Method for determining purity of gamma-aminopropyltriethoxysilane by automatic nitrogen determination apparatus

Abstract

The application discloses a method for determining the purity of gamma-aminopropyl triethoxysilane by using an automatic nitrogen determination instrument, and the steps comprise the following steps: mixing gamma-aminopropyl triethoxysilane standard and gamma-chloropropyl triethoxysilane standard according to different mass ratios to obtain a series of standard samples; performing digestion treatment on the standard samples, then detecting the nitrogen content by using the automatic nitrogen determination instrument to obtain a linear regression equation of the gamma-aminopropyl triethoxysilane content and the nitrogen content; performing digestion treatment on a gamma-aminopropyl triethoxysilane sample to be measured, then detecting the nitrogen content, and bringing the nitrogen content into the linear regression equation to obtain the purity of the gamma-aminopropyl triethoxysilane. The application firstly proposes to detect the purity of KH550 by using the automatic nitrogen determination instrument, the method is simple and rapid, reduces human errors, reduces the working strength, has high accuracy of the determination result, is easy to popularize and apply, and has substantial significance for determining the purity of KH550.

Description

TECHNICAL FIELD

[0001] The application relates to a method for measuring the purity of gamma-aminopropyl triethoxysilane (KH550), in particular to a method for detecting and analyzing the purity of KH550 by measuring the nitrogen content in KH550 with a Kjeldahl nitrogen determination instrument to determine the content of unreacted gamma2 in KH550, so as to determine the purity of KH550, and belongs to the technical field of chemical analysis. BACKGROUND

[0002] The silane coupling agent KH-550 is a kind of low-molecular organic silicon compound with a special structure, and its general formula is RSiX3, wherein R represents an active functional group with affinity or reaction capacity for a polymer molecule, such as an oxy group, a mercapto group, a vinyl group, an epoxy group, an amide group, an aminopropyl group and the like; and X represents an alkoxyl group capable of hydrolysis, such as a halogen, an alkoxy group, an acyloxy group and the like. The gamma-aminopropyl triethoxysilane (KH-550) is a general-purpose coupling agent, which can almost couple with various resins to meet the requirements for improving the mechanical strength, electrical properties and anti-aging properties of composite materials in the fields of glass fiber reinforced plastic, plastic, adhesive, casting, textile printing and dyeing and the like.

[0003] The existing production process of KH-550 is generally as follows: gamma-chloropropyl triethoxysilane (gamma2) and ammonia are mixed at a molar ratio of about 1:20, and then subjected to amination reaction at a pressure of 5.5-9.0 MPa and a temperature of about 90 DEG C for 6-10 hours; after the reaction, the by-product NH4Cl is separated and removed; and then the filtrate is subjected to vacuum distillation to obtain the product, wherein the impurities in the product are mainly gamma-chloropropyl triethoxysilane (gamma2). Due to the process and technical reasons, the purity of the KH-550 product produced by the existing technology is below 98% (GC), and the main impurity therein is the unreacted gamma-chloropropyl triethoxysilane residue. In the field of glass fiber reinforced composite materials, the purity of KH-550 is required to be high, and the KH-550 with low purity and high impurity content brings great harm to the application and cannot be used in the above-mentioned fields, so it is very important to measure the purity of KH-550.

[0004] At present, the method for detecting the purity of KH-550 mainly is gas chromatography, but the boiling points of the gamma-aminopropyl triethoxysilane (KH-550) and the gamma-chloropropyl triethoxysilane (gamma2) are similar, and the structures are similar, so the two substances are difficult to be well separated by gas chromatography, thereby causing a large error in the test data and the detection result of the purity is not accurate.

