A thermal dissolution process for a heteronaphthalene-biphenyl polyaryletherketone resin

Abstract

The application discloses a kind of poly (heteronaphthalene-biphenyl) poly (aryl ether ketone) resin hot dissolution process, it is related to the field of polymer processing technology. Including the following steps: poly (heteronaphthalene-biphenyl) poly (aryl ether ketone) resin powder is added into organic solvent, and initial mixture is obtained by low-speed stirring mixing;The initial mixture is heated to swelling temperature, and resin particles are fully swollen;Then continue to heat to dissolution temperature, and then constant-temperature stirring is carried out until completely transparent and uniform solution is obtained;Solution is constant-temperature stirring ripening, and after ripening is completed, it is cooled under low-speed stirring, and finally filtered, to obtain clear and transparent poly (heteronaphthalene-biphenyl) poly (aryl ether ketone) resin solution. By using optimized hot dissolution procedure, matching specific solvent system, and combining accurate temperature and time parameter control, rapid and complete dissolution of poly (heteronaphthalene-biphenyl) poly (aryl ether ketone) resin is realized, which has high solid content, low viscosity and excellent long-term storage stability, and meets the needs of industrial processing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer material processing, in particular to a thermal dissolution process of a heteronaphthalene-biphenyl polyaryletherketone resin. BACKGROUND

[0002] As a kind of high-performance special engineering plastics, heteronaphthalene-biphenyl polyaryletherketone (PPEK) exhibits excellent high-temperature resistance, high strength and high modulus, outstanding chemical corrosion resistance and good dielectric properties due to the introduction of rigid heteronaphthalene-biphenyl structure and aryletherketone structure in the main chain. It has important application potential in high-tech fields such as aerospace, electronic information, precision machinery and nuclear energy. However, the molecular chain of this resin is extremely rigid, has a significant crystallization tendency, and the glass transition temperature is usually above 250℃, which leads to its poor solubility in most common organic solvents. Even under high temperature conditions, it is difficult to achieve effective dissolution. This characteristic seriously restricts the processing route of PPEK, especially limits its application and promotion in the fields of coatings, adhesives, composite impregnating liquid, prepreg and film casting that require solution processing technology.

[0003] Currently, the dissolution process of PPEK faces many challenges: the selection of solvent is extremely harsh, and it usually has to rely on strong polarity and high boiling point aprotic solvents such as N-methylpyrrolidone, N,N-dimethylacetamide or N,N-dimethylformamide, etc. Such solvents not only have strong hygroscopicity, but also make the resin solution easily precipitate or separate in the air due to water absorption; the dissolution process is inefficient, traditional methods often take several hours or even tens of hours, consume high energy, and are prone to resin degradation or gelation due to local overheating or uneven stirring, affecting the quality and stability of the solution; the stability of the obtained solution is poor, and turbidity, gel or precipitation often occurs due to resin recrystallization or phase separation during storage or cooling, which is difficult to meet the requirements of long-term stability of the solution for subsequent processing technology; in addition, the existing laboratory dissolution process is difficult to scale up to industrial continuous production, and faces problems such as high equipment requirements, complex process control and high safety risks, for example, the method of using N-methylpyrrolidone as solvent and mechanical stirring at 180-200℃ for a long time can obtain a solution with a certain concentration, but it has problems such as long dissolution period, dark color (may be accompanied by degradation), insufficient stability at high concentration, and easy to produce gel particles after cooling to room temperature.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The present application aims to provide a thermal dissolution process of heteronaphthalene polyphenyl ether ketone resin. The method realizes rapid and complete dissolution of PPEK resin, and obtains a homogeneous resin solution with high solid content, low viscosity and long-term stability, to meet the needs of industrial solution processing, through an optimized thermal dissolution process, a specific solvent system and precise process parameter control.

[0006] The present application is implemented as follows:

[0007] The present application provides a thermal dissolution process of heteronaphthalene polyphenyl ether ketone resin, comprising the following steps: adding heteronaphthalene polyphenyl ether ketone resin powder into an organic solvent, and mixing at low speed to obtain an initial mixture; heating the initial mixture to a swelling temperature to make the resin particles fully swell; then continuously heating to a dissolution temperature for dissolution, and then constant-temperature stirring until a completely transparent and uniform solution is obtained; constant-temperature stirring and aging of the solution, cooling under low-speed stirring after aging is completed, and finally filtering to obtain a clear and transparent heteronaphthalene polyphenyl ether ketone resin solution.

