阅读说明：本技术 一种改性阻燃复合物的制备方法及其应用 (Preparation method and application of modified flame-retardant compound ) 是由 郑玉婴 曹爱萍 于 2019-11-18 设计创作，主要内容包括：本发明涉及一种改性阻燃复合物的制备方法及其应用。首先对粉煤灰进行漂选、羟基化、酸预处理,然后再用偶联剂对预处理过的粉煤灰进行表面改性处理,再负载还原氧化石墨烯,最后再接枝上阻燃协效剂DOPO。采用本发明方法对粉煤灰进行表面改性后,所得表面改性粉煤灰漂珠表面的物理化学性质发生了改变,提高了其在热塑性聚氨酯弹性体中的分散性,增进填料与弹性体等晶体界面的相容性,进而提高热塑性聚氨酯弹性体的力学性能、阻燃性能及其它性能,为粉煤灰的更好利用提供了一种改进方法,减少了对环境的污染。同时也发挥石墨烯的应用,提高热塑性聚氨酯弹性体的抗静电能力和力学性能。添加的阻燃协效剂DOPO能进一步加快惰性气体的产生,并起到很好的阻燃效果。(The invention relates to a preparation method and application of a modified flame-retardant compound. Firstly, fly ash is subjected to bleaching, hydroxylation and acid pretreatment, then the pretreated fly ash is subjected to surface modification treatment by using a coupling agent, reduced graphene oxide is loaded, and finally a flame-retardant synergist DOPO is grafted. After the fly ash is subjected to surface modification by adopting the method disclosed by the invention, the physicochemical property of the surface of the obtained surface-modified fly ash floating bead is changed, the dispersibility of the fly ash floating bead in the thermoplastic polyurethane elastomer is improved, the compatibility of a filler and crystal interfaces of the elastomer and the like is improved, the mechanical property, the flame retardant property and other properties of the thermoplastic polyurethane elastomer are further improved, an improved method is provided for better utilization of the fly ash, and the pollution to the environment is reduced. Meanwhile, the application of graphene is also exerted, and the antistatic capability and the mechanical property of the thermoplastic polyurethane elastomer are improved. The added flame-retardant synergist DOPO can further accelerate the generation of inert gas and has good flame-retardant effect.)

1. A preparation method of a modified flame-retardant compound is characterized by comprising the following steps: modifying fly ash floating beads by using a coupling agent, loading graphene on the modified fly ash floating beads, and finally grafting a flame-retardant synergist DOPO to prepare the composite flame-retardant composition.

2. The method of claim 1, wherein the modified flame retardant compound comprises: the fly ash floating bead is a floating bead which is pretreated and hydroxylated by acid.

3. The method of claim 2, wherein the modified flame retardant compound comprises:

the method for pretreating hydroxylated floating beads by acid specifically comprises the following steps:

step S11, taking 120g of fly ash floating beads subjected to screening pretreatment by a 100-mesh sieve, rinsing and sorting the fly ash floating beads floating on the surface by deionized water, and placing the fly ash floating beads in a 500ml beaker;

step S12, adding 200ml of dilute nitric acid solution with the concentration of 3wt% and stirring for 30min to remove impurities on the surface of the fly ash floating bead;

step S13, pouring 15ml of hydrogen peroxide solution with the concentration of 30wt% and 35ml of concentrated sulfuric acid solution with the concentration of 98wt%, and stirring for 10min on an electric furnace at the temperature of 200 ℃; wherein V_Acid(s)：V_{Hydrogen peroxide solution}=35:15；

Step S14, pumping, filtering and cleaning the sample to be neutral, and drying the sample in a 120 ℃ oven for 3 hours;

and step S15, calcining the dried fly ash floating beads in a tubular furnace with a nitrogen atmosphere at 400 ℃ for 2 hours, and removing surface impurities.

4. The method of claim 1, wherein the modified flame retardant compound comprises: the coupling agent is any one of KH550, KH560, Tc-6 and Tc-114.

