A polyamide composition and its preparation method and application

Abstract

The present invention discloses a polyamide composition and a preparation method and application thereof. The polyamide composition comprises the following components by weight: 38-65 parts of semi-aromatic polyamide; 10-20 parts of halogen-free flame retardant; 15-50 parts of reinforcing filler; 1-3 parts of diatomite; the content of ferric oxide in the diatomite is ≤1.5%. The present invention successfully solves the problem of large color change and poor foaming of high-temperature nylon materials at high temperatures by adding specific diatomite; at the same time, diatomite and flame retardant have a significant synergistic effect on flame retardancy, which can significantly reduce the amount of flame retardant used, and further reduce the risk of foaming and yellowing.

Description

Technical Field

[0001] The invention belongs to the technical field of modified plastics and relates to a polyamide composition and a preparation method and application thereof. Background Art

[0002] At present, the development of highly integrated electronics has made high-precision, fully automated lead-free reflow soldering replace traditional manual soldering and wave soldering to become the mainstream in the industry, but it has also put forward higher requirements on products. Higher-density packaging makes products smaller and thinner, and the temperature of reflow soldering is significantly higher than that of wave soldering, so the unit material is subjected to higher heat, making yellowing and blistering a pain point in the industry.

[0003] The halogen-containing flame-retardant high-temperature nylon that the industry has been using has been praised by the industry for its high thermal stability, low volatility, high yellowing resistance and low foaming. However, Europe has begun to move towards halogen-free, which has led to various terminals also starting to choose halogen-free high-temperature nylon products; however, due to the high processing temperature of high-temperature nylon (basically greater than 300°C, and most will reach 350°C), and the phosphorus-containing flame retardants used in halogen-free flame retardants are all aluminum diethylphosphinate. Although the thermal stability of aluminum diethylphosphinate is already the best among the currently industrialized halogen-free flame retardants, it is still inevitable to decompose when shearing occurs during processing, producing a small amount of acidic substances. These acidic substances will significantly catalyze the aging of nylon in the subsequent reflow soldering process, causing obvious yellowing of the product; at the same time, these small molecules will have a tendency to volatilize at high temperatures, and then cause them to escape in the form of gas, causing the material to foam, and the foaming will significantly affect the size and electrical safety of the material, and may cause cracking and other problems.

[0004] Yellowing and blistering of halogen-free flame-retardant high-temperature nylon after high temperature are common problems in this industry. To address the above problems, the industry has made many attempts. The existing technology proposes to use zinc borate to stabilize diethyl aluminum phosphinate to reduce its decomposition at high temperatures; or to use zinc oxide and molecular sieves and other substances with surface adsorption effects to adsorb small molecules to reduce the impact of decomposition products on them; but in actual use, although zinc borate is helpful for color stability to a certain extent, the effect is not obvious and cannot meet the needs of the industry at all; although zinc oxide and molecular sieves have greatly improved the initial color, after multiple high temperatures, the absorbed acidic small molecules will be released, which will cause the product to turn yellow drastically in the later stage.

[0005] Therefore, it is an urgent problem to improve or avoid the yellowing and blistering phenomenon of halogen-free flame-retardant high-temperature nylon materials when exposed to high temperatures. Summary of the invention

[0006] In order to overcome the defects of the above-mentioned prior art, the present invention proposes a polyamide composition and its preparation method and application. By adding specific diatomaceous earth, the problem of large color change and poor foaming of high-temperature nylon materials at high temperatures is successfully solved; at the same time, diatomaceous earth and flame retardant have a significant synergistic effect on flame retardancy, which can significantly reduce the amount of flame retardant used, and further reduce the risk of foaming and yellowing.

[0007] This is achieved specifically through the following technical solutions:

[0008] A polyamide composition, comprising the following components in parts by weight:

[0009]

[0010] The content of ferric oxide in the diatomite is ≤1.5%. The content of ferric oxide in the diatomite is tested by energy dispersive X-ray spectrometer (EDS), and the method is as follows: the sample powder is evenly applied on the surface of the conductive glue, gold is sprayed, and then the element content is detected under the EDS module of the scanning electron microscope.

