A bio-based flame-retardant polyurethane and preparation method thereof

Abstract

The present invention discloses a bio-based flame-retardant polyurethane and a preparation method thereof. The preparation method of the bio-based flame-retardant polyurethane of the present invention comprises the following steps: reacting diethyl allyl phosphate with 3-mercapto-1,2-propylene glycol to prepare a phosphorus-containing flame-retardant polyol, reacting vegetable oil with 3-mercapto-1,2-propylene glycol to prepare a bio-based polyol; reacting the phosphorus-containing flame-retardant polyol, the bio-based polyol and diisocyanate to prepare the bio-based flame-retardant polyurethane. The preparation method of the bio-based flame-retardant polyurethane of the present invention has the advantages of low energy consumption and good stability, and can realize the large-scale preparation and production of bio-based flame-retardant polyurethane. The bio-based flame-retardant polyurethane of the present invention is prepared by the above-mentioned preparation method, without the need to add a flame retardant, is green and environmentally friendly, and has high-efficiency flame retardancy and excellent mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane materials, and in particular to a bio-based flame-retardant polyurethane and a preparation method thereof. Background Art

[0002] As the global use of petroleum energy increases, non-renewable resources such as oil are becoming increasingly depleted, and the prices of petroleum and petrochemical products continue to rise, people are paying attention to reducing the dependence on and use of petroleum-based plastic products. In order to fundamentally solve this problem, researchers are exploring the use of green, sustainable and renewable resources to replace petrochemical raw materials.

[0003] Bio-based polyols refer to polyol products made from biomass that have similar properties to petroleum-based polyols. They are substitutes for petroleum-based polyols and have important environmental value. The main raw materials of bio-based polyols are biodiesel, vegetable oil, fatty acids or dimerized fatty acids, which come from a wide range of sources, including castor oil, peanut oil, soybean oil, olive oil, safflower oil, neem oil and cottonseed oil.

[0004] Polyurethane (PU) is an organic polymer with a large number of carbamate groups in the molecular chain, which is the result of a chemical reaction between isocyanate and polyol. Compared with polyurethane made from petroleum-based raw materials, polyurethane materials prepared from bio-based polyols are biodegradable, reduce the pressure on the earth's environment, and are green and economical polyurethane materials. Bio-based polyurethanes prepared from polyols liquefied from biomass and renewable resources have attracted the attention of researchers due to their sustainability, abundant availability and eco-friendliness.

[0005] However, bio-based polyurethane is a flammable material. The limiting oxygen index (LOI) of ordinary polyurethane is very low, and the general LOI value is about 18%, which is very easy to cause combustion. At the same time, the combustion process is accompanied by the release of heat and smoke, and the dripping of molten droplets causes secondary combustion. In order to solve the above problems, flame retardants can generally be added to make bio-based polyurethane flame retardant. Specifically, flame retardants are added in the process of synthesizing polymers by physical incorporation. Halogen-containing, phosphorus-nitrogen-containing compounds, as well as traditional flame retardants such as aluminum hydroxide and magnesium hydroxide are usually added. However, these physical flame retardants are added in large amounts, are easy to precipitate, have poor compatibility with polyurethane, and affect the mechanical properties of the material. Halogen-containing flame retardants release large amounts of toxic gases during combustion, and have long been restricted in international use requirements. Summary of the invention

[0006] The purpose of the present invention is to solve the problems that the existing bio-based polyurethane has low flame retardancy, the addition of flame retardants affects the mechanical properties and there are safety hazards during use, and to provide a bio-based flame retardant polyurethane with high efficiency, excellent mechanical properties and green environmental protection.

