Polycarbonate-based non-isocyanate polyurethane ultraviolet curing coating and preparation method thereof

Abstract

The invention discloses a polycarbonate-based non-isocyanate polyurethane ultraviolet curing coating and a preparation method of the polycarbonate-based non-isocyanate polyurethane ultraviolet curing coating. The photocureable coating is prepared from the following components: 10 to 60 percent of polycarbonate acrylate, 5 to 20 percent of urethane acrylate, 10 to 60 percent of reactive diluent, 1 to 5 percent of photoinitiator and 0 to 60 percent of solvent. Comprising the following steps: (1) reacting polycarbonate diol with methacrylic anhydride to obtain polycarbonate acrylate; (2) carbonating the allyl glycidyl ether by using carbon dioxide to obtain corresponding five-membered cyclic carbonate, and reacting with diamine to obtain urethane acrylate; and (3) uniformly mixing the obtained product with a reactive diluent and a photoinitiator to obtain the ultraviolet curing coating. The polycarbonate-based non-isocyanate polyurethane ultraviolet curing coating obtained by the invention is a biodegradable environment-friendly coating, a non-isocyanate polyurethane synthesis route is adopted, the use of isocyanate is avoided, and the coating shows excellent flexibility and pencil hardness on a PC (polycarbonate) base material.

Description

Technical Field

[0001] The present invention relates to the technical field of ultraviolet curable coatings, and particularly relates to a polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating and a preparation method thereof. Background Art

[0002] Ultraviolet curable coatings are considered an energy-saving and environmentally friendly coating due to their advantages such as fast curing speed, low energy consumption, and wide application range. They generally consist of a main resin, an active diluent, a photoinitiator, and other additives. Among them, polyurethane ultraviolet curable coatings have received extensive attention in recent years due to their excellent chemical resistance and wear resistance. Currently, the main resin used in common polyurethane ultraviolet curable coatings on the market is mostly polyurethane acrylate, which does not have biodegradability and has a profound impact on environmental pollution while being widely used.

[0003] Polycarbonate diol is a type of carbon dioxide-based fully biodegradable material, which is copolymerized from carbon dioxide, epoxide, and a chain transfer agent under the action of a catalyst. It can be completely degraded into carbon dioxide, water, mineral salts, and other substances, and is a green and environmentally friendly material. Applying it to coatings can obtain ultraviolet curable coatings that can be biodegradable.

[0004] Secondly, since isocyanate is required as the main raw material in the production process of polyurethane acrylate, the toxicity of isocyanate during production and use has restricted its application in many fields. Based on this, the development of non-isocyanate polyurethane coatings prepared without using isocyanate has been promoted. Non-isocyanate polyurethane coatings conform to the new development concept of green environmental protection and are expected to become a new type of environmentally friendly material to replace traditional polyurethane coatings.

[0005] Therefore, we propose to use polycarbonate diol as the main raw material and adopt a non-isocyanate polyurethane synthesis route to prepare a polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating. Summary of the Invention

[0006] The purpose of the present invention is to provide a polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating with better flexibility and significantly improved pencil hardness and a preparation method thereof in view of the deficiencies existing in the prior art.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating is composed of the following components in weight percentages:

[0009] Polycarbonate acrylate 10 - 60%,

[0010] Polyurethane acrylate: 5 - 20%,

[0011] Reactive diluent: 10 - 60%,

[0012] Photoinitiator: 1 - 5%,

[0013] Solvent: 0 - 60%,

[0014] The polycarbonate acrylate has a structure shown in formula (1), where a≥0, b≥0, c≥0, d≥0, e≥0; a, b, c, d, e are all integers and not all zero at the same time;

[0015]

[0016] where R is the self - polymerization part of at least one of the epoxy monomers in the following;

[0017] The polyurethane acrylate has a structure shown in formula (2);

[0018]

[0019] Preferably, in the above - mentioned polycarbonate - based non - isocyanate polyurethane UV - curable coating, it is composed of components with the following weight percentages:

[0020] Polycarbonate acrylate: 20 - 50%,

[0021] Polyurethane acrylate: 5 - 15%,

[0022] Reactive diluent: 20 - 40%,

[0023] Photoinitiator: 3 - 5%,

[0024] Solvent: 20 - 50%.

