in the polyvinyl alcohol P1.1 is accordingly 80 to 90 wt.%, based on the total weight of the polyvinyl alcohol copolymer P1.1, preferably 82.5 to 89.5 wt.%, more preferably 85 to 89 wt.%.

[0047] Preferably, the ratio of pentaerythritol acrylate repeat units (repeat units of formula (III)) to acrylic acid repeat units (repeat units of formula (IV)) in the polyvinyl alcohol copolymer P1 is in a range of 1:1 to 1:0.

[0048] As previously described, the polyvinyl alcohol component in the polyvinyl alcohol copolymer P1 consists of vinyl alcohol repeat units and vinyl ester repeat units (preferably vinyl acetate repeat units). The proportion of vinyl ester repeat units is in the range of 5 to 25 mol%, based on the total amount of polyvinyl alcohol and vinyl ester repeat units in the polyvinyl alcohol copolymer P1, preferably in the range of 10 to 20 mol%, and particularly preferably in the range of 10 to 15 mol%. In this case, the polyvinyl alcohol component contained in the polyvinyl alcohol copolymer P1 thus comprises vinyl alcohol repeat units in the range of 75 to 95 mol%, preferably in the range of 80 to 90 mol%, and particularly preferably in the range of 85 to 90 mol%, based on the total amount of polyvinyl alcohol and vinyl ester repeat units in the polyvinyl alcohol copolymer P1.This corresponds to a degree of hydrolysis of the polyvinyl alcohol content of 75 to 95 mol%, preferably 80 to 90 mol%, particularly preferably 85 to 90 mol%.

[0049] In other words, the polyvinyl alcohol copolymer P1 in a preferred embodiment comprises: a) 80 to 90 wt.%, preferably 82.5 to 89.5 wt.%, particularly preferably 85 to 89 wt.%, based on the total weight of polyvinyl alcohol copolymer P1, of repeating units of formulas (I) and (II.1), and b) 10 to 20 wt.%, preferably 10.5 to 17.5 wt.%, particularly 11 to 15 wt.%, based on the total weight of polyvinyl alcohol copolymer P1, of repeating units of formulas (III) and (IV), wherein the repeating units of formula (I) constitute 75 to 95 mol%, preferably 80 to 90 mol%, in particular 85 to 90 mol% of the repeating units of formulas (I) and (II.1), based on the sum of the repeating units of formulas (I) and (II.1), and wherein repeating units of formula (III) constitute 50 to 100 mol%, preferably 60 to 100 mol%, of the repeating units of formulas (III) and (IV), based on the sum of the repeating units of formulas (III) and (IV).

[0050] The polyvinyl alcohol copolymers P1 according to the invention exhibit good solubility in aqueous solvents, particularly at low temperatures above 0 °C or at 0 °C, and over a wide pH range. Solubility is also good in aqueous solvents with a comparatively high salt and / or mineral content. Without being bound by theory, it is assumed that the sterically demanding pentaerythritol acrylate repeat units influence the degree of crystallinity of the polyvinyl alcohol and polyvinyl ester repeat units, thereby positively affecting the polymer's solubility in aqueous solvents. The influence of the degree of crystallinity on the solubility of polyvinyl alcohols is described, for example, by M.L. Hallensleben in the chapter "Polyvinyl Compounds, others" in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Vol. 29, Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim, Germany, page 606, left column, third paragraph, described.

[0051] Preferred polyvinyl alcohols P2 according to this invention are polymer compounds comprising repeating units of the following structures (I) and (II): wherein R1 is a linear or branched alkyl group with 1 to 8 carbon atoms, preferably a linear alkyl group with 1 to 5 carbon atoms, and particularly preferably a methyl group or an ethyl group.

[0052] In a preferred embodiment, the polyvinyl alcohol P2 according to the invention comprises or consists of repeating units of the following structures (I) and (II.1):

[0053] The polyvinyl alcohols P2 according to the invention can be produced by the polymerization of monomers with hydrolyzable functional groups (in particular vinyl esters) followed by a polymer-analogous hydrolysis of at least a portion of the hydrolyzable functional groups of the resulting polymer. The degree of hydrolysis of a polyvinyl alcohol P2 therefore indicates the molar fraction of vinyl alcohol repeat units of structure (I) relative to the sum of the vinyl alcohol repeat units of structure (I) and the repeat units obtained from the polymerization of the monomers with hydrolyzable functional groups and remaining as such in the polyvinyl alcohol P2 after the hydrolysis reaction (repeat units of structure (II)).

[0054] The polyvinyl alcohols P2 according to the invention exhibit a degree of hydrolysis in the range of 87 to 95 mol%. This means that these polyvinyl alcohols P2 are composed of 87 to 95 mol% repeat units of structure (I) and 5 to 13 mol% repeat units of structure (II), where the percentages refer to the sum of the repeat units of structure (I) and the repeat units of structure (II).

