A method for preparing perfluorooctanoic acid for semiconductor electronic chemical additives

Abstract

The application discloses a preparation method of perfluorooctanoic acid for semiconductor electronic chemical additives, and relates to the technical field of electronic chemical additive preparation, and comprises the following steps: step S1, raw material pretreatment; step S2, phase interface regulation primary extraction; step S3, gradient temperature secondary extraction, to obtain secondary purification liquid L2 and HF acid liquid U2; step S4, double-stage purification HF reuse and tertiary extraction, to obtain tertiary purification liquid L3, purified HF acid liquid U2' and U3'; and step S5, inert atmosphere gradient partial pressure purification, to obtain perfluorooctanoic acid for semiconductor electronic chemical additives. The perfluorooctanoic acid prepared by the method has high purity and low metal ion content.

Description

Technical Field

[0001] This invention relates to the field of electronic chemical additives preparation technology, and in particular to a method for preparing perfluorooctanoic acid (PFOA) for semiconductor electronic chemical additives. Background Technology

[0002] Perfluorooctanoic acid (PFOA), a highly efficient fluorinated surfactant, is often added in small amounts to electronic-grade cleaning or etching solutions to reduce surface tension and improve wettability and uniformity. However, industrial-grade PFOA raw materials generally suffer from excessive metal ion content, falling far short of the requirements for semiconductor applications. Furthermore, due to its high boiling point, poor thermal stability, and strong corrosiveness, traditional physical purification methods such as distillation and fractionation are ineffective in removing metal ions and can easily cause product decomposition or equipment corrosion.

[0003] Currently, the mainstream methods for purifying and preparing perfluorooctanoic acid (PFOA) as an additive in semiconductor electronic chemicals mainly include solvent extraction, ion exchange resin adsorption, and membrane filtration. However, solvent extraction carries the risk of residual organic solvents, affecting the compatibility of electronic chemicals; ion exchange methods have limited effectiveness in removing non-ionic metals, and resin regeneration is difficult and costly; membrane filtration is limited by low flux and susceptibility to clogging, making it unsuitable for large-scale production. Furthermore, the above methods generally have low yields, consume large amounts of expensive reagents such as HF, and are economically unsustainable.

[0004] For example, invention patent document CN101397245B discloses a distillation method for perfluorooctanoic acid (PFOA), which includes the following steps: 1) providing a mother liquor containing PFOA, hydrogen fluoride, and free fluorine; 2) adding an aluminum sulfate solution to the mother liquor to form an aluminum sulfate-containing mixture, wherein the weight ratio of PFOA to the added aluminum sulfate is 100:1 to 5:1 based on the pure PFOA product; 3) heating the aluminum sulfate-containing mixture at a temperature of 25 to 100°C for 1 to 10 hours; 4) adding glass beads with a particle size of 0.06-0.16 mm to the heated aluminum sulfate-containing mixture, wherein the weight ratio of PFOA to the added glass beads is 50:1 to 1:1 based on the pure PFOA product; and 5) distillation. However, this method requires the introduction of aluminum sulfate (which easily leaves aluminum ions) and glass beads (which may introduce impurities such as silicon and calcium). Furthermore, relying on distillation processes makes it difficult to solve the problem of incomplete separation of metal ions caused by the high boiling point of perfluorooctanoic acid. In addition, it does not involve the recovery and utilization of HF, which poses a risk of secondary pollution from impurities and high material consumption.

[0005] It is evident that developing a method for preparing perfluorooctanoic acid that combines high metal ion removal rate, low HF consumption, high yield, and good stability has become a pressing technical problem to be solved in this field. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of the prior art and provide a method for preparing perfluorooctanoic acid (PFOA) as an additive for semiconductor electronic chemicals. This method solves the problems of incomplete removal of metal ions, high HF consumption, low yield, and poor product stability in the prior art by optimizing the extraction process, realizing the stepwise reuse of HF acid solution, and precisely controlling purification parameters, thereby obtaining ultrapure PFOA that meets the requirements of semiconductor electronic chemicals.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing perfluorooctanoic acid (PFOA) as an additive for semiconductor electronic chemicals, comprising the following steps:

[0008] Step S1, Raw material pretreatment: Perfluorooctanoic acid is melted at a constant temperature and filtered to obtain pretreated perfluorooctanoic acid F1;

[0009] Step S2, Phase Interface Controlled Primary Extraction: Pretreated perfluorooctanoic acid F1 and G5 grade HF are mixed in a PFA reactor with online phase interface monitoring, perfluorobutylmethanol is added, and after mixing evenly, the resulting mixture is placed in an oscillator with acceleration control to obtain the primary extract.

[0010] Step S3: Gradient heating and secondary extraction to obtain secondary purified solution L2 and HF acid solution U2;

[0011] Step S4: Three extractions and two-stage purification of HF for reuse, yielding three purified solutions L3, purified HF acid solutions U2' and U3';

[0012] Step S5: Purification under inert atmosphere gradient pressure yields perfluorooctanoic acid (PFOA) for use as an additive in semiconductor electronic chemicals.

[0013] Preferably, the purity of perfluorooctanoic acid (PFOA) in step S1 is ≥99.0%, moisture content is ≤1%, and total metal ion content is ≤10ppm.

