阅读说明：本技术 一种包覆型无卤纤维状阻燃剂及其制备方法 (Coated halogen-free fibrous flame retardant and preparation method thereof ) 是由 严伟 王奎 黄伟江 田琴 张春梅 涂春云 于 2019-11-18 设计创作，主要内容包括：本发明公开了一种包覆型无卤纤维状阻燃剂及其制备方法,涉及高分子材料的无卤阻燃技术领域。其包括如下步骤：将海泡石纤维的无机酸分散液与氢氧化铝和磷酸混合在酸性条件下进行包覆反应,制得无卤磷酸铝包覆海泡石纤维前驱体,将无卤磷酸铝包覆海泡石纤维前驱体进行烧结得到包覆型无卤纤维状阻燃剂。该制备方法简单易行,有利于大规模生产。通过该制备方法制得的包覆型无卤纤维状阻燃剂具有较好的阻燃效果,海泡石纤维能大幅度降低热释放速率,具有良好的抑烟效果,同时也具有较好的阻燃协效性和隔热性能。(The invention discloses a coated halogen-free fibrous flame retardant and a preparation method thereof, and relates to the technical field of halogen-free flame retardance of high polymer materials. Which comprises the following steps: mixing inorganic acid dispersion liquid of sepiolite fibers with aluminum hydroxide and phosphoric acid, carrying out coating reaction under an acidic condition to obtain a halogen-free aluminum phosphate coated sepiolite fiber precursor, and sintering the halogen-free aluminum phosphate coated sepiolite fiber precursor to obtain the coated halogen-free fibrous flame retardant. The preparation method is simple and feasible, and is beneficial to large-scale production. The coated halogen-free fibrous flame retardant prepared by the preparation method has a good flame retardant effect, and the sepiolite fiber can greatly reduce the heat release rate, has a good smoke suppression effect, and also has good flame retardant synergy and heat insulation performance.)

1. The preparation method of the coated halogen-free fibrous flame retardant is characterized by comprising the following steps: mixing inorganic acid dispersion liquid of sepiolite fibers with aluminum hydroxide and phosphoric acid, carrying out coating reaction under an acidic condition to obtain a halogen-free aluminum phosphate coated sepiolite fiber precursor, and sintering the halogen-free aluminum phosphate coated sepiolite fiber precursor to obtain the coated halogen-free fibrous flame retardant.

2. The method according to claim 1, wherein the method further comprises preparing an inorganic acid dispersion of sepiolite fibers, which comprises dispersing the sepiolite fibers in an inorganic acid to obtain a sepiolite fiber inorganic acid dispersion;

preferably, the inorganic acid is hydrochloric acid;

preferably, the mass concentration of the sepiolite fibers in the sepiolite fiber inorganic acid dispersion liquid is 30-50 g/L;

preferably, the mass concentration of the sepiolite fibers in the sepiolite fiber inorganic acid dispersion liquid is 40-50 g/L.

3. The preparation method according to claim 2, wherein the sepiolite fiber inorganic acid dispersion is obtained under the condition of ultrasonic treatment;

preferably, the ultrasonic treatment time is 30-60min, the ultrasonic treatment power is 80-100W, and the ultrasonic treatment frequency is 80-100 KHz.

4. The method according to claim 1, wherein the molar ratio of the P element in the phosphoric acid to the Al element in the aluminum hydroxide is 1:3 to 1: 10.

5. The preparation method according to claim 1, wherein the mass ratio of the sepiolite fibers, the aluminum hydroxide and the phosphoric acid is 10-20:1-5: 8-35.

6. The preparation method as claimed in claim 1, wherein the sintering temperature is 600-950 ℃, and the sintering treatment time is 1-3 h;

preferably, the sintering temperature is 800-950 ℃, and the sintering treatment time is 2-3 h.

7. The preparation method according to claim 1, further comprising mixing the acid-washed sepiolite fibers with aluminum hydroxide and phosphoric acid and adjusting the pH of the mixed solution;

preferably, the pH of the mixed solution is adjusted to 4 to 6.

