CN1640865A - Hydroxy aluminium oxalate, and its preparing method and hydroxy aluminium oxalate as fire retardant - Google Patents

Abstract

Hydroxy aluminum oxalate and its preparation method of the present invention, hydroxy aluminum oxalate as a flame retardant, the molecular formula of hydroxy aluminum oxalate is: Al ₂ (C ₂ O ₄ )(OH) ₄ , and its X-ray diffraction patterns are respectively at D value of 6.5149 , 4.7263, 4.2957,  have strong diffraction peaks. Hydroxy aluminum oxalate was prepared by (A) carbonization decomposition and (B) modification in a stirred reactor. The hydroxyaluminum oxalate with good dispersibility and complete crystal form is obtained by using the slurry in step (B) through (C) crystal form control treatment. The smallest one-dimensional size of hydroxyaluminum oxalate is controllable between 40 nanometers and several microns, and its extrapolated initial weight loss temperature is above 340°C, and the weight loss rate before 500°C reaches 51%. It is a green and environmentally friendly flame retardant . It can especially be used for flame retardancy of thermoplastics and other polymer materials whose processing temperature is above 210°C.

Description

Hydroxy aluminum oxalate and preparation method thereof, hydroxy aluminum oxalate as flame retardant

field of invention

The invention relates to hydroxyaluminum oxalate and a preparation method thereof. The hydroxyaluminum oxalate is prepared by carbonization, decomposition and modification of sodium metaaluminate solution and carbon dioxide. It is a flame retardant and can be used for flame retardant of polymer materials.

Background technique

Since engineering plastics are widely used in human's daily life, its flame retardant performance has been paid more and more attention. At present, flame-retardant thermoplastic engineering plastics usually use additive flame retardants, and the most commonly used ones are organic halogen flame retardants. As we all know, halogen flame retardants have a large amount of smoke during combustion, and release toxic and corrosive hydrogen halide gas. Inorganic flame retardants have the characteristics of halogen-free, non-toxic, low-smoke, etc., but they have the disadvantages of large amount of addition and poor affinity with the substrate, which has a great impact on the processing performance and mechanical properties of the material, and ordinary aluminum hydroxide can be used at 210 ° C The above begins to decompose and dehydrate. The application of nanotechnology provides a new idea for the development of flame retardant science and technology. The traditional inorganic flame retardant materials are ultrafine, and the quantum size effect, small size effect, and surface effect of the nanoparticles themselves are used to enhance the interface effect, improve the compatibility between the inorganic substance and the polymer matrix, and reduce the dosage. And the purpose of improving flame retardancy.

At present, the applicant has disclosed the ultrafine modified Aluminum hydroxide product and method for its preparation. Its product X-ray diffraction pattern has diffraction peaks at D values of 6.39, 6.16 and 4.67, and its 2θ angles are 13.836, 14.347 and 19.006 respectively. Its preparation method is to use a rotating bed to carry out the reaction of carbon dioxide carbonization of sodium metaaluminate, that is, the prepared sodium metaaluminate solution is in countercurrent contact with the carbon dioxide gas entering from the gas inlet in the filler of the rotating packed bed, and carbonization and decomposition are carried out. reaction. The reaction temperature is adjusted by the water jacket outside the liquid circulation storage tank, the pH value is adjusted with carbon dioxide, and the end point of the reaction is controlled by this, the slurry at the end of the reaction is filtered and washed with deionized water to obtain hydrated alumina gel. Then add specific modifier oxalic acid or oxalate in the autoclave to modify it. The structure of the rotary bed equipment adopted in this method is relatively complicated, and there are many auxiliary equipments, which is inconvenient for maintenance and disassembly, and the high viscosity of hydrated alumina is easy to cause blockage of the channel. In addition, due to the circulating flow of the slurry, the power consumption is large.

Therefore, it is necessary to develop a flame retardant product and process with good thermal stability and high initial weight loss temperature, a production method with relatively simple equipment and low energy consumption.

Contents of the invention

The invention proposes hydroxyaluminum oxalate and a preparation method thereof. The hydroxyaluminum oxalate is used as a flame retardant in the flame retardant application of polymer materials.