[0055] In one embodiment of the invention, the water-soluble polymer composition according to the invention comprises at least one polyvinyl alcohol P2, wherein the polyvinyl alcohol P2 comprises at least one vinyl alcohol repeating unit and at least one vinyl ester repeating unit. The at least one vinyl ester repeating unit is preferably a vinyl acetate repeating unit (i.e., an ethenyl acetate repeating unit, repeating unit of structure (II.1)). The proportion of vinyl ester repeating units in the polyvinyl alcohol P2 according to the invention is in the range of 5 to 13 mol%, based on the composition of the polyvinyl alcohol P2. Correspondingly, the proportion of vinyl alcohol repeating units in the polyvinyl alcohol P2 according to the invention is in the range of 87 to 95 mol%, based on the composition of the polyvinyl alcohol P2.Preferably, the proportion of vinyl alcohol repeating units is in the range of 91 to 94 mol%, particularly preferably in the range of 92 to 93 mol%. Accordingly, the degree of hydrolysis of the polyvinyl alcohol P2 is in the range of 87 to 95 mol%, based on the composition of the polyvinyl alcohol P2, preferably in the range of 91 to 94 mol%, particularly preferably in the range of 92 to 93 mol%. In this case, the polyvinyl alcohol P2 contained in the water-soluble polymer composition therefore has vinyl alcohol repeating units in the range of 87 to 95 mol%, preferably in the range of 91 to 94 mol%, particularly preferably in the range of 92 to 93 mol%, and vinyl acetate repeating units in the corresponding range, i.e., in the range of 5 to 13 mol%, preferably in the range of 4 to 9 mol%, particularly preferably in the range of 7 to 8 mol%.Such a poly(vinyl alcohol-co-vinyl ester), preferably a poly(vinyl alcohol-co-vinyl acetate), exhibits good solubility in aqueous solvents, particularly at a temperature of ≤ 15 °C and over a wide pH range.

[0056] The water-soluble polymer composition can comprise at least one of the polyvinyl alcohol copolymers P1 described herein, or a mixture of a) at least two of the aforementioned polyvinyl alcohol copolymers P1, or b) at least two of the aforementioned polyvinyl alcohol copolymers P1 and polyvinyl alcohols P2. In one embodiment of the invention, the water-soluble polymer composition comprises at least one polyvinyl alcohol copolymer P1 and at least one polyvinyl alcohol P2, i.e., a mixture of at least one polyvinyl alcohol copolymer P1 and at least one polyvinyl alcohol P2.

[0057] In such an embodiment of the invention, the water-soluble polymer composition comprises at least one polyvinyl alcohol copolymer P1.2 and at least one of the aforementioned polyvinyl alcohols P2, wherein the total content of repeating units of the at least one comonomer, selected from pentaerythritol acrylate and optionally acrylic acid, i.e., in particular the total content of repeating units of formulas (III) and (IV), is in the range of 10 to 20 wt.%, based on the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2. In this case, the polyvinyl alcohol copolymer P1, as embodiment P1.2, is thus to be selected such that the specified comonomer content, based on the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2, is maintained. To ensure that the total content of repeating units of formulas (III) and (IV) is in the range of 10 to 20 wt.%,Due to the reference of the content of repeating units of formulas (III) and (IV) to the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2, the comonomer content in polyvinyl alcohol copolymer P1.2 must be chosen to be higher than if only polyvinyl alcohol copolymer P1 or polyvinyl alcohol copolymer P1.1 (i.e., without polyvinyl alcohol P2) were present in the polymer composition, in order to maintain a certain percentage based on the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2. Polyvinyl alcohol copolymer P1.2 thus differs from the embodiment of polyvinyl alcohol copolymer P1.1 described herein, particularly in its comonomer content.

[0058] In a further preferred embodiment of the invention, the water-soluble polymer composition consists of at least 75 wt.%, based on the total weight of the polymer composition, preferably at least 85 wt.%, particularly preferably at least 90 wt.%, of a) at least one polyvinyl alcohol copolymer P1 or b) at least one polyvinyl alcohol copolymer P1 and at least one polyvinyl alcohol P2.

[0059] In a preferred embodiment of the invention, the water-soluble polymer composition consists of at least 75 wt.%, based on the total weight of the polymer composition, preferably at least 85 wt.%, and particularly preferably at least 90 wt.%, of at least one polyvinyl alcohol copolymer P1, wherein the content of repeat units of the at least one comonomer is in the range of 10 to 20 wt.%, based on the total weight of polyvinyl alcohol copolymer P1. This polyvinyl alcohol copolymer P1 corresponds to polyvinyl alcohol copolymer P1.1.

[0060] In an alternative embodiment of the invention, the water-soluble polymer composition consists of at least 75 wt.%, based on the total weight of the polymer composition, preferably at least 85 wt.%, particularly preferably at least 90 wt.%, of at least one polyvinyl alcohol P2.

[0061] In a further alternative embodiment of the invention, the water-soluble polymer composition consists of at least 75 wt.%, based on the total weight of the polymer composition, preferably at least 85 wt.%, and particularly preferably at least 90 wt.%, of a mixture of at least one polyvinyl alcohol copolymer P1 and at least one polyvinyl alcohol P2, wherein the polymer composition has a content of repeating units of the at least one comonomer in the range of 10 to 20 wt.%, based on the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2. The polyvinyl alcohol copolymer P1 to be used therein corresponds to the polyvinyl alcohol copolymer P1.2.

[0062] In addition to the polyvinyl alcohol copolymer P1 or the polyvinyl alcohol P2, the polymer composition preferably comprises water. In one embodiment of the invention, the water content in the polymer composition is preferably in the range of 1 to 7 wt.%, preferably 3 to 6 wt.%, based on the total weight of the polymer composition. In another embodiment of the invention, the water content in the polymer composition is preferably in the range of 1 to 7 wt.%, preferably 3 to 6 wt.%, based on the total weight of polyvinyl alcohol copolymer P1 in the polymer composition. In a further embodiment of the invention, the water content in the polymer composition is preferably in the range of 1 to 7 wt.%, preferably 3 to 6 wt.%, based on the total weight of polyvinyl alcohol P2 in the polymer composition.In a further embodiment of the invention, the water content in the polymer composition is preferably in the range of 1 to 7 wt.%, preferably 3 to 6 wt.%, based on the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2 in the polymer composition. It has been observed that the water content in the polymer composition positively influences both the mechanical properties and the solubility of the polymer composition. It is assumed that the water molecules in the polymer composition influence the degree of crystallinity of the polyvinyl alcohol copolymer P1 and / or the polyvinyl alcohol P2. The water can be present, for example, in the form of residual moisture from the manufacturing process of the polyvinyl alcohol copolymer P1 and / or the polyvinyl alcohol P2. It can also be absorbed from the ambient air.In order to maintain the preferred water contents mentioned herein, it may therefore be necessary to shield the polymer composition or the water-soluble containers according to the invention from environments with high relative humidity.

