Halogen-free intrinsic flame-retardant waterborne polyurethane material and preparation method thereof

Abstract

The invention relates to a halogen-free intrinsic flame-retardant waterborne polyurethane material and a preparation method thereof, and belongs to the field of functional polymer materials and fine chemical engineering. The halogen-based flame-retardant waterborne polyurethane disclosed by the invention is prepared from diisocyanate, long-carbon-chain polyether polyol, a catalyst, a chain extender, deionized water and a salt-forming agent through reaction; the hydrophilic chain extender is prepared from pentaerythritol, phosphorus oxychloride and p-hydroxyphenylpropionitrile through a reaction, and is a flame-retardant chain extender of a diamine structure containing phosphorus and nitrogen flame-retardant elements. The waterborne polyurethane material prepared by the method has a certain flame-retardant effect, and is simple in preparation process, relatively low in cost, very good in practicability and economical efficiency and good in market prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardants, and relates to a halogen-free intrinsically flame-retardant waterborne polyurethane material and a preparation method thereof. The material is obtained by a chemical structure modification method, and has the characteristics of high flame retardant efficiency, good durability, transparency, non-toxicity, low smoke, etc., and provides a new direction for the development of new material technology. Background Art

[0002] Under the background of increasingly stringent environmental regulations around the world, the research and application of environmentally friendly materials are particularly important. As a new type of environmentally friendly material, halogen-free intrinsic flame-retardant waterborne polyurethane material is gradually gaining widespread attention from all walks of life. Its unique flame retardant properties and environmental characteristics not only respond to the global call for reducing the use of harmful substances, but also provide high-performance material options for the modern industrial field.

[0003] With the rapid development of industries such as electronics, construction, and automobiles, the requirements for material performance are becoming increasingly stringent. These industries not only require materials to have excellent flame retardant properties to ensure safety, but also require materials to have good processing performance and environmental protection characteristics. Halogen-free intrinsic flame retardant waterborne polyurethane materials have won wide recognition in the market due to their outstanding performance in this regard.

[0004] Although traditional flame retardant materials have met the needs of the market to a certain extent, they still have many deficiencies in terms of flame retardant effect, environmental protection and processing performance. Therefore, through technological innovation, the development of halogen-free intrinsic flame retardant waterborne polyurethane materials with higher performance will not only help solve the problems facing the current market, but also promote the progress and development of the entire field of materials science.

[0005] As a high-performance environmentally friendly material, waterborne polyurethane materials have been widely used in many fields with their unique advantages. With water as the main solvent, it significantly reduces the emission of volatile organic compounds (VOC), thereby reducing the pollution pressure on the environment. This feature makes it an ideal choice in line with modern environmental protection concepts. With its multiple advantages such as environmental protection, safety, weather resistance and adhesion, waterborne polyurethane materials have become a high-performance material that has attracted much attention in the market today. With the continuous advancement of science and technology and the popularization of environmental protection concepts, waterborne polyurethane materials are expected to demonstrate their excellent performance in more fields and contribute to the sustainable development of society.

[0006] In the research and development and application of flame retardant materials, flame retardant elements and structural design are two crucial aspects. Flame retardant elements, such as phosphorus, nitrogen, silicon, boron, etc., each have a unique flame retardant mechanism, and they improve the flame retardant properties of materials in different ways. Phosphorus can promote the dehydration of materials into carbon during the combustion process, forming a stable carbon layer, thereby isolating the transfer of oxygen and heat. Nitrogen mainly releases non-combustible gases such as nitrogen during combustion, effectively reducing the concentration of combustible gases and playing a role in inhibiting the spread of flames.

[0007] Intrinsic flame retardancy is a chemical modification method that introduces flame retardant elements or groups into the polyurethane molecular chain through chemical reactions, thereby achieving intrinsic flame retardancy of the material. The key to this method is to accurately control the content and distribution of flame retardant elements to ensure the maximum flame retardant effect. Through chemical reactions such as copolymerization, grafting, and cross-linking, the flame retardant components can be effectively and tightly combined with the polyurethane matrix, thereby improving the overall flame retardant properties of the material.

