A method for preparing a polyketone resin with low residual metal nickel

Abstract

The application relates to the technical field of resins, and provides a preparation method of polyketone resin with low residual metal nickel. Solvent, a catalyst, an additive, an anti-reducing agent, a cosolvent and crystal seeds are mixed, carbon monoxide, ethylene and propylene are introduced for copolymerization reaction, the obtained polyketone slurry is mixed with a poor solvent for first precipitation, then solid-liquid separation is carried out, and a crude product is obtained; the crude product is dissolved by using an electrolyte solution, nickel is removed through oxidation adsorption treatment, then second precipitation, solid-liquid separation, washing and drying are carried out, and the polyketone resin with low residual metal nickel is obtained. The application reduces the deactivation of the catalyst by adding the additive and the anti-reducing agent, improves the catalytic activity, removes nickel according to specific steps, and finally obtains the polyketone resin with high molecular weight, low dispersity and extremely low catalyst residue.

Description

Technical Field

[0001] This invention relates to the field of resin technology, and in particular to a method for preparing a polyketone resin with low nickel residue. Background Technology

[0002] Polyketone (POK) is a semi-crystalline thermoplastic polymer formed by alternating copolymerization of carbon monoxide and olefins. Its unique structure, with a polar carbonyl group (C=O) embedded in every three carbon atoms in its molecular chain, endows the material with unique physicochemical properties. In terms of mechanical properties, POK's impact strength is twice that of nylon (PA) and polybutylene terephthalate (PBT), its coefficient of friction is only 1 / 14 that of polyoxymethylene (POM), and it exhibits resistance to brittle fracture at -40°C. Regarding chemical stability, its moisture absorption is 85% lower than PA, and its hydrolysis resistance surpasses that of most engineering plastics. Furthermore, in terms of barrier properties, its oxygen permeability is comparable to polyvinylidene chloride (PVDC), and its carbon dioxide barrier performance reaches the level of ethylene-vinyl alcohol copolymer (EVOH). These characteristics make it a superior alternative to traditional engineering plastics in fields such as automotive transmission components, industrial gears, and food packaging films.

[0003] Currently, nickel-based and palladium-based complexes are the main post-transition metal catalysts used for the alternating copolymerization of carbon monoxide (CO) and olefins to prepare polyketides. While palladium-based catalysts exhibit superior catalytic activity, they suffer from drawbacks such as the easy reduction and deactivation of palladium ions during the reaction, and the difficulty in recovering the catalyst due to polymer precipitation. In contrast, nickel, as an abundant and inexpensive metal in the Earth's crust, makes the development of nickel-based polyketide synthesis routes of significant value for promoting the commercial production of this material.

[0004] However, CO, as a strongly coordinating monomer, readily poisons and deactivates the metal center. Compared to palladium, nickel metal has stronger electrophilicity, which makes the highly electrophilic nickel center more attractive to the polar CO monomer, thus making it more prone to entering a deactivated "dormant state." In this state, the dissociation of CO and coordination with ethylene are hindered, impeding the crucial ethylene insertion reaction. When propylene is introduced to form a ternary copolymer system, the catalyst deactivation phenomenon is even more significant, resulting in a substantial decrease in both the catalytic activity and lifespan of the nickel-based catalyst.

[0005] Nickel-based catalysts deactivate more rapidly during polymerization, especially in the preparation of high molecular weight polyketides, requiring continuous replenishment of fresh catalyst. Due to their low activity and short lifespan, nickel-based catalysts often require higher dosages in applications. These factors collectively lead to a significant increase in the residual nickel content in the final polyketide product. High residual nickel directly affects the subsequent processing performance of the polyketide resin. Therefore, reducing the residual nickel content in polyketide resin has become a critical issue that urgently needs to be addressed in the nickel-based catalyst polyketide synthesis process. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing a polyketone resin with low nickel residue. The polyketone resin prepared by the present invention has high separation yield, low dispersibility, and extremely low nickel residue.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing a polyketone resin with low nickel residue includes the following steps: A solvent, catalyst, additive, anti-reduction agent, co-solvent, and seed crystals are mixed, and then carbon monoxide, ethylene, and propylene are introduced to carry out a copolymerization reaction to obtain a polyketide slurry. The additive is an ether-based additive; the anti-reduction agent is a transition metal salt; the molar amount of ethylene is 0.8 to 2.5 times the molar amount of carbon monoxide; the molar amount of propylene is 0.05 to 1 times the molar amount of carbon monoxide; the catalyst is a nickel catalyst; based on the nickel content in the catalyst, the molar amount of the catalyst is 0.0001 to 0.005 times the molar amount of ethylene; the copolymerization reaction temperature is 60 to 90°C. The polyketone slurry is mixed with a poor solvent for a first precipitation, followed by solid-liquid separation to obtain a crude product; the crude product is then dissolved in an electrolyte solution to obtain a crude product solution. The crude product solution, acidic pH adjuster, oxidant, adsorbent, and ligand are mixed and subjected to oxidative adsorption treatment to obtain a treated solution; the treated solution is then subjected to solid-liquid separation to obtain a liquid material. The liquid material is cooled to allow for a second precipitation, followed by solid-liquid separation, washing, and drying to obtain the polyketone resin with low residual nickel; the residual nickel content in the polyketone resin is ≤5ppm.

