CN115246927B

CN115246927B - Graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester and preparation method thereof

Info

Publication number: CN115246927B
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: 2023-11-14
Anticipated expiration: 2041-04-26
Also published as: CN115246927A

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-phosphorus-nitrogen-silicon composite flame-retardant copolyester comprise polyester monomer, graphene oxide, phosphazene, polyhedral oligomeric silsesquioxane and phosphonic acid, wherein the mass ratio of the graphene oxide to P in the phosphazene to Si in the polyhedral oligomeric silsesquioxane to P in the phosphonic acid is 1: (0.25-4): (0.05-3): (1-6). According to the invention, CEPPA and modified graphene oxide are simultaneously introduced into PET, so that the PET flame retardance, smoke suppression, anti-dripping performance and the like 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 properties, abrasion resistance and dimensional stability, so that the PET is widely applied to the fields of engineering plastics, packaging, electrical and electronic appliances, clothing textile and the like. PET fiber is commonly called polyester fiber, and is the synthetic fiber with the most wide application and the greatest consumption in the world at present. However, PET has an LOI of only 21% and is a flammable material, and whether it is an engineering plastic or a fiber product, there is a serious fire safety hazard during use, and its application in traffic interiors, fire protection equipment, cables, and the like is limited. Therefore, the flame retardant has a crucial meaning for the flame retardant research of PET and products thereof, and the flame retardant research is also in the focus of the flame retardant field.

The significant large specific surface area and excellent barrier properties of graphene have led to increasing attention in their potential application in the field of polymer flame retardance. The synergistic flame retardance of graphene means that graphene and another or more synergistic agents are combined together and added into a matrix so as to exert a larger flame retardance effect or reduce the consumption of the flame retardant.

The co-copolymerization of 2-carboxyethyl phenyl phosphinic acid (CEPPA) and graphene oxide into PET can obviously improve the flame resistance of PET, but CEPPA catalyzes the degradation of PET in the early stage of combustion, so that the smoke release amount is increased, the rescue difficulty is greatly increased, and the life safety of people is endangered.

Therefore, how to improve the performance of PET such as smoke release by using graphene oxide and cepa is a highly desirable problem.

Disclosure of Invention

In order to overcome the problems, the inventor researches out a graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester and a preparation method thereof, wherein phosphazene and polyhedral oligomeric silsesquioxane are utilized to carry out functional modification on graphene oxide, and phosphonic acid and 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 the performances of flame retardance, smoke suppression and molten drop resistance, so that the invention is completed.

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

The mass ratio of the graphene oxide to the P in the phosphazene to the Si in the polyhedral oligomeric silsesquioxane to the P in the phosphonic acid is 1: (0.25-4): (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 suspension for reaction;

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

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

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

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 of aggregation of the graphene oxide at high temperature can be improved, and a 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 PET flame retardance, smoke suppression, anti-dripping performance and the like can be improved. The LOI of the prepared graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester reaches 31%, the UL-94V-0 grade is realized, and simultaneously, the release of heat and smoke is 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 patterns of experimental 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 diagram of smoke generation rates of experimental examples and comparative examples of the present invention.

Detailed Description

The invention is described in further detail below with reference to the drawings and the 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 conductivity, easiness in generating static electricity, easiness in burning and the like. The addition of Graphene Oxide (GO) in the polyester fiber can obviously increase the char formation amount of the system and delay the release of heat and smoke in the combustion process, which benefits from the shielding effect of GO, promotes the char formation in the coacervate phase and further delays the release of inflammables. However, the flame retardant efficiency of the GO used alone is lower, the GO which does not participate in the copolymerization reaction is easily agglomerated after being reduced at high temperature, the interfacial binding force with the polyester fiber is reduced, the compatibility is poor, and the flame retardant and mechanical properties of the polyester fiber are affected. Therefore, the GO is functionally modified, so that aggregation of the GO can be inhibited, and a synergistic flame-retardant effect can be achieved by grafting flame-retardant elements on the surface of the GO.

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

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

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

Preferably, the mass ratio of GO, P in phosphazene, si in polyhedral oligomeric silsesquioxane and P in phosphonic acid is 1: (0.5-3): (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, phenoxy polyphosphazene and hexaphenyl cyclotriphosphazene. More preferably, the phosphazene is Hexachlorocyclotriphosphazene (HCCP).