[0007] The present invention also aims to provide a method for preparing bio-based flame-retardant polyurethane, which can prepare the above-mentioned green, environmentally friendly, highly flame-retardant and excellent mechanical properties bio-based flame-retardant polyurethane.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] The present invention provides a method for preparing a bio-based flame-retardant polyurethane, comprising the following steps:

[0010] A phosphorus-containing flame retardant polyol is prepared by reacting allyl phosphate with 3-mercapto-1,2-propylene glycol, and the molecular formula of the synthesized phosphorus-containing flame retardant polyol is shown in the following formula I; a bio-based polyol is prepared by reacting vegetable oil with 3-mercapto-1,2-propylene glycol, and the molecular formula of the synthesized bio-based polyol is shown in the following formula II;

[0011]

[0012] In the formula, R is a hydrocarbon group in the vegetable oil molecule. When the vegetable oil reacts with 3-mercapto-1,2-propanediol to prepare a bio-based polyol, the hydrocarbon group of the vegetable oil is bonded to the S atom in 3-mercapto-1,2-propanediol to form a bio-based polyol of formula II;

[0013] Specifically, R is a long straight-chain hydrocarbon group having 6 to 10 carbon atoms;

[0014] The bio-based flame retardant polyurethane is prepared by reacting the phosphorus-containing flame retardant polyol, the bio-based polyol and diisocyanate in a mass ratio of (1-3): (3-4): (14-16). The molecular formula of the synthesized bio-based flame retardant polyurethane is shown in the following formula III;

[0015]

[0016] When the phosphorus-containing flame-retardant polyol, the bio-based polyol and diisocyanate are reacted to prepare the bio-based flame-retardant polyurethane, the phosphorus-containing flame-retardant polyol and the bio-based polyol are grafted onto the molecular chain through esterification with diisocyanate, thereby adding flame-retardant elements P and S to the molecular chain to form the bio-based flame-retardant polyurethane.

[0017] The bio-based flame-retardant polyurethane synthesized by the present invention is an intrinsic flame-retardant polyurethane. By adding flame-retardant elements P and S to the molecular chain, the overall flame-retardant effect is achieved, and the dispersion and uniformity of the polyurethane matrix and the flame retardant are not considered, which is more efficient. Compared with the traditional flame-retardant polyurethane with added flame retardants, the problem of incompatibility and easy precipitation of the flame retardant and the matrix is ​​solved, and the mechanical properties are better.

[0018] In a preferred embodiment, the allyl phosphate diethyl ester and the 3-mercapto-1,2-propylene glycol are reacted under the conditions of adding a photoinitiator, pressurizing and irradiating light to prepare the phosphorus-containing flame retardant polyol;

[0019] The photoinitiator is added in an amount of 0.5 to 2.0 wt % based on the total mass of the diethyl allyl phosphate, 3-mercapto-1,2-propylene glycol and the photoinitiator.

[0020] In a further preferred embodiment, the mass ratio of the diethyl allyl phosphate to the 3-mercapto-1,2-propanediol is 3:2 to 2.5.

[0021] In a further preferred embodiment, the photoinitiator is any one or more of the photoinitiators with the trade names of IRGACURE 127, IRGACURE 184, IRGACURE 369, IRGACURE 379, IRGACURE 500, IRGACURE 651 and IRGACURE 819 produced by BASF SE.

[0022] In a further preferred embodiment, the pressurized pressure is 7-8 KPa.

[0023] In a further preferred embodiment, the illumination is ultraviolet illumination.

[0024] In a preferred embodiment, the phosphorus-containing flame retardant polyol has a hydroxyl value of 700-750 mgKOH / g.

[0025] In a preferred embodiment, the vegetable oil comprises one or more of castor oil, peanut oil, soybean oil, olive oil, linseed oil, neem oil and cottonseed oil.

[0026] In a preferred embodiment, the vegetable oil and the 3-mercapto-1,2-propanediol are reacted under the conditions of adding a photoinitiator and irradiation to prepare the bio-based polyol;

[0027] Calculated as a percentage of the total mass of the vegetable oil, 3-mercapto-1,2-propylene glycol and the photoinitiator, the added amount of the photoinitiator is 0.5 to 2.0 wt %.

[0028] In a further preferred embodiment, the mass ratio of the vegetable oil to the 3-mercapto-1,2-propanediol is 2 to 3:1.

[0029] In a further preferred embodiment, the photoinitiator is any one or more of the photoinitiators with the trade names of IRGACURE 127, IRGACURE 184, IRGACURE 369, IRGACURE 379, IRGACURE 500, IRGACURE 651 and IRGACURE 819 produced by BASF SE.

[0030] In a further preferred embodiment, the illumination is ultraviolet illumination.

[0031] In a preferred embodiment, the hydroxyl value of the bio-based polyol is 450-550 mgKOH / g.

