PBT composition resistant to refrigerant precipitation, preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a polybutylene terephthalate (PBT) composition resistant to refrigerant precipitation, a preparation method therefor, and a use thereof. The PBT composition comprises the following components in parts by weight: 70-85 parts of PBT and 15-25 parts of a core-shell toughening agent, wherein the core-shell toughening agent is a toughening agent with silicone rubber and acrylate rubber as a core and PMMA- or PMMA-grafted GMA as a shell; the average particle size of the core-shell toughening agent is 90-350 nm; and the intrinsic viscosity of the PBT is not higher than 1.2 dL / g; and the content of carboxyl in the PBT is less than or equal to 15 mol / t. The PBT composition provided by the present invention has relatively good refrigerant precipitation resistance and relatively good toughness.

Description

A PBT composition resistant to refrigerant precipitation, and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of engineering plastics, and more particularly to a PBT composition resistant to refrigerant precipitation, a preparation method thereof, and applications thereof. Background Art

[0002] In the compressor industry, more and more manufacturers have begun to gradually replace some metal parts in compressors with engineering plastics, such as air-conditioning compressor coil bobbins, refrigerator compressor mufflers, and spring support pins. Due to the special working environment, very high requirements are placed on the material properties used, such as mechanical properties, high and low temperature resistance, and refrigerant resistance. Since these materials are in direct contact with the refrigerant, poor refrigerant resistance and high precipitate content can lead to blockage of the compressor radiator capillaries. Therefore, these materials generally need to have high refrigerant resistance.

[0003] There is relatively much research on refrigerant-resistant PBT in the prior art, but most of it involves glass fiber-reinforced PBT materials. For example, CN 108117726A discloses a method for adding an inorganic porous adsorbent to the system to adsorb small molecules that may precipitate, thereby reducing the precipitate content and achieving refrigerant resistance. However, this method is not applicable to PBT systems without glass fiber; PBT systems without glass fiber are typically used in spring support pins, which generally require the material to have extremely high toughness. While adding an inorganic porous adsorbent can effectively improve refrigerant resistance, it will affect its toughness and make it unable to meet the requirements. Prior art CN 115260710A provides a refrigerant-resistant PBT composition prepared using AX8900. Although it does not become noticeably turbid when in contact with refrigerants, its refrigerant precipitate content is still over 5%, which cannot meet the requirements.

[0004] Therefore, those skilled in the art need to develop a PBT material with better toughness and refrigerant resistance. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects or shortcomings of the above-mentioned prior art and to provide a PBT composition resistant to refrigerant precipitation, wherein the refrigerant-resistant precipitate content of the PBT composition is less than 1% and the notched impact strength is good.

[0006] Another object of the present invention is to provide a method for preparing the refrigerant precipitation-resistant PBT composition.

[0007] Another object of the present invention is to provide applications of the refrigerant precipitation-resistant PBT composition.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A PBT composition resistant to refrigerant precipitation comprises the following components calculated in parts by weight: 70 to 85 parts of polybutylene terephthalate; 15 to 25 parts of a core-shell toughening agent;

[0010] The core-shell toughening agent has a core of silicone rubber and acrylic rubber and a shell of PMMA or PMMA grafted GMA; the average particle size of the core-shell toughening agent is 90 to 350 nm; the intrinsic viscosity of the polybutylene terephthalate is not higher than 1.2 dL / g; and the terminal carboxyl content in the polybutylene terephthalate is ≤15 mol / t.

[0011] After multiple studies, the inventors of the present invention have found that the intrinsic viscosity and terminal carboxyl content of PBT resin play a key role in the refrigerant resistance of the material. The present invention provides a PBT composition with refrigerant precipitation resistance. The PBT composition can obtain a low content of refrigerant precipitates and good toughness by selecting a specific PBT resin and a toughening agent. Specifically, the selection of a PBT resin with a low terminal carboxyl content has a low content of refrigerant precipitates. The reason may be that the PBT resin has a higher cleanliness. The lower terminal carboxyl content can improve the degree of decomposition during the material processing process. Therefore, the PBT resin has relatively few small molecule polymers and is not easy to precipitate. A higher terminal carboxyl content will accelerate the chain segment breakage during the processing of the PBT resin, thereby producing more small molecules, affecting its refrigerant resistance. In addition, regulating the intrinsic viscosity of the PBT resin can make the PBT composition easier to process, thereby avoiding the problem of molecular chain breakage and the generation of small molecules during processing. The core-shell toughening agent can maintain good toughness under both high and low temperature conditions, and has better refrigerant resistance under the protection of its shell layer. When the particle size is too large, it cannot effectively achieve refrigerant resistance.

