Polyamide composite material as well as preparation method and application thereof

Abstract

The invention discloses a polyamide composite material which comprises the following components in parts by weight: 75-95 parts of polyamide; 5 to 20 parts of melamine cyanurate; 0.3 to 1.4 parts of an organic amine acid-base regulator; the content of free cyanuric acid in the melamine cyanurate is 2 to 6 weight percent; and the pH value of the polyamide composite material is 5.0-6.0. According to the invention, the content of free cyanuric acid in melamine cyanurate is controlled, and the pH value of the composite material is regulated by the organic amine acid-base regulator, so that the precipitation of melamine cyanurate in the processing process can be effectively inhibited, and the mold scale is obviously reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a polyamide composite material and a preparation method and application thereof. Background Art

[0002] Polyamide, commonly known as nylon, is an important thermoplastic engineering plastic. It is widely used in automobiles, mechanical parts, electronics, home appliances, new energy and other fields because of its many excellent properties such as high strength, good self-lubrication, wear resistance, oil resistance and easy molding and processing. Nitrogen flame-retardant nylon refers to a modified polyamide using melamine cyanurate (MCA) as a flame retardant. It has the characteristics of high mechanical properties, good flame retardancy, low smoke density, and high relative tracking index. It is widely used in connectors, low-voltage electrical appliances and other industries. However, since MCA is easy to release melamine during processing, mold deposits are easy to generate during injection molding. After the mold deposits accumulate, the exhaust pipe is blocked, which leads to appearance problems of the product. Therefore, the mold deposits need to be cleaned every once in a while, which increases the production cost and is not conducive to continuous production.

[0003] In the prior art, the free cyanuric acid content in melamine cyanurate is generally less than 1wt%. The main methods for modifying the precipitation of melamine cyanurate are: 1. using other halogen-free flame retardants to replace or reduce the amount of MCA added; 2. performing surface modification on the material to inhibit the precipitation of MCA. Summary of the invention

[0004] The object of the present invention is to overcome the above technical defects and provide a polyamide composite material which is resistant to precipitation and has less mold deposit.

[0005] The present invention is achieved through the following technical solutions: A polyamide composite material, comprising the following components in parts by weight: Polyamide 75-95 parts; 5-20 parts of melamine cyanurate; 0.3-1.4 parts of organic amine acid-base regulator; The free cyanuric acid content in the melamine cyanurate is 2-6wt%; The pH value of the polyamide composite material is 5.0-6.0.

[0006] The pH value test method of polyamide composite materials is as follows: take 8g of polyamide composite particles (the diameter of the particles is 1.5-4mm and the length is 3-5mm) and place them in a glass bottle, add 20g of deionized water, seal it, and then place it in an oven at 80°C for 24h, take it out and cool it to room temperature, and use a pH meter to test the pH value of the upper solution.

[0007] Preferably, the pH value of the polyamide composite material is 5.3-5.7.

[0008] Preferably, the free cyanuric acid content in the melamine cyanurate is 3-4wt%.

[0009] Melamine cyanurate with a specific cyanuric acid content can be a commercial product or can be obtained by self-production. Its preparation process is: melamine cyanurate and cyanuric acid are ground to 300-1500 mesh respectively, then fully and evenly mixed according to proportion, put into a high-temperature reactor at 310-330°C, filled with nitrogen, and reacted for 0.5-2h to obtain the target melamine cyanurate.

[0010] Test method for free cyanuric acid content: Weigh 2g of melamine cyanurate on a balance, add it to a certain amount of dimethylformamide solution to fully dissolve the free cyanuric acid in the sample, then filter it, place the filter cake in a vacuum oven at 120℃ to dry, weigh the filter cake, and the free cyanuric acid content is calculated as follows: Free cyanuric acid content = (initial weight of sample - residual weight) / initial weight of sample × 100%.

[0011] The organic amine acid-base regulator is selected from at least one of 4,4'-di(phenylisopropyl)diphenylamine, 4,4'-dioctyldiphenylamine, 4,4'-di(α,α-dimethylbenzyl)diphenylamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N-phenyl-N'-cyclohexyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N-(1-methylisopentyl)-N'-phenyl-p-phenylenediamine, N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, 4,4'-diisooctyldiphenylamine, and N,N'-di(2-naphthyl)p-phenylenediamine.

