Purification method for preparing high-purity sodium carbonate and application of high-purity sodium carbonate in preparation of polyetheretherketone resin

Abstract

The invention provides a purification method for preparing high-purity sodium carbonate and application of the high-purity sodium carbonate in preparation of polyether-ether-ketone resin. The purification method is used for preparing high-purity sodium carbonate, and comprises the following steps: sequentially carrying out dissolving filtration, chemical precipitation, ceramic membrane filtration, evaporative crystallization and drying on industrial sodium carbonate to obtain the high-purity sodium carbonate. When the high-purity sodium carbonate obtained by the purification method is used for preparing polyether-ether-ketone, the gel content can be reduced, and when the high-purity sodium carbonate is used for preparing film products and wire and cable coating materials, the occurrence frequency of crystal points on the surface appearance of the high-purity sodium carbonate is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the field of preparation of polyetheretherketone resin. Specifically, the present invention relates to a method for purifying high-purity sodium carbonate and its use in the preparation of polyetheretherketone resin. Background Art

[0002] The PEEK film manufactured by thermoplastic molding of PEEK resin has the following remarkable characteristics: excellent fatigue resistance, high temperature resistance, self-lubrication, chemical resistance, flame retardancy, peel resistance, etc. It is widely used in the fields of aerospace, automotive manufacturing, industrial fields, medical devices, insulating materials, etc. For example: pressure-sensitive tapes, pressure sensor membranes, printed circuit boards, acoustic speaker membranes, high-temperature labels, capacitors, gaskets in high-speed motors, composite gaskets in mobile phone hinges, laser-printed labels, direct thermal bonding of metal foils, flexible surface heaters, semiconductor process protection films and other related industries.

[0003] The outstanding high temperature resistance, flame retardancy, radiation resistance and good mechanical properties of PEEK insulated wires make them usable as ultra-high temperature wires in the aviation industry; as winding wires and connecting wires for submersible pump motors in the petroleum industry; as winding coils of nuclear island drive mechanisms in nuclear power plants for long-term use under irradiation conditions; the excellent properties such as seawater resistance, light weight, small size and flame retardancy of PEEK insulated wires make them usable in ships;

[0004] When PEEK is applied to films and wires and cables, a problem will be encountered, that is, the problem of surface crystal points. Crystal points, as a kind of surface defect, appear in the appearance of film products and wires and cables. They are not only surface appearance defects but also stress concentration points for product failure. The failure of products often starts from here.

[0005] Crystal points, that is, gels generated during the polymerization process, can be caused by various reasons. The purity of raw materials and fluctuations in process conditions may all bring about the generation of crystal points. And sodium carbonate, as one of the main materials with the largest addition amount in the polymerization raw materials, its purity has a very significant impact on the generation of crystal points. Crystal points appearing on the surface of products are called crystal points, and crystal points are gels in polymers.

[0006] In the prior art, due to the presence of certain impurities in sodium carbonate, it has an adverse effect on the properties of polyetheretherketone produced therein. These properties include one or more of color and color stability, gel content, melt stability, molecular weight and molecular weight distribution, crystallinity, etc. Therefore, how to provide a method for removing trace impurities in this sodium carbonate to obtain higher-purity sodium carbonate is the key to preparing polyetheretherketone with better performance. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides the following technical solutions:

[0008] A purification method for preparing high-purity sodium carbonate, the purification method comprising: sequentially subjecting industrial sodium carbonate to dissolution and filtration, chemical precipitation, ceramic membrane filtration, evaporation crystallization, and drying to obtain the high-purity sodium carbonate.

[0009] According to an embodiment of the present invention, the purity of the industrial sodium carbonate means that the total alkali content is not less than 98% based on the dry weight of sodium carbonate, for example, 98.5%, 99%, or 99.5%.

[0010] According to an embodiment of the present invention, the dissolution and filtration are performed at least twice, for example, 3 to 5 times.

[0011] According to an embodiment of the present invention, the dissolution and filtration specifically include: dissolving industrial sodium carbonate in deionized water to obtain a saturated solution, followed by primary filtration. After removing the water from the filtrate, the above process is optionally repeated at least 1 time to obtain sodium carbonate after primary purification. Preferably, the saturated solution is dissolved at 35.4 °C, at which time the solubility of sodium carbonate reaches the maximum, and the content of sodium carbonate in the saturated solution is 33.2%. Preferably, the primary filtration can be carried out by a method known in the art, for example, suction filtration with a slow quantitative filter paper in a Buchner funnel, and washing the filter residue with deionized water to obtain a filtrate. Preferably, the filter residue after primary filtration is placed in an oven and dried to a constant weight (the drying temperature is 105 ± 2 °C). Preferably, the water in the filtrate can be removed by a method known in the art, for example, heating the filtrate to near dryness and then transferring it to a porcelain crucible and continuing to calcine in a muffle furnace at 300 ± 2 °C for 2 h to remove the water. Preferably, the sodium carbonate after primary purification is ground in a mortar and placed in a desiccator for standby.

[0012] According to an embodiment of the present invention, the chemical precipitation specifically includes: mixing the sodium carbonate after primary purification with deionized water and adding an inorganic base to adjust the pH to 11 - 13, standing for precipitation, and obtaining a clarified mother liquor after secondary filtration. Preferably, the secondary filtration can be carried out by a method known in the art, for example, the same method as the primary filtration can be used.

[0013] According to an embodiment of the present invention, the ceramic membrane filtration specifically refers to: performing tertiary filtration on the above clarified mother liquor using a ceramic membrane with a pore size of 0.1 - 1 μm (for example, 0.8 - 1.0 μm) to obtain a mother liquor to be evaporated.

[0014] According to an embodiment of the present invention, the evaporation crystallization includes heating the mother liquor to be evaporated to obtain sodium carbonate monohydrate crystals.

[0015] According to an embodiment of the present invention, after washing and drying the sodium carbonate monohydrate crystals, the high-purity sodium carbonate is obtained.

[0016] The present invention also provides a high-purity sodium carbonate, which is prepared by the above purification method.

[0017] According to an embodiment of the present invention, the purity of the high-purity sodium carbonate is not less than 98.8%, for example, 98.9%, 99%, 99.5%.

