A method for preparing a low water absorption PC alloy

Abstract

The application discloses a preparation method of a PC alloy with low water absorption, which comprises the following steps: 1) mixing PC resin, an alkaline silane coupling agent and optional antioxidants and flame retardants, and then feeding the mixture into a main feeding port of an extruder; 2) feeding activated talcum powder into a side feeding port; and 3) performing melting and extrusion at a temperature of 240-260 DEG C to obtain the PC alloy. The activated talcum powder is prepared by high mixing of talcum powder and the alkaline silane coupling agent. The PC alloy prepared by the method has low saturated water absorption and good mechanical properties and thermal properties.

Description

Technical Field

[0001] This invention relates to a method for preparing a PC alloy, and more particularly to a method for preparing a PC alloy with low water absorption. Background Technology

[0002] Polycarbonate (PC) is a widely used engineering plastic with excellent properties. However, due to its high ester bond content, it is highly hygroscopic. The absorbed moisture can react with some of the additives in the PC alloy, leading to performance degradation and ineffectiveness. Furthermore, the high temperatures during injection molding can degrade the PC resin, resulting in defects such as silver streaks and air marks on the product surface. Currently, the industry primarily controls moisture content through pre-processing heat treatment, but this inevitably leads to performance degradation caused by moisture absorption during transportation and storage.

[0003] Currently, there are two main ways to improve the water absorption properties of PC resin at the material level: one is by adding low-absorbency substances to reduce the overall water absorption of the product, such as PC+COC or PC+saturated polyolefin; the other is by improving the structure of PC resin through polymerization to reduce the proportion of ester bonds, such as copolymerization of PC with long-chain diols or copolymerization of PC with sorbitol. These methods not only have limited effect on improving water absorption, but also cause a decline in the performance of PC resin to varying degrees.

[0004] Patent CN106147182B discloses a low-water-absorption, flame-retardant, and scratch-resistant polycarbonate composite material and its preparation method. The addition of 15-30 parts of COC material improves the water absorption rate of the PC alloy to a certain extent. However, this patent does not address the performance and cost impacts of introducing high COC content into the polycarbonate.

[0005] Patent CN107722252B discloses a copolymerized polycarbonate capable of reducing water absorption. This is achieved by introducing aromatic formaldehyde and bimetallic cyanide during the copolymerization process, thereby lowering the water absorption rate of the polycarbonate. This patent synthesizes a new polycarbonate, which differs significantly in structure from commercially available bisphenol A type polycarbonate, making direct application for improvement impossible. Furthermore, this invention places high demands on upstream polymerization processes and equipment, resulting in low feasibility.

[0006] There are currently no reports on improving the water absorption resistance of PC resin through modification techniques without causing a decline in the original resin's properties. Summary of the Invention

[0007] To address the above technical problems, this invention proposes a method for preparing a low-water-absorption PC alloy.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a low-water-absorption PC alloy includes the following steps:

[0010] 1) The PC resin, alkaline silane coupling agent, and optionally antioxidant and flame retardant are mixed and fed into the main feed port of the extruder.

[0011] 2) Add activated talc powder through the side feed inlet;

[0012] 3) The PC alloy is obtained by melting and extruding at a temperature of 240-260℃, followed by cooling and granulation.

[0013] The activated talc powder is prepared by high mixing of talc powder and alkaline silane coupling agent; preferably, the high mixing speed is 100-200 rpm and the mixing time is 30-90 s.

[0014] This invention involves adding PC resin and an alkaline silane coupling agent to the initial stage of an extruder, causing a small amount of PC to undergo acid hydrolysis. Then, activated and modified talc is introduced via side feeding. The acid-hydrolyzed PC blocks react with the amino groups of the activated and modified talc, embedding the talc into the PC resin to produce a PC resin with a special structure. This structure increases the steric hindrance of the original ester bonds, reducing their ability to form hydrogen bonds with water, thereby decreasing water absorption. Simultaneously, because the activated talc is more uniformly dispersed in the PC resin, it forms a layered hydrophobic barrier layer, further reducing water absorption. This significantly lowers the water absorption rate of the PC alloy without affecting the original mechanical and thermal properties of the PC resin.

[0015] As a preferred embodiment, the amounts of each raw material used in the method are as follows, in parts by mass:

[0016] 70-94 parts of PC resin, preferably 75-90 parts.

[0017] 0.05-0.5 parts of basic silane coupling agent, preferably 0.1-0.3 parts.

[0018] Antioxidant 0.1-1 part, preferably 0.2-0.5 parts,

[0019] Flame retardant 0-5 parts, preferably 0.5-2 parts,

[0020] 5-20 parts of activated talc powder, preferably 10-20 parts.

