A polyamide composite material, its preparation method and application

Abstract

This invention provides a polyamide composite material, its preparation method, and its application. By weight, the polyamide composite material comprises 30-60 parts polyamide 66 resin, 10-30 parts high-char-forming resin, 4.5-8.5 parts red phosphorus flame retardant, 1-4 parts melamine derivative, and 20-50 parts glass fiber. The high-char-forming resin includes aromatic polyamide; the molecular chain of the aromatic polyamide contains aromatic diamine structural units. In this invention, the polyamide composite material, through the compounding of specific types of high-char-forming resin, red phosphorus flame retardant, and melamine derivative, can improve the oxygen index of the material. Simultaneously, it achieves a balance between mechanical properties and flame retardant properties, resulting in relatively balanced performance. It is halogen-free, high-performance, flame-retardantly stable, and easy to process, meeting the high oxygen index requirements of materials in the rail transit field.

Description

Technical Field

[0001] This invention belongs to the field of engineering plastics technology, specifically relating to a polyamide composite material, its preparation method, and its application. Background Technology

[0002] Rail vehicles are located in relatively enclosed spaces and are also densely populated areas, making escape and rescue difficult in the event of a fire. Fire resistance testing standards for rail vehicle materials vary from country to country. The EU standard EN45545-2 classifies fire hazard levels into three levels: HL1, HL2, and HL3, with different requirements for the flame retardant properties of the materials. EN45545-2 R22 & ​​R23 HL2 requires an oxygen index of 28 or higher, while HL3 requires an oxygen index of 32 or higher. Red phosphorus flame-retardant nylon materials are widely used in the rail vehicle field, especially in low-voltage electrical appliances, switches, and connectors, due to their excellent molding properties and appearance, high relative tracking index, high mechanical properties, low heat distortion temperature, and halogen-free nature.

[0003] However, conventional red phosphorus flame retardant materials primarily rely on condensed-phase flame retardancy, with less emphasis on gas-phase flame retardancy. Within condensed-phase flame retardancy, the dehydration and charring of oxyphosphoric acid are the main mechanisms, effectively blocking both oxygen and combustibles. Therefore, compared to phosphorus-nitrogen flame retardants, its charring effect is weaker, and compared to nitrogen-based flame retardants, its performance is insufficient. This results in a low oxygen index for red phosphorus flame retardant materials, generally below 28, making it difficult to meet the HL2 rating requirement of greater than 28. For example, BASF's classic red phosphorus flame retardant nylon materials, such as A3X2G5 and A3X2G7, only have an oxygen index between 26 and 27. This low oxygen index severely limits the application of red phosphorus flame retardant nylon materials in the rail transportation sector.

[0004] Patent CN110564147A discloses a high oxygen index red phosphorus flame-retardant reinforced nylon 66 composite. By adding organic nano-montmorillonite or a mixture of melamine cyanurate salt and organic nano-montmorillonite, the oxygen index of the red phosphorus flame-retardant material can be increased to over 28. However, montmorillonite reduces the mechanical properties of the material, and the oxygen index of this composite material is still relatively low.

[0005] Therefore, developing a red phosphorus flame-retardant polyamide material with a high oxygen index that does not reduce the material's mechanical properties is an urgent problem to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a polyamide composite material, its preparation method, and its applications. The polyamide composite material possesses both a high oxygen index and good mechanical properties, and is halogen-free, environmentally friendly, and easy to process, thus meeting the high oxygen index requirements of materials in the rail transit field.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a polyamide composite material, wherein, by weight, the polyamide composite material comprises 30-60 parts of polyamide 66 resin, 10-30 parts of high char-forming resin, 4.5-8.5 parts of red phosphorus flame retardant, 1-4 parts of melamine derivative and 20-50 parts of glass fiber; the high char-forming resin comprises aromatic polyamide; and the molecular chain of the aromatic polyamide contains aromatic diamine structural units.