[0012] The polyamide is selected from aliphatic polyamide resin, and the aliphatic polyamide resin is selected from at least one of PA6, PA11, PA12, PA66, PA610, PA612, PA1010, PA1012, and PA1212.

[0013] The relative viscosity of the polyamide is 2-3.4, and the test conditions are 0.01g / mL concentrated sulfuric acid solution at 25°C. The relative viscosity detection method is: weigh 0.5g of polyamide resin, transfer it to a 50ml volumetric flask, add about 40ml of 96% mass fraction concentrated sulfuric acid, and oscillate ultrasonically until the polyamide resin is completely dissolved, cool the solution to 25°C, dilute it to the scale with concentrated sulfuric acid, and mix it evenly, test the flow time of 0.01g / mL polyamide resin solution through the Ubbelohde viscometer at 25°C, record it as t1, use the same viscometer to test the flow time of the solvent concentrated sulfuric acid, record it as t2, and t1 / t2 is the relative viscosity.

[0014] It is possible to choose whether to add 0-2 parts of an auxiliary agent according to actual needs, and the auxiliary agent is selected from at least one of an antioxidant and a lubricant. The antioxidant can be a hindered phenol antioxidant, a phosphite antioxidant, a cuprous halide composite antioxidant, or an antioxidant containing a benzophenone functional group compound, etc. The lubricant can be a hydrocarbon, an ester, an alcohol, a stearate, a fatty acid, a fatty acid amide, etc.

[0015] You can choose to add 0-10 parts of toughening agent according to actual needs.

[0016] The preparation method of the polyamide composite material of the present invention comprises the following steps: mixing the components uniformly according to the proportion, extruding and granulating through a twin-screw extruder, with the barrel temperature ranging from 160 to 250° C., the head temperature being 230 to 260° C., and the rotation speed being 250 to 500 rpm, to obtain the polyamide composite material.

[0017] The polyamide composite material of the present invention is used for preparing connectors, industrial plugs, miniature circuit breaker housings, molded case circuit breaker housings, and the like.

[0018] The present invention has the following beneficial effects: The present invention can effectively inhibit the precipitation of melamine cyanurate during processing by controlling the free cyanuric acid content in melamine cyanurate and adjusting the pH value of the composite material by using an organic amine acid-base regulator, thereby reducing mold scale. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0020] PA66: PA66 EPR24, relative viscosity 2.4, Shenma Group; PA6: PA6 HY2800A, relative viscosity 2.8, Jiangsu Haiyang Chemical Fiber Co., Ltd.; PA610: PA610 F120, relative viscosity 2.2, Shandong Guangyin New Materials Co., Ltd.; Cyanuric acid: Aladdin; Melamine cyanurate B~G are prepared by the following method: melamine cyanurate A and cyanuric acid are ground to a particle size of less than 300 mesh, then fully mixed according to proportion, put into a high-temperature reactor at 320°C, filled with nitrogen, and reacted for 1 hour to obtain melamine cyanurate B, melamine cyanurate C, melamine cyanurate D, melamine cyanurate E, melamine cyanurate F, and melamine cyanurate G, respectively, and finally the free cyanuric acid content is determined.

[0021] Free cyanuric acid content / % source Melamine Cyanurate A 0.09 Shouguang Weidong Chemical Co., Ltd. Melamine Cyanurate B 0.67 self made Melamine Cyanurate C 2.12 self made Melamine Cyanurate D 3.12 self made Melamine cyanurate E 4.00 self made Melamine Cyanurate F 5.95 self made Melamine Cyanurate G 8.44 self made Acid-base regulator A: 4,4'-di(phenylisopropyl)diphenylamine: NAUGARD 445, manufactured by SI Group; Acid-base regulator B: 4,4'-dioctyldiphenylamine, manufactured by Macklin's reagent; Acid-base regulator C: 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, manufactured by Anaiji Chemical; Acid-base regulator D: N-isopropyl-N'-phenyl-p-phenylenediamine, manufactured by Anaiji Chemical; Acid-base regulator E: calcium hydroxide, manufactured by Aladdin; Antioxidant: IRGANOX 1098, hindered phenol antioxidant, manufactured by BASF; Lubricant: BS-3818, calcium stearate, manufactured by Bailihe Chemical (Zhongshan) Co., Ltd. Preparation method of polyamide composite material of embodiment and comparative example: according to the ratio, each component is mixed evenly, and extruded into granules by a twin-screw extruder, the barrel temperature range is 160-250°C, the head temperature is 230-260°C, and the rotation speed is 250-500rpm to obtain a polyamide composite material.

