A flame-retardant polyamide composite material, its preparation method and application

Abstract

A flame-retardant polyamide composite material, characterized in that, by weight, it comprises the following components: 20-35 parts crystalline polyamide, 10-30 parts PA6I / 6T, 10-20 parts dialkyl hypophosphite flame retardant, 1-5 parts melamine derivative flame retardant, and 0.5-2 parts GMA-grafted SEBS. This invention, by adding a certain amount of GMA-grafted SEBS and PA6I / 6T to the dialkyl hypophosphite flame-retardant polyamide composite material, can significantly improve the cantilever beam notched impact strength of the composite material while maintaining good flame-retardant properties.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a flame-retardant polyamide composite material, its preparation method, and its application. Background Technology

[0002] Flame-retardant nylon materials possess excellent strength and toughness, making them widely used in the electronics and electrical industries. Halogen-free flame-retardant reinforced PA, with its lower smoke density and halogen-free nature, is increasingly widely used in these fields. However, halogen-free flame retardants are generally low-molecular-weight powders, which do not disperse well in PA resins. Furthermore, the high dosage often results in less than ideal material performance, particularly in toughness, which is lower than that of halogenated materials. While toughening agents are typically added to improve toughness, in halogen-free systems, adding toughening agents significantly negatively impacts flame retardancy, hindering effective improvement in toughness. With increasing industrial demands for both toughness and environmental friendliness, the need for high-toughness halogen-free flame-retardant PA materials is growing, making their development an urgent priority.

[0003] Currently, the toughness problem of halogen-free flame-retardant polyamide composites is mainly solved by the following two methods: First, using toughening agents, but conventional maleic anhydride-grafted POE cannot solve the problem of reduced flame retardant performance; Second, boiling in water to increase the water absorption rate of halogen-free flame-retardant PA materials and thus improve their toughness, but this increases the processing steps and raises the material cost. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical defects and provide a flame-retardant polyamide composite material with the advantages of V-0 flame retardancy and high cantilever beam notched impact strength.

[0005] This invention is achieved through the following technical solution:

[0006] A flame-retardant polyamide composite material, comprising the following components by weight:

[0007] 20-35 parts of crystalline polyamide;

[0008] PA6I / 6T 10-30 parts;

[0009] 12-20 parts of dialkyl hypophosphite flame retardant;

[0010] 1-5 parts of melamine derivative flame retardant;

[0011] 0.5-2 parts of SEBS grafted onto GMA.

[0012] The crystalline polyamide content that achieves the purpose of this invention is 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 35 parts, etc. The PA6I / 6T content is 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, etc. The dialkyl hypophosphite flame retardant content is 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc. The melamine derivative flame retardant content is 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc. The GMA-grafted SEBS content can be 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, 2 parts, etc.

[0013] The crystalline polyamide accounts for no less than 22 wt% of the flame-retardant polyamide composite material of the present invention.

[0014] Preferably, in the PA6I / 6T, the mass ratio of isophthalic acid to terephthalic acid is (5-9):(5:1), more preferably (6.5-7.5):(3.5-2.5).

[0015] PA6I / 6T can be commercially available or prepared in-house. The preparation method is as follows: Mix a certain amount of terephthalic acid and hexamethylenediamine, add 35-45% deionized water (molar ratio 1:1.01-1.02), adjust the temperature to 45-55℃, stir for 1-3 hours, adjust the pH to approximately 7.3-7.6, and continue the reaction for another 1-3 hours. After the reaction is complete, a clear and transparent PA6T salt solution is obtained. After cooling, filter and dry to obtain white PA6T salt powder. The preparation process for PA6I salt is similar. Add a fixed ratio of PA6I and PA6T salts to a reaction vessel, add a certain amount of additives, check the airtightness, purge with nitrogen at least three times, and pressurize to a slight positive pressure of approximately 0.08-0.12 MPa. Start stirring and heating, raise the temperature to 140-160℃, react for 1-3 hours, then continue heating to 200-220℃ and maintain the temperature and pressure for 3-6 hours. For the first h, maintain the pressure at around 2.1-2.3 MPa, then slowly raise the temperature to 300-320 ℃ over 2-4 h while gradually reducing the pressure to atmospheric pressure. Finally, evacuate the vacuum while observing the torque and current. When the maximum value is reached, stop stirring. At this point, purge with nitrogen to back pressure, open the valve to discharge the material, and obtain the PA6I / 6T product.