[0009] In this invention, red phosphorus produces oxyphosphoric acid during combustion, which coats the material surface, achieving dehydration and char formation, and retards oxygen and combustibles. Aromatic polyamide containing aromatic diamine structural units interacts with oxyphosphoric acid during combustion, synergistically enhancing the effect. The presence of benzene rings improves the overall char formation effect, increasing the char formation efficiency. Melamine derivatives readily decompose upon heating, producing inert gases that dilute the combustible concentration. Simultaneously, they exert a synergistic effect in the condensed phase, further improving the oxygen index of the system. By compounding specific types of high-char-forming resins, red phosphorus flame retardants, and melamine derivatives, the oxygen index of the material can be improved, while simultaneously maintaining both mechanical and flame-retardant properties. The material exhibits relatively balanced performance, is halogen-free, high-performance, flame-retardantly stable, and easy to process, meeting the high oxygen index requirements in the rail transit field.

[0010] In this invention, 30 to 60 parts of polyamide 66 resin can be, for example, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, or any combination of the above values; preferably 35 to 55 parts, more preferably 40 to 50 parts.

[0011] In this invention, 10 to 30 parts of high-carbon-forming resin can be, for example, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts, 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts, 18 parts, 18.5 parts, 19 parts, 19.5 parts, 20 parts, 20.5 parts, 21 parts, 21.5 parts, 22 parts, 22.5 parts, 23.5 parts, 24 parts, 24.5 parts, 25 parts, 25.5 parts, 26 parts, 26.5 parts, 27 parts, 27.5 parts, 28 parts, 28.5 parts, 29 parts, 29.5 parts, 30 parts, or any combination of the above values; preferably 11 to 25 parts, more preferably 13 to 20 parts.

[0012] In this invention, the 4.5 to 8.5 parts of red phosphorus flame retardant can be, for example, 4.5 parts, 4.6 parts, 4.8 parts, 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, 6 parts, 6.2 parts, 6.4 parts, 6.6 parts, 6.8 parts, 7 parts, 7.2 parts, 7.4 parts, 7.6 parts, 7.8 parts, 8 parts, 8.2 parts, 8.4 parts, 8.5 parts, or any combination of the above values; preferably 5 to 8 parts, more preferably 5.5 to 7.5 parts.

[0013] In this invention, 1 to 4 parts of melamine derivative can be, for example, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.7 parts, 2.8 parts, 2.9 parts, 3 parts, 3.1 parts, 3.2 parts, 3.3 parts, 3.4 parts, 3.5 parts, 3.6 parts, 3.7 parts, 3.8 parts, 3.9 parts, 4 parts, or any combination of the above values; preferably 1.5 to 3.5 parts.

[0014] In this invention, 20 to 50 parts of glass fiber can be, for example, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50 parts or any combination of the above values; preferably 22 to 45 parts.

[0015] In this invention, the relative viscosity of the polyamide 66 resin is 2 to 3.5, for example, it can be 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5 or any of the above values; more preferably, the relative viscosity is 2.5 to 3.

[0016] In this invention, the relative viscosity of the high carbonization resin is 2 to 3, for example, it can be 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3 or any of the above values; more preferably, the relative viscosity is 2.1 to 2.8.

[0017] In this invention, the relative viscosity of the polyamide 66 resin or high carbonization resin is obtained according to standard GB / T12006.1-2009, in 96% concentrated sulfuric acid at 25±0.01℃, with a test concentration of 1g / dL.

[0018] Preferably, the aromatic polyamide includes a semi-aromatic polyamide.

[0019] Preferably, the semi-aromatic polyamide includes poly(m-phenylene adipamide) and / or poly(m-phenylene sebacate).

[0020] Preferably, the semi-aromatic polyamide comprises poly(m-phenylene adipamide) and poly(m-phenylene sebacate), wherein the mass ratio of poly(m-phenylene adipamide) and poly(m-phenylene sebacate) is 1:(0.5-4.5), wherein the specific value in (0.5-4.5) can be, for example, 0.5, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.5 or any combination of the above values, more preferably 1:(1.2-3.2).

[0021] Preferably, the red phosphorus flame retardant comprises red phosphorus and / or red phosphorus masterbatch.

[0022] Preferably, the red phosphorus masterbatch comprises polyamide resin-encapsulated red phosphorus.