5. The method of claim 1 or 4, wherein the modified flame retardant compound comprises: the coupling agent modified fly ash floating bead for modifying fly ash floating bead by using the coupling agent is specifically

Step S21, ultrasonic activation is carried out on the hydroxylated fly ash floating bead in 240ml of 90wt% ethanol solution for 10 minutes;

step S22 adding 4.8ml of V_{Anhydrous ethanol}：V_KH550(KH560)=10:2 and stirring the ethanol solution of KH550 or KH560 for 30min at room temperature, stirring under sealed conditions at 60 ℃Stirring for 60 minutes;

and step S23, finally, performing suction filtration on the fly ash floating beads for multiple times by using absolute ethyl alcohol and deionized water, then placing the fly ash floating beads in a drying oven at 90 ℃ for drying for 4 hours, and placing the fly ash floating beads in a dryer for cooling for later use.

6. The method of claim 1, wherein the modified flame retardant compound comprises: the graphene is reduced by graphene oxide prepared by a modified Hummers method.

7. The method of claim 6, wherein the flame retardant compound comprises: the method is characterized in that: the reduction of the graphene oxide comprises the following steps:

step S31, putting a certain amount of graphene oxide prepared by an improved Hummers method into 100ml of deionized water, and carrying out ultrasonic treatment for 2 hours to uniformly disperse the graphene oxide in the water to prepare a graphene oxide solution with the concentration of 1 mg/ml;

step S32, adding 0.5g of nano aluminum and 5mL of 35wt% HCl into 100mL of graphene oxide solution with the concentration of 1mg/mL to obtain reduced graphene oxide with nano aluminum and graphene oxide, standing for 30min at room temperature in the reduction process, and adding 2.5mL of 0.5M HCl into the solution in order to completely remove redundant aluminum powder;

and step S33, performing suction filtration on the solution by using deionized water, washing to be neutral, drying, and grinding into powder for later use.

8. The method of claim 1, wherein the modified flame retardant compound comprises: the specific steps of loading graphene on the modified fly ash floating bead are as follows:

step S41, taking 5g of coupling agent modified fly ash floating beads into a beaker, and adding 50ml of absolute ethyl alcohol;

step S42, adding 1g of reduced graphene oxide, stirring for 1 hour at 65 ℃, and soaking for 24 hours;

step S43, filtering, pumping out, drying in an oven at 80 ℃ for 4 hours;

and step S44, calcining in a 400 ℃ tube furnace filled with nitrogen for 2 hours to finish the preparation.

9. The method of claim 1, wherein the modified flame retardant compound comprises: the grafting flame-retardant synergist DOPO comprises the following steps:

step S51, taking 4g of graphene-loaded modified fly ash floating bead sample, placing the sample in a beaker, and adding 50ml of absolute ethyl alcohol;

step S52 is again m by mass ratio_{Graphene-loaded modified fly ash floating bead}：m_DOPOAdding DOPO in the proportion of 1:6 in N₂Under the condition, stirring and reacting for 9 hours to obtain the graphene-DOPO loaded modified fly ash floating bead K-FB @ RGO-DOPO;

step S53 is washed 3 times by tetrahydrofuran and absolute ethyl alcohol according to the volume ratio of 1:1, filtered and dried, and then dried in an oven at 80 ℃ for 4 hours.

10. Use of a modified flame retardant composite according to claim 1 wherein: the obtained graphene-DOPO loaded modified fly ash floating bead can be applied to the processing and synthesis of thermoplastic polyurethane elastomers.

Technical Field

The invention relates to the application field of fly ash floating bead surface modified loaded graphene and a flame retardant synergist 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), in particular to a method for loading a graphene grafted flame retardant synergist DOPO on a modified fly ash floating bead and application thereof.

