Isobornyl methacrylate, antibacterial polyurethane coating

Abstract

The application discloses a kind of isobornyl methacrylate, antibacterial polyurethane coating, isobornyl methacrylate is used to prepare water-based polyurethane coating, the isobornyl methacrylate is by pretreatment containing combined with ethoxysilane group;The addition amount of the isobornyl methacrylate in water-based polyurethane coating is 3~5%.The isobornyl methacrylate combined with ethoxysilane group is used as modified component in the water-based polyurethane coating system of the application, so that the water-based polyurethane coating not only inherits the original excellent performance, and the tensile strength and thermal stability of coating film are improved, and water absorption is reduced, more waterproof ability and stability.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to an isoborneol methacrylate and antibacterial polyurethane coating. Background Technology

[0002] Waterborne polyurethane is a novel polyurethane system that uses water as the dispersion medium. It possesses many unique advantages and is widely used in various fields, particularly in coatings, where its unique properties have led to its widespread adoption.

[0003] At present, how to modify waterborne polyurethane to adapt to environmental and application requirements has become the focus of research. Using organosiloxanes to modify polyurethane is a common and environmentally friendly method. Although it can improve the heat resistance of water-washed polyurethane to some extent, it still has the problem of low tensile strength at room temperature. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the present invention aims to provide an isoborneol methacrylate and antibacterial polyurethane coating.

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

[0006] In a first aspect, the present invention provides isoborneol methacrylate for preparing waterborne polyurethane coatings, wherein the isoborneol methacrylate is pretreated to incorporate ethoxysilyl groups; and the amount of isoborneol methacrylate added to the waterborne polyurethane coating is 3-5%.

[0007] In conjunction with the first aspect, the present invention also provides a first specific embodiment of the first aspect, wherein the pretreatment includes a Michael addition reaction of isobornyl methacrylate and 3-amino-1,2-propanediol to synthesize a diol containing hydroxyl groups.

[0008] In conjunction with the first aspect, the present invention also provides a second specific embodiment of the first aspect, wherein the pretreatment includes a ring-opening reaction of a diol containing a hydroxyl group with 3-glycidyl etheroxypropyltriethoxysilane, so that isobornyl methacrylate is bonded with an ethoxysilyl group.

[0009] Secondly, the present invention also provides an antibacterial polyurethane coating, the antibacterial polyurethane coating comprising the following raw materials by weight percentage:

[0010] Castor oil 26-30%;

[0011] N-Methyldiethanolamine 5-5.5%;

[0012] 1,3-Propanesulfonate lactone 5-5.5%;

[0013] 8-10% tung oil-based chain extender;

[0014] 4,4-Dicyclohexylmethane diisocyanate 40–45%;

[0015] Dimethylolbutyric acid 5-5.5%;

[0016] Isoborneol methacrylate 3-5%;

[0017] Nano CaCO3 2-3%;

[0018] Modified nanocellulose 0.1-0.3%;

[0019] The isoborneol methacrylate is pretreated to incorporate ethoxysilyl groups.

[0020] In conjunction with the second aspect, the present invention also provides a first specific embodiment of the second aspect, wherein the antibacterial polyurethane coating comprises the following raw materials in weight percentages:

[0021] Castor oil 26%;

[0022] N-Methyldiethanolamine 5.2%;

[0023] 1,3-Propanesulfonate lactone 5.4%;

[0024] 8% tung oil-based chain extender;

[0025] 4,4-Dicyclohexylmethane diisocyanate 44.6%;

[0026] Dimethylolbutyric acid 5%;

[0027] Isoborneol methacrylate 3%;

[0028] Nano CaCO3 2.6%;

[0029] Modified nanocellulose 0.2%.

[0030] In conjunction with the second aspect, the present invention also provides a second specific embodiment of the second aspect, wherein the pretreatment includes Michael addition reaction of isobornyl methacrylate and 3-amino-1,2-propanediol to synthesize a diol containing hydroxyl groups; and ring-opening reaction of the diol containing hydroxyl groups with 3-glycidyl etheroxypropyltriethoxysilane to bind isobornyl methacrylate with ethoxysilyl groups.

[0031] In conjunction with the second aspect, the present invention also provides a third specific embodiment of the second aspect, wherein the nano-CaCO3 is modified by the following method: dissolving nano-CaCO3 in deionized water and stirring thoroughly to obtain a suspension; adding sodium alginate to deionized water and stirring thoroughly to obtain a solution;

[0032] The suspension and solution were mixed and reacted at 50°C for 2 hours. The mixed solution was filtered and washed with ethanol. The collected solid was dried in a vacuum pore at 40°C to obtain sodium alginate modified nano-CaCO3.

