RU2844292C1 - Water-soluble container containing dye and method of producing coloured aqueous alkali metal cyanide solution - Google Patents

Abstract

юFIELD: chemistry.

SUBSTANCE: invention relates to a water-soluble container for producing coloured aqueous solutions of alkali metal cyanides. Proposed is a water-soluble container suitable for holding an additive or additive composition and filled with an additive or additive composition containing at least one dye or at least one colouring composition, wherein the water-soluble container has a wall thickness in range of 5 to 50 mcm, and wherein the water-soluble container consists of a water-soluble polymer or a water-soluble polymer composition, wherein the water-soluble polymer or polymer composition comprises: at least one polyvinyl alcohol copolymer P1 with a degree of hydrolysis in range of 75 to 95 mol.%, wherein at least one comonomer is selected from pentaerythrite acrylate, and optionally acrylic acid; wherein the polymer composition, besides at least one polyvinyl alcohol copolymer P1, can further optionally contain additives; wherein the polymer composition contains at least one polyvinyl alcohol P1 copolymer and does not contain polyvinyl alcohol P2 with a degree of hydrolysis in range of 87 to 95 mol.%, has content of repeating units of at least one comonomer in total in range of 10 to 20 wt.%, with respect to the total weight of the polyvinyl alcohol copolymer P1; and wherein the degree of hydrolysis of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2 is determined by quantitative 1H-NMR spectroscopy, and wherein the composition of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2 is determined by IR and NMR spectroscopy; composition Z1 for producing a coloured aqueous composition comprising the disclosed water-soluble container, a method of producing the disclosed composition Z1, a method of producing coloured aqueous composition Z2 containing the disclosed container, and use of composition Z1 to obtain coloured aqueous composition Z2.

EFFECT: creation of water-soluble container providing in conditions of mines, such as low temperature of environment and water, water with high content of salts and minerals, almost complete dissolution for a good period of time.

14 cl, 1 tbl, 10 ex

Description

The invention relates to a water-soluble container filled with at least one dye or at least one coloring composition. The water-soluble container according to the invention can be used in a method for producing colored aqueous solutions of alkali metal cyanides. The invention also relates to a method for producing a preliminary composition for use, comprising at least one water-soluble container according to the invention and at least one water-soluble alkali metal cyanide compound, as well as to an aqueous composition for use, which can be obtained from it by dissolution.

State of the art

Alkali metal cyanide compounds, especially sodium cyanide, are used as lixiviant agents in mining, particularly in gold and silver mining. Solid alkali cyanide is typically transported to the mine site and dissolved in water or an aqueous solvent on-site at a dissolution plant to produce an aqueous alkali cyanide solution as a lixiviant. The aqueous alkali cyanide solution is contacted with the ore, whereby the available metal in the ore dissolves to form the corresponding metal-cyanide complex. Depending on the geographic location of the mine, the water used for dissolution may have a low temperature, often ≤15°C, high hardness, or high salt content.

The alkali metal cyanide compounds used are hazardous to humans and the environment. The alkali metal cyanide solution is colourless and indistinguishable from water to the naked eye. In particular, in the event of a leak, it is impossible to tell with the naked eye whether it is just water or an alkali metal cyanide solution. To distinguish alkali metal cyanide solutions from water, they can be coloured. For more concentrated alkali metal cyanide solutions, this is required by the International Cyanide Management Institute.

If it is desired to produce both dilute and more concentrated alkali metal cyanide solutions from the same batch of solid alkali metal cyanide supplied, and at the same time to be able to distinguish dilute alkali metal cyanide solutions from concentrated alkali metal cyanide solutions, coloring is carried out at the dissolution station if there is a real need for coloring.

An alternative would be to have two batches of solid alkali cyanide, one undyed for dilute alkali cyanide solutions and one dyed for more concentrated alkali cyanide solutions. However, this would involve correspondingly greater storage requirements and additional capital costs.

Water-soluble containers based on polyvinyl alcohols suitable for accommodating additives are known in the art and are described, for example, in patent documents US 6,124,036, WO 02/16205, EP 0457715 and CH 579667. However, the disclosed water-soluble containers are not suitable for use in aqueous solvents that are often present in mines (aqueous solvents with low temperature, high hardness or high salt content) and under these conditions cannot ensure that the containers dissolve in a sufficiently good time or that they dissolve completely.

The present invention was based on the problem of making it possible to add a dye in a water-soluble container or a coloring composition in a water-soluble container to water or an aqueous solvent at a dissolution station in the simplest possible way and in a good amount of time. In particular, under the conditions prevailing in some mines (low ambient and water temperatures, water with a high content of salts and minerals (in particular NaOH, NaCl, CaCO ₃ , Ca(OH) ₂ and MgCO ₃ )) almost complete dissolution must be ensured in a good amount of time.

Description

This problem is solved according to the invention by means of a water-soluble container suitable for accommodating an additive or additive composition and filled with an additive or additive composition containing at least one dye or at least one coloring 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 a water-soluble polymer composition or consists of a water-soluble polymer composition, wherein the polymer composition comprises:

a) at least one copolymer of polyvinyl alcohol P1 with a degree of hydrolysis in the range from 75 to 95 mol.%,

wherein the polyvinyl alcohol copolymer P1 is a copolymer which contains

- repeating units of vinyl alcohol,

- repeating units of vinyl ester and

- repeating units of at least one comonomer,

wherein at least one comonomer is selected from pentaerythritol acrylate and derivatives of pentaerythritol acrylate, and also, if necessary, acrylic acid;

and/or

b) at least one polyvinyl alcohol P2 with a degree of hydrolysis in the range from 87 to 95 mol.%;

wherein the polymer composition, in addition to at least one copolymer of polyvinyl alcohol P1 and/or at least one polyvinyl alcohol P2, may additionally, if necessary, contain additives;

wherein the polymer composition, if it contains at least one polyvinyl alcohol copolymer P1 and does not contain polyvinyl alcohol P2, has a content of repeating units of at least one comonomer in total in the range from 10 to 20% by weight, based on the total weight of the polyvinyl alcohol copolymer P1; and

wherein the polymer composition, if it contains at least one copolymer of polyvinyl alcohol P1 and at least one polyvinyl alcohol P2, has a content of repeating units of at least one comonomer in total in the range from 10 to 20% by weight, based on the total weight of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2.

Pentaerythritol acrylate derivatives in the context of the present invention are pentaerythritol acrylates in which at least some of the hydrogen atoms contained therein are substituted by alkyl residues, in particular alkyl residues having from 1 to 3 carbon atoms.

In one embodiment, the present invention relates to a water-soluble container suitable for containing an additive or additive composition and filled with an additive or additive composition comprising at least one dye or at least one coloring 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, wherein the polymer composition contains at least one copolymer of polyvinyl alcohol P1, wherein the comonomer content is in the range from 10 to 20% by weight, based on the total weight of the copolymer of polyvinyl alcohol P1. In this embodiment, the polymer composition does not contain polyvinyl alcohol P2 according to the present invention.

