A one-component polyurethane waterproofing coating modified with silicone rubber and a preparation method thereof

Abstract

This invention discloses a silicone rubber-modified exposed single-component polyurethane waterproof coating and its preparation method. The raw materials, by weight, include the following components: 20-30 parts polyether polyol; 1-5 parts silicone rubber; 0.1-1 part light stabilizer; 0.1-0.5 parts dispersant; 0.1-1 part antioxidant; 15-25 parts flame retardant; 15-25 parts pigment and filler; 10-25 parts isocyanate; 0.3-3 parts chain extender; 0.1-0.5 parts catalyst; 0.1-0.5 parts defoamer; 0.1-0.5 parts leveling agent; 3-10 parts curing agent; and 0-5 parts solvent. This invention fully meets the requirements of Type III standard and the limits for Class A hazardous substances in GB / T 19250-2013, and possesses high strength, high abrasion resistance, and excellent exposed weather resistance. It is particularly suitable for waterproofing projects in exposed passageways such as bridges, parking lots, and accessible roofs.

Description

Technical Field

[0001] This invention relates to the field of building waterproofing materials technology, and in particular to a silicone rubber modified exposed single-component polyurethane waterproof coating and its preparation method. Background Technology

[0002] Single-component polyurethane waterproof coatings, as an important engineering waterproofing material, must meet the performance requirements of the national standard GB / T 19250-2013. Type III products, in particular, require coatings with higher physical properties (such as tensile strength ≥12.0MPa, elongation at break ≥250%, tear strength ≥40N / mm, abrasion resistance ≤50mg, etc.) and weather resistance. These products are mainly used in exposed passageways such as bridges, parking lots, and accessible roofs, where they must withstand frequent foot traffic, mechanical friction, and complex climatic conditions. However, currently available single-component polyurethane waterproof coatings generally have the following shortcomings: (1) Insufficient mechanical properties: The tensile strength of most products is between 2-10 MPa, which is difficult to meet the requirement of 12 MPa for Type III.

[0003] (2) Insufficient abrasion resistance: The abrasion resistance (750g / 500r) of existing coatings is generally >60mg, and the coating is prone to damage and cracking under exposed environments such as frequent friction.

[0004] (3) Insufficient weather resistance: When exposed to ultraviolet light or large temperature differences for a long time, the coating is prone to cracking, which affects the long-term protective effect.

[0005] (4) Single function: Most common products are single function products, which are difficult to achieve multiple performances at the same time, especially high strength, high wear resistance and excellent exposed performance, which greatly limits the application of the products. Summary of the Invention

[0006] The purpose of this invention is to provide a silicone rubber-modified exposed single-component polyurethane waterproof coating and its preparation method, so as to solve the technical problem that the prior art is unable to simultaneously achieve high strength, high wear resistance and excellent exposed performance.

[0007] This invention is achieved using the following technical solution: a silicone rubber-modified exposed single-component polyurethane waterproof coating, the raw materials of which include the following components by weight: Polyether polyol 20-30 parts; silicone rubber 1-5 parts; light stabilizer 0.1-1 part; dispersant 0.1-0.5 parts; antioxidant 0.1-1 part; flame retardant 15-25 parts; pigments and fillers 15-25 parts; isocyanate 10-25 parts; chain extender 0.3-3 parts; catalyst 0.1-0.5 parts; defoamer 0.1-0.5 parts; leveling agent 0.1-0.5 parts; curing agent 3-10 parts; solvent 0-5 parts.

[0008] Furthermore, the polyether polyol is one or a mixture of polytetramethylene glycol, PPG polyether glycol, and PPG polyether triol; The light stabilizer is one or a mixture of benzotriazole / hindered amine radical scavenger and hydroxyphenyltriazine / hindered amine radical scavenger.

[0009] Furthermore, the dispersant is one or a mixture of polyurethane polymers and acrylate polymers; Antioxidants are one or more of hindered phenols and phosphites, or a mixture thereof.

[0010] Furthermore, the flame retardant is one or a mixture of aluminum hydroxide, hydrated aluminum oxide, zinc oxide, and ammonium polyphosphate.

