A method for preparing a low-crystallinity, low-melting polyaryletherketone

Abstract

This invention belongs to the field of polyaryletherketone resin preparation technology, and relates to a method for preparing polyaryletherketone with low crystallinity and low melting point. Under nitrogen protection, 4,4'-difluorobenzophenone, anhydrous sodium carbonate, hydroquinone, biphenyl, and bisphenol A are added to a solvent, stirred and mixed evenly, and then heated for polymerization to obtain polyaryletherketone with low crystallinity and low melting point. The molar ratio of hydroquinone, biphenyl, and bisphenol A is 55~75:5~25:5~20. This invention uses a precise compounding system of three phenol monomers, hydroquinone, biphenyl, and bisphenol A, to achieve fine control of the molecular chain structure. By disrupting the regularity of the molecular chain through the quaternary carbon atoms in bisphenol A, the crystallinity and melting point are reduced. Biphenyl compensates for the loss of rigidity, while hydroquinone retains its intrinsic properties. This solves the problem of "reduced melting point inevitably leads to reduced heat resistance / mechanical properties" in existing technologies from the root of molecular structure.

Description

Technical Field

[0001] This invention belongs to the field of polyaryletherketone resin preparation technology, and relates to a method for preparing polyaryletherketone with low crystallinity and low melting point. Background Technology

[0002] Polyetheretherketone (PEEK), due to the benzene rings, ether bonds, and ketone groups in its molecular backbone, possesses excellent high-temperature resistance, mechanical strength, chemical corrosion resistance, biocompatibility, electrical insulation, and radiation resistance. Its long-term operating temperature can reach 260℃, and its melting point is as high as 343℃. Even at high temperatures, it maintains good mechanical properties and dimensional stability, while also exhibiting outstanding advantages such as self-lubrication, flame retardancy, and hydrolysis resistance. It occupies an irreplaceable position in many fields with stringent material performance requirements, including aerospace, electronics, medical devices, and high-end manufacturing.

[0003] Despite the significant performance advantages of PEEK materials, their excessively high melting and processing temperatures (300℃~400℃) limit their further application and contradict the current global advocacy for energy conservation, emission reduction, and green manufacturing. On the one hand, the high processing temperatures place extremely high demands on production equipment, requiring expensive high-temperature molds, heating systems, and specialized processing equipment. This significantly increases initial equipment investment and long-term maintenance costs, limiting the application of PEEK materials to high-end sectors and hindering their widespread adoption in other manufacturing scenarios. On the other hand, high-temperature processing not only consumes a large amount of energy but may also lead to degradation of the material's molecular chains, affecting the consistency of the final product's performance and service life.

[0004] To address these issues, existing technologies attempt to reduce the crystallinity and melting point of polyaryletherketones (PAEs) through copolymerization modification and additive doping. However, these methods often have significant limitations: some modification schemes can only slightly reduce the melting point or crystallinity, failing to meet the requirements for medium- and low-temperature processing; some schemes introduce modifying monomers that disrupt the rigidity of the PAE main chain, leading to a significant decrease in the material's heat resistance and mechanical properties; and other schemes involve complex processes and demanding reaction conditions, making it difficult to achieve industrial-scale mass production. Furthermore, the modified materials exhibit poor processing stability, making them unsuitable for precision molding scenarios.

[0005] For example, patent application CN114213650A uses 4-chloro-4-hydroxybenzophenone as the main raw material, adds 50 mol% of the ortho-isomer (2-chloro-4-hydroxybenzophenone) to copolymerize with the main monomer, and obtains a polyarylether ketone with a controllable melting point (Tm) of 312℃ and a crystallinity of 17.3%. However, this type of technique using molecular chain control generally suffers from defects such as a significant decrease in mechanical strength, complex processes, impaired thermal stability, and a narrowed processing window.

[0006] Therefore, it is of great significance to study a method for preparing polyaryletherketones with low crystallinity and low melting point in order to solve the problems existing in the prior art. Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art and provide a method for preparing polyaryletherketones with low crystallinity and low melting point.

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

[0009] A method for preparing low-crystallinity, low-melting-point polyarylether ketone involves adding 4,4'-difluorobenzophenone, anhydrous sodium carbonate, hydroquinone, biphenyl phenol, and bisphenol A to a solvent under nitrogen protection, stirring and mixing thoroughly, and then heating to carry out a polymerization reaction to obtain low-crystallinity, low-melting-point polyarylether ketone.

[0010] The molar ratio of hydroquinone, biphenyl, and bisphenol A is 55~75:5~25:5~20.

[0011] As a preferred technical solution:

[0012] The preparation method of a low-crystallinity, low-melting-point polyaryletherketone as described above includes the following specific steps:

[0013] (1) Deoxygenate the polymerization unit until the oxygen content in the system is <50ppm;

[0014] (2) Under nitrogen protection, solvent, 4,4'-difluorobenzophenone I, anhydrous sodium carbonate, hydroquinone, biphenyl and bisphenol A are added to the polymerization device in sequence and stirred until a mixed reaction system is obtained.

[0015] (3) The mixed reaction system of step (2) is heated at a rate of 1~10℃ / min. First, the temperature is raised to 220~280℃ and kept for 0.5~1h (prepolymerization stage, to avoid local overheating and decomposition of monomers), and then the temperature is raised to 300~330℃ and kept for 3~4h (main polymerization stage, to achieve full polycondensation) to carry out the polymerization reaction, and the mixture is continuously stirred during the reaction.