[0008] CN 110483735 A discloses a method for preparing a halogen-free intrinsic flame-retardant waterborne polyurethane. First, phosphorus oxychloride and pentaerythritol are reacted to prepare an intermediate product having a diphosphoryl chloride functional group. Then, the intermediate product is reacted with diglycolamine and other substances to prepare a small molecule flame retardant containing phosphorus and nitrogen flame retardant elements. Finally, the small molecule flame retardant is used as a hard segment chain extender and reacted with polyether polyol, isophorone diisocyanate, 2,2-dimethylol propionic acid and other substances to prepare a halogen-free intrinsic flame-retardant waterborne polyurethane. The present invention prepares a reactive halogen-free intrinsic flame-retardant waterborne polyurethane by using a halogen-free flame retardant as a reaction substance. The flame retardant effect is good, the synthesis method is simple, but the ideal flame retardant effect can only be achieved under the condition of a certain amount of flame retardant. Excessive addition will affect the mechanical properties of the polyurethane material and limit its application range to a certain extent. In view of this problem, the present invention develops a halogen-free intrinsic flame-retardant waterborne polyurethane material that is completely halogen-free, has a low flame retardant content and has a good flame retardant effect. Summary of the invention

[0009] Based on the technical problems existing in the background technology, the present invention proposes a halogen-free intrinsic flame-retardant waterborne polyurethane material and a preparation method thereof, which is halogen-free, low-toxic, has good flame-retardant properties, high thermal stability, and high residual carbon rate. The prepared waterborne polyurethane material has the characteristics of being difficult to burn or easy to self-extinguish after burning. Through key links such as raw material selection, formula optimization, and performance testing and evaluation, a halogen-free intrinsic flame-retardant waterborne polyurethane material with excellent flame-retardant properties has been successfully developed. By performing performance testing and evaluation on the material, the environmental performance of the material has been significantly improved while maintaining good physical properties, so that the material has excellent flame-retardant effects while also meeting strict environmental protection regulations at home and abroad. The material not only performs excellently in flame-retardant properties, but also has good physical properties and environmental protection characteristics. Experimental verification shows that the material has shown broad application prospects in multiple fields such as electronics, construction, automobiles, and textiles.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0011] A method for preparing a halogen-free intrinsically flame-retardant waterborne polyurethane material comprises the following steps:

[0012] S1, pentaerythritol, phosphorus oxychloride, p-hydroxyphenylpropionitrile, polyether diol (molecular weight 2000), toluene diisocyanate (TDI), dimethylol propionic acid, tetrahydrofuran, sodium borohydride (NaBH 4 ) and dibutyltin dilaurate (DBTDL, catalyst) were vacuum dried and dehydrated;

[0013] S2, preparing pentaerythritol bisphosphate diphosphoryl chloride (PDD);

[0014] S3, according to the mass fraction, add PDD, p-hydroxyphenylpropionitrile, triethylamine and tetrahydrofuran into the reaction vessel, N 2 The reaction was carried out under protection, and after the reaction was completed, a white solid powder was obtained by suction filtration and then dried;

[0015] S4, according to the mass fraction, the product of S3, NaBH 4 , add anhydrous tetrahydrofuran into the reaction container, react in an ice-water bath under nitrogen, filter and dry after the reaction to obtain a white solid powder, which is a halogen-free phosphorus-nitrogen flame retardant with a diamine end group;

[0016] S5, using the halogen-free phosphorus-nitrogen flame retardant with a diamine end group obtained in S4 as a post-chain extender to prepare a flame-retardant waterborne polyurethane emulsion;

[0017] S6. Pour the flame-retardant water-based polyurethane emulsion obtained by the reaction of S5 onto a polytetrafluoroethylene plate, place it at room temperature and then dry it to obtain a halogen-free intrinsically flame-retardant water-based polyurethane.

[0018] Furthermore, the molecular weight of the polyether diol is 2,000.

[0019] Furthermore, the preparation method of pentaerythritol bisphosphate diphosphoryl chloride (PDD) in step (2) is as follows: 17-34 parts of pentaerythritol are added to a three-necked flask with a reflux device and an exhaust gas treatment device by mass, 115-230 parts of phosphorus oxychloride are weighed and added to the three-necked flask, magnetic stirring and condensing devices are turned on, and the temperature is started. When the system temperature reaches 60°C, the temperature is raised to 105°C after reacting for 1-2h, and the reaction is continued for 6-8h before the reaction is terminated, and the mixture is repeatedly washed with dichloromethane and anhydrous ethanol, filtered and dried to obtain a white powder, which is the intermediate product pentaerythritol bisphosphate diphosphoryl chloride (PDD);

[0020] Furthermore, in step (3), 10-30 parts of PDD, 10-30 parts of p-hydroxyphenylpropionitrile, 20-60 parts of triethylamine, and 100-300 parts of tetrahydrofuran are added into the reaction container by mass to react.

[0021] Furthermore, in step (3), the reaction temperature is 80° C. and the reaction time is 4-6 h.

[0022] Further, in step (4), 15-45 parts of S3 product, 10-30 parts of NaBH 4 , 100-300 parts of anhydrous tetrahydrofuran are added into the reaction container for reaction.

[0023] Furthermore, in step (4), the reaction is carried out in an ice-water bath under nitrogen conditions for 1-2 hours.