[0014] Preferably, the filtration in step S1 uses a PFA microfiltration membrane, and the porosity of the PFA microfiltration membrane is 75%-80%.

[0015] Preferably, the filtration pressure in step S1 is 0.12-0.15 MPa.

[0016] Preferably, the mass ratio of pretreated perfluorooctanoic acid F1, G5 grade HF, and perfluorobutylmethanol in step S2 is 100:100:(0.09-0.14).

[0017] Preferably, the concentration of metal ions in the G5 grade HF in step S2 is <1ppt.

[0018] Preferably, the oscillation temperature in step S2 is 25-28℃, and the oscillation frequency is 180-190 r / min.

[0019] Preferably, the gradient temperature secondary extraction in step S3 specifically involves: transferring the primary extract to a PFA separatory funnel, sealing and allowing it to stand at 25-28°C, collecting the lower primary purified liquid L1 and the upper HF acid solution U1 after separation; mixing L1 with fresh G5 grade HF and perfluorobutyl methanol, heating to 29-32°C, and oscillating at a frequency of 190-200 r / min to obtain the secondary extract; allowing it to stand at 29-32°C to separate the layers, collecting the lower secondary purified liquid L2 and the upper HF acid solution U2; the mass ratio of L1, fresh G5 grade HF, and perfluorobutyl methanol is 100:100:(0.06-0.12).

[0020] Preferably, the dual-stage purification HF reuse and triple extraction in step S4 are as follows: L2 is mixed with fresh G5 grade HF, and 0.05%-0.1% of perfluorobutyl methanol by mass of L2 is added. The mixture is heated to 32-35°C and oscillated at a frequency of 200-210 r / min to obtain a triple extract. The mixture is allowed to stand at 32-35°C to separate into layers. The lower layer of triple-purified liquid L3 is collected, and the upper layer is HF acid solution U3. U2 and U3 are respectively passed into a dual-stage purification system to obtain purified HF acid solutions U2' and U3', wherein U2' is reused in the next batch S2, and U3' is reused in the next batch S3.

[0021] Preferably, the inert atmosphere gradient partial pressure purification in step S5 specifically involves: transferring L3 to a PFA purifier with nitrogen partial pressure control, introducing high-purity nitrogen gas with a purity ≥99.9995%, raising the temperature to 110-120℃ at a rate of 4-6℃ / min, adjusting the nitrogen partial pressure to 0.01-0.02MPa, and holding at this temperature for 1.5-2.5h; then reducing the heating rate to 2-3℃ / min, raising the temperature to 150-160℃, and adjusting the nitrogen flow rate. Increase the nitrogen flow rate to 0.55-0.65 L / min and the partial pressure to 0.02-0.03 MPa, and hold for 1-2 hours. Continue heating to 168-172℃, adjust the nitrogen flow rate to 1.1-1.2 L / min and the partial pressure to 0.04-0.05 MPa, and hold for 1-2 hours. At the same time, add 0.001%-0.01% (by mass) of methyl perfluoropropionate (L3). Stop heating and keep purging with nitrogen until the temperature drops to room temperature to obtain ultrapure perfluorooctanoic acid (PFOA).

[0022] Preferably, the initial flow rate of the high-purity nitrogen gas is 0.5-0.6 L / min.

[0023] Due to the application of the above technical solution, the present invention has the following beneficial effects:

[0024] (1) The method for preparing perfluorooctanoic acid (PFOA) for semiconductor electronic chemical additives disclosed in this invention removes mechanical impurities and long-chain fluorinated derivatives that adsorb metal ions through a refined pretreatment process of PFA filtration, avoiding interference of impurities on the subsequent extraction process, laying the foundation for deep removal of metal ions, and significantly improving the metal ion transfer efficiency in the subsequent extraction stage, thus solving the extraction and impurity removal bottleneck caused by insufficient pretreatment in the prior art.

[0025] (2) The preparation method of perfluorooctanoic acid for semiconductor electronic chemical additives disclosed in this invention adopts a multi-stage extraction mode of "phase interface regulator + gradient temperature and frequency increase + oscillation acceleration control". The phase interface tension is regulated by perfluorobutyl methanol. With the gradual increase of extraction temperature, oscillation frequency and acceleration, the emulsification phenomenon of the extraction system is effectively suppressed, and the stepwise efficient transfer of metal ions from the perfluorooctanoic acid phase to the HF phase is realized. The total removal rate of metal ions under the synergistic effect of three extractions is high, which far exceeds the impurity removal effect of the existing fixed parameter extraction process, and achieves the technical effects of "suppressing emulsification" and "deep impurity removal".

[0026] (3) The preparation method of perfluorooctanoic acid for semiconductor electronic chemical additives disclosed in this invention uses an inert atmosphere gradient partial pressure purification process. Through the synergistic design of "three-stage gradient temperature control + dynamic nitrogen parameter adjustment + anti-degradation agent (methyl perfluoropropionate) assistance", it significantly reduces the volatilization loss and thermal decomposition rate of perfluorooctanoic acid. At the same time, it achieves deep removal of HF residue and moisture by means of dynamic matching of nitrogen flow rate and partial pressure. It solves the contradiction between "high temperature impurity removal and low loss and yield" in the prior art and achieves the technical effect of thorough impurity removal, minimal loss of target material and excellent product stability.

