A pbt composition resistant to refrigerant separation and its preparation method and application

Abstract

This invention discloses a PBT composition resistant to refrigerant precipitation, its preparation method, and its application. The PBT composition comprises the following components in parts by weight: 70-85 parts of polybutylene terephthalate (PET); 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 the core and PMMA or PMMA-grafted GMA as the shell; the average particle size of the core-shell toughening agent is 90-350 nm; the intrinsic viscosity of the PET is not higher than 1.2 dL / g; and the terminal carboxyl group content of the PET is ≤15 mol / t. The PBT composition provided by this invention exhibits good resistance to refrigerant precipitation and good toughness.

Description

Technical Field

[0001] This invention relates to the field of engineering plastics technology, and more specifically, to a PBT composition resistant to refrigerant precipitation, its preparation method, and its application. Background Technology

[0002] In the compressor industry, an increasing number of manufacturers are gradually replacing some metal components in compressors with engineering plastics, such as the coil frame of air conditioner compressors, and the muffler and spring support pins of refrigerator compressors. Due to the special working environment, the materials used have very high requirements for performance, such as mechanical properties, resistance to high and low temperatures, and refrigerant resistance. Since these materials are in direct contact with the refrigerant, if the material has poor refrigerant resistance and a high content of precipitates, it can lead to blockage of the capillary tubes of the compressor radiator. Therefore, these materials usually need to have high refrigerant resistance.

[0003] Existing technologies have relatively abundant research on refrigerant-resistant PBT, but most studies focus on glass fiber reinforced PBT materials. For example, CN108117726A discloses a method that adds an inorganic porous adsorbent to the system to adsorb potentially precipitated small molecules, thereby reducing the precipitate content and achieving refrigerant resistance. However, this method is not suitable for PBT systems without glass fiber reinforcement. PBT systems without glass fiber reinforcement are typically used in spring support pins, and this material usually requires extremely high toughness. While adding an inorganic porous adsorbent can effectively improve refrigerant resistance, it affects the toughness, making it unable to meet the requirements. Existing technology CN 115260710A provides a refrigerant-resistant PBT composition prepared using AX8900. Although it does not produce significant turbidity upon contact with refrigerant, its refrigerant precipitate content is still above 5%, which fails to meet the requirements.

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

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

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

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

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] A PBT composition resistant to refrigerant precipitation, comprising the following components in parts by weight:

[0010] 70-85 parts of polybutylene terephthalate;

[0011] 15-25 parts of core-shell toughening agent;

[0012] The core-shell toughening agent is a toughening agent with silicone rubber and acrylate rubber as the core and PMMA or PMMA grafted with GMA as the shell; the average particle size of the core-shell toughening agent is 90-350 nm; the intrinsic viscosity of the polybutylene terephthalate is not higher than 1.2 dL / g; and the content of terminal carboxyl groups in the polybutylene terephthalate is ≤15 mol / t.

[0013] Through extensive research, the inventors of this invention have discovered that the intrinsic viscosity and end-carboxyl group content of PBT resin play a crucial role in the material's refrigerant resistance. This invention provides a PBT composition resistant to refrigerant precipitation. By selecting specific PBT resins and toughening agents, this composition achieves low refrigerant precipitate content and good toughness. Specifically, selecting PBT resins with lower end-carboxyl group content results in lower refrigerant precipitate content, possibly due to the higher purity of the PBT resin. Lower end-carboxyl group content improves the degree of decomposition during material processing, thus reducing the amount of small-molecule oligomers in the PBT resin and making precipitation less likely. Higher end-carboxyl group content accelerates chain segment breakage during PBT resin processing, generating more small molecules and affecting its refrigerant resistance. Furthermore, controlling the intrinsic viscosity of the PBT resin facilitates processing, preventing the generation of small-molecule substances due to chain breakage during processing. Core-shell toughening agents maintain good toughness under both high and low temperature conditions, and their shell provides better refrigerant resistance. Excessively large particle sizes fail to provide adequate refrigerant resistance.

[0014] It should be noted that in the PBT composition of the present invention, the content of polybutylene terephthalate is not less than 70 wt%.

[0015] It should be noted that the composition of the present invention does not contain any resins other than PBT resin, such as polycarbonate (PC). PC resin will undergo transesterification reaction with PBT resin, which makes it easier to produce small molecules. In addition, PC resin has poor solvent resistance, which leads to a decrease in the refrigerant resistance of the composition.

