Pre-Processing Method

Abstract

In a pretreatment method, in a first step, a sample is dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol to prepare a first solution. In a second step, an organic base that has a lower boiling point than that of HFIP is added to the first solution to prepare a second solution. In a third step, the second solution is heated to obtain a substance in which an anhydrous oxide structure in the sample has been decomposed. In a fourth step, chloroform is added to the second solution to prepare a third solution.

Claims

1. -5. (canceled)

6. A method for pretreating a sample comprising polyester or a polyester decomposition product before carrying out size exclusion chromatography of the sample, the method comprising: dissolving the sample in 1,1,1,3,3,3-hexafluoro-2-propanol to prepare a first solution; adding an organic base that has a lower boiling point than that of the 1,1,1,3,3,3-hexafluoro-2-propanol to the first solution to prepare a second solution; heating the second solution to obtain a substance in which an anhydrous oxide structure in the sample has been decomposed; after heating the second solution, adding chloroform to the second solution to prepare a third solution; and removing the chloroform from the third solution to obtain a solid sample consisting of the substance.

7. The method according to claim 6, further comprising dissolving the solid sample in a solvent for the size exclusion chromatography.

8. The method according to claim 6, wherein a concentration of the organic base in the first solution is greater than 0.05 [mmol/L] and less than 0.4 [mmol/L].

9. The method according to claim 6, wherein a ratio of amount V [mL] of chloroform to amount “a” [ml] of the 1,1,3,3,3-hexafluoro-2-propanol in the third solution is 0.1 < V/a.

10. The method according to claim 6, wherein the organic base comprises any of ethylamine, n-propylamine, i-propylamine, t-butylamine, diethylamine, or dimethylethylamine.

11. A pretreatment method comprising: preparing a first solution by dissolving a sample comprising polyester or a polyester decomposition product in 1,1,1,3,3,3-hexafluoro-2-propanol; preparing a second solution by adding an organic base that has a lower boiling point than that of the 1,1,1,3,3,3-hexafluoro-2-propanol to the first solution, wherein a concentration of the organic base in the first solution is greater than 0.05 [mmol/L] and less than 0.4 [mmol/L]; obtaining a substance in which an anhydrous oxide structure in the sample has been decomposed by heating the second solution; after obtaining the substance, preparing a third solution by adding chloroform to the second solution; obtaining a solid sample consisting of the substance by removing the chloroform from the third solution; and dissolving the solid sample in a solvent for size exclusion chromatography.

12. The pretreatment method according to claim 11, wherein a ratio of amount V [mL] of chloroform to amount “a” [ml] of the 1,1,3,3,3-hexafluoro-2-propanol in the third solution is 0.1 < V/a.

13. The pretreatment method according to claim 11, wherein the organic base comprises any of ethylamine, n-propylamine, i-propylamine, t-butylamine, diethylamine, or dimethylethylamine.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0016] [FIG. 1] FIG. 1 is a flow chart for illustrating a pretreatment method according to an embodiment of the present invention.

[0017] [FIG. 2] FIG. 2 is a configurational diagram showing the molecular structure of deteriorated polyethylene terephthalate.

[0018] [FIG. 3] FIG. 3 is a characteristic diagram showing results of measurement by size exclusion chromatography to which the present invention was applied.

DESCRIPTION OF EMBODIMENTS

[0019] Hereinafter, a pretreatment method according to an embodiment of the present invention will be described with reference to FIG. 1. This pretreatment method relates to the pretreatment of a sample consisting of polyester or a polyester decomposition product (deteriorated thermoplastic polyester) before carrying out size exclusion chromatography of the sample. The thermoplastic polyester is polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyneopentyl terephthalate, polycyclohexyl terephthalate, poly-dicyclohexylmethyl terephthalate, polyethylene isophthalate, polypropylene isophthalate, polybutylene isophthalate, polyneopentyl isophthalate, polyethylene naphthalate, polybutylene naphthalate, or the like. Also, copolymers of these thermoplastic polyesters are included therein. Further, copolymers of polyamide (nylon 6, nylon 11, nylon 12, and nylon 66) or polyacetal and thermoplastic polyester are also included therein.

[0020] First, in first step S101, the sample is dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) to prepare a first solution.

