Phosphorus-nitrogen synergistic flame-retardant polyester polyol and preparation method thereof

Abstract

The present invention belongs to the technical field of polyester polyol preparation, and is specifically related to phosphorus-nitrogen synergistic flame-retardant polyester polyol and a preparation method thereof, wherein a phosphate carboxylic acid compound one, a phosphate carboxylic acid compound two, a small molecule polyol, and a small molecule polyacid are polycondensed under the action of a catalyst to obtain the phosphorus-nitrogen synergistic flame-retardant polyester polyol; wherein a phosphate carboxylic acid compound one is 2-phosphonic acid butane-1,2,4-tricarboxylic acid and coniferyl alcohol are obtained by esterification under the action of concentrated sulfuric acid; a phosphate carboxylic acid compound two is 2-phosphonic acid butane-1,2,4-tricarboxylic acid and 1H-imidazole-5-propanol are obtained by esterification under the action of concentrated sulfuric acid. The present invention synergistically improves flame retardancy through phosphorus-nitrogen, and the aging-resistant performance is improved. The present invention also provides its preparation method.

Description

Technical Field

[0001] The invention belongs to the technical field of polyester polyol preparation, and specifically relates to phosphorus-nitrogen synergistic flame-retardant polyester polyol and a preparation method thereof. Background Art

[0002] In the field of construction, polyurethane rigid foam can be used for moisture-proof, waterproof and heat-insulating roofs, walls and other parts. Its flame retardant performance is conducive to improving the safety of buildings. The flame retardancy of most polyurethane materials is achieved by adding flame retardants. For example, China's invention patent application publication number CN118580458A discloses a high-efficiency flame retardant polyurethane and its preparation method, which is flame-retardant modified by adding microencapsulated flame retardants and modified expandable graphite. Although microencapsulation of flame retardants improves the migration problem of flame retardants, the flame retardants therein are still essentially external flame retardants, and the uniformity and compatibility of mixing cannot be guaranteed, which will affect the final flame retardant effect of the material.

[0003] Polyether polyols and polyester polyols are the main raw materials for the preparation of polyurethane. Introducing flame retardant elements into the molecular structure of polyols through reaction can overcome the problems of uneven mixing and poor compatibility of added flame retardants. China Invention Patent Application Publication No. CN118930836A provides a flame retardant rigid foam polyether polyol, which uses a silane compound containing a primary amino group and a diphenyl phosphorus halide as raw materials, reacts under alkaline conditions to obtain an intermediate; then the intermediate is used as an initiator, and a polymerization reaction is carried out with an oxidized olefin under the action of a polymerization catalyst to obtain a polyether polyol. Halogens and phosphorus elements with flame retardant effects are introduced into polyether polyols, but halogens may release harmful gases, such as hydrogen halides, when burned, which are harmful to the environment and human health. With the increasingly stringent environmental protection regulations, the use of halogen flame retardants may be restricted in certain application scenarios. Phosphorus-nitrogen compounds can form a stable carbon layer and non-combustible gas during the combustion process, which plays a role in heat insulation, oxygen isolation and dilution of combustible gases. This dual flame retardant mechanism enables phosphorus-nitrogen synergistic flame retardant to perform well in reducing the burning speed and heat release rate of materials, thereby effectively reducing the hazards of fire. In addition, phosphorus-nitrogen synergistic flame retardant does not release these harmful gases when burning, which is more friendly to the environment and human health.

[0004] Polyester polyols are an important raw material for preparing polyurethane rigid foams. Compared with polyether polyols, polyester polyols generally have higher mechanical strength, but are more susceptible to aging when used outdoors. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a phosphorus-nitrogen synergistic flame-retardant polyester polyol, which improves the flame retardant performance through phosphorus-nitrogen synergy and improves the aging resistance performance. The present invention also provides a preparation method thereof.

