WO2024087051A1 - Electrically conductive solvent-free pu coating - Google Patents

Electrically conductive solvent-free pu coating Download PDF

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Publication number
WO2024087051A1
WO2024087051A1 PCT/CN2022/127614 CN2022127614W WO2024087051A1 WO 2024087051 A1 WO2024087051 A1 WO 2024087051A1 CN 2022127614 W CN2022127614 W CN 2022127614W WO 2024087051 A1 WO2024087051 A1 WO 2024087051A1
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Prior art keywords
undercoat
coating
composition
coating composition
mdi
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PCT/CN2022/127614
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French (fr)
Inventor
Yongle KE
Qi Wang
Zijian Zeng
Guoqiang Sun
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Sika Technology Ag
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Priority to PCT/CN2022/127614 priority Critical patent/WO2024087051A1/en
Publication of WO2024087051A1 publication Critical patent/WO2024087051A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/16—Catalysts
    • C08G18/22—Catalysts containing metal compounds
    • C08G18/24—Catalysts containing metal compounds of tin
    • C08G18/244—Catalysts containing metal compounds of tin tin salts of carboxylic acids
    • C08G18/246—Catalysts containing metal compounds of tin tin salts of carboxylic acids containing also tin-carbon bonds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/34—Carboxylic acids; Esters thereof with monohydroxyl compounds
    • C08G18/348—Hydroxycarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/38—Low-molecular-weight compounds having heteroatoms other than oxygen
    • C08G18/3802—Low-molecular-weight compounds having heteroatoms other than oxygen having halogens
    • C08G18/3804—Polyhydroxy compounds
    • C08G18/3806—Polyhydroxy compounds having chlorine and/or bromine atoms
    • C08G18/3808—Polyhydroxy compounds having chlorine and/or bromine atoms having chlorine atoms
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/77—Polyisocyanates or polyisothiocyanates having heteroatoms in addition to the isocyanate or isothiocyanate nitrogen and oxygen or sulfur
    • C08G18/78—Nitrogen
    • C08G18/79—Nitrogen characterised by the polyisocyanates used, these having groups formed by oligomerisation of isocyanates or isothiocyanates
    • C08G18/791—Nitrogen characterised by the polyisocyanates used, these having groups formed by oligomerisation of isocyanates or isothiocyanates containing isocyanurate groups
    • C08G18/792—Nitrogen characterised by the polyisocyanates used, these having groups formed by oligomerisation of isocyanates or isothiocyanates containing isocyanurate groups formed by oligomerisation of aliphatic and/or cycloaliphatic isocyanates or isothiocyanates
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C09D175/06—Polyurethanes from polyesters
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/24—Electrically-conducting paints
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/60—Additives non-macromolecular
    • C09D7/61—Additives non-macromolecular inorganic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/70—Additives characterised by shape, e.g. fibres, flakes or microspheres
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • C08K3/041—Carbon nanotubes

Definitions

  • the invention relates to an electrically conductive solvent-free polyurethane coating, to a method for producing a dissipative coating with the electrically conductive solvent-free polyurethane coating, to an electrostatic conductive or dissipative coating system, and to the use of the polyurethane coating for forming dissipative layers.
  • Electrostatic charging and discharge come about as a result of contact, friction or separation of two materials. In the process, one material is positively charged, and the other negatively charged. In the case of floor coatings, this charge is generated by foot traffic or wheeled traffic, with rubber soles or rubber wheels, for example. Charging may also result from sweeping air on insulating surfaces, e.g., paints or coatings.
  • the resistance to ground and also the system resistance can be determined in accordance with the DIN EN 61340-4-1.
  • a dissipative coating or seal coat for example, according to the DIN EN 61340 series, is deemed dissipative or electrostatically dissipative if it has a resistance to ground of less than 10 9 ohms. Coats having a greater resistance to ground are not dissipative. However, in order to have sufficient safety margin, especially with respect to environmental conditions with very low absolute humidity, a resistance to ground of less than 10 7 ohms is desirable.
  • ESD electrostatic discharge
  • solvent based polyurethane product could have the sufficient conductive or dissipative performance, it contains a certain amount of VOC content, which would be a significant burden on the environment.
  • Solvent-free epoxy products are good for environment, but it has poor weather resistance and abrasion resistance.
  • Some water-based epoxy or PU products have been also developed. They can be applied as a thin top coating, but the hardness and abrasion resistance of the coating are poor.
  • the object of the invention was therefore that of providing a solvent-free polyurethane coating composition for producing a dissipative coating system, more particularly floor coating system which may exhibit an electrostatic dissipative resistance of 10 6 –10 9 ohms or a conductive electrostatic resistance of 10 4 –10 6 ohms, and meanwhile result in a cured coating having a high abrasion resistance, good weather resistance, good mechanical properties and excellent chemical resistance.
  • inventive composition is suitable for use as a thin top coat of the dissipative floor coating and also as a renovation material in the repairing of the conducting electrostatic floor.
  • the invention therefore relates to a solvent-free polyurethane coating composition, comprising:
  • SWCNT single walled carbon nanotubes
  • C) carbon fibers having a length below 0.2 mm, preferably below 0.15 mm, more preferably between 0.05 –0.12 mm, in a range of 1.0 –2.4 wt%, such as 1.2 –2.3 wt%, based on the total weight of the composition.
  • the polyurethane coating composition as specified above may be applied in a solvent-free manner as a thin coat and the addition of both single walled carbon nanotubes (SWCNT) and short carbon fibers with the specified amounts may result in simultaneously the desired dissipative or conductive performance and also good weathering and mechanical properties such as the wearing resistance.
  • the inventive polyurethane coating has a very small amount of VOC (volatile organic compounds) .
  • the invention relates to a coating system on a substrate for the protection against electrostatic discharge, comprising in the following order
  • a topcoat layer which is formed by the solvent-free polyurethane coating composition according to the invention.
  • a polymer for example, is a compound having two or more amino groups.
  • a polyepoxide is a compound having two or more epoxy groups.
  • Molecular weight refers to the molar mass (in g/mol) of a molecule. “Average molecular weight” refers to the number average M n of a polydisperse mixture of oligomeric or polymeric molecules, which is typically determined by means of gel permeation chromatography (GPC) against polystyrene as standard.
  • GPC gel permeation chromatography
  • Root temperature refers to a temperature of 23°C.
  • aromatic isocyanate refers to an isocyanate wherein the isocyanate groups are bonded directly to an aromatic carbon atom. Accordingly, isocyanate groups of this kind are referred to as “aromatic isocyanate groups” .
  • aromatic isocyanate groups refers to an isocyanate wherein the isocyanate groups are bonded directly to an aliphatic carbon atom. Accordingly, isocyanate groups of this kind are referred to as “aliphatic isocyanate groups” .
  • a composition is referred to as "stable in storage” if it can be stored at room temperature in a suitable container for a longer period of time, typically for at least 3 months up to 6 months and more, without its application properties being changed by storage to an extent relevant to their use.
  • solvent-free means here that the coating composition contains less than 1.0 wt%, such as 0.5 wt%, preferably less than 0.1 wt%, more preferably less than 0.05 wt%, based on the total weight of the composition, or most preferably free of organic solvents, in particular free of volatile organic compounds.
  • the solvent-free coating composition according to the present invention is preferably prepared and formulated without volatile organic compounds and only contain water as volatile carrier or liquid phase.
  • volatile organic compounds herein means organic compounds that have a boiling point of less than 250°C at a standard pressure of 101.3 kPa.
  • the standard boiling point can be determined, for example, with an ebulliometer.
  • Carbon nanotubes are carbon tubes with a diameter of nanometer scale, in particular in the range from 1 to 50 nm, and a wall made of one or more layers of graphene, i.e. carbon with carbon atoms arranged in a ring.
  • Carbon nanotubes are industrially manufactured and commercially available in various qualities. They are electrically conductive. Single walled carbon nanotubes, so-called “SWCNT” , are particularly suitable in the instant invention. They are all composed of carbon atoms, and their geometric structure can be regarded as crimped by a single layer of graphene. They are preferably used as a dispersion in a liquid carrier material, in particular in a liquid which is highly compatible with epoxy resin compositions, in particular an alkyl glycidyl ether, a fatty acid ester or an ethoxylated alcohol.
  • a dispersion with 10%by weight of carbon nanotubes is preferred, in particular in an alkyl glycidyl ether, in particular a C12 to C14 alkyl glycidyl ether, such as is also used as a reactive diluent for epoxy resins.
  • Such a dispersion is commercially available, for example as Matrix 301 (from OCSIAl) .
  • Carbon fiber is a kind of high strength and high modulus fiber which substantially consists of carbon, for example, above 90%of carbon.
  • Carbon fiber is made of thin, strong crystalline filaments of carbon that is used to strengthen material. It can be generally made of polyacrylonitrile and viscose fibers as raw materials, which are carbonized by high temperature oxidation.
  • the short carbon fiber must be used in the inventive polyurethane coating composition. It has been found that short carbon fiber of below 0.2 mm, preferably below 0.15 mm, more preferably between 0.05 – 0.12 mm, as defined above, may make the Rs and Rg readings lower and more stable for long time, and also result in the best surface effect, especially in combination with the Single walled carbon nanotubes (SWCNT) .
  • SWCNT Single walled carbon nanotubes
  • the inventors have found that the required combination of single walled carbon nanotubes in combination with the carbon fibers in the specified weight ratio or amounts may make it possible for the inventive solvent-free coating composition to be formulated into either a conductive electrostatic system or an electrostatic dissipative system with the desired properties.