[0032] In a preferred embodiment, the isocyanate is any one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and hexamethylene diisocyanate.

[0033] In a preferred embodiment, the step of preparing the bio-based flame retardant polyurethane by reacting the phosphorus-containing flame retardant polyol, the bio-based polyol and the diisocyanate is specifically as follows: after removing water from the phosphorus-containing flame retardant polyol and the bio-based polyol, the diisocyanate is added, and under a nitrogen atmosphere, a chain extender and a catalyst are added to carry out a catalytic reaction to prepare the bio-based flame retardant polyurethane.

[0034] In a further preferred embodiment, the added amount of the chain extender is 3-7wt%, and the added amount of the catalyst is 0.1-0.5wt%, calculated as a percentage of the total mass of the phosphorus-containing flame retardant polyol, the bio-based polyol, the diisocyanate, the chain extender and the catalyst.

[0035] In a further preferred embodiment, the phosphorus-containing flame retardant polyol and the bio-based polyol are heated at 110° C. for 2 hours to remove water.

[0036] In a further preferred embodiment, the catalytic reaction is carried out at 75° C. for 2 hours.

[0037] In a preferred embodiment, in any of the above methods for preparing bio-based flame-retardant polyurethane, the isocyanate index of the prepared bio-based flame-retardant polyurethane is controlled within a range of 0.98 to 1.04.

[0038] A bio-based flame-retardant polyurethane is prepared by any of the above-mentioned preparation methods.

[0039] The bio-based flame-retardant polyurethane of the present invention is specifically a highly efficient flame-retardant vegetable oil-based polyurethane elastomer, which can play a flame-retardant role in both the gas phase and the condensed phase. Specifically, during combustion, the bio-based flame-retardant polyurethane can be cleaved to generate phosphoric acid molecules and capture free radicals required for the combustion reaction, thereby playing a flame-retardant role; secondly, the bio-based polyurethane is dehydrated and carbonized during combustion, which can avoid the generation of combustible gases, and at the same time, a coke layer is formed on the surface of the combustion object, isolating the combustion environment, and achieving a further flame-retardant effect.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] The bio-based flame-retardant polyurethane of the present invention is prepared by reacting phosphorus-containing flame-retardant polyols, bio-based polyols and diisocyanates. The polyurethane prepared with bio-based polyols is derived from renewable resources and is green and environmentally friendly. The green and environmentally friendly phosphorus element introduced therein can be cracked to produce phosphoric acid molecules to play a flame retardant role when combustion occurs, and avoids the release of a large amount of toxic smoke during the combustion process; at the same time, the bio-based polyurethane is dehydrated and carbonized during combustion, and a coke layer is formed on the surface of the combustion object to isolate the combustion environment, which can further improve the flame retardant effect. Thereby, the overall flame retardant effect is achieved, and it has high-efficiency flame retardancy.

[0042] Moreover, the synthesized bio-based flame-retardant polyurethane is an intrinsic flame-retardant polyurethane. No flame retardant is needed to add the bio-based flame-retardant polyurethane, which solves the problems of large amount of flame retardant added, easy precipitation and low flame retardant efficiency in traditional flame-retardant polyurethane, and ensures the excellent mechanical properties of polyurethane.

[0043] In the preparation method of the present invention, a phosphorus-containing flame-retardant polyol, a bio-based polyol and a diisocyanate are reacted to prepare a bio-based flame-retardant polyurethane. The phosphorus-containing flame-retardant polyol is prepared by using diethyl allyl phosphate and 3-mercapto-1,2-propylene glycol under a photocatalytic reaction, and the bio-based polyol is prepared by using vegetable oil and 3-mercapto-1,2-propylene glycol under a photocatalytic reaction. The bio-based polyol has the advantages of being non-toxic, having good stability, high catalytic activity, fast effect, and low energy consumption, and can realize the large-scale preparation and production of the above-mentioned bio-based flame-retardant polyurethane. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is the infrared spectrum of the bio-based flame-retardant polyurethane prepared in Example 1. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments, but the protection scope and implementation mode of the present invention are not limited thereto. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0046] And, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0047] It should be understood that the singular forms used in the present invention, such as "a", include plural references unless otherwise specified. In addition, the terms "including", "containing", and "having" are open-ended definitions rather than closed-ended definitions, that is, they include the contents specified in the present invention, but do not exclude other aspects. In other words, the terms also include "essentially consisting of" or "consisting of".