[0016] The crystalline polyamide is at least one of the following: a polyamide resin obtained by condensation polymerization of a diamine and a dicarboxylic acid, a polyamide resin obtained by ring-opening polymerization of a lactam, a polyamide resin obtained by self-condensation of an aminocarboxylic acid, or a copolymer of the above polyamide resins.

[0017] Specifically, the polyamide resins obtained by polycondensation of diamines and dicarboxylic acids can be: PA66, PA56, PA46, PA610, PA612, PA1010, PA1212;

[0018] The polyamide resin obtained by ring-opening polymerization of lactams can be: PA6;

[0019] Polyamide resins obtained by the self-condensation of aminocarboxylic acids can be: PA11, PA12;

[0020] The copolymers of the above-mentioned polyamide resins can be: copolymer PA66 and copolymer PA6.

[0021] This invention does not limit the intrinsic viscosity of the polyamide, but preferably the intrinsic viscosity range of the polyamide is 2.3-2.7 dL / g. The test method is to measure the intrinsic viscosity according to the ISO 307 test standard.

[0022] The structural formula of the dialkyl hypophosphite flame retardant is as follows:

[0023] Among them, R 1 R 2 Independently selected from linear or branched C1–C6 alkyl and / or aryl groups; M selected from one or more combinations of alkali metals, alkaline earth metals, Al, Zn, Fe, or Ti; m is 1–4.

[0024] Optionally, the dialkyl hypophosphite flame retardant is selected from diethylaluminum hypophosphite.

[0025] The melamine derivative flame retardant mentioned above is melamine polyphosphate.

[0026] In the GMA-grafted SEBS, the grafting rate of GMA ranges from 0.2 to 1.5 wt%, preferably 0.4 to 1.0 wt%, and more preferably 0.6 to 0.8 wt%.

[0027] GMA-grafted SEBS can be obtained from commercially available products or by self-production. The self-production method involves dissolving dicumyl peroxide in GMA, then mixing it with SEBS and extruding the mixture using a twin-screw extruder at a temperature of 200-220°C. The extruded particles are then dissolved in toluene and heated at approximately 100-120°C for 40-100 minutes. After cooling to room temperature, an appropriate amount of phenolphthalein is added, and the mixture is titrated to the endpoint with a specific concentration of sodium hydroxide / methanol. After subtracting the blank value, the GMA content in the grafted product is calculated, thus determining the grafting rate.

[0028] Those skilled in the art can choose whether to add 0-2 parts of additives according to actual needs. The additives are selected from at least one of antioxidants and lubricants. They can also choose whether to add 0-50 parts of glass fiber.

[0029] Antioxidants can be: 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; 2,5-di-tert-butyl-4-hydroxybenzyl dimethylamine; diethyl-3,5-di-tert-butyl-4-hydroxybenzyl phosphate; stearyl-3,5-di-tert-butyl-4-hydroxybenzyl phosphate; 3,5-di-tert-butyl-4-hydroxyphenyl-3,5-distearate-thiotriazolylamine; 2,6-di-tert-butyl-4-hydroxymethylphenol; 2,4-di-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylglycerol allyl ether)-1,3,5-triazine; N,N'-hexamethylene di( 3,5-Di-tert-butyl-4-hydroxy-hydrogenated cinnamamide; N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine; octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; pentaerythritol-tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; triethylene glycol-bis[3-(3,5-dimethyl-4-hydroxyphenyl)propionate]; triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate]; 2,2'-thiodiethyl-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, etc.

[0030] The lubricant may be at least one of the following: stearate lubricant, fatty acid lubricant, and stearate ester lubricant; wherein the stearate lubricant is selected from at least one of calcium stearate, magnesium stearate, and zinc stearate; wherein the fatty acid lubricant is selected from at least one of fatty acids, fatty acid derivatives, and fatty acid esters; and wherein the stearate ester lubricant is selected from at least one of pentaerythritol stearate.

[0031] The preparation method of the flame-retardant polyamide composite material of the present invention includes the following steps: mixing each component evenly according to the formula, extruding and granulating through a twin-screw extruder to obtain the flame-retardant polyamide composite material, wherein the screw length-to-diameter ratio is 40-48:1, the screw barrel temperature is 220-270℃, and the screw speed is 200-450rpm.

[0032] The flame-retardant polyamide composite material of the present invention is used to manufacture electronic and electrical components.

