Method for continuously and efficiently preparing polyether-ether-ketone

Abstract

The invention belongs to the technical field of polymer chemical production, and discloses a method for continuously and efficiently preparing polyether-ether-ketone. The method comprises the following steps: dissolving 4, 4 '-difluorobenzophenone and diphenyl sulfone in a first dissolving tank to obtain a 4, 4'-difluorobenzophenone solution; hydroquinone, a catalyst and diphenyl sulfone are placed in a second dissolving tank to be dissolved, and a hydroquinone solution is obtained; the preparation method comprises the following steps: injecting a 4, 4 '-difluorobenzophenone solution and a hydroquinone solution into a reactor for polymerization reaction to obtain a mixed solution; injecting the mixed solution into a separator through a heat exchanger for separation to obtain polyether-ether-ketone and liquid; distilling the liquid to obtain diphenyl sulfone and sodium fluoride, and returning the obtained diphenyl sulfone to participate in dissolution; all the steps are carried out in a protective atmosphere. The preparation process provided by the invention is a brand new PEEK production process flow, and realizes continuous PEEK production and efficient energy recycling.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical production of polyether ether ketone, and particularly relates to a method for continuously and efficiently preparing polyether ether ketone. BACKGROUND

[0002] Polyether ether ketone (PEEK) is a high polymer composed of repeating units containing a ketone bond and two ether bonds in the main chain structure, belongs to a special polymer material, has physical and chemical properties such as high temperature resistance and chemical corrosion resistance, and is a semi-crystalline polymer material, which can be used as a high-temperature structural material and an electrical insulating material, and can be compounded with glass fibers or carbon fibers to prepare reinforced materials. A kind of polyaromatic ether high polymer is generally obtained by condensation with aromatic dihydric phenol. This material has a large number of applications in the fields of aerospace, medical devices (as artificial bone to repair bone defects) and industry. The tensile strength of PEEK material can reach 90 MPa, which is more than twice that of aluminum alloy and more than three times that of steel. PEEK can replace aviation metals, and under the same conditions, PEEK pipe material can reduce weight by 65% compared with stainless steel pipe material, 45% compared with titanium alloy pipe material, and 30% compared with aluminum alloy pipe material, which can greatly improve the fuel efficiency and reliability of the aircraft. This makes PEEK widely used in occasions that need to bear high strength, such as aerospace, automobiles, rail transit and humanoid robots. PEEK material also has excellent fatigue resistance and can work for a long time under repeated load, so it also has wide application in high-strength fields such as mechanical structures, bearings and gears. Therefore, PEEK material is also known as an engineering plastic without defects.

[0003] There are mainly two synthesis routes for PEEK: electrophilic substitution and nucleophilic substitution.

[0004] The electrophilic substitution route prepares PEEK through low-temperature reaction of diphenyl ether and isophthaloyl chloride. The advantages of this route are mild conditions, easy availability of raw materials, but it has the disadvantages of relatively low purity of synthesized PEEK, large amount of catalyst and solvent, and environmental unfriendliness, etc., so the nucleophilic substitution route is generally used at present.

[0005] The nucleophilic substitution route uses 4,4'-difluorobenzophenone and p-benzene diol as raw materials, sodium carbonate as catalyst, and diphenyl sulfone (DPS) as solvent to carry out polycondensation reaction at 280-340℃ to obtain PEEK resin. This process discards the use of metal-based catalysts and does not rely on stabilizers and additives, has the advantages of easy control of side reactions and high purity of PEEK powder. However, this process has the disadvantages of harsh reaction conditions, complex synthesis process and high cost.

[0006] The polymerization process of PEEK is the core process in production, which needs to be reacted for a long time in a high temperature environment. The raw materials need to be continuously reacted for 8-12 hours at a temperature of 280-340 DEG C. In this process, it is difficult to ensure that the material does not degrade and crosslink excessively. Because once degradation or crosslinking occurs, it will seriously affect the performance and quality of the product. In addition, the polymerization reaction has a high requirement for precision control. The reaction conditions between each kettle need to be kept highly consistent to ensure that the performance of each batch of products is the same. For this purpose, the patent CN107573500A provides a preparation method of high-purity polyether ether ketone resin, which uses 4,4'-difluorobenzophenone and hydroquinone as raw materials, diphenyl sulfone as a solvent, K2CO3 and Na2CO3 as catalysts to prepare polyether ether ketone. However, the preparation method described in the patent has the problems of long production time and low production efficiency.