[0008] In some preferred embodiments, the heteronaphthalene polyphenyl ether ketone resin contains a twisted non-planar heteronaphthalene polyphenyl ether structure, and the intrinsic viscosity is 0.1-1.0 dL / g.

[0009] In some preferred embodiments, the organic solvent is at least one selected from N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide or chloroform.

[0010] In some preferred embodiments, the initial mixture is obtained by placing the organic solvent into a reaction kettle, slowly adding the heteronaphthalene polyphenyl ether ketone resin powder at 20-35℃ and a rotation speed of 100-150 rpm, and stirring for 30-40 min.

[0011] And / or, the volume ratio of the heteronaphthalene polyphenyl ether ketone resin powder to the organic solvent is (1-3):10.

[0012] In some preferred embodiments, the swelling of the initial mixture is carried out under an inert atmosphere, at a rate of 1-3℃ / min to 50-60℃, and stirring at a rotation speed of 100-300 rpm for 20-40 min at this temperature.

[0013] In some preferred embodiments, the dissolution of the initial mixture is carried out under an inert atmosphere, at a rate of 0.5-1.5℃ / min to 80-90℃, and stirring at a rotation speed of 600-1000 rpm for 1-2 h at this temperature.

[0014] In some preferable embodiments, the temperature of the constant temperature stirring is 80-90℃, the stirring speed is 600-1000rpm, and the stirring time is 1-1.5h.

[0015] In some preferable embodiments, the constant temperature stirring ripening is carried out at 80-90℃, the stirring speed is 50-150rpm, and the stirring time is 0.5-1h.

[0016] In some preferable embodiments, the cooling rate of the cooling process is 0.5-2℃ / min, and the stirring speed is 50-150rpm.

[0017] And / or the filtration is carried out by using a composite filtration system composed of a sand core filtration device and a nylon microporous filter membrane with a pore size of 0.22-0.45μm connected in series.

[0018] In some preferable embodiments, the mass percentage concentration of the poly (naphthalene-phenylene ether ketone) resin solution is 10%-30%.

[0019] The present application has the following beneficial effects:

[0020] (1) The hot dissolution process provided by the present application shortens the total dissolution time by adopting the "stepwise temperature rising" strategy, i.e., first swelling the resin at a lower temperature, and then rising to a higher temperature for high-speed stirring and dissolution, and realizes more thorough and homogeneous dissolution, so that the final solution is clear and transparent, without undissolved particles or gel, and the dissolution efficiency and solution quality are both significantly improved.

[0021] (2) The optimized temperature rising procedure of the hot dissolution process provided by the present application, combined with high-speed shearing, ensures that the poly (naphthalene-phenylene ether ketone) resin molecular chain is fully stretched and uniformly dispersed in the solvent, and the subsequent ripening process can effectively inhibit the instability of the resin caused by recrystallization or phase separation during the cooling and storage of the solution, so that the prepared solution has excellent storage stability at room temperature and can be stored for a long time without turbidity, stratification or gelation.

[0022] (3) The hot dissolution process provided by the present application has wide applicability, strong controllability, good process repeatability, and clear operation window, and is easy to realize precise process control and stable scale-up production on an industrial-scale reaction kettle device, laying a solid foundation for industrialized continuous production. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0024] Figure 1 Flow chart of hot dissolution process of the present application;

[0025] Figure 2 Picture of appearance of the heteronaphthalene-biphenyl poly(arylene ether ketone) resin solution prepared in Example 1 of the present application after storage at room temperature for 30 days and 90 days;

[0026] Figure 3 Picture of appearance of the heteronaphthalene-biphenyl poly(arylene ether ketone) resin solution prepared in Example 2 of the present application after storage at room temperature for 90 days;

[0027] Figure 4 Picture of appearance of the heteronaphthalene-biphenyl poly(arylene ether ketone) resin solution prepared in Comparative Example 1 of the present application after storage at room temperature for 0 days, 30 days, 90 days and 120 days;

