Polyisocyanate composition, and coating layer having improved chemical resistance

Abstract

The present invention relates to the field of polyisocyanate compositions. Provided are a polyisocyanate composition and a coating layer having improved chemical resistance. The coating layer formed by a polyurethane coating composition based on the polyisocyanate composition provided by the present invention has remarkably improved chemical resistance and also has good comprehensive properties, such as good hardness and bending strength. The polyisocyanate composition is derived from at least one diisocyanate selected from aliphatic diisocyanates and cycloaliphatic diisocyanates. Among the compounds contained in the polyisocyanate composition, at least part of the compounds have isocyanurate groups, at least part of the compounds have at least one thioallophanate group, and in the polyisocyanate composition, the equivalent ratio of the thioallophanate groups to the isocyanurate groups is > 0 and ≤ 0.3.

Description

Polyisocyanate compositions and coatings with improved chemical resistance Technical Field

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

[0002] Aliphatic / alicyclic polyisocyanates have excellent properties such as weather resistance, wear resistance, and corrosion resistance, and are widely used in the coatings, adhesives, and elastomer industries, especially in the paint industry, including the most widely used polyisocyanate curing agents containing isocyanate groups.

[0003] Aliphatic polyisocyanate compositions containing isocyanurate groups have excellent yellowing resistance and, in addition, have advantages such as low free monomer content, saturated vapor concentration far below occupational safety limits, high functionality, and high downstream crosslinking density. Currently, numerous literature and patents report methods for preparing isocyanurate-containing polyisocyanate compositions from aliphatic and alicyclic diisocyanates in the presence of catalysts (e.g., J. Prakt. Chem. 336 (1994) 185-200, US Pat. No. 4,040,992, US Pat. No. 4,288,586, US Pat. No. 4,419,513, US Pat. No. 6,730,62, US Pat. No. 6,800,714, US Pat. No. 7,001,973, etc.).

[0004] Given the diversity of downstream application formulations, curing agents are often used in conjunction with high-hydroxyl resins to improve the crosslink density, mechanical properties, and chemical resistance of the paint film. However, due to the rigid structure of the isocyanurate ring, its compatibility in high-hydroxyl resin formulations is poor, resulting in thinning, cloudiness, and a bluish cast, which affects the gloss of the resulting paint film. Currently, the main approach to improving the compatibility of polyisocyanate compositions is alcohol modification, which involves introducing an alcohol into the system.

[0005] US460441 reports a polyisocyanate composition containing isocyanurate modified by the polymerization of polyisocyanate with diol or polyol to form a urea ester.

[0006] US6420508 discloses a two-step method for synthesizing a polyisocyanate composition with good compatibility by first self-polymerizing the polyisocyanate and then performing alcohol modification.

[0007] CN1074065 prepares a polyisocyanate composition, controls the isocyanurate trimer content to be ≤59%, and controls the equivalent ratio of allophanate groups to isocyanurate groups to be >0 and ≤0.19, and has good compatibility.

[0008] Although the compatibility problem can be partially solved by alcohol modification, the composition obtained by this route often has disadvantages such as low isocyanate group concentration leading to high curing agent dosage, and poor chemical resistance after film formation.

[0009] Summary of the Invention

[0010] The present invention provides a polyisocyanate composition and a coating with improved chemical resistance. The coating formed from the polyurethane coating composition based on the polyisocyanate composition provided by the present invention has significantly improved chemical resistance and can achieve good hardness and flexural strength.

[0011] To achieve its purpose, the present invention provides the following technical solutions:

[0012] In one aspect, the present invention provides a polyisocyanate composition, which is derived from at least one diisocyanate selected from aliphatic diisocyanates and alicyclic diisocyanates. Among the compounds contained in the polyisocyanate composition, at least some of the compounds have isocyanurate groups, and at least some of the compounds have at least one thioallophanate group. In the polyisocyanate composition, the equivalent ratio of the thioallophanate group to the isocyanurate group is greater than 0 and less than 0.3, for example, 0.001, 0.003, 0.005, 0.007, 0.010, 0.015, 0.020, 0.025, 0.030, 0.050, 0.070, 0.100, 0.150, 0.200, 0.250, 0.270, 0.300, etc.

[0013] The present inventors unexpectedly discovered that by controlling the equivalent ratio of the thioallophonate group to the isocyanurate group in the polyisocyanate composition to be greater than 0 and less than or equal to 0.3, the chemical resistance of the polyurethane coating based on the polyisocyanate composition can be improved while achieving good hardness and flexural strength.

