Flame-retardant modified polyamide as well as preparation method and application thereof

Abstract

The invention belongs to the field of high polymer materials, and discloses flame-retardant modified polyamide as well as a preparation method and application thereof. The flame-retardant modified polyamide comprises a monomer for forming a polyamide matrix and a polyhydroxy organic acid salt monomer serving as a flame-retardant structural unit. The flame-retardant modified polyamide provided by the invention has excellent flame retardance, keeps good mechanical properties and processing fluidity, and can be used for preparing electronic and electrical parts, automobile parts and other parts.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and specifically relates to a flame-retardant modified polyamide, its preparation method, and its application. Background Technology

[0002] Flame-retardant high-temperature nylon, due to its excellent fire safety performance, high-temperature stability, superior mechanical strength, and chemical resistance, has become an indispensable key material in the electronics, automotive, and aerospace industries. Its ability to maintain structural integrity and effectively prevent flame spread in high-temperature environments is of great significance for improving product safety and reliability.

[0003] To impart flame-retardant properties to high-temperature nylon, current technologies generally employ physical blending with flame retardants. However, both halogenated and halogen-free flame retardants (such as nitrogen- and phosphorus-based compounds) have significant limitations. Halogenated flame retardants readily produce toxic gases and corrosive fumes during combustion, posing serious environmental and health risks. Halogen-free flame retardants, on the other hand, typically require higher addition levels to achieve the desired flame-retardant effect, which severely impairs the intrinsic mechanical properties (such as strength and toughness) and processing flowability of the base resin, leading to product appearance defects and affecting long-term reliability.

[0004] Therefore, developing a polyamide modification technology that can maintain the excellent mechanical properties and processing fluidity of high-temperature nylon while achieving high efficiency, stability, and high flame retardant properties has become a key technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0005] The primary objective of this invention is to solve the aforementioned technical problems and provide a flame-retardant modified polyamide with high mechanical properties, good processing fluidity, and highly efficient flame-retardant characteristics.

[0006] A second objective of this invention is to provide a preparation process for the above-mentioned flame-retardant modified polyamide.

[0007] A third objective of this invention is to provide applications of the above-mentioned flame-retardant modified polyamide.

[0008] A fourth objective of this invention is to provide a component.

[0009] This invention is achieved through the following technical solution: A flame-retardant modified polyamide includes a monomer for forming a polyamide matrix and a polyhydroxy organic acid salt monomer as a flame-retardant structural unit.

[0010] In the polyhydroxy organic acid salt monomers described in this invention, the number of hydroxyl groups is ≥2.

[0011] Preferably, the polyhydroxy organic acid salt monomer is selected from at least one of polyhydroxy sulfonates and polyhydroxy carboxylates.

[0012] More preferably, the polyhydroxy organic acid salt monomer is selected from polyhydroxy sulfonates.

[0013] Preferably, the sulfonate portion of the polyhydroxysulfonate is selected from aromatic sulfonates.

[0014] More preferably, the sulfonate portion of the polyhydroxysulfonate is selected from dihydroxynaphthalenesulfonate or azoresorcinolsulfonate.

[0015] Preferably, the metal ion in the polyhydroxy metal salt is selected from Group IA metal ions.

[0016] More preferably, the metal ion is selected from at least one of potassium ions, sodium ions, lithium ions, and rubidium ions.

[0017] More preferably, the metal ion is selected from at least one of potassium ions and sodium ions.

[0018] More preferably, the metal ion is selected from potassium ions. Specifically, the polyhydroxy organic acid salt monomer may be selected from at least one of sodium 2,3-dihydroxynaphthalene-6-sulfonate, potassium 2,3-dihydroxynaphthalene-6-sulfonate, sodium azoresorcinol sulfonate, and lithium azoresorcinol sulfonate.

[0019] Preferably, based on the total repeating units of the flame-retardant modified polyamide, the molar content of the flame-retardant structural unit is 0.3%-5.0%.

