TW201229486A - Method for determining amount of free boric acid - Google Patents

Abstract

Disclosed is a method for determining the amount of the free boric acid present in a polymer composition comprising a polymer and free boric acid, the method comprising the following steps (A), (B), (C), and (D): (A) the step of pulverizing the polymer composition; (B) the step of mixing the polymer composition pulverized in the step (A) with a coordinating compound capable of forming a complex ion with free boric acid; (C) the step of removing the polymer from the mixture obtained in the step (B); and (D) the step of determining the amount of the boric acid contained in the mixture from which the polymer has been removed in the step (C).

Description

201229486 VI. DESCRIPTION OF THE INVENTION: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for quantifying free boric acid. [Prior Art] As a method for quantifying boric acid contained in a polarizing film, a method of directly analyzing a polarizing film by high-frequency inductively coupled plasma (ICP) emission spectrometry is disclosed in Japanese Laid-Open Patent Publication No. 2009-104046. SUMMARY OF THE INVENTION The present invention provides: [1] A method for quantifying free boric acid in a polymer composition containing a high molecular substance and a free boric acid, which comprises the following steps (A), (B), (C And (D): (A) a step of pulverizing the polymer composition; (B) a step of mixing the polymer composition pulverized in the step (A) with a coordinating compound capable of forming a counter ion with free boric acid (C) a step of removing the polymer material from the mixture obtained in the step (B); (D) a step of quantifying the boric acid contained in the mixture of the polymer material removed in the step (C). [2] The method according to [1], wherein the complex compound capable of forming a counter ion with free boric acid is an alcohol compound having two or more hydroxyl groups 201229486 [3] The method described in [2] Among them, the alcohol compound having two or more hydroxyl groups is an alcohol compound having two to six hydroxyl groups. [4] The method according to [2] or [3] wherein the alcohol compound having two or more hydroxyl groups is 2-ethyl-1,3-hexanediol. [5] The method according to any one of [1] to [4] wherein the step (D) is a step of quantifying boric acid by high frequency inductively coupled plasma (ICP) emission spectrometry. [6] The method according to any one of [1] to [5] wherein the polymer composition containing a polymer substance and a free boric acid is a film-like polymer composition [7]. The method of any one of [6], wherein the polymer composition containing a high molecular substance and a free boric acid is a laminated body. The method according to any one of item [7], wherein the polymer material is polyvinyl alcohol. [9] The method according to any one of [8], wherein the step (B) is in the presence of an organic solvent which does not substantially dissolve the polymer substance. A step of mixing the composition with a coordinating compound which forms a mision with free boric acid. [10] The method according to any one of [1] to [9] wherein the mixture obtained by the step (B) is a mixture which is substantially free of water. [11] The method according to any one of the preceding item, wherein the step (A) is a step of pulverizing the polymer composition by a freeze pulverization method. [12] The method of any one of [1] to [丨丨], wherein

-6- S 201229486 The cumulative 粒度% particle diameter of the cumulative particle size distribution of the polymer composition pulverized in the step (A) from the side having a small particle diameter is ο·1 to 50 〇pm. [Embodiment]