[0014] Preferably, in the polyisocyanate composition, the equivalent ratio of the thioallophenate groups to the isocyanurate groups is 0.005-0.250. More preferably, the equivalent ratio of the thioallophenate groups to the isocyanurate groups is 0.005-0.100. Controlling the equivalent ratio of the polyisocyanate composition within the preferred range is beneficial for further improving the coating properties of the resulting polyurethane coating, while also achieving superior chemical resistance, hardness, and flexural strength.

[0015] In the present invention, the isocyanurate group refers to a group having the following structural units:

[0016] In the present invention, the thioallophonate group refers to a group having the following structural units:

[0017] The thioallophanate groups are distributed in polymers such as trimers, pentamers, heptamers and / or nonamers during the trimerization process.

[0018] In the present invention, the polyisocyanate composition, in addition to the isocyanurate group and the thioallophonate group, optionally contains (i.e., contains or does not contain) one or more of an iminooxadiazinedione group, a biuret group, a uretdione group, a thiocarbamate group, and a uretonimine group.

[0019] Wherein, the iminooxadiazinedione group refers to a group having the following structural units:

[0020] A biuret group is a group having the following structural units:

[0021] A uretdione group is a group having the following structural units:

[0022] A thiocarbamate group refers to a group having the following structural units:

[0023] The uretonimine group refers to a group having the following structural units:

[0024] The above structural units can all be detected by nuclear magnetic resonance spectroscopy.

[0025] In the polyisocyanate composition, the content of the isocyanurate group is ≥90 mol% and <100 mol%, based on the total amount of the isocyanurate groups and thioallophanate groups in the composition and the optionally present (i.e., present or absent) iminooxadiazinedione groups, biuret groups, uretdione groups, thiocarbamate groups and uretonimine groups. When the iminooxadiazinedione groups, biuret groups, uretdione groups, thiocarbamate groups and / or uretonimine groups are present, they are included in the total amount; when they are not present, their amount is 0. The content of the isocyanurate group is, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, etc.

[0026] Furthermore, the polyisocyanate composition can be obtained by reacting a reaction mass comprising a diisocyanate and a thiol compound, wherein the thiol compound is selected from at least one linear or branched, optionally substituted thiol compound. Preferably, the group reactive toward isocyanate groups in the thiol compound is a thiol group. Specifically, the thiol compound contains no other groups reactive toward isocyanate groups other than the thiol group. In some embodiments, for example, the thiol compound has a side chain that is inert toward isocyanate groups.

[0027] Preferably, the thiol compound has 1 to 20 carbon atoms, more preferably 6 to 12 carbon atoms; the thiol compound may be one or more of a monothiol and a polythiol. More preferably, the thiol compound is a monothiol, for example, a monothiol having 6 to 12 carbon atoms. The present inventors have found that the use of a monothiol in a subsequent polyurethane coating can better improve the coating performance compared to a polyisocyanate composition obtained by using a polythiol, achieving not only excellent chemical resistance, hardness, and flexural strength, but also excellent adhesion. Among them, the monohydric mercaptan is preferably selected from one or more of 1-hexyl mercaptan, 2-hexyl mercaptan, 3-hexyl mercaptan, 1-methylpentane-2-mercaptan, 3,3-dimethylbutane-1-mercaptan, 2-ethyl-butane-1-mercaptan, 1-methyl-1-pentane mercaptan, 3-methylpentane-2-mercaptan, 1-heptyl mercaptan, 2-heptyl mercaptan, 1-octan mercaptan, 2-octan mercaptan, 2-ethyl-1-hexyl mercaptan, 1-nonyl mercaptan, 2-nonyl mercaptan, 1-decyl mercaptan, 3-decyl mercaptan, 1-undecanethiol, undec-10-ene-1-mercaptan, 1-dodecanethiol, 2-dodecanethiol, and tert-dodecyl mercaptan.

[0028] The polythiol may be ethylene glycol bis(3-mercaptopropionate), butanedithiol, propanedithiol, 1,5-pentanedithiol, propane-1,2,3-trithiol, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), or the like.

[0029] The polyisocyanate composition of the present invention is derived from an aliphatic diisocyanate and / or an alicyclic diisocyanate. The phrase "derived from an aliphatic diisocyanate and / or an alicyclic diisocyanate" means that the primary raw materials used to prepare the polyisocyanate composition include at least an aliphatic diisocyanate and / or an alicyclic diisocyanate. The aliphatic diisocyanate and / or alicyclic diisocyanate used in the preparation process is selected from one or more of hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), 2-methylpentane-1,5-diisocyanate, 2,4,4-trimethyl-1,6-hexane diisocyanate, 2,2,4-trimethyl-1,6-hexane diisocyanate, 4-isocyanatomethyl-1,8-octane diisocyanate, 3-isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI), 4-isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI), isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane and 1,4-bis(isocyanatomethyl)cyclohexane (H6XDI), preferably one or two of hexamethylene diisocyanate (HDI) and pentamethylene diisocyanate (PDI).