[0008] Preferably, the catalyst is a neutral phosphonate nickel catalyst; the neutral phosphonate nickel catalyst is formed by coordination of allyl nickel(II) chloride dimer and 2-(diisopropylphosphono)benzenesulfonic acid ligand.

[0009] Preferably, the ether-based auxiliary agent includes one or more of 18crown 6, polyethylene glycol 200, ethylene glycol ether, and diethylene glycol ether; the molar amount of the ether-based auxiliary agent is 10 to 100 times the molar amount of nickel in the catalyst; The transition metal salt includes one or more of iron and copper salts; the molar amount of the anti-reduction agent is 5 to 50 times the molar amount of nickel in the catalyst.

[0010] Preferably, the solvent is an alcohol solvent; the ratio of the solvent to carbon monoxide is 0.05~0.5L:1mol; The co-solvent is hexafluoroisopropanol; the ratio of the co-solvent to carbon monoxide is 0.5~20mL:1mol.

[0011] Preferably, the seed crystal is a polyketide seed crystal; the mass of the seed crystal is 1 to 30% of the total mass of carbon monoxide, ethylene and propylene.

[0012] Preferably, the copolymerization reaction takes 4 to 24 hours.

[0013] Preferably, the undesirable solvent is water; the mass of the undesirable solvent is 0.5 to 2.5 times the mass of the polyketone slurry; and the first precipitation time is 10 to 60 minutes.

[0014] Preferably, the electrolyte solution is a zinc chloride solution or a zinc bromide solution; the concentration of the zinc chloride solution is greater than 45 wt%; the concentration of the zinc bromide solution is greater than 15 wt%; and the dissolution temperature is 90~150℃.

[0015] Preferably, the acidic pH adjuster is hydrochloric acid; the amount of the acidic pH adjuster is such that the pH of the system is adjusted to 2-7. The oxidant is hydrogen peroxide; the ratio of the oxidant to the crude product is (0.05~2.5) mol: 1 kg; The adsorbent is activated carbon; the mass ratio of the adsorbent to the crude product is 0.01~0.2:1; The ligand is one or both of EDTA and sodium citrate; the ratio of the ligand to the crude product is (0.0005~0.2) mol: 1 kg.

[0016] Preferably, the polyketone resin has a number-average molecular weight of 10,000 to 152,000 and a molecular weight distribution of ≤3.1.

[0017] This invention provides a method for preparing a polyketone resin with low nickel residue, comprising the following steps: mixing a solvent, catalyst, additives, an anti-reduction agent, a co-solvent, and seed crystals, followed by introducing carbon monoxide, ethylene, and propylene to perform a copolymerization reaction, thereby obtaining a polyketone slurry; wherein the additives are ether-based additives; the anti-reduction agent is a transition metal salt; the molar amount of ethylene is 0.8 to 2.5 times the molar amount of carbon monoxide; the molar amount of propylene is 0.05 to 1 times the molar amount of carbon monoxide; the catalyst is a nickel catalyst; and the molar amount of the catalyst, based on the nickel content in the catalyst, is 0.0001 to 0.005 times the molar amount of ethylene. The copolymerization reaction temperature is 60-90℃; the polyketide slurry is mixed with a poor solvent for a first precipitation, followed by solid-liquid separation to obtain a crude product; the crude product is dissolved in an electrolyte solution to obtain a crude product solution; the crude product solution, an acidic pH adjuster, an oxidant, an adsorbent, and a ligand are mixed for oxidative adsorption treatment to obtain a treated liquid; the treated liquid is subjected to solid-liquid separation to obtain a liquid material; the liquid material is cooled for a second precipitation, followed by solid-liquid separation, washing, and drying to obtain the polyketide resin with low nickel residue; the residual nickel content in the polyketide resin is ≤5ppm. The beneficial effects of this invention are: In this invention, an ether-based auxiliary agent is added to the copolymerization reaction. Through its lone pair electrons, the auxiliary agent provides electrons to the nickel center of the catalyst and competes with the coordinated CO, thereby reducing the binding stability of CO at the nickel center and avoiding catalyst deactivation. At the same time, the presence of the ether-based auxiliary agent also increases the electron density of the nickel center, which relatively enhances its adsorption capacity for olefin monomers such as ethylene / propylene.

[0018] This invention incorporates an anti-reduction agent into the polymerization reaction, providing a relatively stable redox potential. When the catalyst tends to be reduced to Ni(O) under the action of CO, the higher oxidation potential of the system helps to suppress the reduction of nickel. After local reduction occurs, the anti-reduction agent passes through Cu... 2+ / Cu + The potential difference can oxidize the generated Ni(0) to a high valence state with catalytic activity, thereby preventing the catalyst from being permanently deactivated by reduction.

[0019] This invention uses an electrolyte solution to dissolve polyketone. By utilizing the special solubility of the electrolyte solution in polyketone, combined with oxidative adsorption treatment to remove nickel, the residual metallic nickel in polyketone resin can be further reduced.

