KR20190138003A - Manufacturing Method of Hypophosphorous Type Flame Retardants - Google Patents

Abstract

The present invention relates to a manufacturing method of a hypophosphite flame retardant and, more specifically, to a manufacturing method of a hypophosphite flame retardant, which finely controls particle size by including reaction with hypophosphite and aluminum salts under ultrasonic energy application and can solve discoloration and heat resistance problems.

Description

Manufacturing Method of Hypophosphorous Type Flame Retardants

The present invention relates to a method for producing a hypophosphite flame retardant. More specifically, the present invention relates to a method for preparing a hypophosphite flame retardant that can finely control particle size and solve discoloration and heat resistance problems, including reacting hypophosphite and aluminum salts under ultrasonic energy.

In general, thermoplastic polymer materials are easily burned and have a fire hazard, and there has been a need for a technique for flame retarding them. The conventional flame retardant has used a halogen-based compound containing bromine or chlorine having flame retardancy and heat resistance. However, these halogen-based flame retardants have toxic substances such as toxic gases and dioxins during combustion, which have harmful problems to the human body and the environment. Accordingly, the use of halogen flame retardants has been tightened, and the development of non-halogen flame retardants excellent in flame retardancy and heat resistance that can replace halogen flame retardants is urgently required.

Phosphorus-based compounds among halogen-based flame retardants are superior to inorganic flame retardants or nitrogen-based flame retardants. However, phosphorus compounds are far less flame retardant and heat resistant than halogen-based compounds. In addition, the heat resistance, corrosion resistance and discoloration resistance is not good, the smoke density during the combustion process is high, there is a problem of low productivity due to the filtration washing process for the treatment of by-products in the manufacturing process.

In addition, inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide are difficult to improve flame retardancy and mechanical properties at the same time, nitrogen-based flame retardants such as melamine cyanurate in most applications except nitrogen-containing resins such as polyamide or polyurethane Due to lack of flame retardancy, it is mainly used as a flame retardant aid.

On the other hand, the adhesive used in FFC (Flexible Flat Cable), which is a field of electronic materials, generally has a thickness of less than 30 μm, so it is difficult to use a flame retardant having a large particle size, and it is also necessary to finely control particle size of the flame retardant. .

The present invention has been made to solve the above problems, to provide a hypophosphorous flame retardant and a method for producing the same to finely control the particle size and excellent heat resistance, discoloration and corrosion resistance and excellent flame resistance The purpose.

In order to achieve the above object, one aspect of the present invention,

(a) a hypophosphite metal salt manufacturing step of reacting an alkali metal salt of hypophosphite with a bivalent metal salt, (b) a washing step of washing the hypophosphite metal salt prepared in step (a) and (c) the (b) In the step 1) comprises a drying step of drying the washed hypophosphorous acid-based metal salt, wherein any one or more of the steps (a) and (b) is performed by applying ultrasonic energy. It is to provide a method for producing a hypophosphite flame retardant represented by.

[Formula 1]

(In Formula 1, R ₁ and R ₂ are independently of each other hydrogen, linear or pulverized (C ₁ -C ₆ ) alkyl, M is one of the metal atoms selected from Ca, Mg, Al, Zn and Ti) N represents an integer selected from 2 to 4.)

In the method for preparing a hypophosphite flame retardant according to an embodiment of the present invention, the divalent to tetravalent metal salt is one selected from the group consisting of nitrates, hydrochlorides, sulfates, and mixtures thereof. Can be.

In the method for producing a hypophosphite flame retardant according to an embodiment of the present invention, the application of the ultrasonic energy may be performed within the wavelength range of 500 to 20,000 W per 10 liters of the reaction solution and 10 to 100 KHz. .

In the method of manufacturing a hypophosphite flame retardant according to an embodiment of the present invention, the application time of the ultrasonic energy may be from 30 minutes to 360 minutes.

In the method for preparing a hypophosphite flame retardant according to an embodiment of the present invention, the alkali metal hypophosphite salt of step (a) is prepared by adding a metal hydroxide to (C ₂ -C ₄ ) alkyl hypophosphorous acid and stirring the mixture. Can be.

