Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
  • G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators

Definitions

• the present invention relates to a method for evaluating a polymer and a method for producing a polymer. More specifically, the present invention relates to a method for evaluating a polymer by detecting foreign matters contained in the polymer, and a polymer including the evaluation method. It relates to a manufacturing method.
• Vinylidene fluoride polymers are used in various applications because they are excellent in heat resistance, chemical resistance and electrochemical stability.
• foreign components such as inorganic components such as metals and metal compounds and organic components such as other polymers may be mixed.
• high-purity vinylidene fluoride polymers that are less contaminated with such foreign substances are required.
• an inorganic component such as a metal
• a decomposition reaction of the vinylidene fluoride polymer is induced at the time of melt molding, or a molded product of vinylidene fluoride polymer such as a pipe for ultrapure water is used.
• the inorganic components and polymer decomposition products are eluted, which causes a problem. Therefore, quality control that reduces the content of foreign matter as much as possible is required.
• an ICP emission analysis method using a high frequency inductively coupled plasma (ICP) as a light source is known.
• ICP emission analysis method a metal component in a polymer is extracted into a solvent such as water and acid, and the solution sample is applied to an ICP emission analysis device to detect an existing metal component.
• Patent Document 1 discloses an image of foreign matter captured by a filter after filtering the liquid matter, detects the foreign matter from this image, and detects the foreign matter. A method for calculating the size and number is described.
• Patent Document 2 uses a determination liquid containing potassium ferricyanide and potassium ferrocyanide to cause a color reaction between iron ions and an indicator, and the degree of mixing of iron ions in the resin-impregnated composition. It is described to know. It is known as a general chemical reaction that potassium ferricyanide reacts with divalent iron ions to give turn blue, and potassium ferrocyanide reacts with trivalent iron ions to give Berlin blue.
• Japanese Patent Publication Japanese Patent Laid-Open No. 2005-221291 (published on August 18, 2005)” Japanese Patent Publication “JP-A-5-172805 (published July 13, 1993)”
• the analysis method of the metal component in the polymer by the ICP emission analysis method is complicated in operation because the metal component in the polymer is extracted into a solvent such as water and acid and the solution sample is applied to the emission analyzer. An ICP emission analyzer is required.
• this analysis method can detect the presence of foreign matter, it has the disadvantage that the number and size of foreign matters cannot be measured.
• Patent Document 2 does not consider the detection of metal foreign objects other than iron, and is not sufficient as a foreign object detection method when a metal other than iron is assumed as the foreign object. is there.
• a general polymer production facility including a vinylidene fluoride polymer is made using SUS304 or SUS316 or an austenitic stainless steel according to these. Therefore, there is a high possibility that stainless steel is mixed as a foreign substance in the polymer. According to the result of confirming the foreign matter in the vinylidene fluoride polymer adhering to the iron remover using the iron remover, stainless steel and iron are mixed as foreign matters in the vinylidene fluoride polymer. .
• an object of the present invention is to provide a method for easily detecting iron and metal foreign matters other than iron contained in a polymer.
• the polymer evaluation method includes a filtration step of filtering a polymer solution in which the polymer is dissolved in a solvent, a hexacyanoiron (II) potassium, and a hexacyanoiron.
• III In the polymer solution captured by the filter by the contact step of bringing the color developing solution containing potassium and acid into contact with the filter after filtration, and color development on the filter caused by the color developing solution.
• a measuring step of detecting foreign matter and measuring at least one of the number and size of the foreign matter, and the pH of the color developing solution is in the range of ⁇ 0.40 to +0.75. .
• the foreign matter mixed in the polymer is captured by the filter by filtration of the polymer solution using a filter. If a foreign substance containing iron is present in the trapped foreign substance, the foreign substance exhibits a blue color due to the reaction with the color developing solution.
• the production quality of the polymer from the viewpoint of the foreign matter mixed in the polymer can be evaluated.