[0018] According to an embodiment of the present invention, the impurities of the high-purity sodium carbonate include metal impurities and other impurities.

[0019] According to an embodiment of the present invention, the metal impurities include at least one of, but not limited to, magnesium (Mg), aluminum (Al), calcium (Ca), iron (Fe), copper (Cu), lead (Pb), nickel (Ni).

[0020] According to an embodiment of the present invention, in the high-purity sodium carbonate, the total content of metal elements in the metal impurities is not more than 0.15% (for example, 0.1%, 0.05%); among them, the total content of calcium and magnesium elements is not more than 0.08% (for example, 0.06%, 0.05%, 0.04%, 0.03%, 0.02%, 0.01%).

[0021] According to an embodiment of the present invention, the high-purity sodium carbonate further includes water-insoluble substances, chlorides and sulfates, wherein the mass content of water-insoluble substances is not more than 0.05%, and the mass content of sulfates is not more than 0.08%.

[0022] According to an embodiment of the present invention, when heated to 300 °C, the loss on drying of the high-purity sodium carbonate is not more than 3.0%.

[0023] According to an embodiment of the present invention, the high-purity sodium carbonate has the following particle size distribution: 40 μm ≤ D50 ≤ 260 μm, and 260 μm ≤ D90 ≤ 500 μm.

[0024] The present invention also provides a method for preparing a polyetheretherketone resin, which includes using the above high-purity sodium carbonate to prepare the polyetheretherketone resin.

[0025] According to an embodiment of the present invention, the preparation method specifically includes the following steps:

[0026] (1) Under the protection of an inert gas, the above high-purity sodium carbonate, potassium carbonate, bisphenol and organic dihalide are mixed to obtain a mixture;

[0027] (2) The mixture obtained in step (1) is heated to a molten state, and then heated to a polymerization reaction temperature for polymerization reaction. Subsequently, a capping agent is added for capping treatment. After the reaction is completed, the mixture in the flask is poured out onto a smooth stainless steel plate to cool, and a reaction product is obtained.

[0028] (3) After cooling, pulverizing, purifying, and drying the reaction product obtained in step (2), the polyetheretherketone resin is obtained.

[0029] According to an embodiment of the present invention, in step (1), the high-purity sodium carbonate has the meaning as described above.

[0030] According to an embodiment of the present invention, step (1) is carried out under the protection of an inert gas (such as nitrogen).

[0031] According to an embodiment of the present invention, in step (1), the D of the potassium carbonate 90 , 20 μm ≤ D 90 ≤ 460 μm.

[0032] According to an embodiment of the present invention, in step (1), the molar ratio of high-purity sodium carbonate to potassium carbonate is 1 to 5: 0.01 to 0.5, for example, 4.8: 0.16.

[0033] According to an embodiment of the present invention, the molar ratio of the high-purity sodium carbonate to the bisphenol is (1.003 to 1.3): 1, for example, 1.2: 1.

[0034] According to an embodiment of the present invention, the molar ratio of the organic dihalide to the bisphenol is (1.01 to 1.025): 1, for example, 1.02: 1.

[0035] According to an embodiment of the present invention, the organic dihalide is selected from at least one or a mixture of two or more of 4,4'-difluorobenzophenone, 2,4'-difluorobenzophenone, 4-chloro-4'-fluorobenzophenone, 4,4'-dichlorobenzophenone, 1,4-bis(4'-fluorobenzoyl)benzene, and is preferably 4,4'-difluorobenzophenone.

[0036] According to an embodiment of the present invention, the bisphenol is selected from at least one or a mixture of two or more of hydroquinone, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenyl ether, 1,4-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, and is preferably hydroquinone.

[0037] According to an embodiment of the present invention, the organic halide is selected from monofluoro-substituted aromatic halides. Preferably, the aromatic halide includes at least two aryl groups, wherein the substituent on one aryl group includes -F, and the substituent on the other aryl group is selected from at least one of a hydrogen atom, -SO3, -NO2, -NH3, -Cl, -Br, -I; for example, selected from 4-fluorobenzophenone, 4-fluoro-4-bromobenzophenone, 4-fluoro-4-iodobenzophenone, 4-fluoro-4-chlorobenzophenone, 4-fluoro-4-nitrobenzophenone, 2-chloro-4-fluorobenzophenone, 4-fluoro-4-chlorobenzophenone, preferably 4-fluorobenzophenone.

[0038] According to an embodiment of the present invention, in step (2), heating to a molten state means that all reactants are in a fluid state; exemplarily, the temperature when heating to a molten state is not less than 150 °C, for example, 180 °C.

[0039] According to an embodiment of the present invention, in step (2), after heating to a molten state, keep the temperature constant for a period of time. For example, when the temperature when heating to a molten state is 180 °C, maintain a constant temperature of 180 °C for 1 hour.

[0040] According to an embodiment of the present invention, in step (2), the polymerization reaction temperature is 250 - 320 °C (for example, 250 °C, 300 °C, 310 °C).

[0041] According to an embodiment of the present invention, in step (2), the polymerization reaction time is not higher than 250 minutes, for example, 230 minutes, 240 minutes.

[0042] According to an embodiment of the present invention, in step (2), the end-capping agent can be a compound known in the art that can be used as an end-capping agent in the preparation process of polyether ether ketone. For example, unsubstituted or substituted benzophenone, wherein the substituent of the substituted benzophenone can be a halogen (such as fluorine or chlorine), C 1-6 alkyl (such as methyl, ethyl, propyl or isopropyl), C 1-6 alkyloxy (such as methoxy, ethoxy, propoxy, isopropoxy), and its examples can be 4-fluorobenzophenone, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, 2,4'-difluorobenzophenone, 4-fluoro-4'-methoxybenzophenone.

[0043] According to an embodiment of the present invention, the conditions for the end-capping treatment include: the temperature is 295 - 320 °C; the time is 15 - 45 min.

[0044] According to an embodiment of the present invention, in step (3), the cooling can be carried out by a method known in the art. For example, place the reaction product on a metal plate (such as a stainless steel plate) for cooling.

[0045] According to an embodiment of the present invention, in step (3), the cooled reaction product is ground into powder particles. Preferably, the size of the powder particles is less than 2.3 mm and greater than 0.22 mm.

