Method for detecting content of silicon dioxide in high-absorptivity resin

Abstract

The invention discloses a method for detecting the content of silicon dioxide in high-absorptivity resin, which comprises the following steps: 1) weighing a resin sample with required mass, putting the resin sample into a container, adding a proper amount of solvent, and melting at high temperature; 2) cooling the molten sample to room temperature, extracting the molten sample with an acid solution, and filtering; 3) taking the filtrate with the required volume, and adding an ammonium molybdate solution to generate silicon molybdenum heteropoly acid; 4) adding a reducing agent to reduce the silicon molybdenum heteropoly acid; (5) after the color development reaction, adding the solution into a cuvette, and determining by using a visible light spectrophotometric method under a specific wavelength; (6) preparing a series of silicon dioxide standard solutions with known concentrations, and treating according to the steps (3)-(5); and 7) drawing a standard curve, and calculating the content of silicon dioxide in an unknown sample through the standard curve. The method has the beneficial effects that the detection method is efficient and simple and convenient to operate, and has the characteristics of good precision and high accuracy.

Description

Technical Field

[0001] The invention relates to the field of chemical detection and analysis, and in particular to a method for detecting silicon dioxide content in a high-absorbency resin. Background Art

[0002] Superabsorbent resin, also known as super absorbent polymer (SAP), is a material that can quickly absorb and retain large amounts of water or other liquids. Such resins are usually three-dimensional network structure polymers synthesized from hydrophilic monomers through cross-linking reactions. Their characteristic is that they can swell to form gels after absorbing liquids, but they will not dissolve in water. These materials are usually non-toxic, harmless, and even biodegradable materials. Their water absorption can reach hundreds or even thousands of times their own weight, and their water absorption capacity far exceeds that of ordinary materials. The hydrogel formed after swelling with water absorption can still maintain a certain structural strength, is not easy to break, can keep water from being lost for a long time, and is difficult to squeeze out water even under pressure. Due to the unique properties of superabsorbent resins, they are widely used in medical and health care, agricultural and horticultural, industrial applications, disaster emergency response, daily life and other fields. With the advancement of technology, new application scenarios are also constantly being developed.

[0003] There are two main methods for making superabsorbent resins: solution polymerization and suspension polymerization. Both methods use hydrophilic monomers (such as acrylic acid), crosslinking agents, and initiators. After the polymerization reaction is completed, subsequent processing steps such as drying and crushing are required to obtain the final product. Different additives are added to optimize product performance to meet different application requirements. Silica powder is usually added as a filler to improve the fluidity and dispersibility of the resin and to increase the mechanical strength and thermal stability of the resin. The amount of silica powder added needs to be carefully controlled to ensure the desired effect without negatively affecting the basic properties of the resin.

[0004] Therefore, controlling and measuring the content of silica in superabsorbent resins is of great significance for producing superabsorbent resins required for specific applications, ensuring product quality, optimizing performance, and improving production processes.

[0005] In summary, there is an urgent need for a method that is simple to operate and quantitatively and accurately detects the content of silicon dioxide in superabsorbent resins. Summary of the invention

[0006] The technical problems to be solved by the present invention are:

[0007] Provided is a method for detecting the content of silicon dioxide in a highly absorbent resin, the method having good precision and high accuracy.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for detecting the content of silicon dioxide in a high absorbent resin comprises the following steps:

[0010] 1) Weigh the required mass of resin sample and place it in a container, add flux and melt it at high temperature;

[0011] 2) Cooling the melted sample to room temperature, extracting the melted sample with an acid solution, and filtering;

[0012] 3) taking the required volume of the filtrate, adding ammonium molybdate solution to generate heteropoly silicomolybdic acid;

[0013] 4) adding a reducing agent to reduce the heteropolysilicomolybdic acid;

[0014] 5) After the color development reaction, the solution is added to a cuvette and measured by visible light spectrophotometry at a specific wavelength;

[0015] 6) preparing a series of silica standard solutions with known concentrations and treating them according to steps 3) to 5);

[0016] 7) Draw a standard curve and calculate the content of silicon dioxide in the unknown sample through the standard curve;

[0017] The calculation formula is: the content of silicon dioxide in the sample C (%) = the silicon dioxide concentration measured in the sample solution (mg / L) × 0.0002 / the mass of the test sample (g).