[0028] Figure 5 Picture of appearance of the heteronaphthalene-biphenyl poly(arylene ether ketone) resin solution prepared in Comparative Example 2 of the present application after 5 min and 6 h;

[0029] Figure 6 Picture of the heteronaphthalene-biphenyl poly(arylene ether ketone) resin solution prepared in Comparative Example 3 of the present application;

[0030] Figure 7 Picture of the heteronaphthalene-biphenyl poly(arylene ether ketone) resin solution prepared in Comparative Example 4 of the present application;

[0031] Figure 8 Picture of the film prepared from the heteronaphthalene-biphenyl poly(arylene ether ketone) resin solution of Example 1 and Comparative Example 1 of the present application;

[0032] Figure 9 Picture of the film prepared from the heteronaphthalene-biphenyl poly(arylene ether ketone) resin solution of Example 2 and Comparative Example 2 of the present application;

[0033] Figure 10 Picture of the heteronaphthalene-biphenyl poly(arylene ether ketone) film of Example 1 of the present application and the industry standard sample;

[0034] Figure 11 Picture of tensile strength test data of the heteronaphthalene-biphenyl poly(arylene ether ketone) film of Example 1 of the present application and the industry standard sample;

[0035] Figure 12 Comparison chart of dissolution effect of Test Example 3 of the present application;

[0036] Figure 13 Comparison chart of kinematic viscosity data of Test Example 3 of the present application. DETAILED DESCRIPTION

[0037] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, the conventional products that can be purchased in the market are adopted.

[0038] The heat dissolution process of the poly (phthalazinone ether ketone) resin according to the present application is described in detail as follows.

[0039] The present application provides a heat dissolution process of poly (phthalazinone ether ketone) resin, as shown in the formula, comprising the following steps: Figure 1

[0040] S1, feeding and premixing: slowly add poly (phthalazinone ether ketone) (PPEK) resin powder into an organic solvent, mix under low speed stirring to obtain an initial mixture.

[0041] In an optional embodiment, the pretreatment process of the poly (phthalazinone ether ketone) (PPEK) resin powder comprises the following steps: vacuum drying the PPEK resin powder at 120-140℃ for 2-3h to remove moisture and volatile impurities.

[0042] In an optional embodiment, in a reaction kettle with heating, stirring, reflux and inert gas protection, first add an organic solvent, then slowly add PPEK resin powder under stirring at room temperature (20-35℃) and a stirring speed of 100-150rpm, and stir for 30-40min to make the resin particles uniformly suspended to avoid local caking.

[0043] In an optional embodiment, the device pretreatment comprises the following steps: replace the reaction kettle with inert protective gas at least 3 times, each time for ≥5min to ensure an oxygen-free environment.

[0044] The organic solvent is selected from at least one of N-methyl pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF) and chloroform (CHCl3). The solvent pretreatment comprises static adsorption with molecular sieves for at least 24h to make the water absorption ≤0.2%.

[0045] It should be noted that single solvent resin liquid can be prepared according to different requirements: PPEK series resin+NMP; PPEK series resin+DMAc; PPEK series resin+DMF; PPEK series resin+CHCl3; or mixed (complex) solvent resin liquid: PPEK series resin+NMP+DMAc; PPEK series resin+NMP+DMF; PPEK series resin+NMP+CHCl3, etc. ​

[0046] Preferably, the volume ratio of the heteronaphthalene-biphenyl polyaryletherketone resin powder and the organic solvent is (1-3):10.

[0047] In some preferred embodiments, the heteronaphthalene-biphenyl polyaryletherketone resin contains twisted non-coplanar perylene-biphenyl structures, and the intrinsic viscosity is 0.1-1.0 dL / g, which is measured in concentrated sulfuric acid at 25℃.

[0048] Further, the method is suitable for PPEK series resins with different intrinsic viscosity and molecular structure (including copolymerization and modified products), and can prepare solutions with different solid content and viscosity to meet the processing requirements of various application scenarios such as coatings, adhesives, films, and composites.

[0049] S2, stepwise temperature rising dissolution: the initial mixture is warmed to the swelling temperature to make the resin particles fully swell;

[0050] Then continue to warm up to the dissolution temperature for dissolution, and then constant temperature stirring until a completely transparent and uniform solution is obtained.