[0024] Furthermore, the preparation method of the flame retardant waterborne polyurethane emulsion in the step (5) is as follows: 30-60 parts of polyether diol with a molecular weight of 2000 treated with S1, 13.5-27 parts of toluene diisocyanate, 4-8 parts of dihydroxymethylpropionic acid and 0.2-0.3 parts of dibutyltin dilaurate are mixed uniformly by mass, slowly heated to 70-80°C and reacted for 150-200 minutes to generate a medium molecular weight polyurethane, cooled to 50°C, 2.5-5 parts of triethylamine, 20-40 parts of acetone, and 5-10 parts of deionized water are added, stirred for 30 minutes, and then 1.0-9.7 parts of a halogen-free phosphorus-nitrogen flame retardant with a terminal diamine group is added as a post-chain extender, further chain extension and crosslinking are carried out, and high-speed stirring is carried out for 20-30 minutes to disperse uniformly to prepare a flame retardant waterborne polyurethane emulsion.

[0025] Furthermore, in step (6), the flame-retardant water-based polyurethane emulsion obtained by reaction S5 is poured onto a polytetrafluoroethylene plate, left at room temperature for 1 day, and then baked in an oven at 40° C. for 2 days to obtain a halogen-free intrinsically flame-retardant water-based polyurethane.

[0026] The present invention also provides a halogen-free intrinsic flame-retardant waterborne polyurethane material prepared by the preparation method. The flame retardant content of the halogen-free intrinsic flame-retardant waterborne polyurethane is 2.1-9.3%.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention proposes a halogen-free intrinsic flame-retardant water-based polyurethane, which uses pentaerythritol and phosphorus oxychloride to react, and the resulting product is then reacted with p-hydroxyphenylpropionitrile to form a reduction product to prepare a diamino flame retardant containing phosphorus and nitrogen elements. Among them, the benzene ring structure in p-hydroxyphenylpropionitrile can improve the cohesive energy and rigidity of the material. Finally, the prepared flame retardant is reacted with polyether diol, toluene diisocyanate, dimethylol propionic acid and other raw materials in the form of a chain extender to prepare a halogen-free intrinsic flame-retardant water-based polyurethane, and the flame retardant properties of the water-based polyurethane are tested, which has good flame retardant properties, high thermal stability, high residual carbon rate, and a small amount of flame retardant is added to have the characteristics of being difficult to burn or easy to self-extinguish after burning. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention, and those skilled in the art in this field can make some non-essential improvements and adjustments based on the content of the above invention.

[0029] Example 1

[0030] The present invention provides a method for preparing a halogen-free intrinsically flame-retardant waterborne polyurethane, comprising the following steps:

[0031] 1. Separately mix pentaerythritol, phosphorus oxychloride, p-hydroxyphenylpropionitrile, polyether diol (molecular weight 2000), toluene diisocyanate (TDI), dimethylol propionic acid, tetrahydrofuran, sodium borohydride (NaBH 4 ), and dibutyltin dilaurate (DBTDL, catalyst) were vacuum dried and dehydrated;

[0032] 2. According to the mass proportion, add 17 parts of pentaerythritol treated in step 1 into a three-necked flask equipped with a reflux device and an exhaust gas treatment device, weigh 115 parts of phosphorus oxychloride, add them into the three-necked flask, turn on the magnetic stirring and condensing device, and start heating. When the system temperature reaches 60°C, react for 1 hour and then heat to 105°C. Continue to react for 6 hours and then terminate the reaction. Wash repeatedly with dichloromethane and anhydrous ethanol, filter and dry to obtain a white powder.

[0033] 3. Add 10 parts of the product from step 2, 10 parts of p-hydroxyphenylpropionitrile, 20 parts of triethylamine and 100 parts of tetrahydrofuran into a reaction vessel. 2 Under protection, the temperature was raised to 80°C and the reaction was carried out for 4 hours. After the reaction was completed, a white solid powder was obtained by suction filtration and dried.

[0034] 4. By mass, 15 parts of the product from step 3, 10 parts of NaBH 4 , 100 parts of anhydrous tetrahydrofuran, react in an ice-water bath under nitrogen for 1 hour. After the reaction is completed, filter and dry to obtain a white solid powder, which is a halogen-free phosphorus-nitrogen flame retardant with a diamine terminal group.

[0035] 5. According to the mass proportion, 30 parts of the polyether diol with a molecular weight of 2000 treated in step 1, 13.5 parts of toluene diisocyanate, 4 parts of dimethylol propionic acid and 0.2 parts of dibutyltin dilaurate were mixed evenly, and the temperature was slowly raised to 70°C for reaction for 150 minutes to generate a polyurethane of medium molecular weight. The mixture was cooled to 50°C and 2.5 parts of triethylamine, 20 parts of acetone and 5 parts of deionized water were added, and the mixture was stirred for 30 minutes. Then, 1.0 part of a halogen-free phosphorus-nitrogen flame retardant with a terminal diamine group was added as a post-chain extender for further chain extension and crosslinking. The mixture was stirred at high speed for 20 minutes to disperse evenly, and a flame-retardant water-based polyurethane emulsion was prepared.