The method for quantifying free boric acid in the polymer composition containing a polymer material and a free boric acid according to the present invention includes the following steps (A), (B), (C) and (D). (A) a step of pulverizing the polymer composition; (B) a step of mixing the polymer composition pulverized in the step (A) with a coordinating compound capable of forming a counter ion with free boric acid; (B) a step of removing the polymer material from the obtained mixture; (D) a step of quantifying the boric acid contained in the mixture of the polymer material removed in the step (C). The polymer composition contains a polymer material and free boric acid, and preferably contains boric acid having a crosslinked structure with a polymer material. The high molecular composition may also contain two or more kinds of high molecular substances. The phrase "boric acid having a crosslinked structure with a polymer material" means a polymer material having a structure in which a boronic acid or a boron-containing group is crosslinked. Hereinafter, a boric acid having a crosslinked structure with a polymer material is also referred to as a boric acid. In the present specification, the term "free boric acid" refers to a group other than the cross-linked boric acid in the boric acid contained in the polymer composition, and includes those which are not bonded to the polymer substance. Further, when the polymer composition is obtained by treating a polymer material with boric acid, "free boric acid" includes boric acid which is not reacted with a polymer substance, that is, "unreacted 201229486 boric acid". When the composition contains two or more kinds of sensible molecular substances, it preferably contains boric acid which forms a crosslinked structure with at least one of the high molecular substances. The high molecular substance may, for example, be polyvinyl alcohol, polyphenol, or poly(b). A water-soluble polymer such as a diol, a polyolefin such as polyethylene or polypropylene, polyethylene terephthalate or polymethyl methacrylate is preferably a water-soluble polymer, and polyvinyl alcohol is more preferable. The polymer material may be a homopolymer or a random copolymer or a block copolymer obtained by copolymerizing two or more kinds of monomers. Further, the functional group in the polymer may also be partially The esterification or the like is changed to another functional group. The monomer may, for example, be an α-olefin having 2 to 30 carbon atoms such as ethylene, propylene, 1·butene or isobutylene; or a (meth)acrylic acid or a salt thereof; Methyl (meth)acrylate, Ethyl methacrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate (meth)acrylate such as 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate; (meth)acrylamide, oxime-methyl (Meth) acrylamide, hydrazine-ethyl (meth) acrylamide, hydrazine, hydrazine-dimethyl (meth) acrylamide, diacetone (meth) acrylamide, (meth) propylene (meth)propane sulfonic acid and its salts, (meth) acrylamidopropyl dimethylamine and its salts, hydrazine-hydroxymethyl (meth) acrylamide or its derivatives (meth) Acrylamide derivative; hydrazine-ethylene carbamide, hydrazine-ethylene acetamide, hydrazine-vinylpyrrolidone, etc. fluorene-vinyl hydrazine; methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isopropyl vinyl Ether, butyl vinyl ether, isobutyl-8

S 201229486 Ethyl ether, tertiary butyl vinyl ether, dodecyl vinyl ether, stearyl sulfonate acid, polyoxyethylene vinyl ether and other vinyl ether; (meth) acrylonitrile and other vinyl cyanide; vinyl chloride , halogenated ethylene such as vinylidene chloride, vinyl fluoride or vinylidene fluoride; ethylene carbonate such as vinyl ethyl carbonate; 3,4-divinyloxy-1-butene, 3,4-diethoxy a dihydroxybutene derivative such as a 1-butene; an allyl compound such as allyl acetate or chloropropene; a maleic acid or a salt or ester thereof; itaconic acid or a salt or ester thereof; a vinyl decyl compound such as oxoxane; and an unsaturated sulfonic acid. The polymer composition is preferably in the form of a film. The polymer composition may be a laminate containing two or more film-like polymer materials. The film-form polymer material forming the laminate may be, for example, a cellulose resin such as triacetyl cellulose, a polyester resin, a polyether sulfonic acid resin, a polyfluorene resin, or a polycarbonate resin, in addition to the above polymer material. , polyamide resin, polyimide resin, polyolefin resin, (meth)acrylic resin, cyclic polyolefin resin (norbornene resin), polyarylate, polystyrene resin , a polyethylene glycol resin, and mixtures thereof. These film-like polymer materials may be various processors such as a hard coat layer treatment, an anti-reflection treatment, a release treatment, a treatment for diffusion, and a treatment for preventing glare. The laminate ' can further contain a glass substrate or an adhesive layer. The polymer composition may be a commercially available product or may be produced by a known method. The step (A) is a step of pulverizing the polymer composition. The method of pulverizing the polymer composition is, for example, a pulverization method using a ball mill, a 201229486 mixing mill, a knife-cutting mill, or a crucible. Preferably, the polymer composition is pulverized by a freeze pulverization method. The freeze pulverization is usually carried out using a freeze pulverizing apparatus. The freezing temperature in the freeze pulverization method is preferably 〇°c or less, more preferably _273 °c, and a range of 100 °C is particularly preferably near the liquid nitrogen temperature (-1 9 6 °C). In order to reduce the variation in the content of boric acid obtained in the step (D) described later, it is preferred to pulverize the polymer composition in an inert gas atmosphere. Inert gas, preferably nitrogen. When the polymer composition is pulverized by the freeze pulverization method, it is preferred that the polymer composition and the pulverizing ball are placed in the pulverization container in a dry box filled with nitrogen gas from the viewpoint of not requiring a large working space. After the container is pulverized, it is taken out from the dry box, and is attached to the freeze pulverizing apparatus in the atmosphere. After the pulverization operation, the pulverization container is placed in a dry box filled with nitrogen to perform unsealing. In the cumulative particle size distribution of the polymer composition obtained by the pulverization, the cumulative 90% particle diameter (hereinafter also referred to as "90% D") from the side having a small particle diameter is preferably 0.1 to 500 μm, more preferably 1~3 00μιη, especially good for 10~ΙΟΟμιη. The cumulative particle size distribution of the pulverized polymer composition can be measured using a commercially available particle size measuring device. The step (Β) is a step of mixing the polymer composition pulverized in the step (Α) with a coordinating compound which can form a wrong ion with free boric acid. A coordinating compound capable of forming a counter ion with a free boric acid (hereinafter, simply referred to as a coordinating compound) may, for example, be 2-ethyl-1,3-hexanediol, ethylene glycol, glycerin or sorbitol. More than two hydroxyl group alcohol compounds; methanol: salicylic acid; and citric acid. Among them, an alcohol having two or more hydroxyl groups

