CN115246927A

CN115246927A - Graphene oxide based phosphorus-nitrogen-silicon composite flame-retardant copolyester and preparation method thereof

Info

Publication number: CN115246927A
Application number: CN202110454617.0A
Authority: CN
Inventors: 王锐; 魏丽菲; 朱志国; 梅锋; 董振峰
Original assignee: Jiangsu New Vision Advanced Functional Fiber Innovation Center Co ltd; Beijing Institute Fashion Technology
Current assignee: Jiangsu New Vision Advanced Functional Fiber Innovation Center Co ltd; Beijing Institute Fashion Technology
Priority date: 2021-04-26
Filing date: 2021-04-26
Publication date: 2022-10-28
Anticipated expiration: 2041-04-26
Also published as: CN115246927B

Abstract

The invention discloses graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester and a preparation method thereof. The raw materials for preparing the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester comprise a polyester monomer, graphene oxide, phosphazene, polyhedral oligomeric silsesquioxane and phosphonic acid, wherein the mass ratio of P in the graphene oxide and the phosphazene to Si in the polyhedral oligomeric silsesquioxane to P in the phosphonic acid is 1: (0.25 to 4): (0.05 to 3): (1-6). According to the invention, CEPPA and modified graphene oxide are simultaneously introduced into PET, so that the flame retardance, smoke suppression, anti-dripping performance and other performances of the PET can be improved.

Description

Graphene oxide based phosphorus-nitrogen-silicon composite flame-retardant copolyester and preparation method thereof

Technical Field

The invention belongs to the technical field of fabric flame-retardant materials, and particularly relates to graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester and a preparation method thereof.

Background

Polyethylene terephthalate (PET) is one of five general plastics, and has excellent mechanical property, friction resistance and dimensional stability, so that the PET is widely applied to the fields of engineering plastics, packaging, electronics, clothing and textile and the like. The PET fiber is commonly called terylene, and is a synthetic fiber which has the widest application and the largest consumption in the world at present. However, the LOI of PET is only 21%, which belongs to flammable materials, and whether it is used as engineering plastics or fiber products, there is a serious fire safety hazard during the use process, and the application of PET in traffic interior, fire protection equipment, cable lines and the like is limited. Therefore, the flame retardant research on PET and products thereof is of great importance and always occupies the research hotspot in the field of flame retardant.

Due to the remarkable large specific surface area and excellent barrier property of graphene, the potential application of graphene in the field of polymer flame retardance gradually gains more and more attention. The graphene synergistic flame retardance refers to that graphene and another or more synergistic agents are combined together and added into a matrix so as to play a greater flame retardant role or reduce the dosage of a flame retardant.

2-carboxyethyl phenyl phosphinic acid (CEPPA) and graphene oxide are copolymerized into PET together, so that the flame resistance of the PET can be obviously improved, but the CEPPA catalyzes the degradation of the PET in the early combustion stage to generally increase the smoke release amount, the increase of the smoke release amount can greatly increase the rescue difficulty, and the life safety of people is harmed.

Therefore, how to improve the performance of PET, such as smoke release, by using graphene oxide and CEPPA is an urgent problem to be solved.

Disclosure of Invention

In order to overcome the problems, the inventor researches a graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester and a preparation method thereof, wherein the graphene oxide is functionally modified by using phosphazene and polyhedral oligomeric silsesquioxane, and phosphonic acid and the modified graphene oxide are simultaneously added into PET to obtain the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester. The graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester has flame retardance, smoke suppression and anti-dripping performances, thereby completing the invention.

In order to achieve the above objects, in a first aspect, the present invention provides a graphene oxide-based phosphorus-nitrogen-silicon composite flame retardant copolyester, which is prepared from raw materials including a polyester monomer, graphene oxide, phosphazene, polyhedral oligomeric silsesquioxane and phosphonic acid, wherein

The mass ratio of P in graphene oxide and phosphazene to Si in polyhedral oligomeric silsesquioxane and P in phosphonic acid is 1: (0.25 to 4): (0.05-3): (1-6).

In a second aspect, the invention provides a preparation method of graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester, which comprises the following steps:

step 1, dispersing graphene oxide to obtain a uniform suspension;

step 2, adding phosphazene and polyhedral oligomeric silsesquioxane into the suspension for reaction;

and 3, adding phosphonic acid and a polyester monomer into the product obtained in the step 2 to react to obtain the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester.

In a third aspect, the invention provides graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester prepared by the method in the second aspect.

In a fourth aspect, the present invention provides an application of the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester prepared by the method of the first aspect or the second aspect or the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester of the third aspect in textile.

The graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester and the preparation method thereof have the beneficial effects that:

(1) According to the invention, the phosphazene and polyhedral oligomeric silsesquioxane are adopted to carry out graft modification on the graphene oxide, so that the phenomenon that the graphene oxide is agglomerated at high temperature can be improved, and the synergistic flame retardant effect can be achieved by grafting flame retardant elements on the surface of GO;

(2) According to the invention, CEPPA and modified graphene oxide are simultaneously introduced into PET, so that the flame retardance, smoke suppression, anti-dripping performance and other performances of the PET can be improved. The LOI of the prepared graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester reaches 31 percent, the UL-94V-0 grade is realized, and meanwhile, the release of heat and smoke is also obviously reduced;

(3) The preparation method of the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester is simple and convenient to operate and high in practicability.

