TW202402893A - Method for producing resin solution - Google Patents

Abstract

The present disclosure provides a method for producing a resin solution in which a resin is dissolved in a solvent, the method involving: stirring a mixture 100 of the solvent and the resin by convection of the solvent, and dissolving the resin into the solvent. The convection of the solvent includes convection generated by circulating the solvent.

Description

Method for manufacturing resin solution

The present invention relates to a method for manufacturing a resin solution.

Resin materials used in optical components such as photosensitive resins used in lithography and plastic optical fibers may sometimes deteriorate in quality due to contamination of foreign matter. Therefore, resins used for optical applications are preferably free of foreign matter. Therefore, in order to remove foreign substances from the resin, a method of preparing a resin solution in which the resin is dissolved in a solvent and filtering the resin has been conventionally used. For example, Patent Document 1 proposes a method of circulating and filtering a photosensitive resin solution using a filter as a purification method for removing foreign matter from the photosensitive resin used in lithography. Prior technical literature patent documents

Patent Document 1: International Publication No. 2017/163922

[Problem to be solved by the invention]

As described above, in order to remove foreign matter from the resin, a method of filtering a resin solution obtained by dissolving the resin in a solvent has been conventionally used. In the case of using this method, a resin solution needs to be obtained first. The resin solution is produced by dissolving the resin to be removed as foreign matter in a solvent. In this case, the mixture of the resin and the solvent needs to be sufficiently stirred. A mixer with a mixing blade is usually used for this kind of mixing.

However, if a mixer is used to dissolve the resin, sliding foreign matter or metal ions generated when the mixing blade rotates may be mixed into the solvent. In order to dissolve the resin in the solvent, sufficient stirring is required. Therefore, when the resin solution is produced only by stirring with a mixer, the amount of foreign matter such as sliding foreign matter and metal ions mixed into the solvent increases. Therefore, it is difficult to fully remove these foreign matter in the subsequent filtration step.

The object of the present invention is to provide a novel method for manufacturing a resin solution, which can obtain a resin solution in which foreign matter is reduced compared to a previous resin solution obtained only by stirring with a mixer. [Technical means to solve problems]

The present invention is a method for manufacturing a resin solution, which is a method for manufacturing a resin solution obtained by dissolving a resin in a solvent, and The above manufacturing methods include: The mixture of the above solvent and the above resin is stirred by causing the above solvent to convect, so that the above resin is dissolved in the above solvent; The convection of the solvent includes convection generated by refluxing the solvent. [Effects of the invention]

According to the present invention, a novel method for manufacturing a resin solution can be provided, which can obtain a resin solution in which foreign matter is reduced compared to a previous resin solution obtained only by stirring with a mixer.

A first aspect of the present invention is a method for producing a resin solution, which is a method for producing a resin solution obtained by dissolving a resin in a solvent, and The above manufacturing methods include: The mixture of the above solvent and the above resin is stirred by causing the above solvent to convect, so that the above resin is dissolved in the above solvent; The convection of the solvent includes convection generated by refluxing the solvent.

In the second aspect of the present invention, for example, in the manufacturing method of the first aspect, the convection of the solvent further includes convection generated by boiling of the solvent.

In the third aspect of the present invention, for example, in the manufacturing method of the first or second aspect, the resin is solid.

In a fourth aspect of the present invention, for example, in the manufacturing method of any one of the first to third aspects, when the mixture is stirred by convection of the solvent, the mixture is heated to the boiling point of the solvent. temperature above.

In a fifth aspect of the present invention, for example, in the manufacturing method of any one of the first to fourth aspects, the resin includes a fluoropolymer.

In the sixth aspect of the present invention, for example, in the manufacturing method of the fifth aspect, the solvent is a fluorine-based solvent, and the boiling point of the solvent is 50°C or more and 80°C or less.

In the seventh aspect of the present invention, for example, in the manufacturing method of the fifth or sixth aspect, the solvent is a fluorine-based solvent, and the viscosity of the solvent at 25°C is 1 mPa･s or more and 10 mPa･s or less. .