The compound of S -10- 201229486 is preferred, and more preferably an alcohol compound having 2 to 6 hydroxyl groups, particularly preferably 2-ethyl-1,3-hexanediol. Here, the "alcohol compound" refers to a compound having an alcoholic hydroxyl group. Theoretically, a coordinating compound of 2 mol or more can be used with respect to 1 mol of free boric acid contained in the polymer composition, but since the content of free boric acid in the polymer composition is generally unknown, it is relatively high. The amount of the molecular component is preferably 1 part by mass to 50 parts by mass, based on 1 part by mass of the molecular composition. Preferably, the polymer composition after the pulverization and the coordinating compound capable of forming a counter ion with free boric acid are mixed in the presence of an organic solvent which does not substantially dissolve the polymer material. By carrying out the mixing in the presence of an organic solvent, the polymer substance can be easily removed in the step (C) described later. The "organic solvent which does not substantially dissolve a polymer substance" means an organic solvent which dissolves only a polymer substance which is generally considered to be insoluble. When the complex compound is a liquid, a coordinating compound can be used as the organic solvent. The organic solvent which does not substantially dissolve the polymer material differs depending on the type of the polymer material in the polymer composition, and can be appropriately selected depending on the polymer material. For example, when the polymer material is polyvinyl alcohol, an aromatic solvent such as benzene or toluene, a halogenated hydrocarbon solvent such as chloroform or dichloromethane is preferred, and chloroform is more preferred. The amount of the organic solvent to be used is usually 10 to 500 parts by mass based on 1 part by mass of the polymer material. The method of mixing the polymer composition and the complexing compound is not particularly limited. The upper limit of the mixing temperature is usually the boiling point of the lower of the boiling point of the coordinating compound used and the organic solvent. The lower limit of the mixing temperature is usually -11 - 201229486. The mixture of the polymer composition and the complexing compound can be used as the lowest temperature at which the compound can exist as a liquid. The mixing temperature varies depending on the coordinating compound to be used, the organic solvent, and the amounts used, and is preferably in the range of 0 °C to 40 °C. It is preferred that the mixture obtained by mixing the polymer composition and the complex compound is substantially free from water. The term "substantially free of water" means that the amount of water in the mixture is usually less than 1%, preferably less than 0. 1%. If the mixture is substantially free of water, selective quantification of free boric acid tends to be easier. The step (C) is a step of removing the high molecular substance from the mixture obtained in the step (B). The mixture obtained in the step (B) is usually composed of a solid containing a polymer substance, a mision ion, that is, a liquid containing a coordinating compound and a free boric acid, and in the step (C), the solid is removed from the mixture. To get the above liquid. The removal of the above solid is usually carried out by a general solid-liquid separation means such as filtration or decantation, and filtration is preferred. The filter to be used for filtration may be a range in which the particles of the polymer composition after the pulverization do not pass. The filtration temperature is preferably in the range of 0 ° C to 40 ° C. The solid to be separated may also be washed with the above organic solvent, and the washing liquid obtained by the washing may be mixed with the liquid obtained in the step (C). Step (D), the step (C) is removed high. The step of quantifying the boric acid contained in the mixture of molecular substances. The method for quantifying boric acid in the mixture may, for example, be methylene blue spectrophotometry, hypomethyl arsenazo spectrophotometry, high frequency inductive coupling