  • an amount of above 0.04 wt%of SWCNT would probably make it possible to obtain an electrostatic dissipative system having a Rs/Rg between 1.0*10 6 to 1.0*10 9 ⁇ and good surface quality, while less than 0.012 wt%of SWCNT would result in such high Rs and Rg resistances that the coating composition could not be suitable for a conductive electrostatic system.
  • the polyisocyanate used in the invention has a low viscosity below 800 mPa. s, preferably below 500 mPa. s. It has been found that higher viscosity of the polyisocyanate may result in much higher Rs or Rg value and also poor solvent-free application of the coating composition.
  • the polyisocyanate contains 18 wt%or more free NCO groups, such as 20 -30 wt%.
  • a suitable polyisocyanate is especially a commercially available polyisocyanate, especially
  • aromatic di-or triisocyanates preferably diphenylmethane 4, 4'-or 2, 4'-or 2, 2'-diisocyanate or any mixtures of these isomers (MDI) , tolylene 2, 4-or 2, 6-diisocyanate or any mixtures of these isomers (TDI) , mixtures of MDI and MDI homologs (polymeric MDI or PMDI) , phenylene 1, 3-or 1, 4-diisocyanate, 2, 3, 5, 6-tetramethyl-1, 4-diisocyanatobenzene, naphthalene 1, 5-diisocyanate (NDI) , 3, 3'-dimethyl-4, 4'-diisocyanatodiphenyl (TODI) , dianisidine diisocyanate (DADI) , tris (4-isocyanatophenyl) methane or tris (4-isocyanatophenyl) thiophosphate; preferably MDI or TD
  • aliphatic, cycloaliphatic or arylaliphatic di-or triisocyanates preferably tetramethylene 1, 4-diisocyanate, 2-methylpentamethylene 1, 5-diisocyanate, hexamethylene 1, 6-diisocyanate (HDI) , 2, 2, 4-and/or 2, 4, 4- trimethylhexamethylene 1, 6-diisocyanate (TMDI) , decamethylene 1, 10-diisocyanate, dodecamethylene 1, 12-diisocyanate, lysine diisocyanate or lysine ester diisocyanate, cyclohexane 1, 3-or 1, 4-diisocyanate, 1-methyl-2, 4-and/or -2, 6-diisocyanatocyclohexane (H 6 TDI) , 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (IPDI) , perhydrodiphenylmethane 2, 4
  • oligomers or derivatives of the di-or triisocyanates mentioned especially derived from HDI, IPDI, MDI or TDI, especially oligomers containing uretdione or isocyanurate or iminooxadiazinedione groups or various groups among these; or di-or polyfunctional derivatives containing ester or urea or urethane or biuret or allophanate or carbodiimide or uretonimine or oxadiazinetrione groups or various groups among these.
  • polyisocyanates of this kind are typically mixtures of substances having different degrees of oligomerization and/or chemical structures. They especially have an average NCO functionality of 2.1 to 4.0.
  • Preferred polyisocyanates are aliphatic, cycloaliphatic or aromatic diisocyanates, especially HDI, TMDI, cyclohexane 1, 3-or 1, 4-diisocyanate, IPDI, H 12 MDI, 1, 3-or 1, 4-bis (isocyanatomethyl) cyclohexane, XDI, TDI, MDI, phenylene 1, 3-or 1, 4-diisocyanate or naphthalene 1, 5-diisocyanate (NDI) .
  • a particularly preferred polyisocyanate is HDI, IPDI, H 12 MDI, TDI, MDI or a form of MDI which is liquid at room temperature, especially HDI, IPDI, TDI or HDI trimer.
  • the polyurethane binder on which the polyurethane coating composition is based may be formed by reacting the polyisocyanate with polyol which examples are desribed below, or with water which may be intentionally added or contained in the components or even derive from the atmosphere, for example the moisture or humidity from the air.
  • the inventive polyurethane coating composition may contain no polyol to react with the polyisocyanate.
  • Suitable polyols for reacting with the polyisocyanate are commercial polyols or mixtures thereof, especially
  • polyether polyols especially polyoxyalkylenediols and/or polyoxyalkylenetriols, especially polymerization products of ethylene oxide or 1, 2-propylene oxide or 1, 2-or 2, 3-butylene oxide or oxetane or tetrahydrofuran or mixtures thereof, where these may be polymerized with the aid of a starter molecule having two or more active hydrogen atoms, especially a starter molecule such as water, ammonia or a compound having multiple OH or NH groups, such as, for example, ethane-1, 2-diol, propane-1, 2-or -1, 3-diol, neopentyl glycol, diethylene glycol, triethylene glycol, the isomeric dipropylene glycols or tripropylene glycols, the isomeric butanediols, pentanediols, hexanediols, heptanediols, octane
  • Preferred polyether polyols are polyoxypropylene diols or polyoxypropylene triols, or what are called ethylene oxide-terminated (EO-endcapped) polyoxypropylene diols or triols.
  • the latter are mixed polyoxyethylene/polyoxypropylene polyols which are especially obtained in that polyoxypropylene diols or triols, on conclusion of the polypropoxylation reaction, are further alkoxylated with ethylene oxide and thereby eventually have primary hydroxyl groups.
  • Preferred polyether polyols have a degree of unsaturation of less than 0.02 meq/g, especially less than 0.01 meq/g.
  • Polyester polyols also called oligoesterols, prepared by known processes, especially the polycondensation of hydroxycarboxylic acids or lactones or the polycondensation of aliphatic and/or aromatic polycarboxylic acids with di-or polyhydric alcohols.
  • polyester diols from the reaction of dihydric alcohols, such as, especially, 1, 2-ethanediol, diethylene glycol, 1, 2-propanediol, dipropylene glycol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, glycerol, 1, 1, 1-trimethylolpropane or mixtures of the abovementioned alcohols, with organic dicarboxylic acids or the anhydrides or esters thereof, such as, especially, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid or hexahydrophthalic acid or mixtures of the abovementioned acids, or polyester polyols from lactones, such as, especially, ⁇ -diol
  • Polycarbonate polyols as obtainable by reaction, for example, of the abovementioned alcohols –used to form the polyester polyols –with dialkyl carbonates, diaryl carbonates or phosgene.
  • Polyhydroxy-functional fats and oils for example natural fats and oils, especially castor oil; or polyols obtained by chemical modification of natural fats and oils –called oleochemical polyols –for example the epoxy polyesters or epoxy polyethers obtained by epoxidation of unsaturated oils and subsequent ring opening with carboxylic acids or alcohols, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils; or polyols obtained from natural fats and oils by degradation processes, such as alcoholysis or ozonolysis, and subsequent chemical linkage, for example by transesterification or dimerization, of the degradation products or derivatives thereof thus obtained.
  • oleochemical polyols for example the epoxy polyesters or epoxy polyethers obtained by epoxidation of unsaturated oils and subsequent ring opening with carboxylic acids or alcohols, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils
  • polyols obtained from natural fats and oils by degradation processes such as alcoholysis
  • Suitable degradation products of natural fats and oils are especially fatty acids and fatty alcohols and also fatty acid esters, especially the methyl esters (FAME) , which can be derivatized to hydroxy fatty acid esters by hydroformylation and hydrogenation, for example.
  • FAME methyl esters
  • Polyhydrocarbon polyols also called oligohydrocarbonols, such as, for example, polyhydroxy-functional polyolefins, polyisobutylenes, polyisoprenes; polyhydroxy-functional ethylene/propylene, ethylene/butylene or ethylene/propylene/diene copolymers, as produced, for example, by Kraton Polymers; polyhydroxy-functional polymers of dienes, especially of 1, 3-butadiene, which can especially also be prepared from anionic polymerization; polyhydroxy-functional copolymers of dienes, such as 1, 3-butadiene, or diene mixtures and vinyl monomers, such as styrene, acrylonitrile, vinyl chloride, vinyl acetate, vinyl alcohol, isobutylene and isoprene, for example polyhydroxy-functional acrylonitrile/butadiene copolymers, as can be prepared, for example, from epoxides or aminoalcohols and carboxyl-terminated acrylonit
  • polyether polyols Preference is given to polyether polyols, polyester polyols, polycarbonate polyols, poly (meth) acrylate polyols or polyhydroxy-functional fats and oils. Particular preference is given to polyester polyols, especially aliphatic polyester polyols, or polyhydroxy-functional fats and oils, especially castor oil. Preference is given to polyols having an average molecular weight in the range from 400 to 20 000 g/mol, preferably from 1000 to 10 000 g/mol. Preference is given to polyols having an average OH functionality in the range from 1.6 to 3.
  • the composition comprises, in addition to the above specified components A) to C) , additionally one or more further constituents that are especially selected from catalysts, fillers, plasticizers and additives for setting the electrical properties.
  • Suitable catalysts are those for the acceleration of the reaction of isocyanate groups, especially organotin (IV) compounds, such as especially dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dichloride, dibutyltin diacetylacetonate, dimethyltin dilaurate, dioctyltin diacetate, dioctyltin dilaurate or dioctyltin diacetylacetonate, complexes of bismuth (III) or zirconium (IV) , especially with ligands selected from alkoxides, carboxylates, 1, 3-diketonates, oxinate, 1, 3-ketoesterates and 1, 3-ketoamidates, or compounds containing tertiary amino groups, such as especially 2, 2'-dimorpholinodiethyl ether (DMDEE) . Also especially suitable are combinations of different catalysts.
  • Suitable fillers are especially ground or precipitated calcium carbonates, optionally coated with fatty acids, especially stearates, barytes, quartz flours, quartz sands, corundum like white corundum, dolomites, wollastonites, kaolins, calcined kaolins, sheet silicates, such as mica or talc, zeolites, aluminum hydroxides, magnesium hydroxides, silicas, including finely divided silicas from pyrolysis processes, cements, gypsums, fly ashes, graphite, metal powders, for example of aluminum, copper, iron, silver or steel, PVC powders or hollow beads.
