One-component polyurethane coating, process for its preparation and use

Abstract

The application relates to the paint technology field, and discloses a single-component polyurethane paint as well as a preparation method and application thereof. The single-component polyurethane paint comprises the following raw materials: alkyd resin polyol, isocyanate monomer, polyether polyol, polyol I, catalyst I, solvent, and additive. The single-component polyurethane paint is prepared by synthesizing long oil alkyd resin polyol semi-finished product as a macromolecular hydroxyl polymer through vegetable oil, adjusting the solvent, adopting specific catalyst and specific terminator, and treating free toluene diisocyanate through post-catalysis polymerization, so that the prepared single-component polyurethane paint has better overall performance, lower free toluene diisocyanate, toluene and xylene (containing ethylbenzene) total content, lower odor, shorter drying time, higher gloss, better fullness, adhesion and construction performance.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a single-component polyurethane coating, its preparation method, and its application. Background Technology

[0002] Polyurethane coatings, often referred to as polyurethane paints or PU paints in the application industry, are a type of coating with excellent mechanical properties and decorative and protective properties, widely used in various fields of industry and daily life. PU wood coatings are an important branch, classified by packaging as single-component PU paints and two-component PU paints. In the PU wood coating application market, it is used on everyday wooden furniture such as beds, wardrobes, and three-piece sets of tables and chairs made of woods such as rubberwood, teak, walnut, sapele, and rosewood. This type of application requires high-quality wood, involves multiple painting processes, offers diverse colors, has high coating requirements, and is costly; it is referred to in the coating industry as "Class I PU wood coatings." Another type is mainly used for coating softwoods such as cedar, pine, eucalyptus, and carbonized solid wood, as well as some household furniture products made of bamboo, such as dining tables, chairs, stools, and folding beds. It is generally a glossy clear varnish, without solid color paint. The coating process usually consists of one coat of sealing primer and one coat of topcoat (referred to as "one primer and one topcoat"). The construction methods include spraying and brushing. It is known in the industry as "Class II PU wood coating".

[0003] Type II PU wood coatings require high gloss and fullness. Currently, two-component PU paints are commonly used. However, factory mixing facilities are often rudimentary, and mixing is mostly based on estimations. This often leads to inaccurate paint mixing, resulting in defects in the coating performance of the finished furniture and necessitating rework, causing a certain degree of cost waste. Furthermore, the total content of toluene and xylene (including ethylbenzene) and the total content of free diisocyanates (limited to toluene diisocyanate (TDI) and hexamethylene diisocyanate (HDI), mainly TDI) in two-component PU paints on the market exceeds the standards, resulting in a strong odor that seriously affects the construction environment. Using Type I PU wood coatings over Type II PU wood coatings results in poor coating effects, a strong odor, and higher costs, making them unsuitable as a substitute for Type II PU wood coatings. Summary of the Invention

[0004] To at least overcome one of the problems existing in the prior art, one objective of this invention is to provide a one-component polyurethane coating that can be directly applied, is more convenient to use than two-component paints, has a better film-forming effect, and has low content of free toluene diisocyanate (mainly TDI), toluene, and xylene (including ethylbenzene), meeting the requirements of GB18581-2020 standard, and has a low odor. A second objective of this invention is to provide a method for preparing the one-component polyurethane coating. A third objective of this invention is to provide applications of the one-component polyurethane coating.

[0005] Therefore, the present invention adopts the following technical solution:

[0006] The first aspect of the present invention provides a one-component polyurethane coating, wherein the raw material components of the one-component polyurethane coating include: alkyd resin polyol, isocyanate monomer, polyether polyol, polyol I, catalyst I, solvent, and additives.

[0007] Preferably, the raw materials for preparing the alkyd resin polyol include vegetable oil, polybasic acid, monobasic acid, polyol II, and catalyst II. More preferably, the weight ratio of vegetable oil, polybasic acid, monobasic acid, polyol II, and catalyst II in the raw materials for preparing the alkyd resin polyol is (56-70):(12-17):(0-9):(18-20):(0-0.02). Preferably, the vegetable oil is selected from at least one of soybean oil, castor oil, and linseed oil. More preferably, the vegetable oil is selected from at least one of soybean oil and castor oil. Even more preferably, the vegetable oil is selected from soybean oil.

