Amide type organic phosphine nitrogen flame retardant compound and preparation method thereof

Abstract

The present invention relates to an amide type organic phosphine nitrogen flame retardant compound and a preparation method thereof. The structure of the compound is shown in the following formula: The preparation method is: in an organic solvent, sodium melamine reacts with 2 to 2.2 times the mole of phenylphosphonic dichloride, and phenylphosphonic dimelamine is obtained after purification. The compound of the present invention has a stable structure, high flame retardant efficiency, good carbon expansion, and a wide range of applications. It can be used as a flame retardant for materials such as epoxy resin, unsaturated polyester resin, polyester resin, polyolefin, polyacrylate, polyacrylamide, polyvinyl alcohol, etc. The process is simple, the equipment investment is small, and it is easy to realize industrial production.

Description

Technical Field

[0001] The invention relates to an amide-type organic phosphine-nitrogen flame retardant compound and a preparation method thereof, and in particular to a phenylphosphonic acid dimelamine compound and a preparation method thereof. The compound can be used as a flame retardant for materials such as epoxy resin, unsaturated polyester resin, polyester resin, polyolefin, polyacrylate, polyacrylamide, polyvinyl alcohol, etc. Background Art

[0002] At present, with the improvement of environmental protection and human health awareness, the research of new high-efficiency, low-toxic, halogen-free and environmentally friendly flame retardants has become a hot topic. Among them, phosphorus-nitrogen flame retardants are widely developed and applied, such as melamine phosphate, melamine pyrophosphate, melamine polyphosphate, etc. Although the above compounds have good flame retardancy, they are easy to ionize due to the structure of salt-bonded ionic compounds, which makes them easy to absorb moisture, migrate, frost and have poor permanence in application. Therefore, in the molecular structure design of the compound, the salt-bonded ions of the compound are changed to a stable covalent bond structure to overcome the shortcomings brought by the above-mentioned ionic bonds, so as to meet the great market application needs.

[0003] The invention discloses a phenylphosphonyl dimelamine compound and a preparation method thereof. The flame retardant phenylphosphonyl dimelamine is prepared with phenylphosphonyl dichloride and melamine sodium salt as main raw materials, with simple process, low cost and easy conversion into industrial production; the flame retardant of the invention has the advantages of high flame retardant efficiency, good carbonization property, good stability of phosphorus-nitrogen covalent bond combination of amide structure, moderate polarity and good fusion property with materials, wide application range, etc. Therefore, the flame retardant of the invention has very good application development prospects. Summary of the invention

[0004] One of the purposes of the present invention is to provide a flame retardant phenylphosphonic dimelamine compound, which has the advantages of stable amide structure, anti-migration, containing two synergistic flame retardant elements of phosphorus and nitrogen in the molecule, high content of flame retardant elements, good compatibility with materials, wide application range, etc., and can overcome the shortcomings of the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] A flame retardant phenylphosphonyl dimelamine compound, characterized in that the structure of the compound is shown in the following formula:

[0007]

[0008] The second object of the present invention is to provide a method for preparing a flame retardant phenylphosphonic acid dimelamine compound, which has a simple process, is easy to mass produce, requires little equipment investment, and is low in cost.

[0009] The method is:

[0010] Under nitrogen protection, dry melamine sodium salt and an organic solvent are added to a reactor equipped with a stirrer, a thermometer and a reflux device, and phenylphosphoryl dichloride is added dropwise at room temperature within 30 minutes under stirring, and the molar ratio of phenylphosphoryl dichloride to melamine sodium salt is controlled to be 1:2-1:2.2. After the phenylphosphoryl dichloride is added, the temperature is raised to 60-100°C, and the reaction is refluxed for 6-8 hours. The temperature is lowered to 30°C and filtered by suction. The filtrate can be directly recycled and reused. Water required for dissolving the sodium chloride generated by the reaction into a saturated solution is added to the filter cake, and the sodium chloride is completely dissolved by stirring for 1 hour. The filter cake is filtered by suction, and the filter cake is washed three times with water in a volume of twice the theoretical grams of the product mass in milliliters, compacted and dried, and vacuum dried at 80°C to obtain white crystalline phenylphosphoryl dimelamine.

[0011] The organic solvent as mentioned above is chloroform, ethylene dichloride, carbon tetrachloride, acetonitrile or dioxane, and its usage volume in milliliters is 5-7 times the mass in grams of melamine sodium salt.