[0027] (4) The method for preparing perfluorooctanoic acid for semiconductor electronic chemical additives disclosed in this invention, through the synergistic effect of process step parameters, not only achieves low total metal ion content, high purity and yield of the final product, meeting the stringent requirements of semiconductor electronic chemical additives, but also has excellent continuous production stability, solving the problem of unstable product quality in the large-scale production of existing technologies, providing a reliable guarantee for industrial applications, and its comprehensive performance and stability far exceed those of existing similar purification processes. Detailed Implementation

[0028] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0029] Example 1: A method for preparing perfluorooctanoic acid (PFOA) as an additive for semiconductor electronic chemicals, comprising the following steps:

[0030] Step S1, Raw material pretreatment: Take the raw material perfluorooctanoic acid and melt it at a constant temperature of 60℃, then filter it through a 0.22μm pore size PFA microfiltration membrane to obtain pretreated perfluorooctanoic acid F1;

[0031] Step S2, Phase Interface Controlled Primary Extraction: Pretreated perfluorooctanoic acid F1 and HF with a mass percentage concentration of 49% (G5 grade) are mixed in a PFA reactor equipped with online phase interface monitoring. Perfluorobutylmethanol is added and mixed evenly. The resulting mixture is then placed in an oscillator with acceleration control and shaken for 1 hour to obtain the primary extract.

[0032] Step S3: Gradient heating and secondary extraction to obtain secondary purified solution L2 and HF acid solution U2;

[0033] Step S4: Two-stage purification of HF for reuse and three-stage extraction to obtain three-stage purified solution L3, purified HF acid solution U2' and U3';

[0034] Step S5: Purification under inert atmosphere gradient pressure yields perfluorooctanoic acid (PFOA) for use as an additive in semiconductor electronic chemicals.

[0035] The purity of the raw material perfluorooctanoic acid in step S1 is ≥99.0%, the moisture content is ≤1%, and the total metal ion content is ≤10ppm; the porosity of the PFA microfiltration membrane in step S1 is 75%; the filtration pressure in step S1 is 0.12MPa; the mass ratio of the pretreated perfluorooctanoic acid F1, HF with a mass percentage concentration of 49% (G5 grade), and perfluorobutylmethanol in step S2 is 100:100:0.09.

[0036] In step S2, the metal ion concentration in the G5 grade HF with a mass percentage concentration of 49% is <1 ppt; the oscillation temperature in step S2 is 25℃, the oscillation frequency is 180 r / min, and the oscillation acceleration is 0.5 m / s²; the gradient temperature secondary extraction in step S3 specifically involves: transferring the primary extract to a PFA separatory funnel, sealing and allowing it to stand at 25℃ for 30 min, collecting the lower layer of the primary purified solution L1 after separation, and the upper layer being the HF acid solution U1; L1 Fresh G5 grade HF with a mass percentage concentration of 49% and perfluorobutyl methanol were mixed and heated to 29°C. The mixture was then oscillated at a frequency of 190 r / min and an acceleration of 0.6 m / s² for 1 hour to obtain a secondary extract. The mixture was allowed to stand at 29°C for 30 minutes to separate into layers. The lower layer, secondary purified liquid L2, and the upper layer, HF acid solution U2, were collected. The mass ratio of L1, fresh G5 grade HF with a mass percentage concentration of 49%, and perfluorobutyl methanol was 100:100:0.06.

[0037] The dual-stage purification HF reuse and triple extraction described in step S4 are as follows: L2 is mixed with fresh G5 grade HF at a mass ratio of 1:1 (49% by mass). 0.05% of perfluorobutyl methanol (PFM) by mass of L2 is added. The mixture is heated to 32°C and oscillated at a frequency of 200 r / min and an acceleration of 0.7 m / s² for 1 hour to obtain the triple extract. The mixture is then allowed to stand at 32°C for 30 minutes to separate into layers. The lower layer (L3) of the triple-purified solution is collected, and the upper layer is HF acid solution U3. U2 and U3 are then passed into the dual-stage purification system to obtain purified HF acid solutions U2' and U3', respectively. U2' is reused in the next batch S2, and U3' is reused in the next batch S3.

[0038] The inert atmosphere gradient partial pressure purification in step S5 specifically involves: transferring L3 to a PFA purifier with nitrogen partial pressure control, introducing high-purity nitrogen gas with a purity ≥99.9995%, raising the temperature to 110°C at a rate of 5°C / min, adjusting the nitrogen partial pressure to 0.01 MPa, and holding for 1.5 h; reducing the heating rate to 3°C / min, raising the temperature to 150°C, adjusting the nitrogen flow rate to 0.55 L / min and the partial pressure to 0.02 MPa, and holding for 1.5 h; continuing to raise the temperature to 168°C, adjusting the nitrogen flow rate to 1.1 L / min and the partial pressure to 0.04 MPa, and holding for 1 h, while simultaneously adding 0.001% (by mass) of methyl perfluoropropionate from L3; stopping heating, and maintaining nitrogen purging until the temperature drops to room temperature to obtain ultrapure perfluorooctanoic acid; the initial flow rate of the high-purity nitrogen gas is 0.5 L / min.