Drawings

FIG. 1 shows FTIR and WAXD plots for experimental examples and comparative examples of the present invention;

FIG. 2 shows SEM images of experimental examples and comparative examples of the present invention;

fig. 3 shows a schematic of the smoke generation rates of the experimental example and the comparative example of the present invention.

Detailed Description

The invention is explained in more detail below with reference to the drawings and preferred embodiments. The features and advantages of the present invention will become more apparent from the description.

The polyester fiber has the defects of poor electric conduction capability, easy generation of static electricity, easy combustion and the like. The addition of Graphene Oxide (GO) into the polyester fiber can obviously increase the char formation amount of a system and delay the release of heat and smoke in the combustion process, which benefits from the shielding effect of GO, promotes char formation in a condensed phase and further delays the release of combustibles. But the flame retardant efficiency of GO which is used alone is low, the GO which does not participate in copolymerization reaction is easy to agglomerate after being reduced at high temperature, the interface bonding force with polyester fiber is reduced, the compatibility is poor, and the flame retardant and mechanical properties of the polyester fiber are influenced. Therefore, the GO is subjected to functional modification, the agglomeration of the GO can be inhibited, and the synergistic flame-retardant effect can be achieved by grafting the flame-retardant elements on the surface of the GO.

Polyhedral oligomeric silsesquioxanes, abbreviated as POSS, have the general structural formula (RSiO1.5) n, are inorganic cores composed of silicon-oxygen frameworks alternately connected by Si-O, and the groups R connected by Si atoms on the apex angles are reactive or inert groups. The three-dimensional size of POSS is 1.3nm, wherein the distance between Si atoms is 0.5nm, the distance between R groups is 1.5nm, and the POSS belongs to a nano compound. POSS is often used as an additive to be added into a polymer, so that the heat resistance, the mechanical property, the processing property and the flame retardance of the modified polymer can be effectively improved.

In a first aspect, the invention provides graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester, and raw materials for preparing the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester comprise a polyester monomer, graphene oxide, phosphazene, polyhedral oligomeric silsesquioxane and phosphonic acid, wherein the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester comprises a graphene oxide monomer, a phosphorus-nitrogen-silicon oxide monomer, a phosphorus-silicon oxide monomer, a polyhedral oligomeric silsesquioxane and phosphonic acid

The mass ratio of P in Graphene Oxide (GO), phosphazene, si in polyhedral oligomeric silsesquioxane and P in phosphonic acid is 1: (0.25-4): (0.05 to 3): (1-6).

Preferably, the mass ratio of the GO to the P in the phosphazene to the Si in the polyhedral oligomeric silsesquioxane to the P in the phosphonic acid is 1: (0.5 to 3): (0.25-3): (1.5-4).

In a preferred embodiment of the invention, the polyester monomer is selected from monomers formed by reacting a poly (terephthalic acid) with a polyol.

Further preferably, the polyester monomer is a polyethylene terephthalate (PET) monomer or a polybutylene terephthalate monomer.

More preferably, the polyester monomer is a PET monomer.

In a preferred embodiment of the present invention, the phosphazene is selected from at least one of Hexachlorocyclotriphosphazene (HCCP), ethoxy-pentafluoro-cyclotriphosphazene, phenoxypolyphosphazene and hexaphenylcyclotriphosphazene. More preferably, the phosphazene is Hexachlorocyclotriphosphazene (HCCP).

HCCP is a typical hexaatomic ring formed by connecting phosphorus and nitrogen atoms alternately by single bonds and double bonds, and the high-phosphorus and high-nitrogen structure enables HCCP to play a role in both gas phase and condensed phase, thereby endowing HCCP with great flame-retardant potential. Meanwhile, chlorine atoms on the six-membered ring are easily substituted by alcohols, phenols and amines, so that the chemical stability and the thermal stability of the HCCP are enhanced.

Therefore, the invention introduces HCCP on the GO surface by adopting a covalent bond grafting method.

In a preferred embodiment of the present invention, the polyhedral oligomeric silsesquioxanes contain at least one reactive functional group,

preferably, the polyhedral oligomeric silsesquioxane is an aminopropyl butyl polyhedral oligomeric silsesquioxane (NH) ₂ -POSS), methacryloxy polyhedral oligomeric silsesquioxane and at least one of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-polyhedral oligomeric silsesquioxane (DOPO-POSS). Wherein NH ₂ POSS from hybrid plastics; DOPO-POSS was purchased from flame retardant technology, inc., of Beijing institute of technology.

NH ₂ -POSS having the formula:

wherein NH ₂ POSS is a typical organic-inorganic hybrid material with a three-dimensional spatial structure, the interior of the POSS is a cage-shaped inorganic framework consisting of Si and O, seven outer Si atoms are connected with isobutyl groups, the other Si atom is connected with aminopropyl, and active amino groups enable NH ₂ POSS can react with hydroxyl, carboxyl and other groups. In addition, the inorganic frame structure of the polyhedron ensures NH ₂ Heat resistance of POSS, NH after a temperature exceeding the POSS limit temperature ₂ The cage structure of POSS is transformed into a net structure and decomposed into SiO ₂ And a dense oxide film is formed.

More preferably, the present invention employs HCCP and NH ₂ Grafting of GO with POSSModified so that HCCP and NH are ₂ POSS are all covalently grafted on the GO sheet surface.

The structural formula of the polyhedral oligomeric silsesquioxane is as follows:

wherein, when R is CH ₂ ＝C(CH ₃ )COOCH ₂ CH ₂ CH ₂ When the compound is used, the compound is marked as methacryloxy polyhedral oligomeric silsesquioxane; or when R is

When it is stated as 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-polyhedral oligomeric silsesquioxane (DOPO-POSS).

