Special solvent-resistant polyurethane for coating roller as well as preparation method and application of special solvent-resistant polyurethane

Abstract

The invention relates to the technical field of functional polyurethane, in particular to special solvent-resistant polyurethane for a coating roller as well as a preparation method and application of the special solvent-resistant polyurethane. The special solvent-resistant polyurethane for the coating roller is prepared from a polyurethane prepolymer and a chain extender, and the mass ratio of the polyurethane prepolymer to the chain extender is (30-50): 1; the polyurethane prepolymer is prepared from the following raw materials in parts by mass: 30 to 40 parts of fluorine-containing isocyanate, 20 to 30 parts of isophorone diisocyanate, 50 to 70 parts of polytetrahydrofuran ether glycol and 0.1 to 1 part of a catalyst, and the fluorine-containing isocyanate is diphenylmethane diisocyanate of which one side of a perfluoro chain segment is terminated. The special solvent-resistant polyurethane for the coating roller has excellent solvent resistance, and has an excellent bonding effect with a roller core.

Description

Technical Field

[0001] The present application relates to the technical field of functional polyurethane, and more specifically, to a solvent-resistant polyurethane specially used for coating rollers, and a preparation method and application thereof. Background Art

[0002] The coating roller is a mechanism used to evenly coat materials such as paint, glue, and ink on the surface of an object. It is mainly composed of a roller core and a coating material. The roller core is generally made of metal or high-strength plastic with a certain strength and rigidity, and is mainly used to support and drive the entire coating roller to rotate; the coating material covers the surface of the roller core, and is mainly used to protect the roller core, buffer and reduce shock, and improve the material coating effect.

[0003] At present, the coating material mainly adopts polyurethane coating. The reason is that polyurethane coating has excellent weather resistance and anti-aging performance, can resist the influence of ultraviolet rays, oxygen and temperature, and at the same time, polyurethane has stronger adhesion to the metal-based roller core, so during the coating process, polyurethane coating is less likely to separate from the roller core. However, the solvent resistance of polyurethane coating is insufficient, and the coating, glue and ink in the coating process contain a large amount of solvents. After the coating roller is used for a long time, the mechanical properties of polyurethane coating will deteriorate significantly, thus affecting the normal use of the coating roller. Summary of the invention

[0004] In order to improve the solvent resistance of the polyurethane coating of a coating roller, the present application provides a solvent-resistant polyurethane specially used for a coating roller, and a preparation method and application thereof.

[0005] In the first aspect, the present application provides a solvent-resistant polyurethane for a coating roller, which adopts the following technical solution: A solvent-resistant polyurethane specially used for a coating roller is prepared from a polyurethane prepolymer and a chain extender, wherein the mass ratio of the polyurethane prepolymer to the chain extender is (30-50):1; The polyurethane prepolymer comprises the following raw materials in parts by weight: 30-40 parts of fluorine-containing isocyanate, 20-30 parts of isophorone diisocyanate, 50-70 parts of polytetramethylene ether diol, and 0.1-1 part of a catalyst. The fluorine-containing isocyanate is diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side.

[0006] The introduction of halogens can give polyurethane elastomers many excellent properties, such as flame retardancy, hydrolysis resistance, chemical corrosion resistance, and chemical stability. The reason is that halogen atoms have strong electronegativity. After introducing halogens into polyurethane elastomers, the molecular polarity can be increased and the intermolecular forces can be enhanced, thereby making the polyurethane elastomer more difficult to be dissolved or swollen by solvents. At the same time, the chemical bond energy formed by halogen atoms is relatively high, which can increase the material's resistance to chemical corrosion and solvent erosion. The introduction of fluoride can also reduce the surface energy of polyurethane elastomers, thereby making the surface of polyurethane elastomers more hydrophobic and oleophobic, effectively reducing the adsorption and penetration of solvents, and indirectly improving the solvent resistance of polyurethane elastomers.

[0007] In the present application, diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side is selected to introduce fluorine into the polyurethane coating, effectively improving the solvent resistance of the polyurethane coating of the coating roller. At the same time, diphenylmethane diisocyanate also contains a benzene ring, which has a large steric hindrance, thereby effectively hindering the chemical attack of chemical media on the polyurethane molecular chain, further improving the solvent resistance of the polyurethane coating.

[0008] Preferably, the catalyst is one or a mixture of two of dibutyltin dilaurate and bismuth laurate.