[0046] According to an embodiment of the present invention, in step (3), the purification includes first washing the powder particles with an organic solvent and then performing multiple water washes.

[0047] Preferably, the washing of the powder particles with the organic solvent specifically includes: mixing the powder particles with the organic solvent, removing impurities in the powder particles (such as the solvent added in step (1)), and then removing the organic solvent. Preferably, a suitable separation device is used to remove the organic solvent, such as using a Soxhlet extractor for separation. Further, during washing, the organic solvent is selected from organic solvents miscible with water, such as acetone.

[0048] Preferably, the water wash specifically includes: performing a first water wash on the powder particles with ultrapure water and / or deionized water to remove the organic solvent, and then performing a rinse with deionized water or pure water under heating conditions, and the heating temperature is 60 - 80 °C.

[0049] Preferably, the number of times of the water wash is not specifically limited, as long as the conductivity of the filtered water after rinsing is less than 10 μS / cm.

[0050] According to an embodiment of the present invention, in step (3), the drying can be carried out by a method known in the art as long as the washed polyetheretherketone resin can be dried.

[0051] The present invention also provides a polyetheretherketone resin obtained by the above preparation method.

[0052] According to an embodiment of the present invention, the gel content of the polyetheretherketone is less than 1%, preferably less than 1%, such as 0.05%, 0.06%.

[0053] According to an embodiment of the present invention, the molecular weight distribution PDI of the polyetheretherketone is 3.0 - 4.0, such as 3.28, 3.31, 3.26.

[0054] According to an embodiment of the present invention, the melt viscosity MV of the polyetheretherketone is less than 385 Pa·s, such as 382.6 Pa·s, 383.5 Pa·s, 383.9 Pa·s.

[0055] According to an embodiment of the present invention, the polyetheretherketone has thermal stability, for example, the initial decomposition temperature is above 580 °C, such as 585.5 °C, 585.7 °C, 585.8 °C.

[0056] According to an embodiment of the present invention, in the chromaticity of the polyether ether ketone, the L value is greater than 72, for example, 74.58, 73.69, 75.77, 73.95, 75.31, 74.99; the a value is 1 to 2.5, for example, 2.15, 2.23, 2.05; the b value is not greater than 6, preferably 5 to 6, for example, 5.24, 5.18, 5.26.

[0057] The present invention also provides the application of the above polyether ether ketone resin in the fields of aerospace, medical, electronic and electrical appliances, automobile manufacturing, petrochemical industry, etc., for example, the application in film products and wire and cable products.

[0058] Preferably, for the film product prepared from the above polyether ether ketone resin, the number of crystal points on both sides is less than 5, for example, 3.

[0059] Preferably, for the cable insulation layer prepared from the above polyether ether ketone resin, the number of crystal points on the surface is less than 5, for example, 3 or 4.

[0060] Beneficial effects

[0061] For film products and wire and cable coating layers, the appearance of crystal points on the surface is fatal to the performance and service life of the products, rather than simply unqualified appearance, which is a fatal defect leading to the failure of the products. The high-purity sodium carbonate obtained by the purification method of the present invention, when used to prepare polyether ether ketone, can not only reduce the gel content, but also greatly reduce the frequency of crystal points on the surface appearance when used to prepare film products and wire and cable coating materials. Specific embodiments

[0062] The technical solutions of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only for illustrative and explanatory purposes of the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection of the present invention.

[0063] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products, or can be prepared by known methods.

[0064] The test methods used in the present invention are specifically as follows:

[0065] Method 1. Determination method of water-insoluble matter, microporous filtration membrane method:

[0066] 1.1 Principle

[0067] The sample is dissolved in water at 40 °C, and the insoluble matter is weighed after filtration, washing, and drying.

[0068] 1.2 Reagents or materials

[0069] Phenolphthalein indicator solution: 10 g / L ethanol solution.

[0070] 1.3 Instrument and equipment

[0071] Membrane filtration device: 1000 mL.

[0072] Microfiltration membrane: Made of hydrophilic polytetrafluoroethylene, with a pore size of 0.45 μm and a diameter of 47 mm - 50 mm.

[0073] Electric thermostatic drying oven: The temperature can be controlled at 110°C ± 5°C.

[0074] 1.4 Test procedure

[0075] Put the microfiltration membrane into a weighing bottle, place it in an electric thermostatic drying oven, and dry it at 110°C ± 5°C until the mass is constant, accurate to 0.0002 g.

[0076] Weigh 20 g - 40 g of the sample, accurate to 0.01 g, put it into a beaker, dissolve it with about 200 mL - 400 mL of water (about 40°C), and maintain the temperature of the test solution at 50°C ± 5°C. Assemble the microfiltration membrane and the membrane filtration device together, and filter the test solution. Wash the insoluble matter with water at 50°C ± 5°C until the color presented after adding 2 drops of phenolphthalein indicator solution to 20 mL of the washing solution and 20 mL of water is the same. Carefully remove the microfiltration membrane and put it into the original weighing bottle, and dry it in an electric thermostatic drying oven at 110°C ± 5°C until the mass is constant.

[0077] 1.5 Test data processing

[0078] The content of water-insoluble matter is calculated as the mass fraction w according to the following formula:

[0079] w = (m1 - m2) / m(1 - w) × 100%

[0080] Where:

[0081] M1--The value of the mass of the dried weighing bottle, microfiltration membrane and insoluble matter, in grams (g);

[0082] M2,-The value of the mass of the dried weighing bottle and microfiltration membrane, in grams (g);

[0083] m--The value of the mass of the test sample, in grams (g);

[0084] w--The mass fraction of the ignition loss measured by Method 2 below.

[0085] Take the arithmetic mean of the parallel determination results as the determination result, and the absolute difference between the two parallel determination results should not be greater than 0.006%.

[0086] Method 2: Determination of Loss on Ignition

[0087] 2.1 Principle

[0088] The test sample is heated at 300 °C until the mass is constant. During heating, free moisture, water, and carbon dioxide decomposed from sodium bicarbonate are lost, and the loss on ignition is calculated.

[0089] 2.2 Instruments and Equipment

[0090] 2.2.1 Weighing bottle: Or porcelain crucible, with a capacity of about 30 mL.