The POSS flame retardant mechanism is mainly that the decomposition of the organic part of POSS consumes a part of heat, so that the decomposition speed of the polymer material is reduced; the POSS combustion process consumes oxygen and produces gases that do not have combustion properties (e.g., N) ₂ 、NH ₃ Etc.), can play the role of diluting combustible organic gas, thus reduce the intensity of burning of the high molecular material; after combustion of POSS, silicon oxide (SiO) is formed ₂ ) The combustible gas is deposited on the surface of the polymer which is not burnt yet, and a part of the combustible gas forms a protective layer, so that the combustible gas has the effects of slowing down heat transfer, inhibiting the volatilization of the combustible gas and preventing the combustible gas and oxygen from being mixed to a certain extent; POSS can gradually migrate to the surface of the polymer melt to form a barrier layer with high thermal stability, so that the POSS plays a role in inhibiting heat and mass transfer to a certain extent.

In a preferred embodiment of the present invention, the phosphonic acid is selected from at least one of tetraphenyl (bisphenol-a) diphosphate, tetraphenylresorcinol diphosphate, and 2-carboxyethylphenylphosphinic acid (CEPPA). More preferably, the phosphonic acid is 2-carboxyethylphenylphosphinic acid (CEPPA).

The flame retardant mechanism of phosphonic acid is: (1) Forming phosphoric acid as dehydrating agent and promoting toChar, the formation of which reduces heat transfer from the flame to the condensed phase; (2) Phosphoric acid absorbs heat and prevents oxidation of CO to CO ₂ Reducing the heating process; (3) A thin glassy or liquid protective layer is formed on the condensed phase, so that oxygen diffusion and heat and mass transfer between a gas phase and a solid phase are reduced, a carbon oxidation process is inhibited, and thermal decomposition of the phosphorus-nitrogen-silicon composite flame retardant is reduced. The phosphonic acid combustion was changed as follows: phosphorus flame retardant → metaphosphoric acid → phosphoric acid → polymetaphosphoric acid, which is a stable compound not easy to volatilize, has strong dehydration property, and is isolated from air on the surface of the polymer; the removed water vapor absorbs a large amount of heat, so that the flame retardant on the surface of the polymer is heated and decomposed to release volatile phosphide, and mass spectrometry shows that the concentration of hydrogen atoms is greatly reduced, which shows that PO & captures H & gt, namely PO & lt + H & gt = HPO.

According to the invention, the graphene oxide phosphorus-nitrogen-silicon composite flame-retardant copolyester comprises N, P and Si elements which are flame-retardant elements and have a synergistic effect on flame retardance and smoke suppression.

In a second aspect, the present invention provides a method for preparing graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester, preferably a method for preparing graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester of the first aspect of the present invention, the method comprising the following steps:

step 1, dispersing GO to obtain a uniform suspension.

In a preferred embodiment of the present invention, in step 1: GO was dispersed in Tetrahydrofuran (THF), acetonitrile, acetone or N, N-Dimethylformamide (DMF).

In order to make the GO dispersed more uniformly, the GO is dissolved in THF, and after fully stirring, ultrasonic dispersion is carried out. Illustratively, the stirring may be selected from oscillatory stirring or magnetic stirring. Preferably, the dispersion mode adopts ultrasonic dispersion, and the dispersion time is 0.5-5 h. More preferably, the ultrasonic dispersion is carried out for 1 to 3 hours, for example 2 hours.

In order to obtain a stable suspension according to the present invention, preferably, step 1 further comprises adding Triethylamine (TEA) to the suspension and standing. The purpose of the addition of triethylamine is to create a basic environment in which nucleophilic substitution can occur.

Preferably, the temperature of the standing is-10 to 10 ℃, and the standing time is 0.5 to 5 hours. More preferably, the temperature is-5 to 5 ℃ and the mixture is left to stand for 1 to 3 hours, for example, the temperature is 0 to 4 ℃ in an ice water bath and the mixture is left to stand for 1 hour.

And 2, adding the phosphazene and the polyhedral oligomeric silsesquioxane into the suspension for reaction.

In order to accelerate the reaction process, in a preferred embodiment of the present invention, step 2 comprises:

and 2-1, adding phosphazene or phosphazene solution into the suspension for staged reaction to obtain the graphene oxide-based phosphorus-nitrogen composite flame retardant (HGO).

Preferably, the reaction temperature of the first stage is-10 ℃, and the reaction time is 1-5 h. More preferably, the first stage reaction temperature is-5 to 5 ℃ and the reaction is carried out for 2 to 3 hours, for example, an ice water bath at 0 to 4 ℃ and the reaction is carried out for 2 hours. And/or

The reaction temperature of the second stage is 30-80 ℃, and the reaction time is 1-6 h. More preferably, the reaction temperature in the second stage is 50-70 ℃ and the reaction is carried out for 2-4 h, for example, the reaction temperature is 60 ℃ and the reaction is carried out for 3h.

In order to exclude oxygen from the system, it is preferable to carry out the reaction under a nitrogen or argon atmosphere.

Illustratively, the HCCP-THF solution was slowly added dropwise to the mixed solution of step 1, wherein the dropwise addition time and the first-stage reaction time were kept consistent. Then, the first-stage reaction is carried out under the protection of nitrogen, the temperature is increased to 60 ℃ after the first-stage reaction time is reached, and the reflux reaction is carried out for 3 hours.

