Method for producing aqueous compositions low in 2-methylisothiazolin-3-one (MIT)

Abstract

The invention relates to a method for producing an aqueous composition having a content of 2-methyl-isothiazolin-3-one (MIT) of less than 1.5 ppm, characterised in that an aqueous composition containing isothiazolinone and having a content of the isothiazolinone 2-methylisothiazolin-3-one ( MIT) of at least 1.5 ppm is treated by adding 3,6-dioxa-1,8-octane-dithiol (DMDO), optionally in combination with one or more reducing agents, wherein at least 2.5 ppm of DMDO and optionally co-used reducing agent are used for every 1 ppm of isothiazolinone contained in the aqueous composition.

Description

[0001] P001 01244A

[0002] - 1 - Method for the preparation of 2-methylisothiazolin-3-one (MIT)-poor aqueous compositions

[0003] The present invention relates to a process for producing an aqueous composition low in MIT, such as a coating material, for example a paint or a plaster, with a 2-methylisothiazolin-3-one (MIT) content of less than 1.5 ppm, characterized in that an isothiazolinone-containing aqueous composition with a 2-methylisothiazolin-3-one (MIT) content of at least 1.5 ppm is treated by adding 3,6-dioxa-1,8-octanedithiol (DMDO), optionally in combination with one or more reducing agents.

[0004] Preservatives are used in many aqueous systems to combat microbial growth. An important application is the preservation of coating materials such as paints and plasters, as these are subject to microbiological degradation and will spoil if preservatives are not added.

[0005] To ensure the long-term durability of coatings, the majority of all water-based coatings available today for interior and exterior use are therefore mixed with preservatives from the isothiazolinone family.

[0006] It has been known for years that contact with isothiazolones can trigger allergic reactions. 5-Chloro-2-methyl-4-isothiazolinone (CIT) exhibits by far the greatest sensitizing potential. However, since it has up to 100 times the antimicrobial efficacy of 2-methylisothiazolin-3-one (MIT), CIT is still used to preserve components, for example, in coatings such as paints or plasters. A key component of paints and plasters is the binder or polymer dispersion, which, prior to the production of the respective coating, usually already contains the cost-effective and highly effective 5-chloro-2-methyl-4-isothiazolinone, mostly in combination with 2-methylisothiazolin-3-one (MIT), in amounts ranging from 5 to 20 ppm.This results in a coating manufacturer producing a coating with a significant content of 5-chloro-2-methyl-4-isothiazolin-one as well as 2-methylisothiazolin-3-one (MIT) when using such a polymer dispersion.

[0007] However, due to the comparatively high sensitizing potential of 5-chloro-2-methyl-4-isothiazolone, it was desirable that it be contained in coating materials in the smallest possible amounts, in a range of 0 to 1 ppm.

[0008] Therefore, in WO2015 / 082063 an attempt was made to selectively P001 01244A the CIT in the presence of MIT and BIT

[0009] - 2 - to reduce with suitable destroyers such as cysteine.

[0010] However, coatings containing 2-methylisothiazolin-3-one (MIT) are no longer desirable for end users. Therefore, it would be advantageous to more effectively destroy the isothiazolinone 2-methylisothiazolin-3-one (MIT) during the transition from industrial to end-user applications.

[0011] Furthermore, the CIT destroyers known from W02015 / 082063, such as cysteine, have the disadvantage of only destroying MIT to a very small extent.

[0012] The object of the present invention was therefore to reduce the content of an aqueous composition of 2-methylisothiazolin-3-one (MIT) more effectively from at least 1.5 ppm to less than 1.5 ppm, preferably to less than 1.0 ppm, and in particular to less than 0.8 ppm.

[0013] The invention therefore relates to a process for producing an aqueous composition with a 2-methylisothiazolin-3-one (MIT) content of less than 1.5 ppm, characterized in that an isothiazolinone-containing aqueous composition with a content of the isothiazolinone 2-methylisothiazolin-3-one (MIT) of at least 1.5 ppm is treated by adding 3,6-dioxa-1,8-octanedithiol (DMDO), optionally in combination with one or more reducing agents, wherein at least 2.5 ppm of DMDO and optionally the reducing agent are used for every 1 ppm of isothiazolinone contained in the aqueous composition.

