阅读说明：本技术 亚磷酸铝微胶囊化赤磷阻燃剂及其制备方法 (Aluminum phosphite microencapsulated red phosphorus flame retardant and preparation method thereof ) 是由 马兴良 王斌 梁俊兰 万俊成 吕润陶 陈云峰 后雪松 刘霄 于 2020-11-20 设计创作，主要内容包括：本发明公开了亚磷酸铝微胶囊化赤磷阻燃剂及其制备方法。该产品是在赤磷颗粒表面包覆一层亚磷酸铝阻燃剂,其制备方法包括(1)亚磷酸与含铝化合物加热预反应；(2)将步骤(1)中的预反应产物粉碎；(3)步骤(2)中得到的预反应物粉末与赤磷初混合后放入高能磨中,在惰性气体保护下混合粉碎；(4)在惰性气体保护下,搅拌热处理步骤(3)得到的混合物粉末,使亚磷酸与含铝化合物之间进一步完成反应,在赤磷颗粒表面形成一层亚磷酸铝包覆层；(5)在搅拌下冷却步骤(4)中的产物后即得到亚磷酸铝微胶囊化赤磷阻燃剂产品。该产品能产生协同阻燃效果,制备过程控制简单方便,工艺过程无“三废”产生。(The invention discloses an aluminum phosphite microencapsulated red phosphorus flame retardant and a preparation method thereof. The product is prepared by coating a layer of aluminum phosphite flame retardant on the surface of red phosphorus particles, and the preparation method comprises (1) heating and pre-reacting phosphorous acid and an aluminum-containing compound; (2) crushing the pre-reaction product in the step (1); (3) preliminarily mixing the pre-reactant powder obtained in the step (2) with red phosphorus, putting the mixture into a high-energy mill, and mixing and crushing the mixture under the protection of inert gas; (4) stirring the mixture powder obtained in the heat treatment step (3) under the protection of inert gas to further complete the reaction between phosphorous acid and an aluminum-containing compound, and forming an aluminum phosphite coating layer on the surface of red phosphorus particles; (5) and (5) cooling the product obtained in the step (4) under stirring to obtain the aluminum phosphite microencapsulated red phosphorus flame retardant product. The product can generate a synergistic flame retardant effect, the preparation process is simple and convenient to control, and the process does not generate three wastes.)

1. The aluminum phosphite microencapsulated red phosphorus flame retardant is characterized in that: coating an aluminum phosphite coating layer generated by mixing and reacting phosphorous acid and an aluminum-containing compound on the surface of red phosphorus with the average particle size of less than 20 microns;

the product is prepared by the following steps:

(1) mixing phosphorous acid and an aluminum-containing compound, heating to 100-150 ℃, pre-reacting for 2-4 hours, and cooling;

(2) after the pre-reactant in the step (1) is primarily crushed, the pre-reactant is further mixed and crushed in a high-energy mill, so that the average particle size of the pre-reactant reaches 3 to 0.1 micron;

(3) mixing red phosphorus and the pre-reactant powder obtained in the step (2) according to the weight ratio of 1: 0.1-1: 0.3, putting the mixture into a high-energy mill under the protection of inert gas, mixing and crushing to ensure that the average particle size of the mixture is between 5 and 20 microns;

(4) under the protection of inert gas, reacting the mixture fine powder obtained in the step (3) for 2-4 hours at the temperature of 150-180 ℃ under the conditions of stirring and mixing, so that the pre-reactant powder is reacted on the surfaces of red phosphorus particles;

(5) and (3) cooling the material subjected to heat treatment in the step (4) to normal temperature under the stirring condition to obtain the microencapsulated red phosphorus flame retardant product coated by the aluminum phosphite.

2. The microencapsulated red phosphorus flame retardant of aluminum phosphite of claim 1, characterized by: the ratio of the mole number of the phosphorus in the phosphorous acid to the mole number of the aluminum in the aluminum-containing compound is 1:1 to 1.5:1, and the mass fraction of the aluminum phosphite coating layer in the product is 10 to 30 percent.

3. The microencapsulated red phosphorus flame retardant of aluminum phosphite of claim 1, characterized by: the aluminum-containing compound includes aluminum oxide, aluminum hydroxide, aluminum oxyhydroxide, aluminum carbonate, aluminum hydroxycarbonate, boehmite, diaspore and mixtures thereof.

Technical Field

The invention belongs to the technical field of chemical industry, and relates to an environment-friendly preparation method of an aluminum phosphite microencapsulated red phosphorus flame retardant.

