Semi-aromatic polyamide composition as well as preparation method therefor and use thereof

Abstract

A semi-aromatic polyamide composition comprises the following components in parts by weight: 52-75 parts of a semi-aromatic polyamide resin, 25-45 parts of a glass fiber and 0-3 parts of an elastomer. The concentration of a terminal amino group of the semi-aromatic polyamide resin is 100-150 mol / t, and the concentration of a terminal carboxyl group of the semi-aromatic polyamide resin is ≤ 50 mol / t. The average diameter of the glass fiber is 0.1-15 microns. By means of investigation of the concentration of the terminal amino group, the concentration of the terminal carboxyl group and the relative viscosity of the semi-aromatic polyamide, and exploration of the diameter of the glass fiber, the composition achieves remarkably improved hydrolysis resistance.

Description

A semi-aromatic polyamide composition and its preparation method and application Technical Field

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

[0002] Semi-aromatic polyamide resins offer excellent mechanical strength, heat resistance, chemical resistance, wear resistance, self-lubrication, and a low coefficient of friction. They are widely used in electronics, automotive components, furniture, building materials, and fiber applications, and have become one of the most important engineering plastics. However, due to the presence of amide bonds in polyamide materials, hydrolysis can occur in high-temperature and high-humidity environments, leading to performance degradation and a shortened service life. The automotive cooling system is a crucial component of the engine system. Currently, automotive engines generally utilize water-cooled cooling systems. Coolant (typically a 1:1 mixture of ethylene glycol and water, which may also contain additives such as corrosion inhibitors, defoamers, and stabilizers) is forced to circulate via a water pump. The coolant flows through components including the water pump, engine cooling jacket, radiator, thermostat, outlet, and cooling system piping, removing excess heat from the engine and dissipating it to the surrounding environment through the radiator. Water pumps are mostly made of polyamide. However, with the maturity and widespread adoption of turbocharging technology, engine compartment temperatures are rising, placing a greater strain on coolant-damaged components like the water pump impeller and housing, as well as other components with high strength and dimensional requirements. Furthermore, some OEMs currently require polyamide compositions to have a tensile strength of ≥105 MPa after aging in coolant at 135°C for 1000 hours. Therefore, they place certain requirements on the initial tensile strength of semi-aromatic polyamide compositions.

[0003] As engines become smaller, the requirements for coolant resistance will become increasingly stringent. Therefore, for applications in engine cooling systems, it is necessary to develop materials that are resistant to hydrolysis / alcoholysis for a long time in order to meet the increasing demands of customers. Existing technologies mainly achieve improvements in hydrolysis resistance through the following methods:

[0004] CN108587151A discloses an alcoholysis-resistant nylon material for use in automotive cooling systems and its preparation method. The material comprises the following raw materials, by weight: 47-90% nylon; 10-50% alcoholysis-resistant glass fiber; 0.5-2% alcoholysis-resistant additive; and 0-1% lubricant and antioxidant. The invention's technical solution involves reacting multiple active functional groups in a copolymer of ethylene and maleic anhydride with active functional groups on the surface of the glass fiber and the terminal functional groups of the nylon molecular chain, thereby increasing the interfacial bonding between the nylon and glass fiber and effectively improving the composite's alcoholysis resistance.

[0005] CN113773640A discloses a hydrolysis-resistant glass fiber reinforced polyamide composite material, which is prepared by the following components in parts by weight: 30-80 parts of polyamide resin, 0.5-1.0 parts of dispersant, 3-10 parts of toughener, 0.05-0.2 parts of initiator, 0.1-0.2 parts of nucleator, 10-50 parts of modified glass fiber, 0.2-0.4 parts of antioxidant; wherein, modified glass fiber is a glass fiber coated with glycidyl methacrylate (Glycidyl methacylate, GMA) on the outer surface. The invention technical solution uses the glass fiber modified by GMA, which is more conducive to improving the mechanical properties of polyamide composite materials and the mechanical property retention rate after high temperature boiling. At the same time, the addition of GMA can effectively avoid the hydrolysis of amide bonds in polyamide molecular chains, resulting in degradation tendency, ensuring melt strength and mechanical properties.