In an eighth aspect of the present invention, for example, in the manufacturing method of any one of the first to seventh aspects, the resin is an optical resin.

Hereinafter, embodiments of the method for producing the resin solution of the present invention will be described.

The method for producing a resin solution according to this embodiment is a method for producing a resin solution in which a resin is dissolved in a solvent. The manufacturing method of the resin solution of this embodiment includes: The mixture of the solvent and the resin is stirred by convection of the solvent, so that the resin is dissolved in the solvent.

In the method for producing a resin solution of this embodiment, the convection of the solvent includes convection generated by refluxing the solvent. That is, in the manufacturing method of the resin solution of this embodiment, the solvent is volatilized, the volatilized solvent is cooled and condensed, and the condensed solvent is returned to the mixture of the solvent and the resin, whereby convection of the solvent is generated, and the convection of the solvent is utilized. Convection and stir the mixture. Here, the convection generated by refluxing the solvent includes, for example, natural convection of the solvent and forced convection of the solvent. The natural convection of the solvent is caused by the cooling of the solvent that condenses and returns to the mixture and the solvent that is heated in the mixture to vaporize. The forced convection of the solvent is caused by the falling of the condensed solvent.

In the method for producing a resin solution of this embodiment, the mixture of the resin and the solvent is stirred by convection of the solvent including convection generated by refluxing the solvent as described above. In this kind of stirring by convection, foreign matter will not be mixed in like mixing with a mixer (for example, sliding foreign matter or metal ions mixed in when the stirring blade rotates). Therefore, according to the manufacturing method of the resin solution of this embodiment, it is possible to obtain a resin solution in which foreign matter is reduced compared to the previous resin solution obtained only by stirring with a mixer.

In order to generate the convection of the solvent as described above, for example, the mixture of the solvent and the resin is heated. The heating temperature can be appropriately selected according to the type of resin and the boiling point of the resin.

Furthermore, in the method for producing a resin solution according to this embodiment, the volatilized solvent can be returned to the mixture again by refluxing as described above. Therefore, according to the resin solution manufacturing method of this embodiment, even if the resin solution is manufactured in an unsealed container, there will be no problem that the solvent amount is reduced due to volatilization of the solvent, resulting in a significant change in the concentration of the resin solution. In addition, since there is no need to seal the container, there is no need to take countermeasures against an increase in the internal pressure of the container due to solvent volatilization during the production of the resin solution, such as pressure design of the container and valves, thereby suppressing an increase in manufacturing costs.

In the manufacturing method of the resin solution of this embodiment, the convection of the solvent may further include convection generated by boiling of the solvent. Here, the convection generated by the boiling of the solvent refers to the forced convection caused by the vapor bubbles of the solvent generated from the solvent due to the boiling of the solvent. In this case, the mixture is stirred not only by the convection generated by refluxing the solvent but also by the convection generated by boiling the solvent, whereby the mixture can be stirred more efficiently and fully.

In order to generate convection caused by boiling of the solvent, it is preferable to heat the mixture to a temperature higher than the boiling point of the solvent when stirring the mixture by convection of the solvent.

The appropriate time for stirring by convection of the solvent varies depending on various conditions such as the type of resin, the type of solvent, the amount of resin, the amount of solvent, and the heating temperature during stirring, so there is no particular limited. As an example, the time for stirring the solvent by convection generated by refluxing the solvent may be, for example, 0.5 hours or more, or may be 1 hour or more. The upper limit of the time for stirring the solvent by convection generated by refluxing the solvent is not particularly limited, but may be, for example, 30 hours or less. When the solvent is stirred by combining the convection generated by refluxing the solvent and the convection generated by boiling the solvent, the stirring time may be, for example, 0.5 hours or more or 1 hour or more. When the solvent is stirred by combining the convection generated by refluxing the solvent and the convection generated by boiling the solvent, the upper limit of the stirring time is not particularly limited, but may be, for example, 30 hours or less.