[0014] Aqueous compositions

[0015] Basically, all possible aqueous compositions containing at least 2-methylisothiazolin-3-one (MIT) as isothiazolinone, the amount of which is to be reduced, are suitable.

[0016] Preferred aqueous compositions are aqueous solutions, emulsions, suspensions or dispersions.

[0017] Preferred aqueous suspensions include, for example, mineral suspensions. Mineral suspensions, also called slurries, preferably contain calcium carbonate, titanium dioxide, or other mineral fillers or pigments as their mineral base. They are frequently essential raw materials for the production of dispersion paints and paper. The mineral substances are preferably finely ground and dispersed in water. Such aqueous compositions are treated, for example, with a CMIT / MIT biocide mixture P001 01244A to prevent microbial degradation.

[0018] - 3 -preserved.

[0019] Preferred aqueous dispersions include, for example, polymer dispersions, especially those whose polymers are of natural origin such as natural latex from the rubber tree, starch or casein, as well as those whose polymers can be produced synthetically by polymerization of one or more monomers such as styrene, acrylic acid and vinyl acetate, for example by means of emulsion or suspension polymerization, but also polyalkylene glycols.

[0020] Also preferred are aqueous compositions containing or based on polymer dispersions. These include, in particular, coating materials such as paints (e.g., emulsion paints) or plasters, as well as adhesives.

[0021] Also preferred are aqueous compositions based on surfactants and, if necessary, water-soluble polymers (e.g., polyalkylene glycols) as used in the fields of cleaning agents, toiletries, cosmetic products, and process fluids in paper processing, textile manufacturing, leather production, and metalworking.

[0022] Preferred polymer dispersions contain polymer particles in an aqueous phase, with the size of the polymer particles typically ranging from 20 nanometers to 200 micrometers. The colloidal stability of the dispersion is usually achieved by surface-active agents, such as surfactants or protective colloids.

[0023] Polymer dispersions are susceptible to microbial infestation and are therefore often preserved with the CIT / MIT biocide mixture.

[0024] Polymer dispersions also form the basis for many adhesives. These polymer dispersions are sometimes combined with additives such as plasticizers, thickeners, and fillers. These adhesives are used, among other things, in self-adhesive labels, tile adhesives, and wood glues.

[0025] Aqueous surfactant solutions or emulsions are commonly used as cleaning and washing agents. These surfactant solutions or emulsions may be further enhanced with additives such as dyes, fragrances, thickeners, wetting agents, and pH regulators.

[0026] Preferred coating materials are water-based paints and plasters. The paint can be for interior or exterior use. The plaster can also be a P001 01244A

[0027] - 4 - Plaster for both exterior and interior use. According to a preferred embodiment of the invention, the coating material is a paint with a pH value in the range of 7.5 to 10, preferably a paint with a pH value in the range of 7.5 to 9.0. According to a preferred embodiment of the invention, the coating material is a plaster with a pH value in the range of 8 to 11, preferably a paint with a pH value in the range of 8.5 to 10.5.

[0028] Other components of the aqueous composition, in particular of the preferred coating agent, may include water, binders, for example in the form of polymer dispersions, pigments, wetting agents, thickeners, thixotropic agents, pH-regulating compounds, fillers and dispersants.

[0029] If the aqueous composition is a coating agent, the 2-methylisothiazolin-3-one (MIT) and optionally other isothiazolinones can be added to the finished coating agent, but preferably the addition is made via ingredients of the coating agent stabilized with 2-methylisothiazolin-3-one (MIT) and optionally other isothiazolinones, in particular preferably polymer dispersions used.

[0030] In addition to 2-methylisothiazolin-3-one (MIT), the aqueous composition, in particular the polymer dispersion or the coating agent, may also contain other isothiazolinones, especially 5-chloro-2-methyl-4-isothiazolinone (CIT) and 2-n-octylisothiazolin-3-one (OIT). These, preferably CIT, are also destroyed by the agent containing 3,6-dioxa-1,8-octanedithiol (DMDO). If other isothiazolinones are present, the proportion of DMDO is preferably increased, optionally in combination with one or more reducing agents.

[0031] Typically, the aqueous composition to be treated according to the invention, in particular the polymer dispersion or the coating agent, contains a proportion of MIT of 2 to 20 ppm, preferably of 4 to 15 ppm and preferably a proportion of isothiazolinones totaling 10 to 100 ppm, preferably of 10 to 50 ppm.

