A high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings and its preparation method

Abstract

This invention discloses a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings and its preparation method. The preparation method includes the following steps: mixing 1,3-dihydroxymethylurea, polyol, and caprolactone, adding an acid catalyst for reaction, and after the caprolactone has completely reacted, adding a single-ended epoxy-based polysiloxane and a cationic ring-opening catalyst dropwise. After the addition is complete, the reaction continues until the epoxy value decreases to below 1% of the initial value. Then, distilled water is added to decompose the cationic ring-opening catalyst. The mixture is then distilled under high vacuum conditions and cooled before being discharged to obtain the high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester. The high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester of this invention has advantages such as long activation period, low application viscosity, high application solids content, good chemical resistance of the coating film, fluorine-free properties, and good stain resistance when applied to polyurethane coatings.

Description

Technical Field

[0001] This invention relates to polyurethane automotive coatings, specifically to a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings and its preparation method. Background Technology

[0002] Traditional solvent-based coatings contain over 50% organic solvents, which pollute the environment when released into the atmosphere. However, solvent-based coatings offer high decorative properties, strong chemical resistance, and durability, making them difficult to replace with other coatings such as water-based, solvent-free, and UV-cured coatings. The development trend is towards high-solids content coatings, particularly two-component polyurethane coatings (2K-PU). The key technology lies in preparing high-solids, low-viscosity hydroxyl resins. The synthesis process of traditional solvent-based 2K-PU coatings is similar to that of hydroxyl polyesters, generally prepared through a polycondensation reaction of polyols and polyacids (or anhydrides) at high temperatures (180-240 °C). This process involves high reaction temperatures, the use of xylene as a dehydrating agent which is not environmentally friendly, and the resulting resins often have a linear molecular structure, resulting in high molecular weight, high viscosity, and low solids content—a trade-off between low viscosity and high solids content. Furthermore, the synthesis process requires high temperatures and energy, and contains harmful xylene solvents.

[0003] Hyperbranched polymers and star polymers have advantages such as less intermolecular chain entanglement, good solubility, low melt and solution viscosity, and a large number of end functional groups. Patent application CN104262599A discloses the use of caprolactone, fatty acids and monoglycidyl ether to modify hyperbranched hydroxyl polyesters, and the use of benzene compounds such as xylene as a dehydrating agent to promote the polycondensation reaction. This results in xylene residue in the product, which does not meet increasingly stringent environmental protection requirements. Patent application CN106279659A discloses a star-shaped hydroxyl polyester with a polyol core, its preparation method, and its application. The method involves mixing a small-molecule polyol, caprolactone, and anhydride, and reacting them under nitrogen protection at 80–140°C to prepare a matrix star-shaped polyester. The carboxyl groups are then reacted with monoglycidyl ether at 90–150°C to prepare the star-shaped hydroxyl polyester. This method involves multi-step feeding, resulting in a complex process and time-consuming synthesis steps. When applied to 2K-PU coatings, the resulting film performance is inferior to traditional hydroxyl resins, exhibiting a short activation period (within 2 hours). The aforementioned hydroxyl resins have high polarity and viscosity, resulting in coatings with solids content below 70%, VOCs above 300 g / L, and poor chemical resistance, anti-fouling, and self-cleaning properties, making them unsuitable for automotive coatings, especially repair paints. Coatings prepared from commonly used silicone-containing hydroxyl resins typically have poor adhesion, are prone to peeling during use, and have a shortened service life. Chinese patent application CN118772779A discloses a weather-resistant self-cleaning coating, its preparation method, and its uses. It is a two-component polyurethane coating, wherein the hydroxyl resin comprises 5-30 parts of terminally hydroxyl hyperbranched polysiloxane, 5-30 parts of hydroxyl fluorocarbon resin, and 5-30 parts of non-isocyanate polyurethane polyol, and the curing agent is an isocyanate curing agent. The coating exhibits high mechanical properties and weather resistance, low surface energy, high light transmittance, and self-cleaning function. However, this antifouling coating contains hydroxyl fluorocarbon resin, and fluorine is physiologically inert, limiting its application. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of this invention is to provide a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for anti-fouling automotive coatings and its preparation method. When applied to polyurethane coatings, it has the advantages of long activation period, low application viscosity, high application solids content, good chemical resistance of the coating film, fluorine-free, and good stain resistance.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention provides a method for preparing a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings, comprising the following steps:

[0007] 1,3-Dihydroxymethylurea, polyol, and caprolactone were mixed, and an acid catalyst was added. The mixture was reacted at 100-120°C under nitrogen protection for 4-6 hours. After the caprolactone was completely reacted, a single-ended epoxy polysiloxane and a cationic ring-opening catalyst were added dropwise. After the addition was complete, the temperature was raised to 60-65°C and the reaction was carried out for 4-6 hours. When the epoxy value decreased to less than 1% of the initial value, distilled water was added to decompose the cationic ring-opening catalyst. The mixture was then distilled under reduced pressure under high vacuum conditions and cooled to obtain a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester.