[0063] In addition to a) the polyvinyl alcohol copolymer P1 or b) the polyvinyl alcohol copolymer P1 and the polyvinyl alcohol P2, the water-soluble polymer composition may optionally comprise up to 18 wt.% based on the total weight of the polymer composition, preferably up to 15 wt.%, and in particular up to 5 wt.%, of additives. These serve in particular to further improve the properties of the polymer composition.

[0064] Suitable optional additives are known to those skilled in the art and can be selected according to the requirements regarding mechanical and chemical stability as well as processability. Suitable additives within the meaning of the present invention include, for example, stabilizers and antioxidants, agents against thermal decomposition and decomposition by ultraviolet light, lubricants and demolding agents, dyes and pigments, and plasticizers. The optional additives may also optionally include further polymers, in particular water-soluble polymers, which differ from the polyvinyl alcohol copolymers P1 and polyvinyl alcohols P2 disclosed herein.

[0065] Antioxidants and heat stabilizers that can be added to the polymer composition include, for example, halides of Group I metals of the periodic table, such as sodium, potassium, and / or lithium halides. Zinc fluoride and zinc chloride can also be used. Furthermore, sterically hindered phenols, hydroquinones, substituted members of this group, secondary aromatic amines, optionally in combination with phosphorus-containing acids or their salts, and mixtures of these compounds, preferably in concentrations up to 1% by weight of the polymer composition, can be used.

[0066] Examples of UV stabilizers include various substituted resorcinols, salicylates, benzotriazoles and benzophenones, which are generally used in amounts up to 2 wt%, based on the weight of the polymer composition.

[0067] Lubricants and demolding agents, which can generally be added in amounts up to 1% by weight of the polymer composition, include stearic acid, stearyl alcohol, stearic acid alkyl esters and amides, and pentaerythritol esters with long-chain fatty acids. Salts of calcium, zinc, or aluminum of stearic acid, as well as dialkyl ketones, e.g., distearyl ketone, can also be used. Zinc, magnesium, and calcium stearate are particularly suitable according to the invention. N,N '-Ethylene-bis-stearamide. Calcium stearate is particularly preferably added as an additive to the polymer composition.

[0068] Preferably, the water-soluble container can have an average wall thickness in the range of 10 to 45 µm, particularly preferably in the range of ≥ 20 to ≤ 35 µm. This allows an optimal balance between good solubility and good mechanical stability of the water-soluble container to be achieved.

[0069] The size of the water-soluble container can be selected by a person skilled in the art with regard to the quantity of dye or dye composition to be contained. If the container is designed as a foil bag, it could, for example, have dimensions in length and / or width ranging from 10 to 200 mm.

[0070] The water-soluble container according to the invention is filled with an additive or additive composition. This additive or additive composition comprises at least one dye or at least one dye composition. The additive or additive composition may optionally comprise further substances that are to be added to an aqueous solvent. The container according to the invention thus also simplifies the addition of the further substances. Examples of suitable additives or additive compositions, which are frequently used in aqueous alkali metal cyanide solutions in mines, include pH buffer salts, pH correctors, bases (e.g., NaOH), water softening salts, and mixtures thereof.

[0071] The dye or dye composition is preferably water-soluble.

[0072] In the context of this invention, "water-soluble" means, with regard to the dye or dye composition, that it dissolves to at least 50% by weight, preferably to at least 75% by weight, and particularly to at least 95% by weight. Most preferably, the water-soluble dye or dye composition dissolves completely, i.e., to 100% by weight, in the aqueous solvent. The at least one water-soluble dye or dye composition preferably has a minimum solubility in water of 100 g / L.

[0073] Preferably, a dye or dye composition is used which is chemically stable in aqueous solutions of alkali metal cyanide compounds in a temperature range of 0 to 50 °C and / or with a pH value in the range of 6 to 14. This means in particular that the dye or dye composition, after dissolving in an aqueous solvent containing at least one alkali metal cyanide compound and which also has a temperature in the range of 0 to 50 °C and / or a pH value in the range of 6 to 14, does not undergo any chemical reactions with the contained components, especially the alkali metal cyanide ions and the hydroxide ions, which would result in a change in the color of the dye or the dye(s) contained in the dye composition in the aqueous solution with regard to color intensity and / or hue.This helps to ensure that a constant and reproducible coloration of the aqueous solution containing alkali metal cyanide can be obtained.

[0074] In a preferred embodiment of the invention, the at least one dye or dye composition comprises at least one water-soluble azo dye. Suitable azo dyes are known to those skilled in the art. More preferably, the at least one dye or dye composition comprises at least one azo dye which has a red or blue hue in an aqueous solvent containing alkali metal cyanide ions and optionally hydroxide ions.

[0075] In a particularly preferred embodiment of the invention, the at least one dye or dye composition comprises at least one water-soluble azo dye selected from disodium 6-hydroxy-5-[(E)-(2-methoxy-5-methyl-4-sulfonatophenyl)diazenyl]-2-naphthalenesulfonate (Allura Red, Red 40, E 129), disodium 4-hydroxy-3-[(E)-(4-sulfonato-1-naphthyl)diazenyl]naphthalene-1-sulfonate (Carmoisine, Food Red 3, Azorubine, Acid Red 14, E 122), and combinations thereof. The chemical structures of these compounds are shown below.