[0023] Preferably, the red phosphorus content in the red phosphorus masterbatch is 35% to 55% by mass, for example, it can be any of the above values ​​of 35%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, and 55%.

[0024] In this invention, the polyamide resin in the red phosphorus flame retardant includes polycaprolactam resin (PA6).

[0025] Preferably, the melamine derivative includes at least one of melamine cyanurate, melamine polyphosphate, or melamine borate.

[0026] Preferably, the melamine derivative comprises melamine cyanurate and melamine polyphosphate, wherein the mass ratio of melamine cyanurate to melamine polyphosphate is 1:(0.5-2.5), wherein the specific value of (0.5-2.5) can be, for example, 0.5, 0.52, 0.55, 0.58, 0.6, 0.62, 0.65, 0.68, 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, 0.98, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5 or any range of the above values, more preferably 1:(1-2).

[0027] Preferably, the glass fiber comprises alkali-free chopped glass fiber.

[0028] Preferably, the chopped length of the glass fiber is 3 to 4.5 mm, for example, it can be 3 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm or any combination of the above values; the fiber diameter is 9 to 13 μm, for example, it can be 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm or any combination of the above values.

[0029] Preferably, the polyamide composite material further includes 0.2 to 5 parts of other additives by weight, for example, 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, or any combination of the above values.

[0030] Preferably, the other additives include antioxidants and / or lubricants.

[0031] Preferably, the other additives include 0.1 to 2 parts lubricant and 0.1 to 3 parts antioxidant.

[0032] Preferably, the antioxidant includes at least one of hindered phenolic antioxidants, hindered amine antioxidants, thioester antioxidants, or phosphite antioxidants, and more preferably a compound system of hindered phenolic antioxidants and phosphite antioxidants.

[0033] Preferably, the lubricant comprises at least one of silicone, polyethylene wax, or pentaerythritol ester.

[0034] Preferably, the oxygen index of the polyamide composite material is ≥30, more preferably ≥35.

[0035] In a second aspect, the present invention provides a method for preparing a polyamide composite material according to the first aspect, the method comprising the following steps:

[0036] Polyamide 66 resin, high carbonization resin, red phosphorus flame retardant, melamine derivative and glass fiber are mixed and extruded to obtain the polyamide composite material.

[0037] Preferably, the mixed material also includes other additives.

[0038] Preferably, the extrusion temperature is 230–270°C, for example, it can be 230°C, 240°C, 250°C, 260°C, 270°C or any combination of the above values.

[0039] In this invention, the extrusion is carried out in a twin-screw extruder, the twin-screw extruder having a length-to-diameter ratio of 36 to 48:1 and a screw speed of 300 to 500 rpm.

[0040] In this invention, the mixing process includes premixing polyamide 66 resin, high carbonization resin, lubricant and antioxidant in a high-speed mixer for 1 to 3 minutes, then adding flame retardant, melamine derivative and glass fiber from the side feed port, mixing evenly, and then adding it to a twin-screw extruder for extrusion through a metering scale.

[0041] Thirdly, the present invention provides a low-voltage electrical device, wherein the material of the low-voltage electrical device includes the polyamide composite material described in the first aspect.

[0042] In this invention, the low-voltage electrical equipment includes low-voltage electrical appliances, switches, connectors, etc., and is particularly suitable for low-voltage electrical equipment in the rail transit field.

[0043] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] The polyamide composite material provided by this invention, through the compounding of specific types of high char-forming resins, melamine derivatives and red phosphorus flame retardants, can give the material a high oxygen index and good mechanical properties, which can meet the high requirements for high oxygen index in the rail transit field. Detailed Implementation

[0046] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] All materials used in this invention are commercially available.

[0048] PA66: EPR27, Shenma Group;

[0049] Poly(m-phenylene adipamide): PAMXD6, Shanghai Yinggu Chemical Co., Ltd.

[0050] Poly(m-phenylene sebacate): PA MXD10, Shanghai Yinggu Chemical Co., Ltd.

