Polyamide composition as well as preparation method and application thereof

Abstract

The invention discloses a polyamide composition which comprises the following components in parts by weight: 39-61 parts of polyamide resin; 5 to 40 parts of potassium titanate whisker; 0.6-3 parts of a weld mark improving auxiliary agent; in the potassium titanate whisker, the molar ratio of K to Ti is 1: (1-3). According to the invention, the potassium titanate whiskers with a specific molar ratio of K / Ti are selected, the crystallization temperature of the polyamide resin is selected to be 255-290 DEG C, and the weld mark improving auxiliary agent is added, so that the weld mark strength can be obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly to a polyamide composition, a preparation method and an application thereof. Background Art

[0002] High-temperature nylon materials have both the strength and toughness of ordinary nylon and a relatively high heat resistance temperature, and are currently widely used in industries such as electronics and electrical appliances, automobiles, and military industries; however, because they have a relatively high melting point and a relatively high crystallization temperature, their processing window is narrow. Especially for parts with complex size and structure, the injection-molded parts will inevitably encounter the problem of weld line strength. As is well known, the weld line position of a part is a structural defect position, and this is the weakest part of the strength of the part. Therefore, the weld line strength determines the actual use strength of the structural part. And because high-temperature nylon generally has a relatively high crystallization temperature and a narrow processing window, it is more difficult to improve the weld line strength of nylon composites at high crystallization temperatures.

[0003] Patent CN114736513B provides a method for improving the weld line strength of PA66 by controlling the glass fiber content and different glass fiber aspect ratios. However, because the PA66 material has a relatively low crystallization temperature and a wide processing window, and the first glass fiber aspect ratio is too large, the surface of the material will be too rough, severely limiting the use of the material. Summary of the Invention

[0004] The purpose of the present invention is to provide a polyamide composition with high weld line strength, a preparation method and an application thereof.

[0005] The present invention is achieved by the following technical solutions: A polyamide composition, by weight, comprises the following components: 39 - 61 parts of polyamide resin; 5 - 40 parts of potassium titanate whiskers; 0.6 - 3 parts of weld line improvement additive; The crystallization temperature of the polyamide resin is 255 - 290 °C; In the potassium titanate whiskers, the molar ratio of K / Ti is 1:(1 - 3); The weld line improvement additive is selected from at least one of 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol, aniline black, 8-methoxy-2-propionamidotetralin, p-toluenesulfonyl semicarbazide, 2-(benzoylamino)benzoic acid, 3-[acetyl(methyl)amino]propionic acid, and benzoylglycylaminoacetic acid.

[0006] In the polyamide composition of the present invention, the polyamide resin accounts for not less than 35 wt% of the total weight.

[0007] The test method for the crystallization temperature of the polyamide resin refers to ASTM D3418-2003. Using a Perkin Elmer Diamond DSC analyzer, in a nitrogen atmosphere with a flow rate of 40 mL / min, during the test, first heat up to 340 °C at a rate of 10 °C / min, hold at 340 °C for 2 min, and then cool to 50 °C at a rate of 10 °C / min. The peak temperature that appears during the cooling process is the crystallization temperature of the material.

[0008] The average diameter of the potassium titanate whiskers described is 0.2 - 0.6 microns, and the average length is 10 - 20 microns.

[0009] Preferably, the average diameter of the potassium titanate whiskers is 0.3 - 0.5 microns, and the average length is 12 - 17 microns. The applicant found that by controlling the whisker length and diameter within the preferred range, the whiskers can better break the interface at the weld line position, reduce the distribution of whiskers along the flow direction, and further enhance the interface strength of the weld line.

[0010] Preferably, in the potassium titanate whiskers, the molar ratio of K / Ti is 1:(1.6 - 2.4), and more preferably 1:2.

[0011] The potassium titanate whiskers can be obtained commercially or prepared by conventional methods in the art, such as the sintering method. In one embodiment, the potassium titanate whiskers are self-made by the sintering method. After uniformly mixing titanium dioxide and a potassium source (such as potassium oxide or potassium carbonate, etc.) according to the ratio, heat to 1000 - 1300 °C in a box furnace for sintering for 0.5 - 3 hours. Then slowly cool to room temperature, and then disperse at a humidity of 50 - 100% and a temperature of 50 - 300 °C. Then obtain potassium titanate whiskers with different lengths and diameters through screening.

[0012] The average diameter and average length of the potassium titanate whiskers can be obtained by controlling the sintering time, grinding, and screening.

[0013] The polyamide resin described is selected from semi-aromatic polyamide resins. Preferably, the diacid unit of the semi-aromatic polyamide resin is derived from terephthalic acid, and the diamine unit of the semi-aromatic polyamide resin is derived from an aliphatic diamine with 5 to 12 carbon atoms; more preferably at least one of PA5T, PA6T, and PA10T; preferably PA6T.