[0008] Preferably, the polybasic acid is selected from at least one of phthalic anhydride, adipic acid, isophthalic acid, and terephthalic acid. More preferably, the polybasic acid is selected from at least one of phthalic anhydride, isophthalic acid, and terephthalic acid. Even more preferably, the polybasic acid is selected from at least one of phthalic anhydride and isophthalic acid.

[0009] Preferably, the monoacid is selected from at least one of benzoic acid and rosin. More preferably, the monoacid is selected from benzoic acid.

[0010] Preferably, the polyol II is selected from at least one of pentaerythritol, glycerol, and trimethylolpropane. More preferably, the polyol II is selected from at least one of pentaerythritol and glycerol.

[0011] Preferably, the catalyst II is selected from organotin compounds. More preferably, the catalyst II is butyltin oxide.

[0012] Preferably, the first method for preparing the alkyd resin polyol includes the following steps:

[0013] (1) Add vegetable oil, polyol II and catalyst II, purge with nitrogen, heat to 237-245℃ for 2-3 hours and keep warm. When the alcoholysis reaches a volume ratio of 1:9 with anhydrous ethanol, the solution becomes transparent.

[0014] (2) Cool down to 150-130℃, add polyacid and solvent, raise the temperature to 180-200℃ in 1-2 hours, keep it at the temperature for 1-2 hours, then raise the temperature to 215-225℃ in 1-2 hours, keep it at the temperature and reflux until the acid value is ≤1mgKOH / g. Then remove the residual solvent by vacuum, restore normal pressure, cool down, filter, and obtain the alkyd resin polyol.

[0015] Preferably, the second method for preparing the alkyd resin polyol includes the following steps:

[0016] (1) Add vegetable oil, polyol II, monoacid and solvent, purge with nitrogen, heat to 237-245℃ for 2-3 hours and keep warm under reflux until the acid value is ≤1mgKOH / g.

[0017] (2) Cool down to 150-130℃, add polyacid and solvent, raise the temperature to 180-200℃ in 1-2 hours, keep it at the temperature for 1-2 hours, then raise the temperature to 215-225℃ in 1-2 hours, keep it at the temperature and reflux until the acid value is ≤1mgKOH / g. Then remove the residual solvent by vacuum, restore normal pressure, cool down, filter, and obtain the alkyd resin polyol.

[0018] Preferably, the isocyanate monomer is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, and polyphenylmethylene polyisocyanate.

[0019] More preferably, the mass percentage of the toluene diisocyanate to the total mass of the isocyanate monomer is 20% to 80%.

[0020] Preferably, the polyether polyol is selected from at least one of polypropylene triol and polypropylene diol. More preferably, the polyether polyol is selected from polypropylene triol.

[0021] Preferably, the polyol I is selected from at least one of diethylene glycol, methyl propylene glycol, neopentyl glycol, and ethyl butyl propylene glycol. More preferably, the polyol I is selected from at least one of diethylene glycol, methyl propylene glycol, and neopentyl glycol. Even more preferably, the polyol I is selected from at least one of diethylene glycol and neopentyl glycol.

[0022] Preferably, catalyst I is selected from at least one of tris(dimethylaminopropyl)hexahydrotriazine, tris(dimethylaminopropyl)amine, 2,4,6-tris(dimethylaminomethyl)phenol, pentamethyldiethylenetriamine, tributylphosphine, and potassium isooctanoate. More preferably, catalyst I is selected from at least one of tris(dimethylaminopropyl)amine, 2,4,6-tris(dimethylaminomethyl)phenol, and pentamethyldiethylenetriamine.

[0023] Preferably, the solvent includes aromatic solvents, dearomatic solvents, and acid ester solvents.

[0024] Preferably, the aromatic solvent is selected from xylene and trimethylbenzene.

[0025] Preferably, the dearomatic solvent is selected from D30 solvent or D40 solvent.

[0026] Preferably, the ester solvent is selected from at least one of ethyl acetate, dimethyl carbonate, butyl acetate, propylene glycol methyl ether acetate, and divalent esters. More preferably, the ester solvent is selected from at least one of ethyl acetate, dimethyl carbonate, butyl acetate, and divalent esters. Even more preferably, the ester solvent is selected from at least one of ethyl acetate, dimethyl carbonate, and divalent esters.