[0011] Furthermore, the filler is one or a mixture of calcium carbonate, talc, mica powder, silica fume, and barium sulfate; The pigment is one or more of titanium dioxide, carbon black, and iron oxide, or a mixture thereof.

[0012] Furthermore, the isocyanate is one or a mixture of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and HDI trimer polyisocyanate; The chain extender is one or a mixture of 1,4-butanediol, diethylene glycol, triethylene glycol, trimethylolpropane, low molecular weight PPG polyether glycol, and low molecular weight PPG polyether triol.

[0013] Furthermore, the catalyst is one or a mixture of stannous octoate, dibutyltin dilaurate, zinc isooctanoate, bismuth isooctanoate, bismorpholino diethyl ether, and N,N-dimethylbenzylamine.

[0014] Furthermore, the defoamer is one or a mixture of non-silicone and organosilicon types; The leveling agent is one or a mixture of polyacrylates and modified polysiloxanes; The curing agent is one or more of the following: oxazolidines and imines containing hydrogen-containing groups.

[0015] Furthermore, the solvent is one or more of ethyl acetate, butyl acetate, dicarboxylic acid ester, and high-boiling-point aromatic solvents.

[0016] A method for preparing a silicone rubber-modified exposed one-component polyurethane waterproof coating, comprising the following steps: Polyether polyol, silicone rubber, light stabilizer, dispersant, and defoamer are added to the reactor and stirred evenly. Then antioxidant, flame retardant, pigments and fillers are added, the temperature is raised to 110~120℃, and dehydrated under vacuum of -0.09~-0.10MPa for 2~4 hours. After dehydration is complete, the vacuum is turned off and the temperature is lowered to 80-85°C. Then, isocyanate is added and the reaction is carried out for 2-3 hours. Heat to 90-95℃, add chain extender, and react for 1-2 hours; First, cool the temperature to 85-90℃, add the curing agent, and react for 0.5-1 hour; In the second stage, the temperature is lowered to 80-85℃, and the catalyst, leveling agent, and solvent are added and stirred for 0.5-1 hour. Turn on the vacuum pump and degas under vacuum at -0.09~-0.10MPa for 0.5 hours. Then turn off the vacuum pump, stop stirring, purge with nitrogen for protection, and then discharge the material.

[0017] The beneficial effects of this invention are as follows: (1) It takes into account multiple properties: it solves the problem of balancing high strength, high wear resistance and exposed performance, and can meet the technical standards of Type III in GB / T 19250-2013.

[0018] (2) Excellent wear resistance: wear resistance ≤30mg, far superior to the standard requirement of ≤50mg, and can withstand long-term traffic loads and friction in places such as bridges, parking lots, and accessible roofs.

[0019] (3) Excellent weather resistance: After 1500 hours of artificial climate aging, its tensile strength retention rate is ≥90%, which is far superior to conventional products, ensuring that it will not powder or crack in the long-term exposed environment; at the same time, its excellent weather resistance can extend the service life of exposed projects, greatly reduce the later maintenance and renovation costs, and has a lower overall cost.

[0020] (4) Good temperature resistance: The bending resistance at low temperature reaches -40℃ without cracking. At the same time, it has excellent high temperature resistance and is suitable for a wide range of regions from the frigid Northeast to the hot South China.

[0021] (5) Good workability: As a single-component product, it is easy to construct and does not require on-site weighing and mixing, thus avoiding engineering quality problems that may be caused by incorrect proportions of multi-component products; at the same time, the product has a fast surface drying time (≤3h), which can effectively reduce surface defects caused by environmental factors such as rain during construction.

[0022] (6) Environmentally friendly: It does not contain harmful substances such as benzene, anthracene, naphthalene, and free TDI, and meets Class A environmental protection requirements (VOC≤50g / L). It is more friendly to construction workers and the environment, and can also be used in places with high environmental protection requirements such as schools, hospitals, and residences. Detailed Implementation

[0023] To more clearly illustrate the technical solutions of this invention, the technical solutions of this invention will be described in detail below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] It should also be noted that, without conflict, the following embodiments and features can be combined with each other.