In the method for producing a hypophosphite flame retardant according to an embodiment of the present invention, the metal hydroxide may be any one or more selected from the group consisting of aluminum hydroxide, calcium hydroxide and magnesium hydroxide.

In the method for preparing a hypophosphite flame retardant according to an embodiment of the present invention, the (C ₂ -C ₄ ) alkyl hypophosphorous acid is prepared by stirring hypophosphorous acid, (C ₂ -C ₄ ) alkene, radical initiator and water It may be.

Further, another aspect of the present invention relates to a flame retardant produced by the above-described manufacturing method.

Flame retardant according to an embodiment of the present invention may satisfy the following relation 1.

[Relationship 1]

300 ℃ ≤ T _CG ≤ 400 ℃

(In Equation 1, T _CG is the first temperature at which the weight loss of 1.0% is observed under a thermogravimetric analysis of a temperature increase rate of 10 ° C./min and a nitrogen flow rate of 20 ml / min.)

Another aspect of the present invention relates to a molded article prepared by including the above flame retardant. The molded body may be a flexible flat cable or a flexible copper clad laminate.

The present invention can lower the content of impurities by applying ultrasonic energy in the reaction and washing process, and has the advantage of finely controlling the particle size. In addition, it has the advantage of manufacturing a hypophosphite flame retardant that can realize excellent flame resistance while excellent heat resistance, discoloration resistance and corrosion resistance. In addition, it is possible to implement excellent performance in the use of adhesives for manufacturing FFC and FCCL, and has the advantage of providing a non-halogen-based eco-friendly flame retardant.

Figure 1 shows the results of H-NMR analysis of diethylhypophosphorous acid (DEPA) according to Preparation Example 1.
Figure 2 shows a photograph measured to determine whether yellowing and aggregation of the flame retardant particles according to Comparative Example 3 (a), Example 12 (b) and Example 13 (c).

Hereinafter, a method for preparing a hypophosphite flame retardant of the present invention and a flame retardant prepared therefrom will be described in detail. The invention can be better understood by the following examples. The following examples are for illustrative purposes of the invention and are not intended to limit the scope of protection defined by the appended claims. In this case, unless otherwise defined, the technical and scientific terms used have the meanings that are commonly understood by those of ordinary skill in the art.

The inventors of the present invention have a problem of high smoke density in the case of phosphorus-based flame retardant for improving flame retardancy, and poor physical properties such as heat resistance and discoloration resistance. By providing a method for preparing hypophosphorous flame retardant, which includes carrying out a reaction or washing process under the conditions, it is possible to lower the impurity content, and in addition to excellent flame retardant performance, it is possible to realize the effect of improving physical properties of discoloration resistance, heat resistance, and corrosion resistance. Discovered to complete the present invention.

Hereinafter, a method for preparing a hypophosphite flame retardant according to an aspect of the present invention and a flame retardant prepared therefrom will be described in more detail.

Hypophosphorous flame retardant manufacturing method represented by the formula (1) according to an aspect of the present invention

(a) a hypophosphite-based metal salt preparation step of reacting an alkali metal salt of hypophosphite with a divalent to tetravalent metal salt,

(b) a washing step of washing the hypophosphite-based metal salt prepared in step (a);

(c) a drying step of vacuum drying the hypophosphorous acid-based metal salt washed in step (b)

Including;

At least one of the steps (a) and (b) may be performed including applying ultrasonic energy.

[Formula 1]

(In Formula 1, R ₁ and R ₂ are independently of each other hydrogen, linear or pulverized (C ₁ -C ₆ ) alkyl, M is one of the metal atoms selected from Ca, Mg, Al, Zn and Ti) N represents an integer selected from 2 to 4.)

Hypophosphorous flame retardant manufacturing method according to an aspect of the present invention includes a method using hypophosphorous acid as the raw material or a hypophosphite metal salt.