[0076] The additive or additive composition can be present in the water-soluble container in solid form, for example as a powder, granules, or in compressed form, for example as a tablet, as a suspension, or as a solution. If the additive or additive composition is present in the water-soluble container as a suspension or solution, the liquid component(s) of the suspension or solution are not suitable for dissolving or inactivating the polymer composition from which the water-soluble container is formed. Suitable solvents are organic solvents that are themselves readily water-soluble. Acetone and ethanol are particularly noteworthy. The amounts of organic solvents introduced during the application for coloring aqueous cyanide solutions are negligible and do not interfere with further use.

[0077] For additives or additive compositions in powder form, the large surface area of ​​the powder contributes to rapid solubility. Powders are often inexpensive and readily available.

[0078] Additives or additive compositions in the form of granules (as well as tablets and briquettes) tend to produce less dust compared to powders. This is particularly desirable for compositions containing dyes, in order to prevent discoloration of the production equipment. Dust avoidance is also desirable when dealing with potentially hazardous substances.

[0079] Additives or additive compositions in the form of suspensions reduce the risk of the additive or additive composition extracting some of the water from the polymer composition of the container according to the invention. Reducing the water content in the polymer composition can impair its solubility.

[0080] When additives or additive compositions are used in solution form, the solution itself facilitates the dissolving process. The actual dissolution of the additives or additive compositions thus occurs in a preliminary step. The solution then only needs to be mixed with the desired solvent and diluted. This is particularly relevant for additives or additive compositions with lower water solubility. At the same time, dust formation can be avoided.

[0081] In granular or pressed form, the additive or additive composition can also contain at least one binder, preferably a water-soluble binder. Advantageously, for example, a water-soluble polymer can be used as the binder, in particular a water-soluble polyvinyl alcohol copolymer P1 and / or a water-soluble polyvinyl alcohol P2 according to the invention.

[0082] The water-soluble container according to the invention is advantageously used with at least one solid, water-soluble alkali metal cyanide compound. This use enables a simple process for the preparation of a colored, aqueous composition Z2, comprising at least one alkali metal cyanide compound and at least one dye. The at least one alkali metal cyanide compound and the at least one dye can advantageously be provided in the form of a pre-application composition (composition Z1), which, when dissolved in an aqueous solvent, yields the application composition (composition Z2).

[0083] The invention therefore also relates to a composition Z1 comprising at least one solid, water-soluble alkali metal cyanide compound and at least one water-soluble container according to the invention. The solid, water-soluble alkali metal cyanide compound used in this composition Z1 preferably comprises at least one alkali metal cyanide salt. Particularly preferred embodiments of the invention include at least sodium cyanide, potassium cyanide, or mixtures of these alkali metal cyanides, particularly preferably sodium cyanide. These are used especially in the mining industry as leaching agents in gold and silver extraction.

[0084] The solid, water-soluble alkali metal cyanide compound can be in the form of, for example, powder, granules, tablets or briquettes.

[0085] The water-soluble container used in composition Z1 corresponds to the water-soluble container according to the invention described above. All previously made definitions and described embodiments of the water-soluble container according to the invention are also applicable and transferable in connection with composition Z1 according to the invention.

[0086] It was observed that the water-soluble containers according to the invention continue to exhibit good solubility in aqueous solvents even after prolonged storage in contact with the aforementioned alkali metal cyanide compound.

[0087] Preferably, the weight ratio (mass of dye / mass of alkali metal cyanide) of water-soluble dye to water-soluble alkali metal cyanide compound in the composition Z1 according to the invention is in a range of 0.00002 : 5 to 0.0002 : 5.

[0088] Preferably, composition Z1 is provided in a container, in particular a container conventionally used for the sale, transport, and / or further processing of the alkali metal cyanide compounds used. Preferably, the container is selected from a container, a big bag, a box, a big bag in a box, a drum, in particular a container, a 1000 kg big bag in a box, or a 1000 kg big bag. The container can be designed such that the dissolution process in the dissolution station can take place directly in the container by adding the aqueous solvent. Preferably, composition Z1 is protected from contact with high relative humidity in the container. This reduces the absorption of water by both the alkali metal cyanide compounds and the containers according to the invention and ensures optimal dissolution properties of composition Z1 for the user.

[0089] A further object of the invention is a process for producing the previously described composition Z1, comprising at least one solid, water-soluble alkali metal cyanide compound and at least one water-soluble container according to the invention, wherein the process at least comprises combining the at least one water-soluble container with the at least one solid, water-soluble alkali metal cyanide compound, and wherein the water-soluble container contains an additive or an additive composition with at least one water-soluble dye or at least one water-soluble dye composition. Preferably, the process for producing composition Z1 comprises at least the following process steps: (i) Providing a predetermined quantity of the at least one solid, water-soluble alkali metal cyanide compound in a container; (ii) Adding the at least one water-soluble container to the at least one alkali metal cyanide compound in the container, wherein the water-soluble container contains an additive or additive composition comprising at least one water-soluble dye or at least one water-soluble dye composition; wherein the quantity of the at least one water-soluble alkali metal cyanide compound in the container and the quantity of the at least one dye or dye composition in the at least one water-soluble container are such that, after dissolving the resulting composition Z1 in a predetermined quantity of an aqueous solvent, a colored aqueous alkali metal cyanide solution of a predetermined concentration with a predetermined extinction coefficient is obtained. The extinction coefficient can be adjusted to the specific requirements to ensure sufficiently strong coloration of the colored aqueous composition Z2 and the easy identification of cyanide-containing solutions. This is ensured. The extinction coefficient can be determined using UV / Vis spectroscopy or photometry.