[0027] Preferably, the weight ratio of xylene:trimethylbenzene:(sum of D30 solvent and D40 solvent):(sum of ethyl acetate and dimethyl carbonate):(sum of butyl acetate and propylene glycol methyl ether acetate):divalent ester in the solvent is (15-20):(5-14):(4-12):(4-12):(0-3):(0-3).

[0028] Preferably, the additives include a terminator, a defoamer, and a leveling agent.

[0029] Preferably, the terminator is selected from at least one of benzoyl chloride, phosphoric acid, methyl p-toluenesulfonate, and dimethyl sulfate. More preferably, the terminator is selected from at least one of benzoyl chloride and phosphoric acid.

[0030] Preferably, the defoamer is a polysiloxane.

[0031] Preferably, the leveling agent is polyether-modified polydimethylsiloxane.

[0032] Preferably, in the raw materials of the single-component polyurethane coating, the weight ratio of alkyd resin polyol, isocyanate monomer, and polyether polyol is (21-30):(18-24):(3-7).

[0033] Preferably, in the raw materials of the single-component polyurethane coating, the weight ratio of alkyd resin polyol, isocyanate monomer, polyether polyol, and polyol I is (21-30): (18-24): (3-7): (0.5-2).

[0034] Preferably, in the raw materials of the single-component polyurethane coating, the weight ratio of alkyd resin polyol, isocyanate monomer, polyether polyol, polyol I, and catalyst I is (21-30): (18-24): (3-7): (0.5-2): (0.05-0.15).

[0035] Preferably, in the raw materials of the single-component polyurethane coating, the weight ratio of alkyd resin polyol, isocyanate monomer, polyether polyol, polyol I, catalyst I, and solvent is (21-30): (18-24): (3-7): (0.5-2): (0.05-0.15): (30-54).

[0036] Preferably, in the raw materials of the single-component polyurethane coating, the weight ratio of alkyd resin polyol, isocyanate monomer, polyether polyol, polyol I, catalyst I, solvent, and additives is (21-30): (18-24): (3-7): (0.5-2): (0.05-0.15): (30-54): (0.24-0.72).

[0037] The single-component polyurethane coating of this invention uses a long-oil-strength alkyd resin polyol semi-finished product synthesized from vegetable oil as a macromolecular hydroxyl polymer. The vegetable oil contains a large amount of C... 18 The long carbon chain, high oil content, and low viscosity of the vegetable oil provide sufficient low-viscosity space for the subsequent reaction with isocyanate monomers, resulting in a final product with good gloss and fullness in Class II PU wood coatings. Furthermore, vegetable oil is a green, bio-based raw material with lower cost, which helps reduce product costs. The specific catalyst I of this invention, under specific process conditions, can effectively reduce free TDI in single-component polyurethane coatings, reduce harmful substances and odors in the product, and shorten the coating drying time.

[0038] In addition, the present invention uses a specific solvent composition to adjust the appropriate dissolving power, thereby reducing the phenomenon of strong penetration during the construction process that causes the coating film to become flat and thin. On the other hand, it adjusts the odor of the mixed solvent to make the product have a low odor and low free TDI, thus meeting the basic needs of users.

[0039] Preferably, the method for preparing the single-component polyurethane coating includes the following steps:

[0040] After adding the various raw material components and carrying out the polymerization reaction, the mixture is diluted to obtain the single-component polyurethane coating.

[0041] More preferably, the method for preparing the single-component polyurethane coating includes the following steps:

[0042] S1: Mix isocyanate monomer, alkyd resin polyol, polyether polyol, polyol I, and solvent, heat and react to obtain polyurethane prepolymer;

[0043] S2: Cool down, add catalyst I and solvent, continue the reaction, and add terminator;

[0044] S3: Add solvent, defoamer, and leveling agent, stir, and obtain the single-component polyurethane coating.

[0045] Preferably, in step S1, the reaction temperature is 80–100°C.

[0046] Preferably, in step S1, the reaction time is 2 to 4 hours. More preferably, in step S1, the reaction time is 2 to 3 hours.

[0047] Preferably, in step S2, the reaction temperature is 30–70°C, and the free TDI value is ≤0.4% when the terminator is added.