[0016] (4) Add the end-capping agent 4,4'-difluorobenzophenone II to the polymerization apparatus, keep warm and stir for 60~90 min to terminate the polymerization reaction;

[0017] (5) The product obtained from the reaction was successively cooled, crushed, washed with acetone, washed with water, and dried under vacuum to obtain a polyarylether ketone with low crystallinity and low melting point.

[0018] It should be noted that the serial numbers I and II in the above-mentioned 4,4'-difluorobenzophenone I and 4,4'-difluorobenzophenone II of the present invention are only a formal distinction and are not a limitation on the properties of the substances themselves.

[0019] In the preparation method of a low crystallinity, low melting point polyarylether ketone as described above, the oxygen removal method in step (1) is inert gas purging, and the inert gas purging flow rate is 30~50mL / min.

[0020] In the preparation method of low crystallinity and low melting point polyarylether ketone described above, the solvent in step (2) is diphenyl sulfone, and the molar ratio of diphenyl sulfone, 4,4'-difluorobenzophenone I, anhydrous sodium carbonate and hydroquinone is 4.4~6.0:1.35~1.85:1.51~2.06:1.

[0021] In the preparation method of low crystallinity, low melting point polyaryletherketone described above, the water content of anhydrous sodium carbonate in step (2) is ≤0.2% (mass percentage), and the mesh size is 200 mesh. This invention performs a fine pretreatment on the salt-forming agent sodium carbonate, drying it to a water content ≤0.2% to avoid water causing bubbles in the system and affecting polymerization uniformity; pulverizing it to 200 mesh increases the specific surface area, making the salt-forming reaction more complete and avoiding insufficient local salt formation leading to polymerization termination.

[0022] In the preparation method of a low crystallinity, low melting point polyarylether ketone as described above, the stirring speed in step (3) is 300~600 r / min.

[0023] In the preparation method of low crystallinity and low melting point polyarylether ketone described above, the molar ratio of end-capping agent 4,4'-difluorobenzophenone II to hydroquinone in step (4) is 0.0244~0.033:1. If the ratio is higher than this, excessive end-capping agent will lead to excessive chain termination and low molecular weight. If the ratio is lower than this, branching or gelation will be triggered, both of which will significantly reduce the melt viscosity and fail to meet the requirements of high-performance processing.

[0024] In the preparation method of a low crystallinity, low melting point polyarylether ketone described above, cooling in step (5) refers to cooling by pouring into deionized water, and the temperature of vacuum drying is 120~150℃.

[0025] The method for preparing low-crystallinity, low-melting-point polyaryletherketone (PAEK) as described above results in PAEK with a melting point of 278–305°C, a glass transition temperature of 147–153°C, a crystallinity of <15%, a long-term service temperature of 240–250°C, a tensile strength of 96–111 MPa, a tensile modulus of 3300–4200 MPa, and a notched cantilever beam impact strength of 6.2–8.2 KJ / m. 2The bending strength is 140~180MPa, and the bending modulus is 3200~4200MPa.

[0026] Invention principle:

[0027] This invention utilizes a ternary complex of hydroquinone, biphenyl, and bisphenol A, with precise control of the molar ratio, for nucleophilic polycondensation with 4,4'-difluorobenzophenone. This is the first time that hydroquinone, biphenyl, and bisphenol A have been used in a controllable combination, breaking through the technical bottleneck of traditional single-component or binary combinations. This ternary synergistic system retains the inherent advantages of each monomer while generating a significant synergistic effect, resulting in polyarylether ketones that maintain excellent heat resistance and mechanical properties while significantly reducing crystallinity and melting point, achieving a synergistic effect greater than the sum of its parts (1+1+1>3). The specific synergistic mechanism is as follows:

[0028] From the perspective of molecular action, hydroquinone has the highest phenolic hydroxyl activity and is prone to redox reactions, but its molecular rigidity is insufficient and its heat resistance is limited; biphenyl is extremely rigid, but its phenolic hydroxyl activity is low, and its intermolecular packing is too dense, resulting in extremely poor processing fluidity; bisphenol A is more flexible and has excellent processing performance, but its heat resistance and antioxidant activity are both weak. When used in combination, the three components work together to construct a ternary system of "active site-rigid support-flexible regulation" through the combined effects of the highly active phenolic hydroxyl groups of hydroquinone, the rigid conjugated benzene ring of biphenyl, and the flexible isopropyl group of bisphenol A. The strongly polar hydroxyl groups of hydroquinone form a transient hydrogen bond network with the ether / hydroxyl groups in bisphenol A or biphenyl. At the same time, the conjugated benzene ring of biphenyl forms π-π stacking with the benzene ring of hydroquinone, which improves the rigidity and mechanical strength of the network. The isopropyl group of bisphenol A is interspersed throughout, which alleviates the tight packing between biphenyl molecules, effectively reducing the stacking density and melting point of the chain segments, avoiding brittleness caused by excessive cross-linking, and making the overall performance more excellent.

