Halogen-free flame retardant DOPO-NH2 and preparation method of halogen-free flame retardant polyamide

Abstract

The invention belongs to the technical field of high polymer materials, and particularly discloses a halogen-free flame retardant DOPO-NH2 and a preparation method of halogen-free flame-retardant polyamide of the halogen-free flame retardant DOPO-NH2. The halogen-free flame retardant DOPO-NH2 is prepared by taking DOPO and 1, 4-butanediol as raw materials, and carrying out nitration and hydrogenation reduction reaction. The flame retardant DOPO-NH2 is mixed with binary acid and water to prepare a flame retardant organic salt solution, and then the flame retardant organic salt solution is subjected to polymerization reaction with a polyamide salt solution formed by a salt forming reaction of diamine and binary acid to prepare the halogen-free flame-retardant polyamide resin. The halogen-free flame-retardant polyamide prepared by the invention is excellent in flame retardant property, and can obtain a good flame retardant effect under different addition amounts; the limit oxygen index is basically more than 33%, the vertical combustion test reaches the UL94V-0 level, and the flame-free flame retardant is self-extinguished in the combustion test, and no molten drop is generated; the preparation method and process are simple, mild in condition and easy to operate.

Description

1. Technical field:

[0001] The invention relates to the technical field of polymer materials, and in particular to a preparation method of a halogen-free flame retardant DOPO-NH2 and a halogen-free flame retardant polyamide thereof. 2. Technical background:

[0002] Polyamide can be synthesized into AABB type polymers through the condensation reaction of diacids and diamines, or AB type polymers can be obtained by condensation of AB type amino acids. In addition, AB type polyamide can also be produced through the ring-opening polymerization process of lactam. Polyamide has been widely used in modern industry due to its excellent mechanical properties, electrical properties, chemical corrosion resistance, wear resistance and good processability. However, due to its high methylene content, polyamide is flammable and releases a lot of heat and smoke when burning. What is more serious is that the burning polyamide is accompanied by molten droplets, which accelerates the spread of fire and increases additional safety risks. Therefore, when polyamide is used in electrical related products, it must be flame retardant modified.

[0003] According to the different relationships between flame retardants and polyamide matrix materials, they can be divided into two types: one is additive flame retardant and the other is reactive flame retardant. At present, most of the flame retardant modification of polyamide uses additive flame retardants. According to the flame retardant elements in the flame retardant molecules, they can be divided into halogen, nitrogen, phosphorus and other types. Although traditional halogen flame retardants are effective, they may release harmful substances during processing and application, polluting the environment and endangering human health. Therefore, the development of a halogen-free flame retardant polyamide material has important research significance and application value.

[0004] Phosphorus is a multifunctional and highly effective flame retardant element, and its flame retardant can play a flame retardant role in both the gas phase and the condensed phase. Phosphorus flame retardants are mainly divided into two categories: organic phosphorus and inorganic phosphorus, covering red phosphorus, organic aluminum hypophosphite, flame retardant DOPO and its derivatives.

[0005] At present, there are also relevant patent literature reports on halogen-free flame-retardant polyamide. For example: the invention patent CN 201710009055.2 discloses a halogen-free flame-retardant polyamide 66 and its preparation method. The method first obtains a flame retardant salt by reacting a DPO-based reactive phosphorus flame retardant with a diamine, and then adds components such as an additive phosphorus flame retardant and a flame retardant salt to obtain a halogen-free flame-retardant polyamide 66 during the polymerization of the 66 salt into polyamide 66. The molecular chain of the halogen-free flame-retardant polyamide 66 consists of a polyamide segment and a DPO-based reactive phosphorus flame retardant segment, the content of phosphorus in the molecular chain is 0.4-0.8wt%, and the molecular chain contains 4-9wt% of an additive phosphorus flame retardant.

[0006] In summary, existing traditional polymer flame retardants often use halogenated additives, which release toxic and corrosive gases when burned and generate non-biodegradable harmful residues. These substances not only have a negative impact on the environment, but also accumulate in organisms, posing a potential threat to human health. Therefore, the application of halogenated additives is strictly restricted. In contrast, phosphorus-containing flame retardants in halogen-free flame retardants have become a hot topic in the field of flame retardant research due to their low smoke characteristics and structural diversity, showing great development potential. 3. Summary of the invention:

[0007] The technical problem to be solved by the present invention is: in view of the technical problem that the existing traditional halogen-based polymer flame retardants release toxic and corrosive gases when burned, generate non-biodegradable harmful residues, have a negative impact on the environment, and accumulate in organisms, thereby posing a potential threat to human health, the present invention provides a new type of halogen-free flame retardant DOPO-NH2 and a preparation method of halogen-free flame retardant polyamide. The technical scheme of the present invention uses 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as a starting material to synthesize a new type of DOPO-based flame retardant, namely DOPO-NH2, which is mixed with a dibasic acid solution to obtain a flame retardant organic salt solution, and then polymerizes with a polyamide salt solution formed by a diamine and a dibasic acid to obtain a halogen-free flame retardant polyamide resin. The flame-retardant polyamide resin prepared by the present invention has a wide range of application prospects, and is particularly suitable for the fields of electronic appliances, automobiles and engineering accessories.

[0008] In order to solve the above problems, the technical solution adopted by the present invention is:

[0009] The present invention provides a halogen-free flame retardant DOPO-NH2, wherein the halogen-free flame retardant DOPO-NH2 is prepared by the following method:

[0010] a. Using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide DOPO as the starting material, firstly add solvent ethanol and triethyl orthoformate thereto, heat to 50-70°C for reaction, and the reaction time is 4-6h;

[0011] b. conducting an ester exchange reaction between the obtained reaction product and 1,4-butanediol at 100-160° C. for 10-16 hours to obtain compound 1;

[0012] c. A nitric acid solution is added to the obtained compound 1 for nitration treatment. After the nitration treatment, hydrogen is introduced for reduction reaction to reduce the nitro group to an amino group, thereby preparing a flame retardant DOPO-NH2.

[0013] According to the above-mentioned halogen-free flame retardant DOPO-NH2, the molar ratio of DOPO and triethyl orthoformate added in step a is 1:1.5-3; the volume mass ratio of the solvent ethanol and DOPO added is 5-10mL:1g;

[0014] In step b, the molar ratio of DOPO to 1,4-butanediol added is 1:0.4-0.5;

[0015] In the nitration process of step c, the temperature is controlled at 20-50°C and the reaction time is 5-9h; in the reduction reaction process, the temperature is controlled at 70-90°C and the reaction time is 3-6h;

[0016] The concentration of the nitric acid solution in step c is 40-70%, the volume mass ratio of the nitric acid solution to DOPO is 5-10 mL:1 g; the pressure of the hydrogen gas is 2-5 bar.

[0017] In addition, a method for preparing a halogen-free flame retardant polyamide using a halogen-free flame retardant DOPO-NH2 is provided, the method comprising the following steps:

[0018] 1) Preparation of flame retardant organic salt solution: adding flame retardant DOPO-NH2, dibasic acid and water into a reaction container for mixing reaction, and obtaining flame retardant organic salt solution after reaction;

[0019] 2) Preparation of polyamide salt solution: desalted water and diamine are added to a salt-forming reaction kettle in sequence, stirring is started, and then a dibasic acid is added to perform a heating salt-forming reaction, and a polyamide salt solution is obtained after the reaction;

[0020] 3) Polymerization reaction: after the polyamide salt solution obtained in step 2) and the flame retardant organic salt solution obtained in step 1) are sequentially added into a polymerization kettle, the kettle is filled with nitrogen and vacuumized for 2 to 3 times to replace the air in the kettle, and then filled with nitrogen; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 220 to 280° C. and the pressure to 1.4 to 2.2 MPa, after the pressure reaches 1.4 to 2.2 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by a condenser, the condensate enters a condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to a slightly positive pressure, and the material is discharged after vacuuming to obtain a halogen-free flame-retardant polyamide.

[0021] According to the above-mentioned method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2, the molar ratio of the flame retardant DOPO-NH2 and the dibasic acid added in step 1) is 1:1-2, and the concentration of the reaction solution is controlled to be 30-70%; during the mixing reaction, the reaction temperature is 50-80°C, the reaction time is 2-4h, and the stirring speed is 100-500r / min.

[0022] According to the above-mentioned method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2, the molar ratio of the dibasic acid and the diamine added in step 2) is 1:1-3; the concentration of the reaction solution is controlled to be 40-60%; during the salt-forming reaction, the reaction temperature is controlled to be 40-70°C and the reaction time is 1-3h.

[0023] According to the above method for preparing halogen-free flame-retardant polyamide using halogen-free flame retardant DOPO-NH2, the concentration of the polyamide salt solution obtained in step 2) is 40-60% and the pH value is 7.0-8.5.