[0033] The present invention has the following beneficial effects:

[0034] This invention achieves toughening while maintaining V-0 flame retardancy by adding a certain amount of GMA-grafted SEBS to a dialkyl hypophosphite flame-retardant polyamide composite material. This is because MAH has a greater impact on the flame retardancy of the material than GMA grafting in the flame-retardant system of this invention. Furthermore, the presence of more benzene rings in SEBS also reduces its impact on the flame retardancy. Amorphous PA6I / 6T, with its numerous benzene ring structures, is beneficial for improving flame retardancy and can also significantly improve the cantilever beam notched impact strength of the composite material.

[0035] Meanwhile, for crystalline polyamide materials, adding a large amount of amorphous material can significantly affect the crystallization rate, thus impacting the material's demolding performance. Furthermore, the looser molecular chains in the amorphous regions can weaken the flame retardant effect. PA6I / 6T, however, possesses certain benzene ring segments and has a rigid molecular chain, thus avoiding the material sticking to the mold and reducing its impact on flame retardancy. Detailed Implementation

[0036] 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.

[0037] The raw materials used in this invention are sourced from the following sources:

[0038] PA6: PA66 EP-158, Zhejiang Huafeng Group;

[0039] PA66: PA6 HY-2500A, Jiangsu Haiyang Chemical Fiber Co., Ltd.;

[0040] PA6I / 6T-1: selar PA 3426, isophthalic acid and terephthalic acid in a mass ratio of 7:3, dupont;

[0041] PA6I / 6T-2: The mass ratio of isophthalic acid to terephthalic acid is 6.5:3.5, prepared in-house;

[0042] PA6I / 6T-3: The mass ratio of isophthalic acid to terephthalic acid is 7.5:2.5, prepared in-house;

[0043] PA6I / 6T-4: The mass ratio of isophthalic acid to terephthalic acid is 5.5:4.5, prepared in-house;

[0044] PA6I / 6T-5: The mass ratio of isophthalic acid to terephthalic acid is 8.5:1.5, prepared in-house;

[0045] PA6I / 6T can be commercially available or prepared in-house. The preparation method is as follows: Mix a certain amount of terephthalic acid and hexamethylenediamine, add 35-45% deionized water (molar ratio 1:1.01-1.02), adjust the temperature to 45-55℃, stir for 1-3 hours, adjust the pH to approximately 7.3-7.6, and continue the reaction for another 1-3 hours. After the reaction is complete, a clear and transparent PA6T salt solution is obtained. After cooling, filter and dry to obtain white PA6T salt powder. The preparation process for PA6I salt is similar. Add a fixed ratio of PA6I and PA6T salts to a reaction vessel, add a certain amount of additives, check the airtightness, purge with nitrogen at least three times, and pressurize to a slight positive pressure of approximately 0.08-0.12 MPa. Start stirring and heating, raise the temperature to 140-160℃, react for 1-3 hours, then continue heating to 200-220℃ and maintain the temperature and pressure for 3-6 hours. For h, the pressure is maintained at around 2.1-2.3 MPa. Then, the temperature is slowly increased to 300-320 ℃ over 2-4 h, while the pressure is gradually reduced to atmospheric pressure. Finally, a vacuum is drawn, and the torque and current are observed. When the maximum value is reached, the stirring is stopped. At this time, nitrogen is introduced to back pressure, the valve is opened to discharge the material, and PA6I / 6T is obtained.

[0046] PA MACM12: Grilamid TR90, EMS Corporation;

[0047] PA6I: KFHP51, Zhuhai Wantong Special Engineering Plastics Co., Ltd.;

[0048] PA6T: KFHP41, Zhuhai Wantong Special Engineering Plastics Co., Ltd.;

[0049] Diethylaluminum hypophosphite: Exolit OP 1230, Clariant;

[0050] Melamine polyphosphate: Melapur 200 / 70, purchased from BASF SE;

[0051] Toughening agent A: GMA grafted onto SEBS, with a GMA grafting rate of 1.0 wt%, self-made;

[0052] Toughening agent B: GMA grafted onto SEBS, with a GMA grafting rate of 0.8 wt%, self-made;

[0053] Toughening agent C: GMA grafted onto SEBS, with a GMA grafting rate of 0.6 wt%, self-made;

[0054] Toughening agent D: GMA grafted onto SEBS, with a GMA grafting rate of 0.4 wt%, self-made;

[0055] Toughening agent E: GMA grafted onto SEBS, with a GMA grafting rate of approximately 0.8 wt%, KT-35L, Shenyang Ketong;

[0056] Toughening agent F: GMA grafted with POE, KT-35, grafting rate 0.8%, Shenyang Ketong;