[0029] From an electronic perspective, the core structure of bisphenol A consists of two phenolic hydroxyl groups linked by a central carbon atom (quaternary carbon), which is then bonded to two methyl groups (i.e., isopropylidene groups). Methyl groups (-CH3) are typical electron-donating groups. Because the two methyl groups are directly attached to the central carbon atom connecting the two benzene rings, this electron-donating effect is transferred along the carbon chain to the benzene rings, thus affecting the phenolic hydroxyl groups. Therefore, the electron cloud density of the oxygen atom on the phenolic hydroxyl group increases, slightly enhancing the polarity of the OH bond. The lone pair electrons on the oxygen atom become more active, strengthening the hydrogen bonding between bisphenol A and hydroquinone and biphenyl. In condensation reactions, the hydroxyl group of bisphenol A has an enhanced ability to attack the carbonyl carbon as a nucleophile, resulting in higher reactivity than ordinary phenolic hydroxyl groups unaffected by the electron-donating effect. The two benzene rings of biphenyl are directly connected, forming a highly conjugated large π-bond system. This structure leads to a highly delocalized and aggregated electron cloud throughout the biphenyl backbone. While this high electron cloud density endows the material with rigidity and heat resistance, it also leads to strong π-π stacking between molecular chains, resulting in an extremely high melting point and making it difficult to melt. However, when bisphenol A is introduced into the resorcinol system through copolymerization, the bisphenol A unit acts as an "electron buffer" inserted between resorcinol units in the copolymer chain. This breaks the long-range conjugation that might occur between resorcinol units through chemical bonds. Through the spatial field effect, it fine-tunes the electron cloud distribution on the benzene rings of adjacent resorcinol units, reducing the originally extremely high, localized peak electron cloud density of resorcinol. This alleviates the strong π-π stacking between resorcinol molecules, reduces intermolecular forces, lowers the melting point, and widens the thermal processing window. Simultaneously, the isopropyl group of bisphenol A absorbs some stress through internal rotation, making the entire molecular chain more extended and homogenized in the flow field. This allows the molecular chains to slide more easily under shear, exhibiting better fluidity.

[0030] Beneficial effects:

[0031] (1) The present invention provides a method for preparing polyaryletherketone with low crystallinity and low melting point. By using bisphenol A as the main monomer, the regularity of the polyaryletherketone molecular chain is destroyed, the molecular chain packing density is effectively reduced, and the melting point is reduced to about 300°C. Compared with traditional polyaryletherketone (melting point above 343°C), the processing temperature is reduced by more than 18%, which can be adapted to conventional medium and high temperature processing equipment. No special high temperature resistant equipment is required, which greatly reduces processing energy consumption and equipment threshold. At the same time, the low crystallinity slows down the cooling and crystallization rate after the material melts, and the molded parts are less likely to have defects such as warping, cracking, and yellow spots, which improves the molding consistency and yield. It is especially suitable for precision processing scenarios such as 3D printing, composite material impregnation, and precision coating.

[0032] (2) The present invention provides a method for preparing low crystallinity and low melting point polyarylether ketones by using a precise compounding system of three phenol monomers, hydroquinone, biphenyl and bisphenol A, which achieves fine control of molecular chain structure and solves the problem of "low melting point inevitably reduces heat resistance / mechanical properties" in the prior art from the root of molecular structure. While reducing melting point and improving processability, it effectively maintains high glass transition temperature, high strength and high toughness.

[0033] (3) The preparation method of low crystallinity and low melting point polyarylether ketone of the present invention breaks through the technical bottleneck of traditional single component or binary combination by first controlling the use of three monomers, hydroquinone, biphenyl and bisphenol A; this ternary synergistic system retains the inherent advantages of each monomer while generating a significant technical synergistic effect, achieving the technical effect of 1+1+1>3.

[0034] (4) The preparation method of low crystallinity and low melting point polyaryletherketone of the present invention adopts uniform heating + two-stage fixed heat preservation, combined with constant speed stirring, which avoids the problems of local overheating, monomer decomposition and uneven polymerization in the existing process, and ensures the full and uniform polycondensation of ternary monomers.

[0035] (5) The present invention provides a method for preparing low crystallinity and low melting point polyarylether ketone. The introduction of bisphenol A significantly reduces the cost of raw materials. The preparation process adopts programmed temperature rise polymerization, the process parameters are easy to control, the reaction conditions are mild, no complex equipment is required, the post-processing is simple, it can be directly adapted to existing polyarylether ketone production lines, and it is easy to industrialize. Attached Figure Description

[0036] Figure 1 This is the DSC spectrum of a low-crystallinity, low-melting-point polyaryletherketone from Example 1 of the present invention;

[0037] Figure 2 The Fourier Transform (FTIR) spectrum of a low-crystallinity, low-melting-point polyaryletherketone in Example 1 of this invention.

[0038] Figure 3 NMR of low-crystallinity, low-melting-point polyaryletherketone for Example 1 of the Invention 1 H spectrum;

[0039] Figure 4 NMR of low-crystallinity, low-melting-point polyaryletherketone (PAGE) as described in Example 1 of this invention 13 C spectrum. Detailed Implementation

[0040] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0041] The test standards involved in the performance indicators of the embodiments and comparative examples of this invention are as follows:

[0042] Melt mass flow rate: The melt mass flow rate was tested according to standard GB / T 3682.1-2018 at 400℃ and 2.16kg.

[0043] Tensile strength and tensile modulus: Tested according to standard GB / T 1040.2-2022, using type 1A dumbbell-shaped specimens.