[0032] Preferably, the aqueous composition to be treated according to the invention contains isothiazolinones, which in total consist of more than 95 wt.%, preferably more than 99 wt.% of MIT and optionally 5-chloro-2-methyl-4-isothiazolone (CIT).

[0033] The process according to the invention preferably leads to aqueous compositions, in particular to coating materials with an MIT content of less than 1 ppm,P001 01244A

[0034] - 5 - especially less than 0.8 ppm.

[0035] 3,6-Dioxa-1,8-octane-dithiol (DMDO)

[0036] Preferably, at least 2.5 ppm, in particular at least 2.8 ppm, preferably 2.5 to 200 ppm of 3,6-dioxa-1,8-octanedithiol (DMDO) and optionally a reducing agent are used for every 1 ppm of isothiazolinone contained in the aqueous composition, preferably in the polymer dispersion or in the coating agent. The amounts used therefore always refer to the sum of DMDO and any reducing agent used. This already allows a significant reduction of the MIT content to less than 1.5 ppm to be achieved.

[0037] DMDO, optionally in combination with a reducing agent, which is also a formulation of the invention, can be used as such, but preferably in the form of an aqueous formulation. Both are described below. Preferably, the formulations according to the invention are used in the process according to the invention.

[0038] DMDO is preferably used as an aqueous composition with a DMDO content of 0.5 to 5 wt.%.

[0039] Furthermore, the DMDO can be used in the form of an aqueous solution containing at least one emulsifier and / or at least one antioxidant, preferably ascorbic acid, and / or at least one defoamer, preferably hexyl alcohol. A further description of the DMDO formulation according to the invention is given below.

[0040] Combination:

[0041] It is particularly preferred to use DMDO in combination with at least one reducing agent. In this case, for every 1 ppm of isothiazolinone contained in the aqueous composition, preferably in the polymer dispersion or in the coating material, preferably 2.5 ppm, in particular at least 2.8 ppm, and preferably 2.5 to 200 ppm of such a combination are used. Suitable reducing agents include, in particular, sodium bisulfite (NaHSO₄), sodium metabisulfite (Na₂S₂O₅), sodium sulfite (Na₂SO₄), and sodium thiosulfate (Na₂S₂O₅).

[0042] It is particularly preferred to use DMDO in combination with the reducing agent sodium bisulfite.

[0043] It is particularly preferred that 3,6-dioxa-1,8-octane-dithiol (DMDO) be added as the reducing agent, P001 01244A

[0044] - 6 -in particular to sodium bisulfite, sodium metabisulfite, sodium sulfite and / or sodium thiosulfate, in a weight ratio of 5:1 to 1:5, preferably 3:1 to 1:3, in particular 2.5:1 to 1:2.5.

[0045] DMDO + Reducing Agent Formulation

[0046] The invention also relates to a formulation containing 3,6-dioxa-1,8-octane-dithiol (DMDO) and at least one reducing agent, preferably at least one selected from the group consisting of sodium bisulfite, sodium metabisulfite, sodium sulfite and sodium thiosulfate.

[0047] Preferably, the formulation according to the invention contains 3,6-dioxa-1,8-octane-dithiol (DMDO) and sodium bisulfite; particularly preferably, the combination of DMDO and reducing agent in the formulation according to the invention consists in total of more than 95 wt.%, preferably more than 99 wt.% of DMDO and sodium bisulfite.

[0048] The formulation according to the invention contains in particular 3,6-dioxa-1,8-octane-dithiol (DMDO) in an amount of 0.5 to 5 wt.%, based on the formulation.

[0049] In a further preferred form, the formulation according to the invention is characterized in that it contains DMDO and sodium bisulfite in a weight ratio of 5:1 to 1:5, preferably of 3:1 to 1:3, in particular of 2.5:1 to 1:2.5.

[0050] The formulation according to the invention particularly preferably contains DMDO and the reducing agent, in particular sodium bisulfite, in a total amount of 1 to 6 wt.%, based on the formulation.

[0051] It is further preferred that the formulation according to the invention is an aqueous formulation.

[0052] Preferably, the formulation according to the invention contains at least one emulsifier and / or at least one antioxidant, such preferably ascorbic acid, and / or at least one defoamer, such preferably hexyl alcohol. Other organic solvents, such as C1-C4 alcohols, in particular ethanol, can also be used.

