Mixed isocyanate composition and application thereof in coating

Abstract

The invention provides a mixed isocyanate composition and application of the mixed isocyanate composition in a coating. The mixed isocyanate composition comprises a TMP-PDI prepolymer and a polyisocyanate curing agent. The mixed isocyanate composition provided by the invention comprises a TMP-PDI prepolymer and a polyisocyanate curing agent, and when the mixed isocyanate composition is applied to a curing agent of a two-component polyurethane coating, the weather resistance, chemical medium resistance, wear resistance, self-repairing property, pollution resistance and flexibility of a coating film can be remarkably improved, the potlife time of a coating solution is prolonged, and the coating film is not prone to falling off. And meanwhile, the coating also has other original properties of the two-component polyurethane coating.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, specifically relates to the field of isocyanates, more specifically relates to a mixed isocyanate composition and its application in coatings, and more specifically relates to a mixed isocyanate composition and its application in two-component polyurethane coatings. Background Art

[0002] At present, the demand for isocyanate curing agents in the coatings industry is large, and there are many types of curing agents, but they can basically be divided into three categories: aliphatic isocyanates, alicyclic isocyanates and aromatic isocyanates. When all isocyanate curing agents are used in two-component polyurethane coatings, we hope that they can play a better coating liquid construction, better coating film appearance, better coating film durability, better coating film physical and chemical properties and more competitive cost advantages.

[0003] CN117946358A discloses a polyisocyanate composition (tetramer) based on isophorone diisocyanate (IPDI) for use as a polyurethane coating, which can significantly improve the brittleness of the paint film and enhance the impact resistance of the paint film.

[0004] CN109627957A discloses a mixed isocyanate of TDI and HDI as a polyurethane coating curing agent component B, which is matched with a suitable polyurethane coating component A to prepare a coating for melamine boards, which has the characteristics of good adhesion, good yellowing resistance, good hardness, high gloss and the like.

[0005] CN109423178A discloses a polyurethane coating, which is prepared through the synergistic effect of various components, and has a bright paint film, good yellowing resistance, hardness, wear resistance, and is not easy to powder.

[0006] Although the above methods can improve some properties of polyurethane coatings, some other properties, such as coating liquid construction properties, coating film physical and chemical properties, coating film weather resistance, etc., still need to be further improved to enhance the reliability of polyurethane coatings in the fields of automotive protection, photovoltaic protection, and wind power protection in response to extreme climatic conditions, such as strong ultraviolet radiation, strong winds and sand, extreme cold, and high humidity environments in coastal areas, overcome the limitations of existing coatings, and comprehensively improve the performance of coatings.

[0007] Therefore, it is urgent to develop a mixed isocyanate composition, which can be used as a curing agent component of polyurethane coatings to improve the overall performance of polyurethane coatings and adapt to a wider range of application scenarios. Summary of the invention

[0008] In view of the deficiencies in the prior art, one of the objects of the present invention is to provide a mixed isocyanate composition. The second object of the present invention is to innovatively apply the mixed isocyanate composition as a curing agent B component of a two-component polyurethane coating and component A with an anti-aging additive added in the coating.

[0009] The present invention utilizes a synthesized TMP-PDI prepolymer (trimethylolpropane-pentamethylene diisocyanate prepolymer) mixed with a polyisocyanate curing agent as a coating component B, and a coating component A added with an anti-aging additive to form a two-component polyurethane coating, and can prepare a polyurethane coating that is superior to the two-component polyurethane coating using only a polyisocyanate curing agent in terms of coating liquid construction performance, coating film weather resistance, coating film physical and chemical properties, etc.

[0010] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a mixed isocyanate composition, wherein the mixed isocyanate composition comprises a TMP-PDI prepolymer and a polyisocyanate curing agent.

[0012] The mixed isocyanate composition provided by the present invention includes a TMP-PDI prepolymer and a polyisocyanate curing agent. When used as a curing agent for a two-component polyurethane coating, the weather resistance, chemical resistance, wear resistance, self-repairing property, anti-fouling property, and flexibility of the coating film can be significantly improved, and the potlife time (coating construction window time) of the coating liquid can be extended, while at the same time having other original properties of the two-component polyurethane coating.

[0013] Preferably, the TMP-PDI prepolymer is terminated with an isocyanate group and is obtained by reacting a polyisocyanate component containing PDI and an alcohol component containing TMP.

[0014] Preferably, the polyisocyanate other than PDI in the polyisocyanate component includes any one of aliphatic isocyanate, alicyclic isocyanate or aromatic isocyanate, or a combination of at least two thereof.

[0015] Preferably, the alcohol other than TMP in the alcohol component includes a diol and / or a triol having a molecular weight of 62 to 200.

[0016] Preferably, the diol includes any one of methylpropylene glycol, 1,3-butanediol, 1,4-butanediol, diethylene glycol, ethylene glycol, dipropylene glycol, 1,3-propanediol, 1,2-propanediol, neopentyl glycol or 1,6-hexanediol, or a combination of at least two thereof.

[0017] Preferably, the triol includes any one of glycerol, 1,2,6-hexanetriol, and trimethylolethane, or a combination of at least two thereof.