[0020] In the flame-retardant modified polyamide of the present invention, based on the total repeating structural units of the flame-retardant modified polyamide, the molar content (unit, %) of the flame-retardant structural units can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, or any range formed by any two of the above values.

[0021] More preferably, based on the total repeating structural units of the flame-retardant modified polyamide, the molar content of the flame-retardant structural units is 0.5%-2%.

[0022] More preferably, based on the total repeating structural units of the flame-retardant modified polyamide, the molar content of the flame-retardant structural units is 0.5%-1.5%.

[0023] More preferably, based on the total repeating structural units of the flame-retardant modified polyamide, the molar content of the flame-retardant structural units is 0.5%-1.0%.

[0024] In some specific embodiments, based on the total repeating structural units of the flame-retardant modified polyamide, the molar content of the flame-retardant structural units is 0.5%, 0.8%, and 1.0%.

[0025] Preferably, the monomers used to form the polyamide matrix include diacids and diamines.

[0026] Preferably, the dicarboxylic acid is selected from at least one of terephthalic acid, isophthalic acid, or adipic acid; and the diamine is selected from at least one of decanediamine, nonanediamine, hexamethylenediamine, pentanediamine, m-phenylenediamine, or 1,12-dodecanediamine.

[0027] Preferably, the polyamide matrix is ​​one or more blends or copolymers of Nylon 10T, Nylon 5T, Nylon 6T, Nylon 9T, Nylon 4T, Nylon 11T, Nylon 12T, Nylon 6, Nylon 66, Nylon 11, Nylon 12, Nylon 612, Nylon 1012 or Nylon 1313.

[0028] More preferably, the polyamide matrix is ​​a blend or copolymer of one or more of nylon 10T, nylon 6, and nylon 66.

[0029] More preferably, the polyamide matrix is ​​nylon 10T.

[0030] This invention provides a method for preparing the above-mentioned flame-retardant modified polyamide, comprising the following steps: S1: A nylon salt is obtained by reacting a mixture of a diacid, a diamine, and water. S2: The nylon salt, polyhydroxy organic acid salt monomer, and water obtained in S1 are mixed and reacted to generate the flame-retardant modified polyamide.

[0031] Preferably, the reaction conditions in S1 are: under an inert atmosphere, the reaction is carried out at 40-80°C for 1-4 hours, and after the reaction is completed, the nylon salt is obtained by filtration, washing and drying.

[0032] Preferably, in S1, the washing process involves washing with anhydrous ethanol and deionized water 2-8 times.

[0033] Specifically, in S1, the reaction temperature (unit, °C) can be: 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, or any range formed by any two of the above values.

[0034] Specifically, in S1, the reaction time (in hours) can be 1, 1.5, 2, 2.5, 3, 3.5, 4, or a range formed by any two of the above values.

[0035] In this invention, the nylon salt can be homemade or commercially available.

[0036] Preferably, the reaction conditions for S2 are as follows: after replacing the air with an inert gas, the temperature is raised to 210-230℃ within 1-3 hours under a pressure ≤2.0MPa, and the temperature and pressure are maintained at this level for 1-3 hours; then the pressure is slowly released to atmospheric pressure, and a vacuum is drawn to negative pressure, and the temperature is raised to 250-270℃ to continue the reaction for 2-4 hours to obtain flame-retardant modified polyamide.

[0037] Preferably, in S2, the reaction apparatus can be a high-pressure polymerization reactor.

[0038] Preferably, the inert gas is selected from nitrogen.

[0039] Specifically, in S2, the temperature (unit: °C) can be raised to 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, or any range formed by any two of the above values.

[0040] Specifically, in S2, the temperature can be increased again (in °C) to 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, or any range formed by any two of the above values.

[0041] Specifically, in S2, the pressure (unit, MPa) can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or any range formed by any two of the above values.