[0012] It should be noted that, in the PBT composition of the present invention, the content of polybutylene terephthalate is not less than 70 wt %.

[0013] It should be noted that the composition of the present invention does not contain any resin other than PBT resin, such as polycarbonate (PC). PC resin will undergo an ester exchange reaction with PBT resin, which is more likely to produce small molecules. In addition, PC resin has poor solvent resistance, resulting in poor refrigerant resistance of the composition.

[0014] In the present invention, the terminal carboxyl content of the polybutylene terephthalate is ≤15 mol / t, and specifically can be less than or equal to 1 mol / t, 2 mol / t, 3 mol / t, 4 mol / t, 5 mol / t, 6 mol / t, 7 mol / t, 8 mol / t, 9 mol / t, 10 mol / t, 11 mol / t, 12 mol / t, 13 mol / t, 14 mol / t, 15 mol / t, etc., all of which can achieve the present invention.

[0015] Furthermore, the intrinsic viscosity of the polybutylene terephthalate is measured using a capillary viscometer method in accordance with GB / T 14190-2008.

[0016] In a specific embodiment, the intrinsic viscosity is measured using a solvent of phenol / 1,1,2,2-tetrachloroethane (mass ratio 50:50) at a test temperature of 25°C.

[0017] Furthermore, the intrinsic viscosity of the polybutylene terephthalate is 0.8 to 1.1 dL / g.

[0018] Furthermore, the terminal carboxyl group content is determined by potentiometric titration, as follows:

[0019] Weigh a certain mass of sample, denoted as m, and heat, reflux, and dissolve the sample in 50 mL of a mixed solvent (a 1:1 volume ratio of o-cresol and chloroform) at 120°C. Add 0.5 mL of formaldehyde solution to the dissolved and cooled sample. Slowly add potassium hydroxide-ethanol standard titrant (C(KOH) = 0.035 mol / L) to the solution at room temperature through a liquid addition system. Continuously monitor the changes in the system mV. Determine the titration endpoint based on the volume consumed in the titrant and the corresponding mV value. Record the number of milliliters of potassium hydroxide-ethanol standard titrant consumed, denoted as V.

[0020] The terminal carboxyl content is calculated according to the following formula: X = CV × 10 3 / m;

[0021] Among them, where:

[0022] V is the volume of potassium hydroxide-ethanol standard titration solution consumed by the sample solution, in milliliters (mL);

[0023] C is the concentration of the potassium hydroxide-ethanol standard titration solution, in moles per liter (mol / L);

[0024] m is the mass of the sample, in grams (g);

[0025] X is the terminal carboxyl content, the unit is mole per ton (mol / t).

[0026] The average value of the measured values ​​of two parallel tests represents the test result. The relative error of two tests on the same sample is no more than 10%.

[0027] Furthermore, the refrigerant precipitation-resistant PBT composition comprises the following components calculated in parts by weight: 78 to 82 parts of polybutylene terephthalate; and 18 to 22 parts of a core-shell toughening agent.

[0028] The toughness and refrigerant resistance of the PBT composition can be further balanced by adjusting the amount of PBT resin and the amount of core-shell toughening agent.

[0029] Furthermore, the mass ratio of the polybutylene terephthalate to the core-shell toughening agent is 3.6 to 6.0.

[0030] Furthermore, the core-shell toughening agent can be commercially available or homemade.

