Environment-friendly light-cured polyurethane coating and preparation method thereof

Abstract

The application belongs to the technical field of polyurethane coatings, and particularly relates to an environmentally-friendly light-cured polyurethane coating and a preparation method thereof, raw materials of the coating include, in parts by weight, polyurethane acrylate 50-80 parts, methyl methacrylate 8-16 parts, calcium carbonate 5-25 parts, amino resin 1-15 parts, modified toluene diisocyanate 40-100 parts, polyhydric alcohol 50-80 parts, photoinitiator 2-5 parts, and pigment 0.5-15 parts. The polyurethane coating has good wear resistance and service life, and improves the flexibility of the film layer, and solves the problem of hard and brittle film layer caused by the curing of the amino resin raw material.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane coating technology, specifically relating to an environmentally friendly photocurable polyurethane coating and its preparation method. Background Technology

[0002] Polyurethane coatings are a cost-effective UV-curable coating. Due to their low price and good processability, they are widely favored. However, in some applications, the flexibility and abrasion resistance of polyurethane coatings are still insufficient. Those skilled in the art have made certain improvements to polyurethane coatings.

[0003] Chinese invention patent application number 200810159384.6 discloses a light-curable polyurethane coating and its preparation method. The coating includes 369 parts of light-cured dihydroxyethyl isocyanurate, 0.5 parts of hydroquinone, 84 parts of hexamethylene diisocyanate, 0.1 parts of triethylamine, 50 parts of compound A, 50 parts of neopentyl glycol diacrylate, and 1842 parts of Sgacuse. It can be cured quickly by UV and has good flexibility and hardness.

[0004] Chinese invention patent application number 201110007852.X discloses a polyurethane coating film-forming material, a polyurethane coating and its application, including: a mixture of a first polyisocyanate and a polyol; or a mixture of a second polyisocyanate and a polyol dispersion; or a polyurethane dispersion, which can effectively reduce the release of formaldehyde in acid-cured coatings or substrates, which is beneficial to environmental protection and the health of construction workers and users.

[0005] The aforementioned patents improve the performance of polyurethane coatings through formula adjustments. However, due to the high reactivity of isocyanate in the formula, it is highly reactive with moisture and other components in the air, resulting in a decrease in the density of the final coating film and insufficient wear resistance.

[0006] Therefore, the urgent technical problem to be solved is how to reduce the activity and polymerization rate of isocyanates to make the coating film denser, while also having better environmental protection, flexibility and wear resistance. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide an environmentally friendly photocurable polyurethane coating and its preparation method, which can improve the density of the coating film, has a good environmental protection effect, requires only a low temperature for processing, saves energy and reduces emissions, and also has good flexibility and wear resistance.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] This invention provides an environmentally friendly photocurable polyurethane coating, which, by weight, comprises the following raw materials: 50-80 parts polyurethane acrylate, 8-16 parts methyl methacrylate, 5-25 parts calcium carbonate, 1-15 parts amino resin, 40-100 parts modified toluene diisocyanate, 50-80 parts polyol, 2-5 parts photoinitiator, and 0.5-15 parts pigment.

[0010] In some embodiments, the photoinitiator is at least one of 184, MBF, 1173, TPO-L, and TMO.

[0011] Preferably, the photoinitiator is 184.

[0012] Photoinitiator 184 has a photoinitiator wavelength range of 200nm-800nm.

[0013] In some embodiments, the preparation method of the modified toluene diisocyanate is as follows:

[0014] By weight, add 8-12 parts of toluene diisocyanate and 7-14 parts of 4-chlorobutyl methyl ether to dichloromethane, mix and stir for 10-20 min, add 7.5-15 parts of catalyst under inert gas protection, after the reaction is complete, add dilute hydrochloric acid to the reaction solution to adjust the pH to 4-5, separate the liquid and extract the aqueous phase with dichloromethane, combine the organic layers, wash with water, dry, and evaporate to dryness to obtain modified toluene diisocyanate.

[0015] Polyurethane coatings are prone to pore formation when reacting with moisture or other substances in the air, leading to reduced density and shortened service life. The applicant addresses this by using a modified toluene diisocyanate obtained through the alkylation reaction of 4-chlorobutyl methyl ether and toluene diisocyanate as a raw material. This modified toluene diisocyanate results in a more dense polyurethane coating film with a longer service life. The likely reason is that the modified toluene diisocyanate is grafted with an electron-donating methoxy group, increasing the electron cloud density of the carbon atoms on the isocyanate group. This reduces the reactivity of the toluene diisocyanate, thus lowering the polymerization rate and resulting in a denser coating film with a longer service life.