[0057] Toughening agent G: MAH grafted SEBS, SEBS FG1901 GT, Kraton, USA;

[0058] Toughening agent H: POE, POE 9061, ExxonMobil;

[0059] Toughening agent I: Ethylene-butyl acrylate copolymer, ELVALOY AC34035, purchased from DuPont, USA;

[0060] Toughening agent J: SEBS, SEBS G1651, Kraton (USA);

[0061] Glass fiber: ECS301CL-3, Chongqing International Composite Materials Co., Ltd.;

[0062] Antioxidant: Irganox@1098, BASF;

[0063] Preparation method of flame-retardant polyamide composite material in the examples and comparative examples: According to the formula, the components are mixed evenly and extruded and granulated by a twin-screw extruder to obtain flame-retardant polyamide composite material. The screw length-to-diameter ratio is 40-48:1, the screw barrel temperature is 220-270℃, and the screw speed is 200-450rpm.

[0064] Test methods:

[0065] (1) Flame retardant: 125×13×1.6mm specimens were made by injection molding and tested according to UL 94 standard. At the same time, the flame extinguishing time (the sum of the two burning times of the 5 specimens) was recorded.

[0066] (2) Notched impact strength of cantilever beam: Injection molded ISO 180 standard specimens to test the notched impact strength of cantilever beam.

[0067] Table 1: Test results of each component in the flame-retardant polyamide composites of Examples 1-7 by weight

[0068] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 PA6 20 35 25 25 25 25 PA66 25 PA6I / 6T-1 30 10 20 20 PA6I / 6T-2 20 PA6I / 6T-3 20 PA6I / 6T-4 20 Aluminum diethylphosphite 20 12 15 15 15 15 15 melamine polyphosphate 1 5 3 3 3 3 3 Toughening agent A 0.5 2 1 1 1 1 1 Fiberglass 10 0 20 20 20 20 20 antioxidants 0.5 0 0.5 0.5 0.5 0.5 0.5 Flame retardancy V-0 V-0 V-0 V-0 V-0 V-0 V-0 Flame extinction time s 33.6 35.4 35.3 31.3 30.2 34.6 42.4 <![CDATA[Notch impact strength kJ / m 2 > 7.5 5.8 9.8 9.7 9.5 9.4 9.1

[0069] As can be seen from Examples 3 / 5 / 6 / 7 / 8, the flame extinguishing time is shorter during combustion tests when the preferred PA6I / 6T repeating unit content is used.

[0070] Table 2: Test results of each component in the flame-retardant polyamide composites of Examples 8-12 by weight

[0071] Example 8 Example 9 Example 10 Example 11 Example 12 PA6 25 25 25 25 25 PA6I / 6T-1 20 20 20 20 PA6I / 6T-5 20 Aluminum diethylphosphite 15 15 15 15 15 melamine polyphosphate 3 3 3 3 3 Toughening agent A 1 Toughening agent B 1 Toughening agent C 1 Toughening agent D 1 Toughening agent E 1 Fiberglass 20 20 20 20 20 antioxidants 0.5 0.5 0.5 0.5 0.5 Flame retardancy V-0 V-0 V-0 V-0 V-0 Flame extinction time s 39.6 33.1 32.4 37.2 32.8 <![CDATA[Notch impact strength kJ / m 2 > 9.3 9.6 9.3 9.1 9.7

[0072] As can be seen from Examples 3 / 9-12, the flame extinguishing time is shorter when the toughening agent with the preferred maleic anhydride content is used in the combustion test.

[0073] Table 3: Test results of each component in the flame-retardant polyamide composites of Comparative Examples 1-5 by weight.

[0074] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 PA6 25 25 35 25 25 PA6I / 6T-1 5 40 PA MACM12 20 PA6I 20 PA6T 20 Aluminum diethylphosphite 15 15 12 15 15 melamine polyphosphate 3 3 5 3 3 Toughening agent A 1 1 2 1 1 Fiberglass 20 20 0 20 20 antioxidants 0.5 0.5 0 0.5 0.5 Flame retardancy V-1 V-1 * * V-1 Flame extinction time s 72.5 56.2 * * 64.3 <![CDATA[Izod impact strength kJ / m 2 <![CDATA[]]> 10.5 7.6 *Difficult to demold *Difficult to demold 6.8

[0075] As can be seen from Comparative Example 1, although PA MACM12 is also a non-crystalline polyamide, it cannot achieve the effect of improving flame retardancy.