[0031] Specifically, the toughening agent of the present invention can be obtained by referring to the synthesis method mentioned in paragraphs 4-35 of the specification of JP2003277450A, and the average particle size can be controlled by adjusting the amount of the emulsifier sodium dodecylbenzenesulfonate used in the synthesis of polyorganosiloxane to 1-50 g / L. The average particle size generally decreases with increasing the amount of emulsifier used.

[0032] It should be noted that the average particle size is defined in JP2003277450A. Specifically, 0.1 mL of latex was diluted with water to a solids concentration of approximately 3%. The particle size distribution was measured using a CHDF2000 particle size distribution analyzer at a flow rate of 1.4 mL / min, a pressure of 2.76 MPa (approximately 4000 psi), and a temperature of 35°C, using a capillary filter element for particle separation and a neutral carrier liquid. The particle size calibration curve was constructed by measuring the particle size at 13 points from 0.02 μm to 1.0 μm using monodisperse polystyrene of known particle size as the standard particle size material.

[0033] The core-shell toughening agent of the present invention has an average particle size of 90 to 350 nm, such as, but not limited to, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, or 350 nm, and specific values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific values ​​included in the range. Further, the average particle size of the core-shell toughening agent is 100 to 200 nm.

[0034] Furthermore, the average particle size of the core-shell toughening agent is 135-145 nm.

[0035] Specifically, when the core-shell toughening agent is a toughening agent with silicone rubber and acrylic rubber as the core and PMMA grafted GMA as the shell, the mass percentage of GMA in the core-shell toughening agent is 0.1-10%.

[0036] Furthermore, the core-shell toughening agent has a melt flow rate of 1 to 30 g / 10 min at 190° C. and a load of 2.16 kg.

[0037] Furthermore, the melt flow rate of the core-shell toughening agent is measured according to ISO 1133-2011. In the present invention, commonly used lubricants can be selected based on existing technologies, such as, but not limited to, one or more of ester lubricants, amide lubricants, polyethylene lubricants, or stearic acid lubricants. Furthermore, the lubricant is an ester lubricant.

[0038] Specifically, the ester lubricant is one or more of lower alcohol esters of fatty acids, higher alcohol esters of fatty acids, polyol esters or polyethylene glycol esters.

[0039] In the present invention, commonly used antioxidants can be selected according to existing technologies, such as but not limited to one or more of phosphite antioxidants, thioether antioxidants, hindered phenol antioxidants or diphenylamine antioxidants.

[0040] Specifically, the phosphite antioxidant is one or more of 2,4-di-tert-butylphenol (Irganox 168), bis(2,6-di-tert-butyl-4-tolyl) pentaerythritol phosphite (PEP-36), 627A or S-9228; the thioether antioxidant is one or more of distearyl thiodipropionate, dilauryl thiodipropionate or pentaerythritol dodecathiopropyl ester; the hindered phenol antioxidant is N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide (Irganox 1098), pentaerythritol tetrakis[1093,5-di-tert-butyl-4-hydroxyphenyl) propionate (Irganox 1010), triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate (Irganox 1010), 259), β-(4-hydroxy-3,5-di-tert-butylphenyl) propionate (Iragno 1076) or spiroglycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] (ADK AO-80) or more; the diphenylamine antioxidant is one of butyl / octyl diphenylamine and dioctyl diphenylamine.

[0041] Furthermore, the antioxidant is a mixture of a thioether antioxidant and a phosphite antioxidant.

[0042] Furthermore, the mass ratio of the thioether antioxidant to the phosphite antioxidant in the antioxidant is 3:1 to 1:3.

[0043] The present invention also provides a method for preparing the above-mentioned refrigerant precipitation-resistant PBT composition, comprising the following steps:

[0044] Polybutylene terephthalate, a core-shell toughening agent, a lubricant and an antioxidant are uniformly mixed, melt-blended and extruded into granules to obtain a PBT composition resistant to refrigerant precipitation.

[0045] Furthermore, the mixing speed is 200 to 400 rpm.

[0046] Furthermore, the mixing time is 2 to 4 minutes.

[0047] Furthermore, the extrusion granulation is carried out in a twin-screw extruder.