S -12- 201229486 Electrochemical (ICP) emission spectrometry, ICP mass spectrometry (above, refer to JIS K 0102), neutralization titration, curcumin-oxalic acid method (above, refer to 曰本Experimental Science Lecture 9 Analytical Chemistry "Jiusan' Vol. 1 (1976), p. 76-80), and fluorescent X-ray analysis (for example, refer to Japanese Patent Laid-Open Publication No. 2007-334307). Among them, ICP emission spectrometry is preferred. For example, in the ICP emission spectrometry, the boron obtained from the boron content in the test sample is generally regarded as being derived from boric acid, and the obtained boron content can be converted into a boric acid content to obtain a polymer. The amount of free boric acid in the composition. The content of free boric acid in the polymer composition can be determined by the method of the present invention. In particular, in the polymer composition, the content of free boric acid can be selectively measured even if the polymer material forms a free boronic acid having a crosslinked structure. EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples. <Particle size measurement condition 1> Apparatus: SALD-2000J (manufactured by Shimadzu Corporation) Using tank: batch tank dispersion solvent·dispersant: hexane + .10% sulfosuccinate di(2-ethylhexyl) Sodium dispersion method: (Agitator stirring + ultrasonic irradiation) 1 minute -13 - 201229486 Refractive index: 1. 7 0 - 0.2 0 i Measurement start time: Immediately after inputting the batch tank < Particle size measurement condition 2 > :MT-3 3 00EX II (made by Nikkiso Co., Ltd.) Use tank: Stainless steel tank dispersion solvent • Dispersant: None (dry) Refractive index: 1. 5 0 Measurement start time: Immediately after input into the tank < Determination of boric acid Condition 1 > Device: ICP emission spectrometer ICPS4100 (manufactured by Shimadzu Corporation) Measurement wavelength: B 249.773 nm Standard used for the production of the calibration line: Determination of boron standard stock solution (100 ppm) for atomic spectrometry by Kanto Chemical Co., Ltd. Sample: The amount of the filtrate corresponding to 6 g of the filtrate was measured, and methanol was added to prepare 10 mL of the sample solution for measurement. Further, the boron to be analyzed is regarded as being derived from boric acid, and the obtained boron content is converted into a boric acid content. <Measurement conditions of boric acid 2> Apparatus: ICP emission spectrometer SPS 5 520 (manufactured by SII Nano Technology Co., Ltd.)