[0005] The Kjeldahl nitrogen analyzer is an instrument that calculates protein content by measuring the nitrogen content in a sample, based on the principle that the nitrogen content in proteins is constant. Because the method used to measure and calculate protein content is called the Kjeldahl method, it is called a Kjeldahl nitrogen analyzer. Currently, there are reports of Kjeldahl nitrogen analyzers being used in the detection of grains, food, feed, water, soil, and sludge, demonstrating a good cost-performance ratio. However, no applications of Kjeldahl nitrogen analyzers in the detection of KH-550 samples have been reported. Summary of the Invention

[0006] To address the problems of existing analytical methods' difficulty in separating γ-aminopropyltriethoxysilane (KH-550) and γ-chloropropyltriethoxysilane (γ2), and the low accuracy of γ-aminopropyltriethoxysilane (KH-550) purity detection results, this invention provides a method for determining the purity of γ-aminopropyltriethoxysilane using an automated nitrogen analyzer. This method utilizes the characteristic that KH-550 contains nitrogen while γ2 does not, employing an automated nitrogen analyzer to detect the nitrogen content in the sample, thereby determining the purity of KH-550. The detection method is simple and highly accurate.

[0007] The specific technical solution of this invention is as follows:

[0008] A method for determining the purity of γ-aminopropyltriethoxysilane using an automated nitrogen analyzer, the method comprising the following steps:

[0009] (1) Preparation of standard samples: γ-aminopropyltriethoxysilane standard and γ-chloropropyltriethoxysilane standard were mixed in different mass ratios to obtain a series of standard samples;

[0010] (2) The standard samples from step (1) are placed into the digestion tubes of the digestion furnace for digestion treatment to obtain a series of standard sample solutions.

[0011] (3) The standard sample solutions after digestion and cooling in step (2) were tested by an automatic nitrogen analyzer to obtain the nitrogen content of different standard samples.

[0012] (4) A standard curve of γ-aminopropyltriethoxysilane content versus nitrogen content was prepared, and a linear regression equation was obtained;

[0013] (5) Add the γ-aminopropyltriethoxysilane sample to be tested into the digestion tube of the digestion furnace for digestion treatment to obtain the sample solution to be tested.

[0014] (6) The sample solution from step (5) is tested using an automatic nitrogen analyzer to obtain the nitrogen content of the sample.

[0015] (7) Substitute the nitrogen content of the sample to be tested into the linear regression equation to obtain the content of γ-aminopropyltriethoxysilane in the sample to be tested.

[0016] Furthermore, the automatic nitrogen analyzer is a Kjeldahl nitrogen analyzer, which is an existing instrument with a high degree of automation and is easy to operate.

[0017] Furthermore, in step (1), both the γ-aminopropyltriethoxysilane standard and the γ-chloropropyltriethoxysilane standard are pure products with high purity, and their purity is greater than 99%.

[0018] Further, in step (1), γ-aminopropyltriethoxysilane standard and γ-chloropropyltriethoxysilane standard are mixed to obtain a series of standard samples, wherein the γ-aminopropyltriethoxysilane standard and γ-chloropropyltriethoxysilane standard are mixed according to the rule that the mass percentage of γ-aminopropyltriethoxysilane standard in the standard sample is 100%, 90%, 80%, 70%, 60%, and 50%, respectively.

[0019] Furthermore, in step (1), since the nitrogen content in the γ-aminopropyltriethoxysilane standard and the γ-chloropropyltriethoxysilane standard is fixed, the theoretical nitrogen content ω in different standard samples can be calculated according to the formula.

[0020]

[0021] Where m1 is the mass of KH-550;

[0022] m2 is the mass of γ2.

[0023] Furthermore, in steps (2) and (5), the digestion process is as follows: 0.1-0.2g of standard sample or test sample is placed into the digestion tube of the digestion furnace, 3.2g of catalyst and 10ml of concentrated sulfuric acid are added, and then the sample is heated on the digestion furnace to dissolve the sample. The digestion is continued until the sample solution turns yellow-green or blue-green, and then the digestion is stopped and the sample is cooled.

[0024] Furthermore, during the digestion process, the catalyst is a mixture of potassium sulfate and anhydrous copper sulfate in a mass ratio of 15:1.