[0053] The emulsifiers are preferably selected from the group consisting of fatty alcohol ethoxylates, fatty alcohol ether sulfates, alkyl sulfates, block copolymers based on ethylene and propylene oxide, tristyrylphonol ethoxylates, tristyrylphonol ethoxylate sulfates and polysorbates.

[0054] Preferentially selected antioxidants are substances from the group consisting of P001 01244A

[0055] - 7 - Ascorbic acid and ascorbic acid salts.

[0056] The defoamers are preferably selected from the group consisting of hexyl alcohol, heptyl alcohol, monoglycerides, diglycerides and tributyl phosphates.

[0057] Preferably, the composition further contains at least one reducing agent in the amount of 0.5 to 5 wt.%. The preferred reducing agents are those mentioned above, and the ratio of DM DO to reducing agent also corresponds to that mentioned above for the process according to the invention.

[0058] Preferably, the formulation according to the invention is used in the process according to the invention.

[0059] The formulation according to the invention is added to the aqueous composition, preferably the polymer dispersion or the coating agent, in such a quantity that for every 1 ppm in the aqueous composition, preferably in the coating agent or the polymer dispersion containing isothiazolinones, preferably 2 to 5 ppm of DMDO and the reducing agent used are eliminated.

[0060] In the process according to the invention, the 2-methylisothiazol-3-one (MIT), and optionally the 5-chloro-2-methyl-4-isothiazolone it may contain, is preferably decomposed or broken down within a period of up to 24 hours, more preferably within a period of 0.5 to 12 hours, and particularly preferably within a period of 2 to 6 hours, so that after this period, particularly within 24 hours, the content of MIT, and preferably also of 5-chloro-2-methyl-4-isothiazolone (CIT), based on the prepared aqueous composition, in particular the prepared coating material or the polymer dispersion, is less than 1.5 ppm, particularly less than 1 ppm, preferably in the range of less than 0.8 ppm, and particularly preferably in the range of 0 to 0.2 ppm. "Within a period of up to 24 hours" means that the entire MIT and optionally the 5-chloro-2-methyl-4-isothiazolone (CIT) are decomposed or broken down within this timeframe.The 5-chloro-2-methyl-4-isothiazoline (CIT) present is decomposed within 24 hours of contact with DMDO, possibly in combination with at least one reducing agent, so that the total content of MIT and any 5-chloro-2-methyl-4-isothiazoline (CIT) present after these 24 hours is in the range of 0 to 1 ppm, based on the prepared aqueous composition, in particular the prepared coating material or the polymer dispersion.

[0061] Through the decomposition of MIT and any 5-chloro-2-methyl-4-isothiazoline (CIT) present, the produced aqueous composition, in particular the produced coating agent, would be almost free of preservatives and would then correspond to P001 01244A

[0062] - 8 -are subject to microbiological degradation and may spoil. It is therefore preferred if new preservatives are added. Therefore, in the process according to the invention, preferably following MIT destruction, at least one preservative selected from the group consisting of 1,2-benzisothiazolin-3-one (BIT), N-methyl-1,2-benzisothiazolin-3-one (M-BIT), 2-n-octylisothiazolin-3-one (OIT), bronopol, phenoxyethanol, sodium pyrithione and zinc pyrithione is added.

[0063] The application concentrations of the preservatives added following MIT destruction are, based on all added preservatives, usually in the range of 10 to 1000 ppm, preferably in the range of 20 to 500 ppm, and particularly preferably in the range of 30 to 200 ppm, based on their concentration in the aqueous composition to be stabilized, in particular the coating material to be stabilized.

[0064] According to a preferred embodiment of the invention, 1,2-benzisothiazolin-3-one (BIT) is added as a preservative following MIT destruction. Surprisingly, it has been found that the 1,2-benzisothiazolin-3-one (BIT) is only minimally degraded or degraded by DMDO and any reducing agent used. Specifically, it was found that the 1,2-benzisothiazolin-3-one (BIT) added after MIT destruction is degraded or degraded by the DMDO or any reducing agent used over a 24-hour period by less than 10% by weight, preferably less than 5% by weight.