According to the invention, in step 2-1, after the reaction is finished, washing and drying are carried out, wherein solvents used for washing are THF and absolute ethyl alcohol for multiple times, and THF is preferably used for multiple centrifugal washing, and then absolute ethyl alcohol is used for multiple centrifugal washing.

According to the invention, in the step 2-1, drying is carried out after washing, wherein the drying is vacuum drying, the drying temperature is 30-90 ℃, and the drying time is 5-15 h. More preferably, the drying temperature is 50 to 70 ℃ and the drying time is 8 to 13 hours. For example, drying at 60 deg.C for 12h.

In the invention, the grafting amount on the GO sheet layer is gradually increased along with the increase of the addition amount of HCCP, however, when the addition amount of HCCP reaches a certain proper range, the addition amount of HCCP is continuously increased, the grafting amount on the GO surface is not changed greatly, and most of hydroxyl groups on the GO surface are replaced.

And 2-2, adding polyhedral oligomeric silsesquioxane or polyhedral oligomeric silsesquioxane solution into the dispersion liquid of the HGO to obtain the graphene oxide-based phosphorus-nitrogen-silicon composite flame retardant (HPGO).

Preferably, the polyhedral oligomeric silsesquioxane solution is dropwise added into the dispersion liquid dissolved with the HGO to carry out a staged reaction to obtain the HPGO.

More preferably, step 2-2 may comprise:

step 2-2-1, HGO was dispersed in THF, acetonitrile, acetone or DMF.

Illustratively, step 2-2-1 further comprises adding TEA dropwise.

And 2-2-2, dropwise adding the polyhedral oligomeric silsesquioxane solution into the mixed solution obtained in the step 2-2-1 to perform a staged reaction to obtain the HPGO.

Preferably, the reaction temperature of the third stage is 40-80 ℃ and the reaction time is 1-10 h. More preferably, the reaction temperature of the third stage is 50-70 ℃, and the reaction time is 2-8 h; for example, the reaction temperature is 60 ℃, and the reaction time is 6h. And/or

The reaction temperature of the fourth stage is 5-40 ℃, and the reaction time is 5-15 h. More preferably, the reaction temperature in the fourth stage is 15 to 30 ℃ and the reaction time is 8 to 12 hours, for example, the reaction temperature is 25 ℃ and the reaction time is 10 hours.

Preferably, when the reaction time of the third stage reaches a preset time, deionized water with a preset mass is dripped.

It should be noted that the present invention does not specifically limit the specific values of the preset time and the preset mass, and those skilled in the art can select the values according to the actual reaction conditions, for example, the preset time is 2 or 3h, that is, when the reaction time of the third stage reaches 2 or 3h, deionized water is added.

Illustratively, the HGO obtained in step 2-1 was dispersed in THF, TEA was added, and the three systems were mixedAfter homogenizing, slowly adding NH dropwise ₂ POSS-THF solutions, the dropping time being controlled within 0.5-2 h, for example 1h. And (3) carrying out reflux reaction at 60 ℃ for 3h, then dropwise adding deionized water with preset mass, continuing the reaction for 3h, then reducing the temperature to 25 ℃, and continuing the reaction for 10h.

According to the invention, in step 2-2, after the reaction is finished, washing and drying are carried out, wherein solvents used for washing are THF and absolute ethyl alcohol for multiple times, and THF is preferably used for centrifugal washing for multiple times and then absolute ethyl alcohol is used for centrifugal washing for multiple times.

According to the invention, in the step 2-2, drying is carried out after washing, wherein the drying is vacuum drying, the drying temperature is 30-90 ℃, and the drying time is 5-15 h. More preferably, the drying temperature is 50 to 70 ℃ and the drying time is 8 to 13 hours. For example, drying at 60 deg.C for 12h.

In the present invention, NH is accompanied by ₂ Increasing the amount of POSS added, the grafting amount on GO sheet also increases gradually, when NH ₂ -when POSS addition reaches a certain suitable range, continue to increase NH ₂ POSS addition amount and small change of grafting amount of GO surface indicate that carboxyl groups on the GO surface are replaced.

According to the invention, the phosphazene and the polyhedral oligomeric silsesquioxane are adopted to graft and modify the graphene oxide, so that the phenomenon that the graphene oxide is agglomerated at high temperature can be improved, and the synergistic flame retardant effect can be achieved by grafting flame retardant elements on the surface of GO.

In a preferred embodiment of the present invention, HGO or HPGO is dispersed in Ethylene Glycol (EG), and ultrasonically dispersed for 1-6 h under stirring.

In a preferred embodiment of the present invention, step 3 comprises:

step 3-1, mixing the product obtained in the step 2, phosphonic acid, terephthalic acid (PTA), ethylene Glycol (EG) and a catalyst for reaction;

concretely, the product obtained in the step 2, phosphonic acid, terephthalic acid (PTA) and ethylene glycolAlcohol (EG) and catalyst Sb ₂ O ₃ Placing in a 1L polymerization kettle for fully pulping. After the completion of the beating, 150KPa nitrogen gas was charged into the polymerization vessel and heated. The internal pressure of the kettle is controlled to be 280-320 KPa. The esterification reaction is continuously carried out along with the rise of the temperature in the kettle, the water generated by the reaction flows towards the top of the tower, the temperature of the top of the tower is also continuously raised, and the water is discharged by controlling the pressure when the temperature of the top of the tower reaches about 140 ℃. And when the water yield reaches 95 percent of the theoretical water yield or no excessive water flows out, the esterification reaction stage is finished.