FIG. 1 is a schematic diagram illustrating an example of a method for producing a resin solution in the embodiment. The mixture 100 of resin and solvent is contained inside the container 1 and stirred. The container 1 has an exhaust port 2 , an infusion port 3 for transporting the solvent to the inside of the container 1 , and a drain port 4 for discharging the produced resin solution to the outside of the container 1 . A temperature control device 5 such as a heater for heating the container 1 is provided on the outer periphery of the container 1 . A heat exchanger 6 is provided at the exhaust port 2 of the container 1 . The exhaust port 2 is open to the external space via the heat exchanger 6 . An air filter 7 is provided in a passage open to the outside from the heat exchanger 6 to prevent foreign matter from being mixed in from the outside. Furthermore, a safety valve 8 for adjusting the pressure inside the container 1 is provided in a passage open to the outside from the heat exchanger 6 . The volatilized solvent vapor is discharged from the exhaust port 2 and enters the heat exchanger 6, where it is cooled and condensed. The condensed solvent returns to the container 1 and drips into the mixture. In the heat exchanger 6, the refrigerant cooled by the cooler 9 circulates, and the volatilized solvent vapor is cooled and condensed by heat exchange with the refrigerant, and then returned to the liquid.

Referring to FIG. 1 , an example of a method for producing a resin solution according to this embodiment will be described. The resin is placed inside the container 1 and the solvent is transferred therein through the infusion port 3 . The temperature control machine 5 is used to heat the mixture 100 in the container 1 to a predetermined temperature through the container 1 to volatilize the solvent. The vaporized solvent vapor enters the heat exchanger 6 through the exhaust port 2 of the container 1, and is cooled and condensed by the heat exchanger 6. The condensed solvent returns to vessel 1 and drips into mixture 100 . By repeatedly performing the reflux of the solvent, that is, volatilization of the solvent → cooling and condensation of the volatile solvent → the condensed solvent is returned to the container 1 and dropped into the mixture, thereby generating convection, and the mixture 100 is stirred by this convection. Furthermore, when the mixture 100 is heated to a temperature higher than the boiling point of the solvent, convection caused by the boiling of the solvent is also generated, and the mixture 100 is also stirred by this convection.

Furthermore, the resin solution manufacturing method of this embodiment can be applied to the resin solution manufacturing method for each time, that is, the resin solution manufacturing method in the batch process, and can also be used as an integrated production line for removing foreign matter from the resin. One of the processes is the process of resin solution. The manufacturing method of the resin solution of this embodiment can reduce the foreign matter mixed into the solution when manufacturing the resin solution, and the obtained resin solution is less likely to change in concentration and has less risk of excessive increase in the internal pressure of the container. Therefore, the manufacturing method of the resin solution of this embodiment is a method suitable for use as a process in an integrated production line, and can improve the workability of the process of removing foreign matter from the resin, thereby ensuring the quality of the resin after the foreign matter has been removed. Increased mass production. When the manufacturing method of the resin solution of this embodiment is used as one process in an integrated production line, the resin solution discharged from the drain port 4 in FIG. 1 is transported to the next process (such as a filtration process) through pipes.

The method for producing a resin solution according to this embodiment can be applied to any resin used as a method of dissolving the resin in a solvent. The method for producing a resin solution according to the present embodiment is particularly suitable for use in resins (optical resins) used in optical applications where contamination of foreign matter is strictly restricted. In particular, the method for producing a resin solution according to this embodiment can be suitably used when preparing a resin solution to be used in a pretreatment for removing foreign matter from a raw resin as a pretreatment for optical resin used in optical fibers. As a method of producing the resin solution.

The resin used in the manufacturing method of the resin solution of this embodiment is not specifically limited. The resin may be solid at room temperature (25°C), for example. For example, solid resin powder can be used as the resin.

For example, the resin may be a resin containing a fluoropolymer. Fluoropolymers are resins for optical applications that can be used as resin materials for optical components such as photosensitive resins used in lithography or plastic optical fibers (hereinafter referred to as "POF"). Therefore, the resin solution obtained by the method for producing a resin solution of the present embodiment using a resin containing a fluoropolymer can be suitably used in pretreatment for removing foreign matter in resins for optical applications such as POF. Therefore, for example, in the manufacturing method of POF, by applying the method of manufacturing the resin solution of this embodiment to the pretreatment for removing foreign matter in the POF material, it is possible to obtain POF with reduced foreign matter and high quality.

