Antistatic coating system

Abstract

The subject matter of the present invention is a coating system comprising a fraction (A) comprising at least one polyol bearing two or more hydroxyl groups and a fraction (B) comprising at least one isocyanate bearing two or more isocyanate groups and comprising carbon nanotubes wherein fractions (A) and (B) are physically separated from each other, and wherein the coating produced by mixing parts (A) and (B) has an electrical resistance of < = 80 k [Omega], measured according to DIN EN 61340-4: 2016-04, and a bond strength of > = 1.5 MPa, measured according to DIN EN 1542: 1999-07.

Description

Field of the Invention

[0001] The present invention relates to antistatic coating systems, coatings prepared from such systems, the use of such coating systems, and coating methods. Background of the Invention

[0003] In the construction industry, surfaces and especially concrete surfaces often require coatings to provide the desired surface properties. For example, in the harsh chemical environments of the processing industry such as sewers and storage tanks, coatings resistant to chemicals are often required. However, especially in the processing industry, in the past decade, the demand for the antistatic properties of coating systems and coatings made therefrom has increased respectively. Here, antistatic means reducing, preventing, or otherwise suppressing electrostatic discharge. In the case of handling flammable substances to avoid ignition of such flammable substances by static charges, antistatic properties are particularly desirable. However, many known coating systems such as epoxy systems and polyurethane systems do not provide coatings that are sufficiently antistatic.

[0004] To provide coating systems with antistatic properties, for example, in EP 3 670 470 A1, the incorporation of conductive fibers such as carbon fibers, conductive polymer fibers, and carbon nanotubes (CNT) into such systems has been considered. The use of CNT in coating systems has recently been considered in various aspects (see, for example, CN 108219658 A, CN 111808464, CN112852269 A, US2022 / 0056277A1, WO 2022 / 049070A1, and WO 2022 / 049071A1). However, the described systems may at least partially not result in coatings with antistatic properties sufficient to prevent the ignition of flammable substances. In addition, from, for example, EP2 315 810 B1, it is known that CNTs generally show unfavorable low dispersibility when incorporated into coating systems, and the processing viscosity is generally unfavorably high.

[0005] In addition, known coating systems generally result in coatings with poor adhesion and thus are prone to delamination. This is especially a problem when the coatings formed from such coating systems are to act as diffusion barriers to protect the substrates formed thereon. Therefore, another diffusion barrier is usually required to provide antistatic properties and diffusion barrier properties to the substrates, especially concrete substrates.

[0006] In general, there is still a general expectation for improved antistatic coating systems.

[0007] Problem underlying the invention

[0008] An object of the present invention is to provide a coating system that at least partially overcomes the disadvantages encountered in the art.

[0009] Another object of the present invention is to provide a coating system which can form a coating having improved antistatic properties and improved adhesion to substrates, in particular to concrete substrates.

[0010] Another object of the present invention is to provide a coating system in which carbon nanotubes can be more uniformly distributed and / or at a reduced processing viscosity profile.

[0011] Furthermore, an object of the present invention is to provide a cost-effective coating system.

[0012] Another object of the present invention is to provide a coating, its use and a coating method, which at least partially overcome the disadvantages encountered in the art. Summary of the Invention

[0013] Surprisingly, it has been found that the problems of the present invention are overcome by the coating system, coating, use and coating method according to the claims. Other embodiments of the present invention are outlined throughout the specification.

[0014] The subject matter of the present invention is a coating system comprising:

[0015] Part (A), comprising at least one polyol having two or more hydroxyl groups, and

[0016] Part (B), comprising at least one isocyanate having two or more isocyanate groups and comprising carbon nanotubes,

[0017] wherein part (A) and (B) are physically separated from each other, and

[0018] wherein the coating prepared by mixing part (A) and (B) has:

[0019] a resistance of ≤ 80 kΩ measured according to DIN EN 61340-4 1:2016-04, and

[0020] a bond strength of ≥ 1.5 MPa measured according to DIN EN 1542:1999-07.

[0021] As used herein, polyols should be understood in the usual technical sense, i.e., as organic compounds bearing or having two or more hydroxyl groups (≥2 OH groups). Preferably, the polyol is selected from 1,2-ethanediol or ethylene glycol, 1,2-propanediol or 1,2-propylene glycol, 1,3-propanediol or 1,3-propylene glycol, 1,4-butanediol or 1,4-butylene glycol, 1,6-hexanediol or 1,6-hexamethylene glycol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol or neopentyl glycol, 1,4-bis(hydroxymethyl)cyclohexane or cyclohexanedimethanol, 1,2,3-propanetriol or glycerol, 2-hydroxymethyl-2-methyl-1,3-propanediol or trimethylolethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol or trimethylolpropane, 2,2-bis(hydroxymethyl)-1,3-propanediol or pentaerythritol, or mixtures thereof. Particularly preferred is 1,4-butanediol. Further preferably, the polyol is selected from polyether polyols, especially polyether polyols for polymer-analogous transformation reactions, which generally bear two or more hydroxyl groups (≥2 OH groups), i.e., their functionality ≥2. Also contemplated is that the preferred polyol is selected from polyols having a polyester backbone or a polybutadiene backbone, which polyol also generally bears two or more hydroxyl groups (≥2 OH groups).