Step 3-2, adding an antioxidant, an anti-hydrolysis agent and a predetermined amount of ethylene glycol into the reaction system in the step 3-1 under normal pressure, and then reacting;

specifically, the temperature at the top of the tower is reduced to be below 100 ℃, the pressure in the kettle is reduced to be normal pressure, and the temperature in the kettle is more than 250 ℃. Then, respectively adding an antioxidant (such as triphenyl phosphite), an anti-hydrolysis agent (such as 1010) and a proper amount of EG into the reaction kettle, and reacting for 20-50 min, for example 30min, at normal pressure.

And 3-3, vacuumizing and continuing to react until the viscosity of the polyester monomer reaches a preset value, and stopping the reaction.

Specifically, the temperature in the autoclave was raised to about 270 ℃ and vacuum was applied, so that the pressure in the autoclave was reduced to 50Pa or less. Controlling the temperature in the kettle to be about 275 ℃, reacting for 2-3 h, stopping the reaction when the stirring power reaches a certain specific value, namely the viscosity of the PET reaches a preset viscosity value, and finishing the polycondensation reaction.

After step 3-3, post-processing is also included.

The post-treatment process comprises the following steps: reducing the pressure in the kettle to normal pressure, then continuously introducing nitrogen to pressurize, extruding the melt under the pressure of the nitrogen, cooling the melt by cold water to form strips, drying the moisture on the surfaces of the sample strips, and cutting the strips into polyester chips with the diameter of 2-3 mm by a granulator.

In the prior art, because the molecules of the polyester fiber material only contain ester groups with very small polarity, macromolecular chains are easy to break under the action of strong acid or strong alkali, but the molecules of the polyester fiber material are tightly piled and have high crystallinity and orientation degree, so that the polyester fiber material is difficult to react with chemical reagents such as acid and alkali, and the like, and the modification difficulty is increased.

Depending on the combustion process of PET, its flame-retardant properties can be improved by corresponding measures. For example, (1) adding a free radical inhibitor into PET to weaken combustion in a gas phase and delay degradation of PET; (2) The carbonization is promoted in the condensed phase, the volatilization of inflammable substances is reduced, and the isolation effect of the gas phase and the condensed phase is enhanced; (3) The PET is added with additives with shielding effect, so that the transmission of heat and oxygen is reduced, and the spread of combustion is inhibited.

Based on the structure and performance of polyester and the flame retardant mechanism of the flame retardant, HGO and HPGO are selected as a shielding agent and a smoke suppressant, CEPPA is selected as a char forming agent and a free radical inhibitor, and the obtained product is polymerized in situ into PET to obtain the graphene oxide-based phosphorus-nitrogen-silicon composite flame retardant copolyester.

According to the invention, after CEPPA is introduced into the main chain of the polyester fiber, the LOI and UL-94 combustion grades of the polyester fiber are greatly improved, and the polyester fiber is endowed with excellent flame resistance and anti-dripping performance.

After CEPPA and HPGO are simultaneously introduced into the polyester fiber, the performances of flame retardance, smoke suppression, molten drop resistance and the like can be improved. The LOI of the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester reaches 31 percent, the UL-94V-0 grade is realized, and meanwhile, the release of heat and smoke volume is also obviously reduced, which shows that the graphene-based nitrogen-phosphorus-silicon integrated composite flame retardant can effectively improve the flame retardance of polyester fibers and improve the fire safety.

According to the invention, under the premise of fixing the amounts of HCCP and CEPPA, the total heat release and total smoke release of the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester are accompanied by NH ₂ Increase and decrease in POSS addition. However when NH is present ₂ When the adding amount of POSS reaches a certain proper range, namely when most of carboxyl on the GO surface is replaced, following NH ₂ The POSS addition continued to increase with insignificant changes in total heat release and total smoke release.

According to the invention, HCCP and NH are fixed ₂ On the premise of POSS (polyhedral oligomeric silsesquioxane) content, the total smoke release of the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester is increased along with the increase of the addition amount of CEPPA (chlorinated polyethylene-co-propylene-amine)And decreases.

In a third aspect, the invention provides graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester prepared by the method in the third aspect.

For further understanding of the present invention, the graphene oxide-based phosphorus-nitrogen-silicon composite flame retardant copolyester provided by the present invention is described below with reference to the following examples, and the scope of the present invention is not limited by the following examples.

Examples

Example 1

Step 1, dissolving 1.4g of GO in 800mL of THF, fully stirring, performing ultrasonic dispersion for 2 hours to obtain a uniform suspension, dropwise adding 15.12g of TEA, and placing the suspension in an ice-water bath at 0-4 ℃ for 1 hour;

and step 2-1, slowly dripping 9g of HCCP-50mL of THF solution into the solution for 2 hours under the protection of nitrogen, and reacting for 2 hours. Raising the temperature to 60 ℃, and carrying out reflux reaction for 3 hours;

after the reaction is finished, repeatedly using THF and ethanol, separating and washing the THF and the ethanol by a centrifuge, and drying the THF and the ethanol at 60 ℃ in vacuum for 12 hours to obtain brown solid powder which is marked as HGO;

step 2-2, dispersing the HGO obtained in the step 2-1 in 500mL of THF, and adding 9.45g of TEA;

2.8g of NH were slowly added dropwise ₂ POSS-50mL THF solution, the dropping time is controlled within 1h. Carrying out reflux reaction at 60 ℃ for 3h, dropwise adding 0.4g of deionized water, continuously reacting for 3h, reducing the temperature to 25 ℃, and continuously reacting for 10h;

after the reaction is finished, THF and ethanol are used for separation and washing through a centrifuge, and vacuum drying is carried out for 12 hours at the temperature of 60 ℃ to obtain brown solid powder which is marked as HPGO;

step 3, dispersing 3.5g of HPGO in 300mL of EG, fully stirring, and performing ultrasonic dispersion for 2 hours to obtain HPGO-EG dispersion liquid;

adding 350g of PTA and 5.5g of CEPPA into the HPGO-EG dispersion liquid, soaking for 20min, taking out, washing and drying to obtain FRPET-HPGO.