[0048] In addition, "and combinations thereof" in the specification refers to any combination of all listed items. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0049] Unless otherwise specified, all technical and scientific terms used herein have the standard meaning in the field to which the claimed subject matter belongs. If there are multiple definitions for a term, the definition herein shall prevail.

[0050] Unless otherwise indicated, this invention employs standard nomenclature and standard laboratory procedures and techniques of analytical chemistry, synthetic organic chemistry, and optics.

[0051] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0052] The technical solution of the present invention is described in detail below in conjunction with specific embodiments.

[0053] Example 1

[0054] The steps for preparing the bio-based flame retardant polyurethane of this embodiment are as follows:

[0055] (1) Add 30 g of diethyl allyl phosphate, 20.7 g of 3-mercapto-1,2-propylene glycol, and 0.6 g of IRGACURE369 photoinitiator into a photochemical reactor; react for 5 h at room temperature under 365 nm ultraviolet radiation and 8 KPa pressure to obtain a phosphorus-containing polyol (hydroxyl value of 720 mgKOH / g);

[0056] The synthetic reaction formula is as follows:

[0057]

[0058] (2) Add 200 g of soybean oil, 81.2 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a soybean oil-based polyol (hydroxyl value of 500 mgKOH / g);

[0059] The synthetic reaction formula is as follows:

[0060]

[0061] (3) Add 250 g of bio-based polyol and 36 g of phosphorus-containing polyol into a three-necked flask, remove water at 110 ° C for 2 h; then cool to 75 ° C, add 54 g of toluene diisocyanate, react for 2 h under nitrogen atmosphere, and then remove bubbles in vacuum; then add 1,4-butanediol chain extender 17 g and dibutyltin dilaurate 0.7 g, stir for 1 min to mix evenly;

[0062] The synthetic bio-based flame retardant polyurethane is shown below:

[0063]

[0064] In the formula, the value range of n is 28.

[0065] Finally, it was poured on a flat vulcanizer at 110° C. and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 1.01) sheet was obtained.

[0066] The infrared spectrum of the bio-based flame-retardant polyurethane prepared in this example is as follows: Figure 1 As shown, at 1540cm -1 NH deformation at 3332cm -1 NH stretching vibration at 1732 cm -1 The C=O stretching vibration at 1235cm-1 and the symmetric and antisymmetric stretching vibration peaks of PO at 1070cm-1 and 880cm-1 are all characteristic structural peaks of urethane.

[0067] Example 2

[0068] The steps for preparing the bio-based flame retardant polyurethane of this embodiment are as follows:

[0069] (1) Add 30 g of diethyl allyl phosphate, 20.7 g of 3-mercapto-1,2-propylene glycol, and 0.6 g of IRGACURE369 photoinitiator into a photochemical reactor; react for 5 h at room temperature under 365 nm ultraviolet radiation and 7 KPa pressure to obtain a phosphorus-containing polyol (hydroxyl value of 740 mgKOH / g).

[0070] (2) Add 200 g of soybean oil, 81.2 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a soybean oil-based polyol (hydroxyl value of 500 mgKOH / g).

[0071] (3) Add 250 g of bio-based polyol and 27 g of phosphorus-containing polyol into a three-necked flask and remove water at 110 °C for 2 h; then cool to 75 °C, add 52 g of toluene diisocyanate, react for 2 h under nitrogen atmosphere and remove bubbles in vacuum; then add 16 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, stir for 1 min to mix evenly.

[0072] Finally, it was poured on a flat vulcanizer at 110° C. and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 0.99) sheet was obtained.

[0073] Example 3

[0074] The steps for preparing the bio-based flame retardant polyurethane of this embodiment are as follows:

[0075] (1) Add 30 g of diethyl allyl phosphate, 20.7 g of 3-mercapto-1,2-propylene glycol, and 0.6 g of IRGACURE369 photoinitiator into a photochemical reactor; react for 5 h at room temperature under 365 nm ultraviolet radiation and 7.5 KPa pressure to obtain a phosphorus-containing polyol (hydroxyl value: 730 mgKOH / g).