[0008] The molar ratio of 1,3-dihydroxymethylurea, polyol, caprolactone, and mono-epoxy polysiloxane is 1:1:(1-6):(1-6).

[0009] The mass of the acid catalyst is 0.1~0.6% of the mass of caprolactone;

[0010] The mass of the cationic ring-opening catalyst is 0.01-0.5% of the mass of the single-terminated epoxy polysiloxane.

[0011] In some embodiments of the present invention, the polyol is one of trimethylolpropane, bis(trimethylolpropane), pentaerythritol, and bispentaerythritol.

[0012] In some embodiments of the present invention, the number-average molecular weight of the single-terminated epoxy polysiloxane is 1000-10000.

[0013] In some embodiments of the present invention, the acid catalyst is at least one of dibutyltin dilaurate, stannous octoate, anhydrous zinc acetate, and tetrabutyl titanate.

[0014] In some embodiments of the present invention, the cationic ring-opening catalyst is at least one of boron trifluoride diethyl ether, boron trifluoride ethanol, and boron trifluoride tetrahydrofuran.

[0015] In some embodiments of the present invention, the high vacuum condition is a vacuum degree of less than 2000 Pa; the vacuum distillation temperature is 80-120°C, and the vacuum time is 0.5-1.5 h.

[0016] In some embodiments of the present invention, the amount of distilled water added is 10 to 20 times the mass of the cationic ring-opening catalyst.

[0017] The present invention also provides a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings, which is prepared by the preparation method of the high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings.

[0018] The present invention also provides an antifouling automotive coating, comprising a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester and a polyurethane curing agent; wherein the NCO:OH molar ratio of the polyurethane curing agent to the silicon-containing multi-arm star-shaped hydroxyl polyester is 1.05-1.25.

[0019] In some embodiments of the present invention, during the film formation process of the antifouling automotive coating, silicon-containing groups migrate to the interface between the coating and the air, and silicon elements migrate directionally from the coating bulk to the coating interface and accumulate at the coating interface.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) The antifouling automotive coating of the present invention is fluorine-free and has excellent antifouling self-cleaning performance and adhesion. By introducing high molecular weight polysiloxane into the multi-arm star-shaped hydroxyl polyester molecular chain, during the film formation process, the silicon-containing groups will migrate to the interface between the coating and the air. The silicon element will migrate directionally from the coating body to the coating interface and accumulate at the coating interface, giving the coating excellent antifouling self-cleaning performance. On the other hand, the introduction of urea bonds into the hydroxyl resin gives the upper component coating excellent adhesion, overcoming the defect of poor adhesion of traditional silicon-containing coatings.

[0022] (2) The antifouling automotive coating of the present invention has a high construction solids content and a VOC content of less than 280 g / L. By adding a single-terminated epoxy polysiloxane, the intermolecular hydrogen bonds are reduced, which can easily reduce the construction viscosity of the high solids content hydroxyl resin. On the other hand, the viscosity of the coating is related to the magnitude of the hydrogen bonding between hydroxyl groups. The hydrogen bonding between primary hydroxyl groups is usually greater than that between secondary hydroxyl groups and between primary and secondary hydroxyl groups. The present invention uses a ring-opening reaction between a polyol and caprolactone. The generated primary hydroxyl group reacts with a monoepoxide compound to prepare a four-armed star-shaped hydroxyl resin. One primary hydroxyl group is consumed and one secondary hydroxyl group is generated at the same time. Under the condition that the hydroxyl functionality remains unchanged, the resin viscosity is reduced from the resin structure. Furthermore, due to the generation of secondary hydroxyl groups, the hydrogen bonding between hydroxyl groups is reduced, which further reduces the viscosity of the resin and the coating.

[0023] (3) The preparation process of the high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester of the present invention is simple, the raw materials are widely available, the cost is low, and the reaction process is carried out at a relatively low temperature, which is energy-saving and environmentally friendly. Compared with the traditional preparation of hydroxyl polyester or alkyd resin by polycondensation reaction of polyacids and polyols at high temperature (200-240℃), the present method uses the ring-opening reaction of caprolactone and hydroxyl groups and the ring-opening reaction of hydroxyl groups and epoxy groups. The reaction temperature is below 120℃, no water is produced, the reaction does not require benzene-based dehydrating agents, and a one-step feeding method is adopted, which is more convenient in terms of process. The 2K-PU coating formulated with the product resin has a high solids content, low VOC content, long activation period, and excellent chemical resistance, and is an environmentally friendly product. The product of the present invention uses low-cost single-terminated epoxy polysiloxanes, without using low molecular weight epoxy siloxanes and fluorinated monomers, which makes the prepared hydroxyl resin low in cost. Attached Figure Description

[0024] Figure 1 The high solids content silicon-containing multi-arm hydroxyl resin molecular structure and synthesis process of Example 1 of the present invention are described.