[0030] The reaction is carried out in the presence of a catalyst.

[0031] The catalyst is preferably selected from one or more of quaternary ammonium hydroxides, quaternary ammonium carboxylates, compounds containing aminosilyl groups, tertiary amine compounds, and Mannich base compounds. The quaternary ammonium hydroxide is, for example, selected from one or more of tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, tetraethylammonium hydroxide, dimethylethylcyclohexylammonium hydroxide, and hydrates thereof, preferably one or more of tetramethylammonium hydroxide and trimethylbenzylammonium hydroxide, and hydrates thereof. The quaternary ammonium carboxylate is selected from, for example, tetramethylammonium hydroxide-2-ethylhexanoate, tetramethylammonium hydroxide-octanoate, trimethylbenzylammonium hydroxide-2-ethylhexanoate, trimethylbenzylammonium hydroxide-octanoate, tetramethylammonium hydroxide-formate, tetramethylammonium hydroxide-acetate, tetramethylammonium hydroxide-pivalate, trimethylbenzylammonium hydroxide-pivalate, tetramethylammonium hydroxide-decanoate, trimethylbenzylammonium hydroxide-decanoate, tetramethylammonium hydroxide-tetradecanoate, tetramethylammonium hydroxide-2-ethylhexanoate, tetramethylammonium hydroxide-octanoate, trimethylbenzylammonium hydroxide-2-ethylhexanoate, and one or more of trimethylbenzylammonium hydroxide-octanoate. The compound containing an aminosilyl group is selected from, for example, one or more of hexamethyldisilazane, silylamine, and heptamethyldisilazane, preferably hexamethyldisilazane. Further, the tertiary amine compound is, for example, one or two of triethylamine and tripropylamine, preferably triethylamine; Mannich base compounds are such as tris (N, N-dimethylaminomethyl) phenol, etc. The present inventors have found that the use of the above-mentioned preferred metal-free catalyst is conducive to obtaining a polyisocyanate composition that meets the equivalent ratio of thioallophenate groups to isocyanurate groups required in the present invention, and in particular, the target product can be obtained at a relatively low reaction temperature, for example, the target product of the present invention can be obtained at a reaction temperature not exceeding 80°C (e.g., 30-79°C, such as 45-75°C). In the present invention, the catalyst can be used as a pure substance or optionally dissolved in a solvent at any concentration. The amount of the catalyst added is preferably 0.001-0.1wt% of the starting diisocyanate used to prepare the polyisocyanate composition, such as 0.001wt%, 0.005wt%, 0.01wt%, 0.05wt%, 0.1wt%, etc., preferably 0.005-0.05wt%. The preferred catalyst amount is conducive to obtaining a polyisocyanate composition that meets the equivalent ratio of thioallophenate groups to isocyanurate groups required in the present invention.

[0032] In some preferred embodiments, when a polyisocyanate composition is prepared by reacting a starting diisocyanate and a thiol compound in the presence of a catalyst, the reaction temperature can be 10-150°C, for example, 10°C, 30°C, 50°C, 100°C, 120°C, 150°C, etc., preferably 30-79°C, more preferably 45-75°C. Reacting at the preferred temperature is conducive to obtaining a polyisocyanate composition that meets the equivalent ratio of thioalloylate groups to isocyanurate groups required by the present invention, while also taking into account good operational safety.

[0033] The polyisocyanate composition meeting the required equivalent ratio of thioalloylate groups to isocyanurate groups in the present invention can be obtained by adjusting the amounts of diisocyanate and mercapto compound, the NCO% value of the reaction system at the reaction end point, the type and amount of catalyst, and / or the reaction temperature.

[0034] In some embodiments, in the reaction system for preparing the polyisocyanate composition, the amounts of the diisocyanate and the thiol compound are such that the equivalent ratio of the thiol groups provided by the thiol compound to the isocyanate groups provided by the diisocyanate is greater than 0 and ≤ 0.06, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, etc. The specific amounts of the diisocyanate and the thiol compound used are determined so that the equivalent ratio of the thioallophenate groups to the isocyanurate groups in the prepared polyisocyanate composition meets the requirements of the present invention.