[0018] As a further improvement of this scheme, in step 1),

[0019] The mass of the resin sample is 0.1 to 0.5 g;

[0020] The container is a platinum crucible.

[0021] As a further improvement of this scheme, in step 1),

[0022] The flux is at least one of sodium carbonate, potassium carbonate and lithium carbonate;

[0023] Furthermore, the amount of flux added is 0.5 to 5.0 g.

[0024] As a further improvement of this solution, in step 1), the high temperature is 600-1000° C., and the melting time is 10-30 min.

[0025] As a further improvement of this scheme, in step 2), the acid solution is at least one of sulfuric acid, nitric acid, and hydrochloric acid;

[0026] Furthermore, the acid solution is an acid solution prepared by mixing 1 volume of concentrated acid with 1 volume of water or an acid solution prepared by mixing 1 volume of concentrated acid with 2 volumes of water;

[0027] Furthermore, the amount of the acid solution added is 5 to 100 ml.

[0028] As a further improvement of this solution, in step 2), the obtained extract is filtered using a 0.45 μm water-based microporous filter head.

[0029] As a further improvement of this scheme,

[0030] In step 3), the sampling volume of the filtrate is 1 to 20 ml.

[0031] The volume of the ammonium molybdate solution is 2 to 10 ml;

[0032] And, the concentration of the ammonium molybdate solution is 100 g / L.

[0033] As a further improvement of this scheme, in step 4), the reducing agent is at least one of ascorbic acid, potassium sodium tartrate, ferrous sulfate, ammonium ferrous sulfate, and stannous chloride;

[0034] Furthermore, the concentration of the reducing agent is 100 g / L;

[0035] Furthermore, the amount of the reducing agent added is 2 to 10 ml.

[0036] As a further improvement of this scheme,

[0037] In step 5), the temperature of the color development reaction is 20-30°C;

[0038] And, the reaction time is 10 to 40 minutes.

[0039] The optical path of the cuvette is 5 to 30 mm;

[0040] Moreover, the test wavelength of the visible light spectrophotometry is 640 nm. Compared with the prior art, the present invention is reasonably designed and has the following beneficial effects:

[0041] 1) High sensitivity, can effectively detect low concentration (0.01% ~ 0.10%) of silica;

[0042] 2) Accurate quantitative analysis, based on the absorption characteristics of substances to a specific wavelength of 640nm light for concentration measurement;

[0043] 3) Easy to operate, sample preparation steps and instrument operation procedures are relatively simple;

[0044] 4) Environmentally friendly. Compared with some methods that require the use of a large amount of chemical reagents, the method of the present invention generates less waste. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described below in conjunction with embodiments:

[0046] Example 1

[0047] A method for detecting the content of silicon dioxide in a high absorbent resin comprises the following steps:

[0048] 1) Weigh a certain amount of resin sample and place it in a clean container, add an appropriate amount of flux and melt it at high temperature;

[0049] 2) Cooling the melted sample to room temperature, extracting the melted sample with an acid solution, and filtering;

[0050] 3) taking a certain volume of the filtrate, adding ammonium molybdate solution to generate heteropoly silicomolybdic acid;

[0051] 4) adding a reducing agent to reduce the heteropolysilicomolybdic acid;

[0052] 5) After the color development reaction has taken place for a certain period of time, the solution is added to a cuvette and measured by visible light spectrophotometry at a specific wavelength;

[0053] 6) preparing a series of silica standard solutions with known concentrations and treating them according to steps 3) to 5);

[0054] 7) Draw a standard curve and calculate the content of silica in unknown samples using the standard curve.