[0025] A silicone rubber-modified exposed single-component polyurethane waterproof coating comprises the following components by weight: 20-30 parts polyether polyol; 1-5 parts silicone rubber; 0.1-1 part light stabilizer; 0.1-0.5 parts dispersant; 0.1-1 part antioxidant; 15-25 parts flame retardant; 15-25 parts pigment and filler; 10-25 parts isocyanate; 0.3-3 parts chain extender; 0.1-0.5 parts catalyst; 0.1-0.5 parts defoamer; 0.1-0.5 parts leveling agent; 3-10 parts curing agent; and 0-5 parts solvent.

[0026] The polyether polyol is one or more of polytetramethylene glycol, PPG polyether glycol, and PPG polyether triol. Preferably, the polyether polyol is one or more of polytetramethylene glycol PTG-1000, polytetramethylene glycol PTG-2000, polyether glycol DL-1000D, polyether glycol DL-2000D, and polyether triol EP-330NG.

[0027] The silicone rubber is one or more mixtures of polydimethylsiloxanes with different viscosities containing hydroxyl groups. Preferably, the silicone rubber is one or more mixtures of monohydroxyl-containing polydimethylsiloxane liquid XHG-213 with a viscosity from 500 mPa·s to 5000 mPa·s and dihydroxyl-containing polydimethylsiloxane liquid RTV-107 with a molecular weight from 500 mPa·s to 5000 mPa·s.

[0028] The light stabilizer is one or more of benzotriazole / hindered amine radical scavengers and hydroxyphenyltriazine / hindered amine radical scavengers. Preferably, the light stabilizer is one or more of the following: benzotriazole / hindered amine radical scavenger Tinuvin 5050, benzotriazole / hindered amine radical scavenger Tinuvin 5060, benzotriazole / hindered amine radical scavenger Tinuvin 5151, hydroxyphenyltriazine / hindered amine radical scavenger Tinuvin 5248, and hydroxyphenyltriazine / hindered amine radical scavenger Tinuvin 5251.

[0029] The dispersant is one or more of polyurethane polymers and acrylate polymers. Preferably, the dispersant is one or more of the following polyurethane polymers: Efka PU 4046, Efka PU 4047, Efka PU 4061, Ffka PX 4320, and Ffka PX 4330.

[0030] The antioxidant is one or more of hindered phenols and phosphites. Preferably, the antioxidant is one or more of hindered phenols Irganox 245, hindered phenols Irganox 1010, hindered phenols Irganox 1076, hindered phenols Irganox 1135, phosphites Irgafos 126, and phosphites Irgafos 168.

[0031] The flame retardant is one or a mixture of aluminum hydroxide, hydrated aluminum oxide, zinc oxide, and ammonium polyphosphate. Preferably, the flame retardant has a mesh size of 1250-3000 mesh.

[0032] The filler is one or more of calcium carbonate, talc, mica powder, silica fume, and barium sulfate; the pigment is one or more of titanium dioxide, carbon black, and iron oxide. Preferably, the filler has a mesh size of 800-1250 mesh.

[0033] The isocyanate is one or a mixture of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and HDI trimer polyisocyanate.

[0034] The chain extender is one or more of 1,4-butanediol, diethylene glycol, triethylene glycol, trimethylolpropane, low molecular weight PPG polyether glycol, and low molecular weight PPG polyether triol. Preferably, the chain extender is one or more of 1,4-butanediol, diethylene glycol, triethylene glycol, trimethylolpropane, polyether glycol DL-400, and polyether triol MN-500.

[0035] The catalyst is one or a mixture of stannous octoate, dibutyltin dilaurate, zinc isooctanoate, bismuth isooctanoate, bismorpholino diethyl ether, and N,N-dimethylbenzylamine.

[0036] The defoamer is one or more of the following: non-silicone and silicone. Preferably, the defoamer is one or more of the following: non-silicone Efka PB 2020, non-silicone Efka PB 2720, silicone Efka PB 2744, silicone Efka SI 2040, and silicone Efka SI 2741.

[0037] The leveling agent is one or more mixtures of polyacrylates and modified polysiloxanes. Preferably, the leveling agent is one or more mixtures of polyacrylate Efka FL 3600, polyacrylate Efka FL 3766, polyacrylate Efka FL 3777, modified polysiloxane Efka SL 3033, and modified polysiloxane Efka SL 3239.