[0033] In conjunction with the second aspect, the present invention also provides a fourth specific embodiment of the second aspect, wherein the modified nanocellulose is modified by the following method: nanocellulose is added to deionized water and ultrasonically dispersed to obtain a dispersion; silane coupling agent KH560 is added to a mixed solution of ethanol and water, and the KH560 solution is stirred for 1 hour until hydrolysis.

[0034] The hydrolyzed KH560 solution was slowly added to the well dispersed liquid and stirred at 110°C. The reaction product was centrifuged and then repeatedly centrifuged and washed with anhydrous ethanol to remove unreacted silane coupling agent KH560.

[0035] Ethanol was removed by fractional distillation at 80°C, followed by freeze drying to obtain modified nanocellulose powder.

[0036] In conjunction with the second aspect, the present invention also provides a fifth specific embodiment of the second aspect, wherein the antibacterial polyurethane coating is prepared by the following method:

[0037] A waterborne polyurethane prepolymer was synthesized by reacting castor oil, N-methyldiethanolamine, 4,4-dicyclohexylmethane diisocyanate, dimethylolbutyric acid, and isobornyl methacrylate at 75°C for 2 h. Subsequently, the WPU chain of the waterborne polyurethane prepolymer was extended by a tung oil-based chain extender for 4 h, and the WPU molecular backbone of the waterborne polyurethane prepolymer was zwitterionic with 1,3-propanesulfonate lactone.

[0038] After the temperature drops to 40℃, add an appropriate amount of triethylamine and stir for 20 min; add nano-CaCO3 to waterborne polyurethane and drop the modified nano-cellulose aqueous dispersion into waterborne polyurethane; stir at 2000 rpm for 30 min using a homogenizer; remove methyl ethyl ketone under a vacuum of 0.09 MPa to obtain antibacterial polyurethane coating.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] 1. This invention provides isoborneol methacrylate for preparing waterborne polyurethane coatings, wherein the isoborneol methacrylate is pretreated to contain ethoxysilyl groups; the amount of isoborneol methacrylate added to the waterborne polyurethane coating is [amount missing]. 3-5%.

[0041] This invention uses isobornyl methacrylate with ethoxysilyl groups as a modifying component in waterborne polyurethane coating systems. This allows the waterborne polyurethane coatings to not only inherit the original excellent properties, but also improve the tensile strength and thermal stability of the coating film, and reduce the water absorption rate, thus improving the waterproof ability and stability.

[0042] 2. This invention provides an antibacterial polyurethane coating, comprising the following raw materials in weight percentages: castor oil 26-30%; N-methyldiethanolamine 5-5.5%; 1,3-propanesulfonate lactone 5-5.5%; tung oil-based chain extender 8-10%; 4,4-dicyclohexylmethane diisocyanate 40-45%; dimethylolbutyric acid 5-5.5%; isobornyl methacrylate 3-5%; nano-CaCO3 2-3%; modified nanocellulose 0.1-0.3%. The isobornyl methacrylate is pretreated to incorporate ethoxysilyl groups.

[0043] This invention utilizes isobornyl methacrylate with ethoxysilyl groups, nano-CaCO3, and modified nanocellulose as modifying components in a polyurethane system. The synergistic effect of isobornyl methacrylate, nano-CaCO3, and modified nanocellulose allows the polyurethane to not only inherit its original excellent properties but also possess superior performance parameters, including significantly improved tensile strength, thermal stability, and waterproofing properties of the coating film. Furthermore, the polyurethane system exhibits additional functionality; through the zwitterionic ionization of the WPU molecular backbone by 1,3-propanesulfonate lactone, and in conjunction with a tung oil-based chain extender, the polyurethane system achieves a synergistic antibacterial effect. Attached Figure Description

[0044] Figure 1 The synthetic route of isoborneol methacrylate in the antibacterial polyurethane coating of the present invention. Figure 1 ;

[0045] Figure 2 The synthetic route of isoborneol methacrylate in the antibacterial polyurethane coating of the present invention. Figure 2 . Detailed Implementation

[0046] To facilitate understanding of the present invention, the technical solutions and advantages of the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Any mechanisms or methods not elaborated in this invention can be referred to in the prior art. The specific structures and features of the present invention are illustrated below by way of example and should not be construed as limiting the present invention in any way. Furthermore, any of the technical features mentioned below (including implicit or disclosed features), as well as any technical features directly shown or implied in the figures, can be arbitrarily combined or deleted among these technical features to form more other embodiments that may not be directly or indirectly mentioned in this invention. The accompanying drawings show preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0047] Currently, modifying polyurethane with organosiloxanes is a common and environmentally friendly method. Introducing polydimethylsiloxane into waterborne polyurethanes, taking advantage of the low surface energy and good compatibility of organosiloxanes, improves the hydrophobicity and heat resistance of the polyurethane. However, this type of modification suffers from relatively low tensile strength at room temperature.