• the pH of the color developing solution is lower than 0.75, even if the foreign material is, for example, stainless steel having high corrosion resistance, the color developing reaction proceeds and a blue color is exhibited.
• the foreign material is a metal other than iron, it can be detected based on color development. Further, since the pH of the color developing solution is higher than ⁇ 0.40, when the foreign material is iron, it can be prevented from being lost, and the foreign material can be detected while maintaining the size of the foreign material. it can.
• the manufacturing method of the polymer which concerns on this invention manufactures a polymer by polymerization reaction, the manufacturing process of obtaining the powder of this polymer by drying, and the obtained said polymer A part of the powder is dissolved in a solvent having a polymer dissolving ability and not having a foreign substance dissolving ability, and a filtration is performed by filtering the polymer solution in which the polymer is dissolved in the solvent with a filter.
• a polymer is produced by a polymerization reaction and then dried to obtain a polymer powder.
• a part of the powder is dissolved in a solvent having the ability to dissolve the polymer and not the foreign substance, thereby preparing a polymer solution.
• the foreign matter mixed in the polymer powder is captured by the filter by filtration of the polymer solution using a filter. If a foreign substance containing iron is present in the trapped foreign substance, the foreign substance exhibits a blue color due to the reaction with the color developing solution. Foreign matter is detected based on this color development, and at least one of the number and size is measured. And based on the measurement result, the production quality of the polymer from the viewpoint of the foreign matter mixed in the polymer is determined.
• the pH of the color developing solution is lower than 0.75, even if the foreign material is, for example, stainless steel having high corrosion resistance, the color developing reaction proceeds and a blue color is exhibited. Therefore, even if the foreign material is a metal other than iron, it can be detected based on color development. Further, since the pH of the color developing solution is higher than ⁇ 0.40, when the foreign material is iron, it can be prevented from being lost, and the foreign material can be detected while maintaining the size of the foreign material. it can. Therefore, the produced polymer can be sorted according to production quality, and a polymer having a desired production quality can be provided.
• the detection of foreign matter by color development caused by the reaction of a color developing solution containing hexacyano iron (II) potassium, hexacyano iron (III) potassium and an acid with foreign matter captured by a filter is in the range of ⁇ 0.40 to +0.75. Therefore, it is possible to easily detect iron and metal foreign matters other than iron contained in the polymer.
• the polymer evaluation method according to the present invention is suitably incorporated as part of the polymer production method, and more suitably incorporated into the vinylidene fluoride polymer production method. Therefore, below, one Embodiment of the manufacturing method of the vinylidene fluoride polymer in which the evaluation method of the polymer based on this invention was integrated is described.
• the polymer evaluation method according to the present invention is not limited to the one incorporated in the polymer production method, and the polymer is not limited to the vinylidene fluoride polymer.
• the manufacturing method of the vinylidene fluoride polymer in the present embodiment includes a manufacturing process of manufacturing a vinylidene fluoride polymer by a polymerization reaction and obtaining a vinylidene fluoride polymer powder by drying, and a manufactured vinylidene fluoride polymer.
• a dissolution step for dissolving in a solvent, a filtration step for filtering a polymer solution in which a vinylidene fluoride polymer is dissolved in a solvent, a hexacyano iron (II) potassium, a hexacyano iron (III) potassium and an acid are included.
• a vinylidene fluoride is polymerized in an aqueous medium together with a monomer capable of being copolymerized alone or copolymerized to produce a vinylidene fluoride polymer, and the powder is obtained by drying.
• the “vinylidene fluoride polymer” includes not only a homopolymer of vinylidene fluoride but also a copolymer of vinylidene fluoride and other monomers.
• the polymerization method of the vinylidene fluoride polymer is not particularly limited, and solution polymerization, emulsion polymerization, and suspension polymerization can be used.
• the slurry of the vinylidene fluoride polymer obtained by the polymerization reaction is subjected to dehydration treatment and water washing treatment, and then dried in an oven at a temperature of 50 ° C. or higher and lower than 150 ° C., for example. Thereby, the powder of a vinylidene fluoride polymer is obtained.