[0014] The crystallization temperature of PA5T is: 267 - 283 °C.

[0015] The crystallization temperature of PA6T is: 255 - 271 °C.

[0016] The crystallization temperature of PA10T is: 273 - 290 °C.

[0017] There is no particular limitation on the viscosity of the polyamide resin of the present invention. The polyamide viscosity range that can achieve the purpose of the present invention is 1.8 - 2.7, and the test method is carried out with reference to GB12006.1 - 89. Specifically: measure the relative viscosity ηr of the polyamide with a concentration of 0.25 g / dL in 98% concentrated sulfuric acid at 25 ± 0.01°C.

[0018] Preferably, the weld line improving aid is selected from at least one of 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol and 8-methoxy-2-propionamidotetrahydronaphthalene, and more preferably 8-methoxy-2-propionamidotetrahydronaphthalene.

[0019] To meet the enhanced requirements, 0 - 60 parts of glass fiber can be selected to be added. The average diameter of the retained length of glass fiber in the particles can be 9 - 13 microns, and the average length can be 0.2 - 0.45 mm.

[0020] 0 - 3 parts of processing aids can be selected to be added according to actual needs, and the processing aids are selected from at least one of antioxidants, light stabilizers, and lubricants.

[0021] The preparation method of the polyamide composition of the present invention includes the following steps: according to parts by weight, mix each component evenly, and extrude and pelletize through a twin-screw extruder to obtain the polyamide composition. The rotation speed range of the screw is 200 - 700 revolutions per minute; the highest temperature of the barrel is 15 - 20°C higher than the melting point of the polyamide resin.

[0022] The present invention also relates to an injection molded part with a weld, which is made using the above polyamide composition.

[0023] The average length and average diameter of potassium titanate whiskers are tested by the following method: randomly sample potassium titanate whiskers, then soak the potassium titanate whiskers with deionized water, disperse them using ultrasonic waves, measure the length and diameter of the whiskers through a Leica microscope for the dispersed whiskers, randomly select areas each time, count more than 1000 whiskers, count the normal distribution of the whiskers, and calculate their average length and average diameter.

[0024] In potassium titanate whiskers, the molar ratio of K / Ti is tested by the ICP method to measure the molar ratio of the content of K element and Ti element in potassium titanate whiskers.

[0025] The present invention has the following beneficial effects: By selecting potassium titanate whiskers with a specific molar ratio of K / Ti, and choosing the crystallization temperature of the polyamide resin to be 255 - 290°C, and supplementing with a weld line improving aid, the present invention can significantly improve the weld line strength.

[0026] If the K / Ti value is low, the rigidity of the whiskers increases, making it more difficult for the resin to coat and increasing the anisotropy of the material. When a force is applied along the direction of the whiskers, the strength of the weld line of the material will be insufficient; if the K / Ti value is high, the rigidity of the whiskers is insufficient and it is difficult to play a strengthening role.

[0027] The crystallization temperature of polyamide cannot be too high. If the crystallization temperature is too high, it will cause the weld line interface to cool and solidify earlier, increasing the microscopic surface gap at the interface and making it impossible for the whiskers to play a strengthening role.

[0028] The principle of the weld line improvement additive is to increase the gap between the original polyamide molecular chains through a structure similar to polyamide and by utilizing the principle of amide exchange. While improving the fluidity of the material, it can delay crystallization, increase the bonding strength between the molecular chains at the weld line position of the material, and at the same time increase the polar chain segments, increasing the bonding strength between the molecular chains and the whiskers, further improving the weld line strength. Specific embodiments

[0029] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made. These all belong to the protection scope of the present invention.

[0030] The raw materials used in the examples and comparative examples of the present invention are as follows: PA5T: The crystallization temperature is 276 °C, Vicnyl 7100 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.; PA6T: The crystallization temperature is 265 °C, Vicnyl 500 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.; PA10T: The crystallization temperature is 285 °C, Vicnyl 700 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.; PA10T copolymer A: The crystallization temperature is 245 °C, Vicnyl 68100 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.; PA10T copolymer B: The crystallization temperature is 190 °C, Vicnyl 68200 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.; PA6T copolymer: The crystallization temperature is 300 °C, Vicnyl 3100 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.; Potassium titanate whisker A: The molar ratio of K / Ti is 1:1, the average diameter is 0.4 microns, and the average length is 14.3 microns.