[0022] Various test methods: (1) Flame retardancy: The flame retardancy of the injection-molded 125*13*0.8 mm burning specimen was tested according to UL 94 standard.

[0023] (2) pH value of polyamide composite materials: 8 g of plastic particles were placed in a glass bottle, 20 g of deionized water was added, and the bottle was sealed. The bottle was then placed in an oven at 80 °C for 24 h. After being taken out, the bottle was cooled to room temperature and the pH value of the upper solution was tested with a pH meter.

[0024] (3) Mold deposit weight: A groove is designed at the exhaust end of the mold, and a metal sheet is placed inside it to collect mold deposits (both the movable mold and the fixed mold have metal sheets for collecting mold deposits). The injection temperature is set to 290°C, the injection cycle is 20s, and the continuous injection is 150 molds. The weight of mold deposits is calculated by the following formula: Mold deposit weight = weight of metal sheet after injection molding - weight of metal sheet before injection molding.

[0025] Table 1: Content of each component and test results of polyamide composite materials of Examples 1-6 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 PA610 75 PA66 85 85 85 85 PA6 95 Melamine cyanurate label E E E C D F Melamine cyanurate content 20 10 5 10 10 10 Acid-base regulator label A A A A A A Acid-base regulator content 1.4 0.9 0.3 0.9 0.9 0.9 Antioxidants 0.2 0.2 0.2 0.2 0.2 Lubricants 0.5 0.5 0.5 0.5 0.5 pH 5.06 5.36 5.45 5.64 5.55 5.11 Flame retardant V-0 V-0 V-0 V-0 V-0 V-0 Mould deposit weight, mg 1.0 0.5 0.5 0.9 0.6 1.0 It can be seen from Examples 2 / 4 / 5 / 6 that when melamine cyanurate has a preferred free cyanuric acid content, there is less mold deposit.

[0026] Table 2: Content of each component and test results of polyamide composite materials of Examples 7-12 Example 7 Example 8 Example 9 Example 10 Embodiment 11 Example 12 PA66 85 85 85 85 85 85 Melamine cyanurate E 10 10 10 10 10 10 Acid-base regulator label B C D A A A Acid-base regulator content 0.9 0.9 0.9 0.3 1.2 1.4 Antioxidants 0.2 0.2 0.2 0.2 0.2 0.2 Lubricants 0.5 0.5 0.2 0.2 0.2 0.2 pH 5.58 5.86 5.52 5.02 5.67 5.81 Flame retardant V-0 V-0 V-0 V-0 V-0 V-0 Mould deposit weight, mg 0.7 0.9 0.6 0.9 0.6 1.0 It can be seen from Examples 2 / 7-12 that the mold deposit content is better when the pH is within the preferred range.

[0027] Table 3: Content of each component and test results of comparative polyamide composite materials Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 PA66 85 85 85 85 Melamine cyanurate label A B G G Melamine cyanurate content 10 10 10 10 Acid-base regulator label A A A A Acid-base regulator content 1.2 0.9 1.4 1.5 Antioxidants 0.2 0.2 0.2 0.2 Lubricants 0.5 0.5 0.5 0.5 pH 5.92 5.81 4.88 5.03 Flame retardant V-0 V-0 V-0 V-0 Mould deposit weight, mg 3.2 2.5 3.7 3.4 It can be seen from Comparative Example 1 / 2 that when the free cyanuric acid content in melamine cyanurate is too low, mold deposit is excessive even if the pH is within the range of the present invention.

[0028] It can be seen from Comparative Examples 3 / 4 that if the free cyanuric acid content in melamine cyanurate is too high, even if the pH is adjusted to within the range of the present invention by adding an acid-base regulator, there will be too much mold deposit.