The fluorine-containing polymer may have, for example, a fluorine-containing aliphatic ring structure. The fluorine-containing aliphatic ring structure may be included in the main chain of the fluoropolymer or in the side chain of the fluoropolymer. The fluorine-containing polymer has, for example, a structural unit (A) represented by the following structural formula (1). [Chemical 1]

In formula (1), R _ff ¹ to R _ff ⁴ each independently represent a fluorine atom, a perfluoroalkyl group having 1 to 7 carbon atoms, or a perfluoroalkyl ether group having 1 to 7 carbon atoms. R _ff ¹ and R _ff ² may be connected to form a ring. "Perfluoro" means that all hydrogen atoms bonded to carbon atoms have been replaced by fluorine atoms. In formula (1), the number of carbon atoms of the perfluoroalkyl group is preferably 1 to 5, more preferably 1 to 3, and still more preferably 1. The perfluoroalkyl group may be linear or branched. Examples of the perfluoroalkyl group include trifluoromethyl, pentafluoroethyl, heptafluoropropyl, and the like.

In formula (1), the carbon number of the perfluoroalkyl ether group is preferably 1 to 5, more preferably 1 to 3. The perfluoroalkyl ether group may be linear or branched. Examples of the perfluoroalkyl ether group include perfluoromethoxymethyl and the like.

When R _ff ¹ and R _ff ² are connected to form a ring, the ring may be a 5-member ring or a 6-member ring. Examples of the ring include a perfluorotetrahydrofuran ring, a perfluorocyclopentane ring, a perfluorocyclohexane ring, and the like.

Specific examples of the structural unit (A) include structural units represented by the following formulas (A1) to (A8). [Chemicalization 2]

The structural unit (A) may be the structural unit (A2) among the structural units represented by the above formulas (A1) to (A8), that is, the structural unit represented by the following formula (2). [Chemical 3]

The fluorine-containing polymer may contain one or more than two structural units (A). In the fluorine-containing polymer, the content of structural unit (A) may be 20 mol% or more or 40 mol% or more relative to the total of all structural units. By containing more than 20 mol% of the structural unit (A), the fluoropolymer tends to have higher heat resistance. When it contains more than 40 mol% of the structural unit (A), the fluoropolymer tends to have higher transparency and higher mechanical strength in addition to higher heat resistance. In the fluorine-containing polymer, the content of structural unit (A) may be 95 mol% or less or 70 mol% or less relative to the total of all structural units.

The structural unit (A) is derived from a compound represented by the following formula (3), for example. In the formula (3), R _ff ¹ to R _ff ⁴ are the same as the formula (1). In addition, the compound represented by formula (3) can be obtained by a known manufacturing method represented by the manufacturing method disclosed in Japanese Patent Publication No. 2007-504125, for example. [Chemical 4]

Specific examples of the compound represented by the above formula (3) include compounds represented by the following formulas (M1) to (M8). [Chemistry 5]

The fluoropolymer may also contain other structural units in addition to the structural unit (A).

The fluorine-containing polymer may also be a fluorine-containing polymer containing the structural unit (B) represented by the following formula (4). [Chemical 6] (In formula (4), m and n are arbitrary integers)

The solvent is not particularly limited as long as it can dissolve the resin according to the type of resin. The solvent used in the manufacturing method of the resin solution of this embodiment is preferably a solvent that easily generates convection due to reflux. For example, a solvent that is liquid at room temperature (25° C.) and has a lower boiling point is suitably used.

For example, when the resin contains a fluoropolymer, the solvent is preferably a fluorine-based solvent. As the fluorine-based solvent, for example, 1,1,1,2,2,3,4,5,5,5-decafluoropentane, hexafluorobenzene, and perfluorohexane can be suitably used.