Comparative example 1

PET was used as the sample of comparative example 1.

Comparative example 2

Preparation was carried out analogously to example 1, with the only difference that NH ₂ The amount of POSS varied and the product obtained was designated FRPET-HPGO-1-3, see Table 1. The mass percentages and element mass percentages in table 1 are relative percentages of 350g terephthalic acid (PTA).

TABLE 1 raw material ratio of graphene-based phosphorus-nitrogen-silicon composite flame-retardant copolyester

Comparative example 3

A similar procedure was followed as in example 1, except that,

in the step 3, dispersing 2.8g of HGO in 300mL of EG, fully stirring, and performing ultrasonic dispersion for 2 hours to obtain HGO-EG dispersion liquid;

adding 350g PTA and 5.5g CEPPA into HGO-EG dispersion, soaking for 20min, taking out, washing and drying to obtain FRPET-HGO.

Comparative example 4

A similar procedure to example 1 was followed, except that 350g of PTA was added to the HPGO-EG dispersion to give PET-HPGO.

Examples of the experiments

Experimental example 1

In order to explore the structure of GO after covalent modification, infrared spectroscopy (FTIR) and wide-angle X-ray diffraction spectroscopy (WAXD) tests were performed on GO, HGO and HPGO respectively, and the results are shown in FIG. 1. FIG. 1 a) is an FTIR plot of GO, HGO and HPGO; FIG. 1 b) WAXD graph for GO, HGO and HPGO.

As can be seen from figure 1 a) it is shown that,

(1-1)3312cm ^-1 、1724cm ^-1 、1621cm ^-1 、1263cm ^-1 and 1063cm ^-1 Absorption peaks at are respectively corresponding to GO sheetsAnd (3) stretching vibration absorption peaks of O-H, C = O, C = C, C-O-C and C-O on the surface of the layer. After the grafting reaction with HCCP is carried out, the peak intensities of C = O and C = C in HGO are obviously reduced, which indicates that GO is subjected to a reduction reaction in the grafting process of HCCP. At 1180, 873 and 1032cm simultaneously ^-1 Three new infrared absorption peaks of P-N, P = N and P-O-C appear, and therefore, HCCP is grafted on the GO surface in a chemical bond mode.

(1-2) with NH ₂ After the POSS reaction, the peak intensities of C = O and C = C in HPGO were further reduced. In addition to several absorption peaks identical to HGO, at 2955 and 1485cm ^-1 The appearance of significant-CH ₂ Absorption peaks of stretching and bending vibrations, indicating the presence of methylene groups in HPGO, at 1109 and 1410cm ^-1 The absorption peaks at the positions correspond to the absorption peak of the Si-O asymmetric stretching vibration and the absorption peak of the Si-C bending vibration respectively. Thus, it is known that NH ₂ POSS was also successfully covalently grafted on the surface of GO.

As can be seen from figure 1 b),

and (2-1) the characteristic peak of the GO (002) crystal face is at 11 degrees, and the corresponding interlayer spacing is 0.8nm according to the calculation of a Bragg equation. After GO is grafted and modified by HCCP, the 2 theta angle of the characteristic peak of (002) crystal face is shifted to 9.9 degrees, and the interlayer spacing is increased to 0.99nm. The HCCP is subjected to nucleophilic substitution reaction on the surface of GO so that the HCCP is intercalated and grafted on the surface of GO, and the intercalation destroys the stacking structure among the lamellar layers, thereby increasing the lamellar spacing.

(2-2) with NH ₂ The further functionalization of POSS (polyhedral oligomeric silsesquioxane), the 2 theta angle of the characteristic peak of (002) crystal face is smaller and smaller, and the GO lamella spacing is larger and larger, which shows that with NH ₂ POSS was also successfully intercalated between GO sheets. Where 12.1 ° and 19 ° correspond to the (120) and (113) crystal planes of the HPGO crystal, respectively.

Experimental example 2

Morphology analysis was performed on the sample of comparative example 1 and the sample of the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester obtained in examples 3 to 4, and the obtained SEM result is shown in FIG. 2, wherein the unit scale is 10 μm.

As can be seen from FIG. 2, the surface of PET is smooth and the cross-section is clear and free of particles. After GO is added, the poly-GO aggregates appear on the brittle fracture surface of PET-GO, because the oxygen-containing functional groups on the surface of GO are reduced under the high-temperature condition, the Van der Waals force between GO sheet layers is enhanced, and except the GO which is subjected to copolymerization reaction with PET, the GO dispersed in the matrix is re-aggregated.

It can be seen by comparison of PET-HPGO that the dispersion of HPGO in the PET matrix is improved due to HCCP and NH ₂ The grafting reaction of POSS on GO sheets expands the interlayer spacing of GO, causing weakening of the inter-sheet van der waals forces. Comparing the sectional views of FRPET-HGO and FRPET-HPGO, the dispersibility of HGO or HPGO in FRPET can be further improved.

Experimental example 3

The samples of comparative examples 1-4 and the graphene oxide based phosphorus-nitrogen-silicon composite flame retardant copolyester sample obtained in example 1 were subjected to flame retardant performance analysis, and the obtained results are shown in tables 2-6.

