Polyisocyanate composition and coating composition

Abstract

The invention discloses a polyisocyanate composition and a coating composition, the polyisocyanate composition contains an isocyanurate structure and a uretdione structure, when the molar ratio of the uretdione structure larger than a trimolecular polymer in the composition to the uretdione structure in the composition is (0.1-20): 100, the molar ratio of the uretdione structure larger than the trimolecular polymer in the composition to the uretdione structure in the composition is (0.1-20): 100. The composition not only has lower viscosity, but also has better heat resistance, and can ensure the comprehensive properties such as better glossiness and excellent appearance of a coating film.

Description

Technical Field

[0001] The present invention relates to a polyisocyanate composition, and more particularly to a polyisocyanate composition and a coating composition. Background Art

[0002] Since aliphatic polyisocyanates containing isocyanurate structures have excellent weather resistance, chemical resistance, and heat resistance, they are widely used in high-end fields such as automotive original paints, repair paints, and varnishes. In recent years, due to the continuous improvement of environmental protection requirements, in order to reduce the use of organic solvents in the application process of aliphatic polyisocyanate compositions, the polyisocyanates used as curing agents have gradually developed towards low viscosity.

[0003] Currently, the methods that have been disclosed for preparing low-viscosity polyisocyanate compositions containing isocyanurate structures mainly include reducing the reaction conversion rate, using special catalysts, and introducing modified components, etc. For example:

[0004] US4801663A describes a low-viscosity polyisocyanate composition, in which the proportion of isocyanurate monocyclic polymers is as high as 70-75%, but the reaction conversion rate can only reach 12-21%, and the total yield of the reaction is significantly reduced. This method requires removing a large amount of unreacted monomers from the final reaction product, greatly increasing the cost of this method.

[0005] CN107868226A prepared a narrow-distribution diisocyanate trimer by using a mesoporous material-supported N-alkylated solid catalyst. The polyisocyanate composition has a lower viscosity, but the catalyst preparation process is complex and cannot be extended to industrial production.

[0006] CN101291970A and US5124427 can reduce the viscosity of the polyisocyanate composition by modifying with a monoalcohol to obtain a urethane structure, but the crosslinkability and compatibility of the urethane structure obtained by modifying with a monoalcohol are poor, and the appearance and gloss of the paint film obtained when applied to a coating composition are insufficient.

[0007] CN1757639A discloses a method for preparing a low-viscosity polyisocyanate. This patent uses a quaternary ammonium salt or phosphonium salt of polyfluoric acid as a catalyst to prepare a polyisocyanate containing an iminooxadiazinedione group, which can reduce the viscosity of the polyisocyanate composition, but the iminooxadiazinedione structure has poor stability, and the introduction of fluorine elements makes this method less safe and environmentally friendly.

[0008] US5354834A realizes the reduction of the product viscosity by controlling the content of isocyanurate trimers in the composition to be less than 60% and the content of uretidione dimers to be more than 10%. The increase in the content of uretidione dimers is beneficial to reducing the viscosity of the composition. However, the composition also contains uretidione structures with relatively high molecular weights, and the crosslinkability and compatibility of the high-molecular-weight uretidione structures are poor, which is disadvantageous to the hardness and appearance of the paint film.

[0009] JP2014214301A realizes the reduction of the product viscosity by controlling the content ratio of iminooxadiazinedione structures and uretidione structures to isocyanurate structures in the composition. However, the crosslinkability of the said composition needs to be further improved.

[0010] It can be known from the prior art that the viscosity of isocyanurate polyisocyanate compositions can be reduced by uretidione modification. However, it is difficult to ensure excellent properties of the prepared paint film while introducing uretidione structures. Therefore, it is necessary to develop an aliphatic polyisocyanate that can reduce the viscosity while maintaining good crosslinkability, so as to ensure excellent properties of the obtained paint film. Summary of the Invention

[0011] To solve the above technical problems, the present invention first proposes a polyisocyanate composition. Through continuous research, the inventors of the present invention have found that when the molar ratio of the uretidione structure in polymers with more than three molecules to the uretidione structure in the said composition in the polyisocyanate composition is (0.1 - 20):100, the said composition not only has a lower viscosity, but also has better crosslinkability, and can ensure comprehensive properties such as better gloss and excellent appearance of the coating film.