[0035] During the reaction process of preparing the polyisocyanate composition, the NCO% value of the reaction system is monitored. Preferably, the reaction endpoint of the reaction is when the NCO% value of the reaction system is in the range of 30-50%, for example, 30%, 35%, 37%, 40%, 45%, 47%, 50%, etc. When the reaction system reaches the target NCO%, the polymerization reaction is terminated. The inventors have found that when the NCO% value is greater than 50%, it often leads to problems such as low conversion rate, high monomer consumption and increased energy consumption required for subsequent monomer removal, and low functionality of the composition; when the NCO% value is less than 30%, the viscosity of the polyisocyanate composition is too high, which has an adverse effect on the convenience of downstream construction and the leveling of the paint film. Specifically, the polymerization reaction can be terminated by adding a catalyst poison to the reaction system. As catalyst poisons, acidic reactive substances such as protonic acids (for example, dibutyl phosphate) or acylating agents (for example, isophthalic acid dichloride) can be considered. In some examples, the catalyst poison is selected from one or more of a protonic acid and an acylating agent, preferably one or more of phosphoric acid, benzoic acid, diisooctyl phosphate, and dibutyl phosphate. It will be appreciated by those skilled in the art that different types of polymerization catalysts used in the reaction system may result in different amounts of the catalyst poison. In the reaction system of the present invention, the amount of the catalyst poison added is such that the polymerization catalyst in the system is inactivated.

[0036] In the present invention, the reaction liquid obtained by preparing the polyisocyanate composition can be treated with a single-stage or multi-stage thin film evaporator to remove unreacted monomers (diisocyanates). Specifically, for example, after treatment, the residual monomer content in the polyisocyanate composition is less than 0.5 wt % based on the mass of the composition.

[0037] In some embodiments, the viscosity of the polyisocyanate composition provided by the present invention is 2000-20000cp / 25°C, for example, 2000, 2500, 3000, 5000, 7000, 9000, 10000, 15000, 20000cp / 25°C, etc., for example, 2000-15000cp / 25°C, and the isocyanate group content is 20-25%.

[0038] The present inventors have discovered that, in a polyisocyanate composition obtained by reacting an aliphatic diisocyanate and / or an alicyclic diisocyanate with a monohydric thiol, under substantially the same conditions, a polyisocyanate composition having an equivalent ratio of thioallophenate groups to isocyanurate groups of >0 and ≤0.3 can produce a polyurethane coating composition obtained from a polyisocyanate composition that does not satisfy this equivalent ratio, particularly a two-component polyurethane coating system formed from an isocyanate group-reactive binder. The isocyanate group-reactive binder can be a type commonly used in the polyurethane coating field, such as one or more of polyether polyols, polyester polyols, polyurethane polyols, polysiloxane polyols, polycarbonate polyols, polyether polyamines, polyaspartic acid, polybutadiene polyols, polyacrylate polyols, and polyacrylic acid polyols.

[0039] In the present invention, NCO content (NCO%) is determined according to the method of GB / T 12009.4-2016, wherein NCO% refers to the mass percentage of isocyanate. Viscosity is measured using a BrookField DVI Prime viscometer with an S21 rotor at 25°C.

[0040] The present invention also provides use of the polyisocyanate composition described above as a crosslinking agent in a coating composition.

[0041] The present invention also provides a two-component polyurethane coating composition, comprising component A and component B, wherein component A comprises at least one of the polyisocyanate compositions described above, and component B comprises at least one adhesive that is reactive toward isocyanate groups. Regarding the two-component polyurethane coating composition, in addition to the polyisocyanate composition provided in the present invention, the remaining components and / or the amounts of each component can be conventionally selected for two-component polyurethane coating compositions, and there are no particular restrictions on this. Specifically, the adhesive that is reactive toward isocyanate groups is a hydroxyl resin. In some embodiments, the adhesive that is reactive toward isocyanate groups is one or more of polyether polyols, polyester polyols, polyurethane polyols, polysiloxane polyols, polycarbonate polyols, polyether polyamines, polyaspartic acid, polybutadiene polyols, polyacrylate polyols, polyacrylic acid polyols, and the like.

[0042] In some embodiments, in the two-component polyurethane coating composition, the molar ratio of the polyisocyanate composition, calculated based on the -NCO group content, to the hydroxyl content in the hydroxyl resin is 1:0.9-1:1.1.

[0043] In some embodiments, in the two-component polyurethane coating composition, other components may be added to component A and / or component B according to application requirements, for example, leveling agents, other auxiliary agents, additives, etc. The specific selection and specific amount of other components may be adjusted and determined according to actual application requirements.

[0044] The polyisocyanate composition of the present invention is present as a curing agent in a polyurethane coating composition. By preparing a polyurethane coating composition based on the polyisocyanate composition of the present invention, and particularly by introducing the polyisocyanate composition of the present invention into a two-component polyurethane coating composition having an isocyanate group-reactive binder as a main resin, a coating having significantly improved chemical resistance and good comprehensive properties such as pendulum hardness and flexural strength can be obtained.