[0055] The sample treatment process includes the following steps: weighing 0.2g of a high absorbent resin sample and placing it in a clean preheated platinum crucible, adding 2.0g of sodium carbonate, heating to 800°C on an electric furnace, melting for 30min, taking the crucible out of the electric furnace and cooling it naturally to room temperature, adding 40ml of a 1:1 (volume ratio) sulfuric acid solution to the crucible, stirring it sufficiently to ensure complete dissolution, filtering the resulting extract with a 0.45μm water-based microporous filter head, taking 10ml of the filtrate and adding it to a 50ml plastic volumetric flask, adding 3ml of ammonium molybdate, placing it at 23°C for 15min, adding 3ml of ascorbic acid solution, placing it at 23°C for 20min, and diluting it to 50ml with pure water. The solution is added to a 20mm cuvette and detected with a spectrophotometer at a wavelength of 640nm.

[0056] Take 0.00, 0.50, 1.00, 2.00, 3.00, 4.00 mL of a standard silica solution with a concentration of 100 mg / L and add it to 6 50 ml plastic volumetric bottles, add 10 ml of 1:1 (volume ratio) sulfuric acid solution, add 3 ml of ammonium molybdate, place at 23 ° C for 15 minutes, add 3 ml of ascorbic acid solution, place at 23 ° C for 20 minutes, and then dilute to 50 ml with pure water. The above standard solutions are added to a 20 mm colorimetric dish in turn, and the absorbance value is measured at 640 nm with a spectrophotometer. Draw a standard curve with the concentration of silica as the horizontal coordinate and the absorbance as the vertical coordinate. The linear coefficient of the standard curve can reach 0.995 or even higher.

[0057] Using water as a reference, measure the absorbance of the sample solution and obtain the concentration of silicon dioxide in the sample solution from the standard curve.

[0058] Calculation: The content of silicon dioxide in the sample C (%) = the silicon dioxide concentration measured in the sample solution (mg / L) × 0.0002 / the mass of the test sample (g)

[0059] Example 2

[0060] A method for detecting the content of silicon dioxide in a highly absorbent resin specifically comprises the following steps: 1) weighing a certain amount of resin sample and placing it in a clean container, adding an appropriate amount of flux and melting it at high temperature; 2) cooling the melted sample to room temperature, extracting the melted sample with an acid solution, and filtering; 3) taking a certain volume of filtrate, adding ammonium molybdate solution to generate silicomolybdic heteropoly acid; 4) adding a reducing agent to reduce the silicomolybdic heteropoly acid; 5) after a certain period of color development reaction, adding the solution to a colorimetric dish, and measuring it by visible light spectrophotometry at a specific wavelength; 6) preparing a series of silicon dioxide standard solutions with known concentrations, and processing them according to steps 3) to 5); 7) drawing a standard curve, and calculating the content of silicon dioxide in unknown samples by the standard curve.

[0061] The sample treatment process includes the following steps: weighing 0.2g of a high absorbent resin sample and placing it in a clean preheated platinum crucible, adding 2.0g of sodium carbonate, heating to 900°C on an electric furnace, melting for 20min, removing the crucible from the electric furnace and cooling it naturally to room temperature, adding 40ml of a 1:1 (volume ratio) sulfuric acid solution to the crucible, stirring it sufficiently to ensure complete dissolution, filtering the resulting solution with a 0.45μm water-based microporous filter head, taking 10ml of the filtrate and adding it to a 50ml plastic volumetric flask, adding 3ml of ammonium molybdate, placing it at 28°C for 10min, adding 3ml of ascorbic acid solution, placing it at 28°C for 15min, and diluting it to 50ml with pure water. The solution is added to a 20mm cuvette and detected with a spectrophotometer at a wavelength of 640.

