Flame-retardant modified halloysite grafted waterborne polyurethane material and preparation method thereof

Abstract

The invention relates to the technical field of new materials, and discloses a flame-retardant modified halloysite grafted waterborne polyurethane material, three flame-retardant elements N, P and S are introduced to the surface of halloysite, so that the obtained waterborne polyurethane material has excellent flame-retardant property, the surface of a halloysite tube is organically modified, and the flame-retardant property of the halloysite tube is improved. The self-agglomeration of the halloysite nanotubes can be effectively inhibited, and meanwhile, the halloysite enables a polyurethane molecular chain to be grafted on the halloysite in situ through the terminated hydroxyl, so that the dispersity of the halloysite in a polyurethane matrix can be effectively enhanced, a cross-linking center is formed, the compatibility of the polyurethane and the halloysite at a molecular level is achieved, and the self-agglomeration of the halloysite nanotubes can be effectively inhibited. The halloysite is added, so that the microphase separation structure of the composite material is influenced, the mechanical property of polyurethane is improved, the halloysite with high length-diameter ratio can effectively limit the movement of a polyurethane molecular chain, and the thermal stability of the composite material is improved.

Description

Technical Field

[0001] The invention relates to the technical field of new materials, in particular to a flame-retardant modified halloysite grafted waterborne polyurethane material and a preparation method thereof. Background Art

[0002] Polyurethane is a polymer with a repetitive nitrogen-based carbamate structure in the main chain of the molecule. Polyurethane has the advantages of adjustable soft and hard end structure, low temperature resistance, good flexibility, etc., so it has a wide range of applications. Among them, water-based polyurethane is an environmentally friendly polyurethane that uses water as a solvent and has little harm to the environment. Therefore, it is widely used in coatings, composite materials, adhesives, fabrics, etc. However, like most common organic polymer materials, polyurethane has poor flame retardant properties and decomposes very quickly when burned. In order to reduce the safety hazards when using polyurethane, it is necessary to functionalize polyurethane with flame retardancy.

[0003] Chinese patent CN101977995B "Halogen flame retardant thermoplastic polyurethane" discloses a polyurethane composed of a halogen brominated flame retardant and an antimony oxide compound for synergistic flame retardancy. The polyurethane has good flame retardancy and can be used in optical fiber cable protective sheaths or wires and other fields. However, chlorine-containing flame retardants release toxic substances when burned, while nitrogen-phosphorus flame retardants and sulfur-containing flame retardants do not release toxic substances when burned, and can also have a very good flame retardant effect. In addition to enhancing the flame retardant effect, mechanical properties are also one of the very important properties of the material. The inorganic filler halloysite has excellent mechanical properties and can have a good reinforcing and toughening effect on polyurethane. However, inorganic materials such as halloysite have poor dispersibility in the polyurethane matrix, resulting in poor reinforcing effect. The dispersion problem can be well solved by grafting. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a flame retardant modified halloysite grafted waterborne polyurethane material and a preparation method, which solves the problems of poor flame retardancy of polyurethane and poor dispersibility of halloysite in a polyurethane matrix.

[0005] To achieve the above object, the present invention provides the following technical solution: A method for preparing a flame retardant modified halloysite grafted waterborne polyurethane material comprises the following steps: (1) Add pentaerythritol diphosphate diphosphoryl chloride with a molecular formula of C5H8Cl2O6P2 to a dimethylformamide solvent, then add halloysite, disperse by ultrasonication, evacuate, maintain for 1-3 hours, heat to 80-100°C, react for 8-16 hours, and after the reaction is completed, wash with dimethylformamide and deionized water, and vacuum dry to obtain phosphate-based flame-retardant modified halloysite; (2) adding the phosphate-based flame-retardant modified halloysite to an acetone solvent, stirring and dispersing, adding potassium thiocyanate, heating to 60-100° C., reacting for 6-12 hours, and after the reaction is completed, filtering, washing with deionized water and anhydrous ethanol, and vacuum drying to obtain isothiocyanate-based flame-retardant halloysite; (3) adding isothiocyanate-based flame-retardant halloysite and methanol into a reaction container, then adding ethanolamine, stirring and mixing, reacting at 40-60° C. for 10-20 hours, and after the reaction is completed, hydroxyl-terminated NPS synergistic flame-retardant modified halloysite is obtained; (4) Add isothiocyanate-based flame-retardant halloysite to acetone solvent, then add isophorone diisocyanate and dibutyltin dilaurate, heat to 80-100°C, react for 1-2 hours, then add polyether polyol polytetrahydrofuran diol and hydrophilic chain extender dihydroxymethylpropionic acid, react for 1-2 hours, then add deionized water, high-speed shear dispersion to form an emulsion, evaporate acetone under reduced pressure, then add film-forming aid diethylene glycol butyl ether, stir and mix evenly, pour into a polytetrafluoroethylene plate, level and dry to obtain a flame-retardant modified halloysite grafted waterborne polyurethane material.