[0048] Therefore, this application provides isoborneol methacrylate for preparing waterborne polyurethane coatings, wherein the isoborneol methacrylate is pretreated to incorporate ethoxysilyl groups.

[0049] This invention uses isobornyl methacrylate with ethoxysilyl groups as a modifying component in waterborne polyurethane coating systems. This allows the waterborne polyurethane coatings to not only inherit the original excellent properties, but also improve the tensile strength and thermal stability of the coating film, and reduce the water absorption rate, thus improving the waterproof ability and stability.

[0050] In some possible implementations, such as Figure 1 and Figure 2 As shown in the synthetic route, isobornyl methacrylate is pretreated through the following pretreatment steps:

[0051] Step (1) Michael addition reaction:

[0052] In a container, isobornyl methacrylate and 3-amino-1,2-propanediol were added in a mass ratio of 5:2. Then, an appropriate amount of acetonitrile was added as a solvent to prepare a mixed solution. At room temperature, nitrogen gas was bubbled into the mixed solution and the mixture was magnetically stirred for 10–15 minutes until homogeneous. The container was then heated to 70°C and reacted for 4 hours.

[0053] Finally, a diol containing hydroxyl groups was obtained by Michael reaction of isobornyl methacrylate and 3-amino-1,2-propanediol.

[0054] Understandably, this reaction is carried out under inert nitrogen protection to prevent unnecessary oxidation and impurity formation. The amino group undergoes Michael addition to the unsaturated double bond, generating an intermediate containing both a hydroxyl and an amino group. The carboxyl group (-COOH) of isobornyl methacrylate reacts with the amino group (-NH2) of 3-amino-1,2-propanediol to form (-CO-NH-).

[0055] Step (II) Ring-opening reaction:

[0056] After cooling to room temperature, 3-glycidyl etheroxypropyltriethoxysilane was added to the above mixed solution, with a mass ratio of 3-glycidyl etheroxypropyltriethoxysilane to the hydroxyl-containing diol of 1.7:1. After stirring for 30 min, the temperature was raised to 60 °C to carry out the ring-opening reaction, which lasted for 4 h, thus obtaining the synthesized diol containing isobornyl methacrylate and ethoxysilane groups.

[0057] Understandably, the epoxy group in the 3-glycidyl etheroxypropyltriethoxysilane molecule undergoes a ring-opening reaction with the hydroxyl group on the intermediate product generated in step (I) to form a stable covalent bond, thus successfully grafting the ethoxysilyl group onto isobornyl methacrylate.

[0058] In some possible implementations, after the reaction is complete, acetonitrile is removed by vacuum distillation. The modified isobornyl methacrylate is then separated by precipitation (using ethanol or water). It is then separated by filtration or centrifugation and finally dried.

[0059] An ethoxysilyl group was introduced into isobornyl methacrylate via a two-step synthesis method, and its application in waterborne polyurethane material systems significantly improved the performance of waterborne polyurethane coatings. This modification method of isobornyl methacrylate provides an effective approach for achieving high performance in waterborne polyurethane coatings.

[0060] In specific polyurethane coating applications, the amount of isoborneol methacrylate added to the polyurethane coating is: 3–5%. The addition range is a ratio verified through experiments, achieving a significant improvement in the performance of waterborne polyurethane coatings. Specifically, the effect of isoborneol methacrylate in waterborne polyurethane coatings is detailed in the experimental results below.

[0061] This embodiment also provides an antibacterial polyurethane coating, which comprises the following raw materials by weight percentage:

[0062] Castor oil 26-30%;

[0063] N-Methyldiethanolamine 5-5.5%;

[0064] 1,3-Propanesulfonate lactone 5-5.5%;

[0065] 8-10% tung oil-based chain extender;

[0066] 4,4-Dicyclohexylmethane diisocyanate 40–45%;

[0067] Dimethylolbutyric acid 5-5.5%;

[0068] Isoborneol methacrylate 3-5%;

[0069] Nano CaCO3 2-3%;

[0070] Modified nanocellulose 0.1-0.3%.

[0071] Among them, the isoborneol methacrylate in the antibacterial polyurethane coating is a diol that has been pretreated to bind isoborneol methacrylate with ethoxysilyl groups.

[0072] In this application, castor oil is used as the main bio-based polyol. Castor oil contains abundant hydroxyl groups and unsaturated bonds, which endow the polyurethane system with good flexibility and adhesion, while improving the wear resistance and environmental performance of the coating film.

[0073] In this application, N-methyldiethanolamine, as a triol-type chain extender and neutralizer, participates in the polyurethane synthesis process, improves the hydrophilicity and dispersibility of the molecular chain, and enhances the stability and application performance of the coating.

[0074] In this application, 1,3-propanesulfonic acid lactone provides sulfonic acid groups, which enhances the ionic hydrophilicity of the coating, improves the stability and dispersion of the aqueous system, and imparts antibacterial activity to the coating film.

