Polyamide composition, preparation method therefor and use thereof

Abstract

Disclosed in the present invention is a polyamide composition, comprising the following components in parts by weight: 39-61 parts of a polyamide resin; 5-40 parts of potassium titanate whiskers; and 0.6-3 parts of a weld-line improving additive. In the potassium titanate whiskers, the molar ratio of K to Ti is 1:(1-3). By selecting the potassium titanate whiskers having a specific molar ratio of K to Ti and selecting the polyamide resin having a crystallization temperature of 255-290°C, and using the weld-line improving additive, the present invention can significantly improve weld-line strength.

Description

A polyamide composition, its preparation method and application Technical Field

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

[0002] High-temperature nylon materials, possessing both the strength and toughness of ordinary nylon and a high heat resistance, are widely used in industries such as electronics, automobiles, and military. However, due to their high melting point and high crystallization temperature, their processing window is narrow. Especially for parts with complex dimensions and structures, injection-molded parts inevitably encounter weld line strength issues. As is well known, the weld line is the location of a structural defect, the weakest point in the part's strength. Therefore, the weld line strength determines the actual service strength of the structural part. Because high-temperature nylon generally has a high crystallization temperature and a narrow processing window, improving the weld line strength of nylon composites at high crystallization temperatures is even more difficult.

[0003] Patent CN114736513B provides a method to improve the weld line strength of PA66 by controlling the glass fiber content and different glass fiber aspect ratios. However, because PA66 material has a 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, which seriously limits the use of the material. Summary of the Invention

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

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

[0006] A polyamide composition, by weight, comprises the following components:

[0007] 39-61 parts of polyamide resin;

[0008] 5-40 parts of potassium titanate whiskers;

[0009] 0.6-3 parts of weld line improving agent;

[0010] The crystallization temperature of the polyamide resin is 255-290℃;

[0011] In the potassium titanate whiskers, the molar ratio of K / Ti is 1:(1-3).

[0012] The weld line improving agent is selected from at least one of 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol, aniline black, 8-methoxy-2-propamidotetrahydronaphthalene, p-toluenesulfonylaminourea, 2-(benzoylamino)benzoic acid, 3-[acetyl(methyl)amino]propionic acid, and benzoylglycylaminoacetic acid.

[0013] In the polyamide composition of the present invention, the polyamide resin accounts for not less than 35 wt% of the total weight.

[0014] The test method for the crystallization temperature of polyamide resin is based on ASTM D3418-2003. A Perkin Elmer Diamond DSC analyzer is used in a nitrogen atmosphere at a flow rate of 40 mL / min. During the test, the temperature is first increased to 340°C at a rate of 10°C / min, held at 340°C for 2 min, and then cooled to 50°C at a rate of 10°C / min. The peak temperature that occurs during the cooling process is the crystallization temperature of the material.

[0015] The potassium titanate whiskers have an average diameter of 0.2-0.6 micrometers and an average length of 10-20 micrometers.

[0016] Preferably, the potassium titanate whiskers have an average diameter of 0.3-0.5 micrometers and an average length of 12-17 micrometers. The applicant has found that by controlling the whisker length and diameter within the preferred range, the whiskers can better break the interface at the weld line location, reduce the distribution of whiskers along the flow direction, and further enhance the strength of the weld line interface.

[0017] Preferably, the molar ratio of K / Ti in the potassium titanate whiskers is 1:(1.6-2.4), and more preferably 1:2.

[0018] Potassium titanate whiskers are commercially available or prepared using conventional methods in the art, such as sintering. In one embodiment, potassium titanate whiskers are prepared in-house using a sintering method. Titanium dioxide and a potassium source (potassium oxide or potassium carbonate, etc.) are mixed uniformly according to a specified ratio, and then sintered in a box furnace at 1000-1300°C for 0.5-3 hours. The mixture is then slowly cooled to room temperature and dispersed at 50-100% humidity and 50-300°C. Finally, potassium titanate whiskers of different lengths and diameters are obtained through sieving.

[0019] The average diameter and average length of potassium titanate whiskers can be obtained by controlling the sintering time, grinding, and screening.

[0020] The polyamide resin 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, it is at least one of PA5T, PA6T, and PA10T; PA6T is preferred.