[0025] Furthermore, during the digestion process, the temperature of the sample dissolved in the digestion furnace is first raised from room temperature to 180°C for 20 minutes, then raised to 350°C for 20 minutes, and then raised to 420°C for 60 minutes.

[0026] Furthermore, in steps (3) and (6), the step of using an automatic nitrogen analyzer to detect nitrogen content is as follows: the detection conditions of the automatic nitrogen analyzer are set as follows: the volume of water is 20 ml, the volume of 40% (W / V) sodium hydroxide solution is 40 ml, and the volume of boric acid mixed solution is 20 ml; after the conditions are set, the digestion tube is placed on the automatic nitrogen analyzer for distillation for 5 min, and while distilling, it is titrated with 0.1 mol / L hydrochloric acid standard titration solution. The titration ends when the solution changes from blue-green to light red. The nitrogen content can be calculated based on the amount of hydrochloric acid standard titration solution used. The automatic nitrogen analyzer can automatically calculate the nitrogen content data.

[0027] Furthermore, the boric acid mixed solution is obtained by mixing methyl red and bromocresol green mixed indicator with 20 g / L boric acid solution at a volume ratio of 1:100, and the methyl red and bromocresol green mixed indicator is obtained by mixing equal volumes of 1 g / L methyl red ethanol solution and 5 g / L bromocresol green ethanol solution.

[0028] This invention rapidly determines the nitrogen content in KH550 using an automated nitrogen analyzer, thereby determining the γ2 content and purity of KH550. The automated nitrogen analyzer has a testing range of 0.1 mg to 240 mg, and KH-550 contains amino functional groups, with its nitrogen content falling within this range, providing better analytical basis. This invention is the first to propose using an automated nitrogen analyzer to determine the purity of KH550. This method is simple, rapid, reduces human error, lowers workload, and provides high accuracy, making it easy to promote and apply. It has substantial significance for determining the purity of KH550. Attached Figure Description

[0029] Figure 1 This is a standard curve showing the relationship between the content of KH550 standard and the detected nitrogen content. Detailed Implementation

[0030] The technical solution of the present invention will be further explained and described below through specific embodiments. It should be understood that the following non-limiting embodiments can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0031] In the following examples, the purity of the γ-aminopropyltriethoxysilane standard used was 99.4%, purchased from Bailingwei; the purity of the γ-chloropropyltriethoxysilane standard used was 99.2%, purchased from Bailingwei.

[0032] In the following examples, the γ-aminopropyltriethoxysilane sample was obtained from Shandong Yanggu Huatai Chemical Co., Ltd.

[0033] Example 1

[0034] An automated nitrogen analyzer was used to determine the linear relationship between the KH550 content and nitrogen content in mixtures of KH-550 and γ2 in known proportions. The steps are as follows:

[0035] (1) Filter the γ-aminopropyltriethoxysilane (KH-550) standard and the γ-chloropropyltriethoxysilane (γ2) standard through a 0.22 μm filter and set aside for later use;

[0036] (2) Accurately weigh the filtered γ-aminopropyltriethoxysilane (KH-550) standard and γ-chloropropyltriethoxysilane (γ2) standard, and mix the γ-aminopropyltriethoxysilane standard and γ-chloropropyltriethoxysilane standard in proportions of 100%, 90%, 80%, 70%, 60% and 50% by mass of γ-aminopropyltriethoxysilane standard to obtain six sets of standard samples.

[0037] (3) Take 0.1814g of each of the above standard samples and put them into the digestion tube of the digestion furnace. Add 3.0g of K2SO4 and 0.2g of CuSO4·5H2O to the digestion tube, then add 10mL of concentrated sulfuric acid. Then place the digestion tube in the digestion furnace and first heat it from room temperature to 180℃ for 20min, then heat it to 350℃ for 20min, then heat it to 420℃ for 60min. The sample solution turns blue-green. The digestion is finished. Cool it to room temperature.