[0036] 6. Pour the flame-retardant water-based polyurethane solution obtained in step 5 onto the pre-prepared polytetrafluoroethylene plate, place it at room temperature for 1 day, and then bake it in an oven at 40°C for 2 days to obtain a halogen-free intrinsically flame-retardant water-based polyurethane.

[0037] Example 2

[0038] The present invention provides a method for preparing a halogen-free intrinsically flame-retardant waterborne polyurethane, comprising the following steps:

[0039] 1. Separately mix pentaerythritol, phosphorus oxychloride, p-hydroxyphenylpropionitrile, polyether diol (molecular weight 2000), toluene diisocyanate (TDI), dimethylol propionic acid, tetrahydrofuran, sodium borohydride (NaBH 4 ), and dibutyltin dilaurate (DBTDL, catalyst) were vacuum dried and dehydrated;

[0040] 2. According to the mass proportion, add 20 parts of pentaerythritol treated in step 1 into a three-necked flask with a reflux device and an exhaust gas treatment device, weigh 140 parts of phosphorus oxychloride, add it into the three-necked flask, turn on the magnetic stirring and condensing device, and start heating. When the system temperature reaches 60°C, react for 1 hour and then heat to 105°C. Continue to react for 6.5 hours and then terminate the reaction. Wash repeatedly with dichloromethane and anhydrous ethanol, filter and dry to obtain a white powder.

[0041] 3. 15 parts of the product from step 2, 13 parts of p-hydroxyphenylpropionitrile, 28 parts of triethylamine, and 130 parts of tetrahydrofuran were added into the reaction vessel. 2 Under protection, the temperature was raised to 80°C and the reaction was carried out for 4.5 hours. After the reaction was completed, a white solid powder was obtained by suction filtration and dried.

[0042] 4. By mass, 22 parts of the product from step 3, 14 parts of NaBH 4 , 125 parts of anhydrous tetrahydrofuran, react in an ice-water bath under nitrogen for 1 hour. After the reaction is completed, filter and dry to obtain a white solid powder, which is a halogen-free phosphorus-nitrogen flame retardant with a diamine terminal group.

[0043] 5. According to the mass proportion, 37 parts of the polyether diol with a molecular weight of 2000 treated in step 1, 16 parts of toluene diisocyanate, 5 parts of dimethylol propionic acid and 0.22 parts of dibutyltin dilaurate were mixed evenly, and the temperature was slowly raised to 70°C for reaction for 160 minutes to generate a medium molecular weight polyurethane, and the temperature was lowered to 50°C, and 3 parts of triethylamine, 24 parts of acetone and 6 parts of deionized water were added, and the mixture was stirred for 30 minutes. Then, 2.0 parts of a halogen-free phosphorus-nitrogen flame retardant with a terminal diamine group was added as a post-chain extender for further chain extension and crosslinking, and the mixture was evenly dispersed after high-speed stirring for 20 minutes to prepare a flame-retardant waterborne polyurethane emulsion;

[0044] 6. Pour the solution obtained in step 5 onto the prepared polytetrafluoroethylene plate, place it at room temperature for 1 day, and then bake it in an oven at 40°C for 2 days to obtain halogen-free intrinsically flame-retardant water-based polyurethane.

[0045] Example 3

[0046] The present invention provides a method for preparing a halogen-free intrinsically flame-retardant waterborne polyurethane, comprising the following steps:

[0047] 1. Separately mix pentaerythritol, phosphorus oxychloride, p-hydroxyphenylpropionitrile, polyether diol (molecular weight 2000), toluene diisocyanate (TDI), dimethylol propionic acid, tetrahydrofuran, sodium borohydride (NaBH 4 ), and dibutyltin dilaurate (DBTDL, catalyst) were vacuum dried and dehydrated;

[0048] 2. According to the mass proportion, add 23 parts of pentaerythritol treated in step 1 into a three-necked flask equipped with a reflux device and an exhaust gas treatment device, weigh 170 parts of phosphorus oxychloride, add it into the three-necked flask, turn on the magnetic stirring and condensing device, and start heating. When the system temperature reaches 60°C, react for 1 hour and then heat to 105°C. Continue to react for 7 hours and then terminate the reaction. Wash repeatedly with dichloromethane and anhydrous ethanol, filter and dry to obtain a white powder.