[0021] The crystallization temperature of PA5T is 267-283℃.

[0022] The crystallization temperature of PA6T is 255-271℃.

[0023] The crystallization temperature of PA10T is 273-290℃.

[0024] This invention does not impose any particular limitation on the viscosity of the polyamide resin. The viscosity range of the polyamide that can achieve the purpose of this invention is 1.8-2.7. The test method refers to GB12006.1-89, specifically: the relative viscosity ηr of polyamide with a concentration of 0.25 g / dL is measured in 98% concentrated sulfuric acid at 25 ± 0.01℃.

[0025] Preferably, the weld line improving agent is selected from at least one of 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol and 8-methoxy-2-propamidotetrahydronaphthalene, more preferably 8-methoxy-2-propamidotetrahydronaphthalene.

[0026] To meet specific requirements, 0-60 parts of glass fiber can be added. The average diameter of the glass fiber retained in the particles can be 9-13 micrometers, and the average length can be 0.2-0.45 mm.

[0027] 0-3 parts of processing aids may be added as needed, wherein the processing aids are selected from at least one of antioxidants, light stabilizers, and lubricants.

[0028] The method for preparing the polyamide composition of the present invention includes the following steps: mixing the components evenly according to parts by weight, and granulating by extrusion through a twin-screw extruder to obtain the polyamide composition. The screw speed range is 200-700 rpm; the maximum temperature of the screw barrel is 15-20°C higher than the melting point of the polyamide resin.

[0029] The present invention also relates to an injection molded part having a weld joint, which is made using the above-described polyamide composition.

[0030] The average length and average diameter of potassium titanate whiskers were tested by the following method: potassium titanate whiskers were randomly sampled, then soaked in deionized water, dispersed by ultrasonication, and the length and diameter of the dispersed whiskers were measured by a Leica microscope. Each time, a random area was selected, and more than 1000 whiskers were counted. The normal distribution of the whiskers was statistically analyzed, and their average length and average diameter were calculated.

[0031] In potassium titanate whiskers, the molar ratio of K / Ti was determined by ICP method, which was used to test the molar ratio of K and Ti elements in the potassium titanate whiskers.

[0032] The present invention has the following beneficial effects:

[0033] This invention significantly improves weld line strength by selecting potassium titanate whiskers with a specific K / Ti molar ratio and choosing a polyamide resin with a crystallization temperature of 255-290℃, and by adding a weld line improvement agent.

[0034] If the K / Ti value is low, the stiffness of the whiskers will increase, making it more difficult for the resin to coat them and increasing the anisotropy of the material. When subjected to a force along the whisker direction, the weld line strength of the material will be insufficient. If the K / Ti value is high, the stiffness of the whiskers will be insufficient, making it difficult to play a reinforcing role.

[0035] The crystallization temperature of polyamide should not be too high. If the crystallization temperature is too high, the interface of the weld line will cool and solidify earlier, the gap between the microscopic surfaces of the interface will increase, and the whiskers will not be able to play a reinforcing role.

[0036] The principle of weld line improvement additives is to increase the gap between the original polyamide molecular chains through a structure similar to polyamide and by utilizing the amide exchange principle. This improves the material's fluidity and delays crystallization, increases the bonding strength between molecular chains at the weld line location, and increases polar segments, thereby increasing the bonding strength between molecular chains and whiskers and further improving the weld line strength. Detailed Implementation

[0037] 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.

[0038] The raw materials used in the embodiments and comparative examples of this invention are as follows:

[0039] PA5T: Crystallization temperature is 276℃, Vicnyl 7100 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.;

[0040] PA6T: Crystallization temperature is 265℃, Vicnyl 500 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.;

[0041] PA10T: Crystallization temperature is 285℃, Vicnyl 700 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.

[0042] PA10T copolymer A: crystallization temperature 245℃, Vicnyl 68100 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.;

[0043] PA10T copolymer B: crystallization temperature is 190℃, Vicnyl 68200 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.;

[0044] PA6T copolymer: crystallization temperature 300℃, Vicnyl 3100 NC003, Zhuhai Wantong Special Engineering Plastics Co., Ltd.;

[0045] The potassium titanate whiskers have a molar ratio of A:K / Ti of 1:1, an average diameter of 0.4 micrometers, and an average length of 14.3 micrometers.