[0045] The present invention further provides a coating having improved chemical resistance, obtained by applying the polyurethane coating composition described above to the surface of a substrate. This coating can be a film formed by applying the polyurethane coating to the surface of a substrate used in the fields of automobiles, wood products, etc. and acting as an adhesive.

[0046] The technical solution provided by the present invention has the following beneficial effects:

[0047] The polyisocyanate composition of the present invention is applied to polyurethane coatings, which is beneficial to improving the performance of the resulting coating film, enabling the resulting coating film to have improved chemical resistance and hardness, while also taking into account comprehensive properties such as good bending strength. DETAILED DESCRIPTION

[0048] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items.

[0050] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. Reagents or instruments used without specifying the manufacturer are all commercially available conventional products.

[0051] Description of the detection method:

[0052] NCO content: NCO content is determined according to the method of GB / T 12009.4-2016;

[0053] Residual monomer content: According to the method of GB / T18583-2008, the residual monomer content in the reaction system was determined by gas chromatography;

[0054] Viscosity: obtained using a BrookField DV-I Prime viscometer with an S21 spindle at 25°C;

[0055] In the present invention, the content (mol%) and equivalent ratio (mol ratio) of thioallophenate group and isocyanurate group in the polyisocyanate composition can be 13 The specific test conditions are as follows:

[0056] 13 C-NMR equipment: AVANCE600 (Bruker), equipped with a BBO probe (Bruker);

[0057] Sample concentration: 30wt%;

[0058] Resonance frequency: 150MHz;

[0059] Shift standard: 77.0ppm (CDCl3);

[0060] Pulse program: zgig30;

[0061] Spectral width: 240ppm;

[0062] Spectral center: 100ppm;

[0063] Chemical shift of isocyanurate group: 148ppm; Chemical shift of thioallophanate group: 173ppm and 153ppm; Chemical shift of iminooxadiazinedione group: 135ppm, 145ppm and 148ppm; Chemical shift of biuret group: 156ppm; Chemical shift of uretdione group: 157ppm; Chemical shift of thiocarbamate group: 167ppm, chemical shift of uretonimine group: 159ppm. In the embodiments and comparative examples, the content (% by mole) of isocyanurate group is based on the total amount of isocyanurate group, thioallophanate group and possible iminooxadiazinedione group, biuret group, uretdione group, thiocarbamate group and uretonimine group in the polyisocyanate composition prepared.

[0064] The equivalent ratio of the thioallophenate group to the isocyanurate group was calculated from the ratio of the integrated value near 148.5 ppm to (integrated value near 173 ppm + 153 ppm) / 2.

[0065] Materials and reagents:

[0066] HDI: Hexamethylene diisocyanate, Wanhua Chemical Group Co., Ltd.

[0067] PDI: Pentamethylene diisocyanate, Wanhua Chemical Group Co., Ltd.

[0068] 1-Hexanethiol: Aladdin Reagents;

[0069] 1-Octanethiol: Aladdin Reagents;

[0070] 1-Dodecanethiol: Aladdin Reagents;

[0071] Tetramethylammonium hydroxide-2-ethylhexanoate: Kent Chemical Co., Ltd.;

[0072] Tetramethylammonium hydroxide pentahydrate: Yinuokai Technology Co., Ltd.;

[0073] Acetone: Inokai Technology Co., Ltd.

[0074] Polyacrylic acid polyol: ACR6780, Foshan Gaoming Tongde Chemical Co., Ltd.

[0075] Ethylene glycol bis(3-mercaptopropionate): Aladdin Reagent Company.

[0076] [Example 1]

[0077] 750 g of PDI was added to a reaction kettle and heated to 50° C. under a nitrogen atmosphere with stirring. 13.5 g of 1-dodecanethiol was then added to the kettle and maintained at 50° C. 0.68 g of a 20 wt% solution of tetramethylammonium hydroxide-2-ethylhexanoate in acetone was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% value dropped to 39.4%, 0.09 g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature: 150° C., pressure: 12 Pa) to remove unreacted PDI monomer, thereby obtaining a polyisocyanate composition 1.

[0078] [Example 2]

[0079] 800 g of PDI was added to a reaction kettle and heated to 55°C under a nitrogen atmosphere with stirring. 8 g of 1-dodecanethiol was then added to the kettle and maintained at 55°C. 0.96 g of a 20 wt% solution of tetramethylammonium hydroxide-2-ethylhexanoate in acetone was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% dropped to 39.2%, 0.13 g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature: 150°C, pressure: 12 Pa) to remove unreacted PDI monomer, thereby obtaining polyisocyanate composition 2.

