Preparation method of low-viscosity polyether-ether-ketone

Abstract

The invention discloses a preparation method of low-viscosity polyether-ether-ketone, which belongs to the technical field of polymer synthesis, and is characterized by comprising the following steps: under inert atmosphere and high-temperature conditions, carrying out polycondensation reaction on a difluoro monomer and a bisphenol monomer in the presence of alkali carbonate, and before the polycondensation reaction is finished, carrying out condensation polymerization on the difluoro monomer and the bisphenol monomer to obtain the low-viscosity polyether-ether-ketone. Adding a compound containing a p-methylphenyl group as a fluidity modifier to prepare low-viscosity polyether-ether-ketone; according to the invention, the specific p-methylphenyl group-containing compound is introduced into the polymerization reaction, so that the viscosity at a high shear rate is greatly improved on the premise of not sacrificing the melt index of the material, and the processing fluidity is improved.

Description

Technical Field

[0001] This invention relates to a method for synthesizing special engineering plastics in the field of polymer synthesis, specifically a method for preparing low-viscosity polyether ether ketone. Background Technology

[0002] Currently, polyetheretherketone (PEEK) synthesis technology uses diphenyl sulfone as a solvent, 4,4'-difluorobenzophenone and hydroquinone as copolymers, and alkali metal carbonates as salt-forming reactants, polymerizing at high temperatures (above 300°C). The resulting PEEK product has high shear viscosity, making it suitable for injection molding and compression molding applications. However, due to its high viscosity, it is not suitable for extruding sheets or rods or for preparing prepregs.

[0003] However, existing standard polyetheretherketone (PEEK) resins have certain limitations in processing. Traditional PEEK, in the molten state, especially within the molecular weight range suitable for extruding sheets, rods, or preparing continuous fiber prepregs, often exhibits extremely high shear viscosity. This high viscosity leads to the following drawbacks: Drawback 1: High shear viscosity results in a large load on the extruder during processing, causing significant frictional heat generation and easily leading to polymer degradation or surface defects in the finished product. Drawback 2: When preparing carbon fiber / glass fiber prepregs, the high-viscosity resin struggles to fully wet the fiber bundles, resulting in a decrease in the interlaminar shear strength of the composite material.

[0004] While existing technologies exist for preparing low-viscosity oligomers via phenylacetylene end-capping (e.g., CN101759546B), these methods require subsequent high-temperature cross-linking, transforming them into thermosetting materials and losing the advantages of thermoplastic materials, such as recyclability and secondary processing. Low-temperature aqueous phase synthesis methods (e.g., CN116120540A) also exist, which reduce synthesis energy consumption, but they still have limitations in precisely controlling the rheological properties suitable for high-end extrusion processing.

[0005] Therefore, developing a preparation method that maintains the excellent thermoplastic physical properties of polyetheretherketone (PEEK) while exhibiting significantly lower shear viscosity at a specific melt index is an urgent need in the field of high-performance engineering plastics. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing low-viscosity polyether ether ketone.

[0007] The technical solution adopted in this invention is as follows: A method for preparing low-viscosity polyether ether ketone includes the following steps: under an inert atmosphere and high temperature, a difluoro monomer and a bisphenol monomer are subjected to a polycondensation reaction in the presence of an alkali metal carbonate; before the polycondensation reaction is completed, a compound containing a p-methylphenyl group is added as a flow modifier to prepare low-viscosity polyether ether ketone.

[0008] Further settings include: The flowability modifier is p-methylphenylhydroxyacetic acid.

[0009] The alkali metal carbonate is sodium carbonate.

[0010] The temperature of the polycondensation reaction is 220℃~320℃.

[0011] The fluidity modifier is added at a temperature of 260℃ to 320℃, preferably 280℃ to 310℃. Adding it within this temperature range most effectively seals the end groups, disrupts the strong interactions between molecular chains, and provides an "internal lubrication" effect.

[0012] Preferably, the polycondensation reaction is first heated to 220°C and held for 1-2 hours, then heated to 280°C, p-methylphenylhydroxyacetic acid is added, and then the temperature is further increased to 320°C and the reaction is carried out for 1-2 hours. By introducing a specific compound containing a p-methylphenyl group for end-capping in the later stage of the polymerization reaction, the viscosity of the resin at high shear rates can be significantly reduced without sacrificing the molecular weight (melt index) of the material, thereby improving its processing fluidity.

[0013] The low-viscosity polyether ether ketone prepared by this invention has a shear viscosity of 400–480 Pa·s.

[0014] The beneficial effects of this invention are as follows: (1) Rheological property optimization (viscosity-melt index decoupling): Compared with traditional fluorine-terminated or hydroxyl-terminated PEEK, the present invention utilizes the special side group structure of p-methylphenylhydroxyacetic acid, so that the shear viscosity of the polymer is reduced by about 15%-20% at the same melt index (MI).