[0006] Preferably, in step (1), the mass ratio of dimethylformamide solvent, pentaerythritol diphosphate diphosphoryl chloride, and halloysite is 5000-15000:8-20:100.

[0007] Preferably, in step (2), the mass ratio of acetone, phosphate-based flame-retardant modified halloysite, and potassium thiocyanate is 8000-16000:100:4-10.

[0008] Preferably, in step (3), the mass ratio of methanol, isothiocyanate-based flame-retardant halloysite and ethanolamine is 10000-20000:100:5-15.

[0009] Preferably, in step (4), the mass ratio of acetone, isothiocyanate-based flame retardant halloysite, isophorone diisocyanate, dibutyltin dilaurate, polytetrahydrofuran diol, dimethylol propionic acid and diethylene glycol butyl ether is 3000-6000:2-6:32-48:0.2-0.4:100:5-8:7-12.

[0010] Compared with the prior art, the present invention has the following experimental principles and beneficial technical effects: The flame retardant modified halloysite grafted waterborne polyurethane material comprises the following steps: firstly, the phosphoryl chloride group on pentaerythritol diphosphate diphosphoryl chloride is subjected to an esterification reaction with the surface of the halloysite nanotube, thereby modifying the surface of the halloysite nanotube to obtain a phosphate-based flame retardant modified halloysite containing a terminal phosphoryl chloride group; then, potassium thiocyanate is used to isocyanate the phosphoryl chloride group to obtain an isothiocyanate-based flame retardant halloysite; then, ethanolamine is subjected to an addition reaction with the isothiocyanate group to obtain a hydroxyl-terminated flame retardant modified halloysite containing three flame retardant elements of N, P and S; finally, the terminal hydroxyl group is reacted with diisocyanate, and the polyurethane is added. Ether polyol, hydrophilic chain extender dimethylol propionic acid and film-forming aid are used to obtain flame-retardant modified halloysite grafted waterborne polyurethane material. Since three flame-retardant elements N, P and S are introduced into the surface of halloysite, the presence of P element can promote the carbonization of isocyanate during combustion, while N element can generate non-flammable gas during combustion and promote the expansion of the carbon layer, thereby blocking heat and combustion-supporting gas and achieving a flame-retardant effect. The presence of S element can also promote the formation of a highly cross-linked carbon layer on the surface of polyurethane. Under the synergistic effect of the three flame-retardant elements N, P and S, the obtained waterborne polyurethane material can have excellent flame-retardant properties.