[0090] The container used in the process is preferably one used for the sale, transport, and / or further processing of the alkali metal cyanide compounds used. Preferably, the container is selected from a container, a big bag, a box, a big bag inside a box, a drum, a container, a 1000 kg big bag inside a box, or a 1000 kg big bag. The container can be designed such that the dissolution process in the dissolution station can take place directly within the container by adding the aqueous solvent.

[0091] Optionally, the at least one solid, water-soluble alkali metal cyanide compound and the at least one water-soluble container according to the invention can be mixed to achieve a uniform distribution of the components in the container.

[0092] The amount of solid, water-soluble alkali metal cyanide compound and the at least one dye or dye composition can be optimally balanced and adapted to the needs of the intended use. This makes it possible to easily produce colored aqueous alkali metal cyanide solutions with a predetermined alkali metal cyanide and dye concentration. Alkali metal cyanide solutions of the same concentration will then exhibit the same color intensity.

[0093] Preferably, the weight ratio (mass of dye / mass of alkali metal cyanide) of water-soluble dye to water-soluble alkali metal cyanide compound in the inventive process for producing the previously described composition Z1, comprising at least one water-soluble alkali metal cyanide compound and at least one water-soluble container according to the invention, is in a range of 0.00002 : 5 to 0.0002 : 5.

[0094] The composition Z1 obtained according to the inventive process can advantageously be used in the inventive process described below for the preparation of a colored aqueous composition Z2. The presented process for the preparation of composition Z1 corresponds to process steps (i) and (ii) of the inventive process for the preparation of a colored aqueous composition Z2, comprising at least one water-soluble alkali metal cyanide compound and at least one water-soluble dye.

[0095] A further object of the invention is a process for producing a colored aqueous composition Z2, which comprises at least one alkali metal cyanide compound and at least one dye. The process comprises introducing at least one water-soluble container according to the invention into an aqueous solvent, wherein the at least one water-soluble container contains at least one water-soluble dye or at least one water-soluble dye composition.

[0096] The inventive process for producing a colored aqueous composition Z2, comprising at least one water-soluble alkali metal cyanide compound and at least one water-soluble dye, preferably comprises at least the following process steps: (i) Providing at least one water-soluble container according to the invention, wherein the water-soluble container contains an additive or additive composition with at least one water-soluble dye or at least one water-soluble dye composition; (ii) Providing at least one solid, water-soluble alkali metal cyanide compound; (iii) Introducing the at least one water-soluble container and the at least one solid, water-soluble alkali metal cyanide compound into an aqueous solvent; and (iv) optionally mixing the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound with the aqueous solvent to assist in dissolving the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound in the aqueous solvent.

[0097] The water-soluble container used in the process for producing a colored aqueous composition Z2, which comprises at least one water-soluble alkali metal cyanide compound and at least one water-soluble dye, corresponds to the water-soluble container according to the invention described above. All previously made definitions and described embodiments of the water-soluble container according to the invention are also applicable and transferable in connection with the process according to the invention for producing a colored aqueous composition Z2.

[0098] The alkali metal cyanide compound used in the process comprises at least one water-soluble alkali metal cyanide compound, preferably at least one alkali metal cyanide salt. Particularly preferred embodiments of the invention comprise at least sodium cyanide, potassium cyanide, or mixtures of these alkali metal cyanides. These are used particularly in the mining industry as leaching agents in gold and silver extraction. Sodium cyanide is particularly preferred due to its availability.

[0099] The alkali metal cyanide compound is in the form of a solid, for example as a powder, granules, tablets or briquettes.

[0100] To produce a colored aqueous composition Z2 according to the process according to the invention, the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound are introduced into an aqueous solvent.

[0101] In one embodiment of the invention, the at least one water-soluble container, which contains an additive or an additive composition with at least one water-soluble dye or at least one water-soluble dye composition, and the at least one water-soluble alkali metal cyanide compound are simultaneously introduced into the aqueous solvent.

[0102] In an alternative embodiment of the invention, the at least one water-soluble container is first introduced into the aqueous solvent and subsequently, i.e., at a later time interval, the at least one water-soluble alkali metal cyanide compound is introduced into the aqueous solvent.

[0103] In a further alternative embodiment of the invention, the at least one water-soluble alkali metal cyanide compound is first introduced into the aqueous solvent, and subsequently, i.e., at a later time interval, the at least one water-soluble container is introduced into the aqueous solvent.

[0104] Preferably, the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound are introduced into the aqueous solvent simultaneously. This makes it possible for the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound to be mixed together before being introduced into the aqueous solvent. The color of the aqueous solution then allows simple optical means to identify that an aqueous alkali metal cyanide solution is present and to estimate its concentration. Within the scope of this embodiment of the invention, the previously described composition Z1, comprising at least one solid, water-soluble alkali metal cyanide compound and at least one water-soluble container according to the invention, can be used particularly advantageously.

[0105] Advantageously, in the process for producing a colored aqueous composition Z2, the at least one water-soluble container and the at least one solid, water-soluble alkali metal cyanide compound in the form of the previously described composition Z1, which comprises at least one solid, water-soluble alkali metal cyanide compound and at least one water-soluble container according to the invention, can be used.

[0106] In a further embodiment of the invention, the at least one water-soluble container and the at least one solid, water-soluble alkali metal cyanide compound are initially introduced into only a portion of the aqueous solvent. After the at least one water-soluble container and / or the at least one water-soluble alkali metal cyanide compound has dissolved in this portion of the aqueous solvent, the remaining aqueous solvent is then added to achieve the desired concentration of the colored aqueous composition Z2.

