A copolyamide 6 resin with a synergistic flame retardant effect and a preparation method thereof

Abstract

The present invention discloses a copolymerized nylon 6 resin with a synergistic flame retardant effect and a preparation method thereof. The molecular structure of the copolymerized nylon 6 resin with a synergistic flame retardant effect involved in the present invention is shown in Formula I. The preparation method includes preparing component A by a salt formation reaction of a phosphorus-containing dibasic acid and a low molecular weight amino-terminated silicone (Mn ≤ 2000), and then copolymerizing with caprolactam to obtain a copolymerized nylon 6 resin with a synergistic flame retardant effect. By regulating the molecular weight of the amino-terminated silicone and the copolymerization ratio of component A, a copolymerized nylon 6 resin with excellent mechanical and flame retardant properties is obtained, and its synthesis route is simple and the process is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to a copolyamide 6 resin with excellent mechanical and flame retardant properties, and its synthesis route is simple and the process is environmentally friendly. Background Art

[0002] With the continuous improvement of the level of science and technology, new materials and their products are becoming increasingly rich, among which polymer materials are particularly prominent. There are a wide variety of polymer materials with excellent properties. Nylon materials are a kind of polymer materials with relatively good comprehensive properties and a wide range of application fields. However, like the vast majority of polymer materials, nylon materials are a kind of combustible materials and cannot self-extinguish when encountering fire, resulting in countless fires, posing a serious threat to people's lives and property safety. Therefore, it is very necessary to conduct research on its flame retardant modification. Nylon 6 is the most common and largest-yielding one among nylon materials. It has excellent mechanical properties, electrical insulation properties, weather resistance and self-lubrication properties, and is a widely used engineering plastic. At the same time, due to its advantages such as light weight, wear resistance and not being easily eaten by insects, it is used to manufacture synthetic fibers. However, usually nylon 6 resin is flammable, its limiting oxygen index is low, it generates a large amount of heat when burning, the flame propagation speed is fast and it will produce a large amount of thick smoke and molten droplets, thus restricting its application in fields with high flame retardant requirements such as military clothing, fire fighting clothing, outdoor products, and fabric decorations in public places. Therefore, developing a flame retardant nylon 6 resin with excellent comprehensive properties is of great significance for expanding its application range and increasing its added value.

[0003] Studies have found that when flame retardant modification is carried out on nylon 6 resin, it will inevitably have an adverse impact on its other properties. Therefore, while improving the flame retardant performance, the weakening of other properties should be reduced; on the other hand, to achieve industrial production, issues such as cost and environment must also be considered. Currently, the methods commonly used to prepare flame retardant nylon 6 resin mainly include two categories: blending method and polymerization method. The traditional method for preparing flame retardant nylon 6 resin is mainly to add some flame retardants without reactive groups to the nylon matrix. The addition amount of such flame retardants is relatively large, and they are unevenly dispersed in the resin, easily resulting in poor physical and mechanical properties of the obtained flame retardant nylon 6 resin; secondly, adding some flame retardants containing reactive functional groups (DOPO type), their thermal stability is poor, and they are easily decomposed during the nylon synthesis process, resulting in a lower viscosity of the nylon resin and unable to meet the strength requirements of engineering plastics. Currently, the vast majority of scientific researchers mainly focus on preparing flame retardant nylon by adding inorganic or organic flame retardants, and there is less research on the synthesis of reactive flame retardants and the preparation of bulk flame retardant nylon resin. Therefore, designing and developing a kind of flame retardant monomer with good thermal stability, high flame retardant element content and strong reaction activity has become the key technical problem for preparing flame retardant nylon 6 resin.