[0076] (2) Add 200 g of soybean oil, 81.2 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a soybean oil-based polyol (hydroxyl value of 500 mgKOH / g).

[0077] (3) Add 250 g of bio-based polyol and 20 g of phosphorus-containing polyol into a three-necked flask and remove water at 110 °C for 2 h; then cool to 75 °C, add 72 g of toluene diisocyanate, react for 2 h under nitrogen atmosphere and remove bubbles in vacuum; then add 16 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, stir for 1 min to mix evenly.

[0078] Finally, it was poured on a flat vulcanizer at 110°C and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 1.04) sheet was obtained.

[0079] Example 4

[0080] The steps for preparing the bio-based flame retardant polyurethane of this embodiment are as follows:

[0081] (1) Add 30 g of diethyl allyl phosphate, 20.7 g of 3-mercapto-1,2-propylene glycol, and 0.6 g of IRGACURE369 photoinitiator into a photochemical reactor; react for 5 h at room temperature under 365 nm ultraviolet radiation and 8 KPa pressure to obtain a phosphorus-containing polyol (hydroxyl value of 720 mgKOH / g).

[0082] (2) Add 200 g of castor oil, 81.2 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator into a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a castor oil-based polyol (hydroxyl value of 500 mgKOH / g).

[0083] (3) Add 250 g of bio-based polyol and 36 g of phosphorus-containing polyol into a three-necked flask and remove water at 110 °C for 2 h; then cool to 75 °C, add 54 g of toluene diisocyanate, react for 2 h under nitrogen atmosphere and remove bubbles in vacuum; then add 17 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, stir for 1 min to mix evenly.

[0084] Finally, it was poured on a flat vulcanizer at 110° C. and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 1.01) sheet was obtained.

[0085] Example 5

[0086] The steps for preparing the bio-based flame retardant polyurethane of this embodiment are as follows:

[0087] (1) Add 30 g of diethyl allyl phosphate, 20.7 g of 3-mercapto-1,2-propylene glycol, and 0.6 g of IRGACURE369 photoinitiator into a photochemical reactor; react for 5 h at room temperature under 365 nm ultraviolet radiation and 8 KPa pressure to obtain a phosphorus-containing polyol (hydroxyl value of 720 mgKOH / g).

[0088] (2) Add 200 g of peanut oil, 81.2 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain peanut oil-based polyol (hydroxyl value of 550 mgKOH / g).

[0089] (3) Add 250 g of bio-based polyol and 36 g of phosphorus-containing polyol into a three-necked flask and remove water at 110 °C for 2 h; then cool to 75 °C, add 54 g of toluene diisocyanate, react for 2 h under nitrogen atmosphere and remove bubbles in vacuum; then add 17 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, stir for 1 min to mix evenly.

[0090] Finally, it was poured on a flat vulcanizer at 110 degrees Celsius, and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, a polyurethane (isocyanate index is 1.01) sheet was obtained.

[0091] Example 6

[0092] The steps for preparing the bio-based flame retardant polyurethane of this embodiment are as follows:

[0093] (1) Add 30 g of diethyl allyl phosphate, 20.7 g of 3-mercapto-1,2-propylene glycol, and 0.6 g of IRGACURE369 photoinitiator into a photochemical reactor; react for 5 h at room temperature under 365 nm ultraviolet radiation and 8 KPa pressure to obtain a phosphorus-containing polyol (hydroxyl value of 720 mgKOH / g).

[0094] (2) Add 200 g of soybean oil, 81.2 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a soybean oil-based polyol (hydroxyl value of 500 mgKOH / g).

[0095] (3) Add 250 g of bio-based polyol and 15.6 g of phosphorus-containing polyol into a three-necked flask and remove water at 110 °C for 2 h; then cool to 75 °C, add 53 g of toluene diisocyanate, react for 2 h under nitrogen atmosphere and remove bubbles in vacuum; then add 17 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, stir for 1 min to mix evenly.

[0096] Finally, it was poured on a flat vulcanizer at 110° C. and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 1.02) sheet was obtained.

[0097] Comparative Example 1

[0098] The bio-based flame retardant polyurethane of this comparative example is prepared in the following steps:

[0099] (1) Add 200 g of soybean oil, 81.2 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a bio-based polyol (hydroxyl value of 500 mgKOH / g).