[0046] Potassium titanate whiskers B, with a K / Ti molar ratio of 1:2, were ground and sieved to obtain the following raw material:

[0047] Potassium titanate whiskers B-1: average diameter 0.23 micrometers, average length 10.2 micrometers;

[0048] Potassium titanate whiskers B-2: average diameter 0.31 micrometers, average length 12.3 micrometers;

[0049] Potassium titanate whiskers B-3: average diameter 0.48 μm, average length 17.0 μm;

[0050] Potassium titanate whiskers B-4: average diameter 0.60 micrometers, average length 19.5 micrometers;

[0051] Potassium titanate whiskers with a C:K / Ti molar ratio of 1:3, an average diameter of 0.5 micrometers, and an average length of 15.7 micrometers were prepared in-house.

[0052] Potassium titanate whiskers with a D:K / Ti molar ratio of 1:0.5, an average diameter of 0.3 micrometers, and an average length of 13.5 micrometers were prepared in-house.

[0053] Potassium titanate whiskers with a molar ratio of E:K / Ti of 1:4, an average diameter of 0.4 micrometers, and an average length of 16.2 micrometers were prepared in-house.

[0054] Titanium dioxide and potassium oxide were mixed evenly according to a certain ratio and then sintered in a box furnace at 1200℃ for 2 hours. Afterwards, the mixture was slowly cooled to room temperature and then dispersed at 130℃ with 60-70% humidity. Potassium titanate whiskers of different lengths and diameters were then obtained by sieving.

[0055] Potassium titanate whiskers F: SIC-TKW-4, Shanghai Institute of Ceramics, Chinese Academy of Sciences, with a K / Ti molar ratio of 1:2, have an average diameter of 0.38 micrometers and an average length of 14.1 micrometers after screening.

[0056] Weld line improver A: 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol, Disperse Black 9, Shanghai Maclean Biochemical Technology Co., Ltd.;

[0057] Weld line improvement additive B: Aniline black, melanin, Shanghai Maclean Biochemical Technology Co., Ltd.;

[0058] Weld line improver C: 8-methoxy-2-propamidotetrahydronaphthalene, 8-M-PDOT, Shanghai Maclean Biochemical Technology Co., Ltd.;

[0059] Weld line improving agent D: p-toluenesulfonylaminourea, Beijing Bailingwei Technology Co., Ltd.;

[0060] E: 2-(benzoylamino)benzoic acid, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0061] Weld line improving agent F: 3-[acetyl(methyl)amino]propionic acid, Shanghai Bide Pharmaceutical Technology Co., Ltd.;

[0062] Weld line improver G: Benzoylglycylaminoacetic acid, Beijing Bailingwei Technology Co., Ltd.;

[0063] Antioxidant: IRGANOX 1098, Beijing Bailingwei Technology Co., Ltd.;

[0064] Lubricant: Polypropylene wax, PP 6102, Klein Specialty Chemicals Co., Ltd.;

[0065] Fiberglass: E7CS10-03-568H, China Jushi Co., Ltd.;

[0066] The preparation method of the polyamide compositions in the examples and comparative examples includes the following steps: mixing the components evenly according to parts by weight, and granulating by extrusion through a twin-screw extruder to obtain the polyamide composition. The screw speed range is 200-700 rpm; the maximum temperature of the barrel is 15-20°C higher than the melting point of the polyamide resin.

[0067] Test methods:

[0068] (1) Weld line strength: Refer to the tensile strength test method of ISO 527-2 / 1A; the specific test method is as follows: 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 maximum temperature is 15-20℃ higher than the melting point of polyamide resin. Mechanical test specimens for weld lines in injection molding standards; use the tensile strength test method in ISO 527-2 / 1A, with conditions of 10mm / min, to test the tensile strength of the weld line of the material.

[0069] Table 1: Weight parts of each component and test results of the polyamide compositions in Examples 1-7

[0070] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 PA5T4050605050 PA6T50 PA10T50 Potassium titanate whiskers A520402020 Potassium titanate whiskers B-120 Potassium titanate whiskers B-220 Weld line improving agent A0.61.531.51.51.51.5 Antioxidant 0.3 Lubricant 0.30.30.30.30.30.3 Glass fiber 10306030303030 Weld line strength, MPa 105 122 113 126 118 115 125

[0071] As can be seen from Examples 2 / 4 / 5, PA6T is preferred.