[0011] Further, the semi-aromatic polyamide is derived from the following repeating units: 50 mol % of terephthalic acid-based repeating units and 50 mol % of diamine-based repeating units.

[0012] The diamine-based repeating unit is selected from NH(C2H4NH2)2, H2N[C2H4NH]2C2H4NH2, H2N[C2H4NH]3C2H4NH2, NH[(CH2)4NH2]2, NH[(CH2)5NH2]2, NH[(CH2)6NH2]2, NH[(CH2)7NH2]2, NH[(CH2)8NH2]2, NH[(CH2)9NH2]2, NH[(CH2) 10 NH2]2、NH[(CH2) 11 NH2]2, N[(CH2) 12 NH2]3, NH[(CH2) 13 NH2]2, NH[(CH2)14NH2)2, NH[(CH2) 15 NH2]2、NH[(CH2) 16 NH2]2、NH[(CH2) 17 NH2]2、NH[(CH2) 18 NH2]2, H2N(H2C) 10 NH(CH2)5NH2、H2N(H2C) 10 NH(CH2)6NH2、H2N(H2C) 10 NH(CH2)7NH2、H2N(H2C)10 NH(CH2)8NH2、H2N(H2C) 10 NH(CH2)9NH2、H2N(H2C) 10 NH(CH2) 11 NH2, H2N(H2C) 10 NH(CH2) 12 One or more of NH2, H2N(H2C)9NH(CH2)6CH(CH3)CH2NH2, H2N(H2C)9NHCH2CH(CH3)(CH2)6NH2, NH[(CH2)6CH(CH3)CH2NH2]2, and NH[CH2CH(CH3)(CH2)6NH2]2.

[0013] Preferably, the semi-aromatic polyamide is PA6T or PA10T, preferably PA10T.

[0014] Furthermore, the D50 particle size of the diatomite is ≤10 μm. By adding diatomite with a specified particle size and ferric oxide content, on the one hand, the amount of flame retardant can be significantly reduced, reducing the risk of the flame retardant producing acidic small molecules, while ensuring a good flame retardant effect; on the other hand, adding diatomite with a specified particle size and ferric oxide content has a good adsorption effect of acidic small molecules at high temperature, thereby significantly improving blistering and color before and after the furnace.

[0015] Furthermore, the halogen-free flame retardant is aluminum diethylphosphinate.

[0016] Furthermore, the reinforcing filler is one or more of a fibrous reinforcing material or a two-dimensional planar reinforcing material.

[0017] Furthermore, the fibrous reinforcing material is one or both of glass fiber and carbon fiber, and the two-dimensional plane reinforcing material is one or both of talc and mica. Preferably, the reinforcing filler is glass fiber.

[0018] Furthermore, the polyamide composition further comprises 0.5-1 part of a flow modifier. Specifically, the flow modifier can be selected from one or more of sodium montanate, lithium stearate, sodium stearate, oxidized polyethylene wax or oxidized propylene wax.

[0019] Furthermore, the polyamide composition further comprises 0.5-1 part of an auxiliary agent. Specifically, the auxiliary agent is one or both of an antioxidant and a lubricant.

[0020] Specifically, the antioxidant may be selected from one or more of hindered phenol antioxidants, hindered amine antioxidants, thioether antioxidants and phosphite antioxidants.

[0021] The present invention also provides a method for preparing the polyamide composition, comprising the following steps:

[0022] The components are weighed according to the proportion, and the components except the reinforcing filler and the halogen-free flame retardant are pre-mixed and then put into the feed port of the extruder. Meanwhile, the reinforcing filler is added into the first side feed port of the extruder, and the halogen-free flame retardant is added into the second side feed port. The polyamide composition is obtained by melt blending at a processing temperature of 290-330°C.