[0025] Preferably, in the above - mentioned polycarbonate - based non - isocyanate polyurethane UV - curable coating, the reactive diluent is a small - molecule acrylate monomer, which is at least one of 2 - hydroxyethyl methacrylate, 1,6 - hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

[0026] Preferably, in the above - mentioned polycarbonate - based non - isocyanate polyurethane UV - curable coating, the photoinitiator includes at least one of benzoin dimethyl ether, 1 - hydroxycyclohexyl phenyl ketone, diphenyl(2,4,6 - trimethylbenzoyl)phosphine oxide, and 2 - hydroxy - 2 - methylpropiophenone.

[0027] Preferably, in the above polycarbonate-based non-isocyanate polyurethane UV-curable coating, the solvent is at least one of acetone, butyl acetate, propylene glycol monomethyl ether, and propylene glycol methyl ether acetate.

[0028] Preferably, in the above polycarbonate-based non-isocyanate polyurethane UV-curable coating, the preparation method of the polycarbonate acrylate comprises the following steps:

[0029] (1) Under the protection of an inert gas and in the presence of a catalyst, react a polycarbonate diol and methacrylic anhydride in a solvent to obtain a crude product;

[0030] The polycarbonate diol has a structure shown in formula (3), where a≥0, b≥0, c≥0, d≥0, e≥0, a, b, c, d, e are all integers and not all zero at the same time;

[0031]

[0032] where R is the self-polymerized part of at least one of the epoxy monomers in the formula.

[0033] (2) Wash and dry the obtained crude product to obtain the polycarbonate acrylate.

[0034] Preferably, in the above polycarbonate-based non-isocyanate polyurethane UV-curable coating, in step (1), the polycarbonate diol has a number average molecular weight in the range of 1000 - 3000 g / mol, and the content of polycarbonate in the main chain is 50% - 95%; the molar ratio of the polycarbonate diol, methacrylic anhydride, and catalyst is 1:2 - 10:0.25 - 0.3; the reaction temperature is 25 - 100 °C, and the reaction time is 3 - 36 h; the catalyst is the basic catalyst 4-dimethylaminopyridine; an antioxidant 2,6-di-tert-butyl-p-cresol is also added; the solvent is at least one of dichloromethane, ethyl acetate, butyl acetate, and N,N-dimethylformamide.

[0035] Step (2) is: Wash the obtained crude product with ethanol or ether at least three times to remove unreacted methacrylic anhydride, by-product methacrylic acid, solvent, residual catalyst, and antioxidant in the crude product, and dry after washing to obtain the polycarbonate acrylate; the drying is vacuum drying, the drying temperature is 25 - 80 °C, and the time is 24 - 48 h.

[0036] Preferably, in the above polycarbonate-based non-isocyanate polyurethane UV-curable coating, the preparation method of the polyurethane acrylate comprises the following steps:

[0037] (1) React glycidyl methacrylate with carbon dioxide under the action of a catalyst in the presence of an antioxidant to obtain the corresponding five-membered cyclic carbonate;

[0038] (2) React the obtained five-membered cyclic carbonate with hexamethylenediamine to obtain polyurethane acrylate.

[0039] Preferably, in the above-mentioned polycarbonate-based non-isocyanate polyurethane ultraviolet-curable coating, in step (1), the reaction temperature is 100 °C, the reaction time is 24 h, the pressure of carbon dioxide is 3.0 MPa, the catalyst is tetrabutylammonium bromide, and the catalyst dosage is 0.1% of the weight of glycidyl methacrylate. The antioxidant is 2,6-di-tert-butyl-p-cresol, and the antioxidant dosage is 0.5% of the weight of glycidyl methacrylate; in step (2), the molar ratio of the five-membered cyclic carbonate to hexamethylenediamine is 1:1 - 1:1.2.

