Intumescent nitrogen-phosphorus flame retardant and preparation method thereof

Abstract

The invention discloses an intumescent nitrogen-phosphorus flame retardant and a preparation method thereof. The method comprises the following steps: reacting a cyanuric acid derivative with polyphosphoric acid to obtain a product, and carrying out salt forming reaction on the product and an amine compound to obtain the intumescent nitrogen-phosphorus flame retardant. The method is simple in synthesis step, high in yield, free of toxic volatile matters and suitable for industrial production. The obtained flame retardant has high nitrogen and phosphorus content, shows good expansion capacity when meeting fire, is good in compatibility with various water-based adhesives, is not prone to moisture absorption and has good application prospects.

Description

Technical Field

[0001] The invention relates to a method for preparing a flame retardant, which is a simple and efficient method for preparing an intumescent nitrogen-phosphorus flame retardant and the intumescent nitrogen-phosphorus flame retardant prepared according to the method. Background Art

[0002] Nitrogen-phosphorus composite flame retardant is a flame retardant with nitrogen and phosphorus as the main flame retardant elements. It is usually formed by condensation of nitrogen- and phosphorus-containing monomers or prepolymers, and has the advantages of high flame retardant efficiency and low toxicity. However, the flame retardant mechanism of nitrogen-phosphorus composite flame retardant is mainly gas phase flame retardant of nitrogen compounds, supplemented by condensed phase flame retardant of phosphorus compounds. Because the protective carbon layer produced at high temperature is not dense enough, inorganic particles are often introduced to synergize with nitrogen-phosphorus composite flame retardant to enhance the flame retardant effect of the condensed phase of nitrogen-phosphorus composite flame retardant. For example, 202211342446.3 discloses a method for preparing a flame retardant, which combines adenosine phosphate-nitrogen flame retardant with inorganic materials to enhance the flame retardancy of natural rubber. However, the compatibility between inorganic particles and polymer matrix and nitrogen-phosphorus composite flame retardant is poor, and it takes dozens of hours of ball milling to be well dispersed in the matrix, which greatly increases the production cost. Therefore, in order to obtain a dense condensed phase more easily, a component that can expand at high temperature is added to the formula and structural design of the nitrogen-phosphorus composite flame retardant, so that it forms an intumescent protective carbon layer during the combustion process, effectively isolates heat and oxygen, and has good smoke suppression ability, thereby significantly improving the flame retardant properties of the material. The present invention uses cyanuric acid derivatives, polyphosphoric acid and amine compounds to synthesize a triazine compound containing a phosphoric acid group, introduces a phosphoric acid group on the basis of a multi-branched nitride, and realizes nitrogen-phosphorus synergistic flame retardancy. The flame retardant can not only significantly improve the flame retardant properties of water-soluble resin adhesives / coatings, but also, due to its structural characteristics, is beneficial to the stability of the cross-linked network structure inside the resin. Summary of the invention

[0006] In view of the shortcomings of existing flame retardants, the present invention provides a method for preparing an intumescent nitrogen-phosphorus flame retardant, wherein a phosphoric acid group is introduced into a triazine compound structure to form a multi-branched nitrogen-phosphide compound, thereby achieving nitrogen-phosphorus synergistic flame retardancy. The flame retardant has good compatibility with a variety of water-based artificial board adhesives, can effectively improve the flame retardant properties of the adhesive, is green and environmentally friendly, and meets the market demand for green flame retardants.