  • fatty acids especially stearates, barytes, quartz flours, quartz sands, corundum like white corundum, dolomites, wollastonites, kaolins, calcined kaolins, sheet silicates, such as mica or talc, zeolites, aluminum hydroxides, magnesium hydroxides, sili
  • the inventive polyurethane composition contains wear particles as fillers, such as corumdums, ceramics, silicium carbide and so on.
  • Suitable plasticizers are especially carboxylic acid esters, such as phthalates, especially diisononyl phthalate (DINP) , diisodecyl phthalate (DIDP) or di (2-propylheptyl) phthalate (DPHP) , hydrogenated phthalates, especially hydrogenated diisononyl phthalate or diisononyl cyclohexane-1, 2-dicarboxylate (DINCH) , terephthalates, especially dioctyl terephthalate, trimellitates, adipates, especially dioctyl adipate, azelates, sebacates, benzoates, glycol ethers, glycol esters, organic phosphoric or sulfonic acid esters, polybutenes, polyisobutenes or plasticizers derived from natural fats or oils, especially epoxidized soybean or linseed oil.
  • carboxylic acid esters such as phthalates,
  • Suitable additives for setting the electrical properties are conductive additives, for example conductive fillers, such as conductive pigments or conductive fibers, salts, ionic liquids, ionic and nonionic surfactants, and combinations thereof.
  • Specific conductive additives for setting the electrical properties are, for example, carbon fibers, carbon black, graphite, silicon carbide, metal oxides, metals, such as iron, ammonium salts, metal-containing or heavy metal-containing fillers, especially antimony-and tin-containing fillers based on titanium dioxide or mica, ionic liquids, ionic and nonionic surfactants, melamine sulfonates and polycarboxylate ethers, and combinations thereof.
  • the conductive additives for setting the electrical properties can, for example, be added in the form of powders, fibers, turnings, in liquid form, flakes or granules. Conductive salts can also optionally be added as solutions.
  • composition may comprise further additives commonly used for polyurethane compositions. More particularly, the following auxiliaries and additives may be present:
  • coloring agents such as colored quartz, dyes, pigments and color chips
  • desiccants especially molecular sieve powder, calcium oxide, highly reactive isocyanates, such as p-tosyl isocyanate, monomeric diisocyanates or orthoformic esters;
  • adhesion promoters especially organoalkoxysilanes, especially epoxysilanes, such as especially 3-glycidoxypropyltrimethoxysilane or 3- glycidoxypropyltriethoxysilane, (meth) acrylosilanes, anhydridosilanes, carbamatosilanes, alkylsilanes or iminosilanes, or oligomeric forms of these silanes, or titanates;
  • latent curing agents or crosslinkers especially aldimines, ketimines, enamines or oxazolidines
  • catalysts which accelerate the reaction of the isocyanate groups especially salts, soaps or complexes of tin, zinc, bismuth, iron, aluminum, molybdenum, dioxomolybdenum, titanium, zirconium or potassium, especially tin (II) 2-ethylhexanoate, tin (II) neodecanoate, zinc (II) acetate, zinc (II) 2- ethylhexanoate, zinc (II) laurate, zinc (II) acetylacetonate, aluminum lactate, aluminum oleate, diisopropoxytitanium bis (ethyl acetoacetate) or potassium acetate; compounds containing tertiary amino groups, especially N-ethyldiisopropylamine, N, N, N', N'-tetramethylalkylenediamines, pentamethylalkylenetriamines and higher homologs thereof, bis (
  • rheology modifiers especially thickeners, especially sheet silicates, such as bentonites, derivatives of castor oil, hydrogenated castor oil, polyamides, polyamide waxes, polyurethanes, urea compounds, fumed silicas, cellulose ethers or hydrophobically modified polyoxyethylenes;
  • nonreactive polymers especially homo-or copolymers of unsaturated monomers, especially from the group comprising ethylene, propylene, butylene, isobutylene, isoprene, vinyl acetate or alkyl (meth) acrylates, especially polyethylenes (PE) , polypropylenes (PP) , polyisobutylenes, ethylene/vinyl acetate copolymers (EVA) or atactic poly- ⁇ -olefins (APAO) ;
  • PE polyethylenes
  • PP polypropylenes
  • EVA ethylene/vinyl acetate copolymers
  • APAO atactic poly- ⁇ -olefins
  • flame-retardant substances especially the aluminum hydroxide or magnesium hydroxide fillers already mentioned, and also especially organic phosphoric acid esters, such as especially triethyl phosphate, tricresyl phosphate, triphenyl phosphate, diphenyl cresyl phosphate, isodecyl diphenyl phosphate, tris (1, 3-dichloro-2-propyl) phosphate, tris (2-chloroethyl) phosphate, tris (2-ethylhexyl) phosphate, tris (chloroisopropyl) phosphate, tris (chloropropyl) phosphate, isopropylated triphenyl phosphate, mono-, bis-or tris (isopropylphenyl) phosphates of different degrees of isopropylation, resorcinol bis (diphenylphosphate) , bisphenol A bis (diphenylphosphate) or ammonium poly
  • additives especially wetting agents, leveling agents, defoamers, deaerators, stabilizers against oxidation, heat, light or UV radiation, or biocides;
  • the composition is especially produced with exclusion of moisture and stored at ambient temperature in moisture-tight containers.
  • a suitable moisture-tight container especially consists of an optionally coated metal and/or plastic, and is especially a drum, a transport box, a hobbock, a bucket, a canister, a can, a bag, a tubular bag, a cartridge or a tube.
  • composition may be in the form of a one-component composition or in the form of a multi-component, especially two-component, composition.
  • a composition referred to as a "one-component" composition is one in which all constituents of the composition are in the same container and which is storage-stable per se.
  • composition referred to as a "two-component" composition is one in which the constituents of the composition are in two different components which are stored in separate containers and are not mixed with one another until shortly before or during the application of the composition.
  • a two-or multi-component composition it is applied after the mixing of the two or more components and begins to cure by internal reaction, and the curing may be completed by the action of external moisture.
  • the two or more components can be mixed continuously or batchwise with dynamic mixers or static mixers.
  • the composition is preferably applied at ambient temperature, especially in the range from about 0 to 50°C, preferably in the range from 5 to 40°C.
  • the composition is preferably likewise cured at ambient temperature.
  • the invention relates to a coating system on a substrate for the protection against electrostatic discharge, comprising in the following order
  • a topcoat layer which is formed by the solvent-free polyurethane coating composition according to the invention.
  • a conductive electrostatic system or an electrostatic disspative system may be obtained after curing the coating composition according to the invention.
  • the inventive coating system may be obtained in forms of above both systems which may be usually distinguished from each other in view of the different requirements on the resistance Rs or Rg.
  • Rs or Rg in an electrostatic dissipative resistance is in a range of 10 6 –10 9 ohms
  • Rs or Rg in a conductive electrostatic resistance is in a range of 10 4 –10 6 ohms, such as 5.0*10 4 –1.0*10 6 ohms.
  • the skilled person may refer to e.g. the standard GB/T 22374-2018.
  • the undercoat applied on the substrate may optionally also contain levelling on the substrate and the undercoat may be preferably conductive per se or have no conductive or dissipative function.
  • the dissipative synthetic resin layer (4) applied between the undercoat and the topcoat is conductive and thus preferably may have a resistance to ground according to VDE-0100-410 of at least 100 kohm. It goes without saying that the dissipative synthetic resin layer is different from the topcoat layer which is formed by the inventive solvent-free polyurethane coating composition and may be any kind of the prior art dissipative synthetic resin layer.
  • Dissipative layers may also be called conductive electrostatic layers or electrostatically dissipative layers. As opposed to non-dissipative or insulating layers, they permit an electrostatic charge that is building up to dissipate. For this purpose, dissipative layers have a certain electrical conductivity.
  • the coating system according to the invention can be a floor coating system or a wall coating system, wherein it is preferably a floor coating system.
  • the coating system has broad commercial utility and exhibits numerous advantages compared to the systems according to the prior art. This system structure is suitable for the simple, cost-advantageous and rapid conversion of existing purely insulating coating structures into ESD-capable systems.
  • the coating system according to the invention is suitable for all floors, industrial floors and walls for which ESD protection is required, especially for floors. Sectors in which such floors or walls are required are, for example, the electrical and electronics industry, microelectronics, high-precision optics, biotechnology, lithography, pharmaceuticals, life sciences, the automotive industry or in the manufacturing of data carriers.
  • the coating systems according to the invention are suitable, for example, for clean rooms, production facilities, assembly facilities, laboratories and the like, in which electrostatic charges should or must be avoided.
  • the dissipation capacity can be determined, for example, by way of the resistance to ground of the layer.
  • the resistance to ground of a layer can be determined according to the standard IEC 61340-4-1.
  • a layer is considered conductive or electrostatically conductive if it has a resistance to ground of no more than 109 ohm. Layers having higher resistances to ground are non-dissipative.
  • the dissipative synthetic resin layer 4 and, insofar as the preferred synthetic resin undercoat is used as the undercoat, the undercoat as well are based on a synthetic resin.
  • the optional scratch coat can be based on a synthetic resin. Synthetic resin layers as floor coverings or wall coverings are well known to the person skilled in the art and are widely used in this field. If not stated otherwise, the following statements apply equally to the synthetic resin layers, the synthetic resin undercoat and the optional scratch coat.
  • Synthetic resin layers are made of cured reaction resins or reactions resin compounds, wherein reaction resin compounds are usually understood to mean reaction resins containing one or more additives, for example, fillers and/or solvents.