The hydroxyaluminum oxalate provided by the present invention is a new chemical substance, its molecular formula is: Al ₂ (C ₂ O ₄ )(OH) ₄ , and its X-ray diffraction patterns are respectively at D values of 6.5149, 4.7263, 4.2957, and 3.7387 There are strong diffraction peaks at , and their 2θ correspond to 13.580°, 18.760°, 20.660°, and 23.780°, respectively.

The preparation method of hydroxyaluminum oxalate of the present invention comprises the following steps:

(A) carbonization decomposition

Under the condition of 20-60°C in a stirred reactor, stir and mix sodium metaaluminate solution with a concentration of 0.5-2.5 mol/L and carbon dioxide gas to carry out carbonization decomposition reaction, and the pH value of the solution at the end of the reaction is 11.5-8.0; The slurry is filtered and washed to obtain an aluminum hydroxide filter cake;

(B) Modification treatment

Stir the aluminum hydroxide filter cake obtained in step (A) with deionized water and then mix it with modifier oxalic acid. The molar ratio of oxalic acid to aluminum hydroxide is 0.65-1.0, and react at a reaction temperature of 150-180°C for 30 Minutes to 2 hours, the generated slurry is filtered, washed and dried to obtain aluminum oxalate.

The present invention also includes (C) crystal form control treatment in the operation steps, and the operation steps are as follows: add a crystal form control agent to the slurry generated in step (B), the crystal form control agent is sodium phosphate or sodium metaphosphate, and the crystal form control agent is sodium phosphate or sodium metaphosphate. The dosage of the type control agent is 0.5%-1% of the hydroxyaluminum oxalate; the temperature is 70-80° C., the constant temperature is stirred for 1 hour, and then filtered, washed and dried to obtain the hydroxyaluminum oxalate.

The hydroxyaluminum oxalate of the present invention has an extrapolated initial weight loss temperature above 340°C and a weight loss rate of 51% before 500°C, and can be used as a flame retardant for flame retardancy of polymer materials. Especially as a flame retardant, it can be used for the flame retardancy of thermoplastics whose processing temperature is above 210°C.

The invention provides an ultrafine modified aluminum hydroxide, that is, aluminum hydroxy oxalate, which is a white powder with a bulk density of 0.28-0.77g/cm ³ and a compact density of 0.44-1.16g/cm ³ . According to chemical analysis, it contains 26.4% Al, 60.8% O, 2.0% H, and 11.3% C. Therefore, it is speculated that its molecular formula is: Al ₂ (C ₂ O ₄ )(OH) ₄ . The method of the invention can prepare hydroxyaluminum oxalate products with different particle sizes and shapes and the minimum one-dimensional size ranging from 40nm to 5000nm.

In the method of the present invention, the main purpose of the carbonization and decomposition process in step (A) is to provide a precursor-aluminum hydroxide for the next modification process.

In step (A), the gas containing carbon dioxide can be industrially pure carbon dioxide or a mixed gas containing carbon dioxide.

In step (A), the concentration of the sodium metaaluminate solution may be 0.5-2.5 mol/l, preferably 0.8-2 mol/l.

In step (B), the modifier oxalic acid used may be a solution or a crystal.

The aluminum hydroxide used in the step (B) is the aluminum hydroxide filter cake obtained in the carbonization decomposition process of the step (A), and the molar ratio of the modifying agent to the aluminum hydroxide filter cake from the step (A) is 0.65 to 1.0, preferably 0.7 to 0.8.

The reaction time of step (B) can vary widely, depending on the amount of reactants, the size of the reactor volume, and the like. Usually 30 minutes to 2 hours, preferably 45 minutes to 1 hour.

In step (C), adding a crystal form control agent can further disperse and refine the particles, narrow the particle size distribution, and control the shape of the hydroxyaluminum oxalate crystal.

The filtrate in steps (B) and (C) can be recovered and recycled in the modification process.

Spherical or spindle-shaped hydroxyaluminum oxalate products can be obtained through the above two operating steps (A) and (B). After three operation steps (A), (B) and (C), the aluminum oxalate product in the shape of hexagonal flakes or diamond flakes can be obtained.

The equipment used in the method of the invention is an ordinary stirring reaction kettle, which has simple structure, convenient operation and no problem of equipment blockage.