[0049] 3. 20 parts of the product from step 2, 18 parts of p-hydroxyphenylpropionitrile, 37 parts of triethylamine, and 175 parts of tetrahydrofuran were added into the reaction vessel. 2 Under protection, the temperature was raised to 80°C and the reaction was carried out for 5 hours. After the reaction was completed, a white solid powder was obtained by suction filtration and then dried;

[0050] 4. By mass, 28 parts of the product from step 3, 20 parts of NaBH 4, 170 parts of anhydrous tetrahydrofuran, react in an ice-water bath under nitrogen for 1.5 hours, filter and dry after the reaction to obtain a white solid powder, which is a halogen-free phosphorus-nitrogen flame retardant with a diamine terminal group;

[0051] 5. According to the mass proportion, 45 parts of the polyether diol with a molecular weight of 2000 treated in step 1, 19 parts of toluene diisocyanate, 6 parts of dimethylol propionic acid and 0.24 parts of dibutyltin dilaurate were mixed evenly, and the temperature was slowly raised to 70°C for reaction for 170 minutes to generate a polyurethane of medium molecular weight. The mixture was cooled to 50°C and 3.5 parts of triethylamine, 28 parts of acetone and 7 parts of deionized water were added, and the mixture was stirred for 30 minutes. Then, 3.5 parts of a halogen-free phosphorus-nitrogen flame retardant with a terminal diamine group was added as a post-chain extender for further chain extension and crosslinking. The mixture was stirred at high speed for 24 minutes to disperse evenly, and a flame-retardant water-based polyurethane emulsion was prepared.

[0052] 6. Pour the solution obtained in step 5 onto the prepared polytetrafluoroethylene plate, place it at room temperature for 1 day, and then bake it in an oven at 40°C for 2 days to obtain halogen-free intrinsic flame-retardant water-based polyurethane.

[0053] Example 4

[0054] The present invention provides a method for preparing a halogen-free intrinsically flame-retardant waterborne polyurethane, comprising the following steps:

[0055] 1. Separately mix pentaerythritol, phosphorus oxychloride, p-hydroxyphenylpropionitrile, polyether diol (molecular weight 2000), toluene diisocyanate (TDI), dimethylol propionic acid, tetrahydrofuran, sodium borohydride (NaBH 4 ), and dibutyltin dilaurate (DBTDL, catalyst) were vacuum dried and dehydrated;

[0056] 2. According to the mass proportion, add 27 parts of pentaerythritol treated in step 1 into a three-necked flask equipped with a reflux device and an exhaust gas treatment device, weigh 190 parts of phosphorus oxychloride, add it into the three-necked flask, turn on the magnetic stirring and condensing device, and start heating. When the system temperature reaches 60°C, react for 1 hour and then heat to 105°C. Continue to react for 7.5 hours and then terminate the reaction. Wash repeatedly with dichloromethane and anhydrous ethanol, filter and dry to obtain a white powder.

[0057] 3. 23 parts of the product from step 2, 22 parts of p-hydroxyphenylpropionitrile, 46 parts of triethylamine, and 210 parts of tetrahydrofuran were added into the reaction vessel. 2 Under protection, the temperature was raised to 80°C and the reaction was carried out for 5.5 hours. After the reaction was completed, a white solid powder was obtained by suction filtration and then dried;

[0058] 4. By mass, 35 parts of the product from step 3, 24 parts of NaBH 4, 205 parts of anhydrous tetrahydrofuran, react in an ice-water bath under nitrogen for 1.5 hours, filter and dry after the reaction to obtain a white solid powder, which is a halogen-free phosphorus-nitrogen flame retardant with a diamine terminal group;

[0059] 5. According to the mass proportions, 50 parts of the polyether diol with a molecular weight of 2000 treated in step 1, 22 parts of toluene diisocyanate, 7 parts of dimethylol propionic acid and 0.26 parts of dibutyltin dilaurate were mixed evenly, and the temperature was slowly raised to 80°C for reaction for 180 minutes to generate a medium molecular weight polyurethane, and the temperature was lowered to 50°C, and 4 parts of triethylamine, 32 parts of acetone and 8 parts of deionized water were added, and the mixture was stirred for 30 minutes, and then 5.6 parts of a halogen-free phosphorus-nitrogen flame retardant with a terminal diamine group was added as a post-chain extender for further chain extension and crosslinking, and the mixture was stirred at a high speed for 26 minutes to disperse evenly to prepare a flame-retardant waterborne polyurethane emulsion;

[0060] 6. Pour the solution obtained in step 5 onto the prepared polytetrafluoroethylene plate, place it at room temperature for 1 day, and then bake it in an oven at 40°C for 2 days to obtain halogen-free intrinsically flame-retardant water-based polyurethane.