[0042] Preferably, the water in S1 and S2 is selected from deionized water.

[0043] The present invention also provides an application of the above-mentioned flame-retardant modified polyamide for the preparation of polyamide parts.

[0044] The present invention provides a component comprising the above-described flame-retardant modified polyamide.

[0045] The components described in this invention can be electronic and electrical components, automotive parts, interior parts for public transportation vehicles, electrical and electronic components, or mechanical equipment parts.

[0046] Specifically, the electronic components may be connectors, circuit breakers, switches, coil frames, chip bases, or semiconductor device packages.

[0047] Specifically, the automotive components may be engine compartment components, automotive connectors, sensor housings, transmission components, and braking system components.

[0048] Specifically, the interior components of the public transportation vehicle can be train interior components or aircraft interior components.

[0049] Specifically, the electrical components can be household appliances or power tools.

[0050] Specifically, the mechanical equipment component can be a gear, bearing, or sleeve.

[0051] Compared with the prior art, the present invention has the following advantages: This invention significantly improves the flame-retardant behavior of polyamide materials by introducing polyhydroxy organic acid salt monomers into the polyamide molecular backbone, achieving a qualitative improvement in flame-retardant performance. The combined effect of the polyhydroxy structure and organic acid functional groups promotes the formation of a dense and stable char layer during combustion, effectively isolating heat and oxygen, and significantly suppressing melt dripping. This allows the modified high-temperature nylon to achieve a high flame-retardant rating, solving the technical bottleneck of existing technologies that cannot completely overcome the dripping problem.

[0052] Since the flame-retardant functional groups are precisely bonded to the molecular chain as comonomers at a low molar content, rather than being physically blended, the flame-retardant modified polyamide provided by this invention achieves a balance of excellent comprehensive performance. While endowing the material with inherent flame-retardant properties, it retains the excellent mechanical properties of the polyamide matrix to the maximum extent, avoiding the drawbacks such as material embrittlement and strength reduction caused by traditional high-addition flame retardants.

[0053] The flame-retardant modified polyamide provided by this invention has a uniform distribution in the molecular chain and does not significantly hinder melt flow like physically added flame-retardant particles. Therefore, the flame-retardant modified polyamide of this invention maintains good melt processing performance, is easy to injection mold, and is suitable for manufacturing thin-walled parts with complex structures and high precision requirements.

[0054] This invention employs a halogen-free organic acid salt system, which meets environmental protection requirements. Its preparation process is highly compatible with existing polyamide polymerization processes, requiring no complex modifications. The reaction process is controllable, offering significant advantages for industrial application and broad market prospects. Detailed Implementation

[0055] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0056] All raw materials used in this invention are commercially available.

[0057] Test methods: (1) Flame retardant performance test: The sample was obtained by injection molding. The sample size was 125×13×3mm. The flame retardant performance was tested according to UL94 standard.

[0058] (2) Tensile property test: The sample was obtained by injection molding, with a sample size of 150×10×4mm. The test was carried out in accordance with GB / T1040.2-2022, and the crosshead movement speed of the universal testing machine was 50 mm / min.

[0059] (3) Bending performance test: The sample was obtained by injection molding. The sample size was 80×10×4mm. The test was carried out in accordance with GB / T9341-2008. The crosshead of the universal testing machine moved at a speed of 5 mm / min.

[0060] (4) Impact performance test: The sample obtained by injection molding is 80×10×4mm in size and is tested in accordance with GB / T1843-2008 standard.

[0061] (5) Melt flow index test: The melt flow index test shall be conducted in accordance with GB / T3682.1-2018 standard, with a test temperature of 280℃ and a load of 2.16kg.