As a specific aspect, the method using hypophosphorous acid as a raw material

Iii) stirring the hypophosphorous acid, (C ₂ -C ₄ ) alkene, radical initiator and water to produce (C ₂ -C ₄ ) alkyl hypophosphorous acid,

Ii) adding an alkali metal salt to the (C ₂ -C ₄ ) alkyl hypophosphorous acid of step iii) to prepare an alkali metal hypophosphite salt,

Iii) a hypophosphite-based metal salt preparation step of reacting the hypophosphite alkali metal salt of step ii) with a divalent to tetravalent metal salt;

Iii) a water washing step of washing the hypophosphite-based metal salt prepared in step iii) with water;

Iii) a vacuum drying step of the hypophosphorous metal salt washed in step iii);

Any one or more of the steps iii) and iii) may be performed under conditions of applying ultrasonic energy.

However, when using hypophosphorous acid directly to prepare a hypophosphorous flame retardant substituted with hydrogen instead of an alkyl group, the step iii) is omitted.

In another embodiment, the method using the alkali metal hypophosphite as a raw material

′ ′) Stirring the alkali metal salt of hypophosphite, (C ₂ -C ₄ ) alkene, radical initiator and water to prepare a (C ₂ -C ₄ ) alkyl hypophosphite alkali metal salt,

Ii ′) a hypophosphite-based metal salt preparation step of reacting an alkali metal salt of (C ₂ -C ₄ ) alkyl hypophosphite of step VII ′ with a divalent to tetravalent metal salt;

Ⅲ ′) a washing step of washing the hypophosphite-based metal salt prepared in step ii ′) with water;

Ⅳ ′) comprising a drying step of vacuum drying the hypophosphorous metal salt washed in step VII ′),

At least one of the steps ii ') and iii') may be performed under conditions for applying ultrasonic energy.

However, in the case of using a hypophosphite alkali metal salt directly to prepare a hypophosphite flame retardant in which hydrogen is substituted for an alkyl group, the process of step ′ ′) is omitted.

According to one aspect of the invention, the conditions for applying the ultrasonic energy is not limited significantly within the range that can achieve the desired effect of the present invention, but preferably 500 W to 20,000 W per 1,000 L of reaction solution, More preferably, the power may be performed within a power range of 1,000 W to 15,000 W and a wavelength range of 10 to 100 KHz, more preferably 20 to 80 KHz. In addition, the application time of the ultrasonic energy may be 30 minutes to 360 minutes, preferably 60 minutes to 300 minutes. It is possible to increase the purity of the flame retardant in the above range, effective in improving productivity and process efficiency, and furthermore, in terms of improving physical properties of heat resistance, corrosion resistance and discoloration resistance.

According to an aspect of the present invention, the (C ₂ -C ₄ ) alkene includes any one or more selected from alkenes having 2 to 4 carbon atoms, and specifically, ethylene is effective in terms of improving flame retardancy.

According to one aspect of the present invention, the radical initiator is not limited to, for example, 2,2-azobis (2-amidinopropene) dihydrochloride, sodium persulfate, potassium persulfate and ammonium persulfate Any one or a mixture of two or more selected from the group consisting of may be used. The content of the radical initiator may be 0.5 to 15 mol%, and preferably 1 to 10 mol% relative to hypophosphorous acid. In the above range, the reaction rate can be increased and effective in terms of reducing the cost. However, this is only an example and is not limited to the numerical range.

The step iii) is a process for preparing (C ₂ -C ₄ ) alkyl hypophosphorous acid, in terms of improving reaction rate and purity, and efficiency of manufacturing equipment, with a reaction temperature of 50 to 150 ° C. and a reaction pressure of 2 to 10 atm. It is preferred to be maintained, but is not necessarily limited thereto.

Step ii) is a step of preparing the phosphoric acid or the (C ₂ -C ₄ ) alkyl hypophosphorous acid prepared in step iii) with an alkali metal salt to react with other metal salts, including the step to improve the yield of the flame retardant It is more effective in terms of controlling the particle size and finely.