[0007] Therefore, it is of great significance to research a PEEK production process that can efficiently recover energy, has low cost, short production time and can be continuously produced under the premise of ensuring product quality. SUMMARY

[0008] Therefore, the present application provides a method for continuously and efficiently preparing polyether ether ketone, which aims to solve the technical problems that the existing preparation process of polyether ether ketone cannot simultaneously consider product quality and cost reduction.

[0009] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0010] The present application provides a method for continuously and efficiently preparing polyether ether ketone, which comprises the following steps:

[0011] 1) mixing 4,4'-difluorobenzophenone and diphenyl sulfone to obtain a 4,4'-difluorobenzophenone solution;

[0012] 2) mixing hydroquinone, a catalyst and diphenyl sulfone to obtain a hydroquinone solution;

[0013] 3) injecting the 4,4'-difluorobenzophenone solution and the hydroquinone solution into a reactor for polymerization reaction to obtain a mixed solution;

[0014] 4) injecting the mixed solution through a heat exchanger into a separator for separation to obtain polyether ether ketone solids and liquid;

[0015] 5) distilling the liquid to obtain diphenyl sulfone and sodium fluoride, and the obtained diphenyl sulfone is returned to step 1) and step 2) for dissolution;

[0016] The above steps are all carried out in a protective atmosphere.

[0017] Preferably, in the step 1), the mass ratio of 4,4'-difluorobenzophenone to diphenyl sulfone is 1:1.8-5.

[0018] Preferably, in the step 2), the molar ratio of hydroquinone to catalyst is 1:1-1.1.

[0019] The mass ratio of hydroquinone to diphenyl sulfone is 1:3.7-10.

[0020] Preferably, in the step 2), the catalyst is sodium carbonate or potassium carbonate.

[0021] Preferably, in the step 1) and step 2), the temperature of mixing is independently 200-250 DEG C, and the mixing time is independently 60-120 min.

[0022] Preferably, in the step 3), the molar ratio of 4,4'-difluorobenzophenone to hydroquinone is 1:1-1.1.

[0023] The temperature of polymerization reaction is 300-340 DEG C, the time of polymerization reaction is 3-6 h, and the pressure of polymerization reaction is 0.1-1 MPa.

[0024] Preferably, in the step 3), the reactor is externally provided with a heat preservation layer and internally provided with a cooling device.

[0025] Preferably, in the step 4), the temperature of the solution after the heat exchanger is 130-150 DEG C.

[0026] Preferably, in the step 5), the distillation is fractional distillation.

[0027] Preferably, the protective atmosphere is nitrogen, carbon dioxide, argon or helium, etc.

[0028] According to the technical solution, compared with the prior art, the application has the following beneficial effects:

[0029] The preparation process is a new PEEK production process, which realizes the continuous and automatic production of PEEK and improves the production efficiency of the system.

[0030] Compared with the traditional process, the production efficiency is greatly improved, the time, cost and energy consumption in the production process of PEEK are greatly reduced, the energy efficient recycling is realized under the premise of ensuring product quality, and the production cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only belong to the embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of the provided drawings.

[0032] Figure 1 A flowchart for continuously and efficiently preparing polyether ether ketone;

[0033] Figure 2 A flowchart for the application shown in Example 2 for super large production. DETAILED DESCRIPTION

[0034] The present application provides a method for continuously and efficiently preparing polyether ether ketone, comprising the following steps:

[0035] 1) mixing 4,4'-difluorobenzophenone and diphenyl sulfone to obtain a 4,4'-difluorobenzophenone solution;

[0036] 2) mixing hydroquinone, a catalyst and diphenyl sulfone to obtain a hydroquinone solution;

[0037] 3) injecting the 4,4'-difluorobenzophenone solution and the hydroquinone solution into a reactor for polymerization reaction to obtain a mixed solution;

[0038] 4) injecting the mixed solution through a heat exchanger into a separator for separation to obtain polyether ether ketone solids and liquid;

[0039] 5) distilling the liquid to obtain diphenyl sulfone and sodium fluoride, and the obtained diphenyl sulfone is returned to step 1) and step 2) for dissolution;

[0040] The above steps are all carried out in a protective atmosphere.