[0044] Notched impact strength of cantilever beam: tested according to standard GB / T 1843-2008.

[0045] Bending strength and bending modulus: tested according to standard GB / T 9341-2008.

[0046] Long-term service temperature: Tested according to Method B in standard GB / T 7141-2008. Long-term thermal aging tests were conducted on polyaryletherketone standard samples in a forced-ventilation oven with temperature gradients of 160℃, 180℃, 200℃, 220℃, 240℃, and 260℃. For each temperature, samples were taken at different time intervals of 100h, 300h, 500h, 1000h, 2000h, and 3000h to test tensile, bending, and impact properties. The long-term service temperature was extrapolated from a performance retention rate of 50%.

[0047] Example 1

[0048] A method for preparing a low-crystallinity, low-melting-point polyaryletherketone, comprising the following steps:

[0049] (1) Nitrogen gas was used to purge the polymerization unit to remove oxygen. The inert gas purging flow rate was 30 mL / min until the oxygen content in the system was 30 ppm.

[0050] (2) Pretreatment of anhydrous sodium carbonate:

[0051] Anhydrous sodium carbonate was dried at 110°C until the moisture content was 0.2%, and then pulverized to 200 mesh.

[0052] (3) Under nitrogen protection, diphenyl sulfone, 4,4'-difluorobenzophenone I, pretreated anhydrous sodium carbonate, hydroquinone, biphenyl and bisphenol A were added to the polymerization device in sequence and stirred until a mixed reaction system was obtained.

[0053] The molar ratio of diphenyl sulfone, 4,4'-difluorobenzophenone I, anhydrous sodium carbonate and hydroquinone is 4.4:1.35:1.51:1; the molar ratio of hydroquinone, biphenyl and bisphenol A is 75:15:10.

[0054] (4) The mixed reaction system of step (3) is heated at a rate of 1℃ / min. First, it is heated to 250℃ and kept at that temperature for 0.5h, then heated to 310℃ and kept at that temperature for 3h to carry out the polymerization reaction. During the reaction, the mixture is continuously stirred at a speed of 300r / min.

[0055] (5) Add the end-capping agent 4,4'-difluorobenzophenone II to the polymerization apparatus, keep it warm and stir for 60 min to terminate the polymerization reaction;

[0056] The mass ratio of the end-capping agent 4,4'-difluorobenzophenone II to hydroquinone is 0.024:1.

[0057] (6) The product obtained from the reaction was successively cooled with deionized water at 20°C, pulverized, washed with acetone, washed with water, and dried under vacuum at 135°C to obtain polyarylether ketone with low crystallinity and low melting point.

[0058] The final low-crystallinity, low-melting-point polyaryletherketone (PAEK) exhibited a melt flow rate of 44.35 g / 10 min, a melting point of 301.44 °C, a glass transition temperature of 152.67 °C, a crystallization temperature of 242.33 °C, a crystallinity of 14.12%, a long-term service temperature of 250 °C, a tensile strength of 111 MPa, a tensile modulus of 4200 MPa, and a notched cantilever beam impact strength of 8.2 KJ / m. 2 The bending strength is 180 MPa and the bending modulus is 4200 MPa.

[0059] like Figure 1 As shown, the sample has a glass transition temperature of 152.67℃, a crystallization temperature of 242.33℃, and a melting point of 301.44℃. The melting peak is located in the 350℃ region and exhibits a single broad endothermic peak. The melting point of the copolymer is significantly higher than that of the pure monomers (hydroquinone: 170℃, bisphenol A: 158℃, biphenyl: 280℃), proving that the intermolecular forces are enhanced and the heat resistance is excellent. The broad peak shape indicates that there are moderate defects in the crystal lattice, achieving a balance between high heat resistance and processability, and solving the common industry problem of difficult processing of traditional PEEK.

[0060] like Figure 2As shown, the Fourier Transmission Infrared (FTIR) test results indicate that the infrared spectrum is in the range of 3000~3100 cm⁻¹. -1 Characteristic peaks of aromatic ring CH stretching vibration appear at 2900~3000 cm⁻¹. -1 The characteristic peak of the bisphenol A isopropyl saturated CH stretching vibration appears at 1650~1700 cm⁻¹. -1 A characteristic peak of strong ketone carbonyl C=O stretching vibration appears at 1200~1300 cm⁻¹. -1 A very strong characteristic peak of the asymmetric stretching vibration of aromatic ether COC appears at 700~900cm. -1 Multiple sets of aromatic ring CH out-of-plane bending vibration characteristic peaks appeared at the location.

[0061] like Figure 3 As shown, 1 The HCl spectrum shows a broad aromatic hydrogen peak at 6.5–7.8 ppm and a characteristic peak of bisphenol A methyl groups at 1.6–1.8 ppm; for example, Figure 4 As shown, 13 The C-ray spectroscopy shows a ketone carbonyl carbon signal at 190–200 ppm, an aromatic backbone carbon at 115–160 ppm, and bisphenol A quaternary carbon and methyl carbon at 30–45 ppm.

[0062] The above spectra indicate that hydroquinone, biphenyl, and bisphenol A monomers were successfully copolymerized, with bisphenol A successfully participating in the polymerization.

[0063] Comparative Example 1

[0064] A method for preparing polyaryletherketone is basically the same as in Example 1, except that the preparation method in Example 5 of patent CN102250299A is adopted.

