A component analysis method for polyamide or its copolymer

Abstract

The present invention belongs to the field of polymer characterization technology, and specifically relates to a method for analyzing the components of polyamide or its copolymers. Polyamide (nylon) and its copolymers are difficult to dissolve in conventional deuterated reagents, and therefore conventional polymer characterization and identification cannot be performed. The present invention uses a mixed solvent of a special solvent, deuterated phenol, and a deuterated chloroform reagent to dissolve polyamide and its copolymer samples, and performs related quantitative nuclear magnetic resonance hydrogen spectrum characterization to analyze the molecular weight of the polyamide or its copolymer samples and the content of the comonomer in the polyamide copolymer, thereby achieving accurate quantification of the polyamide or its copolymer.

Description

Technical Field

[0001] The present invention relates to the technical field of polyamide characterization, in particular to a component analysis method of polyamide or its copolymer. Background Art

[0002] Polyamide (nylon) is renowned for its toughness, self-lubrication, wear resistance, oil resistance, and corrosion resistance. It exhibits strong resistance to common chemicals and, under normal operating conditions, is unaffected by alcohols, acids, ethers, hydrocarbons, oils, and detergents, making it an excellent engineering plastic. It is widely used as a structural, wear-resistant, and dielectric material in the electrical, electronics, automotive, medical, and light industrial sectors. It is commonly used in gears, bearings, pump impellers, fan blades, oil pipelines, oil storage containers, electrical appliance mounts, and motorcycle and automobile structural components. Nylon 6, nylon 66, and nylon 610 are the most widely used.

[0003] The polyamide copolymer obtained by copolymerizing caprolactone and aminocaproic acid as monomers has better processing performance and toughness, and has the potential to be used in high value-added materials such as polyamide elastomers.

[0004] However, polyamides and their copolymers are generally difficult to dissolve in common solvents, making conventional polymer characterization impossible. Molecular weights are typically characterized by measuring their viscosity in a m-cresol solution, or by dissolving them in a mixed solvent of deuterated trifluoroacetic acid and deuterated chloroform and then using nuclear magnetic resonance (HNMR) spectroscopy to determine their composition and molecular weight. However, the viscosity method only characterizes viscosity, not absolute molecular weight, and cannot perform component analysis. Furthermore, deuterated trifluoroacetic acid reacts with the polymer and causes degradation, altering its composition, making it impossible to accurately characterize the structure of polyamides and their copolymers.

[0005] Therefore, there is an urgent need for a component analysis method that can accurately determine polyamide and its copolymers, realize the structural characterization of polyamide and its copolymers, establish the corresponding structure-activity relationship, and modify the corresponding properties to meet broader market demands. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the technical problem in the prior art that the structures of polyamide and its copolymers cannot be accurately characterized.

[0007] Conventional polymer characterization is currently impossible due to the difficulty of dissolving polyamide and its copolymer samples in common solvents. Using deuterated phenol alone as a solvent, without the presence of a conventional deuterated reagent for locking the field, results in poor test accuracy and makes testing impossible. Using deuterated chloroform as a solvent, however, has poor solubility for polyamide and its copolymer samples, making NMR analysis impossible. Furthermore, using mixed solvents to dissolve polyamide and its copolymers directly for testing, as the water contained in the deuterated phenol will overlap with the proton peaks adjacent to the terminal hydroxyl or amino groups, prevents accurate results.

[0008] In order to solve the above technical problems, the present invention develops a method for quantitative nuclear magnetic resonance hydrogen spectroscopy ( 1 The molecular weight of polyamides and their copolymers, as well as the comonomer content (molar ratio) in the polyamide copolymers, is analyzed using H NMR (H NMR) characterization methods. Specifically, the present invention employs a mixture of deuterated phenol and deuterated chloroform, a special solvent dehydrated with magnesium sulfate, to dissolve polyamide and its copolymer samples. Quantitative H NMR spectroscopy is then performed to analyze the molecular weight of the polyamide and its copolymer samples and the molar ratio of the two comonomers, caprolactone and aminocaproic acid. This provides a foundation for structural characterization of the polyamide and its copolymer samples and establishes their structure-activity relationship.