[0039] Example 2: A method for preparing perfluorooctanoic acid (PFOA) as an additive for semiconductor electronic chemicals, comprising the following steps:

[0040] Step S1, Raw material pretreatment: Take the raw material perfluorooctanoic acid and melt it at a constant temperature of 62℃, then filter it through a 0.22μm pore size PFA microfiltration membrane to obtain pretreated perfluorooctanoic acid F1;

[0041] Step S2, Phase Interface Controlled Primary Extraction: Pretreated perfluorooctanoic acid F1 and HF with a mass percentage concentration of 49% (G5 grade) are mixed in a PFA reactor equipped with online phase interface monitoring. Perfluorobutylmethanol is added and mixed evenly. The resulting mixture is then placed in an oscillator with acceleration control and shaken for 1 hour to obtain the primary extract.

[0042] Step S3: Gradient heating and secondary extraction to obtain secondary purified solution L2 and HF acid solution U2;

[0043] Step S4: Two-stage purification of HF for reuse and three-stage extraction to obtain three-stage purified solution L3, purified HF acid solution U2' and U3';

[0044] Step S5: Purification under inert atmosphere gradient pressure yields perfluorooctanoic acid (PFOA) for use as an additive in semiconductor electronic chemicals.

[0045] The purity of the perfluorooctanoic acid (PFOA) raw material in step S1 is ≥99.0%, moisture content is ≤1%, and total metal ion content is ≤10ppm; the porosity of the PFA microfiltration membrane in step S1 is 77%; the filtration pressure in step S1 is 0.13MPa; the mass ratio of the pretreated PFOA F1, HF with a mass percentage concentration of 49% (G5 grade), and perfluorobutylmethanol in step S2 is 100:100:0.1; the metal ion concentration in the HF with a mass percentage concentration of 49% (G5 grade) in step S2 is <1ppt; the oscillation temperature in step S2 is 26℃, the oscillation frequency is 183r / min, and the oscillation acceleration is 0.5m / s².

[0046] The gradient temperature secondary extraction in step S3 is as follows: the primary extract is transferred to a PFA separatory funnel, sealed and allowed to stand for 30 minutes at 26°C, and the lower layer of the primary purified liquid L1 is collected after separation, while the upper layer is HF acid solution U1; L1, fresh G5 grade HF with a mass percentage concentration of 49% and perfluorobutyl methanol are mixed, heated to 30°C, and oscillated at an oscillation frequency of 193 r / min and an oscillation acceleration of 0.6 m / s² for 1 hour to obtain the secondary extract; the secondary extract is allowed to stand at 30°C for 30 minutes to separate into layers, and the lower layer of the secondary purified liquid L2 is collected, while the upper layer is HF acid solution U2; the mass ratio of L1, fresh G5 grade HF with a mass percentage concentration of 49% and perfluorobutyl methanol is 100:100:0.07.

[0047] The dual-stage purification HF reuse and triple extraction described in step S4 are as follows: L2 is mixed with fresh G5 grade HF at a mass ratio of 1:1 (49% by mass). 0.07% of perfluorobutylmethanol (by mass of L2) is added, and the mixture is heated to 33°C and oscillated at a frequency of 203 r / min and an acceleration of 0.7 m / s² for 1 hour to obtain the triple extract. The mixture is then allowed to stand at 33°C for 30 minutes to separate into layers. The lower layer (L3) of the triple-purified solution is collected, and the upper layer is HF acid solution U3. U2 and U3 are then passed into the dual-stage purification system to obtain purified HF acid solutions U2' and U3', respectively. U2' is reused in the next batch S2, and U3' is reused in the next batch S3.

[0048] The inert atmosphere gradient partial pressure purification in step S5 specifically involves: transferring L3 to a PFA purifier with nitrogen partial pressure control, introducing high-purity nitrogen gas with a purity ≥99.9995%, heating to 113°C at a rate of 5°C / min, adjusting the nitrogen partial pressure to 0.013 MPa, and holding for 1.5 hours; reducing the heating rate to 3°C / min, heating to 153°C, adjusting the nitrogen flow rate to 0.58 L / min and the partial pressure to 0.023 MPa, and holding for 1.5 hours; continuing to heat to 169°C, adjusting the nitrogen flow rate to 1.1 L / min and the partial pressure to 0.043 MPa, and holding for 1 hour, while simultaneously adding 0.003% (by mass) of methyl perfluoropropionate from L3; stopping heating, and maintaining nitrogen purging until the temperature drops to room temperature to obtain ultrapure perfluorooctanoic acid; the initial flow rate of the high-purity nitrogen gas is 0.53 L / min.

[0049] Example 3: A method for preparing perfluorooctanoic acid (PFOA) as an additive in semiconductor electronic chemicals, comprising the following steps:

[0050] Step S1, Raw material pretreatment: Take the raw material perfluorooctanoic acid and melt it at a constant temperature of 63℃, then filter it through a 0.22μm pore size PFA microfiltration membrane to obtain pretreated perfluorooctanoic acid F1;

[0051] Step S2, Phase Interface Controlled Primary Extraction: Pretreated perfluorooctanoic acid F1 and HF with a mass percentage concentration of 49% (G5 grade) are mixed in a PFA reactor equipped with online phase interface monitoring. Perfluorobutylmethanol is added and mixed evenly. The resulting mixture is then placed in an oscillator with acceleration control and shaken for 1 hour to obtain the primary extract.