[0065] The final polyaryletherketone had a melting point of 334℃, a glass transition temperature of 149℃, a tensile strength of 94MPa, a tensile modulus of 3300MPa, a flexural strength of 152MPa, and a flexural modulus of 3700MPa.

[0066] Comparing Example 1 and Comparative Example 1, it can be found that the melting point of Example 1 is lower and the glass transition temperature is higher. This is because the bisphenol A introduced into the copolymer system contains isopropyl side groups, and the introduced biphenyl has a rigid biphenyl bending structure, which destroys the regular linear symmetry structure of the original polyaryletherketone molecular chain, weakens the compactness of the molecular chain and the regularity of crystallization, reduces the lattice order of the molecular chain and the perfection of the crystal; the van der Waals forces between molecular chains are weakened, and the heat energy required to destroy the crystal structure is reduced, which is macroscopically manifested as a significant decrease in the melting point; the biphenyl has a rigid aromatic ring structure, which greatly increases the rotational steric hindrance within the polymer chain after being introduced into the main chain, restricting the degree of freedom of chain segment movement. At the same time, the benzene ring structure of bisphenol A further strengthens the rigidity of the main chain, making it more difficult for the molecular chain segments to relax and move when heated, requiring higher temperatures to achieve chain segment thawing movement, thus significantly increasing the glass transition temperature.

[0067] Comparative Example 2

[0068] A method for preparing polyaryletherketone is basically the same as in Example 1, except that in step (3), bisphenol A is replaced by an equimolar amount of biphenyl hydroquinone, i.e., bisphenol A is not added.

[0069] The final polyaryletherketone (POGK) has a melting point of 303℃, a glass transition temperature of 152℃, a long-term service temperature of 220℃, a tensile strength of 95MPa, a tensile modulus of 3600MPa, and a notched cantilever beam impact strength of 6.5KJ / m. 2 The bending strength is 140 MPa and the bending modulus is 3200 MPa.

[0070] Comparing Example 1 and Comparative Example 2, it can be found that the mechanical properties of Comparative Example 2 are significantly reduced. This is because after introducing bisphenol A in Example 1, the proportion of rigid units in the molecular backbone increases, the inter-chain forces are enhanced, and the tensile, bending strength and modulus are effectively improved. At the same time, the appropriate molecular chain structure regulation refines the material crystal grains, improves the interfacial compatibility, and makes the stress distribution and transmission more uniform. This not only improves rigidity and strength, but also improves notched impact toughness, thus achieving a simultaneous enhancement of comprehensive mechanical properties.

[0071] Comparative Example 3

[0072] A method for preparing polyaryletherketone is basically the same as in Example 1, except that in step (3), bisphenol A is used to replace biphenyl hydrochloride, i.e., no biphenyl hydrochloride is added.

[0073] The final polyaryletherketone (POG) has a melting point of 310℃, a glass transition temperature of 135℃, a long-term service temperature of 180℃, a tensile strength of 90 MPa, a tensile modulus of 3000 MPa, and a notched cantilever beam impact strength of 6.2 KJ / m. 2The bending strength is 115 MPa and the bending modulus is 2700 MPa.

[0074] Comparing Example 1 and Comparative Example 3, it can be found that Comparative Example 3 has an increased melting point, but a significantly decreased glass transition temperature, long-term service temperature, and mechanical properties. This is because the introduction of a rigid conjugated structure of biphenyl into the molecular chain of Example 1 increases the rigidity and steric hindrance of the molecular chain, restricts the movement of molecular chain segments, and thus increases the glass transition temperature, significantly enhancing the heat resistance of the material and consequently greatly increasing the long-term service temperature. The rigid skeleton of the biphenyl structure enhances the inter-chain forces and overall structural regularity, effectively improving the tensile and flexural mechanical strength and modulus of the material, resulting in superior rigid load-bearing performance. The introduction of biphenyl units optimizes the flexibility and crystallization balance of the polymer molecular chain, moderately reducing the crystallization regularity and causing a slight decrease in the melting point, which is beneficial for material processing and molding. The rigid structure of biphenyl can disperse external impact and inhibit crack propagation, thereby improving the notched impact strength and improving the toughness and impact resistance of the material.

[0075] Comparative Example 4

[0076] A method for preparing polyaryletherketone is basically the same as in Example 1, except that in step (3), hydroquinone is replaced with an equimolar amount of biphenyl, i.e., hydroquinone is not added.

[0077] The final polyaryletherketone (POG) has a melting point of 320℃, a glass transition temperature of 140℃, a long-term service temperature of 200℃, a tensile strength of 93 MPa, a tensile modulus of 3200 MPa, and a notched cantilever beam impact strength of 5.8 KJ / m. 2 The bending strength is 120MPa and the bending modulus is 2800MPa.