[0065] The following examples serve to further illustrate the present invention. P001 01244A

[0066] Examples

[0067] 1. Comparative example

[0068] Comparative studies on the degradation of MIT in aqueous solution show that even with a 4-fold excess of cysteine, the MIT content cannot be reduced below 1.5 ppm. In contrast, even with a 2-fold excess of DMDO, the MIT content is already reduced below 1.5 ppm. Table 1 shows the analysis of the MIT fractions after different treatment times (24 hours, 72 hours, and 7 days) of the process according to the invention.

[0069] In this experiment, aqueous solutions containing 4.9 ppm MIT were mixed with aqueous solutions of cysteine ​​(1.5% cysteine ​​in water) or DMDO (1.5% DMDO in a water / ethanol mixture (9:1)) such that the following weight equivalents of cysteine ​​or DMDO were present relative to the MIT: 1-fold, 2-fold, 3-fold, and 4-fold. The MIT content of the MIT solution without the addition of cysteine ​​or DMDO solution was always determined as a reference during the respective assays at the respective time points.

[0070] Table 1:

[0071]

[0072] P001 01244A

[0073] - 10-

[0074] 2. Production of a dispersion paint

[0075] 2.1 Polymer dispersion

[0076] The production of a dispersion paint based on an ethylene-vinyl acetate (EVA) polymer dispersion was carried out by mixing a 53% aqueous polymer dispersion, preserved with 45 ppm of a CMIT / MIT mixture (11 ppm MIT and 34 ppm CMIT), with a color paste consisting of pigments, fillers, wetting and dispersing agents, rheology additives and water.

[0077] The 53% aqueous polymer dispersion was prepared by dispersing 530 g of Nexiva® CT 115 (vinyl acetate-ethylene copolymer in powder form) in 470 g of water. The powdered Nexiva® CT 115 was dispersed in the water at room temperature using a dispersant while stirring.

[0078] The resulting polymer dispersion was preserved with 30g of a 10% solution and 30g of a 0.15% CMIT / MIT solution (MIT:CMIT = 11:34) (corresponding to 45ppm CMIT / MIT in the dispersion).

[0079] 2.2 Color Paste

[0080] The color paste was prepared by mixing 3g methylhydroxycellulose (Tylose® MH 30,000 YG8), 0.5g sodium polyphosphate (Calgon® N), 3.5g potassium polyacrylate (40% in water) (Lopon® 859), 2g defoamer (Agitan® 281), 90g titanium dioxide (Kronos® 2044), 20g talc (Polywhite B), 175g calcium carbonate d50 ~2.5 µg / ml, and 135g calcium carbonate d50 ~5 µg / ml in 240g water. After thorough mixing, the paste was adjusted to a pH of 8 by adding 2g sodium hydroxide solution (20%).

[0081] 2.3 Dispersion paint

[0082] To produce the dispersion paint, 330g of the polymer dispersion were mixed with 670g of the color paste.

[0083] The resulting paint had a CIT / MIT content of 14ppm (4ppm MIT and 10ppm CIT) and a pH value of 8.P001 01244A

[0084] - 11 - 3. MIT degradation reagents

[0085] 3.1 DMDO solution (degradation reagent A1)

[0086] A 1.5% DMDO solution in water was prepared by intensive mixing of the components water, DMDO, lauryl ether sulfate (emulsifier = Genapol LRO liq.), defoamer (hexyl alcohol) and stabilizer (ascorbic acid).

[0087] Table 2: Composition of the degradation reagent A1 (DMDO)

[0088]

[0089] 3.2 DMDO / Na-bisulfite solution (degradation reagent A2)

[0090] A DMDO / Na-bisulfite solution (1:1 mass ratio) in water was prepared by intensive mixing of the components water, DMDO, sodium bisulfite solution, lauryl ether sulfate (emulsifier = Genapol LRO liq), defoamer (hexyl alcohol) and stabilizer (ascorbic acid).

[0091] Table 3: Composition of the degradation reagent A2 (DMDO:Na-bisulfite = 1:1)

[0092]

[0093] 3.3 DMDO / Na-bisulfite solution (degradation reagent A3)

[0094] A DMDO / sodium bisulfite solution (1:0.5 mass ratio) in water was prepared by intensive mixing of the components water, DMDO, sodium bisulfite solution, lauryl ether sulfate (emulsifier = Genapol LRO liq), defoamer (hexyl alcohol), and stabilizer (ascorbic acid). P001 01244A

[0095] - 12 -

[0096] Table 4: Composition of the degradation reagent A3 (DMDO: bisulfite = 2:1)

[0097]

[0098] 3.4 DM DO solution (degradation reagent B1)

[0099] A solution of DMDO was prepared by mixing 1.5 g of DMDO with 10 g of ethanol and 88.5 g of water.