[0040] A method for preparing a polycarbonate-based non-isocyanate polyurethane ultraviolet-curable coating includes the following steps: Mix polycarbonate acrylate, polyurethane acrylate, active diluent, photoinitiator, and solvent to obtain a polycarbonate-based non-isocyanate polyurethane ultraviolet-curable coating. Coating the coating into a film, drying and then curing under ultraviolet light irradiation to obtain a polycarbonate-based non-isocyanate polyurethane ultraviolet-curable coating. The polycarbonate acrylate has unsaturated double bonds at the ends of the molecular chain and can crosslink and polymerize under ultraviolet light irradiation. The number-average molecular weight of the polycarbonate acrylate is in the range of 1000 - 3000 g / mol, the functionality is 2, and the content of polycarbonate in the main chain is 50% - 95%.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] (1) The polycarbonate acrylate used in the present invention as the main raw material of the ultraviolet-curable coating successfully introduces active unsaturated double bonds at both ends of the polymer chain while ensuring that the carbonate bonds in the molecular structure of the polycarbonate diol do not degrade, enabling it to crosslink and polymerize under ultraviolet light irradiation. In addition, since the raw material polycarbonate diol for preparing the polycarbonate acrylate is polymerized from carbon dioxide and epoxide as the main raw materials and is an environmentally friendly material that can be completely degraded, the polycarbonate acrylate prepared by the present invention also has biodegradability. Applying it to the coating is expected to obtain a biodegradable photocurable product.

[0043] (2) The present invention utilizes the synthesis route of non-isocyanate polyurethane to prepare a polyurethane acrylate prepolymer, which is used as one of the main raw materials for ultraviolet (UV) curable coatings. This synthesis route does not require the addition of toxic isocyanate as a raw material. By using the reaction of five-membered cyclic carbonate and diamine, a polyurethane acrylate containing characteristic urethane groups in the molecular structure and unsaturated double bonds at both ends is prepared. The raw materials are inexpensive and easily available. When applied to coatings, compared with traditional polyurethane coatings, it exhibits lower toxicity during both production and use.

[0044] (3) The present invention selects common mono-functional or multi-functional active diluents and adds them to the coating formulation, which can not only effectively improve the compatibility of polycarbonate acrylate and polyurethane acrylate, but also contribute to the reduction of the system viscosity. In addition, the active diluent can also participate in the UV curing cross-linking polymerization process, which is beneficial to the improvement of the cross-linking density of the system and the enhancement of water resistance and adhesion performance.

[0045] (4) By dissolving the self-made polycarbonate acrylate, polyurethane acrylate, active diluent, and photoinitiator in a suitable solvent according to a specific ratio, the present invention can obtain a polycarbonate-based non-isocyanate polyurethane UV curable coating. This coating is a new type of environmentally friendly coating. When applied to PC substrates, it exhibits excellent light transmittance, adhesion performance, flexibility, and good hardness. Moreover, after soaking in hot water at 60 °C for 240 h, the adhesion remains good, indicating that the coating prepared has good water resistance. Description of the Drawings

[0046] Figure 1 It is the molecular structure of the polycarbonate diol used in Examples 1-5 of the present invention.

[0047] Figure 2 It is the 1H NMR spectrum (using deuterated chloroform as the solvent) of the polycarbonate acrylate product obtained in Example 1 of the present invention.

[0048] Figure 3 It is the 1H NMR spectrum (using deuterated chloroform as the solvent) of the polycarbonate acrylate product obtained in Example 3 of the present invention.

[0049] Figure 4 It is the 1H NMR spectrum (using deuterated chloroform as the solvent) of the polyurethane acrylate product obtained in Example 6 of the present invention. Detailed Embodiments

[0050] The following further illustrates the present invention in conjunction with the drawings of the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0051] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0052] Example 1. Preparation of Polycarbonate Acrylate

[0053] 18.46 g of polycarbonate diol (PPCDL, see figure a in Figure 1 , Mn = 2250 g / mol) was heated under vacuum to 110 °C. After no bubbles were generated, nitrogen was introduced and it was cooled to 70 °C. 250.6 mg of 4-dimethylaminopyridine was weighed, dissolved completely in an appropriate amount of N,N-dimethylformamide and then transferred to a flask. 3.794 g of methacrylic anhydride was added, and the reaction was continued for 5 h under a nitrogen atmosphere.

[0054] The obtained product was washed three times with ethanol to remove the N,N-dimethylformamide solvent, unreacted methacrylic anhydride and by-product methacrylic acid, and then vacuum dried at room temperature for 48 h to obtain the polycarbonate acrylate product.