[0078] Comparing Example 1 and Comparative Example 4, it can be found that the melting point of Comparative Example 4 is higher, while the glass transition temperature and mechanical properties are significantly lower. This is because the introduction of hydroquinone monomer in Example 1 increases the variety of molecular chain unit structures, which disrupts the regularity and crystal order of the polyaryletherketone molecular chain, inhibits perfect crystal growth, and thus significantly lowers the melting point, which is beneficial to improving the material's melt processing fluidity and molding processability. Hydroquinone forms a multi-component copolymer system with biphenyl and bisphenol A, increasing the proportion of rigid molecular chain structures and the degree of resistance to rotation within chain segments, thus restricting the movement of polymer chain segments, raising the glass transition temperature, and enhancing the bulk heat resistance. Multi-component copolymerization optimizes the molecular chain stacking mode and intermolecular forces, improves the degree of cross-linking entanglement, and strengthens the synergistic effect of the rigid skeleton, thereby significantly improving tensile strength, flexural strength, and modulus, resulting in superior structural load-bearing rigidity. The linear rigid structure of hydroquinone can adjust the flexibility of the molecular chain, effectively disperse impact stress, hinder crack initiation and propagation, greatly improve the material's toughness, and significantly improve the notched impact strength of the cantilever beam.

[0079] Comparative Example 5

[0080] A method for preparing polyaryletherketone is basically the same as in Example 1, except that the molar ratio of hydroquinone, biphenyl and bisphenol A in step (3) is 45:30:25.

[0081] The final polyaryletherketone (POG) has a melting point of 275.11℃, a glass transition temperature of 145.03℃, a long-term service temperature of 220℃, a tensile strength of 90 MPa, a tensile modulus of 3000 MPa, and a notched cantilever beam impact strength of 5.5 KJ / m. 2 The bending strength is 115 MPa and the bending modulus is 2700 MPa.

[0082] Comparing Comparative Example 5 with Example 1, it can be found that although the melting point of Comparative Example 5 decreased significantly, the glass transition temperature also decreased significantly, resulting in an overall reduction in mechanical properties. This is because biphenyl contains a large rigid side group, and bisphenol A has an isopropyl hydrophobic flexible group and a benzene ring side group. When the molar ratio of these two increases, it will disrupt the regularity and crystallinity of the polyaryletherketone molecular chain, resulting in loose molecular chain stacking and reduced crystallinity, which in turn leads to a decrease in melting point and glass transition temperature. The isopropyl flexible group in bisphenol A increases the distance between molecular chains and weakens the inter-chain forces. At the same time, the large volume structure of biphenyl and bisphenol A will hinder the tight entanglement of molecular chains, reducing the rigidity, strength, and modulus of the material. The deterioration of molecular chain regularity, the decrease in crystallinity, and the increase in internal defects make it easy to generate stress concentration under stress, resulting in a decrease in notched impact strength, a decrease in toughness, and a reduction in flexural load-bearing capacity and flexural modulus.

[0083] Example 2

[0084] A method for preparing a low-crystallinity, low-melting-point polyaryletherketone, comprising the following steps:

[0085] (1) Nitrogen gas was used to purge the polymerization unit to remove oxygen. The inert gas purging flow rate was 30 mL / min until the oxygen content in the system was 35 ppm.

[0086] (2) Pretreatment of anhydrous sodium carbonate:

[0087] Anhydrous sodium carbonate was dried at 110°C until the moisture content was 0.2%, and then pulverized to 200 mesh.

[0088] (3) Under nitrogen protection, diphenyl sulfone, 4,4'-difluorobenzophenone I, pretreated anhydrous sodium carbonate, hydroquinone, biphenyl and bisphenol A were added to the polymerization device in sequence and stirred until a mixed reaction system was obtained.

[0089] The molar ratio of diphenyl sulfone, 4,4'-difluorobenzophenone I, anhydrous sodium carbonate and hydroquinone is 4.4:1.35:1.51:1; the molar ratio of hydroquinone, biphenyl phenol and bisphenol A is 75:10:15.

[0090] (4) The mixed reaction system of step (3) is heated at a rate of 1℃ / min. First, it is heated to 250℃ and kept at that temperature for 0.5h, then heated to 310℃ and kept at that temperature for 3h to carry out the polymerization reaction. During the reaction, the mixture is continuously stirred at a speed of 300r / min.

[0091] (5) Add the end-capping agent 4,4'-difluorobenzophenone II to the polymerization apparatus, keep it warm and stir for 60 min to terminate the polymerization reaction;

[0092] The mass ratio of the end-capping agent 4,4'-difluorobenzophenone II to hydroquinone is 0.024:1.

[0093] (6) The product obtained from the reaction was successively cooled with deionized water at 20°C, pulverized, washed with acetone, washed with water, and dried under vacuum at 135°C to obtain polyarylether ketone with low crystallinity and low melting point.

[0094] The final low-crystallinity, low-melting-point polyaryletherketone (PAEK) exhibited a melt flow rate of 46.12 g / 10 min, a melting point of 304.79 °C, a glass transition temperature of 150.81 °C, a crystallization temperature of 250.39 °C, a crystallinity of 14.56%, a long-term service temperature of 248 °C, a tensile strength of 108 MPa, a tensile modulus of 3800 MPa, and a notched cantilever beam impact strength of 7.8 KJ / m. 2 The bending strength is 175 MPa and the bending modulus is 3900 MPa.

[0095] Example 3

[0096] A method for preparing a low-crystallinity, low-melting-point polyaryletherketone, comprising the following steps:

[0097] (1) The polymerization unit was deoxygenated by nitrogen purging. The inert gas purging flow rate was 30 mL / min until the oxygen content in the system was 48 ppm.