(1) Different amount of NH ₂ The Limiting Oxygen Index (LOI) and the vertical burn test results (UL-94) of the POSS grafted FRPET-HPGO are shown in Table 2.

TABLE 2 LOI and UL-94 for FRPET-HPGO

As can be seen from table 2, it is,

(1-1) compared with FRPET-HGO, the LOI value of FRPET-HPGO is reduced to a certain extent after silicon element is added into the system. The addition of silicon extends the burning time of the flame above the splines, causing heat to be transferred to the underside of the splines, rather than being carried away in the form of molten droplets. The radical scavenger released by degrading CEPPA in FRPET-HPGO in advance can quench the radical reaction of inflammable micromolecules in gas phase, so the LOI of FRPET-HPGO is still kept above 30% and is a flame-retardant material.

(1-2) the after flame time after the FRPET-HPGO is out of fire is prolonged compared to that of FRPET-HGO due to NH ₂ The POSS forms a network structure to coat the molten drops, and the gaseous flame retardant effect of the CEPPA ensures that the molten drops can completely inhibit combustibility and do not ignite when the molten drops carry away heatAbsorbent cotton under the sample bar, UL-94, still maintained the V-0 rating. The FRPET-HPGO is self-extinguished after being separated from fire and drops flameless molten drops in a real fire, so that the hazard of the fire can be greatly reduced, and the spread of the fire is inhibited.

(1-3) with NH ₂ The increase in POSS grafting, the variation of LOI values with UL-94 rating is not significant, due to the limited copolymerization of HPGO of large size in PET compared to CEPPA, most of which is dispersed in the PET matrix in doped form. At the processing temperature of PET, HPGO which does not participate in copolymerization reaction can be thermally degraded, thereby weakening NH ₂ Effect of POSS grafting amount on PET properties.

(2) Different amount of NH ₂ Cone calorimetry analysis of-POSS grafted FRPET-HPGO with analytical results shown in tables 3-5.

TABLE 3 time parameters for FRPET-HPGO

As can be seen from Table 3, the addition of silicon has a small effect on the ignition time (TTI), but causes a decrease in the Peak Heat Release Rate (PHRR) time (t-PHRR), the peak effective heat of combustion time (t-PEHC), and the peak smoke generation rate time (t-PSPR). This is due to NH ₂ The grafting reaction of POSS further destroys the integrity of GO layers, GO defects are increased, the shielding effect on combustible gas and heat is weakened, combustible fragments released by FRPET-HPGO in the thermal degradation period can be diffused into gas phase more quickly, and once ignited by electric spark, the combustible fragments gathered on the surface of the material can be combusted quickly, so that the peak values of heat release rate and smoke release rate are achieved.

TABLE 4 Heat parameters of FRPET-HPGO

As can be seen from Table 4, the GO surface is grafted with a certain amount of NH ₂ After POSS, not only will lead to advance of heat release, but also will increaseAnd (4) heat release amount. Compared with PET, FRPET-HPGO has obviously reduced heat release and improved fire safety. However, the Peak Heat Release Rate (PHRR), total Heat Released (THR), and average available heat of combustion (av-EHC) were increased by 9.5%, 18.9%, and 4.3%, respectively, for FRPET-HPGO compared to FRPET-HGO. The defects of GO lamella accelerate mass and heat transfer of gas phase and condensed phase, and promote the degradation of PET internal material. More combustible fragments in the FRPET-HPGO diffuse into the gas phase than in the FRPET-HGO, whereas the radical scavenger released by CEPPA is constant, thus leading to an increase in the rate and total amount of heat released.

TABLE 5 Smoke parameters for FRPET-HPGO

As can be seen from Table 5, the smoke generation rate peak (PSPR) of FRPET-HGO is from 0.308m of PET ² Increase of/S to 0.390m ² S, which is associated with CEPPA catalytic degradation and incomplete combustion in the gas phase. It is obvious that with the addition of HPGO, the PSPR of FRPET-HPGO is obviously reduced, compared with the PSPR of FRPET-HGO, the PSPR of FRPET-HPGO-1, FRPET-HPGO-2 and FRPET-HPGO-3 are respectively reduced by 40.77%, 45.13%, 53.33% and 51.79%, which shows that NH is added ₂ The introduction of POSS has obvious inhibiting effect on the release of smoke.

FIG. 3 is a graph showing a smoke generation rate curve for FRPET-HPGO. As can be seen in FIG. 3, the smoke generation rate (SPR) curve for FRPET-HPGO shows two peaks, the first of which occurs earlier than PET. This is because the premature decomposition of CEPPA promotes the degradation of PET in the early stages of combustion, which in turn produces a large number of fragments dispersed in the gas phase, rapidly forming the first PSPR peak. The catalytic degradation of CEPPA also promotes the formation of a carbon layer in the condensed phase, with NH ₂ The heated silicon-containing network structure of POSS locks the fragments in the condensed phase to form a carbon layer, which retards the heat transfer and delays the continued degradation of the internal substrate, resulting in a reduced PSPR. With the accumulation of heat under the carbon layer, when reaching a certain energy, the flame breaks through the carbon layer and is generated againThe large amount of heat causes the degradation of the PET internal substrate to be exacerbated, forming new PSPR peaks. In the later combustion period, the gradient of the SPR curve of the RPET-HPGO is obviously slowed down, and the smoke release rate is reduced, which is caused by that a more continuous and compact carbon layer is formed in the later combustion period, and the isolation effect is enhanced. From the whole combustion process, the HPGO has an obvious inhibiting effect on the smoke release amount of the RPET, and the increase of the smoke release amount caused by the addition of the CEPPA can be completely offset. Especially NH ₂ When POSS is added in an amount of 0.2wt% based on the silicon content, the TSP of the RPET-HPGO is 23.74m of that of the RPET-HGO ² Reduced to 17.21m ² And the reduction is 27.51%.