[0048] The single-component polyurethane coating prepared by this invention is a moisture-curing polyurethane product, and the free TDI content needs to be controlled to ≤0.4% to meet the requirements of GB18581-2020 standard. In the above reaction, after step S1, a large amount of unreacted TDI remains in the polyurethane prepolymer. In step S2, catalyst I is added to perform post-catalytic polymerization treatment on the free TDI. The schematic diagram of the post-catalytic polymerization reaction is as follows:

[0049]

[0050] Post-catalytic polymerization generates trimers or polymers, which are then converted into non-volatile substances that form part of the coating film. At the same time, small molecules are greatly reduced, thereby improving the drying properties of the final product and reducing the irritating odor during application.

[0051] A third aspect of the invention provides the application of the single-component polyurethane coating according to the first aspect of the invention.

[0052] Preferably, the single-component polyurethane coating can be used for coating material surfaces, particularly in Class II PU wood coating applications.

[0053] Compared with the prior art, the beneficial effects of the present invention are:

[0054] The single-component polyurethane coating of the present invention has better overall performance, with lower total content of free TDI, toluene and xylene (including ethylbenzene), lower odor, good drying properties, high gloss, and good fullness, adhesion and workability.

[0055] Specifically:

[0056] (1) The single-component polyurethane coating of the present invention uses a semi-finished product of long-oil alkyd resin polyol synthesized from vegetable oil as a macromolecular hydroxy polymer, which provides sufficient low viscosity space for the next step of reaction with isocyanate monomer, so that the coating film has good gloss and fullness.

[0057] (2) The present invention uses a specific solvent composition to adjust the appropriate dissolving power to reduce the phenomenon of strong penetration during the construction process, which makes the coating film flat and thin, especially in the application of Class II PU wood coating with one primer and one top coat on cork substrate; on the other hand, it adjusts the odor of the mixed solvent to make the product have a low odor and low free TDI, so as to meet the basic needs of users.

[0058] (3) The present invention uses a specific catalyst I to effectively reduce the free TDI content, reduce odor, and shorten drying time through a post-catalytic polymerization process. In particular, the free TDI content is reduced by more than 10 times compared with that without the post-catalytic polymerization process.

[0059] (4) The single-component polyurethane coating of the present invention has the following content: total free diisocyanate content, total toluene and xylene (including ethylbenzene) content, and volatile organic compound (VOC) content all meet the restrictive standard requirements of GB18581-2020; single-component packaging allows for direct application, which is more convenient than two-component PU paint, eliminates the need for paint mixing, and avoids losses caused by paint mixing errors. Detailed Implementation

[0060] The present invention will be further described in detail below through specific embodiments, comparative examples and tables, but is not limited to all the discussions and data.

[0061] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents, or apparatus used in this invention can all be obtained through conventional commercial channels. Specifically, the alkyd resin polyol in this invention is prepared according to the formulation and preparation method of this invention.

[0062] Table 1. Mass ratio of alkyd resin polyol raw material components in Examples 1-4 and Comparative Example 1 (unit: g)

[0063]

[0064] The preparation steps of the alkyd resin polyols used in Examples 1, 3, 4, and Comparative Example 1 are as follows:

[0065] (1) Add vegetable oil, polyol II, monoacid, and part of the solvent, purge with nitrogen, and heat to 240℃ within 2-3 hours and keep warm under reflux until the acid value is ≤1mgKOH / g.

[0066] (2) Cool down to 150°C, add polyacid and the remaining solvent, raise the temperature to 190°C within 2 hours, keep it at the temperature for 1 hour, then raise the temperature to 220°C within 1 hour, keep it at the temperature and reflux until the acid value is ≤1mgKOH / g, then remove the residual solvent by vacuum, restore normal pressure, cool down, filter, and obtain the alkyd resin polyol.

[0067] The preparation steps of the alkyd resin polyol used in Example 2 are as follows:

[0068] (1) Add vegetable oil, polyol II and catalyst II, purge with nitrogen, raise the temperature to 240°C within 2-3 hours, keep warm for 1 hour, and alcoholyze until the volume ratio of alcohol to anhydrous ethanol is 1:9, at which point the solution becomes transparent.