Background

The polymer material is widely suitable for the production and daily life of human beings today due to a plurality of advantages, but the polymer material also brings great threat to the life and property of human beings due to the characteristics of combustibility and flammability. In many fires, the fire source ignites the polymeric material causing the fire to occupy a considerable proportion. A large number of facts and practices prove that the fire hazard can be effectively reduced by flame-retardant treatment of the high polymer material. For a long time, the flame retardant technology of polymer materials and the flame retardant applied to polymer materials have been the hot spots of global research.

At present, the environmental protection problem is increasingly paid attention by society, and the environmental protection law of governments in various countries is gradually increased. The pollution is prevented and controlled from the source, and the environment-friendly product is inevitably developed and produced. The fire retardant is no exception, and the fire retardant is required to be produced, circulated and used until the fire retardant enters waste treatment and other links to reduce the emission of toxic and harmful pollutants so as to achieve the effect of green fire retardation. Therefore, the flame retardant material must satisfy both the requirements of flame retardant standard and environmental protection regulation, and thus, the development of the flame retardant is bound to the trend of no halogenation, no smoke and no toxicity, high thermal stability and good compatibility. The use of phosphorus-based flame retardants is one of the important ways to achieve these objectives.

Since the Bayer company (Bayer) in Germany in the early sixties of the last century, red phosphorus is found to be used as a high molecular polymer flame retardant, and the application of red phosphorus is gradually converted from traditional safe matches, fireworks, pesticides and metal phosphide to a high molecular material flame retardant. Particularly, in recent years, the application field of phosphorus flame retardants is expanding due to the global drive of halogen-free flame retardants, and the amount of phosphorus flame retardants is rapidly increasing. Red phosphorus is widely applied as an efficient non-halogenated phosphorus flame retardant, but because the red phosphorus has low ignition point, is easy to spontaneously combust, is easy to explode, and has the defects of generating oxyacid of phosphorus and highly toxic and flammable phosphine gas by disproportionation reaction with water in the air, the safety and protection problems of the red phosphorus in the production, storage, transportation and use processes are more prominent; on the other hand, when red phosphorus is used as a flame retardant, the flame retardant performance of the red phosphorus is improved along with the reduction of the particle size of the red phosphorus, but the specific surface area of the red phosphorus is improved along with the reduction of the particle size, so that the defects are worsened, and the compatibility, the additive property, the mechanical property and the electrical property of the red phosphorus in polymer processing are seriously influenced.

The most effective and versatile method for overcoming the above-mentioned drawbacks when red phosphorus is used as a flame retardant is microencapsulation of red phosphorus. The principle is that red phosphorus particles are taken as core materials, a layer of wall material of a coating layer is formed outside the particles, so that the red phosphorus particles are wrapped, and the red phosphorus is isolated from the outside such as air, moisture and the like, thereby achieving the purpose of stabilization and improving the processing performance, the mechanical property and the electrical property between the red phosphorus flame retardant and a polymer; meanwhile, a material capable of generating a better flame-retardant synergistic effect with red phosphorus can be selected as a wall material, and the flame retardant property of the red phosphorus can be greatly improved after the red phosphorus is microencapsulated.

The current red phosphorus microencapsulation process is generally as follows: the red phosphorus is firstly dispersed in a water phase for wet grinding, the red phosphorus suspension with qualified grain diameter is treated by a sol-gel method, so that one or more layers of wall materials are deposited on the surface of the red phosphorus, the treated red phosphorus suspension is filtered, and a filter cake is washed and dried to obtain the product. According to different wall materials deposited on the surface of red phosphorus, different microencapsulation methods such as inorganic, organic-inorganic or inorganic-organic are adopted. In the methods, a large amount of wastewater containing inorganic matters or organic matters is generated in the preparation process and needs to be further treated, and a small amount of extremely fine red phosphorus particles generated in the wet grinding process are easy to generate percolation in the filtering and washing processes and enter the wastewater, so that the percolation loss is generated and the wastewater treatment is further difficult.

In recent years, aluminum Phosphite has received great attention as a Phosphorus flame retardant or a flame retardant synergist, and RyoOyama et al (development of aluminum phosphate and its application, phosphorous Research Bulletin, vol.32 (2016): 10-13) analyzed the preparation and related physicochemical properties of an aluminum Phosphite (APA-100) flame retardant product commercialized in japan, which is a hard foam generating property when heated to be an effective polymer flame retardant, and also shows better corrosion resistance to metals when polymer processing, which can be used as a flame retardant alone or in combination with other Phosphorus flame retardants as a synergist, while having a higher decomposition temperature and lower water solubility.