[0041] In the present application, in step 1), the mass ratio of 4,4'-difluorobenzophenone to diphenyl sulfone is preferably 1:1.8-5, further preferably 1:2-4, and more preferably 1:3-3.6.

[0042] In the present application, in step 2), the molar ratio of hydroquinone to catalyst is preferably 1:1-1.1, further preferably 1:1.02-1.08, and more preferably 1:1.04-1.06.

[0043] The mass ratio of hydroquinone to diphenyl sulfone is preferably 1:3.7-10, further preferably 1:5-9, and more preferably 1:6-8.

[0044] In the present application, in step 2), the catalyst is preferably sodium carbonate or potassium carbonate.

[0045] In the present application, the temperature of mixing in step 1) and step 2) is independently preferably 200-250℃, further preferably 210-240℃, more preferably 220-230℃, and the mixing time is independently preferably 60-120min, further preferably 70-110min, more preferably 90-100min.

[0046] In the present application, the mixing in step 1) and step 2) is preferably carried out in a dissolving tank.

[0047] In the present application, the molar ratio of 4,4'-difluorobenzophenone to hydroquinone in step 3) is preferably 1:1-1.1, further preferably 1:1.02-1.08, more preferably 1:1.04-1.06;

[0048] The temperature of the polymerization reaction is preferably 300-340℃, further preferably 310-330℃, more preferably 320-325℃, the time of the polymerization reaction is preferably 3-6h, further preferably 4-5.5h, more preferably 4.5-5h, and the pressure of the polymerization reaction is preferably 0.1-1.0MPa, further preferably 0.5-0.8MPa, more preferably 0.6-0.7MPa.

[0049] In the present application, the reactor in step 3) is preferably provided with a heat insulation layer on the outside and a cooling device in the inside.

[0050] In the present application, the cooling device is preferably a water-cooled wall or a cooling jacket; the cooling device functions to control the heat release of the reaction.

[0051] In the present application, the number of reactors is preferably ≥1, further preferably ≥2, more preferably ≥3; the number of heat exchangers is the same as the number of reactors.

[0052] In the present application, the temperature of the solution after passing through the heat exchanger in step 4) is preferably 130-150℃, further preferably 131-140℃, more preferably 133-135℃.

[0053] In the present application, the mixed solution in step 4) is injected into the separator through the heat exchanger via the reactor bottom valve and the downcomer. The solvent (water or methanol) at 50℃ is pre-placed in the separator, and the mixed solution is rapidly cooled under stirring to promote the precipitation of PEEK. The solid PEEK is solidified and settled at the bottom of the separator, which is the solid obtained after separation, and the remaining liquid is the liquid in step 4).

[0054] The volume ratio of the mixed solution to the solvent is preferably 1:3-5, further preferably 1:3.5-4.5, and more preferably 1:4-4.2; and the precipitation time under stirring is preferably 30-60 min, further preferably 35-55 min, and more preferably 40-50 min.

[0055] In the present application, in step 4), the obtained solid is preferably washed, screened and purified after separation;

[0056] The obtained solid after separation comprises polyether ether ketone, sodium fluoride (NaF) and diphenyl sulfone;

[0057] The washing is based on the characteristics that NaF is soluble in water but PEEK is not, and the solid after separation is crushed into a powder with a particle size of <1 mm to increase the contact volume, and then washed with water for multiple times to dissolve NaF; the number of washing is preferably 3-6 times, further preferably 4-5 times, the temperature of washing is preferably 50-98℃, further preferably 70-95℃, and more preferably 85-90℃; wherein the solubility of NaF in water at 25℃ is 4 g / 100 mL, and the temperature of washing is preferably 50-98℃ to increase the solubility;

[0058] The screening is preferably centrifugation or pressure filtration; the centrifugation is preferably a horizontal screw centrifuge, the rotation speed of centrifugation is preferably 1500-2000 rpm, further preferably 1600-1900 rpm, and more preferably 1700-1800 rpm, and the centrifugation time is preferably 3-5 min, further preferably 4 min;

[0059] The purification is preferably evaporation crystallization.