S -14- 201229486 Measurement wavelength: B 249.678 nm Standard used for making the calibration curve: Boron analyzed by solvent mixed standard solution (500 ppm) is considered to be derived from boric acid, and the obtained boron content is converted into Boric acid content. <Measurement sample 1 > Measurement sample 1 is a polarizing element used in various liquid crystal display devices such as televisions, computers, and mobile phones. The polarizing element ' is produced by dyeing and uniaxially stretching a polyvinyl alcohol (PVA) film. The film is immersed in an aqueous solution containing boric acid and stretched, and subjected to a water resistance treatment by crosslinking. After the hydration treatment, it is washed with water. The structural formula of polyvinyl alcohol is represented by the following formula (I). (1)

-(CE^-CIDii -(CH2 -CH)in-I I HO CH3(0=)C0 &lt;Measurement sample 2 &gt; Measurement sample 2 was obtained after the weakened water resistance treatment of the measurement sample 1 Water-washing polarizing element. [Measurement sample 3 &gt; On the single side of the measurement sample 2, a saponified triethylene cellulose film (KC8UX2M, Konica Minolta Precision Optics) ), thickness: 80μιη), laminated through the adhesive layer, and on the other side, a corona-treated cycloaliphatic resin film (ZeonorFilm, ( -15- 201229486) OTPis, thickness: 60μιη A polarizing plate was produced by laminating the adhesive layer, and the produced polarizing plate was used as the measurement sample 3. <Measurement sample 4 &gt; One side of the measurement sample 1 was subjected to saponification treatment in advance. Triacetyl cellulose film (KC8UX2M, Konica Minolta Precision Optics Co., Ltd. 'thickness: 80μηι) 'Laminated by an adhesive layer, on the other side, saponified triethyl cellulose Film (KC4FR-1, Konica Minolta Precision Optics, thickness: 42μηι), through The agent layer was laminated to prepare a polarizing plate, and the produced polarizing plate was used as the measurement sample 4. <Measurement sample 5> On one side of the measurement sample 4, an adhesive layer was provided to prepare a polarizing plate. The polarizing plate produced was used as the measurement sample 5. Example 1 The sample 1 was measured, and 50 mg of a side of about 1 cm was cut with a pair of scissors, and placed in a sample container together with the steel ball. Thereafter, the JFC was frozen and pulverized. -3 00 (manufactured by Nippon Analytical Industry Co., Ltd.), a sample container was attached, liquid nitrogen was used as a refrigerant, pre-cooling was carried out for 7 minutes, and pulverization was carried out under the conditions of vibration for 5 minutes. The pulverized measurement sample was allowed to stand at room temperature. The mixture was allowed to stand for about 30 minutes, and the weight of the obtained powder was 50 mg. This operation was repeated once again to obtain 100 mg of the pulverized measurement sample 1. The above <measurement condition 1 &gt;

S 201229486 The particle size of the sample 1 after the pulverization was measured, and 90% D was 47.8 μm. Further, 10% D is 3·36 μmη, 50% D is 14·0 μιη» 100 mg of the pulverized measurement sample 1 and 2-ethyl-1,3-hexanediol/chloroform (volume ratio: 10/) 90) A mixed solvent of 3.5 mL was mixed, and the resulting mixture was allowed to stand at room temperature for 24 hours. The obtained mixture was filtered through a filter having a pore size of 0.2 μm. The boron in the obtained filtrate was analyzed by the above-mentioned &lt;quantitative condition 1 of boric acid&gt;, and the boron content was 〇.〇3 mass%, and the boric acid content was 0.20 mass%. The result of mixing the mixture of the measurement sample 1 and the 2-ethyl-1,3-hexanediol/chloroform mixed solvent after the pulverization was observed, and the polarizing element in the sample 1 was measured and substantially not dissolved in the above solvent. Therefore, it is presumed that the cross-linked boric acid is substantially not eluted into the above mixed solvent, so that the free boric acid in the sample 1 can be selectively quantified. Example 2 In the first embodiment, the measurement sample 2 is cut into a length of about 2 to 5 mm by scissors, instead of cutting the measurement sample 1 into a side length of about 1 cm by scissors, in addition to In the same manner, Example 1 was subjected to freeze pulverization. The particle size of the measurement sample 2 after the pulverization was determined by the above &lt;Measurement Condition 2 &gt; 90% D was 26.0 μm. Further, 10% D is 1 · 3 2 μιη, and 50% D is 5.3 9 μιη. The measurement sample 2 after the pulverization was mixed with 2-ethyl-1,3-hexanediol/chloroform mixed solvent in the same manner as in Example 1, and the resulting mixture was filtered to obtain a filtrate. As a result of analyzing the obtained filtrate by the above-mentioned &lt;boric acid quantitative condition 2 &gt;, the boron content was 0.054% by mass, and the boric acid content was 〇3.77% by mass * V..