[0012] Based on the second aspect of the present invention, the present invention also proposes an application of the said polyisocyanate composition in a coating composition. The paint film prepared from the coating composition has excellent comprehensive properties.

[0013] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0014] A polyisocyanate composition, which is derived from aliphatic / alicyclic diisocyanate monomers, contains trimers and polymers with more than three molecules formed by the said diisocyanates, and contains isocyanurate structures and uretidione structures. Among them, the molar ratio of the uretidione structure in polymers with more than three molecules to the uretidione structure in the said composition is (0.1 - 20):100.

[0015] Under normal circumstances, the aliphatic isocyanurate group polyisocyanate composition mainly includes trimers and polymers with more than three molecules formed by the polymerization reaction of aliphatic diisocyanates under the action of a trimerization catalyst. Among them, the polymers with more than three molecules include pentamers, heptamers, nonamers, multimers, etc. The trimer is a single isocyanurate ring structure, and the polymers with more than three molecules mainly contain multiple isocyanurate rings.

[0016] The polyisocyanate composition obtained by uretdione modification mainly includes dimers, trimers and polymers with more than three molecules whose main component is the uretdione structure formed by the uretdionization reaction of aliphatic diisocyanates. Among them, the dimers and trimers are linear uretdione structures, and the polymers with more than three molecules are linear uretdione structures and structures connected to isocyanurate rings. The low-molecular-weight uretdione structure can effectively reduce the viscosity of the polyisocyanate composition while having little effect on the crosslinking property of the product. The high-molecular-weight uretdione structure has a weak ability to reduce the viscosity of the product and has a greater adverse effect on the crosslinking property of the product.

[0017] Research has found that when the molar ratio of the uretdione structure in the polymers with more than three molecules in the composition to the uretdione structure in the composition is lower than 0.1 / 100, it is impossible to effectively adjust the viscosity of the polyisocyanate composition to meet the application requirements, and the compatibility of the combination is slightly poor; when the molar ratio of the uretdione structure in the polymers with more than three molecules to the uretdione structure in the composition is higher than 20 / 100, the crosslinking property of the polyisocyanate composition is poor. A large number of experiments have proved that when the molar ratio of the uretdione structure in the polymers with more than three molecules in the polyisocyanate composition to the uretdione structure in the composition is (0.1 - 20):100, the polyisocyanate composition not only has a low viscosity but also has good compatibility, thus ensuring excellent film properties when applied to coatings.

[0018] In the polyisocyanate composition of the present invention, it contains isocyanurate structure and uretdione structure;

[0019] Furthermore, the isocyanurate structure is a functional group of a polyisocyanate formed by 3 molecules of diisocyanate monomers, and its specific structure is shown in the following formula (Ⅰ):

[0020]

[0021] Furthermore, the uretdione structure is a functional group of a polyisocyanate formed by 2 molecules of diisocyanate monomers, and its specific structure is shown in the following formula (Ⅱ):

[0022]

[0023] In a preferred embodiment of the present invention, in the polyisocyanate composition, the molar ratio of the uretdione structure to the isocyanurate structure is (0.1 - 10):100. By setting this ratio above the lower limit value, the resulting polyisocyanate composition has a lower viscosity; by setting the above ratio below the upper limit value, the polyisocyanate composition has better crosslinkability.

[0024] In a preferred embodiment of the present invention, the content of the polymer obtained by the reaction of three molecules of diisocyanate monomer (hereinafter referred to as "diisocyanate trimer") in the polyisocyanate composition is 40 - 80 wt%. When the content of the diisocyanate trimer is 40 wt% or more, the viscosity of the polyisocyanate composition can be effectively reduced, thereby reducing the use of solvents when used as a coating; when the content of the diisocyanate trimer is less than 80%, the composition can have better crosslinkability, thereby ensuring excellent application performance of the composition.