[0004] Chinese Patent 201110134496.8 relates to a flame-retardant nylon 6 nanocomposite, which solves the problem of flammability of nylon 6 / layered silicate nanocomposites. The characteristics of this material are that it uses the intumescent flame retardant melamine polyphosphate (MPP) and clay platelets for synergistic flame retardancy. Among them, the organic clay is prepared by reacting protonated ADDT with a clay solution, which can be well exfoliated in the resin matrix and make the composite material reach the UL94-V0 level. Chinese Patent CN200810157191.7 discloses a preparation method of synergistic flame-retardant nylon 6. First, at room temperature, an aqueous sodium hydroxide solution is added to an aqueous solution of aluminum nitrate and magnesium nitrate for reaction; then an aqueous solution of dissolved sodium stearate is added to the above reaction system and the reaction continues; the product is filtered, washed and dried to obtain modified layered double magnesium hydroxide aluminum powder; microencapsulated red phosphorus, modified layered double magnesium hydroxide aluminum powder and nylon 6 pellets are weighed respectively and dried; the above three dried materials are premixed, melt-blended and extruded into pellets in a twin-screw extruder, and the synergistic flame-retardant nylon 6 masterbatch is obtained after drying. The present invention uses ammonium persulfate as an initiator, and the ignition point of the prepared microencapsulated red phosphorus exceeds 450°C; when the vertical burning performance of the nylon 6 composite material reaches the V-0 level and the LOI reaches more than 28%, the amount of flame retardant required is small, and the flame retardants used are all inexpensive halogen-free flame retardants, which can reduce costs. The flame retardant performance of the blended flame-retardant nylon composite material obtained by adding a flame retardant can be significantly improved, but the decrease in its mechanical properties is relatively large. Chinese Patent 201510435858.5 relates to a flame-retardant nylon 66 copolymer material and its preparation method, mainly reacting a phosphorus-containing flame retardant with a diamine or a diol to obtain a flame retardant prepolymer, and then reacting the flame retardant prepolymer with a nylon 66 prepolymer to obtain a flame-retardant nylon 66 copolymer material. The flame-retardant nylon 66 copolymer material prepared by this method has the advantages of less flame retardant addition, excellent mechanical properties, good flame retardant persistence, etc., and the vertical burning test can reach the UL94 V-0 level, and the limiting oxygen index is above 32%. However, the initial decomposition temperature of the introduced phosphorus-containing flame retardant is relatively low, and the resin viscosity of the obtained nylon 66 copolymer material is relatively low, and the mechanical strength is poor. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies existing in the prior art and develop a copolymer nylon 6 resin with excellent mechanical and flame retardant properties, and its synthesis route is simple and the process is environmentally friendly.

[0006] In order to achieve the purpose of the present invention, the general inventive concept is: selecting a phosphorus-containing dibasic acid and a low-molecular-weight amino-terminated organosilicon (Mn≤2000) as raw materials, preparing component A through a salt-forming reaction, and then copolymerizing with caprolactam to obtain a copolymer nylon 6 resin with a synergistic flame retardant effect.

[0007] The present invention is realized through the following technical solutions:

[0008] A copolymerized nylon 6 resin with a synergistic flame retardant effect and a preparation method thereof, characterized in that the structural characteristics of the copolymerized nylon 6 resin with a synergistic flame retardant effect are shown in Formula I.

[0009]

[0010] The above-mentioned n can be any integer from 0 to 23.

[0011] A preparation method of a copolymerized nylon 6 resin with a synergistic flame retardant effect, characterized in that it mainly includes the following steps:

[0012] 1) Select a phosphorus-containing dibasic acid and a low molecular weight amino-terminated silicone (Mn≤2000) as raw materials, and prepare component A through a salt formation reaction in deionized water;

[0013] 2) Component A, caprolactam, and a catalyst are fed in a certain ratio, and a copolymerized nylon 6 resin with a synergistic flame retardant effect can be obtained through copolymerization.

[0014] The structural characteristics of the above-mentioned phosphorus-containing dibasic acid are shown in Formula II, and the structural characteristics of the low molecular weight amino-terminated silicone (Mn≤2000) are shown in Formula III, where n can be any integer from 0 to 23.

[0015]

[0016] The molar ratio of the above-mentioned phosphorus-containing dibasic acid to the low molecular weight amino-terminated silicone (Mn≤2000) for salt formation is 1:1 - 1.01, preferably 1:1 - 1.005, and the addition amount of the deionized water is 10 - 40% of the total mass of the phosphorus-containing dibasic acid and the low molecular weight amino-terminated silicone, preferably 20 - 30%.