[0009] It can be seen from the data of the solvent resistance test of the polyurethane coating that compared with the use of dibutyltin dilaurate as a catalyst, the use of bismuth laurate as a catalyst can further improve the solvent resistance of the polyurethane coating. The reason may be that the bismuth atoms in bismuth laurate have a certain coordination ability and can interact with the polar groups in the polyurethane molecular chain. This interaction effectively enhances the cohesion between molecules, making it more difficult for the polyurethane elastomer to be penetrated or swelled by solvents.

[0010] Preferably, the fluorinated isocyanate is obtained by reacting diphenylmethane diisocyanate and perfluoroalkyl alcohol in a molar ratio of 1:1.

[0011] Preferably, the preparation method of the fluorinated isocyanate is as follows: firstly, a perfluoroalkyl alcohol is dissolved in N,N-dimethylformamide, and then added dropwise to diphenylmethane diisocyanate at a rate of 2-4 d / s, during which stirring is continued and the temperature is controlled at 50-70°C. After the addition is completed, the temperature is lowered to 40-60°C and the reaction is continued for 1-3 hours to obtain the fluorinated isocyanate.

[0012] Preferably, the preparation method of the polyurethane prepolymer is: firstly, the fluorinated isocyanate is heated to 50-70°C, and then polytetramethylene ether diol and a catalyst are added, stirred for reaction for 1-2 hours, and then isophorone diisocyanate is added and stirred for reaction for 0.5-1 hour to obtain the polyurethane prepolymer.

[0013] Preferably, the chain extender consists of 1,4-butanediol and 2-amino-4-hydroxy-6-methylpyrimidine.

[0014] Although the introduction of fluorine can effectively improve the solvent resistance of the polyurethane coating, at the same time, the introduction of fluorine will also lead to a decrease in the surface energy of the polyurethane coating, resulting in insufficient adhesion between the polyurethane coating and the roller core. In the present application, 2-amino-4-hydroxy-6-methylpyrimidine is added to the chain extender, so that 2-amino-4-hydroxy-6-methylpyrimidine participates in the chain extension and end-capping of the polyurethane elastomer, thereby forming a large number of UPy structures, and the UPy structure can form hydrogen bonds with the oxygen atoms in the roller core, thereby obtaining greater shear force, thereby effectively compensating for the defect of poor adhesion of the polyurethane coating caused by the introduction of fluorine.

[0015] Preferably, the mass ratio of the 1,4-butanediol to the 2-amino-4-hydroxy-6-methylpyrimidine is (1-3): (1-2).

[0016] Preferably, the preparation method of the solvent-resistant polyurethane for coating roller is: first, N, N-dimethylformamide and 1,4-butanediol are mixed and added to the polyurethane prepolymer, then 2-amino-4-hydroxy-6-methylpyrimidine is added to react for 1-2 hours, and finally the product is poured into a mold for drying and maturation to obtain the solvent-resistant polyurethane for coating roller.

[0017] In a second aspect, the present application provides a method for preparing a solvent-resistant polyurethane for a coating roller, using the following technical solution: A method for preparing a solvent-resistant polyurethane for a coating roller comprises the following steps: Preparation of fluorinated isocyanate: First, perfluoroalkyl alcohol is dissolved in N, N-dimethylformamide, and then added dropwise to diphenylmethane diisocyanate at a rate of 2-4 d / s, during which stirring is continued and the temperature is controlled at 50-70°C. After the addition is completed, the temperature is lowered to 40-60°C and the reaction is continued for 1-3 hours to obtain fluorinated isocyanate; Preparation of polyurethane prepolymer: First, heat the fluorinated isocyanate to 50-70°C, then add polytetramethylene glycol and a catalyst, stir and react for 1-2 hours, then add isophorone diisocyanate and continue stirring and reacting for 0.5-1 hour to obtain a polyurethane prepolymer; Preparation of solvent-resistant polyurethane for coating roller: The polyurethane prepolymer and the chain extender are mixed for 2-4 hours, and then the product is poured into a mold for drying to obtain the solvent-resistant polyurethane for coating roller.

[0018] In a third aspect, the present application provides an application of a solvent-resistant polyurethane for a coating roller, using the following technical solution: The invention discloses an application of a special solvent-resistant polyurethane for a coating roller. The special solvent-resistant polyurethane for a coating roller is suitable for the surface coating of a coating roller, a printing roller and a embossing roller.