[0016] In some embodiments, the catalyst is anhydrous aluminum chloride.

[0017] In some embodiments, the amino resin is a modified polyamide epichlorohydrin resin.

[0018] In some embodiments, the preparation method of the modified polyamide epichlorohydrin resin is as follows:

[0019] (1) By weight, add 8-12 parts of dicarboxylic acid, 8-10 parts of polyamine and 0.1-1 parts of 85-95wt% concentrated sulfuric acid to the reactor, heat to 120-160℃, keep the temperature for 8-12h, cool to 80-90℃, stir for 20-40min to obtain the prepolymer, polyamide polyamine;

[0020] (2) Add the polyamide polyamine obtained in step (1) and water to the reaction vessel, stir for 10-30 min, add epichlorohydrin and water, control the temperature at 60-65℃, keep warm for 1-3 h, cool down to 30-40℃, add 40-45wt% dilute sulfuric acid solution, adjust the pH to 6-7, stir for 20-40 min, and obtain polyamide epichlorohydrin resin;

[0021] (3) Add 3-7wt% sodium hydroxide aqueous solution to the polyamide epichlorohydrin resin in step (2), heat to 120-180℃, stir for 20-30min to obtain solution A;

[0022] (4) Add 2-(N-methylperfluorooctanesulfonamide)acetic acid, 85-95wt% concentrated sulfuric acid and solution A obtained in step (3) to methanol in sequence, stir for 10-20 min, heat to 80-85℃ and reflux for 3-5 h, cool to room temperature after the reaction is completed, purify, and obtain modified polyamide epichlorohydrin resin.

[0023] Polyamide epichlorohydrin resin, as an amino resin, has good high-temperature resistance and is not easily melted or deformed. However, after curing alone, the film layer of amino resin is relatively hard and brittle, which affects the service life of the finished product. By using sodium hydroxide and 2-(N-methylperfluorooctanesulfonylamino)acetic acid to modify polyamide epichlorohydrin resin, the applicant has significantly improved the flexibility of the coating and solved the defect of brittle film layer after curing polyamide epichlorohydrin resin. At the same time, the applicant unexpectedly found that the environmental performance of the finished coating has been improved. It is speculated that the possible reason is that the perfluorinated structure has good stability, does not produce toxicity during processing, and can be processed at low temperature, thus saving energy and reducing emissions.

[0024] In some embodiments, in step (2), the molar ratio between the polyamide polyamine and epichlorohydrin is 1:(1.2-2).

[0025] Preferably, the molar ratio between the polyamide polyamine and epichlorohydrin is 1:1.6.

[0026] In some embodiments, the dicarboxylic acid is adipic acid or azelaic acid.

[0027] Preferably, the dicarboxylic acid is adipic acid.

[0028] In some embodiments, the polyamine is diethylenetriamine or triethylenetetramine.

[0029] Preferably, the polyamine is diethylenetriamine.

[0030] In another aspect, the present invention provides a method for preparing the environmentally friendly photocurable polyurethane coating described in the above technical solution, comprising the following steps:

[0031] S1. Heat polyurethane acrylate to 70-80℃, add methyl methacrylate, amino resin, pigment and calcium carbonate, stir at 100-120 rpm for 30-80 min, then disperse at 1000-1200 rpm for 20-40 min to obtain mixed solution A.

[0032] S2. Heat the polyol to 80-90℃, add the modified toluene diisocyanate and stir for 1-4 hours, cool to 40-45℃ and filter to obtain mixed solution B;

[0033] S3. Mix and stir the mixed solution A, mixed solution B and photoinitiator for 5-10 minutes under light-protected conditions to obtain the polyurethane coating.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. This invention improves the wear resistance and service life of UV-cured polyurethane coatings, while also increasing the flexibility of the film layer, thus solving the problem that the film layer becomes hard and brittle after the amino resin raw material is cured.

[0036] 2. This invention modifies toluene diisocyanate, increasing the electron cloud density of carbon atoms on the isocyanate groups, thereby reducing the overall polymerization rate of modified toluene diisocyanate, resulting in a denser coating with stronger wear resistance and a longer service life.