[0006] It can be seen that the main technical solution of the existing technology is to improve the hydrolysis resistance of the polyamide composition by increasing the bonding strength between the glass fiber and the polyamide resin. This has a certain improvement effect in aliphatic polyamides with poor hydrolysis resistance, such as PA6 and PA66 materials, but the improvement effect is not obvious in semi-aromatic polyamide systems with relatively good water resistance. Summary of the Invention

[0007] The object of the present invention is to provide a semi-aromatic polyamide composition with good hydrolysis resistance and a tensile strength of ≥105 MPa after aging in a coolant at 135° C. for 1000 h.

[0008] The present invention is achieved through the following technical solutions:

[0009] A semi-aromatic polyamide composition comprising the following components in parts by weight:

[0010] 52-75 parts of semi-aromatic polyamide resin;

[0011] 25-45 parts of glass fiber;

[0012] Elastomer 0-3 parts;

[0013] Wherein, the terminal amine group concentration of the semi-aromatic polyamide resin is 100-150 mol / t and the terminal carboxyl group concentration is ≤50 mol / t;

[0014] The average diameter of the glass fiber is 0.1-15 microns;

[0015] The semi-aromatic polyamide resin is selected from at least one of PA6T / 6I, PA6T / 6I / 66, PA6T / M5T, PA5T / 6T, PA9T, PA9T / 66, PA10T, PA10T / 66, PA10T / 10I, PA10T / 1010, PA10T / 1012, and PA12T.

[0016] Preferably, the semi-aromatic polyamide resin has a terminal amine group concentration of 110-130 mol / t and a terminal carboxyl group concentration of 30-40 mol / t.

[0017] The method for testing the concentration of terminal amine groups in the resin matrix of semi-aromatic polyamide composite materials is as follows: titrate the sample's terminal amine content using a fully automatic positional titrator. Add 45 ml of phenol and 3 ml of anhydrous methanol to 0.5 g of the semi-aromatic polyamide resin, heat under reflux to dissolve, filter out insoluble matter, and titrate with a standardized hydrochloric acid solution to determine the terminal amine content. The method for testing the concentration of terminal carboxyl groups in the resin matrix of semi-aromatic polyamide composite materials is as follows: titrate the sample's terminal carboxyl content using a fully automatic positional titrator. Add 50 ml of o-cresol to 0.5 g of the semi-aromatic polyamide resin, heat under reflux to dissolve, filter out insoluble matter, cool to room temperature, quickly add 400 μL of formaldehyde solution, and titrate with a standardized potassium hydroxide ethanol solution to determine the terminal carboxyl content.

[0018] In the present invention, the semi-aromatic polyamide resin is preferably selected from at least one of PA6T / 6I and PA6T / 6I / 66. The preferred semi-aromatic polyamide resin has a higher initial tensile strength.

[0019] The present invention does not limit the relative viscosity of the semi-aromatic polyamide. Generally, the relative viscosity of commercially available semi-aromatic polyamide is 2.2-2.6, preferably 2.4-2.6. The test method is to refer to GB / T 12006.1 Polyamide Viscosity Determination Method, and measure the relative viscosity of the polyamide with a concentration of 0.25 g / dL in 98% concentrated sulfuric acid at 25±0.01°C.

[0020] The semi-aromatic polyamide of the present invention can be a commercially available product or can be prepared in-house. The preparation method comprises the following steps: adding a diamine and a diacid in a certain proportion to a pressure autoclave; then adding a capping agent, a catalyst and deionized water; evacuating the autoclave, filling the autoclave with high-purity nitrogen as a protective gas, heating the autoclave to 210-230° C. within 1-3 hours under stirring, stirring the reaction mixture for 0.5-1.5 hours, and then raising the temperature of the reactants to 230-250° C. under stirring; continuing the reaction at a constant temperature and pressure for 1-3 hours, maintaining the pressure constant by removing formed water, discharging the prepolymer after completion of the reaction, and vacuum drying the prepolymer at 75-85° C. to obtain a prepolymer product; and subjecting the prepolymer product to solid-phase viscosity-enhancing at a vacuum condition of 240-260° C. and 40-60 Pa for 8-12 hours to obtain a polyamide resin.

[0021] The concentration of terminal amino groups and terminal carboxyl groups can be controlled by conventional means such as adjusting the content of the end-capping agent. The end-capping agent can be an amine compound, such as ammonia monohydrate, ethylamine, n-propylamine, n-butylamine, n-pentylamine, n-hexylamine, or benzylamine.

[0022] Preferably, the diameter of the glass fiber is 0.1-8 microns.

[0023] The elastomer is selected from at least one of polyethylene elastomer, polypropylene elastomer, EPDM rubber and ethylene-octene copolymer.