When the solvent is a fluorine-based solvent, the boiling point of the solvent is preferably 50° C. or more and 80° C. or less, for example, so that convection due to reflux can easily occur.

When the solvent is a fluorine-based solvent, the viscosity of the solvent at 25°C is preferably 1 mPa･s or more and 10 mPa･s or less in order to generate convection caused by reflux.

In the manufacturing method of the resin solution of this embodiment, stirring using a stirring blade may also be used together. That is, in the manufacturing method of the resin solution of this embodiment, stirring by solvent convection including convection generated by refluxing the solvent and blade stirring using a stirring blade may be used together. According to this method, for example, even if the amount of the resin solution to be produced is increased, sufficient stirring can be performed without greatly increasing the stirring time. Even if the stirring blade is used in combination, the solvent is stirred by the convection generated by refluxing the solvent. Therefore, the amount of sliding foreign matter or metal ions generated when the stirring blade is rotated and mixed into the solvent can be suppressed. Therefore, in the resin solution manufacturing method of this embodiment, even when a stirring blade is used together, it is possible to manufacture a resin solution in which foreign matter is reduced compared to the previous resin solution obtained only by stirring with a stirrer. Example

(Example) [Preparation of resin solution] A polymer of perfluoro-4-methyl-2-methylene-1,3-dioxolane (the compound of the above formula (M2), "PFMMD") was prepared as a resin. Perfluoro-4-methyl-2-methylene-1,3-dioxolane is synthesized as follows: first, 2-carboxymethyl-2-trifluoromethyl-4-methyl-1 is synthesized , 3-dioxolane, and then fluorinate it, and then decarboxylate and separate the carboxylate obtained. In the polymerization of perfluoro-4-methyl-2-methylene-1,3-dioxolane, perfluorobenzoyl peroxide is used as the polymerization initiator.

The following is the synthesis of 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane, 2-carboxymethyl-2-trifluoromethyl-4-methyl-1 , Fluorination of 3-dioxolane, synthesis of perfluoro-4-methyl-2-methylene-1,3-dioxolane, and perfluoro-4-methyl-2-methylene - Detailed description of the polymerization of 1,3-dioxolane.

＜Synthesis of 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane＞ Prepare a 3 L three-necked flask equipped with a water-cooled cooler, a thermometer, a magnetic stirrer, and isobaric Using a dropping funnel, put 139.4 g (a total of 1.4 mol) of the mixture of 2-chloro-1-propanol and 1-chloro-2-propanol into the flask. The flask was cooled to 0°C, and methyl trifluoropyruvate was slowly added thereto, followed by stirring for 2 hours. After adding 100 mL of dimethylstyrene (DMSO) and 194 g of potassium carbonate thereto over 1 hour, stirring was continued for 8 hours to obtain a reaction mixture. Mix the resulting reaction mixture with 1 L of water, separate the aqueous phase, and extract it with methylene chloride. Then mix the methylene chloride solution with the organic reaction mixture, and use magnesium sulfate to extract the solution. Allow to dry. After removal of the solvent, 245.5 g of crude product were obtained. The crude product was fractionated under reduced pressure (12 Torr) to obtain 230.9 g of a purified product of 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane. The boiling point of the refined product is 77 to 78°C, and the yield is 77%. Furthermore, in the case where the obtained purified product is 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane, it can be determined by HNMR (Hydrogen-Nuclear Magnetic Resonance) , Hydrogen-Nuclear Magnetic Resonance) and ¹⁹ FNMR (Fluorine-19 Nuclear Magnetic Resonance, 19 Fluorine-Nuclear Magnetic Resonance) to confirm.