  • reaction resins known to the expert can be used to produce the dissipative synthetic resin layer, and the synthetic resin undercoat and the optional scratch coat.
  • the same or different reaction resins can be used for the individual layers.
  • the reaction resins, especially those mentioned hereinafter, can be used in solvent-free or water-based form.
  • reaction resins used for the respective layer or optionally the undercoat or the scratch coat are preferably selected independently of one another from epoxy resins, polyurethanes, polyureas, mixtures of polyurethanes and polyureas, poly (meth) acrylates, cementitious hybrid systems and polymer-modified cementitious mixtures (PCC "polymer cement concrete” ) .
  • the additives can already be present in the reaction resin or be mixed to the reaction resin before processing.
  • examples of possible additives, in addition to solvents and water, are coloring agents, such as colored quartz, dyes, pigments and color chips; fillers, such as quartz sand, ceramic powder, sand, chalk, fibers, hollow spheres and glass beads; emulsifiers, thixotropic agents, and film-forming aids as well as suitable additives for setting the electrical properties as described above.
  • substrates present in edifices are suitable for use as the substrate for the coating, especially the floor or flooring coating.
  • suitable substrates are concrete, cement screed, magnesium oxide screed, ceramic tiles, asphalt, and optionally any synthetic resin coatings already present.
  • the undercoat is applied to the underlay, optionally after conventional substrate pretreatment, for example, grinding, sand-blasting, shot blasting or stripping with solvents or acids.
  • a conventional undercoat composition is applied, for example, a reaction resin or a reaction resin compound, or alternatively a water-based synthetic resin dispersion, and cured. This is preferably a synthetic resin undercoat based on cured reaction resins.
  • the grounding device for grounding the coating system may be installed in the coating system.
  • the grounding device may be arranged on the top of it or directly between the undercoat and the topcoat.
  • the grounding device may be arranged below the undercoat or between the undercoat and the substrate.
  • the grounding device is connected to the equipotential bonding.
  • the grounding device can, for example, be formed by a grounding conductor or an arrangement of grounding conductors, which are connected to the equipotential bonding. The bonding to the equipotential bonding or ground potential can take place via one or more grounding connections.
  • Suitable grounding conductors include, for example, copper tapes and/or so-called conductor sets, which are installed to dissipate the potential. Self-adhesive copper strips may be used. Conductor sets are commercially available; for example, the conductor set. The conductor set is made up of pegs with copper tapes, washers and a threaded rod. In this way a so-called grounding point is established, which can subsequently be connected to ground by a skilled electrician.
  • the individual layers can also be designed as double layers or multiple layers, but this is generally not preferred. It is also possible for additional intermediate layers to be optionally arranged in the coating system. Examples of such intermediate layers are those that also have crack-bridging properties (for example, 350 or 390) .
  • Fig. 1 one variant of the coating system according to the invention.
  • Fig. 2 another variant of the coating system according to the invention.
  • the coating system is consisting of (1) substrate, (2) grounding device such as copper tapes, (4) dissipative synthetic resin layer and (5) topcoat formed by the inventive coating composition.
  • the coating system is consisting of (3) undercoat which has no conductive function, (2) grounding device such as copper tapes, and (5) topcoat formed by the inventive coating composition.
  • the substrate below the undercoat is not shown in the figure.
  • the coating compositions were prepared by mixing four components, i.e. Component A, Component B, Component C and Component D, under stirring in a suitable container with a weight ratio of A : B : C : D of 2.83 : 0.75 : 2.13 : 0.62 until a homogenous mixture was obtained.
  • Component A was formulated on basis of two HDI trimer having different viscosity.
  • the component A was based on 100 wt%of Tolonate HDT LV while in the remaining examples, the component A was based on 100 wt%of DESMODUR N 31000.
  • Component B was formulated by mixing the individual ingredients with the amounts specified in the following table.
  • Component C was consisting of 100wt%of white corundum having the particle size of 220 Mesh (70-75 ⁇ m) .
  • Component D was formulated by mixing 36.7 wt%of CFAME (Chlorinated fatty acid methyl ester) , 6.8 wt%of K-FLEX DP, 2 wt%of UNIQ 680U and the remaining parts of green-clored fillers to form a green slurry.
  • a conductive electrostatic system was prepared by coating on the substrate, a non-asbestos fiber cement board, in order the primer Sikafloor-220W, the medium coating Sikafloor-206W and the coating compositions of each examples.
  • an electrostatic dissipative system was also prepared by coating on the substrate, a non-asbestos fiber cement board, in order the primer Sikafloor-220W, the medium coating Sikafloor-237EDF and the coating compositions of each examples.
  • the VOC content is measured in accord with the standard GBT 23985-2009.
  • the testing mixture was prepared by mixing Components A, B, C and D under stirring and then placed in a testing oven at 105 ⁇ 2°C for 1 hour after a 24-hour conditioning under 23 ⁇ 2°C and humidity of 50 ⁇ 5%.
  • VOC contents as measured for Examples 2, 3 and 4 are 42.4 g/L, 48.3 g/L and 40.9 g/L respectively, all below 60 g/L which is the permissible limit according to the national standard.
  • Example 5 As can be seen from Example 5, with a lower amount (0.8 wt%) of carbon fibers, the value of Rg of the conductive electrostatic system was higher in many cases. Meanwhile, some resistances Rs of the electrostatic dissipative system were also much higher which may possibly deteriorate the electrostatic dissipative effects of the system in the long term.
  • Example 6 when the amount of carbon fibers was as high as 2.5 wt%, the resistance Rg of the electrostatic dissipative system was overly lower than the requirements on the electrostatic dissipative resistance. Furthermore, due to the high amount of carbon fibers, it is was found that the surface quality of the coating was bad and it was difficult to obtain the homogeneous coating film.
  • Example 7 With a high mount (0.05wt%) of SWCNT, a satisfactory electrostatic dissipative system could be hardly obtained because of unduly low resistances Rs and Rg. Furthermore, the surface quality of the film was also questioned and it was difficult to obtain the homogeneous coating film.

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Abstract

The invention relates to a solvent-free polyurethane coating composition, comprising A) a polyisocyanate having a low viscosity below 800 mPa. s, B) single walled carbon nanotubes (SWCNT) in a range of 0.012 –0.04 wt%, based on the total weight of the composition, and C) carbon fibers having a length below 0.2 mm in a range of 1.0 –2.4 wt%, based on the total weight of the composition. Furthermore, the invention also relates to a coating system on a substrate for the protection against electrostatic discharge comprising the inventive solvent-free polyurethane coating composition.

Description

Electrically conductive solvent-free PU coating Description Technical field
The invention relates to an electrically conductive solvent-free polyurethane coating, to a method for producing a dissipative coating with the electrically conductive solvent-free polyurethane coating, to an electrostatic conductive or dissipative coating system, and to the use of the polyurethane coating for forming dissipative layers.
Prior art
Many segments of industry nowadays impose exacting requirements on optimum ambient conditions. Of the utmost importance in this context, in particular, is the prevention of uncontrolled electrostatic charging and discharge.
Electrostatic charging and discharge come about as a result of contact, friction or separation of two materials. In the process, one material is positively charged, and the other negatively charged. In the case of floor coatings, this charge is generated by foot traffic or wheeled traffic, with rubber soles or rubber wheels, for example. Charging may also result from sweeping air on insulating surfaces, e.g., paints or coatings.
In sensitive areas, therefore, the requirement is for floors and walls with low resistances to ground, which dissipate electrostatic charging immediately and in a controlled manner.
The resistance to ground and also the system resistance can be determined in accordance with the DIN EN 61340-4-1. A dissipative coating or seal coat, for example, according to the DIN EN 61340 series, is deemed dissipative or  electrostatically dissipative if it has a resistance to ground of less than 10 9 ohms. Coats having a greater resistance to ground are not dissipative. However, in order to have sufficient safety margin, especially with respect to environmental conditions with very low absolute humidity, a resistance to ground of less than 10 7 ohms is desirable.
There are coating systems known with ESD protection (ESD = "electrostatic discharge" ) , i.e., with protection from electrostatic discharge. Employed normally are dissipative systems based on epoxy resin or polyurethane.
However, most of the epoxy resin or polyurethane dissipative systems are solvent based polyurethane system or solvent-free epoxy system in the market. Although solvent based polyurethane product could have the sufficient conductive or dissipative performance, it contains a certain amount of VOC content, which would be a significant burden on the environment. Solvent-free epoxy products are good for environment, but it has poor weather resistance and abrasion resistance.
Some water-based epoxy or PU products have been also developed. They can be applied as a thin top coating, but the hardness and abrasion resistance of the coating are poor.
Summary of the invention
The object of the invention was therefore that of providing a solvent-free polyurethane coating composition for producing a dissipative coating system, more particularly floor coating system which may exhibit an electrostatic dissipative resistance of 10 6 –10 9 ohms or a conductive electrostatic resistance of 10 4 –10 6 ohms, and meanwhile result in a cured coating having a high abrasion resistance, good weather resistance, good mechanical properties and excellent chemical resistance.
In particular the inventive composition is suitable for use as a thin top coat of the dissipative floor coating and also as a renovation material in the repairing of the conducting electrostatic floor.
In a first aspect, the invention therefore relates to a solvent-free polyurethane coating composition, comprising:
A) a polyisocyanate having a low viscosity below 800 mPa. s, preferably below 500 mPa. s,
B) single walled carbon nanotubes (SWCNT) in a range of 0.012 –0.04 wt%, such as 0.016 –0.035 wt%, based on the total weight of the composition,
C) carbon fibers having a length below 0.2 mm, preferably below 0.15 mm, more preferably between 0.05 –0.12 mm, in a range of 1.0 –2.4 wt%, such as 1.2 –2.3 wt%, based on the total weight of the composition.