[0018] Preferably, in the polyisocyanate component, the mass percentage of PDI is 50% to 100%, for example, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 100%, etc., preferably 100%.

[0019] Preferably, in the alcohol component, the mass percentage of TMP is 50% to 100%, for example, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 100%, etc., preferably 100%.

[0020] The main component structure of the TMP-PDI prepolymer is as follows:

[0021]

[0022] Preferably, the TMP-PDI prepolymer is prepared by the following method:

[0023] The polyisocyanate component containing PDI and the alcohol component containing TMP are reacted to obtain a reaction liquid, and then the unreacted polyisocyanate component is removed to obtain the TMP-PDI prepolymer.

[0024] Preferably, the molar ratio of -NCO in the polyisocyanate component to -OH in the alcohol component is (2-20):1, for example 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1, 20:1, etc., preferably (5-10):1.

[0025] Preferably, the reaction temperature is 50-120°C, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, etc., preferably 60-110°C.

[0026] The reaction is stopped when the isocyanate content in the system no longer changes. Preferably, the reaction time is 0.5 to 10 hours, such as 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc., preferably 1 to 5 hours.

[0027] Preferably, the removing of the unreacted polyisocyanate component specifically comprises removing the unreacted polyisocyanate component by using a thin film evaporation device.

[0028] Preferably, when removing the unreacted polyisocyanate component, the separation temperature is 80-160°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, etc., preferably 80-120°C, and the separation pressure is 5-200Pa, for example, 5Pa, 10Pa, 20Pa, 40Pa, 60Pa, 80Pa, 100Pa, 120Pa, 140Pa, 160Pa, 180Pa, 200Pa, etc., preferably 5-50Pa.

[0029] Preferably, the polyisocyanate curing agent contains any one of an isocyanurate ring, a benzene ring or a n-hexyl ring, or a combination of at least two of them.

[0030] Preferably, the polyisocyanate curing agent includes any one of aliphatic isocyanate, alicyclic isocyanate or aromatic isocyanate curing agent or a combination of at least two, preferably PDI trimer curing agent, HDI trimer curing agent, isophorone diisocyanate (IPDI) curing agent, hydrogenated benzyl diisocyanate curing agent, diphenylmethane diisocyanate (MDI) curing agent, toluene diisocyanate (TDI) curing agent, benzyl diisocyanate curing agent or TDI-TMP prepolymer curing agent or any one of a combination of at least two.

[0031] Preferably, based on the total mass of the mixed isocyanate composition as 100%, the content of the TMP-PDI prepolymer is 5% to 90%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc., preferably 20% to 80%.

[0032] The present invention does not specifically limit the preparation method of the mixed isocyanate composition. For example, the mixed isocyanate composition can be obtained by uniformly mixing the TMP-PDI prepolymer and the polyisocyanate curing agent.

[0033] In a second aspect, the present invention provides a two-component polyurethane coating, the two-component polyurethane coating comprising component A and component B;

[0034] The component A comprises the following components in parts by weight:

[0035]

[0036] The B component comprises the following components in parts by weight:

[0037] 70 to 90 parts of the mixed isocyanate composition of the first aspect;

[0038] 10-30 parts of solvent;

[0039] The auxiliary agent in the A component includes an anti-aging auxiliary agent.

[0040] The present invention uses the mixed isocyanate composition containing at least TMP-PDI prepolymer provided in the first aspect as the B component of the two-component polyurethane coating, and adds a two-component polyurethane coating component A to which a specific anti-aging additive is added. This synergistic combination can prepare a two-component polyurethane coating with higher performance than using only a polyisocyanate curing agent or a TMP-PDI prepolymer as the B component of the coating. This high performance is mainly reflected in the following aspects: a. Better weather resistance of the coating, which is specifically manifested in better gloss retention and resistance to paint cracking after the QUV-B test; b. Better medium resistance of the coating, which is specifically manifested in better color retention after the gasoline test; c. Better wear resistance and self-repairing of the coating, which are specifically manifested in better gloss retention after the wear test and higher gloss recovery after low-temperature baking of the coating again; d. Better stain resistance of the coating, which is specifically manifested in better gloss retention and color retention after the stain test; e. Better flexibility, which is specifically manifested in that the coating has better bending flexibility and impact resistance without losing hardness; f. Longer coating liquid construction window time, which is specifically manifested in that the time for the coating liquid viscosity to double is significantly extended under construction conditions; at the same time, it also has other original properties of polyurethane two-component coatings.

[0041] In the present invention, the amount of the resin in component A can be 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, etc., preferably 50 to 70 parts.

[0042] In the present invention, the amount of pigment and filler in component A can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, etc., by weight.

[0043] In the present invention, the amount of the solvent in component A can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, etc., preferably 30 to 50 parts.

[0044] In the present invention, the amount of the auxiliary agent in component A can be 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts, 1 parts, 2 parts, 3 parts, 4 parts, 5 parts, etc., based on parts by weight.

[0045] In the present invention, the amount of component B in the mixed isocyanate composition described in the first aspect can be 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, etc., calculated by weight.

[0046] In the present invention, the amount of the solvent in component B can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, etc., based on parts by weight.