HNMR(ppm): 4.2 - 4.6, 3.8 - 3.6(CHCH ₂ , multiplet(multiplet), 3H), 3.85 - 3.88(COOCH ₃ , multiplet, 3H), 1.36 - 1.43(CCH ₃ , multiplet, 3H) ¹⁹ FNMR (ppm): -81.3(CF ₃ , s, 3F)

<Fluorination of 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane> Inject 4 L of 1,1,2-trichlorotrifluoroethane into a 10 L stirred reaction tank. In the stirred reaction tank, nitrogen gas was flowed at a flow rate of 1340 cc/min, and fluorine gas was flowed at a flow rate of 580 cc/min, thereby establishing a nitrogen/fluorine gas atmosphere. After 5 minutes, 290 g of the previously prepared 2-carboxymethyl-2-trifluoromethyl-4-methyl-1,3-dioxolane was dissolved in 750 mL of 1,1,2-trichlorotris. Fluoroethane solution was added to the reaction tank at a rate of 0.5 ml/min. The reaction tank was cooled to 0°C. After adding all the dioxolane over 24 hours, the fluorine gas flow was stopped. After blowing with nitrogen, a potassium hydroxide aqueous solution was added until it became weakly alkaline.

After removing volatile substances under reduced pressure, the surroundings of the reaction tank were cooled, and then dried under reduced pressure at 70° C. for 48 hours to obtain a solid reaction product. Dissolve the solid reaction product in 500 mL of water, and add excess hydrochloric acid to separate it into an organic phase and an aqueous phase. The organic phase is separated and distilled under reduced pressure to obtain perfluoro-2,4-dimethyl-1,3-dioxolane-2-carboxylic acid. The boiling point of the main distillate is 103℃-106℃/100 mmHg. The fluorination yield was 85%.

<Synthesis of perfluoro-4-methyl-2-methylene-1,3-dioxolane> Neutralize the above distillate with a potassium hydroxide aqueous solution to obtain perfluoro-2,4-dimethyl- 2-Potassium carboxylate-1,3-dioxolane. The potassium salt was vacuum dried at 70°C for 1 day. Decompose the salt at 250°C to 280°C in a nitrogen or argon atmosphere. It was condensed using a freezing trap cooled to -78°C, and perfluoro-4-methyl-2-methylene-1,3-dioxolane was obtained in a yield of 82%. The boiling point of the product is 45°C/760 mmHg. The product was identified using ¹⁹ FNMR and GC-MS (Gas Chromatography-Mass Spectrometer, gas chromatography-mass spectrometer).

¹⁹ FNMR: -84 ppm(3F, CF ₃ ), -129 ppm(2F, =CF ₂ ) GC-MS: m/e244(Molecular ion) 225, 197, 169, 150, 131, 100, 75, 50

＜Polymerization of perfluoro-4-methyl-2-methylene-1,3-dioxolane＞ 100 g of perfluoro-4-methyl-2-methylene-1,3-dioxolane and 1 g of perfluorobenzoyl peroxide obtained by the above method were sealed into a glass tube. The glass tube uses a freezing degassing method to remove oxygen from the system, then is filled with argon again and heated at 50°C for several hours. The content became solid, but if it was further heated at 70°C overnight, 100 g of a transparent rod was obtained.

The obtained transparent rod was dissolved in Fluorinert FC-75 (manufactured by Sumitomo 3M), and the obtained solution was poured onto a glass plate to obtain a polymer film. The obtained polymer had a glass transition temperature of 117°C and was completely amorphous. The product was purified by dissolving the transparent rod in hexafluorobenzene and adding chloroform to precipitate it. The glass transition temperature of the purified polymer is approximately 131°C. This polymer is used as a resin for preparing a resin solution.

1,1,1,2,2,3,4,5,5,5-decafluoropentane was used as the solvent.

The resin prepared in the above manner and the solvent were mixed so that the concentration of the resin became 7% by mass, and the mixture was placed in a glass flask. The total amount of mixture is 6100 g. A cooling tube is installed at the mouth of the glass flask as a heat exchanger, and cooling water at 5°C is circulated in the heat exchanger.

The glass flask was heated using a heating mantle so that the surface temperature of the glass flask became 75° C., the solvent was refluxed, and the mixture of the resin and the solvent was stirred for 9 hours using the convection generated thereby. A resin solution is prepared in this way.