[0020] The results of the examples show that the polyketone resin prepared by the present invention has a number average molecular weight of 10,000 to 152,000, a molecular weight distribution PDI ≤ 3.1, and a nickel residue of ≤ 5 ppm. Detailed Implementation

[0021] This invention provides a method for preparing a polyketone resin with low nickel residue, comprising the following steps: A solvent, catalyst, additives, anti-reduction agent, co-solvent, and seed crystals are mixed, and then carbon monoxide, ethylene, and propylene are introduced to carry out a copolymerization reaction to obtain a polyketide slurry. The additives are ether-based additives; the anti-reduction agent is a transition metal salt; the molar amount of ethylene is 0.8 to 2.5 times the molar amount of carbon monoxide; the molar amount of propylene is 0.05 to 1 times the molar amount of carbon monoxide; the catalyst is a nickel catalyst; based on the nickel content in the catalyst, the molar amount of the catalyst is 0.0001 to 0.005 times the molar amount of ethylene; the copolymerization reaction temperature is 60 to 90°C. The polyketone slurry is mixed with a poor solvent for a first precipitation, followed by solid-liquid separation to obtain a crude product; the crude product is then dissolved in an electrolyte solution to obtain a crude product solution. The crude product solution, acidic pH adjuster, oxidant, adsorbent, and ligand are mixed and subjected to oxidative adsorption treatment to obtain a treated solution; the treated solution is then subjected to solid-liquid separation to obtain a liquid material. The liquid material is cooled to allow for a second precipitation, followed by solid-liquid separation, washing, and drying to obtain the polyketone resin with low residual nickel; the residual nickel content in the polyketone resin is ≤5ppm.

[0022] This invention involves mixing a solvent, catalyst, additives, anti-reduction agent, co-solvent, and seed crystals, followed by introducing carbon monoxide, ethylene, and propylene to undergo a copolymerization reaction, yielding a polyketide slurry. In this invention, the solvent is preferably an alcohol solvent, more preferably one or more of methanol, ethanol, and isopropanol, and more preferably methanol; the ratio of solvent to carbon monoxide is preferably 0.05~0.5L:1mol, more preferably 0.1~0.3L:1mol.

[0023] In this invention, the catalyst is preferably a neutral phosphonate nickel catalyst; the neutral phosphonate nickel catalyst is preferably formed by coordination of allyl nickel(II) chloride dimer ([Ni(allyl)Cl]2) and 2-(diisopropylphosphono)benzenesulfonic acid ligand; the present invention does not have special requirements for the preparation method of the 2-(diisopropylphosphono)benzenesulfonic acid ligand, and any method well known to those skilled in the art can be used; the molar ratio of the allyl nickel(II) chloride dimer to the 2-(diisopropylphosphono)benzenesulfonic acid ligand is preferably 3:1; in this invention, the structural formula of the neutral phosphonate nickel catalyst is shown in Formula I: Formula I.

[0024] In this invention, the catalyst is preferably used in the form of a catalyst solution; the preparation method of the catalyst solution preferably includes: mixing 2-(diisopropylphosphino)benzenesulfonic acid ligand, sodium carbonate and dichloromethane to obtain a ligand mixture, dissolving allyl nickel(II) chloride dimer in dichloromethane to obtain an allyl nickel(II) chloride dimer solution, adding the allyl nickel(II) chloride dimer solution dropwise to the ligand mixture, stirring for 3 hours, and then adding dichloromethane to make up the volume to obtain the catalyst solution.

[0025] In this invention, the molar amount of the catalyst, based on the nickel content in the catalyst, is 0.0001 to 0.005 times the molar amount of ethylene, more preferably 0.0002 to 0.0005 times, specifically 0.0001, 0.0003 or 0.0005 times.

[0026] In this invention, the auxiliary agent is an ether-based auxiliary agent; preferably, the ether-based auxiliary agent includes one or more of 18-crown 6, polyethylene glycol 200, ethylene glycol ether, and diethylene glycol ether; the molar amount of the ether-based auxiliary agent is preferably 10 to 100 times the molar amount of nickel in the catalyst, more preferably 20 to 40 times, specifically 10, 25, or 100 times. Under high pressure, carbon monoxide (CO) readily forms stable coordination bonds with the active center nickel (Ni), leading to the occupation of the catalyst's active sites and entry into a stable dormant state. The ether oxygen atom possesses lone pair electron characteristics, and the introduced ethylene glycol methyl ether molecule possesses Lewis basicity, enabling it to compete with the Ni active center for coordination, weakening the coordination strength of CO, promoting the dissociation of the Ni-CO bond in the dormant complex, and allowing olefin monomers to enter the coordination, thus achieving continuous start-up and maintenance of the catalytic cycle. This extends the catalyst's lifespan under high-pressure reaction conditions. The electron-donating effect of ethylene glycol methyl ether can increase the electron cloud density of Ni centers, balance the charge, and enhance the redox potential of Ni(II), thereby inhibiting the reduction of nickel to zero oxidation state and thus preventing catalyst deactivation. Simultaneously, ethylene glycol methyl ether molecules form a coordination shielding layer around the Ni active sites through a solvation effect, reducing collisions and aggregation between active site species and enhancing the chemical stability of the catalytic system.