[0019] In summary, this application has the following beneficial effects: The introduction of halogens can give polyurethane elastomers many excellent properties, such as flame retardancy, hydrolysis resistance, chemical corrosion resistance, and chemical stability. The reason is that halogen atoms have strong electronegativity. The introduction of halogens into polyurethane elastomers can increase molecular polarity and enhance intermolecular forces, making polyurethane elastomers more difficult to be dissolved or swollen by solvents. At the same time, the chemical bond energy formed by halogen atoms is relatively high, which can increase the material's resistance to chemical corrosion and solvent erosion. The introduction of fluoride can also reduce the surface energy of polyurethane elastomers, thereby making the surface of polyurethane elastomers more hydrophobic and oleophobic, effectively reducing the adsorption and penetration of solvents, and indirectly improving the solvent resistance of polyurethane elastomers. In the present application, diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side is selected to introduce fluorine into the polyurethane coating, effectively improving the solvent resistance of the polyurethane coating of the coating roller; at the same time, diphenylmethane diisocyanate also contains a benzene ring, which has a large steric hindrance, thereby effectively hindering the chemical attack of chemical media on the polyurethane molecular chain, further improving the solvent resistance of the polyurethane coating.

[0020] 2. From the test data of the solvent resistance of the polyurethane coating, it can be seen that compared with the use of dibutyltin dilaurate as a catalyst, the use of bismuth laurate as a catalyst can further improve the solvent resistance of the polyurethane coating. The reason may be that the bismuth atoms in bismuth laurate have a certain coordination ability and can interact with the polar groups in the polyurethane molecular chain. This interaction effectively enhances the cohesive force between molecules, making it more difficult for the polyurethane elastomer to be penetrated or swelled by solvents.

[0021] 3. Although the introduction of fluorine can effectively improve the solvent resistance of the polyurethane coating, at the same time, the introduction of fluorine will also lead to a decrease in the surface energy of the polyurethane coating, resulting in insufficient adhesion between the polyurethane coating and the roller core; in the present application, 2-amino-4-hydroxy-6-methylpyrimidine is additionally added to the chain extender, so that 2-amino-4-hydroxy-6-methylpyrimidine participates in the chain extension and end-capping of the polyurethane elastomer, thereby forming a large number of UPy structures, and the UPy structure can form hydrogen bonds with the oxygen atoms in the roller core, thereby obtaining greater shear force, thereby effectively compensating for the defect of poor adhesion of the polyurethane coating caused by the introduction of fluorine. DETAILED DESCRIPTION

[0022] The present application is further described in detail below in conjunction with Examples 1 to 8 and Comparative Examples 1 to 2.

[0023] raw material Diphenylmethane diisocyanate CAS: 101-68-8; Perfluoroalkyl alcohol TEOH-10; Isophorone diisocyanate CAS: 4098-71-9; Polytetramethylene ether glycol Green Union (Jining) Chemical; N,N-dimethylformamide CAS: 68-12-2; 1,4-butanediol CAS: 110-63-4; 2-amino-4-hydroxy-6-methylpyrimidine CAS: 3977-29-5.

[0024] Example 1 A solvent-resistant polyurethane specially used for a coating roller is prepared from a polyurethane prepolymer and a chain extender, wherein the mass ratio of the polyurethane prepolymer to the chain extender is 40:1; wherein the chain extender is 1,4-butanediol.

[0025] The preparation method of the solvent-resistant polyurethane for coating roller is as follows: firstly, the polyurethane prepolymer and the chain extender are mixed for 3 hours, then the product is poured into a mold for drying, and then matured for 8 hours to obtain the solvent-resistant polyurethane for coating roller.

[0026] The polyurethane prepolymer includes the following raw materials: 35g of fluorinated isocyanate, 25g of isophorone diisocyanate, 60g of polytetramethylene ether diol, and 0.5g of a catalyst. The fluorinated isocyanate is diphenylmethane diisocyanate with a perfluorinated segment blocked on one side, and the catalyst is bismuth laurate.

[0027] The preparation method of the polyurethane prepolymer comprises the following steps: First, the fluorinated isocyanate is heated to 60° C., and then polytetramethylene ether diol and a catalyst are added, stirred and reacted for 2 hours, and then isophorone diisocyanate is added and stirred and reacted for 1 hour to obtain a polyurethane prepolymer.

[0028] The fluorinated isocyanate is obtained by reacting diphenylmethane diisocyanate and perfluoroalkyl alcohol in a molar ratio of 1:1; The preparation method of fluorinated isocyanate is as follows: first, N, N-dimethylformamide is slowly added to perfluoroalkyl alcohol until the perfluoroalkyl alcohol is completely dissolved, and then the solution is added to diphenylmethane diisocyanate at a rate of 4 d / s, during which stirring is continued and the temperature is controlled at 60°C. After the addition is completed, the temperature is lowered to 50°C and the reaction is continued for 2 hours to obtain fluorinated isocyanate.