[0025] Figure 2 The curves showing the changes in the contact angle and roll-off angle between the coating water and hexadecane as a function of the number of cycles in Example 1 of the present invention are shown.

[0026] Figure 3 XPS spectra of the coating film of Example 1 of the present invention were used to analyze the elemental content of the surface (a) and bulk (b) of the two-component polyurethane coating.

[0027] Figure 4 These are Si element distribution mapping images of the coating surface (a) and the bulk (b) of Embodiment 1 of the present invention.

[0028] Figure 5 The resin molecular structure and synthesis process of Example 2 of the present invention are shown.

[0029] Figure 6 The resin molecular structure and synthesis process of Example 3 of the present invention are shown.

[0030] Figure 7 The resin molecular structure and synthesis process of Example 4 of the present invention are shown.

[0031] Figure 8 The resin molecular structure and synthesis process of Example 5 of the present invention are shown.

[0032] Figure 9 The resin molecular structure and synthesis process of Example 6 of the present invention are shown. Detailed Implementation

[0033] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0034] The control product Desmophen 670BA used in the following examples is a lightly branched hydroxyl polyester resin produced by Bayer Covestro. It is mainly used in two-component polyurethane systems. The coating film has excellent weather resistance and outstanding low-temperature flexibility. It is currently a polyester resin with a relatively large market share.

[0035] In the following examples, the properties of the star-shaped hydroxyl polyester resin and the two-component polyurethane coating were tested using the following methods: resin viscosity was determined using an NDJ type I rotational viscometer according to GB / T21059-2007; resin acid value was determined according to GB / T 6743-2008; coating drying time was determined according to GB / T 1728-1989; coating hardness was determined according to GB / T 6739-2006; coating adhesion was determined according to GB / T9286-1998; coating impact resistance was determined according to GB / T 1732-1993; and the coating hardness was determined according to GB / T9754-2007 using a 60°C method. The gloss of the coating was measured using a WGG60-E4 gloss meter. The water resistance of the coating was determined using the room temperature immersion method according to GB / T 5209-1985. The contact angle and roll-off angle of the coating were tested using a Dataphysics OCA20 contact angle meter. Hexadecane and deionized water were used as representative test media. For the contact angle test, the droplet volume was controlled at 5.0 μL. For the roll-off angle test, 10 μL of deionized water droplets and 5.0 μL of hexadecane droplets were used respectively. The final result was the arithmetic mean of five parallel sets of data. For durability testing, a 200 g weight wrapped in cotton cloth was placed on the coating surface and moved back and forth at a speed of 4.0 cm / s. Each 12.0 cm reciprocating movement constituted one cycle. After multiple mechanical durability cycles, the contact angle, roll-off angle, and anti-graffiti performance of the coating surface were tested. Characterization of elemental composition and distribution on the coating surface and cross-section: A Thermo Scientific K-Alpha X-ray photoelectron spectroscopy (XPS) instrument was used for quantitative analysis of the elemental composition and content on the coating surface. The elemental distribution on the surface and cross-section of the coating was tested using the X-ray (EDX) elemental mapping function of a Hitachi SU-8820 scanning electron microscope (SEM). Other properties of the coating were determined according to GB / T 23985-2009, etc.

[0036] Example 1

[0037] 1. Raw material composition

[0038] 25.03 g (0.1 mol) of bis(trimethylolpropane)

[0039] 1,3-Dihydroxymethylurea 12.01 g (0.1 mol)

[0040] Caprolactone 68.48g (0.6mol)

[0041] SR-4, a mono-epoxylated polysiloxane (molecular weight 4000), 40.0 g (0.1 mol)

[0042] Anhydrous zinc acetate 0.12g

[0043] 0.2g of boron trifluoride diethyl ether

[0044] 2. Preparation: The synthesis process of silicon-containing multi-arm star-shaped hydroxyl polyester is as follows: Figure 1 .