[0022] As used herein, isocyanates are to be understood in the conventional manner in the art of organic chemistry as organic compounds carrying or having an isocyanate group (-N=C=O group). At least one isocyanate in part (B) of the coating system according to the invention carries two or more isocyanate groups (≥2 -N=C=O groups). Preferably, the isocyanate carrying two or more isocyanate groups is selected from toluene 2,4 - diisocyanate (also known as toluene 2,4 - diisocyanate, toluene 2,6 - diisocyanate (toluene 2,6 - diisocyanate), mixtures of these isomers (TDI), diphenylmethane 4,4'-diisocyanate, diphenylmethane - 2,4'-diisocyanate or diphenylmethane - 2,2'-diisocyanate, mixtures of these isomers (MDI), benzene - 1,3 - diisocyanate or benzene - 1,4 - diisocyanate, 2,3,5,6 - tetramethyl - 1,4 - diisocyanatobenzene, naphthalene - 1,5 - diisocyanate (NDI), 3,3'-dimethyl - 4,4'-diisocyanatobiphenyl (TODI), dianisidine diisocyanate (DADI), tetramethylene - 1,4 - diisocyanate, 2 - methylpentamethylene - 1,5 - diisocyanate, hexamethylene - 1,6 - diisocyanate (HDI), 2,2,4 - trimethylhexamethylene - 1,6 - diisocyanate, 2,4,4 - trimethylhexamethylene - 1,6 - diisocyanate, mixtures of these isomers (TMDI), decamethylene - 1,10 - diisocyanate, dodecamethylene - 1,12 - diisocyanate, cyclohexane - 1,3 - diisocyanate, cyclohexane - 1,4 - diisocyanate, 1 - methyl - 2,4 - diisocyanatocyclohexane, 1 - methyl - 2,6 - diisocyanatocyclohexane, mixtures of these isomers (HTDI or H6TDI), 1 - isocyanato - 3,3,5 - trimethyl - 5 - isocyanatomethylcyclohexane (isophorone diisocyanate or IPDI), perhydro(diphenylmethane) - 2,4'-diisocyanate, perhydro(diphenylmethane) - 4,4'-diisocyanate (HMDI or H12MDI), 1,4 - diisocyanato - 2,2,6 - trimethylcyclohexane (TMCDI), 1,3 - bis(isocyanatomethyl)cyclohexane, 1,4 - bis(isocyanatomethyl)cyclohexane, m - xylylene diisocyanate (m - XDI), p - xylylene diisocyanate (p - XDI), m - tetramethylxylylene - 1,3 - diisocyanate, m - tetramethylxylylene - 1,4 - diisocyanate (m - TMXDI), p - tetramethylxylylene - 1,3 - diisocyanate, p - tetramethylxylylene - 1,4 - diisocyanate (p - TMXDI), bis(1 - isocyanato - 1 - methylethyl) - naphthalene and mixtures thereof.Particularly preferred are diphenylmethane-2,4'-diisocyanate, diphenylmethane-2,2'-diisocyanate, or a mixture of these isomers (MDI), with MDI being most preferred.

[0023] For MDI, the following isomers or positional isomers of MDI are used and form part of the mixture in which industrial grade MDI typically occurs:

[0024]

[0025] (diphenylmethane-2,2'-diisocyanate)

[0026]

[0027] (diphenylmethane-2,4'-diisocyanate)

[0028]

[0029] (diphenylmethane-4,4'-diisocyanate)

[0030] The polymeric isocyanate according to the invention can be represented by the following general formula:

[0031]

[0032] (polymeric isocyanate)

[0033] As used herein, carbon nanotubes (CNT) should be understood in the usual technical sense. Carbon nanotubes with a single wall are also referred to as single-walled carbon nanotubes (SWCNT). Such single-walled carbon nanotubes are allotropes of carbon and can be regarded, for example, as an intermediate between a fullerene cage and flat graphene, typically having a diameter in the nanometer range. A single-walled carbon nanotube can be idealized as a cut-out from a two-dimensional hexagonal lattice of carbon atoms rolled up along one of the Bravais lattice vectors of the hexagonal lattice to form a hollow cylinder. In this structure, periodic boundary conditions are imposed along the length of the winding vector to produce a helical lattice of carbon atoms with seamless connections on the cylindrical surface. Multi-walled carbon nanotubes (MWCNT) consist of nested single-walled carbon nanotubes that are weakly bound together by van der Waals interactions in an annual ring-like structure. Multi-walled carbon nanotubes include double-walled and triple-walled carbon nanotubes.

[0034] In the coating system according to the present invention, part (A) and part (B) are physically separated from each other, that is, there is no physical contact between them. Therefore, part (A) and part (B) can be placed in two separate containers, for example, part (A) in the first container and part (B) in the second container. The coating system according to the present invention can thus also be referred to as a two-component system or a kit product comprising part (A) and (B). The physical separation of part (A) and (B) can be achieved by storing part (A) and (B) in two different containers or in two different compartments of a single container. The physical separation can particularly ensure that no reaction occurs between at least one polyol comprised in part (A) and at least one isocyanate comprised in part (B).

[0035] When part (A) and (B) are mixed or come into contact with each other, at least one polyol comprised in part (A) and at least one isocyanate comprised in part (B) will react with each other to form a polyurethane comprising urethane groups (-NH-(C=O)-O- groups). Therefore, the coating system according to the present invention can also be referred to as a polyurethane coating system. When the reaction between at least one polyol comprised in part (A) and at least one isocyanate comprised in part (B) and all other possible reactions between the components of part (A) and part (B) are potentially completed via intermediates, a coating is formed from the mixture of part (A) and (B). The completion of these reactions can be determined, for example, by measuring the temperature of the mixture of part (A) and (B). Once no further temperature change of the mixture of part (A) and (B) can be observed - in an additional isothermal environment, a coating is formed. The coating is usually formed within 24 hours. Once the coating is formed, its properties can be determined according to established protocols in the art.

[0036] A coating formed from the coating system according to the present invention as described above, that is, by mixing part (A) and (B), has a resistance of ≤ 80 kΩ (80,000 Ohm or less). Here, the resistance is measured according to DIN EN 61340-4 1:2016-04, "Standard test methods for special applications - Resistance of floor coverings and installed floors".

[0037] A coating formed from the coating system according to the present invention as described above, that is, by mixing part (A) and (B), further has an adhesion strength of ≥ 1.5 MPa. Here, the adhesion strength is measured according to DIN EN 1542:1999-07, "Products and systems for the protection and repair of concrete structures - Test methods - Determination of adhesion strength by pull-off".

[0038] Due to its low resistance, the coating formed from the coating system according to the invention has improved antistatic properties. Furthermore, due to its high bond strength, the coating formed from the coating system according to the invention has improved adhesion to the substrate, in particular improved adhesion to a concrete substrate. In addition, the coating system according to the invention can eliminate the requirement for an additional diffusion barrier layer. Without wishing to be bound by theory, it is believed that the improved antistatic properties and the simultaneously improved bond strength are at least partly due to the orientation of the carbon nanotubes and / or their agglomeration at the coating surface (surface effect).