[0009] A first object of the present invention is to provide a component analysis method for polyamide or its copolymer, comprising the following steps:

[0010] (1) Mixing deuterated phenol and deuterated chloroform, adding anhydrous magnesium sulfate or anhydrous sodium sulfate, and allowing to stand to remove water from the solvent to obtain a mixed solvent;

[0011] (2) dissolving the polyamide or its copolymer in the mixed solvent described in step (1) to obtain a polyamide solution, and then performing quantitative nuclear magnetic resonance spectroscopy characterization, wherein the conditions for nuclear magnetic resonance spectroscopy characterization are: a relaxation time d1 value greater than or equal to 10 seconds, and a scanning number greater than or equal to 16 times;

[0012] (3) Based on the results of the quantitative hydrogen nuclear magnetic resonance spectrum characterization in step (2), the molecular weight of the polyamide or its copolymer and the molar fraction of the comonomer in the polyamide copolymer are calculated using the integral values ​​of the proton peak at the ortho position of the terminal hydroxyl or amino group, the proton peak at the ortho position of the ester bond carbonyl group, and the proton peak at the ortho position of the amide bond carbonyl group, thereby achieving component analysis of the polyamide or its copolymer.

[0013] In one embodiment of the present invention, in step (1), the standing time is 8 hours to 24 hours.

[0014] In one embodiment of the present invention, the volume ratio of the deuterated phenol to the deuterated chloroform is 1:(2-6). Furthermore, the volume ratio of the deuterated phenol to the deuterated chloroform is 1:(3-5), 1:(4-5), 1:(3-6), 1:(4-6). Specifically, the volume ratio is 1:2, 1:3, 1:4, 1:5, 1:6, or any value between any two values.

[0015] In one embodiment of the present invention, the concentration of the solution of polyamide or its copolymer is 5 mg / mL to 20 mg / mL. Further, the concentration is 5 mg / mL to 10 mg / mL, 10 mg / mL to 20 mg / mL, etc., specifically 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL, 20 mg / mL; or any value between any two concentration values.

[0016] In one embodiment of the present invention, in step (2), the relaxation time d1 is 10 seconds to 60 seconds, and the number of scans is 16 to 48 times.

[0017] In one embodiment of the present invention, the polyamide is nylon 6, and the polyamide copolymer is a copolymer of aminocaproic acid and caprolactone.

[0018] In one embodiment of the present invention, the molecular weight of the polyamide copolymer is calculated as follows:

[0019] ,

[0020] in, M n is the molecular weight of the polyamide copolymer; I 1 is the integral value of the chemical shift in the 2.1ppm-3.1ppm region, I 2 is the integral value in the 1.8ppm-2.1ppm region, I 3 It is the integrated value at 3.4ppm-3.7ppm.

[0021] In one embodiment of the present invention, the molecular weight of the polyamide is calculated as follows:

[0022] ,

[0023] in, M n ( PA) is the molecular weight of the polyamide; I 4 is the integral value of the chemical shift in the region of 1.8ppm-2.4ppm, I 5 It is the integrated value in the 2.6ppm-2.8ppm region.

[0024] In one embodiment of the present invention, the mole fraction of the comonomer of the polyamide copolymer is calculated as follows:

[0025] ,

[0026] Wherein, x is the mole fraction of the comonomer caprolactone in the polyamide copolymer, and y is the mole fraction of the comonomer aminocaproic acid in the polyamide copolymer; I 1 is the integral value of the chemical shift in the 2.1ppm-3.1ppm region, I 2 It is the integrated value in the range of 1.8ppm-2.1ppm.

[0027] In one embodiment of the present invention, the molecular formula of the polyamide copolymer is:

[0028] ,

[0029] Among them, a is 1~10, b is 1~30, and n is 30~100.