[0069] (2) Cool down to 150°C, add polyacid and solvent, raise the temperature to 190°C within 2 hours, keep it at 1 hour, raise the temperature to 220°C within 1 hour, keep it at reflux reaction until the acid value is ≤1mgKOH / g, then remove the residual solvent by vacuum, restore normal pressure, cool down, filter, and obtain the alkyd resin polyol.

[0070] The component contents of the single-component polyurethane coatings in Examples 1-4 and Comparative Example 1 are shown in Table 2:

[0071] Table 2. Mass ratios of components in the single-component polyurethane coatings of Examples 1-4 and Comparative Example 1 (unit: g)

[0072]

[0073]

[0074] According to the preparation method of the single-component polyurethane coating of the present invention, the mass of each raw material is as follows, according to the corresponding examples and comparative examples in Table 2:

[0075] Example 1:

[0076] S1: The alkyd resin polyol, toluene diisocyanate, diphenylmethane diisocyanate, polyoxypropylene triol (molecular weight 3000), diethylene glycol, xylene, and dimethyl carbonate prepared in Example 1 are sequentially added to the reaction vessel, stirred, nitrogen gas is introduced, the temperature is raised to 90°C within 30-60 minutes, and kept at the temperature for 3 hours.

[0077] S2: Cool to 50℃, add ethyl acetate and tris(dimethylaminopropyl)hexahydrotriazine, react until the free TDI value is ≤0.4% (based on the total formula), immediately add benzoyl chloride, heat to 90℃, keep warm for 10 min, and then cool down;

[0078] S3: Add thiol, D30 solvent, D40 solvent, propylene glycol methyl ether acetate, divalent ester, polysiloxane, and polyether-modified polydimethylsiloxane, and stir until homogeneous to obtain a one-component polyurethane coating.

[0079] Example 2:

[0080] S1: The alkyd resin polyol, toluene diisocyanate, diphenylmethane diisocyanate, polyoxypropylene triol (molecular weight 5000), methyl propylene glycol, xylene, and dimethyl carbonate prepared in Example 2 are sequentially added to the reaction vessel, stirred, and nitrogen gas is introduced. The temperature is raised to 90°C within 30-60 minutes and kept at that temperature for 3 hours.

[0081] S2: Cool to 50℃, add ethyl acetate and tris(dimethylaminopropyl)amine, react until the free TDI value is ≤0.4% (based on the total formula), immediately add benzoyl chloride, heat to 90℃, keep warm for 10 min, and then cool down;

[0082] S3: Add thiol, D30 solvent, butyl acetate, divalent ester, polysiloxane, and polyether-modified polydimethylsiloxane, and stir until homogeneous to obtain a one-component polyurethane coating.

[0083] Example 3:

[0084] S1: Add the alkyd resin polyol, toluene diisocyanate, polyphenyl polymethylene polyisocyanate, polyoxypropylene glycol (molecular weight 2000), xylene, and dimethyl carbonate obtained in Example 3 into the reactor, stir, then add neopentyl glycol, purge with nitrogen, heat to 90°C within 30-60 minutes, and keep warm for 3 hours.

[0085] S2: Cool to 50℃, add ethyl acetate and 2,4,6-tris(dimethylaminomethyl)phenol, react until the free TDI value is ≤0.4% (based on the total formula), then immediately add phosphoric acid;

[0086] S3: Add thiol, D30 solvent, divalent ester, polysiloxane, and polyether-modified polydimethylsiloxane, and stir evenly to obtain a one-component polyurethane coating.

[0087] Example 4:

[0088] S1: Add the alkyd resin polyol, toluene diisocyanate, polyphenyl polymethylene polyisocyanate, polyoxypropylene glycol (molecular weight 1000), diethylene glycol, dimethyl carbonate, and xylene obtained in Example 4 into the reactor, stir, purge with nitrogen, raise the temperature to 90°C within 30-60 min, and keep warm for 3 h.

[0089] S2: Cool to 50℃, add ethyl acetate and pentamethyldiethylenetriamine, react until the free TDI value is ≤0.4% (based on the total formula), immediately add methyl p-toluenesulfonate and dimethyl sulfate, heat to 90℃, keep warm for 10 min, and then cool down;

[0090] S3: Add thiol, D30 solvent, D40 solvent, propylene glycol methyl ether acetate, divalent ester, polysiloxane, and polyether-modified polydimethylsiloxane, and stir until homogeneous to obtain a one-component polyurethane coating.