[0038] The curing agent is one or more of the following: oxazolidines and imines containing hydrogen-containing groups. Preferably, the curing agent is one or more of the following: oxazolidine Incozol 4, oxazolidine HY-902, imine Aldirez BH, and imine VESTAMIN A139.

[0039] The solvent is one or more of ethyl acetate, butyl acetate, dicarboxylic acid ester, and high-boiling-point aromatic solvents. Preferably, the solvent is one or more of ethyl acetate, butyl acetate, dicarboxylic acid ester (DBE), high-boiling-point aromatic solvent SA-1000, high-boiling-point aromatic solvent SA-1500, and high-boiling-point aromatic solvent SA-1800.

[0040] Example 1 Silicone rubber modified exposed one-component polyurethane waterproof coating, by weight, contains the following components: Polyether polyols: DL-1000D, 15 parts; DL-2000D, 7 parts; Silicone rubber: RTV-107 (2000 mPa•s), 5 parts; Light stabilizer: Tinuvin 5050, 0.5 parts; Dispersant: Efka PU 4046, 0.5 parts; Antioxidants: Irganox 1010, 0.5 parts; Irgafos 168, 0.2 parts; Flame retardant: Zinc oxide, 24 parts; Pigments and fillers: calcium carbonate, 6 parts; silica powder, 12 parts; carbon black, 1 part; Isocyanate: IPDI, 19 parts; Chain extender: 1,4-butanediol, 1 part; Catalyst: Dibutyltin dilaurate, 0.1 parts; Defoamer: Efka PB 2020, 0.3 parts; Efka PB 2744, 0.1 parts; Leveling agent: Efka FL 3600, 0.3 parts; Hardener: Incozol 4, 5.5 parts; Solvent: Ethyl acetate, 2 parts.

[0041] Its preparation method includes the following steps: Polyether polyol, silicone rubber, light stabilizer, dispersant, and defoamer are added to the reactor and stirred evenly. Then antioxidant, flame retardant, pigments and fillers are added, the temperature is raised to 110~120℃, and dehydrated under vacuum of -0.09~-0.10MPa for 2~4 hours.

[0042] After dehydration is complete, the vacuum is turned off, and the temperature is lowered to 80-85°C. Then, isocyanate is added, and the reaction is carried out for 2-3 hours.

[0043] Heat to 90-95℃, add chain extender, and react for 1-2 hours.

[0044] Cool to 85~90℃, add curing agent, and react for 0.5~1 hour.

[0045] Cool to 80-85℃, add catalyst, leveling agent and solvent, and stir for 0.5-1 hour.

[0046] Turn on the vacuum pump and degas under vacuum at -0.09~-0.10MPa for 0.5 hours. Then turn off the vacuum pump, stop stirring, purge with nitrogen for protection, and then discharge the material.

[0047] Example 2 Silicone rubber modified exposed one-component polyurethane waterproof coating, by weight, contains the following components: Polyether polyols: DL-1000D, 18 parts; EP-330NG, 5 parts; Silicone rubber: XHG-213 (5000 mPa•s), 1 part; RTV-107 (1500 mPa•s), 2 parts; Light stabilizer: Tinuvin 5060, 0.5 parts; Dispersant: Efka PU 4047, 0.5 parts; Antioxidants: Irganox 1076, 0.5 parts; Irgafos 126, 0.2 parts; Flame retardant: Ammonium polyphosphate, 23 parts; Pigments and fillers: silica powder, 10 parts; mica powder, 6 parts; iron oxide, 2 parts; Isocyanate: IPDI, 20 parts; Chain extender: DL-400, 3 parts; Catalyst: Zinc isooctanoate, 0.3 parts; Defoamer: Efka PB 2720, 0.2 parts; Efka SI 2040, 0.2 parts; Leveling agent: Efka FL 3600, 0.3 parts; Hardener: HY-902, 6.3 parts; Solvent: SA-1800, 1 part.

[0048] The preparation method is the same as in Example 1.