Step iii) from the group consisting of divalent to tetravalent metal salts, specifically nitrates, hydrochlorides, sulfates and mixtures thereof of (C ₂ -C ₄ ) alkyl hypophosphite alkali metal salts for use as flame retardants. It is a process of reacting with any component selected. This is more effective in improving the water resistance as well as synergistic properties of the flame retardant. The divalent to tetravalent metal salt is, in one embodiment, any one or a mixture of two or more selected from the group consisting of aluminum chloride, calcium chloride, magnesium chloride, aluminum sulfate, calcium sulfate, magnesium sulfate, aluminum nitrate, calcium nitrate and magnesium nitrate. However, the present invention is not limited thereto. Preferably, the use of aluminum chloride, aluminum sulfate or aluminum nitrate is more effective in terms of improving heat resistance and water resistance. More preferably, aluminum sulfate is mentioned.

Step iii) is a step of removing the initiator, reaction by-products and unreacted components, which are impurities contained in the manufactured hypophosphite-based metal salts, to thereby increase the purity. The process may be carried out including washing with distilled water several times, specifically 2 to 4 times in a temperature range of 50 ℃ or more, specifically 50 to 150 ℃, but is not necessarily limited thereto.

According to one aspect of the invention, the process may be carried out under the conditions of applying ultrasonic energy. This can increase the efficiency of removing impurities and can reduce the number of times of washing, thereby improving process efficiency and productivity, such as reducing the amount of wastewater generated.

Specifically, the divalent to tetravalent metal salts, such as sodium sulfate, among the impurities, have high hygroscopicity when they remain, thereby increasing water content in the flame retardant product, and aluminum salts of hypophosphorous acid have a property of separating from water and are included in non-polar flame retardant crystals. Sodium hypophosphite, which is difficult to access water, is not easy to remove impurities including these components. Thus, by including a washing step performed under the condition of applying the ultrasonic energy to increase the kinetic energy of the water molecules to enable the penetration into the crystal, it has the effect of further increasing the removal efficiency of the impurities.

In addition, the particle size of the flame retardant can be finely adjusted. Specifically, sodium hypophosphite itself has a property of agglomeration of flame retardant particles, and prevents agglomeration of particles through a washing process performed under the condition of applying the ultrasonic energy, and reduces the average particle size of the product by miniaturizing the particle size. It is possible to lower and extend the application to the adhesive field where the use is limited due to the particle size.

Step iii) is a step of removing the water used in the reaction and washing steps, and vacuum drying is performed. Although the conditions of the said vacuum drying are not restrict | limited significantly, Specifically, it can carry out at 100-150 degreeC and 10 mmHg or less. The vacuum drying conditions are effective in the above ranges, but are not particularly limited as long as they can remove moisture at 1% by weight or less.

Hypophosphorous flame retardant according to an aspect of the present invention is represented by the following formula (1).

[Formula 1]

(In Formula 1, R ₁ and R ₂ are independently of each other hydrogen, linear or pulverized (C ₁ -C ₆ ) alkyl, M is one of the metal atoms selected from Ca, Mg, Al, Zn and Ti) N represents an integer selected from 2 to 4.)

In addition, the hypophosphite flame retardant according to an aspect of the present invention may satisfy the following relationship 1.

[Relationship 1]

300 ℃ ≤ T _CG ≤ 400 ℃

(In Equation 1, T _CG is the first temperature at which the weight loss of 1.0% is observed under a thermogravimetric analysis of a temperature increase rate of 10 ° C./min and a nitrogen flow rate of 20 ml / min.)

Hypophosphorous flame retardant according to an aspect of the present invention is very excellent in corrosion resistance, heat resistance and discoloration resistance, can finely control the particle size can be achieved particularly excellent physical properties when applied to the pressure-sensitive adhesive layer It has the advantage of extending the application range.

A molded article including a hypophosphite flame retardant according to an aspect of the present invention may be provided, and may be applied to, for example, a flexible flat cable or a flexible copper clad laminate, but is not limited thereto. It is not. Specifically, the hypophosphite flame retardant may be applied to the adhesive field. As a specific example, in the flexible flat cable (FFC) used in electronic materials, the thickness of the coating layer is about 20 μm, and the use of the flame retardant having a large particle size is limited. However, according to an aspect of the present invention, it is applied by easily miniaturizing the particle size. It has this easy property.