[0012] The flame retardant phenylphosphoryl dimelamine compound of the present invention is a white solid, with a starting decomposition temperature of 275±5°C, a rapid decomposition temperature of 300±5°C, a product yield of 86.0-93.5%, and can be used as a flame retardant for materials such as epoxy resin, unsaturated polyester resin, polyester resin, polyolefin, polyacrylate, polyacrylamide, and polyvinyl alcohol. The preparation principle of the flame retardant phenylphosphoryl dimelamine compound is shown in the following formula:

[0013]

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] ① The flame retardant phenylphosphoryl dimelamine compound of the present invention has phosphorus and nitrogen bonded by covalent bonds, and the product has good structural stability, which can overcome the disadvantage of easy deliquesce and ionization migration of melamine phosphate salts.

[0016] ② The flame retardant phenylphosphoryl dimelamine of the present invention is an amide structure compound with good stability. In addition, due to the introduction of electron multidirectional benzene ring in the molecule, the polarity of the molecular structure is moderate and has good compatibility with materials. It has a wide range of applications.

[0017] ③ The flame retardant phenylphosphoryl dimelamine of the present invention is an amide compound, has good expansion and carbonization properties, is a high-efficiency environmentally friendly flame retardant, has a good anti-melting dripping effect, and can overcome the deficiency of secondary ignition of dripping.

[0018] ④ The flame retardant phenylphosphoryl dimelamine of the present invention is an amide compound. Studies have shown that the use of phenylphosphoryl dimelamine in unsaturated polyester resin fiberglass can give the material better toughness, indicating that the flame retardant phenylphosphoryl dimelamine has a certain plasticizing property.

[0019] ⑤ The flame retardant phenylphosphoryl dimelamine of the present invention has a high content of effective flame retardant elements (nitrogen content 44.92%, phosphorus content 8.29%) of 53.21%, meets the requirements of green chemical synthesis, has high atomic utilization rate and less pollution.

[0020] ⑥ The preparation method of the flame retardant phenylphosphoryl dimelamine compound of the present invention is a one-step reaction, the raw materials are easily available, the process is simple, the equipment investment is small, the operation is convenient, and it is easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to further illustrate the structure and performance of the flame retardant phenylphosphoryl dimelamine of the present invention, the following drawings are provided.

[0022] Figure 1 This is the infrared spectrum of phenylphosphoryl dimelamine;

[0023] Figure 1 It shows that 3467cm -1 、3419cm -1 is the stretching vibration absorption peak of NH2 of melamine, 3100cm -1 The characteristic absorption peak of benzene ring is 1651cm -1 NH bending vibration absorption peak, 1551cm -1 The stretching vibration absorption peak of the triazine ring C=N of melamine is 1200cm -1 is the stretching vibration absorption peak of P=0, 842cm -1 、790cm -1 The vibration absorption peak of the PN bond appearing at further proves that the molecular structure of phenylphosphoryl dimelamine has determined the formation of a new covalent nitrogen-phosphorus bond.

[0024] Figure 2 It is the NMR spectrum of phenylphosphoryl dimelamine;

[0025] Figure 2It shows that when deuterated DMSO is used as solvent, δ=2.5 is the solvent proton peak of deuterated DMSO; δ=3.3 is the water peak when deuterated DMSO is used as solvent; δ=5.33 is the hydrogen peak of the free imino group (NH) of phosphoryl melamine in the deuterated DMSO solvent; δ=7.27 is the hydrogen peak of the free amino group (NH2) of phosphoryl melamine in the deuterated DMSO solvent; δ=7.43 is the hydrogen peak on the benzene ring, and the theoretical value of the ratio of the number of hydrogens of the imino group, amino group and benzene ring in phenylphosphoryl dimelamine is 1:4:5, and the ratio of the peak areas obtained by actual integration is close to it.

[0026] Figure 3 This is the thermal analysis curve of phenylphosphoryl dimelamine;

[0027] Figure 3 It shows that when phenylphosphoryl dimelamine is placed in a micro differential thermal balance, the heating rate is controlled at 10℃ / min and the scanning range is 0~800℃ under nitrogen atmosphere. Phenylphosphoryl dimelamine begins to decompose at about 270℃ and 38% of carbon remains when heated to 700℃. It can be seen from the figure that the product is relatively stable under high temperature conditions.

[0028] Figure 4 This is the morphology of phenylphosphoryl dimelamine used in the combustion of unsaturated resin;

[0029] Figure 4 It shows that a is the combustion photo of the blank sample, b is the combustion photo of 10% added amount, c is the combustion photo of 20% added amount, and d is the combustion photo of 25% added amount; all of them show that phenylphosphoryl dimelamine has good expansion performance and charring performance when used for the combustion of unsaturated resin.