[0039] Furthermore, it has been found that the carbon nanotubes can be more evenly distributed in the coating system according to the invention, more specifically in part (B) thereof. In addition, the carbon nanotubes can be incorporated into the coating system according to the invention, more specifically into part (B) thereof, without experiencing an adverse increase in viscosity, i.e., the carbon nanotubes can be incorporated at a reduced processing viscosity.

[0040] For the coating system according to the invention, a resistance ≤20 kΩ is preferred, more preferably ≤10 kΩ. Due to such a particularly low resistance, the coating formed from this coating system can have particularly improved antistatic properties. However, reducing the resistance to almost zero may require the addition of an excessive and thus uneconomical amount of carbon nanotubes. Therefore, for the coating system according to the invention, a resistance ≥0.1 kΩ is preferred, more preferably ≥1 kΩ. Therefore, for the coating system according to the invention, it is particularly preferred that the resistance is in the range of ≥0.1 kΩ to ≤80 kΩ, more preferably in the range of ≥0.1 kΩ to ≤20 kΩ, and even more preferably in the range of ≥1 kΩ to ≤10 kΩ.

[0041] For the coating system according to the invention, a bond strength ≥3.0 MPa is preferred. Due to such a particularly high bond strength, the coating formed from the coating system can have particularly improved adhesion to the substrate. However, an almost infinite increase in bond strength may require the use of particularly designed and thus expensive and uneconomical polyols in part (A) and / or isocyanates in part (B). Therefore, for the coating system according to the invention, a bond strength ≤10.0 MPa is preferred, more preferably ≤5.0 MPa. Therefore, for the coating system according to the invention, it is particularly preferred that the bond strength is in the range of ≥1.5 MPa to ≤10.0 MPa, and even more preferably in the range of ≥3.0 MPa to ≤5.0 MPa.

[0042] It has also surprisingly been found that the electrical resistance of the coatings obtained with the coating systems according to the invention decreases in the following order: polymeric aromatic isocyanates > carbodiimide-modified aromatic isocyanates ≈ monomeric aromatic isocyanates as component of part (B). In other words, coatings obtained by using polymeric aromatic isocyanates in part (B) of the coating systems according to the invention show a higher electrical resistance than coatings obtained by using carbodiimide-modified aromatic isocyanates or monomeric aromatic isocyanates in part (B); coatings obtained by using carbodiimide-modified aromatic isocyanates in part (B) have a resistance similar (same order of magnitude) to those obtained by using monomeric aromatic isocyanates in part (B), as indicated by the symbol "≈" above.

[0043] For the coating systems according to the invention, it is preferred that at least one isocyanate is a carbodiimide-modified isocyanate. Carbodiimide-modified isocyanates (compounds) are obtained by converting two isocyanate groups in an isocyanate compound of the general formula O═C═N—R—N═C═O into a carbodiimide of the following general formula, where R is selected, for example, from alkylene and arylene, which may be substituted by one or more isocyanate groups, as in the polymeric isocyanates of the following formula,

[0044]

[0045] The general formula of said carbodiimide is shown below,

[0046]

[0047] (carbodiimide-modified isocyanate)

[0048] where carbon dioxide is lost, usually carried out catalytically (e.g., catalyzed by an oxidation phosphine of the general formula R 1 R 2 R 3 PO, where the substituents R 1 R 2 R 3 are independently selected from alkyl and aryl, where the said substituents may be the same or different or two substituents may form a ring), as is well known in the art; this leaves a carbodiimide unit in the main chain and two free terminal isocyanate groups, i.e., one isocyanate group at each end of the corresponding isocyanate compound obtained, as shown in the general formula of the above carbodiimide-modified isocyanate.

[0049] In the case where the isocyanate is MDI, R represents a symmetric or asymmetric substitution pattern at two phenyl rings in the ortho or para positions (with a very small to negligible proportion of substitution in the meta position), as shown by the formulas of diphenylmethane 4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, and diphenylmethane-2,2'-diisocyanate, all of which are described above.

[0050] When at least one isocyanate is a carbodiimide-modified isocyanate, the resistance can be further reduced, and thus the antistatic performance can be further improved. Without wishing to be bound by theory, it is believed that the improved resistance is at least partially caused by the delocalized π-electrons in the carbodiimide unit of the carbodiimide-modified isocyanate. Preferably, the carbodiimide-modified isocyanate is used together with a fatty acid ester-based plasticizer in part (B), that is, part (B) contains a fatty acid ester-based plasticizer. This can lead to a further improvement in the antistatic performance of the resulting coating.

[0051] The polymeric aromatic isocyanate can be mixed or blended with the monomeric and / or carbodiimide-modified aromatic isocyanate for use. However, by increasing the proportion of the polymeric aromatic isocyanate in the total content of the aromatic isocyanate, the effect of reducing the resistance is less obvious or decreases. This is because the presence of the monomeric and / or carbodiimide-modified aromatic isocyanate in the part (B) composition can reduce the resistance of the coating obtained by using this part (B) composition more than the case where the polymeric aromatic isocyanate is present. Preferably, the polymeric isocyanate is used together with a fatty acid ester-based plasticizer in part (B), that is, part (B) contains a fatty acid ester-based plasticizer, which can lead to a further improvement in the antistatic performance of the resulting coating. More preferably, the polymeric isocyanate is used together with a quaternary ammonium salt in part (B), that is, the part (B) contains a quaternary ammonium salt, which can also lead to an even further improvement in the antistatic performance of the resulting coating.

[0052] Particularly preferred for the coating system according to the invention is that at least one isocyanate is a monomeric isocyanate. When at least one isocyanate is a monomeric isocyanate, the carbon nanotubes can be even more uniformly distributed in part (B) of the coating system and can be distributed at a reduced processing viscosity. Preferably, the monomeric isocyanate is used in part (B) together with a fatty acid ester-based plasticizer, i.e., part (B) contains a fatty acid ester-based plasticizer, which can lead to an even further improved antistatic property of the resulting coating. Further preferably, the monomeric isocyanate is used in part (B) together with a quaternary ammonium salt, i.e., part (B) contains a quaternary ammonium salt, which can also lead to a further improvement in the antistatic property of the resulting coating. Without wishing to be bound by theory, it is believed that the improved antistatic property and the simultaneously improved bond strength observed when using a monomeric isocyanate in part (B) of the coating system according to the invention are at least partly caused by an improved dispersion of the carbon nanotubes in part (B) of the system and by the subsequent orientation and / or agglomeration of the carbon nanotubes at the surface of the coating formed by the coating system (i.e., by the subsequent surface effect of the previously dispersed carbon nanotubes).