[0006] The phosphorus-nitrogen synergistic flame-retardant polyester polyol of the present invention is obtained by polycondensing a phosphate carboxylic acid compound 1, a phosphate carboxylic acid compound 2, a small molecule polyol, and a small molecule polyacid under the action of a catalyst; the mass ratio of the phosphate carboxylic acid compound 1, the phosphate carboxylic acid compound 2, the small molecule polyol, and the small molecule polyacid is (5-8): (5-8): (40-55): (35-40).

[0007] Wherein, the catalyst is an organic titanium catalyst or an organic tin catalyst;

[0008] The phosphate carboxylic acid compound 1 is obtained by esterification reaction of 2-phosphonobutane-1,2,4-tricarboxylic acid and coniferyl alcohol under the action of concentrated sulfuric acid. In the preparation of the phosphate carboxylic acid compound 1, the amount of concentrated sulfuric acid added is 0.03%-0.05% of the total mass of 2-phosphonobutane-1,2,4-tricarboxylic acid and coniferyl alcohol;

[0009] The phosphate carboxylic acid compound II is obtained by esterification reaction of 2-phosphonobutane-1,2,4-tricarboxylic acid and 1H-imidazole-5-propanol under the action of concentrated sulfuric acid. In the preparation of the phosphate carboxylic acid compound II, the amount of concentrated sulfuric acid added is 0.03%-0.05% of the total mass of 2-phosphonobutane-1,2,4-tricarboxylic acid and 1H-imidazole-5-propanol.

[0010] Preferably, the small molecule polyol is one or more of ethylene glycol, diethylene glycol and glycerol.

[0011] Preferably, the small molecule polyacid is one or more of phthalic acid, isophthalic acid, and terephthalic acid.

[0012] Preferably, the catalyst is added in an amount of 0.02-0.03% of the total mass of the phosphate carboxylic acid compound 1, the phosphate carboxylic acid compound 2, the small molecule polyol, and the small molecule polyacid. Further preferably, the catalyst is one of T-12 and n-butyl titanate.

[0013] Preferably, the phosphate carboxylic acid compound 1 is prepared from 2-phosphonobutane-1,2,4-tricarboxylic acid and coniferyl alcohol in a molar ratio of 1:1; the phosphate carboxylic acid compound 2 is prepared from 2-phosphonobutane-1,2,4-tricarboxylic acid and 1H-imidazole-5-propanol in a molar ratio of 1:1.

[0014] The method for preparing the phosphorus-nitrogen synergistic flame-retardant polyester polyol of the present invention comprises the following steps:

[0015] (1) Add concentrated sulfuric acid to a mixture of 2-phosphonobutane-1,2,4-tricarboxylic acid and coniferyl alcohol, and carry out esterification reaction at 190-200° C. for 8-10 hours to obtain a phosphate carboxylic acid compound 1; add concentrated sulfuric acid to a mixture of 2-phosphonobutane-1,2,4-tricarboxylic acid and 1H-imidazole-5-propanol, and carry out esterification reaction at 160-180° C. for 6-8 hours to obtain a phosphate carboxylic acid compound 2;

[0016] (2) Polycondensing the phosphate carboxylic acid compound 1, the phosphate carboxylic acid compound 2, a small molecule polyol, and a small molecule polyacid under the action of a catalyst to obtain the phosphorus-nitrogen synergistic flame-retardant polyester polyol.

[0017] Preferably, step (2) is specifically as follows: placing the phosphate carboxylic acid compound 1, the phosphate carboxylic acid compound 2, the small molecule polyol, the small molecule polyacid and the catalyst in a reactor and stirring, heating to 160-170°C, keeping the temperature for 2-3 hours after the water is discharged, and then heating to 220-230°C, controlling the reflux tower temperature at 98-102°C during the heating period, keeping the temperature for 2-3 hours, evacuating until the acid value is less than 2.0 mgKOH / g, stopping evacuating, and cooling to obtain the product.