[0107] In an optional process step, the dissolution of the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound in the aqueous solvent can be supported by actively mixing the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound with the aqueous solvent, for example by means of a mechanical mixing process, whereby a static or a dynamic mixer can be used.

[0108] According to the invention, the colored aqueous composition Z2 comprises at least one water-soluble dye, at least one water-soluble alkali metal cyanide compound, and at least water as a solvent. The colored aqueous composition Z2 also comprises the components of the dissolved polymer composition of the water-soluble container. The concentration of water-soluble dye in the colored aqueous composition Z2 is preferably in the range of 0.000001 to 0.0006 mol / L, more preferably in the range of 0.000006 to 0.00006 mol / L. The concentration of water-soluble alkali metal cyanide compound in the colored aqueous composition Z2 is preferably in the range of 1.5 to 10 mol / L. The molar ratio of water-soluble dye to water-soluble alkali metal cyanide compound in the colored aqueous composition Z2 is preferably in the range of 0.00002 : 5 to 0.0001 : 5.

[0109] The non-binding recommendation of the International Cyanide Management Institute specifies a concentration of 0.03 g (dye) / L aqueous NaCN solution with a NaCN content of 23%.

[0110] According to the invention, the pH value and temperature of the aqueous solvent used can vary over a wide range. This allows the process to be carried out under different external conditions, particularly in mines in very different regions of the world.

[0111] The aqueous solvent may have a pH value in the range of pH 6 to pH 14 at the beginning of process step (iii), preferably in the range of pH 6.5 to pH 13, and particularly in the range of pH 6.5 to pH 12.5. The aqueous solvent may have a temperature of 0 to 50 °C at the beginning of process step (iii), particularly 0 to 25 °C or 0 to 15 °C.

[0112] The invention will be explained in more detail using the following examples. Examples

[0113] Comparative tests with polyvinyl alcohol films with a hydrolysis degree of more than 95 mol% showed that these did not dissolve at the desired rate. For example, even after dissolution times of approximately 20 minutes, visible pieces of film were still present in the aqueous solvent, especially at temperatures ≤ 15 °C.

[0114] Polymer pouches according to the invention, filled with a water-soluble dye, were produced. The solubility behavior of the filled pouches was then investigated by placing them in an aqueous solution and determining the time t (Ex. max ) until the solution was maximally colored (maximum absorbance of the dye) by the dye.

[0115] A defined amount of the dye carmoisine is calculated so that the final concentration of 0.03 g / L is achieved in the experiment. This quantity of dye is packaged in containers in the form of bags made of commercially available, water-soluble polyvinyl alcohol with a degree of hydrolysis of 91–94 mol% (PVOH-1: poly(vinyl alcohol-co-vinyl acetate), manufacturer: GS-go soluble wasserlösunge Verpackungen GmbH, D-65582 Diez), commercially available, water-soluble polyvinyl alcohol copolymer with a degree of hydrolysis of 85 mol% (PVOH-2: poly(vinyl alcohol-co-vinyl acetate-co-pentaerythritol acrylate), manufacturer: GS-go soluble wasserlösunge Verpackungen GmbH, D-65582 Diez), and commercially available, water-soluble polyvinyl alcohol copolymer with a degree of hydrolysis of 85 mol% and a proportion of repeat units derived from pentaerythritol acrylate of 13 mol% (PVOH-3: poly(vinyl alcohol-co-vinyl acetate-co-pentaerythritol acrylate)).Manufacturer: GS-go soluble water-soluble packaging GmbH, D-65582 Diez) with a defined format, weighed, and sealed with a heat sealer to obtain a dye-filled polymer bag. The polyvinyl alcohols and polyvinyl alcohol copolymers used were analyzed by IR and / or NMR spectroscopy as described herein. 1H and 13C NMR spectroscopy was performed in DMSO-D6 as the solvent (Bruker Avance III 600; 600 MHz (H1); DMSO-D6; 27 °C; 1H NMR: 32 scans, 30° pulse, acquisition time 2.7 sec., time domain 65536; 13C: 400 scans, 30° pulse, acquisition time 1.8 sec., time domain 131072, power-gated decoupling). 13C-NMR spectroscopy was additionally performed in the solid state (Bruker Avance III HD; 400MHz (H1); ambient temperature (approx. 22°C); pulse sequence: cross polarization with ramp, rotation frequency 9 kHz, 12735 scans, relaxation delay 5 sec).

[0116] This polymer bag is then placed in a defined 600 ml wide-mouth beaker containing a defined liquid (demineralized water, optionally with added NaOH) at a defined pH and stirred at a defined speed (300 rpm) and temperature using a magnetic stirrer. Upon release of the initial color, a sample is rapidly taken at defined intervals (1, 2, 4, 5, 7, 10, 15, 20 minutes) and the absorbance is determined colorimetrically at a wavelength of 516 nm. A standard spectrometer (LICO 690, spectral colorimeter from Hach / measurement in a 10 mm round cuvette) is used for this purpose. The samples are quickly returned to the beaker after each measurement. The dye is completely dissolved when the absorbance maximum is reached. The absorbance maximum is reached when no further increase in the absorbance value is observed in two consecutive measurements.