[Foreign body assessment] Take 50 mL of the prepared resin solution into a container and use it as a sample for the foreign matter evaluation test. The container uses a transparent container that is transparent to laser light with a wavelength of 520 nm. In a darkroom, the sample of the resin solution in the container is irradiated with laser light (PL201 manufactured by THORLABS, wavelength: 520 nm, laser power: 1 mW) from one direction, and the distance between the sample and the laser light irradiated to the sample is In the direction orthogonal to the direction of travel, use a microscope (optical microscope VHX7000 (lens: VH-Z00R)) to photograph the sample illuminated by light at a shutter speed of 100 ms to obtain image data. Use the acquired image data to measure the number of identifiable foreign objects. FIG. 2 is a graph showing the number of foreign matter found from each image after taking 50 images of the resin solution obtained by the manufacturing method of the Example. In the graph of Figure 2, the graph marked "reflow" is the result of the embodiment. Furthermore, the results shown in Figure 2 are obtained by extracting three 50 mL samples from the prepared resin solution and obtaining the number of foreign matter. The numerical value of the bar graph shown in Figure 2 represents the average of three times, and the error bar represents the maximum and minimum values of the three times.

(Comparative example) [Preparation of resin solution] The same resin, solvent, and stirring method as in the Examples were used to prepare a resin solution. This solution was separately stirred using a stirring blade without refluxing it. Specifically, a stirring blade having a folded blade shape was used, and the mixture was stirred at a rotation speed of 300 rpm for 9 hours.

[Foreign body assessment] The prepared resin solution was evaluated for foreign matter in the same manner as in the Examples. The graph in FIG. 2 shows the number of foreign matter in the resin solution obtained by the manufacturing method of the comparative example. Among the graphs in Figure 2, the graph marked "Blade Stirring" is the result of the comparative example.

As shown in the graph of FIG. 2 , compared with the resin solution using stirring blades in the comparative example, the resin solution obtained in the example in which the solvent was stirred by refluxing had less foreign matter. industrial availability

The method for producing a resin solution of the present invention is useful for obtaining a resin solution for pretreatment (for example, filtration treatment) to remove foreign matter from the resin while suppressing contamination of foreign matter and dissolving the resin in a solvent.

1: Container 2:Exhaust port 3: Infusion port 4: Drainage port 5: Temperature regulating machine 6:Heat exchanger 7:Air filter 8:Safety valve 9:Cooler 100:Mixture

FIG. 1 is a schematic diagram illustrating an example of a method for producing a resin solution in the embodiment. FIG. 2 is a graph showing the number of foreign matter in the resin solution obtained by the manufacturing methods of Examples and Comparative Examples.

1: Container

2:Exhaust port

3: Infusion port

4: Drainage port

5: Temperature regulating machine

6:Heat exchanger

7:Air filter

8:Safety valve

9:Cooler

100:Mixture

Claims (8)

A method for producing a resin solution, which is a method for producing a resin solution obtained by dissolving a resin in a solvent, and The above manufacturing methods include: The mixture of the above solvent and the above resin is stirred by causing the above solvent to convect, so that the above resin is dissolved in the above solvent; The convection of the solvent includes convection generated by refluxing the solvent. Such as the manufacturing method of claim 1, wherein The convection of the above-mentioned solvent further includes the convection generated by the boiling of the above-mentioned solvent. Such as the manufacturing method of claim 1, wherein The above resin is solid. Such as the manufacturing method of claim 1, wherein While stirring the mixture by causing the solvent to convect, the mixture is heated to a temperature above the boiling point of the solvent. Such as the manufacturing method of claim 1, wherein The above-mentioned resin contains fluoropolymer. Such as the manufacturing method of claim 5, wherein The above solvent is a fluorine-based solvent, and The boiling point of the above solvent is 50°C or more and 80°C or less. Such as the manufacturing method of claim 5, wherein The above solvent is a fluorine-based solvent, and The viscosity of the above solvent at 25°C is 1 mPa･s or more and 10 mPa･s or less. Such as the manufacturing method of claim 1, wherein The above-mentioned resin is an optical resin.