HCCP is a typical six-atom ring formed by alternating single and double bonds of phosphorus and nitrogen atoms, and this high phosphorus and nitrogen structure allows HCCP to function simultaneously in the gas phase and in the condensed phase, thus imparting great flame retardant potential. Meanwhile, the chlorine atom on the six-membered ring is easily replaced by alcohols, phenols and amines, so that the chemical stability and the thermal stability of the HCCP are enhanced.

Therefore, the invention adopts a covalent bond grafting method to introduce HCCP on the surface of GO.

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

preferably, the polyhedral oligomeric silsesquioxane is an aminopropylbutyl polyhedral oligomeric silsesquioxane (NH) ₂ -POSS), methacryloxy polyhedral oligomeric silsesquioxanes, and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-polyhedral oligomeric silsesquioxanes (DOPO-POSS). Wherein NH is ₂ POSS is available from hybrid plastics company; DOPO-POSS is available from Beijing academy of technology, inc.

NH ₂ The structural formula of the POSS is:

wherein NH is ₂ POSS is a typical organic-inorganic hybrid material with a three-dimensional space structure, the inside of the POSS is a cage-shaped inorganic framework composed of Si and O, seven Si atoms on the outside are connected with isobutyl, the other Si atom is connected with aminopropyl, and the active amino groups enable NH ₂ POSS can react with hydroxyl, carboxyl, etc. In addition, the inorganic frame structure of the polyhedron ensures NH ₂ Heat resistance of POSS, NH when the temperature exceeds the POSS limit temperature ₂ The cage structure of the POSS is converted 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 Graft modification of GO by POSS to HCCP and NH ₂ The POSS is covalently grafted on the surface of the GO sheet layer.

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 it is used, it is called methacryloxy polyhedral oligomeric silsesquioxane; or when R is

When this is the case, it is designated 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 slowed down; oxygen is consumed during the combustion of POSS to produce gases (e.g., N) ₂ 、NH ₃ Etc.), the flame retardant agent can play a role in diluting the combustible organic gas, thereby reducing the intensity of combustion of the high polymer material; after combustion of POSS, a silicon oxygen compound (SiO ₂ ) The polymer is deposited on the surface of the polymer which is not combusted, and a part of the polymer forms a protective layer, so that the effects of slowing down heat transfer, inhibiting volatilization of combustible gas and blocking mixing of the combustible gas and oxygen are achieved to a certain extent; POSS is able to migrate progressively to the surface of the polymer melt to form a barrier layer with higher thermal stability, to some extent inhibiting heat and mass transfer.

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

The flame retardant mechanism of phosphonic acid is: (1) Forming phosphoric acid as a dehydrating agent and promoting char formation, the char formation reducing heat transfer from the flame to the condensed phase; (2) Phosphoric acid absorbs heat to prevent oxidation of CO to CO ₂ The heating process is reduced; (3) A thin glassy or liquid protective layer is formed on the condensed phase, so that the heat and mass transfer between oxygen diffusion and gas phase and solid phase are reduced, the carbon oxidation process is inhibited, and the thermal decomposition of the phosphorus-nitrogen-silicon composite flame retardant is reduced. The phosphonic acid combustion varies as follows: phosphorus flame retardant- & gt metaphosphoric acid- & gt phosphoric acid- & gt polymetaphosphoric acid, wherein polymetaphosphoric acid is a stable compound which is not easy to volatilize, has strong dehydration property and is isolated from air on the surface of a polymer; the removed water vapor absorbs a great deal of heat, so that the flame retardant on the surface of the polymer is heatedThe decomposition releases volatile phosphides, and mass spectrometry analysis shows that the concentration of hydrogen atoms is greatly reduced, which indicates that PO is trapped in H, namely PO+H=HPO.

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

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

and 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).

To make the GO dispersion more uniform, GO was dissolved in THF and after stirring thoroughly, ultrasonic dispersion was performed. For example, agitation may be selected from shaking agitation or magnetic agitation. 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.

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

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

And 2, adding phosphazene and 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 to perform a staged reaction, so as to obtain the graphene oxide based phosphorus-nitrogen composite flame retardant (HGO).

Preferably, the reaction temperature of the first stage is-10 to 10 ℃ and the reaction time is 1 to 5 hours. More preferably, the first stage reaction temperature is from-5 to 5℃and is from 2 to 3 hours, for example from 0 to 4℃in an ice-water bath, and is reacted 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 second stage reaction temperature is 50 to 70℃and the reaction is carried out for 2 to 4 hours, for example, 60℃and 3 hours.