[0037] 3. This invention improves the flexibility of the coating by modifying polyamide epichlorohydrin resin with sodium hydroxide and 2-(N-methylperfluorooctanesulfonylamino)acetic acid, while enabling processing at lower temperatures, saving energy and reducing emissions. The perfluorinated structure has good stability and does not produce toxicity during processing, thus possessing good environmental protection properties. Detailed Implementation

[0038] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0039] An environmentally friendly light-curing polyurethane coating was prepared according to the proportions of the components specified in the following examples. The components of the environmentally friendly light-curing polyurethane coating were prepared by mixing according to the methods described in the examples and comparative examples.

[0040] Polyurethane acrylate was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; polycarbonate diol was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; other raw materials, unless otherwise specified, can be purchased from the market.

[0041] Preparation Example 1

[0042] Modified polyamide epichlorohydrin resin A was prepared according to the following method:

[0043] (1) Add 10g adipic acid, 9g diethylenetriamine and 0.5g 90wt% concentrated sulfuric acid to the reactor, heat to 140℃, keep the reaction at 10h, cool to 85℃, stir for 30min to obtain prepolymer, polyamide polyamine, with a molecular weight of 1200.

[0044] (2) Add 4.6g of prepolymer and 200ml of water obtained in step (1) to the reactor, stir for 20min, add 0.56g of epichlorohydrin and 100ml of water, control the temperature at 60℃, keep warm for 2h, cool down to 35℃, add 45wt% dilute sulfuric acid solution to adjust the pH to 6.5, stir for 30min to obtain polyamide epichlorohydrin resin;

[0045] (3) Add the amide epichlorohydrin resin obtained in step (2) to 8 ml of 4.5 wt% sodium hydroxide aqueous solution, heat to 150 °C, stir for 25 min to obtain solution A;

[0046] (4) Add 11g of 2-(N-methylperfluorooctanesulfonylamino)acetic acid, 2ml of 90wt% concentrated sulfuric acid and solution A obtained in step (3) to 500ml of methanol, stir for 15min, heat to 80℃ and reflux for 4h, cool to 25℃ after the reaction is completed, purify, and obtain modified polyamide epichlorohydrin resin A.

[0047] Preparation Example 2

[0048] Modified polyamide epichlorohydrin resin B is prepared in the same way as in preparation example 1, except that the amount of epichlorohydrin added in step (2) is 0.3g.

[0049] Preparation Example 3

[0050] Modified toluene diisocyanate was prepared according to the following method:

[0051] Add 20g of toluene diisocyanate and 21g of 4-chlorobutyl methyl ether to 250ml of dichloromethane, mix and stir for 15min, add 19g of anhydrous aluminum chloride under nitrogen protection, after the reaction is complete, add 1mol / L dilute hydrochloric acid to the reaction solution to adjust the pH to 4.5, separate the layers, extract the aqueous phase with dichloromethane, combine the organic layers, wash with water, dry, and evaporate to dryness to obtain modified toluene diisocyanate.

[0052] Example 1

[0053] This embodiment provides a method for preparing an environmentally friendly photocurable polyurethane coating, which, by weight, includes the following raw materials: 65 parts polyurethane acrylate, 10 parts methyl methacrylate, 15 parts calcium carbonate, 10 parts modified polyamide epichlorohydrin resin A, 80 parts modified toluene diisocyanate and 75 parts polycarbonate diol, 3 parts photoinitiator 184, and 10 parts pigment.

[0054] The preparation method of the environmentally friendly photocurable polyurethane coating in this embodiment specifically includes the following steps:

[0055] S1. Heat polyurethane acrylate to 75°C, add methyl methacrylate, modified polyamide epichlorohydrin resin A, pigment and calcium carbonate, stir at 110 rpm for 65 min, then disperse at 1100 rpm for 30 min to obtain mixed solution A.

[0056] S2. Heat polycarbonate diol to 85°C, add modified toluene diisocyanate and stir for 2 hours, then cool to 43°C and filter to obtain mixed solution B;

[0057] S3. Mix and stir the mixed solution A, mixed solution B and photoinitiator 184 for 8 minutes under light-protected conditions to obtain the polyurethane coating.

