Thermal dissolution process of phthalazinone polyaryletherketone resin

Abstract

The invention discloses a thermal dissolution process of phthalazinone polyaryletherketone resin, and relates to the technical field of high polymer material processing. Comprising the following steps: adding phthalazinone polyaryletherketone resin powder into an organic solvent, and stirring and mixing at a low speed to obtain an initial mixture; heating the initial mixture to a swelling temperature, so that the resin particles are fully swelled; continuously heating to a dissolving temperature, dissolving, and stirring at a constant temperature until a completely transparent and uniform solution is obtained; stirring and curing the solution at a constant temperature, cooling under low-speed stirring after curing, and finally filtering to obtain a clear and transparent poly (phthalazinone ether ketone) resin solution. By adopting an optimized thermal dissolution procedure, matching with a specific solvent system and combining with accurate temperature and time parameter control, rapid and thorough dissolution of the phthalazinone polyaryletherketone resin is realized, and the phthalazinone polyaryletherketone resin has high solid content, low viscosity and excellent long-term storage stability, and meets industrial processing requirements.

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 poly (phthalazinone ether ketone) resin. The method realizes fast and complete dissolution of PPEK resin, and obtains a homogeneous resin solution with high solid content, low viscosity and long-term stability by optimizing the thermal dissolution process, a specific solvent system and precise process parameter control, so as to meet the needs of industrial solution processing.

[0006] The present application is implemented as follows: The present application provides a thermal dissolution process of poly (phthalazinone ether ketone) resin, which comprises the following steps: adding poly (phthalazinone ether ketone) resin powder into an organic solvent, 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 to dissolve, and then stirring at constant temperature until a completely transparent and uniform solution is obtained; stirring the solution at constant temperature to mature, cooling under low-speed stirring after maturation, and finally filtering to obtain a clear and transparent poly (phthalazinone ether ketone) resin solution.

[0007] In some preferred embodiments, the poly (phthalazinone ether ketone) resin contains a twisted non-planar phthalazinone biphenyl structure, and the intrinsic viscosity is 0.1-1.0 dL / g.

[0008] In some preferred embodiments, the organic solvent is at least one selected from N-methyl pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide or chloroform.

[0009] In some preferred embodiments, the initial mixture is obtained by placing the organic solvent into a reaction kettle, slowly adding the poly (phthalazinone ether ketone) resin powder at 20-35℃ and a rotation speed of 100-150 rpm, and stirring for 30-40 min. And / or, the volume ratio of the poly (phthalazinone ether ketone) resin powder to the organic solvent is (1-3): 10.

[0010] In some preferred embodiments, the swelling of the initial mixture is carried out under an inert atmosphere, the temperature is raised to 50-60℃ at a rate of 1-3℃ / min, and stirring is carried out at 100-300 rpm for 20-40 min at this temperature.

[0011] In some preferred embodiments, the dissolution of the initial mixture is carried out under an inert atmosphere, the temperature is raised to 80-90℃ at a rate of 0.5-1.5℃ / min, and stirring is carried out at 600-1000 rpm for 1-2 h at this temperature.

[0012] In some preferred embodiments, the constant temperature stirring is carried out at a temperature of 80-90℃ and a rotation speed of 600-1000 rpm for 1-1.5 h.

[0013] In some preferable embodiments, the constant temperature stirring ripening is carried out at 80-90℃ for 0.5-1h with stirring speed of 50-150rpm.

[0014] In some preferable embodiments, the cooling rate of the cooling process is 0.5-2℃ / min, and the stirring speed is 50-150rpm. 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 pore size of 0.22-0.45 μm connected in series.

[0015] In some preferable embodiments, the mass percentage concentration of the heteronaphthalene-biphenyl polyaryletherketone resin solution is 10%-30%.

[0016] The present application has the following advantages: (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.

[0017] (2) The optimized temperature rising procedure of the hot dissolution process provided by the present application in combination with high-speed shearing ensures that the molecular chains of the heteronaphthalene-biphenyl polyaryletherketone resin are 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.