[0055] The purified product was taken for nuclear magnetic resonance analysis and calculation. Approximately 100% of both ends of the polymer chain were successfully grafted with methacrylate groups. The test results of gel permeation chromatography (GPC) showed that the number-average molecular weight M n of the polycarbonate diol before the reaction was 2250 g / mol, and the number-average molecular weight M n of the polycarbonate acrylate obtained after the reaction was 2460 g / mol. The proton nuclear magnetic resonance spectrum (using deuterated chloroform as the solvent) of the polycarbonate acrylate product obtained in Example 1 is as shown in Figure 2 . It can be seen from Figure 2 that the obtained product is the target product.

[0056] Example 2. Preparation of Polycarbonate Acrylate

[0057] 25.32 g of polycarbonate diol (PECDL, see figure b in Figure 1 , Mn = 1270 g / mol) was heated under vacuum to 110 °C. After no bubbles were generated, nitrogen was introduced and it was cooled to 40 °C. 608.9 mg of 4-dimethylaminopyridine was weighed, dissolved completely in an appropriate amount of N,N-dimethylformamide and then transferred to a flask. 9.220 g of methacrylic anhydride was added, and the reaction was continued for 10 h under a nitrogen atmosphere.

[0058] The obtained product was washed three times with ethanol to remove the N,N-dimethylformamide solvent, unreacted methacrylic anhydride and by-product methacrylic acid, and then vacuum dried at 60 °C for 24 h to obtain the polycarbonate acrylate product.

[0059] The purified product was subjected to nuclear magnetic resonance analysis and calculation, and about 100% of the two ends of the polymer chain were successfully grafted with methyl propionate groups. The test results of gel permeation chromatography (GPC) showed that the number-average molecular weight M n of the polycarbonate diol before the reaction was 1270 g / mol, and the number-average molecular weight M n of the polycarbonate acrylate obtained after the reaction was 1450 g / mol.

[0060] Example 3. Preparation of polycarbonate acrylate

[0061] 15.28 g of polycarbonate diol (PPCPDL, see Figure 1 Figure c therein, Mn = 2180 g / mol) was evacuated and heated to 110 °C. After no bubbles were generated, nitrogen was introduced and cooled to 100 °C. 214.1 mg of 4-dimethylaminopyridine was weighed, dissolved in an appropriate amount of N,N-dimethylformamide, transferred to a flask, and 3.242 g of methacrylic anhydride was added. The reaction was continued for 3 h under a nitrogen atmosphere.

[0062] The obtained product was washed three times with ethanol to remove the N,N-dimethylformamide solvent, unreacted methacrylic anhydride, and by-product methacrylic acid, and then vacuum dried at 80 °C for 24 h to obtain a polycarbonate acrylate product.

[0063] The purified product was subjected to nuclear magnetic resonance analysis and calculation, and about 100% of the two ends of the polymer chain were successfully grafted with methyl propionate groups. The test results of gel permeation chromatography (GPC) showed that the number-average molecular weight M n of the polycarbonate diol before the reaction was 2180 g / mol, and the number-average molecular weight M n of the polycarbonate acrylate obtained after the reaction was 2410 g / mol. The proton nuclear magnetic resonance spectrum (using deuterated chloroform as the solvent) of the polycarbonate acrylate product obtained in Example 3 is as shown in Figure 3 and it can be seen from Figure 3 that the obtained product is the target product.

[0064] Example 4. Preparation of polycarbonate acrylate

[0065] 30.21 g of polycarbonate diol (PCPCDL, see Figure 1 Figure d therein, Mn = 2450 g / mol) was evacuated and heated to 110 °C. After no bubbles were generated, nitrogen was introduced and cooled to 80 °C. 376.6 mg of 4-dimethylaminopyridine was weighed, dissolved in an appropriate amount of N,N-dimethylformamide, transferred to a flask, and 5.703 g of methacrylic anhydride was added. The reaction was continued for 5 h under a nitrogen atmosphere.

[0066] The obtained product was washed three times with ethanol to remove the N,N-dimethylformamide solvent, unreacted methacrylic anhydride, and by-product methacrylic acid, and then vacuum dried at 60 °C for 24 h to obtain the polycarbonate acrylate product.

[0067] The purified product was taken for nuclear magnetic analysis and calculation, and about 100% of the polymer chain ends were successfully grafted with methacrylate groups. The test results of gel permeation chromatography (GPC) showed that the number-average molecular weight M n of the polycarbonate diol before the reaction was 2450 g / mol, and the number-average molecular weight M n of the polycarbonate acrylate obtained after the reaction was 2670 g / mol.