[0075] In this application, the tung oil-based chain extender is a chain extender based on tung oil, which increases the toughness and elasticity of the coating film, and has excellent weather resistance and corrosion resistance.

[0076] The synergistic antibacterial effect of waterborne polyurethane materials is controlled by adjusting the ratio of N-methyldiethanolamine, 1,3-propanesulfonic acid lactone, and tung oil-based chain extender. Quaternary ammonium groups possess typical antibiological activity. The positively charged quaternary ammonium groups interact destructively with the cell wall, killing bacteria by disrupting the cell barrier. The three conjugated double bonds in the tung oil-based chain extender have cytotoxic effects on bacteria, inhibiting bacterial growth by affecting normal cellular physiological activities and division processes. This results in a multi-layered synergistic antibacterial effect.

[0077] In this application, 4,4-dicyclohexylmethane diisocyanate (HMDI) is an isocyanate raw material that provides hard segment structures for the construction of the polyurethane backbone, improves the mechanical strength and wear resistance of the coating film, and improves the heat resistance of the coating film due to its cyclic structure.

[0078] In this application, dimethylolbutyric acid (DMPO) improves the hydrophilicity and dispersibility of the coating film by introducing hydroxyl and carboxyl groups, which helps to regulate the crosslinking density and final properties of polyurethane.

[0079] In this application, isobornyl methacrylate with ethoxysilyl groups, nano-CaCO3, and modified nanocellulose are used as modifying components in a polyurethane system. The synergistic effect of isobornyl methacrylate, nano-CaCO3, and modified nanocellulose allows the polyurethane to not only inherit its original excellent properties but also possess superior performance parameters, including significantly improved tensile strength, thermal stability, and waterproofing properties of the coating film. Furthermore, the polyurethane system exhibits additional functionality; through the zwitterionic ionization of the WPU molecular backbone by 1,3-propanesulfonate lactone, and in conjunction with a tung oil-based chain extender, the polyurethane system achieves a synergistic antibacterial effect.

[0080] It should be noted that the antibacterial modification of waterborne polyurethane coatings is mostly based on blended antibacterial agents or single antibacterial mechanisms, which cannot take into account both the mechanical properties and antibacterial properties of the material. Furthermore, the antibacterial effect is overly dependent on the release efficiency of the antibacterial agent, which limits its application in daily life.

[0081] Therefore, this embodiment uses castor oil (CO), N-methyldiethanolamine (MDEA), 1,3-propanesulfonic acid lactone (1,3-PS), tung oil-based chain extender (TOP), isobornyl methacrylate, nano-CaCO3, and modified nanocellulose as raw materials to construct a composite WPU coating with high mechanical strength, multiple antibacterial properties, and strong hydrophobicity. Through the synergistic effect of conjugated double bonds, zwitterions, and micro / nano surface structures, the prepared waterborne polyurethane exhibits excellent antibacterial and antifungal properties.

[0082] In some possible implementations, the nano-CaCO3 is modified through the following modification step one:

[0083] Step (1): Dissolve nano-CaCO3 in deionized water and stir thoroughly to obtain a suspension; add sodium alginate to deionized water and stir thoroughly to obtain a solution.

[0084] In some specific implementations, 3g of nano-CaCO3 is added per 100ml of deionized water. The amount of sodium alginate added is 2% of the mass of the deionized water.

[0085] Step (2): After mixing the suspension and solution, react at 50°C for 2 hours. Filter the mixed solution and wash with ethanol. Dry the collected solid in a vacuum pore at 40°C to obtain sodium alginate modified nano-CaCO3.

[0086] It should be noted that unmodified nano-CaCO3 particles agglomerate together, forming clusters with poor dispersion and a tendency to re-agglomerate. Because unmodified CaCO3 itself has high surface energy, it is incompatible with the polymer matrix, making it difficult to disperse uniformly within the polymer matrix. This results in a large number of agglomerates within the polymer, exhibiting aggregates that are detached from the matrix.

[0087] It should be noted that sodium alginate, as a natural anionic polymer, has a large number of negatively charged carboxyl groups, in which the oxygen atom on the G block can... 2+ Chemical chelation occurs, with the negatively charged carboxylic acid group (-COO-) coordinating with Ca... 2+ Ion interactions. Ca on the surface of nano-CaCO3. 2+ It can serve as an active site for sodium alginate adsorption on the particle surface, enabling it to form a coating layer on the surface of nano-CaCO3 through chelation. After modification with sodium alginate, the nano-CaCO3 particles exhibit better interfacial separation, significantly reduced agglomeration, greater separation between individual particles, and easier dispersion, thereby improving dispersibility.

[0088] The sodium alginate on the surface of nano-CaCO3 can form hydrogen bonds with the urethane groups of WPU through the large number of hydroxyl and carboxyl groups in its structure, thereby improving the dispersibility and compatibility of nano-CaCO3 in waterborne polyurethane and thus improving the performance of waterborne polyurethane materials.