Chinese patent CN104093663B describes that the aluminum phosphite adopts superfine aluminum hydroxide and phosphorous acid as raw materials and adopts solid phase direct heating neutralization reaction to obtain a product, and the product and diethyl aluminum hypophosphite are matched to be used as a flame retardant, so that the aluminum phosphite shows good flame retardant synergy.

Chinese patent CN104364305B describes a method for preparing aluminum phosphite with various molecular structures, the method adopts aluminum hydroxide and phosphorous acid as raw materials, the reaction is completed in an autoclave under stirring, feed liquid is filtered, washed and dried to obtain a product, the product has higher thermal stability, and the aluminum phosphite and diethyl aluminum hypophosphite of the types are matched to be used as synergists, and the product has good flame-retardant synergistic performance.

Chinese patent CN109385080A proposes that sulfite, diethyl aluminum hypophosphite and melamine polyphosphate are adopted as flame retardant synergists to show good flame retardant performance, and meanwhile, polymer processing has good fluidity and discoloration resistance, and polymer products also show excellent electrical properties.

Japanese patent JP5341031B proposes a method for improving the thermal stability of an aluminum phosphite flame retardant and reducing the amount of hydrogen phosphide gas generation, in which one or more of oxides, hydroxides and carbonates of transition metals such as nickel, copper and iron are supported on the surface of aluminum phosphite, and the aluminum phosphite flame retardant treated by the method exhibits higher thermal stability and flame retardancy when applied to thermoplastic plastics.

Disclosure of Invention

The invention aims to search for a more environment-friendly red phosphorus microcapsule preparation process method, which does not generate three wastes, can overcome the defect that waste water containing organic or inorganic pollutants generated in the prior process method needs to be further treated, and provides a more economical and applicable preparation method of the aluminum phosphite microcapsule red phosphorus flame retardant; meanwhile, the method has a flame retardant mixture which takes red phosphorus (core material) as a flame retardant and aluminum phosphite (wall material) as a synergist, and can meet the requirement of higher flame retardant property of polymers.

In the wall material, phosphorous acid is used as a phosphorous source, an aluminum-containing compound is used as an aluminum source, and alumina, aluminum hydroxide, aluminum oxyhydroxide, aluminum carbonate, aluminum hydroxycarbonate, boehmite, diaspore and a mixture thereof are selected. Phosphorous acid and aluminum-containing compound are pre-reacted, and the crushed pre-reactant is deposited on the surface of red phosphorus particle with average particle size smaller than 20 microns to form the microencapsulated red phosphorus flame retardant with red phosphorus particle as core and aluminum phosphite attached to the surface to form wall material. The preparation process comprises the following steps:

(1) mixing phosphorous acid and an aluminum-containing compound for pre-reaction treatment and cooling;

(2) crushing the pre-reaction product in the step (1), placing the crushed pre-reaction product in a high-energy mill for further crushing, and taking out the crushed pre-reaction product for later use;

(3) mixing the fine powder obtained in the step (2) with red phosphorus, placing the mixture into a high-energy mill under the protection of inert gas, and mixing and crushing the mixture;

(4) sending the mixed powder obtained in the step (3) into a stirring device capable of being heated or cooled, and heating under the protection of inert gas;

(5) and (4) cooling the product after the reaction in the step (4) to room temperature to obtain the aluminum phosphite microencapsulated red phosphorus product.

In the invention, the high-energy mill is a planetary mill, a vibration mill, a stirring mill, a ball mill and the like, and the stirring equipment capable of heating or cooling is a kneader, an internal mixer, a ribbon mixer and the like.

The ratio of the mole number of phosphorus in the phosphorous acid to the mole number of aluminum in the aluminum-containing compound in the step (1) is 1:1 to 1.5:1, when the ratio is less than 1:1, the pH value of the product is low, which is very unfavorable for the stability of red phosphorus, and when the ratio is more than 1.5:1, more unreacted aluminum-containing raw materials are mixed in the product of the wall material, which is also unfavorable for the stability improvement of red phosphorus. The temperature of the pre-reaction is between 100 ℃ and 150 ℃ and below 100 ℃ the reaction rate is extremely slow, above 150 ℃ a phosphorous acid disproportionation decomposition occurs which is undesirable for the products claimed in the present invention. The pre-reaction time is between 2 hours and 4 hours, and the pre-reaction time depends on factors such as the pre-reaction temperature, the particle size and the type of the aluminum-containing compound and the like.