[0024] According to the above method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2, expressed in parts by weight, the added amounts of polyamide salt solution and flame retardant organic salt solution in step 3) are 80-100 parts and 0-20 parts respectively.

[0025] According to the above method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2, in step 3), when the condensed water reaches the target value, the amount of condensed water accounts for 30-60% of the mass of the added polyamide salt solution.

[0026] According to the above method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2, the pressure of the slight positive pressure in step 3) is 0.01-0.04 MPa.

[0027] According to the above method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2, the diamine is pentamethylenediamine or hexamethylenediamine; the dibasic acid is adipic acid, sebacic acid or dodecanedioic acid.

[0028] The synthetic route of the flame retardant DOPO-NH2 of the present invention is as follows:

[0029]

[0030] The novel DOPO-based flame retardant prepared by the technical solution of the present invention, namely the flame retardant DOPO-NH2, has biphenyl and phenanthrene ring structures incorporated into its molecular structure, and in particular, the side phosphorus group is introduced in the form of a cyclic O=PO bond, which gives the flame retardant higher thermal stability and chemical stability than ordinary uncyclic organic phosphates, thereby improving its flame retardant properties. In addition, the novel DOPO-based flame retardant is modified by amino groups, which significantly improves its reactivity, allowing it to participate in the polymerization process of polyamide, effectively preventing the migration and precipitation of the flame retardant. As a reactive flame retardant, it has little effect on the original properties of polymer materials and has a long-lasting flame retardant effect.

[0031] The positive beneficial effects of the present invention are:

[0032] 1. Reactive flame retardant of the present invention: The present invention synthesizes a new DOPO-based flame retardant with amino groups at both ends by reacting and aminated DOPO molecules. The biphenyl and phenanthrene ring structures are introduced into the new flame retardant molecule, and the side chain O=PO phosphorus group gives it good thermal stability and chemical stability. At the same time, the amino functional groups at both ends of the flame retardant molecule further enhance the reaction activity, allowing it to directly participate in the polymerization process of polyamide, effectively avoiding the migration and precipitation of the flame retardant, and the flame retardant performance is long-lasting.

[0033] 2. The novel flame retardant DOPO-NH2 prepared by the present invention is easy to synthesize, halogen-free, smoke-free and non-toxic.

[0034] 3. The novel flame retardant DOPO-NH2 prepared by the present invention has both condensed phase and gas phase flame retardant effects: the flame retardant DOPO-NH2 acts in both the gas phase and the condensed phase, which can promote the formation of the carbon layer, thereby isolating the bottom from the heat and oxygen transfer outside and limiting the generation of volatile fuel fragments to terminate the combustion of the polymer. At the same time, the phosphorus-containing free radicals generated by pyrolysis can capture free radicals such as H· and OH· in the flame area, interrupting the polymer free radical chain reaction and exothermic process, thereby inhibiting the combustion of the polymer gas phase product.

[0035] 4. The halogen-free flame retardant PA56 prepared by the novel flame retardant DOPO-NH2 of the present invention has excellent mechanical properties: tensile strength 73-87MPa, elongation at break 34-41%, flexural strength 84-98Mpa and notched impact strength 4.3-5.0. The tensile strength of unmodified PA56 is about 85-90MPa, elongation at break is about 39-42%, flexural strength is about 95-100Mpa and notched impact strength is about 4.8-5.0.

[0036] 5. The halogen-free flame-retardant polyamide prepared by the present invention has excellent flame retardant properties and can obtain good flame retardant effects at different addition amounts. The limiting oxygen index is basically above 33%, the vertical combustion test reaches UL94 V-0 level, and the flame is self-extinguished in the combustion test without the generation of molten droplets.

[0037] 6. The preparation method and process of the halogen-free flame-retardant polyamide of the present invention are simple, the conditions are mild, and the operation is easy. 4. Description of the drawings:

[0038] Figure 1 The NMR image of the flame retardant DOPO-NH2 prepared by the present invention.

[0039] Depend on Figure 1It can be seen that the signals with chemical shifts in the range of 6.9 to 7.9 are attributed to the hydrogen atoms on the benzene ring; the signals with chemical shifts around 4.6 correspond to the hydrogen atoms on the amino group; and the signals with chemical shifts around 1.5 and 4 are respectively attributed to the hydrogen atoms on the methylene group (due to the presence of phosphorus, the chemical shift value of the methylene group directly connected to it will shift to the high field). It can be seen that the amino group has been successfully connected to the structure of the flame retardant molecule. V. Specific implementation methods:

[0040] The present invention is further described below in conjunction with embodiments, but the protection scope of the technical solution of the present invention is not limited thereto.