[0117] The test parameters and measurement results are summarized in Table 1. Table 1 Example. Water-soluble container liquid pH T [°C] t (Ex. max ) [min] material Dimensions [mm] Wall thickness [µm] Pretreatment 1* PVOH-1 100 x 130 30 --- H₂O 6,5 20 approximately 2.5 2* PVOH-1 100 x 130 30 --- H₂O + NaOH 11,0±0,2 18 approximately 4 3 PVOH-2 100 x 130 30 --- H₂O + NaOH 11,0±0,2 8-9 approximately 4 4 PVOH-3 100 x 130 30 --- H₂O + NaOH 11,0±0,2 8-9 approximately 4 5 PVOH-2 50 x 50 30 --- H₂O + NaOH 11,0±0,2 8-9 approximately 4.5 6 PVOH-2 50 x 50 30 --- H₂O + NaOH 11,0±0,2 2-4 approximately 7 7 PVOH-2 50 x 50 30 after 2 weeks of storage in a drying oven at 40°C H₂O + NaOH 11,0±0,2 8-10 approximately 16 8 PVOH-2 50 x 50 30 after 1 month of storage in a drying oven at 40°C H₂O + NaOH 11,0±0,2 8-10 approximately 15 9 PVOH-2 50 x 50 30 after 1 month of storage at room temperature in NaCN granules H₂O + NaOH 11,0±0,2 8-10 approximately 19 10 PVOH-2 50 x 50 30 after 1 month of storage at room temperature in the laboratory H₂O + NaOH 11,0±0,2 8-10 approximately 10 *not according to the invention

[0118] Example 1 shows that the dye is rapidly released through the polymer bags (not according to the invention) in an aqueous solvent at a temperature of 20 °C and a pH of 6.5. The maximum absorbance is reached after only 2.5 minutes.

[0119] At a pH of 11, the time until maximum absorbance is reached increases only slightly to approximately 4 minutes. Even with a reduction in the solvent temperature to 8–9 °C, this period does not increase (see Examples 2 to 4). The dimensions of the polymer bag have only a minor influence on the solution properties (see Example 5). At a temperature in the range of 2–4 °C, rapid dissolution is still achieved, with maximum absorbance of the solution after approximately 7 minutes (see Example 6).

[0120] Examples 7 to 10 investigate the influence of storing the polymer bag according to the invention under different conditions. For this purpose, the filled polymer bag is stored at room temperature (see Example 10), at 40 °C (see Examples 7 and 8), and in a container with sodium cyanide granules at room temperature (see Example 9) before the dissolution test. Comparison with Example 5 shows that the storage conditions result in the maximum absorbance of the solution being reached later. The greatest delay is observed in the polymer bag that was previously stored in a container with sodium cyanide granules at room temperature (see Example 9). Nevertheless, the maximum absorbance is reached in less than 20 minutes. This period is sufficiently short for use in a mine, as this time is also required for the dissolution of the alkali metal cyanide compound.

[0121] A comparison of Examples 5, 7, and 8 shows that the solubility of the polymer bag according to the invention deteriorates upon storage at elevated temperatures. Without being bound by theory, it is assumed that this is due to a reduction in the water content of the polymer composition of the polymer bag during storage in the drying oven at 40 °C and possibly an increase in the degree of crystallinity.

[0122] The examples according to the invention also show that the container according to the invention dissolves at a good rate and therefore releases the dye at a good rate.

[0123] Experiments with polyvinyl alcohol copolymer films (PVOH-3) have shown that the good solubility properties of the water-soluble containers according to the invention can also be achieved in aqueous solvents with a high salt content.

[0124] The invention enables the addition of defined quantities of dye to a polymer container containing an alkali metal cyanide compound in its commercial packaging. For use in the mine, i.e., for the production of a colored alkali metal cyanide solution, the polymer container with the dye or dye composition can be dissolved together with the alkali metal cyanide compound in water in a conventional dissolving station. This avoids an additional step in the dissolving process or the need to modify the dissolving station. Using the water-soluble container also reduces the risk of contamination of, for example, the production plant for manufacturing the alkali metal cyanide compounds with the dye or dye composition.

Claims

1. Water-soluble receptacle which is suitable for accommodating an additive or an additive composition and is filled with an additive or an additive composition comprising at least one dye or at least one dye composition, wherein the water-soluble receptacle has a wall thickness in the range from 5 to 50 µm, and wherein the water-soluble receptacle comprises a water-soluble polymer composition or consists of a water-soluble polymer composition, wherein the polymer composition comprises: a) at least one polyvinyl alcohol copolymer P1 having a degree of hydrolysis in the range from 75 to 95 mol%, wherein the polyvinyl alcohol copolymer P1 is a copolymer which comprises - vinyl alcohol repeating units, - vinyl ester repeating units and - repeating units of at least one comonomer, wherein the at least one comonomer is selected from pentaerythritol acrylate and also optionally acrylic acid; or b) at least one polyvinyl alcohol copolymer P1 having a degree of hydrolysis in the range from 75 to 95 mol%, wherein the polyvinyl alcohol copolymer P1 is a copolymer which comprises - vinyl alcohol repeating units, - vinyl ester repeating units and - repeating units of at least one comonomer, wherein the at least one comonomer is selected from pentaerythritol acrylate and also optionally acrylic acid; and at least one polyvinyl alcohol P2 having a degree of hydrolysis in the range from 87 to 95 mol%; wherein, in addition to the at least one polyvinyl alcohol copolymer P1 or the at least one polyvinyl alcohol copolymer P1 and the at least one polyvinyl alcohol P2, the polymer composition can additionally optionally contain additive substances; wherein the polymer composition, in the case in which it comprises at least one polyvinyl alcohol copolymer P1 and no polyvinyl alcohol P2, has a content of repeating units of the at least one comonomer in a range from in total 10% to 20% by weight, based on the total weight of polyvinyl alcohol copolymer P1; and wherein the polymer composition, in the case in which it comprises at least one polyvinyl alcohol copolymer P1 and at least one polyvinyl alcohol P2, has a content of repeating units of the at least one comonomer in a range from in total 10% to 20% by weight, based on the total weight of polyvinyl alcohol copolymer P1 and polyvinyl alcohol P2, wherein the degree of hydrolysis of the polyvinyl alcohol copolymer P1 and of the polyvinyl alcohol P2 is determined by means of quantitative 1H NMR spectroscopy as disclosed in the description, and wherein the composition of the polyvinyl alcohol copolymer P1 and of the polyvinyl alcohol P2 is determined by means of IR and NMR spectroscopy as disclosed in the description.