[0068] Example 5. Preparation of polycarbonate acrylate

[0069] 10.06 g of polycarbonate diol (PCHCDL, see e diagram in Figure 1 , Mn = 2870 g / mol) was evacuated and heated to 110 °C. After no bubbles were generated, nitrogen was introduced and cooled to 70 °C. 107.1 mg of 4-dimethylaminopyridine was weighed, dissolved in an appropriate amount of N,N-dimethylformamide and transferred to a flask, and 1.621 g of methacrylic anhydride was added. The reaction was continued for 5 h under a nitrogen atmosphere.

[0070] The obtained product was washed three times with ethanol to remove the N,N-dimethylformamide solvent, unreacted methacrylic anhydride, and by-product methacrylic acid, and then vacuum dried at 60 °C for 24 h to obtain the polycarbonate acrylate product.

[0071] The purified product was taken for nuclear magnetic analysis and calculation, and about 100% of the polymer chain ends were successfully grafted with methacrylate groups. The test results of gel permeation chromatography (GPC) showed that the number-average molecular weight M n of the polycarbonate diol before the reaction was 2870 g / mol, and the number-average molecular weight M n of the polycarbonate acrylate obtained after the reaction was 3010 g / mol.

[0072] Example 6. Preparation of polyurethane acrylate

[0073] Under anhydrous and anaerobic conditions, 12.0 g of glycidyl methacrylate, 0.1 g of tetrabutylammonium bromide, and 0.06 g of 2,6-di-tert-butyl-p-cresol were weighed into a reaction kettle. After heating to 100 °C, 3.0 MPa of carbon dioxide gas was introduced, and the reaction was continued for 24 h under magnetic stirring. After the reaction was completed, methylacrylic acid five-membered cyclic carbonate was obtained.

[0074] Add 7.446 g of the above-synthesized five-membered cyclic carbonate of methacrylic acid and 2.324 g of hexamethylenediamine into a flask, heat to 100 °C, and stir and react for 2 h under the condition of connecting to the outside air to obtain a polyurethane acrylate product. The nuclear magnetic resonance hydrogen spectrum (using deuterated chloroform as the solvent) of the polyurethane acrylate obtained in Example 6 is as Figure 4 shown. It can be seen from Figure 4 that the obtained product is the target product.

[0075] Example 7. Preparation of UV-curable coating

[0076] Mix 25 parts of the polycarbonate acrylate prepared in Example 1, 8 parts of the polyurethane acrylate prepared in Example 6, 34 parts of 1,6-hexanediol diacrylate, 30 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the above parts are by mass. Then, apply the above coating on the PC surface by scraping to form a film, dry it in an oven at 60 °C for 30 min, and then irradiate it with a UV lamp with a wavelength of 365 nm for 5 min to cure it into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0077] Example 8. Preparation of UV-curable coating

[0078] Mix 30 parts of the polycarbonate acrylate prepared in Example 1, 10 parts of the polyurethane acrylate prepared in Example 6, 27 parts of 1,6-hexanediol diacrylate, 30 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the above parts are by mass. Then, apply the above coating on the PC surface by scraping to form a film, dry it in an oven at 60 °C for 30 min, and then irradiate it with a UV lamp with a wavelength of 365 nm for 5 min to cure it into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0079] Example 9. Preparation of UV-curable coating

[0080] Mix 35 parts of the polycarbonate acrylate prepared in Example 1, 12 parts of the polyurethane acrylate prepared in Example 6, 20 parts of 1,6-hexanediol diacrylate, 30 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the above parts are by mass. Then, apply the above coating on the PC surface by scraping to form a film, dry it in an oven at 60 °C for 30 min, and then irradiate it with a UV lamp with a wavelength of 365 nm for 5 min to cure it into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0081] Example 10. Preparation of UV-curable coating

[0082] Mix 25 parts of the polycarbonate acrylate prepared in Example 1, 8 parts of the polyurethane acrylate prepared in Example 6, 34 parts of trimethylolpropane triacrylate, 30 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the parts above are by mass. Then, apply the above coating on the PC surface by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate it with a UV lamp with a wavelength of 365 nm for 3 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0083] Example 11. Preparation of UV-curable coating