[0076] As shown in Comparative Example 2, if the content of PA6I / 6T is too low, the flame retardancy will not reach V-0.

[0077] As shown in Comparative Example 3, if the content of PA6I / 6T is too high, it will cause difficulties in demolding.

[0078] As shown in Comparative Example 4, demolding is difficult when using crystalline PA6I instead of PA6I / 6T.

[0079] As shown in Comparative Example 5, the flame retardancy is poor when crystalline PA6T is used instead of PA6I / 6T.

[0080] Table 4: Test results of each component in the flame-retardant polyamide composites of Comparative Examples 6-10 by weight.

[0081] Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 PA6 25 25 25 25 25 PA6I / 6T-1 20 20 20 20 20 Aluminum diethylphosphite 15 15 15 15 15 melamine polyphosphate 3 3 3 3 3 toughening agent F 1 Toughening agent G 1 toughening agent H 1 Toughening agent I 1 Toughening agent J 1 Fiberglass 20 20 20 20 20 antioxidants 0.5 0.5 0.5 0.5 0.5 Flame retardancy V-1 V-1 V-1 V-1 V-1 Flame extinction time s 62.7 54.6 60.2 58.1 55.6 <![CDATA[Notch impact strength kJ / m 2 > 9.1 10.1 10.3 8.3 7.2

[0082] As can be seen from Comparative Example 6, the application of GMA-grafted POE in the flame retardant system of this invention cannot achieve V-0.

[0083] As can be seen from Comparative Example 7, the maleic anhydride-grafted toughening agent cannot achieve V-0 when applied in the flame retardant system of the present invention.

[0084] As can be seen from Comparative Examples 8-10, conventional POE, ethylene-butyl acrylate copolymer, and SEBS cannot achieve V-0 flame retardancy.

[0085] As can be seen from the above examples and comparative examples, the flame-retardant polyamide composite material of the present invention has V-0 flame retardancy, flame extinguishing time < 45s, and notched impact strength > 5 kJ / m. 2 .

Claims

1. A flame-retardant polyamide composite material, characterized in that, By weight, it includes the following components: 20-35 parts of crystalline polyamide; PA6I / 6T 10-30 parts; 12-20 parts of dialkyl hypophosphite flame retardant; 1-5 parts of melamine derivative flame retardant; GMA grafted with SEBS 0.5-2 parts; The crystalline polyamide is an aliphatic polyamide.

2. The flame-retardant polyamide composite material according to claim 1, characterized in that, In the PA6I / 6T, the mass ratio of isophthalic acid to terephthalic acid is (6.5-7.5):(3.5-2.5).

3. The flame-retardant polyamide composite material according to claim 1, characterized in that, The aliphatic polyamide is selected from polylactams.

4. The flame-retardant polyamide composite material according to claim 1, characterized in that, The structural formula of the dialkyl hypophosphite flame retardant is as follows: ， Among them, R 1 R 2 Independently selected from linear or branched C1-C6 alkyl groups; M is selected from one or more combinations of alkali metals, alkaline earth metals, Al, Zn, Fe or Ti; m is 1-4.

5. The flame-retardant polyamide composite material according to claim 4, characterized in that, The dialkyl hypophosphite flame retardant is selected from diethyl aluminum hypophosphite.

6. The flame-retardant polyamide composite material according to claim 1, characterized in that, The melamine derivative flame retardant mentioned above is melamine polyphosphate.

7. The flame-retardant polyamide composite material according to claim 1, characterized in that, In the GMA-grafted SEBS, the grafting rate of GMA ranges from 0.4 to 1.0 wt%.

8. The flame-retardant polyamide composite material according to claim 7, characterized in that, In the GMA-grafted SEBS, the grafting rate of GMA ranges from 0.6 to 0.8 wt%.

9. The flame-retardant polyamide composite material according to claim 1, characterized in that, The product also includes 0-2 parts by weight of additives selected from at least one of antioxidants and lubricants; and 0-50 parts by weight of glass fiber.

10. A method for preparing the flame-retardant polyamide composite material according to any one of claims 1-9, characterized in that, The process includes the following steps: mixing the components evenly according to the formula, extruding and granulating them through a twin-screw extruder to obtain a flame-retardant polyamide composite material. The screw length-to-diameter ratio is 40-48:1, the barrel temperature is 220-270℃, and the screw speed is 200-450rpm.

11. The application of the flame-retardant polyamide composite material according to any one of claims 1-9, characterized in that, Used for manufacturing electronic and electrical components.

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