In another embodiment, the present invention relates to a water-soluble container suitable for containing an additive or additive composition and filled with an additive or additive composition containing at least one dye or at least one coloring 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, wherein the polymer composition comprises at least one polyvinyl alcohol P2. The copolymer of polyvinyl alcohol P2 is a copolymer of repeating units of vinyl alcohol and repeating units of vinyl ester. In this embodiment, the polymer composition does not contain the copolymer of polyvinyl alcohol P1 according to the present invention.

In another embodiment, the present invention relates to a water-soluble container suitable for containing an additive or additive composition and filled with an additive or additive composition containing at least one dye or at least one coloring 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 a water-soluble polymer composition or consists of a water-soluble polymer composition, wherein the polymer composition comprises at least one copolymer of polyvinyl alcohol P1 and at least one polyvinyl alcohol P2, wherein the comonomer content in total is in the range of 10 to 20% by weight, based on the total weight of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2. In this embodiment, the polymer composition comprises a mixture of at least one copolymer of polyvinyl alcohol P1 and at least one polyvinyl alcohol P2 according to the present invention.

The container with the additive or additive composition can be added to water or an aqueous solvent at the dissolution station. It dissolves, thereby releasing the additive or additive composition with the dye or coloring composition.

Thus, from the same batch of solid alkali metal cyanide, it is possible to obtain uncolored solutions of alkali metal cyanide (i.e., the container with the additive or additive composition is not added to water or an aqueous solvent) and colored solutions of alkali metal cyanide (i.e., the container with the additive or additive composition is added to water or an aqueous solvent).

Alternatively, the solid alkali metal cyanide can also be supplied together with the attached container according to the invention with the additive or additive composition, for example in a common package. 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 hand, there is no need to change the established processes at or in the dissolution station at the mine. The mentioned combination can simply be mixed with water or an aqueous solvent, as a result of which the additive or additive composition is released.

It has been found that the polyvinyl alcohol copolymer P1 according to the invention with a degree of hydrolysis in the range of 75 to 95 mol % has a particularly good solubility in water, even when the liquid aqueous solvent has a temperature of about ≤15 °C, in particular about 1 to 10 °C, and/or the liquid aqueous solvent has a pH in the range of 6 to 14. This means that even in the case of a mine with water or aqueous solvents having low temperatures (≤15 °C, in particular 1 to 10 °C) or a pH in the range of 6 to 14, the container material according to the invention dissolves at a good rate. The good solubility in water of the container according to the invention is also achieved in liquid aqueous solvents with a comparatively high content of salts and/or minerals (in particular NaCl, CaCO ₃ and MgCO ₃ ), such as sea water.

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

The mixture of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2, in the case where the comonomer content in total is in the range of 10 to 20% by weight, based on the total weight of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2, also has particularly good solubility in water, even when the liquid aqueous solution has a temperature of about ≤15°C, in particular about 1 to 10°C, and/or the liquid aqueous solvent has a pH in the range of 6 to 14.

In particular, water-soluble containers according to the invention, which contain a polyvinyl alcohol copolymer P1, are characterized by the fact that the 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 wishing to be limited by this theory, it is assumed that in these aging processes an important role is played by the crystallization of the polymer during storage, chemical reactions with the surrounding environment, in particular cyanide compounds, during storage, and the water content of the polymer composition.

According to the invention, the total content of repeating units of at least one comonomer selected from pentaerythritol acrylate and derivatives of pentaerythritol acrylate and, if necessary, acrylic acid is in the range from 10 to 20% by weight, based on the total weight of the polyvinyl alcohol copolymer P1 and, if necessary, polyvinyl alcohol P2. If polyvinyl alcohol P2 is absent, the comonomer content is calculated only on the weight of the polyvinyl alcohol copolymer P1. It has been noted that in order to achieve sufficient heterogeneity in the polymer chains of the polymer composition to suppress the crystallization of the polymers and to ensure solubility even after long-term storage, a comonomer content of at least 10% by weight is required. Even after storage in a chemically aggressive environment (for example, in the presence of cyanide compounds), good dissolution characteristics were observed for polyvinyl alcohol copolymers P1 with a comonomer content in total from 10 to 20% by weight. A comonomer content of more than 20% by weight, in turn, negatively affects the behavior of the polymer composition during dissolution and, therefore, is disadvantageous.

With a container wall thickness in the range of 5 to 50 μm, the container walls have a good surface to volume ratio. This means that the thickness of the material through which liquid water or liquid aqueous solvent must "break through" is relatively small. This also helps the container dissolve at a good rate. In addition, containers with a wall thickness in the range of 5 to 50 μm have fairly good mechanical strength.

The copolymer of polyvinyl alcohol P1, like polyvinyl alcohol P2, has thermoplastic properties. Therefore, the material obtained from this polymer composition can be thermoplastically deformed and joined by fusion welding. Accordingly, the walls of the container can be joined to each other by fusion welding.

"Container" in the context of the present invention is a three-dimensional structure that serves to accommodate substances and at least partially encloses them. It can be made, for example, in the form of a dimensionally stable container or in the form of a bag. Film bags are particularly preferred. Film bags can be obtained, for example, by welding two layers of film, folding the film and welding the open sides, or, which is preferable, from film tubes by welding both ends.

In the context of the present invention, "water-soluble" or "soluble" means, with respect to a container, that the container dissolves in a sufficient amount of an aqueous solvent by at least 50% by weight, preferably by at least 75% by weight, in particular by at least 95% by weight, based on the total weight of the water-soluble container. Accordingly, any water-insoluble components of the polymer composition are "released" as a result of dissolution of the water-soluble components.

In this case, the dissolution rate of the water-soluble container can be determined, for example, by dissolving the water-soluble container, which contains a given amount of at least one water-soluble dye or at least one water-soluble coloring composition, at a given temperature, in particular a temperature given by the planned application (for example, a temperature of ≤15°C), with stirring in an aqueous solvent and determining the time required to achieve the maximum concentration of the dye in the solution. In order to calculate when the maximum concentration of the dye has been achieved, the extinction of the solution can, for example, be determined at regular intervals, for example by optical (UV/visible light) spectroscopy or photometry. The method for determining the dissolution rate of the water-soluble container is described in the examples. A person skilled in the art can adapt the method described there to the relevant requirements.

The completeness of dissolution of the water-soluble container can be determined, for example, optically. Large polymer residues in the case of incomplete dissolution (if necessary after filtration) are visually distinguishable. Due to the Tyndall effect, small polymer residues can be detected using suitable optical methods, for example, by nephelometry. Suitable methods are known to those skilled in the art.

It is particularly preferable to use a polymer composition that dissolves without residue, i.e. the water-soluble container dissolves 100% by weight in an aqueous solvent. This avoids polymer composition residues that can lead to clogging of filtration systems and/or pumps when used in a mine.