2. Water-soluble receptacle according to Claim 1, wherein the water-soluble polymer composition comprises at least one polyvinyl alcohol copolymer P1 having a degree of hydrolysis in the range from 80 to 90 mol%.

3. Water-soluble receptacle according to Claim 1 or 2, wherein the water-soluble polymer composition comprises at least one polyvinyl alcohol P2 having a degree of hydrolysis in the range from 91 to 94 mol%.

4. Water-soluble receptacle according to one of Claims 1 to 3, wherein the water-soluble polymer composition comprises at least one polyvinyl alcohol copolymer P1 selected from poly(vinyl alcohol-co-vinyl ester-co-pentaerythritol acrylate), poly (vinyl alcohol-co-vinyl ester-co-pentaerythritol acrylate-co-acrylic acid) and derivatives thereof.

5. Water-soluble receptacle according to one of Claims 1 to 4, wherein the water-soluble polymer composition comprises at least one polyvinyl alcohol P2 selected from a poly(vinyl alcohol-co-vinyl ester).

6. Water-soluble receptacle according to one of Claims 1 to 5, wherein the water-soluble polymer composition consists of the at least one polyvinyl alcohol copolymer P1 and / or the at least one polyvinyl alcohol P2 to an extent of at least 75% by weight, preferably at least 85% by weight, particularly preferably at least 90% by weight, based on the total weight of the polymer composition.

7. Water-soluble receptacle according to one of Claims 1 to 6, wherein the polymer composition comprises: - at least one polyvinyl alcohol P2; and - 1% to 7% by weight of water, based on the total weight of polyvinyl alcohol P2.

8. Water-soluble receptacle according to one of Claims 1 to 7, wherein the polymer composition comprises: - at least one polyvinyl alcohol copolymer P1; and - 1% to 7% by weight of water, based on the total weight of polyvinyl alcohol copolymer P1.

9. Water-soluble receptacle according to one of Claims 1 to 6, wherein the polymer composition comprises 1% to 7% by weight of water, based on the total weight of the polymer composition.

10. Water-soluble receptacle according to one of Claims 1 to 9, wherein the at least one dye or the at least one dye composition comprises at least one water-soluble azo dye, preferably selected from disodium 6-hydroxy-5-[(E)-(2-methoxy-5-methyl-4-sulfonatophenyl)diazenyl]-2-naphthalenesulfonate, disodium 4-hydroxy-3-[(E)-(4-sulfonato-1-naphthyl)diazenyl]naphthalene-1-sulfonate and mixtures thereof.

11. Composition Z1, comprising at least one solid water-soluble alkali metal cyanide compound and at least one water-soluble receptacle according to one of Claims 1 to 10.

12. Method for producing a composition Z1 according to Claim 11, wherein the method comprises at least the addition of the at least one water-soluble receptacle according to one of Claims 1 to 10 to the at least one alkali metal cyanide compound.

13. Method according to Claim 12 for producing a composition Z1 according to Claim 11, wherein the method comprises at least the following method steps: (i) providing a predetermined amount of the at least one solid water-soluble alkali metal cyanide compound in a package; (ii) adding the at least one water-soluble receptacle according to one of Claims 1 to 10 to the at least one alkali metal cyanide compound in the package; wherein the amount of the at least one water-soluble alkali metal cyanide compound in the package and the amount of the at least one dye or of the at least one dye composition in the at least one water-soluble receptacle are dimensioned such that, after the dissolution of the obtained composition Z1 in a predefined amount of an aqueous solvent, a dyed aqueous alkali metal cyanide solution having a predefined concentration and having a predetermined extinction coefficient is obtained.

14. Use of a composition Z1 according to Claim 11 in a method for producing a coloured aqueous composition Z2.

15. Method for producing a dyed aqueous composition Z2 comprising at least one alkali metal cyanide compound and at least one dye, wherein the method comprises introducing at least one water-soluble receptacle according to one of Claims 1 to 10 into an aqueous solvent, and wherein the at least one water-soluble receptacle contains at least one water-soluble dye or at least one water-soluble dye composition.

16. Method according to Claim 15 for producing a dyed aqueous composition Z2, wherein the method comprises at least the following method steps: (i) providing at least one water-soluble receptacle according to one of Claims 1 to 10, wherein the water-soluble receptacle contains an additive or an additive composition comprising at least one water-soluble dye or at least one water-soluble dye composition; (ii) providing at least one solid water-soluble alkali metal cyanide compound; (iii) introducing the at least one water-soluble receptacle and the at least one solid water-soluble alkali metal cyanide compound into an aqueous solvent; (iv) optionally mixing the at least one water-soluble receptacle and the at least one water-soluble alkali metal cyanide compound with the aqueous solvent in order to promote the dissolution of the at least one water-soluble receptacle and the at least one water-soluble alkali metal cyanide compound in the aqueous solvent.

17. Method according to Claim 15 or 16 for producing a coloured aqueous composition Z2, wherein the at least one water-soluble receptacle and the at least one solid water-soluble alkali metal cyanide compound are used in the form of a composition Z1 according to Claim 11.