[0060] In the present application, in step 5), the distillation is preferably fractional distillation;

[0061] The steps of the fractional distillation are preferably as follows: first, primary distillation is performed to evaporate the solvent, then secondary distillation is performed to evaporate DPS, and the remaining liquid is sequentially filtered and washed with water to obtain NaF;

[0062] The primary distillation is preferably reduced pressure distillation or atmospheric distillation; in the reduced pressure distillation, the vacuum degree is preferably -0.085 to -0.095 MPa, further preferably -0.088 to -0.094 MPa, and more preferably -0.09 to -0.092 MPa; when the solvent is water, the distillation temperature is preferably 50℃, and when the solvent is methanol, the distillation temperature is preferably 40℃; in the atmospheric distillation, when the solvent is water, the distillation temperature is preferably 100-110℃, further preferably 102-108℃, and more preferably 105-106℃; when the solvent is methanol, the distillation temperature is preferably 60-70℃, further preferably 62-68℃, and more preferably 64-66℃.

[0063] The secondary distillation is preferably reduced pressure distillation, the vacuum preferably being -0.075 to -0.085 MPa, further preferably -0.076 to -0.082 MPa, and more preferably -0.078 to -0.08 MPa, and the temperature of the distillation preferably being 287 to 390°C, further preferably 300 to 360°C, and more preferably 320 to 350°C.

[0064] In the present application, the preparation process is carried out in a protective atmosphere, which is preferably nitrogen, carbon dioxide, argon or helium, etc.; the purpose of the protective atmosphere is to isolate the entire process from oxygen.

[0065] The technical solutions provided by the present application will be described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0066] Example 1

[0067] The processes in this example are carried out in a nitrogen atmosphere;

[0068] 4,4'-difluorobenzophenone and diphenyl sulfone are placed in a first dissolving tank in a mass ratio of 1:2, dissolved at 200°C for 120 min, and 500 L of a 4,4'-difluorobenzophenone solution is obtained;

[0069] p-phenylenediamine, diphenyl sulfone and sodium carbonate (the molar ratio of p-phenylenediamine to sodium carbonate is 1:1.1, and the mass ratio of p-phenylenediamine to diphenyl sulfone is 1:3.7) are placed in a second dissolving tank, dissolved at 200°C for 120 min, and 500 L of a p-phenylenediamine solution is obtained;

[0070] The 4,4'-difluorobenzophenone solution and the p-phenylenediamine solution are injected into the reactor through a nozzle in a molar ratio of 4,4'-difluorobenzophenone to p-phenylenediamine of 1:1, and polymerized at a pressure of 0.7 MPa and 300°C for 5 h to obtain a mixed solution, the reactor being provided with a heat preservation layer outside and a water-cooled wall inside;

[0071] The mixed solution is passed through a heat exchanger through a valve at the bottom of the reactor and a downcomer, and after the temperature of the mixed solution is reduced to 130°C, it is injected into a separator. 3300 L of deionized water at 50°C is pre-placed in the separator, and the mixed solution is stirred in the separator for 60 min. The solid components in the mixed solution are solidified and settled at the bottom of the separator to obtain a solid and a liquid after separation;

[0072] The solid obtained after separation is washed with water at 85°C for 5 times, and then sequentially subjected to centrifugation (at a speed of 1500 rpm for 4 min) and evaporation crystallization to remove sodium fluoride in the solid, and a polyether ether ketone solid is obtained;

[0073] The obtained liquid after separation is sent into a distillation column, and distilled at 110℃ under normal pressure, and then distilled at 380℃ after water is distilled, to obtain diphenyl sulfone and sodium fluoride, and the obtained diphenyl sulfone is returned to the first dissolving tank and the second dissolving tank to participate in dissolving.