[0053] For the preferred case where at least one isocyanate is a monomeric isocyanate and this monomeric isocyanate is the only isocyanate in part (B), it is preferred that the coating system according to the invention does not contain a fatty acid ester-based plasticizer, and more preferably does not contain any plasticizer. The absence of a fatty acid ester-based plasticizer, especially the absence of any plasticizer, in such a coating system avoids an undesired increase in resistance.

[0054] Particularly preferred for the coating system according to the invention is that the at least one isocyanate is an aromatic isocyanate. When the at least one isocyanate is an aromatic isocyanate, the resistance can be further reduced, and thus the antistatic property can be further improved. Without wishing to be bound by theory, it is believed that the improved resistance is at least partly caused by the delocalized π-electrons in the aromatic units of the aromatic isocyanate. Additionally, aromatic isocyanates are generally cheaper than aliphatic isocyanates, such that using aromatic isocyanates can improve the cost efficiency of the coating system according to the invention. Particularly preferably, the aromatic isocyanate is MDI, and more preferably carbodiimide-modified MDI and / or monomeric MDI.

[0055] For the coating system according to the invention, it is preferred that part (B) comprises two different isocyanates. When part (B) comprises two different isocyanates, the carbon nanotubes can be even more uniformly distributed in part (B) of the coating system and can be distributed at a reduced processing viscosity. Even more preferably for the coating system according to the invention, the two different isocyanates are two different aromatic isocyanates. Even more preferably for the coating system according to the invention, the two different isocyanates are a monomeric aromatic isocyanate and a carbodiimide-modified aromatic isocyanate. Again, the carbon nanotubes can be even more uniformly distributed in part (B) of the coating system and can be distributed at a reduced processing viscosity. In particular, the monomeric aromatic isocyanate allows for better distribution of the carbon nanotubes and a reduced processing viscosity. At the same time, the electrical resistance can be further reduced and thus the antistatic properties can be further improved. Without wishing to be bound by theory, it is believed that the improved electrical resistance is caused at least in part by delocalized π-electrons in the aromatic units of the two aromatic isocyanates, in particular by the aromatic units in the monomeric aromatic isocyanate and the carbodiimide-modified aromatic isocyanate, which are thus considered to contribute particularly to reducing the electrical resistance.

[0056] For the coating system according to the invention, it is preferred that part (B) comprises a monomeric aromatic isocyanate, preferably monomeric MDI or TDI, more preferably monomeric MDI. Using such an isocyanate mixture in part (B), further improved antistatic properties can be obtained.

[0057] For the coating system according to the invention, it is preferred that part (B) comprises a carbodiimide-modified aromatic isocyanate, preferably carbodiimide-modified MDI or TDI, more preferably carbodiimide-modified MDI. Using such an isocyanate mixture in part (B), further improved antistatic properties can be obtained.

[0058] For the coating system according to the invention, it is preferred that part (B) comprises a monomeric aromatic isocyanate and a carbodiimide-modified aromatic isocyanate, preferably monomeric MDI and carbodiimide-modified MDI or monomeric TDI and carbodiimide-modified TDI, more preferably monomeric MDI and carbodiimide-modified MDI. Using such an isocyanate mixture in part (B), further improved antistatic properties can be obtained.

[0059] For the coating system according to the invention, it is preferred that part (B) comprises a carbodiimide-modified aromatic isocyanate and a polymeric aromatic isocyanate, preferably carbodiimide-modified MDI and polymeric MDI or carbodiimide-modified TDI and polymeric TDI, more preferably carbodiimide-modified MDI and polymeric MDI. Using such an isocyanate mixture in part (B), further improved antistatic properties can be obtained.

[0060] For the coating system according to the invention, preferably part (B) comprises monomeric aromatic isocyanates and polymeric aromatic isocyanates, preferably monomeric MDI and polymeric MDI or monomeric TDI and polymeric TDI, more preferably monomeric MDI and polymeric MDI. By using such a mixture of isocyanates in part (B), a further improved dispersibility of the carbon nanotubes in part (B) can be achieved.

[0061] For the coating system according to the invention, preferably part (B) comprises carbodiimide-modified aromatic isocyanates, preferably carbodiimide-modified MDI or TDI, more preferably carbodiimide-modified MDI, and a plasticizer, preferably a fatty acid ester-based plasticizer. By using such a composition comprising part (B), further improved processability, such as a reduced viscosity, can be obtained.

[0062] For the coating system according to the invention, preferably part (B) comprises polymeric aromatic isocyanates, preferably polymeric MDI or TDI, more preferably polymeric MDI, and a plasticizer, preferably a fatty acid ester-based plasticizer. By using such a composition comprising part (B), further improved processability, such as a reduced viscosity, can be obtained.

[0063] For the coating system according to the invention, preferably part (B) comprises monomeric aromatic isocyanates, preferably monomeric MDI or TDI, more preferably monomeric MDI, and a plasticizer, preferably a fatty acid ester-based plasticizer. By using such a composition comprising part (B), further improved processability, such as a reduced viscosity, can be obtained.

[0064] For the coating system according to the invention, preferably part (B) comprises carbodiimide-modified aromatic isocyanates, preferably carbodiimide-modified MDI or TDI, more preferably carbodiimide-modified MDI, and a quaternary ammonium salt. By using such a composition comprising part (B), further improved antistatic properties can be obtained.

[0065] For the coating system according to the invention, preferably part (B) comprises polymeric aromatic isocyanates, preferably polymeric MDI or TDI, more preferably polymeric MDI, and a quaternary ammonium salt. By using such a composition comprising part (B), further improved antistatic properties can be obtained.