[0091] Comparative Example 1:

[0092] S1: Add the alkyd resin polyol, toluene diisocyanate, polyphenyl polymethylene polyisocyanate, polyoxypropylene glycol (molecular weight 1000), and xylene obtained in proportion 1 to the reaction vessel, stir, then add diethylene glycol and dimethyl carbonate, purge with nitrogen, raise the temperature to 90°C within 30-60 min, and keep at the temperature for 3 h.

[0093] S2: Cool to 50℃, add solvents tricresyl, D30 solvent, D40 solvent, propylene glycol methyl ether acetate, ethyl acetate, divalent ester, polysiloxane, and polyether-modified polydimethylsiloxane, and stir evenly to obtain a one-component polyurethane coating.

[0094] Comparative Example 2:

[0095] Commercially available two-component polyurethane coatings.

[0096] Material performance testing:

[0097] (1) Test and analyze the viscosity (Ford cup 4 / 25℃), free TDI, and total content of toluene and xylene (including ethylbenzene) of the sample;

[0098] (2) The substrate is solid fir wood (44-50cm long, 11-13cm wide, and 1.5-2cm thick). After sanding it smooth with 240-grit sandpaper, apply a coat of urea-formaldehyde resin adhesive primer and let it stand for 24 hours. Then, lightly sand it smooth with 320-grit sandpaper and remove dust. Apply a coat with a coverage of 130g / m². 2 For the test samples, single-component coatings were applied directly by brushing, while two-component coatings were mixed according to the instructions before application, and their application performance was observed. The prepared samples were placed in a constant temperature environment of 25℃ and 60% humidity to test surface drying time, complete drying time, and odor. After standing for 7 days, the coating appearance, gloss (20°), gloss (60°), fullness, and adhesion were tested. The test standards are as follows:

[0099] Viscosity (Ford Cup 4 / 25℃): Tested according to GB / T 1723 standard;

[0100] Free TDI: Tested according to GB / T 18446 standard;

[0101] Total content of toluene and xylene (including ethylbenzene): Tested according to section 8.4.3 of GB / T 23990-2009;

[0102] Construction performance: Comparative tests were conducted according to the above specifications;

[0103] Surface drying time: Tested according to Method B in GB / T 1728 standard;

[0104] Actual testing time: Tested according to Method A in GB / T 1728 standard;

[0105] Odor: Smell the sample within 20-30 minutes after the film has formed and conduct a comparative test;

[0106] Coating appearance: The sample is visually observed under diffused sunlight. If the coating is uniform and free from defects such as sagging, blooming, pinholes, cracking, and peeling, it is rated as "normal" or "smooth and glossy".

[0107] Gloss (60°): Tested according to GB / T9754 standard;

[0108] Fullness: The fullness of the coating film was compared by visually observing the samples under diffused sunlight;

[0109] Adhesion: Tested according to GB / T 9286 standard, with a cutting spacing of 2mm.

[0110] The test properties of the single-component polyurethane coating of Examples 1-4 and Comparative Example 1, and the two-component polyurethane coating of Comparative Example 2 are shown in Table 3 below:

[0111] Table 3 shows the performance test results of Examples 1-4 and Comparative Examples 1-2.

[0112]

[0113]

[0114] The single-component polyurethane coating prepared by this invention exhibits superior overall performance, moderate viscosity, and low levels of free TDI, toluene and xylene (including ethylbenzene), and VOC content, meeting the requirements of GB18581-2020 standard. It also features low odor, short drying time, high gloss, and good fullness, adhesion, and application performance. It can be applied directly, simplifying on-site construction operations and optimizing the on-site construction environment.

[0115] The difference between Comparative Example 1 and Example 4 is that Comparative Example 1 did not undergo post-catalytic polymerization treatment to remove free TDI. The results showed that the free TDI content of the one-component polyurethane coating in Comparative Example 1 was 13.2 times that of Example 4, its surface drying time was 2.4 times that of Example 4, its actual drying time was 1.3 times that of Example 4, and it had a stronger odor. This indicates that the post-catalytic polymerization process effectively reduces the free TDI content, alleviates the odor, and shortens the surface drying time and actual drying time.