Background

The fly ash floating bead is a fly ash hollow ball capable of floating on water surface, is offwhite, is thin and hollow in wall, has light weight and volume weight of 720kg/m³(heavy), 418.8kg/m³(light weight), the grain diameter is about 0.1 mm, the surface is closed and smooth, and the filling material has large specific surface area, strong filling capacity and uniform size. The fly ash floating bead mainly comprises silicon dioxide and aluminum oxide, wherein the silicon dioxide is about 50-65%, and the aluminum oxide is about 25-35%. The flyash floating bead has thin and hollow wall, semi-vacuum cavity, and trace non-flammable gas (N)₂、H₂And CO₂Etc.), the heat conduction is extremely slow and minute. Also has the characteristics of high strength, wear resistance, high temperature resistance, heat insulation, flame retardance and the like. But the application range and the application energy efficiency are limited, and surface or structure modification is necessary to enhance the activity, such as acid solution modification and active agent modificationAnd modifying with a coupling agent.

The coupling agent is mainly used as a surface treating agent of inorganic fillers such as glass fiber, carbon black, wollastonite and the like, and improves the bonding force with polymer resin such as polyurethane and the like by activating the fillers. The function of the organosilane coupling agent and the solid inorganic substance can be bonded with the surface of the filler in a hydrogen bond mode through a hydrolytic group, and the organosilane coupling agent and the solid inorganic substance are mutually condensed to form a stable monomolecular covering layer, and meanwhile, the organosilane coupling agent and the solid inorganic substance can be adsorbed on a hydrolytic layer of the silane coupling agent in a chemical adsorption and physical adsorption mode by the inorganic filler.

The surface modification of the coupling agent of the fly ash floating bead is mainly used as a filling material of an organic material, and a plurality of coupling agents such as titanate and silane have been developed in recent years, wherein the silane coupling agent has the characteristics of simple synthesis, excellent performance, low cost and the like.

The action mechanism of the coupling agent and the fly ash accords with the chemical bond theory, the fly ash floating bead is rich in hydroxyl on the surface after being hydroxylated, the fly ash floating bead and the hydroxyl of the coupling agent are subjected to dehydration condensation reaction, and the monomolecular layer coupling agent is adsorbed on the surface, so that the improvement of the compatibility and the associativity between inorganic and organic materials is facilitated.

Graphene is a two-dimensional lamellar carbonaceous material, and is formed by tightly packing carbon atoms in a hexagonal honeycomb shape on the same plane. The graphene has novel structure and excellent electrical, thermal, mechanical and optical properties. Due to the unique two-dimensional layered structure of the graphene, the graphene has an excellent flame retardant effect, and the two-dimensional layered structure of the graphene has a lamellar barrier effect, so that the heat transfer, the diffusion and the escape of pyrolysis products and the diffusion and the mixing of oxygen can be delayed. In addition, graphene also contains a large number of oxygen-containing functional groups, such as hydroxyl, carboxyl and epoxy groups, and can form a strong interface effect with a polymer matrix through chemical bonds.

At present, many halogen-free flame retardant systems are studied, including inorganic hydroxide flame retardants, intumescent flame retardants, organic phosphorus flame retardants, organic nitrogen flame retardants, and the like. In general, inorganic hydroxide flame retardants and intumescent flame retardants require a gas source, a carbon source, and an acid source, and have a delay effect in their action, i.e., they can only act after a sufficient carbon layer has been formed. The organic phosphorus flame retardant has an excellent effect of preventing the polymer from being ignited due to a gas-phase flame retardant mechanism. The synthesis route of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is reported as follows:

because DOPO contains a bi-benzene ring structure and a phenanthrene ring structure, compared with non-cyclic phosphate, the DOPO has better thermal stability and rigidity, and is commonly used for improving the mechanical property, the flame retardant property and the hydrolysis resistance of a high polymer material. Meanwhile, the structure of DOPO contains active PH bond, has extremely activity to olefin, epoxy bond, carbonyl and the like, and can react to generate a plurality of derivatives.

When the DOPO-based flame retardant is burnt in the high polymer material, polyphosphoric acid, phosphorous acid and phosphoric acid can be formed to dehydrate the surface of the material to form a carbon layer, so that oxygen and heat generated by burning are isolated from being transferred to the interior of the material, and condensed phase flame retardance is realized; meanwhile, the gas generates a flame-retardant gas during combustion, the concentration of the combustible gas is diluted, and the generated radicals such as P & PO & can quench high-activity H & HO & free radicals generated by pyrolysis, and the combustion free radical reaction is interrupted, so that gas-phase flame retardance is realized.