[0066] For the coating system according to the invention, preferably part (B) comprises monomeric aromatic isocyanates, preferably monomeric MDI or TDI, more preferably monomeric MDI, and a quaternary ammonium salt. By using such a composition comprising part (B), further improved antistatic properties can be obtained.

[0067] For the coating system according to the invention, it is preferred that the carbon nanotubes are single-walled carbon nanotubes. The dispersibility of single-walled carbon nanotubes in part (B) is generally better than that of multi-walled carbon nanotubes, resulting in a better distribution of carbon nanotubes in part (B). Moreover, multi-walled carbon nanotubes generally increase the processing viscosity of the carbon nanotubes in part (B), so that single-walled carbon nanotubes are also preferred from the viewpoint of reducing the processing viscosity.

[0068] For the coating system according to the invention, it is preferred that part (A) contains Ca(OH) 2 , preferably ≥ 20 wt% of Ca(OH) 2 , based on the total weight of part (A). When part (A) and part (B) of the coating system according to the invention are mixed to form a coating, part (A) and part (B) react with each other. First, at least one polyol in part (A) and at least one isocyanate in part (B) react with each other to form polyurethane. In addition, the isocyanate in part (B) can react with water (H 2 O), especially with the water optionally contained in part (A), to obtain a urea group (-NH-C(=O)-NH-group; which is subsequently present in the final coating) and carbon dioxide (CO 2 ). The generated CO 2 can cause undesirable foaming of the coating, but Ca(OH) 2 acts as a CO 2 scavenger and reacts with CO 2 to produce CaCO 3 and H 2 O. In this way, Ca(OH) 2 preferably contained in part (A) can prevent undesirable foaming of the coating. When Ca(OH) 2 is more preferably contained in part (A) in an amount of ≥ 20% by weight, this effect is particularly obvious, where the weight percentage is calculated based on the total weight of part (A).

[0069] For the coating system according to the invention, it is preferred that part (A) contains particles of at least one alkaline metal compound and at least one chelating agent, the alkaline metal compound being independently selected from alkaline metal oxide compounds and alkaline metal hydroxide compounds, and the chelating agent containing at least two functional groups capable of binding to the cation of the metal. The alkaline metal compound is preferably selected from calcium oxide, magnesium oxide, calcium hydroxide and magnesium hydroxide, more preferably calcium oxide and calcium hydroxide, and most preferably calcium oxide. The presence of the alkaline metal compound captures or quenches the CO 2To prevent the formation of bubbles or blisters in the coating from the coating composition of the present invention, especially on the coating surface. The chelating agent is preferably selected from amino acids, especially naturally occurring amino acids, more preferably proteinogenic amino acids, polyphosphonic acids, including diphosphonic acids, triphosphonic acids, tetraphosphonic acids and pentaphosphonic acids, phosphoric acid, phosphonic acid, sulfonic acids, including monosulfonic acids, disulfonic acids and polysulfonic acids having at least one other functional group selected from amino and hydroxyl groups, superplasticizers, carboxylic acid esters, carboxylic anhydrides, polyhydroxycarboxylic acids, carboxylic acids, polycarboxylic acids such as dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids and polycarboxylic acids, bidentate chelating agents such as acetylacetone (acac), ethylenediamine (en), oxalate (ox), tartrate (tart), dimethylglyoxime (dmg), 8-hydroxyquinoline (oxin), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), dimercaptosuccinic acid (DMSA) and 1,2-bis(diphenylphosphino)ethane, tridentate chelating agents such as 2-(2-aminoethylamine)ethanol (AEEA), diethylenetriamine (dien), iminodiacetate (ida) and citrate (cit), tetradentate chelating agents such as triethylenetetramine (trien, TETA), triaminotriethylamine (tren), nitrilotriacetate (nta), bis(salicylidene)ethylenediamine (salen), pentadentate chelating agents such as ethylenediaminetriacetate (ted), hexadentate chelating agents such as ethylenediaminetetraacetate (EDTA), octadentate chelating agents such as diethylenetriaminepentaacetate (DTPA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) and decadentate chelating agents such as triethylenetetraminehexaacetate (TTHA).

[0070] For the coating system according to the present invention, preferably part (A) is an aqueous emulsion, i.e., an emulsion of at least one polyol in water. In the aqueous emulsion, the at least one polyol contained in part (A) can be stored in a safe manner and its concentration can be easily adjusted as needed. In addition, optional additional components of part (A), such as CO 2 scavengers such as Ca(OH) 2 , can be easily dispersed in part (A).

[0071] For the coating system according to the present invention, preferably part (A) contains a source of chemically bound water participating in the urea formation reaction. Contrary to physically bound water, the term chemically bound water refers to water bound in crystalline form, such as water bound in ettringite, calcium silicate hydrate, aluminum hydroxide, zeolite, etc. These materials can also be used in combination with each other and / or in combination with CO 2 scavengers, more preferably in combination with Ca(OH) 2 .

[0072] For the composition of part (B), it is preferred that the content of aliphatic isocyanate is from 0 wt% to 100 wt%, based on the total weight of part (B) (corresponding to from 0 wt% to 70 wt%, based on the total weight of the coating system), and / or the content of aromatic isocyanate is from 0 wt% to 80 wt%, based on the total weight of part (B) (corresponding to from 0 wt% to 60 wt%, based on the total weight of the coating system).

[0073] For the aromatic isocyanate in part (B), it is preferred that, based on the total weight of part (B), the content of carbodiimide-modified aromatic isocyanate is in the range of from 0 wt% to 90 wt% (corresponding to the range of from 0 wt% to 60 wt% based on the total weight of the coating system), the content of polymeric aromatic isocyanate is in the range of from 0 wt% to 75 wt% based on the total weight of part (B) (corresponding to the range of from 0 wt% to 50 wt% based on the total weight of the coating system), and / or the content of monomeric aromatic isocyanate is in the range of from 0 wt% to 90 wt% based on the total weight of part (B) (corresponding to the range of from 0 wt% to 60 wt% based on the total weight of the coating system).

[0074] The above weight percentage ranges are particularly applicable to those coating systems and / or compositions of part (B) in which the aromatic isocyanate is MDI, especially polymeric MDI, carbodiimide-modified MDI and / or monomeric MDI, preferably carbodiimide-modified MDI and / or monomeric MDI.