[0098] (2) Pretreatment of anhydrous sodium carbonate:

[0099] Anhydrous sodium carbonate was dried at 110°C until the moisture content was 0.2%, and then pulverized to 200 mesh.

[0100] (3) Under nitrogen protection, diphenyl sulfone, 4,4'-difluorobenzophenone I, pretreated anhydrous sodium carbonate, hydroquinone, biphenyl and bisphenol A were added to the polymerization device in sequence and stirred until a mixed reaction system was obtained.

[0101] The molar ratio of diphenyl sulfone, 4,4'-difluorobenzophenone I, anhydrous sodium carbonate and hydroquinone is 6.0:1.85:2.06:1; the molar ratio of hydroquinone, biphenyl and bisphenol A is 55:25:20.

[0102] (4) The mixed reaction system of step (3) is heated at a rate of 1℃ / min. First, it is heated to 250℃ and kept at that temperature for 0.5h, then heated to 310℃ and kept at that temperature for 3h to carry out the polymerization reaction. During the reaction, the mixture is continuously stirred at a speed of 300r / min.

[0103] (5) Add the end-capping agent 4,4'-difluorobenzophenone II to the polymerization apparatus, keep it warm and stir for 60 min to terminate the polymerization reaction;

[0104] The mass ratio of the end-capping agent 4,4'-difluorobenzophenone II to hydroquinone is 0.033:1.

[0105] (6) The product obtained from the reaction was successively cooled with deionized water at 20°C, pulverized, washed with acetone, washed with water, and dried under vacuum at 135°C to obtain polyarylether ketone with low crystallinity and low melting point.

[0106] The final low-crystallinity, low-melting-point polyaryletherketone (PAEK) exhibited a melt flow rate of 50.18 g / 10 min, a melting point of 297.63 °C, a glass transition temperature of 148.33 °C, a crystallization temperature of 240.27 °C, a crystallinity of 14.61%, a long-term service temperature of 242 °C, a tensile strength of 96 MPa, a tensile modulus of 3400 MPa, and a notched cantilever beam impact strength of 6.2 KJ / m. 2 The bending strength is 165 MPa and the bending modulus is 3200 MPa.

[0107] Example 4

[0108] A method for preparing a low-crystallinity, low-melting-point polyaryletherketone, comprising the following steps:

[0109] (1) Nitrogen gas was used to purge the polymerization unit to remove oxygen. The inert gas purging flow rate was 40 mL / min until the oxygen content in the system was 45 ppm.

[0110] (2) Pretreatment of anhydrous sodium carbonate:

[0111] Anhydrous sodium carbonate was dried at 110°C until the moisture content was 0.15%, and then pulverized to 200 mesh.

[0112] (3) Under nitrogen protection, diphenyl sulfone, 4,4'-difluorobenzophenone I, pretreated anhydrous sodium carbonate, hydroquinone, biphenyl and bisphenol A were added to the polymerization device in sequence and stirred until a mixed reaction system was obtained.

[0113] The molar ratio of diphenyl sulfone, 4,4'-difluorobenzophenone I, anhydrous sodium carbonate and hydroquinone is 5.07:1.56:1.74:1; the molar ratio of hydroquinone, biphenyl and bisphenol A is 65:25:10.

[0114] (4) The mixed reaction system of step (3) is heated at a rate of 5℃ / min. First, it is heated to 220℃ and kept for 1h, then heated to 300℃ and kept for 4h to carry out the polymerization reaction. During the reaction, the mixture is continuously stirred at a speed of 300r / min.

[0115] (5) Add the end-capping agent 4,4'-difluorobenzophenone II to the polymerization apparatus, keep warm and stir for 75 min to terminate the polymerization reaction;

[0116] The mass ratio of the end-capping agent 4,4'-difluorobenzophenone II to hydroquinone is 0.028:1.

[0117] (6) The product obtained from the reaction was successively cooled with deionized water at 20°C, pulverized, washed with acetone, washed with water, and dried under vacuum at 120°C to obtain polyarylether ketone with low crystallinity and low melting point.

[0118] The final low-crystallinity, low-melting-point polyaryletherketone (PAEK) exhibited a melt flow rate of 52.22 g / 10 min, a melting point of 302.55 °C, a glass transition temperature of 150.26 °C, a crystallization temperature of 242.51 °C, a crystallinity of 14.47%, a long-term service temperature of 247 °C, a tensile strength of 98 MPa, a tensile modulus of 3600 MPa, and a notched cantilever beam impact strength of 6.5 KJ / m. 2 The bending strength is 150 MPa and the bending modulus is 3600 MPa.

[0119] Example 5

[0120] A method for preparing a low-crystallinity, low-melting-point polyaryletherketone, comprising the following steps:

[0121] (1) Nitrogen gas was used to purge the polymerization unit to remove oxygen. The inert gas purging flow rate was 50 mL / min until the oxygen content in the system was 40 ppm.

[0122] (2) Pretreatment of anhydrous sodium carbonate:

[0123] Anhydrous sodium carbonate was dried at 110°C until the moisture content was 0.1%, and then pulverized to 200 mesh.

[0124] (3) Under nitrogen protection, diphenyl sulfone, 4,4'-difluorobenzophenone I, pretreated anhydrous sodium carbonate, hydroquinone, biphenyl and bisphenol A were added to the polymerization device in sequence and stirred until a mixed reaction system was obtained.