[0047] Preferably, the anti-aging aid comprises an ultraviolet light absorber and / or a free radical scavenger.

[0048] Preferably, the anti-aging aid comprises an ultraviolet light absorber and a free radical scavenger in a mass ratio of 1:3 to 3:1 (eg, 1:3, 1:2, 1:1, 2:1, 3:1, etc.).

[0049] Preferably, the ultraviolet light absorber includes any one of hydroxymethylphenolbenzotriazoles and hydroxyphenoltriazines, or a combination of at least two of them.

[0050] Preferably, the free radical scavenger includes any one of a hindered phenol light stabilizer and a hindered amine light stabilizer or a combination of at least two thereof, and a particularly recommended free radical scavenger structure is 2,2,6,6-tetramethylpiperidine and its substituted derivative series.

[0051] Preferably, the recommended brands of ultraviolet light absorbers are: TINUVIN 1130, TINUVIN 400, TINUVIN 384-2, etc.

[0052] Preferably, the recommended free radical scavenger brands are: TINUVIN 123, TINUVIN 292, etc.

[0053] Preferably, the resin comprises any one or a combination of at least two of hydroxy acrylic resin, polyester polyol resin or polyhydroxy alkyd resin used in surface coatings. Recommended resin grades include: SETALUX 1753SS-70, SETALUX1910 BA-75, SETAL1606 BA-80, ETERKYD 3106-X-70, etc.

[0054] Preferably, the main feature of the solvent in the A component and the B component is one or more combinations of polyurethane-grade aprotic solvents. Recommended solvents include: any one of butyl acetate (e.g., n-butyl acetate BAC), S-100A, propylene glycol methyl ether acetate, and ethylene glycol butyl ether acetate, or a combination of at least two thereof.

[0055] Preferably, the auxiliary agent in the A component further includes a substrate wetting and leveling agent and / or a defoaming agent.

[0056] Preferably, the substrate wetting and leveling agent recommended is BYK306, BYK358N, etc.

[0057] Preferably, the defoaming agent recommended is BYK024, BYK093, etc.

[0058] Preferably, the additives in component A include 0.1 to 4 parts (e.g., 0.1, 0.5, 0.8, 1, 2, 3, 4, etc.) of anti-aging additives, 0.05 to 0.5 parts (e.g., 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, etc.) of substrate wetting and leveling agents, and 0 to 0.2 parts (e.g., 0, 0.05, 0.1, 0.2, etc.) of defoaming agents.

[0059] Preferably, the auxiliary agent in the component A also includes a drying agent.

[0060] Preferably, the drying agent comprises T-12 drying agent.

[0061] Preferably, the molar ratio of -NCO in the B component to -OH in the A component is (0.8-1.2):1, for example, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, etc.

[0062] The present invention does not specifically limit the preparation method of the two-component polyurethane coating. For example, the two-component polyurethane coating can be obtained by mixing component A and component B.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] Compared with using a single polyisocyanate curing agent or TMP-PDI prepolymer as the coating component B, the mixed isocyanate composition provided by the present invention as the coating component B, and the coating component A with the addition of an anti-aging additive can prepare a higher performance two-component polyurethane coating. The high performance is specifically reflected in: the coating liquid has a longer potlife time, the coating film has better gloss retention and resistance to paint film cracking after the QUV-B test, the coating film has better color retention after the gasoline resistance test, the coating film has better gloss retention after the wear resistance test and higher gloss recovery after the coating film is baked at low temperature again, the coating film has better gloss retention and color retention after the stain resistance test, and the coating film has better bending flexibility and impact resistance without losing hardness. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 , Figure 2 This is a GPC test result diagram of the TMP-PDI prepolymer synthesized in the present invention, wherein: Figure 1 is the peak time diagram, Figure 2 Molecular weight distribution diagram. DETAILED DESCRIPTION

[0066] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0067] The following test method is used in the implementation case of the present invention:

[0068] (1) Viscosity measurement method: Viscosity was measured at 25°C using a BrookeField DV-NT viscometer in accordance with the national standard GB 12009.3.

[0069] (2) NCO group test method: The isocyanate content was determined using a method based on the national standard GB 12009.4.

[0070] (3) Chromaticity test method: Tested using a Sanx YS6060 spectrophotometer and a 10*50 mm cuvette.

[0071] (4) Potlife measurement method: The DING-4 cup method is used for measurement.

[0072] (5) Gloss measurement method: BYK gloss meter was used for testing in accordance with GB / T 9754-2007.

[0073] (6) Color difference measurement method: X-rite Ci60 spectrophotometer was used for measurement.

[0074] (7) Medium resistance measurement method: The test is carried out based on the method of GB / T 9274-1988 A (immersion method).

[0075] (8) Flexibility and impact resistance measurement method: The test is carried out using methods based on national standards GB / T 6742-2007 and GB / T1732-2020.

[0076] (9) Paint film drying and hardness measurement method: Inspection is carried out using methods based on national standards GB / T 1730-2007 and GB / T1728-2020.

[0077] (10) Weather resistance measurement method: The test was conducted using the method based on Appendix C of GB / T 14522-2008 and Cycel A of GB / T1865-2009.