• the solvent has the ability to dissolve the polymer and does not have the ability to dissolve foreign matter, that is, can dissolve vinylidene fluoride polymer, dissolves iron and stainless steel mixed as foreign matter in the vinylidene fluoride polymer
• NMP N-methyl-2-pyrrolidone
• N, N-dimethylformamide, N, N-dimethylacetamide and the like can be used.
• NMP N-methyl-2-pyrrolidone
• NMP N, N-dimethylformamide, N, N-dimethylacetamide and the like
• the concentration of the vinylidene fluoride polymer in the prepared polymer solution is preferably 20% by mass or less, and more preferably 10% by mass or less. .
• the charging of the vinylidene fluoride polymer into the solvent may be either batch charging or split charging. Further, in order to disperse the vinylidene fluoride polymer in the solvent so that the vinylidene fluoride polymer can be easily dissolved, it is preferable that the vinylidene fluoride polymer is charged and dissolved while stirring the solvent.
• the temperature at which the vinylidene fluoride polymer is dissolved in the solvent is not limited, but it is preferably dissolved at 60 ° C. to 80 ° C. By dissolving at 60 ° C. or higher, the dissolution time can be shortened. Accordingly, it is possible to shorten the time required from detection of the mixed foreign matter after the vinylidene fluoride polymer is obtained by the polymerization reaction.
• the filtration step the polymer solution in which the vinylidene fluoride polymer is dissolved in the solvent is filtered by a filter, so that foreign matters mixed in the vinylidene fluoride are captured by the filter.
• Filtration may be performed using a general filtration device, and suction filtration is preferable from the viewpoint of improving the filtration rate.
• the filter may be any filter that does not contain a metal and has resistance to a solvent.
• a known membrane filter formed of a fluororesin and cellulose acetate can be used.
• the pore diameter of the filter may be appropriately determined according to the size of the foreign substance to be detected.
• a filter having a pore diameter of 1 to 20 ⁇ m can be used, and a filter having a pore diameter of 5 to 15 ⁇ m is preferably used. It is done.
• the temperature of the polymer solution in the filtration step is preferably 30 ° C. to 100 ° C., and more preferably 50 ° C. to 80 ° C.
• the solution temperature is 30 ° C. or higher in the filtration step, the solution viscosity decreases, thereby shortening the time required for filtration and improving the work efficiency.
• the solution temperature is 100 ° C. or lower, the risk of burns when an operator touches the solvent is reduced, and the risk of the solvent igniting is also reduced.
• the filter is washed with a solvent and acetone, and then the filter is dried.
• the solvent is further passed after filtration, and then acetone is passed to remove the solvent remaining on the filter.
• the solvent used for cleaning the filter may be any solvent that can dissolve the vinylidene fluoride polymer.
• the same type of solvent as that used for preparing the polymer solution can be used.
• acetone is used to remove the solvent remaining on the filter.
• the solvent is not limited to acetone as long as the solvent can be removed. For example, methanol and ethanol can be used.
• the color developing solution in the present embodiment is an aqueous solution containing hexacyano iron (II) potassium, hexacyano iron (III) potassium and an acid, and may contain other components as long as the effects of the present invention are not impaired.
• the acid used in the color developing solution is not particularly limited, but for example, inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid are preferable, and hydrochloric acid is more preferable.
• the color developing solution in this embodiment can be prepared, for example, by dissolving 0.1 to 5 parts by weight of a mixture of potassium hexacyanoiron (II) and hexacyanoiron (III) potassium in 100 parts by weight of an acidic aqueous solution. it can.
• the main foreign substances to be detected are iron and stainless steel.
• Stainless steel is known to have strong corrosion resistance. Therefore, when the acid concentration is low, even if the color developing solution comes into contact with stainless steel, hexacyano iron (II) potassium and hexacyano iron (III) potassium cannot react with sufficient iron ions and detection is possible. Color development does not occur to the extent. Therefore, stainless steel cannot be detected using color development as an index. In addition, if the acid concentration is too high, iron as a foreign matter is lost. As a result, the presence or absence of foreign matter or the size of foreign matter cannot be measured correctly.