The silicon-containing compound can promote combustion to form carbon in a solid phase, can capture active free radicals in a gas phase state, and is expected to obtain a better flame retardant effect when applied to TPU. The nitrogen is inert gas, and in the combustion process, the nitrogen can effectively prevent more combustible gas from entering a combustion system, so that a flame-retardant gas source is formed, and the flame-retardant effect is achieved. If the flame-retardant system simultaneously contains other flame-retardant elements such as N, Si and the like, the elements realize synergistic flame retardance, and the performance of the flame retardant in condensed phase and gas phase flame retardance is improved, so that the flame retardant capability and the thermal stability of the high polymer material are enhanced.

Meanwhile, the DOPO contains a biphenyl ring structure and a phenanthrene ring structure, and has better thermal stability and rigidity compared with non-cyclized phosphate, so that the DOPO-based flame retardant can reduce the influence of the flame retardant on the mechanical property of the high polymer material as much as possible, and even can enhance the mechanical property of the high polymer material.

Active H in a P-H structure in DOPO is an electrophilic group, and can form a C-H bond with C ═ C pi bond electrophilic addition on the surface of graphene under a certain condition, and particularly can perform addition reaction with carbon atoms with higher reactivity at edge defects. While the positive charges appearing on the remaining C atoms are intercepted by P, forming a P-C bond. The outermost edge, which makes the graphene layer more detached and has higher activity, shows a warped state due to the grafting of DOPO. The modified flame retardant of the modified floating bead-loaded graphene grafted flame-retardant synergist DOPO can be obtained by the mechanism.

Disclosure of Invention

The invention aims to provide a preparation method and application of modified fly ash floating bead loaded graphene aiming at the defects of the prior art. The method comprises the steps of carrying out a series of treatments of removing surface impurities on fly ash floating beads, then carrying out coupling agent modification treatment on the surfaces of the floating beads, and finally loading reduced graphene oxide. The flame retardant property of the thermoplastic polyurethane elastomer is combined with the characteristics of the thermoplastic polyurethane elastomer and the thermoplastic polyurethane elastomer. The fly ash floating bead loaded with the modified graphene has better mechanical property and flame retardant property in the processing process of the thermoplastic polyurethane elastomer, and has wide application prospect and market demand in practical application.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a modified flame-retardant compound is specifically prepared by modifying fly ash floating beads with a coupling agent, loading graphene on the modified fly ash floating beads, and finally grafting a flame-retardant synergist DOPO.

Further, the fly ash floating bead is a floating bead pretreated and hydroxylated by acid, and the method comprises the following specific steps:

step S11, taking 120g of fly ash floating beads subjected to screening pretreatment by a 100-mesh sieve, rinsing and sorting the fly ash floating beads floating on the surface by deionized water, and placing the fly ash floating beads in a 500ml beaker;

step S12, adding 200ml of dilute nitric acid solution with the concentration of 3wt% and stirring for 30min to remove impurities on the surface of the fly ash floating bead;

step S13 pouring 15ml30 wt% hydrogen peroxide and 35ml98 wt% concentrated sulfuric acid solution, stirring on electric furnace at 200 deg.C for 10min, wherein V_Acid(s)：V_{Hydrogen peroxide solution}＝35:15；

Step S14, pumping, filtering and cleaning the sample to be neutral, and drying the sample in a 120 ℃ oven for 3 hours;

and step S15, calcining the dried fly ash floating beads in a tubular furnace with a nitrogen atmosphere at 400 ℃ for 2 hours, and removing surface impurities.

Further, the coupling agent is any one of KH550, KH560, Tc-6 and Tc-114.