[0075] The above weight percentage ranges are also particularly applicable to those coating systems and / or compositions of part (B) in which the aromatic isocyanate is TDI, especially polymeric TDI, carbodiimide-modified TDI and / or monomeric TDI, preferably carbodiimide-modified TDI and / or monomeric TDI.

[0076] For the coating system according to the invention, it is preferred that the coating system does not contain amine compounds. Amine compounds (especially primary amines having -NH 2 groups and / or secondary amines having -NHR groups, where R is a hydrocarbon group such as an alkyl, alkenyl and alkynyl group) may interfere with the reaction between at least one polyol contained in part (A) and at least one isocyanate contained in part (B), and may especially react with the isocyanate contained in part (B) itself. Such interference may reduce the adhesion strength of the formed coating. Therefore, it is preferred that there are no amine compounds (or amines) in the coating system according to the invention.

[0077] For the coating system of the present invention, it is preferred that the coating system does not contain epoxides. Epoxides can interfere with the reaction between at least one polyol contained in part (A) and at least one isocyanate contained in part (B), and in particular can react with the polyol contained in part (A) by itself. Such interference can reduce the adhesion strength of the formed coating. Therefore, it is preferred that there are no epoxides in the coating system according to the present invention.

[0078] The subject matter of the present invention is also a coating prepared by mixing components (A) and (B) with the coating system according to the present invention. The preferred embodiments of the coating system described in the claims herein are equally preferably used for this coating in a similar manner. Due to its low resistance, such a coating can have improved antistatic properties, and due to its high adhesion strength, such a coating can have improved adhesion to a substrate, especially to a concrete substrate.

[0079] The subject matter of the present invention is also the use of the coating system of the present invention for coating a substrate. The substrate is preferably a concrete substrate. The preferred embodiments of the coating system described in the claims herein are equally preferably used for the use of the present invention in a similar manner. The use according to the present invention results in a coated substrate or a substrate with a coating. Due to the high adhesion strength of the coating, the adhesion between the substrate and the coating can be improved. Additionally, due to the low resistance of the coating, the substrate can be advantageously used in environments that require antistatic properties, especially in the presence of flammable substances. Additionally, since the coating simultaneously has low resistance and high adhesion strength, it is not necessary to apply an additional coating such as a diffusion barrier layer.

[0080] Therefore, the coating system according to the present invention can be used, for example, for floors, coating walls or ceilings, forming (waterproof) membranes, coating truck beds and vehicles (such as cars, trucks, railway wagons and carriages), and loading areas in marine vehicles (such as ferries and ships) and aircraft. Particularly advantageous are the above applications related to loading, reloading, storing, and / or transporting dangerous goods, especially flammable goods.

[0081] The subject matter of the present invention is also a coating method, comprising the following steps:

[0082] (i) providing a substrate,

[0083] (ii) mixing part (A) and (B) of the coating system according to the present invention, and

[0084] (iii) applying the mixture obtained in step (ii) to the substrate.

[0085] The substrate is preferably concrete, such as a concrete slab or a concrete surface. The preferred embodiments of the coating system described in the claims are similarly preferably used in the coating method of the present invention. The coating method according to the present invention provides a coating having improved antistatic properties and improved adhesion to the substrate, particularly to a concrete substrate. Additionally, due to its simultaneously improved antistatic properties and adhesion to the substrate, the coated substrate obtained by the coating method according to the present invention does not require an additional diffusion barrier layer. Furthermore, prior to step (ii), part (B) of the coating system is conventionally prepared by mixing at least one isocyanate and carbon nanotubes. It has been found that in the coating method according to the present invention, the carbon nanotubes are more evenly distributed in part (B). Additionally, the carbon nanotubes are incorporated into part (B) with a reduced processing viscosity. Examples

[0086] Method

[0087] Here, the resistance is measured according to DIN EN 61340-4 1:2016-04. More specifically, a copper strip is glued in the middle of a Pavatex panel of about 0.24 m 2 (40×60 cm 2 ) such that it overlaps inwards and outwards by about 5 cm. Then, MasterTop P687WAS conductive varnish (24 g consumed per panel) is roll-coated in a cross pattern. After drying overnight at room temperature, the leakage resistance of the plate can be measured, which should be <10 kΩ. The Pavatex plate prepared in this way is sealed around with a pre-laid tape so that no material can leak out. Parts (A) and (B) of the coating system to be tested are weighed out in a suitable mixing ratio and mixed evenly with a wooden trowel. The resulting mixture is evenly applied onto the conductive varnish with a toothed spreader. Then the sample is cured at room temperature on a horizontal surface for 24 hours. Then the resistance is measured using Unilap ISO as a suitable test device. The standard conditions defined for this measurement are 23 °C and 50 ± 10% humidity. The measured resistance value is read on the display of the measuring device and then recorded. 20 measurements are made at different points on each sample plate so that the average value can be determined therefrom. The resistance thus determined is reported in Ohm (Ω). However, if the determined value exceeds 2.999 GΩ, the discharge capacity is too low and it is evaluated as an incorrect measurement.

[0088] Here, the bond strength is determined according to DIN EN 1542:1999-07. More specifically, the surface of a 40×40 cm concrete slab is sandblasted to make it grease-free, dry and smooth. Then a coating prepared by mixing parts (A) and (B) of an exemplary coating system is applied to the surface of the concrete slab. On top of it, at 0.8 kg / m 2Apply MasterSeal M790 AS in an amount as the body coating. Use a drill bit with a diameter of 5 cm each to form four annular grooves on the coated concrete slab. Glue four threaded punches to the annular grooves using a two-component epoxy resin as the adhesive. Dry the thus-made specimen for seven days (under the standard climate of 23 °C and 50% relative humidity). After that, screw the testing device (Freundl F 20+5 Easy DM 20200 - 20 kN) onto the threads of the punches. Start the motor of the testing device, and the device pulls the punches out from the coated concrete slab with a defined force of 6 kN. According to the punches with a given diameter and the force when the punches are completely pulled out, determine the bond strength and report it in N / mm 2 or MPa.