[0018] 2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) is a phosphorus-containing compound with potential flame retardant properties. Its chemical structure is as follows:

[0019] .

[0020] The chemical structure of coniferyl alcohol is as follows:

[0021] .

[0022] The chemical structure of 1H-imidazole-5-propanol is as follows:

[0023] .

[0024] From the perspective of molecular structure, 2-phosphonobutane-1,2,4-tricarboxylic acid is a pentabasic acid, which not only has two active carboxyl groups on the primary carbon atom, but also has a phosphonic acid structure. Therefore, it can undergo esterification reaction with hydroxyl groups in the presence of a catalyst. Compared with carboxyl groups, the hydroxyl groups in the phosphonic acid groups tend to participate in the esterification reaction first to generate esters. Therefore, the esterified product of the present invention still contains multiple carboxyl groups, which can be used as a polyacid to introduce phosphorus into polyester polyols. Coniferyl alcohol and 1H-imidazole-5-propanol both contain hydroxyl groups in their molecular structures, and both can undergo esterification reaction with 2-phosphonobutane-1,2,4-tricarboxylic acid to generate phosphate carboxylic acid compound 1 and phosphate carboxylic acid compound 2, respectively. Due to the presence of steric hindrance, the esterification reaction needs to be carried out at a higher temperature and in the presence of a catalyst.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Coniferyl alcohol is one of the main components of lignin and can be extracted from lignin. Lignin can be derived from the recycling of waste or by-products containing a large amount of lignin, such as fallen leaves, crop straw and grass, wood hydrolysis waste liquid and papermaking black liquor. The present invention expands the application scope of lignin and can realize waste utilization, with the advantages of low cost and environmental protection;

[0027] 2. Phosphate carboxylic acid compound 1 contains a benzene ring structure and an ether bond, and can be used to prepare polyurethane rigid foam to increase the compressive strength. At the same time, the anti-aging performance is increased due to the introduction of coniferyl alcohol structure. As an antioxidant, coniferyl alcohol contains phenolic hydroxyl and methoxy groups in its molecular structure. These functional groups can react with free radicals, thereby preventing the occurrence of free radical chain reactions and reducing oxidative damage. Phosphate carboxylic acid compound 2 introduces nitrogen-containing heterocycles into phosphorus-containing compounds, which synergizes with phosphorus elements to further improve the flame retardancy of the product. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments.

[0029] Unless otherwise specified, all raw materials used in the examples are commercially available.

[0030] Example 1

[0031] The method for preparing the phosphorus-nitrogen synergistic flame-retardant polyester polyol comprises the following steps:

[0032] (1) Add 270.13 g (1 mol) of 2-phosphonobutane-1,2,4-tricarboxylic acid and 180.2 g (1 mol) of coniferyl alcohol into a reaction kettle A and stir and mix, then add 0.135 g of concentrated sulfuric acid into the reaction kettle A, and perform an esterification reaction at 190° C. for 10 h to obtain a phosphate carboxylic acid compound 1;

[0033] 270.13 g (1 mol) of 2-phosphonobutane-1,2,4-tricarboxylic acid and 126.16 g (1 mol) of 1H-imidazole-5-propanol were added to the reaction kettle B and stirred and mixed, and then 0.120 g of concentrated sulfuric acid was added to the reaction kettle B to carry out esterification reaction at 180° C. for 6 hours to obtain phosphate carboxylic acid compound II;

[0034] (2) Phosphate carboxylic acid compound 1, phosphate carboxylic acid compound 2, diethylene glycol, ethylene glycol, glycerol and terephthalic acid are placed in a reaction kettle C at a mass ratio of 5:5:30:20:5:35 and stirred, and n-butyl titanate accounting for 0.02% of the total mass of phosphate carboxylic acid compound 1, phosphate carboxylic acid compound 2, diethylene glycol, ethylene glycol, glycerol and terephthalic acid is added, and the temperature is raised to 160°C. After the water is discharged, the temperature is kept for 2 hours, and then the temperature is raised to 220°C. During the heating period, the temperature of the reflux tower is controlled at 98-102°C. The temperature is kept for 2 hours, and vacuum is applied. The reaction is continued for 5 hours. The vacuum is stopped and the temperature is lowered to obtain the product.