"Aqueous solvent" in the context of the present invention is a solvent which consists of at least 50% by weight, in particular at least 60% by weight, based on the total weight of the solvent, of water. Furthermore, the aqueous solvent can comprise dissolved additives, in particular alkaline additives (for example hydroxide salts such as NaOH and KOH), salts (such as NaCl, CaCO ₃ , Ca(OH) ₂ , MgCO ₃ ), and also at least one cyanide compound. Suitable cyanide compounds are in particular alkali metal cyanide compounds, for example sodium cyanide (NaCN) and potassium cyanide (KCN).

In principle, the water used can be of any origin. This can be drinking water, demineralized water, groundwater, river water, sea water, purified water, for example, process water, especially from the mining industry (e.g. spent leach solution). The solvent composition refers to the solvent and the substances dissolved in it. Solid substances, such as sediments in river water, are not taken into account.

Polyvinyl alcohols are generally produced on an industrial scale by first preparing a polyvinyl ester using suitable polymerization methods. The resulting polyvinyl ester is then converted to polyvinyl alcohol in a backbone-invariant 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 reported as a mole percent and is referred to as the degree of hydrolysis of the polyvinyl alcohol.

Therefore, the polyvinyl alcohol copolymers P1 according to the invention or the polyvinyl alcohols P2 according to the invention cannot be obtained by direct copolymerization of their constituent monomers, since they are obtained by polymerization followed by hydrolysis of the resulting polymer.

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

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

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

The degree of hydrolysis of the polyvinyl alcohol copolymer P1 or polyvinyl alcohol P2 can be determined by quantitative ¹ H-NMR spectroscopy. In order to avoid proton exchange of the polyvinyl alcohol, the solid-state ¹ H-NMR spectrum is recorded with a suitable internal standard. By quantifying the areas of the individual signals in ^{the 1} H-NMR spectrum, which can be attributed to protons in the polymer, the degree of hydrolysis can be quantitatively determined.

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

The polyvinyl alcohol copolymers P1 according to the invention can be obtained by hydrolysis of a copolymer of vinyl ester and pentaerythritol acrylate and its derivatives, in particular by hydrolysis of a copolymer of vinyl acetate and pentaerythritol acrylate and its derivatives. If the hydrolysis of the copolymer of vinyl ester and pentaerythritol acrylate is stopped before all the repeating units of vinyl acetate have reacted, a copolymer of vinyl alcohol, vinyl ester and pentaerythritol acrylate can be obtained. Complete hydrolysis of the repeating units of the vinyl ester of the copolymer of vinyl ester and pentaerythritol acrylate makes it possible to obtain a copolymer of vinyl alcohol and pentaerythritol acrylate. A copolymer of vinyl alcohol, vinyl ester and pentaerythritol acrylate and a copolymer of vinyl alcohol, vinyl ester, pentaerythritol acrylate and acrylic acid and derivatives thereof can be produced in a targeted manner by suitable reaction conditions.

Preferred copolymers of polyvinyl alcohol P1 in the context of the present invention are polymeric compounds which comprise or consist of repeating units, in particular of the following structures (I), (II) and (III):

in which R1 is a linear or branched alkyl residue containing from 1 to 8 carbon atoms, preferably a linear alkyl residue containing from 1 to 5 carbon atoms, and more preferably a methyl residue or an ethyl residue.

In addition, the polyvinyl alcohol copolymers P1 according to the invention may, if necessary, contain repeating units of the following structure (IV):

.

In this case, the repeating units of vinyl alcohol of structure (I) are usually obtained by hydrolysis of the repeating units of vinyl ester of structure (II). In this case, the repeating units of acrylic acid of structure (IV) are usually obtained by hydrolysis of the repeating units of pentaerythritol acrylate of structure (III).

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

In another preferred embodiment, the polyvinyl alcohol copolymer P1 according to the invention contains repeating units of the following structures (I), (II.1), (III) and, if appropriate, (IV) or consists of them:

.

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

The polyvinyl alcohol copolymers P1 according to the invention are obtained by copolymerizing monomers with hydrolyzable functional groups (in particular vinyl esters) and (derivatives of) pentaerythritol acrylate, followed by hydrolysis, which does not change the polymer backbone, of at least some of the hydrolyzable functional groups of the resulting polymer. The degree of hydrolysis of the polyvinyl alcohol copolymer P1 indicated in this document indicates the molar fraction of the repeating units of vinyl alcohol of structure (I), calculated on the sum of the repeating units of vinyl alcohol of structure (I) and the repeating units formed as a result of the polymerization of monomers with hydrolyzable functional groups (in particular the repeating units of structure (II) or (II.1)). Other comonomers, in particular the repeating units of structure (III) and (VI), are not taken into account in the context of the present invention when determining the degree of hydrolysis of the polyvinyl alcohol copolymer P1. However, other comonomers, in particular repeating units of structure (III), can also undergo hydrolysis reactions. In particular, repeating units of structure (IV) are obtained in a hydrolysis reaction that does not change the polymer backbone by hydrolysis of repeating units of structure (III).

The polyvinyl alcohol copolymers P1 according to the invention have a degree of hydrolysis in the range from 75 to 95 mol %, preferably from 80 to 90 mol %, more preferably from 85 to 90 mol %. This means that the polyvinyl alcohol regions of these polyvinyl alcohol copolymers P1 consist of 75 to 95 mol % repeating units of structure (I) and 5 to 25 mol % repeating units of structure (II), wherein the percentage is calculated on the sum of the repeating units of structure (I) and the repeating units of structure (II). In addition, the polyvinyl alcohol copolymers P1 contain repeating units of structure (III) and, if appropriate, repeating units of structure (IV), which do not influence the degree of hydrolysis or are not taken into account when calculating the degree of hydrolysis.

In a preferred embodiment of the invention, the polymer composition comprises at least one polyvinyl alcohol copolymer P1 comprising at least one repeating unit of vinyl alcohol, at least one repeating unit of vinyl acetate and at least one repeating unit of pentaerythritol acrylate. In one embodiment, the polyvinyl alcohol copolymer P1 also comprises repeating units of acrylic acid. Thus, the polyvinyl alcohol copolymer P1 can preferably be selected from a copolymer of vinyl alcohol, vinyl acetate and pentaerythritol acrylate or a derivative thereof, a copolymer of vinyl alcohol, vinyl ester, pentaerythritol acrylate and acrylic acid or a derivative thereof, or a mixture of the above. The polyvinyl alcohol copolymer P1 is preferably a copolymer of vinyl alcohol, vinyl acetate and pentaerythritol acrylate, a copolymer of vinyl alcohol, vinyl acetate, pentaerythritol acrylate and acrylic acid) or a mixture of the above.

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

The ratio of repeating units of pentaerythritol acrylate (repeating units of formula (III)) and/or repeating units of pentaerythritol acrylate derivatives to repeating units of acrylic acid (repeating units of formula (IV)) in the polyvinyl alcohol copolymer P1 is preferably in the range from 1:1 to 1:0.

