Fungicide Mixtures

Abstract

The invention refers to a fungicide mixture comprising the biocides TBZ and PYM in the weight ratio of 20:1 to 1.1:1, in particular 10:1 to 1.1:1, preferably 5:1 to 1.1:1, wherein the total amount of TBZ and PYM based on the entire amount of biocidal actives is greater than 99 wt. % and its use for protecting wallboards.

Claims

1. A fungicide mixture comprising the biocides thiabendazole (TBZ) and pyrimethanil (PYM) in the weight ratio of 20:1 to 1.1:1, wherein the total amount of TBZ and PYM based on the entire amount of biocidal actives is greater than 99 wt. %.

2. The fungicide mixture according to claim 1, wherein the mixture is an aqueous supension containing the biocidal actives in an amount of 1 to 60 wt.

3. The fungicide mixture according to claim 1, wherein the sum of biocidal active and water is 80 to 99 wt % based on the mixture.

4. The fungicide mixture according to claim 1, wherein the mixture contains the biocidal actives and water and 0.2 to 5 wt. % of at least one dispersant, 0.05 to 5 wt. % thickener, 0 to 1 wt. % defoamer,.

5. The fungicide mixture according to claim 1, wherein the average particle size of the biocidal actives is smaller than 100 μm.

6. A process for the manufacturing of the fungicide mixture according to claim 1, wherein the biocides TBZ and PYM are mixed.

7. The process according to claim 6, comprises the following steps: a) mixing the biocidal actives TBZ and PYM, and at least one surfactant and water and optionally a wetting agent, a defoaming agent and an in-can preservatives, b) homogenize the mixture under a) by a high speed stirrer in a respective tank or other suitable vessel, in particular with shear forces, c) optionally further treat such homogenized mixture under b) in a bead mill and d) adding optionally a thickener before, during and/or after the milling step.

8. A wallboard comprising a gypsum core and a facing layer, containing the biocides TBZ and PYM in the weight ratio of 20:1 to 1.1:1, wherein the total amount of TBZ and PYM based on the entire amount of biocidal actives is greater than 99 wt. %.

9. The wallboard according to claim 8 wherein the facing layer is paper or glass fibre mat.

10. The wallboard according to claim 8 wherein the total amount of biocidal actives in the wallboard is from 10 ppm to 3000 ppm.

11. The wallboard according to claim 8, wherein the biocidal actives are included in the gypsum core of the wallboard.

12. The wallboard according to claim 8, wherein the biocidal actives are included in or on the facing layer, which in particular is paper.

13. The wallboard according to claim 8, wherein the biocidal actives is contained in the gypsum core and the facing layer.

14. A process for manufacturing the wallboard according to claim 8 wherein the wallboard is treated with a the fungicide mixture during the manufacturing process of said wallboard and/or thereafter.

15. The process for manufacturing the wallboard according to claim 14, wherein the fungicide mixture according to claim 1 is added during the manufacturing process: a) to a gypsum slurry before the gypsum core is formed and/or b) to the surface of the gypsum core of the wallboard before the facing layer, in particular the paper is applied and/or c) to the facing layer making process, in particular the paper making process, and/or d) to the surface of the facing layer, in particular the paper layer.

Description

EXAMPLES

[0107] The following examples are presented to illustrate the invention and are not meant to limit its scope.

Example 1: Synergism of Mixtures of Thiabendazole (TBZ) and Pyrimethanil (PYM)

[0108] The term synergism is used when the action of a combination of antimicrobial substances is being evaluated. When combining two different actives, several different effects may occur, which usually cannot be foreseen, but have to be determined by adequate testing: [0109] Additive Effect [0110] The additive effect of a combination of antimicrobial substances is one in which the effects of the combination is equal to that of the sum of the effect of the individual components. [0111] Synergistic Effect [0112] Synergistic action of a combination of antimicrobial substances is present if the effect of the combination exceeds the additive effects of the individual components. [0113] Antagonistic Effect [0114] Antagonism is present if a reduced effect of a combination of antimicrobial substances is observed in comparison with the effect of the most effective individual substance.

[0115] The synergism found for the mixtures according to the invention can be determined via the following mathematical mathematical formula (cf. F. C. Kull, P. C. Elisman, H. D.