[0061] Example 5

[0062] The present invention provides a method for preparing a halogen-free intrinsically flame-retardant waterborne polyurethane, comprising the following steps:

[0063] 1. Separately mix pentaerythritol, phosphorus oxychloride, p-hydroxyphenylpropionitrile, polyether diol (molecular weight 2000), toluene diisocyanate (TDI), dimethylol propionic acid, tetrahydrofuran, sodium borohydride (NaBH 4 ), and dibutyltin dilaurate (DBTDL, catalyst) were vacuum dried and dehydrated;

[0064] 2. According to the mass proportion, add 30 parts of pentaerythritol treated in step 1 into a three-necked flask equipped with a reflux device and an exhaust gas treatment device, weigh 210 parts of phosphorus oxychloride, add them into the three-necked flask, turn on the magnetic stirring and condensing device, and start heating. When the system temperature reaches 60°C, react for 1 hour and then heat to 105°C. Continue to react for 8 hours and then terminate the reaction. Wash repeatedly with dichloromethane and anhydrous ethanol, filter and dry to obtain a white powder.

[0065] 3. 27 parts of the product from step 2, 26 parts of p-hydroxyphenylpropionitrile, 52 parts of triethylamine, and 250 parts of tetrahydrofuran were added into the reaction vessel. 2 Under protection, the temperature was raised to 80°C and the reaction was carried out for 6 hours. After the reaction was completed, a white solid powder was obtained by suction filtration and then dried;

[0066] 4. By mass, 40 parts of the product from step 3, 26 parts of NaBH 4, 255 parts of anhydrous tetrahydrofuran, react in an ice-water bath under nitrogen for 2 hours, filter and dry after the reaction to obtain a white solid powder, which is a halogen-free phosphorus-nitrogen flame retardant with a diamine terminal group;

[0067] 5. According to the mass proportion, 55 parts of the polyether diol with a molecular weight of 2000 treated in step 1, 24 parts of toluene diisocyanate, 7.5 parts of dimethylol propionic acid and 0.28 parts of dibutyltin dilaurate were mixed evenly, and the temperature was slowly raised to 80°C for reaction for 190 minutes to generate a polyurethane of medium molecular weight. The mixture was cooled to 50°C and 4.5 parts of triethylamine, 36 parts of acetone and 9 parts of deionized water were added, and the mixture was stirred for 30 minutes. Then, 7.8 parts of a halogen-free phosphorus-nitrogen flame retardant with a terminal diamine group was added as a post-chain extender for further chain extension and crosslinking. The mixture was stirred at high speed for 28 minutes to disperse evenly, and a flame-retardant water-based polyurethane emulsion was prepared.

[0068] 6. Pour the solution obtained in step 5 onto the prepared polytetrafluoroethylene plate, place it at room temperature for 1 day, and then bake it in an oven at 40°C for 2 days to obtain halogen-free intrinsically flame-retardant water-based polyurethane.

[0069] Example 6

[0070] The present invention provides a method for preparing a halogen-free intrinsically flame-retardant waterborne polyurethane, comprising the following steps:

[0071] 1. Separately mix pentaerythritol, phosphorus oxychloride, p-hydroxyphenylpropionitrile, polyether diol (molecular weight 2000), toluene diisocyanate (TDI), dimethylol propionic acid, tetrahydrofuran, sodium borohydride (NaBH 4 ), and dibutyltin dilaurate (DBTDL, catalyst) were vacuum dried and dehydrated;

[0072] 2. According to the mass proportion, 34 parts of pentaerythritol treated in step 1 were added into a three-necked flask equipped with a reflux device and an exhaust gas treatment device. 230 parts of phosphorus oxychloride were weighed and added into the three-necked flask. The magnetic stirring and condensing device were turned on, and the temperature began to rise. When the system temperature reached 60°C, the temperature was raised to 105°C after the reaction for 2 hours. The reaction was terminated after the reaction was continued for 8 hours. The powder was washed repeatedly with dichloromethane and anhydrous ethanol, filtered and dried to obtain a white powder.

[0073] 3. Add 30 parts of the product from step 2, 30 parts of p-hydroxyphenylpropionitrile, 60 parts of triethylamine and 300 parts of tetrahydrofuran into a reaction vessel. 2 Under protection, the temperature was raised to 80°C and the reaction was carried out for 6 hours. After the reaction was completed, a white solid powder was obtained by suction filtration and then dried;

[0074] 4. By mass, 45 parts of the product from step 3, 30 parts of NaBH 4, 300 parts of anhydrous tetrahydrofuran, react in an ice-water bath under nitrogen for 2 hours, filter and dry after the reaction to obtain a white solid powder, which is a halogen-free phosphorus-nitrogen flame retardant with a diamine terminal group;