[0011] The flame-retardant modified halloysite grafted waterborne polyurethane material has excellent mechanical properties and nanometer size effect, but is also very easy to agglomerate in an organic matrix. By first organically modifying the surface of the halloysite tube, the agglomeration of the halloysite nanotube itself can be effectively inhibited. At the same time, the polyurethane molecular chain is in situ grafted onto the halloysite through the blocked hydroxyl group of the halloysite, which can effectively enhance the dispersibility of the halloysite in the polyurethane matrix and form a cross-linking center, so that the polyurethane and the halloysite are compatible at the molecular level. The covalent bond is formed between the halloysite and the isocyanate hard segment, thereby affecting the microphase separation structure of the composite material. Also because of its nanometer effect, it has a large interface effect and interaction with the polyurethane matrix, thereby further improving the mechanical properties of the polyurethane without affecting the ductility of the polyurethane. The high aspect ratio of the halloysite can effectively limit the movement of the polyurethane molecular chain, hinder the dispersion of heat and volatile decomposition products, improve the thermal stability of the composite material, and play a synergistic flame retardant role with the surface-modified flame retardant element. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Reaction diagram for the synthesis of isothiocyanate-based flame-retardant halloysite; Figure 2 Reaction diagram for the synthesis of hydroxyl-terminated NPS synergistic flame retardant modified halloysite. DETAILED DESCRIPTION

[0013] A method for preparing a flame retardant modified halloysite grafted waterborne polyurethane material, characterized in that it comprises the following steps: Tensile strength performance test: According to GB / T 10654-2001 standard, standard tensile specimens were made and the tensile strength was measured using a WDW-200JE universal testing machine.

[0014] Flame retardant performance test: According to GB / T 2406.1-2008 standard, use K-R2406S oxygen index analyzer to test the limiting oxygen index. Example 1

[0015] (1) 0.16 g of pentaerythritol diphosphate diphosphoryl chloride with a molecular formula of C5H8Cl2O6P2 was added to 100 g of dimethylformamide solvent, followed by adding 2 g of halloysite, ultrasonically dispersed, vacuumized, maintained for 1 h, heated to 80°C, reacted for 8 h, and after the reaction was completed, washed with dimethylformamide and deionized water, and vacuum dried to obtain phosphate-based flame-retardant modified halloysite; (2) Add 0.5 g of phosphate-based flame-retardant modified halloysite to 40 g of acetone solvent, stir and disperse, then add 0.02 g of potassium thiocyanate, heat to 60° C., react for 6 h, and after the reaction is completed, filter, wash with deionized water and anhydrous ethanol, and vacuum dry to obtain isothiocyanate-based flame-retardant halloysite; (3) 0.4 g of isothiocyanate-based flame-retardant halloysite and 40 g of methanol were added into a reaction container, followed by the addition of 0.02 g of ethanolamine, the mixture was stirred and mixed, and the mixture was reacted at 40° C. for 10 h. After the reaction was completed, hydroxyl-terminated NPS synergistic flame-retardant modified halloysite was obtained; (4) 1.6 g of isothiocyanate-based flame-retardant halloysite was added to 240 g of acetone solvent, followed by the addition of 26 g of isophorone diisocyanate and 0.16 g of dibutyltin dilaurate. The temperature was raised to 80 °C and the reaction was continued for 1 h. Then, 80 g of polyether polyol polytetrahydrofuran diol and 4 g of hydrophilic chain extender dihydroxymethylpropionic acid were added and the reaction was continued for 1 h. Then, deionized water was added and dispersed by high-speed shearing to form an emulsion. The acetone was evaporated under reduced pressure, and then 5.6 g of film-forming aid diethylene glycol butyl ether was added. The mixture was stirred and mixed evenly, and the mixture was poured into a polytetrafluoroethylene plate. The mixture was leveled and dried to obtain a flame-retardant modified halloysite grafted waterborne polyurethane material. The tensile strength was measured to be 32.8 MPa and the limiting oxygen index was 28.3%. Example 2