[0007] To achieve the above object, the present invention provides the following technical solutions: An intumescent nitrogen-phosphorus flame retardant is composed of the following raw materials in parts by weight: 1 to 3 parts of cyanuric acid derivatives, 1 to 6 parts of polyphosphoric acid, and 2 to 6 parts of amine compounds. The preparation method of the intumescent nitrogen-phosphorus flame retardant comprises the following steps: S1. Add 1 to 3 parts of cyanuric acid derivatives and 1 to 6 parts of polyphosphoric acid into a reactor equipped with a temperature control device, a stirring device and a condensing device, and react for 3 to 5 hours at a constant temperature of 120° C. to 140° C. to obtain a phospholipid intermediate; S2. Add 2 to 6 parts of amine compounds to the phospholipid intermediate product obtained in step S1 and mix them evenly. Keep the temperature at 90 to 100° C. for 1 to 4 hours. After the reaction is complete, cool, filter, purify, and vacuum dry to obtain a white powder flame retardant. The raw material composition of the expandable nitrogen-phosphorus flame retardant described in S1 is characterized in that the cyanuric acid derivative is one or more of 1,3,5-tris(2-hydroxyethyl)isocyanurate, 1,3,5-tris(2-vinyl)isocyanurate, 1,3,5-tris(2-aminoethyl)cyanuric acid, 1,3,5-triamino-s-triazine, 1,3,5-tris(2-hydroxypropyl)cyanuric acid and 1,3,5-tris(2-phenylethyl)cyanuric acid. The raw material composition of the intumescent nitrogen-phosphorus flame retardant described in S1 is characterized in that the polyphosphoric acid is one or more of phosphoric acid, phytic acid and polyphosphoric acid. The raw material composition of the intumescent nitrogen-phosphorus flame retardant described in S2 is characterized in that the amine compound is one or more of melamine, dicyandiamide, and urea. Compared with the prior art, the present invention has the following beneficial effects: (1) Highly effective flame retardant: The flame retardant achieves both gas phase flame retardant and condensed phase flame retardant mechanisms, and has a significant flame retardant effect. After the flame retardant is blended with urea-formaldehyde resin, the limiting oxygen index (LOI) is increased to 86.9% at the highest. (2) Compatible with water-based polymers: This flame retardant has good compatibility with water-based adhesives, coatings, resins and other polymers. Because it contains a large number of polar functional groups such as amino groups and phosphates, which match the water-based resins, the nitrogen-phosphorus composite flame retardant can be evenly dispersed in the resin matrix to form a stable mixture, effectively improving the flame retardancy of the matrix material. (3) Improve the mechanical strength of the matrix: The flame retardant has a multi-branched structure with a large number of internal cavities and loose molecular chains, which can form a stable interpenetrating network structure with the resin molecules, helping to improve the mechanical strength and bonding properties of the resin. DETAILED DESCRIPTION

[0008] The technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The present invention will be further described below in conjunction with the embodiments. The following embodiments are only used to more clearly illustrate the technical scheme of the present invention, and cannot be used to limit the scope of protection of the present invention.