[0041] Embodiment 1:

[0042] The halogen-free flame retardant DOPO-NH2 of the present invention is prepared by the following method:

[0043] a. First, add 30 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide DOPO into a reaction container, then add 150 mL of solvent ethanol and 41 g of triethyl orthoformate, and heat to 60° C. for reaction for 5.5 h.

[0044] b. Add 28 g of 1,4-butanediol to the reaction product obtained in step a, heat to 120° C. for ester exchange reaction for 12 h to obtain compound 1;

[0045] c. 150 mL of 50% nitric acid solution was added to the obtained compound 1, and the mixture was nitrated at 35° C. for 7 h. After the nitration, hydrogen was introduced (the pressure of the hydrogen was controlled to be 3 bar), and a reduction reaction was carried out at 75° C. for 5 h to reduce the nitro group to the amino group, thereby preparing the flame retardant DOPO-NH2.

[0046] Embodiment 2:

[0047] The halogen-free flame retardant DOPO-NH2 of the present invention is prepared by the following method:

[0048] a. First, add 40 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide DOPO into a reaction container, then add 200 mL of solvent ethanol and 55 g of triethyl orthoformate, and heat to 65° C. for reaction for 5 hours;

[0049] b. Add 40 g of 1,4-butanediol to the reaction product obtained in step a, heat to 120° C. for ester exchange reaction for 12 h to obtain compound 1;

[0050] c. Add 200 mL of 60% nitric acid solution to the obtained compound 1, and nitrate it at 40°C for 7 hours. After the nitration, introduce hydrogen (the pressure of the hydrogen is controlled to be 4 bar), and carry out reduction reaction at 80°C for 4 hours to reduce the nitro group to the amino group, thereby preparing the flame retardant DOPO-NH2.

[0051] Embodiment 3:

[0052] The halogen-free flame retardant DOPO-NH2 of the present invention is prepared by the following method:

[0053] a. First, add 50 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide DOPO into a reaction container, then add 250 mL of solvent ethanol and 70 g of triethyl orthoformate, and heat to 65° C. for reaction for 5.5 h.

[0054] b. Add 50 g of 1,4-butanediol to the reaction product obtained in step a, heat to 120° C. for ester exchange reaction for 12 h to obtain compound 1;

[0055] c. Add 250 mL of 70% nitric acid solution to the obtained compound 1, and nitrate it at 35°C for 7.5 hours. After the nitration, introduce hydrogen (the pressure of hydrogen is 2 bar), and perform reduction reaction at 80°C for 4 hours to reduce the nitro group to the amino group, thereby preparing the flame retardant DOPO-NH2.

[0056] Embodiment 4 (comparative example):

[0057] The preparation method of the flame retardant polyamide PA56 of the present invention comprises the following detailed steps:

[0058] 1) Preparation of polyamide PA56 salt solution: 500 g of desalted water and 210 g of pentamethylenediamine were added to a salt-forming reaction kettle in sequence, stirring was started, and then 290 g of adipic acid was added to carry out a heating salt-forming reaction, and the reaction temperature was controlled to be 60° C. and the reaction time was 2 h; after the reaction, a polyamide PA56 salt solution was obtained (the concentration of the obtained polyamide salt solution was 50% and the pH value was 8.1);

[0059] 2) Polymerization reaction: After adding 100 parts of the polyamide PA56 salt solution obtained in step 1) into a polymerization kettle, the kettle was filled with nitrogen and evacuated for 3 times to replace the air in the kettle, and then filled with nitrogen; the polymerization reaction was carried out under the conditions of controlling the temperature of the polymerization kettle to 250° C. and the pressure to 1.8 MPa. After the pressure reached 1.8 MPa, the pressure in the kettle was stabilized, the steam exhaust valve was opened, and water vapor began to be released uniformly. After the released water vapor was condensed by the condenser, the condensate entered the condensate metering tank. When the condensed water reached the target value, the exhaust valve was closed, and then the pressure in the kettle was reduced to 0.02 MPa. After evacuation, the material was discharged to obtain flame-retardant polyamide PA56.