[0091] 2.2.2 Electrothermal constant temperature drying oven or high-temperature furnace: The temperature can be controlled at 300 °C ± 5 °C.

[0092] 2.3 Test Procedures

[0093] Weigh about 2 g of the test sample, accurate to 0.0002 g, place it in a weighing bottle or porcelain crucible that has been pre-heated to a constant mass at 300 °C, put it into the electrothermal constant temperature drying oven or high-temperature furnace, and heat it at 300 °C until the mass is constant.

[0094] 2.4 Processing of Test Data

[0095] The loss on ignition is calculated as the mass fraction w according to the following formula:

[0096] w = (m3 - m4) / m × 100%

[0097] Where:

[0098] M3--The value of the mass of the test portion and the weighing bottle (or porcelain crucible), in grams (g);

[0099] M4--The value of the mass of the dried test portion and the weighing bottle (or porcelain crucible), in grams (g);

[0100] m--The value of the mass of the test portion, in grams (g).

[0101] Take the arithmetic mean of the parallel determination results as the determination result, and the absolute difference of the parallel determination results should not be greater than 0.04%.

[0102] Method 3: Test Method for the Contents of Elements Magnesium (Mg), Aluminum (Al), Calcium (Ca), Iron (Fe), Copper (Cu), Lead (Pb), and Nickel (Ni)

[0103] The concentrations of magnesium, aluminum, calcium, iron, copper, lead, and nickel in sodium carbonate are measured by measuring the element concentrations through inductively coupled plasma atomic emission spectroscopy. Weigh approximately 3 g of sodium carbonate samples into multiple platinum crucibles using an analytical balance. Add two drops of concentrated trace metal grade sulfuric acid to each sample and place these crucibles in a muffle furnace set at 250 °C. Raise the furnace temperature to 525 °C for 1 hour to remove any organic residues. Dissolve the metallic residues by adding 1 ml of concentrated hydrochloric acid to the crucibles. After adding 5 ml of deionized water and additional heating, quantitatively transfer the contents of the crucibles to a 25-ml volumetric flask, dilute to the mark with deionized water, and mix well. Then analyze these diluted solutions by ICP-AES using certified magnesium, aluminum, calcium, iron, copper, lead, and nickel standard solutions. Monitor the emissions of the elements of interest at the following wavelengths: magnesium: 279.553 nm; aluminum: 167.019 nm; calcium: 422.673 nm; iron: 238.204 nm; copper: 327.395 nm; lead: 220.353 nm; nickel: 231.604 nm. The plasma conditions for this analysis are: plasma input power: 1300 watts, plasma argon gas flow rate: 15 liters / minute, auxiliary argon gas flow rate: 0.5 liters / minute, nebulizer flow rate: 1.2 liters / minute, and sample flow rate: 1.5 ml / minute. Calculate the element concentrations in these samples from the element emission line intensities through the ICP operating software.

[0104] Method 4, Test of Molecular Weight

[0105] Use an Agilent Technologies PL-GPC220 High Temperature Chromatograph, with α-chloronaphthalene as the solvent and 1,2,4-trichlorobenzene as the diluent. The column temperature is 125 °C, and the mobile phase uses a mixture of α-chloronaphthalene and 1,2,4-trichlorobenzene, with their mass ratio being α-chloronaphthalene:1,2,4-trichlorobenzene = 1:2.2. The test parameters are taken as K = 14.2 and α = 0.72.

[0106] Method 5, Test of Melt Viscosity MV

[0107] Use a Dynisco LCR 7001 capillary rheometer, with a test temperature of 400 °C, a load of 10 KN, and take the shear flow rate at 1000 (1 / S) as the test result.

[0108] Method 6, Test of Color

[0109] Measure the L value, a value, and b value of the sample using a color difference meter;

[0110] Method 7, Thermal Stability Test

[0111] The thermal stability of polyetheretherketone resin was characterized by thermogravimetric analysis (TGA). Among them, the initial decomposition temperature measured by TGA was used to characterize the thermal stability of polyetheretherketone resin, because the initial decomposition temperature is the temperature at which the TGA curve begins to deviate from the baseline point and has good repeatability.

[0112] Method 8: Gel content test

[0113] The gel content in polyetheretherketone resin was determined by filtration method

[0114] (1) Take a certain mass of polyetheretherketone resin. After keeping it at a constant temperature of 120 °C for 6 hours, the measured moisture content should be ≤ 0.1%. Take 1.0 - 1.5 g of the above-mentioned dried polyetheretherketone resin, accurately weigh its mass with an analytical balance, and record the mass as M0. Dissolve the weighed polyetheretherketone resin sample in trichlorotoluene solvent, seal it, and place it on a shaker oscillator at 180 °C for 30 hours.

[0115] (2) Select a microporous filter membrane of appropriate specification that has been treated (soaked in formic acid solution until the mass is constant), with a pore size range of 0.2 - 0.4 microns, and record the mass of the filter membrane as M1.

[0116] (3) Install a sand core filtration device and a circulating water vacuum pump, and prevent foreign matter contamination during the filtration process.

[0117] (4) After filtration, rinse with a certain amount of deionized water and absolute ethanol, remove the filter membrane and dry it to a constant weight, and record the mass as M2.

[0118] The gel content in polyetheretherketone resin was calculated according to the following formula:

[0119] Gel content = (M2 - M1) / M0 * 100%

[0120] Method 9: Measurement of the number of crystal points on the surface of the cable and the surface of the film

[0121] Take a certain mass of polyetheretherketone resin. After keeping it at a constant temperature of 120 °C for 6 hours, the measured moisture content should be ≤ 0.2%. Then perform the following operations respectively:

[0122] 1. Use a small cable extrusion device to prepare a cable with a diameter of 6 ± 0.1 mm and a thickness of 0.3 mm from the above polyetheretherketone resin. The cooling method is natural air cooling. The internal conductor of the cable is a copper conductor. After the current is stable during the extrusion process, take a sample of 1000 mm, and carefully observe and record the number of crystal points of the sample under a magnifying glass.