[0029] It should be noted that the solvent-resistant polyurethane specially used for coating rollers in this embodiment is suitable for surface coating of coating rollers, printing rollers, and embossing rollers.

[0030] Example 2 The difference from Example 1 is that the addition amount of each component of the polyurethane prepolymer is different, as follows: The polyurethane prepolymer includes the following raw materials: 30g of fluorinated isocyanate, 30g of isophorone diisocyanate, 70g of polytetramethylene ether diol, and 1g of a catalyst. The fluorinated isocyanate is diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side, and the catalyst is bismuth laurate.

[0031] Example 3 The difference from Example 1 is that the addition amount of each component of the polyurethane prepolymer is different, as follows: The polyurethane prepolymer includes the following raw materials: 40g of fluorinated isocyanate, 20g of isophorone diisocyanate, 50g of polytetramethylene ether diol, and 0.1g of a catalyst. The fluorinated isocyanate is diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side, and the catalyst is bismuth laurate.

[0032] Example 4 The difference from Example 1 is that the specific components of the polyurethane prepolymer are different, as follows: The polyurethane prepolymer includes the following raw materials: 35g of fluorinated isocyanate, 25g of isophorone diisocyanate, 60g of polytetramethylene ether diol, and 0.5g of a catalyst. The fluorinated isocyanate is diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side, and the catalyst is dibutyltin dilaurate.

[0033] Example 5 The difference from Example 1 is that the specific components of the polyurethane prepolymer are different, as follows: The polyurethane prepolymer includes the following raw materials in mass: 35g of fluorinated isocyanate, 25g of isophorone diisocyanate, 60g of polytetramethylene ether diol, and 0.5g of a catalyst, wherein the fluorinated isocyanate is diphenylmethane diisocyanate terminated at one side of a perfluorinated segment, and the catalyst is a mixture of dibutyltin dilaurate and bismuth laurate, and the mass ratio of dibutyltin dilaurate to bismuth laurate is 1:1.

[0034] Example 6 The difference from Example 1 is that the chain extender is composed of 1,4-butanediol and 2-hydroxy-4-amino-6-methylpyrimidine, and the mass ratio of 1,4-butanediol to 2-hydroxy-4-amino-6-methylpyrimidine is 4:3; The preparation method of the solvent-resistant polyurethane for coating rollers is as follows: first, N, N-dimethylformamide and 1,4-butanediol are mixed and added to the polyurethane prepolymer, then 2-hydroxy-4-amino-6-methylpyrimidine is added to react for 2 hours, and finally the product is poured into a mold for drying, and then matured for 8 hours to obtain the solvent-resistant polyurethane for coating rollers.

[0035] Example 7-Example 8 The difference from Example 6 is that the mass ratio of 1,4-butanediol and 2-hydroxy-4-amino-6-methylpyrimidine is different, as shown in Table 1.

[0036]

[0037] Table 1 Mass ratio of each component of the chain extender in Example 6-Example 8 Comparative Example 1 The difference from Example 1 is that the specific components of the polyurethane prepolymer are different, as follows: The polyurethane prepolymer includes the following raw materials: 35g of diphenylmethane diisocyanate, 25g of isophorone diisocyanate, 60g of polytetramethylene ether diol, and 0.5g of a catalyst. The fluorinated isocyanate is diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side, and the catalyst is bismuth laurate.

[0038] Comparative Example 2 The difference from Example 1 is that the specific components of the polyurethane prepolymer are different, as follows: The polyurethane prepolymer includes the following raw materials: 60g of isophorone diisocyanate, 60g of polytetramethylene ether diol, and 0.5g of a catalyst. The fluorinated isocyanate is diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side, and the catalyst is bismuth laurate.

[0039] Performance testing 1. Solvent resistance test Three samples were taken from each of Examples 1 to 5 and Comparative Examples 1 to 2, and then the samples were immersed in a cyclohexanone solution for 48 hours, the temperature was controlled at 25° C., and finally the expansion ratio was calculated and the average value was taken.

[0040] The test data are shown in Table 2.

[0041]

[0042] Table 2 Test data table of Example 1-Example 5 and Comparative Example 1-Comparative Example 2 2. Adhesion performance test Three samples were taken from Example 1 and Example 6-Example 8 respectively, and then the samples were attached to steel plates and dried and aged according to ISO4587-2003 "Determination of tensile shear strength of adhesives". Finally, the tensile shear strength of the samples was tested and the average value was taken.