[0060] Embodiment 5:

[0061] The present invention uses the halogen-free flame retardant DOPO-NH2 described in Example 1 to prepare a halogen-free flame retardant polyamide PA56, and the detailed steps are as follows:

[0062] 1) Preparation of flame retardant organic salt solution: 30 g of flame retardant DOPO-NH2, 8 g of adipic acid and 40 g of desalted water were added into a reaction vessel for mixed reaction at a reaction temperature of 50° C., a reaction time of 2.5 h and a stirring speed of 200 r / min; after the reaction, a flame retardant organic salt solution was obtained;

[0063] 2) Preparation of polyamide PA56 salt solution: 490 g of desalted water and 205 g of pentamethylenediamine were added to a salt-forming reaction kettle in sequence, stirring was started, and then 280 g of adipic acid was added to carry out a heated salt-forming reaction, and the reaction temperature was controlled to be 50° C. and the reaction time was 1.5 h; after the reaction, a polyamide PA56 salt solution was obtained (the concentration of the obtained polyamide salt solution was 50% and the pH value was 8.2);

[0064] 3) Polymerization reaction: 99 parts of the polyamide PA56 salt solution obtained in step 2) and 1 part of the flame retardant organic salt solution obtained in step 1) are sequentially added into a polymerization kettle, and then nitrogen is filled and evacuated for 3 times to replace the air in the kettle, and then nitrogen is filled; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 230° C. and the pressure to 2.0 MPa. After the pressure reaches 2.0 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.03 MPa, and the material is discharged after vacuuming to obtain halogen-free flame-retardant polyamide PA56.

[0065] Embodiment 6:

[0066] The present invention uses the halogen-free flame retardant DOPO-NH2 described in Example 1 to prepare a halogen-free flame retardant polyamide PA56, and the detailed steps are as follows:

[0067] 1) Preparation of flame retardant organic salt solution: 35 g of flame retardant DOPO-NH2, 10 g of adipic acid and 46 g of desalted water were added into a reaction container for mixed reaction at a reaction temperature of 75° C., a reaction time of 2 h and a stirring speed of 250 r / min; after the reaction, a flame retardant organic salt solution was obtained;

[0068] 2) Preparation of polyamide PA56 salt solution: 480 g of desalted water and 200 g of pentamethylenediamine were added to a salt-forming reaction kettle in sequence, stirring was started, and then 275 g of adipic acid was added to carry out a heated salt-forming reaction, and the reaction temperature was controlled to be 70° C. and the reaction time was 1 h; after the reaction, a polyamide PA56 salt solution was obtained (the concentration of the obtained polyamide salt solution was 50% and the pH value was 8.1);

[0069] 3) Polymerization reaction: 98 parts of the polyamide PA56 salt solution obtained in step 2) and 2 parts of the flame retardant organic salt solution obtained in step 1) are sequentially added into a polymerization kettle, and then nitrogen is filled and evacuated for 3 times to replace the air in the kettle, and then nitrogen is filled; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 220° C. and the pressure to 2.2 MPa. After the pressure reaches 2.2 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.04 MPa, and the material is discharged after vacuuming to obtain halogen-free flame-retardant polyamide PA56.

[0070] Embodiment 7:

[0071] The present invention uses the halogen-free flame retardant DOPO-NH2 described in Example 1 to prepare a halogen-free flame retardant polyamide PA56, and the detailed steps are as follows:

[0072] 1) Preparation of flame retardant organic salt solution: 40 g of flame retardant DOPO-NH2, 11 g of adipic acid and 52 g of desalted water were added into a reaction vessel for mixed reaction at a reaction temperature of 50° C., a reaction time of 4 h and a stirring speed of 300 r / min; after the reaction, a flame retardant organic salt solution was obtained;

[0073] 2) Preparation of polyamide PA56 salt solution: 470 g of desalted water and 195 g of pentamethylenediamine were added to a salt-forming reaction kettle in sequence, stirring was started, and then 270 g of adipic acid was added to carry out a heated salt-forming reaction, and the reaction temperature was controlled to be 40° C. and the reaction time was 3 h; after the reaction, a polyamide PA56 salt solution was obtained (the concentration of the obtained polyamide salt solution was 50% and the pH value was 8.1);

[0074] 3) Polymerization reaction: 94 parts of the polyamide PA56 salt solution obtained in step 2) and 6 parts of the flame retardant organic salt solution obtained in step 1) are sequentially added into a polymerization kettle, and then the kettle is filled with nitrogen and evacuated twice to replace the air in the kettle, and then filled with nitrogen; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 230° C. and the pressure to 1.6 MPa. After the pressure reaches 1.6 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.02 MPa, and the material is discharged after evacuation to obtain halogen-free flame-retardant polyamide PA56.