[0016] (1) 0.24 g of pentaerythritol diphosphate diphosphoryl chloride with a molecular formula of C5H8Cl2O6P2 was added to 130 g of dimethylformamide solvent, followed by adding 2 g of halloysite, ultrasonically dispersed, vacuumized, maintained for 1 h, heated to 85°C, reacted for 10 h, and after the reaction was completed, washed with dimethylformamide and deionized water, and vacuum dried to obtain phosphate-based flame-retardant modified halloysite; (2) adding 0.5 g of phosphate-based flame-retardant modified halloysite to 50 g of acetone solvent, stirring and dispersing, adding 0.03 g of potassium thiocyanate, heating to 70° C., reacting for 8 h, and after the reaction is completed, filtering, washing with deionized water and anhydrous ethanol, and vacuum drying to obtain isothiocyanate-based flame-retardant halloysite; (3) 0.4 g of isothiocyanate-based flame-retardant halloysite and 50 g of methanol were added into a reaction container, followed by the addition of 0.03 g of ethanolamine, the mixture was stirred and mixed, and the mixture was reacted at 45° C. for 12 h. After the reaction was completed, hydroxyl-terminated NPS synergistic flame-retardant modified halloysite was obtained; (4) 2.4 g of isothiocyanate-based flame-retardant halloysite was added to 300 g of acetone solvent, followed by the addition of 29 g of isophorone diisocyanate and 0.2 g of dibutyltin dilaurate. The temperature was raised to 90 °C and the mixture was reacted for 1.5 h. Then, 80 g of polyether polyol polytetrahydrofuran diol and 4.8 g of hydrophilic chain extender dihydroxymethylpropionic acid were added and the mixture was reacted for 1 h. Deionized water was then added and dispersed under high-speed shearing to form an emulsion. The acetone was evaporated under reduced pressure, and 6.7 g of film-forming aid diethylene glycol butyl ether was added. The mixture was stirred and mixed evenly, and the mixture was poured into a polytetrafluoroethylene plate. The mixture was leveled and dried to obtain a flame-retardant modified halloysite grafted waterborne polyurethane material. The tensile strength was measured to be 38.7 MPa and the limiting oxygen index was 29.4%. Example 3

[0017] (1) 0.28 g of pentaerythritol diphosphate diphosphoryl chloride with a molecular formula of C5H8Cl2O6P2 was added to 200 g of dimethylformamide solvent, followed by adding 2 g of halloysite, ultrasonically dispersed, vacuumized, maintained for 2 h, heated to 90°C, reacted for 12 h, and after the reaction was completed, washed with dimethylformamide and deionized water, and vacuum dried to obtain phosphate-based flame-retardant modified halloysite; (2) adding 0.5 g of phosphate-based flame-retardant modified halloysite to 60 g of acetone solvent, adding 0.03 g of potassium thiocyanate after stirring and dispersing, heating to 80° C., reacting for 9 h, and after the reaction is completed, filtering, washing with deionized water and anhydrous ethanol, and vacuum drying to obtain isothiocyanate-based flame-retardant halloysite; (3) 0.4 g of isothiocyanate-based flame-retardant halloysite and 60 g of methanol were added into a reaction container, followed by the addition of 0.03 g of ethanolamine, the mixture was stirred and mixed, and the mixture was reacted at 50° C. for 15 h. After the reaction was completed, hydroxyl-terminated NPS synergistic flame-retardant modified halloysite was obtained; (4) 3.2 g of isothiocyanate-based flame-retardant halloysite was added to 360 g of acetone solvent, followed by the addition of 32 g of isophorone diisocyanate and 0.24 g of dibutyltin dilaurate. The temperature was raised to 90 °C and the reaction was continued for 1.5 h. Then, 80 g of polyether polyol polytetrahydrofuran diol and 5.8 g of hydrophilic chain extender dihydroxymethylpropionic acid were added and the reaction was continued for 1 h. Then, deionized water was added and dispersed by high-speed shearing to form an emulsion. The acetone was evaporated under reduced pressure. Then, 7.2 g of film-forming aid diethylene glycol butyl ether was added and the mixture was stirred and mixed evenly. The mixture was poured into a polytetrafluoroethylene plate, leveled and dried to obtain a flame-retardant modified halloysite grafted waterborne polyurethane material. The tensile strength was measured to be 45.9 MPa and the limiting oxygen index was 29.6%. Example 4