In order to exclude oxygen in the system, the reaction is preferably carried out under a nitrogen or argon atmosphere.

Illustratively, the HCCP-THF solution is slowly added dropwise to the mixed solution of step 1, wherein the addition time and the first stage reaction time remain 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, the solvent adopted in the washing is THF and absolute ethyl alcohol for multiple times of washing, preferably THF is adopted for multiple times of centrifugal washing, and absolute ethyl alcohol is adopted for multiple times of centrifugal washing.

According to the invention, in step 2-1, the washing is followed by drying, 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, at a drying temperature of 60℃for 12 hours.

In the invention, as the HCCP addition amount increases, the grafting amount on the GO sheet layer also gradually increases, however, when the HCCP addition amount reaches a certain proper range, the HCCP addition amount continues to increase, the grafting amount on the GO surface does not change much, which indicates that most of the hydroxyl groups on the GO surface have been 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 dripped into the dispersion liquid dissolved with HGO to carry out a staged reaction, so as to obtain HPGO.

More preferably, step 2-2 may comprise:

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

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

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

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

The reaction temperature in 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 25℃for 10 hours.

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

It should be noted that the specific values of the preset time and the preset quality are not particularly limited in the present invention, and those skilled in the art can select the specific values according to the actual reaction situation, for example, the preset time is 2 or 3 hours, that is, deionized water is added when the reaction time in the third stage reaches 2 or 3 hours.

Illustratively, the HGO obtained in step 2-1 is dispersed in THF, TEA is added, and after the three systems are uniformly mixed, NH is slowly added dropwise ₂ -POSS-THF solution, wherein the drop time is controlled within 0.5-2 h, e.g. 1h. After reflux reaction for 3 hours at 60 ℃, dropwise adding deionized water with preset mass, continuing to react for 3 hours, then reducing the temperature to 25 ℃, and continuing to react for 10 hours.

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

According to the invention, in step 2-2, the washing is followed by drying, 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, at a drying temperature of 60℃for 12 hours.

In the present invention, with NH ₂ The grafting amount on the GO sheet gradually increases when the addition amount of POSS increases, when NH ₂ When the addition amount of POSS reaches a certain proper range, the NH is continuously increased ₂ The amount of POSS added, the grafting amount of the GO surface, was not changed much, indicating that the carboxyl groups of the GO surface have been replaced.

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 of aggregation of the graphene oxide 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 the dispersion is stirred and sonicated for 1 to 6 hours.

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;

specifically, the product obtained in the step 2, phosphonic acid, terephthalic acid (PTA), ethylene Glycol (EG) and a catalyst Sb ₂ O ₃ Placing in a 1L polymerization kettle for fully pulping. After the pulping is finished, 150KPa nitrogen is flushed into the polymerization kettle and heated. Controlling the internal pressure of the kettle to be 280-320 KPa. Along with the increase of the temperature in the kettle, the esterification reaction is continuously carried out, water generated by the reaction flows towards the top of the tower, the temperature of the top of the tower is also continuously increased, and when the temperature of the top of the tower reaches about 140 ℃, the water is discharged by controlling the pressure. And when the water yield reaches 95% of the theoretical water yield or no excessive water flows out, ending the esterification reaction stage.

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

specifically, the temperature of the top of the tower is reduced to below 100 ℃, the pressure in the kettle is reduced to normal pressure, and meanwhile, the temperature in the kettle is Wen Dayu ℃. Then, an antioxidant (such as triphenyl phosphite), an anti-hydrolysis agent (such as 1010) and a proper amount of EG are respectively added into the reaction kettle, and the reaction is carried out for 20 to 50 minutes at normal pressure, for example, 30 minutes.

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

Specifically, the temperature in the kettle is increased to about 270 ℃ and vacuumized, so that the pressure in the kettle is reduced to below 50 Pa. Controlling the temperature in the kettle to be about 275 ℃ for 2-3 hours, stopping the reaction when the stirring power reaches a certain value, namely the viscosity of PET reaches a preset viscosity value, and ending the polycondensation reaction.

After step 3-3, a post-treatment is also included.

The post-treatment process comprises the following steps: and (3) reducing the pressure in the kettle to normal pressure, then continuously introducing nitrogen for pressurizing, extruding the melt under the pressure of nitrogen, cooling with cold water to form strips, airing the water on the surface of the strips, and shearing the strips into 2-3 mm polyester chips by using a granulator.