[0025] In a preferred embodiment of the present invention, the viscosity of the polyisocyanate composition measured at 25 °C is 100 - 4000 mPa·s. When the viscosity is less than 100 mPa·s, the crosslinkability of the polyisocyanate composition is poor; when the viscosity is higher than 4000 mPa·s, the amount of solvent used when the composition is used as a coating is large, which is not conducive to environmental protection.

[0026] Hereinafter, an example of the manufacturing method of the polyisocyanate composition of the present invention will be described, which specifically includes the following steps:

[0027] S1: Add an isocyanuration catalyst to the aliphatic / alicyclic diisocyanate monomer, react it to a certain extent, and stop the reaction by adding a terminator to obtain reaction solution X;

[0028] S2: Add a uretdionization catalyst to the aliphatic / alicyclic diisocyanate monomer, react it to a certain extent, and stop the reaction by adding a terminator to obtain reaction solution Y;

[0029] S3: Blend reaction solutions X and Y, add a certain amount of aliphatic / alicyclic diisocyanate monomer to obtain a mixed system, and react the mixed system at a high temperature for a certain time to obtain reaction solution Z;

[0030] S4: Remove the unreacted diisocyanate monomer from reaction solution Z to obtain the polyisocyanate composition.

[0031] In a preferred embodiment of the present invention, the diisocyanate monomer is selected from one or more of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, lysine diisocyanate, preferably pentamethylene diisocyanate and / or hexamethylene diisocyanate.

[0032] Preferably, the isocyanurate esterification catalyst includes quaternary ammonium base catalysts and / or quaternary ammonium salt catalysts, preferably any one or at least two combinations of choline hydroxide, trimethylhydroxyethylammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, tetraethylammonium formate, tetraethylammonium acetate, tetrabutylammonium decanoate, trimethylhydroxypropylammonium formate, trimethylhydroxypropylammonium acetate, trimethylhydroxypropylammonium decanoate, trimethylhydroxyethylammonium formate, and more preferably benzyltrimethylammonium hydroxide and tetrabutylammonium decanoate.

[0033] Preferably, the uretdione catalyst is one or more of trialkylphosphines such as tri-n-butylphosphine and tri-n-octylphosphine, tris-(dimethylamino)phosphine, cyclohexyl-di-n-hexylphosphine, etc.;

[0034] Preferably, the dosage of the isocyanurate esterification catalyst is 20-500 ppm relative to the total mass of the aliphatic / alicyclic diisocyanate monomer in step S1; the dosage of the uretdione catalyst is 50-5000 ppm relative to the total mass of the aliphatic / alicyclic diisocyanate monomer in step S2.

[0035] Preferably, in step S3, the mass of the added aliphatic / alicyclic diisocyanate monomer is 5-20% of the total mass of the diisocyanate monomers in steps S1 and S2;

[0036] Preferably, the polymerization reaction temperature in steps S1 and S2 is 30-120 °C, and the reaction temperature in step S3 is 100-180 °C.

[0037] Preferably, in steps S1 and S2, the catalyst is poisoned by adding a terminator. Feasible terminators are, for example, di-n-butyl phosphate, diisooctyl phosphate, phosphoric acid, p-toluenesulfonic acid, etc. The method of selecting a suitable terminator according to the catalyst type to terminate the reaction is known and is not restricted by the present invention here.

[0038] Preferably, in step S4, the unreacted diisocyanate monomer is removed by any one or a combination of the following methods: thin film evaporation method, falling film evaporation method, short path evaporation method, vacuum rectification method; preferably, the unreacted monomer is removed by a two-stage thin film evaporation method, for example, thin film evaporation is carried out at 120-180 °C.

[0039] Preferably, the content of unreacted diisocyanate monomer in the polyisocyanate composition is controlled to be below 0.2 wt%.

[0040] The above preparation process is only provided to conveniently provide a preparation process for the polyisocyanate composition, but this process is generally not used as any limitation on the polyisocyanate composition. According to the inventive concept disclosed above in the present invention, those skilled in the art are capable of obtaining a polyisocyanate composition that meets the requirements through other schemes. For example:

[0041] By mixing a commercially available uretdione group polyisocyanate composition, a diisocyanate monomer, and an isocyanurate group polyisocyanate composition in a certain proportion, heating for a certain time, and then removing the excess diisocyanate monomer, a polyisocyanate composition that meets the requirements is obtained.