[0009] Embodiment 1: 1,3,5-tris(2-hydroxyethyl)cyanuric acid and phosphoric acid were mixed in a ratio of 1:3 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 90° C. to obtain reactant A; A certain amount of melamine was added to the mixture A, the molar ratio of the amount of melamine added to 1,3,5-tris(2-hydroxyethyl)cyanuric acid being 1:3, and the temperature was maintained at 100°C for continuous reaction until the reaction was completed when the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0010] Embodiment 2: 1,3,5-tris(2-hydroxyethyl)cyanuric acid and phosphoric acid were mixed in a ratio of 1:3 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 100° C. to obtain reactant A; A certain amount of melamine was added to the mixture A, and the molar ratio of the amount of melamine added to 1,3,5-tris(2-hydroxyethyl)cyanuric acid was 1:3, and the temperature was maintained at 100°C for continuous reaction until the pH was 6-7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0011] Embodiment three: 1,3,5-tri(2-vinyl)isocyanurate and phosphoric acid were mixed in a ratio of 1:3 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120° C. to obtain reactant A; A certain amount of melamine was added to the mixture A, the molar ratio of the amount of melamine added to 1,3,5-tri(2-vinyl)isocyanurate being 1:3, and the temperature was maintained at 100°C for continuous reaction until the reaction was completed when the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0012] Embodiment 4: 1,3,5-tri(2-vinyl)isocyanurate and phytic acid were mixed in a ratio of 1:4 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120° C. to obtain a reactant A; A certain amount of melamine was added to the mixture A, the molar ratio of the amount of melamine added to 1,3,5-tri(2-vinyl)isocyanurate being 1:3, and the temperature was maintained at 100°C for continuous reaction until the reaction was completed when the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0013] Embodiment five: 1,3,5-tris(2-aminoethyl)cyanuric acid and phosphoric acid were mixed in a ratio of 1:4 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120° C. to obtain reactant A; A certain amount of melamine was added to the mixture A, the molar ratio of the amount of melamine added to 1,3,5-tris(2-aminoethyl)cyanuric acid being 1:4, and the temperature was maintained at 100°C for continuous reaction until the reaction was completed when the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0014] Embodiment six: 1,3,5-tris(2-aminoethyl)cyanuric acid and phytic acid were mixed in a ratio of 1:4 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120° C. to obtain a reactant A; A certain amount of melamine was added to the mixture A, the molar ratio of the amount of melamine added to 1,3,5-tris(2-aminoethyl)cyanuric acid being 1:4, and the temperature was maintained at 100°C for continuous reaction until the reaction was completed when the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0015] Embodiment seven: 1,3,5-triamino-s-triazine and phytic acid were mixed in a ratio of 1:4 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120° C. to obtain a reactant A; A certain amount of melamine was added to the mixture A, and the molar ratio of the amount of melamine added to 1,3,5-triamino-s-triazine was 1:4, and the temperature was maintained at 100°C for continuous reaction until the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0016] Embodiment eight: 1,3,5-triamino-s-triazine and polyphosphoric acid were mixed in a ratio of 1:4 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120°C to obtain a reactant A; A certain amount of melamine was added to the mixture A, and the molar ratio of the amount of melamine added to 1,3,5-triamino-s-triazine was 1:4, and the temperature was maintained at 100°C for continuous reaction until the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0017] Embodiment nine: 1,3,5-tri(2-hydroxypropyl)cyanuric acid and phosphoric acid were mixed in a ratio of 1:4 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120° C. to obtain reactant A; A certain amount of melamine was added to the mixture A, the molar ratio of the amount of melamine added to 1,3,5-tris(2-hydroxypropyl)cyanuric acid being 1:4, and the temperature was maintained at 100°C for continuous reaction until the reaction was completed when the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0018] Embodiment ten: 1,3,5-tri(2-hydroxypropyl)cyanuric acid and polyphosphoric acid were mixed in a ratio of 1:4 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120° C. to obtain a reactant A; A certain amount of melamine was added to the mixture A, the molar ratio of the amount of melamine added to 1,3,5-tris(2-hydroxypropyl)cyanuric acid being 1:4, and the temperature was maintained at 100°C for continuous reaction until the reaction was completed when the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0019] Embodiment eleven: 1,3,5-tri(2-phenylethyl)cyanuric acid and phosphoric acid were mixed in a ratio of 1:4 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120° C. to obtain reactant A; A certain amount of melamine was added to the mixture A, the molar ratio of the amount of melamine added to 1,3,5-tri(2-phenylethyl)cyanuric acid being 1:4, and the temperature was maintained at 100°C for continuous reaction until the reaction was completed when the pH was 6 to 7. The crude product was washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder.