[0078] (11) Abrasion resistance and self-healing property measurement method: 2500 mesh 3M 401Q circular sandpaper and 500 g weight were used to sand the paint film surface twice, and then the dust was wiped off with a dust-free cloth. The gloss of the sanded area was tested with a gloss meter to evaluate the degree of gloss loss. The sanded coating was then placed in a 60°C oven for 2 h. After being taken out, the gloss of the sanded area was tested with a gloss meter to evaluate the degree of gloss recovery.

[0079] (12) Stain resistance measurement method: Prepare a resin-free black slurry aqueous solution with a carbon black content of 5%, immerse the test sample in the black slurry solution, place it in a 40°C water bath for 48 hours, then take it out, rinse the coating surface with clean water and evaluate the gloss and color change of the coating surface.

[0080] The preparation of component A of the polyurethane coating, the selection of raw materials and the amount (parts by weight) are as follows:

[0081]

[0082] The above components were put into a container in sequence, dispersed and mixed evenly with a high-speed disperser at 600 rpm for 20 min, and used as component A of the polyurethane coating.

[0083] The preparation process of TMP-PDI prepolymer is as follows:

[0084] TMP pretreatment: Remove moisture from TMP by vacuum distillation at 105°C until the water content of TMP is ≤500ppm.

[0085] Preparation of reaction solution: Control the molar ratio of NCO to OH to be 8:1, and drop the molten TMP into the PDI component within 1 hour. After the dropwise addition is completed, control the reaction temperature of the materials to 90°C, react for 2 hours, and obtain a TMP-PDI reaction solution.

[0086] Monomer removal: The remaining PDI monomer is removed by thin film evaporation. The separation temperature of the thin film evaporation is 140° C. and the vacuum degree is 10 Pa. After the monomer is removed, TMP-PDI prepolymer is obtained.

[0087] After testing, the product parameters of the obtained TMP-PDI prepolymer are as follows:

[0088] GPC test results are shown in the figure Figure 1 , Figure 2 As shown, Figure 1 is the peak time diagram, Figure 2 is the molecular weight distribution diagram;

[0089] Viscosity @25℃: 62800mpa.s;

[0090] NCO group content: 18.88%;

[0091] Color value: 5.

[0092] Examples 1-3

[0093] Provide a coating B component respectively, the selection and amount of raw materials (parts by weight) are as follows:

[0094] Curing agent formula name Example 1 Example 2 Example 3 TMP-PDI prepolymer 16 40 64 ALIPHANE PT 3000 64 40 16 n-Butyl acetate 20 20 20 Viscosity (25℃)mpa.s 156 238 500 NCO content 18.82％ 17.30％ 16.12％ Hazen 10 8 5

[0095] Among them, ALIPHANE PT 3000 is a PDI trimer produced by Moga (Shanghai) Biotechnology Co., Ltd. (specifications are shown in the table below).

[0096] characteristic Numeric unit Test Method NCO content 25±0.3 ％ Dibutylamine method Viscosity (23℃) 3000±500 mPa·s Rotational viscometer method Hazen ＜40 Platinum-cobalt colorimetry Monomer PDI ＜0.1 ％ Gas chromatography Trimer content ＞60 ％ GPC Gel Permeation Chromatography

[0097] Embodiment 4-6

[0098] Provide a coating B component respectively, the selection and amount of raw materials (parts by weight) are as follows:

[0099] Curing agent formula name Example 4 Example 5 Example 6 TMP-PDI prepolymer 16 40 64 Desmodur N3300 64 40 16 n-Butyl acetate 20 20 20 Viscosity (25℃)mpa.s 161 242 510 NCO content 16.85％ 16.12％ 15.46％ Hazen 8 6 5

[0100] Comparative Examples 1-3

[0101] Provide a coating B component respectively, the selection and amount of raw materials (parts by weight) are as follows:

[0102]

[0103]

[0104] Application Examples

[0105] The coating component B obtained in the above examples 1, 2, 3, 4, 5, 6 and comparative examples 1, 2, 3 was used in combination with the prepared polyurethane coating component A 1 and 2, and the coating property test was carried out. The test items are as follows:

[0106] (1) Construction potlife performance test

[0107] The isocyanate curing agent component B obtained in the above Examples 1, 2, 3, 4, 5, 6 and Comparative Examples 1, 2, 3 was mixed with the prepared coating component A 2 at a molar ratio of -NCO to -OH of 1:1, and after mixing evenly, the construction viscosity was tested using the DIN-4 cup method.

[0108] Table 1: Variation of coating liquid viscosity at 35°C (0% T-12 catalyst, DIN-4 cup / 25°C, unit: s)

[0109] 0h 1h 3h 5h 7h Example 1 18.12 20.53 28.35 43.67 95.73 Example 2 18.32 19.89 25.88 36.78 61.55 Example 3 18.56 19.05 20.66 24.89 35.68 Example 4 18.16 21.23 30.43 55.28 150.80 Example 5 18.43 20.46 26.74 38.92 65.43 Example 6 18.67 19.25 21.03 25.36 37.84 Comparative Example 1 18.03 22.03 35.62 68.86 210.20 Comparative Example 2 18.10 22.45 45.21 95.35 300 Comparative Example 3 18.98 19.10 19.81 22.67 24.93

[0110] The isocyanate curing agent component B obtained in the above Examples 1, 2, 3, 4, 5, 6 and Comparative Examples 1, 2, 3 was mixed with the prepared coating component A 2 at a molar ratio of -NCO to -OH of 1:1, and 0.03% by mass of the T-12 catalyst based on the solid content of the two-component varnish was added and mixed. After mixing evenly, the construction viscosity was tested using the DIN-4 cup method.