[0123] 2. Use a small hot pressing and film-forming device to prepare a film with a thickness of 0.2 ± 0.02 mm from the above polyether ether ketone resin. The cooling method is natural air cooling. Cut a film with a size of 200 mm * 200 mm and carefully observe and record the total number of crystal points on both sides of the film under a magnifying glass.

[0124] Example 1

[0125] The purification method of sodium carbonate is as follows:

[0126] (1) Primary dissolution and filtration

[0127] At 35.4 °C, the solubility of sodium carbonate reaches the maximum, and the content of sodium carbonate in the saturated solution at this time is 33.2%. Weigh industrial sodium carbonate produced by Shandong Haihua Co., Ltd. and dissolve it completely in deionized water at 35.4 °C. Filter it with a slow quantitative filter paper in a Buchner funnel, wash the filter residue with deionized water, and place the filter residue in an oven at 105 ± 2 °C to dry to constant weight. When the mother liquor is heated and evaporated to almost dry, transfer it to a porcelain crucible and continue to calcine it in a muffle furnace at 300 ± 2 °C for 2 h to remove water, obtaining purified sodium carbonate. Grind it with a mortar and place it in a desiccator for later use.

[0128] (2) Secondary dissolution and filtration

[0129] Repeat the operation in step 2.1 for the sodium carbonate prepared above to obtain sodium carbonate purified for the second time.

[0130] (3) Chemical precipitation

[0131] Use the sodium carbonate purified for the second time obtained in step 2.2 and deionized water. After preparing a solution, add NaOH to adjust the pH value to 11 - 13, and let it stand and precipitate in a clarification tank; after filtration, obtain a clarified mother liquor.

[0132] (4) Ceramic membrane filtration method

[0133] Filter the clarified mother liquor obtained in step 2.3 using a ceramic membrane with a pore size of 0.8 - 1.0 μm.

[0134] (5) After filtration, evaporate and crystallize the clarified mother liquor to obtain sodium carbonate monohydrate crystals; wash and dry the crystals obtained by evaporation to obtain high-purity anhydrous sodium carbonate products.

[0135] Use a laser particle size distribution analyzer to test the particle size distribution of the purified sodium carbonate in this example.

[0136] The particle size distribution of the purified sodium carbonate is the same as that before purification.

[0137] The industrial sodium carbonate before and after purification has the following impurity contents as shown in the table:

[0138] Before purification After purification Types of impurities Impurity content Impurity content Insoluble matter in water 0.15％ 0.03％ Loss on drying (300°C) 3.8％ 1.2％ Sulfate 0.15％ 0.04％ Total content of metal elements 0.16％ 0.09％ Total content of calcium and magnesium elements 0.14％ 0.06％

[0139] Example 2

[0140] The purification method of sodium carbonate is as follows:

[0141] (1) Primary dissolution and filtration

[0142] At 35.4 °C, the solubility of sodium carbonate reaches the maximum, and the content of sodium carbonate in the saturated solution at this time is 33.2%. Weigh the industrial sodium carbonate produced by Shandong Haihua Co., Ltd. and dissolve it completely in deionized water at 35.4 °C. Filter it with a slow quantitative filter paper in a Buchner funnel, wash the filter residue with deionized water, and place the filter residue in an oven at 105 ± 2 °C to dry to constant weight. When the mother liquor is heated and evaporated to almost dry, transfer it to a porcelain crucible and continue to calcine it in a muffle furnace at 300 ± 2 °C for 2 h to remove water, obtaining the purified sodium carbonate. Grind it with a mortar and place it in a desiccator for standby.

[0143] (2) Secondary dissolution and filtration

[0144] Repeat the operation of step 2.1 for the sodium carbonate prepared above to obtain the sodium carbonate purified for the second time.

[0145] (3) Chemical precipitation

[0146] Use the sodium carbonate purified for the second time obtained in step 2.2 and deionized water. After preparing a solution, add NaOH to adjust the pH value to 11 - 13, and let it stand and precipitate in a clarification tank; obtain the clarified mother liquor after filtration.

[0147] (4) Ceramic membrane filtration method

[0148] Filter the clarified mother liquor obtained in step 2.3 with a ceramic membrane with a pore size of 0.8 - 1.0 μm.

[0149] (5) After filtration, evaporate and crystallize the clarified mother liquor to obtain sodium carbonate monohydrate crystals; wash and dry the crystals obtained by evaporation to obtain high-purity anhydrous sodium carbonate products.

[0150] Use a laser particle size distribution analyzer to test the particle size distribution of the purified sodium carbonate in this example.

[0151] The particle size distribution of the purified sodium carbonate is the same as that before purification.

[0152] The industrial sodium carbonate before and after purification has the following impurity contents shown in the table:

[0153] Before purification After purification Types of impurities Impurity content Impurity content Insoluble matter in water 0.33％ 0.03％ Loss on drying (300°C) 4.2％ 1.1％ Sulfate 0.21％ 0.04％ Total content of metal elements 0.27％ 0.11％ Total content of calcium and magnesium elements 0.15％ 0.05％

[0154] Example 3

[0155] The purification method of sodium carbonate is as follows:

[0156] (1) Primary dissolution and filtration

[0157] At 35.4 °C, the solubility of sodium carbonate reaches its maximum, and the content of sodium carbonate in the saturated solution is 33.2%. Weigh the industrial sodium carbonate produced by Shandong Haihua Co., Ltd. and dissolve it completely in deionized water at 35.4 °C. Filter it with a slow quantitative filter paper in a Buchner funnel, wash the filter residue with deionized water, and place the filter residue in an oven at 105 ± 2 °C to dry to a constant weight. Heat and evaporate the mother liquor until it is almost dry, then transfer it to a porcelain crucible and continue to calcine it in a muffle furnace at 300 ± 2 °C for 2 h to remove the moisture, obtaining the purified sodium carbonate. Grind it with a mortar and place it in a desiccator for later use.

[0158] (2) Secondary dissolution and filtration

[0159] Repeat the operation of step 2.1 for the sodium carbonate prepared above to obtain the sodium carbonate purified twice.

[0160] (3) Chemical precipitation

[0161] Use the sodium carbonate purified twice obtained in step 2.2 and deionized water to prepare a solution, then add NaOH to adjust the pH value to 11 - 13, and let it stand and precipitate in a clarification tank; after filtration, obtain the clarified mother liquor.