[0051] Poly(hexamethylene terephthalamide): PA6T, A3000, Mitsui Chemicals, Japan;

[0052] Poly(diamyl adipamide): PA56, PA56 Ecopent-1273, Cathay Biotech;

[0053] Red phosphorus flame retardant: Microencapsulated red phosphorus masterbatch with polylactam resin (PA6) as carrier, the red phosphorus content in the masterbatch is 50% by mass, FR9950KF, Tongcheng Xinde New Materials;

[0054] Melamine polyphosphate: BUDIT 3141, BUDENHEIM IBERICA, SLU;

[0055] Melamine cyanurate: Nitrogen-based flame retardant lubricant MCA, Sichuan Fine Chemical Research and Design Institute;

[0056] Melamine borate: MB, Zhuoan Technology;

[0057] Fiberglass: ECS10-03-568H, Jushi Group;

[0058] Antioxidant: A compound antioxidant composed of N,N′-1,6-hexylene-di-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide) (IRGANOX 1098) and bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate (PEP-36) in a mass ratio of 1:1.5;

[0059] Lubricant: TR044W, STRUKTOL Co.

[0060] Examples 1-14, Comparative Examples 1-9

[0061] Examples 1-14 and Comparative Examples 1-9 each provide a polyamide composite material. The formulations of the polyamide composite materials are shown in Tables 1-4 by weight, where " / " indicates that the component is not in the formulation, and the content of red phosphorus flame retardant is the actual content of red phosphorus in the masterbatch.

[0062] The preparation method of the polyamide composite material includes:

[0063] Polyamide 66 resin, high-carbon resin, lubricant, and antioxidant were mixed in a high-speed mixer for 2 minutes and then added to the main feed port of a twin-screw extruder. Red phosphorus flame retardant, melamine derivative, and glass fiber were added from the side feed port. The mixed materials were then fed into the twin-screw extruder via a metering scale for extrusion granulation to obtain the polyamide composite material. The twin-screw extruder had a length-to-diameter ratio of 48:1, a screw speed of 400 rpm, and an extrusion temperature of 230°C in zones 6-10.

[0064] Table 1

[0065]

[0066] Table 2

[0067]

[0068]

[0069] Table 3

[0070]

[0071] Table 4

[0072]

[0073] Performance testing

[0074] After drying the polyamide composite materials provided in Examples 1-14 and Comparative Examples 1-9 in an oven at 120°C for 4 hours, ISO mechanical and UL flame retardant test strips were injection molded to evaluate the mechanical and flame retardant properties of the materials. ISO heat distortion test strips were injection molded, machined and ground to the required thickness, and the oxygen index of the materials was tested.

[0075] The flame retardant performance is tested according to the UL94 vertical burning test standard, and the material thickness is 1.6 mm. The tensile strength test is performed according to ISO 527-2-2012, the flexural strength test is performed according to ISO 178-2010, the cantilever beam notched impact strength test is performed according to ISO 180-2019, and the oxygen index test is performed according to ISO 4589-2:2017, with a sample thickness of 4 mm.

[0076] The specific test results are shown in Table 5.

[0077] Table 5

[0078]

[0079] As shown in Table 5, the polyamide composite material provided by this invention, through the compounding of specific types of high-char-forming resins, melamine derivatives, and red phosphorus flame retardants, can achieve a high oxygen index, low smoke density, and good mechanical properties, meeting the requirements for flame retardancy rating; the polyamide composite material has an oxygen index ≥30, a smoke density ≤150, and a cantilever beam notched impact strength ≥6.2kJ / m². 2 The tensile strength is ≥138MPa, the flexural strength is ≥205MPa, and more preferably, the oxygen index of the polyamide composite material is ≥35, the smoke density is ≤100, and the notched impact strength of the cantilever beam is ≥7.0kJ / m. 2 Tensile strength ≥143MPa, flexural strength ≥213MPa.

[0080] As can be seen from the comparison between Example 1 and Comparative Examples 1, 2 and 9, the combination of non-specific types of high carbon-forming resins, melamine derivatives and red phosphorus flame retardants does not have a significant effect on improving the oxygen index.

[0081] As can be seen from the comparison between Example 1 and Comparative Examples 3 to 6, the content of the high carbonization resin or melamine derivative is not within the specified range, and the oxygen index decreases or the mechanical properties deteriorate.