[0015] (2) Strong processing adaptability: This low shear viscosity characteristic is particularly suitable for the preparation of high-filled composite materials, continuous fiber prepregs, and the extrusion of thick-walled plates / rods. It can significantly improve the resin's wetting speed on the fibers and reduce the torque load on the extruder. Moreover, unlike phenylacetylene-terminated crosslinked PEEK, the product obtained by this invention is still fully thermoplastic and has good toughness and reprocessing ability. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments. Unless otherwise specified, the raw materials and reagents used in the embodiments are all known technologies or commercially available products in the art.

[0017] Example 1

[0018] Add 218.2 g of 4,4'-difluorobenzophenone, 110.1 g of hydroquinone, and 106 g of sodium carbonate to a three-necked flask. Purge with argon gas at a flow rate of 150 ml / min and heat the flask. Once the contents have melted, stir at 60 rpm. When the temperature reaches 220°C, maintain this temperature for 1 hour, then continue heating to 280°C. Add 16.6 g of p-methylphenylhydroxyacetic acid and continue heating to 320°C. React for 1 hour to obtain a viscous polyetheretherketone mixture. While still hot, pour the mixture into an iron pan, cool, and pulverize. Wash five times with ethanol and five times with distilled water, then dry at 150°C for 6 hours to obtain polyetheretherketone.

[0019] Example 2

[0020] 218.2 g of 4,4'-difluorobenzophenone, 110.1 g of hydroquinone, 95.4 g of sodium carbonate, and 13.8 g of potassium carbonate were added to a three-necked flask. Argon gas was introduced at a flow rate of 150 ml / min, and the flask was heated. After the contents of the flask melted, the mixture was stirred at 60 rpm. The temperature was raised to 220°C and maintained at a constant temperature for 1 hour. The temperature was then raised to 290°C, and 16.6 g of p-methylphenylhydroxyacetic acid was added. The temperature was raised to 320°C, and the reaction was carried out for 1 hour to obtain a viscous polyetheretherketone mixture. The mixture was poured into an iron pan while hot, cooled, and pulverized. It was washed 5 times with an appropriate amount of ethanol and 5 times with distilled water, and dried at 150°C for 6 hours to obtain polyetheretherketone.

[0021] Example 3

[0022] 218.2 g of 4,4'-difluorobenzophenone, 110.1 g of hydroquinone, 95.4 g of sodium carbonate, and 13.8 g of potassium carbonate were added to a three-necked flask. Argon gas was introduced at a flow rate of 150 ml / min, and the flask was heated. After the contents of the flask melted, the mixture was stirred at 60 rpm. The temperature was raised to 220°C and maintained at a constant temperature for 1 hour. The temperature was then raised to 300°C, and 16.6 g of p-methylphenylhydroxyacetic acid was added. The temperature was raised to 320°C, and the reaction was carried out for 1 hour to obtain a viscous polyetheretherketone mixture. The mixture was poured into an iron pan while hot, cooled, and pulverized. It was washed 5 times with an appropriate amount of ethanol and 5 times with distilled water, and dried at 150°C for 6 hours to obtain polyetheretherketone.

[0023] Example 4

[0024] 218.2 g of 4,4'-difluorobenzophenone, 110.1 g of hydroquinone, 95.4 g of sodium carbonate, and 13.8 g of potassium carbonate were added to a three-necked flask. Argon gas was introduced at a flow rate of 150 ml / min, and the flask was heated. After the contents of the flask melted, the mixture was stirred at 60 rpm. The temperature was raised to 220°C and maintained at a constant temperature for 1 hour. The temperature was then raised to 310°C, and 16.6 g of p-methylphenylhydroxyacetic acid was added. The temperature was raised to 320°C, and the reaction was carried out for 1 hour to obtain a viscous polyetheretherketone mixture. The mixture was poured into an iron pan while hot, cooled, and then pulverized. It was washed 5 times with an appropriate amount of ethanol and 5 times with distilled water, and dried at 150°C for 6 hours to obtain polyetheretherketone.

[0025] Comparative Example 1 218.2 g of 4,4'-difluorobenzophenone, 110.1 g of hydroquinone, and 106 g of sodium carbonate were added to a three-necked flask. Argon gas was introduced at a flow rate of 150 ml / min, and the flask was heated. After the contents of the flask melted, the mixture was stirred at 60 rpm. The temperature was raised to 220°C and maintained at this temperature for one hour. The temperature was then increased to 320°C and the reaction was continued for one hour to obtain a viscous polyetheretherketone mixture. The mixture was poured into an iron pan while hot, cooled, and then pulverized. It was washed five times with an appropriate amount of ethanol and five times with distilled water, and then dried at 150°C for 6 hours to obtain polyetheretherketone.