[0111] Table 2: Variation of coating fluid viscosity at 35°C (0.03% T-12 catalyst, DIN-4 cup / 25°C, unit: s)

[0112] 0h 1h 2h 3h 4h Example 1 18.03 24.31 41.28 86.23 180.94 Example 2 18.21 23.25 35.62 60.58 120.69 Example 3 18.46 22.53 27.85 37.23 72.83 Example 4 18.14 25.72 54.89 100.75 280 Example 5 18.42 24.62 39.88 78.39 160.63 Example 6 18.56 23.02 29.31 43.65 90.27 Comparative Example 1 18.01 26.25 46.38 101.24 260.01 Comparative Example 2 18.08 27.43 57.69 158.92 300 Comparative Example 3 18.88 21.62 24.83 30.45 43.62

[0113] (2) Coating weather resistance test

[0114] 70mm*150m*0.8mm specification aluminum plate, use 1000 mesh sandpaper to polish the surface of the aluminum plate evenly, and then use butyl acetate to wipe the surface of the aluminum plate. The aluminum plate that has been cleaned is sprayed with plain white primer, and the spray film thickness DFT is controlled to be 20-25μm. After the plain white primer is sprayed, the surface is dried at room temperature for 15-20min. The curing agent B component of the above-mentioned embodiments 1, 2, 3, 4, 5, 6 and comparative examples 1, 2, 3 is respectively mixed with the prepared coating A component 1 and 2 according to the molar ratio of -NCO to -OH of 1.1:1 to prepare varnish, and the prepared varnish is sprayed on the plain white primer, and the varnish spray film thickness DFT is controlled to be 40-50μm. After the varnish is sprayed, it is leveled at room temperature for 10-15min, and then placed in an 80℃ oven for drying for 30min, and then placed at room temperature for 7d for curing until it is completely cured. Subsequently, the coating weather resistance test was carried out based on the national standards GB / T 1865-2009 cycel A (xenon lamp aging) and GB / T 14522-2008 Appendix C (QUV-B ultraviolet aging).

[0115] Table 3

[0116] Coating film xenon lamp aging test data (coating A component 1 is matched with examples 1-6 and comparative examples 1-3 respectively)

[0117]

[0118]

[0119]

[0120] Table 4 Coating Xenon lamp aging test data (Coating A component 2 is matched with Examples 1-6 and Comparative Examples 1-3)

[0121]

[0122]

[0123] Table 5 Coating QUV-B test data (coating A component 1 is matched with examples 1-6 and comparative examples 1-3)

[0124]

[0125] Table 6 Coating QUV-B test data (Coating A component 2 is matched with comparative examples 1-3 and examples 1-6 respectively)

[0126]

[0127]

[0128] (3) Effect of anti-aging additive ratio on coating weather resistance

[0129] 70mm*150m*0.8mm specification aluminum plate, use 1000 mesh sandpaper to polish the surface of the aluminum plate evenly, and then use butyl acetate to wipe the surface of the aluminum plate. The aluminum plate that has been cleaned is sprayed with plain white primer, and the spray film thickness DFT is controlled to be 20-25μm. After the plain white primer is sprayed, the surface is dried at room temperature for 15-20min. The curing agent B component of the above-mentioned embodiments 2 and 5 is respectively mixed with the prepared coating A component 2, 3, 4, and 5 according to the molar ratio of -NCO to -OH of 1.1:1 to prepare varnish, and the prepared varnish is sprayed on the plain white primer, and the varnish spray film thickness DFT is controlled to be 40-50μm. After the varnish is sprayed, it flows at room temperature for 10-15min, and then puts it into an 80℃ oven for drying for 30min, and then puts it at room temperature for 7d to cure until it is completely cured. Subsequently, the coating weather resistance test was carried out using a method based on Appendix C (QUV-B ultraviolet aging) of GB / T 14522-2008.

[0130] Table 7 Coating QUV-B test data (coating A components 2-5 are matched with embodiments 2 and 5 respectively)

[0131]

[0132]

[0133] (4) Chemical resistance test

[0134] 70mm*150mm*0.6mm specification PPG electrophoresis steel plate, wipe the surface of the electrophoresis steel plate with butyl acetate. Then spray white primer, spray white primer on the electrophoresis steel plate after cleaning, control the spray film thickness DFT = 20-25μm, and dry at room temperature for 15-20min after the white primer is sprayed. Mix the curing agent B component of the above examples 1, 2, 3, 4, 5, 6 and comparative examples 1, 2, 3 with the prepared coating A component 2 according to the molar ratio of -NCO to -OH of 1:1 to prepare varnish, spray the prepared varnish on the white paint surface, control the spray film thickness DFT = 40-50μm, and level the varnish at room temperature for 10-15min, then put it in an 80℃ oven to dry for 30min, and then leave it at room temperature for 7d to cure until it is completely cured. The coating medium resistance performance test is carried out by the method of national standard GB / T 9274-1988 A method (immersion method).