[0021] In a preferred embodiment, the mass ratio of talc to alkaline silane coupling agent in the activated talc is (100-200):1.

[0022] Preferably, a high-speed mixer can be used to mix talc powder and alkaline silane coupling agent.

[0023] As a preferred embodiment, in step 2), activated talc powder is fed into the side feed port of the extruder from the 2nd to 5th section.

[0024] As a preferred embodiment, the screw speed of the extruder is 200-1000 rpm, the vacuum degree of the vacuum device in the metering section of the extruder is controlled to be less than -0.8 bar, and the material is cooled in a cooling water tank at 30-80°C after extrusion.

[0025] Preferably, the extruder is a twin-screw extruder.

[0026] Preferably, in the twin-screw extruder, the temperature of each zone from the main feed port to the die head can be set in segments: 240-250℃ for the main feed port, 245-255℃ for each of the 1st to 4th side feed ports, and 250-260℃ for each of the 5th to 7th side feed ports.

[0027] As a preferred embodiment, the PC resin is a polycarbonate with a melt flow index between 3-40 g / 10 min, preferably between 10-25 g / 10 min, under test conditions of 300°C and a load of 1.2 kg. More preferably, it is one or more of aromatic polycarbonate, aliphatic polycarbonate, and aromatic aliphatic polycarbonate. Bisphenol A type polycarbonate is even more preferred, and one or more of Wanhua Chemical 2070, 2100, 2150, 2220, and 2350 are even more preferred.

[0028] As a preferred embodiment, the alkaline silane coupling agent is one or more of γ-aminopropyltriethoxysilane KH550, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane KH602, and γ-aminoethylaminopropyltrimethoxysilane KH900.

[0029] As a preferred embodiment, the antioxidant is one or more of hindered phenols, benzofurans, acryloyl-modified phenols, and hydroxylamine antioxidants, preferably hindered phenols, and more preferably one or more of Irganox 1076, Irganox 1010, and Irganox 168.

[0030] As a preferred embodiment, the flame retardant is one of sulfonate flame retardants, brominated flame retardants, and silicone flame retardants, preferably sulfonate flame retardants, and more preferably one or more of potassium perfluorobutyl sulfonate (PFBS), potassium benzenesulfonylbenzenesulfonate (KSS), and sodium 2,4,5-trichlorobenzenesulfonate (STB).

[0031] The PC alloy prepared by the method of this invention has a low saturated water absorption rate and good optical, mechanical and thermal properties. Detailed Implementation

[0032] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0033] I. The main sources of raw materials in the examples and comparative examples are shown in Table 1 below:

[0034] Table 1. Raw Material Source Information

[0035]

[0036]

[0037] Unless otherwise specified, all other raw materials and reagents were obtained through commercially available channels.

[0038] II. The performance test parameters and corresponding test methods for the PC alloy in the examples and comparative examples are as follows:

[0039] The processing equipment used was: a twin-screw extruder, KraussMaffei ZE28 x40D BD, with a length-to-diameter ratio of 40 and a screw diameter of 28cm;

[0040] The performance test parameters and corresponding test methods for PC alloy are as follows:

[0041] Equilibrium water absorption rate (%): The extruded PC alloy particles were placed in a constant temperature and humidity room (temperature 23℃, humidity 50%) and left to stand for 24 hours. Then, the equilibrium water absorption rate was tested according to the standard in ISO 62-2001 "Determination of water absorption of plastics".

[0042] Saturated water absorption rate (%): PC alloy particles were immersed in distilled water and left to stand at room temperature for 24 hours. Then, the saturated water absorption rate of the PC alloy particles was determined according to ISO 62-2001 "Determination of water absorption of plastics" to characterize the maximum water absorption rate of the sample under free water absorption conditions.

[0043] Impact strength (MPa): Tested according to ISO 180-2000 "Plastics - Determination of Izod impact strength";

[0044] Flexural strength (MPa): Tested according to ASTM D790-2017, "Standard Test Method for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulators";

[0045] Heat distortion temperature (°C): Tested according to ISO 75 / B "Plastics - Test method for heat distortion temperature";

[0046]

Example 1

[0047] Low water absorption PC alloy was prepared using the following raw materials and formulation:

[0048]

[0049] The activated talc powder was prepared by adding talc powder HM4 and silane coupling agent KH550 to a high-speed mixer at a mass ratio of 100:1 and mixing for 60 seconds at a speed of 200 rpm.