[0035] Example 2

[0036] The method for preparing the phosphorus-nitrogen synergistic flame-retardant polyester polyol comprises the following steps:

[0037] (1) Add 270.13 g (1 mol) of 2-phosphonobutane-1,2,4-tricarboxylic acid and 180.2 g (1 mol) of coniferyl alcohol into a reaction kettle A, stir and mix, then add 0.135 g of concentrated sulfuric acid into the reaction kettle A, and perform an esterification reaction at 200° C. for 8 h to obtain a phosphate carboxylic acid compound 1;

[0038] 270.13 g (1 mol) of 2-phosphonobutane-1,2,4-tricarboxylic acid and 126.16 g (1 mol) of 1H-imidazole-5-propanol were added to the reaction kettle B and stirred and mixed, and then 0.120 g of concentrated sulfuric acid was added to the reaction kettle B, and an esterification reaction was carried out at 160° C. for 8 hours to obtain a phosphate carboxylic acid compound II;

[0039] (2) Phosphate carboxylic acid compound I, phosphate carboxylic acid compound II, diethylene glycol, glycerol and phthalic acid are placed in a reaction kettle C in a mass ratio of 8:7:35:10:40, and stirred. T-12 accounting for 0.02% of the total mass of phosphate carboxylic acid compound I, phosphate carboxylic acid compound II, diethylene glycol, glycerol and phthalic acid is added, and the temperature is raised to 170°C. After the water is discharged, the temperature is kept for 3 hours, and then the temperature is raised to 230°C. During the heating period, the temperature of the reflux tower is controlled at 98-102°C. The temperature is kept for 3 hours, and vacuum is applied. The reaction is continued for 6 hours. The vacuum is stopped and the temperature is lowered to obtain the product.

[0040] Example 3

[0041] The method for preparing the phosphorus-nitrogen synergistic flame-retardant polyester polyol comprises the following steps:

[0042] (1) Add 270.13 g (1 mol) of 2-phosphonobutane-1,2,4-tricarboxylic acid and 180.2 g (1 mol) of coniferyl alcohol into a reaction kettle A and stir and mix them to form reactant A. Then, add 0.18 g of concentrated sulfuric acid into the reaction kettle A and perform an esterification reaction at 195° C. for 8 h to obtain a phosphate carboxylic acid compound 1.

[0043] 270.13 g (1 mol) of 2-phosphonobutane-1,2,4-tricarboxylic acid and 126.16 g (1 mol) of 1H-imidazole-5-propanol were added to the reaction kettle B and stirred and mixed, and then 0.160 g of concentrated sulfuric acid was added to the reaction kettle B, and an esterification reaction was carried out at 170° C. for 8 hours to obtain a phosphate carboxylic acid compound II;

[0044] (2) Phosphate carboxylic acid compound I, phosphate carboxylic acid compound II, diethylene glycol, glycerol and isophthalic acid are placed in a reaction kettle C at a mass ratio of 5:5:35:15:40, and stirred. n-butyl titanate accounting for 0.03% of the total mass of phosphate carboxylic acid compound I, phosphate carboxylic acid compound II, diethylene glycol, glycerol and isophthalic acid is added. The temperature is raised to 165°C, and the temperature is kept for 2.5 hours after the water is discharged. The temperature is then raised to 225°C. During the heating period, the temperature of the reflux tower is controlled at 98-102°C. The temperature is kept for 2.5 hours, and vacuum is applied. The reaction is continued for 6.5 hours. The vacuum is stopped and the temperature is lowered to obtain the product.