[0018] (3) The hot dissolution process provided by the present application has wide applicability, strong controllability, good process repeatability, clear operation window, and is easy to realize precise process control and stable scale-up production on an industrial-scale reaction kettle device, which lays a solid foundation for industrialized continuous preparation. BRIEF DESCRIPTION OF DRAWINGS

[0019] 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 considered as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0020] Figure 1 The flow chart of the hot dissolution process of the present application; Figure 2These are images showing the appearance of the naphthalene-biphenyl polyarylether ketone resin solution prepared in Example 1 of this invention after being stored at room temperature for 30 days and 90 days. Figure 3 These are images showing the appearance of the naphthalene-biphenyl polyarylether ketone resin solution prepared in Example 2 of this invention after being stored at room temperature for 90 days. Figure 4 These are images showing the appearance of the naphthalene-biphenyl polyarylether ketone resin solution prepared in Comparative Example 1 of the present invention after being stored at room temperature for 0, 30, 90 and 120 days. Figure 5 Images showing the appearance of the naphthalene-biphenyl polyarylether ketone resin solution prepared in Comparative Example 2 of this invention after 5 min and 6 h. Figure 6 The image shows the naphthalene-biphenyl polyarylether ketone resin solution prepared in Comparative Example 3 of this invention. Figure 7 The image shows the naphthalene-biphenyl polyarylether ketone resin solution prepared in Comparative Example 4 of this invention. Figure 8 Images showing the film formation of the heteronaphthyl biphenyl polyarylether ketone resin solution in Example 1 and Comparative Example 1 of this invention; Figure 9 Images showing the film formation of the heteronaphthyl biphenyl polyarylether ketone resin solution in Example 2 and Comparative Example 2 of the present invention; Figure 10 Images of the naphthalene-biphenyl polyaryletherketone film of Example 1 of the present invention and an industry standard sample; Figure 11 The graph shows the tensile strength test data of the naphthalene-biphenyl polyaryletherketone film of Example 1 of the present invention and the industry standard sample; Figure 12 This is a comparison chart of the dissolution effects in Experiment Example 3 of the present invention; Figure 13 This is a comparison chart of kinematic viscosity data from Experiment Example 3 of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] The following is a detailed description of the thermal dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin proposed in this invention.

[0023] This invention provides a thermal dissolution process for heteronaphthyl biphenyl polyarylether ketone resins, such as... Figure 1 As shown, it includes the following steps: S1. Feeding and Premixing: Slowly add the naphthalene-biphenyl polyarylether ketone (PPEK) resin powder to the organic solvent and stir at low speed to obtain the initial mixture.

[0024] In an optional embodiment, the pretreatment process of the polyarylether ketone (PPEK) resin powder includes the following steps: vacuum drying the PPEK resin powder at 120-140°C for 2-3 hours to remove moisture and volatile impurities.

[0025] In an optional embodiment, in a reactor equipped with heating, stirring, reflux and inert gas protection, an organic solvent is first added, and then PPEK resin powder is slowly added under stirring at room temperature (20-35°C) and a speed of 100-150 rpm. The mixture is stirred for 30-40 minutes to ensure that the resin particles are uniformly suspended and to avoid local agglomeration.

[0026] In an optional implementation, the equipment pretreatment includes the following steps: purging the reactor with an inert protective gas at least 3 times, each purging lasting ≥5 minutes, to ensure an oxygen-free environment.

[0027] The organic solvent is selected from at least one of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and chloroform (CHCl3). The solvent pretreatment includes static adsorption using molecular sieves for at least 24 hours to achieve a water absorption rate ≤0.2%.

[0028] It should be noted that, depending on different needs, single-solvent resin solutions can be prepared: PPEK series resin + NMP; PPEK series resin + DMAc; PPEK series resin + DMF; PPEK series resin CHCl3; mixed (compound) solvent resin solutions can also be prepared: PPEK series resin + NMP + DMAc; PPEK series resin + NMP + DMF; PPEK series resin + NMP + CHCl3, etc.