[0052] Step S3: Gradient heating and secondary extraction to obtain secondary purified solution L2 and HF acid solution U2;

[0053] Step S4: Two-stage purification of HF for reuse and three-stage extraction to obtain three-stage purified solution L3, purified HF acid solution U2' and U3';

[0054] Step S5: Purification under inert atmosphere gradient pressure yields perfluorooctanoic acid (PFOA) for use as an additive in semiconductor electronic chemicals.

[0055] The purity of the raw material perfluorooctanoic acid in step S1 is ≥99.0%, moisture content is ≤1%, and total metal ion content is ≤10ppm; the porosity of the PFA microfiltration membrane in step S1 is 78%; the filtration pressure in step S1 is 0.14MPa; the mass ratio of the pretreated perfluorooctanoic acid F1, HF with a mass percentage concentration of 49% (G5 grade), and perfluorobutylmethanol in step S2 is 100:100:0.11; the metal ion concentration in the HF with a mass percentage concentration of 49% (G5 grade) in step S2 is <1ppt; the oscillation temperature in step S2 is 27℃, the oscillation frequency is 185r / min, and the oscillation acceleration is 0.5m / s².

[0056] The gradient temperature secondary extraction in step S3 is as follows: the primary extract is transferred to a PFA separatory funnel, sealed and allowed to stand at 27°C for 30 min, and after separation, the lower layer of the primary purified liquid L1 is collected, and the upper layer is HF acid solution U1; L1, fresh G5 grade HF with a mass percentage concentration of 49% and perfluorobutyl methanol are mixed, heated to 31°C, and oscillated at an oscillation frequency of 195 r / min and an oscillation acceleration of 0.6 m / s² for 1 h to obtain the secondary extract; after standing at 31°C for 30 min, the secondary purified liquid L2 is collected, and the upper layer is HF acid solution U2; the mass ratio of L1, fresh G5 grade HF with a mass percentage concentration of 49% and perfluorobutyl methanol is 100:100:0.09.

[0057] The dual-stage purification HF reuse and triple extraction described in step S4 are as follows: L2 is mixed with fresh G5 grade HF at a mass ratio of 1:1 (49% by mass). 0.08% of perfluorobutylmethanol (by mass of L2) is added, and the mixture is heated to 34°C and oscillated at a frequency of 205 r / min and an acceleration of 0.7 m / s² for 1 hour to obtain the triple extract. The mixture is then allowed to stand at 33°C for 30 minutes to separate into layers. The lower layer (L3) of the triple-purified solution is collected, and the upper layer is HF acid solution U3. U2 and U3 are then passed into the dual-stage purification system to obtain purified HF acid solutions U2' and U3', respectively. U2' is reused in the next batch S2, and U3' is reused in the next batch S3.

[0058] The inert atmosphere gradient partial pressure purification in step S5 specifically involves: transferring L3 to a PFA purifier with nitrogen partial pressure control, introducing high-purity nitrogen gas with a purity ≥99.9995%, raising the temperature to 115°C at a rate of 5°C / min, adjusting the nitrogen partial pressure to 0.015 MPa, and holding for 1.5 h; reducing the heating rate to 3°C / min, raising the temperature to 155°C, adjusting the nitrogen flow rate to 0.6 L / min and the partial pressure to 0.025 MPa, and holding for 1.5 h; continuing to raise the temperature to 170°C, adjusting the nitrogen flow rate to 1.2 L / min and the partial pressure to 0.045 MPa, and holding for 1 h, while simultaneously adding 0.006% (by mass) of methyl perfluoropropionate from L3; stopping heating, and maintaining nitrogen purging until the temperature drops to room temperature to obtain ultrapure perfluorooctanoic acid; the initial flow rate of the high-purity nitrogen gas is 0.55 L / min.

[0059] Example 4: A method for preparing perfluorooctanoic acid (PFOA) as an additive in semiconductor electronic chemicals, comprising the following steps:

[0060] Step S1, Raw material pretreatment: Take the raw material perfluorooctanoic acid and melt it at a constant temperature of 64℃, then filter it through a 0.22μm pore size PFA microfiltration membrane to obtain pretreated perfluorooctanoic acid F1;

[0061] Step S2, Phase Interface Controlled Primary Extraction: Pretreated perfluorooctanoic acid F1 and HF with a mass percentage concentration of 49% (G5 grade) are mixed in a PFA reactor equipped with online phase interface monitoring. Perfluorobutylmethanol is added and mixed evenly. The resulting mixture is then placed in an oscillator with acceleration control and shaken for 1 hour to obtain the primary extract.

[0062] Step S3: Gradient heating and secondary extraction to obtain secondary purified solution L2 and HF acid solution U2;

[0063] Step S4: Two-stage purification of HF for reuse and three-stage extraction to obtain three-stage purified solution L3, purified HF acid solution U2' and U3';

[0064] Step S5: Purification under inert atmosphere gradient pressure yields perfluorooctanoic acid (PFOA) for use as an additive in semiconductor electronic chemicals.