[0089] Example 1:

[0090] Prepare part (B) of the coating system of the present invention using the following composition:

[0091] Trade name Chemical characterization Composition (parts by weight) Lupranat MM 103 Carbodiimide-modified MDI 72.90 Lupranat M 20R Polymeric MDI 12.80 TuballMatrix 202 Single-walled carbon nanotubes (CNT) 1.10 Oxfilm 351 Fatty acid ester-based plasticizer 13.20 100.0 (total)

[0092] Mix the isocyanates Lupranat MM 103 and Lupranat M 20R in a nitrogen atmosphere in a mixer (dissolver), and then stir at about 500 rpm for 5 minutes. Subsequently, add carbon nanotube Tuball Matrix 202 and stir the composition at 700 rpm for another 5 minutes. Subsequently, disperse the carbon nanotubes evenly in the composition by stirring at about 2000 rpm until a paste consistency is obtained (obtained after 5 min). Then increase the stirring speed to 3000 rpm and continue stirring for another 10 - 15 minutes. Then reduce the stirring speed to 1200 rpm and continue stirring at 1200 rpm until a gel-like consistency is obtained (obtained after 10 minutes). Then, add the fatty acid ester-based plasticizer Oxfilm 351 to the composition and finally stir at 800 - 1000 rpm for 5 minutes to obtain component (B).

[0093] Then mix part (B) with the standard polyol-containing part (A) of the MasterSeal P 770 two-component polyurethane system at a weight ratio of part (A): part (B) = 100:125. Measure the electrical resistance of the obtained coating as described herein, and it is found to be 9.8 kΩ (9800 Ohm). Measure the bond strength (sometimes also called adhesion strength or pull-off strength) of the obtained coating as described herein, and it is found to be 3.5 MPa (N / mm 2 ).

[0094] Example 1 shows that the combined use of carbodiimide-modified MDI and polymeric MDI in part (B) of the coating system according to the invention simultaneously results in improved electrical resistance and improved bond strength.

[0095] Example 2

[0096] Part (B) of the coating system according to the invention was prepared using the following composition:

[0097]

[0098] Part (B) was prepared in the same manner as in Example 1, except that Lupranat MI was used instead of Lupranat MM 103. Then, the coating was prepared in the same manner as in Example 1, and its electrical resistance was measured. As a result, the measured electrical resistance was 16 kΩ (16000 Ohm). Moreover, the bond strength of the resulting coating was measured as described herein and found to be 3.3 MPa (N / mm 2 ).

[0099] Example 2 shows that the use of monomeric MDI in part (B) of the coating system according to the invention simultaneously results in improved electrical resistance and improved bond strength.

[0100] Comparative Example 1

[0101] Part (A) of a comparative coating system was prepared using the following composition:

[0102]

[0103]

[0104] The standard polyol-containing part (A) of the MasterSeal P770 two-component polyurethane system (“P 770 PTA”) was added to a mixer and stirred at approximately 600 rpm. Thereafter, 10% of Tuball Matrix 202 in Disflamoll DPK was added as carbon nanotubes and mixed into part (A) at approximately 700 rpm. Next, the carbon nanotubes were dispersed at approximately 2000 rpm. During the dispersion process, the rotational speed was increased to 3000 rpm, and they were dispersed for a total of approximately 30 minutes until a gel-like consistency was reached. At this stage, the mixer was slowed down to 1200 rpm, and then the dispersion process was stopped.

[0105] The prepared part (A) showed decomposition and non-uniformity. Part (A) was further mixed with the isocyanate-containing standard part (B) of the MasterSealP 770 two-component polyurethane system at a weight ratio of part (A): part (B) = 100:125. The resistance of the resulting coating was measured as described herein and found to be >2999 GΩ (>2.9*10 12 Ohm). The bond strength of the resulting coating was measured as described herein and found to be 3.5 MPa (N / mm 2 ).

[0106] In addition, an attempt was made to stabilize and homogenize the prepared part (A) by adding 1 wt% Byk P 104S as a dispersion additive. However, no improvement was achieved.

[0107] Comparative Example 2

[0108] Part (A) of the comparative coating system was prepared using the following composition:

[0109]

[0110] Part (A) was prepared in the same manner as in Comparative Example 1, except that 5% of Tuball Matrix 202 in Novares LA 700 was used as the carbon nanotube. The resulting part (A) showed decomposition and was non-uniform. The coating was prepared in the same manner as in Comparative Example 1, and the resistance was also measured in the same manner as in Comparative Example 1. As a result, the measured resistance was >2999 GΩ (>2.9*10 12 Ohm). The bond strength of the resulting coating was measured as described herein and found to be 3.1 MPa (N / mm 2 ).

[0111] As in Comparative Example 1, an attempt was also made to stabilize and homogenize the prepared part (A) by adding 1 wt% Byk P 104S as a dispersion additive. However, no improvement was achieved.

[0112] Examples 3 and Comparative Examples 3 and 4

[0113] The corresponding part (B) of the coating system of the present invention was prepared using the following composition:

[0114]

[0115] Part (B) was prepared in a manner similar to Example 1. The resulting part (B) was then mixed with the standard polyol-containing part (A) (MsealP 770PTA standard) of the two-component polyurethane system at a weight ratio of part (A): part (B) = 100:125. To obtain the final coating, the Mseal P 770PTA standard was applied in an amount of 0.25 - 0.4 kg / m 2 2.

[0116] After 7 days, the electrical resistance of the resulting coating was measured as described herein. The measured resistances are summarized in the following table:

[0117] Comparative Example 3 Example 3 Comparative Example 4 Resistance (R) 280 kΩ 13.7 kΩ 50 kΩ

[0118] As described in the context of Example 1, Lupranat M 20R used in Comparative Example 3 is polymeric MDI, and Lupranat MM 103 used in Comparative Example 4 is carbodiimide-modified MDI. As described in the context of Example 2, Lupranat MI used in Example 3 is monomeric MDI (2,4`-MDI and 4,4`-MDI, weight ratio 50 / 50). As described in the context of Example 1, TuballMatrix 202 used in Comparative Example 3 and 4 and Example 3 consists of single-walled carbon nanotubes (SCNT). It can be seen from the measured resistances that the use of monomeric MDI in part (B) of the coating composition of the present invention results in a particularly improved antistatic performance of the resulting coating. It can also be seen that the resistance decreases in the order of polymeric MDI > carbodiimide-modified MDI ≈ monomeric MDI as components of part (B). In other words, the coating obtained by using polymeric MDI in part (B) of the coating system shows a higher resistance than the coatings obtained by using carbodiimide-modified MDI or monomeric MDI in part (B); the coatings obtained by using carbodiimide-modified MDI in part (B) have resistances similar (same order of magnitude) to those obtained by using monomeric MDI in part (B), as indicated by the symbol "≈" above.