[0062] The embodiments of the present invention are obtained by the following methods: Diacid, diamine, and deionized water were added to a three-hole flask, respectively. Mechanical stirring was initiated, and the reaction temperature was gradually increased to 60°C under a nitrogen atmosphere. After reacting continuously for 2 hours, the precipitated white nylon salt crystals were collected by vacuum filtration. The crystals were repeatedly washed with anhydrous ethanol and deionized water to remove residual impurities and solvents. The sample was then dried in a vacuum oven for 12 hours to obtain the nylon salt.

[0063] In some embodiments, different types of diacids and / or diamines can be selected to repeat the above steps to obtain different nylon salts, thereby enabling the copolymerization of multiple nylons.

[0064] The dried nylon salt, polyhydroxy organic acid salt monomer, and deionized water were placed in a high-pressure polymerization reactor. The reactor was purged with nitrogen three times, and then filled with 0.3 MPa of nitrogen gas before heating began. The temperature was raised to 220°C over two hours, maintaining the pressure inside the reactor below 1.8 MPa during this period. After the pressure stabilized, the temperature and pressure were maintained for 2 hours. The pressure was slowly released, and a vacuum was created to negative pressure. The temperature was then raised to 260°C, and the reaction continued for another 3 hours to obtain the flame-retardant modified polyamide.

[0065] Table 1. Preparation process and test results of Examples 1-7 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 diacid terephthalic acid terephthalic acid terephthalic acid terephthalic acid terephthalic acid terephthalic acid terephthalic acid diamine Sebacdiamine Sebacdiamine Sebacdiamine Sebacdiamine Sebacdiamine Sebacdiamine Sebacdiamine Nylon salt 10T Nylon Salt 10T Nylon Salt 10T Nylon Salt 10T Nylon Salt 10T Nylon Salt 10T Nylon Salt 10T Nylon Salt Polyhydroxy organic acid salt monomers Potassium dihydroxynaphthalene-6-sulfonate Potassium dihydroxynaphthalene-6-sulfonate Potassium dihydroxynaphthalene-6-sulfonate Potassium dihydroxynaphthalene-6-sulfonate Sodium dihydroxynaphthalene-6-sulfonate Sodium azoresorcinol sulfonate Lithium azoresorcinol sulfonate Content of polyhydroxy organic acid salt monomers in the total repeating structural units of the final polymer (mole fraction: %) 0.5 0.8 1.0 5.0 0.8 0.8 0.8 Flame retardant properties V-0 V-0 V-0 V-0 V-0 V-0 V-0 Tensile strength (MPa) 79 79 78 72 74 77 75 Bending strength (MPa) 110 109 108 105 105 109 108 <![CDATA[Impact strength (kJ / m 2 )]]> 6.4 6.3 6.2 4.9 5.5 6.2 5.8 Melt index (g / 10min) 14.5 14.3 14 10 13 14.5 13.8 Table 2. Preparation process and test results of Examples 8-10 and Comparative Examples 1-2 Example 8 Example 9 Comparative Example 1 Comparative Example 2 The first type of diacid terephthalic acid terephthalic acid terephthalic acid The first type of diamine Sebacdiamine Sebacdiamine Sebacdiamine The first type of nylon salt 10T Nylon Salt Commercially available 10T nylon salt 10T Nylon Salt 10T Nylon Salt The second type of diacid adipic acid The second type of diamine Hexamethylenediamine The second type of nylon salt Nylon 66 Salt Commercially available nylon 6 salt Polyhydroxy organic acid salt monomers Potassium dihydroxynaphthalene-6-sulfonate Potassium dihydroxynaphthalene-6-sulfonate / Potassium hydroxyethylsulfonate Content of polyhydroxy organic acid salt monomers in the total repeating structural units of the final polymer (mole fraction: %) 0.8 0.8 / 0.8 Flame retardant properties V-0 V-0 HB V-1 Tensile strength (MPa) 75 76 80 78 Bending strength (MPa) 102 103 112 110 <![CDATA[Impact strength (kJ / m 2 )]]> 7.5 6.4 6.5 6 Melt index (g / 10min) 18 15.8 15 14 Table 3. Preparation process and test results of Comparative Examples 3-4 Comparative Example 3 Comparative Example 4 The first type of diacid terephthalic acid terephthalic acid The first type of diamine Sebacdiamine Sebacdiamine The first type of nylon salt 10T Nylon Salt 10T Nylon Salt Polyhydroxy organic acid salt monomers Diethylphosphite Diethylphosphite Flame retardant content in the final polymer (mass percentage: %) 0.8 20 Flame retardant properties HB V-0 Tensile strength (MPa) 80 65 Bending strength (MPa) 112 88 Impact strength (kJ / m2) 6.5 4.2 Melt index (g / 10min) 15 8 As can be seen from Examples 1-10, the flame-retardant modified polyamide provided in the embodiments of the present invention can achieve a flame-retardant rating of V-0, and also has the characteristics of high mechanical properties and good processing fluidity.