[0082] As can be seen from the comparison between Example 1 and Comparative Examples 7-8, the formulation lacks high carbonization resin or melamine derivative, resulting in a lower oxygen index.

[0083] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A polyamide composite material, characterized in that, By weight, the polyamide composite material comprises 30-60 parts of polyamide 66 resin, 10-30 parts of high char-forming resin, 4.5-8.5 parts of red phosphorus flame retardant, 1.3-4 parts of melamine derivative and 20-50 parts of glass fiber; The high carbonization resin includes aromatic polyamide; The molecular chain of the aromatic polyamide contains aromatic diamine structural units; The melamine derivatives include at least one of melamine cyanurate, melamine polyphosphate, or melamine borate.

2. The polyamide composite material according to claim 1, characterized in that, The aromatic polyamides include semi-aromatic polyamides.

3. The polyamide composite material according to claim 2, characterized in that, The semi-aromatic polyamide includes poly(m-phenylene adipamide) and / or poly(m-phenylene sebacate).

4. The polyamide composite material according to claim 2, characterized in that, The semi-aromatic polyamide includes poly(m-phenylene adipamide) and poly(m-phenylene sebacate), wherein the mass ratio of poly(m-phenylene adipamide) to poly(m-phenylene sebacate) is 1:(0.5~4.5).

5. The polyamide composite material according to claim 4, characterized in that, The mass ratio of poly(m-phenylene adipamide) to poly(m-phenylene sebacate) is 1:(1.2~3.2).

6. The polyamide composite material according to claim 1, characterized in that, The red phosphorus flame retardant includes red phosphorus and / or red phosphorus masterbatch; the content of the red phosphorus flame retardant is the actual content of red phosphorus in the masterbatch.

7. The polyamide composite material according to claim 6, characterized in that, The red phosphorus masterbatch comprises polyamide resin-encapsulated red phosphorus.

8. The polyamide composite material according to claim 6, characterized in that, The red phosphorus masterbatch contains 35-55% red phosphorus by mass.

9. The polyamide composite material according to claim 1, characterized in that, The melamine derivatives include melamine cyanurate and melamine polyphosphate, wherein the mass ratio of melamine cyanurate to melamine polyphosphate is 1:(0.5~2.5).

10. The polyamide composite material according to claim 9, characterized in that, The mass ratio of melamine cyanurate to melamine polyphosphate is 1:(1~2).

11. The polyamide composite material according to claim 1, characterized in that, The glass fiber includes alkali-free chopped glass fiber.

12. The polyamide composite material according to claim 1, characterized in that, The glass fiber has a chopped length of 3-4.5 mm and a fiber diameter of 9-13 μm.

13. The polyamide composite material according to claim 1, characterized in that, The polyamide composite material further includes 0.2 to 5 parts of other additives by weight.

14. The polyamide composite material according to claim 13, characterized in that, The other additives include antioxidants and / or lubricants.

15. The polyamide composite material according to claim 14, characterized in that, The antioxidant includes at least one of hindered phenolic antioxidants, hindered amine antioxidants, thioester antioxidants, or phosphite antioxidants.

16. The polyamide composite material according to claim 15, characterized in that, The antioxidant is a compound system of hindered phenolic antioxidants and phosphite antioxidants.

17. The polyamide composite material according to claim 14, characterized in that, The lubricant includes at least one of silicone, polyethylene wax, or pentaerythritol ester.

18. The polyamide composite material according to claim 1, characterized in that, The oxygen index of the polyamide composite material is ≥30.

19. A method for preparing a polyamide composite material according to any one of claims 1 to 18, characterized in that, The preparation method includes the following steps: Polyamide 66 resin, high carbonization resin, red phosphorus flame retardant, melamine derivative and glass fiber are mixed and extruded to obtain the polyamide composite material.

20. The preparation method according to claim 19, characterized in that, The extrusion temperature is 230~270℃.

21. A low-voltage electrical device, characterized in that, The material of the low-voltage electrical equipment includes the polyamide composite material as described in any one of claims 1 to 18.

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