It has been surprisingly found that the polyurethane coating composition as specified above may be applied in a solvent-free manner as a thin coat and the addition of both single walled carbon nanotubes (SWCNT) and short carbon fibers with the specified amounts may result in simultaneously the desired dissipative or conductive performance and also good weathering and mechanical properties such as the wearing resistance. In addition, the inventive polyurethane coating has a very small amount of VOC (volatile organic compounds) .
In a second aspect, the invention relates to a coating system on a substrate for the protection against electrostatic discharge, comprising in the following order
a) an undercoat on the substrate,
b) optionally a dissipative synthetic resin layer, and
c) a topcoat layer which is formed by the solvent-free polyurethane coating composition according to the invention.
Preferred embodiments of the composition are reproduced in the dependent claims.
Embodiment of the invention
Compound names beginning with "poly" identify substances which formally per molecule contain two or more of the functional groups which occur in their name. The compound may be monomeric, oligomeric, or polymeric. A polyamine, for example, is a compound having two or more amino groups. A polyepoxide is a compound having two or more epoxy groups.
"Molecular weight" refers to the molar mass (in g/mol) of a molecule. “Average molecular weight” refers to the number average M n of a polydisperse mixture of oligomeric or polymeric molecules, which is typically determined by means of gel permeation chromatography (GPC) against polystyrene as standard.
“Room temperature” refers to a temperature of 23℃.
An "aromatic isocyanate" refers to an isocyanate wherein the isocyanate groups are bonded directly to an aromatic carbon atom. Accordingly, isocyanate groups of this kind are referred to as "aromatic isocyanate groups" . An "aliphatic isocyanate" refers to an isocyanate wherein the isocyanate groups are bonded directly to an aliphatic carbon atom. Accordingly, isocyanate groups of this kind are referred to as "aliphatic isocyanate groups" .
A composition is referred to as "stable in storage" if it can be stored at room temperature in a suitable container for a longer period of time, typically for at least 3 months up to 6 months and more, without its application properties being changed by storage to an extent relevant to their use.
The term “solvent-free” means here that the coating composition contains less than 1.0 wt%, such as 0.5 wt%, preferably less than 0.1 wt%, more preferably less than 0.05 wt%, based on the total weight of the composition, or most preferably free of organic solvents, in particular free of volatile organic compounds. The solvent-free coating composition according to the present  invention is preferably prepared and formulated without volatile organic compounds and only contain water as volatile carrier or liquid phase.
The term “volatile organic compounds” (VOC) herein means organic compounds that have a boiling point of less than 250℃ at a standard pressure of 101.3 kPa. The standard boiling point can be determined, for example, with an ebulliometer.
"Carbon nanotubes" are carbon tubes with a diameter of nanometer scale, in particular in the range from 1 to 50 nm, and a wall made of one or more layers of graphene, i.e. carbon with carbon atoms arranged in a ring.
Carbon nanotubes are industrially manufactured and commercially available in various qualities. They are electrically conductive. Single walled carbon nanotubes, so-called “SWCNT” , are particularly suitable in the instant invention. They are all composed of carbon atoms, and their geometric structure can be regarded as crimped by a single layer of graphene. They are preferably used as a dispersion in a liquid carrier material, in particular in a liquid which is highly compatible with epoxy resin compositions, in particular an alkyl glycidyl ether, a fatty acid ester or an ethoxylated alcohol.
A dispersion with 10%by weight of carbon nanotubes is preferred, in particular in an alkyl glycidyl ether, in particular a C12 to C14 alkyl glycidyl ether, such as is also used as a reactive diluent for epoxy resins. Such a dispersion is commercially available, for example as
Figure PCTCN2022127614-appb-000001
Matrix 301 (from OCSIAl) .
Carbon fiber is a kind of high strength and high modulus fiber which substantially consists of carbon, for example, above 90%of carbon. Carbon fiber is made of thin, strong crystalline filaments of carbon that is used to strengthen material. It can be generally made of polyacrylonitrile and viscose fibers as raw materials, which are carbonized by high temperature oxidation.
In the invention, the short carbon fiber must be used in the inventive  polyurethane coating composition. It has been found that short carbon fiber of below 0.2 mm, preferably below 0.15 mm, more preferably between 0.05 – 0.12 mm, as defined above, may make the Rs and Rg readings lower and more stable for long time, and also result in the best surface effect, especially in combination with the Single walled carbon nanotubes (SWCNT) .
The inventors have found that the required combination of single walled carbon nanotubes in combination with the carbon fibers in the specified weight ratio or amounts may make it possible for the inventive solvent-free coating composition to be formulated into either a conductive electrostatic system or an electrostatic dissipative system with the desired properties.
In the coating composition according to the invention, an amount of above 0.04 wt%of SWCNT would probably make it possible to obtain an electrostatic dissipative system having a Rs/Rg between 1.0*10 6 to 1.0*10 9 Ω and good surface quality, while less than 0.012 wt%of SWCNT would result in such high Rs and Rg resistances that the coating composition could not be suitable for a conductive electrostatic system.
As for the carbon fibers, less than 1.0 wt%would probably result in higher Rg resistance that required for the conductive electrostatic system and also be adverse to the long term use of an electrostatic dissipative system. More than 2.4 wt%would probably result in overly low Rg in the electrostatic dissipative system and also lead to the difficulty of applying or processing the coating composition.
The polyisocyanate used in the invention has a low viscosity below 800 mPa. s, preferably below 500 mPa. s. It has been found that higher viscosity of the polyisocyanate may result in much higher Rs or Rg value and also poor solvent-free application of the coating composition.
Preferably, the polyisocyanate contains 18 wt%or more free NCO groups, such as 20 -30 wt%.
A suitable polyisocyanate is especially a commercially available polyisocyanate, especially
– aromatic di-or triisocyanates, preferably diphenylmethane 4, 4'-or 2, 4'-or 2, 2'-diisocyanate or any mixtures of these isomers (MDI) , tolylene 2, 4-or 2, 6-diisocyanate or any mixtures of these isomers (TDI) , mixtures of MDI and MDI homologs (polymeric MDI or PMDI) , phenylene 1, 3-or 1, 4-diisocyanate, 2, 3, 5, 6-tetramethyl-1, 4-diisocyanatobenzene, naphthalene 1, 5-diisocyanate (NDI) , 3, 3'-dimethyl-4, 4'-diisocyanatodiphenyl (TODI) , dianisidine diisocyanate (DADI) , tris (4-isocyanatophenyl) methane or tris (4-isocyanatophenyl) thiophosphate; preferably MDI or TDI;
– aliphatic, cycloaliphatic or arylaliphatic di-or triisocyanates, preferably tetramethylene 1, 4-diisocyanate, 2-methylpentamethylene 1, 5-diisocyanate, hexamethylene 1, 6-diisocyanate (HDI) , 2, 2, 4-and/or 2, 4, 4- trimethylhexamethylene 1, 6-diisocyanate (TMDI) , decamethylene 1, 10-diisocyanate, dodecamethylene 1, 12-diisocyanate, lysine diisocyanate or lysine ester diisocyanate, cyclohexane 1, 3-or 1, 4-diisocyanate, 1-methyl-2, 4-and/or -2, 6-diisocyanatocyclohexane (H 6TDI) , 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (IPDI) , perhydrodiphenylmethane 2, 4'-and/or 4, 4'-diisocyanate (H 12MDI) , 1, 3-or 1, 4-bis (isocyanatomethyl) cyclohexane, m-or p-xylylene diisocyanate, tetramethylxylylene 1, 3-or 1, 4-diisocyanate, 1, 3, 5-tris (isocyanatomethyl) benzene, bis (1-isocyanato-1-methylethyl) naphthalene, dimer or trimer fatty acid isocyanates, such as, especially, 3, 6-bis (9-isocyanatononyl) -4, 5-di (1-heptenyl) cyclohexene (dimeryl diisocyanate) ; preferably H 12MDI or HDI or IPDI;
– oligomers or derivatives of the di-or triisocyanates mentioned, especially derived from HDI, IPDI, MDI or TDI, especially oligomers containing uretdione or isocyanurate or iminooxadiazinedione groups or various groups among these; or di-or polyfunctional derivatives containing ester or urea or urethane or biuret or allophanate or carbodiimide or uretonimine or oxadiazinetrione groups or various groups among these. In practice, polyisocyanates of this kind are typically mixtures of substances having  different degrees of oligomerization and/or chemical structures. They especially have an average NCO functionality of 2.1 to 4.0.
Preferred polyisocyanates are aliphatic, cycloaliphatic or aromatic diisocyanates, especially HDI, TMDI, cyclohexane 1, 3-or 1, 4-diisocyanate, IPDI, H 12MDI, 1, 3-or 1, 4-bis (isocyanatomethyl) cyclohexane, XDI, TDI, MDI, phenylene 1, 3-or 1, 4-diisocyanate or naphthalene 1, 5-diisocyanate (NDI) .
A particularly preferred polyisocyanate is HDI, IPDI, H 12MDI, TDI, MDI or a form of MDI which is liquid at room temperature, especially HDI, IPDI, TDI or HDI trimer.
The polyurethane binder on which the polyurethane coating composition is based may be formed by reacting the polyisocyanate with polyol which examples are desribed below, or with water which may be intentionally added or contained in the components or even derive from the atmosphere, for example the moisture or humidity from the air.
In an advantageous embodiment, the inventive polyurethane coating composition may contain no polyol to react with the polyisocyanate.