[0100] Table 5: Composition of the degradation reagent B1

[0101]

[0102] 3.5 DMDO / Sodium bisulfite solution (degradation reagent B2)

[0103] A 1.5% DMDO / sodium bisulfite mixture (1:1 ratio) was prepared by mixing 0.75g DMDO and 1.94g of a 39% sodium bisulfite solution with 87.3g water and 10g ethanol.

[0104] Table 6: Composition of the degradation reagent B2 (DMDO:Na-bisulfite = 1:1)

[0105]

[0106] 3.6 DMDO / Sodium bisulfite solution (degradation reagent B3)

[0107] A 1.5% DMDO / sodium bisulfite mixture (2:1 ratio) was prepared by mixing 1.0g DMDO and 1.3g of a 39% sodium bisulfite solution with 87.7g water and 10g ethanol.

[0108] Table 7: Composition of the degradation reagent B3 (DMDO:Na-bisulfite = 2:1)

[0109]

[0110] 3.7 Cysteine ​​solution (degradation reagent C1)

[0111] A solution of cysteine ​​was prepared by mixing 1.5 g of cysteine ​​with 10 g of ethanol and 88.5 g of P001 01244A

[0112] - 13 - Water produced.

[0113] Table 8: Composition of the degradation reagent C1

[0114]

[0115] 3.8 Cysteine / sodium bisulfite solution (degradation reagent C3)

[0116] A 1.5% cysteine / sodium bisulfite mixture (1:1 ratio) was prepared by mixing 1.0g cysteine ​​and 1.3g of a 39% sodium bisulfite solution with 87.3g water and 10g ethanol.

[0117] Table 9: Composition of the degradation reagent C3 (cysteine: bisulfite = 2:1)

[0118]

[0119] Example 1: Degradation of CIT and MIT in a dispersion paint by adding DMDO-containing solutions

[0120] In 100g of the dispersion paint described above, 0.38g and 0.51g of the degradation reagents were added while stirring. This corresponds to a mass ratio of CIT / MIT to (DMDO / Na-bisulfite) of 1:3 and 1:4, respectively.

[0121] The concentrations of CIT and MIT were determined by HPLC after 24 hours, 72 hours, and 7 days. The baseline values ​​were the CIT and MIT concentrations of the dye before the addition of the degradation reagents. For reference, the CIT and MIT concentrations of the dye without the addition of degradation reagents were also determined at each time point.

[0122] Table 10: Degradation of CIT and MIT in a dispersion paint by adding the degradation reagents A1-A3 in 3 times the amount

[0123] < < <

[0124] < < <

[0125]

[0126] < < <

[0127] A 3-fold excess of the degradation reagents, based on the total CIT and MIT content, leads to an M IT degradation to a P001 01244A for all degradation reagents (A1-A3).

[0128] - 14- Content of less than 1.5ppm.

[0129] The concentrations of CIT and MIT were determined by HPLC after 24 hours, 72 hours, and 7 days. The baseline values ​​were the CIT and MIT concentrations of the dye before the addition of the degradation reagents. For reference, the CIT and MIT concentrations of the dye without the addition of degradation reagents were also determined at each time point.

[0130] Table 11: Degradation of CIT and MIT in a dispersion paint by adding the degradation reagents A1-A3 in 4-fold excess

[0131] < < <

[0132] < < <

[0133]

[0134] < < <

[0135] A 4-fold excess of the degradation reagents, based on the total CIT and MIT content, leads to an M IT degradation to a content of less than 0.8 ppm for all degradation reagents (A1-A3).

[0136] Example 2A: Degradation of CIT and MIT in a dispersion paint by adding DMDO and Na-bisulfite solutions

[0137] 0.3g and 0.4g of the degradation reagents B1-B3 were added to 100g of the dispersion paint while stirring. This corresponds to a mass ratio of CIT / MIT to (DMDO / Na-bisulfite) of 1:3 and 1:4, respectively.

[0138] The concentrations of CIT and MIT were determined by HPLC after 24 hours, 72 hours, and 7 days. The baseline values ​​were the CIT and MIT concentrations of the dye before the addition of the degradation reagents. For reference, the CIT and MIT concentrations of the dye without the addition of degradation reagents were also determined at each time point.