[0021] Next, in second step S102, an organic base that has a lower boiling point than that of HFIP is added to the first solution to prepare a second solution. The concentration of the organic base in the second solution is larger than 0.05 [mmol/L] and less than 0.4 [mmol/L]. The organic base having a lower boiling point than that of HFIP and chloroform can be used. For example, ethylamine, diethylamine, n-propylamine, i-propylamine (isopropylamine), t-butylamine, and dimethylethylamine can be used as the organic base having a lower boiling point than that of HFIP and chloroform.

[0022] Next, in third step S103, the second solution is heated to obtain a substance in which an anhydrous oxide structure in the sample has been decomposed. This substance is dissolved in the second solution at this stage.

[0023] Subsequently, in fourth step S104, chloroform is added to the second solution to prepare a third solution. The ratio of amount V [mL] of chloroform to amount “a” [ml] of HFIP in the third solution is 0 < V/a.

[0024] Then, in fifth step S105, the solvent is removed from the third solution to obtain a solid sample consisting of the substance in which an anhydrous oxide structure in the sample has been decomposed. The solvent can be vaporized by heating and thereby removed, for example. Alternatively, the solvent may be removed from the third solution by concentration under reduced pressure to obtain a solid sample.

[0025] The solid sample is thus obtained, and for subsequent size exclusion chromatography, the obtained solid sample is dissolved in a solvent (eluent) for size exclusion chromatography (sixth step).

[0026] Here, the deterioration of thermoplastic polyester will be described. As the deterioration of thermoplastic polyester progresses due to heat (heating) or light (light reception), its molecular chain scission reaction and cross-linking reaction progress, causing reduction in performance such as deterioration in strength. The course of reaction leading to molecular chain scission includes a pathway leading to molecular chain scission by only light, such as “Norrish II” reaction.

[0027] A molecular structure represented by the chemical structural formula (1) given below is converted to a molecular structure represented by the chemical structural formula (2) through photooxidation reaction and then converted to a molecular structure represented by the chemical structural formula (3) through ambient oxygen to form an acid anhydride structure which is a molecular structure weak in water. Then, the pathway leads to molecular chain scission as represented by the chemical structural formula (4) through hydrolysis.

##STR00001##

[0028] In the course of reaction to form a cross-linked structure, a molecular structure represented by the chemical structural formula (5) given below is converted to a molecular structure represented by the chemical structural formula (7) through the withdrawal of a hydrogen radical by radical R.Math. as represented by the chemical structural formula (6), and two molecular structures of the chemical structural formula (7) form a cross-linked structure through radicals to yield a molecular structure represented by the chemical structural formula (8). Such a course of reaction increases the number of cross-linked structures so that the thermoplastic polyester is insolubilized.

##STR00002##

[0029] For example, when the thermoplastic polyester polyethylene terephthalate (PET) is deteriorated, as shown in FIG. 2, acid anhydride structure 102 is formed halfway molecular chain 101. Also, cross-linked structure 103 which links two adjacent molecular chains 101 is formed, for example. The formation of such a network structure based on the cross-linked structure 103 involving the acid anhydride structure 102 is responsible for insolubilization. In such a molecular structure ascribable to deterioration, the decomposition of the acid anhydride structure 102 renders the network structure sparse, causing solubilization.

[0030] Hereinafter, the present invention will be described in more detail with reference to experimental results. First, the addition of an organic base that had a lower boiling point than that of HFIP was tested. In this test, solid samples were prepared by a pretreatment method under varying conditions, and the solid sample prepared under each condition was analyzed for the state of ester bonds and the state of an acid anhydride structure.

[0031] The state of ester bonds was evaluated as decrease in the number of ester bonds by analyzing (quantifying) increase in the number of hydroxy group ends formed through the decomposition of ester bonds in the solid sample by nuclear magnetic resonance (NMR) measurement. More specifically, .sup.1H NMR (300 MHz) was measured using nuclear magnetic resonance device Oxford from Varian Medical Systems, Inc.

[0032] A sample was dissolved in a solvent of deuterated chloroform [containing 0.03% (v/v)Me.sub.4Si] CDCl.sub.3 and 1,1,1,3,3,3-hexafluoro-2-propanol-2d (HFIP-2d) mixed at a volume ratio of 1:1.

[0033] Measurement was carried out under a temperature condition of 50° C. For the measurement, the Me.sub.4Si peak of deuterated chloroform [containing 0.03% (v/v)Me.sub.4Si] CDCl.sub.3 was defined as 0 ppm.