[0116] Sylwestrowicz and P. K. Mayer, Appl. Microbiol. 9, 538 (1961):

[00001]$\mathrm{synergistic}\mathrm{index}\left(\mathrm{SI}\right)=\frac{Q_a}{Q_A}+\frac{Q_b}{Q_B}$

[0117] where

[0118] Q.sub.a=amount of component A in the active substance mixture which achieves the desired effect, i. e. no microbial growth,

[0119] Q.sub.A=amount of component A which, when used alone, suppresses the growth of the microorganisms,

[0120] Q.sub.b=amount of component B in the active substance mixture which suppresses the growth of the microorganisms,

[0121] Q.sub.B=amount of component B which, when used alone, suppresses the growth of the microorganisms

[0122] If the sum of the ratios for a mixture Qa/Q.sub.A+Q.sub.b/Q.sub.B=1, additivity is indicated; if it is <1, synergism has occurred; a value of >1 is indicative of antagonism.

[0123] Synergism of Mixtures of Thiabendazole and Pyrimethanil

[0124] To determine the antimicrobial efficacy and synergy of active ingredients mixtures, the Minimum Inhibitory Concentration (MIC) of the active substances and their respective combinations were determined. The Minimum Inhibitory

[0125] Concentration of a given antimicrobial compound or mixture is the lowest concentration expressed in mg/mL (ppm) that under defined in vitro conditions inhibits the growth of a given micro-organism (for example bacteria, mould fungi, yeasts). The growth of the microorganisms is observed on petri dishes containing a defined nutrient agar. In the case of fungi, typical strains according to this test design for example would be species like those as indicated in tables 1a) and 1b)

TABLE-US-00001 TABLE 1a TBZ/PYM mixtures—MIC and synergistic indices (in ppm) Fungi TBZ:PYM SI TBZ:PYM SI TBZ:PYM SI TBZ:PYM SI tested TBZ PYM 4:1 4:1 4:2 4:2 4:3 4:3 4:4 4:4 Alternaria 250 25 25 0.28 25 0.39 10 0.18 10 0.22 alternata Aspergillus 25 250 25 0.82 25 0.71 25 0.60 100 >1 niger Fusarium 250 1000 250 0.90 250 0.75 250 0.68 500 >1 solani Stachybotris 50 100 50 0.90 50 0.83 50 0.79 100 >1 chartarum

TABLE-US-00002 TABLE 1b further TBZ/PYM mixtures—MIC and synergistic indices (in ppm) Fungi TBZ:PYM SI TBZ:PYM SI tested TBZ PYM 10:1 10:1 19:1 19:1 Alternaria 250 5 25 0.54 25 0.35 alternata Aspergillus niger 250 500 250 0.96 250 0.98 Fusarium solani 250 1501 250 0.92 250 0.96 Stachybotris 50 100 50 0.96 50 0.98 chartarum

[0126] As can be seen in tables 1a) and 1b), by the combination of TBZ with PYM there can be achieved, depending on fungal species and ratios, noticeable synergistic performance effects, indicated by synergistic indices of <1.

Example 2: Gypsum Board Efficacy Testing (Core Protection)

[0127] The fungicide mixtures as of the present invention and of the comparison example to be tested were made as follows: The respective actives were mixed in their respective weight ratio (see table 2) together with water and 1 wt. % dispersant Tristyrylphenol ethoxylate (in form of Soprophor® S 25), as thickener 0.1 wt. % of Xanthan gum and 1 wt. % wetting agent non-ionic EO/PO-Copolymer (in form of Pluronic 127 F), where the wt. % are based on the entire mixture and were homogenized with a high speed mixer (IKA Ultra Turrax Labor Dispergator) to give an aqueous suspension having a viscosity measured in accordance with CIPAC 192 method of 500-600 mPas and a particle size of the biocides of smaller than 30 μm measured in accordance with the CIPAC 187 method.

[0128] The following antifungal compounds and respective formulations were used: [0129] Thiabendazole (TBZ) [0130] Pyrimethanil (PYM) [0131] Comparative examples: Thiabendazole as only active; Thiabendazole /Azoxystrobin (AZO) as mixture.