[0023] The present invention also provides the use of the above-mentioned polyamide composition in the preparation of electronic and electrical parts, which is particularly suitable for lead-free reflow soldering process, for example, it can be used to prepare TYPE-C, USB and PCIE interfaces.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. When using aluminum diethylphosphinate alone, a large amount of aluminum diethylphosphinate must be used to achieve compliance with flame retardant performance. However, due to the large amount of aluminum diethylphosphinate used, a lot of small molecular weight is produced at high temperature. If the activity or surface area of ​​the adsorbate is not enough, it cannot be completely adsorbed, and it is also easy to desorb at high temperature. Diatomaceous earth has a large surface area and many pores. At the same time, it is mainly composed of highly acid-resistant substances such as silicon dioxide. It has very good adsorption effect and adsorption stability, and can ensure the material's yellowing resistance and blistering resistance. In addition, due to its microscopic porous and fluffy structure and the adsorption of acidic small molecules at high temperature, diatomaceous earth will play a good role in filling the carbon layer, making the carbon layer dense and airtight, which significantly improves the flame retardant effect.

[0026] 2. Diatomaceous earth is cheap. Even if the impurity content and particle size of metal oxides are well controlled, the price is only about 30 RMB / KG, while the current price of flame retardants is 90 RMB / KG, which can greatly reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 This is a comparison chart of the vertical combustion test results of Example 2 of the present invention and Comparative Example 1;

[0029] Figure 2 The following is a color comparison chart of Comparative Example 1, Example 2 and Example 7 of the present invention before and after the baking resistance discoloration test. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The raw materials used in the examples and comparative examples of the present invention are homemade or commercially available, but are not limited to these materials:

[0032] Semi-aromatic polyamide A: PA10T, homemade, containing 50 mol% of terephthalic acid, the rest being decanediamine among the diamines mentioned above, with a relative viscosity of 2.4, and a specific homemade method is as follows: according to the proportion, decanediamine, terephthalic acid, benzoic acid end-capping agent, bis(hexamethylene)triamine and deionized water are added into a reactor with a nitrogen atmosphere and a pressure of 2-4 MPa, the reactor is heated to 160-220° C. and kept at this temperature for 0.5-1.5 hours, and then heated to 230-240° C. and kept at this temperature for 10-15 hours to obtain PA10T;

[0033] Semi-aromatic polyamide B: PA6T, homemade, containing 50 mol% of terephthalic acid, the rest being hexamethylenediamine among the diamines mentioned above, with a relative viscosity of 2.4, and a specific homemade method is as follows: adding hexamethylenediamine, terephthalic acid, benzoic acid end-capping agent, bis(hexamethylene)triamine and deionized water into a reactor with a nitrogen atmosphere and a pressure of 2-4 MPa, heating the reactor to 160-220° C. and keeping the temperature constant for 0.5-1.5 hours, heating to 230-240° C. and keeping the temperature constant for 10-15 hours to obtain PA6T;

[0034] Flame retardant: aluminum diethylphosphinate, purchased from Clariant;

[0035] Diatomaceous earth A: The D50 particle size of diatomaceous earth is 8 μm, the content of ferric oxide in diatomaceous earth is 2.6%, the brand is MN23, and it was purchased from Yipin Minerals, USA;

[0036] Diatomaceous earth B: The D50 particle size of diatomaceous earth is 12.4 μm, the content of ferric oxide in diatomaceous earth is less than 1.5%, the brand is LCS3, purchased from Yipin Minerals, USA;

[0037] Diatomaceous earth C: The D50 particle size of diatomaceous earth is 10 μm, the content of ferric oxide in diatomaceous earth is less than 1.5%, the brand is MN5, purchased from Yipin Minerals, USA;

[0038] Glass fiber: brand ECS301HP, purchased from Chongqing International Composite Materials Co., Ltd.;

[0039] Zinc oxide: analytical grade, purchased from Anaiji Chemical;

[0040] Antioxidants: Hindered phenols, commercially available, the same commercial product was used in parallel experiments;

[0041] Flow modifier: sodium montanate, commercially available, the same commercial product was used in parallel experiments.

[0042] The preparation methods of the embodiments of the present invention and the comparative examples are as follows:

[0043] According to the ratio, semi-aromatic polyamide, diatomaceous earth and other additives are weighed and pre-mixed, and then put into the feed port of a twin-screw extruder. At the same time, glass fiber is added into the first side feed port of the twin-screw extruder, and a halogen-free flame retardant is added into the second side feed port of the twin-screw extruder. The polyamide composition is obtained by melt blending at a processing temperature of 310°C.

[0044] The screw length-to-diameter ratio of the twin-screw extruder is 65:1, the barrel temperature is 310°C, the screw speed is 100rpm, and the feeding rate is 50Kg / h.