[0051] In some preferred embodiments, the swelling of the initial mixture is carried out under inert atmosphere at a rate of 1-3℃ / min to 50-60℃, and stirring at a speed of 100-300 rpm for 20-40 min at this temperature; the dissolution of the initial mixture is carried out under inert atmosphere at a rate of 0.5-1.5℃ / min to 80-100℃, and stirring at a speed of 600-1000 rpm for 1-2 h at this temperature; the temperature of the constant temperature stirring is 80-90℃, and the stirring speed is 600-1000 rpm for 1-1.5 h.

[0052] By the "stepwise temperature rising" strategy, the resin is first fully swollen at a lower temperature, avoiding the problem of surface rapid dissolution and crust formation caused by direct high temperature heating, and then dissolved at a higher temperature with high speed stirring, greatly shortening the total dissolution time (30%-50% shorter than the prior art), and the solution obtained is clear and transparent without undissolved particles or gel. The temperature rising rate and stirring speed are dynamically related to the dissolution stage. In the swelling stage, moderate stirring and medium temperature rising rate are adopted, and in the dissolution stage, high speed shearing stirring and precise control of slow temperature rising are adopted, realizing efficient use of process energy and accurate control of dissolution quality. And the optimized temperature rising program and high speed shearing ensure the full stretching and uniform dispersion of molecular chains in the solvent, which effectively inhibits the tendency of recrystallization and phase separation of the resin during solution cooling and storage. The prepared solution can be stored stably at room temperature (more than 3 months) without turbidity, stratification or gel phenomenon.

[0053] It should be noted that during the entire temperature rising dissolution process of step S2, the reaction system is always kept under the protection of inert gas (such as nitrogen, argon) to prevent the resin from being oxidized and degraded at high temperature. And the viscosity of the system, the dissolution state are monitored, and the safety control is opened, when the real-time monitoring temperature > 90℃, the pressure > 0.2MPa will automatically cut off the heating and start the pressure relief.

[0054] S3, constant temperature curing and defoaming: constant temperature stirring and curing of the solution.

[0055] In some preferred embodiments, the constant temperature stirring and curing is stirring at 80-100℃, 50-150rpm for 0.5-1h, which makes the dissolution more thorough and is beneficial to the escape of bubbles in the solution.

[0056] In addition, the constant temperature curing is a process of molecular chain relaxation and solution homogenization, which plays a crucial role in improving the long-term storage stability of the solution.

[0057] S4, cooling and filtering: after the curing is completed, the solution is cooled under low speed stirring, and finally filtered to obtain a clear and transparent poly (naphthalene-phenylene ether ketone) resin solution.

[0058] In some preferred embodiments, the cooling process has a cooling rate of 0.5-2℃ / min and a stirring speed of 50-150rpm; the filtering uses a composite filtering system composed of a sand core filtering device and a nylon microporous filter membrane with a pore size of 0.22-0.45 μm in series to remove unsolved trace gel particles or impurities.

[0059] The thermal dissolution process provided by the present application clearly defines the key process parameters such as temperature, heating rate, stirring speed and time at each stage, has good process repeatability, and is easy to realize precise control and large-scale production on an industrial reaction kettle.

[0060] In some preferred embodiments, the mass percentage concentration of the poly (naphthalene-phenylene ether ketone) resin solution is 10%-30%, preferably 15%-25%.

[0061] The features and properties of the present application are further described in detail below in combination with embodiments.

[0062] Example 1

[0063] This embodiment provides a thermal dissolution process of poly (naphthalene-phenylene ether ketone) resin.

[0064] Raw materials: poly (naphthalene-phenylene ether ketone) (PPEK) resin, intrinsic viscosity 0.65 dL / g; solvent: N-methyl pyrrolidone (NMP).

[0065] Comprising the following steps:

[0066] S1, in a 1L reaction kettle with jacket, anchor stirring paddle, nitrogen inlet and condensation reflux device, 800g NMP was added, stirred at a speed of 100 rpm, and protected by nitrogen, then 200g PPEK powder was slowly added, after the addition was completed, it was continuously stirred at 45℃ for 30 minutes, so that the resin powder was uniformly dispersed in the solvent.