[0162] (4) First, perform ceramic membrane filtration

[0163] Filter the clarified mother liquor obtained in step 2.3 using a ceramic membrane with a pore size of 0.6 - 0.8 μm.

[0164] (5) Second, perform ceramic membrane filtration

[0165] Filter the clarified mother liquor obtained in step 2.4 again using a ceramic membrane with a pore size of 0.6 - 0.8 μm.

[0166] (6) After filtration, evaporate and crystallize the clarified mother liquor to obtain sodium carbonate monohydrate crystals; wash and dry the crystals obtained by evaporation to obtain high-purity anhydrous sodium carbonate products.

[0167] Use a laser particle size distribution analyzer to test the particle size distribution of the purified sodium carbonate in this example.

[0168] The particle size distribution of the purified sodium carbonate is the same as that before purification.

[0169] The industrial sodium carbonate before and after purification has the following impurity contents shown in the table:

[0170] Before purification After purification Types of impurities Impurity content Impurity content Insoluble matter in water 0.37％ 0.03％ Loss on drying (300°C) 3.9％ 1.0％ Sulfate 0.22％ 0.04％ Total content of metal elements 0.32％ 0.07％ Total content of calcium and magnesium elements 0.18％ 0.03％

[0171] From the impurity contents of sodium carbonate before and after purification in Example 1 and Example 2, it can be seen that the unpurified sodium carbonate has problems of high impurity content and large fluctuations in impurity content; after purification, the impurity content of sodium carbonate is greatly reduced and the impurity content is stable, indicating the stability and effectiveness of this purification method, which is of great significance for the stability of the production process.

[0172] From the impurity contents of sodium carbonate before and after purification in Example 3, it can be seen that by using a ceramic membrane with a finer pore size for two - stage filtration, purified sodium carbonate with lower calcium and magnesium element contents can be obtained.

[0173] Comparative Example 1

[0174] For the unpurified sodium carbonate, the impurity contents are as shown in the following table:

[0175] Types of impurities Impurity content Insoluble matter in water 0.39％ Loss on drying (300°C) 3.6％ Sulfate 0.23％ Total content of metal elements 0.35％ Total content of calcium and magnesium elements 0.19％

[0176] Comparative Example 2

[0177] The purification method of sodium carbonate is as follows:

[0178] (1) Primary dissolution and filtration

[0179] At 35.4 °C, the solubility of sodium carbonate reaches the maximum, and the content of sodium carbonate in the saturated solution at this time is 33.2%. Weigh industrial sodium carbonate produced by Shandong Haihua Co., Ltd. and dissolve it completely in deionized water at 35.4 °C. Then, filter it with a slow - speed quantitative filter paper in a Buchner funnel, wash the filter residue with deionized water, and place the filter residue in an oven at 105 ± 2 °C to dry to constant weight. When the mother liquor is heated and evaporated to almost dry, transfer it to a porcelain crucible and continue to calcine it in a muffle furnace at 300 ± 2 °C for 2 h to remove water, obtaining purified sodium carbonate. Grind it with a mortar and place it in a desiccator for standby.

[0180] (2) Secondary dissolution and filtration

[0181] Repeat the operation in step 2.1 of the above - prepared sodium carbonate to obtain sodium carbonate purified for the second time.

[0182] (3) After filtration, evaporate and crystallize the clarified mother liquor to obtain sodium carbonate monohydrate crystals; wash and dry the crystals obtained by evaporation to obtain purified anhydrous sodium carbonate products.

[0183] The industrial sodium carbonate before and after purification has the following impurity contents as shown in the table:

[0184] Before purification After purification Types of impurities Impurity content Impurity content Insoluble matter in water 0.41％ 0.22％ Loss on drying (300°C) 3.8％ 2.7％ Sulfate 0.25％ 0.21％ Total content of metal elements 0.36％ 0.31％ Total content of calcium and magnesium elements 0.19％ 0.18％

[0185] Comparative Example 3

[0186] The purification method of sodium carbonate is as follows:

[0187] (1) Primary dissolution and filtration

[0188] At 35.4 °C, the solubility of sodium carbonate reaches its maximum, and the content of sodium carbonate in the saturated solution at this time is 33.2%. Weigh industrial sodium carbonate produced by Shandong Haihua Co., Ltd. and dissolve it completely in deionized water at 35.4 °C. Filter it with a slow quantitative filter paper in a Buchner funnel, wash the filter residue with deionized water, and place the filter residue in an oven at 105 ± 2 °C to dry to a constant weight. Heat the mother liquor to near dryness and transfer it to a porcelain crucible, then continue to calcine it in a muffle furnace at 300 ± 2 °C for 2 h to remove water, obtaining purified sodium carbonate. Grind it with a mortar and place it in a desiccator for later use.

[0189] (2) Secondary dissolution and filtration

[0190] Repeat the operation in step 2.1 for the sodium carbonate prepared above to obtain sodium carbonate purified twice.

[0191] (3) Ceramic membrane filtration method

[0192] Filter the clarified mother liquor obtained in step 2.3 using a ceramic membrane with a pore size of 0.8 - 1.0 μm.

[0193] (4) After filtration, evaporate and crystallize the clarified mother liquor to obtain sodium carbonate monohydrate crystals; wash and dry the crystals obtained by evaporation to obtain high-purity anhydrous sodium carbonate products.

[0194] Use a laser particle size distribution analyzer to test the particle size distribution of the purified sodium carbonate in this example.

[0195] The particle size distribution of the purified sodium carbonate is the same as that before purification.

[0196] The industrial sodium carbonate before and after purification has the following impurity contents as shown in the table below:

[0197]

[0198]

[0199] Comparative Example 4

[0200] The purification method of sodium carbonate is as follows:

[0201] (1) Primary dissolution and filtration

[0202] At 35.4 °C, the solubility of sodium carbonate reaches its maximum, and the content of sodium carbonate in the saturated solution at this time is 33.2%. Weigh industrial sodium carbonate produced by Shandong Haihua Co., Ltd. and dissolve it completely in deionized water at 35.4 °C. Filter it with a slow quantitative filter paper in a Buchner funnel, wash the filter residue with deionized water, and place the filter residue in an oven at 105 ± 2 °C to dry to a constant weight. Heat the mother liquor until it is almost dry, transfer it to a porcelain crucible, and continue to burn it in a muffle furnace at 300 ± 2 °C for 2 h to remove the moisture, obtaining purified sodium carbonate. Grind it with a mortar and place it in a desiccator for later use.