[0045] The specific steps include the following: In a four-necked flask equipped with a mechanical stirrer, thermometer, spherical condenser, and nitrogen port, add 25.03g of bis(trimethylolpropane) and 12.01g of... 1,3-Dihydroxymethylurea, 68.48 g of caprolactone, and 0.12 g of anhydrous zinc acetate were reacted at 120 °C under nitrogen protection for 6 h. Infrared spectroscopy showed that the characteristic infrared peak of caprolactone in the reaction system disappeared. The temperature was lowered to below 30 °C, and 0.2 g of boron trifluoride ether (BF3·Et2O) was added. Under nitrogen protection, 400.0 g of SR-4 was added dropwise over 2 h using a peristaltic pump. After the addition was complete, the temperature was raised to 60 °C and the reaction continued for 6 h. The epoxy value of the reaction system was detected to drop to below 1 wt% of the initial value. 4 g of distilled water was added to quench the boron trifluoride ether catalyst. The mixture was then subjected to high vacuum conditions (vacuum degree <2000 Pa) at 120 °C for 1.5 h to remove water, and then cooled to obtain a silicon-containing multi-arm star-shaped hydroxyl polyester (SiHP-1).

[0046] 3. Performance testing: The viscosity of the silicon-containing multi-arm star-shaped hydroxyl polyester at 25℃ is 1000 mPa.s; the hydroxyl value is 200 mgKOH / g. Solubility: It is miscible with esters such as ethyl acetate, butyl acetate, propylene glycol, and methyl ether acetate; aromatic hydrocarbons such as toluene and xylene; and ketones such as acetone, butanone, 2-heptanone, and cyclohexanone.

[0047] 4. Coating formulation and performance:

[0048] Coating preparation: Take 50g of the product (SiHP-1) obtained in this example, then add 36.2g of N3300 polyurethane curing agent, 0.20g of BYK370 leveling agent, 0.20g of BYK141 defoamer, and add 15g of methyl isopentyl ketone to dilute the coating to a solid content of 60wt%. After stirring and dispersing, apply the coating to tinplate, glass plate and wood plate respectively.

[0049] Coating performance: The coating performance of the above-prepared coating is compared with that of the two-component polyurethane coating prepared by Covestro Arcol Polyol 3553 polyester polyol (curing agent N3300) in Table 1 below:

[0050] Table 1 Coating performance test results

[0051]

[0052] Table 1 illustrates that the sample in Example 1 has significant advantages over the Covestro sample in terms of adhesion, water contact angle, corrosion resistance, and VOC content. This invention uses a polyol and 1,3-dihydroxymethylurea to react with caprolactone to generate urea-containing polycaprolactone diol, which then reacts with the epoxy functional groups of mono-epoxy-terminated polydimethylsiloxane (PDMS) to prepare a multi-armed star-shaped hydroxyl resin containing urea and polysiloxane, with the structural formula shown below. Figure 1 The flexibility of the silicon-containing segments further reduces the resin viscosity to 1000 cp, and its solution viscosity is only about 50 mPa·s at 80% solid content, while the viscosity of alkyd resin at the same solid content is as high as 20,000 to 60,000 cp or more. This indicates that the heteropolyarm star-shaped hydroxyl polyester prepared by this invention is suitable for formulating high solid content two-component polyurethane coatings.

[0053] This invention uses a high-molecular-weight, single-terminated epoxy polydimethylsiloxane (PDMS) modified multi-arm star-shaped hydroxyl resin, which is biocompatible, reasonably priced, and environmentally friendly, and has a coating water contact angle of 108°. o Hexadecane contact angle 45° o The surface energy is significantly higher than that of the Covestro coating, indicating that the introduction of silicon segments reduces the surface energy of the coating. To test the coating's durability in practical applications, a mechanical durability cycle test was conducted, such as... Figure 2 As shown, with increasing mechanical durability cycles, the contact angles of water and n-hexadecane on the coating surface gradually decrease, while the corresponding roll-off angles increase. Nevertheless, even after 2500 mechanical durability cycles, the contact angles of the coating surface with water and n-hexadecane remain at a high level, 90.3° and 29.7°, respectively; the roll-off angles also remain at a low level, 27.1° and 9.2°, respectively. Water and n-hexadecane droplets can still slide freely on the coating surface without leaving any residue, indicating that the prepared coating has excellent antifouling durability.

[0054] To test the silicon content on the coating surface and in the bulk, XPS was used to perform a systematic quantitative elemental analysis of the coating surface and cross-section. For example... Figure 3As shown, the silicon (Si) content on the coating surface is as high as 20.0%; while the silicon content in its cross-section is only 2.8%, approximately 14% of the surface content. This indicates that silicon-containing segments have significantly enriched on the coating surface. This is attributed to the low surface energy of the polysiloxane itself and its incompatibility with the polyurethane segments. These two factors jointly drive the migration of silicon-containing segments to the coating-air interface during curing, ultimately leading to enrichment on the surface. This is the key reason why the coating possesses excellent antifouling, hydrophobic, and oleophobic properties. Elemental surface distribution analysis was performed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). Figure 4 The complementary results of the addition of Example 1 and XPS analysis further confirm that the surface silicon content of the coating is much higher than that of the cross section, which further proves that the mechanism of silicon-containing segments migrating to the surface is supported. This migration process significantly reduces the surface energy of the coating and also lays a solid elemental basis for the coating's excellent anti-fouling performance.