[0058] Example 2

[0059] This embodiment provides an environmentally friendly photocurable polyurethane coating, which, by weight, comprises the following raw materials: 50 parts polyurethane acrylate, 8 parts methyl methacrylate, 5 parts calcium carbonate, 1 part modified polyamide epichlorohydrin resin A, 40 parts modified toluene diisocyanate and 50 parts polycarbonate diol, 2 parts photoinitiator 184, and 0.5 parts pigment.

[0060] The preparation method of the environmentally friendly photocurable polyurethane coating in this embodiment specifically includes the following steps:

[0061] S1. Heat polyurethane acrylate to 70°C, add methyl methacrylate, modified polyamide epichlorohydrin resin A, pigment and calcium carbonate, stir at 100 rpm for 80 min, and then disperse at 1000 rpm for 40 min to obtain mixed solution A.

[0062] S2. Heat polycarbonate diol to 80°C, add modified toluene diisocyanate and stir for 4 hours, then cool to 40°C and filter to obtain mixed solution B;

[0063] S3. Mix and stir the mixed solution A, mixed solution B and photoinitiator 184 for 5 minutes under light-protected conditions to obtain the polyurethane coating.

[0064] Example 3

[0065] This embodiment provides an environmentally friendly photocurable polyurethane coating, which, by weight, comprises the following raw materials: 80 parts polyurethane acrylate, 16 parts methyl methacrylate, 25 parts calcium carbonate, 15 parts modified polyamide epichlorohydrin resin A, 100 parts modified toluene diisocyanate and 80 parts polycarbonate diol, 5 parts photoinitiator 184, and 15 parts pigment.

[0066] The preparation method of the environmentally friendly photocurable polyurethane coating in this embodiment specifically includes the following steps:

[0067] S1. Heat polyurethane acrylate to 80°C, add methyl methacrylate, modified polyamide epichlorohydrin resin A, pigment and calcium carbonate, stir at 120 rpm for 30 min, then disperse at 1200 rpm for 20 min to obtain mixed solution A;

[0068] S2. Heat polycarbonate diol to 90°C, add modified toluene diisocyanate and stir for 1 hour, then cool to 45°C and filter to obtain mixed solution B;

[0069] S3. Mix and stir the mixed solution A, mixed solution B and photoinitiator 184 for 10 minutes under light-protected conditions to obtain the polyurethane coating.

[0070] Example 4

[0071] An environmentally friendly photocurable polyurethane coating and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the modified polyamide epichlorohydrin resin A is replaced by an equal amount of modified polyamide epichlorohydrin resin B.

[0072] Example 5

[0073] An environmentally friendly light-curing polyurethane coating and its preparation method are described. The specific implementation method is the same as that in Example 1, except that the modified polyamide epichlorohydrin resin A is replaced by an equal amount of polyamide epichlorohydrin resin, which is obtained by step (2) of Preparation Example 1.

[0074] Comparative Example 1

[0075] An environmentally friendly light-curing polyurethane coating and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the modified toluene diisocyanate is replaced by an equal amount of commercially available toluene diisocyanate.

[0076] Performance testing:

[0077] The environmentally friendly photocurable polyurethane coatings described in Examples 1-5 and Comparative Example 1 were subjected to abrasion resistance and flexibility tests. The test results are shown in Table 1.

[0078] Abrasion resistance test: Tested according to GB / T 1768-2006, and abrasion resistance is judged according to the loss mass.

[0079] Flexibility test: According to GB / T 1731-1993, the test involves bending the shaft of a certain diameter, and the minimum diameter of the shaft that does not cause damage to the paint film after bending is used to represent the flexibility.

[0080] Table 1

[0081] Loss of mass (grams) Flexibility (mm) Example 1 0.02 2 Example 2 0.02 2 Example 3 0.03 2 Example 4 0.02 3 Example 5 0.03 4 Comparative Example 1 0.05 2

[0082] As can be seen from Table 1, the environmentally friendly photocurable polyurethane coatings of Examples 1-3 in this invention have excellent flexibility and wear resistance. It is speculated that the modified toluene diisocyanate obtained by the alkylation reaction of 4-chlorobutyl methyl ether and toluene diisocyanate as a raw material can make the polyurethane coating film more dense in the air, thereby having stronger wear resistance.

[0083] The flexibility of Examples 4 and 5 decreased. It is speculated that the reason is that modified polyamide epichlorohydrin resin B and commercially available polyamide epichlorohydrin resin were used instead of modified polyamide epichlorohydrin resin A in Examples 4 and 5, respectively. After the amino resin was cured, the film layer was more brittle and the flexibility decreased. The loss of mass in grams in the wear resistance test did not change significantly, so the wear resistance performance did not change significantly.