[0067] S2, start the stepwise temperature rise: increase the temperature to 60℃ at a rate of 1℃ / min, keep stirring for 30 minutes, then increase the temperature to 90℃ at a rate of 2℃ / min, and increase the stirring speed to 800 rpm at the same time, high-speed shear stirring for 2 hours under this condition, it was observed that the material in the kettle became transparent viscous liquid.

[0068] S3, reduce the stirring speed to 100 rpm, continue to keep the temperature at 90℃ for 1 hour, stop heating, and naturally cool the solution to room temperature under continuous stirring. The obtained solution was clear and transparent like amber.

[0069] S4, filter using a filter combination device composed of a sand core filter device and an organic DMSO nylon microporous filter membrane to remove possible trace amounts of gel particles or impurities, and package the final PPEK resin solution.

[0070] The prepared PPEK resin solution has a solid content of 20wt%, as shown in Figure 2 After 30 days of storage at room temperature, it still remained uniform and transparent without any precipitation or gel, and the viscosity of the solution at 30℃ measured by an Ubbelohde viscometer was 4500 mPa·s; after 90 days of storage at room temperature, it still remained uniform and transparent without any precipitation or gel, and the viscosity of the solution at 30℃ measured by an Ubbelohde viscometer was 4500 mPa·s.

[0071] Example 2

[0072] This example provides a hot dissolution process of a heteronaphthalene polyphenyl ether ketone resin.

[0073] Raw materials: heteronaphthalene polyphenyl ether ketone (PPEK) resin, intrinsic viscosity 0.842 dL / g; solvent: NMP and DMAc mixed solvent with a mass ratio of 7:3.

[0074] Comprising the following steps:

[0075] S1, in a 1L reaction kettle with jacket, anchor stirring paddle, nitrogen inlet and condensation reflux device, 800g NMP was added, stirred at a speed of 100 rpm, and protected by nitrogen, then 200g PPESK powder was slowly added, after the addition was completed, it was continuously stirred at 45℃ for 30 minutes, so that the resin powder was uniformly dispersed in the solvent.

[0076] S2, start the temperature ramping: increase the temperature to 65°C at a rate of 1°C / min, keep the temperature constant for 50 minutes, then increase the temperature to 85°C at a rate of 2°C / min, and increase the stirring speed to 1000 rpm at the same time, under the condition of high-speed shearing stirring for 3 hours, it is observed that the material in the kettle becomes transparent viscous liquid.

[0077] S3, reduce the stirring speed to 100 rpm, continue to keep the temperature constant at 90°C for 1 hour, stop heating, and naturally cool the solution to room temperature under continuous stirring. The obtained solution is clear and transparent like amber.

[0078] S4, filter using a filter combination device composed of a sand core filter device and an organic DMSO nylon microporous filter membrane to remove possible trace amounts of gel particles or impurities, and package the final PPEK resin solution.

[0079] The prepared PPEK resin solution has a solid content of 25wt%, as shown in Figure 3 After 90 days of storage at room temperature, it still remains uniform and transparent without any precipitation or gel. The viscosity of the solution at 30°C is measured by an Ubbelohde viscometer to be 5870 mPa·s.

[0080] Comparative Example 1

[0081] This comparative example provides a thermal dissolution process of a heteronaphthalene polyphenyl ether ketone resin, the steps and raw materials are the same as Example 1, the only difference is that after adding the solvent and resin into the reaction kettle, the temperature is directly increased to 210°C, and the stirring speed is 400 rpm. The solution is basically transparent after about 4.5 hours of total dissolution time.

[0082] The prepared PPEK resin solution has a solid content of 20wt%, as shown in Figure 4 After cooling to room temperature, the solution is slightly yellow, and after standing for one month, the resin is degraded at high temperature due to long-time mechanical stirring at high temperature, the resin solution recrystallizes or phase separates, becomes turbid and gel flocculent, the viscosity of the solution at 30°C is measured by an Ubbelohde viscometer to be 3270 mPa·s, white flocculent starts to precipitate after 90 days, and completely precipitates after 120 days, which is difficult to filter. The white flocculent is a "molecular denaturation" phenomenon caused by high-temperature dissolution, which is an insoluble substance of the solvent NMP.