[0027] In this invention, the anti-reduction agent is a transition metal salt; the transition metal salt preferably includes one or more of iron and copper salts; the iron salt is preferably ferric chloride; the copper salt preferably includes one or more of copper chloride, copper bromide, and copper acetate, more preferably copper chloride; the molar amount of the anti-reduction agent is preferably 5 to 50 times the molar amount of nickel in the catalyst, more preferably 10 to 20 times, specifically 5, 15, or 50 times. By adding the anti-reduction agent, this invention can inhibit the reduction reaction of CO and Ni, reducing the deactivation caused by Ni reduction.

[0028] In this invention, the co-solvent is preferably hexafluoroisopropanol; the ratio of the co-solvent to carbon monoxide is preferably 0.5~20mL:1mol, more preferably 2~5mL:1mol. The precipitated polyketone encapsulates part of the solvent and catalyst, not only reducing material recycling efficiency but also causing a decrease in the molecular weight and quality of the resin because the polymer inside the particles cannot participate in polymerization. Therefore, this invention introduces hexafluoroisopropanol as a co-solvent, utilizing its hydrogen bonding with the carbonyl group of polyketone to improve the solubility of the polyketone segments. By improving the solvent environment, the resulting polyketone powder particles are regular and have a uniform morphology, thereby obtaining high-quality polyketone with stable molecular weight and uniform structure.

[0029] In this invention, the seed crystal is preferably a polyketide seed crystal; the mass of the seed crystal is preferably 1-30% of the total mass of carbon monoxide, ethylene and propylene, specifically 5-15%; the seed crystal is the starting material for initiating polymerization.

[0030] In this invention, the molar amount of ethylene is preferably 0.8 to 2.5 times the molar amount of carbon monoxide, more preferably 0.8 to 1.2 times, specifically 0.8, 1, or 1.2 times; the molar amount of propylene is preferably 0.05 to 1 times the molar amount of carbon monoxide, more preferably 0.2 to 0.8 times, specifically 0.2, 0.5, or 0.8 times.

[0031] In this invention, the temperature of the copolymerization reaction is 60~90℃, more preferably 70~80℃, specifically 60℃, 75℃, or 90℃; the time of the copolymerization reaction is preferably 4~24h, more preferably 6h. In a specific embodiment of this invention, it is preferable to first add the solvent, catalyst solution, additives, anti-reduction agent, co-solvent, and seed crystals to a high-pressure reactor, then inject carbon monoxide, ethylene, and propylene after gas replacement, and then carry out the copolymerization reaction at the above temperature. After the reaction is completed, a polyketide slurry is obtained.

[0032] After obtaining the polyketone slurry, the present invention mixes the polyketone slurry with a poor solvent for a first precipitation, followed by solid-liquid separation to obtain a crude product. In the present invention, the poor solvent is preferably water; the mass of the poor solvent is preferably 0.5 to 2.5 times the mass of the polyketone slurry, more preferably 0.8 to 1.2 times; the first precipitation time is preferably 10 to 60 minutes, more preferably 30 minutes; the first precipitation temperature is preferably 50°C; in a specific embodiment of the present invention, the poor solvent is preferably added to the polyketone slurry after preheating. The present invention can ensure full precipitation of polyketone by controlling the temperature of the first precipitation; after full precipitation of polyketone, the obtained precipitate is subjected to solid-liquid separation, which can be pressure filtration, atmospheric pressure filtration, or vacuum filtration, more preferably vacuum filtration using a Buchner funnel.

[0033] After obtaining the crude product, the present invention dissolves the crude product in an electrolyte solution to obtain a crude product solution. In the present invention, the electrolyte solution is preferably a zinc chloride solution or a zinc bromide solution; the concentration of the zinc chloride solution is preferably greater than 45 wt%, more preferably 45-90 wt%, specifically 85 wt%; the concentration of the zinc bromide solution is preferably greater than 15 wt%, specifically 15-50 wt%; the dissolution temperature is preferably 90-150°C, specifically 110°C.

[0034] After obtaining the crude product solution, the present invention mixes the crude product solution, an acidic pH adjuster, an oxidant, an adsorbent, and a ligand for oxidative adsorption treatment to obtain a treated solution. In the present invention, the acidic pH adjuster is preferably hydrochloric acid, and the concentration of the hydrochloric acid is preferably 35 wt%; the amount of the acidic pH adjuster is preferably used to adjust the pH of the system to 2-7, more preferably 3-5.

[0035] In this invention, the oxidant is preferably hydrogen peroxide, which is preferably used in the form of hydrogen peroxide solution. The concentration of the hydrogen peroxide solution is preferably 15~50wt%, specifically 40wt%. The ratio of the oxidant to the crude product is preferably (0.05~2.5)mol:1kg, more preferably (0.2~0.5)mol:1kg.

[0036] In this invention, the adsorbent is preferably activated carbon; the mass ratio of the adsorbent to the crude product is preferably 0.01~0.2:1, more preferably 0.02~0.08:1.

[0037] In this invention, the ligand is preferably one or both of EDTA and sodium citrate; the ratio of the ligand to the crude product is preferably (0.0005~0.2) mol:1 kg, more preferably (0.02~0.1) mol:1 kg.

[0038] In this invention, the oxidation adsorption time is preferably 30-120 min, specifically 60 min, and the oxidation adsorption temperature is preferably 100-130℃. During the oxidation adsorption process, the oxidant oxidizes the zero-valent nickel in the system, and the oxidized nickel and ligands form a nickel complex. The nickel complex is adsorbed by activated carbon, thereby achieving efficient removal of nickel.