[0045] Example 4

[0046] The method for preparing the phosphorus-nitrogen synergistic flame-retardant polyester polyol comprises the following steps:

[0047] (1) Add 270.13 g (1 mol) of 2-phosphonobutane-1,2,4-tricarboxylic acid and 180.2 g (1 mol) of coniferyl alcohol into a reaction kettle A and stir to mix them as reactant A. Then, add 0.225 g of concentrated sulfuric acid into the reaction kettle A and perform an esterification reaction at 195° C. for 8 h to obtain a phosphate carboxylic acid compound 1.

[0048] 270.13 g (1 mol) of 2-phosphonobutane-1,2,4-tricarboxylic acid and 126.16 g (1 mol) of 1H-imidazole-5-propanol were added to the reaction kettle B and stirred and mixed, and then 0.20 g of concentrated sulfuric acid was added to the reaction kettle B, and an esterification reaction was carried out at 170° C. for 8 hours to obtain a phosphate carboxylic acid compound II;

[0049] (2) Phosphate carboxylic acid compound 1, phosphate carboxylic acid compound 2, diethylene glycol, ethylene glycol and terephthalic acid are placed in a reaction kettle C in a mass ratio of 7:8:30:10:35, and stirred. 0.02% of n-butyl titanate, which accounts for the total mass of phosphate carboxylic acid compound 1, phosphate carboxylic acid compound 2, diethylene glycol, ethylene glycol and terephthalic acid, is added. The temperature is raised to 170°C, and the temperature is kept for 2 hours after the water is discharged. The temperature is then raised to 230°C. During the heating period, the temperature of the reflux tower is controlled at 98-102°C. The temperature is kept for 2 hours, and vacuum is applied. The reaction is continued for 7 hours. The vacuum is stopped and the temperature is lowered to obtain the product.

[0050] Comparative Example 1

[0051] The difference between Comparative Example 1 and Example 1 is that in step (2), an equal amount of a phosphate carboxylic acid compound is used to replace a phosphate carboxylic acid compound 1.

[0052] Comparative Example 2

[0053] The difference between Comparative Example 2 and Example 1 is that in step (2), an equal amount of phosphate carboxylic acid compound 1 is used to replace phosphate carboxylic acid compound 2.

[0054] Performance Testing

[0055] The indicators of the polyester polyols obtained in Examples 1-4 and Comparative Examples 1-2 are shown in Table 1. The oxygen index test standard is: GB / T16581-1996;

[0056] Table 1 Polyester polyol index table for Examples 1-4 and Comparative Examples 1-2

[0057]

[0058] The polyester polyols obtained in Examples 1-4 and Comparative Examples 1-2 were formulated according to Table 2 to obtain material A, and then MDI-50 was used as material B and formulated according to an -NCO index of 1.05 to prepare polyurethane foam samples.

[0059] Table 2: Formula of polyurethane foam material A of Examples 1-4 and Comparative Examples 1-2

[0060]

[0061] The polyurethane foam samples obtained in Examples 1-4 and Comparative Examples 1-2 were subjected to performance tests, and the results are shown in Table 3. The change rate of tensile strength and the change rate of compressive strength were determined by testing the tensile strength and compressive strength of the samples after high temperature aging and ultraviolet aging treatment according to GB / T9640-2008 and GB / T16422.3-1997 (light source UV-A340, exposure mode 1), the tensile strength was tested according to GB / T528-2009, and the compressive strength was tested according to GB / T8813-2008.