The aluminum hydroxy oxalate provided by the invention has a high initial weight loss temperature and a high weight loss rate, and is very suitable as a flame retardant for flame retardant products. Moreover, the flame retardant does not contain halogen, and no toxic gas is released when it is decomposed by heat, so it is a green and environment-friendly flame retardant. Through flame retardant and smoke elimination experiments and physical property measurements of acrylonitrile-butadiene-styrene copolymer (abbreviated as ABS) and polyamide 66 (referred to as Nylon66), on the premise of ensuring that the mechanical properties of the matrix material meet the application standards, The oxygen index can reach 29. Therefore, the hydroxyaluminum oxalate of the present invention can be used in materials such as ABS and Nylon66 that conventional ultrafine aluminum hydroxide cannot use. The preparation method provided by the present invention has simple process and equipment, stable product quality, can prepare hydroxyaluminum oxalate with the smallest one-dimensional size between 40 nanometers and several microns, and can control the size and shape of the particles, and extrapolate the initial weight loss temperature It is a new type of inorganic flame retardant with a temperature above 340°C and a weight loss rate of about 51% before 500°C, so it can be used for flame retardancy of thermoplastics and other polymer materials whose processing temperature is above 210°C.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) pattern of aluminum oxalate of the present invention.

Fig. 2 is the thermogravimetric (TG) and differential thermal analysis (DTA) curves of the hydroxyaluminum oxalate prepared in Example 3 of the present invention.

Fig. 3 is the Fourier transform infrared spectrum (FTIR) figure of aluminum oxalate of the present invention.

Fig. 4 is the transmission electron microscope (TEM) photograph of the aluminum oxalate hydroxy produced in Example 1 of the present invention.

Fig. 5 is a transmission electron microscope (TEM) photo of the aluminum oxalate oxalate prepared in Example 3 of the present invention.

Fig. 6 is a transmission electron microscope (TEM) photo of aluminum oxalate hydroxy produced in Example 4 of the present invention.

Fig. 7 is a transmission electron microscope (TEM) photo of aluminum oxalate hydroxy produced in Example 5 of the present invention.

Fig. 8 is a transmission electron microscope (TEM) photograph of aluminum oxalate hydroxy produced in Example 6 of the present invention.

The hydroxyaluminum oxalate of the present invention can be seen from the X-ray diffraction (XRD) spectrum of Figure 1, the hydroxyaluminum oxalate has strong diffraction peaks at 2θ of 13.580°, 18.760°, 20.660°, 23.780°, etc. The diffraction peak intensities when 2θ is 13.580°, 18.760°, 20.660°, and 23.780° are 37.9%, 100.0%, 16.6%, and 25.1%, respectively. Consult the standard library PDF that contains the spectra of Al, O, H and the elements contained in the modifier, where the diffraction peak with D value at 6.5149 is close to Bohmite (21-1307), and the diffraction peak with D value at 4.2957 and 3.7387 It is close to Bayerite (20-0011), but there is no crystal phase that matches the diffraction peaks of aluminum hydroxy oxalate in the diffraction pattern in Figure 1, indicating that aluminum hydroxy oxalate of the present invention is a new chemical substance. The XRD patterns of the aluminum hydroxy oxalate prepared in other examples are all the same as those shown in Figure 1.

Fig. 2 is the thermogravimetric (TG) and differential thermal analysis (DTA) curves of aluminum oxalate prepared in Example 3 of the present invention. The experimental condition is to heat up from room temperature to 580°C with a temperature rise rate of 10°C/min under a nitrogen atmosphere, and analyze the thermal weight loss curve obtained by the thermal analysis system of Beijing Optical Instrument Factory. As can be seen from Figure 2, the hydroxyaluminum oxalate of the present invention The extrapolated initial weight loss temperature is 356°C, the peak temperature is 399°C, and the weight loss rate before 500°C is 50.73%. The initial weight loss temperature of commercially available aluminum hydroxide flame retardant without modification treatment is 210°C, and the overall weight loss rate is only 34%. The preparation conditions of the hydroxyaluminum oxalate of the present invention are different, and the particle size and shape of the obtained product are different, and the weight loss temperature is slightly different, but their thermal weight loss curve and differential thermal analysis curve shape are the same as those in Fig. 2, and their extrapolated initial The weight loss temperature is above 340°C.

It can be seen that Fig. 3 is a Fourier transform infrared spectrum (FTIR) picture of aluminum oxalate oxalate of the present invention. The hydroxyaluminum oxalate product of the present invention has absorption peaks at wave numbers 3657.52, 1708.96, 1368.40, etc., among which the absorption peak at wave number 1708.96 indicates that there is a carbonyl group in the product, which can explain the successful modification of aluminum hydroxide and oxalic acid. The FTIR figures of the hydroxyaluminum oxalate produced by each embodiment of the present invention are the same.