[0089] In some possible implementations, the modified nanocellulose is modified by the following second modification step:

[0090] Step (1): Add nanocellulose to deionized water and disperse it by ultrasound to obtain a dispersion; add silane coupling agent KH560 to a mixed solution of ethanol and water, and stir the KH560 solution for 1 hour until hydrolysis.

[0091] In some specific implementations, the volume ratio of ethanol to water is 9:1.

[0092] Step (2): Slowly add the hydrolyzed KH560 solution to the well dispersed liquid and stir at 110℃ for 3 hours. Centrifuge the reaction product and wash it repeatedly with anhydrous ethanol 3-5 times to remove unreacted silane coupling agent KH560.

[0093] Step (3): Remove ethanol by fractional distillation at 80℃, and then freeze-dry to finally obtain modified nanocellulose powder.

[0094] After modification with silane coupling agents, the steric hindrance effect of the silane coupling agent molecular chains and the reduction of hydroxyl groups on the molecular surface result in better dispersibility, achieving a more uniform distribution in the waterborne polyurethane system. The reduced number of water-adsorbing hydroxyl groups on the surface of nanocellulose leads to a decrease in its hydrophilicity, thereby improving the hydrophobicity of the waterborne polyurethane material.

[0095] In some possible embodiments, the antibacterial polyurethane coating is prepared by the following coating preparation steps, specifically including:

[0096] Step (1): Castor oil, N-methyldiethanolamine, 4,4-dicyclohexylmethane diisocyanate, dimethylolbutyric acid and isobornyl methacrylate were reacted at 75°C for 2 h to synthesize a waterborne polyurethane prepolymer. Subsequently, the WPU chain of the waterborne polyurethane prepolymer was extended by a tung oil-based chain extender for 4 h, and the WPU molecular backbone of the waterborne polyurethane prepolymer was zwitterionic with 1,3-propanesulfonate lactone.

[0097] Step (2): When the temperature drops to 40℃, add an appropriate amount of triethylamine and stir for 20 min; add nano-CaCO3 to waterborne polyurethane and drop the modified nano-cellulose aqueous dispersion into waterborne polyurethane; use a homogenizer to stir at 2000 rpm for 30 min; remove methyl ethyl ketone under a vacuum of 0.09 MPa to obtain antibacterial polyurethane coating.

[0098] Specifically, this application provides the following specific embodiments for illustration:

[0099] Example 1

[0100] This embodiment 1 provides an antibacterial polyurethane coating, which comprises the following raw materials by weight percentage:

[0101] Castor oil 30%;

[0102] N-Methyldiethanolamine 5.2%;

[0103] 1,3-Propanesulfonate lactone 5.2%;

[0104] 8% tung oil-based chain extender;

[0105] 4,4-Dicyclohexylmethane diisocyanate 41%;

[0106] Dimethylolbutyric acid 5.5%;

[0107] Isoborneol methacrylate 3%;

[0108] Nano CaCO32%;

[0109] Modified nanocellulose 0.1%.

[0110] Specifically, the raw material isobornyl methacrylate is pretreated using the pretreatment steps described above. The raw material nano-CaCO3 is modified using the modification treatment step one described above. The raw material modified nano-cellulose is modified using the modification treatment step two described above.

[0111] Antibacterial polyurethane coatings are prepared through the following coating preparation steps, specifically including:

[0112] Step (1): Castor oil, N-methyldiethanolamine, 4,4-dicyclohexylmethane diisocyanate, dimethylolbutyric acid and isobornyl methacrylate were reacted at 75°C for 2 h to synthesize a waterborne polyurethane prepolymer. Subsequently, the WPU chain of the waterborne polyurethane prepolymer was extended by a tung oil-based chain extender for 4 h, and the WPU molecular backbone of the waterborne polyurethane prepolymer was zwitterionic with 1,3-propanesulfonate lactone.

[0113] Step (2): When the temperature drops to 40℃, add an appropriate amount of triethylamine and stir for 20 min; add nano-CaCO3 to waterborne polyurethane and drop the modified nano-cellulose aqueous dispersion into waterborne polyurethane; use a homogenizer to stir at 2000 rpm for 30 min; remove methyl ethyl ketone under a vacuum of 0.09 MPa to obtain antibacterial polyurethane coating.

[0114] Example 2

[0115] This embodiment 2 provides an antibacterial polyurethane coating, which comprises the following raw materials by weight percentage:

[0116] Castor oil 26%;

[0117] N-Methyldiethanolamine 5.2%;

[0118] 1,3-Propanesulfonate lactone 5.4%;

[0119] 8% tung oil-based chain extender;

[0120] 4,4-Dicyclohexylmethane diisocyanate 44.6%;

[0121] Dimethylolbutyric acid 5%;

[0122] Isoborneol methacrylate 3%;

[0123] Nano CaCO3 2.6%;

[0124] Modified nanocellulose 0.2%.