[0029] Preferably, the volume ratio of the naphthalene-biphenyl polyarylether ketone resin powder to the organic solvent is (1-3):10.

[0030] In some preferred embodiments, the naphthalene-biphenyl polyarylether ketone resin contains a distorted, non-coplanar diazanaphthalene-biphenyl structure and has an intrinsic viscosity of 0.1-1.0 dL / g, which is determined in concentrated sulfuric acid at 25°C.

[0031] Furthermore, this method is applicable to PPEK series resins (including copolymers and modified products) with different intrinsic viscosities and molecular structures, and can prepare solutions with different solid contents and viscosities to meet the processing needs of various application scenarios such as coatings, adhesives, films, and composite materials.

[0032] S2, Stepwise heating and dissolution: The initial mixture is heated to the swelling temperature to allow the resin particles to fully swell; Then continue heating to the dissolution temperature to dissolve, and then stir at a constant temperature until a completely transparent and homogeneous solution is obtained.

[0033] In some preferred embodiments, 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 dissolution of the initial mixture is achieved by heating to 80-100°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 isothermal stirring is performed at a temperature of 80-90°C and a speed of 600-1000 rpm for 1-1.5 h.

[0034] This invention employs a "step-by-step heating" strategy. First, the resin is fully swollen at a lower temperature, avoiding the problems of rapid surface dissolution and crusting, and difficulty in internal dissolution caused by direct high-temperature heating. Then, a higher temperature is raised for high-speed stirring and dissolution, significantly shortening the total dissolution time (30%-50% shorter than existing technologies) and resulting in a more thorough dissolution. The resulting solution is clear and transparent, free of undissolved particles or gel. The heating rate and stirring speed are dynamically correlated with the dissolution stage. Mild stirring and a moderate heating rate are used during the swelling stage, while high-speed shear stirring and precisely controlled slow heating are employed during the dissolution stage, achieving efficient energy utilization and precise control of dissolution quality. Furthermore, the optimized heating program and high-speed shear ensure the full extension and uniform dispersion of molecular chains in the solvent. Combined with the curing process, this effectively suppresses recrystallization and phase separation tendencies of the resin during solution cooling and storage. The prepared solution can be stably stored at room temperature (for more than 3 months) without turbidity, layering, or gelation.

[0035] It should be noted that throughout the entire heating and dissolution process in step S2, the reaction system is always kept under the protection of an inert gas (such as nitrogen or argon) to prevent the resin from oxidizing and degrading at high temperatures. Furthermore, the system viscosity and dissolution state are monitored, and safety controls are activated. When the real-time monitored temperature exceeds 90°C and the pressure exceeds 0.2 MPa, heating will be automatically cut off and pressure relief will be initiated.

[0036] S3. Constant temperature curing and degassing: The solution is cured by stirring at a constant temperature.

[0037] In some preferred embodiments, the constant temperature stirring and maturation is carried out at 80-100°C with stirring at 50-150 rpm for 0.5-1 hours to make the dissolution more thorough and to facilitate the escape of air bubbles in the solution.

[0038] In addition, isothermal maturation 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.

[0039] S4. Cooling and Filtration: After aging, the solution is cooled under low-speed stirring and finally filtered to obtain a clear and transparent solution of naphthalene-biphenyl polyarylether ketone resin.

[0040] In some preferred embodiments, the cooling process has a cooling rate of 0.5-2℃ / min and a stirring speed of 50-150rpm; the filtration adopts 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 to remove undissolved trace gel particles or impurities.

[0041] The hot melting process proposed in this invention clearly defines the key process parameters such as temperature, heating rate, stirring speed and time at each stage. The process has good repeatability and is easy to achieve precise control and scale-up production in industrial reactors.

[0042] In some preferred embodiments, the mass percentage concentration of the naphthalene-biphenyl polyarylether ketone resin solution is 10%-30%, preferably 15%-25%.