[0062] Take 0.00, 0.50, 1.00, 2.00, 3.00, 4.00 mL of a standard silica solution with a concentration of 100 mg / L and add it to 6 50 ml plastic volumetric bottles, add 10 ml of 1:1 (volume ratio) sulfuric acid solution, add 3 ml of ammonium molybdate, place at 28 ° C for 10 minutes, add 3 ml of ascorbic acid solution, place at 28 ° C for 15 minutes, and then dilute to 50 ml with pure water. Add the above standard solutions to a 20 mm colorimetric dish in turn, and measure the absorbance value at 640 nm with a spectrophotometer. Draw a standard curve with the concentration of silica as the horizontal coordinate and the absorbance as the vertical coordinate. Using water as a reference, measure the absorbance of the sample solution, and find the concentration of silica in the sample solution from the standard curve. The linear coefficient of the standard curve can reach 0.995 or even higher.

[0063] Calculation: The content of silicon dioxide in the sample C (%) = the silicon dioxide concentration measured in the sample solution (mg / L) × 0.0002 / the mass of the test sample (g)

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 1 is that 0.2 g of a resin sample with a known silicon dioxide content of 0.1% is taken and melt-treated without using sodium carbonate, while the other steps are the same as those in Example 1.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 2 is that the amount of ammonium molybdate solution added is 0 ml, and the other steps, including drawing the standard curve, are the same as those in Example 2.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 2 is that the amount of ammonium molybdate solution added is 1 ml, and the other steps, including drawing the standard curve, are the same as those in Example 2.

[0070] Comparative Example 4

[0071] The difference between this comparative example and Example 2 is that the amount of ascorbic acid solution added is 0 ml, and the other steps, including drawing the standard curve, are the same as those in Example 2.

[0072] Comparative Example 5

[0073] The difference between this comparative example and Example 2 is that the amount of ascorbic acid solution added is 1 ml, and the other steps, including drawing the standard curve, are the same as those in Example 2.

[0074] Performance Test:

[0075] 1. Precision test: Weigh 6 samples of water-absorbent resin and perform tests according to the above steps. Relative standard deviation = (standard deviation of test results / average value of results)*100%.

[0076] 2. Accuracy test: Perform a spike recovery test, spike recovery rate = (spike sample measurement value - sample measurement value) / spike amount × 100%.

[0077] Specific performance test data is shown in Table 1.

[0078] Table 1: Performance test results

[0079] content,% Relative standard deviation, % Spike recovery, % Example 1 0.096 1.18 98.5 Example 2 0.102 1.36 97.7 Comparative Example 1 Not detected / / Comparative Example 2 Not detected / / Comparative Example 3 0.052 7.61 60.7 Comparative Example 4 Not detected / / Comparative Example 5 0.067 5.38 71.8

[0080] It can be seen from Table 1 that the relative standard deviation and the spiked recovery rate of Example 1 and Example 2 of the present invention are better than those of Comparative Example 3 and Comparative Example 5. The relative standard deviation of the embodiments is small, and the spiked recovery rate is closer to 100%, indicating that the detection method described in the present invention has good precision and high accuracy.

[0081] Compared with Example 1, the melting temperature of Example 2 is increased by 100°C, the color development temperature is increased by 5°C, the melting time is shortened by 10 minutes, and the color development time is shortened by 5 minutes. The final test results show that the effects of the two examples are basically the same.

[0082] The results of Comparative Example 1 show that no silicon dioxide was detected in the sample solution, indicating that the silicon dioxide in the resin cannot be converted into soluble silicates using only sulfuric acid at room temperature. However, Examples 1 and 2 show that silicon dioxide can react with sodium carbonate in a high-temperature molten state to be converted into soluble silicon, and then converted into silicates after adding sulfuric acid. The pretreatment method using high-temperature melting of sodium carbonate can improve the sample processing efficiency and ensure the complete extraction of silicon, laying the foundation for subsequent accurate determination.

[0083] In Comparative Example 2, since ammonium molybdate was not added, silicate was not converted into yellow silicomolybdic heteropoly acid, and the subsequent addition of ascorbic acid could not produce a color reaction, and accordingly, silicon dioxide could not be detected.