• the acid concentration in the color developing solution is within a range in which color development occurs due to the reaction with the stainless steel by contact with the color developing solution and iron is not lost.
• the concentration of the acid that satisfies such conditions varies depending on the type of acid.
• the concentration of hydrochloric acid in the color developing solution is 0.5 to 4.0% by mass, preferably 1.0 to 4.0% by mass, and more preferably 2.0 to 3. 0% by mass. If the concentration of hydrochloric acid in the color developing solution is 0.5% by mass or more, color development occurs due to the reaction between the stainless steel as a foreign material and the color developing solution, so that the stainless steel contained as a foreign material can be detected.
• the concentration of hydrochloric acid is 4.0% by mass or less, iron melting can be prevented, and thus iron contained as foreign matter can be detected while maintaining the size as foreign matter.
• the color developing solution (potassium hexacyanoiron (II): 0.5% by mass, potassium hexacyanoiron (III): 0.5% by mass, hydrochloric acid: 0.5% by mass or 4.0% by mass, solvent: water)
• the pH was measured using a pH meter (manufactured by Toa Denpa Kogyo Co., Ltd., model: HM-30V).
• the pH of the color developing solution containing hydrochloric acid at a concentration of 0.5% by mass was 0.75.
• the pH of the color developing solution contained at a concentration of 0% by mass was ⁇ 0.40. Therefore, a color developing solution that satisfies the above conditions can be defined as a color developing solution having a pH in the range of ⁇ 0.40 to +0.75.
• the pH of the color developing solution containing hydrochloric acid at a concentration of 2.0% by mass was 0.05, and the pH of the color developing solution containing a concentration of 3.0% by mass was ⁇ 0.19. Therefore, a color developing solution having a pH in the range of ⁇ 0.19 to +0.05 is more preferably used.
• the method of bringing the color developing solution into contact with the filter is not particularly limited as long as the foreign matter captured by the filter can react with the color developing solution, but it is preferable to spray the color developing solution on the filter surface. According to the contact by spraying, the trapped foreign matter can be prevented from flowing away from the filter.
• the colored portion is observed using a microscope, the foreign matter in the colored portion is observed, the number of the whole on the filter is measured, and the size of each is measured. It is not limited to this.
• the foreign matter in the color development portion may be observed and the number thereof on the entire filter may be measured.
• the size of the foreign material in a color development part may be measured, and the presence or absence of the foreign material exceeding a specific size may be confirmed.
• the measurement object in the measurement process is appropriately determined by the user of the production method according to the present invention according to the use of the produced vinylidene fluoride polymer or the user's request to use the produced vinylidene fluoride polymer. That's fine.
• the production quality of the vinylidene fluoride polymer from the viewpoint of the foreign matter mixed in is determined based on the measurement result in the measurement step described above. That is, the quality of the produced vinylidene fluoride polymer is determined based on the number of foreign substances contained in the produced vinylidene fluoride polymer and / or the size thereof. For example, a threshold is set for the number or size of foreign matter to be detected, and when there is a foreign matter exceeding the threshold, the lot can be determined as a defective lot. Alternatively, a finer standard can be set and the quality can be determined based on the standard.
• the threshold value or the standard for determining the quality is determined by the user of the production method according to the present invention according to the use of the produced vinylidene fluoride polymer or the user's request to use the produced vinylidene fluoride polymer. What is necessary is just to determine suitably. For example, when the number of foreign matters detected from 1 g of the produced vinylidene fluoride polymer exceeds 10, the lot is regarded as a defective product, and when the number of foreign matters is 4 to 10, the lot is usually As an example, the standard is that the lot is a high-purity product when the number of foreign materials is 2 or 3, and the lot is an ultra-high-purity product when the number of foreign materials is 1 or less. it can.