Suitable polyols for reacting with the polyisocyanate are commercial polyols or mixtures thereof, especially
– polyether polyols, especially polyoxyalkylenediols and/or polyoxyalkylenetriols, especially polymerization products of ethylene oxide or 1, 2-propylene oxide or 1, 2-or 2, 3-butylene oxide or oxetane or tetrahydrofuran or mixtures thereof, where these may be polymerized with the aid of a starter molecule having two or more active hydrogen atoms, especially a starter molecule such as water, ammonia or a compound having multiple OH or NH groups, such as, for example, ethane-1, 2-diol, propane-1, 2-or -1, 3-diol, neopentyl glycol, diethylene glycol, triethylene glycol, the isomeric dipropylene glycols or tripropylene glycols, the isomeric butanediols, pentanediols, hexanediols, heptanediols, octanediols,  nonanediols, decanediols, undecanediols, cyclohexane-1, 3-or -1, 4- dimethanol, bisphenol A, hydrogenated bisphenol A, 1, 1, 1-trimethylolethane, 1, 1, 1-trimethylolpropane, glycerol or aniline, or mixtures of the abovementioned compounds. Likewise suitable are polyether polyols with polymer particles dispersed therein, especially those with styrene/acrylonitrile (SAN) particles or polyurea or polyhydrazodicarbonamide (PHD) particles.
Preferred polyether polyols are polyoxypropylene diols or polyoxypropylene triols, or what are called ethylene oxide-terminated (EO-endcapped) polyoxypropylene diols or triols. The latter are mixed polyoxyethylene/polyoxypropylene polyols which are especially obtained in that polyoxypropylene diols or triols, on conclusion of the polypropoxylation reaction, are further alkoxylated with ethylene oxide and thereby eventually have primary hydroxyl groups.
Preferred polyether polyols have a degree of unsaturation of less than 0.02 meq/g, especially less than 0.01 meq/g.
– Polyester polyols, also called oligoesterols, prepared by known processes, especially the polycondensation of hydroxycarboxylic acids or lactones or the polycondensation of aliphatic and/or aromatic polycarboxylic acids with di-or polyhydric alcohols. Preference is given to polyester diols from the reaction of dihydric alcohols, such as, especially, 1, 2-ethanediol, diethylene glycol, 1, 2-propanediol, dipropylene glycol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, glycerol, 1, 1, 1-trimethylolpropane or mixtures of the abovementioned alcohols, with organic dicarboxylic acids or the anhydrides or esters thereof, such as, especially, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid or hexahydrophthalic acid or mixtures of the abovementioned acids, or polyester polyols from lactones, such as, especially, ε-caprolactone. Particular preference is given to polyester polyols from adipic acid or sebacic acid or dodecanedicarboxylic acid and hexanediol or neopentyl glycol.
– Polycarbonate polyols as obtainable by reaction, for example, of the abovementioned alcohols –used to form the polyester polyols –with dialkyl carbonates, diaryl carbonates or phosgene.
– Block copolymers bearing at least two hydroxyl groups and having at least two different blocks having polyether, polyester and/or polycarbonate structure of the type described above, especially polyether polyester polyols. 
– Polyacrylate polyols and polymethacrylate polyols.
– Polyhydroxy-functional fats and oils, for example natural fats and oils, especially castor oil; or polyols obtained by chemical modification of natural fats and oils –called oleochemical polyols –for example the epoxy polyesters or epoxy polyethers obtained by epoxidation of unsaturated oils and subsequent ring opening with carboxylic acids or alcohols, or polyols obtained by hydroformylation and hydrogenation of unsaturated oils; or polyols obtained from natural fats and oils by degradation processes, such as alcoholysis or ozonolysis, and subsequent chemical linkage, for example by transesterification or dimerization, of the degradation products or derivatives thereof thus obtained. Suitable degradation products of natural fats and oils are especially fatty acids and fatty alcohols and also fatty acid esters, especially the methyl esters (FAME) , which can be derivatized to hydroxy fatty acid esters by hydroformylation and hydrogenation, for example.
– Polyhydrocarbon polyols, also called oligohydrocarbonols, such as, for example, polyhydroxy-functional polyolefins, polyisobutylenes, polyisoprenes; polyhydroxy-functional ethylene/propylene, ethylene/butylene or ethylene/propylene/diene copolymers, as produced, for example, by Kraton Polymers; polyhydroxy-functional polymers of dienes, especially of 1, 3-butadiene, which can especially also be prepared from anionic polymerization; polyhydroxy-functional copolymers of dienes, such as 1, 3-butadiene, or diene mixtures and vinyl monomers, such as styrene, acrylonitrile, vinyl chloride, vinyl acetate, vinyl alcohol, isobutylene and isoprene, for example polyhydroxy-functional acrylonitrile/butadiene copolymers, as can be prepared, for example, from epoxides or aminoalcohols and carboxyl-terminated acrylonitrile/butadiene copolymers  (commercially available, for example, under the
Figure PCTCN2022127614-appb-000002
CTBN or CTBNX or ETBN name from Emerald Performance Materials) ; and hydrogenated polyhydroxy-functional polymers or copolymers of dienes.
Also especially suitable are mixtures of polyols.
Preference is given to polyether polyols, polyester polyols, polycarbonate polyols, poly (meth) acrylate polyols or polyhydroxy-functional fats and oils. Particular preference is given to polyester polyols, especially aliphatic polyester polyols, or polyhydroxy-functional fats and oils, especially castor oil. Preference is given to polyols having an average molecular weight in the range from 400 to 20 000 g/mol, preferably from 1000 to 10 000 g/mol. Preference is given to polyols having an average OH functionality in the range from 1.6 to 3.
Preferably, the composition comprises, in addition to the above specified components A) to C) , additionally one or more further constituents that are especially selected from catalysts, fillers, plasticizers and additives for setting the electrical properties.
Suitable catalysts are those for the acceleration of the reaction of isocyanate groups, especially organotin (IV) compounds, such as especially dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dichloride, dibutyltin diacetylacetonate, dimethyltin dilaurate, dioctyltin diacetate, dioctyltin dilaurate or dioctyltin diacetylacetonate, complexes of bismuth (III) or zirconium (IV) , especially with ligands selected from alkoxides, carboxylates, 1, 3-diketonates, oxinate, 1, 3-ketoesterates and 1, 3-ketoamidates, or compounds containing tertiary amino groups, such as especially 2, 2'-dimorpholinodiethyl ether (DMDEE) . Also especially suitable are combinations of different catalysts.
Suitable fillers are especially ground or precipitated calcium carbonates, optionally coated with fatty acids, especially stearates, barytes, quartz flours, quartz sands, corundum like white corundum, dolomites, wollastonites, kaolins, calcined kaolins, sheet silicates, such as mica or talc, zeolites, aluminum  hydroxides, magnesium hydroxides, silicas, including finely divided silicas from pyrolysis processes, cements, gypsums, fly ashes, graphite, metal powders, for example of aluminum, copper, iron, silver or steel, PVC powders or hollow beads.
Preferably, the inventive polyurethane composition contains wear particles as fillers, such as corumdums, ceramics, silicium carbide and so on.
Suitable plasticizers are especially carboxylic acid esters, such as phthalates, especially diisononyl phthalate (DINP) , diisodecyl phthalate (DIDP) or di (2-propylheptyl) phthalate (DPHP) , hydrogenated phthalates, especially hydrogenated diisononyl phthalate or diisononyl cyclohexane-1, 2-dicarboxylate (DINCH) , terephthalates, especially dioctyl terephthalate, trimellitates, adipates, especially dioctyl adipate, azelates, sebacates, benzoates, glycol ethers, glycol esters, organic phosphoric or sulfonic acid esters, polybutenes, polyisobutenes or plasticizers derived from natural fats or oils, especially epoxidized soybean or linseed oil.
Suitable additives for setting the electrical properties are conductive additives, for example conductive fillers, such as conductive pigments or conductive fibers, salts, ionic liquids, ionic and nonionic surfactants, and combinations thereof. Specific conductive additives for setting the electrical properties are, for example, carbon fibers, carbon black, graphite, silicon carbide, metal oxides, metals, such as iron, ammonium salts, metal-containing or heavy metal-containing fillers, especially antimony-and tin-containing fillers based on titanium dioxide or mica, ionic liquids, ionic and nonionic surfactants, melamine sulfonates and polycarboxylate ethers, and combinations thereof. The conductive additives for setting the electrical properties can, for example, be added in the form of powders, fibers, turnings, in liquid form, flakes or granules. Conductive salts can also optionally be added as solutions.