As already described, the polyvinyl alcohol portion in the polyvinyl alcohol copolymer P1 consists of repeating units of vinyl alcohol and repeating units of vinyl ester (preferably repeating units of vinyl acetate). The proportion of the repeating units of vinyl ester is in the range of from 5 to 25 mol %, based on the total amount of repeating units of polyvinyl alcohol and repeating units of vinyl ester in the polyvinyl alcohol copolymer P1, preferably in the range of from 10 to 20 mol %, and more preferably in the range of from 10 to 15 mol %. In this case, the content of polyvinyl alcohol in the polyvinyl alcohol copolymer P1 thus comprises repeating units of vinyl alcohol in the range of from 75 to 95 mol %, preferably in the range of from 80 to 90 mol %, particularly preferably in the range of from 85 to 90 mol %, based on the total number of repeating units of polyvinyl alcohol and repeating units of vinyl ester in the polyvinyl alcohol copolymer P1. This corresponds to a degree of hydrolysis of the polyvinyl alcohol region of from 75 to 95 mol %, preferably from 80 to 90 mol %, particularly preferably from 85 to 90 mol %.

In other words, in a preferred embodiment, the polyvinyl alcohol copolymer P1 comprises:

a) from 80 to 90% by weight, preferably from 82.5 to 89.5% by weight, particularly preferably from 85 to 89% by weight, based on the total weight of the polyvinyl alcohol copolymer P1, of repeating units of formula (I) and (II.1), and

b) from 10 to 20% by weight, preferably from 10.5 to 17.5% by weight, in particular from 11 to 15% by weight, based on the total weight of the polyvinyl alcohol copolymer P1, of repeating units of formulae (III) and (IV),

wherein the repeating units of formula (I) constitute from 75 to 95 mol.%, preferably from 80 to 90 mol.%, in particular from 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 the repeating units of formula (III) constitute from 50 to 100 mol.%, preferably from 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).

The polyvinyl alcohol copolymers P1 according to the invention have good solubility in aqueous solvents, in particular at low temperatures above 0°C or at 0°C, and also in a wide range of pH values. The solubility is also good in aqueous solvents with a comparatively high content of salts and/or minerals. Without wishing to be bound by any theory, it is assumed that the sterically hindered repeating units of pentaerythritol acrylate influence the degree of crystallization of the repeating units of polyvinyl alcohol and polyvinyl ester and thus have a positive effect on the solubility of the polymer in aqueous solvents. The influence of the degree of crystallization 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, Volume 29, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, page 606, left column, third paragraph.

Preferred polyvinyl alcohols P2 in the context of the present invention are polymeric compounds which comprise repeating units of the following structures (I) and (II):

in which R1 is a linear or branched alkyl residue containing from 1 to 8 carbon atoms, preferably a linear alkyl residue containing from 1 to 5 carbon atoms, and more preferably a methyl residue or an ethyl residue.

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

.

Polyvinyl alcohols P2 according to the invention can be obtained by polymerization of monomers with hydrolyzable functional groups (in particular, vinyl ester) and subsequent hydrolysis, which does not change the polymer framework, of at least some of the hydrolyzable functional groups of the obtained polymer. Therefore, the degree of hydrolysis of polyvinyl alcohol P2 indicates the molar fraction of repeating units of vinyl alcohol of structure (I), calculated as the sum of the repeating units of vinyl alcohol of structure (I) and the repeating units formed as a result of polymerization of monomers with hydrolyzable functional groups and remaining as such after the hydrolysis reaction of polyvinyl alcohol P2 (repeating units of structure (II)).

According to the invention, polyvinyl alcohol P2 has a degree of hydrolysis in the range from 87 to 95 mol%. This means that these polyvinyl alcohols P2 consist of 87 - 95 mol. repeating units of structure (I) and 5 - 13 mol. repeating units of structure (II), wherein the percentage content is calculated as the sum of the repeating units of structure (I) and the repeating units of structure (II).

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 repeating unit of vinyl alcohol and at least one repeating unit of vinyl ester. The at least one repeating unit of vinyl ester is preferably a repeating unit of vinyl acetate (i.e. a repeating unit of ethenyl acetate, a repeating unit of structure (II.1)). The proportion of repeating units of vinyl ester in the polyvinyl alcohol P2 according to the invention is in the range of from 5 to 13 mol %, based on the composition of the polyvinyl alcohol P2. The proportion of repeating units of vinyl alcohol in the polyvinyl alcohol P2 according to the invention is accordingly in the range of from 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 from 91 to 94 mol %, particularly preferably in the range of from 92 to 93 mol %. Accordingly, the degree of hydrolysis of the polyvinyl alcohol P2 is in the range of from 87 to 95 mol %, based on the composition of the polyvinyl alcohol P2, preferably in the range of from 91 to 94 mol %, particularly preferably in the range of from 92 to 93 mol %. In this case, the polyvinyl alcohol P2 contained in the water-soluble polymer composition thus has vinyl alcohol repeating units in the range of from 87 to 95 mol %, preferably in the range of from 91 to 94 mol %, particularly preferably in the range of from 92 to 93 mol %. and vinyl acetate repeating units in the respective range in each case, 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 copolymer of vinyl alcohol and vinyl ester, preferably a copolymer of vinyl alcohol and vinyl acetate, has good solubility in aqueous solvents, in particular at a temperature of ≤15°C and over a wide range of pH values.

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

In such an embodiment of the invention, the water-soluble polymer composition comprises at least one copolymer of polyvinyl alcohol P1.2 and at least one of the above-mentioned polyvinyl alcohols P2, wherein the total content of repeating units of at least one comonomer selected from pentaerythritol acrylate and derivatives of pentaerythritol acrylate, and optionally acrylic acid, i.e. in particular, the total content of repeating units of formulae (III) and (IV) is in the range from 10 to 20% by weight, based on the total weight of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2. In this case, the copolymer of polyvinyl alcohol P1 in the form of embodiment P1.2 must be selected such that a given content of comonomer is maintained, based on the total weight of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2. In order to maintain the total content of repeating units of formulas (III) and (IV) in the range from 10 to 20% by weight, based on the total weight of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2, in a polymer composition that contains both the copolymer of polyvinyl alcohol P1 and the polyvinyl alcohol P2, due to the ratio of the content of repeating units of formulas (III) and (IV) to the total weight of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2, the content of the comonomer in the copolymer of polyvinyl alcohol P1.2 must be selected higher than if only the copolymer of polyvinyl alcohol P1 or the copolymer of polyvinyl alcohol P1.1 (i.e. without polyvinyl alcohol P2) were present in the polymer composition. Thus, the polyvinyl alcohol copolymer P1.2 differs from the embodiment of the polyvinyl alcohol copolymer P1.1 described in this document, in particular, in the comonomer content.

In another preferred embodiment of the invention, the water-soluble polymer composition consists of at least 75% by weight, based on the total weight of the polymer composition, preferably at least 85% by weight, particularly preferably at least 90% by weight, of at least one polyvinyl alcohol copolymer P1 and/or at least one polyvinyl alcohol P2.