[0042] As a feasible implementation scheme, further examples are as follows:

[0043] After blending 100 g of commercially available product HDI, 200 g of commercially available product N3400 (uretdione group polyisocyanate), and 500 g of commercially available product N3300 (isocyanurate group polyisocyanate), reacting at 150 °C for 120 min under the protection of nitrogen, then quickly cooling to room temperature, and removing the excess HDI by thin-film evaporation, the target product can be obtained.

[0044] Unless otherwise specified, "wt%" in the present invention all refers to mass percentage.

[0045] The present invention also provides a coating composition prepared from the polyisocyanate composition described above.

[0046] The coating composition includes the polyisocyanate composition provided above and a polyol, and their dosages are calculated according to the molar ratio of isocyanate groups to hydroxyl groups, for example, (1 - 1.5):1.

[0047] The polyol can be any known auxiliary curing component, including but not limited to acrylic polyols, polyester polyols, etc. The acrylic polyol is, for example, polymerized from one or more of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate; the polyester polyol is, for example, prepared by a condensation reaction of one or more of succinic acid, adipic acid, sebacic acid, and maleic anhydride with one or more alcohols selected from ethylene glycol, propylene glycol, diethylene glycol, and neopentyl glycol.

[0048] The molecular weight of the polyol is preferably 2000 or more and 8000 or less. When the molecular weight of the polyol is less than 2000, the crosslinking degree is poor when it is applied to the coating composition. When the molecular weight of the polyol is more than 8000, the film compatibility is poor when it is applied to the coating composition, further affecting the gloss and texture of the film. When the molecular weight of the polyol is 2000 or more and 8000 or less, excellent crosslinking degree and compatibility of the coating composition can be ensured simultaneously.

[0049] The beneficial effects of the present invention are as follows:

[0050] By defining the content ratio of the uretdione structure in the polymer with more than three molecules in the polyisocyanate composition to the uretdione structure in the composition, the product can have both a lower viscosity and better crosslinkability. After being used in the coating composition, the amount of solvent used can be significantly reduced, making it more environmentally friendly, and it also has better film properties, with obvious improvements in multiple aspects such as gloss and appearance performance. Specific embodiments

[0051] The present invention will be further described below through specific examples. The examples described in the present invention are only for the illustration of the present invention and do not limit the scope of the present invention.

[0052] <Main raw material information>

[0053] HDI: Hexamethylene diisocyanate, Covestro AG

[0054] PDI: Pentamethylene diisocyanate, Covestro AG

[0055] Acrylic polyol AC1100B, Guangdong Tongde New Materials Co., Ltd.

[0056] N,N,N-Trimethylbenzylammonium hydroxide, Aladdin reagent platform

[0057] Tri-n-butylphosphine, Aladdin reagent platform

[0058] Isooctanol, Aladdin reagent platform

[0059] Dibutyl phosphate, Aladdin reagent platform

[0060] <Determination of product viscosity>

[0061] The viscosity of the products in the examples and comparative examples was measured using a Brookfield RC / S rheometer, with the rotor model CC-40, a constant temperature water bath, and the temperature controlled at 25 ± 0.1 °C. The shear rate was 25 S-1 - 250 S-1.

[0062] <Reaction conversion rate and diisocyanate trimer>

[0063] The reaction conversion rate refers to the mass ratio of the reacted diisocyanate based on the mass of the starting diisocyanate raw material. The conversion rate of the reaction is monitored by quantitatively analyzing the diisocyanate monomer through gel permeation chromatography.

[0064] The determination of the content of the diisocyanate trimer is carried out by a gel permeation chromatograph, and the peak equivalent to three times the molecular weight of the diisocyanate is defined as the trimer.

[0065] The gel permeation chromatograph is LC-20AD / RID-10A, and the chromatographic columns are MZ-Gel SDplus 10E3A 5μm (8.0×300mm), MZ-Gel SDplus 500A 5μm (8.0×300mm), and MZ-Gel SDplus 100A 5μm (8.0×300mm) connected in series, manufactured by Shimadzu; the mobile phase is tetrahydrofuran; the flow rate is 1.0 mL / min; the analysis time is 40 min, and the column temperature is 35°C.