[0132] For examination of the antifungal performance of the inventive mixtures the various mixtures prepared above were tested. The testing directly made in gypsum boards provides realistic and practically relevant data for evaluation. To achieve such data, gypsum boards were produced in the laboratory. For this purpose, a typical slurry recipe as given below for board production is used.

[0133] Preparation of Gypsum Board Samples

[0134] Gypsum board recipe:

[0135] Slurry components:

TABLE-US-00003 Gypsum/plaster (CaSO.sub.4x 0.5 H.sub.2O) 9500 g Tap water 5700 g Starch  285 g

[0136] The gypsum slurry is formed by mixing the dry components and the wet components together. The slurry is then mixed to achieve a homogeneous consistency. The fungicide mixtures as prepared above are then incorporated into the wet gypsum slurry respectively (total amount of actives in ppm see table 2) by adding and thoroughly mixing. For sandwiching the gypsum core, untreated cardboard (without fungicide) with a grammage of appr. 180 g/m.sup.2 was used and after assembly of the plate the hand sheets are dried.

[0137] The mould resistance of the gypsum board samples was evaluated according to the test method ASTM G 21-09. Following to this method, the manufactured gypsum boards as described above and after having been cut to an adequate size are placed on an agarplate and superficially are spoiled with fungal spores for a determined period of time of at the most 4 weeks. The respective total amount of actives in ppm based in gypsum/plaster (CaSC.sub.4x 0.5H.sub.2O) can be seen in the table.

[0138] Spore suspensions are produced for each fungi (spore concentrations of approximately 10.sup.6/ml). Organisms which are included in ASTM G 21 comprise Aspergillus niger (ATCC 9642), Aureobasidium pullulans (ATCC 15233) Chaetomium globosum (ATCC 6205), Gliocladium virens (ATCC 6459) and Penicillium pinophilium (ATCC 11797) (as pure culture but also as mixed inoculum), however any other fungi species known to be able to grow in gypsum boards may be used in addition or instead. Mineral agar (according to ASTM G21 of 2009) was used as growth media in the agar plates. Before inoculation the gypsum board hand sheets are cut into pieces of appr. 5×5 cm.

[0139] For every concentration level, 3 test pieces are used in the test. Each sample is placed in a separate petri dish and then inoculated with the fungi mixture. The samples are then incubated at 28-30° C. for 28 days. Pre-reading of the samples may be performed at approximately 10 days after inoculation. The activity of the treatments may be assessed visually, using a rating system of 0-4 for growth inhibition of fungal growth.

TABLE-US-00004 Observed Growth Rating None 0 Traces of growth (less than 10%) 1 Light growth (10 to 30%) 2 Medium growth (30 to 60%) 3 Heavy growth (60% to complete coverage) 4

[0140] Results: The results as recorded after 4 weeks testing at 28-30° C. according to the requirements of test method ASTM G 21 are summarized in table 2.

TABLE-US-00005 TABLE 2 ASTM G 21 testing results Fungicides added to the core, amount in ppm on dry stucco (facing papers not treated) Fungi ppm Mix.sup.1) Control sample 0 4 TBZ 25 4 TBZ 50 4 TBZ 100 4 TBZ 200 4 TBZ 300 3 TBZ-AZO 1.3:1 25 3 TBZ-AZO 1.3:1 50 2 TBZ-AZO 1.3:1 100 0 TBZ-AZO 1.3:1 200 0 TBZ-AZO 1.3:1 300 0 TBZ-PYM 1.3:1 25 1 TBZ-PYM 1.3:1 50 0 TBZ-PYM 1.3:1 100 0 TBZ-PYM 1.3:1 200 0 TBZ-PYM 1.3:1 300 0 .sup.1)The Fungi Mix is composed of the standard ASTM G 21-09 species

[0141] Interpretation of Table 2:

[0142] The control sample (no fungicide in the gypsum core) exhibits heavy growth of fungi. The comparison test with TBZ alone in the tested concentration range is not good enough for control of fungi growth. According to WO2006/134347, mixtures of TBZ and Azoxystrobin (AZO) are disclosed with high suitability to protect wallboards against fungal decay. In comparison with the inventive TBZ/PYM mixtures, the TBZ/AZO composition is less effective, demonstrating the benefit of the new combinations.