[0065] The purity of the perfluorooctanoic acid (PFOA) raw material in step S1 is ≥99.0%, moisture content is ≤1%, and total metal ion content is ≤10ppm; the porosity of the PFA microfiltration membrane in step S1 is 79%; the filtration pressure in step S1 is 0.14MPa; the mass ratio of the pretreated PFOA F1, HF with a mass percentage concentration of 49% (G5 grade), and perfluorobutylmethanol in step S2 is 100:100:0.12; the metal ion concentration in the HF with a mass percentage concentration of 49% (G5 grade) in step S2 is <1ppt; the oscillation temperature in step S2 is 27℃, the oscillation frequency is 188r / min, and the oscillation acceleration is 0.5m / s².

[0066] The gradient temperature secondary extraction in step S3 is as follows: the primary extract is transferred to a PFA separatory funnel, sealed and allowed to stand for 30 minutes at 27°C, and the lower layer of the primary purified liquid L1 is collected after separation, while the upper layer is HF acid solution U1; L1, fresh G5 grade HF with a mass percentage concentration of 49% and perfluorobutyl methanol are mixed, heated to 31°C, and oscillated at an oscillation frequency of 198 r / min and an oscillation acceleration of 0.6 m / s² for 1 hour to obtain the secondary extract; the secondary extract is allowed to stand at 31°C for 30 minutes to separate into layers, and the lower layer of the secondary purified liquid L2 is collected, while the upper layer is HF acid solution U2; the mass ratio of L1, fresh G5 grade HF with a mass percentage concentration of 49% and perfluorobutyl methanol is 100:100:0.11.

[0067] The dual-stage purification HF reuse and triple extraction described in step S4 are as follows: L2 is mixed with fresh G5 grade HF at a mass ratio of 1:1 (49% by mass). 0.09% of perfluorobutylmethanol (by mass of L2) is added, and the mixture is heated to 34°C and oscillated at a frequency of 209 r / min and an acceleration of 0.7 m / s² for 1 hour to obtain the triple extract. The mixture is then allowed to stand at 34°C for 30 minutes to separate into layers. The lower layer (L3) of the triple-purified solution is collected, and the upper layer is HF acid solution U3. U2 and U3 are then passed into the dual-stage purification system to obtain purified HF acid solutions U2' and U3', respectively. U2' is reused in the next batch S2, and U3' is reused in the next batch S3.

[0068] The inert atmosphere gradient partial pressure purification in step S5 specifically involves: transferring L3 to a PFA purifier with nitrogen partial pressure control, introducing high-purity nitrogen gas with a purity ≥99.9995%, heating to 118°C at a rate of 5°C / min, adjusting the nitrogen partial pressure to 0.018 MPa, and holding for 1.5 hours; reducing the heating rate to 3°C / min, heating to 158°C, adjusting the nitrogen flow rate to 0.63 L / min and the partial pressure to 0.028 MPa, and holding for 1.5 hours; continuing to heat to 171°C, adjusting the nitrogen flow rate to 1.2 L / min and the partial pressure to 0.048 MPa, and holding for 1 hour, while simultaneously adding 0.008% (by mass) of methyl perfluoropropionate from L3; stopping heating, and maintaining nitrogen purging until the temperature drops to room temperature to obtain ultrapure perfluorooctanoic acid; the initial flow rate of the high-purity nitrogen gas is 0.58 L / min.

[0069] Example 5: A method for preparing perfluorooctanoic acid (PFOA) as an additive in semiconductor electronic chemicals, comprising the following steps:

[0070] Step S1, Raw material pretreatment: Take the raw material perfluorooctanoic acid and melt it at a constant temperature of 65℃, then filter it through a 0.22μm pore size PFA microfiltration membrane to obtain pretreated perfluorooctanoic acid F1;

[0071] Step S2, Phase Interface Controlled Primary Extraction: Pretreated perfluorooctanoic acid F1 and HF with a mass percentage concentration of 49% (G5 grade) are mixed in a PFA reactor equipped with online phase interface monitoring. Perfluorobutylmethanol is added and mixed evenly. The resulting mixture is then placed in an oscillator with acceleration control and shaken for 1 hour to obtain the primary extract.

[0072] Step S3: Gradient heating and secondary extraction to obtain secondary purified solution L2 and HF acid solution U2;

[0073] Step S4: Two-stage purification of HF for reuse and three-stage extraction to obtain three-stage purified solution L3, purified HF acid solution U2' and U3';

[0074] Step S5: Purification under inert atmosphere gradient pressure yields perfluorooctanoic acid (PFOA) for use as an additive in semiconductor electronic chemicals.

[0075] The purity of the perfluorooctanoic acid (PFOA) raw material in step S1 is ≥99.0%, moisture content is ≤1%, and total metal ion content is ≤10ppm; the porosity of the PFA microfiltration membrane in step S1 is 80%; the filtration pressure in step S1 is 0.15MPa; the mass ratio of the pretreated PFOA F1, HF with a mass percentage concentration of 49% (G5 grade), and perfluorobutylmethanol in step S2 is 100:100:0.14; the metal ion concentration in the HF with a mass percentage concentration of 49% (G5 grade) in step S2 is <1ppt; the oscillation temperature in step S2 is 28℃, the oscillation frequency is 190r / min, and the oscillation acceleration is 0.5m / s².