[0119] Examples 4 and Comparative Examples 5 and 6

[0120] The corresponding part (B) of the coating system of the present invention was prepared using the following compositions:

[0121]

[0122] Part (B) was prepared in a manner similar to Example 1. The resulting part (B) was then mixed with the polyol-containing standard part (A) (MsealP 770PTA standard) of the two-component polyurethane system at a weight ratio of part (A): part (B) = 100:125. To obtain the final coating, the Mseal P 770PTA standard was applied in an amount of 0.25 - 0.4 kg / m 2 of.

[0123] The electrical resistance of the resulting coating was measured as described herein after 7 days. The measured electrical resistances are summarized in the table below:

[0124]

[0125] As described in the context of Example 1, the material Oxfilm 351 additionally used in these (comparative) examples is a fatty acid ester-based plasticizer. It can be seen that the use of this plasticizer reduces the electrical resistance of the compositions containing monomeric MDI in part (B) and the compositions containing carbodiimide-modified MDI in part (B). Although the plasticizer slightly increases the electrical resistance of the composition containing monomeric MDI in part (B), the same trend as before is observed, that is, the electrical resistance decreases in the order of polymeric MDI > carbodiimide-modified MDI ≈ monomeric MDI as the component of part (B). In other words, the coatings obtained using polymeric MDI in part (B) of the coating system show higher electrical resistance than those obtained using carbodiimide-modified MDI or monomeric MDI in part (B); the coatings obtained by using carbodiimide-modified MDI in part (B) have electrical resistances similar (same order of magnitude) to those obtained by using monomeric MDI in part (B), as indicated by the symbol "≈" above.

[0126] Examples 5 and 6 and Comparative Example 7

[0127] The corresponding part (B) of the coating system of the present invention was prepared using the following compositions:

[0128]

[0129] Part (B) was prepared in a manner similar to Example 1. The resulting part (B) was then mixed with the polyol-containing standard part (A) (Mseal P 770PTA standard) of the two-component polyurethane system at a weight ratio of part (A): part (B) = 100:125. To obtain the final coating, the MSEAL P 770PTA standard was applied in an amount of 0.25 to 0.4 kg / m 2 of.

[0130] After 7 days, the electrical resistance of the resulting coating was measured as described herein. The measured electrical resistances are summarized in the table below:

[0131] Example 5 Example 6 Comparative Example 7 Resistance (R) 727 kΩ 10.9 kΩ 43.5 kΩ

[0132] The material EFKAIO 6783 additionally used in these (comparative) examples consists of a liquid quaternary ammonium salt, which acts as a conductive additive and reduces the resistance in all cases. However, it can be seen that the resistance is particularly reduced when carbodiimide-modified MDI or monomer MDI is used as the isocyanate component in part (B) of the respective coating system. In addition, the same trend as before is again observed, that is, the resistance decreases in the order of polymeric MDI > carbodiimide-modified MDI ≈ monomer MDI as the component of part (B). In other words, the coatings obtained by using polymeric MDI in part (B) of the coating system show a higher resistance than those obtained by using carbodiimide-modified MDI or monomer MDI in part (B); the coatings obtained by using carbodiimide-modified MDI in part (B) have a resistance similar (same order of magnitude) to those obtained by using monomer MDI in part (B), as indicated by the symbol "≈" above.

Claims

1. A coating system, comprising: Part (A), comprising at least one polyol having two or more hydroxyl groups, and Part (B), comprising at least one isocyanate having two or more isocyanate groups and comprising carbon nanotubes, wherein Part (A) and (B) are physically separated from each other, and wherein the coating prepared by mixing Part (A) and (B) has: A resistance of ≤ 80 kΩ measured according to DIN EN 61340-4 1:2016-04, and An adhesion strength of ≥ 1.5 MPa measured according to DIN EN 1542:1999-07.

2. The coating system according to claim 1, wherein the resistance is ≤ 20 kΩ.

3. The coating system according to claim 1 or 2, wherein the adhesion strength is ≥ 3.0 MPa.

4. The coating system according to at least one of claims 1 to 3, wherein the at least one isocyanate is a carbodiimide-modified isocyanate.

5. The coating system according to at least one of claims 1 to 3, wherein the at least one isocyanate is a monomeric isocyanate.

6. The coating system according to at least one of the preceding claims, wherein the at least one isocyanate is an aromatic isocyanate.

7. The coating system according to at least one of the preceding claims, wherein Part (B) comprises two different isocyanates.

8. The coating system of claim 7, wherein the two different isocyanates are a monomeric aromatic isocyanate and a carbodiimide-modified aromatic isocyanate.

9. The coating system according to at least one of the preceding claims, wherein the carbon nanotubes are single-walled carbon nanotubes.

10. A coating system according to at least one of the preceding claims, wherein part (A) comprises Ca(OH) 2 , preferably ≥ 20% by weight of Ca(OH) 2 , based on the total weight of part (A).

11. The coating system according to at least one of the preceding claims, wherein Part (A) is an aqueous emulsion.

12. The coating system according to at least one of the preceding claims, wherein the coating system (i) does not contain amine compounds, and / or (ii) does not contain epoxy compounds.

13. A coating prepared by a method comprising the step of mixing Part (A) and (B) of the coating system according to at least one of the preceding claims.

14. Use of the coating system according to at least one of claims 1-12 for coating a substrate.

15. A coating method, comprising the following steps: (i) Providing a substrate, (ii) Mixing Part (A) and (B) of the coating system according to at least one of claims 1 to 12, and (iii) Applying the mixture obtained in step (ii) to the substrate.

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