In the prior art, the polyester fiber material molecules only contain ester groups with very small polarity, so that macromolecular chains are easy to break under the action of strong acid or strong alkali, but the polyester fiber material molecules are tightly packed, and the polyester fiber material has 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 difficulty is increased for modification of the polyester fiber material.

According to the burning process of PET, the flame retardant property of PET can be improved by corresponding measures. For example, (1) adding a free radical inhibitor into PET, weakening combustion in the gas phase, and delaying degradation of PET; (2) Promote the formation of carbon in the condensed phase, reduce the volatilization of inflammable substances and enhance the isolation effect of gas phase and condensed phase; (3) Additives with shielding effect are added into PET, so that heat and oxygen transfer is reduced, and combustion spread is inhibited.

According to the invention, from the structure and the performance of polyester and the flame retardant mechanism of a flame retardant, HGO and HPGO are selected as shielding agents and smoke suppressants, CEPPA is used as a char forming agent and a free radical inhibitor, and the CEPPA is polymerized into PET in situ to obtain 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 grade of the polyester fiber are greatly improved, and excellent flame resistance and anti-dripping performance are provided for the polyester fiber.

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%, the UL-94V-0 grade is realized, and simultaneously, the release of heat and smoke is obviously reduced, so that the graphene oxide-based phosphorus-nitrogen-silicon integrated composite flame retardant can effectively improve the flame retardance of polyester fibers and improve the fire safety.

According to the invention, on 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 follow NH ₂ An increase in the amount of POSS added and a decrease. However when NH ₂ When the addition amount of POSS reaches a certain proper range, i.e. when most of carboxyl groups on the GO surface have been replaced, NH is followed ₂ The amount of POSS added continues to increase with insignificant changes in total heat release and total smoke release.

According to the invention, HCCP and NH are immobilized ₂ On the premise of the POSS amount, the total smoke release of the graphene oxide-based phosphorus-nitrogen-silicon composite flame-retardant copolyester increases with the increase of the CEPPA addition amount, but the heat is reduced.

In a third aspect, the present invention provides a graphene oxide-based phosphorus-nitrogen-silicon composite flame retardant copolyester prepared according to the method of 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 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 uniform suspension, dropwise adding 15.12g of TEA, and placing the suspension in an ice water bath at 0-4 ℃ for 1 hour;

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

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

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

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

separating and washing with THF and ethanol by a centrifuge after the reaction is finished, and vacuum drying at 60 ℃ for 12 hours to obtain brown solid powder, wherein the brown solid powder is marked as HPGO;

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

350g PTA and 5.5g CEPPA are added into HPGO-EG dispersion liquid, soaked for 20min, taken out, washed and dried to obtain FRPET-HPGO.

Comparative example 1

PET was used as a sample of comparative example 1.

Comparative example 2

The procedure is similar to that of example 1, except that NH ₂ The amount of POSS varies and the resulting product is designated FRPET-HPGO-1-3, see in particular Table 1. In Table 1, the mass percentages and the elemental mass percentages 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

The procedure was similar to that of example 1, except that,

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

350g PTA and 5.5g CEPPA are added into HGO-EG dispersion liquid, soaked for 20min, taken out, washed and dried to obtain FRPET-HGO.

Comparative example 4

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

Experimental example

Experimental example 1

To investigate the covalently modified structure of GO, infrared spectroscopy (FTIR) and wide angle X-ray diffraction spectroscopy (WAXD) 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) is a WAXD plot of GO, HGO and HPGO.

As can be seen from figure 1 a),

(1-1)3312cm ^-1 、1724cm ^-1 、1621cm ^-1 、1263cm ^-1 1063cm ^-1 The absorption peaks at the positions correspond to the telescopic vibration absorption peaks of O-H, C = O, C = C, C-O-C, C-O on the surface of the GO sheet layer respectively. After grafting reaction with HCCP, the intensities of the c=o and c=c peaks in HGO were significantly reduced, indicating that the grafting process of HCCP caused GO to undergo reduction reaction. At 1180, 873 and 1032cm simultaneously ^-1 Three new infrared absorption peaks of P-N, P =n and P-O-C appear, from which HCCP is chemically grafted to GO surface.