[0038] (4) Set the detection conditions of the Kjeldahl automatic nitrogen analyzer as follows: 20 ml of water, 40 ml of 40% (W / V) sodium hydroxide solution, and 20 ml of boric acid mixed solution. The boric acid mixed solution is obtained by mixing methyl red and bromocresol green mixed indicator with 20 g / L boric acid solution at a volume ratio of 1:100. The methyl red and bromocresol green mixed indicator is obtained by mixing equal volumes of 1 g / L methyl red ethanol solution and 5 g / L bromocresol green ethanol solution.

[0039] After setting the conditions, the digestion tube, cooled to room temperature, was placed on an automatic nitrogen analyzer for distillation for 5 minutes. During distillation, it was titrated with a 0.1 mol / L hydrochloric acid standard titration solution. The titration endpoint was reached when the solution changed from blue-green to light red. The Kjeldahl nitrogen analyzer calculated the nitrogen content of different standard samples based on the amount of hydrochloric acid standard titration solution used, as shown in Table 1 below.

[0040] According to the formula The theoretical nitrogen content of different standard samples was calculated, and the results are shown in Table 1 below.

[0041] Where m1 is the mass of the KH-550 standard product;

[0042] m2 represents the mass of the γ2 standard.

[0043] Table 1 Sample Test Data Results

[0044]

[0045] As can be seen from Table 1, the nitrogen content obtained by the method of the present invention is very close to the theoretical nitrogen content, and the accuracy of the detection results is high.

[0046] (5) Compile a standard curve of the mass ratio of KH-550 standard and γ2 standard versus the detected nitrogen content, i.e., a standard curve of KH-550 standard content versus detected nitrogen content, and obtain a linear regression equation, such as... Figure 1 As shown in the figure, the correlation coefficient of the linear regression equation is 0.9991, indicating a good linear relationship between KH-550 content and nitrogen content. Therefore, it is feasible to use nitrogen content to determine KH-550 content.

[0047] Example 2

[0048] The purity of an unknown KH550 sample was determined using the following method:

[0049] 1. Filter the KH550 sample through a 0.22μm filter, and then weigh four 0.1668g portions of the KH550 sample for later use;

[0050] 2. Place 0.1668g of KH550 sample into a digestion tube in a digestion furnace. Add 3.0g of K2SO4 and 0.2g of CuSO4·5H2O to the digestion tube, followed by 10mL of concentrated sulfuric acid. Then place the digestion tube in the digestion furnace and digest at 180℃ for 20 minutes, then at 350℃ for 20 minutes, and finally at 420℃ for 60 minutes. The sample solution will turn blue-green. Digestion is then complete. Cool to room temperature. The procedure is the same for each KH550 sample.

[0051] 3. Set the detection conditions of the Kjeldahl automatic nitrogen analyzer as follows: 20 ml of water, 40 ml of 40% (w / v) sodium hydroxide solution, and 20 ml of boric acid mixed solution. The boric acid mixed solution is prepared by mixing methyl red and bromocresol green mixed indicator with 20 g / L boric acid solution at a volume ratio of 1:100. The methyl red and bromocresol green mixed indicator is prepared by mixing equal volumes of 1 g / L methyl red ethanol solution and 5 g / L bromocresol green ethanol solution.

[0052] After setting the conditions, the digestion tubes, cooled to room temperature, were placed in an automatic nitrogen analyzer for distillation for 5 minutes. During distillation, titration was performed using a 0.1 mol / L hydrochloric acid standard titration solution. The titration endpoint was reached when the solution changed from blue-green to pale red. The nitrogen content of the KH550 sample was calculated based on the volume of hydrochloric acid standard titration solution used. The nitrogen contents of the four samples were 6.199%, 6.217%, 6.206%, and 6.198%, respectively. The average nitrogen content of these four groups was taken as 6.205%, which was used as the nitrogen content of the sample.