[0066] As can be seen from Comparative Example 1, without the addition of the polyhydroxy organic acid salt provided by this invention, the flame retardant performance is only HB level.

[0067] As shown in Comparative Example 2, the flame retardancy rating of sulfonates containing only a single hydroxyl group is V-1.

[0068] As can be seen from Comparative Examples 3-4, conventional phosphorus-containing halogen-free flame retardants require a relatively high addition amount to achieve the same flame retardant effect. At this addition amount, the mechanical properties and flowability of polyamide are significantly degraded.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A flame-retardant modified polyamide, characterized in that, It includes monomers used to form the polyamide matrix and polyhydroxy organic acid salt monomers as flame-retardant structural units.

2. The flame-retardant modified polyamide according to claim 1, characterized in that, The polyhydroxy organic acid salt monomer is selected from at least one of polyhydroxy sulfonates and polyhydroxy carboxylates, preferably polyhydroxy sulfonates.

3. The flame-retardant modified polyamide according to claim 2, characterized in that, The sulfonate portion of the polyhydroxysulfonate is selected from aromatic sulfonates, preferably dihydroxynaphthalene sulfonate or azoresorcinol sulfonate.

4. The flame-retardant modified polyamide according to claim 1, characterized in that, The metal ions in the polyhydroxy organic acid salt are selected from Group IA metal ions, preferably at least one of potassium ions, sodium ions, lithium ions, and rubidium ions.

5. The flame-retardant modified polyamide according to claim 1, characterized in that, Based on the total repeating units of the flame-retardant modified polyamide, the molar content of the flame-retardant structural unit is 0.3%-5.0%, preferably 0.5%-2%, and more preferably 0.5%-1.5%.

6. The flame-retardant modified polyamide according to claim 1, characterized in that, The monomers used to form the polyamide matrix include a dicarboxylic acid and a diamine; the dicarboxylic acid is preferably at least one of terephthalic acid, isophthalic acid or adipic acid; the diamine is preferably at least one of decanediamine, nonanediamine, hexamethylenediamine, pentanediamine, m-phenylenediamine or 1,12-dodecanediamine.

7. The flame-retardant modified polyamide according to claim 1, characterized in that, The polyamide matrix is ​​one or more blends or copolymers of Nylon 10T, Nylon 5T, Nylon 6, Nylon 66, Nylon 11, Nylon 12, Nylon 612, Nylon 1012 or Nylon 1313.

8. A method for preparing a flame-retardant modified polyamide according to any one of claims 1-7, characterized in that, It includes the following steps: S1: A nylon salt is obtained by reacting a mixture of a diacid, a diamine, and water. S2: The nylon salt, polyhydroxy organic acid salt monomer, and water obtained in S1 are mixed and reacted to generate the flame-retardant modified polyamide.

9. The application of the flame-retardant modified polyamide according to any one of claims 1-7, characterized in that, Used to prepare polyamide parts.

10. A component, characterized in that, It includes a flame-retardant modified polyamide as described in any one of claims 1-7.