[0084] Mix 30 parts of the polycarbonate acrylate prepared in Example 1, 10 parts of the polyurethane acrylate prepared in Example 6, 27 parts of trimethylolpropane triacrylate, 30 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the parts above are by mass. Then, apply the above coating on the PC surface by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate it with a UV lamp with a wavelength of 365 nm for 3 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0085] Example 12. Preparation of UV-curable coating

[0086] Mix 35 parts of the polycarbonate acrylate prepared in Example 1, 12 parts of the polyurethane acrylate prepared in Example 6, 20 parts of trimethylolpropane triacrylate, 30 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the parts above are by mass. Then, apply the above coating on the PC surface by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate it with a UV lamp with a wavelength of 365 nm for 3 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0087] Example 13. Preparation of UV-curable coating

[0088] Mix 29 parts of the polycarbonate acrylate prepared in Example 1, 5 parts of the polyurethane acrylate prepared in Example 6, 34 parts of 1,6-hexanediol diacrylate, 29 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the parts above are by mass. Then, apply the above coating on the PC surface by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate it with a UV lamp with a wavelength of 365 nm for 5 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0089] Example 14. Preparation of UV-curable coating

[0090] Mix 29 parts by mass of the polycarbonate acrylate prepared in Example 1, 5 parts by mass of the polyurethane acrylate prepared in Example 6, 34 parts by mass of trimethylolpropane triacrylate, 29 parts by mass of propylene glycol monomethyl ether, and 3 parts by mass of 1-hydroxycyclohexyl phenyl ketone evenly. Then, apply the above coating on the surface of PC by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate with a UV lamp with a wavelength of 365 nm for 3 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0091] Example 15. Preparation of UV-curable coating

[0092] Mix 34 parts by mass of the polycarbonate acrylate prepared in Example 1, 6 parts by mass of the polyurethane acrylate prepared in Example 6, 27 parts by mass of trimethylolpropane triacrylate, 30 parts by mass of propylene glycol monomethyl ether, and 3 parts by mass of 1-hydroxycyclohexyl phenyl ketone evenly. Then, apply the above coating on the surface of PC by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate with a UV lamp with a wavelength of 365 nm for 3 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0093] Example 16. Preparation of UV-curable coating

[0094] Mix 40 parts by mass of the polycarbonate acrylate prepared in Example 1, 7 parts by mass of the polyurethane acrylate prepared in Example 6, 20 parts by mass of trimethylolpropane triacrylate, 30 parts by mass of propylene glycol monomethyl ether, and 3 parts by mass of 1-hydroxycyclohexyl phenyl ketone evenly. Then, apply the above coating on the surface of PC by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate with a UV lamp with a wavelength of 365 nm for 3 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0095] Example 17. Preparation of UV-curable coating

[0096] Mix 25 parts by mass of the polycarbonate acrylate prepared in Example 2, 8 parts by mass of the polyurethane acrylate prepared in Example 6, 34 parts by mass of trimethylolpropane triacrylate, 30 parts by mass of propylene glycol monomethyl ether, and 3 parts by mass of 1-hydroxycyclohexyl phenyl ketone evenly. Then, apply the above coating on the surface of PC by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate with a UV lamp with a wavelength of 365 nm for 5 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0097] Example 18. Preparation of UV-curable coating

[0098] Mix 25 parts of the polycarbonate acrylate prepared in Example 3, 8 parts of the polyurethane acrylate prepared in Example 6, 34 parts of trimethylolpropane triacrylate, 30 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the above parts are by mass. Then, apply the above coating on the PC surface by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate it with a UV lamp with a wavelength of 365 nm for 5 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0099] Example 19. Preparation of UV-curable coating

[0100] Mix 25 parts of the polycarbonate acrylate prepared in Example 4, 8 parts of the polyurethane acrylate prepared in Example 6, 34 parts of trimethylolpropane triacrylate, 30 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the above parts are by mass. Then, apply the above coating on the PC surface by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate it with a UV lamp with a wavelength of 365 nm for 5 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0101] Example 20. Preparation of UV-curable coating