[0203] (2) Secondary dissolution and filtration

[0204] Repeat the operation of step 2.1 for the sodium carbonate prepared above to obtain sodium carbonate purified twice.

[0205] (3) Chemical precipitation

[0206] Use the sodium carbonate purified twice obtained in step 2.2 and deionized water to prepare a solution, add NaOH to adjust the pH value to 11 - 13, and let it stand and precipitate in a clarification tank; after filtration, obtain a clarified mother liquor.

[0207] (4) After filtration, evaporate and crystallize the clarified mother liquor to obtain sodium carbonate monohydrate crystals; wash and dry the crystals obtained by evaporation to obtain high-purity anhydrous sodium carbonate products.

[0208] Use a laser particle size distribution analyzer to test the particle size distribution of the purified sodium carbonate in this example.

[0209] The particle size distribution of the purified sodium carbonate is the same as that before purification.

[0210] The industrial sodium carbonate before and after purification has the following impurity contents shown in the table below:

[0211] Before purification After purification Types of impurities Impurity content Impurity content Insoluble matter in water 0.15％ 0.05％ Loss on drying (300°C) 3.8％ 1.0％ Sulfate 0.15％ 0.05％ Total content of metal elements 0.18％ 0.13％ Total content of calcium and magnesium elements 0.15％ 0.11％

[0212] Application Example 1

[0213] Take the high-purity sodium carbonate of Example 1 and use it to prepare polyetheretherketone resin. The specific steps are as follows:

[0214] In a 3 L glass reaction vessel, under the condition of continuously introducing an inert gas such as nitrogen, add 16 mol of diphenyl sulfone, 4.0 mol of hydroquinone, 4.0 mol of 4,4'-difluorobenzophenone, 4.8 mol of high-purity sodium carbonate, and 0.16 mol of potassium carbonate;

[0215] After heating to melting, the materials are stirred evenly at a stirring speed of 80 r / min, then continue to heat to 180 °C for 1 hour, and then heat to 310 °C for about 1 - 2 hours. When the torque sensor of the stirrer reaches the target value, 0.050 mol of 4,4'-difluorobenzophenone is added at one time for end-capping treatment. After another 30 minutes, the mixture in the flask is poured out onto a smooth stainless steel plate to cool. The cooled materials are ground and crushed (maximum size < 2 mm), washed 5 - 7 times with pure acetone until diphenyl sulfone is no longer detected in the acetone washing solution, washed 5 - 7 times with deionized water at 70 °C until the conductivity value of the washing solution < 3 μS / cm. The washed materials are loaded into a stainless steel tray and dried in an oven at 150 °C for 8 hours to obtain a polyether ether ketone product.

[0216] Application Example 2

[0217] Take the high-purity sodium carbonate of Example 2 for the preparation of polyether ether ketone resin. The specific steps are basically the same as those of Application Example 1, except that the high-purity sodium carbonate of Example 1 is replaced with the high-purity sodium carbonate of Example 2.

[0218] Application Example 3

[0219] Take the high-purity sodium carbonate of Example 3 for the preparation of polyether ether ketone resin. The specific steps are basically the same as those of Application Example 1, except that the high-purity sodium carbonate of Example 1 is replaced with the high-purity sodium carbonate of Example 3.

[0220] Comparative Application Example 1

[0221] Take the sodium carbonate of Comparative Example 1 to prepare polyether ether ketone resin. The specific steps are as follows:

[0222] In a 3 L glass reaction vessel, under the condition of continuously introducing an inert gas such as nitrogen, add 16 mol of diphenyl sulfone, 4.0 mol of hydroquinone, 4.0 mol of 4,4'-difluorobenzophenone, 4.8 mol of sodium carbonate, and 0.16 mol of potassium carbonate;

[0223] After heating to melting, the materials are stirred evenly at a stirring speed of 80 r / min, then continue to heat to 180 °C for 1 hour, and then heat to 310 °C for about 1 - 2 hours. When the torque sensor of the stirrer reaches the target value, 0.050 mol of 4,4'-difluorobenzophenone is added at one time for end-capping treatment. After another 30 minutes, the mixture in the flask is poured out onto a smooth stainless steel plate to cool. The cooled materials are ground and crushed (maximum size < 2 mm), washed 5 - 7 times with pure acetone until diphenyl sulfone is no longer detected in the acetone washing solution, washed 5 - 7 times with deionized water at 70 °C until the conductivity value of the washing solution < 3 μS / cm. The washed materials are loaded into a stainless steel tray and dried in an oven at 150 °C for 8 hours to obtain a polyether ether ketone product.

[0224] Comparative Application Example 2

[0225] Take the purified sodium carbonate from Comparative Example 2 and use it to prepare polyetheretherketone resin. The specific steps are basically the same as those in Comparative Application Example 1, except that the sodium carbonate in Comparative Example 1 is replaced with the purified sodium carbonate from Comparative Example 2.

[0226] Comparative Application Example 3

[0227] Take the purified sodium carbonate from Comparative Example 3 and use it to prepare polyetheretherketone resin. The specific steps are basically the same as those in Comparative Application Example 1, except that the sodium carbonate in Comparative Example 1 is replaced with the purified sodium carbonate from Comparative Example 3.

[0228] Comparative Application Example 4

[0229] Take the purified sodium carbonate from Comparative Example 4 and use it to prepare polyetheretherketone resin. The specific steps are basically the same as those in Comparative Application Example 1, except that the sodium carbonate in Comparative Example 1 is replaced with the purified sodium carbonate from Comparative Example 4.

[0230] Test Example

[0231] Take the polyetheretherketone prepared in the above Application Examples and Comparative Application Examples as samples, and test the various properties of the prepared polyetheretherketone resin according to the above test method. The test results are as follows.