Further, the coupling agent modified fly ash floating bead for the fly ash floating bead is modified by the coupling agent, and the specific steps are

Step S21, ultrasonic activation is carried out on the hydroxylated fly ash floating bead in 240ml of 90wt% ethanol solution for 10 minutes;

step S22 adding 4.8ml of V_{Anhydrous ethanol}：V_KH550(KH560)Stirring a KH550 or KH560 ethanol solution at room temperature for 30min at 10:2, and stirring for 60 min under sealed conditions at 60 ℃;

and step S23, finally, performing suction filtration on the fly ash floating beads for multiple times by using absolute ethyl alcohol and deionized water, then placing the fly ash floating beads in a drying oven at 90 ℃ for drying for 4 hours, and placing the fly ash floating beads in a dryer for cooling for later use.

Further, the graphene is reduced by graphene oxide prepared by a modified Hummers method. The reduction of the graphene oxide comprises the following steps:

step S31, taking a certain amount of graphene oxide prepared by an improved Hummers method, putting the graphene oxide into 100ml of deionized water, and carrying out ultrasonic treatment for 2 hours to uniformly disperse the graphene oxide in the water to prepare a graphene oxide solution with the concentration of 1 mg/ml;

step S32, adding 0.5g of nano aluminum and 5mL of 35wt% HCl into 100mL of 1mg/mL graphene oxide solution to obtain nano aluminum graphene oxide reduced graphene oxide, standing for 30min at room temperature in the reduction process, and adding 2.5mL of 0.5M HCl into the solution in order to completely remove redundant aluminum powder;

and step S33, performing suction filtration on the solution by using deionized water, washing to be neutral, drying, and grinding into powder for later use.

Further, the specific steps of loading the graphene on the modified fly ash floating bead are as follows:

step S41, taking 5g of coupling agent modified fly ash floating beads into a beaker, and adding 50ml of absolute ethyl alcohol;

step S42, adding 1g of reduced graphene oxide, stirring for 1 hour at 65 ℃, and soaking for 24 hours;

step S43, filtering, pumping out, drying in an oven at 80 ℃ for 4 hours;

and step S44, calcining in a 400 ℃ tube furnace filled with nitrogen for 2 hours to finish the preparation.

The grafting flame-retardant synergist DOPO comprises the following steps:

step S51, loading 4g of graphene on a modified fly ash floating bead sample in a beaker, and adding 50ml of absolute ethyl alcohol;

step S52 is again based on mass ratio m_{Graphene-loaded modified fly ash floating bead}：m_DOPO1:6 adding DOPO in N₂Under the condition, stirring and reacting for 9 hours to obtain the graphene-DOPO loaded modified fly ash floating bead K-FB @ RGO-DOPO;

step S53 is washed 3 times by tetrahydrofuran and absolute ethyl alcohol according to the volume ratio of 1:1, filtered and dried, and then dried in an oven at 80 ℃ for 4 hours.

The obtained modified fly ash floating bead loaded graphene grafted flame-retardant synergist DOPO is applied to the flame-retardant and antistatic effects in the processing synthesis of thermoplastic polyurethane elastomers.

The invention has the beneficial effects that:

the modified fly ash floating bead loaded graphene grafted flame-retardant synergist DOPO prepared by the invention can better recycle the waste generated when the pulverized coal is combusted in a boiler. And the characteristics of the fly ash floating bead and the graphene and the effect of the synergistic flame retardant DOPO are combined, so that the flame retardant is applied to the flame retardance of the thermoplastic polyurethane elastomer. The fly ash floating bead grafted with the modified graphene loaded by DOPO has better mechanical property, flame retardant property and antistatic effect in the processing process of the thermoplastic polyurethane elastomer, and has wide application prospect and market demand in practical application.

Drawings

FIG. 1 is a SEM image of fly ash floating beads;

FIG. 2 is an SEM image of a modified fly ash floating bead;

FIG. 3 is an SEM image of modified fly ash floating bead-loaded graphene;

FIG. 4 is a K-FB @ RGO-DOPOSEM map.

Detailed Description

For further disclosure, but not limitation, the present invention is described in further detail below with reference to examples.