[0020] Embodiment 12: 1,3,5-tri(2-phenylethyl)cyanuric acid and polyphosphoric acid were mixed in a ratio of 1:4 and added into a three-necked flask equipped with a thermometer, a condenser and a stirring device at a temperature of 120° C. to obtain reactant A; A certain amount of melamine is added to the mixture A, and the molar ratio of the amount of melamine added to 1,3,5-tri(2-phenylethyl)cyanuric acid is 1:4, and the temperature is maintained at 100°C for continuous reaction until the pH is 6-7. The crude product is washed and purified with ethanol, and dried in an oven at 60°C to obtain a nitrogen-phosphorus flame retardant powder. Application examples of the above flame retardants The intumescent flame retardant can be used for the preparation of flame-retardant adhesives, coatings, resins, etc. The flame retardants of Examples 1-5 were sampled and mixed with water-based adhesives and subjected to limiting oxygen index (LOI) tests. The water-based adhesive selected urea-formaldehyde resin with a molar ratio of 1 and was mixed with the flame retardant at a weight ratio of 10:1. Different amounts of flame retardant were added to the urea-formaldehyde resin, and after mixing evenly, the mixture was poured into a polytetrafluoroethylene mold and heated to 130°C in an oven for curing. After curing, it was cooled to room temperature to obtain urea-formaldehyde resin cured products with different amounts of flame retardants. The LOI is shown in Table 1. Table 1 Sample No. P (wt%) N (wt%) LOI RAW 0 0 23.1 Example 1 7.58 13.95 78.6 Example 2 7.98 13.54 78.8 Example 3 8.36 13.85 84.7 Example 4 8.55 13.95 86.1 Example 5 8.58 13.98 86.9 Example 6 8.02 14.01 78.8 Example 7 8.45 13.99 79.8 Example 8 8.89 12.41 75.1 Example 9 8.95 7.66 61.5 Example 10 8.75 7.78 60.1 Embodiment 11 8.69 6.52 58.6 Example 12 7.99 6.50 56.7

[0021] It can be seen from Examples 1-12 and Table 1 that the intumescent flame retardant produced by the method of the present invention has a high limiting oxygen index, good flame retardant effect, large nitrogen and phosphorus loading, high reaction activity, and good compatibility with water-soluble adhesives or coatings such as urea-formaldehyde resins.

[0022] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is determined by the appended claims and their equivalents.

Claims

1. An intumescent nitrogen-phosphorus flame retardant, characterized in that The invention is composed of the following raw materials in parts by weight: 1 to 3 parts of cyanuric acid derivatives, 1 to 6 parts of polyphosphoric acid and 2 to 6 parts of amine compounds.

2. The method for preparing the intumescent nitrogen-phosphorus flame retardant according to claim 1, characterized in that The following steps are involved: S1. Evenly mix 1 to 3 parts of cyanuric acid derivatives and 1 to 6 parts of polyphosphoric acid, and reflux and stir for 3 to 5 hours at a constant reaction temperature of 120° C. to 140° C. to obtain a phospholipid intermediate; S2. Add 2 to 6 parts of amine compounds to the phospholipid intermediate product obtained in step S1 and mix them evenly, react for 1 to 4 hours, keep the temperature at 90 to 100° C., cool, filter, purify and dry to obtain a white powder, i.e., an expandable nitrogen-phosphorus flame retardant.

3. The intumescent nitrogen-phosphorus flame retardant according to claim 1, characterized in that The cyanuric acid derivative in the raw material composition is one or more of 1,3,5-tris(2-hydroxyethyl)isocyanurate, 1,3,5-tris(2-vinyl)isocyanurate, 1,3,5-tris(2-aminoethyl)cyanuric acid, 1,3,5-triamino-s-triazine, 1,3,5-tris(2-hydroxypropyl)cyanuric acid and 1,3,5-tris(2-phenylethyl)cyanuric acid.

4. The intumescent nitrogen-phosphorus flame retardant according to claim 1, characterized in that The polyphosphate in the raw material composition is one or more of phosphoric acid, phytic acid and polyphosphoric acid.

5. The intumescent nitrogen-phosphorus flame retardant according to claim 1, characterized in that The amine compound in the raw material composition is one or more of melamine, dicyandiamide and urea.

6. The intumescent nitrogen-phosphorus flame retardant according to claim 1 can be used for the preparation of flame-retardant adhesives, coatings, resins, etc.