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

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

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

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 the polyvinyl alcohol copolymer P1 in 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 the polyvinyl alcohol P2 in the polymer composition. In another embodiment of the invention, the water content of the polymer composition is preferably in the range of 1 to 7% by weight, preferably 3 to 6% by weight, based on the total weight of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2 in the polymer composition. It has been observed that the water content of the polymer composition has a positive effect on both the mechanical properties and the solubility of the polymer composition. It is believed that the water molecules in the polymer composition affect the degree of crystallization of the copolymer of polyvinyl alcohol P1 and/or polyvinyl alcohol P2. Water can be present, for example, in the form of residual moisture from the process for producing the copolymer of polyvinyl alcohol P1 and/or polyvinyl alcohol P2. It can also be absorbed from the surrounding air. In order to be able to maintain the preferred water content mentioned herein, it may be necessary to shield the polymer composition or the water-soluble containers according to the invention from an environment with high relative humidity.

In addition to the copolymer of polyvinyl alcohol P1 and/or polyvinyl alcohol P2, the water-soluble polymer composition may, if necessary, additionally contain up to 18% by weight, based on the total weight of the polymer composition, preferably up to 15% by weight, in particular up to 5% by weight of additives. They serve, in particular, to further improve the properties of the polymer composition.

Suitable optional additives are known to those skilled in the art and can be selected taking into account the needs for mechanical and chemical stability as well as processability. Examples of suitable additives in the context of the present invention are stabilizers and antioxidants, agents for preventing thermal degradation and degradation under the influence of ultraviolet light, a lubricant and a mold release agent, dyes and pigments, and plasticizers. Optional additives may also optionally include additional polymers, in particular water-soluble polymers, which differ from the copolymers of polyvinyl alcohol P1 and polyvinyl alcohol P2 disclosed herein.

Antioxidants and heat stabilizers that can be added to the polymer composition are, for example, halides of metals of group I of the periodic table, for example, sodium, potassium and/or lithium halides. In addition, zinc fluoride and zinc chloride can be used. In addition, sterically hindered phenols, hydroquinones, substituted representatives of this group, secondary aromatic amines, if necessary in combination with phosphorus-containing acids or their salts, and mixtures of these compounds, preferably in concentrations of up to 1% by weight, based on the weight of the polymer composition, are also applicable.

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

The lubricant and mold release agent, which can be added as a rule in amounts of up to 1% by weight, based on the weight of the polymer composition, are stearic acid, stearyl alcohol, alkyl esters and amides of stearic acid, and also esters of pentaerythritol with long-chain fatty acids. Calcium, zinc or aluminum salts of stearic acid and such dialkyl ketones, for example distearyl ketone, can also be used. According to the invention, zinc, magnesium and calcium stearate, as well as N,N'-ethylene bis-stearamide, are particularly suitable. Calcium stearate is particularly preferably added to the polymer composition as an additive.

The water-soluble container may preferably have an average wall thickness in the range of 10 to 45 μm, particularly preferably in the range of ≥20 to ≤35 μm. As a result, an optimal ratio between good solubility and good mechanical strength of the water-soluble container can be achieved.

The size of the water-soluble container can be selected by a person skilled in the art depending on the amount of dye or coloring composition to be placed. If the container is made in the form of a film package, it can, for example, have a length and/or width in the range of 10 to 200 mm in each case.

The water-soluble container according to the invention is filled with an additive or additive composition. The one or the other contains at least one dye or at least one coloring composition. The additive or additive composition may optionally contain other substances that are to be added to the aqueous solvent. The container according to the invention also simplifies the addition of other substances. Examples of suitable additives or additive compositions that are often used in aqueous solutions of alkali metal cyanides in mines are pH buffer salts, pH correctors, bases (e.g. NaOH), water softening salts and mixtures thereof.

The dye or colouring composition is preferably water-soluble. In the context of the present invention, "water-soluble" means, depending on the dye or colouring composition, that the dye or colouring composition is soluble by at least 50% by weight, preferably by at least 75% by weight, based on the total weight of the dye or colouring composition, in particular by at least 95% by weight. Particularly preferably, the water-soluble dye or water-soluble colouring composition is soluble without residue, i.e. the dye or colouring composition is 100% by weight soluble in the aqueous solvent.

At least one water-soluble dye or at least one water-soluble colouring composition preferably has a solubility in water (demin.) of 100 g/l.

Preferably, a dye or colouring composition is used which is chemically stable with respect to aqueous solutions of alkali metal cyanides in the temperature range from 0 to 50°C and/or in the pH range from 6 to 14. This means in particular that the dye or colouring composition, after dissolution in an aqueous solvent which contains at least one alkali metal cyanide compound and which also has a temperature in the range from 0 to 50°C and/or a pH value in the range from 6 to 14, does not enter into chemical reactions with the components contained, in particular with alkali metal cyanide ions and hydroxide ions, which could lead to a change in the colour of the dye or the dye or dyes contained in the colouring composition, in the aqueous solution with respect to the colour intensity and/or shade. This results in the fact that a constant and reproducible colouring of the aqueous solution containing the alkali metal cyanide can be obtained.

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

In a particularly preferred embodiment of the invention, the at least one dye or at least one coloring 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, E129), disodium 4-hydroxy-3-[(E)-(4-sulfonato-1-naphthyl)diazenyl]naphthalene-1-sulfonate (Carmoisine, Food Red 3, Azorubine, Acid Red 14, E122) and combinations thereof. The chemical structures of these compounds are shown below.

The additive or additive composition may be present in the water-soluble container in the form of a solid, such as a powder, granules or in a pressed form, such as a tablet, in the form of a suspension or in the form of a solution. If the additive or additive composition is present in the water-soluble container in the form of a suspension or solution, the liquid component(s) of the suspension or solution must not be suitable for dissolving the polymer composition from which the water-soluble container is made. Suitable solvents are organic solvents which are themselves readily soluble in water. Particularly noteworthy are acetone and ethanol. Thus, the amounts of organic solvents introduced when using aqueous solutions of cyanides for coloring are negligible and do not interfere with further use.

In the case of additives or additive compositions in powder form, the large surface area of the powder facilitates rapid solubility. Powders are often inexpensive and readily available.

Additives or additive compositions in the form of granules (as well as tablets and briquettes) tend to form less dust than powders. This is particularly desirable in the case of compositions containing dyes, in order to avoid staining the production plant. It is also desirable to avoid dust formation in the case of potentially hazardous substances.

Additives or additive compositions in the form of suspensions reduce the risk that the additive or additive composition will take away some of the water contained in the polymer composition of the container according to the invention. As a result, a decrease in the proportion of water in the polymer composition may worsen its solubility.

If additives or additive compositions are used as solutions, the form of the solution supports the dissolution process. The actual dissolution of the additives or additive compositions thus already takes place in the preceding stage. The solution then only needs to be mixed with the desired solvent and thus diluted. This is particularly true for additives or additive compositions with reduced solubility in water. At the same time, dust formation can be avoided.