[0075] 5. According to the mass proportion, 60 parts of the polyether diol with a molecular weight of 2000 treated in step 1, 27 parts of toluene diisocyanate, 8 parts of dimethylol propionic acid and 0.3 parts of dibutyltin dilaurate were mixed evenly, and the temperature was slowly raised to 80°C for reaction for 200 minutes to generate a medium molecular weight polyurethane, and the temperature was lowered to 50°C, and 5 parts of triethylamine, 40 parts of acetone and 10 parts of deionized water were added, and the mixture was stirred for 30 minutes. Then, 9.7 parts of a halogen-free phosphorus-nitrogen flame retardant with a terminal diamine group was added as a post-chain extender, and further chain extension and crosslinking were performed, and the mixture was evenly dispersed by high-speed stirring for 30 minutes to prepare a flame-retardant waterborne polyurethane emulsion;

[0076] 6. Pour the solution obtained in step 5 onto the prepared polytetrafluoroethylene plate, place it at room temperature for 1 day, and then bake it in an oven at 40°C for 2 days to obtain halogen-free intrinsically flame-retardant water-based polyurethane.

[0077] Comparative Example 1

[0078] The preparation method of the halogen-free intrinsic flame-retardant waterborne polyurethane of this comparative example is as follows:

[0079] 1. Polyether diol (molecular weight 2000), toluene diisocyanate (TDI), dimethylol propionic acid and dibutyltin dilaurate (DBTDL, catalyst) were vacuum dried and dehydrated respectively;

[0080] 2. Mix 50 parts of the polyether diol with a molecular weight of 2000 treated in step 1, 22 parts of toluene diisocyanate, 7 parts of dimethylol propionic acid and 0.26 parts of dibutyltin dilaurate evenly by mass, slowly heat to 80°C and react for 180 minutes to generate a medium molecular weight polyurethane, cool to 50°C, add 4 parts of triethylamine, 32 parts of acetone and 8 parts of deionized water, stir for 30 minutes to prepare a flame retardant waterborne polyurethane emulsion;

[0081] 3. Pour the solution obtained by reaction 2 onto a pre-prepared polytetrafluoroethylene plate, place it at room temperature for 1 day, and then bake it in an oven at 40°C for 2 days to obtain a halogen-free intrinsically flame-retardant water-based polyurethane.

[0082] Comparative Example 2

[0083] The method for preparing the halogen-free intrinsically flame-retardant waterborne polyurethane disclosed in CN 110483735 A was used to prepare the polyurethane (Example 4).

[0084] Table 1 Combustion properties of halogen-free intrinsic flame retardant waterborne polyurethane

[0085]

[0086] Table 2 Thermal decomposition properties of halogen-free intrinsic flame retardant waterborne polyurethane

[0087]

[0088]

[0089] It can be seen from Table 1 that the preparation method of the halogen-free intrinsically flame-retardant waterborne polyurethane proposed in the present invention, by introducing phosphorus and nitrogen elements having flame-retardant effects, the prepared waterborne polyurethane has good flame retardancy.

[0090] The invention adopts p-hydroxyphenylpropionitrile to synthesize a small molecule diamine flame retardant chain extender containing phosphorus and nitrogen flame retardant elements and capable of improving the rigidity and cohesion of a substrate, and uses the flame retardant to perform post-chain extension flame retardant modification on a waterborne polyurethane material, thereby preparing a halogen-free intrinsically flame retardant waterborne polyurethane material. By analyzing the combustion performance and thermal decomposition performance of the material, the prepared waterborne polyurethane material has good flame retardancy.

[0091] It can be seen from Table 2 that the introduction of phosphorus improves the thermal decomposition performance of the flame-retardant waterborne polyurethane material. The phosphorus forms a stable phosphate layer during the combustion process, covering the surface of the polyurethane material to prevent the further spread of the flame, and can also reduce the release of combustible gases. As the amount of flame retardant added increases, the amount of residual carbon will also increase accordingly, effectively improving the flame retardant effect of the material. When the flame retardant effect is similar to that of Comparative Example 2, the content of the flame retardant in the present invention is significantly reduced (the content of the flame retardant in Example 3 is 4.8%). When the content of the flame retardant is substantially equal to that in Comparative Example 2 (Example 5), the residual carbon at 600°C of the present invention is 12.96%, which is significantly higher than 9.71% of Comparative Example 2, and the flame retardant effect of the present invention is better.