[0075] Embodiment 8:

[0076] The present invention uses the halogen-free flame retardant DOPO-NH2 described in Example 1 to prepare a halogen-free flame retardant polyamide PA56, and the detailed steps are as follows:

[0077] 1) Preparation of flame retardant organic salt solution: 45 g of flame retardant DOPO-NH2, 12 g of adipic acid and 59 g of desalted water were added into a reaction vessel for mixed reaction at a reaction temperature of 80° C., a reaction time of 2 h, and a stirring speed of 300 r / min; after the reaction, a flame retardant organic salt solution was obtained;

[0078] 2) Preparation of polyamide PA56 salt solution: 430 g of desalted water and 180 g of pentamethylenediamine were added to a salt-forming reaction kettle in sequence, stirring was started, and then 245 g of adipic acid was added to carry out a heating salt-forming reaction, and the reaction temperature was controlled to be 60° C. and the reaction time was 2 h; after the reaction, a polyamide PA56 salt solution was obtained (the concentration of the obtained polyamide salt solution was 50% and the pH value was 8.2);

[0079] 3) Polymerization reaction: 88 parts of the polyamide PA56 salt solution obtained in step 2) and 12 parts of the flame retardant organic salt solution obtained in step 1) are added to a polymerization kettle in sequence, and then nitrogen is filled and evacuated for 3 times to replace the air in the kettle, and then nitrogen is filled; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 250° C. and the pressure to 1.8 MPa. After the pressure reaches 1.8 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.02 MPa, and the material is discharged after vacuuming to obtain halogen-free flame-retardant polyamide PA56.

[0080] Embodiment 9:

[0081] The present invention uses the halogen-free flame retardant DOPO-NH2 described in Example 1 to prepare a halogen-free flame retardant polyamide PA56, and the detailed steps are as follows:

[0082] 1) Preparation of flame retardant organic salt solution: 50 g of flame retardant DOPO-NH2, 14 g of adipic acid and 65 g of desalted water were added into a reaction vessel for mixed reaction at a reaction temperature of 70° C., a reaction time of 3 h, and a stirring speed of 200 r / min; after the reaction, a flame retardant organic salt solution was obtained;

[0083] 2) Preparation of polyamide PA56 salt solution: 400 g of desalted water and 170 g of pentamethylenediamine were added to a salt-forming reaction kettle in sequence, stirring was started, and then 230 g of adipic acid was added to carry out a heated salt-forming reaction, and the reaction temperature was controlled to be 50° C. and the reaction time was 2.5 h; after the reaction, a polyamide PA56 salt solution was obtained (the concentration of the obtained polyamide salt solution was 50% and the pH value was 8.2);

[0084] 3) Polymerization reaction: 83 parts of the polyamide PA56 salt solution obtained in step 2) and 17 parts of the flame retardant organic salt solution obtained in step 1) are added to a polymerization kettle in sequence, and then nitrogen is filled and evacuated for 3 times to replace the air in the kettle, and then nitrogen is filled; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 250° C. and the pressure to 1.8 MPa. After the pressure reaches 1.8 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.03 MPa, and the material is discharged after vacuuming to obtain halogen-free flame-retardant polyamide PA56.

[0085] The performance test results of the products prepared in Examples 4-9 of the present invention are shown in Table 1.

[0086] Table 1 Performance test results of the products prepared in Examples 4-9 of the present invention

[0087]

[0088] It can be seen from the data in Table 1 that when the addition amount of the flame retardant is between 2% and 20%, the limiting oxygen index of the PA56 resin is maintained between 29% and 38%, the vertical burning test reaches UL94 V-0, the tensile strength is 73-87MPa, the elongation at break is 34-41%, the flexural strength is 84-98Mpa and the notched impact strength is 4.3-5.0. Compared with the unmodified PA56 resin (Example 4), the flame retardant performance is significantly improved, and the mechanical properties change little.

[0089] Embodiment 10:

[0090] The present invention uses the halogen-free flame retardant DOPO-NH2 described in Example 1 to prepare a halogen-free flame retardant polyamide PA66, and the detailed steps are as follows:

[0091] 1) Preparation of flame retardant organic salt solution: 40 g of flame retardant DOPO-NH2, 11 g of adipic acid and 52 g of desalted water were added into a reaction vessel for mixed reaction at a reaction temperature of 65° C., a reaction time of 3 h and a stirring speed of 300 r / min; after the reaction, a flame retardant organic salt solution was obtained;