Hereinafter, a method for preparing a hypophosphite flame retardant according to the present invention and a hypophosphite flame retardant prepared therefrom will be described in more detail. However, the following examples are only one reference for describing the present invention in detail, and the present invention is not limited thereto and may be implemented in various forms.

[Production Example 1]

Synthesis of Diethyl Hypophosphoric Acid

1,200 kg (9089.5 mol) of 50% by weight hypophosphoric acid is added to a 3,000 L high-pressure reactor equipped with a stirrer, filled with ethylene to 6 Kg / cm 2 pressure, then emptied and filled again with ethylene until the same pressure Removed. The valve was opened in connection with the ethylene storage tank to maintain the pressure during the reaction. In a separately prepared 1,000 L container, 100 kg of ammonium persulfate was dissolved in 400 kg of water and continuously injected at a rate of 20 L / hour using a high pressure plunger pump. After 12 hours of reaction at 70 ° C., ethylene was no longer consumed. In this state, it was assumed that the ethylene substitution reaction was completed, and the reaction was terminated to obtain a diethyl hypophosphite solution. 200 g of the sample was taken from the solution, cooled to 20 ° C., and water was removed by a rotary evaporator. The sample obtained by filtration of the precipitate was analyzed by 300 MHz H-NMR to confirm that diethylhypophosphorous acid (DEPA) was synthesized (FIG. 1). The pure DEPA content in the reaction solution was 56.3 wt%.

[Production Example 2]

Synthesis of Sodium Diethylphosphinate

Diethyl hypophosphorous acid solution (1301.2 kg, 6,000 mol) prepared in Preparation Example 1 in a 5,000-l stainless steel reactor equipped with a jacket capable of adding steam or cold / hot water and equipped with an ultrasonic oscillator (16.2 kW). Was added. Sodium hydroxide (727.3 kg, 33% aqueous solution, 6,000 mol) was added slowly at 25 ° C. while stirring the solution. The temperature of the reactor was raised to 78 ℃, the cooling water was added to the reactor jacket and cooled to 25 ℃.

Comparative Example 1

Synthesis of Aluminum diethylphosphinate

The temperature of the reactor containing sodium diethylphosphinate prepared in Preparation Example 2 was adjusted to 35 ° C., and aluminum sulfate (Aluminum sulfate, 1,394 kg, 1,100 mol) was slowly added for 60 minutes. After the test was carried out for 60 minutes, it was transferred to a filter and filtered. 940 kg of distilled water was added four times, followed by washing with water four times, and then 10 kg of undried sample was collected, and the remainder was vacuum-dried at 114 ° C / 1.0 mmHg to obtain 727 kg of aluminum diethylphosphinate (yield 94 %).

Example 1

50 g of the sample taken in Comparative Example 1 was placed in a 500 mL beaker and 200 g of distilled water was added, followed by sonication with varying time at 90% output at 800 W Bench Top Sonicator. Examples 1 to 5 were sonicated for 1 hour, 2 hours, 3 hours, 4 hours and 5 hours, respectively. Thereafter, a part of the sample was taken and compared by measuring particle size by laser scattering method (Bettersize Instrument Ltd, model: BT-9300S). As a result, as can be seen in Table 1, the longer the ultrasonic treatment time, the smaller the particle size, and the larger the ultrasonic output, the higher the effect.

division ultrasonic wave
Authorization time
(minute) Ultrasonic Power (90%) Ultrasonic power (10%) Particle size (D50%) Particle size (D98%) Particle size (D50%) Particle size (D98%) Comparative Example 1 0 19.20 41.39 19.20 41.39 Example 1 60 13.59 22.16 18.89 40.76 Example 2 120 12.64 28.36 18.53 38.92 Example 3 180 9.50 22.72 17.50 37.98 Example 4 240 8.11 17.61 16.94 37.25 Example 5 300 7.46 16.74 16.62 36.66