Figures 4 to 8 are several representative transmission electron microscope (TEM) photos of aluminum oxalate oxalate of the present invention. According to the different preparation conditions, the aluminum hydroxy oxalate of the present invention can produce products with different particle sizes and shapes, the smallest one-dimensional size ranging from 40nm to 5000nm, and the shapes include spindle, chain-like spherical, diamond-shaped sheet, spherical, etc.

Detailed ways

The present invention is further described below with embodiment.

Example 1

Add 45 grams of industrial sodium hydroxide to 100 ml of tap water, heat, add 65 grams of industrial aluminum hydroxide after the solution boils, boil for 30 minutes, then add tap water to 800 ml, filter, and remove impurities to obtain partial aluminum Sodium acid solution, its concentration is about 1.0mol/L. Put this sodium metaaluminate solution in a stirred reaction kettle, at 20°C, let in the carbon dioxide gas from the decompressed steel cylinder, and start the agitator at the same time, when the pH value of the solution becomes 10.5, the carbonization and decomposition will end reaction. The resulting slurry is filtered and washed to obtain an aluminum hydroxide filter cake. Then stir the filter cake with deionized water, add solid oxalic acid, make a suspension according to the molar ratio of aluminum hydroxide and oxalic acid 1:0.7, put it in an autoclave for modification treatment, heat it to a temperature of 160°C, and 45 minutes at constant temperature. After the modification is completed, the material is taken out, put into another stirring tank, add 1% (mass ratio of sodium metaphosphate to aluminum oxalate) sodium metaphosphate, stir at 70°C to 80°C for 1 hour, and filter the slurry , washing, and drying of the filter cake, diamond-shaped hydroxyaluminum oxalate with good dispersion performance and regular shape was obtained. The electron micrograph is shown in Figure 4. The extrapolated initial weight loss temperature is 352.1°C, and the peak temperature is 398.6°C. The temperature before 500°C The weight loss rate is 50.62%, the bulk density is 0.44g/cm ³ , and the compact density is 0.67g/cm ³ .

Example 2

Except that following operating conditions change, all the other are the same as embodiment 1. 108 grams of sodium hydroxide are added to 150 milliliters of tap water, and the aluminum hydroxide of 158 grams is added after being heated to solution boiling. Continue heating, boil for 30 minutes, and obtain a sodium metaaluminate solution with a concentration of about 2.5mol/L after filtering. It is carbonized and decomposed at 60°C, and the pH value of the end point of carbonization is 11.5. During the modification treatment, the constant temperature was 180° C., the time was 30 minutes, and the molar ratio of oxalic acid to aluminum hydroxide was 1. The slurry obtained after modification is directly filtered, washed, and the filter cake is dried without adding a crystal form control agent to obtain a hydroxyaluminum oxalate product.

Example 3

Except that following operating conditions change, all the other are the same as embodiment 1. During the modification process, the temperature was maintained at 170° C. for 60 minutes. The prepared modified slurry is directly filtered, washed and the filter cake is dried without adding a crystal form control agent to obtain a chain-like spherical hydroxyaluminum oxalate product. Its TEM photo is shown in Figure 5. The extrapolated initial weight loss temperature is 356°C, the peak temperature is 399°C, the weight loss rate before 500°C is 50.73%, its bulk density is 0.51g/cm ³ , and its compact density is 0.87g/cm ³ .

Example 4

Except that following operating conditions change, all the other are the same as embodiment 1. During the modification process, the molar ratio of oxalic acid to aluminum hydroxide was 0.65. During the crystal form control process, 0.5% sodium phosphate was added for dispersion and crystal form control. The TEM photo of the modified product is shown in Figure 6. The hydroxyaluminum oxalate is a hexagonal flake product; the extrapolated initial weight loss temperature is 363°C, the peak temperature is 403°C, and the weight loss rate before 500°C is 51.33%. Its bulk density is 0.28g/cm ³ and compact density is 0.44g/cm ³ .

