Polyamide composite material, and preparation method therefor and use thereof

Abstract

Provided in the present application are a polyamide composite material, and a preparation method therefor and the use thereof. The polyamide composite material comprises, in parts by weight, 30-60 parts of a polyamide 66 resin, 10-30 parts of a resin with a high char yield, 4.5-8.5 parts of a red phosphorus flame retardant, 1-4 parts of a melamine derivative, and 20-50 parts of glass fibers, wherein the resin with a high char yield comprises an aromatic polyamide, and an aromatic diamine structural unit is comprised in the molecular chain of the aromatic polyamide. In the present application, by compounding specific types of a resin with a high char yield, a red phosphorus flame retardant and a melamine derivative, the oxygen index of the polyamide composite material can be improved; moreover, the material has relatively balanced mechanical properties and flame retardancy, has the characteristics of being halogen-free, high performance, stable flame retardancy and good processability, and can meet high requirements for the oxygen index of materials in the field of rail transit.

Description

A polyamide composite material, its preparation method and application Technical Field

[0001] This application relates to the field of engineering plastics technology, such as 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] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] The purpose of this application is to provide a polyamide composite material, its preparation method, and its application. 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 transportation field.

[0008] To achieve this objective, the following technical solution is adopted in this application:

[0009] In a first aspect, this application provides a polyamide composite material, which, by weight, 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.

[0010] In this application, 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, thus increasing the char formation efficiency. Melamine derivatives readily decompose upon heating, producing inert gases that dilute the concentration of combustibles. Simultaneously, they exert a synergistic effect in the condensed phase, further increasing 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 balancing its 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.

[0011] In this application, 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; it can be optionally 35 to 55 parts, and more preferably 40 to 50 parts.

[0012] In this application, 10 to 30 parts of high-carbon 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; it can be selected as 11 to 25 parts, and more preferably 13 to 20 parts.

[0013] In this application, 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; it can be selected as 5 to 8 parts, and more preferably 5.5 to 7.5 parts.

[0014] In this application, 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; it can be selected as 1.5 to 3.5 parts.

[0015] In this application, the amount of glass fiber is 20 to 50 parts, 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; it can be selected as 22 to 45 parts.

[0016] In this application, 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; further, the relative viscosity can be 2.5 to 3.

[0017] In this application, 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; further, the relative viscosity can be 2.1 to 2.8.

[0018] In this application, the relative viscosity of the polyamide 66 resin or high carbonization resin is obtained according to standard GB / T 12006.1-2009, in 96% concentrated sulfuric acid at 25±0.01℃, with a test concentration of 1g / dL.

[0019] In one embodiment, the aromatic polyamide includes a semi-aromatic polyamide.

[0020] In one embodiment, the semi-aromatic polyamide includes poly(m-phenylene adipamide) and / or poly(m-phenylene sebacate).

[0021] In one embodiment, 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, and can be selected as 1:(1.2~3.2).

[0022] In one embodiment, the red phosphorus flame retardant comprises red phosphorus and / or red phosphorus masterbatch.

[0023] In one embodiment, the red phosphorus masterbatch comprises polyamide resin-encapsulated red phosphorus.

[0024] In one embodiment, the red phosphorus masterbatch contains 35% to 55% red phosphorus by mass, for example, any of the following values: 35%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 55%.

[0025] In this application, the polyamide resin in the red phosphorus flame retardant includes polycaprolactam resin (PA6).

[0026] In one embodiment, the melamine derivative includes at least one of melamine cyanurate, melamine polyphosphate, or melamine borate.

[0027] In one embodiment, 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, and can be selected as 1:(1~2).

[0028] In one embodiment, the glass fiber comprises alkali-free chopped glass fiber.

[0029] In one embodiment, 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.

[0030] In one embodiment, the polyamide composite material further includes 0.2 to 5 parts by weight of other additives, such as 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.

[0031] In one embodiment, the other additives include antioxidants and / or lubricants.

[0032] In one embodiment, the other additives include 0.1 to 2 parts lubricant and 0.1 to 3 parts antioxidant.

[0033] In one embodiment, the antioxidant includes at least one of hindered phenolic antioxidants, hindered amine antioxidants, thioester antioxidants, or phosphite antioxidants, and may be a compound system of hindered phenolic antioxidants and phosphite antioxidants.

[0034] In one embodiment, the lubricant includes at least one of silicone, polyethylene wax, or pentaerythritol ester.

[0035] In one embodiment, the oxygen index of the polyamide composite material is ≥30, and more preferably ≥35.

[0036] Secondly, this application provides a method for preparing the polyamide composite material according to the first aspect, the method comprising the following steps:

[0037] 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.

[0038] In one embodiment, the mixed material also includes other additives.

[0039] In one embodiment, 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.

[0040] In this application, 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.

[0041] In this application, the mixing 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 adding it to a twin-screw extruder for extrusion through a metering scale.

[0042] Thirdly, this application provides a low-voltage electrical device, the material of which includes the polyamide composite material described in the first aspect.

[0043] In this application, the low-voltage electrical equipment includes low-voltage electrical appliances, switches, connectors, etc., and is particularly applicable to low-voltage electrical equipment in the rail transit field.