(3) Different amount of NH ₂ Other analyses of the POSS grafted FRPET-HPGO, the results of which are shown in Table 6.

TABLE 6 other parameters of FRPET-HPGO

As can be seen from Table 6, the Flame Growth Index (FGI) of FRPET-HPGO decreased while the Fire Performance Index (FPI) increased, indicating an increased safety profile for fire. However, FRPET-HPGO shows a tendency of increased FGI and decreased FPI compared with FRPET-HGO. The increase in FGI indicates that FRPET-HPGO is able to reach the peak heat release rate quickly due to the reduced shielding effect of HPGO early in combustion. FPI is characterized by the ratio of TTI to PHRR, and from the time parameters, HPGO has little effect on TTI, but PHRR value is increased, so FPI is reduced.

Meanwhile, the shielding effect and char formation effect of FRPET-HPGO are increased compared to FRPET-HGO. The shielding effect of FRPET-HPGO is increased from 2.64% to 10.38%, and the char formation effect is also increased from 9.81% to 24.55%. This is due to the NH in the HPGO from the overall combustion process perspective ₂ POSS can fix more fragments generated by the decomposition of PET in condensed phase, so that the strength and compactness of the carbon layer are enhanced, and the shielding effect and the carbon forming effect are enhanced.

The invention has been described in detail with reference to the preferred embodiments and illustrative examples. It should be noted, however, that these specific embodiments are only illustrative of the present invention and do not limit the scope of the present invention in any way. Various modifications, equivalent substitutions and alterations can be made to the technical content and embodiments of the present invention without departing from the spirit and scope of the present invention, and these are within the scope of the present invention. The scope of the invention is defined by the appended claims.

Claims

1. The graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester is characterized in that raw materials for preparing the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester comprise a polyester monomer, graphene oxide, phosphazene, polyhedral oligomeric silsesquioxane and phosphonic acid, wherein the raw materials comprise the following components

The mass ratio of P in graphene oxide and phosphazene to Si in polyhedral oligomeric silsesquioxane and P in phosphonic acid is 1: (0.25 to 4): (0.05 to 3): (1-6).

2. The phosphorus-nitrogen-silicon composite flame-retardant copolyester of graphite oxide according to claim 1,

the phosphazene is selected from at least one of hexachlorocyclotriphosphazene, ethoxy-pentafluoro-cyclotriphosphazene, phenoxypolyphosphazene and hexaphenylcyclotriphosphazene.

3. The graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester according to claim 1,

the polyhedral oligomeric silsesquioxanes contain at least one reactive functional group,

preferably, the polyhedral oligomeric silsesquioxane is at least one of an aminopropyl butyl polyhedral oligomeric silsesquioxane, a methacryloxy polyhedral oligomeric silsesquioxane and a 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide polyhedral oligomeric silsesquioxane.

4. The graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester according to claim 1,

the phosphonic acid is selected from at least one of tetraphenyl (bisphenol-A) diphosphate, tetraphenylresorcinol diphosphate, and 2-carboxyethylphenylphosphinic acid.

5. A preparation method of graphene oxide based phosphorus-nitrogen-silicon composite flame-retardant copolyester is characterized by comprising the following steps:

step 1, dispersing graphene oxide to obtain a uniform suspension;

6. The method according to claim 5,

in the step 1: the dispersion mode adopts ultrasonic dispersion, and the dispersion time is 0.5-5 h;

preferably, step 1 further comprises adding triethylamine to the suspension, standing,

more preferably, the temperature during the standing is-10 to 10 ℃, and the standing time is 0.5 to 5 hours.

7. The method according to claim 5, wherein the step 2 comprises:

step 2-1, adding phosphazene into the suspension to perform staged reaction;

preferably, the reaction temperature of the first stage is-10 to 10 ℃, and the reaction time is 1 to 5 hours; and/or

The reaction temperature of the second stage is 30-80 ℃, the reaction time is 1-6 h,

step 2-2, adding polyhedral oligomeric silsesquioxane into the solution of the product obtained in the step 2-1, and carrying out a staged reaction;

preferably, the reaction temperature of the third stage is 40-80 ℃, and the reaction time is 1-10 h; and/or

The reaction temperature of the fourth stage is 5-40 ℃, and the reaction time is 5-15 h;

8. The method according to claim 5, wherein the step 3 comprises:

step 3-1, mixing the product obtained in the step 2, phosphonic acid, terephthalic acid, ethylene glycol and a catalyst for reaction;

step 3-2, adding an antioxidant, an anti-hydrolysis agent and ethylene glycol into the reaction system in the step 3-1 under normal pressure, and then carrying out reaction;

9. The graphene-based phosphorus-nitrogen-silicon composite flame-retardant copolyester obtained by the preparation method according to any one of claims 5 to 8.

10. Use of the graphene oxide-based phosphorus-nitrogen-silicon composite flame retardant copolyester of any one of claims 1 to 4 or prepared according to the method of any one of claims 5 to 8 or the graphene oxide-based phosphorus-nitrogen-silicon composite flame retardant copolyester of claim 9 in textile.