[0050] The specific preparation method of the PC alloy is as follows:

[0051] According to the formula, PC resin 2220, silane coupling agent KH550, antioxidant, and flame retardant are fed into the main feed port of the twin-screw extruder; activated talc powder is fed into the second side feed port of the twin-screw extruder; the vacuum degree of the vacuum device in the metering section of the twin-screw is controlled to be less than 0.08 MPa, the screw speed is 200 rpm, and the screw temperature from the feed port to the die head is set in segments of 240℃, 250℃, 250℃, 250℃, 255℃, 255℃, 255℃, 255℃, for melting, extrusion, cooling, and pelletizing to obtain a low water absorption PC alloy.

[0052]

Example 2

[0053] Low water absorption PC alloy was prepared using the following raw materials and formulation:

[0054]

[0055] The activated talc powder was prepared by adding talc powder 51210L and silane coupling agent KH602 to a high-speed mixer at a mass ratio of 200:1 and mixing for 30 seconds at a speed of 150 rpm.

[0056] The specific preparation method of the PC alloy is as follows:

[0057] According to the formula, PC resin 2150, silane coupling agent KH602, antioxidant, and flame retardant are fed into the main feed port of the twin-screw extruder; activated talc powder is fed into the second side feed port of the twin-screw extruder; the vacuum degree of the vacuum device in the metering section of the twin-screw is controlled to be less than 0.08 MPa, the screw speed is 400 rpm, and the screw temperature from the feed port to the die head is set in segments of 245℃, 255℃, 255℃, 255℃, 260℃, 260℃, 260℃, 260℃, for melting, extrusion, cooling, and pelletizing to obtain a low water absorption PC alloy.

[0058]

Example 3

[0059] Low water absorption PC alloy was prepared using the following raw materials and formulation:

[0060]

[0061]

[0062] The activated talc powder was prepared by adding talc powder 51210L and silane coupling agent KH900 to a high-speed mixer at a mass ratio of 150:1 and mixing for 90 seconds at a speed of 100 rpm.

[0063] The specific preparation method of the PC alloy is as follows:

[0064] According to the formula, PC resin 2405, silane coupling agent KH550, antioxidant, and flame retardant are fed into the main feed port of the twin-screw extruder; activated talc powder is fed into the second side feed port of the twin-screw extruder; the vacuum degree of the vacuum device in the metering section of the twin-screw is controlled to be less than 0.08MPa, the screw speed is 600rpm, and the screw temperature from the feed port to the die head is set in segments of 250℃, 255℃, 255℃, 255℃, 260℃, 260℃, 260℃, 260℃, for melting, extrusion, cooling, and pelletizing to obtain a low water absorption PC alloy.

[0065]

Example 4

[0066] Low water absorption PC alloy was prepared using the following raw materials and formulation:

[0067]

[0068] The activated talc powder was prepared by adding talc powder 51210L and silane coupling agent KH602 in a high-speed mixer at a mass ratio of 100:1 and mixing them at 120 rpm for 50 seconds.

[0069] The specific preparation method of the PC alloy is as follows:

[0070] According to the formula, PC resin 2150, silane coupling agent KH602, antioxidant, and flame retardant are fed into the main feed port of the twin-screw extruder; activated talc powder is fed into the second side feed port of the twin-screw extruder; the vacuum degree of the vacuum device in the metering section of the twin-screw is controlled to be less than 0.08 MPa, the screw speed is 800 rpm, and the screw temperature from the feed port to the die head is set in segments of 240℃, 245℃, 245℃, 245℃, 260℃, 260℃, 260℃, 260℃, for melting, extrusion, cooling, and pelletizing to obtain a low water absorption PC alloy.

[0071]

Example 5

[0072] Low water absorption PC alloy was prepared using the following raw materials and formulation:

[0073]

[0074] The activated talc powder was prepared by adding talc powder 51210L and silane coupling agent KH602 to a high-speed mixer at a mass ratio of 200:1 and mixing at 180 rpm for 40 seconds.

[0075] The specific preparation method of the PC alloy is as follows:

[0076] According to the formula, PC resin 2150, silane coupling agent KH602, antioxidant, and flame retardant are fed into the main feed port of the twin-screw extruder; activated talc powder is fed into the second side feed port of the twin-screw extruder; the vacuum degree of the vacuum device in the metering section of the twin-screw is controlled to be less than 0.08 MPa, the screw speed is 1000 rpm, and the screw temperature from the feed port to the die head is set in segments of 240℃, 245℃, 245℃, 245℃, 250℃, 250℃, 250℃, 250℃, and so on. The mixture is melted, extruded, cooled, and pelletized to obtain a low water absorption PC alloy.

[0077] Comparative Example 1

[0078] PC alloys were prepared using essentially the same raw material formulation and method as in Example 1, except that activated talc powder was fed into the main feed port together with PC resin 2220.