[0048] Furthermore, the temperature of zone one of the twin-screw extruder is 200-230°C, the temperature of zone two is 240-260°C, the temperature of zone three is 235-255°C, the temperature of zone four is 235-255°C, the temperature of zone five is 235-255°C, the temperature of zone six is ​​240-260°C, the temperature of zone seven is 240-260°C, the temperature of zone eight is 220-240°C, the temperature of zone nine is 220-240°C, and the temperature of zone ten is 240-260°C. The screw speed of the twin-screw extruder is 200-450 rpm.

[0049] The present invention also protects the use of the above-mentioned refrigerant precipitation-resistant PBT composition in the preparation of materials such as refrigerator muffler spring support pins and air conditioner compressor coil skeletons.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention provides a PBT composition resistant to refrigerant precipitation. The PBT composition improves the refrigerant resistance of the PBT composition by adjusting the viscosity and the content of terminal carboxyl groups of the PBT resin and cooperating with a core-shell toughening agent. The prepared PBT composition has good refrigerant resistance and toughness. Specifically, the notched impact strength is not less than 25 kJ / m 2 , the refrigerant precipitate content is less than 1%. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] FIG1 is a physical picture of the PBT compositions prepared in Example 2 and Comparative Examples 1-2 after mixing with ethanol; from left to right are the PBT composition prepared in Example 2, the PBT composition prepared in Comparative Example 1, and the PBT composition prepared in Comparative Example 2. DETAILED DESCRIPTION

[0053] The present invention will be further described below in conjunction with specific embodiments, but the examples do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the examples of the present invention are conventionally purchased raw materials and reagents.

[0054] The raw materials used in the embodiments and comparative examples of the present invention are:

[0055] Polybutylene terephthalate:

[0056] PBT resin 1: PBT GX122J, intrinsic viscosity 1.05 dL / g, end carboxyl content 6.5 mol / t, purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.

[0057] PBT resin 2: PBT GX112J, intrinsic viscosity 0.85 dL / g, end carboxyl content 7.5 mol / t, purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.

[0058] PBT resin 3: PBT GX121J, intrinsic viscosity 0.98 dL / g, end carboxyl content 5.2 mol / t, purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.

[0059] PBT resin 4: PBT GL236, intrinsic viscosity 1.28 dL / g, end carboxyl content 8.6 mol / t, purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.;

[0060] PBT resin 5: PBT GX 112, intrinsic viscosity 0.82 dL / g, end carboxyl content 20.5 mol / t, purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.;

[0061] The intrinsic viscosity of polybutylene terephthalate was determined according to GB / T 14190-2008; the terminal carboxyl group content was determined according to potentiometric titration.

[0062] Toughening agent:

[0063] Core-shell toughening agent 1: toughening agent S-2200 with silicone rubber and acrylic rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 200 nm, purchased from Mitsubishi Rayon Co., Ltd.

[0064] Core-shell toughening agent 2: toughening agent S-2501 with silicone rubber and acrylic rubber as the core and PMMA as the shell, with an average particle size of 200 nm, purchased from Mitsubishi Rayon Co., Ltd.

[0065] Core-shell toughening agent 3: a toughening agent with silicone rubber and acrylic rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 100 nm, homemade;

[0066] Core-shell toughening agent 4: a toughening agent with silicone rubber and acrylic rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 140 nm, homemade;

[0067] Core-shell toughening agent 5: a toughening agent with silicone rubber and acrylic rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 180 nm, homemade;

[0068] Core-shell toughening agent 6: a toughening agent with silicone rubber and acrylic rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 200 nm, homemade;

[0069] Core-shell toughening agent 7: a toughening agent with silicone rubber and acrylic rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 80 nm, homemade;

[0070] Core-shell toughening agent 8: a toughening agent with silicone rubber and acrylic rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 650 nm, homemade;

[0071] The core-shell toughening agent 8 of the present invention was obtained by referring to Example 1 in JP2003277450A, and its average particle size was 650 nm. By adjusting the amount of emulsifier, a series of core-shell toughening agents 3-7 with different particle sizes were obtained.