The average particle size of the crushed pre-reaction product in the step (2) is between 0.1 and 3 microns, when the average particle size is higher than 3 microns, the surface coating of the final product is not uniform, the stability of the final product is influenced, when the average particle size is lower than 0.1 micron, the crushing time is too long and the crushing is not economical, and the value is selected to be related to the average particle size of the final product, and when the average particle size of the final product is large, the value is selected to be at a high limit, and vice.

The weight ratio of red phosphorus to pre-reaction product powder in the step (3) is 1:0.1 to 1:0.3, and controlling the average particle size of the mixture crushed to be between 5 and 20 microns.

In the step (4), the mixture fine powder obtained in the step (3) is heated at a temperature of 150 ℃ to 180 ℃ for 2 hours to 4 hours.

And (5) cooling the heat treatment product in the step (5) in an indirect mode, wherein room-temperature air or water is used as a cooling medium for removing heat of the material.

The preparation method of the microcapsule of the red phosphorus flame retardant avoids the problem of 'three wastes' in the production process, is simple and convenient to operate and control in the production process, can obtain the microcapsule red phosphorus flame retardant product with high thermal stability and good flame retardant effect, and is particularly suitable for engineering plastics processed at high temperature, such as nylon, polycarbonate, polyester and the like.

According to the invention, the prepared product is a composite flame retardant taking red phosphorus as a main flame retardant and aluminum phosphite as a synergist, and microencapsulated red phosphorus flame retardant products with different coating contents and different particle sizes can be prepared according to different requirements of polymer types and flame retardant grades so as to meet the requirements of the microencapsulated red phosphorus flame retardant products under different application conditions.

Detailed Description

The invention is described in detail by the following specific embodiments, and the specific embodiments described in detail are only examples within the scope defined in the claims and do not represent the full scope of the claims. For example, the aluminum-containing compound in the examples is only aluminum hydroxide, and the other aluminum-containing substances listed in the claims are similar to aluminum hydroxide in principle or in common to those of ordinary skill in the art, and thus are not listed by way of example in the examples.

The raw materials used in all the examples

A. Raw material for preparing microencapsulated red phosphorus flame retardant

Industrial red phosphorus: the average particle size of the product is less than 100 μm.

Phosphorous acid: shijiazhuang Tiancheng auxiliary agent factory, phosphorous acid (H)₃PO₃) The mass fraction is more than or equal to 98 percent.

Aluminum hydroxide: yunnan Metallurgical group Co., Ltd, Al (OH)₃Not less than 98%, and average particle size greater than 60 μm.

B. Raw materials for evaluating flame retardant performance of flame retardant

Nylon (PA 66): U.S. DuPont 101F

Glass fiber: ECS 14-4.5-588 of Jushi group Limited

The main equipment used in the examples is as follows:

C. equipment for preparing microencapsulated flame retardant

The pre-reaction of the phosphorous acid and the aluminum-containing compound in the step (1) is carried out in a high-temperature oven;

crushing the pre-reaction product in the step (2) in a 5 liter vibration mill using a stainless steel ball as a grinding medium;

crushing the mixture of the red phosphorus and the pre-reaction powder in the step (3) in a vertical planetary mill with a 4L stainless steel ball milling tank, wherein the grinding medium is a stainless steel ball;

and (5) adopting a 5-liter kneader, heating or cooling the jacket by using heat conduction oil, electrically heating the heat conduction oil, indirectly cooling the heat conduction oil by using water, and arranging a material temperature measuring instrument at the side part of the kneader.

D. Equipment for evaluating flame retardant performance of flame retardant

An extruder: TSH-35B of Tengda machinery equipment Limited in Nanjing

An injection molding machine: SA860/26G of Haitian Plastic machine group Co., Ltd

UL94 horizontal vertical burning test machine: guangzhou Automation Equipment Co., Ltd GC-UL-A

The detection and evaluation methods of the final products obtained in the examples are as follows:

coating amount: dissolving the sample in dilute hydrochloric acid, boiling to dissolve the coating layer, filtering, washing and separating red phosphorus, and measuring the red phosphorus content according to the industrial red phosphorus standard (GB/T4947-2003) so as to calculate the weight ratio of the coating layer.