[0016] In this invention, the content of the terminal carboxyl group of the polybutylene terephthalate is ≤15mol / t, and can be less than or equal to 1mol / t, 2mol / t, 3mol / t, 4mol / t, 5mol / t, 6mol / t, 7mol / t, 8mol / t, 9mol / t, 10mol / t, 11mol / t, 12mol / t, 13mol / t, 14mol / t, 15mol / t, etc., all of which can achieve the present invention.

[0017] Furthermore, the intrinsic viscosity of the polybutylene terephthalate was determined according to the capillary viscometer method in GB / T 14190-2008 standard.

[0018] In a specific embodiment, the solvent for measuring the intrinsic viscosity is phenol / 1,1,2,2-tetrachloroethane (mass ratio 50:50), and the test temperature is 25°C.

[0019] Furthermore, the intrinsic viscosity of the polybutylene terephthalate is 0.8–1.1 dL / g.

[0020] Furthermore, the content of the terminal carboxyl groups was determined by potentiometric titration, as follows:

[0021] Weigh a certain mass of sample, denoted as m. Dissolve the sample at 120℃ using 50mL of a mixed solvent (a 1:1 mixture of o-cresol and chloroform). Add 0.5mL of formaldehyde solution to the cooled sample. At room temperature, slowly add potassium hydroxide-ethanol standard titration solution (C(KOH)=0.035mol / L) to the solution using a dispensing system. Continuously monitor the changes in mV of the system. Determine the titration endpoint by the volume of titrant consumed and the corresponding mV value. Record the number of milliliters of potassium hydroxide-ethanol standard titration solution consumed, denoted as V.

[0022] The content of terminal carboxyl groups is calculated according to the following formula:

[0023] X = CV × 10 3 / m;

[0024] Wherein:

[0025] V represents the volume of potassium hydroxide-ethanol standard titration solution consumed by the sample solution, in milliliters (mL).

[0026] C represents the concentration of the potassium hydroxide-ethanol standard titration solution, expressed in moles per liter (mol / L).

[0027] m is the mass of the sample, in grams (g);

[0028] X represents the content of terminal carboxyl groups, expressed in moles per ton (mol / t).

[0029] The average value of two parallel tests represents the test result, and the relative error between the two tests on the same sample is no more than 10%.

[0030] Furthermore, the PBT composition resistant to refrigerant precipitation comprises the following components in parts by weight:

[0031] 78-82 parts of polybutylene terephthalate;

[0032] 18-22 parts of core-shell toughening agent.

[0033] By adjusting the amount of PBT resin and the amount of core-shell toughening agent, the toughness and refrigerant resistance of the PBT composition can be further balanced.

[0034] Furthermore, the mass ratio of polybutylene terephthalate to core-shell toughening agent is 3.6 to 6.0.

[0035] Furthermore, the core-shell toughening agent can be commercially available or self-made.

[0036] 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 JP2003277450A, and the average particle size can be controlled by adjusting the amount of sodium dodecylbenzenesulfonate emulsifier used in the synthesis of polyorganosiloxane to 1-50 g / L. The average particle size generally decreases with the increase of emulsifier amount.

[0037] It should be noted that the average particle size is defined according to JP2003277450A, specifically as follows: 0.1 mL of latex is diluted with water to a solids concentration of approximately 3%, and tested using a CHDF2000 particle size 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 cartridge for particle separation and a neutral carrier solution. The particle size calibration curve is 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.

[0038] The core-shell toughening agent described in this invention has an average particle size of 90–350 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, as well as specific values ​​between the above ranges. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range. Further, the average particle size of the core-shell toughening agent is 100–200 nm.

[0039] Furthermore, the core-shell toughening agent has an average particle size of 135–145 nm.

[0040] Specifically, when the core-shell toughening agent is a toughening agent with silicone rubber and acrylate rubber as the core and PMMA grafted with GMA as the shell, the mass percentage of GMA in the core-shell toughening agent is 0.1% to 10%.

[0041] Furthermore, the core-shell toughening agent has a melt flow rate of 1–30 g / 10 min at 190 °C and a load of 2.16 kg.