[0034] Concentration C.sub.OH of hydroxy group ends was determined for repeat units from the intensity ratio between the peak of a proton on an aromatic ring δ8.10 ppm) and the peak of a proton on a methylene group at hydroxy group ends δ4.05 ppm) resulting from the decomposition of ester bonds.

[0035] The state of an acid anhydride structure was analyzed (quantified) as the presence or absence of a residual acid anhydride structure in a solid sample by infrared spectroscopy (FT-IR). More specifically, measurement was performed by reflection ATR with a single-reflection diamond ATR plate using FT-IR analysis device Frontier Gold manufactured by PerkinElmer, Inc. The residual acid anhydride structure was confirmed from A.sub.1785/A.sub.1016 wherein the absorbance of 1785 cm.sup.-1 (light absorption by the acid anhydride structure) was normalized with the absorbance of 1016 cm.sup.-1 (light absorption by an aromatic ring).

[0036] ΔA.sub.1785/A.sub.1016 = (A.sub.1785/A.sub.1016 when a deteriorated sample is pretreated) - (A.sub.1785/A.sub.1016 of an undeteriorated sample)

Sample

[0037] Light-deteriorated PET (approximately 10 mg) was used as deteriorated thermoplastic polyester.

Organic Base

[0038] Any of the following organic bases were used. [0039] Isopropylamine (boiling point: 34° C.) [0040] Diethylamine (boiling point: 56° C.) [0041] n-Butylamine (boiling point: 78° C.) [0042] Triethylamine (boiling point: 89° C.)

Solvent

[0043] HFIP (boiling point: 59° C.) and chloroform (boiling point: 61° C.) were used.

Test 1

[0044] In test 1, light-deteriorated PET (10 mg) was dissolved in HFIP (2 mL) (first solution). To this solution, the organic base mentioned above was added at C mmol/L (second solution), followed by warming at 50° C. for 1 h. A small aliquot of this solution (second solution) was collected and subjected to NMR measurement, and “ΔC.sub.CH2OH before solvent removal” was calculated. Then, the solvent was removed to obtain a solid sample. The obtained solid sample was subjected to NMR measurement, and “ΔC.sub.CH2OH after solvent removal” was calculated. The calculation results are shown in Table 1 below.

TABLE-US-00001 Base C Δ C.sub.CH2OH before solvent removal Δ C.sub.CH2OH after solvent removal Triethylamine (boiling point 89° C.) 0.25 0 2.1 n-Butylamine (boiling point 78° C.) 0.25 0 2.5 Diethlamine (boiling point 56° C.) 0.25 0 0.2 Isopropylamine (boiling point 34° C.) 0.05 0 0.1 0.10 0 0.2 0.25 0 0.3 0.30 0 0.3 0.40 0 0.7 0.50 0 0.7

[0045] As shown in Table 1, there was neither increase in the number of hydroxy group ends nor the decomposition of ester bonds before removal of the solvent in all the cases. On the other hand, the number of hydroxy group ends was increased after removal of the solvent, demonstrating that the decomposition of ester bonds progressed during the course of removal of the solvent.

Test 2

[0046] In test 2, light-deteriorated PET (10 mg) was dissolved in HFIP (2 mL) (first solution). To this solution, the organic base mentioned above was added at C mmol/L (second solution), followed by warming at 50° C. for 1 h. To this solution (second solution), v mL of chloroform was added, and the mixture was thoroughly stirred (third solution). Then, the obtained solution was heated for the removal of the solvent to obtain a solid sample. The obtained solid sample was subjected to NMR measurement, and “ΔC.sub.CH2OH after solvent removal” was calculated. Also, the obtained solid sample was subjected to FT-IR measurement, and “ΔA.sub.1785/A.sub.1016” was calculated. The results of each calculation are shown in Table 2 below.