[0043] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0044] Example 1 This embodiment provides a thermal dissolution process for heteronaphthyl biphenyl polyarylether ketone resins. Raw material: polyaryletherketone (PPEK) resin with intrinsic viscosity of 0.65 dL / g; solvent: N-methylpyrrolidone (NMP).

[0045] Includes the following steps: S1. In a 1L reactor with a jacket, anchor-type agitator, nitrogen inlet and reflux condenser, add 800g NMP, stir at 100rpm and purge with nitrogen for protection, then slowly add 200g PPEK powder. After the addition is complete, continue stirring at 45℃ for 30 minutes to ensure that the resin powder is evenly dispersed in the solvent.

[0046] S2. Start stepwise heating: Heat to 60°C at a rate of 1°C / min, stir at a constant temperature for 30 minutes, then heat to 90°C at a rate of 2°C / min, while increasing the stirring speed to 800 rpm. Under these conditions, stir at high speed for 2 hours to dissolve the material. Observe that the material in the vessel becomes a transparent viscous liquid.

[0047] S3. Reduce the stirring speed to 100 rpm and continue to mature at 90°C for 1 hour. Then stop heating and allow the solution to cool naturally to room temperature while continuing to stir. The resulting solution is clear and transparent like amber.

[0048] S4. Use a filtration combination device consisting of a sand core filter and an organic DMSO nylon microporous filter membrane to filter and remove any trace amounts of gel particles or impurities that may be present. The final PPEK resin solution is then packaged.

[0049] The prepared PPEK resin solution has a solid content of 20 wt%, such as Figure 2 As shown, after being stored at room temperature for 30 days, the solution remained homogeneous and transparent, without any precipitation or gel. The viscosity of the solution at 30°C was measured to be 4500 mPa·s using an Ubbelohde viscometer. After being stored at room temperature for 90 days, the solution remained homogeneous and transparent, without any precipitation or gel. The viscosity of the solution at 30°C was measured to be 4500 mPa·s using an Ubbelohde viscometer.

[0050] Example 2 This embodiment provides a thermal dissolution process for heteronaphthyl biphenyl polyarylether ketone resins. Raw materials: poly(aryletherketone) resin with naphthalene-biphenyl (PPEK) and intrinsic viscosity of 0.842 dL / g; solvent: a mixture of NMP and DMAc in a mass ratio of 7:3.

[0051] Includes the following steps: S1. In a 1L reactor with a jacket, anchor-type agitator, nitrogen inlet and reflux condenser, add 800g NMP, stir at 100rpm and purge with nitrogen for protection, then slowly add 200g PPESK powder. After the addition is complete, continue stirring at 45℃ for 30 minutes to ensure that the resin powder is evenly dispersed in the solvent.

[0052] S2. Start stepwise heating: Heat to 65°C at a rate of 1°C / min, stir at a constant temperature for 50 minutes, then heat to 85°C at a rate of 2°C / min, while increasing the stirring speed to 1000 rpm. Under these conditions, dissolve by high-speed shearing for 3 hours. Observe that the material in the vessel becomes a transparent viscous liquid.

[0053] S3. Reduce the stirring speed to 100 rpm and continue to mature at 90°C for 1 hour. Then stop heating and allow the solution to cool naturally to room temperature while continuing to stir. The resulting solution is clear and transparent like amber.

[0054] S4. Use a filtration combination device consisting of a sand core filter and an organic DMSO nylon microporous filter membrane to filter and remove any trace amounts of gel particles or impurities that may be present. The final PPEK resin solution is then packaged.

[0055] The prepared PPEK resin solution had a solid content of 25 wt%, such as Figure 3 As shown, after 90 days of storage at room temperature, the solution remained homogeneous and transparent, without any precipitation or gelation. The viscosity of the solution at 30°C was measured to be 5870 mPa·s using an Ubbelohde viscometer.