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

The water-soluble container according to the invention is expediently used with at least one solid water-soluble alkali metal cyanide compound. This use allows a simple method for producing a coloured aqueous composition Z2 comprising at least one alkali metal cyanide compound and at least one dye. For this purpose, the at least one alkali metal cyanide compound and at least one dye can be advantageously provided in the form of a preliminary composition for use (composition Z1), which by dissolving it in an aqueous solvent provides a composition for use (composition Z2).

Therefore, the invention also provides 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 comprise at least sodium cyanide, potassium cyanide or mixtures of these alkali metal cyanides, particularly preferably sodium cyanide. They are used in particular in the mining industry as a leaching agent in the extraction of gold and silver.

The solid water-soluble alkali metal cyanide compound may be present, for example, in the form of powder, granules, tablets or briquettes.

The water-soluble container used in the composition Z1 corresponds to the water-soluble container according to the invention described above. All the above definitions and described embodiments of the water-soluble container according to the invention are also valid and applicable with respect to the composition Z1 according to the invention.

It has been observed that the water-soluble containers according to the invention also have good solubility in aqueous solvents even after long-term storage in contact with the said alkali metal cyanide compound.

The mass ratio (mass _{of dye} /mass of _{alkali metal cyanide} ) of the water-soluble dye to the water-soluble alkali metal cyanide compound in the composition Z1 according to the invention is preferably in the range from 0.00002:5 to 0.0002:5.

The composition Z1 is preferably supplied in a package, in particular in a package that is commonly used for the sale, transport and/or further processing of the alkali metal cyanide compounds used. Preferably, the package is selected from a container, a big bag, a box, a big bag in a box, a drum, in particular from a container, a 1000 kg big bag in a box or a 1000 kg big bag. The package can be designed in such a way that the dissolution process at the dissolution station can be carried out directly in the package by adding an aqueous solvent. Preferably, the composition Z1 in the package is protected from contact with high relative humidity. 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 the composition Z1 for the user.

Another object of the present invention is a method for producing the above-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 method comprises at least combining at least one water-soluble container together with at least one solid water-soluble alkali metal cyanide compound, and wherein the water-soluble container comprises an additive or additive composition with at least one water-soluble dye or at least one soluble coloring composition. The method for producing the composition Z1 preferably comprises at least the following process steps:

(i) providing a predetermined amount of at least one solid water-soluble alkali metal cyanide compound in the package;

(ii) adding at least one water-soluble container to at least one alkali metal cyanide compound in the package, wherein the water-soluble container comprises an additive or additive composition with at least one water-soluble dye or at least one water-soluble coloring composition;

wherein the amount of at least one water-soluble alkali metal cyanide compound in the package and the amount of at least one dye or at least one coloring composition in at least one water-soluble container are measured in such a way that after dissolving the resulting composition Z1 in a given amount of aqueous solvent, a colored aqueous solution of alkali metal cyanide of a given concentration with a given extinction coefficient is obtained. In this case, the extinction coefficient can be adapted to the relevant requirements in such a way as to ensure a sufficiently strong coloring of the colored aqueous composition Z2 and to guarantee easy identification of cyanide-containing solutions. The extinction coefficient can be determined using optical (UV/visible light) spectroscopy or photometry.

The packaging used in the method is preferably a packaging that is used for selling, transporting and/or further processing the alkali metal cyanide compounds used. Preferably, the packaging is selected from a container, a big bag, a box, a big bag in a box, a drum, a container, a 1000 kg big bag in a box or a 1000 kg big bag. In this case, the packaging can be designed in such a way that the dissolution process at the dissolution station can be carried out directly in the packaging by adding an aqueous solvent.

If necessary, mixing of at least one solid aqueous alkali metal cyanide compound and at least one water-soluble container according to the invention can be carried out to achieve uniform distribution of the components in the package.

The amount of solid water-soluble alkali metal cyanide compound and at least one dye or at least one coloring composition can be optimally matched to one another and adapted to the requirements of the subsequent application. In this way, colored aqueous solutions of alkali metal cyanide can be produced in a simple manner, which have a given concentration of alkali metal cyanide and a concentration of dye. In this case, alkali metal cyanide solutions of the same concentration have the same color intensity.

Preferably, the weight ratio (weight _{of dye} /weight of _{alkali metal cyanide} ) of the water-soluble dye to the water-soluble alkali metal cyanide compound in the method according to the invention for producing the above-described composition Z1, containing at least one water-soluble alkali metal cyanide compound and at least one water-soluble container according to the invention, is in the range of 0.00002:5 to 0.0002:5.

The composition Z1 obtained by the method according to the invention can be advantageously used in the following described method for producing a coloured aqueous composition Z2 according to the invention. In this case, the presented method for producing the composition Z1 corresponds to the process steps (i) and (ii) of the method according to the invention for producing a coloured aqueous composition Z2 containing at least one water-soluble alkali metal cyanide compound and at least one water-soluble dye.

Another object of the present invention is a method for producing a colored aqueous composition Z2, which contains at least one alkali metal cyanide compound and at least one dye. The method comprises introducing at least one water-soluble container according to the invention into an aqueous solvent, wherein at least one water-soluble container contains at least one water-soluble dye or at least one water-soluble coloring composition.

A method according to the invention for producing a coloured aqueous composition Z2, which contains at least one water-soluble alkali metal cyanide compound and at least one water-soluble dye, wherein the method 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 comprises an additive or additive composition with at least one water-soluble dye or at least one water-soluble coloring composition;

(ii) providing at least one solid water-soluble alkali metal cyanide compound;

(iii) introducing at least one water-soluble container and at least one solid water-soluble alkali metal cyanide compound into an aqueous solvent; and

(i) optionally mixing at least one water-soluble container and at least one water-soluble alkali metal cyanide compound with an aqueous solvent to facilitate dissolution of the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound in the aqueous solvent.

The water-soluble container used in the method for producing the colored aqueous composition Z2, which contains at least one water-soluble alkali metal cyanide compound and at least one water-soluble dye, corresponds to the previously described water-soluble container according to the invention. All the above definitions and described embodiments of the water-soluble container according to the invention are also valid and applicable with respect to the method for producing the colored aqueous composition Z2 according to the invention.

The alkali metal cyanide compound used in the method 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. They are used in particular in the mining industry as a leaching agent in the extraction of gold and silver. Sodium cyanide is particularly preferably used due to its availability.

The alkali metal cyanide compound is in the form of a solid such as powder, granules, tablets or briquettes.

To obtain a coloured aqueous composition Z2 in accordance with the method according to the invention, at least one water-soluble container and at least one water-soluble alkali metal cyanide compound are introduced into an aqueous solvent.

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

In an alternative embodiment of the invention, at least one water-soluble container is first introduced into the aqueous solvent, and then, i.e. with a time offset, at least one water-soluble alkali metal cyanide compound is introduced into the aqueous solvent.

In yet another alternative embodiment of the invention, at least one water-soluble alkali metal cyanide compound is first introduced into the aqueous solvent, and then, i.e., with a time shift, at least one water-soluble container is introduced into the aqueous solvent.