[0024] The addition of 0-2 parts of an auxiliary agent may be selected based on actual needs; the auxiliary agent is selected from at least one of an antioxidant and a lubricant. The lubricant may be sodium montanate, calcium montanate, lithium stearate, calcium stearate, a small molecule amide compound, a polyol, a polyamine, a hyperbranched polymer, or a dendrimer.

[0025] The semi-aromatic polyamide composition of the present invention has a tensile strength retention rate of ≥50%, preferably ≥55%, after 135°C / 1000h coolant aging. The testing method is as follows: an ISO standard tensile specimen is placed in a high-pressure tank containing coolant (ethylene glycol and water mixed in a mass ratio of 1:1) (the specimen is completely immersed in the coolant), and then the high-pressure tank is sealed and placed in an aging oven at 135°C for a high-temperature test for 1000h.

[0026] The preparation method of the semi-aromatic polyamide composition is characterized by comprising the following steps: uniformly mixing the components according to a proportion, and extruding and granulating the components through a twin-screw extruder at a temperature range of 270-330° C. and a rotation speed range of 200-500 rpm to obtain the semi-aromatic polyamide composition.

[0027] The semi-aromatic polyamide composition of the present invention is used for preparing hydrolysis-resistant parts, such as water pumps, water valves, thermostats, engine cooling water jackets, water pipe joints, radiators, etc.

[0028] The present invention has the following beneficial effects

[0029] The present invention achieves significant improvement in hydrolysis resistance by investigating the concentrations of terminal amine groups and terminal carboxyl groups of the semi-aromatic polyamide to achieve acid-base balance in the semi-aromatic polyamide composition, and exploring the diameter of the glass fiber and the relative viscosity of the semi-aromatic polyamide. DETAILED DESCRIPTION

[0030] 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 are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0031] The raw materials used in the present invention come from the following sources:

[0032] PA6T6I-A: terminal amine concentration 103 mol / t, terminal carboxyl concentration 46 mol / t, relative viscosity 2.42, homemade;

[0033] PA6T6I-B: terminal amine concentration 148 mol / t, terminal carboxyl concentration 21 mol / t, relative viscosity 2.40, homemade;

[0034] PA6T6I-C: terminal amine concentration 111 mol / t, terminal carboxyl concentration 37 mol / t, relative viscosity 2.46, homemade;

[0035] PA6T6I-D: terminal amine concentration 130 mol / t, terminal carboxyl concentration 32 mol / t, relative viscosity 2.43, homemade;

[0036] PA6T6I-E: terminal amine concentration 128 mol / t, terminal carboxyl concentration 31 mol / t, relative viscosity 2.56, homemade;

[0037] PA6T6I-F: terminal amine concentration 129 mol / t, terminal carboxyl concentration 30 mol / t, relative viscosity 2.20, homemade;

[0038] PA6T6I-G: terminal amine concentration 86 mol / t, terminal carboxyl concentration 43 mol / t, relative viscosity 2.51, homemade;

[0039] PA6T6I-H: terminal amine concentration 102 mol / t, terminal carboxyl concentration 83 mol / t, relative viscosity 2.59, homemade;

[0040] PA6T6I-I: terminal amine concentration 157 mol / t, terminal carboxyl concentration 55 mol / t, relative viscosity 2.44, homemade;

[0041] PA6T6I-J: terminal amine concentration 107 mol / t, terminal carboxyl concentration 124 mol / t, relative viscosity 2.44, homemade

[0042] PA6T / 6I / 66-1: terminal amine concentration 126 mol / t, terminal carboxyl concentration 36 mol / t, relative viscosity 2.43, homemade;

[0043] PA10T: terminal amine concentration 108 mol / t, terminal carboxyl concentration 43 mol / t, relative viscosity 2.53, homemade;

[0044] PA6T / 6I / 66-2: terminal amine concentration 126 mol / t, terminal carboxyl concentration 107 mol / t, relative viscosity 2.43, homemade;

[0045] PA6T / 6I / 66-3: terminal amine concentration 82 mol / t, terminal carboxyl concentration 93 mol / t, relative viscosity 2.51, homemade;

[0046] PA66: terminal amine concentration 113 mol / t, terminal carboxyl concentration 36 mol / t, relative viscosity 2.58, homemade;

[0047] PA66 / 6T: terminal amine concentration 115 mol / t, terminal carboxyl concentration 39 mol / t, relative viscosity 2.43, homemade;

[0048] Glass fiber A: average diameter of 7 μm, purchased from Jushi Group;

[0049] Glass fiber B: average diameter 10 μm, purchased from Jushi Group;

[0050] Glass fiber C: average diameter 11 μm, purchased from Jushi Group;

[0051] Glass fiber D: average diameter 13 μm, purchased from Jushi Group;

[0052] The above-mentioned glass fibers are all E-type glass fibers.