[0139] Table 12: Degradation of CIT and MIT in a dispersion paint by adding the degradation reagents B1, B2 and B3 in 3 times the amount

[0140] < < <

[0141] < < <

[0142]

[0143] < < <

[0144] After 24 hours, 72 hours and 7 days, the level of CIT and MIT was measured using HPLCP001 01244A

[0145] - 15-determined. The CIT and MIT content of the paint before the addition of the degradation reagents was determined as a baseline value. For reference, the CIT and MIT content of the paint without the addition of degradation reagents was also determined at each time point.

[0146] Table 13: Degradation of CIT and MIT in a dispersion paint by adding the degradation reagents B1, B2 and B3 in 4-fold excess

[0147] < < <

[0148] < < <

[0149]

[0150] < < <

[0151] Example 2B: Degradation of CIT and MIT in a dispersion paint by adding cysteine-containing solutions

[0152] In 100g of the dispersion paint described above, 0.3g and 0.4g of the degradation reagents were added while stirring. This corresponds to a mass ratio of CIT / MIT to (cysteine / Na-bisulfite) of 1:3 and 1:4, respectively.

[0153] The concentrations of CIT and MIT were determined by HPLC after 24 hours, 72 hours, and 7 days. The baseline values ​​were the CIT and MIT concentrations of the dye before the addition of the degradation reagents. For reference, the CIT and MIT concentrations of the dye without the addition of degradation reagents were also determined at each time point.

[0154] Table 14: Degradation of CIT and MIT in a dispersion paint by adding the degradation reagents C1 and C3 in 3 times the amount

[0155] < < <

[0156]

[0157] < <

[0158] A threefold excess of the degradation reagents, based on the total CIT and MIT content, leads to incomplete MIT degradation for degradation reagents C1 and C3, resulting in levels of 3.1 ppm and 4.0 ppm, respectively. In the case of C3, MIT regeneration is observed after 7 days compared to the lower 24h and 72h values ​​of 3.1 ppm and 1.9 ppm, respectively.

[0159] The CIT and MIT content was determined by HPLC after 24 hours, 72 hours, and 7 days. The CIT and MIT content of the dye before the addition of P001 01244A served as the baseline value.

[0160] - 16- Degradation reagents were determined. For reference, the CIT and MIT content of the paint to which no degradation reagents were added was also determined at each time point.

[0161] Table 15: Degradation of CIT and MIT in a dispersion paint by adding the degradation reagents A1-A3 in 4-fold excess

[0162] < < <

[0163]

[0164] < < <

[0165] A fourfold excess of the degradation reagents, based on the total CIT and MIT content, leads to incomplete MIT degradation for degradation reagents C1 and C3, resulting in levels of 3.9 ppm and 4.0 ppm, respectively, after 7 days. In both cases, MIT regeneration is observed after 7 days compared to the significantly lower 24h and 72h values.

[0166] Cysteine-based degradation reagents can only degrade MIT to a limited extent. Reducing the MIT concentration to below 1.5 ppm from typical initial levels above 3.5 ppm is not possible with these degradation reagents.

[0167] Example 3: Degradation of CIT and MIT in a polymer dispersion by the addition of DMDO- or DMDO / sodium bisulfite-containing solutions.

[0168] A 53% aqueous polymer dispersion as described above was preserved with approximately 45 ppm CIT / MIT.

[0169] 0.6g of the degradation reagents were added to every 100g of the polymer emulsion while stirring. This corresponds to a mass ratio of CIT / MIT to DMDO of 1:4.

[0170] The CIT and MIT content was determined by HPLC after 24 hours, 72 hours, and 7 days. The CIT and MIT content of the dye before the addition of the degradation reagents served as the baseline. For reference, the CIT and MIT content of the dye without the addition of degradation reagents was also determined at each time point. P001 01244A

[0171] - 17- Table 16: Degradation of CIT and MIT in a polymer dispersion by addition of the degradation reagents A1-A3 in 4-fold excess

[0172] < < < < <

[0173] < < <

[0174]

[0175] < < <

[0176] The concentrations of CIT and MIT were determined by HPLC after 24 hours, 72 hours, and 7 days. The baseline values ​​were the CIT and MIT concentrations of the dye before the addition of the degradation reagents. For reference, the CIT and MIT concentrations of the dye without the addition of degradation reagents were also determined at each time point.

