CN112409567A

CN112409567A - Preparation method of P-N type flame retardant based on DOPO

Info

Publication number: CN112409567A
Application number: CN202011249664.3A
Authority: CN
Inventors: 宋晓峰; 孙奇浩; 张宝昌; 魏君格; 沈月石; 陈兴
Original assignee: Changchun University of Technology
Current assignee: Changchun University of Technology
Priority date: 2020-11-11
Filing date: 2020-11-11
Publication date: 2021-02-26
Anticipated expiration: 2040-11-11
Also published as: CN112409567B

Abstract

The invention discloses a preparation method of a P-N type flame retardant based on 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The invention synthesizes a hydroxyethyl Schiff base intermediate by the ring opening reaction of P-phenylenediamine Schiff base and ethylene carbonate under the base catalysis condition; then, the hydroxyethyl Schiff base intermediate and the P-H bond of DOPO are subjected to Michael addition reaction to synthesize a DOPO hydroxyethyl Schiff base derivative; and finally, carrying out chain extension reaction by using hexamethylene diisocyanate to obtain the P-N flame retardant. The flame retardant structure contains phosphorus, nitrogen and imino, and the phosphorus and the nitrogen are synergistic in flame retardance, so that the comprehensive performance of the material can be improved.

Description

Preparation method of P-N type flame retardant based on DOPO

Technical Field

The invention belongs to the technical field of flame retardance, and particularly relates to a preparation method of a P-N type flame retardant based on DOPO.

Background

Polymer materials have been widely used due to their excellent properties, but they have flammability, burn rapidly, generate rich smoke and toxic gases, and severely limit their further use in safety. For improving the flame retardant property of the high polymer material, adding the flame retardant is the most feasible modification method; therefore, additive-type flame retardants are widely used. However, conventional halogenated flame retardants are prohibited from use due to harmful byproducts generated during combustion. Therefore, it is necessary to develop an environmentally friendly, chemically stable flame retardant.

The phosphorus-nitrogen flame retardant is an environment-friendly flame retardant, and can concentrate the advantages of phosphorus flame retardants and nitrogen flame retardants: on one hand, the phosphorus flame retardant can generate acidic substances such as phosphoric acid or polyphosphoric acid and the like during pyrolysis to promote the degradation of polymers to form a carbon layer, and meanwhile PO. and PO can be generated during the combustion process of the flame retardant₂Phosphorus-containing free radicals can quench free radicals generated by pyrolysis of the polymer, and can be crosslinked with a polymer matrix to form a polymer network with good thermal stability; on the other hand, nitrogen-containing gases such as ammonia gas and nitrogen oxides can be released in the combustion process of the nitrogen flame retardant, and the gases are released from the polymer matrix and can play a certain role in cooling and diluting combustible gas, so that the nitrogen oxides are formed to consume oxygen to inhibit combustion; meanwhile, the escape of gas generated during combustion of the nitrogen-containing flame retardant can promote the polymer to form holes, so that a porous heat-insulating carbon layer is formed. However, most of the conventional phosphorus-nitrogen flame retardants are small-molecule additive type flame retardants, and since the additive type flame retardants lack reactive groups and are mostly small molecules, they are likely to migrate during use. Therefore, from the perspective of molecular design of the flame retardant, a multielement synergistic flame retardant with macromolecules having reactive groups is designed, and the flame retardant has great application potential.

Disclosure of Invention

In order to solve the problems in the background, the invention provides a preparation method of a DOPO-based P-N type flame retardant, which structurally comprises phosphorus, nitrogen and imino groups, wherein the phosphorus and the nitrogen have a synergistic flame retardant effect, a phosphorus compound can promote the formation of carbon, and a nitrogen compound can inhibit the combustion and promote the formation of a porous carbon layer. The imino group can also participate in chemical reaction, so that the performance of the material is improved.

The invention provides a DOPO-based P-N type flame retardant, which has the following structure:

the technical solution will be clearly and completely described below with reference to the embodiments of the present invention, but the described embodiments are embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The phosphorus-nitrogen flame retardant shown in the figure is synthesized by performing hydroxyethylation reaction on p-phenylenediamine Schiff base, performing addition reaction on the p-phenylenediamine Schiff base and DOPO, and finally performing HDI chain extension reaction. The following is a description of the preparation:

the reaction circuit related by the invention is as follows:

description of the drawings:

FIG. 1: infrared spectrum of target product

FIG. 2 is a drawing: nuclear magnetic map of target product

FIG. 3: thermogravimetric curve of target product

FIG. 4 is a drawing: LOI test data of phosphorus-nitrogen flame retardant PLLA composite material

The specific embodiment is as follows:

synthesis of p-phenylenediamine schiff base (PHPD): adding 1g of p-aminophenol and 2.26 g of p-hydroxybenzaldehyde into an ampoule bottle, then performing nitrogen replacement on the ampoule bottle for 3 times, and injecting 20ml of absolute ethyl alcohol into the ampoule bottle after nitrogen replacement; the ampoule bottle is placed in an oil bath kettle, the stirring is started, and the temperature is raised to 60 ℃ for reaction for 4 hours. After the reaction is finished, cooling the reaction mixture to room temperature, carrying out suction filtration, and washing the obtained solid product with absolute ethyl alcohol; the product was then dried in a vacuum oven at 80 ℃ for 24 hours to give a yellow powder product.