[0030] Figure 5 This is a scanning electron microscope (SEM) image of the carbon residue formed after phenylphosphoryl dimelamine was used in the combustion of unsaturated resin;

[0031] Figure 5 It shows that e is the SEM photo of the blank sample combustion, and f is the SEM photo of the combustion with 20% addition. The contrast between the blank sample picture and the sample picture is very obvious. After the blank sample is burned, glass fibers are left, and all organic matter is burned out. After the sample is burned, a solid and dense covering layer is formed. This is a dense expanded carbon layer connected by the polyphosphonic acid membrane, which can prevent the invasion of heat and oxygen, thereby protecting the internal material from further combustion, laying the foundation for the excellent expanded carbon flame retardant effect. Specific embodiments

[0032] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0033] Example 1 Under nitrogen protection, 29.62 g (0.20 mol) of dry melamine sodium salt and 180 mL of chloroform were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 60°C, refluxed for 6 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 83.4%.

[0034] Example 2 Under nitrogen protection, 29.62 g (0.20 mol) of dry melamine sodium salt and 180 mL of dichloroethane were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 80°C, refluxed for 6 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 86.3%.

[0035] Example 3 Under nitrogen protection, 29.62 g (0.20 mol) of dry melamine sodium salt and 180 mL of carbon tetrachloride were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 75°C, refluxed for 6 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 81.1%.

[0036] Example 4 Under nitrogen protection, 29.62 g (0.20 mol) of dry melamine sodium salt and 180 mL of acetonitrile were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 80°C, refluxed for 6 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 82.2%.

[0037] Example 5 Under nitrogen protection, 29.62 g (0.20 mol) of dry melamine sodium salt and 180 mL of dioxane were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 100° C. and refluxed for 6 hours. The temperature was then lowered to 30° C. and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 87.3%.

[0038] Example 6 Under nitrogen protection, 31.10 g (0.21 mol) of dry melamine sodium salt and 200 mL of chloroform were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 60°C, refluxed for 5 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 87.4%.

[0039] Example 7 Under nitrogen protection, 31.10 g (0.21 mol) of dry melamine sodium salt and 200 mL of dichloroethane were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 80°C, refluxed for 5 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 89.4%.

[0040] Example 8 Under nitrogen protection, 31.10 g (0.21 mol) of dry melamine sodium salt and 200 mL of acetonitrile were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 80°C, and after reflux reaction for 5 hours, the temperature was lowered to 30°C and filtered. The filtrate can be directly recovered and reused. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 84.5%.

[0041] Example 9 Under nitrogen protection, 31.10 g (0.21 mol) of dry melamine sodium salt and 200 mL of carbon tetrachloride were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 75°C, refluxed for 5 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 86.3%.

[0042] Example 10 Under nitrogen protection, 31.10 g (0.21 mol) of dry melamine sodium salt and 200 mL of dioxane were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 100° C. and refluxed for 5 hours. The temperature was then lowered to 30° C. and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 89.4%.

[0043] Example 11 Under nitrogen protection, 32.58 g (0.22 mol) of dry melamine sodium salt and 220 mL of chloroform were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 60°C, refluxed for 4 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 88.5%.

[0044] Example 12 Under nitrogen protection, 32.58 g (0.22 mol) of dry melamine sodium salt and 220 mL of dichloroethane were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 80°C, refluxed for 4 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 91.6%.

[0045] Example 13 Under nitrogen protection, 32.58 g (0.22 mol) of dry melamine sodium salt and 220 mL of acetonitrile were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 80°C, and after reflux reaction for 4 hours, the temperature was lowered to 30°C and filtered. The filtrate can be directly recovered and reused. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 88.6%.

[0046] Example 14 Under nitrogen protection, 32.58 g (0.22 mol) of dry melamine sodium salt and 220 mL of carbon tetrachloride were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dichloride was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 75°C, refluxed for 4 hours, cooled to 30°C, and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 87.7%.

[0047] Example 15 Under nitrogen protection, 32.58 g (0.22 mol) of dry melamine sodium salt and 220 mL of dioxane were added to a 500 mL four-necked flask equipped with a stirrer, a thermometer and a reflux condenser. 19.50 g (0.10 mol) of phenylphosphoryl dioxane was added dropwise at room temperature within 30 minutes under stirring. After the addition was completed, the temperature was raised to 100° C. and refluxed for 4 hours. The temperature was then lowered to 30° C. and filtered. The filtrate can be directly recycled. 30 mL of water was added to the filter cake and stirred for 1 hour to dissolve all the sodium chloride. The filter cake was filtered and washed three times with 75 mL of water to obtain white crystalline phenylphosphoryl dimelamine with a yield of 92.4%.