[0232] Table 1 Color Test Results of Polyetheretherketone Resin

[0233] Sample L value a value b value Application Example 1 76.34 2.15 5.24 Application Example 2 76.84 2.23 5.18 Application Example 3 79.21 2.05 5.26 Comparative Application Example 1 71.35 2.47 5.65 Comparative Application Example 2 72.14 2.95 5.39 Comparative Application Example 3 72.76 2.36 5.38 Comparative Application Example 4 72.59 2.65 5.26

[0234] As can be seen from Table 1, the color of the polyetheretherketone resin prepared using the purified sodium carbonate from Examples 1 - 3 is significantly better than that of the polyetheretherketone resin prepared using the sodium carbonate from Comparative Examples 1 - 4. And the color stability is very good.

[0235] Table 2 Molecular Weight Distribution (Polydispersity Index PDI = Mw / Mn), Thermal Stability, and Melt Viscosity of Polyetheretherketone Resin

[0236] Sample Polydispersity index PDI Thermal stability Melt viscosity MV Application Example 1 3.28 585.5°C (initial decomposition temperature) 382.6 Pa.s Application Example 2 3.31 585.7°C (initial decomposition temperature) 383.5 Pa.s Application Example 3 3.36 585.8°C (initial decomposition temperature) 383.9 Pa.s Comparative Application Example 1 4.85 565.8°C (initial decomposition temperature) 408.5 Pa.s Comparative Application Example 2 4.76 577.6°C (initial decomposition temperature) 393.6 Pa.s Comparative Application Example 3 4.58 575.4°C (initial decomposition temperature) 416.40 Pa.s Comparative Application Example 4 4.39 574.3°C (initial decomposition temperature) 387.2 Pa.s

[0237] As can be seen from Table 2, the molecular weight distribution, thermal stability, and melt viscosity stability of the polyetheretherketone resin prepared using the purified sodium carbonate from Examples 1 - 3 are significantly better than those of the polyetheretherketone resin prepared using the sodium carbonate from Comparative Examples 1 - 4.

[0238] Table 3 Gel Content Test Results of Polyetheretherketone Resin

[0239] Sample Gel content % Application Example 1 0.06 Application Example 2 0.05 Application Example 3 0.05 Comparative Application Example 1 2.3 Comparative Application Example 2 2.1 Comparative Application Example 3 2.2 Comparative Application Example 4 1.9

[0240] As can be seen from Table 3, the gel content of the polyetheretherketone resin prepared with the purified sodium carbonate of Examples 1-3 is greatly reduced.

[0241] Table 4 Test Results of the Number of Crystal Points of Polyetheretherketone Resin

[0242]

[0243] As can be seen from Table 4, for the polyetheretherketone resin prepared with the purified sodium carbonate of Examples 1-3, when preparing wire and cable products and film products, the number of surface crystal points is greatly reduced.

[0244] The sodium carbonate obtained by using the purification method of the present invention has lower calcium and magnesium element contents. When the polyetheretherketone resin prepared therefrom is used to prepare wire and cable products and film products, the number of crystal points on the surface appearance is reduced.

[0245] The above describes the exemplary embodiments of the present invention. However, the protection scope of this application is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A purification method for preparing high-purity sodium carbonate, characterized in that: The purification method comprises: subjecting industrial sodium carbonate to dissolution filtration, chemical precipitation, ceramic membrane filtration, evaporation crystallization and drying in sequence to obtain the high-purity sodium carbonate.

2. The purification method according to claim 1, characterized in that The purity of the industrial sodium carbonate refers to a total alkali content of not less than 98% based on the dry weight of the sodium carbonate.

3. The purification method according to claim 1, characterized in that The dissolution filtration is performed at least twice; And / or, the dissolution filtration specifically comprises: dissolving industrial sodium carbonate in deionized water to obtain a saturated solution, then performing a primary filtration to remove water from the filtrate, and then optionally repeating the process at least once to obtain a purified sodium carbonate; And / or, the chemical precipitation specifically comprises: mixing the once purified sodium carbonate and deionized water, adding an inorganic base to adjust the pH to 11-13, allowing to stand for precipitation, and obtaining a clarified mother liquor after secondary filtration.

4. The purification method according to claim 1, characterized in that The ceramic membrane filtration specifically refers to: using a ceramic membrane with a pore size of 0.1-1 μm to perform three-stage filtration on the clarified mother liquor to obtain the mother liquor to be evaporated; And / or, the evaporative crystallization includes heating the mother liquor to be evaporated to obtain sodium carbonate monohydrate crystals; And / or, the sodium carbonate monohydrate crystals are washed and dried to obtain the high-purity sodium carbonate.

5. A high-purity sodium carbonate, characterized in that The high-purity sodium carbonate is prepared by the purification method according to any one of claims 1 to 4.

6. High-purity sodium carbonate according to claim 5, characterized in that, The purity of the high-purity sodium carbonate is not less than 98.8%; And / or, the impurities of the high-purity sodium carbonate include metal impurities and other impurities; And / or, the metal impurities include at least one of magnesium, aluminum, calcium, iron, copper, lead, and nickel; And / or, in the high-purity sodium carbonate, the total content of metal elements in the metal impurities is not more than 0.15%; wherein the total content of calcium and magnesium elements is not more than 0.08%; And / or, the other impurities further include water-insoluble matter, chloride and sulfate, wherein the mass content of the water-insoluble matter is not greater than 0.05%, and the mass content of the sulfate is not greater than 0.08%.

7. High-purity sodium carbonate according to claim 5, characterized in that When heated to 300° C., the drying loss of the high-purity sodium carbonate is no more than 3.0%; And / or, the high-purity sodium carbonate has the following particle size distribution: 40 μm≤D50≤260 μm, and 260 μm≤D90≤500 μm.

8. A method for preparing a polyetheretherketone resin, the method comprising using the high-purity sodium carbonate according to any one of claims 5 to 7 to prepare the polyetheretherketone resin.

9. A polyetheretherketone resin, characterized in that The polyetheretherketone resin is obtained by the preparation method according to claim 8; And / or, the polyetheretherketone has a gel content of less than 1%.

10. Application of the polyetheretherketone resin according to claim 9 in the fields of aerospace, medical treatment, electronic appliances, automobile manufacturing, petrochemical industry, etc.

Images