[0055] Compared with reference patents CN104262599A and CN 106279659A, this embodiment uses a single-terminated epoxy polysilane to reduce the viscosity of the hydroxyl resin. The two-component polyurethane coating prepared with this material not only has a lower VOC content, but also the silicon-containing segments impart excellent anti-fouling and self-cleaning properties to the coating. Compared with reference patent CN118772779A, the hydroxyl resin prepared in this invention contains urea bonds. Since urea bonds can form double hydrogen bonds with the substrate, they impart excellent adhesion to the coating. Moreover, this invention does not contain fluorocarbon resin, and has advantages in safety, environmental protection, and a high performance-price ratio.

[0056] Example 2

[0057] 1. Raw material composition

[0058] 13.42 g (0.1 mol) of trimethylolpropane

[0059] 1,3-Dihydroxymethylurea 12.01 g (0.1 mol)

[0060] Caprolactone 45.66g (0.4mol)

[0061] SR-6, a mono-epoxylated polysiloxane (molecular weight 6000), 120.0g (0.2mol)

[0062] Tetrabutyl titanate 0.24g

[0063] 0.6g of boron trifluoride diethyl ether

[0064] 2. Preparation: The synthesis of silicon-containing four-armed star-shaped hydroxyl polyester specifically includes the following steps:

[0065] In a four-necked flask equipped with a mechanical stirrer, thermometer, spherical condenser, and nitrogen port, add 13.42 g of trimethylolpropane and 12.01 g of... 1,3-Dihydroxymethylurea, 45.66 g caprolactone, and 0.24 g tetrabutyl titanate were reacted at 120 °C under nitrogen protection for 6 h. Infrared spectroscopy revealed the disappearance of the characteristic infrared peak of caprolactone in the reaction system. The temperature was lowered to below 30 °C, and 0.6 g boron trifluoride ether (BF3·Et2O) was added. Under nitrogen protection, 120.0 g of SR-6 was added dropwise over 2 h using a peristaltic pump. After the addition was complete, the temperature was raised to 60 °C and the reaction continued for 6 h. The epoxy value of the reaction system was detected to have decreased to below 1 wt% of the initial value. 4 g of distilled water was added to quench the boron trifluoride ether catalyst. The mixture was then subjected to high vacuum conditions (vacuum degree <2000 Pa) at 120 °C for 1.5 h to remove water, followed by cooling and discharge to obtain a silicon-containing multi-arm star-shaped hydroxyl polyester (SiHP-2). Its synthesis process and molecular structure are as follows. Figure 5 As shown.

[0066] 3. Performance testing: The viscosity of the silicon-containing multi-arm star-shaped hydroxyl polyester at 25℃ is 2200 mPa.s; the hydroxyl value is 120 mgKOH / g. Solubility: It is miscible with esters such as ethyl acetate, butyl acetate, propylene glycol, and methyl ether acetate; aromatic hydrocarbons such as toluene and xylene; and ketones such as acetone, butanone, 2-heptanone, and cyclohexanone.

[0067] 4. Coating formulation and performance:

[0068] Coating preparation: Take 50g of the product (SiHP-2) obtained in this example, then add 30.5g of N3390 polyurethane curing agent, 0.20g of BYK370 leveling agent, 0.20g of BYK141 defoamer, and add 15g of methyl isopentyl ketone to dilute the coating to a solid content of 60wt%. After stirring and dispersing, apply the coating to tinplate, glass plate and wood plate respectively.

[0069] Coating performance: The coating performance of the above-prepared coating is compared with that of the two-component polyurethane coating prepared by Covestro Arcol Polyol 3553 polyester polyol (curing agent N3300) in Table 2 below:

[0070] Table 2 Coating performance test results

[0071]

[0072] Example 3

[0073] 1. Raw material composition

[0074] Dipentaerythritol 25.48g (0.1mol)

[0075] 1,3-Dihydroxymethylurea 12.01 g (0.1 mol)

[0076] Caprolactone 11.41g (0.1mol)

[0077] SR-6, a mono-epoxylated polysiloxane (molecular weight 6000), 600.0g (0.1mol)

[0078] 0.12g dibutyltin dilaurate

[0079] 0.1g boron trifluoride ethanol

[0080] 2. Preparation: The synthesis of silicon-containing four-armed star-shaped hydroxyl polyester specifically includes the following steps:

[0081] In a four-necked flask equipped with a mechanical stirrer, thermometer, spherical condenser, and nitrogen port, add 25.48 g of dipentaerythritol and 12.01 g of... 1,3-Dihydroxymethylurea, 11.41 g caprolactone, and 0.12 g dibutyltin dilaurate were reacted at 100-110 °C under nitrogen protection for 4 h. Infrared spectroscopy revealed the disappearance of the characteristic infrared peak of caprolactone in the reaction system. The temperature was lowered to below 30 °C, and 0.1 g boron trifluoride ethanol was added. Under nitrogen protection, 600.0 g SR-6 was added dropwise over 1 h using a peristaltic pump. After the addition was complete, the temperature was raised to 60-65 °C and the reaction continued for 4 h. The epoxy value of the reaction system was detected to have decreased to below 1 wt% of the initial value. 1 g distilled water was added to quench the boron trifluoride diethyl ether catalyst. The mixture was then subjected to high vacuum conditions (vacuum degree <2000 Pa) at 80-100 °C for 0.5 h to remove water, followed by cooling and discharge to obtain a silicon-containing multi-arm star-shaped hydroxyl polyester (SiHP-3). Its synthesis process and molecular structure are as follows. Figure 6 As shown.

[0082] 3. Performance testing: The viscosity of the silicon-containing multi-arm star-shaped hydroxyl polyester at 25℃ is 1500 mPa.s; the hydroxyl value is 100 mgKOH / g. Solubility: It is miscible with esters such as ethyl acetate, butyl acetate, propylene glycol, and methyl ether acetate; aromatic hydrocarbons such as toluene and xylene; and ketones such as acetone, butanone, 2-heptanone, and cyclohexanone.

[0083] 4. Coating formulation and performance:

[0084] Coating preparation: Take 50g of the product (SiHP-3) obtained in this example, then add 26.2g of N75 polyurethane curing agent, 0.20g of BYK370 leveling agent, 0.20g of BYK141 defoamer, and add 15g of methyl isopentyl ketone to dilute the coating to a solid content of 60wt%. After stirring and dispersing, apply the coating to tinplate, glass plate and wood plate respectively.

[0085] Coating performance: The coating performance of the above-prepared coating is compared with that of the two-component polyurethane coating prepared by Covestro Arcol Polyol 3553 polyester polyol (curing agent N3300) in Table 3 below:

[0086] Table 3 Coating performance test results

[0087]

[0088] Example 4

[0089] 1. Raw material composition

[0090] 25.03 g (0.1 mol) of bis(trimethylolpropane)

[0091] 1,3-Dihydroxymethylurea 12.01 g (0.1 mol)

[0092] Caprolactone 34.25g (0.3mol)

[0093] SR-8, a mono-epoxylated polysiloxane (molecular weight 8000), 800.0g (0.1mol)

[0094] Stannous octanoate 0.15g

[0095] 0.2g of boron trifluoride tetrahydrofuran

[0096] 2. Preparation: The synthesis of silicon-containing four-armed star-shaped hydroxyl polyester specifically includes the following steps:

[0097] In a four-necked flask equipped with a mechanical stirrer, thermometer, spherical condenser, and nitrogen port, add 25.03 g of bis(trimethylolpropane) and 12.01 g of... 1,3-Dihydroxymethylurea, 68.48 g caprolactone, and 0.15 g stannous octoate were reacted at 100-110 °C under nitrogen protection for 5 h. Infrared spectroscopy revealed the disappearance of the characteristic infrared peak of caprolactone in the reaction system. The temperature was lowered to below 30 °C, and 0.2 g boron trifluoride tetrahydrofuran was added. Under nitrogen protection, 800.0 g SR-8 was added dropwise over 2 h using a peristaltic pump. After the addition was complete, the temperature was raised to 60-65 °C and the reaction continued for 6 h. The epoxy value of the reaction system was detected to have decreased to below 1 wt% of the initial value. 2 g distilled water was added to quench the boron trifluoride diethyl ether catalyst. The mixture was then subjected to high vacuum conditions (vacuum degree <2000 Pa) at 100-110 °C for 1.5 h to remove water, followed by cooling and discharge to obtain a silicon-containing multi-arm star-shaped hydroxyl polyester (SiHP-4). Its synthesis process and molecular structure are as follows. Figure 7 As shown.

[0098] 3. Performance testing: The viscosity of the silicon-containing multi-arm star-shaped hydroxyl polyester at 25℃ is 1800 mPa.s; the hydroxyl value is 150 mgKOH / g. Solubility: It is miscible with esters such as ethyl acetate, butyl acetate, propylene glycol, and methyl ether acetate; aromatic hydrocarbons such as toluene and xylene; and ketones such as acetone, butanone, 2-heptanone, and cyclohexanone.

[0099] 4. Coating formulation and performance:

[0100] Coating preparation: Take 50g of the product (SiHP-4) obtained in this example, then add 35.5g of HT600 polyurethane curing agent, 0.20g of BYK370 leveling agent, 0.20g of BYK141 defoamer, and add 15g of methyl isopentyl ketone to dilute the coating to a solid content of 60wt%. After stirring and dispersing, apply the coating to tinplate, glass plate and wood plate respectively.