[0030] The above technical solution of the present invention has the following advantages over the prior art:

[0031] The present invention successfully obtains quantitative H-NMR spectra of polyamide and its copolymer samples by dissolving them in a mixed solvent of deuterated phenol and deuterated chloroform from which water has been removed. 1 H NMR) diagram; then the quantitative nuclear magnetic resonance hydrogen spectrum of polyamide and its copolymer samples ( 1 H NMR) to analyze the molecular weight and the contents of the two comonomers, caprolactone and aminocaproic acid. The component analysis method of the present invention for polyamide and its copolymers was verified to be accurate by using polyamide copolymers with a known comonomer content.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following embodiments of the present invention are described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0034] Figure 1 The synthetic route of the polyamide and its copolymer sample PACL of the present invention;

[0035] Figure 2 Quantitative H NMR spectra of three nylon 6 samples in Example 1 (mixed solvent of deuterated chloroform and deuterated phenol, v:v = 3:1);

[0036] Figure 3 This is the quantitative H NMR spectrum of the PACL-1.3 sample of Example 4 of the present invention (deuterated chloroform and deuterated phenol mixed solvent, v:v = 5:1);

[0037] Figure 4 This is the quantitative H NMR spectrum of the PACL-1.3 sample in Example 5 of the present invention (deuterated chloroform and deuterated phenol mixed solvent, v:v = 4:1);

[0038] Figure 5 Quantitative H NMR spectrum of the PACL-1.3 sample in Example 6 of the present invention (mixed solvent of deuterated chloroform and deuterated phenol, v:v = 3:1);

[0039] Figure 6 This is the quantitative H NMR spectrum of the PACL-3 / 5 sample in Example 7 of the present invention (mixed solvent of deuterated chloroform and deuterated phenol, v:v = 6:1);

[0040] Figure 7 Quantitative H NMR spectrum of the PACL-3 / 5 sample of Example 8 of the present invention (mixed solvent of deuterated chloroform and deuterated phenol, v:v = 3:1);

[0041] Figure 8 Quantitative H NMR spectra of pure solvents deuterated chloroform and deuterated phenol (v:v = 3:1) without removing water. DETAILED DESCRIPTION

[0042] Nylon 6 and its copolymers are materials with excellent properties. The polyamide copolymer PACL, obtained through the ring-opening condensation cascade polymerization of aminocaproic acid and caprolactone, exhibits excellent mechanical properties and has great application potential in the field of polyamide elastomers. This paper proposes a method for component analysis of polyamides and their copolymers for the first time, providing accurate results and suitable for characterization of nylon 6 and PACL series products.

[0043] The specific embodiments of the present invention are further described in detail below in conjunction with the examples. The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention. In PACL-1.3, the molar fraction of aminocaproic acid monomer is 57%, and the molar fraction of caprolactone is 43%; in PACL-3 / 5, the molar fraction of aminocaproic acid monomer is 38%, and the molar fraction of caprolactone is 62%; the accuracy of the method of the present invention is verified by taking PACL-1.5 and PACL-3 / 5 as examples below, and the specific preparation operation is conventional technology. The nuclear magnetic hydrogen spectrum test was performed on an Agilent 600 MHz nuclear magnetic resonance spectrometer, and the nuclear magnetic parameters were: relaxation time of 20 seconds, and number of scans of 32 times. The molecular weight calculation formula of polyamide and its copolymer is as follows:

[0044] ,

[0045] In the formula, M n is the molecular weight of the polyamide or its copolymer; I 1 is the integral value of the chemical shift in the 2.1-3.1 ppm region, I 2 is the integral value in the 1.8-2.1 ppm region, I 3 is the integrated value at 3.4-3.7 ppm.

[0046] The calculation formula for the molar ratio of the two comonomers caprolactone and aminocaproic acid in the polyamide copolymer is as follows:

[0047] ,

[0048] In the formula, x is the mole fraction of the comonomer caprolactone in the polyamide copolymer, and y is the mole fraction of the comonomer aminocaproic acid in the polyamide copolymer; I 1 is the integral value of the chemical shift in the 2.1-3.1 ppm region, I 2 is the integrated value in the 1.8-2.1 ppm region. Example 1

[0049] This example provides a synthesis of a polyamide copolymer sample PACL-1.3, as shown below:

[0050] Add aminocaproic acid (30.3 g) and caprolactone (14.7 ml) to a 250 ml three-necked flask, remove oxygen with nitrogen, add 94 μl of n-butyl titanate, stir mechanically, heat to 240°C, react for 30 minutes under nitrogen atmosphere, and then vacuum polymerize for 180 minutes to synthesize the corresponding polyamide copolymer. The molar ratio of the comonomers aminocaproic acid and caprolactone is 1.5:1. The synthesis route is as follows: Figure 1 shown. Example 2

[0051] This example provides a synthesis of a polyamide copolymer sample PACL-3 / 5, as shown below:

[0052] In a 250 ml three-necked flask, aminocaproic acid (30.3 g) and caprolactone (43 ml) were added, nitrogen was passed through to remove oxygen, and 136 μl of n-butyl titanate was added. The mixture was mechanically stirred and heated to 240°C. The mixture was reacted for 30 minutes under a nitrogen atmosphere, and then vacuum polymerized for 180 minutes to synthesize the corresponding polyamide copolymer PACL-3 / 5. The molar ratio of the comonomers aminocaproic acid and caprolactone was 3:5. The synthesis route is as follows: Figure 1 shown. Example 3

[0053] This embodiment provides a component analysis method for nylon 6, which is specifically as follows:

[0054] Mix 0.2 mL of deuterated phenol and 0.6 mL of deuterated chloroform, add 200 mg of magnesium sulfate, let it stand for 12 hours, take 0.5 mL of the supernatant to dissolve 6.2 mg of nylon 6 sample to obtain a polyamide solution (deuterated chloroform: deuterated phenol = 3:1, v / v), and then perform quantitative nuclear magnetic resonance spectroscopy test, such as Figure 2 As shown in the figure, the sample peaks of polyamide near the amide bond are very clear, and the corresponding peaks are marked on the figure. Among them, the integral value of the 1.8-2.4 ppm region ( I 4) is 2120, the integral value of the 2.6-2.8 ppm region ( I 5) is 10. Based on the integral value, the molecular weight of nylon 6 is calculated to be 24.0 kg / mol. Example 4

[0055] This embodiment provides a component analysis method for a polyamide copolymer PACL-1.3, as follows:

[0056] 0.2 mL of deuterated phenol and 1.0 mL of deuterated chloroform were mixed, 200 mg of magnesium sulfate was added, and the mixture was allowed to stand for 12 hours. 0.5 mL of the supernatant was taken to dissolve 7.0 mg of the polyamide copolymer PACL-1.3 sample prepared in Example 1 to obtain a polyamide solution (deuterated chloroform: deuterated phenol = 5:1, v / v), and then quantitative nuclear magnetic resonance spectroscopy was performed. Figure 3 As shown in the figure, the sample peaks near the amide bond of the polyamide copolymer are very clear, and the corresponding peaks are marked on the figure. The integral value of the 2.1-3.1 ppm region ( I 1) is 762, the integral value in the 1.8-2.1 ppm region ( I 2) is the integral value of 1011, 3.4-3.7 ppm region ( I3) is 10. According to the integral value, the molecular weight of the polyamide copolymer is calculated to be 20.1 kg / mol, x:y = 762:1011, the molar fraction of the comonomer caprolactone is 43%, and the molar fraction of the comonomer aminocaproic acid is 57%.

[0057] The above experiment was repeated three times, with one day between each experiment. Based on the integral values, the caprolactone content of the polyamide copolymer PACL-1.3 was calculated to be 44% and the aminocaproic acid content was 56%, respectively. This demonstrates the high accuracy of the method of the present invention. Example 5

[0058] This embodiment provides a component analysis method for a polyamide copolymer PACL-1.3, as follows:

[0059] 0.2 mL of deuterated phenol and 0.8 mL of deuterated chloroform were mixed, 200 mg of magnesium sulfate was added, and the mixture was allowed to stand for 12 hours. 0.5 mL of the supernatant was taken to dissolve 5.8 mg of the polyamide copolymer PACL-1.3 sample prepared in Example 1 to obtain a polyamide solution (deuterated chloroform: deuterated phenol = 4:1, v / v), and then quantitative nuclear magnetic resonance spectroscopy was performed. Figure 4 As shown in the figure, the sample peaks near the amide bond of the polyamide copolymer are very clear, and the corresponding peaks are marked on the figure. The integral value of the 2.1-3.1 ppm region ( I 1) is 762, the integral value in the 1.8-2.1 ppm region ( I 2) is 1010, the integral value of the 3.4-3.7 ppm region ( I 3) is 10. According to the integral value, the molecular weight of the polyamide copolymer is calculated to be 20.2 kg / mol, x:y = 765:1010, the molar fraction of the comonomer caprolactone is 43%, and the molar fraction of the comonomer aminocaproic acid is 57%. Example 6

[0060] This embodiment provides a component analysis method for a polyamide copolymer PACL-1.3, as follows:

[0061] 0.2 mL of deuterated phenol and 0.6 mL of deuterated chloroform were mixed, 200 mg of magnesium sulfate was added, and the mixture was allowed to stand for 12 hours. 0.5 mL of the supernatant was taken to dissolve 6.4 mg of the polyamide copolymer PACL-1.3 sample prepared in Example 1 to obtain a polyamide solution (deuterated chloroform: deuterated phenol = 3:1, v / v), and then quantitative nuclear magnetic resonance spectroscopy was performed. Figure 5 As shown in the figure, the sample peaks near the amide bond of the polyamide copolymer are very clear, and the corresponding peaks are marked on the figure. The integral value of the 2.1-3.1 ppm region (I 1) is 758, the integral value in the 1.8-2.1 ppm region ( I 2) is 1006, the integral value of the 3.4-3.7 ppm region ( I 3) is 10. According to the integral value, the molecular weight of the polyamide copolymer is calculated to be 20.1 kg / mol, x:y = 758:1005, the molar fraction of the comonomer caprolactone is 43%, and the molar fraction of the comonomer aminocaproic acid is 57%. Example 7

[0062] This example provides a component analysis method for a polyamide copolymer PACL-3 / 5, as follows:

[0063] 0.2 mL of deuterated phenol and 1.2 mL of deuterated chloroform were mixed, 200 mg of magnesium sulfate was added, and the mixture was allowed to stand for 10 hours. 0.5 mL of the supernatant was taken to dissolve 10.1 mg of the polyamide copolymer PACL-3 / 5 sample prepared in Example 2 to obtain a polyamide solution (deuterated chloroform: deuterated phenol = 6:1, v / v), and then quantitative nuclear magnetic resonance spectroscopy was performed. Figure 6 As shown in the figure, the sample peaks near the amide bond of the polyamide copolymer are very clear, and the corresponding peaks are marked on the figure. The integral value of the 2.1-3.1 ppm region ( I 1) is 904, the integral value in the 1.8-2.1 ppm region ( I 2) is 541, the integral value in the 3.4-3.7 ppm region ( I 3) is 10. According to the integral value, the molecular weight of the polyamide copolymer is calculated to be 16.4 kg / mol, x:y = 904:541, the molar fraction of the comonomer caprolactone is 62%, and the molar fraction of the comonomer aminocaproic acid is 38%. Example 8

[0064] This example provides a component analysis method for a polyamide copolymer PACL-3 / 5, as follows:

[0065] 0.4 mL of deuterated phenol and 1.2 mL of deuterated chloroform were mixed, 400 mg of magnesium sulfate was added, and the mixture was allowed to stand for 15 hours. 0.5 mL of the supernatant was taken to dissolve 9.2 mg of the polyamide copolymer PACL-3 / 5 sample prepared in Example 2 to obtain a polyamide solution (deuterated chloroform: deuterated phenol = 3:1, v / v), and then quantitative nuclear magnetic resonance spectroscopy was performed. Figure 7 As shown in the figure, the sample peaks near the amide bond of the polyamide copolymer are very clear, and the corresponding peaks are marked on the figure. The integral value of the 2.1-3.1 ppm region ( I1) is 899, the integral value in the 1.8-2.1 ppm region ( I 2) is 539, the integral value in the 3.4-3.7 ppm region ( I 3) is 10. According to the integral value, the molecular weight of the polyamide copolymer is calculated to be 16.3 kg / mol, x:y = 899:539, the molar fraction of the comonomer caprolactone is 62%, and the molar fraction of the comonomer aminocaproic acid is 38%.