• threshold value or reference is, for example, when the size of a foreign material is measured in the measurement process and a foreign material larger than 50 ⁇ m is found, the lot is regarded as a defective product, and no foreign material exceeding 50 ⁇ m is found. In this case, it is possible to exemplify a standard for making the lot a normal product.
• a vinylidene fluoride polymer having a desired quality can be provided as the final manufactured product.
• the polymer evaluation method according to the present invention includes a filtration step of filtering a polymer solution in which a polymer is dissolved in a solvent, a hexacyanoiron (II) potassium, and a hexacyanoiron (III).
• a foreign substance in the polymer solution captured by the filter is detected by a contacting step in which a coloring solution containing potassium and an acid is brought into contact with the filter after filtration, and coloring on the filter caused by the coloring solution.
• a measuring step for measuring at least one of the number and size of the foreign substances, and the pH of the color developing solution is in the range of ⁇ 0.40 to +0.75.
• the acid is preferably hydrochloric acid
• the color developing solution preferably contains hydrochloric acid at a concentration of 0.5 to 4.0% by mass.
• the color developing solution in the contact step, it is preferable that the color developing solution is brought into contact with the filter by spraying the color developing solution.
• the foreign material is preferably at least one of iron and stainless steel.
• the polymer is preferably a vinylidene fluoride polymer.
• the solvent is a solvent having a polymer dissolving ability and a foreign substance dissolving ability
• the polymer powder is dissolved in the solvent to dissolve the polymer. It further includes a dissolution step of preparing a solution, and in the dissolution step, the powder is preferably dissolved at 60 to 80 ° C.
• the solvent is preferably N-methyl-2-pyrrolidone.
• the color developing solution is a mixture of the hexacyano iron (II) potassium and the hexacyano iron (III) potassium in an amount of 0.1 to 5 with respect to 100 parts by weight of the aqueous solution containing the acid. It is preferable that the part by weight is dissolved.
• the content ratio of hexacyano iron (II) potassium and hexacyano iron (III) potassium in the mixture is preferably in the range of 1: 5 to 5: 1.
• Example 1 Confirmation of color development and erosion
• concentration of hydrochloric acid in each color developing solution is 0.02, 0.25, 2.5, or 4.5 mass%.
• Each color developing solution contains potassium hexacyanoiron (II) and hexacyanoiron (III) at a concentration of 0.5% by mass.
• the solvent of the color developer is water.
• each of a plurality of color developing solutions having different hydrochloric acid concentrations was sprayed on powdery SUS316 (hereinafter referred to as SUS powder), and it was confirmed using a microscope whether the SUS powder had a blue color.
• each of a plurality of coloring solutions having different hydrochloric acid concentrations was sprayed on the iron powder, and the state of the iron powder was confirmed using a microscope.
• Example 2 Production of vinylidene fluoride polymer
• An autoclave with an internal volume of 2 L is charged with 1,024 g of ion-exchanged water, 0.20 g of methyl cellulose, 11.2 g of ethyl acetate, 2.0 g of diisopropyl peroxydicarbonate, and 400 g of vinylidene fluoride, and the temperature is raised to 26 ° C. in 1 hour. Then, suspension polymerization was performed for 25.5 hours from the start of temperature increase. After completion of the polymerization, the polymer was washed with 5 L of ion exchange water while dehydrating the resulting polymer slurry. Then, it heated for 10 hours in 80 degreeC oven, and obtained the powder of the dried vinylidene fluoride polymer.
• the prepared polymer solution was put into a funnel of a filtration device, and suction filtered using a membrane filter (pore diameter: 10 ⁇ m). After suction filtration, NMP and acetone were passed through the membrane filter in this order to wash the membrane filter. After washing, the membrane filter was dried. After the membrane filter was transferred to a petri dish, a coloring solution was sprayed on the membrane filter to cause a color reaction. Using a microscope, the number and size of foreign matters that were colored on the membrane filter were measured.
• the present invention can be used for the production of a vinylidene fluoride polymer and its quality evaluation.

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