(1-2) with NH ₂ After 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 obvious-CH appearance ₂ -telescopic and flexural vibration absorptionPeaks, indicating the presence of methylene in HPGO, at 1109 and 1410cm ^-1 The absorption peaks at the positions correspond to Si-O asymmetric telescopic vibration absorption peaks and Si-C bending vibration absorption peaks respectively. Thus, it can be seen that NH ₂ POSS also successfully grafted covalently to the surface of GO.

As can be seen from figure 1 b) of the drawings,

the characteristic peak of the (2-1) GO (002) crystal face is at 11 DEG, and the corresponding interlayer distance is 0.8nm according to the Bragg equation. After the GO is grafted and modified by HCCP, the 2 theta angle of the (002) crystal face characteristic peak is shifted to 9.9 degrees, and the interlayer distance is increased to 0.99nm. This is because HCCP undergoes nucleophilic substitution reaction on GO surface to cause intercalation and splicing on GO surface, and intercalation breaks the stacked structure between sheets, resulting in an increase in sheet spacing.

(2-2) with NH ₂ Further functionalization of POSS, the characteristic peak of (002) crystal face has smaller and smaller 2 theta angle, and the GO sheet spacing is larger and larger, which shows that with NH ₂ POSS also successfully intercalated between GO sheets. Wherein 12.1 ° and 19 ° correspond to the (120) and (113) crystal planes, respectively, of the HPGO crystal.

Experimental example 2

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

As can be seen from FIG. 2, the PET has a smooth surface and a clear cross section without particles. After adding GO, the brittle fracture surface of PET-GO is subjected to GO agglomeration, because oxygen-containing functional groups on the surface of GO are reduced at high temperature, van der Waals force among GO sheets is enhanced, and besides GO undergoing copolymerization with PET, GO dispersed in a matrix is agglomerated again.

As can be seen from comparison of PET-HPGO, HPGO has improved dispersibility in PET matrix due to HCCP and NH ₂ The grafting reaction of POSS on GO sheets enlarges the GO interlayer spacing, making the inter-sheet van der waals forces weaker. Comparing the cross-sectional views of FRPET-HGO and FRPET-HPGO, it can be seen that the dispersibility of HGO or HPGO in FRPET is further improved.

Experimental example 3

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

(1) Different amounts of NH ₂ The Limiting Oxygen Index (LOI) and vertical burn test results (UL-94) of FRPET-HPGO after POSS grafting are listed in Table 2.

TABLE 2 LOI and UL-94 of FRPET-HPGO

As can be seen from the table 2,

(1-1) compared with FRPET-HGO, after silicon element is added into the system, the LOI value of the FRPET-HPGO is reduced to a certain extent. The addition of silicon lengthens the flame burn time above the spline, causing heat to be transferred below the spline, rather than taking it away in the form of droplets. CEPPA in FRPET-HPGO is degraded in advance to release a free radical scavenger which can quench the free radical reaction of inflammable micromolecules in gas phase, so that the LOI of the FRPET-HPGO is still maintained above 30%, and the FRPET-HPGO is a flame retardant material.

(1-2) the after flame time after FRPET-HPGO was from fire was prolonged compared to FRPET-HGO due to NH ₂ The network structure formed by the POSS is caused by the coating effect of the molten drops, and meanwhile, the gas-phase flame retardant effect of the CEPPA enables the molten drops to take away heat while the molten drops drop, so that combustibility is completely inhibited, absorbent cotton below a spline cannot be ignited, and the UL-94 can still keep the V-0 grade. The FRPET-HPGO self-extinguishes from the fire and drops down to flameless molten drops, so that the hazard of the fire can be greatly reduced in the real fire, and the spread of the flame can be restrained.

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

(2) Different amounts of NH ₂ Cone calorimetric analysis of FRPET-HPGO after POSS grafting, analysis results are shown in tables 3-5.

TABLE 3 time parameters of FRPET-HPGO

As can be seen from table 3, the addition of silicon has less effect on the ignition time (TTI), but causes a decrease in the heat release rate peak (phr) time (t-phr), the effective combustion heat peak time (t-PEHC), and the smoke generation rate peak time (t-PSPR). This is due to NH ₂ The grafting reaction of the POSS further damages the integrity of the GO sheet layers, the GO defect is increased, the shielding effect on inflammable gas and heat is weakened, inflammable fragments released by FRPET-HPGO in the thermal degradation period can be more rapidly diffused into a gas phase, and once the inflammable fragments are ignited by electric sparks, the inflammable fragments accumulated on the surface of the material can be rapidly combusted, so that the peak value of the heat release rate and the smoke release rate is reached.