[0125] Specifically, the pretreatment and modification treatments of isoborneol methacrylate, nano-CaCO3, and modified nanocellulose used in Example 2 are exactly the same as those in Example 1. Furthermore, the preparation method of the antibacterial polyurethane coating is exactly the same as that in Example 1.

[0126] Example 3

[0127] This embodiment 3 provides an antibacterial polyurethane coating, which comprises the following raw materials by weight percentage:

[0128] Castor oil 27.4%;

[0129] N-Methyldiethanolamine 5.2%;

[0130] 1,3-Propanesulfonate lactone 5.2%;

[0131] 8% tung oil-based chain extender;

[0132] 4,4-Dicyclohexylmethane diisocyanate 42.6%;

[0133] Dimethylolbutyric acid 5%;

[0134] Isoborneol methacrylate 4%;

[0135] Nano CaCO3 2.4%;

[0136] Modified nanocellulose 0.2%.

[0137] Specifically, the pretreatment and modification treatments of isoborneol methacrylate, nano-CaCO3, and modified nanocellulose used in Example 3 are exactly the same as those in Example 1. Furthermore, the preparation method of the antibacterial polyurethane coating is exactly the same as that in Example 1.

[0138] Example 4

[0139] This embodiment 4 provides an antibacterial polyurethane coating, which comprises the following raw materials by weight percentage:

[0140] Castor oil 26.2%;

[0141] 5% N-methyldiethanolamine;

[0142] 1,3-Propanesulfonate lactone 5%;

[0143] 10% tung oil-based chain extender;

[0144] 4,4-Dicyclohexylmethane diisocyanate 40.5%;

[0145] Dimethylolbutyric acid 5%;

[0146] Isoborneol methacrylate 5%;

[0147] Nano CaCO33%;

[0148] Modified nanocellulose 0.3%.

[0149] Specifically, the pretreatment and modification treatments of isoborneol methacrylate, nano-CaCO3, and modified nanocellulose used in Example 4 are exactly the same as those in Example 1. Furthermore, the preparation method of the antibacterial polyurethane coating is exactly the same as that in Example 1.

[0150] Comparative Example 1

[0151] Based on the antibacterial polyurethane coating of Example 2, isoborneol methacrylate was not pretreated in any way, and the proportions of each raw material were kept consistent with those of Example 2. The modification treatment of nano-CaCO3 and modified nanocellulose, as well as the coating preparation steps of the antibacterial polyurethane coating, were exactly the same as those of Example 2.

[0152] The molecular structural formula of isobornyl methacrylate is as follows: .

[0153] Based on Examples 1-4 and Comparative Example 1, performance tests were conducted on the antibacterial polyurethane coating:

[0154] I. Tensile property test:

[0155] The antibacterial polyurethane coatings prepared in Examples 1-4 and Comparative Example 1 were poured into dumbbell-shaped polytetrafluoroethylene molds (effective length 20 mm, width 4.0 ± 0.1 mm, thickness 1.0 ± 0.1 mm), dried at room temperature for 1 day, and then dried under vacuum at 50°C for 3 days to prepare multiple samples. The tensile rate was 100 mm / min. The mechanical properties of the samples were tested using a Chinese CMT4204 universal tensile testing machine according to the standard GB / T528-2009. Each group of samples was tested 5 times, and the average value of the results was taken.

[0156]

[0157] This application achieves superior mechanical properties through a multi-scale composite effect: Pretreated isobornyl methacrylate exhibits silane groups that hydrolyze and condense in an aqueous polyurethane system to form a siloxane network, creating crosslinking points and a three-dimensional network structure. This crosslinked network enhances the rigidity and mechanical strength of the polyurethane while restricting the free movement of polymer chains and reducing the material's plastic deformation capacity. The presence of tung oil-based chain extenders and dimethylolbutyric acid increases the hard segment content and the number of polar groups, strengthening inter-segment hydrogen bonding and intermolecular forces, further enhancing the material's strength.

[0158] On the other hand, the modified nano-CaCO3 enhances the interfacial bonding between the nano-CaCO3 and the polyurethane matrix through hydrogen bonding (sodium alginate forms hydrogen bonds with the urethane groups of the polyurethane matrix through a large number of active groups such as hydroxyl and carboxyl groups in its structure). It can also form physical cross-linking structures with the long chains of the polyurethane matrix, improving stress transfer efficiency. The polyurethane matrix can effectively transfer pressure loads to the rigid nano-CaCO3 particles. The uniformly dispersed and well-bonded nanofillers effectively avoid stress concentration caused by the introduction of inorganic rigid particles.