[0101] Coating performance: The coating performance of the above-prepared coating is compared with that of the two-component polyurethane coating prepared by Covestro Arcol Polyol 3553 polyester polyol (curing agent N3300) in Table 4 below:

[0102] Table 4 Coating performance test results

[0103]

[0104] Example 5

[0105] 1. Raw material composition

[0106] Pentaerythritol 13.62 g (0.1 mol)

[0107] 1,3-Dihydroxymethylurea 12.01 g (0.1 mol)

[0108] Caprolactone 68.48g (0.6mol)

[0109] SR-8, a mono-epoxylated polysiloxane (molecular weight 8000), 320.0 g (0.4 mol)

[0110] Anhydrous zinc acetate 0.12g

[0111] 0.2g of boron trifluoride diethyl ether

[0112] 2. Preparation: The synthesis of silicon-containing four-armed star-shaped hydroxyl polyester specifically includes the following steps:

[0113] In a four-necked flask equipped with a mechanical stirrer, thermometer, spherical condenser, and nitrogen port, add 13.62 g of pentaerythritol and 12.01 g of... 1,3-Dihydroxymethylurea, 68.48 g caprolactone, and 0.12 g anhydrous zinc acetate were reacted at 110-120 °C under nitrogen protection for 6 h. Infrared spectroscopy revealed the disappearance of the characteristic infrared peak of caprolactone in the reaction system. The temperature was lowered to below 30 °C, and 0.2 g boron trifluoride ether (BF3·Et2O) was added. Under nitrogen protection, 320.0 g of SR-8 was added dropwise over 2 h using a peristaltic pump. After the addition was complete, the temperature was raised to 60-65 °C and the reaction continued for 6 h. The epoxy value of the reaction system was detected to have decreased to below 1 wt% of the initial value. 4 g of distilled water was added to quench the boron trifluoride ether catalyst. The mixture was then subjected to high vacuum conditions (vacuum degree <2000 Pa) at 110-120 °C for 1.5 h to remove water, followed by cooling and discharge to obtain a silicon-containing multi-arm star-shaped hydroxyl polyester (SiHP-5). Its synthesis process and molecular structure are as follows. Figure 8 As shown.

[0114] 3. Performance testing: The viscosity of the silicon-containing multi-arm star-shaped hydroxyl polyester at 25℃ is 1300 mPa.s; the hydroxyl value is 108 mgKOH / g. Solubility: It is miscible with esters such as ethyl acetate, butyl acetate, propylene glycol, and methyl ether acetate; aromatic hydrocarbons such as toluene and xylene; and ketones such as acetone, butanone, 2-heptanone, and cyclohexanone.

[0115] 4. Coating formulation and performance:

[0116] Coating preparation: Take 50g of the product (SiHP-5) obtained in this example, then add 36.2g of HT100 polyurethane curing agent, 0.20g of BYK370 leveling agent, 0.20g of BYK141 defoamer, and add 15g of methyl isopentyl ketone to dilute the coating to a solid content of 60wt%. After stirring and dispersing, apply the coating to tinplate, glass plate and wood plate respectively.

[0117] Coating performance: The coating performance of the above-prepared coating is compared with that of the two-component polyurethane coating prepared by Covestro Arcol Polyol 3553 polyester polyol (curing agent N3300) in Table 5 below:

[0118] Table 5 Coating performance test results

[0119]

[0120] Example 6

[0121] 1. Raw material composition

[0122] Dipentaerythritol 13.62 g (0.1 mol)

[0123] 1,3-Dihydroxymethylurea 12.01 g (0.1 mol)

[0124] Caprolactone 64.48g (0.6mol)

[0125] SR-10, a mono-epoxylated polysiloxane (molecular weight 10000), 600.0g (0.6mol)

[0126] Anhydrous zinc acetate 0.12g

[0127] 0.2g of boron trifluoride diethyl ether

[0128] 2. Preparation: The synthesis of silicon-containing four-armed star-shaped hydroxyl polyester specifically includes the following steps:

[0129] In a four-necked flask equipped with a mechanical stirrer, thermometer, spherical condenser, and nitrogen port, add 13.62 g of pentaerythritol and 12.01 g of... 1,3-Dihydroxymethylurea, 68.48 g caprolactone, and 0.12 g anhydrous zinc acetate were reacted at 110-120 °C under nitrogen protection for 6 h. Infrared spectroscopy revealed the disappearance of the characteristic infrared peak of caprolactone in the reaction system. The temperature was lowered to below 30 °C, and 0.2 g boron trifluoride ether (BF3·Et2O) was added. Under nitrogen protection, 600.0 g SR-10 was added dropwise over 2 h using a peristaltic pump. After the addition was complete, the temperature was raised to 60-65 °C and the reaction continued for 6 h. The epoxy value of the reaction system was detected to have decreased to below 1 wt% of the initial value. 4 g distilled water was added to quench the boron trifluoride ether catalyst. The mixture was then subjected to high vacuum conditions (vacuum degree <2000 Pa) at 110-120 °C for 1.5 h to remove water, followed by cooling and discharge to obtain a silicon-containing multi-arm star-shaped hydroxyl polyester (SiHP-6). Its synthesis process and molecular structure are as follows. Figure 9 As shown.