Preferably, at least one water-soluble container and at least one water-soluble alkali metal cyanide compound are introduced into the aqueous solvent simultaneously. This allows the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound to be mixed with each other immediately before they are introduced into the aqueous solvent. The colouring of the aqueous solution allows the presence of an aqueous alkali metal cyanide solution to be recognised by simple optical means and the concentration of this solution to be assessed. In the context of this embodiment of the invention, the above-described composition Z1 can be used particularly preferably, comprising at least one solid water-soluble alkali metal cyanide compound and at least one water-soluble container according to the invention.

Preferably, in the method for producing the coloured aqueous composition Z2, at least one water-soluble container and at least one solid water-soluble alkali metal cyanide compound in the form of the above-described composition Z1 can be used, which contains at least one solid water-soluble alkali metal cyanide compound and at least one water-soluble container according to the invention.

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

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

According to the invention, the coloured 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. Furthermore, the coloured aqueous composition Z2 comprises components of the dissolved polymer composition of the water-soluble container. The concentration of the water-soluble dye in the coloured 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 the water-soluble alkali metal cyanide compound in the coloured aqueous composition Z2 is preferably in the range of 1.5 to 10 mol/l. The molar ratio of the water-soluble dye to the water-soluble alkali metal cyanide compound in the coloured aqueous composition Z2 is preferably in the range of 0.00002:5 to 0.0001:5.

The International Cyanide Management Institute's non-mandatory recommendation is a concentration of 0.03 g (dye)/L of an aqueous NaCN solution containing 23% NaCN.

According to the invention, the pH value and temperature of the aqueous solvent used can vary over a wide range. This makes it possible to carry out the method under various external conditions, in particular in mines in various regions of the world.

The aqueous solvent at the start of process step (iii) may have a pH value in the range from pH 6 to pH 14, preferably in the range from pH 6.5 to pH 13, in particular in the range from pH 6.5 to pH 12.5. The aqueous solvent at the start of process step (iii) may have a temperature of from 0 to 50°C, in particular from 0 to 25°C or from 0 to 15°C.

The invention is now described in more detail using examples.

Examples

Comparative tests of polyvinyl alcohol films with a degree of hydrolysis of more than 95 mol.% showed that they did not dissolve at the desired rate. For example, even after dissolution for about 20 minutes in an aqueous solvent, visible pieces of film still remained, especially at temperatures ≤ 15°C.

Polymer bags according to the invention were prepared, which were filled with a water-soluble dye. Then the dissolution characteristics of the filled bags were investigated by placing them in an aqueous solution and determining the time t (Ex. _max ) until the maximum coloration of the solution (maximum extinction of the dye) by means of the dye.

A certain amount of carmoisine dye is calculated so that a final concentration of 0.03 g/l is achieved in the experiment. This amount of dye is weighed into containers obtained in the form of bags made of commercially available water-soluble polyvinyl alcohol with a degree of hydrolysis of 91 - 94 mol % (PVOH-1: copolymer of vinyl alcohol and vinyl acetate, manufacturer: GS-go soluble wasserlösliche Verpackungen GmbH, D-65582 Dietz), a commercially available water-soluble copolymer of polyvinyl alcohol with a degree of hydrolysis of 85 mol % (PVOH-2: copolymer of vinyl alcohol, vinyl acetate and pentaerythritol acrylate, manufacturer: GS-go soluble wasserlose Verpackungen GmbH, D-65582 Dietz), and a commercially available water-soluble copolymer of polyvinyl alcohol with a degree of hydrolysis of 85 mol %. and a proportion of repeating units derived from pentaerythritol acrylate 13 mol % (PVOH 3: copolymer of vinyl alcohol, vinyl acetate and pentaerythritol acrylate), manufacturer: GS-go soluble wasserlose Verpackungen GmbH, D-65582 Diez) of a defined format and sealed using a film sealing apparatus, so that a polymer bag filled with dye is obtained. The polyvinyl alcohols and polyvinyl alcohol copolymers used were analyzed by IR and/or NMR spectroscopy as described herein. ¹ H- and ¹³ C-NMR spectroscopy was performed in DMSO-D6 as solvent (Bruker Avance III 600; 600 MHz (H1); DMSO-D6; 27 °C; ¹ H-NMR: 32 scans, 30° pulse, 2.7 s acquisition time, 65536 time domain; ¹³ C: 400 scans, 30° pulse, 1.8 s acquisition time, 131072 time domain, energy-chopped decoupling). ¹³ C-NMR spectroscopy was additionally performed in solid (Bruker Avance III HD; 400 MHz (H1); ambient temperature (ca. 22 °C); pulse sequence: cross-polarization with ramp, spin frequency 9 kHz, 12735 scans, 5 s relaxation delay).

This polymer packet is then placed in a beaker of a certain size (600 ml, wide) with a certain liquid (demineralized water, if necessary with the addition of NaOH) at a certain pH and stirred with a magnetic stirrer at a certain speed (300 rpm) and temperature. With the release of the first color, a sample is quickly taken at certain time intervals (1, 2, 4, 5, 7, 10, 15, 20 minutes) and the extinction at a wavelength of 516 nm is determined colorimetrically. A commercially available spectrometer (LICO 690, spectral colorimeter from Hach / measurement in a round cuvette with a diameter of 10 mm) is used for this. After each measurement, the samples are quickly returned back to the beaker. When the maximum extinction is reached, the dye is completely dissolved. The maximum extinction is reached when no further increase in the extinction value is observed in two consecutive measurements.

The experimental parameters and measurement results are presented in Table 1.

Table 1 Pr. Water soluble container Liquid pH T
[°C] t (Ex. _max )
[min] Material Dimensions
[mm] Wall thickness
[µm] Pre-processing 1 PVOH-1 100x130 30 --- _H2O 6.5 20 approx. 2.5 2 PVOH-1 100x130 30 --- _H2O +NaOH 11.0±0.2 18 approx. 4 3 PVOH-2 100x130 30 --- _H2O +NaOH 11.0±0.2 8-9 approx. 4 4 PVOH-3 100x130 30 --- _H2O + NaOH 11.0±0.2 8-9 approx. 4 5 PVOH-2 50x50 30 --- _H2O +NaOH 11.0±0.2 8-9 approx. 4.5 6 PVOH-2 50x50 30 --- _H2O +NaOH 11.0±0.2 2-4 approx. 7 7 PVOH-2 50x50 30 after 2 weeks of storage in a drying cabinet at 40°C _H2O +NaOH 11.0±0.2 8-10 approx. 16 8 PVOH-2 50x50 30 after 1 month of storage in a drying cabinet at 40°C _H2O +NaOH 11.0±0.2 8-10 approx. 15 9 PVOH-2 50x50 30 after 1 month of storage at room temperature in NaCN granules _H2O +NaOH 11.0±0.2 8-10 approx. 19 10 PVOH-2 50x50 30 after 1 month of storage at room temperature in the laboratory _H2O +NaOH 11.0±0.2 8-10 approx. 10

Example 1 demonstrates that the polymer bags according to the invention rapidly release the dye in an aqueous solvent at a temperature of 20°C and a pH of 6.5. The maximum extinction is achieved after only 2.5 minutes.