[0029] Table 3: Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 PA66 85 85 85 85 Melamine cyanurate label E E E E Melamine cyanurate content 10 10 10 10 Acid-base regulator label A A E E Acid-base regulator content 0 2 0.9 0.3 Antioxidants 0.2 0.2 0.2 0.2 Lubricants 0.5 0.5 0.5 0.5 pH 4.55 6.36 6.74 5.91 Flame retardant V-0 V-2 V-2 V-2 Mould deposit weight, mg 1.8 2.8 4.2 3.3 It can be seen from Comparative Example 5, Examples 10 / 2 / 11 / 12, and Comparative Example 6 that when the pH value is not within the range of the present invention, the mold deposit content is too high, and when the pH value of Comparative Example 6 is too high, the flame retardancy is also affected.

[0030] It can be seen from Comparative Example 7 that calcium hydroxide, because it remains in a granular state in the barrel and has a small specific surface area, does not consume enough free cyanuric acid. At the same time, due to its strong alkalinity, it corrodes the resin matrix, resulting in a decrease in flame retardancy and an increase in mold deposit.

[0031] It can be seen from Comparative Example 8 that even if the pH value within the scope of the present invention is obtained by adjusting the calcium hydroxide content, the strong alkalinity of the calcium hydroxide itself destroys the resin matrix, resulting in poor flame retardancy and a lot of mold deposits.

Claims

1. A polyamide composite material, characterized in that: By weight, it includes the following components: Polyamide 75-95 parts; 5-20 parts of melamine cyanurate; 0.3-1.4 parts of organic amine acid-base regulator; The free cyanuric acid content in the melamine cyanurate is 2-6wt%; The pH value of the polyamide composite material is 5.0-6.

0.

2. The polyamide composite material according to claim 1, characterized in that: The pH value of the polyamide composite material is 5.3-5.

7.

3. The polyamide composite material according to claim 1, characterized in that: The free cyanuric acid content in the melamine cyanurate is 3-4wt%; the pH value test method of the polyamide composite material is: take 8g of plastic particles and put them in a glass bottle, add 20g of deionized water, seal it, and then put it in an oven at 80°C for 24h, take it out and cool it to room temperature, and use a pH meter to test the pH value of the upper solution.

4. The polyamide composite material according to claim 1, characterized in that: The organic amine acid-base regulator is selected from at least one of 4,4'-di(phenylisopropyl)diphenylamine, 4,4'-dioctyldiphenylamine, 4,4'-di(α,α-dimethylbenzyl)diphenylamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N-phenyl-N'-cyclohexyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N-(1-methylisopentyl)-N'-phenyl-p-phenylenediamine, N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, 4,4'-diisooctyldiphenylamine, and N,N'-di(2-naphthyl)p-phenylenediamine.

5. The polyamide composite material according to claim 1, characterized in that: The polyamide is selected from aliphatic polyamide resin, and the aliphatic polyamide resin is selected from at least one of PA6, PA11, PA12, PA66, PA610, PA612, PA1010, PA1012, and PA1212.

6. The polyamide composite material according to claim 1, characterized in that: The relative viscosity of the polyamide is 2-3.4, and the test conditions are 0.01 g / mL concentrated sulfuric acid solution at 25°C.

7. The polyamide composite material according to claim 1, characterized in that: By weight, the invention further comprises 0-2 parts of auxiliary agents, wherein the auxiliary agents are selected from at least one of antioxidants and lubricants.

8. The polyamide composite material according to claim 1, characterized in that: By weight, 0-10 parts of toughening agent are also included.

9. The method for preparing the polyamide composite material according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: mixing the components uniformly according to the proportion, extruding and granulating through a twin-screw extruder, with the barrel temperature ranging from 160 to 250° C., the die head temperature being 230 to 260° C., and the rotation speed being 250 to 500 rpm, to obtain a polyamide composite material.

10. Use of the polyamide composite material according to any one of claims 1 to 8, characterized in that: Used to prepare connectors, industrial plugs, miniature circuit breaker housings, molded case circuit breaker housings, etc.