[0072] Toughener 9: AX8900, purchased from Arkema;

[0073] Toughening agent 10: ELVALOY AC RESIN 1125, purchased from DuPont; Antioxidant:

[0074] Antioxidant 1: CHINOX 1076, commercially available;

[0075] Antioxidant 2: CYANOX 1790, commercially available;

[0076] Antioxidant 3: a mixture of S-9228 and 412S in a mass ratio of 1:1, wherein S-9228 and 412S are both commercially available;

[0077] Lubricant: ester lubricant, PETS, commercially available; the same lubricant was used in the parallel experiments of Examples 1 to 14 and Comparative Examples 1 to 6.

[0078] Examples 1 to 14 and Comparative Examples 1 to 6

[0079] According to the formula in Tables 1 and 2, a refrigerant-resistant PBT composition was prepared according to the following preparation method:

[0080] PBT resin, toughening agent, antioxidant and lubricant are placed in a high-speed mixer and mixed for 2-4 minutes at a rotation speed of 200-400 rpm; then the mixture is added to a twin-screw extruder for melt blending and extrusion granulation to obtain a PBT composition resistant to refrigerant precipitation; the temperature of zone 1 of the twin-screw extruder is 200-230° C., the temperature of zone 2 is 240-260° C., the temperature of zone 3 is 235-255° C., the temperature of zone 4 is 235-255° C., the temperature of zone 5 is 235-255° C., the temperature of zone 6 is 240-260° C., the temperature of zone 7 is 240-260° C., the temperature of zone 8 is 220-240° C., the temperature of zone 9 is 220-240° C., and the temperature of zone 10 is 240-260° C.; and the screw speed of the twin-screw extruder is 200-450 rpm.

[0081] Table 1 Amount of each component in the refrigerant-resistant PBT composition in Examples 1 to 10 (parts by weight)

[0082] Table 2 Amount of each component in the PBT composition of Examples 11 to 14 and Comparative Examples 1 to 6 (Unit: parts by weight)

[0083] Performance Testing

[0084] 1. Test Method

[0085] The PBT compositions prepared in the above examples and comparative examples were subjected to performance tests:

[0086] (1) Izod notched impact test: The PBT compositions prepared in the above examples and comparative examples were tested according to the ISO-180-2019 standard.

[0087] (2) Refrigerant resistance test: Weigh a certain amount of clean and dry PBT composition, denoted as m1, and place it in a round-bottom flask. Add a certain amount of xylene solvent and heat under reflux for 24 hours for extraction. Filter while hot to remove the solvent. Wash twice with xylene and anhydrous ethanol. Place the resin in an oven at 160°C for 8 hours, then let it cool to room temperature and weigh it, denoted as m2. Calculate the precipitate content according to the formula: (m1-m2) / m1×100%.

[0088] During the refrigerant resistance test, the turbidity of the extraction solvent was observed. Then, during the xylene and anhydrous ethanol washing processes, the turbidity of xylene and anhydrous ethanol was observed. The solvent was considered clear if no turbidity appeared during all the processes. The solvent was considered clear if it appeared clear and transparent; slightly turbid if it appeared slightly whitish; and turbid if it appeared milky white.

[0089] 2. Test results

[0090] The performance test results of the PBT composition prepared by the above method are shown in Table 3.

[0091] Table 3 Performance test results of Examples 1 to 14 and Comparative Examples 1 to 6

[0092] As can be seen from Table 3 and Figure 1, the refrigerant-resistant PBT compositions prepared in the embodiments of the present invention have good toughness and refrigerant-resistant precipitation performance. Specifically, the precipitate content of the refrigerant-resistant PBT compositions prepared in the embodiments is less than 1%, and the solvent is clear during the extraction process, indicating that the refrigerant-resistant PBT compositions prepared in the present invention have good refrigerant resistance and the notched impact strength is not less than 25 kJ / m 2 The notched impact strength of most embodiments is not less than 50 kJ / m 2 .

[0093] It can be seen from Examples 1 to 3 that when the amount of the core-shell toughening agent is further adjusted to 18 to 22 parts, the comprehensive properties of the refrigerant-resistant PBT composition obtained are better, wherein the notched impact strength is not less than 58 kJ / m 2 , the precipitate content is not higher than 0.65%.