[0039] After obtaining the treatment liquid, the present invention performs solid-liquid separation on the treatment liquid to obtain liquid material; the solid-liquid separation is preferably filtration, and the filtration is preferably carried out while hot; the present invention removes activated carbon adsorbing nickel complexes through solid-liquid separation.

[0040] After obtaining the liquid material, the present invention cools the liquid material to allow for a second precipitation, followed by solid-liquid separation, washing, and drying to obtain the polyketone resin with low nickel residue. Specifically, the cooling involves cooling the liquid material to room temperature, during which the polyketone resin precipitates from the liquid phase. The solid-liquid separation is preferably filtration, resulting in a filter cake. The washing agent is preferably deionized water, and the washing is preferably performed until the filtrate is neutral. The mass of the deionized water used for washing is preferably 1 to 3 times the mass of the filter cake, specifically 2 times. The drying is preferably vacuum drying. The drying temperature is preferably 40 to 80°C, specifically 50°C; the drying pressure is preferably 0.005 to 0.05 MPa, specifically 0.01 MPa; and the drying time is preferably 0.5 to 2 hours, specifically 1 hour.

[0041] In this invention, the number-average molecular weight of the polyketone resin is preferably 10,000 to 152,000, the molecular weight distribution PDI is preferably ≤3.1, and the residual amount of metallic nickel is ≤5ppm.

[0042] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] Preparation Example 1: Ligand Synthesis Weigh 24.5 g (155 mmol) of anhydrous benzenesulfonic acid into a 2 L three-necked flask. Under nitrogen protection, add 1000 mL of anhydrous tetrahydrofuran (THF) and stir until completely dissolved. Then cool the system to -78 °C. Slowly add 124 mL (310 mmol) of n-butyllithium solution (2.5 mol / L, hexane solvent) dropwise using a constant pressure dropping funnel, keeping the temperature below -78 °C during the addition, to obtain a red solution. After stirring continuously at -78 °C for 4.0 h, slowly add 23.6 g (155 mmol) of diisopropylphosphine chloride, maintain the reaction at -78 °C for 30 min, then remove the cold bath and stir at room temperature for 12 h.

[0044] After the reaction was complete, the solvent was removed by vacuum distillation, and the residue was dissolved in 500 mL of distilled water. Concentrated hydrochloric acid was added to the mixture to adjust the pH to approximately 2, followed by extraction three times with dichloromethane (CH₂Cl₂) (approximately 167 mL each time, total volume 500 mL). The organic phases were combined, dried over anhydrous sodium sulfate (Na₂SO₄), filtered, and concentrated under reduced pressure to remove the solvent, yielding the crude product. The crude product was recrystallized at room temperature using a methanol / ether mixture, and the precipitated white crystals were collected by filtration and dried under vacuum to obtain 32.92 g of the target colorless solid ligand, with a yield of 77%.

[0045] 1 ¹H NMR (600 MHz, deuterated chloroform) δ: 8.27–8.21 (m, 1H), 7.84–7.77 (m, 1H), 7.70–7.62 (m, 1H), 7.58–7.53 (m, 1H), 3.63–3.28 (m, 2H), 1.60–1.45 (m, 6H), 1.30–1.11 (m, 6H).

[0046] The analysis methods used in the following embodiments are as follows: The residual nickel content of polyketone was determined using a PerkinElmerAVIO 500 inductively coupled plasma optical emission spectrometer (ICP-OES). Digestion was performed using a sulfuric acid-nitric acid system, specifically as follows: 100 mg of polyketone was weighed into a 25 mL flask, and 4 mL of sulfuric acid (H₂SO₄) was added dropwise at room temperature. The mixture was stirred at 100 °C for 2 h to carbonize the polyketone. Then, 4 mL of nitric acid (HNO₃) was slowly added dropwise at room temperature, and the mixture was stirred at 100 °C for 4 h to obtain a clear yellow solution. Finally, the solution was diluted to volume with deionized water.

[0047] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography (GPC) at 40℃ and a flow rate of 1.0 mL / min, using 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) as the eluent. Polymethyl methacrylate (PMMA) standards (molecular weight range 1.59 × 10⁻⁶) were used for calibration. 7 The instrument is an Agilent 1260 model, equipped with an Agilent differential refractive index detector (RI) and a PLHFIPgel 300×7.5mm column (g / mol).

[0048] Example 1 Weigh 20.6 g (1.5 eq, 0.075 mol, 274.3 Da) of 2-(diisopropylphosphino)benzenesulfonic acid ligand and 10.6 g (2 eq, 0.1 mol, 106 Da) of sodium carbonate and place them in a 500 mL three-necked flask. Add 150 mL of dichloromethane (CH2Cl2) and stir at room temperature for 0.5 h to ensure homogeneity. Then, dissolve 6.76 g (0.5 eq, 0.025 mol, 270.4 Da) of [Ni(allyl)Cl]2 in 50 mL of dichloromethane and slowly add it dropwise to the above mixture. Continue stirring at room temperature for 3 h. Add dichloromethane to bring the prepared brownish-yellow catalyst solution to a final volume of 250 mL (containing 0.0117 g / mL nickel), seal, and refrigerate for later use.