[0042] Furthermore, the standard for determining the melt flow rate of the core-shell toughening agent is ISO 1133-2011. In this invention, commonly used lubricants can be selected according to existing technology, such as, but not limited to, one or more of ester lubricants, amide lubricants, polyethylene lubricants, or stearic acid lubricants. Further, the lubricant is an ester lubricant.

[0043] Specifically, ester lubricants are one or more of the following: lower alcohol esters of fatty acids, higher alcohol esters of fatty acids, polyol esters, or polyethylene glycol esters.

[0044] In this invention, commonly used antioxidants can be selected according to existing technology, such as, but not limited to, one or more of phosphite antioxidants, thioether antioxidants, hindered phenolic antioxidants, or diphenylamine antioxidants.

[0045] 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 distearate thiodipropionate, dilaurate thiodipropionate, or pentaerythritol-based dodecathiopropyl ester; the hindered phenolic antioxidant is N,Nˋ-hexamethylene bis(3,5-di-tert-butyl-4-hydroxyphenylpropionamide) (Irganox 1098), pentaerythritol tetrakis[1093,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010), or triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate (Iragnox). 259), β-(4-hydroxy-3,5-di-tert-butylphenyl)propionate n-octadecyl ester (Iragno 1076) or spiroethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] (ADK AO-80); the diphenylamine antioxidant is one of butyl / octyl diphenylamine or dioctyl diphenylamine.

[0046] Furthermore, the antioxidant is a mixture of thioether antioxidants and phosphite antioxidants.

[0047] Furthermore, the mass ratio of thioether antioxidants to phosphite antioxidants in the antioxidant is 3:1 to 1:3.

[0048] This invention also protects a method for preparing the above-mentioned PBT composition resistant to refrigerant precipitation, comprising the following steps:

[0049] After uniformly mixing polybutylene terephthalate, core-shell toughening agent, lubricant and antioxidant, a PBT composition resistant to refrigerant precipitation is obtained by melt blending and extrusion granulation.

[0050] Furthermore, the mixing speed is 200-400 rpm.

[0051] Furthermore, the mixing time is 2 to 4 minutes.

[0052] Furthermore, the extrusion granulation is carried out in a twin-screw extruder.

[0053] Furthermore, the temperature of the twin-screw extruder is 200-230℃ in zone 1, 240-260℃ in zone 2, 235-255℃ in zone 3, 235-255℃ in zone 4, 235-255℃ in zone 5, 240-260℃ in zone 6, 240-260℃ in zone 7, 220-240℃ in zone 8, 220-240℃ in zone 9, and 240-260℃ in zone 10. The screw speed of the twin-screw extruder is 200-450 rpm.

[0054] This invention also protects the application of the above-mentioned refrigerant-resistant PBT composition in the preparation of materials such as refrigerator muffler spring support pins and air conditioner compressor coil frames.

[0055] Compared with the prior art, the beneficial effects of the present invention are:

[0056] This invention provides a PBT composition resistant to refrigerant precipitation. The PBT composition improves its refrigerant resistance by adjusting the viscosity of the PBT resin, the content of terminal carboxyl groups, and synergistically using a core-shell toughening agent. The resulting PBT composition exhibits good refrigerant resistance and toughness; specifically, its notched impact strength is not less than 25 kJ / m. 2 The refrigerant leaching content was all below 1%. Attached Figure Description

[0057] Figure 1 The images show the PBT compositions prepared in Examples 2 and Comparative Examples 1-2 after being mixed with ethanol. From left to right, the images show 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 Implementation

[0058] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0059] Raw materials used in the various embodiments and comparative examples of this invention:

[0060] Polybutylene terephthalate:

[0061] PBT resin 1: PBT GX122J, intrinsic viscosity of 1.05 dL / g, end carboxyl group content of 6.5 mol / t, purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.

[0062] PBT resin 2: PBT GX112J, with an intrinsic viscosity of 0.85 dL / g and a terminal carboxyl group content of 7.5 mol / t, was purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.

[0063] PBT resin 3: PBT GX121J, intrinsic viscosity of 0.98 dL / g, end carboxyl group content of 5.2 mol / t, purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.

[0064] PBT resin 4: PBT GL236, intrinsic viscosity of 1.28 dL / g, end carboxyl group content of 8.6 mol / t, purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.

[0065] PBT resin 5: PBT GX 112, with an intrinsic viscosity of 0.82 dL / g and a terminal carboxyl group content of 20.5 mol / t, was purchased from Jiangsu Yizheng Chemical Fiber Co., Ltd.