S-17-201229486 It is understood from the results of Example 1 and Example 2 that the measurement sample 2 which is weak in water washing after the hydration treatment has a large amount of free boric acid remaining. [Example 3] In Example 1, the measurement sample 3 was cut into a length of about 2 to 5 mm by scissors, instead of cutting the measurement sample 1 into a length of about 1 cm by scissors, and the same was carried out. Example 1 was similarly subjected to freeze pulverization. The particle size of the measurement sample 3 after the pulverization was determined by the above &lt;Measurement Condition 2 &gt; 90% D was 269 μm. Further, 1〇%〇 is 22·6μηι, and 50%D is 206μηι. The measurement sample 3 after the pulverization was mixed with 2-ethyl-1,3·hexanediol/chloroform mixed solvent in the same manner as in Example 1, and the obtained mixture was filtered to obtain a filtrate. The results of the obtained filtrate were analyzed by the above-mentioned &lt;boric acid quantitative condition 2 &gt; The boron content was 0.009% by mass, and the boric acid content was 0.054% by mass. In Example 3, the polarizing element in the measurement sample was also substantially insoluble in the mixed solvent, and it was found that the free boric acid contained in the sample can be selectively quantitatively measured. [Example 4] In Example 1, the measurement sample 4 was cut into a length of about 2 to 5 mm by scissors, and the measurement sample 1 was cut into scissors to have a side length of about 1 cm. In the same manner, Example 1 was subjected to freeze pulverization. The particle size of the measurement sample 4 after the pulverization was determined by the above &lt;Measurement Condition 1 &gt; 90% D was 58.5 μm. Further, 32 μηι, 5〇%1) is 13 2μηι. -18- s 201229486 The measurement sample 4 after the pulverization was mixed with a mixed solvent of 2-ethyl-1,3·hexanediol/chloroform in the same manner as in Example 1, and the obtained mixture was filtered to obtain a filtrate. The results of the obtained filtrate were analyzed by the above-mentioned &lt;boric acid quantitative condition 2 &gt;, boron content was 0.007 mass%, and boric acid content was 0.040 mass%. In the fourth embodiment, the polarizing element in the measurement sample was also substantially insoluble in the mixed solvent, and it was found that the free boric acid contained in the sample can be selectively quantitatively measured. [Example 5] In the first embodiment, the measurement sample 5 is cut into a length of about 2 to 5 mm by scissors, instead of cutting the measurement sample 1 into a length of about icm by scissors, and Example 1 was similarly subjected to freeze pulverization. The measurement sample 5 after the pulverization was mixed with a mixed solvent of 2-ethyl-1,3-hexanediol/chloroform in the same manner as in Example 1, and the obtained mixture was filtered to obtain a filtrate. As a result of analyzing the filtrate obtained by the above &lt;quantitative condition of boric acid 1 &gt;, the boron content was 0.006 mass%, and the boric acid content was 0.034 mass%. In Example 5, the polarizing element in the measurement sample was also substantially insoluble in the mixed solvent, and it was found that the free boric acid contained in the sample can be selectively quantitatively measured. Reference Example 1 The measurement sample 1 was cut into 35 mg of 2 mm with scissors, and mixed with 3.5 mL of a mixed solvent of 2-ethyl-1,3-hexanediol/chloroform (volume ratio: 10 / 90) to obtain the obtained sample. The mixture was allowed to stand at room temperature for 1680 hours, and the resulting solution of the mixed -19-201229486 was analyzed by the above-mentioned &lt;boric acid quantitative condition 1 &gt;. The boron content in the sample was determined to be less than 0.01% by mass (less than the lower limit of detection). From the results of Reference Example 1, it is understood that it is necessary to measure the amount of free boron in the measurement sample and to pulverize the measurement sample. Reference Example 2 The same procedure as in Reference Example 1 was carried out except that the mixed solvent of 2-ethyl-1,3-hexanediol/chloroform (volume ratio: 10/90) was used in the reference example. The boron content in the measurement sample was 1.5% by mass, and the boric acid content was 8.7% by mass. Reference Example 3 In Reference Example 2, the mixture obtained by mixing the measurement sample 1 and the heavy water was allowed to stand at 80 ° C for 1 hour, and was placed at room temperature for 168 hours, except for Reference Example 1. Implemented in the same way. The boron content in the measurement sample was 3.9 mass%, and the boric acid content was 22 mass%. In Reference Example 2 and Reference Example 3, the results of mixing the measurement sample 1 with heavy water were visually confirmed, and it was observed that one of the measurement samples was partially dissolved in heavy water. Therefore, in Reference Example 2 and Reference Example 3, the cross-linked boric acid in the measurement sample was dissolved in heavy water, and the cross-linked boric acid in the measurement sample could not be distinguished from the free boric acid. According to the present invention, the free boric acid contained in the polymer composition can be selectively quantified.