[0102] Mix 25 parts of the polycarbonate acrylate prepared in Example 5, 8 parts of the polyurethane acrylate prepared in Example 6, 34 parts of trimethylolpropane triacrylate, 30 parts of propylene glycol monomethyl ether, and 3 parts of 1-hydroxycyclohexyl phenyl ketone evenly. All the above parts are by mass. Then, apply the above coating on the PC surface by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate it with a UV lamp with a wavelength of 365 nm for 5 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0103] Comparative Example 1. Commercially available polyurethane UV-curable coating

[0104] Use a commercially available polyurethane UV-curable coating, which contains 25 parts of polyurethane acrylate oligomer, 18 parts of reactive diluent, 2 parts of photoinitiator, and 55 parts of solvent. Apply it on the PC surface by scraping to form a film. After drying in an oven at 60 °C for 30 min, irradiate it with a UV lamp with a wavelength of 365 nm for 2 min to cure into a 30-μm-thick coating. The test results of the coating properties are shown in Table 1.

[0105] Test Example

[0106] (1) Flexibility test: According to the regulations in GB / T 1731-2020 "Determination method for flexibility of paint films and putty films", test the flexibility of the coatings in Examples 7-20 and Comparative Example 1.

[0107] (2) Pencil hardness test: According to the provisions in GB / T 6739-2022 "Paints and varnishes - Determination of film hardness by pencil test", the pencil hardness of the coatings in Examples 7-20 and Comparative Example 1 on the PC substrate was tested.

[0108] (3) Adhesion test: According to the provisions in GB / T 9286-2021 "Paints and varnishes - Cross-cut test", the adhesion performance of the coatings in Examples 7-20 and Comparative Example 1 on the PC substrate was tested.

[0109] (4) Water resistance test: The coatings obtained by coating Examples 7-20 and Comparative Example 1 on the PC substrate were placed in hot water at 60 °C and soaked for 240 h, then taken out, the surface moisture was blotted dry with filter paper, and after standing at room temperature for at least 24 h, the adhesion performance was tested again.

[0110] (5) Gel content test: The cured films obtained from Examples 7-20 and Comparative Example 1 on the polytetrafluoroethylene substrate were taken, and the gel content of the prepared cured films was tested by the Soxhlet extraction method. Using acetone as the solvent, a cured film sample with a mass of m0 was taken, placed in a Soxhlet extractor and extracted for 24 h, then dried at 110 °C for 24 h, weighed to obtain the mass m1, and the gel content of the sample was calculated according to formula (1).

[0111] Gel content % = m1 / m0 × 100% (1)

[0112] (6) Transmittance test: According to the provisions in GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics", a transmittance / haze meter of model WGT-S was used to test the transmittance of the PC substrate, the coatings in Examples 7-20 and Comparative Example 1 after being coated on the PC substrate.

[0113] Table 1 Performance comparison of polycarbonate-based non-isocyanate polyurethane UV-curable coatings

[0114]

[0115] Note: For the PC substrate without coating, the transmittance is 90.2%.

[0116] As can be seen from Table 1, the polycarbonate-based non-isocyanate polyurethane UV-curable coating synthesized in the present invention exhibits better flexibility than the commercially available polyurethane UV-curable coatings, and its pencil hardness is between 2H and 4H, which is higher than that of the commercially available polyurethane UV-curable coatings. Secondly, the coating prepared in the present invention has excellent adhesion on the PC substrate. After the coating is immersed in hot water at 60 °C for 240 h, its adhesion on the PC substrate remains basically unchanged, indicating that the coating has good water resistance. The gel content test results show that the cured film obtained from the polycarbonate-based non-isocyanate polyurethane UV-curable coating prepared in the present invention has a relatively high degree of crosslinking. In addition, by comparing the light transmittance of the PC substrate before and after coating, it can be found that the light transmittance remains basically unchanged, indicating that the coating prepared in the present invention has excellent light transmittance performance.

Claims

1. A polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating, characterized in that It is composed of components with the following weight percentages: Polycarbonate acrylate 10 - 60%, Polyurethane acrylate 5 - 20%, Reactive diluent 10 - 60%, Photoinitiator 1 - 5%, Solvent 0 - 60%, The polycarbonate acrylate has the structure shown in formula (1), where a≥0, b≥0, c≥0, d≥0, e≥0; a, b, c, d, e are all integers and not all zero at the same time; wherein R is an epoxy monomer the self-polymerized part of at least one of The polyurethane acrylate has the structure shown in formula (2); 2. The polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating according to claim 1, wherein, It is composed of components with the following weight percentages: Polycarbonate acrylate 20 - 50%, Polyurethane acrylate 5 - 15%, Reactive diluent 20 - 40%, Photoinitiator 3 - 5%, Solvent 20 - 50%.