[0049] In a 5L stainless steel high-pressure reactor, 2.5 kg of anhydrous methanol, 20.0 mL of the prepared catalyst solution (containing 4 mmol of nickel), 7.5 g of ethylene glycol methyl ether (25 times the amount of Ni, 0.1 mol, 76.1 Da), 7.9 g of anhydrous copper chloride (15 times the amount of Ni, 0.06 mol, 134.4 Da), 48 mL of hexafluoroisopropanol (HFIP) as a co-solvent, and 92.5 g of polyketide as seed crystals were added sequentially. After purging the reactor with nitrogen, 336.1 g of carbon monoxide (1 eq, 12 mol, 28.01 Da), 336.6 g of ethylene (1 eq, 12 mol, 28.05 Da), and 252.5 g of propylene (0.5 eq, 6 mol, 42.1 Da) were injected into the reactor. The stirring and heating devices were turned on to stabilize the reactor temperature at 75°C. The reaction continued for 6 hours until the pressure inside the reactor dropped below 1.5 bar.

[0050] After the reaction is complete, heating is stopped and the mixture is allowed to cool naturally to below 50°C. The pressure is slowly released and the reactor is opened. The milky white slurry containing polyketide is transferred from the reactor to a washing vessel. Mechanical stirring is started, and the temperature inside the vessel is maintained at 50°C. 3 kg of preheated deionized water (preheated to 50°C) is added, and the mixture is continuously stirred and washed for 30 minutes to obtain a mixture of emulsified washing slurry and aqueous phase. While still hot, the mixture is transferred to a Buchner funnel for filtration to achieve preliminary solid-liquid separation. The solid (i.e., the crude product) is returned to the washing vessel.

[0051] Add 1.6 kg of 85 wt% zinc chloride solution to the washing vessel and heat to 110 °C to dissolve the polyketide resin. Adjust the pH to less than 5 with 35 wt% hydrochloric acid. After stirring, add 25.5 g (0.3 mol, 34.0 Da) of 40% hydrogen peroxide dropwise to the vessel, along with 50 g of activated carbon and 14.7 g (0.05 mol, 294.1 Da) of sodium citrate dihydrate, and continue stirring for 1 hour. Transfer the material to a Buchner funnel and filter while hot to remove the activated carbon adsorbing nickel complexes. Cool the resulting filtrate to room temperature, and filter again after the polyketide has fully separated. Use 1.5 kg of deionized water to neutralize the resulting polyketide filter cake. Place the polyketide filter cake in a vacuum drying oven and dry at 50 °C and 0.01 MPa for 1 hour to obtain a loose polyketide resin powder.

[0052] A total of 910.4 g of polyketone resin powder was obtained (after deducting the mass of the polyketone seed). The product's number-average molecular weight Mn = 68754, molecular weight distribution PDI = 2.21, and residual nickel content was 0.9 ppm. The calculated catalyst activity is 3.89 kg polyketone / g nickel.

[0053] Examples 2-3 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. Based on Example 1, the amounts of ethylene and propylene added were changed from 336.6 g (1 eq, 12 mol, 28.05 Da) ethylene and 252.5 g (0.5 eq, 6 mol, 42.1 Da) propylene in Example 1 to 269.3 g (0.8 eq, 9.6 mol, 28.05 Da) ethylene and 404.2 g (0.8 eq, 9.6 mol, 42.1 Da) propylene in Example 2, and 403.9 g (1.2 eq, 14.4 mol, 28.05 Da) ethylene and 101 g (0.2 eq, 2.4 mol, 42.1 Da) propylene in Example 3. The remaining reaction conditions and processing steps remained consistent with Example 1.

[0054] Examples 4-5 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. Based on Example 1, the amount of catalyst solution added was changed from 20.0 mL (containing 4 mmol of nickel) in Example 1 to 6.0 mL (containing 1.2 mmol of nickel) in Example 4 and 30.0 mL (containing 6 mmol of nickel) in Example 5. The remaining reaction conditions and processing steps were consistent with those in Example 1.

[0055] Examples 6-7 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. Based on Example 1, the reaction temperature and reaction time of the polymerization reaction were changed from 75°C and 6h in Example 1 to 60°C and 24h in Example 6, and 90°C and 4h in Example 7, respectively. The remaining reaction conditions and processing steps were consistent with those in Example 1.

[0056] Examples 8-9 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. Based on Example 1, the amount of the auxiliary agent ethylene glycol methyl ether was changed from 7.5 g (25 times that of Ni, 0.1 mol, 76.1 Da) in Example 1 to 3.0 g (10 times that of Ni, 0.04 mol, 76.1 Da) in Example 8 and 30.0 g (100 times that of Ni, 0.4 mol, 76.1 Da) in Example 9. The remaining reaction conditions and processing steps remained consistent with Example 1.

[0057] Examples 10-11 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. Based on Example 1, the amount of the anti-reduction agent copper chloride was changed from 7.9 g (15 times that of Ni, 0.06 mol, 134.4 Da) in Example 10 to 2.69 g (5 times that of Ni, 0.02 mol, 134.4 Da) in Example 10, and 26.88 g (50 times that of Ni, 0.2 mol, 134.4 Da) in Example 11. The remaining reaction conditions and processing steps remained consistent with Example 1.