[0100] (2) Add 280 g of bio-based polyol into a three-necked flask and remove water at 110°C for 2 h; then cool to 75°C, add 52 g of toluene diisocyanate, react for 2 h under nitrogen atmosphere, and then remove bubbles in vacuum; then add 16 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, and stir for 1 min to mix evenly.

[0101] Finally, it was poured on a flat vulcanizer at 110° C. and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 1.03) sheet was obtained.

[0102] Comparative Example 2

[0103] (1) Add 200 g of soybean oil, 81.2 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a soybean oil-based polyol (hydroxyl value of 500 mgKOH / g).

[0104] (2) Add 280 g of bio-based polyol to a three-necked flask and remove water at 110° C. for 2 h; then cool to 75° C., add 54 g of toluene diisocyanate, react for 2 h under a nitrogen atmosphere, add 36 g of dimethyl methyl phosphate flame retardant, stir and mix in a vacuum for 1 h, remove bubbles, then add 16 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, stir for 1 min and mix evenly;

[0105] Finally, it was poured on a flat vulcanizer at 110°C and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 1.04) sheet was obtained.

[0106] Comparative Example 3

[0107] The steps for preparing the bio-based flame retardant polyurethane of this embodiment are as follows:

[0108] (1) Add 30 g of diethyl allyl phosphate, 17 g of 3-mercapto-1,2-propylene glycol, and 0.6 g of IRGACURE369 photoinitiator into a photochemical reactor; react for 5 h at room temperature under 365 nm ultraviolet radiation and 7 KPa pressure to obtain a phosphorus-containing polyol (hydroxyl value: 690 mgKOH / g).

[0109] (2) Add 200 g of soybean oil, 60 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a soybean oil-based polyol (hydroxyl value of 440 mgKOH / g).

[0110] (3) Add 250 g of soybean oil-based polyol and 13 g of phosphorus-containing polyol into a three-necked flask and remove water at 110° C. for 2 h; then cool to 75° C., add 74 g of toluene diisocyanate, react for 2 h under nitrogen atmosphere, and remove bubbles in vacuo; then add 16 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, and stir for 1 min to mix evenly.

[0111] Finally, it was poured on a flat vulcanizer at 110° C. and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 1.06) sheet was obtained.

[0112] Comparative Example 4

[0113] The steps for preparing the bio-based flame retardant polyurethane of this embodiment are as follows:

[0114] (1) Add 30 g of diethyl allyl phosphate, 30 g of 3-mercapto-1,2-propylene glycol, and 0.6 g of IRGACURE369 photoinitiator into a photochemical reactor; react for 5 h at room temperature under 365 nm ultraviolet radiation and 7 KPa pressure to obtain a phosphorus-containing polyol (hydroxyl value of 770 mg KOH / g).

[0115] (2) Add 200 g of soybean oil, 110 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a soybean oil-based polyol (hydroxyl value of 580 mgKOH / g).

[0116] (3) Add 250 g of soybean oil-based polyol and 73 g of phosphorus-containing polyol into a three-necked flask and remove water at 110° C. for 2 h; then cool to 75° C., add 50 g of toluene diisocyanate, react for 2 h under nitrogen atmosphere, and remove bubbles in vacuum; then add 16 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, and stir for 1 min to mix evenly.

[0117] Finally, it was poured on a flat vulcanizer at 110° C. and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 0.94) sheet was obtained.

[0118] Comparative Example 5

[0119] (1) Add 200 g of soybean oil, 81.2 g of 3-mercapto-1,2-propylene glycol and 5 g of IRGACURE369 photoinitiator to a photochemical reactor, and react under ultraviolet light at room temperature for 2 hours to obtain a soybean oil-based polyol (hydroxyl value of 500 mgKOH / g).

[0120] (2) Add 280 g of bio-based polyol to a three-necked flask and remove water at 110° C. for 2 h; then cool to 75° C., add 54 g of toluene diisocyanate, react for 2 h under a nitrogen atmosphere, add 36 g of ammonium polyphosphate flame retardant, stir and mix in a vacuum for 1 h, remove bubbles, then add 16 g of 1,4-butanediol chain extender and 0.7 g of dibutyltin dilaurate, stir for 1 min to mix evenly;

[0121] Finally, it was poured on a flat vulcanizer at 110°C and compression molded at a pressure of 10 MPa for 30 minutes. After cooling to room temperature, the polyurethane (isocyanate index: 1.04) sheet was obtained.