[0135] Table 8

[0136] Test data of coating film medium resistance performance (coating A component 2 is matched with examples 1-6 and comparative examples 1-3 respectively)

[0137]

[0138] (5) Coating wear resistance and self-healing performance test

[0139] A4 specification tinplate, wipe the surface of the substrate with butyl acetate, and spray the cleaned tinplate with plain white primer, control the spray film thickness DFT = 20-25μm, and dry the surface at room temperature for 15-20min after the plain white primer is sprayed. The curing agent B component of the above examples 1, 2, 3, 4, 5, 6 and comparative examples 1, 2, 3 and the prepared coating A component 2 are mixed with the molar ratio of -NCO to -OH of 1:1 to prepare varnish, and the prepared varnish is sprayed on the plain white primer, and the varnish spray film thickness DFT = 40-50μm is controlled. After the varnish is sprayed, it is leveled at room temperature for 10-15min, then placed in an 80℃ oven for 30min, and then placed at room temperature for 7d to cure until it is completely cured. The wear resistance and self-repairing measurement method is used to test the wear resistance and self-repairing properties of the coating film.

[0140] Table 9

[0141] Test data of coating film wear resistance and self-repair performance (coating A component 2 is matched with examples 1-6 and comparative examples 1-3 respectively)

[0142]

[0143] (6) Film stain resistance test

[0144] The surface of the PPG electrophoresis steel plate with a specification of 70mm*150mm*0.6mm was wiped with butyl acetate, and the substrate after cleaning was sprayed with a plain white primer, and the spray film thickness DFT was controlled to be 20-25μm. After the plain white primer was sprayed, the surface was dried at room temperature for 15-20min. The curing agent B component of the above-mentioned Examples 1, 2, 3, 4, 5, 6 and Comparative Examples 1, 2, 3 and the prepared coating A component 2 were mixed at a molar ratio of -NCO to -OH of 1:1 to prepare a varnish, and the prepared varnish was sprayed on the plain white primer, and the spray film thickness DFT was controlled to be 40-50μm. After the varnish was sprayed, it was leveled at room temperature for 10-15min, and then placed in an 80℃ oven for drying for 30min, and then placed at room temperature for 7d to cure until it was completely cured. The stain resistance measurement method was used for testing.

[0145] Table 10

[0146] Test data of coating film stain resistance (coating A component 2 is matched with examples 1-6 and comparative examples 1-3 respectively)

[0147] Gloss retention rate (20° / 60°) Color retention (ΔE) Example 1 92％ / 98％ 2.0 Example 2 95％ / 99％ 1.5 Example 3 91％ / 97％ 2.2 Example 4 93％ / 98％ 2.1 Example 5 96％ / 100％ 1.6 Example 6 92％ / 98％ 2.4 Comparative Example 1 90％ / 97％ 3.0 Comparative Example 2 91％ / 97％ 3.2 Comparative Example 3 85％ / 95％ 3.5

[0148] (7) Flexibility and impact test

[0149] For a tinplate with a specification of 70mm*150mm*0.4mm, use 1000 mesh sandpaper to evenly polish the surface of the tinplate and clean the surface of the tinplate with a dust-free wipe cloth dipped in butyl acetate. The isocyanate curing agent B component obtained in the above Examples 1, 2, 3, 4, 5, 6 and Comparative Examples 1, 2, 3 is mixed with the prepared coating A component 2 at a molar ratio of -NCO to -OH of 1:1 to prepare a varnish, and the varnish is scraped on the tinplate using a 100μm wire rod. After scraping, level at room temperature for 10-15min, and completely dry and solidify the coating film in an oven at 80℃ for 8h. The prepared test sample adopts the national standard GB / T 6742-2007 and GB / T 1732-2020 to test the flexibility and impact resistance of the coating film.

[0150] Table 11

[0151] Coating film flexibility test data (coating A component 2 is matched with comparative examples 1-3 and examples 1-6 respectively)

[0152]

[0153]

[0154] (8) Film drying test

[0155] The isocyanate curing agent component B obtained in the above Examples 1, 2, 3, 4, 5, 6 and Comparative Examples 1, 2, 3 and the prepared coating component A 2 were mixed at a molar ratio of -NCO to -OH of 1:1 to prepare a two-component varnish. The T-12 drier addition scheme selected a 0% T-12 scheme and a 0.03% addition scheme accounting for the solid content of the two-component varnish. The varnish was evenly scraped on a tinplate using a 100 μm wire rod and dried according to the specified conditions. The surface drying and actual drying properties of the coating film were evaluated by the touch surface drying test method of GB / T1728-2020 and the filter paper actual drying test method. At the same time, the K pendulum hardness test method of GB / T 1730-2007 was used to measure the coating film hardness.