[0017] The feeding mass ratio of the above-mentioned component A to caprolactam is 1:5 - 15, preferably 1:6 - 10.

[0018] The above-mentioned catalyst is one of phosphoric acid, phosphorous acid, and sodium hypophosphite, and the addition amount is 0.1 - 0.5% of the total mass of component A and caprolactam.

[0019] The specific process of the above-mentioned copolymerization is as follows: After feeding, replace the air in the high-temperature and high-pressure reaction kettle with high-purity nitrogen 3 - 4 times, heat up to 200 - 210°C, maintain the pressure in the kettle at 2.0 - 2.5 MPa, keep the pressure for 2.0 - 3.0 h, then slowly release the gas, and continue to heat up to 240 - 250°C, release the gas to normal pressure, discharge the water in the system, and then gradually evacuate to make the system decompress to -0.05 - -0.09 MPa, and discharge the material to obtain the copolymerized nylon 6 resin with a synergistic flame retardant effect.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) Select a phosphorus-containing dibasic acid with high purity, high flame retardant element content, and good thermal stability as one of the comonomers, effectively solving the problem that some reactive flame retardants are prone to decomposition when heated;

[0022] (2) Introduce a low molecular weight terminal amino silicone (Mn≤2000) structure into the main chain of the nylon molecule, which can exert the synergistic flame retardant effect of nitrogen-phosphorus-silicon and can improve the toughness and impact resistance to a certain extent;

[0023] (3) To meet the different requirements of specific downstream application sites for the strength, toughness, and flame retardant grade of the copolymerized nylon 6 resin, realize customized, differentiated, and functional production, and greatly enrich the product variety of the copolymerized nylon 6 resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The infrared curve of the copolymerized nylon 6 resin with a synergistic flame retardant effect prepared in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be further described below with reference to specific embodiments.

[0026] Example 1

[0027] Weigh 2485.2 g of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (when n = 0, the corresponding terminal amino silicone) and 1600.0 g of deionized water. Under stirring conditions (rotation speed 200 r / min), add 5343.7 g of the phosphorus-containing dibasic acid shown in the structure of Formula II, and prepare Component A through a salt-forming reaction 1 .

[0028] Weigh 2000.0 g of Component A 1 , 20000.0 g of caprolactam, and 28.0 g of sodium hypophosphite, put them into a high-temperature and high-pressure reaction kettle, displace the air in the kettle with high-purity nitrogen 3 to 4 times, heat up to 205 °C, keep the pressure in the kettle at 2.2 MPa, keep the pressure for 2.5 h, then slowly release the gas, and continue to heat up to 250 °C, release the gas to normal pressure, discharge the water in the system, and then gradually evacuate to make the system decompress to -0.7 MPa, and discharge the material to obtain the copolymerized nylon 6 resin with a synergistic flame retardant effect.

[0029] Example 2

[0030] Weigh 2485.2 g of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (the terminal amino silicone corresponding to n = 0) and 1600.0 g of deionized water. Under stirring conditions (rotation speed 200 r / min), add 5343.7 g of the phosphorus-containing dibasic acid shown in the structure of Formula II, and prepare Component A through a salt-forming reaction. 1 .

[0031] Weigh 2000.0 g of Component A 1 , 18000.0 g of caprolactam, and 28.0 g of sodium hypophosphite, put them into a high-temperature and high-pressure reaction kettle, displace the air in the kettle with high-purity nitrogen 3 - 4 times, heat up to 205 °C, maintain the pressure in the kettle at 2.2 MPa, keep the pressure for 2.5 h, then slowly release the gas, and continue to heat up to 250 °C, release the gas to atmospheric pressure, discharge the water in the system, and then gradually evacuate to make the system decompress to -0.7 MPa, and discharge the material to obtain the copolymerized nylon 6 resin with a synergistic flame-retardant effect.

[0032] Example 3

[0033] Weigh 2485.2 g of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (the terminal amino silicone corresponding to n = 0) and 1600.0 g of deionized water. Under stirring conditions (rotation speed 200 r / min), add 5343.7 g of the phosphorus-containing dibasic acid shown in the structure of Formula II, and prepare Component A through a salt-forming reaction. 1 .