[0130] 3. Performance testing: The viscosity of the silicon-containing multi-arm star-shaped hydroxyl polyester at 25℃ is 1800 mPa.s; the hydroxyl value is 105 mgKOH / g. Solubility: It is miscible with esters such as ethyl acetate, butyl acetate, propylene glycol, and methyl ether acetate; aromatic hydrocarbons such as toluene and xylene; and ketones such as acetone, butanone, 2-heptanone, and cyclohexanone.

[0131] 4. Coating formulation and performance:

[0132] Coating preparation: Take 50g of the product (SiHP-6) obtained in this example, then add 25.0g of N3390 polyurethane curing agent, 0.20g of BYK370 leveling agent, 0.20g of BYK141 defoamer, and add 15g of methyl isopentyl ketone to dilute the coating to a solid content of 60wt%. After stirring and dispersing, apply the coating to tinplate, glass plate and wood plate respectively.

[0133] Coating performance: The coating performance of the above-prepared coating is compared with that of the two-component polyurethane coating prepared by Covestro Arcol Polyol 3553 polyester polyol (curing agent N3300) in Table 6 below:

[0134] Table 6 Coating performance test results

[0135]

[0136] Those skilled in the art will readily understand that the above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings, characterized in that, Includes the following steps: 1,3-Dihydroxymethylurea, polyol, and caprolactone were mixed, and an acid catalyst was added. The mixture was reacted at 100-120°C under nitrogen protection for 4-6 hours. After the caprolactone was completely reacted, a single-ended epoxy polysiloxane and a cationic ring-opening catalyst were added dropwise. After the addition was complete, the temperature was raised to 60-65°C and the reaction was carried out for 4-6 hours. When the epoxy value decreased to less than 1% of the initial value, distilled water was added to decompose the cationic ring-opening catalyst. The mixture was then distilled under reduced pressure under high vacuum conditions and cooled to obtain a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester. The molar ratio of 1,3-dihydroxymethylurea, polyol, caprolactone, and mono-epoxy polysiloxane is 1:1:(1-6):(1-6). The mass of the acid catalyst is 0.1~0.6% of the mass of caprolactone; The mass of the cationic ring-opening catalyst is 0.01-0.5% of the mass of the single-terminated epoxy polysiloxane.

2. The method for preparing high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings according to claim 1, characterized in that, The polyol is one of trimethylolpropane, bis(trimethylolpropane), pentaerythritol, and bispentaerythritol.

3. The method for preparing high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings according to claim 1, characterized in that, The number average molecular weight of the single-terminated epoxy polysiloxane is 1000-10000.

4. The method for preparing high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings according to claim 1, characterized in that, The acid catalyst is at least one of dibutyltin dilaurate, stannous octoate, anhydrous zinc acetate, and tetrabutyl titanate.

5. The method for preparing a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings according to claim 1, characterized in that, The cationic ring-opening catalyst is at least one of boron trifluoride diethyl ether, boron trifluoride ethanol, and boron trifluoride tetrahydrofuran.

6. The method for preparing a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings according to claim 1, characterized in that, The high vacuum condition is a vacuum degree of less than 2000 Pa; the vacuum distillation temperature is 80-120℃ and the vacuum time is 0.5-1.5h.

7. The method for preparing a high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings according to claim 1, characterized in that, The amount of distilled water added is 10 to 20 times the mass of the cationic ring-opening catalyst.

8. A high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings, characterized in that, It is prepared by the method for preparing high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester for antifouling automotive coatings according to any one of claims 1 to 7.

9. Anti-fouling automotive coating, characterized in that, It includes the high-solids-content silicon-containing multi-arm star-shaped hydroxyl polyester and polyurethane curing agent for antifouling automotive coatings as described in claim 8; the NCO:OH molar ratio of the polyurethane curing agent to the silicon-containing multi-arm star-shaped hydroxyl polyester is 1.05-1.

25.

10. The anti-fouling automotive coating according to claim 9, characterized in that, During the film formation process of antifouling automotive coatings, silicon-containing groups migrate to the interface between the coating and the air, and silicon elements migrate directionally from the coating bulk to the coating interface and accumulate at the coating interface.

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