[0177] Table 17: Degradation of CIT and MIT in a polymer dispersion by adding the degradation reagents B1-B3 in 4-fold excess

[0178] < < < < <

[0179] < < < < <

[0180]

[0181] < < < < <

Claims

P001 01244A - 18 - Patent claims 1. A process for producing an aqueous composition with a 2-methylisothiazolin-3-one (MIT) content of less than 1.5 ppm, characterized in that an isothiazolinone-containing aqueous composition with a content of the isothiazolinone 2-methylisothiazolin-3-one (MIT) of at least 1.5 ppm is treated by adding 3,6-dioxa-1,8-octanedithiol (DMDO), optionally in combination with one or more reducing agents, wherein at least 2.5 ppm of DMDO and optionally the reducing agent are used for every 1 ppm of isothiazolinone contained in the aqueous composition.

2. Method according to claim 1, characterized in that at least 2.5 ppm, preferably 2.8 to 200 ppm of 3,6-dioxa-1,8-octane-dithiol (DMDO), optionally in combination with one or more reducing agents, are used for every 1 ppm of isothiazolinone contained in the aqueous composition.

3. The method according to claim 1, characterized in that 3,6-dioxa-1,8-octane-dithiol (DMDO) and at least one reducing agent selected from the group consisting of sodium bisulfite, sodium metabisulfite, sodium sulfite and sodium thiosulfate are used.

4. Method according to claim 1, characterized in that the isothiazolinones of the aqueous composition consist in total of more than 95 wt.%, preferably more than 99 wt.% of MIT and optionally 5-chloro-2-methyl-4-isothiazolone (CIT).

5. The method according to claim 1, characterized in that the 3,6-dioxa-1,8-octane-dithiol (DMDO) is added in combination with sodium bisulfite or sodium thiosulfate.

6. Method according to claim 1, characterized in that 3,6-dioxa-1,8-octane-dithiol (DMDO) is present in the total amount of at least one reducing agent, in particular sodium bisulfite, sodium metabisulfite, sodium sulfite and / or sodium thiosulfate, in a weight ratio of 5:1 to 1:5, preferably 3:1 to 1:3, in particular 2.5:1 to 1:2.

5.

7. Method according to claim 1, characterized in that the 3,6-dioxa-1,8-octanedithiol (DMDO) in combination with sodium bisulfite, sodium metabisulfite, sodium sulfiteP001 01244A - 19- and / or sodium thiosulfate and at least one emulsifier is added.

8. A method according to at least one of claims 1 to 6, characterized in that, after adding DM DO, optionally in combination with one or more reducing agents and reducing the MIT content to less than 1.5 ppm to the aqueous composition, at least one preservative selected from the group consisting of 1,2-benzisothiazolin-3-one (BIT), N-methyl-1,2-benzisothiazolin-3-one (M-BIT), 2-n-octylisothiazolin-3-one (OIT), bronopol, phenoxyethanol, sodium pyrithione and zinc pyrithione is added.

9. Formulation containing 3,6-dioxa-1,8-octane-dithiol (DMDO) and at least one reducing agent, preferably at least one selected from the series sodium bisulfite, sodium metabisulfite, sodium sulfite and sodium thiosulfate.

10. Formulation according to claim 9, comprising 3,6-dioxa-1,8-octane-dithiol (DMDO) and sodium bisulfite.

11. Formulation according to claim 9, characterized in that it contains 3,6-dioxa-1,8-octane-dithiol (DMDO) in an amount of 0.5 to 5 wt%, based on the formulation.

12. Formulation according to claim 9, characterized in that it contains DMDO and sodium bisulfite in a weight ratio of 5:1 to 1:5, preferably of 3:1 to 1:3, in particular 2.5:1 to 1:2.

5.

13. Formulation according to claim 9, characterized in that it contains DMDO and the reducing agent, in particular sodium bisulfite, in an amount of 1 to 6 wt%, based on the formulation.

14. Formulation according to claim 9, characterized in that it is an aqueous formulation.

15. Formulation according to claim 9, characterized in that it contains at least one emulsifier and / or at least one antioxidant, in particular ascorbic acid, and / or at least one defoamer, in particular hexyl alcohol.

Images