[0018] (1) 0.32 g of pentaerythritol diphosphate diphosphoryl chloride with a molecular formula of C5H8Cl2O6P2 was added to 250 g of dimethylformamide solvent, followed by adding 2 g of halloysite, ultrasonically dispersed, vacuumized, maintained for 2 h, heated to 90°C, reacted for 14 h, and after the reaction was completed, washed with dimethylformamide and deionized water, and vacuum dried to obtain phosphate-based flame-retardant modified halloysite; (2) adding 0.5 g of phosphate-based flame-retardant modified halloysite to 70 g of acetone solvent, stirring and dispersing, adding 0.04 g of potassium thiocyanate, heating to 90° C., reacting for 10 h, and after the reaction is completed, filtering, washing with deionized water and anhydrous ethanol, and vacuum drying to obtain isothiocyanate-based flame-retardant halloysite; (3) 0.4 g of isothiocyanate-based flame-retardant halloysite and 70 g of methanol were added into a reaction container, followed by the addition of 0.04 g of ethanolamine, the mixture was stirred and mixed, and the mixture was reacted at 55° C. for 18 h. After the reaction was completed, hydroxyl-terminated NPS synergistic flame-retardant modified halloysite was obtained; (4) 4.2 g of isothiocyanate-based flame-retardant halloysite was added to 420 g of acetone solvent, followed by the addition of 34 g of isophorone diisocyanate and 0.28 g of dibutyltin dilaurate. The temperature was raised to 90 °C and the reaction was continued for 2 h. Then, 80 g of polyether polyol polytetrahydrofuran diol and 6 g of hydrophilic chain extender dihydroxymethylpropionic acid were added and the reaction was continued for 2 h. Then, deionized water was added and dispersed by high-speed shearing to form an emulsion. The acetone was evaporated under reduced pressure. Then, 8.4 g of film-forming aid diethylene glycol butyl ether was added and the mixture was stirred and mixed evenly. The mixture was poured into a polytetrafluoroethylene plate, leveled and dried to obtain a flame-retardant modified halloysite grafted waterborne polyurethane material. The tensile strength was measured to be 42.9 MPa and the limiting oxygen index was 30.2%. Example 5

[0019] (1) 0.4 g of pentaerythritol diphosphate diphosphoryl chloride with a molecular formula of C5H8Cl2O6P2 was added to 300 g of dimethylformamide solvent, followed by adding 2 g of halloysite, ultrasonically dispersed, vacuumized, maintained for 3 h, heated to 100 °C, reacted for 16 h, and after the reaction was completed, washed with dimethylformamide and deionized water, and vacuum dried to obtain phosphate-based flame-retardant modified halloysite; (2) adding 0.5 g of phosphate-based flame-retardant modified halloysite to 80 g of acetone solvent, stirring and dispersing, adding 0.05 g of potassium thiocyanate, heating to 100 °C, reacting for 12 h, and after the reaction is completed, filtering, washing with deionized water and anhydrous ethanol, and vacuum drying to obtain isothiocyanate-based flame-retardant halloysite; (3) 0.4 g of isothiocyanate-based flame-retardant halloysite and 80 g of methanol were added into a reaction container, followed by the addition of 0.05 g of ethanolamine, the mixture was stirred and mixed, and the mixture was reacted at 60° C. for 20 h. After the reaction was completed, hydroxyl-terminated NPS synergistic flame-retardant modified halloysite was obtained; (4) 4.8 g of isothiocyanate-based flame-retardant halloysite was added to 480 g of acetone solvent, followed by the addition of 38 g of isophorone diisocyanate and 0.32 g of dibutyltin dilaurate. The temperature was raised to 100 °C and the reaction was continued for 2 h. Then, 80 g of polyether polyol polytetrahydrofuran diol and 6.4 g of hydrophilic chain extender dihydroxymethylpropionic acid were added and the reaction was continued for 2 h. Then, deionized water was added and dispersed by high-speed shearing to form an emulsion. The acetone was evaporated under reduced pressure. Then, 9.6 g of film-forming aid diethylene glycol butyl ether was added and the mixture was stirred and mixed evenly. The mixture was poured into a polytetrafluoroethylene plate, leveled and dried to obtain a flame-retardant modified halloysite grafted waterborne polyurethane material. The tensile strength was measured to be 35.3 MPa and the limiting oxygen index was 30.8%.