TABLE-US-00002 Base C V Δ C.sub.CH2OH after solvent removal Δ A.sub.1785 / A.sub.1016 Triethylamine (boiling point 89° C.) 0.25 0.5 0.7 0 n-Butylamine (boiling point 78° C.) 0.25 0.5 0.5 0 Diethylamine (boiling point 56° C.) 0.25 0.5 0 0 Isopropylamine (boiling point 34° C.) 0.05 0.5 0 0.12 0.10 0.5 0 0 0.25 0.5 0 0 0.30 0.5 0 0 0.40 0.5 0.1 0 0.50 0.5 0.3 0 0.25 0.2 0.2 0 0.25 0.3 0 0

[0047] As shown in Table 2, for triethylamine and n-butylamine, the number of hydroxy group ends was increased after removal of the solvent, and the decomposition of ester bonds progressed. This is presumably because, since the boiling points of these bases were higher than that of chloroform and HFIP, the concentration and removal of the solvent facilitated elevating the base concentration. For diethylamine and isopropylamine which had a lower boiling point than that of chloroform and HFIP, the number of hydroxy group ends was increased when the amount of the base added was 0.40 mmol/L or more, demonstrating the progression of decomposition of ester bonds. On the other hand, the number of hydroxy group ends was not increased when the amount of these bases added was in the range of 0.10 to 0.30 mmol/L, demonstrating that the decomposition of ester bonds did not progress.

[0048] When 0.05 mmol/L of isopropylamine was added, ΔA.sub.1785/A.sub.1016 > 0 held, demonstrating that when the amount of the organic base added is small, the decomposition of an acid anhydride structure is not completed. When the amount of chloroform added was 0.2 mL, the number of hydroxy groups was increased, demonstrating the decomposition of ester bonds.

[0049] From these results, first of all, it was found that an organic base having a lower boiling point than that of chloroform and HFIP is suitable. It was also found that the concentration of the organic base added is suitably 0.05 < c < 0.4. When the amount of HFIP is defined as “a” mL, it is evidently desired that amount V mL of chloroform added should be 0.2 < V. In other words, when the amount of HFIP used in the dissolution of the sample is defined as “a” mL, it is evidently desired that amount V mL of chloroform added should satisfy the relationship of “0.1 < V/a”.

Experimental results

[0050] Hereinafter, results of carrying out the pretreatment method of the present invention and carrying out measurement by size exclusion chromatography will be described. In this experiment, light-deteriorated PET (10 mg) was dissolved in HFIP (2 mL) (first solution). Isopropylamine was added thereto as an organic base at 0.25 mmol/L (second solution), followed by warming at 50° C. for 1 h. Then, 0.5 mL of chloroform was added thereto, and the mixture was thoroughly stirred (third solution). The obtained solution was heated for the removal of the solvent to obtain a solid sample. The obtained solid sample was measured by size exclusion chromatography.

Measurement equipment

[0051] For measurement, SEC device AQUICTY APC from Waters Corp. was used. Also, APC-XT, 186006995, 186006998, 186007003, and 186007254 were used as columns.

Standard sample

[0052] Six types of commercially available polymethyl methacrylate (PMMA) standard samples having a peak top molecular weight of 102500, 56900, 24400, 10900, 8350, or 4250 were used to carry out measurement. A triple calibration curve was prepared.

Sample preparation

[0053] The solid sample obtained by pretreatment was dissolved at 1 mg/1 mL in an eluent of HFIP containing 10 mmol/L of sodium trifluoroacetate. A sample bottle of the obtained solution was capped and left standing overnight. The sample was added to a vial for measurement, filtered through a PTFE syringe filter having a pore size of 0.2 .Math.m, and subjected to measurement.

Measurement conditions

[0054] Eluent: HFIP containing 10 mmol/L of sodium trifluoroacetate [0055] Column temperature: 40° C. [0056] Flow rate: 0.25 mL/min [0057] Sample concentration: 1 mg/mL [0058] Injection volume: 0.2 .Math.L/run [0059] Detector: RI detector (40° C.)

[0060] The measurement results are shown in FIG. 3. In FIG. 3, line 201 depicts results of measuring undeteriorated PET without pretreatment. Line 202 depicts results of measuring an undeteriorated PET pretreated according to the present invention. Line 203 depicts results of measuring light-deteriorated PET without pretreatment. Line 204 depicts results of measuring light-deteriorated PET pretreated according to the present invention.

[0061] As described above, according to the present invention, the decomposition of ester bonds can be suppressed in the pretreatment of a sample consisting of polyester or a polyester decomposition product for carrying out size exclusion chromatography, because an organic base that has a lower boiling point than that of HFIP is added.

[0062] The present invention is not limited by the embodiments described above. It is obvious that those ordinarily skilled in the art are capable of carrying out many modifications and combinations without departing from the technical brief of the present invention.

REFERENCE SIGNS LIST

[0063] 101 Molecular chain [0064] 102 Acid anhydride structure [0065] 103 Cross-linked structure [0066] 201,202,203,204 Line