Example 5

Except that following operating conditions change, all the other are the same as embodiment 1. In the process of carbonization and decomposition, carbonization and decomposition are carried out at 30°C, and the pH value of the end point of carbonization is 11.0. The modification treatment time is 65min. After modification, the slurry is directly filtered, washed, and the filter cake is dried without adding a crystal form control agent to obtain a spindle-shaped hydroxyaluminum oxalate product. The TEM photo of the product is shown in Figure 7, the bulk density is 0.38g/cm ³ and the compact density is 0.60g/cm ³ .

Example 6

Except that following operating conditions change, all the other are the same as embodiment 1. During the modification treatment process, the modification treatment temperature was 150° C., and the temperature was kept constant for 2 hours. After modification, the slurry is directly filtered, washed, and the filter cake is dried without adding a crystal form control agent to obtain a spherical hydroxyaluminum oxalate product. The TEM photo of the product is shown in Figure 8, the bulk density is 0.47g/cm ³ and the compact density is 0.77g/cm ³ .

Example 7

Except that following operating conditions change, all the other are the same as embodiment 1. In the process of carbonization and decomposition, the pH value of the end point of carbonization is 8.0. During the modification process, the modification time was 65 minutes, the modification temperature was 160° C., and the molar ratio of oxalic acid to aluminum hydroxide was 1. The bulk density of the product aluminum hydroxy oxalate is 0.77g/cm ³ , and the compact density is 1.16g/cm ³ .

Example 8

Except that following operating conditions change, all the other are the same as embodiment 1. During the carbonization decomposition process, 65 grams of sodium hydroxide was added to 150 milliliters of tap water, and the aluminum hydroxide of 95 grams was added after being heated to solution boiling. Continue heating, boil for 30 minutes, and obtain a sodium metaaluminate solution with a concentration of about 1.5 mol/L after filtration. It is carbonized and decomposed at 40°C, and the pH value of the end point of carbonization is 10.8. During the modification treatment, the constant temperature was 160° C., the constant temperature time was 50 minutes, and the molar ratio of oxalic acid to aluminum hydroxide was 0.65. After modification, no crystal form control agent is added to the slurry, and the product is obtained by directly filtering, washing, and drying the filter cake to obtain the hydroxyaluminum oxalate product. Its bulk density is 0.48g/cm ³ and compact density is 0.69g/cm ³ .

Claims (5)

1. A hydroxyaluminum oxalate whose molecular formula is: Al ₂ (C ₂ O ₄ )(OH) ₄ , and its X-ray diffraction pattern has strong diffraction peaks at D values of 6.5149, 4.7263, 4.2957, and 3.7387  respectively, Their 2θ correspond to 13.580°, 18.760°, 20.660°, and 23.780°, respectively. 2. The preparation method of hydroxyaluminum oxalate according to claim 1, comprising the following steps: (A) carbonization decomposition Under the condition of 20-60°C in a stirred reactor, stir and mix sodium metaaluminate solution with a concentration of 0.5-2.5 mol/L and carbon dioxide gas to carry out carbonization decomposition reaction, and the pH value of the solution at the end of the reaction is 11.5-8.0; The slurry is filtered and washed to obtain an aluminum hydroxide filter cake; (B) Modification treatment Stir the aluminum hydroxide filter cake obtained in step (A) with deionized water and then mix it with modifier oxalic acid. The molar ratio of oxalic acid to aluminum hydroxide is 0.65-1.0, and react at a reaction temperature of 150-180°C for 30 Minutes to 2 hours, the generated slurry is filtered, washed and dried to obtain aluminum oxalate. 3. The method according to claim 2, characterized in that: (C) crystal form control treatment is also included in the operation steps, and the operation steps are as follows: In the slurry generated in step (B), add a crystal form control agent, the crystal form control agent is sodium phosphate or sodium metaphosphate, and the consumption of the crystal form control agent is 0.5% to 1% of hydroxyaluminum oxalate; the temperature is 70 to 80 °C, stirred at constant temperature for 1 hour, then filtered, washed, and dried to obtain hydroxyaluminum oxalate. 4. The hydroxyaluminum oxalate according to claim 1, characterized in that its extrapolated initial weight loss temperature is above 340°C, and the weight loss rate before 500°C reaches 51%, and it can be used as a flame retardant for polymer materials. burn. 5. The hydroxyaluminum oxalate according to claim 4, characterized in that it can be used as a flame retardant for the flame retardant of thermoplastics whose processing temperature is above 210°C.

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