[0116] Comparative Example 2 is a commercially available two-component polyurethane coating. Although its surface drying time, actual drying time, and adhesion are comparable to those of Examples 1-4, Comparative Example 2 has a strong odor and a high total content of free TDI, toluene, and xylene (including ethylbenzene), all of which exceed the limits of GB18581-2020, thus adversely affecting the construction environment.

Claims

1. A one-component polyurethane coating, characterized in that, The raw material components include: alkyd resin polyol, isocyanate monomer, polyether polyol, polyol I, catalyst I, solvent, and additives; The raw materials for preparing the alkyd resin polyol include vegetable oil, polyacid, monoacid, polyol II, and catalyst II. The catalyst I is selected from at least one of tris(dimethylaminopropyl)amine, 2,4,6-tris(dimethylaminomethyl)phenol, and pentamethyldiethylenetriamine; The adjuvant includes a terminator; The terminating agent is selected from at least one of benzoyl chloride and phosphoric acid; The preparation method of the single-component polyurethane coating includes the following steps: S1: Mix isocyanate monomer, alkyd resin polyol, polyether polyol, polyol I, and solvent, and heat to carry out the reaction; S2: Cool down, add catalyst I and solvent, continue the reaction, and add terminator; add catalyst I to perform post-catalytic polymerization treatment on free TDI; the free TDI value is ≤0.4% when the terminator is added; S3: Add solvent, defoamer, and leveling agent, stir, and obtain the single-component polyurethane coating; The solvents include aromatic solvents, dearomatic solvents, and acid ester solvents.

2. The single-component polyurethane coating according to claim 1, characterized in that, The alkyd resin polyol comprises the following raw material components in parts by weight: 56-70 parts vegetable oil; 12-17 parts of polybasic acids; 0-9 parts of monoacid; Polyol II 18-20 parts; Catalyst II 0~0.02 parts.

3. The single-component polyurethane coating according to claim 2, characterized in that, The vegetable oil is selected from at least one of soybean oil, castor oil, and linseed oil; And / or, the polyacid is selected from at least one of phthalic anhydride, adipic acid, isophthalic acid, and terephthalic acid; And / or, the monoacid is selected from at least one of benzoic acid and rosin; And / or, the polyol II is selected from at least one of pentaerythritol, glycerol, and trimethylolpropane; And / or, the catalyst II is an organotin compound.

4. The single-component polyurethane coating according to claim 1, characterized in that, The isocyanate monomer is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, and polyphenyl polymethylene polyisocyanate; And / or, the polyether polyol is selected from at least one of polyoxypropylene triol and polyoxypropylene diol; And / or, the polyol I is selected from at least one of diethylene glycol, methyl propylene glycol, neopentyl glycol, and ethyl butyl propylene glycol; And / or, the additives may also include defoamers and leveling agents.

5. The single-component polyurethane coating according to claim 4, characterized in that, The aromatic solvent is selected from xylene and trimethylbenzene; The dearomatic solvent is selected from D30 solvent and D40 solvent; The ester solvent is selected from at least one of ethyl acetate, dimethyl carbonate, butyl acetate, propylene glycol methyl ether acetate, and divalent esters.

6. The one-component polyurethane coating according to any one of claims 1 to 5, characterized in that, Its raw materials include the following components in parts by weight: 21-30 parts of alkyd resin polyol; 18–24 parts isocyanate monomer; 3-7 parts of polyether polyol; Polyol I 0.5–2 parts; Catalyst I: 0.05–0.15 parts; Solvent 30-54 parts; Additives: 0.24~0.72 parts.

7. A method for preparing a one-component polyurethane coating as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Mix isocyanate monomer, alkyd resin polyol, polyether polyol, polyol I, and solvent, and heat to carry out the reaction; S2: Cool down, add catalyst I and solvent, continue the reaction, and add terminator; S3: Add solvent, defoamer, and leveling agent, stir, and obtain the single-component polyurethane coating.

8. The method for preparing a single-component polyurethane coating according to claim 7, characterized in that, In step S1, the reaction temperature is 80–100°C, and the reaction time is 2–3 hours. In step S2, the reaction temperature is 30–70°C, and the free toluene diisocyanate value is ≤0.4% when the terminator is added.

9. The application of the single-component polyurethane coating according to any one of claims 1 to 6 in coating.

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