[0122] Performance Testing

[0123] The mechanical properties and flame retardant properties of the bio-based flame retardant polyurethane sheets prepared in Examples 1-6 and Comparative Examples 1-5 were tested.

[0124] Among them, the tensile properties and elongation at break of the polyurethane sheet were tested according to GB / T 528-2009, the vertical burning (UL-94) of the polyurethane sheet was tested according to GB / T2408-2021, and the limiting oxygen index (LOI) of the polyurethane sheet was tested according to GB / T 2406.2-2008. The test results are shown in Table 1 below.

[0125] Table 1 Performance test results of bio-based flame retardant polyurethane prepared in Examples 1-6 and Comparative Examples 1-5

[0126]

[0127]

[0128] As can be seen from Table 1 above, the intrinsic bio-based flame-retardant polyurethane prepared by reacting the phosphorus-containing polyol synthesized from diethyl allyl phosphate and 3-mercapto-1,2-propylene glycol, the bio-based polyol synthesized from vegetable oil and 3-mercapto-1,2-propylene glycol, and diisocyanate in Examples 1-6 has both high flame retardant properties and excellent mechanical properties. Compared with the bio-based flame-retardant polyurethane of Comparative Example 1 without the addition of phosphorus-containing polyol, it has a significant flame retardant effect. Compared with other additive phosphorus-containing flame retardants in Comparative Examples 2 and 5, the phosphorus-containing polyol can achieve flame retardant V-0 level with less addition, improve the limiting oxygen index, have efficient flame retardant properties, and have little effect on the mechanical properties of the polyurethane body.

[0129] The bio-based flame-retardant polyurethane prepared in Comparative Examples 3 and 4 not only has a poor flame retardant property, but also has reduced mechanical properties. However, the intrinsic bio-based flame-retardant polyurethane synthesized by controlling the hydroxyl value of the phosphorus-containing polyol to 700-750 mgKOH / g and the hydroxyl value of the bio-based polyol to 700-750 mgKOH / g and controlling the isocyanate index to 0.98-1.04 can achieve better matrix properties of the flame-retardant polyurethane.

[0130] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, this specification does not describe all possible combinations of the technical features in the above-mentioned embodiments. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. Moreover, the above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent.

[0131] It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a bio-based flame-retardant polyurethane, characterized in that: The steps include: Phosphorus-containing flame-retardant polyols were prepared by reacting allyl diethyl phosphate with 3-mercapto-1,2-propylene glycol in a mass ratio of 3:2-2.5; bio-based polyols were prepared by reacting soybean oil with 3-mercapto-1,2-propylene glycol in a mass ratio of 2-3:1; The molecular formula of the soybean oil is: ； The bio-based flame-retardant polyurethane is prepared by reacting the phosphorus-containing flame-retardant polyol, the bio-based polyol and diisocyanate in a mass ratio of (1-3): (14-16): (3-4); The hydroxyl value of the phosphorus-containing flame-retardant polyol is 700-750 mgKOH / g, and the hydroxyl value of the bio-based polyol is 450-550 mgKOH / g; The allyl phosphate diethyl ester and the 3-mercapto-1,2-propylene glycol are reacted with a photoinitiator under a pressure of 7 to 8 KPa and light conditions to prepare the phosphorus-containing flame retardant polyol; The added amount of the photoinitiator is 0.5-2.0wt% based on the total mass of the diethyl allyl phosphate, 3-mercapto-1,2-propylene glycol and the photoinitiator.

2. The method for preparing the bio-based flame-retardant polyurethane according to claim 1, characterized in that: The diisocyanate is any one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and hexamethylene diisocyanate.

3. The method for preparing the bio-based flame-retardant polyurethane according to any one of claims 1 to 2, characterized in that: The isocyanate index of the prepared bio-based flame-retardant polyurethane is controlled within the range of 0.98 to 1.

04.

4. A bio-based flame retardant polyurethane, characterized in that: The preparation method is described in any one of claims 1 to 3.

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