[0092] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a halogen-free intrinsically flame-retardant waterborne polyurethane material, characterized in that: The following steps are involved: S1, respectively vacuum drying and dehydrating pentaerythritol, phosphorus oxychloride, p-hydroxyphenylpropionitrile, polyether diol (molecular weight 2000), toluene diisocyanate (TDI), dimethylol propionic acid, tetrahydrofuran, sodium borohydride (NaBH4) and dibutyltin dilaurate (DBTDL, catalyst); S2, preparing pentaerythritol bisphosphate diphosphoryl chloride (PDD); S3, according to the mass fraction, PDD, p-hydroxyphenylpropionitrile, triethylamine and tetrahydrofuran were added into the reaction container, and the reaction was carried out under the protection of N2. After the reaction was completed, the white solid powder was filtered and dried; S4, according to the mass fraction, add the product of S3, NaBH4 and anhydrous tetrahydrofuran into the reaction container, react in an ice-water bath under nitrogen, and after the reaction, filter and dry to obtain a white solid powder, which is a halogen-free phosphorus-nitrogen flame retardant with a diamine end group; S5, using the halogen-free phosphorus-nitrogen flame retardant with a diamine end group obtained in S4 as a post-chain extender to prepare a flame-retardant waterborne polyurethane emulsion; S6. Pour the flame-retardant water-based polyurethane emulsion obtained by the reaction of S5 onto a polytetrafluoroethylene plate, place it at room temperature and then dry it to obtain a halogen-free intrinsically flame-retardant water-based polyurethane.

2. The method for preparing the halogen-free intrinsically flame-retardant waterborne polyurethane material according to claim 1, characterized in that: The molecular weight of the polyether diol is 2000.

3. The method for preparing the halogen-free intrinsically flame-retardant waterborne polyurethane material according to claim 1, characterized in that: The preparation method of pentaerythritol bisphosphate diphosphoryl chloride (PDD) in step (2) is as follows: 17-34 parts of pentaerythritol are added into a three-necked flask equipped with a reflux device and an exhaust gas treatment device according to mass fractions, 115-230 parts of phosphorus oxychloride are weighed and added into the three-necked flask, magnetic stirring and condensing devices are turned on, and the temperature is started to rise. When the system temperature reaches 60°C, the temperature is raised to 105°C after reacting for 1-2 hours, and the reaction is continued for 6-8 hours before the reaction is terminated. The powder is repeatedly washed with dichloromethane and anhydrous ethanol, filtered and dried to obtain a white powder, which is the intermediate product pentaerythritol bisphosphate diphosphoryl chloride (PDD).

4. The method for preparing the halogen-free intrinsically flame-retardant waterborne polyurethane material according to claim 1, characterized in that: In the step (3), 10-30 parts of PDD, 10-30 parts of p-hydroxyphenylpropionitrile, 20-60 parts of triethylamine, and 100-300 parts of tetrahydrofuran are added into a reaction container by mass to carry out a reaction.

5. The method for preparing the halogen-free intrinsically flame-retardant waterborne polyurethane material according to claim 1, characterized in that: In the step (3), the reaction temperature is 80° C. and the reaction time is 4-6 h.

6. The method for preparing the halogen-free intrinsically flame-retardant waterborne polyurethane material according to claim 1, characterized in that: In the step (4), 15-45 parts of the S3 product, 10-30 parts of NaBH4, and 100-300 parts of anhydrous tetrahydrofuran are added into a reaction container by mass to carry out a reaction.

7. The method for preparing the halogen-free intrinsically flame-retardant waterborne polyurethane material according to claim 1, characterized in that: In the step (4), the reaction is carried out in an ice-water bath under nitrogen conditions for 1-2 h.

8. The method for preparing the halogen-free intrinsically flame-retardant waterborne polyurethane material according to claim 1, characterized in that: The preparation method of the flame retardant waterborne polyurethane emulsion in the step (5) is as follows: 30-60 parts of polyether diol with a molecular weight of 2000 treated with S1, 13.5-27 parts of toluene diisocyanate, 4-8 parts of dimethylol propionic acid and 0.2-0.3 parts of dibutyltin dilaurate are mixed uniformly by mass, and the mixture is slowly heated to 70-80°C and reacted for 150-200 minutes to generate a medium molecular weight polyurethane. The mixture is cooled to 50°C and 2.5-5 parts of triethylamine, 20-40 parts of acetone and 5-10 parts of deionized water are added, and stirred for 30 minutes. Then, 1.0-9.7 parts of a halogen-free phosphorus-nitrogen flame retardant with a terminal diamine group is added as a post-chain extender to further extend the chain and crosslink. The mixture is stirred at a high speed for 20-30 minutes to disperse the mixture uniformly, and the flame retardant waterborne polyurethane emulsion is prepared.

9. The method for preparing the halogen-free intrinsically flame-retardant waterborne polyurethane material according to claim 1, characterized in that: In the step (6), the flame-retardant water-based polyurethane emulsion obtained by the reaction of S5 is poured onto a polytetrafluoroethylene plate, left at room temperature for 1 day, and then baked in an oven at 40° C. for 2 days to obtain a halogen-free intrinsically flame-retardant water-based polyurethane.

10. The halogen-free intrinsically flame-retardant waterborne polyurethane material prepared according to any one of claims 1 to 9, characterized in that: The flame retardant content of the halogen-free intrinsically flame-retardant waterborne polyurethane is 2.1-9.3%.

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