[0053] Ethylene-octene copolymer: FUSABOND N216, purchased from Dow Chemical.

[0054] EPDM rubber: FUSABOND N416, purchased from Dow Chemical.

[0055] The semi-aromatic polyamide composition of the embodiments and comparative examples was prepared by uniformly mixing the components according to the proportions, and extruding and granulating the components through a twin-screw extruder. The temperatures of the screw zones were set to 110°C-300°C-330°C-320°C-300°C-290°C-280°C-270°C-270°C-280°C-300°C-330°C, and the speed range was 300 rpm to obtain a semi-aromatic polyamide composition.

[0056] Various test methods:

[0057] (1) Tensile strength: The obtained semi-aromatic polyamide resin composition was dehumidified and dried at 120°C for 5 h, heated and melted at a barrel temperature of an injection molding machine of 290-330°C, and injection molded into standard tensile specimens. The tensile properties were tested in accordance with the international standard ISO 527-2-2019. The test conditions were: temperature 23°C, tensile rate 10 mm / min.

[0058] (2) Tensile strength retention after hydrolysis resistance test:

[0059] According to ISO standards, two specimens were injection molded and tested as follows:

[0060] Hydrolysis resistance test 1: ISO standard tensile specimens are placed in a high-pressure tank containing distilled water (the specimens are completely immersed in the coolant), then the high-pressure tank is sealed and placed in an aging oven at 100°C for 168 hours.

[0061] Hydrolysis resistance test 2: ISO standard tensile specimens were placed in a high-pressure tank containing coolant (ethylene glycol and water mixed in a mass ratio of 1:1) (the specimens were completely immersed in the coolant). The high-pressure tank was then sealed and placed in an aging oven at 135°C for 1000 hours.

[0062] After the hydrolysis resistance test, the specimens were removed, their surfaces wiped dry, and placed in a 23°C / 50% RH environment for 24 hours. Tensile properties were then tested according to ISO 527-2-2019, using the following conditions: temperature 23°C, tensile rate 10 mm / min. Tensile strength retention = tensile strength after hydrolysis resistance test / tensile strength before hydrolysis resistance test * 100%. In the table below, retention (1) / retention (2) correspond to hydrolysis resistance test 1 / hydrolysis resistance test 2, respectively.

[0063] Table 1: Content (parts by weight) of each component of the semi-aromatic polyamide composition of Examples 1-7 and test results

[0064] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 PA6T6I-A60 60 60 60 5 27 56 5 Glass fiber A30 Glass fiber B30 25 45 35 Glass fiber C30 Glass fiber D30 Ethylene-octene copolymer 1 1 1 1 1 0 Initial tensile strength, MPa 2 4 6 2 3 5 2 3 2 2 3 2 3 2 5 4 2 4 2 Retention rate (1) % 87.0 84.7 84.0 82.9 84.5 87.0 85.1 Retention rate (2) % 58.1 5 3.6 5 3.4 5 2.9 5 3.6 5 9.1 5 5.0

[0065] It can be seen from Examples 1-4 that the smaller the diameter of the glass fiber, the higher the hydrolysis resistance.

[0066] Table 2: Content (parts by weight) of each component of the semi-aromatic polyamide composition of Examples 8-12 and test results

[0067] Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 PA6T6I-B6060 PA6T6I-C60 PA6T6I-D60 PA6T6I-E60 PA6T6I-F60 PA6T / 6I / 66-160 PA10T60 Glass fiber B 30 30 30 30 30 30 30 Ethylene-octene copolymer 1 1 1 1 1 1 EPDM rubber 1 Initial tensile strength, MPa 20 6 2 3 0 2 1 2 2 6 2 1 8 2 2 0 2 0 2 2 0 Retention rate (1) % 88.39 0.29 1.38 9.38 5.38 6.89 1.68 8.9 Retention rate (2) % 56.26 1.26 2.06 0.15 4.15 6.86 8.85 7.2

[0068] It can be seen from Examples 1 / 8-10 that the semi-aromatic polyamide resin preferably has a terminal amine group concentration of 110-130 mol / t and a terminal carboxyl group concentration of 30-40 mol / t.