-20- S

Claims (1)

201229486 VII. Application for Patent Park: 1. A method for quantifying free boric acid, which is a method for quantifying free boric acid in a polymer composition of a high molecular substance and a free boric acid, which comprises the following steps (A), (B), (C) and (D): (A). a step of pulverizing the polymer composition; CB) a polymer composition which is pulverized in the step (A) and a mision capable of forming a wrong ion with the free boric acid a step of mixing a bit compound; (C) a step of removing the polymer material from the mixture obtained in the step (B); (D) a step of quantifying the boric acid contained in the mixture of the polymer material removed in the step (C) . 2. The method of claim 1, wherein the coordinating compound capable of forming a counter ion with free boric acid is an alcohol compound having two or more hydroxyl groups. 3. The method of claim 2, wherein the alcohol compound having two or more hydroxyl groups is an alcohol compound having 2 to 6 hydroxyl groups. 4. The method of claim 2, wherein the alcohol compound having two or more hydroxyl groups is 2-ethyl-1,3·hexanediol. The method of any one of claims 1 to 4, wherein the step (D) is a step of quantifying boric acid by high frequency inductively coupled plasma (ICP) emission spectrometry. 6. The method according to any one of claims 1 to 5, wherein the polymer composition containing the polymer material and the free boric acid is a film-like polymer composition. The method according to any one of claims 1 to 5, wherein the polymer composition containing a high molecular substance and a free boric acid is a layered product. 8. The method of any one of claims 1 to 7 wherein the high molecular weight is a polyvinyl alcohol. The method of any one of claims 1 to 8, wherein This step (B) is a step of mixing the pulverized polymer composition and a coordinating compound capable of forming a counter ion with free boric acid in the presence of an organic solvent which does not substantially dissolve the polymer material. 10. The method of any one of claims 1 to 9 wherein the mixture obtained in the step (B) is a mixture substantially free of water 〇1 1 as in the scope of claims 1 to 10 The method according to any one of the preceding claims, wherein the step (A) is a step of pulverizing the polymer composition by a freeze pulverization method. The method according to any one of claims 1 to 11, wherein the cumulative particle size distribution of the polymer composition pulverized in the step (A) is accumulated from the side having a small particle diameter. The % particle size 'is 〇·1~5 0 0 μ m. S -22- 201229486 IV. Designation of representative drawings: (1) The representative representative of the case is: No (2) The symbol of the symbol of the representative figure is simple: No 201229486 If there is a chemical formula in the case, please reveal the best indication of the characteristics of the invention. Chemical formula: no -4- δ