[0080] [Example 3]

[0081] 800 g of HDI was added to a reactor and heated to 70°C under a nitrogen atmosphere with stirring. 4 g of 1-dodecanethiol was then added to the reactor and maintained at 70°C. 1.12 g of a 5 wt% tetramethylammonium hydroxide pentahydrate solution (in acetone) was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% dropped to 40.2%, 0.04 g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature: 150°C, pressure: 12 Pa) to remove unreacted HDI monomer, yielding polyisocyanate composition 3.

[0082] [Example 4]

[0083] 900 g of PDI was added to a reaction kettle and heated to 60° C. under a nitrogen atmosphere with stirring. 3.6 g of 1-hexanethiol was then added to the kettle and maintained at 60° C. 0.95 g of a 20 wt% solution of tetramethylammonium hydroxide-2-ethylhexanoate in acetone was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% dropped to 47.6%, 0.13 g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature: 155° C., pressure: 10 Pa) to remove unreacted PDI monomer, thereby obtaining polyisocyanate composition 4.

[0084] [Example 5]

[0085] 800 g of PDI was added to a reaction kettle and heated to 55° C. under a nitrogen atmosphere with stirring. 14.4 g of 1-octanethiol was then added to the kettle and maintained at 55° C. 0.72 g of a 20 wt% solution of tetramethylammonium hydroxide-2-ethylhexanoate in acetone was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% value dropped to 37.5%, 0.10 g of diisooctyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature: 155° C., pressure: 10 Pa) to remove unreacted PDI monomer, thereby obtaining a polyisocyanate composition 5.

[0086] [Example 6]

[0087] 800 g of PDI was added to a reaction kettle and heated to 55° C. under a nitrogen atmosphere with stirring. 10.25 g of 1-dodecanethiol was then added to the kettle and maintained at 55° C. 0.60 g of a 20 wt% solution of tetramethylammonium hydroxide-2-ethylhexanoate in acetone was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% value dropped to 37.6%, 0.08 g of diisooctyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 160° C., pressure 10 Pa) to remove unreacted PDI monomer, thereby obtaining a polyisocyanate composition 6.

[0088] [Example 7]

[0089] 750 g of PDI was added to a reaction kettle and heated to 55° C. under a nitrogen atmosphere with stirring. 32.0 g of 1-dodecanethiol was then added to the kettle and maintained at 55° C. 1.58 g of a 20 wt% solution of tetramethylammonium hydroxide-2-ethylhexanoate in acetone was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% value dropped to 37.2%, 0.22 g of diisooctyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature: 180° C., pressure: 18 Pa) to remove unreacted PDI monomer, thereby obtaining polyisocyanate composition 7.

[0090] [Example 8]

[0091] 800 g of PDI was added to a reaction kettle and heated to 55° C. under a nitrogen atmosphere with stirring. 42.8 g of 1-dodecanethiol was then added to the kettle and maintained at 55° C. 0.95 g of a 20 wt% solution of tetramethylammonium hydroxide-2-ethylhexanoate in acetone was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% dropped to 45.5%, 0.13 g of phosphoric acid was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature: 150° C., pressure: 12 Pa) to remove unreacted PDI monomer, thereby obtaining polyisocyanate composition 8.

[0092] [Comparative Example 1]

[0093] 800 g of PDI was added to a reaction kettle and heated to 55° C. under a nitrogen atmosphere with stirring. 80 g of 1-dodecanethiol was then added to the kettle and maintained at 55° C. 0.80 g of a 20 wt% solution of tetramethylammonium hydroxide-2-ethylhexanoate in acetone was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% value dropped to 30.2%, 0.11 g of diisooctyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature: 150° C., pressure: 12 Pa) to remove unreacted PDI monomer, thereby obtaining a polyisocyanate composition A.

[0094] [Comparative Example 2]

[0095] The reaction was carried out in accordance with Example 3, except that 1-dodecanethiol was not added to the reaction system. The remaining operations were carried out in accordance with Example 3.

[0096] Comparative Example 2 obtained polyisocyanate composition B.

[0097] [Example 9]

[0098] 750g of PDI was added to a reaction kettle and heated to 50°C with stirring under a nitrogen atmosphere. Then, 7.95g of ethylene glycol bis(3-mercaptopropionate) was added to the kettle and maintained at 50°C. 0.68g of a 20wt% solution of tetramethylammonium hydroxide-2-ethylhexanoate in acetone was added dropwise to the system, and the NCO% of the reaction solution was measured. When the NCO% dropped to 38.4%, 0.09g of dibutyl phosphate was added to terminate the reaction. The reaction solution was separated using a short-path evaporator (separation temperature 150°C, pressure 12 Pa) to remove unreacted PDI monomer, yielding polyisocyanate composition C.