[0034] Weigh 2000.0 g of Component A 1 , 16000.0 g of caprolactam, and 28.0 g of sodium hypophosphite, put them into a high-temperature and high-pressure reaction kettle, displace the air in the kettle with high-purity nitrogen 3 - 4 times, heat up to 205 °C, maintain the pressure in the kettle at 2.2 MPa, keep the pressure for 2.5 h, then slowly release the gas, and continue to heat up to 250 °C, release the gas to atmospheric pressure, discharge the water in the system, and then gradually evacuate to make the system decompress to -0.7 MPa, and discharge the material to obtain the copolymerized nylon 6 resin with a synergistic flame-retardant effect.

[0035] Example 4

[0036] Weigh 2485.2 g of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (the terminal amino silicone corresponding to n = 0) and 1600.0 g of deionized water. Under stirring conditions (rotation speed 200 r / min), add 5343.7 g of the phosphorus-containing dibasic acid shown in the structure of Formula II, and prepare Component A through a salt-forming reaction. 1 .

[0037] Weigh 2000.0 g of Component A 1, 14000.0 g of caprolactam and 28.0 g of sodium hypophosphite are put into a high-temperature and high-pressure reactor. The air in the reactor is replaced with high-purity nitrogen 3 - 4 times. The temperature is raised to 205 °C, and the pressure in the reactor is maintained at 2.2 MPa. After maintaining the pressure for 2.5 h, the gas is slowly released, and the temperature is further raised to 250 °C. The gas is released until the pressure reaches atmospheric pressure, and the water in the system is discharged. Then, the vacuum is gradually applied to reduce the pressure of the system to -0.7 MPa, and the material is discharged to obtain a copolymerized nylon 6 resin with a synergistic flame retardant effect.

[0038] Example 5

[0039] Weigh 2485.2 g of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (when n = 0, the corresponding amino-terminated organosilicon) and 1600.0 g of deionized water. Under stirring conditions (rotation speed 200 r / min), add 5343.7 g of the phosphorus-containing dibasic acid shown in the structure of formula II, and component A is prepared through a salt-forming reaction. 1 .

[0040] Weigh 2000.0 g of component A 1 , 12000.0 g of caprolactam and 28.0 g of sodium hypophosphite are put into a high-temperature and high-pressure reactor. The air in the reactor is replaced with high-purity nitrogen 3 - 4 times. The temperature is raised to 205 °C, and the pressure in the reactor is maintained at 2.2 MPa. After maintaining the pressure for 2.5 h, the gas is slowly released, and the temperature is further raised to 250 °C. The gas is released until the pressure reaches atmospheric pressure, and the water in the system is discharged. Then, the vacuum is gradually applied to reduce the pressure of the system to -0.7 MPa, and the material is discharged to obtain a copolymerized nylon 6 resin with a synergistic flame retardant effect.

[0041] Example 6

[0042] Weigh 6192.7 g of amino-terminated organosilicon (n = 5) and 2400.0 g of deionized water. Under stirring conditions (rotation speed 200 r / min), add 5343.7 g of the phosphorus-containing dibasic acid shown in the structure of formula II, and component A is prepared through a salt-forming reaction. 2 .

[0043] Weigh 2000.0 g of component A 2 , 12000.0 g of caprolactam and 28.0 g of sodium hypophosphite are put into a high-temperature and high-pressure reactor. The air in the reactor is replaced with high-purity nitrogen 3 - 4 times. The temperature is raised to 205 °C, and the pressure in the reactor is maintained at 2.2 MPa. After maintaining the pressure for 2.5 h, the gas is slowly released, and the temperature is further raised to 250 °C. The gas is released until the pressure reaches atmospheric pressure, and the water in the system is discharged. Then, the vacuum is gradually applied to reduce the pressure of the system to -0.7 MPa, and the material is discharged to obtain a copolymerized nylon 6 resin with a synergistic flame retardant effect.

[0044] Example 7

[0045] Weigh 9900.2 g of amino-terminated silicone (n = 10) and 3100.0 g of deionized water. Under stirring conditions (rotation speed 200 r / min), add 5343.7 g of phosphorus-containing dibasic acid shown in Formula II, and prepare Component A through a salt-forming reaction. 3 .