[0058] Comparative Example 1 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. Based on Example 1, the amounts of ethylene and propylene added were changed from 336.6 g (1 eq, 12 mol, 28.05 Da) ethylene and 252.5 g (0.5 eq, 6 mol, 42.1 Da) propylene in Example 1 to 202.0 g (0.6 eq, 7.2 mol, 28.05 Da) ethylene and 505.2 g (1 eq, 12 mol, 42.1 Da) propylene in Comparative Example 1. The remaining reaction conditions and processing steps remained consistent with Example 1.

[0059] Comparative Examples 2-3 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. Based on Example 1, the amount of catalyst solution added was changed from 20.0 mL (containing 4 mmol of nickel) in Example 1 to 3.0 mL (containing 0.6 mmol of nickel) in Comparative Example 2 and 120.0 mL (containing 24 mmol of nickel) in Comparative Example 3. The remaining reaction conditions and processing steps were consistent with those in Example 1.

[0060] Comparative Examples 4-5 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. Based on Example 1, the reaction temperature and reaction time of the polymerization reaction were changed from 75°C and 6h in Example 1 to 55°C and 48h in Comparative Example 4, and 100°C and 3h in Comparative Example 5, respectively. The remaining reaction conditions and processing steps were consistent with those in Example 1.

[0061] Comparative Example 6 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. However, the amount of the auxiliary agent ethylene glycol methyl ether was changed from 7.5 g (25 times that of Ni, 0.1 mol, 76.1 Da) in Example 1 to 0 in Comparative Example 6, i.e., no ethylene glycol methyl ether was added. The remaining reaction conditions and processing steps remained consistent with those in Example 1.

[0062] Comparative Example 7 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. However, the amount of copper chloride, the anti-reduction agent, was changed from 7.9 g (15 times that of Ni, 0.06 mol, 134.4 Da) in Example 1 to 0 in Comparative Example 7, i.e., no copper chloride was added. The remaining reaction conditions and processing steps remained consistent with Example 1.

[0063] Comparative Example 8 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. The difference was that the amount of co-solvent added was changed from 48 mL (4 mL / mol CO) in Example 1 to 0 in Comparative Example 8, i.e., no co-solvent was added. The remaining reaction conditions and processing steps remained consistent with Example 1.

[0064] Comparative Example 9 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. However, the amount of polyketone seed crystals added was changed from 92.5 g (10%) in Example 1 to 0 g (no polyketone seed crystals) in Comparative Example 9. The remaining reaction conditions and processing steps remained consistent with Example 1.

[0065] Comparative Example 10 The ternary copolymer polyketone resin was prepared according to the same scheme as in Example 1. The difference from Example 1 is that after the reaction, a poor solvent was added to the reaction system to allow the polymer to precipitate completely. The nickel removal step was not performed. The obtained filter cake was directly washed and dried. The remaining reaction conditions and processing steps were consistent with those in Example 1.

[0066] The data from the above embodiments and comparative examples were organized and statistically analyzed, and the results are shown in Table 1: Table 1 Test results of the examples and comparative examples

[0067] Examples 1-3 and Comparative Example 1 explored the synthesis of terpolymer polyketone resins with different propylene / ethylene ratios. As the propylene ratio increased, the catalyst efficiency decreased.

[0068] In Examples 4-5 and Comparative Examples 2-3, the dosage range of nickel catalyst was investigated. When the catalyst dosage was too low, the reaction conversion rate was difficult to reach the ideal range. However, when the catalyst dosage was too high, the product quality was not improved, but the residual nickel increased.

[0069] Examples 6-7 and Comparative Examples 4-5 show that, within appropriate ranges, by adjusting the reaction temperature and time, it is possible to prepare polyketide resins with different molecular weight ranges while maintaining a high reaction yield.

[0070] In Examples 8-9 and Comparative Example 6, the dosage range of the catalyst promoter ethylene glycol methyl ether was investigated, clarifying its effect on the reaction yield. As a catalyst promoter, ether promoters can donate electrons to the nickel center through their lone pair electrons and compete with the coordinated CO, thereby reducing the binding stability of CO at the nickel center. The presence of ether promoters also increases the electron density of the nickel center, relatively enhancing its adsorption capacity for olefin monomers such as ethylene / propylene. By adjusting the activity gap between the two key steps of CO removal and olefin adsorption in the nickel catalyst, the situation where excessive adsorption of CO due to the strong electrophilicity of nickel hinders olefin insertion is alleviated. In Comparative Example 6, the promoter was removed from the reaction. During the reaction, CO poisoning led to a sharp decline in catalyst activity, incomplete reaction conversion, and a significantly reduced yield.

[0071] In Examples 10-11 and Comparative Example 7, the dosage range of the anti-reduction agent was investigated, clarifying its influence on the reaction yield. The anti-reduction agent in the reaction system can provide a relatively stable redox potential. When the nickel catalyst tends to be reduced to Ni(0) under the action of CO, the higher oxidation potential of the system helps to inhibit the reduction of nickel. After local reduction occurs, copper chloride passes through Cu 2+ / Cu + The potential difference can oxidize the generated Ni(0) to a catalytically active high-valence state, thereby preventing the catalyst from being permanently deactivated by reduction. In Comparative Example 7, the anti-reduction agent copper chloride was removed from the reaction. During the reaction, the nickel catalyst was deactivated, resulting in a decrease in reaction activity and incomplete reaction conversion.