[0159] On the other hand, as a reinforcing phase, the modified nanocellulose forms strong hydrogen bonds and partial covalent bonds with the silane groups on its surface and the urethane groups in the polyurethane. This good interfacial bonding is conducive to the transfer of stress from the polyurethane matrix to the nanocellulose, thereby improving the overall mechanical properties of the composite material.

[0160] II. Preparation of waterborne polyurethane films and coatings using antibacterial polyurethane coatings:

[0161] The antibacterial polyurethane coatings prepared in Examples 1-4 were poured into polytetrafluoroethylene molds and dried at room temperature for 1 day, then dried under vacuum at 50°C for 3 days to obtain an aqueous polyurethane film with a thickness of 0.4 ± 0.03 mm. Multiple samples were prepared for each example, with 5 samples forming a group.

[0162] An appropriate amount of the antibacterial polyurethane coatings prepared in Examples 1-4 were drop-coated onto the edge of a glass substrate. A waterborne polyurethane coating with a thickness of 300±20µm was then applied using a coating machine at a speed of 5mm / s. Multiple samples were prepared for each example, with 5 samples forming a group.

[0163] (1) Water contact angle test:

[0164] The tests were conducted using a Chinese CA200 contact angle measuring instrument with a deionized water volume of 2.0 μL. The contact angle (WCA) and sliding angle (SA) of the coating were measured using the seat drop method at room temperature.

[0165]

[0166] By improving the hydrophobicity of the coating, the adhesion of microorganisms to the coating surface is reduced, further improving the antibacterial properties of the material.

[0167] (2) Water absorption test:

[0168] The waterborne polyurethane film was placed in a 60℃ oven until its mass stabilized, and its mass was recorded as m1. Then, it was placed in a beaker containing deionized water and soaked at room temperature for 24 hours. The surface moisture of the waterborne polyurethane film was wiped off with filter paper, and the mass of the waterborne polyurethane film was recorded as m2. According to... Calculate the water absorption rate W of the waterborne polyurethane film. Test the water absorption rate of 3 waterborne polyurethane films in each group, and take the average value of the results.

[0169]

[0170] Castor oil, a natural fatty oil, possesses good hydrophobicity and film-forming properties, effectively preventing water penetration and thus reducing water absorption. On the other hand, 4,4-dicyclohexylmethane diisocyanate and dimethylolbutyric acid contribute to the formation of a polyurethane network with high cross-linking density, improving film density and preventing water absorption. Furthermore, the addition of pretreated isobornyl methacrylate introduces an organosilicon structure, resulting in low surface energy and synergistic hydrophobicity with the micro / nano structure, further enhancing the hydrophobicity of the coating surface. Nano-CaCO3, as an inorganic nanofiller, fills polymer gaps, increasing film density and hindering water penetration; the synergistic effect of nano-CaCO3 and modified nanocellulose reduces microscopic defects and pores, enhancing the waterproof barrier effect.

[0171] (3) Antibacterial and antifungal properties tests:

[0172] The antibacterial effect of waterborne polyurethane coatings against *Escherichia coli* and *Staphylococcus aureus* was studied using a plate count assay. 100 μL (2 × 10⁻⁶) of waterborne polyurethane coating was used as the antibacterial agent. 8 A bacterial suspension (CFU / mL) was placed in a 96-well plate, and PBS (control) and aqueous polyurethane (20 µg / mL) were added. After incubation at 37°C for 20 min, 100 µL of the bacterial suspension (diluted 1000 times) was spread onto an LB agar plate. After incubation at 37°C for 24 h, the bacterial colony count was recorded.

[0173] All experiments were conducted in triplicate. The formula for calculating antibacterial efficiency is as follows: In the formula: B is the number of bacterial colonies in the control group, and C is the number of bacterial colonies in the experimental group.

[0174]

[0175] Experimental results showed that all four examples exhibited significant antibacterial activity, with antibacterial efficiencies exceeding 90%.

[0176] (4) Thermal stability test:

[0177] Take 15 mg of the samples prepared in Examples 1 to 4 respectively and place them in crucibles. Perform thermal stability analysis using a thermogravimetric analyzer. Set the heating rate to 20 °C / min, the N2 flow rate to 50 mL / min, and the temperature range to 30–600 °C.

[0178] Experiments show that the antibacterial polyurethane coating samples of this application exhibit three weight loss stages. The first stage of weight loss (80–240 °C) mainly involves the release of trace amounts of volatile residual small molecules, indicating that the material has excellent initial thermal stability and only slight weight loss. The second stage of weight loss (240–390 °C) is the onset of pyrolysis of the polyurethane hard segment (isocyanate + chain extender structure), mainly involving the breaking of urethane bonds (–NH–COO–), releasing gases such as CO2. The pyrolysis temperature is higher than that of ordinary polyurethane systems, reflecting the stability of the crosslinked structure. The third stage of weight loss (390–540 °C) corresponds to the breaking and thermal decomposition of the soft segment (castor oil, tung oil-based fatty chains) and the isoborneol methacrylate main chain, with a large number of organic components being converted into small molecule volatiles and the polymer decomposing. The significant weight loss only occurs after the temperature reaches 390 °C, indicating strong heat resistance of the main structure and reflecting good thermal resistance.