[0046] Weigh 2000.0 g of Component A 3 , 12000.0 g of caprolactam, and 28.0 g of sodium hypophosphite, put them into a high-temperature and high-pressure reaction kettle, displace the air in the kettle with high-purity nitrogen 3 - 4 times, heat up to 205 °C, maintain the pressure in the kettle at 2.2 MPa, keep the pressure for 2.5 h, then slowly release the gas, and continue to heat up to 250 °C, release the gas to atmospheric pressure, discharge the water in the system, then gradually evacuate the air, reduce the pressure of the system to -0.7 MPa, and discharge the material to obtain a copolymerized nylon 6 resin with a synergistic flame retardant effect.

[0047] Example 8

[0048] Weigh 17315.2 g of amino-terminated silicone (n = 20) and 4600.0 g of deionized water. Under stirring conditions (rotation speed 200 r / min), add 5343.7 g of phosphorus-containing dibasic acid shown in Formula II, and prepare Component A through a salt-forming reaction. 4 .

[0049] Weigh 2000.0 g of Component A 4 , 12000.0 g of caprolactam, and 28.0 g of sodium hypophosphite, put them into a high-temperature and high-pressure reaction kettle, displace the air in the kettle with high-purity nitrogen 3 - 4 times, heat up to 205 °C, maintain the pressure in the kettle at 2.2 MPa, keep the pressure for 2.5 h, then slowly release the gas, and continue to heat up to 250 °C, release the gas to atmospheric pressure, discharge the water in the system, then gradually evacuate the air, reduce the pressure of the system to -0.7 MPa, and discharge the material to obtain a copolymerized nylon 6 resin with a synergistic flame retardant effect.

[0050] Comparative Example 1

[0051] Weigh 20000.0 kg of caprolactam, 40.0 g of sodium hypophosphite, and 1000 g of deionized water in sequence, put them into a high-temperature and high-pressure reaction kettle, displace the air in the kettle with high-purity nitrogen 3 - 4 times, heat up to 205 °C, maintain the pressure in the kettle at 2.2 MPa, keep the pressure for 2.5 h, then slowly release the gas, and continue to heat up to 250 °C, release the gas to atmospheric pressure, discharge the water in the system, then gradually evacuate the air, reduce the pressure of the system to -0.7 MPa, and discharge the material to obtain ordinary nylon 6 resin.

[0052] Comparative Example 2

[0053] Weigh 1162.1 g of hexamethylenediamine and 1400.0 g of deionized water. Under stirring conditions (rotation speed: 200 r / min), add 5343.7 g of the phosphorus-containing dibasic acid shown in the structure of formula II, and prepare component A through a salt-forming reaction. 5 .

[0054] Weigh 2000.0 g of component A 5 , 12000.0 g of caprolactam, and 28.0 g of sodium hypophosphite, and put them into a high-temperature and high-pressure reactor. Replace the air in the reactor with high-purity nitrogen 3 to 4 times, heat up to 205 °C, maintain the pressure in the reactor at 2.2 MPa, keep the pressure for 2.5 h, then slowly release the gas, and continue to heat up to 250 °C, release the gas to atmospheric pressure, discharge the water in the system, and then gradually evacuate to make the pressure in the system reduced to -0.7 MPa, and discharge the material to obtain the copolymerized nylon 6 resin with phosphorus-containing flame retardant elements.

[0055] Table 1 Performance data of the copolymerized nylon 6 resin with synergistic flame retardant effect prepared in each example and the comparative examples

[0056]

[0057] Test standard:

[0058] Test conditions for tensile, flexural, and impact properties: Place the tensile, flexural, and impact specimens in a constant temperature and humidity chamber for 24 h, and use a testing machine for testing. The test standards are GB / T 1040.2 - 2006, GB / T 9341 - 2008, and GB / T 1043.1 - 2008 respectively. Flame retardant performance test: Test according to ANSI / UL94 - 2013, using the vertical burning method, and the specimen size is 125 mm × 13 mm × 1.6 mm. Limiting oxygen index test: Test according to GB / T 2406.2 - 2009, the specimen size is 80 mm × 10 mm × 4 mm, the gas flow rate is 40 mm / s, the initial oxygen concentration is 25%, and the top surface ignition method is used.