[0056] Comparative Example 1 This comparative example provides a thermal dissolution process for naphthalene-biphenyl polyaryletherketone resins. The steps and raw materials are the same as in Example 1, except that after adding the solvent and resin to the reactor, the temperature is directly raised to 210°C, and the solution is stirred at 400 rpm to dissolve. The solution becomes basically transparent after approximately 4.5 hours of total dissolution time.

[0057] The prepared PPEK resin solution has a solid content of 20 wt%, such as Figure 4 As shown, after cooling to room temperature, the solution appeared slightly yellow. After standing for one month, due to prolonged mechanical stirring at high temperatures, the resin underwent high-temperature degradation, resulting in recrystallization or phase separation, leading to turbidity and gel-like flocculent matter. The viscosity of the solution at 30°C was measured to be 3270 mPa·s using an Ubbelohde viscometer. White flocculent matter began to precipitate after 90 days, and completely precipitated after 120 days, making filtration difficult. The white flocculent matter is a phenomenon of "molecular denaturation" caused by high-temperature dissolution and is an insoluble component of the solvent NMP.

[0058] Comparative Example 2 This comparative example provides a thermal dissolution process for naphthalene-biphenyl polyarylether ketone resins. The steps and raw materials are the same as in Example 1, except that after adding the solvent and resin to the reaction vessel, the mixture is stirred at 60°C and 400 rpm until dissolved.

[0059] The final PPEK resin solution prepared is as follows: Figure 5 As shown, after cooling to room temperature, the solution turned brownish-brown. Six hours after cooling to room temperature, a small amount of "white flocculent precipitate" was visible to the naked eye at the bottom of the bottle. Because the molecular chains were not "denatured" at 60℃, they stretched out and exhibited a dissolved state. Using a single swelling temperature for dissolution instead of a step-wise heating method resulted in poor stability of the "dissolved state" of the PPEK resin solution. As the ambient temperature decreased, the PPEK molecular chains "left" the solvent NMP, resulting in the "precipitation" of PPEK resin and the visible "white flocculent precipitate".

[0060] Comparative Example 3 This comparative example provides a hot dissolution process for a naphthalene-biphenyl polyarylether ketone resin. The steps and raw materials are the same as in Example 1, except that the temperature is increased to 150°C at a rate of 3°C / min, and stirred at 1500 rpm for 5 minutes at a constant temperature. Then, the temperature is decreased to 60°C at a rate of 2-3°C / min, and stirred at 50 rpm at a constant temperature for 30 minutes.

[0061] The final PPEK resin solution prepared is as follows: Figure 6 As shown, the extremely rapid heating and cooling operations cause instability in the solution dissolution system due to temperature changes, resulting in gel particles and ultimately forming a "gel ball," which severely affects the dissolution quality and efficiency of PPEK resin. The rapid heating and cooling process significantly impacts the uniformity and stability of PPEK resin dissolution. Excessive heating rates cause excessive swelling of the resin particle surface while the interior remains undissolved, resulting in a heterogeneous structure of "swollen outer shell, undissolved core." Simultaneously, the drastic temperature fluctuations disrupt the thermodynamic equilibrium of the dissolution system, triggering a Gibbs free energy mutation, causing the resin molecular chains to self-aggregate and precipitate due to entropy reduction. Furthermore, insufficient matching between stirring parameters and temperature changes means that high-speed stirring during the heating phase may exacerbate local overheating and surface crusting, while low-speed stirring during the cooling phase cannot effectively disperse the formed microgel nuclei, causing them to aggregate and grow into noticeable gel particles under insufficient shear force. Rapid temperature changes compress the time required for the "swell-diffusion-dissociation" process of resin dissolution, resulting in insufficient solvent penetration and molecular chain dissociation. The incompletely dissolved resin re-entangles under intermolecular forces, eventually forming an irreversible gel structure.

[0062] Comparative Example 4 This comparative example provides a thermal dissolution process for naphthalene-biphenyl polyaryletherketone resins. The steps and raw materials are the same as in Example 1, except that the temperature is increased to 100°C at a rate of 1°C / min, stirred at a constant temperature for 10 minutes, and then increased to 150°C at a rate of 2°C / min while increasing the stirring speed to 800 rpm. Under these conditions, the resin is dissolved by high-speed shear stirring for 2 hours, and a color change is observed in the PPEK resin solution in the reactor.