Synthesis of hydroxyethylated p-phenylenediamine schiff base (ECPD): an ampoule bottle was charged with 2g of PHPD and 0.02g of Na₂CO₃To the ampoule bottlePerforming nitrogen replacement for 3 times, and then injecting 1.2g of Ethylene Carbonate (EC) and 15mL of N, N-dimethylacetamide into the ampoule bottle; the ampoule was placed in an oil bath and the reaction was stirred at 150 ℃ for 16 hours. The mixture was cooled to room temperature, then the reaction mixture was poured into deionized water for precipitation, and the precipitate was filtered, washed with water and alcohol, and then dried in a vacuum oven at 80 ℃ for 24h to give yellow powder ECPD.

Synthesis of DOPO and hydroxyethyl schiff base addition product (DEPD): adding 1.07g of DOPP and 1g of ECPD into an ampoule bottle, performing nitrogen replacement on the ampoule bottle for 3 times, and then injecting 15mL of absolute ethyl alcohol; the ampoule bottle is placed in an oil bath kettle and stirred for reaction for 16h at 60 ℃. And after the reaction is finished, cooling the mixture to room temperature, then pouring the reaction mixture into petroleum ether for precipitation, carrying out suction filtration on the precipitate, recrystallizing the precipitate with ethanol and petroleum ether, and then drying the precipitate for 24 hours in a vacuum drying oven at the temperature of 60 ℃ to obtain white powdery DEPD.

Synthesis of polyurethane type P-N flame retardant of DOPO (HDEPP): adding 1.4g of DEPD into an ampoule bottle, vacuumizing and replacing with nitrogen for 3 times, and then injecting 15mL of 0.295g of hexamethylene diisocyanate and anhydrous N, N-dimethylformamide; the ampoule bottle is placed in an oil bath kettle and stirred for reaction for 4 hours at 100 ℃. And after the reaction is finished, cooling the mixture to room temperature, then pouring the reaction mixture into deionized water to precipitate a product, carrying out suction filtration on the precipitate, washing the precipitate with water and methanol, filtering, and drying the solid product in a vacuum drying oven at the temperature of 80 ℃ for 24 hours to obtain powdered HDEPD.

Preparing a flame-retardant composite material: mixing polylactic acid and the synthesized phosphorus-nitrogen flame retardant in chloroform according to different proportions, slowly pouring the mixed solution into a mold, and naturally volatilizing the solvent. And then drying in a 60 ℃ oven for 5 days in vacuum, preparing samples, testing the oxygen index (LOI) of sample strip oxygen index testers with different blending ratios, and adding polyphosphate into polylactic acid to obviously improve the LOI of the polylactic acid. The test results are shown in figure 4.

Claims

1. A P-N type flame retardant based on DOPO is characterized in that the structure is shown as 1:

。

2. the method for preparing a DOPO-based P-N type flame retardant as defined in claim 1, comprising the steps of:

carrying out reflux reaction on p-hydroxybenzaldehyde and p-phenylenediamine, cooling to room temperature, filtering, washing and drying to obtain a product, namely hydroxyl-terminated Schiff base; then, in N, N-dimethylacetamide solvent, carrying out hydroxyethylation reaction on the hydroxyl Schiff base at the temperature of 150 ℃ under the catalysis of sodium carbonate and the catalysis of 1:2 feeding mol, and carrying out water precipitation, washing and filtering, methanol washing and filtering and drying on the product to obtain the hydroxyethyl Schiff base.

3. And (2) performing addition reaction on the hydroxyethyl Schiff base and the DOPO in ethanol at the temperature of 60 ℃ according to the molar ratio of 1:2, pouring the reaction liquid into petroleum ether for precipitation after the reaction is finished, and performing suction filtration, washing and drying to obtain the hydroxyethyl DOPO derivative.

4. Performing chain extension reaction on a dihydroxyethyl DOPO derivative and hexamethylene diisocyanate in a molar ratio of 1:1 in N, N-dimethylacetamide at the temperature of 100 ℃, precipitating, filtering and drying a product, and finally synthesizing the P-N type flame retardant based on the DOPO as claimed in claim 1.