[0066] <Determination of the content of free diisocyanate monomer>

[0067] Based on the method of GB / T18583-2008, the present invention uses an Agilent GC-7890B gas chromatograph manufactured by Agilent to determine the content of residual monomers in the reaction system.

[0068] <NCO content (NCO%)>

[0069] The test of the NCO% content refers to the standard GB / T 12009.4.

[0070] <Determination of the content of the uretidione structure in polymers with more than three molecules>

[0071] According to the following method, the ratio D of the molar amount of the uretidione structure in polymers with more than three molecules in the polyisocyanate composition to the total molar amount of the uretidione structure in the composition is obtained. Specifically, the polyisocyanate composition is collected through gel permeation chromatography to obtain polymer components with more than three molecules, denoted as A. Through 13 13C NMR is used to test the content a of the uretidione structure in component A. The molar proportion of component A relative to the polyisocyanate composition is obtained by testing the mass proportion through gel permeation chromatography and conversion, denoted as m; the polyisocyanate composition is denoted as B. Through 13 13C NMR is used to test the content b of the uretidione structure in B. Then, the ratio D of the molar amount of the uretidione structure in polymers with more than three molecules in the composition to the total molar amount of the uretidione structure in the composition can be expressed as D = a*m / b.

[0072] Among them, gel permeation chromatography and 13The C-NMR test method refers to other test methods.

[0073] <Determination of the molar ratio of uretdione group to isocyanurate group>

[0074] In the polyisocyanate composition of the present invention, the molar ratio of the uretdione group to the isocyanurate group is determined by quantitative 13 CNMR test. The specific test conditions are as follows:

[0075] 13 C-NMR equipment: AVANCE600 (Bruker); BBO probe (Bruker); sample concentration: 30 wt%; resonance frequency: 150 MHz; chemical shift reference: 77.0 ppm (CDCl3); pulse program: zgig30; spectral width: 240 ppm; spectral center: 100 ppm

[0076] Isocyanurate group: integral value near 148.5 ppm / 3; Uretdione group: integral value near 157.5 ppm / 2.

[0077] <Coating film ethanol rubbing resistance test>

[0078] Mix the hydroxypropyl resin (AC1100B, Tongde Resin) and the polyisocyanate composition to prepare a coating, where the raw materials are added according to the molar ratio of isocyanate group to hydroxyl group of 1.1:1, the solid content of the coating is 40%, and the solvent is butyl acetate and xylene with a mass ratio of 1:1;

[0079] Ethanol rubbing resistance test: After the paint film is scrape-coated, it is baked at 70 °C for 30 min, left for 24 h, and then the ethanol rubbing resistance test is carried out using a solvent-resistant wiping instrument, and the number of rubbing resistances is recorded.

[0080] <Appearance and gloss of the coating film>

[0081] Mix the acrylic polyol AC1100B and the polyisocyanate composition in a ratio such that the molar ratio (NCO / OH) of the NCO group of the polyisocyanate composition to the OH group of the acrylic polyol is 1.0, and use "SOLVESSO #100" (trade name, an aromatic solvent manufactured by Exxon Corporation) to adjust to a solid content of 55% by mass to prepare a coating composition. Then, use spraying to coat the coating composition on an ABS board (acrylonitrile-butadiene-styrene resin; black, 150 mm × 75 mm) with a dry film thickness of 50 μm. After baking it under the conditions of 60 °C for 30 minutes, leave it standing for 1 week under the conditions of 23 °C and 50% humidity to form a coating film on the ABS board;

[0082] Appearance of the coating film (sharpness and surface smoothness): Measured along the long side direction of the ABS board using the digital oscilloscope "Wave Scan DOI" (manufactured by BYK Gardner). The "Wave Scan DOI" is configured as follows: The point light source of the laser irradiates the laser light at an angle of 60° relative to the perpendicular line to the film surface, and the detector receives the reflected light on the opposite side of the perpendicular line at the same angle. The device moves the point light source of the laser on the film surface and scans it, thereby measuring the brightness and darkness of the reflected light point by point at a specified interval, and can detect the optical profile of the film surface. The detected optical profile is subjected to spectral analysis through a filter, and the surface structure can be analyzed. Among them, the values in the Wb region (wavelength 0.3 - 1.0 mm) and Wc region (wavelength 1.0 - 3.0 mm) of the coating film are used for evaluation. The measured value is the arithmetic mean of three measured values. Both Wb and Wc are indicators of the appearance of the coating film. Wb is an indicator of the sharpness of the coating film, and Wc is an indicator of smoothness. The smaller the value, the better the judgment;