[0092] 2) Preparation of polyamide PA66 salt solution: 460 g of desalted water and 210 g of hexamethylenediamine were added to a salt-forming reaction kettle in sequence, stirring was started, and then 260 g of adipic acid was added to carry out a heating salt-forming reaction, and the reaction temperature was controlled to be 60° C. and the reaction time was 2 h; after the reaction, a polyamide PA66 salt solution was obtained (the concentration of the obtained polyamide salt solution was 50% and the pH value was 7.7);

[0093] 3) Polymerization reaction: 94 parts of the polyamide PA66 salt solution obtained in step 2) and 6 parts of the flame retardant organic salt solution obtained in step 1) are sequentially added into a polymerization kettle, and then nitrogen is filled and evacuated for 3 times to replace the air in the kettle, and then nitrogen is filled; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 250° C. and the pressure to 1.8 MPa. After the pressure reaches 1.8 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.02 MPa, and the material is discharged after vacuuming to obtain halogen-free flame-retardant polyamide PA66.

[0094] Embodiment 11:

[0095] The present invention uses the halogen-free flame retardant DOPO-NH2 described in Example 1 to prepare a halogen-free flame retardant polyamide PA610, and the detailed steps are as follows:

[0096] 1) Preparation of flame retardant organic salt solution: 40 g of flame retardant DOPO-NH2, 11 g of sebacic acid and 52 g of desalted water were added into a reaction vessel for mixed reaction at a reaction temperature of 65° C., a reaction time of 3 h and a stirring speed of 300 r / min; after the reaction, a flame retardant organic salt solution was obtained;

[0097] 2) Preparation of polyamide PA610 salt solution: 470 g of desalted water and 170 g of hexamethylenediamine were added to a salt-forming reaction kettle in sequence, stirring was started, and then 295 g of sebacic acid was added to carry out a heating salt-forming reaction, and the reaction temperature was controlled to be 60° C. and the reaction time was 2 h; after the reaction, a polyamide PA610 salt solution was obtained (the concentration of the obtained polyamide salt solution was 50% and the pH value was 7.5);

[0098] 3) Polymerization reaction: 94 parts of the polyamide PA610 salt solution obtained in step 2) and 6 parts of the flame retardant organic salt solution obtained in step 1) are sequentially added into a polymerization kettle, and then nitrogen is filled and evacuated for 3 times to replace the air in the kettle, and then nitrogen is filled; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 250° C. and the pressure to 1.8 MPa. After the pressure reaches 1.8 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by a condenser, the condensate enters a condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.03 MPa, and the material is discharged after evacuation to obtain halogen-free flame-retardant polyamide PA610.

[0099] Embodiment 12:

[0100] The present invention uses the halogen-free flame retardant DOPO-NH2 described in Example 1 to prepare a halogen-free flame retardant polyamide PA612, and the detailed steps are as follows:

[0101] 1) Preparation of flame retardant organic salt solution: 40 g of flame retardant DOPO-NH2, 11 g of dodecane dibasic acid and 52 g of desalted water were added into a reaction vessel for mixed reaction at a reaction temperature of 65° C., a reaction time of 3 h and a stirring speed of 300 r / min; after the reaction, a flame retardant organic salt solution was obtained;

[0102] 2) Preparation of polyamide PA612 salt solution: 470 g of desalted water and 160 g of hexamethylenediamine were added to a salt-forming reaction kettle in sequence, stirring was started, and then 310 g of dodecanedioic acid was added to carry out a heating salt-forming reaction, and the reaction temperature was controlled to be 60° C. and the reaction time was 2 h; after the reaction, a polyamide PA612 salt solution was obtained (the concentration of the obtained polyamide salt solution was 50% and the pH value was 7.5);

[0103] 3) Polymerization reaction: 94 parts of the polyamide PA612 salt solution obtained in step 2) and 6 parts of the flame retardant organic salt solution obtained in step 1) are sequentially added into a polymerization kettle, and then nitrogen is filled and evacuated for 3 times to replace the air in the kettle, and then nitrogen is filled; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 250° C. and the pressure to 1.8 MPa. After the pressure reaches 1.8 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by the condenser, the condensate enters the condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to 0.03 MPa, and the material is discharged after vacuuming to obtain halogen-free flame-retardant polyamide PA612.

[0104] The performance test results of the products prepared in Examples 10-12 of the present invention are shown in Table 2.

[0105] Table 2 Performance test results of the products prepared in Examples 9-11 of the present invention

[0106]

[0107] It can be seen from the data in Table 2 that when the flame retardant addition amount is about 6%, PA66, PA610 and PA612 resins all show good flame retardancy, and the mechanical properties change less than ordinary resins without adding flame retardants.