[0076] The gradient temperature secondary extraction described in step S3 is as follows: the primary extract is transferred to a PFA separatory funnel, sealed and allowed to stand at 28°C for 30 min, and after separation, the lower layer of the primary purified liquid L1 is collected, and the upper layer is HF acid solution U1; L1, fresh G5 grade HF with a mass percentage concentration of 49% and perfluorobutyl methanol are mixed, heated to 32°C, and oscillated at an oscillation frequency of 200 r / min and an oscillation acceleration of 0.6 m / s² for 1 h to obtain the secondary extract; after standing at 32°C for 30 min, the secondary purified liquid L2 is collected, and the upper layer is HF acid solution U2; the mass ratio of L1, fresh G5 grade HF with a mass percentage concentration of 49% and perfluorobutyl methanol is 100:100:0.12.

[0077] The dual-stage purification HF reuse and triple extraction described in step S4 are as follows: L2 is mixed with fresh G5 grade HF at a mass ratio of 1:1 (49% by mass). 0.1% of perfluorobutylmethanol (by mass of L2) is added, and the mixture is heated to 35°C and oscillated at a frequency of 210 r / min and an acceleration of 0.7 m / s² for 1 hour to obtain the triple extract. The mixture is then allowed to stand at 35°C for 30 minutes to separate into layers. The lower layer (L3) of the triple-purified solution is collected, and the upper layer is HF acid solution U3. U2 and U3 are then passed into the dual-stage purification system to obtain purified HF acid solutions U2' and U3', respectively. U2' is reused in the next batch S2, and U3' is reused in the next batch S3.

[0078] The inert atmosphere gradient partial pressure purification in step S5 specifically involves: transferring L3 to a PFA purifier with nitrogen partial pressure control, introducing high-purity nitrogen gas with a purity ≥99.9995%, raising the temperature to 120°C at a rate of 5°C / min, adjusting the nitrogen partial pressure to 0.02 MPa, and holding for 1.5 h; reducing the heating rate to 3°C / min, raising the temperature to 160°C, adjusting the nitrogen flow rate to 0.65 L / min and the partial pressure to 0.03 MPa, and holding for 1.5 h; continuing to raise the temperature to 172°C, adjusting the nitrogen flow rate to 1.2 L / min and the partial pressure to 0.05 MPa, and holding for 1 h, while simultaneously adding 0.01% (by mass) of methyl perfluoropropionate from L3; stopping heating, and maintaining nitrogen purging until the temperature drops to room temperature to obtain ultrapure perfluorooctanoic acid; the initial flow rate of the high-purity nitrogen gas is 0.6 L / min.

[0079] Comparative Example 1

[0080] This example provides a method for preparing perfluorooctanoic acid (PFOA) as an additive for semiconductor electronic chemicals, which is basically the same as in Example 5, except that there is no raw material pretreatment step.

[0081] Comparative Example 2

[0082] This example provides a method for preparing perfluorooctanoic acid (PFOA) as an additive for semiconductor electronic chemicals, which is basically the same as in Example 5, except that there is no phase interface control extraction step.

[0083] Comparative Example 3

[0084] This example provides a method for preparing perfluorooctanoic acid (PFOA) as an additive for semiconductor electronic chemicals, which is basically the same as in Example 5, except that there is no gradient temperature secondary extraction step.

[0085] Comparative Example 4

[0086] This example provides a method for preparing perfluorooctanoic acid (PFOA) as an additive for semiconductor electronic chemicals, which is basically the same as in Example 5, except that the two-stage purification HF recycling and three-stage extraction steps are omitted.

[0087] Comparative Example 5

[0088] This example provides a method for preparing perfluorooctanoic acid (PFOA) as an additive for semiconductor electronic chemicals, which is basically the same as in Example 5, except that there is no inert atmosphere gradient pressure purification step.

[0089] To further illustrate the beneficial technical effects of the preparation method of perfluorooctanoic acid (PFOA) for semiconductor electronic chemical additives involved in the embodiments of this application, relevant performance tests were conducted on the PFOA prepared by the preparation method of PFOA for semiconductor electronic chemical additives involved in Example 5 and Comparative Examples 1-5. The test results are shown in Table 2, and the test methods are as follows:

[0090] Referring to GB / T 30903-2014 "Determination of Impurity Elements in Inorganic Chemical Products by Inductively Coupled Plasma Mass Spectrometry", the total amount of metal ions (11 elements) in the purified perfluorooctanoic acid was determined.

[0091] The purity of purified perfluorooctanoic acid was determined by high performance liquid chromatography (HPLC). The chromatographic column was a C18 column, the mobile phase was methanol-water (80:20 v / v), the detection wavelength was 210 nm, and the flow rate was 1.0 mL / min.

[0092] Experimental materials: Perfluorooctanoic acid (PFOA) product from a certain factory, and the analytical results are shown in Table 1.