[0053] 4. Substituting the above average nitrogen content into the linear regression equation of Example 1, we obtained that the KH550 content of the sample was 98.3%, that is, the KH550 purity of the sample was 98.3%.

[0054] The above description is only a partial embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining the purity of γ-aminopropyltriethoxysilane using an automated nitrogen analyzer, characterized in that: Includes the following steps: (1) Preparation of standard samples: γ-aminopropyltriethoxysilane standard and γ-chloropropyltriethoxysilane standard were mixed in different mass ratios to obtain a series of standard samples; (2) The standard samples from step (1) are placed into the digestion tubes of the digestion furnace for digestion treatment to obtain a series of standard sample solutions. (3) The standard sample solutions after digestion and cooling in step (2) were tested by an automatic nitrogen analyzer to obtain the nitrogen content of different standard samples. (4) Plot the standard curve of γ-aminopropyltriethoxysilane content versus nitrogen content to obtain the linear regression equation; (5) Add the γ-aminopropyltriethoxysilane sample to be tested into the digestion tube of the digestion furnace for digestion treatment to obtain the sample solution to be tested. (6) The sample solution from step (5) is tested using an automatic nitrogen analyzer to obtain the nitrogen content of the sample. (7) Substitute the nitrogen content of the sample to be tested into the linear regression equation to obtain the content of γ-aminopropyltriethoxysilane in the sample to be tested.

2. The method according to claim 1, characterized in that: The automatic nitrogen analyzer is a Kjeldahl nitrogen analyzer.

3. The method according to claim 1, characterized in that: In step (1), γ-aminopropyltriethoxysilane standard and γ-chloropropyltriethoxysilane standard are mixed at a mass percentage of 100%, 90%, 80%, 70%, 60% and 50% respectively to obtain a series of standard samples.

4. The method according to claim 1, characterized in that: In step (1), the purity of both γ-aminopropyltriethoxysilane standard and γ-chloropropyltriethoxysilane standard is greater than 99%.

5. The method according to claim 1, characterized in that: In steps (2) and (5), the digestion process is as follows: 0.1-0.2g of standard sample or test sample is placed into the digestion tube of the digestion furnace, 3.2g of catalyst and 10ml of concentrated sulfuric acid are added, and then the sample is heated on the digestion furnace to dissolve the sample. The digestion is continued until the sample solution turns yellow-green or blue-green, and then the digestion is stopped and the sample is cooled.

6. The method according to claim 5, characterized in that: During digestion, the catalyst is a mixture of potassium sulfate and anhydrous copper sulfate in a mass ratio of 15:

1.

7. The method according to claim 5, characterized in that: During the digestion process, the temperature of the sample was first raised from room temperature to 180℃ for 20 minutes, then raised to 350℃ for 20 minutes, and then raised to 420℃ for 60 minutes.

8. The method according to claim 1, characterized in that: In steps (3) and (6), the steps for detecting nitrogen content using an automatic nitrogen analyzer are as follows: Set the detection conditions of the automatic nitrogen analyzer to: water volume of 20 ml, sodium hydroxide solution volume of 40 ml, and boric acid mixed solution volume of 20 ml; after setting the conditions, place the digestion tube on the automatic nitrogen analyzer for distillation for 5 min, and titrate with 0.1 mol / L hydrochloric acid standard titration solution while distilling. The titration ends when the solution changes from blue-green to light red. The Kjeldahl nitrogen analyzer automatically calculates the nitrogen content based on the amount of hydrochloric acid standard titration solution used.

9. The method according to claim 8, characterized in that: The boric acid mixed solution is obtained by mixing methyl red and bromocresol green mixed indicator with 20 g / L boric acid solution at a volume ratio of 1:

100. The methyl red and bromocresol green mixed indicator is obtained by mixing equal volumes of 1 g / L methyl red ethanol solution and 5 g / L bromocresol green ethanol solution.

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