8. The preparation method according to claim 1, wherein the temperature of the coating reaction is 20-40 ℃ and the time is not less than 30 min.

9. The preparation method of claim 1, wherein the coating reaction is further carried out by sequentially washing, centrifuging and drying the reaction product to obtain a halogen-free aluminum phosphate coated sepiolite fiber precursor;

preferably, the coating reaction is carried out under stirring conditions; the stirring speed is 60-100 rpm;

preferably, the drying temperature is 60-100 ℃, and the drying time is 6-8 h;

preferably, the drying temperature is 60-80 ℃, and the drying time is 7-8 h.

10. The coated halogen-free fibrous flame retardant prepared by the preparation method according to any one of claims 1 to 9, wherein the diameter of the coated halogen-free fibrous flame retardant is 30 to 50 nm.

Technical Field

The invention relates to the technical field of halogen-free flame retardance of high polymer materials, and particularly relates to a coated halogen-free fibrous flame retardant and a preparation method thereof.

Background

Epoxy resin (EP) is often used as a matrix material and widely applied to the fields of electronics, electrical equipment, aerospace and the like, but the EP is extremely easy to burn and has great fire hazard problems. At present, the preparation of flame-retardant epoxy resin mainly relates to the following two aspects: (1) adding an additive flame retardant in the curing and forming process; (2) functional groups containing flame retardant elements (such as bromine, phosphorus and silicon) are introduced into the molecular structure of the curing agent or the epoxy resin.

Smoke and toxic gas released after the bromine-containing flame-retardant epoxy resin is combusted pose great threats to the environment and human health, and the use of the flame retardant in the epoxy resin is hindered. The phosphorus-containing and silicon-containing epoxy resins have the problems of harsh production conditions of phosphorus-containing monomers, high preparation cost, complex preparation process, reduced glass transition degree, deteriorated dielectric properties and mechanical properties and the like in the development and application processes.

In the research of designing and preparing the enhanced halogen-free additive flame retardant, the importance of researchers is brought about by constructing the coated halogen-free flame retardant to improve the flame retardant property and the mechanical property of the high polymer material. The existing halogen-free flame retardant has complex preparation method, higher addition amount and larger limitation, and is not beneficial to large-scale production.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a coated halogen-free fibrous flame retardant and a preparation method thereof to solve the technical problems.

The invention is realized by the following steps:

a preparation method of a coated halogen-free fibrous flame retardant comprises the following steps: mixing inorganic acid dispersion liquid of sepiolite fibers with aluminum hydroxide and phosphoric acid for coating reaction to prepare a halogen-free aluminum phosphate coated sepiolite fiber precursor, and sintering the halogen-free aluminum phosphate coated sepiolite fiber precursor to obtain the coated halogen-free fibrous flame retardant.

The sepiolite fibers are dispersed firstly, so that the surfaces of the sepiolite fibers can be organically acidified, the surfaces of the sepiolite fibers are activated, and the coating of aluminum phosphate is facilitated. The preparation method provided by the invention can realize the acidification of the sepiolite fibers only by dispersing the sepiolite fibers in inorganic acid. Adding aluminum hydroxide and phosphoric acid on the acidified sepiolite fibers, carrying out chemical reaction on the aluminum hydroxide and the phosphoric acid to generate aluminum phosphate, and carrying out coprecipitation under an acidic condition to obtain the halogen-free aluminum phosphate coated sepiolite fiber precursor. The distribution of aluminum phosphate in the precursor is not uniform, and the coated halogen-free fibrous flame retardant with more uniform distribution can be obtained only after the precursor is sintered.

At high temperature, the aluminum phosphate is uniformly coated on the surface of the sepiolite fiber in a certain thickness. The aluminum phosphate has the functions of inflaming retarding and heat release rate reduction, and the sepiolite fiber can form a protective layer with proper thickness and good spatial structure on the surface of the epoxy resin; the sepiolite fiber can also greatly reduce the heat release rate, and the fibrous structure has good smoke suppression effect. Furthermore, sepiolite fibers may provide a catalytic surface, promoting char formation reactions. The sepiolite fiber has better flame retardant synergy and heat insulation performance. Under the cladding of aluminum phosphate, the flame retardant property and the heat insulation property of the sepiolite fiber are greatly improved.