[0031] Potassium titanate whisker B, K / Ti molar ratio 1:2, is obtained by grinding and screening as follows: Potassium titanate whisker B-1: average diameter 0.23 μm, average length 10.2 μm; Potassium titanate whiskers B-2: average diameter 0.31 μm, average length 12.3 μm; Potassium titanate whiskers B-3: average diameter 0.48 μm, average length 17.0 μm; Potassium titanate whisker B-4: average diameter 0.60 μm, average length 19.5 μm; Potassium titanate whiskers C: The molar ratio of K / Ti is 1:3, the average diameter is 0.5 μm, the average length is 15.7 μm, and they are homemade.

[0032] Potassium titanate whiskers D: K / Ti molar ratio 1:0.5, average diameter 0.3 μm, average length 13.5 μm, homemade.

[0033] Potassium titanate whiskers E: The molar ratio of K / Ti is 1:4, the average diameter is 0.4 μm, the average length is 16.2 μm, and they are homemade.

[0034] Titanium dioxide and potassium oxide are mixed evenly according to the ratio, and then heated to 1200℃ in a box furnace for sintering for 2 hours. Then slowly cooled to room temperature, and then dispersed at a humidity of 60-70% and a temperature of 130℃. Potassium titanate whiskers of different lengths and diameters are obtained by screening.

[0035] Potassium titanate whisker F: SIC-TKW-4, Shanghai Institute of Ceramics, Chinese Academy of Sciences, K / Ti molar ratio is 1:2, the average diameter after screening is 0.38 microns, and the average length is 14.1 microns.

[0036] Weld mark improvement agent A: 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol, Disperse Black 9, Shanghai MacLean Biochemical Technology Co., Ltd.; Weld mark improvement additive B: aniline black, melanin, Shanghai MacLean Biochemical Technology Co., Ltd.; Weld mark improvement agent C: 8-methoxy-2-propionamidotetralin, 8-M-PDOT, Shanghai MacLean Biochemical Technology Co., Ltd.; Weld mark improvement agent D: p-toluenesulfonyl semicarbazide, Beijing Bailingwei Technology Co., Ltd.; Weld mark improvement agent E: 2-(benzoylamino)benzoic acid, Shanghai Aladdin Biochemical Technology Co., Ltd.; Weld mark improvement agent F: 3-[acetyl(methyl)amino]propionic acid, Shanghai Bid Pharmaceutical Technology Co., Ltd.; Weld mark improvement agent G: benzoylglycylaminoacetic acid, Beijing Bailingwei Technology Co., Ltd.; Antioxidant: IRGANOX 1098, Beijing Bailingwei Technology Co., Ltd.; Lubricant: polypropylene wax, PP 6102, Klein Specialty Chemical Products Co., Ltd.; Glass fiber: E7CS10-03-568H, China Jushi Co., Ltd.; The preparation method of the polyamide composition of the embodiment and the comparative example comprises the following steps: mixing the components uniformly according to weight parts, extruding and granulating through a twin-screw extruder to obtain the polyamide composition. The speed range of the screw is 200-700 rpm; the maximum temperature of the screw barrel is 15-20° C. higher than the melting point of the polyamide resin.

[0037] Various test methods: (1) Weld line strength: Refer to the tensile strength test method of ISO 527-2 / 1A; the specific test method is: use a specific mold with glue entering at both ends, fix other processes, and adjust the melt temperature of the injection molding machine according to the melting point of the resin. The highest temperature is 15-20℃ higher than the melting point of the polyamide resin. Injection molding standard weld line test mechanical specimen; use the tensile strength test method in ISO527-2 / 1A, the condition is 10mm / min, and test the weld line tensile strength of the material.

[0038] Table 1: Weight parts of each component of polyamide composition of Examples 1-7 and test results Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 PA5T 40 50 60 50 50 PA6T 50 PA10T 50 Potassium titanate whisker A 5 20 40 20 20 Potassium titanate whisker B-1 20 Potassium titanate whisker B-2 20 Weld line improvement aid A 0.6 1.5 3 1.5 1.5 1.5 1.5 Antioxidant 0.3 Lubricant 0.3 0.3 0.3 0.3 0.3 0.3 Glass fiber 10 30 60 30 30 30 30 Weld line strength, MPa 105 122 113 126 118 115 125 It can be seen from Examples 2 / 4 / 5 that PA6T is preferred.

[0039] Table 2: Weight parts of each component of the polyamide composition of Examples 8-14 and test results Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 PA5T 50 50 50 50 50 50 50 Potassium titanate whisker A 20 20 20 20 Potassium titanate whisker B-3 20 Potassium titanate whisker B-4 20 Potassium titanate whisker C 20 Weld line improvement aid A 1.5 1.5 1.5 Weld line improvement aid B 1.5 Weld line improvement aid C 1.5 Weld line improvement aid D 1.5 Weld line improvement aid E 1.5 Lubricant 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Glass fiber 30 30 30 30 30 30 30 Weld line strength, MPa 124 114 119 118 127 112 115 It can be seen from Examples 6-9 that the weld mark strength is higher when the average diameter of the potassium titanate whiskers is preferably 0.3-0.5 microns and the average length is 12-17 microns.