TABLE 4 thermal 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 can the heat release be advanced, but also the heat release amount can be increased. Compared with PET, the FRPET-HPGO has obviously reduced heat release and improved fire safety. But the Peak Heat Release Rate (PHRR), total Heat Release (THR) and average effective heat of combustion (av-EHC) of FRPET-HPGO were increased by 9.5%, 18.9% and 4.3%, respectively, compared to FRPET-HGO. The defects of the GO sheets accelerate mass and heat transfer of the gas phase and the condensed phase and promote degradation of the PET internal materials. More inflammable fragments in FRPET-HPGO diffuse into the gas phase than FRPET-HGO, while the CEPPA released radical scavenger is constant, thus resulting in an increase in the rate of heat release and total heat release.

TABLE 5 Smoke parameters of FRPET-HPGO

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

FIG. 3 is a graph of the smoke generation rate profile of FRPET-HPGO. As can be seen from fig. 3, the smoke generation rate (SPR) curve of FRPET-HPGO shows two peaks, wherein the first peak occurs earlier than PET. This is because early decomposition of CEPPA promotes PET degradation during the initial stage of combustion, thereby producing a large amount of fragments dispersed in the gas phase, rapidly forming the first PSPR peak. The catalytic degradation of CEPPA also promotes the formation of a char layer in the coacervate phase, while NH ₂ The silicon-containing network structure formed by the heating of the POSS locks the fragments into the condensed phase to form a carbon layer, which retards heat transfer and delays continued degradation of the internal substrate, resulting in a reduction of PSPR. With the accumulation of heat under the carbon layer, when certain energy is reached, the flame breaks through the carbon layer, and a large amount of heat is generated again, so that degradation of the substrate inside the PET is aggravated, and a new PSPR peak is formed. In the later stage of combustion, 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 the formation of a more continuous and compact carbon layer in the later stage of combustion and the enhancement of the isolation effect. From the whole combustion process, the HPGO has obvious inhibition effect on the smoke release amount of the RPET, and can completely offset the increase of the smoke release amount caused by the addition of CEPPA. In particular NH ₂ When the addition amount of the POSS is 0.2 weight percent of silicon, the TSP of the RPET-HPGO is 23.74m of the RPET-HGO ² Reduced to 17.21m ² The reduction is 27.51%.

(3) Different amounts of NH ₂ Other performance analyses of FRPET-HPGO after POSS grafting, analysis results are shown in Table 6.

TABLE 6 FRPET-HPGO other parameters

As can be seen from table 6, the Flame Growth Index (FGI) of FRPET-HPGO is reduced, while the Fire Performance Index (FPI) is increased, indicating an increase in the safety of fire. However, compared with FRPET-HGO, FRPET-HPGO has the tendency of increasing FGI and decreasing FPI. The increase in FGI suggests that FRPET-HPGO can reach the peak heat release rate quickly due to the reduced shielding effect of HPGO at the beginning of combustion. The FPI is characterized by the ratio of TTI to PHRR, and from the time parameter, HPGO has little effect on TTI, but PHRR value is increased, so FPI is reduced.

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

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

Claims

1. The preparation method of the graphene oxide-phosphorus-nitrogen-silicon composite flame-retardant copolyester is characterized in that raw materials for preparing the graphene oxide-phosphorus-nitrogen-silicon composite flame-retardant copolyester comprise polyester monomers, graphene oxide, phosphazene, polyhedral oligomeric silsesquioxane and phosphonic acid, wherein

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

the phosphazene is hexachlorocyclo triphosphazene,

the polyhedral oligomeric silsesquioxane is amino propylene butyl polyhedral oligomeric silsesquioxane, the phosphonic acid is 2-carboxyethyl phenyl phosphinic acid,

the method comprises the following steps:

step 1, dispersing graphene oxide to obtain a uniform suspension, adding triethylamine into the suspension, and standing;

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

2. The method according to claim 1, wherein,

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

adding triethylamine into the suspension, and standing for 0.5-5 h at the temperature of-10 ℃.

3. The method of claim 1, wherein step 2 comprises:

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

the reaction temperature in 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;

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

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

and when the reaction time in the third stage reaches the preset time, dropwise adding deionized water with preset mass.

4. The method of manufacturing according to claim 1, wherein 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 of step 3-1 under normal pressure, and then carrying out reaction;