[0045] The term "part(s)" in this specification means "part(s) by weight" unless otherwise specified.

[0046] <Test Standard>

[0047] The performance test standards of the embodiments and comparative examples of the present invention are as follows:

[0048] Vertical burning test: refer to UL94 V-0 test standard, standard strip specimen size is 125±5mm long, 13.0±0.5mm wide, 0.8mm thick; 5 specimens are treated at 23±2℃, 50±5%, for at least 48 hours. Aim the flame of the Bunsen burner at the center of the lower end of the specimen, and keep the distance between the center of the top surface of the Bunsen burner tube and the lower end surface of the specimen at 10±1mm, and keep this distance for 10±0.5S: if necessary, the Bunsen burner can be moved according to the change of the length and position of the specimen. After applying the flame to the specimen for 10±0.5S, immediately withdraw the Bunsen burner at a speed of about 300mm / s to at least 150mm away from the specimen. At the same time, use a timing device to measure the flame burning time T1 (in seconds) of the specimen. After the sample stops burning with flame, even if the Bunsen burner is not evacuated 150mm from the sample, immediately move the Bunsen burner to the lower end of the sample and keep a distance of 10±1mm, and apply the flame again for 10±0.5S. If necessary, move the Bunsen burner away to remove drippings. After applying the flame, immediately move the Bunsen burner away from the sample by at least 150mm, and start the timing device to measure the sample's flame time T2 and flameless combustion time T3, and record T2 and T3. If T1+T2+T3 of all 5 specimens is less than 10s, and there is no dripping to ignite the cotton below, it is considered that the V-0 condition is met.

[0049] Test of color change resistance during baking: Heat and melt the halogen-free flame-retardant high-temperature nylon composite material at 290-330℃, and then perform injection molding to make a 60mm*60mm*1mm square plate. Then, pass through the oven at a temperature of 240-260-280-300 and a speed of 480mm / min for 7 minutes and 30 seconds. The LAB value change ΔE of the color of the square plate before and after the oven is tested to measure the color change resistance during baking.

[0050] Foaming test: The halogen-free flame retardant high temperature nylon composite material is heated and melted at 290-330°C, injection molded, and made into a 60mm*60mm*1mm square plate. It is modulated for 168 hours at 85°C / 85% humidity, and then SMT tested at a temperature of 240°C-260°C-280°C-300°C to observe its foaming properties (100 boards are processed and the total number of square boards with foaming is counted).

[0051] Table 1. Formulations of Examples 1-12

[0052]

[0053]

[0054] Table 2. Performance test results of Examples 1-12

[0055]

[0056] Table 3. Comparative Examples 1-10 Formulations

[0057]

[0058]

[0059] Table 4. Performance test results of comparative examples 1-10

[0060]

[0061] According to the test results in Table 2, the halogen-free flame-retardant high-temperature nylon containing diatomite prepared in Examples 1-12 of the present application, when using PA10T, has a color difference value of less than 6.5; using a modified flow agent and an antioxidant within a reasonable range will reduce the friction and decomposition of the system, and further enhance the effect of diatomite (Examples 3-6); the flame retardant grade of the samples using diatomite can reach a stable V-0, which is because the small-particle diatomite absorbs some acidic substances, and then forms carbon on this porous structure during the combustion process, so that the carbon layer expands more and isolates fire, and has a better flame retardant effect (see the effect). Figure 1 , Figure 1The left side is the test sample of comparative example 1, and the right side is the test sample of embodiment 2. Diatomaceous earth of suitable particle size is added in embodiment 2. In the combustion experiment, the carbon layer of embodiment 2 is more expanded, which can better isolate the transfer of flame and heat, and significantly improve the flame retardant performance. Since diatomaceous earth is not added in comparative example 1, a collapsed carbon layer is formed after combustion, which is not conducive to heat insulation, so the flame retardant performance is poor). The water absorption rate of PA10T is 1%, and its blistering risk is low, while the water absorption rate of PA6T is 4.5%. The violent explosion of water vapor at high temperature can easily cause blistering. The scientific use of diatomaceous earth in PA6T can also reduce blistering, improve color and stabilize combustion (Examples 10 and 11).