[0063] The final PPEK resin solution prepared is as follows: Figure 7 As shown, a dense bubble layer first forms, hindering dissolution, then gradually forms gel microspheres, and finally causes color change, uneven solution clarity, and resin precipitation and stratification, which seriously affects the dissolution effect and efficiency of PPEK resin.

[0064] The sudden change in heating rate led to localized overheating of the system, causing the PPEK resin molecular chains to break or oxidize and degrade at high temperatures, producing small colored molecule impurities and impairing resin performance. Simultaneously, the dissolution process was not adequately adapted to the resin's swelling stage: after only 10 minutes of isothermal treatment at 100°C, the temperature was rapidly increased to 150°C and subjected to high-speed shearing. The resin particles, not having fully swelled, were subjected to severe shearing, easily forming a dense layer of microbubbles on their surface, severely hindering further solvent penetration and diffusion into the particles. Ultimately, the resin was not completely dissolved, leaving a large number of incompletely dispersed gel particles or microspheres in the solution, making it impossible to obtain a uniform and stable homogeneous solution.

[0065] Experimental Example 1 The PPEK resin solutions prepared in Example 1 and Comparative Example 1 were used to prepare films, including the following steps: the resin solutions were finely filtered to remove gel particles and impurities; then, the clean solution was uniformly coated onto a flat substrate such as glass using a scraping method to form a wet film; the wet film was then subjected to a step-by-step drying process, first slowly evaporating most of the solvent at a lower temperature, and then gradually increasing the temperature for high-temperature heat treatment to completely remove residual solvent and optimize the film's density and mechanical properties; finally, after the film cooled to room temperature, it was peeled off from the substrate to obtain the final finished film. The results are as follows: Figure 8 As shown.

[0066] The PPEK resin solutions prepared in Example 2 and Comparative Example 2 were used to prepare films, and the results are as follows: Figure 9 As shown.

[0067] like Figure 8 As shown, Example 1 employs a gentle dissolution method using stepped heating and segmented stirring. The resin is first uniformly dispersed at a low temperature, then gradually heated while being stirred at high speed with shear, finally dissolving and maturing at 90°C. The resulting solution is clear and transparent, with a stable viscosity of 4500 mPa·s. Even after 90 days of storage at room temperature, it remains homogeneous without precipitation or gelation, indicating that this process effectively prevents resin degradation and maintains long-term solution stability. In contrast, Comparative Example 1 uses direct high-temperature rapid dissolution. Although the total dissolution time is shorter, the high temperature and prolonged mechanical stirring cause thermal degradation of the resin. The solution turns pale yellow upon cooling, and recrystallization and phase separation occur during storage, producing a white flocculent precipitate with a viscosity of only 3270 mPa·s. Furthermore, the precipitation intensifies over time, making filtration difficult. This indicates that the process induces molecular denaturation, generating NMP-insoluble substances, severely affecting the processability and storage stability of the solution.

[0068] like Figure 9As shown, Example 2 employed a more optimized stepped heating and mixed solvent system. By precisely controlling the heating rate, segmented stirring, and high-temperature curing, a transparent solution with higher solid content, greater viscosity, and long-term storage stability was successfully prepared. This demonstrates that the process not only adapts to resins with higher intrinsic viscosity but also maintains the integrity of molecular chains and uniformity of dissolution under harsh conditions, providing a stable precursor for subsequent film formation. In contrast, Comparative Example 2 used only a mild stirring and dissolution at a constant temperature of 60°C. While this avoided high-temperature degradation, the insufficient temperature prevented the resin molecular chains from fully expanding and dissolving stably. The resulting solution rapidly turned brownish-red upon cooling and precipitated a white flocculent precipitate, indicating that the dissolution process was merely physical swelling rather than true thermodynamically stable dissolution, and the molecular chains were prone to rearrangement and precipitation as the temperature decreased. This "metastable" solution is highly susceptible to phase separation during actual storage and processing, directly leading to a decline in film quality.