[0040] It can be seen from Examples 2 / 7 / 8 / 10 / 18 that the preferred molar ratio of K / Ti is 1:2.

[0041] Table 3: Weight parts of each component of the polyamide composition of Examples 15-18 and test results Example 15 Example 16 Example 17 Example 18 PA5T 50 50 40 50 Potassium titanate whisker A 20 20 5 Potassium titanate whisker F 20 Weld line improvement aid A 0.6 1.5 Weld line improvement aid F 1.5 Weld line improvement aid G 1.5 Lubricant 0.3 0.3 0.3 Glass fiber 30 30 30 Weld line strength, MPa 114 110 101 123 It can be seen from Examples 2 / 11-16 that the weld mark improving aid is preferably 2,2′-[4-(4-aminophenylazo)phenylimino]diethanol or 8-methoxy-2-propionamide tetralin, and more preferably 8-methoxy-2-propionamide tetralin.

[0042] As can be seen from the above embodiments, the weld line strength of the polyamide composition of the present invention > 95 MPa.

[0043] Table 4: Parts by weight of each component of the polyamide composition of the comparative example and test results Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 PA5T 40 40 40 40 40 PA10T copolymer A 40 PA10T copolymer B 40 PA6T copolymer 40 Potassium titanate whisker A 0 50 5 5 5 5 Potassium titanate whisker D 5 Potassium titanate whisker E 5 Weld line improvement aid A 0.6 0.6 0.6 0.6 0 0.6 0.6 0.6 Weld line strength, MPa 78 84 72 82 91 68 57 84 As can be seen from Comparative Examples 1 / 2, when the molar ratio of K / Ti of potassium titanate whiskers is not within the scope of the present invention, the weld mark strength is low.

[0044] As can be seen from Comparative Examples 3 / 4, when potassium titanate whiskers are not contained or the content is too high, the weld mark strength is low.

[0045] As can be seen from Comparative Example 5, when the weld mark improving aid is not contained, the weld mark strength is low.

[0046] As can be seen from Comparative Examples 6-8, when a semi-aromatic polyamide with a crystallization temperature not within the range of 255-290 °C is selected, the weld line strength is insufficient.

Claims

1. A polyamide composition, characterized in that By weight, it includes the following components: 39-61 parts of polyamide resin; Potassium titanate whiskers 5-40 parts; Weld mark improvement additive 0.6-3 parts; The crystallization temperature of the polyamide resin is 255-290°C; In the potassium titanate whiskers, the molar ratio of K / Ti is 1:(1-3); The weld mark improving agent is selected from at least one of 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol, aniline black, 8-methoxy-2-propionamidotetralin, p-toluenesulfonyl semicarbazide, 2-(benzoylamino)benzoic acid, 3-[acetyl(methyl)amino]propionic acid, and benzoylglycylaminoacetic acid.

2. The polyamide composition according to claim 1, characterized in that The potassium titanate whiskers have an average diameter of 0.2-0.6 microns and an average length of 10-20 microns.

3. The polyamide composition according to claim 2, characterized in that The potassium titanate whiskers have an average diameter of 0.3-0.5 microns and an average length of 12-17 microns.

4. The polyamide composition according to claim 1, characterized in that In the potassium titanate whiskers, the molar ratio of K / Ti is 1:(1.6-2.4).

5. The polyamide composition according to claim 1, characterized in that The polyamide resin is selected from semi-aromatic polyamide resin. Preferably, the diacid unit of the semi-aromatic polyamide resin is derived from terephthalic acid, and the diamine unit of the semi-aromatic polyamide resin is derived from an aliphatic diamine having 5 to 12 carbon atoms; more preferably, it is at least one of PA5T, PA6T, and PA10T; and further preferably, PA6T.

6. The polyamide composition according to claim 1, characterized in that The weld mark improving agent is selected from at least one of 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol and 8-methoxy-2-propionamide tetralin, and more preferably 8-methoxy-2-propionamide tetralin.

7. The polyamide composition according to claim 1, characterized in that By weight, 0-60 parts of glass fiber are also included.

8. The polyamide composition according to claim 1, characterized in that By weight, the invention also includes 0-3 parts of processing aids, wherein the processing aids are selected from at least one of antioxidants and lubricants.

9. The method for preparing the polyamide composition according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: uniformly mixing the components according to weight, and extruding and granulating the components through a twin-screw extruder to obtain a polyamide composition.

10. An injection molded part having a weld, characterized in that: The method is prepared by using the polyamide composition according to any one of claims 1 to 8.