[0048] The inventors also applied the above-prepared product phenylphosphoryl dimelamine to 886 unsaturated resin, mixed phenylphosphoryl dimelamine and 886 unsaturated resin in different proportions, added 0.2% methyl ethyl ketone peroxide as an initiator, stirred and mixed, and poured into a mold with a length of 15 cm, a width of 1.0 cm, and a thickness of 0.3 cm, added glass fiber cloth as an inner lining, and then made into a standard sample strip, and studied the flame retardant performance and carbonization of the product. The test data are shown in Table 1-2.

[0049] Table 1 Oxygen index test data and phenomena of phenylphosphoryl dimelamine used in 886 unsaturated resin

[0050]

[0051] Table 1 shows that the limiting oxygen index of 886 unsaturated resin itself is 18%, and when phenylphosphoryl dimelamine is added to 886 unsaturated resin at a dosage of 10%, the LOI is 23%, and when the addition dosage is 20%, the LOI reaches 27%, reaching the flame retardant level. The flame retardant phenylphosphoryl dimelamine has a good flame retardant effect on 886 unsaturated resin, and the material has a good expansion carbonization performance when burning.

[0052] Table 2 Vertical combustion test data and phenomena of phenylphosphoryl dimelamine in 886 unsaturated resin

[0053]

[0054] Table 2 shows that when the flame retardant phenylphosphoryl dimelamine is added to 886 unsaturated resin at a rate of 10%, a good flame retardant effect of V-1 level is achieved, and when the addition rate reaches 20%, an ideal flame retardant effect of V-0 level is achieved. Therefore, the flame retardant phenylphosphoryl dimelamine has good flame retardant properties.

[0055] The inventors also applied the above-prepared product phenylphosphoryl dimelamine to 886 unsaturated resin, added the flame retardant phenylphosphoryl dimelamine to 886 unsaturated resin in different proportions, and made 15 cm long, 1 cm wide, 0.3 cm thick strips for tensile testing. The mechanical properties of the composite material are shown in Table 3.

[0056] Table 3 Mechanical test data of phenylphosphoryl dimelamine added to 886 unsaturated resin

[0057]

[0058] It can be seen from Table 3 that as the addition amount of the flame retardant phenylphosphoryl dimelamine increases, the tensile strength decreases, but the elongation at break of the material increases, and the toughness of the material increases, indicating that the flame retardant phenylphosphoryl dimelamine has a certain plasticity.

Claims

1. An amide-type organic phosphine-nitrogen flame retardant phenylphosphonic acid dimelamine compound, characterized in that: The structure of the compound is shown below:

2. The method for preparing an amide-type organic phosphine-nitrogen flame retardant phenylphosphonic acid dimelamine compound as claimed in claim 1, characterized in that: The method is: Dry sodium melamine salt and an organic solvent are added to a reactor equipped with a stirrer, a thermometer and a reflux device. The chemical structure of the sodium melamine salt is: Under nitrogen protection, stirring is started, and phenylphosphoryl dichloride is added dropwise at room temperature within 30 minutes, and the molar ratio of phenylphosphoryl dichloride to melamine sodium salt is controlled to be 1:2-1:2.

2. After the phenylphosphoryl dichloride is added, the temperature is raised to 60-100°C, and reflux reaction is carried out for 6-8 hours. The temperature is lowered to 30°C, and the filtrate is filtered. The filtrate can be directly recycled and reused. Water required to dissolve the sodium chloride generated by the reaction into a saturated solution is added to the filter cake, and the sodium chloride is stirred for 1 hour to dissolve all the sodium chloride. The filter cake is filtered, and the filter cake is washed three times with water in a volume of twice the theoretical grams of the product mass in milliliters, compacted and dried, and vacuum dried at 80°C to obtain white crystalline phenylphosphoryl dimelamine.

3. The method for preparing an amide-type organic phosphine-nitrogen flame retardant phenylphosphonic acid dimelamine compound as claimed in claim 2, characterized in that: The method is: The organic solvent is chloroform, ethylene dichloride, carbon tetrachloride, acetonitrile or dioxane, and its usage volume in milliliters is 5-7 times the mass in grams of melamine sodium salt.

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