[0043] The test data are shown in Table 3.

[0044]

[0045] Table 3 Adhesion performance test of Example 1 and Example 6-Example 8 Referring to Example 1 and Comparative Examples 1-2 and in combination with Table 2, it can be seen that, relative to Example 1, the 48h swelling rate of Comparative Example 1 is significantly improved, and the 48h swelling rate of Comparative Example 2 is further improved. This shows that the use of diphenylmethane diisocyanate can effectively improve the solvent resistance of the polyurethane coating, and the use of diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side can further improve the solvent resistance of the polyurethane coating.

[0046] The reason is that diphenylmethane diisocyanate also contains benzene rings, which have large steric hindrance, thus effectively hindering the chemical attack of chemical media on the polyurethane molecular chain, thereby effectively improving the solvent resistance of the polyurethane coating.

[0047] When the diphenylmethane diisocyanate with a perfluorinated chain segment at one side is selected, fluorine is introduced into the polyurethane coating, and the introduction of halogens can give polyurethane elastomers many excellent properties, such as flame retardancy, hydrolysis resistance, chemical medium corrosion resistance, and chemical stability. Specifically, the introduction of halogens can give polyurethane elastomers many excellent properties, such as flame retardancy, hydrolysis resistance, chemical medium corrosion resistance, and chemical stability. The reason is that the halogen atoms have strong electronegativity. After the halogens are introduced into the polyurethane elastomer, the molecular polarity can be increased and the intermolecular force can be enhanced, thereby making the polyurethane elastomer more difficult to be dissolved or swollen by solvents. At the same time, the chemical bond energy formed by the halogen atoms is relatively high, which can increase the resistance of the material to chemical corrosion and solvent erosion. The introduction of fluoride can also reduce the surface energy of the polyurethane elastomer, thereby making the surface of the polyurethane elastomer more hydrophobic and oleophobic, effectively reducing the adsorption and penetration of solvents, and indirectly improving the solvent resistance of the polyurethane elastomer.

[0048] With reference to Examples 1 to 3 and in combination with Table 2, it can be seen that, relative to Example 1, the 48h swelling rates of Examples 2 and 3 are improved to a certain extent, which indicates that when the components of the polyurethane prepolymer are added in the amounts of Example 1, the prepared polyurethane coating will have better solvent resistance.

[0049] Referring to Example 1 and Examples 4-5 and in combination with Table 2, it can be seen that, relative to Example 1, the 48h swelling rate of Example 5 is slightly improved, and the 48h swelling rate of Example 4 is further improved, which shows that, relative to the use of dibutyltin dilaurate as a catalyst, the use of bismuth laurate as a catalyst can further improve the solvent resistance of the polyurethane coating. Moreover, relative to the use of bismuth laurate and dibutyltin dilaurate in combination, the effect is relatively better when bismuth laurate is used alone.

[0050] The reason may be that the bismuth atoms in bismuth laurate have a certain coordination ability, which can interact with the polar groups in the polyurethane molecular chain. This interaction effectively enhances the cohesion between molecules, making the polyurethane elastomer more difficult to be penetrated or swelled by solvents.

[0051] Referring to Example 1 and Example 6 and combining with Table 3, it can be seen that the tensile shear strength of Example 6 is significantly improved compared with that of Example 1, which shows that adding 2-hydroxy-4-amino-6-methylpyrimidine to the chain extender can significantly improve the bonding effect between the polyurethane coating and the steel plate.

[0052] The reason is that although the introduction of fluorine can effectively improve the solvent resistance of the polyurethane coating, at the same time, the introduction of fluorine will also lead to a decrease in the surface energy of the polyurethane coating, resulting in insufficient bonding between the polyurethane coating and the roller core.

[0053] In Example 6, 2-amino-4-hydroxy-6-methylpyrimidine is additionally added to the chain extender, so that 2-amino-4-hydroxy-6-methylpyrimidine participates in the chain extension and end-capping of the polyurethane elastomer, thereby forming a large number of UPy structures. The UPy structure can form hydrogen bonds with the oxygen atoms on the surface of the steel plate, thereby obtaining a greater shear force, thereby effectively compensating for the defect of poor adhesion performance of the polyurethane coating caused by the introduction of fluorine.