Claims

1. A halogen-free flame retardant DOPO-NH2, characterized in that: The halogen-free flame retardant DOPO-NH2 is prepared by the following method: a. Using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide DOPO as the starting material, firstly add solvent ethanol and triethyl orthoformate thereto, heat to 50-70°C for reaction, and the reaction time is 4-6h; b. conducting an ester exchange reaction between the obtained reaction product and 1,4-butanediol at 100-160° C. for 10-16 hours to obtain compound 1; c. A nitric acid solution is added to the obtained compound 1 for nitration treatment. After the nitration treatment, hydrogen is introduced for reduction reaction to reduce the nitro group to an amino group, thereby preparing a flame retardant DOPO-NH2.

2. The halogen-free flame retardant DOPO-NH2 according to claim 1, characterized in that: The molar ratio of DOPO and triethyl orthoformate added in step a is 1:1.5-3; the volume mass ratio of the solvent ethanol and DOPO added is 5-10 mL:1 g; In step b, the molar ratio of DOPO to 1,4-butanediol added is 1:0.4-0.5; In the nitration process of step c, the temperature is controlled at 20-50°C and the reaction time is 5-9h; in the reduction reaction process, the temperature is controlled at 70-90°C and the reaction time is 3-6h; The concentration of the nitric acid solution in step c is 40-70%, the volume mass ratio of the nitric acid solution to DOPO is 5-10 mL:1 g; the pressure of the hydrogen gas is 2-5 bar.

3. A method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2, characterized in that: The method comprises the following steps: 1) Preparation of flame retardant organic salt solution: adding flame retardant DOPO-NH2, dibasic acid and water into a reaction container for mixing reaction, and obtaining flame retardant organic salt solution after reaction; 2) Preparation of polyamide salt solution: desalted water and diamine are added to a salt-forming reaction kettle in sequence, stirring is started, and then a dibasic acid is added to perform a heating salt-forming reaction, and a polyamide salt solution is obtained after the reaction; 3) Polymerization reaction: after the polyamide salt solution obtained in step 2) and the flame retardant organic salt solution obtained in step 1) are sequentially added into a polymerization kettle, the kettle is filled with nitrogen and vacuumized for 2 to 3 times to replace the air in the kettle, and then filled with nitrogen; the polymerization reaction is carried out under the conditions of controlling the temperature of the polymerization kettle to 220 to 280° C. and the pressure to 1.4 to 2.2 MPa, after the pressure reaches 1.4 to 2.2 MPa, the pressure in the kettle is stabilized, the steam exhaust valve is opened, and water vapor is uniformly released. After the released water vapor is condensed by a condenser, the condensate enters a condensate metering tank. When the condensed water reaches the target value, the exhaust valve is closed, and then the pressure in the kettle is reduced to a slightly positive pressure, and the material is discharged after vacuuming to obtain a halogen-free flame-retardant polyamide.

4. The method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2 according to claim 3, characterized in that: In step 1), the flame retardant DOPO-NH2 and the dibasic acid are added in a molar ratio of 1:1-2, and the concentration of the reaction solution is controlled to be 30-70%; during the mixed reaction, the reaction temperature is 50-80°C, the reaction time is 2-4h, and the stirring speed is 100-500r / min.

5. The method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2 according to claim 3, characterized in that: In step 2), the molar ratio of the dibasic acid and the diamine added is 1:1-3; the concentration of the reaction solution is controlled to be 40-60%; during the salt-forming reaction, the reaction temperature is controlled to be 40-70°C and the reaction time is controlled to be 1-3h.

6. The method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2 according to claim 3, characterized in that: The concentration of the polyamide salt solution obtained in step 2) is 40-60%, and the pH value is 7.0-8.

5.

7. The method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2 according to claim 3, characterized in that: Expressed in parts by weight, the amounts of the polyamide salt solution and the flame retardant organic salt solution added in step 3) are 80-100 parts and 0-20 parts respectively.

8. The method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2 according to claim 3, characterized in that: In step 3), when the condensed water reaches the target value, the amount of condensed water accounts for 30-60% of the mass of the added polyamide salt solution.

9. The method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2 according to claim 3, characterized in that: The slight positive pressure in step 3) is 0.01-0.04 MPa.

10. The method for preparing halogen-free flame retardant polyamide using halogen-free flame retardant DOPO-NH2 according to claim 3, characterized in that: The diamine is pentamethylenediamine or hexamethylenediamine; the dibasic acid is adipic acid, sebacic acid or dodecanedioic acid.

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