[0083] Comparative Example 2

[0084] This comparative example provides a thermal dissolution process of a heteronaphthalene polyphenyl ether ketone resin, the steps and raw materials are the same as Example 1, the only difference is that after adding the solvent and resin into the reaction kettle, the temperature is directly increased to 210°C, and the stirring speed is 400 rpm. The solution is basically transparent after about 4.5 hours of total dissolution time.

[0085] The final prepared PPEK resin solution is shown in Figure 5 After cooling to room temperature, the solution appears brownish, and a small amount of "white flocculent precipitate" is observed at the bottom of the bottle 6h after cooling to room temperature. Because the molecular chain is in a 60°C temperature environment, the molecular chain is not "denatured" and is in a dissolved state. The use of a swelling temperature dissolution without using a stepwise heating dissolution method results in a "dissolved state" of the PPEK resin solution, which is less stable. As the ambient temperature decreases, the PPEK molecular chain "leaves" the solvent NMP, and the PPEK resin "precipitates", resulting in the formation of a "white flocculent precipitate" that can be observed by the naked eye.

[0086] Comparative Example 3

[0087] This comparative example provides a thermal dissolution process for a hetero-naphthalene polyphenyl ether ketone resin, the steps and raw materials of which are the same as those of Example 1, the only difference being that the temperature is raised to 150°C at a rate of 3°C / min, and then stirred at a constant temperature of 1500 rpm for 5 minutes, and then the temperature is lowered to 60°C at a rate of 2-3°C / min, and then stirred at a constant temperature of 50 rpm for 30 minutes.

[0088] The final prepared PPEK resin solution is shown in Figure 6 Due to the extremely rapid temperature rising and falling operation mode, the solution dissolution system is not stable due to temperature changes, resulting in the formation of gel particles, and finally forming a "gel ball", which seriously affects the dissolution quality and efficiency of the PPEK resin. The rapid temperature rising and falling process seriously affects the uniformity and stability of the dissolution of the PPEK resin. The rapid temperature rising rate leads to excessive swelling of the surface of the resin particles and incomplete dissolution of the inside, forming a "shell swelling, core not dissolved" state with uneven structure; at the same time, the rapid temperature fluctuation destroys the thermodynamic equilibrium of the dissolution system, causing a sudden change in Gibbs free energy, which promotes the self-aggregation of the resin molecular chain due to the entropy reduction tendency and causes the resin molecular chain to precipitate. In addition, the matching of the stirring parameters and the temperature change is insufficient, which may exacerbate the local overheating and surface skinning during the high-speed stirring in the temperature rising stage, and the low-speed stirring in the temperature falling stage cannot effectively disperse the small gel nuclei that have been formed, so that they grow into obvious gel particles under the condition of insufficient shear force. The rapid temperature change compresses the "swelling-diffusion-dissociation" process time required for the dissolution of the resin, resulting in insufficient solvent penetration and molecular chain dissociation, and the incompletely dissolved resin reentangles under the intermolecular force, finally forming an irreversible gel structure.

[0089] Comparative Example 4

[0090] The comparative example provides a thermal dissolution process of a hetero-naphthalene polyphenyl ether ketone resin, the steps and raw materials are the same as those of Example 1, the only difference is that the temperature is raised to 100°C at a rate of 1°C / min, constant temperature stirring for 10 minutes, then the temperature is raised to 150°C at a rate of 2°C / min, and the stirring speed is increased to 800 rpm, under this condition, high-speed shearing stirring is carried out for 2 hours, and it is observed that the PPEK resin solution in the kettle appears color change phenomenon.

[0091] The finally prepared PPEK resin solution is as shown in Figure 7 The dense bubble layer is first formed to hinder dissolution, then the gel microspheres are gradually formed, and finally the color change, solution non-clear and uniform, and resin solution precipitation and stratification phenomenon occur, which seriously affects the dissolution effect and efficiency of PPEK resin.

[0092] The sudden change of the heating rate leads to local overheating of the system, and the PPEK resin molecular chain is broken or oxidatively degraded at high temperature, producing colored small molecule impurities and damaging the performance of the resin. At the same time, the dissolution process is not fully adapted to the swelling stage of the resin: after constant temperature at 100°C for only 10 minutes, the temperature is quickly raised to 150°C and the high-speed shearing is started, and the resin particles are subjected to severe shearing without sufficient swelling, and a dense micro-bubble layer is easily formed on the surface, which seriously hinders the further penetration and diffusion of the solvent into the particle interior. Finally, the resin is not completely dissolved, and a large amount of gel particles or gel microspheres that cannot be completely dispersed are left in the solution, and a uniform and stable homogeneous solution cannot be obtained.