[0069] Experimental Example 2 Tensile tests were conducted on the samples from Example 1, Comparative Example 1, and the industry standard. Figure 10 As shown in Table 1 and Figure 11 As shown.

[0070] Table 1. Tensile Strength Data Chart

[0071] According to Table 1 and Figure 11 It is evident that PPEK resin films prepared using different dissolution processes exhibit significant differences in mechanical properties. The film prepared using the step-wise mild dissolution process of Example 1 achieved a tensile strength of 107.447 MPa, significantly higher than the industry standard (95 MPa), indicating that this process effectively preserved the integrity of the resin molecular chains and formed a homogeneous film with a dense structure and high cohesive strength. In contrast, Comparative Example 1, due to its direct high-temperature dissolution process, resulted in thermal degradation and phase separation of the resin, leading to "ice cracks" on the surface of the resulting film and brittleness. It was even impossible to successfully form a valid test specimen, thus failing to obtain effective tensile strength data. This clearly demonstrates the devastating impact of improper processes on the mechanical properties of materials.

[0072] Experimental Example 3 Three batches of PPEK resin from different batches were used for a comparative analysis of their dissolution states. For the same batch of PPEK resin, three dissolution methods were performed: room temperature dissolution, stepwise heating dissolution, and room temperature dissolution followed by a two-step stepwise heating dissolution. The results were compared under the same solid content concentration, solvent, and measurement conditions, as shown in Table 2. Figure 12 and Figure 13 As shown.

[0073] Table 2. Comparison of kinematic viscosity data measured under constant temperature conditions of 25℃

[0074] According to Table 2, Figure 12 and Figure 13 As shown, the stepped heating dissolution process consistently yields the highest kinematic viscosity and a clear, uniform, and light-colored solution appearance. This indicates that the process most effectively allows resin molecular chains to expand and stably disperse in the solvent, forming a homogeneous, highly cohesive solution system. In contrast, the solution obtained from room temperature dissolution has a significantly lower viscosity and is turbid with a dark yellowish-brown or dark brownish-yellow color. This suggests that the resin did not fully dissolve at room temperature, resulting in numerous swollen clusters or unresolved aggregates, leading to poor system homogeneity and low optical transparency. Notably, for samples that underwent a second stepped heating treatment after room temperature dissolution, the viscosity, color lightening, and more uniform appearance were significantly improved compared to direct room temperature dissolution, approaching or reaching the level of a single stepped heating dissolution. This demonstrates that the stepped heating process plays a crucial, even decisive, role in improving the dissolution state, effectively "repairing" the incomplete state of room temperature dissolution. In summary, regardless of the resin batch number, the stepped heating and dissolution process demonstrates the best and most stable performance in obtaining high-viscosity and highly homogeneous solutions, making it a core process step in ensuring the processing quality of PPEK resin solutions.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A thermal dissolution process for naphthalene-biphenyl polyarylether ketone resins, 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.

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 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. And / or, 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 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.

6. The hot dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin according to claim 1, characterized in that, 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.

7. The hot dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin according to claim 1, characterized in that, The constant temperature stirring is 80-90℃, and the stirring speed is 600-1000rpm for 1-1.5h.

8. The hot dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin according to claim 1, characterized in that, The constant temperature stirring and maturation is carried out at 80-90℃, with stirring at 50-150 rpm for 0.5-1 hours.

9. The hot dissolution process for a heteronaphthyl biphenyl polyarylether ketone resin according to claim 1, characterized in that, The cooling process has a cooling rate of 0.5-2℃ / min and a stirring speed of 50-150rpm. And / or, the filtration adopts a composite filtration system consisting of a sand core filter device connected in series with a nylon microporous filter membrane with a pore size of 0.22-0.45 μm.

10. 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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