[0084] The abrasion resistance of Comparative Example 1 was significantly lower than that of Examples 1-3. It is speculated that the reason may be that commercially available toluene diisocyanate was used in Comparative Example 1. Compared with the use of modified toluene diisocyanate, the mass loss during the abrasion resistance test was significantly increased, resulting in poor abrasion resistance.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An environmentally friendly UV-curable polyurethane coating, characterized in that, By weight, its raw materials include: 50-80 parts of polyurethane acrylate, 8-16 parts of methyl methacrylate, 5-25 parts of calcium carbonate, 1-15 parts of amino resin, 40-100 parts of modified toluene diisocyanate, 50-80 parts of polyol, 2-5 parts of photoinitiator, and 0.5-15 parts of pigment. The specific method for preparing the modified toluene diisocyanate is as follows: By weight, add 8-12 parts of toluene diisocyanate and 7-14 parts of 4-chlorobutyl methyl ether to dichloromethane, mix and stir for 10-20 min, add 7.5-15 parts of catalyst under inert gas protection, after the reaction is complete, add dilute hydrochloric acid to the reaction solution to adjust the pH to 4-5, separate the liquid and extract the aqueous phase with dichloromethane, combine the organic layers, wash with water, dry, and evaporate to dryness to obtain modified toluene diisocyanate; The amino resin is a modified polyamide epichlorohydrin resin; The specific preparation method of the modified polyamide epichlorohydrin resin is as follows: (1) By weight, add 8-12 parts of dicarboxylic acid, 8-10 parts of polyamine and 0.1-1 parts of 85-95wt% concentrated sulfuric acid to the reactor, heat to 120-160℃, keep the temperature for 8-12h, cool to 80-90℃, stir for 20-40min to obtain polyamide polyamine; (2) Add the polyamide polyamine obtained in step (1) and water to the reactor, stir for 10-30 min, add epichlorohydrin and water, control the temperature at 60-65℃, keep warm for 1-3 h, cool down to 30-40℃, add 40-45wt% dilute sulfuric acid solution, adjust the pH to 6-7, stir for 20-40 min, and obtain polyamide epichlorohydrin resin; (3) Add 3-7wt% sodium hydroxide aqueous solution to the polyamide epichlorohydrin resin in step (2), heat to 120-180℃, stir for 20-30min to obtain solution A; (4) Add 2-(N-methylperfluorooctanesulfonamide)acetic acid, 85-95wt% concentrated sulfuric acid and solution A obtained in step (3) to methanol in sequence, stir for 10-20 min, heat to 80-85℃ and reflux for 3-5 h, cool to room temperature after the reaction is completed, purify, and obtain modified polyamide epichlorohydrin resin.

2. The environmentally friendly photocurable polyurethane coating as described in claim 1, characterized in that, The photoinitiator is at least one of 184, MBF, 1173, TPO-L and TMO.

3. The environmentally friendly photocurable polyurethane coating as described in claim 1, characterized in that, The catalyst is anhydrous aluminum chloride.

4. The environmentally friendly photocurable polyurethane coating as described in claim 1, characterized in that, In step (2), the molar ratio between the polyamide polyamine and epichlorohydrin is 1:(1.2-2).

5. The environmentally friendly photocurable polyurethane coating as described in claim 1, characterized in that, The dicarboxylic acid is adipic acid or azelaic acid.

6. The environmentally friendly photocurable polyurethane coating as described in claim 1, characterized in that, The polyamine is diethylenetriamine or triethylenetetramine.

7. A method for preparing an environmentally friendly photocurable polyurethane coating as described in any one of claims 1-6, characterized in that, The preparation method specifically includes the following steps: S1. Heat polyurethane acrylate to 70-80℃, add methyl methacrylate, amino resin, pigment and calcium carbonate, stir at 100-120 rpm for 30-80 min, then disperse at 1000-1200 rpm for 20-40 min to obtain mixed solution A. S2. Heat the polyol to 80-90℃, add the modified toluene diisocyanate and stir for 1-4 hours, cool to 40-45℃ and filter to obtain mixed solution B; S3. Mix and stir the mixed solution A, mixed solution B and photoinitiator for 5-10 minutes under light-protected conditions to obtain the polyurethane coating.