[0093] Table 1. Analysis and detection results of perfluorooctanoic acid raw materials

[0094]

[0095] Table 2 Test Results

[0096]

[0097] As shown in Table 2, the perfluorooctanoic acid (PFOA) prepared by the method for preparing semiconductor electronic chemical additives according to Example 5 of this invention has higher purity and lower total metal ion content compared to the comparative example. The combination of raw material pretreatment, phase interface control primary extraction, gradient temperature secondary extraction, two-stage purification HF recycling and tertiary extraction, and inert atmosphere gradient partial pressure purification has a positive effect on improving the above-mentioned effects.

[0098] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing perfluorooctanoic acid (PFOA) as an additive in semiconductor electronic chemicals, characterized in that, Includes the following steps: Step S1, Raw material pretreatment: Perfluorooctanoic acid (PFOA) is melted at a constant temperature and filtered to obtain pretreated PFOA F1; the filtration is performed using a PFA microfiltration membrane with a porosity of 75%-80%; Step S2, Phase Interface Controlled Primary Extraction: Pretreated perfluorooctanoic acid F1 and G5 grade HF are mixed in a PFA reactor equipped with online phase interface monitoring. Perfluorobutyl methanol is added and mixed evenly. The resulting mixture is then placed in an oscillator with acceleration control and oscillated to obtain the primary extract. The mass ratio of pretreated perfluorooctanoic acid F1, G5 grade HF, and perfluorobutyl methanol is 100:100:(0.09-0.14). Step S3: Gradient heating and secondary extraction to obtain secondary purified solution L2 and HF acid solution U2; Step S4: Three extractions and two-stage purification of HF for reuse, yielding three purified solutions L3, purified HF acid solutions U2' and U3'; Step S5: Purification under inert atmosphere gradient pressure to obtain perfluorooctanoic acid for semiconductor electronic chemical additives; The gradient temperature secondary extraction in step S3 is specifically as follows: the primary extract is transferred to a PFA separatory funnel, sealed and allowed to stand at 25-28℃, and after separation, the lower layer of primary purified liquid L1 is collected, and the upper layer is HF acid solution U1; L1, fresh G5 grade HF and perfluorobutyl methanol are mixed, heated to 29-32℃, and oscillated at a frequency of 190-200 r / min to obtain the secondary extract; after standing at 29-32℃, the secondary purified liquid L2 is collected, and the upper layer is HF acid solution U2; the mass ratio of L1, fresh G5 grade HF and perfluorobutyl methanol is 100:100:(0.06-0.12); The inert atmosphere gradient partial pressure purification described in step S5 is as follows: L3 is transferred to a PFA purifier with nitrogen partial pressure control, high-purity nitrogen with a purity ≥99.9995% is introduced, the temperature is increased to 110-120℃ at a heating rate of 4-6℃ / min, the nitrogen partial pressure is adjusted to 0.01-0.02MPa, and the temperature is maintained for 1.5-2.5h; the heating rate is reduced to 2-3℃ / min, the temperature is increased to 150-160℃, the nitrogen flow rate is adjusted to 0.55-0.65L / min and the partial pressure is adjusted to 0.02-0.03MPa, and the temperature is maintained for 1-2h. Continue heating to 168-172℃, adjust the nitrogen flow rate to 1.1-1.2L / min and the partial pressure to 0.04-0.05MPa, and hold for 1-2 hours. At the same time, add 0.001%-0.01% (by mass) of methyl perfluoropropionate (L3). Stop heating and continue purging with nitrogen until the temperature drops to room temperature to obtain ultrapure perfluorooctanoic acid (PFOA). The initial flow rate of the high-purity nitrogen is 0.5-0.6L / min.

2. The method for preparing perfluorooctanoic acid as a semiconductor electronic chemical additive according to claim 1, characterized in that, The purity of perfluorooctanoic acid (PFOA) in step S1 is ≥99.0%, moisture content is ≤1%, and total metal ion content is ≤10ppm.

3. The method for preparing perfluorooctanoic acid as a semiconductor electronic chemical additive according to claim 1, characterized in that, The filtration pressure in step S1 is 0.12-0.15 MPa.

4. The method for preparing perfluorooctanoic acid as an additive for semiconductor electronic chemicals according to claim 1, characterized in that, The concentration of metal ions in the G5 grade HF described in step S2 is <1ppt.

5. The method for preparing perfluorooctanoic acid as an additive for semiconductor electronic chemicals according to claim 1, characterized in that, The oscillation temperature in step S2 is 25-28℃, and the oscillation frequency is 180-190r / min.

6. The method for preparing perfluorooctanoic acid as a semiconductor electronic chemical additive according to claim 1, characterized in that, The three-stage extraction and dual-stage purification HF reuse described in step S4 are as follows: L2 is mixed with fresh G5 grade HF, and 0.05%-0.1% of perfluorobutyl methanol by mass of L2 is added. The mixture is heated to 32-35℃ and oscillated at a frequency of 200-210 r / min to obtain a three-stage extract. The mixture is allowed to stand at 32-35℃ to separate into layers. The lower layer of the three-stage purified solution L3 is collected, and the upper layer is HF acid solution U3. U2 and U3 are respectively passed into a dual-stage purification system to obtain purified HF acid solutions U2' and U3', of which U2' is reused in the next batch S2 and U3' is reused in the next batch S3.

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