[0156] Table 12

[0157] Film drying test data (adding 0% T-12 drier with two-component varnish solid content, coating A component 2 is matched with examples 1-6 and comparative examples 1-3 respectively)

[0158]

[0159] Table 13

[0160] Film drying test data (adding 0.03% T-12 drier of two-component varnish solid content, coating A component 2 is matched with Table Examples 1-3 and Examples 1-6 respectively)

[0161]

[0162]

[0163] It can be seen from Tables 1 and 2 that Comparative Example 3 using pure TMP-PDI prepolymer as a curing agent has a significantly longer potlife time. Similarly, due to the addition of TMP-PDI prepolymer, the mixed isocyanate curing agent B component prepared in Examples 1-6 also has a longer Potlife time than the isocyanate curing agent B component prepared in Comparative Examples 1-2, and the extent of the potlife time extension is proportional to the amount of TMP-PDI prepolymer mixed.

[0164] As can be seen from Tables 3 to 6, in Examples 1-6, TMP-PDI prepolymer and polyisocyanate curing agent are used as curing agent for coating component B, and then the coating component A to which an anti-aging agent is added can be used to obtain a better coating weathering effect than using only TMP-PDI prepolymer or only polyisocyanate curing agent as curing agent for coating component B in Comparative Examples 1-3, which is mainly manifested in better crack resistance and gloss retention of the coating. This property is affected by the mixing ratio of polyisocyanate curing agent and TMP-PDI prepolymer, and there is an optimal mixing ratio of 1:1. In addition, this property is also affected by the combination and ratio of anti-aging agents added in component A. Taking the combination of TINUVIN400 and TINUVIN292 as an example, the total amount of anti-aging agents added is controlled to be 1.5% of the mass of component A of the coating. When the ratio of TINUVIN400 / TINUVIN292=2 / 1 is selected, the best anti-crack and gloss retention effects of the coating can be obtained (see Table 7).

[0165] The inventors found that when the coating component A does not add an anti-aging agent, the coating performance of the component B using a mixed curing agent is worse than that of a single TMP-PDI prepolymer, but when the component A adds an anti-aging agent, the coating performance of the component B using a mixed curing agent is significantly improved than that of a single TMP-PDI prepolymer, indicating that the anti-aging agent and the TMP-PDI prepolymer have a synergistic effect. The addition of the anti-aging agent protects the resistance to ultraviolet degradation of the carbamate functional group in the TMP-PDI prepolymer, and the addition of the TMP-PDI prepolymer increases the concentration of the carbamate functional group in the final coating, improves the density of the coating, and cooperates with the high rigidity and high weather resistance of the isocyanurate triazine ring in the PDI trimer or HDI trimer, so that the carbamate functional group and the isocyanurate triazine ring and the anti-aging agent in the final coating have a better arrangement, thereby exerting a better synergistic effect. At the same time, the optimization of the arrangement of carbamate functional groups and isocyanurate triazine rings in the final coating also brings about better synergistic effects in terms of media resistance, wear resistance, self-healing, and stain resistance of the coating.

[0166] As can be seen from Table 8, the mixed isocyanate prepared in Examples 1-6 as the curing agent B component has better solvent resistance than the paint film prepared in Comparative Examples 1-3 using only TMP-PDI prepolymer or only polyisocyanate curing agent as the curing agent B component and the coating A component, especially showing better color retention in the gasoline resistance test.

[0167] As can be seen from Table 9, the mixed isocyanate curing agent prepared in Examples 1-6 as component B has better wear resistance and self-healing properties than the paint film prepared in Comparative Examples 1-3 using only TMP-PDI prepolymer or only polyisocyanate curing agent as curing agent component B and coating component A. This is manifested in that the coating film using the curing agent in Examples 1-6 has higher gloss retention after the wear resistance test, and the worn paint film also has higher restored gloss after baking at 60°C*2h.

[0168] As can be seen from Table 10, the mixed isocyanate prepared in Examples 1-6 as the curing agent B component has better stain resistance than the paint film prepared in Comparative Examples 1-3 using only TMP-PDI prepolymer or only polyisocyanate curing agent as the curing agent B component and the coating A component, which is mainly manifested in that the coating film has better color retention after the stain resistance test.

[0169] It can be seen from Table 11 that the comparative example 3 using pure TMP-PDI prepolymer as the curing agent B component and the supporting coating component A has better bending resistance and impact resistance of the coating film. Similarly, due to the addition of TMP-PDI prepolymer, the mixed isocyanate prepared in Examples 1-6 as the curing agent B component also has better bending resistance and impact resistance of the coating film than the comparative example 1-2 using only isocyanate curing agent as the curing agent B component, and the degree of improvement in the flexibility is proportional to the amount of TMP-PDI prepolymer mixed.

[0170] As shown in Tables 12 and 13, in the formula without adding T-12 drier, the use of pure TMP-PDI prepolymer as curing agent in Comparative Example 3 will significantly reduce the drying performance of the coating film. In order to improve this performance, the drying agent is added to improve it. In the formula with the addition of T-12 drier, the coating drying performance of Comparative Example 3 using pure TMP-PDI prepolymer as curing agent is basically equivalent to that of Comparative Examples 1-2. Similarly, in the formula with the addition of T-12 drier, although Example 1-6 uses both TMP-PDI prepolymer and polyisocyanate as curing agents, it has almost the same coating drying performance as Comparative Examples 1-2.