[0066] Comparative Example 1

[0067] This comparative example provides a H NMR spectrum test of a mixed solvent, as follows:

[0068] The mixed solvent of deuterated chloroform and deuterated phenol (v:v = 3:1) was subjected to nuclear magnetic resonance spectroscopy ( 1 H NMR) test, the results of which are as follows Figure 8 As shown in the figure, the solvent peaks were assigned. The peak with a chemical shift of approximately 7.3 ppm was attributed to chloroform, while the peaks at approximately 6.8 ppm, 6.9 ppm, and 7.2 ppm were attributed to phenol.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and such improvements and modifications should also be considered as the scope of protection of the present invention.

Claims

1. A component analysis method for polyamide or its copolymer, characterized in that: The following steps are involved: (1) Mixing deuterated phenol and deuterated chloroform, adding anhydrous magnesium sulfate or anhydrous sodium sulfate, and allowing to stand to remove water from the solvent to obtain a mixed solvent; the volume ratio of the deuterated phenol to the deuterated chloroform is 1: (2-6); (2) dissolving the polyamide or its copolymer in the mixed solvent described in step (1) to obtain a polyamide solution or a polyamide copolymer solution, and then performing quantitative nuclear magnetic resonance spectroscopy characterization, wherein the conditions for nuclear magnetic resonance spectroscopy characterization are: a relaxation time d1 value greater than or equal to 10 seconds, and a scanning number greater than or equal to 16 times; the polyamide is nylon 6, and the polyamide copolymer is a copolymer of aminocaproic acid and caprolactone; (3) Based on the results of the quantitative H-NMR characterization in step (2), the molecular weight of the polyamide or its copolymer and the molar fraction of the comonomer in the polyamide copolymer are calculated using the integral values ​​of the proton peak at the ortho position of the terminal hydroxyl group or amino group, the proton peak at the ortho position of the ester bond carbonyl group, and the proton peak at the ortho position of the amide bond carbonyl group, thereby achieving component analysis of the polyamide or its copolymer; The calculation formula of the molecular weight of the polyamide copolymer is as follows: ， in, M n is the molecular weight of the polyamide copolymer; I 1 is the integral value of the chemical shift in the 2.1ppm-3.1ppm region, I 2 is the integral value in the 1.8ppm-2.1ppm region, I 3 The integral value at 3.4ppm-3.7ppm; The calculation formula of the molecular weight of the polyamide is as follows: ， in, M n ( PA ) is the molecular weight of the polyamide; I 4 is the integral value of the chemical shift in the region of 1.8ppm-2.4ppm, I 5 It is the integral value in the 2.6ppm-2.8ppm region; The formula for calculating the comonomer mole fraction of polyamide copolymers is as follows: ， Wherein, x is the mole fraction of the comonomer caprolactone in the polyamide copolymer, and y is the mole fraction of the comonomer aminocaproic acid in the polyamide copolymer; I 1 is the integral value of the chemical shift in the 2.1ppm-3.1ppm region, I 2 It is the integrated value in the range of 1.8ppm-2.1ppm.

2. The component analysis method of polyamide or its copolymer according to claim 1, characterized in that: The volume ratio of the deuterated phenol to the deuterated chloroform is 1:(3-5).

3. The component analysis method of polyamide or its copolymer according to claim 1, characterized in that: The concentration of the solution of polyamide or its copolymer is 5 mg / mL to 20 mg / mL.

4. The component analysis method of polyamide or its copolymer according to claim 1, characterized in that: In step (2), the relaxation time d1 value is 10 seconds to 60 seconds, and the number of scans is 16 times to 48 times.

5. The component analysis method of polyamide or its copolymer according to claim 1, characterized in that: The molecular formula of the polyamide copolymer is: ， Among them, a is 1~10, b is 1~30, and n is 30~100.

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