[0069] As can be seen from Examples 10-12, the relative viscosity of the semi-aromatic polyamide is preferably 2.4-2.6.

[0070] It can be seen from Examples 13 / 14 that although PA10T has a higher retention rate, PA6T6I and PA6T / 6I / 66 are preferred based on the initial tensile strength value.

[0071] Table 3: Content of each component (parts by weight) and test results of the comparative semi-aromatic polyamide composition

[0072] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 PA6T / 6I-G60 PA6T / 6I-H60 PA6T / 6I-I60 PA6T / 6I-J60 PA6660 PA66 / 6T60 PA6T / 6I / 66-260 PA6T / 6I / 66-360 Glass fiber B 30 30 30 30 30 30 30 Ethylene-octene copolymer 1 1 1 1 1 1 Initial tensile strength, MPa 2 3 8 2 4 2 2 3 7 2 2 3 2 0 8 2 2 6 2 1 8 2 2 0 Retention rate (1) % 79.8 7 0.7 7 2.2 6 8.4 5 5.8 6 2.3 6 5.3 6 9.7 Retention rate (2) % 4 3.3 3 7.8 4 1.7 3 6.2 2 7.9 3 3.6 3 5.1 3 7.4

[0073] It can be seen from Comparative Examples 1-4 / 7-8 that if the end group concentration of PA6T / 6I is not within the range of the present invention, the hydrolysis resistance is poor.

[0074] It can be seen from Comparative Examples 5 / 6 that the technical solution of the present application is insufficient to improve the hydrolysis resistance of aliphatic polyamides such as PA66 and PA66 / 6T or other semi-aromatic polyamides.

Claims

1. A semi-aromatic polyamide composition, characterized in that: By weight, it includes the following components: 52-75 parts of semi-aromatic polyamide resin; Glass fiber 25-45 parts; Elastomer 0-3 parts; Wherein, the terminal amine concentration of the semi-aromatic polyamide resin is 100-150 mol / t, and the terminal carboxyl concentration is ≤50 mol / t; The average diameter of the glass fiber is 0.1-15 microns; The semi-aromatic polyamide resin is selected from at least one of PA6T / 6I, PA6T / 6I / 66, PA6T / M5T, PA5T / 6T, PA9T, PA9T / 66, PA10T, PA10T / 66, PA10T / 10I, PA10T / 1010, PA10T / 1012, and PA12T.

2. The semi-aromatic polyamide composition according to claim 1, characterized in that The terminal amine group concentration of the semi-aromatic polyamide resin is 110-130 mol / t, and the terminal carboxyl group concentration is 30-40 mol / t.

3. The semi-aromatic polyamide composition according to claim 1, characterized in that The semi-aromatic polyamide resin is selected from at least one of PA6T / 6I and PA6T / 6I / 66.

4. The semi-aromatic polyamide composition according to claim 1, characterized in that The relative viscosity of the semi-aromatic polyamide is 2.2-2.6, preferably 2.4-2.

6.

5. The semi-aromatic polyamide composition according to claim 1, characterized in that The diameter of the glass fiber is 0.1-8 microns.

6. The semi-aromatic polyamide composition according to claim 1, characterized in that The elastomer is selected from at least one of polyethylene elastomer, polypropylene elastomer, EPDM rubber and ethylene-octene copolymer.

7. The semi-aromatic polyamide composition according to claim 1, characterized in that By weight, the invention also includes 0-2 parts of auxiliary agents; the auxiliary agents are selected from at least one of antioxidants and lubricants.

8. The semi-aromatic polyamide composition according to any one of claims 1 to 7, characterized in that: The tensile strength retention rate of the semi-aromatic polyamide composition after aging in a cooling liquid at 135°C / 1000h is ≥50%.

9. The method for preparing the semi-aromatic polyamide composition 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 at a temperature range of 270-330 DEG C and a rotation speed range of 200-500 rpm to obtain a semi-aromatic polyamide composition.

10. Use of the semi-aromatic polyamide composition according to any one of claims 1 to 8, characterized in that: The hydrolysis-resistant parts are used for preparing hydrolysis-resistant parts, wherein the hydrolysis-resistant parts are selected from at least one of water pumps, water valves, thermostats, engine cooling water jackets, water pipe joints, and radiators.