In a preferred embodiment of the present invention, the preparation method further comprises preparing an inorganic acid dispersion of sepiolite fibers, which comprises dispersing the sepiolite fibers in an inorganic acid to obtain an inorganic acid dispersion of sepiolite fibers;

preferably, the inorganic acid is hydrochloric acid;

preferably, the mass concentration of the sepiolite fibers in the sepiolite fiber hydrochloric acid dispersion liquid is 30-50 g/L;

preferably, the mass concentration of the sepiolite fibers in the sepiolite fiber hydrochloric acid dispersion liquid is 40-50 g/L.

When the addition concentration of the sepiolite fibers is within the range, the effects of smoke suppression and flame retardance can be effectively achieved. If the amount is less than the above-mentioned addition concentration, the smoke suppression and flame retarding efficiency is lowered. The hydrochloric acid can be used for acidizing the surface of the sepiolite fiber, and the sepiolite fiber treated by the hydrochloric acid is more beneficial to coating of aluminum phosphate.

In a preferred embodiment of the application of the present invention, the sepiolite fiber inorganic acid dispersion is obtained under the condition of ultrasonic treatment;

preferably, the ultrasonic treatment time is 30-60min, the ultrasonic treatment power is 80-100W, and the ultrasonic treatment frequency is 80-100 KHz.

The dispersion degree of substances in the dispersion liquid is improved through ultrasonic treatment, so that the subsequent coating reaction is facilitated.

The molar ratio of the P element in the phosphoric acid to the Al element in the aluminum hydroxide is 1:3-1: 10. Under the molar ratio of the P element to the Al element, the reaction equation can be ensured to proceed towards the direction of the aluminum phosphate, which is beneficial to the full progress of the reaction and the generation of sufficient aluminum phosphate.

The mass ratio of the sepiolite fibers to the aluminum hydroxide to the phosphoric acid is 10-20:1-5: 8-35.

Preferably, in the system consisting of aluminum hydroxide and phosphoric acid, the mass concentration of the aluminum hydroxide is 0.1-10g/L, and the mass concentration of the phosphoric acid solution is 0.1-100 g/L;

preferably, the mass concentration of the aluminum hydroxide is 2-10g/L, and the mass concentration of the phosphoric acid solution in the aluminum phosphate solution system is 8-70 g/L;

preferably, the mass concentration of the aluminum hydroxide is 4-8g/L, and the mass concentration of the phosphoric acid solution in the aluminum phosphate solution system is 20-50 g/L;

preferably, the mass concentration of the aluminum hydroxide is 5-7g/L, and the mass concentration of the phosphoric acid solution in the aluminum phosphate solution system is 30-40 g/L.

In a system consisting of aluminum hydroxide and phosphoric acid, when the mass concentration of the aluminum hydroxide is 0.1-10g/L and the mass concentration of the phosphoric acid solution is 0.1-100g/L, the aluminum hydroxide and the phosphoric acid can be ensured to fully react to prepare the aluminum phosphate particles.

In the preferred embodiment of the present invention, the temperature of the sintering treatment is 600-;

preferably, the temperature of the sintering treatment is 800-950 ℃, and the time of the sintering treatment is 2-3 h.

The distribution of aluminum phosphate particles on the surface of the sepiolite fiber can be promoted to be more uniform through high-temperature treatment, and the reduction of flame retardant property caused by nonuniform coating layers is avoided.

In the embodiment of the invention, the method also comprises the steps of mixing the washed sepiolite fibers with aluminum hydroxide and phosphoric acid, and then adjusting the pH of the mixed solution;

preferably, the pH of the mixed solution is adjusted to 4 to 6.