[0171] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the mixed isocyanate composition of the present invention and its application in coatings, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A mixed isocyanate composition, characterized in that: The mixed isocyanate composition comprises a TMP-PDI prepolymer and a polyisocyanate curing agent.

2. The mixed isocyanate composition according to claim 1, characterized in that: The TMP-PDI prepolymer is terminated with an isocyanate group and is obtained by reacting a polyisocyanate component containing PDI and an alcohol component containing TMP; Preferably, the polyisocyanate other than PDI in the polyisocyanate component includes any one or a combination of at least two of aliphatic isocyanate, alicyclic isocyanate or aromatic isocyanate; Preferably, the alcohols other than TMP in the alcohol component include diols and / or triols having a molecular weight of 62 to 200; Preferably, the diol includes any one or a combination of at least two of methyl propylene glycol, 1,3-butanediol, 1,4-butanediol, diethylene glycol, ethylene glycol, dipropylene glycol, 1,3-propanediol, 1,2-propanediol, neopentyl glycol or 1,6-hexanediol; Preferably, the triol includes any one of glycerol, 1,2,6-hexanetriol, and trimethylolethane, or a combination of at least two thereof.

3. The mixed isocyanate composition according to claim 2, characterized in that: In the polyisocyanate component, the mass percentage of PDI is 50% to 100%; Preferably, in the alcohol component, the mass percentage of TMP is 50% to 100%.

4. The mixed isocyanate composition according to any one of claims 1 to 3, characterized in that: The TMP-PDI prepolymer is prepared by the following method: The polyisocyanate component containing PDI and the alcohol component containing TMP are reacted to obtain a reaction liquid, and then the unreacted polyisocyanate component is removed to obtain the TMP-PDI prepolymer.

5. The mixed isocyanate composition according to claim 4, characterized in that: The molar ratio of -NCO in the polyisocyanate component to -OH in the alcohol component is (2-20):1, preferably (5-10):1; Preferably, the reaction temperature is 50 to 120°C, preferably 60 to 110°C; Preferably, the reaction time is 0.5 to 10 h, preferably 1 to 5 h; Preferably, the removing of the unreacted polyisocyanate component specifically comprises removing the unreacted polyisocyanate component by using a thin film evaporation device; Preferably, when removing the unreacted polyisocyanate component, the separation temperature is 80 to 160° C., preferably 80 to 120° C., and the separation pressure is 5 to 200 Pa, preferably 5 to 50 Pa.

6. The mixed isocyanate composition according to any one of claims 1 to 5, characterized in that: The polyisocyanate curing agent contains any one or a combination of at least two of an isocyanurate ring, a benzene ring or a n-hexyl ring; Preferably, the polyisocyanate curing agent includes any one of aliphatic isocyanate, alicyclic isocyanate or aromatic isocyanate curing agent or a combination of at least two, preferably any one of PDI trimer curing agent, HDI trimer curing agent, isophorone diisocyanate curing agent, hydrogenated benzyl diisocyanate curing agent, diphenylmethane diisocyanate curing agent, toluene diisocyanate curing agent, benzyl diisocyanate curing agent or TDI-TMP prepolymer curing agent or a combination of at least two.

7. The mixed isocyanate composition according to any one of claims 1 to 6, characterized in that: Based on the total mass of the mixed isocyanate composition being 100%, the content of the TMP-PDI prepolymer is 5% to 90%, preferably 20% to 80%.

8. A two-component polyurethane coating, characterized in that: The two-component polyurethane coating comprises component A and component B; The component A comprises the following components in parts by weight: The B component comprises the following components in parts by weight: 70 to 90 parts of the mixed isocyanate composition according to any one of claims 1 to 7; 10-30 parts of solvent; The auxiliary agent in the A component includes an anti-aging auxiliary agent.

9. The two-component polyurethane coating according to claim 8, characterized in that: The anti-aging aid includes an ultraviolet light absorber and / or a free radical scavenger; Preferably, the anti-aging aid comprises an ultraviolet light absorber and a free radical scavenger in a mass ratio of 1:3 to 3:1; Preferably, the ultraviolet light absorber includes any one of hydroxymethylphenol benzotriazoles and hydroxyphenol triazines, or a combination of at least two thereof; Preferably, the free radical scavenger includes any one of a hindered phenol light stabilizer and a hindered amine light stabilizer, or a combination of at least two of them.

10. The two-component polyurethane coating according to claim 8 or 9, characterized in that: The resin includes any one of hydroxy acrylic resin, polyester polyol resin or polyhydroxy alkyd resin or a combination of at least two thereof; Preferably, the solvents in the A component and the B component each independently include any one of butyl acetate, S-100A, propylene glycol methyl ether acetate, and ethylene glycol butyl ether acetate, or a combination of at least two thereof; Preferably, the auxiliary agent in the A component further includes a substrate wetting and leveling agent and / or a defoaming agent; Preferably, the auxiliary agent in the component A also includes a drying agent; Preferably, the drying agent includes T-12 drying agent; Preferably, the molar ratio of -NCO in the B component to -OH in the A component is (0.8-1.2):1.

Images