Example 6

After the addition of the aluminum sulfate solution in Comparative Example 1, the output of the ultrasonic oscillator of 16.2kW was set to 80% and was carried out in the same manner as in Comparative Example 1 except that the reaction was performed for 1 hour while applying ultrasonic energy. 729 kg of ammonium diethylphosphinate was obtained (yield 93%). As a result, as can be seen in Table 2, it was confirmed that in the case of Example 6 subjected to the ultrasonic treatment can be finely adjusted the particle size.

division Particle size (D50%) Particle size (D98%) Remarks Comparative Example 1 19.20 41.39 No ultrasound Example 6 8.90 20.70 Ultrasonic application

Comparative Example 2 Preparation of Aluminum phosphinate

A jacket capable of adding steam or cold and hot water and a 1,500 kg distilled water in a 5,000 liter stainless steel reactor equipped with an ultrasonic oscillator (16.2 kW) were added and stirred while sodium hypophosphite (Sodium hypophosphite ( SHP) monohydrate) 1500 kg (14,150 mol) was added, and then the reactor temperature was raised to 60 ° C. using steam. After SHP was completely dissolved, 3,260 kg (2,358 mol) of 27 wt% aluminum sulfate was slowly added over 100 minutes, and the temperature of the reactor was increased to 80 ° C. for 6 hours. After the reaction was completed, it was transferred to a filter and filtered. After the filtration is completed, the process of washing with distilled water 1,050kg three times, and then washed 10 times the undried sample, the remainder is vacuum-dried under the condition of 114 ℃ / 1.0mmHg 985kg of aluminum phosphinate (Aluminum phosphinate) Obtained (yield about 94%).

Example 7

Ultrasonication of Aluminum phosphinate (1)

50 g of the sample taken in Comparative Example 2 was placed in a 500 mL beaker and 200 g of distilled water was added, followed by sonication with varying time at 90% output from a 800W Bench Top Sonicator. Examples 7 to 11 were sonicated for 1 hour, 2 hours, 3 hours, 4 hours and 5 hours, respectively. Part of the sample was taken and compared by measuring the particle size by laser scattering method (Bettersize Instrument Ltd, Model: BT-9300S). As a result, as can be seen in Table 3, the longer the ultrasonic treatment time, the smaller the particle size, and the larger the ultrasonic output, the higher the effect.

division ultrasonic wave
Authorization time (minutes) D50 D98 Comparative Example 2 0 103.95 177.34 Example 7 60 92.07 150.18 Example 8 120 89.87 148.56 Example 9 180 89.33 148.29 Example 10 240 88.56 147.81 Example 11 300 70.28 144.09

Example 12

Ultrasonication of Aluminum phosphinate (2)

After the addition of the aluminum sulfate solution in Comparative Example 2, the output of the aluminum oscillator of 16.2kW was set to 80% and reacted for 1 hour while applying ultrasonic energy to aluminum force in the same manner as in Comparative Example 2 1,051 kg of aluminum phosphinate was obtained (yield 96%). The apparent specific gravity of the obtained sample was measured (KS M-3002), and the grinding speed by ACM (Air Current Mill) with a rotor diameter of 500 mm and a blow motor capacity of 7.5 kW was measured and compared. As a result, as can be seen in Table 4, in the case of Example 12 subjected to the ultrasonic treatment it was confirmed that the particle size can be finely adjusted, the grinding performance is also improved.

division D50 D98 Apparent weight
(kg / M3) Grinding speed
(kg / hr) Comparative Example 2 87.92 188.41 188.41 35 Example 12 58.54 135.69 135.69 110