At a pH of 11, the time to reach the extinction maximum increases only slightly, to about 4 minutes. Even when the solvent temperature is reduced to 8 - 9°C, this time period does not increase (cf. Notes 2 - 4). The size of the polymer package has only a minor influence on the properties of the solution (see Example 5). At temperatures in the range from 2 to 4°C, dissolution still occurs rapidly, with the extinction maximum of the solution after about 7 minutes (cf. Note 6).

In examples 7-10, the effect of storing the polymer bag according to the invention under different conditions is investigated. 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 experiment. A comparison with example 5 shows that the storage conditions result in the maximum extinction of the solution being reached later. The greatest slowdown is observed in the case of the polymer bag previously stored in a container with sodium cyanide granules at room temperature (see example 9). Nevertheless, the maximum extinction is reached in less than 20 minutes. This time period is short enough for use in a mine, since this time period is also required for the dissolution of the alkali metal cyanide compound.

A comparison of examples 5, 7 and 8 shows that the solubility of the polymer bag according to the invention deteriorates as a result of storage at elevated temperatures. Without wishing to be limited by any theory, it is assumed that this is due to a decrease in the water content of the polymer composition of the polymer bag during storage in a drying cabinet at 40°C and, possibly, with an increase in the degree of crystallization.

From the examples according to the invention it is also evident that the container according to the invention dissolves at a good rate and therefore releases the dye at a good rate.

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

The present invention allows adding certain amounts of dye in a polymer package to an alkali metal cyanide compound in its commercial package. For use in a mine, i.e. for producing a colored alkali metal cyanide solution, the polymer package containing the dye or coloring composition can be dissolved in water together with the alkali metal cyanide compound in a standard dissolution station. This avoids an additional process step in the dissolution process or setting up the dissolution station. The use of a water-soluble container also reduces the risk that, for example, a production plant for producing alkali metal cyanide compounds will be contaminated with the dye or coloring composition.

Claims (32)

1. A water-soluble container suitable for containing an additive or additive composition and filled with an additive or additive composition containing at least one dye or at least one coloring 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 water-soluble polymer or a water-soluble polymer composition, wherein the water-soluble polymer or polymer composition comprises: at least one copolymer of polyvinyl alcohol P1 with a degree of hydrolysis in the range from 75 to 95 mol.%, wherein the polyvinyl alcohol copolymer P1 is a copolymer that contains - repeating units of vinyl alcohol, - repeating units of vinyl ester and - repeating units of at least one comonomer, wherein at least one comonomer is selected from pentaerythritol acrylate and, if necessary, acrylic acid; wherein the polymer composition, in addition to at least one polyvinyl alcohol copolymer P1, may additionally, if necessary, contain additives; wherein the polymer composition contains at least one copolymer of polyvinyl alcohol P1 and does not contain polyvinyl alcohol P2 with a degree of hydrolysis in the range from 87 to 95 mol.%, has a content of repeating units of at least one comonomer in total in the range from 10 to 20% by weight, based on the total weight of the copolymer of polyvinyl alcohol P1; and wherein the degree of hydrolysis of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2 is determined using quantitative ¹ H-NMR spectroscopy, and wherein the composition of the copolymer of polyvinyl alcohol P1 and polyvinyl alcohol P2 is determined using IR and NMR spectroscopy. 2. A water-soluble container according to claim 1, characterized in that the water-soluble polymer composition contains at least one copolymer of polyvinyl alcohol P1 with a degree of hydrolysis in the range from 80 to 90 mol%. 3. A water-soluble container according to claim 1, characterized in that the water-soluble polymer composition contains at least one copolymer of polyvinyl alcohol P1, selected from a copolymer of vinyl alcohol, vinyl ester and pentaerythritol acrylate, a copolymer of vinyl alcohol, vinyl ester, pentaerythritol acrylate and acrylic acid, and their derivatives. 4. A water-soluble container according to claim 1, characterized in that the water-soluble polymer composition consists 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, of at least one polyvinyl alcohol copolymer P1. 5. A water-soluble container according to claim 1, characterized in that the polymer composition additionally contains from 1 to 7% by weight of water, based on the total weight of the polyvinyl alcohol copolymer P1. 6. A water-soluble container according to claim 1, characterized in that the polymer composition additionally contains from 1 to 7% by weight of water, based on the total weight of the polymer composition. 7. A water-soluble container according to one of claims 1-6, characterized in that at least one dye or at least one coloring composition contains 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. 8. Composition Z1 for producing a coloured aqueous composition, containing at least one solid water-soluble alkali metal cyanide compound and at least one water-soluble container according to one of claims 1-7. 9. A method for producing composition Z1 according to claim 8, characterized in that the method comprises at least adding at least one water-soluble container according to one of claims 1-7 to at least one alkali metal cyanide compound. 10. The method according to claim 9 for obtaining the composition Z1 according to claim 8, characterized in that the method includes at least the following process stages: (i) providing a predetermined amount of at least one solid water-soluble alkali metal cyanide compound in the package; (ii) adding at least one water-soluble container according to one of paragraphs 1-7 to at least one alkali metal cyanide compound in the package; wherein the quantity of at least one water-soluble alkali metal cyanide compound in the package and the quantity of at least one dye or at least one coloring composition in at least one water-soluble container are measured in such a way that after dissolving the obtained composition Z1 in a given quantity of an aqueous solvent, a colored aqueous solution of an alkali metal cyanide of a given concentration with a given extinction coefficient is obtained. 11. A method for producing a coloured aqueous composition Z2, which contains at least one alkali metal cyanide compound and at least one dye, characterised in that the method comprises introducing at least one water-soluble container according to one of claims 1-7 and at least one solid water-soluble alkali metal cyanide compound into an aqueous solvent, and wherein at least one water-soluble container contains at least one water-soluble dye or at least one water-soluble colouring composition. 12. The method according to claim 11 for obtaining a coloured aqueous composition Z2, characterised in that the method comprises at least the following process steps: (i) providing at least one water-soluble container according to one of claims 1 to 7, wherein the water-soluble container comprises an additive or additive composition with at least one water-soluble dye or at least one water-soluble colouring composition; (ii) providing at least one solid water-soluble alkali metal cyanide compound; (iii) introducing at least one water-soluble container and at least one solid water-soluble alkali metal cyanide compound into an aqueous solvent; (iv) optionally mixing at least one water-soluble container and at least one water-soluble alkali metal cyanide compound with an aqueous solvent to facilitate dissolution of the at least one water-soluble container and the at least one water-soluble alkali metal cyanide compound in the aqueous solvent. 13. The method according to claim 11 or 12 for obtaining a coloured aqueous composition Z2, characterised in that at least one water-soluble container and at least one solid water-soluble alkali metal cyanide compound are used in the form of composition Z1 according to claim 8. 14. Use of composition Z1 according to claim 8 in the method according to any one of claims 11-13 for producing a coloured aqueous composition Z2.