[0074] Example 2

[0075] This example is applied to super large production, and the processes of this example are all carried out under nitrogen atmosphere;

[0076] 4,4'-difluorobenzophenone and diphenyl sulfone are placed in the first dissolving tank in a mass ratio of 1:2.5, and dissolved at 200℃ for 120 min to obtain a 4,4'-difluorobenzophenone solution;

[0077] p-phenylenediamine, diphenyl sulfone and sodium carbonate (the molar ratio of p-phenylenediamine to sodium carbonate is 1:1.1, and the mass ratio of p-phenylenediamine to diphenyl sulfone is 1:5) are placed in the second dissolving tank, and dissolved at 200℃ for 120 min to obtain a p-phenylenediamine solution;

[0078] The 4,4'-difluorobenzophenone solution and the p-phenylenediamine solution are mixed in a molar ratio of 4,4'-difluorobenzophenone to p-phenylenediamine of 1:1 to obtain a mixed solution, and the obtained mixed solution is injected into reactor 1, reactor 2 and reactor 3 through nozzles, and polymerized at a pressure of 0.8 MPa and at 300℃ for 5 h to obtain mixed solution 1, mixed solution 2 and mixed solution 3, and in this step, the reactors 1, 2 and 3 are externally provided with a heat preservation layer and internally provided with a water-cooled wall;

[0079] The mixed solution 1 is passed through the heat exchanger 1 through the bottom valve and the downcomer of reactor 1 to obtain a mixed solution with a temperature of 130℃, the mixed solution 2 is passed through the heat exchanger 2 through the bottom valve and the downcomer of reactor 2 to obtain a mixed solution with a temperature of 130℃, and the mixed solution 3 is passed through the heat exchanger 3 through the bottom valve and the downcomer of reactor 3 to obtain a mixed solution with a temperature of 130℃, and then the obtained mixed solutions with a temperature of 130℃ are all injected into a separator. The separator is pre-filled with five times the volume of de-methanol of the mixed solution at 50℃, and stirred in the separator for 60 min, and the solid components are solidified and settled at the bottom of the separator to obtain a solid and a liquid after separation;

[0080] The obtained solid after separation is washed with 90℃ water for 5 times, and then sequentially subjected to centrifugation (at a speed of 1500, for 4 min) and evaporation crystallization to remove sodium fluoride in the solid to obtain a polyether ether ketone solid;

[0081] The obtained liquid after separation is sent into a distillation column, and distillation is carried out at 70℃ under normal pressure, and then distillation is carried out at 380℃ after methanol is distilled out, to obtain diphenyl sulfone and sodium fluoride, and the obtained diphenyl sulfone is returned to the first dissolving tank and the second dissolving tank to participate in dissolving.

[0082] Example 3

[0083] In Example 1, "and the polymerization reaction is carried out at 300℃ under a pressure of 0.7 MPa for 5h" is replaced by "and the polymerization reaction is carried out at 320℃ under a pressure of 0.8 MPa for 5h", and the other steps are the same as those in Example 1.

[0084] Example 4

[0085] In Example 1, "4,4'-difluorobenzophenone and diphenyl sulfone are placed in the first dissolving tank at a mass ratio of 1:2" is replaced by "4,4'-difluorobenzophenone and diphenyl sulfone are placed in the first dissolving tank at a mass ratio of 1:3", and the other steps are the same as those in Example 1.

[0086] Example 5

[0087] In Example 1, "the molar ratio of hydroquinone to sodium carbonate is 1:1.1" is replaced by "the molar ratio of hydroquinone to sodium carbonate is 1:1.05", and the other steps are the same as those in Example 1.

[0088] Comparative Example 1

[0089] In this comparative example, the process is carried out under a nitrogen atmosphere;

[0090] The reactor is controlled at 200℃, diphenyl sulfone is placed in the reactor, after dissolving, 4,4'-difluorobenzophenone is added, after dissolving again, hydroquinone is added, after the hydroquinone is dissolved, sodium carbonate is added, and then the reaction is carried out at 200℃ for 120min, and then the temperature is increased to 300℃, and the polymerization reaction is carried out at 300℃ for 5h to obtain a mixed solution;

[0091] The mixed solution is passed through the bottom valve and the downcomer of the reactor through the heat exchanger to obtain a mixed solution with a temperature of 130℃, and then it is injected into a separator. 3300L of deionized water at 50℃ is pre-placed in the separator, and stirring is carried out in the separator for 60min, and the solid components in the mixed solution are solidified and settled at the bottom of the separator to obtain the solid and the liquid after separation;

[0092] The solid obtained after separation is washed with water at 85℃ for 5 times, and then centrifugation (at a speed of 1500, for 4min) and evaporation crystallization are sequentially carried out to remove sodium fluoride in the solid to obtain polyether ether ketone solid;

[0093] The obtained liquid after separation is sent into a distillation column, and distillation is carried out at 110 DEG C under normal pressure, and then distillation is carried out at 380 DEG C after water is distilled, so that diphenyl sulfone and sodium fluoride are obtained, and the obtained diphenyl sulfone is returned to the first dissolving tank and the second dissolving tank to participate in dissolving.