Comparative Example 3 and Examples 12 to 13

Ultrasonic Flush of Aluminum diethylphosphinate

100 g of the slurry sample taken in Comparative Example 1 was diluted with 200 g of distilled water, stirred for 20 minutes, and washed with water. Some of the four wash cycles were sonicated at 90% output from the 800W Bench Top Sonicator. The sample washed four times was dried for 14 hours in a 115 ℃ drying oven. The dried samples were subjected to thermogravimetric analysis to compare the heat resistance. In addition, each sample was placed in an alumina crucible, placed in an electric furnace, and left at 300 ° C. for 30 minutes, and then taken out. As a result, as can be seen in Table 5, in Examples 12 and 13 subjected to the ultrasonic treatment at the time of washing was possible to prevent discoloration, it was confirmed that the heat resistance is improved. In addition, as shown in FIG. 2, in Comparative Example 3, some yellowing occurred and the entire surface became hard due to the aggregation of particles. In contrast, in Examples 12 and 13, discoloration did not occur and aggregation did not occur. Did. In addition, as shown in Figure 3 showed a large difference in heat resistance.

division Comparative Example 3 Example 12 Example 13 Number of ultrasonic washes 0 First time (the fourth) 2 (the first, the fourth) Particle size (D50%) 19.20 14.20 10.20 Particle size (D98%) 41.39 29.36 25.86 Furnace test
(300 ℃, 20 minutes) Some yellowing No discoloration (white) No discoloration (white) Agglomerated No agglomeration No agglomeration TGA heat resistance
(1% loss, ℃) 288 301 351

Although the preferred embodiment of the present invention has been described above, it is clear that the present invention may use various changes, modifications, and equivalents, and that the above embodiments may be appropriately modified in the same manner. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

Claims (11)

(a) preparing a hypophosphite metal salt by reacting an alkali metal salt of hypophosphite with a divalent to tetravalent metal salt,
(b) a washing step of washing the hypophosphite-based metal salt prepared in step (a);
(c) a drying step of vacuum drying the hypophosphorous acid-based metal salt washed in step (b)
Including;
Any one or more of the steps (a) and (b) is a method of producing a hypophosphite flame retardant represented by the following formula (1) is carried out including applying ultrasonic energy.
[Formula 1]

(In Formula 1, R ₁ and R ₂ are independently of each other hydrogen, linear or pulverized (C ₁ -C ₆ ) alkyl, M is one of the metal atoms selected from Ca, Mg, Al, Zn and Ti) N represents an integer selected from 2 to 4.) The method of claim 1,
The divalent tetravalent metal salt is a method for producing a hypophosphite flame retardant is any one selected from the group consisting of nitrates, hydrochlorides, sulfates and mixtures thereof. The method of claim 1,
The application of the ultrasonic energy is a method of producing a hypophosphite flame retardant that is performed within an output of 500 to 20,000 W per 1,000 L of reaction solution and a wavelength range of 10 to 100 KHz. The method of claim 3,
The application time of the ultrasonic energy is 30 minutes to 360 minutes method of manufacturing a hypophosphite flame retardant. The method of claim 1,
The hypophosphorous acid-based alkali metal salt of step (a) is prepared by adding a metal hydroxide to (C ₂ -C ₄ ) alkyl hypophosphorous acid and stirring to prepare the hypophosphorous acid-based flame retardant. The method of claim 5,
The metal hydroxide is a method of producing a hypophosphite flame retardant is at least one selected from the group consisting of aluminum hydroxide, calcium hydroxide and magnesium hydroxide. The method of claim 5,
The (C ₂ -C ₄ ) alkyl hypophosphorous acid is hypophosphorous acid-based flame retardant is a method of manufacturing a hypophosphorous acid-based flame retardant is prepared by stirring the water, (C ₂ -C ₄ ) alkenes, radical initiators and water. Flame retardant prepared by the method of any one of claims 1 to 7. The method of claim 8,
The flame retardant is to satisfy the following relational formula 1.
[Relationship 1]
300 ℃ ≤ T _CG ≤ 400 ℃
(In Equation 1, T _CG is the first temperature at which the weight loss of 1.0% is observed under a thermogravimetric analysis of a temperature increase rate of 10 ° C./min and a nitrogen flow rate of 20 ml / min.) A molded article comprising the flame retardant of claim 8. The method of claim 10,
The molded body is a flexible flat cable (Flexible Flat Cable) or a flexible copper clad laminate (Flexible Copper Clad Laminate).

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