[0072] In Comparative Example 8, the co-solvent was removed, and the polyketide resin precipitated rapidly in the early stage of the reaction. The final product was an irregular coarse agglomerate with a loose internal structure and poor compactness, and the molecular weight of the product was significantly reduced.

[0073] In Comparative Example 9, the seed crystals were removed, resulting in a lack of necessary nucleation centers in the system. The initial reaction exhibited a significant induction period, with a slow reaction initiation. Within the same reaction time, due to limited nucleation, the molecular weight of the resin decreased slightly, the conversion efficiency of the raw material olefin was low, and unreacted monomers were present.

[0074] In Comparative Example 10, the nickel removal step was removed, and the nickel residue in the product increased significantly, indicating that the present invention can effectively reduce the nickel content by removing nickel through specific steps.

[0075] In summary, this invention uses carbon monoxide, ethylene, and propylene as monomers, copolymerizes them under a catalyst and auxiliaries system, and purifies them according to specific steps to obtain polyketide resins with high molecular weight, low dispersion, and extremely low residual nickel. At the same time, this invention has high catalytic efficiency, high product yield, and is easy to industrialize.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a polyketone resin with low nickel residue, characterized in that, Includes the following steps: A solvent, catalyst, auxiliaries, anti-reduction agent, co-solvent, and seed crystals are mixed, and then carbon monoxide, ethylene, and propylene are introduced to carry out a copolymerization reaction to obtain a polyketide slurry. The auxiliaries are ether-based; the anti-reduction agent is a transition metal salt; the molar amount of ethylene is 0.8 to 2.5 times the molar amount of carbon monoxide; the molar amount of propylene is 0.05 to 1 times the molar amount of carbon monoxide; the catalyst is a nickel catalyst; based on the nickel content in the catalyst, the molar amount of the catalyst is 0.0001 to 0.005 times the molar amount of ethylene; the copolymerization reaction temperature is 60 to 90°C; the catalyst is a neutral phosphonate nickel catalyst; the neutral phosphonate nickel catalyst is formed by coordination of allyl nickel(II) chloride dimer and 2-(diisopropylphosphono)benzenesulfonic acid ligand; the ether auxiliaries are ethylene glycol methyl ether; the co-solvent is hexafluoroisopropanol; the seed crystals are polyketide seed crystals; the copolymerization reaction time is 4 to 24 hours. The polyketone slurry is mixed with a poor solvent for a first precipitation, followed by solid-liquid separation to obtain a crude product; the crude product is then dissolved in an electrolyte solution to obtain a crude product solution. The crude product solution, acidic pH adjuster, oxidant, adsorbent, and ligand are mixed and subjected to oxidative adsorption treatment to obtain a treated solution; the treated solution is subjected to solid-liquid separation to obtain a liquid material; the ligand is one or both of EDTA and sodium citrate; The liquid material is cooled to allow for a second precipitation, followed by solid-liquid separation, washing, and drying to obtain the polyketone resin with low residual nickel; the residual nickel content in the polyketone resin is ≤5ppm.

2. The preparation method according to claim 1, characterized in that, The molar amount of the ether-based auxiliary agent is 10 to 100 times the molar amount of nickel in the catalyst; The transition metal salt includes one or more of iron and copper salts; the molar amount of the anti-reduction agent is 5 to 50 times the molar amount of nickel in the catalyst.

3. The preparation method according to claim 1, characterized in that, The solvent is an alcohol-based solvent; the ratio of the solvent to carbon monoxide is 0.05~0.5L:1mol; The ratio of the co-solvent to carbon monoxide is 0.5~20mL:1mol.

4. The preparation method according to claim 1, characterized in that, The mass of the seed crystal is 1 to 30% of the total mass of carbon monoxide, ethylene, and propylene.

5. The preparation method according to claim 1, characterized in that, The unsuitable solvent is water; the mass of the unsuitable solvent is 0.5 to 2.5 times the mass of the polyketone slurry; the first precipitation time is 10 to 60 minutes.

6. The preparation method according to claim 1, characterized in that, The electrolyte solution is a zinc chloride solution or a zinc bromide solution; the concentration of the zinc chloride solution is greater than 45 wt%; the concentration of the zinc bromide solution is greater than 15 wt%; and the dissolution temperature is 90~150℃.

7. The preparation method according to claim 1, characterized in that, The acidic pH adjuster is hydrochloric acid; the amount of the acidic pH adjuster used is based on adjusting the pH of the system to 2-7; The oxidant is hydrogen peroxide; the ratio of the oxidant to the crude product is (0.05~2.5) mol: 1 kg; The adsorbent is activated carbon; the mass ratio of the adsorbent to the crude product is 0.01~0.2:1; The ratio of the ligand to the crude product is (0.0005~0.2) mol: 1 kg.

8. The preparation method according to claim 1, characterized in that, The polyketone resin has a number-average molecular weight of 10,000 to 152,000 and a molecular weight distribution of ≤3.1.

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