[0066] The intrinsic viscosity of polybutylene terephthalate was determined according to GB / T 14190-2008 standard; the content of terminal carboxyl groups was determined by potentiometric titration.

[0067] Toughening agent:

[0068] Core-shell toughening agent 1: S-2200, a toughening agent with silicone rubber and acrylate rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 200nm, was purchased from Mitsubishi Rayon Corporation.

[0069] Core-shell toughening agent 2: Toughening agent S-2501 with silicone rubber and acrylate rubber as core and PMMA as shell, with an average particle size of 200nm, purchased from Mitsubishi Rayon Corporation.

[0070] Core-shell toughening agent 3: A toughening agent with silicone rubber and acrylate rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 100nm, self-made;

[0071] Core-shell toughening agent 4: A toughening agent with silicone rubber and acrylate rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 140nm, self-made;

[0072] Core-shell toughening agent 5: A toughening agent with silicone rubber and acrylate rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 180nm, self-made;

[0073] Core-shell toughening agent 6: A toughening agent with silicone rubber and acrylate rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 200nm, self-made;

[0074] Core-shell toughening agent 7: A toughening agent with silicone rubber and acrylate rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 80nm, self-made;

[0075] Core-shell toughening agent 8: A toughening agent with silicone rubber and acrylate rubber as the core and PMMA grafted GMA as the shell, with an average particle size of 650nm, self-made;

[0076] The core-shell toughening agent 8 of the present invention was obtained by referring to Example 1 in JP2003277450A, with an average particle size of 650 nm. By adjusting the amount of emulsifier, a series of core-shell toughening agents 3-7 with different particle sizes were obtained.

[0077] Toughening agent 9: AX8900, purchased from Arkema;

[0078] Toughening agent 10: ELVALOY AC RESIN 1125, purchased from DuPont; Antioxidant:

[0079] Antioxidant 1: CHINOX 1076, commercially available;

[0080] Antioxidant 2: CYANOX 1790, commercially available;

[0081] Antioxidant 3: A mixture of S-9228 and 412S in a 1:1 mass ratio, wherein S-9228 and 412S are commercially available;

[0082] Lubricant: Ester-based lubricant, PETS, commercially available; the same lubricant was used in the parallel experiments of Examples 1-14 and Comparative Examples 1-6.

[0083] Examples 1-14 and Comparative Examples 1-6

[0084] According to the formulations in Tables 1-2, prepare the PBT composition resistant to refrigerant precipitation using the following preparation method:

[0085] PBT resin, toughening agent, antioxidant, and lubricant are mixed in a high-speed mixer for 2-4 minutes at a speed of 200-400 rpm. The mixture is then fed into a twin-screw extruder for melt blending, extrusion granulation, and finally, a PBT composition resistant to refrigerant precipitation is obtained. The temperatures of the twin-screw extruder are as follows: Zone 1: 200-230℃; Zone 2: 240-260℃; Zone 3: 235-255℃; Zone 4: 235-255℃; Zone 5: 235-255℃; Zone 6: 240-260℃; Zone 7: 240-260℃; Zone 8: 220-240℃; Zone 9: 220-240℃; Zone 10: 240-260℃; and the screw speed of the twin-screw extruder is 200-450 rpm.

[0086] Table 1. Amounts (parts by weight) of each component in the PBT compositions resistant to refrigerant precipitation in Examples 1-10.

[0087]

[0088]

[0089] Table 2. Amounts of each component in the PBT compositions of Examples 11-14 and Comparative Examples 1-6 (unit: parts by weight)

[0090]

[0091]

[0092] Performance testing

[0093] 1. Testing Method

[0094] The PBT compositions prepared in the above examples and comparative examples were subjected to performance tests:

[0095] (1) Cantilever beam notched impact test: The PBT compositions prepared in the above examples and comparative examples were tested according to the standard ISO-180-2019.