[0020] Comparative Example 1 (1) 1.6 g of halloysite was added to 240 g of acetone solvent, followed by the addition of 26 g of isophorone diisocyanate and 0.16 g of dibutyltin dilaurate, and the temperature was raised to 80 °C. After the reaction for 1 h, 80 g of polyether polyol polytetrahydrofuran diol and 4 g of hydrophilic chain extender dimethylol propionic acid were added and the reaction was continued for 1 h. Deionized water was then added and dispersed by high-speed shearing to form an emulsion. The acetone was evaporated under reduced pressure, and then 5.6 g of film-forming aid diethylene glycol butyl ether was added. The mixture was stirred and mixed evenly, and the mixture was poured into a polytetrafluoroethylene plate. The mixture was leveled and dried to obtain a halloysite-grafted waterborne polyurethane material. The tensile strength was measured to be 38.9 MPa and the limiting oxygen index was 24.3%.

Claims

1. A flame retardant modified halloysite grafted waterborne polyurethane material, characterized in that: The method for preparing a flame retardant modified halloysite grafted waterborne polyurethane material comprises the following steps: (1) Add pentaerythritol diphosphate diphosphoryl chloride with a molecular formula of C5H8Cl2O6P2 to a dimethylformamide solvent, then add halloysite, disperse by ultrasonication, evacuate, maintain for 1-3 hours, heat to 80-100°C, react for 8-16 hours, and after the reaction is completed, wash with dimethylformamide and deionized water, and vacuum dry to obtain phosphate-based flame-retardant modified halloysite; (2) adding the phosphate-based flame-retardant modified halloysite to an acetone solvent, stirring and dispersing, adding potassium thiocyanate, heating to 60-100° C., reacting for 6-12 hours, and after the reaction is completed, filtering, washing with deionized water and anhydrous ethanol, and vacuum drying to obtain isothiocyanate-based flame-retardant halloysite; (3) adding isothiocyanate-based flame-retardant halloysite and methanol into a reaction container, then adding ethanolamine, stirring and mixing, reacting at 40-60° C. for 10-20 hours, and after the reaction is completed, hydroxyl-terminated NPS synergistic flame-retardant modified halloysite is obtained; (4) Add isothiocyanate-based flame-retardant halloysite to acetone solvent, then add isophorone diisocyanate and dibutyltin dilaurate, heat to 80-100°C, react for 1-2 hours, then add polyether polyol polytetrahydrofuran diol and hydrophilic chain extender dihydroxymethylpropionic acid, react for 1-2 hours, then add deionized water, high-speed shear dispersion to form an emulsion, evaporate acetone under reduced pressure, then add film-forming aid diethylene glycol butyl ether, stir and mix evenly, pour into a polytetrafluoroethylene plate, level and dry to obtain a flame-retardant modified halloysite grafted waterborne polyurethane material.

2. The flame retardant modified halloysite grafted waterborne polyurethane material according to claim 1, characterized in that: In the step (1), the mass ratio of dimethylformamide solvent, pentaerythritol diphosphate diphosphoryl chloride and halloysite is 5000-15000:8-20:

100.

3. The flame retardant modified halloysite grafted waterborne polyurethane material according to claim 1, characterized in that: In the step (2), the mass ratio of acetone, phosphate-based flame-retardant modified halloysite, and potassium thiocyanate is 8000-16000:100:4-10.

4. The flame retardant modified halloysite grafted waterborne polyurethane material according to claim 1, characterized in that: In the step (3), the mass ratio of methanol, isothiocyanate-based flame-retardant halloysite and ethanolamine is 10000-20000:100:5-15.

5. The flame retardant modified halloysite grafted waterborne polyurethane material according to claim 1, characterized in that: In the step (4), the mass ratio of acetone, isothiocyanate-based flame-retardant halloysite, isophorone diisocyanate, dibutyltin dilaurate, polytetrahydrofuran diol, dihydroxymethylpropionic acid and diethylene glycol butyl ether is 3000-6000:2-6:32-48:0.2-0.4:100:5-8:7-12.

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