[0026] Comparative Example 2 218.2 g of 4,4'-difluorobenzophenone, 110.1 g of hydroquinone, 95.4 g of sodium carbonate, and 13.8 g of potassium carbonate were added to a three-necked flask. Argon gas was introduced at a flow rate of 150 ml / min, and the flask was heated. After the contents of the flask melted, the mixture was stirred at 60 rpm. The temperature was raised to 220°C and maintained at a constant temperature for one hour. The temperature was then further increased to 320°C and the reaction was carried out for one hour to obtain a viscous polyetheretherketone mixture. The mixture was poured into an iron pan while hot, cooled, and then pulverized. It was washed five times with an appropriate amount of ethanol and five times with distilled water, and then dried at 150°C for 6 hours to obtain polyetheretherketone.

[0027] Performance testing The polyether ether ketone products prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to melt index and shear viscosity tests, respectively.

[0028] (1) Melt index test The melt flow rate is tested using a melt flow rate meter, based on the national standard GB / T-3682. The instrument temperature is set to 380℃, the weight mass is 5kg, and the cutting time is set to 60s. The melt flow index is then obtained. Specifically, 5g of polyetheretherketone (PEEK) sample is added to the test cylinder of the melt flow rate meter. After waiting 5 minutes for the PEEK temperature to reach 380℃, the sample is pressed down with the pressure rod, the test weight is placed on top, and the instrument automatically cuts the sample. The cut segment is weighed using a precision balance, the mass is entered into the instrument, and the melt flow index is calculated.

[0029] (2) Shear viscosity test The shear viscosity is tested using a capillary rheometer, according to the national standard GB / T 25278-2010. The instrument temperature is set to 400℃. 10g of polyetheretherketone (PEEK) is added to the instrument barrel, and after waiting for 5 minutes, the instrument is started. The test result is taken as 1000s. -1 The shear viscosity at the specified values.

[0030] The test results are shown in Table 1: Table 1 .

[0031] As shown in Table 1: (1) Referring to Examples 1-4, it can be seen that the temperature at which the end-capping agent is added has a significant impact on the viscosity of the final product. As the temperature at which the end-capping agent is added increases from 280℃ to 300℃, the shear viscosity of the product shows a significant decreasing trend (from 468.4 Pa·s to 407.2 Pa·s), while the melt index remains within the suitable processing range (approximately 9.8-11.7 g / 10min). When the temperature is further increased to 310℃ (Example 4), the viscosity slightly increases. This indicates that 290℃-300℃ is the optimal temperature range for adding p-toluenehydroxyacetic acid, at which point the modifier can most effectively participate in the chain-end reaction and optimize the molecular chain arrangement.

[0032] (2) A comparison of the examples (especially Example 3) with Comparative Examples 1 and 2 shows that: Comparative Examples 1 and 2 represent standard PEEK resins that have not undergone end-capping modification, and their shear viscosity exceeds 500 Pa·s when the melt index is around 10. However, Example 3, with a melt index (9.79 g / 10min) that is close to or even slightly lower than that of the comparative examples, has a shear viscosity (407.2 Pa·s) that is about 100 Pa·s lower than that of the comparative examples (a reduction of about 20%).

[0033] in conclusion: This invention successfully breaks the limitation of the traditional PEEK's "strong coupling between melt index and viscosity" by introducing a p-methylphenylhydroxyacetic acid structure. The resulting polyetheretherketone (PEEK) possesses both good melt strength and superior shear flowability, making it ideal for prepreg preparation processes that require extremely high resin wettability, as well as sheet and rod forming processes that are sensitive to extrusion pressure.

Claims

1. A method for preparing low-viscosity polyetheretherketone, characterized in that: Under inert atmosphere and high temperature conditions, difluorinated monomers and bisphenol monomers undergo a polycondensation reaction in the presence of alkali metal carbonates. Before the polycondensation reaction is completed, a compound containing a p-methylphenyl group is added as a flow modifier to prepare low-viscosity polyether ether ketone.

2. The method for preparing a low-viscosity polyetheretherketone according to claim 1, characterized in that: The flowability modifier is p-methylphenylhydroxyacetic acid.

3. The method for preparing low-viscosity polyetheretherketone according to claim 1, characterized in that: The alkali metal carbonate is sodium carbonate.

4. The method for preparing low-viscosity polyetheretherketone according to claim 1, characterized in that: The temperature of the polycondensation reaction is 220℃~320℃.

5. The method for preparing a low-viscosity polyetheretherketone according to claim 1, characterized in that: The fluidity modifier is added at a temperature of 260℃~320℃.

6. The method for preparing a low-viscosity polyether ether ketone according to claim 5, characterized in that: The fluidity modifier is added at a temperature of 280℃~310℃.

7. The method for preparing low-viscosity polyetheretherketone according to claim 1, characterized in that: The polycondensation reaction is first heated to 220°C and held for 1-2 hours, then heated to 280°C, p-methylphenylhydroxyacetic acid is added, and the temperature is further increased to 320°C for 1-2 hours.

8. The method for preparing low-viscosity polyetheretherketone according to claim 1, characterized in that: The prepared low-viscosity polyether ether ketone has a shear viscosity of 400–480 Pa·s.