3. The polycarbonate-based isocyanate-free polyurethane UV-curable coating according to claim 1, characterized in that, The reactive diluent is a small - molecule acrylate monomer, which is at least one of 2 - hydroxyethyl methacrylate, 1,6 - hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

4. The polycarbonate-based non-isocyanate polyurethane UV-curable coating according to claim 1, characterized in that, The photoinitiator includes at least one of benzoin dimethyl ether, 1 - hydroxycyclohexyl phenyl ketone, diphenyl(2,4,6 - trimethylbenzoyl)phosphine oxide, and 2 - hydroxy - 2 - methylpropiophenone.

5. The polycarbonate-based isocyanate-free polyurethane UV-curable coating according to claim 1, wherein, The solvent is at least one of acetone, butyl acetate, propylene glycol monomethyl ether, and propylene glycol methyl ether acetate.

6. The polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating according to claim 1, wherein The preparation method of the polycarbonate acrylate includes the following steps: (1) Under the protection of an inert gas and in the presence of a catalyst, react polycarbonate diol and methacrylic anhydride in a solvent to obtain a crude product; The polycarbonate diol has the structure shown in formula (3), where a≥0, b≥0, c≥0, d≥0, e≥0, a, b, c, d, e are all integers and not all zero at the same time; wherein R is a self-polymerized moiety of at least one of the epoxy monomers in; (2) Wash and dry the obtained crude product to obtain polycarbonate acrylate.

7. The polycarbonate-based isocyanate-free polyurethane UV-curable coating according to claim 6, characterized in that, In step (1), the number - average molecular weight of the polycarbonate diol is in the range of 1000 - 3000 g / mol, and the content of polycarbonate in the main chain is 50% - 95%; the molar ratio of the polycarbonate diol, methacrylic anhydride, and catalyst is 1:2 - 10:0.25 - 0.3; the reaction temperature is 25 - 100°C, and the reaction time is 3 - 36 h; the catalyst is a basic catalyst 4 - dimethylaminopyridine; an antioxidant 2,6 - di - tert - butyl - p - cresol is also added; the solvent is at least one of dichloromethane, ethyl acetate, butyl acetate, and N,N - dimethylformamide; Step (2) is: Wash the obtained crude product with ethanol or ether at least three times to remove unreacted methacrylic anhydride, by - product methacrylic acid, solvent, residual catalyst, and antioxidant in the crude product, and dry after washing to obtain the polycarbonate acrylate; the drying is vacuum drying, the drying temperature is 25 - 80°C, and the time is 24 - 48 h.

8. The polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating according to claim 1, characterized in that, The preparation method of the polyurethane acrylate includes the following steps: (1) React glycidyl methacrylate and carbon dioxide under the action of a catalyst and in the presence of an antioxidant to obtain the corresponding five - membered cyclic carbonate; (2) React the obtained five-membered cyclic carbonate with hexamethylenediamine to obtain polyurethane acrylate.

9. The polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating according to claim 8, wherein In step (1), the temperature of the reaction is 100 °C, the reaction time is 24 h, the pressure of carbon dioxide is 3.0 MPa, the catalyst is tetrabutylammonium bromide, and the catalyst dosage is 0.1% of the weight of glycidyl methacrylate. The antioxidant is 2,6-di-tert-butyl-p-cresol, and the antioxidant dosage is 0.5% of the weight of glycidyl methacrylate. In step (2), the molar ratio of the five-membered cyclic carbonate to hexamethylenediamine is 1:1 - 1:1.

2.

10. A method for preparing a polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating, characterized in that It includes the following steps: Mix polycarbonate acrylate, polyurethane acrylate, active diluent, photoinitiator, and solvent to obtain a polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating. Coating the coating into a film and curing it under ultraviolet light irradiation after drying to obtain a polycarbonate-based non-isocyanate polyurethane ultraviolet curable coating.

Images