[0099] The index results of the polyisocyanate composition are listed in Table 1.

[0100] Table 1 Basic indicators of polyisocyanate composition products

[0101] The polyisocyanate compositions prepared in the above examples and comparative examples were respectively mixed with a hydroxyl resin (Tongde ACR6780) at an NCO / OH molar ratio of 1:1, and then diluted with a mixed solvent of ethyl acetate / xylene (mass ratio of 1:1) to obtain a paint having a polyisocyanate composition content of 40 wt%. The polyisocyanate compositions of Examples 1-8 corresponding to the final paints were respectively labeled as Paints 1-8, and the polyisocyanate compositions of Comparative Example 1, Comparative Example 2 and Example 9 corresponding to the final paints were respectively labeled as Paints A, B, and C.

[0102] The prepared paint was tested for adhesion and other properties as follows:

[0103] (1) Chemical resistance: GB / T 23989-2009, the sample was placed in a constant temperature and humidity environment (temperature: 75°C, humidity: 50%) for 1 week, the weight was 1 kg, the wiping speed was 60 times / min, the wiping solvent was butanone, and the substrate was tinplate;

[0104] (2) Pendulum hardness test: GB / T 1730, the substrate used is glass plate;

[0105] (3) Adhesion grade test: GB / T 9286, the substrate used is tinplate;

[0106] (4) Flexural strength: GB / T 11185-2009, Paints and varnishes bending test (conical mandrel), the substrate used is tinplate.

[0107] The test results are shown in Table 2.

[0108] Table 2 Test results of paint properties

[0109] The performance test results in Table 1 and Table 2 show that in the paints 1-8 and paint C obtained in Examples 1-9 of the present invention, a polyisocyanate composition in which the equivalent ratio of thioalloylate groups to isocyanurate groups is controlled to be greater than 0 and less than 0.3 is used. The resulting paints all have excellent chemical resistance, pendulum hardness, and flexural strength. However, the chemical resistance and pendulum hardness of paints A and B obtained in Comparative Examples 1 and 2 are significantly inferior to those of the paints obtained in the examples, and cannot simultaneously achieve good chemical resistance, pendulum hardness, and flexural strength.

[0110] While controlling the equivalent ratio of thioallophonate groups to isocyanurate groups in the polyisocyanate composition to be greater than 0 and less than or equal to 0.3, Examples 1-8 use monohydric mercaptan when preparing the polyisocyanate composition. As a result, the resulting paints, compared with the paint of Example 9 in which no monohydric mercaptan is used, not only have excellent chemical resistance, pendulum hardness, and bending strength, but also have excellent adhesion, whereas Example 9 cannot have both excellent adhesion.

[0111] Compared with Examples 1-7, the equivalent ratio of thioallophonate groups to isocyanurate groups in the polyisocyanate composition of Example 8 is not within the more preferred range of 0.005-0.100, and the performance of the resulting paint is inferior to that of the paints obtained in Examples 1-7.

[0112] It will be readily understood that the above embodiments are merely examples for clarity of description and are not intended to limit the present invention to these examples. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all possible implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A polyisocyanate composition, wherein the polyisocyanate composition is derived from at least one diisocyanate selected from aliphatic diisocyanates and alicyclic diisocyanates, wherein at least some of the compounds contained in the polyisocyanate composition have an isocyanurate group, and at least some of the compounds have at least one thioallophenate group; It is characterized in that In the polyisocyanate composition, the equivalent ratio of the thioallophenate group to the isocyanurate group is greater than 0 and less than or equal to 0.

3.

2. The polyisocyanate composition according to claim 1, It is characterized in that In the polyisocyanate composition, the equivalent ratio of the thioallophenate group to the isocyanurate group is 0.005-0.250, more preferably 0.005-0.

100.

3. The polyisocyanate composition according to claim 1 or 2, It is characterized in that In the polyisocyanate composition, the content of the isocyanurate groups is ≥90 mol % and <100 mol %, based on the total amount of the isocyanurate groups and thioalloylate groups in the composition and the optionally present iminooxadiazinedione groups, biuret groups, uretdione groups, thiocarbamate groups and uretonimine groups.

4. The polyisocyanate composition according to any one of claims 1 to 3, It is characterized in that The polyisocyanate composition can be obtained by reacting a reaction mass comprising the diisocyanate and a thiol compound, wherein the thiol compound is selected from at least one linear or branched and optionally substituted thiol compound; preferably, the group in the thiol compound that is reactive toward an isocyanate group is a thiol group.