[0094] It can be seen from Examples 11 to 14 that when the average particle size of the core-shell toughening agent used is 100 to 180 nm, the comprehensive performance of the refrigerant precipitation-resistant PBT composition obtained is better; the more preferred average particle size is 135 to 145 nm.

[0095] It can be seen from Comparative Examples 1 and 2 that when a conventional toughening agent is used instead of the core-shell toughening agent of the present invention, the resulting PBT composition has better toughness, but its resistance to refrigerant precipitation is significantly poorer, with the precipitate content exceeding 5%. In addition, the ethanol during the washing process appears milky white and turbid, which is significantly worse than that of the embodiment.

[0096] It can be seen from Comparative Example 3 that when the intrinsic viscosity of the PBT resin used is too high, even if the terminal carboxyl group content meets the requirements, the refrigerant resistance of the obtained PBT composition is poor. This may be because the high intrinsic viscosity causes the molecular chain to break during the processing of the PBT composition to produce more small molecules, resulting in poor refrigerant resistance.

[0097] It can be seen from Comparative Examples 4 and 5 that if the average particle size of the toughening agent used is too small or too large, the comprehensive performance of the prepared PBT composition will decrease.

[0098] It can be seen from Comparative Example 6 that when the terminal carboxyl content of the PBT resin used is too high, the comprehensive performance of the prepared PBT composition decreases.

[0099] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A PBT composition resistant to refrigerant precipitation, characterized in that: The invention comprises the following components calculated by weight: 70 to 85 parts of polybutylene terephthalate; 15 to 25 parts of core-shell toughening agent; Among them, the core-shell toughening agent is a toughening agent with silicone rubber and acrylic rubber as the core and PMMA or PMMA grafted GMA as the shell; the average particle size of the core-shell toughening agent is 90-350nm; the intrinsic viscosity of the polybutylene terephthalate is not higher than 1.2dL / g; the terminal carboxyl content in the polybutylene terephthalate is ≤15mol / t.

2. The refrigerant-resistant PBT composition according to claim 1, characterized in that: The invention comprises the following components calculated in parts by weight: 78 to 82 parts of polybutylene terephthalate; and 18 to 22 parts of a core-shell toughening agent.

3. The refrigerant-resistant PBT composition according to claim 1, characterized in that: The intrinsic viscosity of the polybutylene terephthalate is 0.8-1.1 dL / g; the intrinsic viscosity is measured according to the capillary viscometer method in the GB / T 14190-2008 standard.

4. The refrigerant-resistant PBT composition according to claim 1, characterized in that: The average particle size of the core-shell toughening agent is 100-200 nm.

5. The refrigerant-resistant PBT composition according to claim 1, characterized in that: The core-shell toughening agent has a melt flow rate of 1 to 30 g / 10 min at 190° C. and a load of 2.16 kg.

6. The refrigerant precipitation-resistant PBT composition according to claim 1, characterized in that: The PBT composition resistant to refrigerant precipitation further comprises 0.1 to 0.3 parts of an antioxidant and 0.5 to 1 parts of a lubricant.

7. The refrigerant precipitation-resistant PBT composition according to claim 1, characterized in that: The antioxidant is one or more of phosphite antioxidants, thioether antioxidants, hindered phenol antioxidants or diphenylamine antioxidants.

8. The refrigerant precipitation-resistant PBT composition according to claim 7, characterized in that: The antioxidant is a mixture of a thioether antioxidant and a phosphite antioxidant.

9. The method for preparing the refrigerant-resistant PBT composition according to any one of claims 1 to 8, characterized in that: The steps include: Polybutylene terephthalate, a core-shell toughening agent, a lubricant and an antioxidant are uniformly mixed, melt-blended and extruded to obtain a PBT composition resistant to cold medium precipitation.

10. Use of the refrigerant precipitation-resistant PBT composition according to any one of claims 1 to 8 in the preparation of refrigerator muffler spring support pins and air-conditioner compressor coil skeleton materials.

Images