[0179] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, it will be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A modified isoborneol methacrylate for preparing waterborne polyurethane coatings, characterized in that: The modified isoborneol methacrylate is pretreated to incorporate ethoxysilyl groups; the modified isoborneol methacrylate is added at a rate of 3-5% in waterborne polyurethane coatings; The pretreatment includes a Michael addition reaction of isobornyl methacrylate and 3-amino-1,2-propanediol to synthesize a hydroxyl-containing diol; the pretreatment includes a ring-opening reaction of the hydroxyl-containing diol with 3-glycidyl etheroxypropyltriethoxysilane to bind isobornyl methacrylate to an ethoxysilyl group.

2. An antibacterial polyurethane coating, characterized in that, The antibacterial polyurethane coating comprises the following raw materials by weight percentage: Castor oil 26-30%; N-Methyldiethanolamine 5-5.5%; 1,3-Propanesulfonate lactone 5-5.5%; 8-10% tung oil-based chain extender; 4,4-Dicyclohexylmethane diisocyanate 40–45%; Dimethylolbutyric acid 5-5.5%; Modified isoborneol methacrylate 3-5%; Nano CaCO3 2-3%; Modified nanocellulose 0.1-0.3%; The modified isoborneol methacrylate is pretreated to incorporate an ethoxysilyl group. The pretreatment includes a Michael addition reaction of isoborneol methacrylate and 3-amino-1,2-propanediol to synthesize a hydroxyl-containing diol; and a ring-opening reaction of the hydroxyl-containing diol with 3-glycidyl etheroxypropyltriethoxysilane to incorporate an ethoxysilyl group into isoborneol methacrylate.

3. The antibacterial polyurethane coating as described in claim 2, characterized in that, The antibacterial polyurethane coating comprises the following raw materials by weight percentage: Castor oil 26%; N-Methyldiethanolamine 5.2%; 1,3-Propanesulfonate lactone 5.4%; 8% tung oil-based chain extender; 4,4-Dicyclohexylmethane diisocyanate 44.6%; Dimethylolbutyric acid 5%; Modified isoborneol methacrylate 3%; Nano CaCO3 2.6%; Modified nanocellulose 0.2%.

4. An antibacterial polyurethane coating as described in claim 2 or 3, characterized in that: The nano-CaCO3 was modified by the following method: nano-CaCO3 was dissolved in deionized water and stirred thoroughly to obtain a suspension; sodium alginate was added to deionized water and stirred thoroughly to obtain a solution; The suspension and solution were mixed and reacted at 50°C for 2 hours. The mixed solution was filtered and washed with ethanol. The collected solid was dried in a vacuum pore at 40°C to obtain sodium alginate modified nano-CaCO3.

5. An antibacterial polyurethane coating as described in claim 2 or 3, characterized in that: The modified nanocellulose was modified by the following method: nanocellulose was added to deionized water and ultrasonically dispersed to obtain a dispersion; silane coupling agent KH560 was added to a mixed solution of ethanol and water, and the KH560 solution was stirred for 1 hour until hydrolysis. The hydrolyzed KH560 solution was slowly added to the well dispersed liquid and stirred at 110°C. The reaction product was centrifuged and then repeatedly centrifuged and washed with anhydrous ethanol to remove unreacted silane coupling agent KH560. Ethanol was removed by fractional distillation at 80°C, followed by freeze drying to obtain modified nanocellulose powder.

6. An antibacterial polyurethane coating as described in claim 2 or 3, characterized in that, The antibacterial polyurethane coating is prepared by the following method: A waterborne polyurethane prepolymer was synthesized by reacting castor oil, N-methyldiethanolamine, 4,4-dicyclohexylmethane diisocyanate, dimethylolbutyric acid, and modified isoborneol methacrylate at 75°C for 2 h. Subsequently, the WPU chain of the waterborne polyurethane prepolymer was extended by reacting with a tung oil-based chain extender for 4 h, and the WPU molecular backbone of the waterborne polyurethane prepolymer was zwitterionic with 1,3-propanesulfonate lactone. After the temperature drops to 40℃, add an appropriate amount of triethylamine and stir for 20 minutes; add nano-CaCO3 to waterborne polyurethane and drop the modified nano-cellulose aqueous dispersion into waterborne polyurethane; stir at 2000 rpm for 30 minutes using a homogenizer; remove methyl ethyl ketone under a vacuum of 0.09 MPa to obtain an antibacterial polyurethane coating.

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