[0049] Example 3 Silicone rubber modified exposed one-component polyurethane waterproof coating, by weight, contains the following components: Polyether polyols: PTG-1000, 8 parts; PTG-2000, 13 parts; DL-2000D, 5 parts; Silicone rubber: RTV-107 (1000 mPa•s), 3 parts; XHG-213 (5000 mPa•s), 1 part; Light stabilizers: Tinuvin 5060, 0.3 parts; Tinuvin 5248, 0.7 parts; Dispersant: Efka PU 4047, 0.2 parts; Ffka PX 4320, 0.3 parts; Antioxidants: Irganox 1135, 0.6 parts; Irgafos 126, 0.2 parts; Flame retardant: zinc oxide, 10 parts; aluminum hydroxide, 10 parts; Pigments and fillers: mica powder, 15 parts; titanium dioxide, 2 parts; carbon black, 0.1 parts; Isocyanates: HMDI, 11 parts; IPDI, 5 parts; Chain extender: MN-500, 1 part; Catalysts: 0.1 parts of bismorpholino diethyl ether and 0.1 parts of N,N-dimethylbenzylamine; Defoamer: Efka PB 2720, 0.1 parts; Efka SI 2741, 0.4 parts; Leveling agents: Efka FL 3777, 0.2 parts; Efka SL 3239, 0.3 parts; Hardener: HY-902, 8.2 parts; VESTAMIN A139, 1.7 parts; Solvent: SA-1000, 2.5 parts.

[0050] The preparation method is the same as in Example 1.

[0051] Example 4 Silicone rubber modified exposed one-component polyurethane waterproof coating, by weight, contains the following components: Polyether polyols: PTG-1000, 20 parts; DL-2000D, 5 parts; Silicone rubber: RTV-107 (750 mPa•s), 4 parts; XHG-213 (5000 mPa•s), 1 part; Light stabilizers: Tinuvin 5050, 0.1 parts; Tinuvin 5251, 0.9 parts; Dispersant: Efka PU 4046, 0.1 parts; Ffka PX 4330, 0.4 parts; Antioxidants: Irganox 245, 0.8 parts; Irgafos 126, 0.2 parts; Flame retardants: ammonium polyphosphate, 10 parts; zinc oxide, 10 parts; Pigments and fillers: Barium sulfate, 10 parts; Titanium dioxide, 15 parts; Isocyanate: HMDI, 14 parts; Chain extender: Trimethylolpropane, 0.3 parts; Catalyst: Stannous octoate, 0.1 parts; Defoamer: Efka PB 2020, 0.4 parts; Efka SI 2741, 0.1 parts; Leveling agents: Efka FL 3766, 0.4 parts; Efka SL 30393, 0.1 parts; Hardener: Incozol 4, 9 parts; Aldirez BH, 1 part; Solvent: SA-1500, 2.1 parts.

[0052] The preparation method is the same as in Example 1.

[0053] Performance test results The performance of the silicone rubber-modified exposed one-component polyurethane waterproof coatings prepared in Examples 1-4 was tested according to GB / T 19250-2013. The results are shown in Table 1 below: Table 1 Performance of Silicone Rubber Modified Exposed One-Component Polyurethane Waterproof Coating

[0054] As shown in Table 1, the performance of the silicone rubber-modified exposed single-component polyurethane waterproof coatings prepared in Examples 1-4 all meet the technical requirements of Type III in GB / T 19250-2013. After 1500 hours of artificial weathering, the tensile strength retention rate is ≥90%, far exceeding the standard requirement of 1000 hours, demonstrating excellent weather resistance. Its abrasion resistance is ≤30mg, which can withstand the requirements of use in places such as bridges, parking lots, and accessible roofs. At the same time, VOC is ≤50g / L, reaching the Class A standard, making it more environmentally friendly to the environment and construction workers.

[0055] This invention is a single-component, easy-to-construct, and fully meets the requirements of Type III standard and Class A hazardous substance limits in GB / T 19250-2013. It also features high strength (tensile strength ≥12MPa), high abrasion resistance (abrasion loss ≤30mg at 750g / 500r) and excellent exposed weather resistance (strength retention rate ≥90% after 1500h of artificial climate aging). It is particularly suitable for waterproofing projects of exposed passageways such as bridges, parking lots, and accessible roofs.

[0056] For the foregoing embodiments, in order to simplify the description, they are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to this application.

[0057] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the invention should be within the protection scope of the appended claims.