[0079] Comparative Example 2

[0080] PC alloys were prepared using essentially the same raw material formulation and method as in Example 1, except that activated talc was replaced with talc HM4, i.e. no activation treatment was performed.

[0081] Comparative Example 3

[0082] PC alloys were prepared using essentially the same raw material formulation and method as in Example 1, except that the siloxane coupling agent KH550 added to the main feed port was replaced with a phosphate coupling agent.

[0083] The PC alloys obtained in each embodiment and comparative example were injection molded in an injection molding machine. The screw temperature was set to 280°C and the screw speed to 250 rpm. The injection molded specimens were obtained and their performance was evaluated. The relevant properties are shown in Table 2.

[0084] Table 2. Performance Test Results

[0085]

[0086]

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-water-absorption PC alloy, characterized in that, Includes the following steps: 1) The PC resin, basic silane coupling agent, antioxidant and optionally flame retardant are mixed and fed into the main feed port of the extruder; 2) Add activated talc powder through the side feed inlet; 3) The PC alloy is obtained by melting and extruding at a temperature of 240-260℃; The activated talc powder is prepared by high mixing of talc powder and basic silane coupling agent, wherein the mass ratio of talc powder to basic silane coupling agent in the activated talc powder is (100-200):1; the basic silane coupling agent is one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and γ-aminoethylaminopropyltrimethoxysilane; The amounts of each raw material, expressed in parts by weight, are as follows: 70-94 parts of PC resin 0.05-0.5 parts of basic silane coupling agent, Antioxidant 0.1-1 part, 0-5 parts flame retardant 5-20 parts of activated talc.

2. The method for preparing the low water absorption PC alloy according to claim 1, characterized in that, The high-speed mixing of the talc powder and the alkaline silane coupling agent is 100-200 rpm, and the mixing time is 30-90 s.

3. The method for preparing the low water absorption PC alloy according to claim 1, characterized in that, The amounts of each raw material used in the method, expressed in parts by mass, are as follows: 75-90 parts of PC resin, 0.1-0.3 parts of basic silane coupling agent, Antioxidant 0.2-0.5 parts, 0.5-2 parts flame retardant, 10-20 parts of activated talc.

4. The method for preparing the low water absorption PC alloy according to any one of claims 1-3, characterized in that, In step 2), activated talc powder is fed into the extruder from the side feed port of section 2-5.

5. The method for preparing the low water absorption PC alloy according to claim 1, characterized in that, The screw speed of the extruder is 200-1000 rpm.

6. The method for preparing the low water absorption PC alloy according to claim 5, characterized in that, The extruder is a twin-screw extruder.

7. The method for preparing the low water absorption PC alloy according to any one of claims 1-3, characterized in that, The PC resin is a polycarbonate with a melt flow index between 3 and 40 g / 10 min under test conditions of 300°C and a load of 1.2 kg.

8. The method for preparing the low water absorption PC alloy according to claim 7, characterized in that, The PC resin is a polycarbonate with a melt flow index between 10-25 g / 10 min under test conditions of 300°C and a load of 1.2 kg.

9. The method for preparing the low water absorption PC alloy according to claim 7, characterized in that, The PC resin is selected from one or more of aromatic polycarbonate, aliphatic polycarbonate, and aromatic aliphatic polycarbonate.

10. The method for preparing the low water absorption PC alloy according to claim 9, characterized in that, The PC resin is selected from bisphenol A type polycarbonate.

11. The method for preparing the low water absorption PC alloy according to claim 10, characterized in that, The PC resin is selected from one or more of Wanhua Chemical's 2070, 2100, 2150, 2220, and 2350.

12. The method for preparing the low water absorption PC alloy according to any one of claims 1-3, characterized in that, The antioxidant is one or more of hindered phenols, benzofurans, acryloyl-modified phenols, and hydroxylamine antioxidants.

13. The method for preparing the low water absorption PC alloy according to claim 12, characterized in that, The antioxidant is a hindered phenol.

14. The method for preparing the low water absorption PC alloy according to claim 13, characterized in that, The antioxidant is one or more of Irganox1076, Irganox1010, and Irganox168.

15. The method for preparing the low water absorption PC alloy according to any one of claims 1-3, characterized in that, The flame retardant is one of the following: sulfonate flame retardant, bromine flame retardant, or silicon flame retardant.

16. The method for preparing the low water absorption PC alloy according to claim 15, characterized in that, The flame retardant is a sulfonate flame retardant.

17. The method for preparing the low water absorption PC alloy according to claim 16, characterized in that, The flame retardant is one or more of potassium perfluorobutyl sulfonate, potassium benzenesulfonylbenzenesulfonate, and sodium 2,4,5-trichlorobenzenesulfonate.

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