[0125] The molar ratio of diphenyl sulfone, 4,4'-difluorobenzophenone I, anhydrous sodium carbonate and hydroquinone is 5.5:1.70:1.89:1; the molar ratio of hydroquinone, biphenyl and bisphenol A is 60:25:15.

[0126] (4) The mixed reaction system of step (3) is heated at a rate of 10℃ / min. First, it is heated to 280℃ and kept at that temperature for 0.75h, and then heated to 330℃ and kept at that temperature for 3.5h to carry out the polymerization reaction. During the reaction, the mixture is continuously stirred at a speed of 300r / min.

[0127] (5) Add the end-capping agent 4,4'-difluorobenzophenone II to the polymerization apparatus, keep warm and stir for 90 min to terminate the polymerization reaction;

[0128] The mass ratio of the end-capping agent 4,4'-difluorobenzophenone II to hydroquinone is 0.031:1.

[0129] (6) The product obtained from the reaction was successively cooled with deionized water at 20°C, pulverized, washed with acetone, washed with water, and dried under vacuum at 150°C to obtain polyarylether ketone with low crystallinity and low melting point.

[0130] The final low-crystallinity, low-melting-point polyaryletherketone (PAEK) exhibited a melt flow rate of 48.16 g / 10 min, a melting point of 278.22 °C, a glass transition temperature of 147.63 °C, a crystallization temperature of 240.13 °C, a crystallinity of 14.59%, a long-term service temperature of 245 °C, a tensile strength of 100 MPa, a tensile modulus of 3300 MPa, and a notched cantilever beam impact strength of 7.3 KJ / m. 2 The bending strength is 140 MPa and the bending modulus is 3800 MPa.

Claims

1. A method for preparing a low-crystallinity, low-melting-point polyaryletherketone, characterized in that: Under nitrogen protection, 4,4'-difluorobenzophenone, anhydrous sodium carbonate, hydroquinone, biphenol and bisphenol A were added to a solvent, stirred and mixed evenly, and then heated to carry out a polymerization reaction to obtain a polyarylether ketone with low crystallinity and low melting point. The molar ratio of hydroquinone, biphenyl, and bisphenol A is 55~75:5~25:5~20.

2. The method for preparing a low-crystallinity, low-melting-point polyaryletherketone according to claim 1, characterized in that, The specific steps are as follows: (1) Deoxygenate the polymerization unit until the oxygen content in the system is <50ppm; (2) Under nitrogen protection, solvent, 4,4'-difluorobenzophenone I, anhydrous sodium carbonate, hydroquinone, biphenyl and bisphenol A are added to the polymerization device in sequence and stirred until a mixed reaction system is obtained. (3) The mixed reaction system of step (2) is heated at a rate of 1~10℃ / min. First, the temperature is raised to 220~280℃ and kept for 0.5~1h, then the temperature is raised to 300~330℃ and kept for 3~4h to carry out the polymerization reaction, and the mixture is continuously stirred during the reaction. (4) Add the end-capping agent 4,4'-difluorobenzophenone II to the polymerization apparatus, keep warm and stir for 60~90 min to terminate the polymerization reaction; (5) The product obtained from the reaction was successively cooled, crushed, washed with acetone, washed with water, and dried under vacuum to obtain a polyarylether ketone with low crystallinity and low melting point.

3. The method for preparing a low-crystallinity, low-melting-point polyaryletherketone according to claim 2, characterized in that, In step (1), the deoxygenation method is inert gas purging, and the inert gas purging flow rate is 30~50mL / min.

4. The method for preparing a low-crystallinity, low-melting-point polyaryletherketone according to claim 2, characterized in that, In step (2), the solvent is diphenyl sulfone, and the molar ratio of diphenyl sulfone, 4,4'-difluorobenzophenone I, anhydrous sodium carbonate and hydroquinone is 4.4~6.0:1.35~1.85:1.51~2.06:

1.

5. The method for preparing a low-crystallinity, low-melting-point polyaryletherketone according to claim 2, characterized in that, In step (2), the anhydrous sodium carbonate has a moisture content of ≤0.2% and a mesh size of 200 mesh.

6. The method for preparing a low-crystallinity, low-melting-point polyaryletherketone according to claim 2, characterized in that, In step (3), the stirring speed is 300~600 r / min.

7. The method for preparing a low-crystallinity, low-melting-point polyaryletherketone according to claim 2, characterized in that, In step (4), the molar ratio of the end-capping agent 4,4'-difluorobenzophenone II to hydroquinone is 0.0244~0.033:

1.

8. The method for preparing a low-crystallinity, low-melting-point polyaryletherketone according to claim 2, characterized in that, In step (5), cooling refers to pouring the product into deionized water for cooling, and the temperature for vacuum drying is 120~150℃.

9. A method for preparing a low-crystallinity, low-melting-point polyaryletherketone according to any one of claims 1 to 8, characterized in that, Low-crystallinity, low-melting-point polyaryletherketones have a melting point of 278–305°C, a glass transition temperature of 147–153°C, a crystallinity of <15%, a long-term service temperature of 240–250°C, a tensile strength of 96–111 MPa, a tensile modulus of 3300–4200 MPa, and a cantilever beam notched impact strength of 6.2–8.2 KJ / m. 2 The bending strength is 140~180MPa, and the bending modulus is 3200~4200MPa.

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