[0062] As can be seen from Table 4, when flame retardant is used alone in Comparative Example 1 compared with Example 2, flame retardancy can only reach V-1 grade, and color difference value Δ E and foamability are all deteriorated.Comparative Example 10 can be seen from Example 2 compared with that the ferric oxide content of diatomite is once high, and free iron ion can play the role of catalytic aging, and although the flame retardancy of material has rising, due to the catalytic aging of iron ion, the aging yellowing and decomposition of product are caused, so color difference value Δ E and foamability are all unimproved.Due to the poor thermal stability of flow modifier, and most of them are small molecules, using more flow modifier can cause the significant increase of foamability and the yellowing of color (Comparative Example 2, Example 4).Although the color difference value before and after the furnace can be significantly reduced using more antioxidants, due to the small molecular weight of antioxidant, gas can be volatilized to form, causing significant foaming (Comparative Example 3, Example 6). The use of large amounts of diatomaceous earth tends to saturate the improvement in color, but due to the high density of diatomaceous earth, it is enriched at the front end during combustion, which will cause dripping and ignition, so that the combustion can only reach V-2 level (Comparative Example 4, Example 2). Using less flame retardant, the flame retardant performance cannot meet the standard, and using more flame retardant will have a significant deterioration effect on the color of the system after the furnace (Comparative Examples 5-6, Example 2). The only difference between Comparative Example 7 and Example 10 is that Comparative Example 7 does not add diatomaceous earth, resulting in the performance of Comparative Example 7 deteriorating. The use of zinc oxide, although there is a certain improvement effect, it cannot meet the demand at all (Comparative Example 8, Example 2). Compared with Example 2, the particle size of the diatomaceous earth in Example 12 is greater than 10μm, resulting in the deterioration of the flame retardant performance and baking resistance of Example 12.

[0063] Figure 2 The color comparison diagram of Comparative Example 1, Example 2 and Example 7 before and after the baking resistance discoloration test is shown in the figure. Figure 2 The first row shows the colors of the samples of comparative example 1, example 2 and example 7 before the furnace. Figure 2The second row shows the colors of the samples of comparative example 1, embodiment 2 and embodiment 7 after the oven. It can be seen that the color of comparative example 1 changes the most before and after the baking resistance discoloration test, indicating that its yellowing resistance is poor, while the color changes of embodiments 2 and 7 before and after the baking resistance discoloration test are less obvious, indicating that embodiments 2 and 7 have better yellowing resistance.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A polyamide composition, characterized in that By weight, it includes the following components: The content of ferric oxide in the diatomite is ≤1.5%; The D50 particle size of the diatomaceous earth is ≤10 μm; The halogen-free flame retardant is aluminum diethylphosphinate.

2. The polyamide composition according to claim 1, characterized in that The reinforcing filler is one or more of a fibrous reinforcing material or a two-dimensional plane reinforcing material.

3. The polyamide composition according to claim 2, characterized in that The fibrous reinforcing material is one or both of glass fiber and carbon fiber, and the two-dimensional plane reinforcing material is one or both of talc and mica.

4. The polyamide composition according to claim 1, characterized in that Also included is 0.5-1 part of a flow improver.

5. The polyamide composition according to claim 4, characterized in that The flow modifier is one or more of sodium montanate, lithium stearate, sodium stearate, oxidized polyethylene wax or oxidized propylene wax.

6. The polyamide composition according to claim 1, characterized in that The invention also comprises 0.5-1 part of an auxiliary agent, wherein the auxiliary agent is one or two of an antioxidant and a lubricant.

7. A method for preparing a polyamide composition according to any one of claims 1 to 6, characterized in that: The following steps are involved: The components are weighed according to the proportion, and the components except the reinforcing filler and the halogen-free flame retardant are pre-mixed and then put into the feed port of the extruder. Meanwhile, the reinforcing filler is added into the first side feed port of the extruder, and the halogen-free flame retardant is added into the second side feed port. The polyamide composition is obtained by melt blending at a processing temperature of 290-330°C.

8. Use of the polyamide composition according to any one of claims 1 to 6 in the preparation of electronic and electrical parts.

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