[0059] It can be seen from the data in Table 1 that compared with the ordinary nylon 6 resin, the copolymerized nylon 6 resin with synergistic flame retardant effect involved in this patent has obvious improvements in terms of elongation at break, notched impact strength, limiting oxygen index, and combustion rating. In particular, the elongation at break has increased by 3.1 to 7.9 times, the limiting oxygen index exceeds 30% for all, and the combustion rating reaches V - 0 for all, showing excellent toughness, impact resistance, and flame retardancy. On the other hand, compared with the copolymerized nylon 6 resin containing phosphorus-containing flame retardant elements, due to the nitrogen - phosphorus - silicon synergistic flame retardant effect, the copolymerized nylon 6 resin with synergistic flame retardant effect involved in this patent has better limiting oxygen index and combustion rating than the copolymerized nylon 6 resin with a single phosphorus-containing flame retardant element, and the toughness is significantly improved.

Claims

1. A method for preparing a copolymerized nylon 6 resin having a synergistic flame retardant effect, characterized in that: The structural characteristics of the copolymerized nylon 6 resin having a synergistic flame retardant effect are shown in Formula I: ； Formula I The preparation method comprises the following steps: 1) Select phosphorus-containing dibasic acid and low molecular weight amino-terminated organosilicon as raw materials, and prepare component A by salt-forming reaction in deionized water, wherein the low molecular weight amino-terminated organosilicon has a Mn of ≤2000; 2) Component A, caprolactam and catalyst are added in a certain ratio, and copolymerization is performed to obtain a copolymerized nylon 6 resin with a synergistic flame retardant effect; the molar ratio of the phosphorus-containing dibasic acid to the low molecular weight amino-terminated silicone is 1:1-1.01, and the amount of deionized water added is 10-40% of the total mass of the phosphorus-containing dibasic acid and the low molecular weight amino-terminated silicone; the mass ratio of component A to caprolactam is 1:5-15; the catalyst is one of phosphoric acid, phosphorous acid and sodium hypophosphite, and the amount added is 0.1-0.5% of the total mass of component A and caprolactam.

2. The method for preparing a copolymerized nylon 6 resin having a synergistic flame retardant effect according to claim 1, characterized in that: The n can be any integer between 0 and 23.

3. The method for preparing a copolymerized nylon 6 resin having a synergistic flame retardant effect according to claim 1, characterized in that: The structural characteristics of the phosphorus-containing dibasic acid are shown in Formula II, and the structural characteristics of the low molecular weight amino-terminated silicone are shown in Formula III, wherein n can be any integer between 0 and 23; Formula II; Formula III.

4. The method for preparing a copolymerized nylon 6 resin having a synergistic flame retardant effect according to claim 1, characterized in that: The molar ratio of the phosphorus-containing dibasic acid to the low molecular weight amino-terminated organosilicon in the salt formation is 1:1-1.005, and the amount of deionized water added is 20-30% of the total mass of the phosphorus-containing dibasic acid and the low molecular weight amino-terminated organosilicon.

5. The method for preparing a copolymerized nylon 6 resin having a synergistic flame retardant effect according to claim 1, characterized in that: The mass ratio of component A to caprolactam is 1:6-10.

6. The method for preparing a copolymerized nylon 6 resin having a synergistic flame retardant effect according to claim 1, characterized in that: The specific process of the copolymerization is: after feeding, the air in the high-temperature and high-pressure reactor is replaced with high-purity nitrogen for 3 to 4 times, the temperature is raised to 200 to 210°C, the pressure in the reactor is maintained at 2.0 to 2.5 MPa, and after maintaining the pressure for 2.0 to 3.0 hours, the gas is slowly released, and the temperature is continued to be raised to 240 to 250°C, the gas is released to normal pressure, the water in the system is discharged, and then the system is gradually vacuumed to reduce the pressure to -0.05 to -0.09 MPa, and the copolymer nylon 6 resin with synergistic flame retardant effect is obtained by releasing the material.

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