[0096] (2) Refrigerant resistance test: Weigh a certain amount of clean and dry PBT composition, record it as m1, put it in a round bottom flask, add a certain amount of xylene solvent, heat and reflux for 24 hours for extraction, filter while hot to remove solvent, wash twice with xylene and anhydrous ethanol, place the resin in an oven at 160℃ for 8 hours, then dry it to room temperature and weigh it, record it as m2, and calculate according to the content of precipitate = (m1-m2) / m1×100%;

[0097] During the refrigerant resistance test, the turbidity of the extraction solvent was observed. Then, during the washing process with xylene and anhydrous ethanol, the turbidity of xylene and anhydrous ethanol was observed. The solvent was considered clear only if no turbidity appeared in any of the processes. Specifically, the solvent was considered clear if it was clear and transparent; slightly whitish if it was slightly turbid; and milky white if it was turbid.

[0098] 2. Test Results

[0099] The performance test results of the PBT composition prepared by the above method are shown in Table 3.

[0100] Table 3 Performance test results of Examples 1-14 and Comparative Examples 1-6

[0101]

[0102] From Table 3 and Figure 1As can be seen from the examples, the PBT compositions resistant to refrigerant precipitation prepared in the embodiments of the present invention have good toughness and resistance to refrigerant precipitation. Specifically, the content of precipitates in the PBT compositions resistant to refrigerant precipitation prepared in the embodiments is less than 1%, and the solvent is clearly visible during the extraction process, indicating that the PBT compositions resistant to refrigerant precipitation prepared in the present invention have good refrigerant resistance, and the notched impact strength is not less than 25 kJ / m. 2 In most embodiments, the notched impact strength is not less than 50 kJ / m. 2 .

[0103] As can be seen from Examples 1-3, when the amount of core-shell toughening agent is further adjusted to 18-22 parts, the overall performance of the PBT composition resistant to refrigerant precipitation is better, wherein the notched impact strength is not less than 58 kJ / m. 2 The content of precipitates is not higher than 0.65%.

[0104] As can be seen from Examples 11 to 14, when the average particle size of the core-shell toughening agent used is 100 to 180 nm, the overall performance of the PBT composition resistant to refrigerant precipitation is better; more preferably, the average particle size is 135 to 145 nm.

[0105] As can be seen from Comparative Examples 1 and 2, when a common toughening agent is used to replace the core-shell toughening agent in this invention, the resulting PBT composition has better toughness, but its resistance to refrigerant precipitation is significantly worse, with the content of precipitates exceeding 5%, and the ethanol appears milky white and turbid during washing, which is significantly worse than in the examples.

[0106] As can be seen from Comparative Example 3, when the intrinsic viscosity of the PBT resin used is too high, even if the end carboxyl group content meets the requirements, the refrigerant resistance of the prepared 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, resulting in more small molecules and thus poor refrigerant resistance.

[0107] As can be seen from Comparative Examples 4 and 5, the overall performance of the PBT composition decreases when the average particle size of the toughening agent used is too small or too large.

[0108] As can be seen from Comparative Example 6, when the content of terminal carboxyl groups in the PBT resin used is too high, the overall performance of the PBT composition decreases.

[0109] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should 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, Includes the following components, calculated in parts by weight: 70-85 parts of polybutylene terephthalate; 18-22 parts of core-shell toughening agent; Antioxidant 0.1~0.3 parts; The core-shell toughening agent is a toughening agent with silicone rubber and acrylate rubber as the core and PMMA or PMMA-grafted GMA as the shell; the intrinsic viscosity of the polybutylene terephthalate is 0.8-1.1 dL / g, and the intrinsic viscosity is determined according to the capillary viscometer method in GB / T 14190-2008 standard; the terminal carboxyl group content of the polybutylene terephthalate is ≤15mol / t; the antioxidant is a mixture of thioether antioxidants and phosphite antioxidants; the average particle size of the core-shell toughening agent is 100-180nm.

2. The PBT composition resistant to refrigerant precipitation according to claim 1, characterized in that, Includes the following components, calculated in parts by weight: 78-82 parts of polybutylene terephthalate.

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

4. The PBT composition resistant to refrigerant precipitation according to claim 1, characterized in that, The PBT composition resistant to refrigerant precipitation also includes 0.5 to 1 part lubricant.

5. The method for preparing the PBT composition resistant to refrigerant precipitation according to any one of claims 1 to 4, characterized in that, Includes the following steps: After the components are mixed evenly, the PBT composition with refrigerant precipitation is obtained by melt blending and extrusion granulation.

6. The application of the refrigerant-resistant PBT composition according to any one of claims 1 to 4 in the preparation of refrigerator muffler spring support pins and air conditioner compressor coil skeleton materials.

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