[0093] Test Example 1

[0094] The PPEK resin solutions prepared in Example 1 and Comparative Example 1 are prepared into films, including the following steps: the resin solution is finely filtered to remove gel particles and impurities; then the clean solution is uniformly coated on a flat substrate such as glass by means of scraping and the like to form a wet film; then the wet film is subjected to stepwise program drying, first slowly volatilizing most of the solvent at a lower temperature, and then gradually increasing the temperature for high-temperature heat treatment to completely remove the residual solvent and optimize the compactness and mechanical properties of the film; finally, after the film is cooled to room temperature, it is peeled off from the substrate, and the final product film is obtained. The results are shown in Figure 8 .

[0095] The PPEK resin solutions prepared in Example 2 and Comparative Example 2 are prepared into films, and the results are shown in Figure 9 .

[0096] As shown in Figure 8As shown, Example 1 adopts a mild dissolution method of stepwise temperature rise and segmented stirring, first uniformly dispersing the resin at low temperature, then gradually increasing the temperature and cooperating with high-speed shearing stirring, finally completing dissolution and ripening at 90°C. The obtained solution is clear and transparent, the viscosity is stable at 4500 mPa·s, and after 90 days of storage at room temperature, it still remains uniform without precipitation or gel phenomenon, indicating that the process can effectively avoid resin degradation and maintain long-term stability of the solution. While Comparative Example 1 adopts direct high-temperature rapid dissolution, although the total dissolution time is shorter, high temperature and long-time mechanical stirring lead to thermal degradation of the resin, the solution is yellow after cooling, and during storage, recrystallization and phase separation occur, producing white flocculent precipitate, the viscosity is only 3270 mPa·s, and the precipitation intensifies with time, making filtration difficult, indicating that the process causes molecular denaturation, generating NMP insoluble, which seriously affects the processability and storage stability of the solution.

[0097] As shown in Figure 9 Example 2 adopts a more optimized stepwise temperature rise and mixed solvent system, through fine control of the temperature rise rate, segmented stirring and high-temperature ripening, a transparent solution with higher solid content, larger viscosity and long-term storage stability is successfully prepared. This shows that this process not only adapts to resins with higher intrinsic viscosity, but also maintains the integrity and uniformity of molecular chains under harsh conditions, providing a quality stable precursor for subsequent film formation. While Comparative Example 2 only uses a mild condition of constant temperature 60°C for stirring and dissolution, although it avoids high-temperature degradation, it fails to fully stretch and stably dissolve the resin molecular chains due to insufficient temperature. The obtained solution quickly turns brown and precipitates white flocculent precipitate after cooling, indicating that the dissolution process is only physical swelling rather than true thermodynamic stable dissolution, and the molecular chains are prone to rearrangement and precipitation when the temperature drops. This "metastable" solution is prone to phase separation in actual storage and processing, directly leading to the decline of film quality.

[0098] Test Example 2

[0099] The samples of Example 1, Comparative Example 1 and industry standard were subjected to tensile test, as shown in Figure 10 The results are shown in Table 1 and Figure 11

[0100] Table 1. Tensile strength data chart

[0101]

[0102] According to Table 1 and Figure 11 ​It can be seen that the PPEK resin films prepared by different dissolution processes have significant differences in mechanical properties. The tensile strength of the film prepared by the stepwise mild dissolution process of Example 1 reaches 107.447 MPa, which is significantly higher than the industry standard (95 MPa), indicating that this process effectively preserves the integrity of the resin molecular chain and forms a homogeneous film with a dense structure and high cohesive strength. In contrast, the direct high-temperature dissolution process used in Comparative Example 1 leads to thermal degradation and phase separation of the resin, resulting in "ice cracks" on the surface of the film and a brittle texture, and even the film cannot be successfully formed into an effective test sample, so the effective tensile strength data cannot be measured, which directly reflects the devastating effect of improper process on the mechanical properties of the material.