[0094] Table 1 process flow results comparison of example 1 and comparative example 1

[0095]

[0096]

[0097] In table 1, "t / y" represents "ton per year".

[0098] As shown in table 1, compared with comparative example 1, example 1 has lower energy consumption, side reaction and reaction time, and higher annual output, daily batch and DPS recovery rate, except for higher equipment cost.

[0099] Therefore, compared with the process in comparative example 1, the preparation process in the application greatly improves production efficiency, greatly reduces the time, cost and energy consumption in the production process, realizes energy efficient recycling under the premise of ensuring product quality, and further reduces production cost.

[0100] The above only describes the preferred embodiments of the application, and it should be pointed out that, for ordinary skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the application.

Claims

1. A method for continuously and efficiently producing polyether ether ketone, characterized by, The method comprises the following steps: 1) mixing 4,4'-difluorobenzophenone and diphenyl sulfone to obtain a 4,4'-difluorobenzophenone solution; 2) mixing hydroquinone, a catalyst and diphenyl sulfone to obtain a hydroquinone solution; 3) injecting the 4,4'-difluorobenzophenone solution and the hydroquinone solution into a reactor to perform a polymerization reaction, thereby obtaining a mixed solution; 4) injecting the mixed solution through a heat exchanger into a separator to perform separation, thereby obtaining polyether ether ketone solids and liquid; 5) distilling the liquid to obtain diphenyl sulfone and sodium fluoride, and the obtained diphenyl sulfone is returned to steps 1) and 2) to participate in dissolution. The above steps are performed in a protective atmosphere.

2. The method for continuously and efficiently preparing poly (ether ether ketone) according to claim 1, characterized in that, In the step 1), the mass ratio of 4,4'-difluorobenzophenone to diphenyl sulfone is 1:1.8-5.

3. The method for continuously and efficiently preparing poly (ether ether ketone) according to claim 1, characterized in that, In the step 2), the molar ratio of hydroquinone to the catalyst is 1:1-1.1; The mass ratio of hydroquinone to diphenyl sulfone is 1:3.7-10.

4. The method for continuously and efficiently preparing poly (ether ether ketone) according to claim 2 or 3, characterized in that, In the step 2), the catalyst is sodium carbonate or potassium carbonate.

5. The method for continuously and efficiently preparing poly (ether ether ketone) according to claim 4, characterized in that, In the steps 1) and 2), the mixing temperature is independently 200-250 DEG C, and the mixing time is independently 60-120 min.

6. The method of claim 1, wherein the method is a continuous method of efficiently producing poly (ether ether ketone). In the step 3), the molar ratio of 4,4'-difluorobenzophenone to hydroquinone is 1:1-1.1; The polymerization reaction temperature is 300-340 DEG C, the polymerization reaction time is 3-6 h, and the polymerization reaction pressure is 0.1-1 MPa.

7. The method of claim 6, wherein the method is a continuous method of efficiently producing poly (ether ether ketone). In the step 3), the reactor is externally provided with a heat insulation layer and internally provided with a cooling device.

8. The method for continuously and efficiently preparing poly (ether ether ketone) according to claim 6 or 7, characterized in that, In the step 4), the temperature of the solution after passing through the heat exchanger is 130-150 DEG C.

9. The method of claim 8, wherein the method is a continuous method of efficiently producing poly (ether ether ketone). In the step 5), the distillation is fractional distillation.

10. The method of claim 1, wherein the method is a continuous method of efficiently producing poly (ether ether ketone). The protective atmosphere is nitrogen, carbon dioxide, argon or helium, etc.

Images