[0072] Table 2: Weight parts of each component and test results of the polyamide compositions in Examples 8-14

[0073] Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 PA5T50505050505050 Potassium titanate whiskers A20202020 Potassium titanate whiskers B-320 Potassium titanate whiskers B-420 Potassium titanate whiskers C20 Weld line improving agent A1.51.51.5 Weld line improving agent B1.5 Weld line improving agent C1.5 Weld line improving agent D1.5 Weld line improving agent E1.5 Lubricant 0.30.30.30.30.30.30.3 Glass fiber 303030303030 Weld line strength, MPa 124 114 119 118 127 112 115

[0074] As can be seen from Examples 6-9, the weld line strength is higher when the average diameter of the potassium titanate whiskers is preferably 0.3-0.5 micrometers and the average length is 12-17 micrometers.

[0075] As can be seen from Examples 2 / 7 / 8 / 10 / 18, the preferred molar ratio of K / Ti is 1:2.

[0076] Table 3: Weight parts of each component and test results of the polyamide compositions in Examples 15-18

[0077] Example 15 Example 16 Example 17 Example 18 PA5T50504050 Potassium titanate whiskers A20205 Potassium titanate whiskers F20 Weld line improving agent A0.61.5 Weld line improving agent F1.5 Weld line improving agent G1.5 Lubricant 0.30.30.3 Glass fiber 303030 Weld line strength, MPa 114110101123

[0078] As can be seen from Examples 2 / 11-16, the weld line improving agent is preferably 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol, 8-methoxy-2-propamidotetrahydronaphthalene, and more preferably 8-methoxy-2-propamidotetrahydronaphthalene.

[0079] As can be seen from the above embodiments, the weld line strength of the polyamide composition of the present invention is >95 MPa.

[0080] Table 4: Weight parts of each component and test results of comparative polyamide compositions

[0081] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 PA5T4040404040PA10T copolymer A 40PA10T copolymer B 40PA6T copolymer 40 Potassium titanate whiskers A 0.505555 Potassium titanate whiskers D5 Potassium titanate whiskers E5 Weld line improving agent A 0.6 0.6 0.6 0.6 0.6 0.6 Weld line strength, MPa 7884728291685784

[0082] As can be seen from Comparative Example 1 / 2, the weld line strength is low when the K / Ti molar ratio of potassium titanate whiskers is not within the range of this invention.

[0083] As can be seen from Comparative Example 3 / 4, the weld line strength is low when potassium titanate whiskers are absent or present in excessive amounts.

[0084] Comparative Example 5 shows that the weld line strength is low when no weld line improvement agent is present.

[0085] As can be seen from Comparative Examples 6-8, the weld line strength is insufficient when semi-aromatic polyamides with crystallization temperatures outside the range of 255-290℃ are selected.

Claims

1. A polyamide composition, characterized in that, By weight, it includes the following components: 39-61 parts of polyamide resin; 5-40 parts of potassium titanate whiskers; 0.6-3 parts of weld line improving agent; The crystallization temperature of the polyamide resin is 255-290℃; In the potassium titanate whiskers, the molar ratio of K / Ti is 1:(1-3). The weld line improving agent is selected from at least one of 2,2'-[4-(4-aminophenylazo)phenylimino]diethanol, aniline black, 8-methoxy-2-propamidotetrahydronaphthalene, p-toluenesulfonylaminourea, 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 micrometers and an average length of 10-20 micrometers.

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

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 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, it is at least one of PA5T, PA6T, and PA10T. Even more preferably, it is PA6T.

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

7. The polyamide composition according to claim 1, characterized in that, It also includes 0-60 parts by weight of glass fiber.

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

9. A method for preparing the polyamide composition according to any one of claims 1-8, characterized in that, The process includes the following steps: mixing the components evenly according to their weight parts, and granulating them by extrusion through a twin-screw extruder to obtain a polyamide composition.

10. An injection molded part having a weld joint, characterized in that, Prepared using the polyamide composition according to any one of claims 1-8.