5. The polyisocyanate composition according to claim 4, It is characterized in that The mercapto compound has 1 to 20 carbon atoms, preferably 6 to 12 carbon atoms; Preferably, the thiol compound is one or more of monohydric thiol and polyhydric thiol, more preferably monohydric thiol; Further preferably, the thiol compound is selected from 1-hexyl mercaptan, 2-hexyl mercaptan, 3-hexyl mercaptan, 1-methylpentane-2-mercaptan, 3,3-dimethylbutane-1-mercaptan, 2-ethyl-butane-1-mercaptan, 1-methyl-1-pentane mercaptan, 3-methylpentane-2-mercaptan, 1-heptyl mercaptan, 2-heptyl mercaptan, 1-octyl mercaptan, 2-octyl mercaptan, 2-ethyl-1-hexyl mercaptan. One or more of alcohol, 1-nonanethiol, 2-nonanethiol, 1-decanethiol, 3-decanethiol, 1-undecanethiol, undec-10-ene-1-thiol, 1-dodecanethiol, 2-dodecanethiol, and tert-dodecylthiol.

6. The polyisocyanate composition according to any one of claims 1 to 5, It is characterized in that The diisocyanate is selected from one or more of hexamethylene diisocyanate, pentamethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, 2,4,4-trimethyl-1,6-hexane diisocyanate, 2,2,4-trimethyl-1,6-hexane diisocyanate, 4-isocyanatomethyl-1,8-octane diisocyanate, 3-isocyanatomethyl-1-methylcyclohexyl isocyanate, 4-isocyanatomethyl-1-methylcyclohexyl isocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane and 1,4-bis(isocyanatomethyl)cyclohexane, preferably one or two of hexamethylene diisocyanate and pentamethylene diisocyanate.

7. The polyisocyanate composition according to any one of claims 4 to 6, It is characterized in that The reaction is carried out in the presence of a catalyst; the amount of the catalyst is preferably 0.001-0.1 wt % of the diisocyanate used to prepare the polyisocyanate composition, more preferably 0.005-0.05 wt %; Preferably, the catalyst is selected from one or more of quaternary ammonium hydroxides, quaternary ammonium carboxylates, aminosilyl-containing compounds, tertiary amine compounds, and Mannich base compounds; Further, the quaternary ammonium hydroxide is, for example, selected from one or more of tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, tetraethylammonium hydroxide, dimethylethylcyclohexylammonium hydroxide and hydrates thereof; Further, the quaternary ammonium carboxylate is, for example, selected from tetramethylammonium hydroxide-2-ethylhexanoate, tetramethylammonium hydroxide-octanoate, trimethylbenzylammonium hydroxide-2-ethylhexanoate, trimethylbenzylammonium hydroxide-octanoate, tetramethylammonium hydroxide-formate, tetramethylammonium hydroxide-acetate, tetramethylammonium hydroxide-pivalate, trimethylbenzylammonium hydroxide-pivalate, tetramethylammonium hydroxide-decanoate, trimethylbenzylammonium hydroxide-decanoate, tetramethylammonium hydroxide-tetradecanoate, tetramethylammonium hydroxide-2-ethylhexanoate, tetramethylammonium hydroxide-octanoate, trimethylbenzylammonium hydroxide-2-ethylhexanoate, and one or more of trimethylbenzylammonium hydroxide-octanoate; Furthermore, the aminosilyl-containing compound is, for example, one or more selected from hexamethyldisilazane, silylamine, and heptamethyldisilazane; Furthermore, the tertiary amine compound is selected from one or two of triethylamine and tripropylamine; Furthermore, the Mannich base compound is, for example, tris(N,N-dimethylaminomethyl)phenol.

8. The polyisocyanate composition according to any one of claims 4 to 7, It is characterized in that The reaction temperature of the reaction is 10-150°C, preferably 30-79°C, more preferably 45-75°C; And / or, the reaction endpoint of the reaction is that the NCO% value of the reaction system is in the range of 30-50%.

9. Use of the polyisocyanate composition according to any one of claims 1 to 8 as a crosslinking agent in a coating composition.

10. A two-component polyurethane coating composition, It is characterized in that The invention comprises component A and component B, wherein component A comprises at least one polyisocyanate composition according to any one of claims 1 to 8, and component B comprises at least one binder reactive to isocyanate groups.

11. A coating having improved chemical resistance, It is characterized in that The coating is obtained by applying the polyurethane coating composition according to claim 10 on the surface of a substrate.

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