[0054] Referring to Example 6-Example 8 and combining with Table 3, it can be seen that relative to Example 6, the tensile shear strength of Example 7-Example 8 is slightly reduced, which shows that when the components of the chain extender adopt the mass proportion of Example 6, the prepared polyurethane coating will have better bonding properties.

[0055] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed. However, as long as it is within the scope of the claims of the present application, it shall be protected by the patent law.

Claims

1. A solvent-resistant polyurethane for coating rollers, characterized in that: The solvent-resistant polyurethane specially used for the coating roller is prepared from a polyurethane prepolymer and a chain extender, and the mass ratio of the polyurethane prepolymer to the chain extender is (30-50):1; The polyurethane prepolymer comprises the following raw materials in parts by weight: 30-40 parts of fluorine-containing isocyanate, 20-30 parts of isophorone diisocyanate, 50-70 parts of polytetramethylene ether diol, and 0.1-1 part of a catalyst. The fluorine-containing isocyanate is diphenylmethane diisocyanate with a perfluorinated chain segment blocked on one side.

2. The solvent-resistant polyurethane for coating roller according to claim 1, characterized in that: The catalyst is one of dibutyltin dilaurate and bismuth laurate or a mixture of both.

3. The solvent-resistant polyurethane for coating roller according to claim 1, characterized in that: The fluorine-containing isocyanate is obtained by reacting diphenylmethane diisocyanate and perfluoroalkyl alcohol in a molar ratio of 1:

1.

4. The solvent-resistant polyurethane for coating roller according to claim 3, characterized in that: The preparation method of the fluorinated isocyanate is as follows: firstly, perfluoroalkyl alcohol is dissolved in N,N-dimethylformamide, and then added dropwise to diphenylmethane diisocyanate at a speed of 2-4 d / s, during which stirring is continued and the temperature is controlled at 50-70° C. After the addition is completed, the temperature is lowered to 40-60° C. and the reaction is continued for 1-3 hours to obtain the fluorinated isocyanate.

5. The solvent-resistant polyurethane for coating roller according to claim 1, characterized in that: The preparation method of the polyurethane prepolymer is as follows: firstly, the fluorine-containing isocyanate is heated to 50-70° C., then polytetramethylene ether diol and a catalyst are added, stirred for reaction for 1-2 hours, and then isophorone diisocyanate is added and stirred for reaction for 0.5-1 hour to obtain the polyurethane prepolymer.

6. The solvent-resistant polyurethane for coating roller according to claim 1, characterized in that: The chain extender consists of 1,4-butanediol and 2-amino-4-hydroxy-6-methylpyrimidine.

7. The solvent-resistant polyurethane for coating roller according to claim 6, characterized in that: The mass ratio of the 1,4-butanediol and 2-amino-4-hydroxy-6-methylpyrimidine is (1-3): (1-2).

8. The solvent-resistant polyurethane for coating roller according to claim 6, characterized in that: The preparation method of the solvent-resistant polyurethane for coating roller is as follows: first, N, N-dimethylformamide and 1,4-butanediol are mixed and added to the polyurethane prepolymer, then 2-amino-4-hydroxy-6-methylpyrimidine is added to react for 1-2 hours, and finally the product is poured into a mold for drying and aging to obtain the solvent-resistant polyurethane for coating roller.

9. A method for preparing the solvent-resistant polyurethane for coating rollers according to any one of claims 1 to 8, characterized in that: The following steps are involved: Preparation of fluorinated isocyanate: First, perfluoroalkyl alcohol is dissolved in N, N-dimethylformamide, and then added dropwise to diphenylmethane diisocyanate at a rate of 2-4 d / s, during which stirring is continued and the temperature is controlled at 50-70°C. After the addition is completed, the temperature is lowered to 40-60°C and the reaction is continued for 1-3 hours to obtain fluorinated isocyanate; Preparation of polyurethane prepolymer: First, heat the fluorinated isocyanate to 50-70°C, then add polytetramethylene glycol and a catalyst, stir and react for 1-2 hours, then add isophorone diisocyanate and continue stirring and reacting for 0.5-1 hour to obtain a polyurethane prepolymer; Preparation of solvent-resistant polyurethane for coating roller: The polyurethane prepolymer and the chain extender are mixed for 2-4 hours, and then the product is poured into a mold for drying to obtain the solvent-resistant polyurethane for coating roller.

10. A method for preparing the solvent-resistant polyurethane for coating rollers according to any one of claims 1 to 8, characterized in that: The solvent-resistant polyurethane specially used for coating rollers is suitable for surface coatings of coating rollers, printing rollers and embossing rollers.

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