The composition may comprise further additives commonly used for polyurethane compositions. More particularly, the following auxiliaries and additives may be present:
– coloring agents, such as colored quartz, dyes, pigments and color chips;
– desiccants, especially molecular sieve powder, calcium oxide, highly reactive isocyanates, such as p-tosyl isocyanate, monomeric diisocyanates or orthoformic esters;
– adhesion promoters, especially organoalkoxysilanes, especially epoxysilanes, such as especially 3-glycidoxypropyltrimethoxysilane or 3- glycidoxypropyltriethoxysilane, (meth) acrylosilanes, anhydridosilanes, carbamatosilanes, alkylsilanes or iminosilanes, or oligomeric forms of these silanes, or titanates;
– latent curing agents or crosslinkers, especially aldimines, ketimines, enamines or oxazolidines;
– catalysts which accelerate the reaction of the isocyanate groups, especially salts, soaps or complexes of tin, zinc, bismuth, iron, aluminum, molybdenum, dioxomolybdenum, titanium, zirconium or potassium, especially tin (II) 2-ethylhexanoate, tin (II) neodecanoate, zinc (II) acetate, zinc (II) 2- ethylhexanoate, zinc (II) laurate, zinc (II) acetylacetonate, aluminum lactate, aluminum oleate, diisopropoxytitanium bis (ethyl acetoacetate) or potassium acetate; compounds containing tertiary amino groups, especially N-ethyldiisopropylamine, N, N, N', N'-tetramethylalkylenediamines, pentamethylalkylenetriamines and higher homologs thereof, bis (N, N-diethylaminoethyl) adipate, tris (3-dimethylaminopropyl) amine, 1, 4-diazabicyclo [2.2.2] octane (DABCO) , 1, 8-diazabicyclo [5.4.0] undec-7-ene (DBU) , 1, 5-diazabicyclo [4.3.0] non-5-ene (DBN) , N-alkylmorpholines, N, N'-dimethylpiperazine; aromatic nitrogen compounds, such as 4-dimethylaminopyridine, N-methylimidazole, N-vinylimidazole or 1, 2-dimethylimidazole; organic ammonium compounds, such as benzyltrimethylammonium hydroxide or alkoxylated tertiary amines; what are called "delayed action" catalysts, which are modifications of known metal or amine catalysts;
– rheology modifiers, especially thickeners, especially sheet silicates, such as bentonites, derivatives of castor oil, hydrogenated castor oil, polyamides, polyamide waxes, polyurethanes, urea compounds, fumed silicas, cellulose ethers or hydrophobically modified polyoxyethylenes;
– nonreactive polymers, especially homo-or copolymers of unsaturated monomers, especially from the group comprising ethylene, propylene, butylene, isobutylene, isoprene, vinyl acetate or alkyl (meth) acrylates, especially polyethylenes (PE) , polypropylenes (PP) , polyisobutylenes, ethylene/vinyl acetate copolymers (EVA) or atactic poly-α-olefins (APAO) ;
– flame-retardant substances, especially the aluminum hydroxide or magnesium hydroxide fillers already mentioned, and also especially organic phosphoric acid esters, such as especially triethyl phosphate, tricresyl phosphate, triphenyl phosphate, diphenyl cresyl phosphate, isodecyl diphenyl phosphate, tris (1, 3-dichloro-2-propyl) phosphate, tris (2-chloroethyl) phosphate, tris (2-ethylhexyl) phosphate, tris (chloroisopropyl) phosphate, tris (chloropropyl) phosphate, isopropylated triphenyl phosphate, mono-, bis-or tris (isopropylphenyl) phosphates of different degrees of isopropylation, resorcinol bis (diphenylphosphate) , bisphenol A bis (diphenylphosphate) or ammonium polyphosphates;
– additives, especially wetting agents, leveling agents, defoamers, deaerators, stabilizers against oxidation, heat, light or UV radiation, or biocides;
or further substances customarily used in moisture-curing compositions.
It may be advisable to chemically or physically dry certain substances before mixing them into the composition.
The composition is especially produced with exclusion of moisture and stored at ambient temperature in moisture-tight containers. A suitable moisture-tight container especially consists of an optionally coated metal and/or plastic, and is especially a drum, a transport box, a hobbock, a bucket, a canister, a can, a bag, a tubular bag, a cartridge or a tube.
The composition may be in the form of a one-component composition or in the form of a multi-component, especially two-component, composition.
A composition referred to as a "one-component" composition is one in which all constituents of the composition are in the same container and which is storage-stable per se.
A composition referred to as a "two-component" composition is one in which the constituents of the composition are in two different components which are stored in separate containers and are not mixed with one another until shortly before or during the application of the composition.
On application of the composition, the process of curing commences. This results in the cured composition.
In the case of a two-or multi-component composition, it is applied after the mixing of the two or more components and begins to cure by internal reaction, and the curing may be completed by the action of external moisture. The two or more components can be mixed continuously or batchwise with dynamic mixers or static mixers.
The composition is preferably applied at ambient temperature, especially in the range from about 0 to 50℃, preferably in the range from 5 to 40℃.
The composition is preferably likewise cured at ambient temperature.
In a second aspect, the invention relates to a coating system on a substrate for the protection against electrostatic discharge, comprising in the following order
a) an undercoat on the substrate,
b) optionally a dissipative synthetic resin layer, and
c) a topcoat layer which is formed by the solvent-free polyurethane coating composition according to the invention.
A conductive electrostatic system or an electrostatic disspative system may be obtained after curing the coating composition according to the invention.
Therefore, the inventive coating system may be obtained in forms of above both systems which may be usually distinguished from each other in view of the different requirements on the resistance Rs or Rg. Generally speaking, Rs  or Rg in an electrostatic dissipative resistance is in a range of 10 6 –10 9 ohms while Rs or Rg in a conductive electrostatic resistance is in a range of 10 4 –10 6 ohms, such as 5.0*10 4 –1.0*10 6 ohms. For more details of both systems, the skilled person may refer to e.g. the standard GB/T 22374-2018.
In the inventive coating system, the undercoat applied on the substrate may optionally also contain levelling on the substrate and the undercoat may be preferably conductive per se or have no conductive or dissipative function. In one exemplary embodiment of the invention, the dissipative synthetic resin layer (4) applied between the undercoat and the topcoat is conductive and thus preferably may have a resistance to ground according to VDE-0100-410 of at least 100 kohm. It goes without saying that the dissipative synthetic resin layer is different from the topcoat layer which is formed by the inventive solvent-free polyurethane coating composition and may be any kind of the prior art dissipative synthetic resin layer.
Dissipative layers may also be called conductive electrostatic layers or electrostatically dissipative layers. As opposed to non-dissipative or insulating layers, they permit an electrostatic charge that is building up to dissipate. For this purpose, dissipative layers have a certain electrical conductivity.
The coating system according to the invention can be a floor coating system or a wall coating system, wherein it is preferably a floor coating system. The coating system has broad commercial utility and exhibits numerous advantages compared to the systems according to the prior art. This system structure is suitable for the simple, cost-advantageous and rapid conversion of existing purely insulating coating structures into ESD-capable systems.
The coating system according to the invention is suitable for all floors, industrial floors and walls for which ESD protection is required, especially for floors. Sectors in which such floors or walls are required are, for example, the electrical and electronics industry, microelectronics, high-precision optics, biotechnology, lithography, pharmaceuticals, life sciences, the automotive  industry or in the manufacturing of data carriers. The coating systems according to the invention are suitable, for example, for clean rooms, production facilities, assembly facilities, laboratories and the like, in which electrostatic charges should or must be avoided.
The dissipation capacity can be determined, for example, by way of the resistance to ground of the layer. As used here and insofar as not stated otherwise, the resistance to ground of a layer can be determined according to the standard IEC 61340-4-1. Here and according to the IEC 61340-4-1 and IEC 61340-5-1 standards, a layer is considered conductive or electrostatically conductive if it has a resistance to ground of no more than 109 ohm. Layers having higher resistances to ground are non-dissipative.
The dissipative synthetic resin layer 4 and, insofar as the preferred synthetic resin undercoat is used as the undercoat, the undercoat as well are based on a synthetic resin. The optional scratch coat can be based on a synthetic resin. Synthetic resin layers as floor coverings or wall coverings are well known to the person skilled in the art and are widely used in this field. If not stated otherwise, the following statements apply equally to the synthetic resin layers, the synthetic resin undercoat and the optional scratch coat.
Synthetic resin layers are made of cured reaction resins or reactions resin compounds, wherein reaction resin compounds are usually understood to mean reaction resins containing one or more additives, for example, fillers and/or solvents.
All conventional reaction resins known to the expert can be used to produce the dissipative synthetic resin layer, and the synthetic resin undercoat and the optional scratch coat. The same or different reaction resins can be used for the individual layers. The reaction resins, especially those mentioned hereinafter, can be used in solvent-free or water-based form.
The reaction resins used for the respective layer or optionally the undercoat or the scratch coat are preferably selected independently of one another from epoxy resins, polyurethanes, polyureas, mixtures of polyurethanes and polyureas, poly (meth) acrylates, cementitious hybrid systems and polymer-modified cementitious mixtures (PCC "polymer cement concrete" ) .
The additives can already be present in the reaction resin or be mixed to the reaction resin before processing. Examples of possible additives, in addition to solvents and water, are coloring agents, such as colored quartz, dyes, pigments and color chips; fillers, such as quartz sand, ceramic powder, sand, chalk, fibers, hollow spheres and glass beads; emulsifiers, thixotropic agents, and film-forming aids as well as suitable additives for setting the electrical properties as described above.
In principle, all substrates present in edifices are suitable for use as the substrate for the coating, especially the floor or flooring coating. Examples of suitable substrates are concrete, cement screed, magnesium oxide screed, ceramic tiles, asphalt, and optionally any synthetic resin coatings already present.
To produce the coating system according to the invention, first the undercoat is applied to the underlay, optionally after conventional substrate pretreatment, for example, grinding, sand-blasting, shot blasting or stripping with solvents or acids. For the undercoat, a conventional undercoat composition is applied, for example, a reaction resin or a reaction resin compound, or alternatively a water-based synthetic resin dispersion, and cured. This is preferably a synthetic resin undercoat based on cured reaction resins.
The grounding device for grounding the coating system may be installed in the coating system. In case of a non-conductive undercoat the grounding device may be arranged on the top of it or directly between the undercoat and the topcoat. In case of a conductive undercoat, the grounding device may be arranged below the undercoat or between the undercoat and the substrate. For  electrically connecting the electrostatically dissipative coating, the grounding device is connected to the equipotential bonding. Such grounding devices are known to the person skilled in the art, and such a person can readily implement them. The grounding device can, for example, be formed by a grounding conductor or an arrangement of grounding conductors, which are connected to the equipotential bonding. The bonding to the equipotential bonding or ground potential can take place via one or more grounding connections.