And (3) moisture absorption rate testing, namely accurately weighing 2.00 g of sample, uniformly dispersing the sample at the bottom of a weighing bottle, putting the weighing bottle into a closed drying box filled with 18.6 +/-0.5% sulfuric acid solution (the relative humidity is 90%), keeping the temperature of the drying box at 30 ℃, standing for 30 days, weighing, calculating the increased weight of the sample, and expressing the moisture absorption rate by the weight gain percentage of each gram of sample.

And (3) ignition point determination: the ignition point was measured by an HY9343 type solid spontaneous ignition tester.

Amount of hydrogen phosphide generated: 10.00 g of a sample is accurately weighed and suspended in a 500 ml three-neck flask containing 100 ml of distilled water, a condensation reflux device is arranged at the outlet of the flask, and the temperature of the gas phase outlet of the reflux device is kept to be less than 30 ℃. The flask was heated in a 120 ℃ silicon oil bath for 2 hours to react the phosphine with HgCl under nitrogen to form insoluble P (HgCl)₃，P(HgCl)₃ Oxidized with iodine and excess iodine was titrated with sodium thiosulfate to calculate the amount of phosphine released per gram of red phosphorus per hour, expressed in μ g/g.h.

And (3) particle size analysis: particle size measurement was carried out using a model LS-909 laser particle sizer.

Evaluation of flame retardant Properties: mixing a flame retardant with nylon 66 and glass fibers according to a certain weight ratio, bracing in an extruder, cooling, crushing and drying to obtain a flame retardant nylon material, and making a test sample strip into a test injection molding machine to carry out UL-94 rating according to the Standard of the horizontal and vertical methods for measuring the combustion performance of plastics (GB/T2408-2008).

Test examples 1 to 10

Step (1), weighing phosphorous acid and aluminum hydroxide according to the amount determined in table 1, uniformly mixing 1000 g of the phosphorous acid and the aluminum hydroxide, placing the mixture in a stainless steel plate, placing the stainless steel plate in a high-temperature oven, pre-reacting the mixture for the time determined in table 1 at the temperature determined in table 1, taking out and weighing the mixture to obtain materials of different pre-reactants, which are respectively expressed by A.B.C.D.E and shown in table 1.

Table 1: prereaction conditions and products

And (2) cooling the pre-reaction product obtained in the step (1), coarsely crushing 350 g of the pre-reaction product, putting the pre-reaction product into a 5L vibration mill for crushing, sieving the crushed pre-reaction product after a period of time for later use, wherein the crushing time of each material and the average particle size index of the crushed material are respectively represented by No. 1 to No. 10, and the detailed table is shown in Table 2.

TABLE 2 grinding conditions and mean particle size after grinding in step (2)

Weighing a certain amount of powder 1# to 10# obtained in the step (3) and the step (2), primarily mixing the powder with 1000 g of industrial red phosphorus, sequentially compiling example numbers 1 to 10 in Table 3, respectively filling the primarily mixed materials into 4L stainless steel ball tanks with stainless steel balls and replacing the stainless steel balls with nitrogen, compacting, replacing the upper space with nitrogen, covering ball mill cover, filling into a vertical planetary mill, grinding until the average particle size is less than 20 micrometers, taking out the materials in the ball mill tanks, and separating the grinding balls to obtain a mixed material.

Table 3: examples 1 to 10 test conditions

And (4) transferring the crushed mixed material obtained in the step (3) into a kneader, stirring, mixing and heating under the protection of nitrogen, keeping the temperature for a certain time when the temperature of the material is raised to a certain temperature, and stopping heating.

And (5) cooling the material subjected to heat treatment in the step (4) to room temperature, and taking out to obtain a final product.

The evaluation results of the tests of microencapsulated red phosphorus products of examples 1 to 10 are shown in Table 4.

Table 4: EXAMPLES 1 TO 10 examination and evaluation results of microencapsulated Red phosphorus product

TABLE 5 flame retardant test and test results for microencapsulated red phosphorus products prepared in examples 1 to 10

Evaluation of flame retardancy of product

Preparation of test specimens

Respectively taking out a certain amount of nylon 66, glass fiber and the flame retardant, uniformly mixing, extruding and granulating the mixture in an extruder, and drying; and (4) carrying out injection molding on the dried material in an injection molding machine to obtain the pattern size specified by various test standards.

Test of flame retardant Properties

The prepared test sample bars are tested according to the GB/T2408-2008 standard, and UL-94 rating is carried out.

The flame retardant test conditions and test results of the microencapsulated red phosphorus products prepared in examples 1 to 10 are shown in Table 5.