And optionally adjusting the pH of the mixed solution to be 4-6, so that the reaction of the aluminum hydroxide and the phosphoric acid is moved to the direction more favorable for generating the aluminum phosphate under the pH condition, and further the sepiolite fiber is promoted to coat thicker aluminum phosphate particles on the surface. If the pH value is lower than 4 or higher than 6, the coating reaction is incomplete, the coating layer formed on the surface of the sepiolite fiber is thin, and the flame retardant property is poor. The agent for adjusting the pH is preferably aqueous ammonia.

In the preferred embodiment of the present invention, the temperature of the coating reaction is 20-40 deg.C, and the time is not less than 30 min.

Under the coating reaction conditions, the prepared flame retardant has the best flame retardant property.

In a preferred embodiment of the application of the invention, after the coating reaction, the method further comprises the steps of washing, centrifuging and drying the product after the reaction in sequence to obtain a halogen-free aluminum phosphate coated sepiolite fiber precursor;

preferably, the coating reaction is carried out under stirring conditions; the stirring speed is 60-100 rpm;

preferably, the drying temperature is 60-100 ℃, and the drying time is 6-8 h;

preferably, the drying temperature is 60-80 ℃, and the drying time is 7-8 h.

And removing the unfinished coated aluminum phosphate and sepiolite fibers by washing and centrifuging, thereby improving the quality of the aluminum phosphate coated sepiolite fiber precursor. The reaction of phosphoric acid with aluminum hydroxide is accelerated by stirring treatment. Too high a stirring rate can affect the coating success rate of the coated reaction product, and too low a stirring rate can increase the coating reaction time cost.

The drying is preferably vacuum drying, and the vacuum degree of the vacuum drying is 0.09-0.1 MPa. The centrifugal rotating speed is preferably 8000-10000 rpm, more preferably 8500-9500 rpm; the time for centrifugation is preferably 10-20min, more preferably 15 min.

The coated halogen-free fibrous flame retardant is prepared by the preparation method of the coated halogen-free fibrous flame retardant, and the diameter of the coated halogen-free fibrous flame retardant is 30-50 nm.

The coated flame retardant has good flame retardant performance and heat insulation performance.

The invention has the following beneficial effects:

the invention provides a preparation method of a coated halogen-free fibrous flame retardant, which comprises the steps of mixing inorganic acid dispersion liquid of sepiolite fibers with aluminum hydroxide and phosphoric acid, carrying out coating reaction under an acidic condition to obtain a precursor of the sepiolite fibers coated with halogen-free aluminum phosphate, and sintering the precursor to obtain the coated halogen-free fibrous flame retardant. The preparation method is simple and feasible, and is beneficial to large-scale production. According to the preparation method, inorganic acid is dispersed to organically acidify the surface of the sepiolite fiber, so that the sepiolite fiber is easier to coat aluminum phosphate, aluminum hydroxide and phosphoric acid are added after the sepiolite fiber is dispersed to generate the aluminum phosphate under an acidic condition, the aluminum phosphate is adsorbed on the sepiolite fiber through intermolecular force, the preparation of a precursor is completed, and the coating type halogen-free fibrous flame retardant with more uniform distribution can be obtained through sintering. The coated halogen-free fibrous flame retardant prepared by the preparation method has a good flame retardant effect, and the sepiolite fiber can greatly reduce the heat release rate, has a good smoke suppression effect, and also has good flame retardant synergy and heat insulation performance.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a scanning electron microscope photograph of an aluminum phosphate coated sepiolite fiber flame retardant prepared in a comparative example;

FIG. 2 is an X-ray diffraction pattern of an aluminum phosphate coated sepiolite fiber;

FIG. 3 is a scanning electron micrograph of the aluminum phosphate coated sepiolite fiber (AlPO4@ Sep IV) prepared in example 4;

FIG. 4 is a graph of the heat release rate and total heat release curve for composites prepared from the aluminum phosphate coated sepiolite fiber (AlPO4@ Sep IV) prepared in example 4 added to an epoxy resin.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The features and properties of the present invention are described in further detail below with reference to examples.