[0083] Gloss of the coating film: Measure the 60° gloss of the coating film using "UGV-6P" (manufactured by Suga Test Instruments Co., Ltd.).

[0084]

Examples and Comparative Examples

[0085] Refer to the following methods and the distinguishing parameters in Table 1 to prepare different polyisocyanate compositions respectively. The physical properties and application evaluation data of the products are shown in Table 1 and Table 2.

[0086] Step 1): Add 1000 g of diisocyanate monomer to a 2 L four-necked flask, heat it to 65 °C under nitrogen protection, add 1 g of an isooctanol solution of N,N,N-trimethylbenzylammonium hydroxide with a mass concentration of 5% under stirring conditions, and start timing. Control the reaction temperature at 65 - 70 °C. When the reaction reaches a certain conversion rate, add 0.08 g of dibutyl phosphate to terminate the reaction, and obtain reaction liquid X.

[0087] Step 2): Add 1000 g of diisocyanate monomer to a 2 L four-necked flask, heat it to 55 °C under nitrogen protection, add 2.0 g of tri-n-butylphosphine catalyst under stirring conditions, and start timing. Control the reaction temperature at 60 - 65 °C during the reaction. When the reaction reaches a certain conversion rate, add 2.1 g of dibutyl phosphate to terminate the reaction, and obtain reaction liquid Y.

[0088] Step 3): Blend 500 g of reaction liquid X, 300 g of reaction liquid Y, and 80 g of diisocyanate monomer, and then react at 160 °C for a certain time under nitrogen protection, and then lower the reaction temperature to room temperature to obtain reaction liquid Z.

[0089] Step 4): Using a thin-film evaporator, distill the above reaction liquid Z twice under the conditions of 160 °C and 10 Pa to obtain a polyisocyanate composition with a diisocyanate monomer content of less than 0.2%.

[0090] Table 1. Process parameters and physical property data of examples / comparative examples

[0091]

[0092] Table 2. Application test data of polyisocyanate compositions of examples / comparative examples

[0093]

[0094]

[0095] It can be seen from the above table data that when the molar ratio of the uretidione structure in the polyisocyanate composition with more than three molecules to the uretidione structure in the composition is (0.1 - 20):100, the composition not only has a lower viscosity but also has good crosslinkability, which can ensure comprehensive properties such as good gloss and excellent appearance of the coating film.

[0096] The present invention uses the above examples to illustrate the detailed method of the present invention, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polyisocyanate composition derived from aliphatic / alicyclic diisocyanate monomers, comprising trimers and polymers with more than three molecules formed by said diisocyanates, and containing isocyanurate structures and uretdione structures, characterized in that, the molar ratio of the uretdione structures in the polymers with more than three molecules in the composition to the uretdione structures in the composition is (0.1 - 20):

100.

2. The polyisocyanate composition according to claim 1, characterized in that, the molar ratio of the uretdione structures to the isocyanurate structures in the composition is (0.1 - 10):

100.

3. The polyisocyanate composition according to claim 1 or 2, characterized in that, the content of the diisocyanate trimer in the polyisocyanate composition is 40 - 80 wt%.

4. The polyisocyanate composition according to any one of claims 1 - 3, characterized in that, the viscosity measured at 25 °C is 100 - 4000 mPa·s.

5. The polyisocyanate composition according to any one of claims 1 - 4, characterized in that, the aliphatic / alicyclic diisocyanate monomer is selected from one or more of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, lysine diisocyanate, preferably pentamethylene diisocyanate or hexamethylene diisocyanate.

6. A coating composition comprising the polyisocyanate composition according to any one of claims 1 - 5.

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