[0044] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0045] Compared with related technologies, the beneficial effects of this application are as follows:

[0046] The polyamide composite material provided in this application, through the compounding of specific types of high char-forming resins, melamine derivatives and red phosphorus flame retardants, can achieve a high oxygen index and good mechanical properties, thus meeting the high requirements for high oxygen index in the rail transit field.

[0047] After reading and understanding the detailed description, other aspects can be understood. Detailed Implementation

[0048] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0049] All materials used in this application are commercially available.

[0050] PA66: EPR27, Shenma Group;

[0051] Poly(m-phenylene adipamide): PA MXD6, Shanghai Yinggu Chemical Co., Ltd.

[0052] Poly(m-phenylene sebacate): PA MXD10, Shanghai Yinggu Chemical Co., Ltd.

[0053] Poly(hexamethylene terephthalamide): PA6T, A3000, Mitsui Chemicals;

[0054] Poly(diamyl adipamide): PA56, PA56 Ecopent-1273, Cathay Biotech;

[0055] 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;

[0056] Melamine polyphosphate: BUDIT 3141, BUDENHEIM IBERICA, SLU;

[0057] Melamine cyanurate: Nitrogen-based flame retardant lubricant MCA, Sichuan Fine Chemical Research and Design Institute;

[0058] Melamine borate: MB, Zhuoan Technology;

[0059] Fiberglass: ECS10-03-568H, Jushi Group;

[0060] 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;

[0061] Lubricant: TR044W, STRUKTOL Co.

[0062] Examples 1-14, Comparative Examples 1-9

[0063] 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.

[0064] The preparation method of the polyamide composite material includes:

[0065] 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.

[0066]

[0067]

[0068]

[0069]

[0070] Performance testing

[0071] 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.

[0072] 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.

[0073] The specific test results are shown in Table 5.

[0074]

[0075] As shown in Table 5, the polyamide composite material provided in this application, 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 ≥6.2 kJ / m². 2 The tensile strength is ≥138 MPa, the flexural strength is ≥205 MPa, and optionally the polyamide composite material has an oxygen index ≥35, a smoke density ≤100, and a cantilever beam notched impact strength ≥7.0 kJ / m². 2 Tensile strength ≥143 MPa, flexural strength ≥213 MPa.

[0076] 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.

[0077] As can be seen from the comparison between Example 1 and Comparative Examples 3-6, the content of the high carbonization resin or melamine derivative is not within the limited range, and the oxygen index decreases or the mechanical properties deteriorate.

[0078] As can be seen from the comparison between Example 1 and Comparative Examples 7-8, the formulation lacks high carbon-forming resin or melamine derivative, resulting in a lower oxygen index.

[0079] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. 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 carbonization resin includes aromatic polyamide; The molecular chain of the aromatic polyamide contains aromatic diamine structural units.

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

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

4. The polyamide composite material according to claim 3, wherein, The semi-aromatic polyamide includes 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), or optionally 1:(1.2~3.2).

5. The polyamide composite material according to any one of claims 1-4, wherein, The red phosphorus flame retardant includes red phosphorus and / or red phosphorus masterbatch.

6. The polyamide composite material according to claim 5, wherein, The red phosphorus masterbatch comprises polyamide resin-encapsulated red phosphorus; Optionally, the red phosphorus masterbatch contains 35-55% red phosphorus by mass.

7. The polyamide composite material according to any one of claims 1-6, wherein, The melamine derivatives include at least one of melamine cyanurate, melamine polyphosphate, or melamine borate.

8. The polyamide composite material according to claim 7, wherein, The melamine derivative includes melamine cyanurate and melamine polyphosphate, wherein the mass ratio of melamine cyanurate to melamine polyphosphate is 1:(0.5~2.5), or optionally 1:(1~2).

9. The polyamide composite material according to any one of claims 1-8, wherein, The glass fiber includes alkali-free chopped glass fiber.

10. The polyamide composite material according to any one of claims 1-9, wherein, The glass fiber has a chopped length of 3-4.5 mm and a fiber diameter of 9-13 μm.

11. The polyamide composite material according to any one of claims 1-10, wherein, The polyamide composite material further includes 0.2 to 5 parts of other additives by weight; Optionally, the other additives include antioxidants and / or lubricants; Optionally, the antioxidant includes at least one of hindered phenolic antioxidants, hindered amine antioxidants, thioester antioxidants, or phosphite antioxidants, and may be a compound system of hindered phenolic antioxidants and phosphite antioxidants. Optionally, the lubricant includes at least one of silicone, polyethylene wax, or pentaerythritol ester.

12. The polyamide composite material according to any one of claims 1-11, wherein, The oxygen index of the polyamide composite material is ≥30.

13. A method for preparing a polyamide composite material according to any one of claims 1-12, wherein, 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.

14. The preparation method according to claim 13, wherein, The mixed materials also include other additives; Optionally, the extrusion temperature is 230~270℃.

15. A low-voltage electrical device, wherein, The material of the low-voltage electrical equipment includes the polyamide composite material as described in any one of claims 1-12.

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