Claims

1. A silicone rubber-modified exposed one-component polyurethane waterproof coating, characterized in that, Its raw materials include the following components by weight: Polyether polyol 20-30 parts; silicone rubber 1-5 parts; light stabilizer 0.1-1 part; dispersant 0.1-0.5 parts; antioxidant 0.1-1 part; flame retardant 15-25 parts; pigments and fillers 15-25 parts; isocyanate 10-25 parts; chain extender 0.3-3 parts; catalyst 0.1-0.5 parts; defoamer 0.1-0.5 parts; leveling agent 0.1-0.5 parts; curing agent 3-10 parts; solvent 0-5 parts.

2. The silicone rubber-modified exposed single-component polyurethane waterproof coating as described in claim 1, characterized in that, The polyether polyol is one or a mixture of polytetramethylene glycol, PPG polyether glycol, and PPG polyether triol; The light stabilizer is one or a mixture of benzotriazole / hindered amine radical scavenger and hydroxyphenyltriazine / hindered amine radical scavenger.

3. The silicone rubber-modified exposed single-component polyurethane waterproof coating as described in claim 1, characterized in that, The dispersant is one or a mixture of polyurethane polymers and acrylate polymers; Antioxidants are one or more of hindered phenols and phosphites, or a mixture thereof.

4. The silicone rubber-modified exposed single-component polyurethane waterproof coating as described in claim 1, characterized in that, The flame retardant is one or a mixture of aluminum hydroxide, hydrated aluminum oxide, zinc oxide, and ammonium polyphosphate.

5. The silicone rubber-modified exposed single-component polyurethane waterproof coating as described in claim 1, characterized in that, The filler is one or a mixture of calcium carbonate, talc, mica powder, silica fume, and barium sulfate; The pigment is one or more of titanium dioxide, carbon black, and iron oxide, or a mixture thereof.

6. The silicone rubber-modified exposed single-component polyurethane waterproof coating as described in claim 1, characterized in that, The isocyanate is one or a mixture of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and HDI trimer polyisocyanate; The chain extender is one or a mixture of 1,4-butanediol, diethylene glycol, triethylene glycol, trimethylolpropane, low molecular weight PPG polyether glycol, and low molecular weight PPG polyether triol.

7. The silicone rubber-modified exposed single-component polyurethane waterproof coating as described in claim 1, characterized in that, The catalyst is one or a mixture of stannous octoate, dibutyltin dilaurate, zinc isooctanoate, bismuth isooctanoate, bismorpholino diethyl ether, and N,N-dimethylbenzylamine.

8. The silicone rubber-modified exposed single-component polyurethane waterproof coating as described in claim 1, characterized in that, The defoamer is one or a mixture of non-silicone and organosilicon types; The leveling agent is one or a mixture of polyacrylates and modified polysiloxanes; The curing agent is one or more of the following: oxazolidines and imines containing hydrogen-containing groups.

9. The silicone rubber-modified exposed single-component polyurethane waterproof coating as described in claim 1, characterized in that, The solvent is one or more of ethyl acetate, butyl acetate, dicarboxylic acid ester, and high-boiling-point aromatic solvents.

10. A method for preparing a silicone rubber-modified exposed one-component polyurethane waterproof coating, used to prepare the silicone rubber-modified exposed one-component polyurethane waterproof coating according to any one of claims 1 to 9, characterized in that, Includes the following steps: Polyether polyol, silicone rubber, light stabilizer, dispersant, and defoamer are added to the reactor and stirred evenly. Then antioxidant, flame retardant, pigments and fillers are added, the temperature is raised to 110~120℃, and dehydrated under vacuum of -0.09~-0.10MPa for 2~4 hours. After dehydration is complete, the vacuum is turned off and the temperature is lowered to 80-85°C. Then, isocyanate is added and the reaction is carried out for 2-3 hours. Heat to 90-95℃, add chain extender, and react for 1-2 hours; First, cool the temperature to 85-90℃, add the curing agent, and react for 0.5-1 hour; In the second stage, the temperature is lowered to 80-85℃, and the catalyst, leveling agent, and solvent are added and stirred for 0.5-1 hour. Turn on the vacuum pump and degas under vacuum at -0.09~-0.10MPa for 0.5 hours. Then turn off the vacuum pump, stop stirring, purge with nitrogen for protection, and then discharge the material.

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