Suitable grounding conductors include, for example, copper tapes and/or so-called conductor sets, which are installed to dissipate the potential. Self-adhesive copper strips may be used. Conductor sets are commercially available; for example, the
Figure PCTCN2022127614-appb-000003
conductor set. The conductor set is made up of pegs with copper tapes, washers and a threaded rod. In this way a so-called grounding point is established, which can subsequently be connected to ground by a skilled electrician.
General processing methods and processing equipment that can be used to produce the individual layers are known to the person skilled in the art. Special advice for processing certain commercially available reaction resin products can usually also be found in the related product data sheets.
The individual layers can also be designed as double layers or multiple layers, but this is generally not preferred. It is also possible for additional intermediate layers to be optionally arranged in the coating system. Examples of such intermediate layers are those that also have crack-bridging properties (for example, 
Figure PCTCN2022127614-appb-000004
350 or
Figure PCTCN2022127614-appb-000005
390) .
Brief Description of the Drawings
Fig. 1: one variant of the coating system according to the invention; and
Fig. 2: another variant of the coating system according to the invention.
In Fig. 1, the coating system is consisting of (1) substrate, (2) grounding device such as copper tapes, (4) dissipative synthetic resin layer and (5) topcoat formed by the inventive coating composition.
In Fig. 2, the coating system is consisting of (3) undercoat which has no conductive function, (2) grounding device such as copper tapes, and (5) topcoat formed by the inventive coating composition. The substrate below the undercoat is not shown in the figure.
List of reference numerals
1    Substrate
2    Grounding device
3    Undercoat
4    Dissipative synthetic resin layer
5    Topcoat
Examples follow which elucidate the invention, but which are not intended in any way to restrict the scope of the invention.
Examples
1.  Commercial products mainly used are as follows:
Raw materials           Specification
DESMODUR N 31000        HDI trimer, Viscosity: 500mPa. s
Tolonate HDT LV         HDI trimer, Viscosity: 1200mPa. s
K-FLEX DP               Dibenzoate plasticizer
TUBALL MATRIX 301       SWCNT, solid 10%
Carbon fibers           Length 0.1 mm
Accelarator             Dibutyltin dilaurate
Dispersant              TEGO Dispers 685
Levelling agent         Tego Flow 300
2.  Preparation of the coating compositions:
The coating compositions were prepared by mixing four components, i.e. Component A, Component B, Component C and Component D, under stirring in a suitable container with a weight ratio of A : B : C : D of 2.83 : 0.75 : 2.13 : 0.62 until a homogenous mixture was obtained.
Component A was formulated on basis of two HDI trimer having different viscosity. In Ex 4, the component A was based on 100 wt%of Tolonate HDT LV while in the remaining examples, the component A was based on 100 wt%of DESMODUR N 31000.
In each of the examples, Component B was formulated by mixing the individual ingredients with the amounts specified in the following table.
Component C was consisting of 100wt%of white corundum having the particle size of 220 Mesh (70-75μm) .
Component D was formulated by mixing 36.7 wt%of CFAME (Chlorinated fatty acid methyl ester) , 6.8 wt%of K-FLEX DP, 2 wt%of UNIQ 680U and the remaining parts of green-clored fillers to form a green slurry.
Table 1. Composition of Component B in examples
Figure PCTCN2022127614-appb-000006
3.  Measuring methods of electrical resistance:
A conductive electrostatic system was prepared by coating on the substrate, a non-asbestos fiber cement board, in order the primer Sikafloor-220W, the medium coating Sikafloor-206W and the coating compositions of each examples.
Correspondingly, an electrostatic dissipative system was also prepared by coating on the substrate, a non-asbestos fiber cement board, in order the primer Sikafloor-220W, the medium coating Sikafloor-237EDF and the coating compositions of each examples.
Two systems were tested in regard to the electrical resistances Rs and Rg using the device METRISO3000 in accord with SJT 11294-2018 General specification of floor coating for electrostatic protection. The results were recorded in the following tables.
4.  Measuring methods of VOC content:
The VOC content is measured in accord with the standard GBT 23985-2009. In the measurement, the testing mixture was prepared by mixing Components A, B, C and D under stirring and then placed in a testing oven at 105±2℃ for 1 hour after a 24-hour conditioning under 23±2℃ and humidity of 50±5%.
The VOC contents as measured for Examples 2, 3 and 4 are 42.4 g/L, 48.3 g/L and 40.9 g/L respectively, all below 60 g/L which is the permissible limit according to the national standard.
Figure PCTCN2022127614-appb-000007
Figure PCTCN2022127614-appb-000008
Figure PCTCN2022127614-appb-000009
Figure PCTCN2022127614-appb-000010
As can be seen from Example 5, with a lower amount (0.8 wt%) of carbon fibers, the value of Rg of the conductive electrostatic system was higher in many cases. Meanwhile, some resistances Rs of the electrostatic dissipative system were also much higher which may possibly deteriorate the electrostatic dissipative effects of the system in the long term.
Regarding Example 6, when the amount of carbon fibers was as high as 2.5 wt%, the resistance Rg of the electrostatic dissipative system was overly lower than the requirements on the electrostatic dissipative resistance. Furthermore, due to the high amount of carbon fibers, it is was found that the surface quality of the coating was bad and it was difficult to obtain the homogeneous coating film.
Regarding Example 7, with a high mount (0.05wt%) of SWCNT, a satisfactory electrostatic dissipative system could be hardly obtained because of unduly low resistances Rs and Rg. Furthermore, the surface quality of the film was also questioned and it was difficult to obtain the homogeneous coating film.
Regarding Example 8, with smaller amount of SWCNT, although the surface quality was found significantly improved, the resistances Rs/Rg of the conductive electrostatic system were much higher.

Claims (10)

  1. A solvent-free polyurethane coating composition, comprising:
    A) a polyisocyanate having a low viscosity below 800 mPa. s, preferably below 500 mPa. s,
    B) single walled carbon nanotubes (SWCNT) in a range of 0.012 –0.04 wt%, such as 0.016 –0.035 wt%, based on the total weight of the composition,
    C) carbon fibers having a length below 0.2 mm, preferably below 0.15 mm, more preferably between 0.05 –0.12 mm, in a range of 1.0 –2.4 wt%, such as 1.2 –2.3 wt%, based on the total weight of the composition.
  2. Coating composition as claimed in claim 1, characterized in that the polyisocyanate is selected from aliphatic, cycloaliphatic or aromatic diisocyanates, especially HDI, TMDI, cyclohexane 1, 3-or 1, 4-diisocyanate, IPDI, H 12MDI, 1, 3-or 1, 4-bis (isocyanatomethyl) cyclohexane, XDI, TDI, MDI, phenylene 1, 3-or 1, 4-diisocyanate or naphthalene 1, 5-diisocyanate (NDI) , more preferably from HDI, IPDI, H 12MDI, TDI, MDI or a form of MDI which is liquid at room temperature, especially HDI, IPDI, TDI or HDI trimer.
  3. Coating composition as claimed in any one of preceding claims, characterized in that the coating composition contains further polyols for reacting with the polyisocyanate which are selected from polyester polyols, especially aliphatic polyester polyols, or polyhydroxy-functional fats and oils, especially castor oil.
  4. Coating composition as claimed in any one of preceding claims, characterized in that the polyisocyanate contains 18 wt%or more free NCO groups, such as 20 -30 wt%.
  5. Coating composition as claimed in any one of preceding claims, characterized in that it further contains wear particles as fillers, such as corumdums, ceramics, silicium carbide and so on, preferably corumdums.
  6. A coating system on a substrate for the protection against electrostatic discharge, comprising in the following order
    a) an undercoat on the substrate,
    b) optionally a dissipative synthetic resin layer, and
    c) a topcoat layer which is formed by the solvent-free polyurethane coating composition according to any one of preceding claims.
  7. A coating system according to claim 5, wherein it contains the grounding device for grounding the coating system.
  8. A coating system according to claim 7, wherein the grounding device is arranged on the top of the undercoat or directly between the undercoat and the topcoat, especially in case of a non-conductive undercoat.
  9. A coating system according to claim 7, wherein the grounding device is arranged below the undercoat or between the undercoat and the substrate, especially in case of a conductive undercoat.
  10. A coating system according to claim 7, wherein the undercoat is conductive.
PCT/CN2022/127614 2022-10-26 2022-10-26 Electrically conductive solvent-free pu coating WO2024087051A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040105726A1 (en) * 2002-05-09 2004-06-03 Hannay Richard C. Conductor polymer backfill composition and method of use as a reinforcement material for utility poles
CN104263226A (en) * 2014-08-31 2015-01-07 青岛海信电器股份有限公司 Antistatic paint as well as conductive composite material and electronic equipment
EP3670470A1 (en) * 2018-12-17 2020-06-24 STO SE & Co. KGaA Coating compositions for floor coverings
CN111662634A (en) * 2020-06-24 2020-09-15 广东达尔新型材料有限公司 Thin-coating type water-based anti-static polyurethane mortar floor coating and preparation method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040105726A1 (en) * 2002-05-09 2004-06-03 Hannay Richard C. Conductor polymer backfill composition and method of use as a reinforcement material for utility poles
CN104263226A (en) * 2014-08-31 2015-01-07 青岛海信电器股份有限公司 Antistatic paint as well as conductive composite material and electronic equipment
EP3670470A1 (en) * 2018-12-17 2020-06-24 STO SE & Co. KGaA Coating compositions for floor coverings
CN111662634A (en) * 2020-06-24 2020-09-15 广东达尔新型材料有限公司 Thin-coating type water-based anti-static polyurethane mortar floor coating and preparation method thereof

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