[0062] Table 3 Polyurethane foam performance test table of Examples 1-4 and Comparative Examples 1-2

[0063]

[0064] From Table 1, it can be seen from the comparison between Example 1 and Comparative Example 1, and between Comparative Example 1 and Comparative Example 2 that the flame retardant properties are improved due to the synergistic effect between the nitrogen-containing heterocycle introduced into the phosphate carboxylic acid compound II and phosphorus; from Table 3, it can be seen from the comparison between Example 1 and Comparative Example 2, and between Comparative Example 1 and Comparative Example 2 that the coniferyl alcohol structure and the benzene ring introduced into the phosphate carboxylic acid compound I increase the strength of the polyurethane, and the phenolic hydroxyl group and methoxy group can prevent the free radical reaction from proceeding, reduce oxidative damage, and improve the high temperature aging resistance and ultraviolet aging resistance of the polyurethane material, so that the polyurethane material is not easy to decompose under high temperature and ultraviolet irradiation, and can still maintain good mechanical properties.

Claims

1. A phosphorus-nitrogen synergistic flame-retardant polyester polyol, characterized in that: The phosphorus-nitrogen synergistic flame-retardant polyester polyol is obtained by polycondensing a phosphate carboxylic acid compound 1, a phosphate carboxylic acid compound 2, a small molecule polyol, and a small molecule polyacid under the action of a catalyst; the mass ratio of the phosphate carboxylic acid compound 1, the phosphate carboxylic acid compound 2, the small molecule polyol, and the small molecule polyacid is (5-8): (5-8): (40-55): (35-40); Wherein, the catalyst is an organic titanium catalyst or an organic tin catalyst; The phosphate carboxylic acid compound 1 is obtained by esterification reaction of 2-phosphonobutane-1,2,4-tricarboxylic acid and coniferyl alcohol under the action of concentrated sulfuric acid; the phosphate carboxylic acid compound 2 is obtained by esterification reaction of 2-phosphonobutane-1,2,4-tricarboxylic acid and 1H-imidazole-5-propanol under the action of concentrated sulfuric acid; The small molecule polyol is one or more of ethylene glycol, diethylene glycol and glycerol; The small molecule polyacid is one or more of phthalic acid, isophthalic acid and terephthalic acid.

2. The phosphorus-nitrogen synergistic flame-retardant polyester polyol according to claim 1, characterized in that: The phosphate carboxylic acid compound 1 is prepared from 2-phosphonobutane-1,2,4-tricarboxylic acid and coniferyl alcohol in a molar ratio of 1:1; the phosphate carboxylic acid compound 2 is prepared from 2-phosphonobutane-1,2,4-tricarboxylic acid and 1H-imidazole-5-propanol in a molar ratio of 1:

1.

3. A method for preparing the phosphorus-nitrogen synergistic flame-retardant polyester polyol according to any one of claims 1 to 2, characterized in that: The steps include: (1) adding concentrated sulfuric acid to a mixture of 2-phosphonobutane-1,2,4-tricarboxylic acid and coniferyl alcohol for esterification reaction to obtain a phosphate carboxylic acid compound 1; adding concentrated sulfuric acid to a mixture of 2-phosphonobutane-1,2,4-tricarboxylic acid and 1H-imidazole-5-propanol for esterification reaction to obtain a phosphate carboxylic acid compound 2; (2) Polycondensing the phosphate carboxylic acid compound 1, the phosphate carboxylic acid compound 2, a small molecule polyol, and a small molecule polyacid under the action of a catalyst to obtain the phosphorus-nitrogen synergistic flame-retardant polyester polyol.

4. The method for preparing phosphorus-nitrogen synergistic flame-retardant polyester polyol according to claim 3, characterized in that: Step (2) specifically comprises: placing a phosphate carboxylic acid compound 1, a phosphate carboxylic acid compound 2, a small molecule polyol, a small molecule polyacid, and a catalyst in a reactor and stirring, heating the reactor to 160-170° C., keeping the temperature for 2-3 hours after the water is discharged, and then heating the reactor to 220-230° C., controlling the temperature of the reflux tower to 98-102° C. during the heating period, keeping the temperature for 2-3 hours, evacuating the reactor, taking a sample to measure the acid value until the acid value is less than 2.0 mgKOH / g, stopping evacuating the reactor, and cooling the reactor to obtain the product.

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