[0103] Test Example 3

[0104] Three batches of PPEK resin with different batch numbers were used for dissolution state comparison and analysis. The same batch number of PPEK resin was dissolved by normal temperature dissolution, stepwise heating dissolution, and normal temperature dissolution twice stepwise heating dissolution, respectively. The same solid content concentration, the same solvent, and the same determination conditions were used for three kinds of dissolution comparison and analysis, as shown in Table 2, Figure 12 and Figure 13 .

[0105] Table 2. Comparison of kinematic viscosity data measured at 25°C constant temperature determination conditions

[0106]

[0107] According to Table 2, Figure 12 and Figure 13 , the stepwise heating dissolution process always obtains the highest solution kinematic viscosity and the apparent state of clear and uniform solution with lighter color, which indicates that this process can most effectively stretch and stably disperse the resin molecular chain in the solvent, forming a uniform and high cohesive solution system. In contrast, the solution viscosity obtained by normal temperature dissolution process is significantly lower, and the solution is turbid and the color is dark yellow brown or dark brown yellow, indicating that the resin does not dissolve completely at room temperature, and there are a large number of swollen clusters or aggregated bodies that are not disentangled, resulting in poor system uniformity and low optical transparency. It is worth noting that for the sample that is dissolved at room temperature and then subjected to a second stepwise heating process, the viscosity and the apparent state of lighter and more uniform color are greatly improved compared to direct room temperature dissolution, and can approach or reach the level of one-step stepwise heating dissolution, which proves that the stepwise heating process plays a key and even decisive role in improving the dissolution state, and can effectively "repair" the incomplete state of room temperature dissolution. In summary, regardless of the change of the resin batch number, the stepwise heating dissolution process shows the most optimal and stable effect in obtaining high viscosity and high uniformity solution, which is the core process link to ensure the quality of PPEK resin solution processing.

[0108] The above descriptions are only the preferred embodiments of the present application, not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the scope of the present application.

Claims

1. A thermal dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin, characterized in that, The process includes the following steps: adding naphthalene-biphenyl polyarylether ketone resin powder to an organic solvent and mixing at low speed to obtain an initial mixture; heating the initial mixture to the swelling temperature to allow the resin particles to fully swell; then continuing to heat to the dissolution temperature to dissolve the resin particles, and then stirring at a constant temperature until a completely transparent and homogeneous solution is obtained; aging the solution by stirring at a constant temperature, and after aging, cooling it under low-speed stirring; and finally filtering to obtain a clear and transparent naphthalene-biphenyl polyarylether ketone resin solution. The initial mixture is prepared by placing the organic solvent in a reaction vessel, slowly adding the naphthalene-biphenyl polyarylether ketone resin powder at 20-35°C and 100-150 rpm, and stirring for 30-40 minutes. The swelling of the initial mixture is achieved by heating to 50-60°C at a rate of 1-3°C / min under an inert atmosphere, and stirring at 100-300 rpm for 20-40 min at this temperature. The initial mixture was dissolved by heating to 80-90°C at a rate of 0.5-1.5°C / min under an inert atmosphere, and stirring at 600-1000 rpm for 1-2 h at this temperature. The constant temperature stirring is 80-90℃, and the stirring speed is 600-1000rpm for 1-1.5h; The constant temperature stirring and maturation is carried out at 80-90℃ and stirring at 50-150 rpm for 0.5-1 hours. The cooling process has a cooling rate of 0.5-2℃ / min and a stirring speed of 50-150rpm.

2. The hot dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin according to claim 1, characterized in that, The polyarylether ketone resin contains a distorted, non-coplanar diazanaphthalene biphenyl structure and has an intrinsic viscosity of 0.1-1.0 dL / g.

3. The hot dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin according to claim 1, characterized in that, The organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, or chloroform.

4. The hot dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin according to claim 1, characterized in that, The volume ratio of the naphthalene-biphenyl polyarylether ketone resin powder to the organic solvent is (1-3):

10.

5. The hot dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin according to claim 1, characterized in that, The filtration system is a composite filtration system consisting of a sand core filter device and a nylon microporous filter membrane with a pore size of 0.22-0.45 μm connected in series.

6. The hot dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin according to claim 1, characterized in that, The mass percentage concentration of the heteronaphthyl biphenyl polyarylether ketone resin solution is 10% - 30%.

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