[0084] In comparative example 3, due to the small amount of ammonium molybdate added, the silicate in the sample solution did not react completely with the ammonium molybdate, and the generated silicomolybdic heteropoly acid was relatively small. Accordingly, the generated amount of silicomolybdic blue was also relatively small, resulting in a low recovery rate and poor precision. The generation of silicomolybdic heteropoly acid by ammonium molybdate and soluble silicon is a key step in this method. It not only specifically identifies the silicon element, but also provides a clear chemical basis for subsequent photometric measurements.

[0085] In Comparative Example 4, since ascorbic acid was not added, silicon still existed in the solution system in the form of silicomolybdic heteropoly acid, which had no obvious absorption peak at 640 nm and could not be detected.

[0086] In Comparative Example 5, due to the small amount of ascorbic acid added, the silicomolybdenum heteropoly acid was not completely reduced by ascorbic acid, and the generated silicomolybdenum blue was relatively small, resulting in a low recovery rate and poor precision.

[0087] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent changes made using the present invention are within the patent protection scope of the present invention.

Claims

1. A method for detecting the content of silicon dioxide in a high absorbent resin, characterized in that: The following steps are included: 1) Weigh the required mass of resin sample and place it in a container, add flux and melt it at high temperature; 2) Cooling the melted sample to room temperature, extracting the melted sample with an acid solution, and filtering; 3) taking the required volume of the filtrate, adding ammonium molybdate solution to generate heteropoly silicomolybdic acid; 4) adding a reducing agent to reduce the heteropolysilicomolybdic acid; 5) After the color development reaction, the solution is added to a cuvette and measured by visible light spectrophotometry at a specific wavelength; 6) preparing a series of silica standard solutions of known concentrations and treating them according to steps 3) to 5); 7) Draw a standard curve and calculate the content of silicon dioxide in the unknown sample through the standard curve; The calculation formula is: the content of silicon dioxide in the sample C (%) = the silicon dioxide concentration measured in the sample solution (mg / L) × 0.0002 / the mass of the test sample (g).

2. The method for detecting the content of silicon dioxide in a highly absorbent resin according to claim 1, characterized in that: In step 1), The mass of the resin sample is 0.1 to 0.5 g; The container is a platinum crucible.

3. The method for detecting the content of silicon dioxide in a highly absorbent resin according to claim 1, characterized in that: In step 1), The flux is at least one of sodium carbonate, potassium carbonate and lithium carbonate; Furthermore, the amount of flux added is 0.5 to 5.0 g.

4. The method for detecting the content of silicon dioxide in a highly absorbent resin according to claim 1, characterized in that: In step 1), the high temperature is 600-1000° C., and the melting time is 10-30 minutes.

5. The method for detecting the content of silicon dioxide in a highly absorbent resin according to claim 1, characterized in that: In step 2), the acid solution is at least one of sulfuric acid, nitric acid, and hydrochloric acid; Furthermore, the acid solution is an acid solution prepared by mixing 1 volume of concentrated acid with 1 volume of water or an acid solution prepared by mixing 1 volume of concentrated acid with 2 volumes of water; Furthermore, the amount of the acid solution added is 5 to 100 ml.

6. The method for detecting the content of silicon dioxide in a highly absorbent resin according to claim 1, characterized in that: In step 2), the obtained extract is filtered using a 0.45 μm water-based microporous filter head.

7. The method for detecting the content of silicon dioxide in a highly absorbent resin according to claim 1, characterized in that: In step 3), the sampling volume of the filtrate is 1 to 20 ml. The volume of the ammonium molybdate solution is 2 to 10 ml; And, the concentration of the ammonium molybdate solution is 100 g / L.

8. The method for detecting the content of silicon dioxide in a highly absorbent resin according to claim 1, characterized in that: In step 4), the reducing agent is at least one of ascorbic acid, potassium sodium tartrate, ferrous sulfate, ammonium ferrous sulfate, and stannous chloride; Furthermore, the concentration of the reducing agent is 100 g / L; Furthermore, the amount of the reducing agent added is 2 to 10 ml.

9. The method for detecting the content of silicon dioxide in a highly absorbent resin according to claim 1, characterized in that: In step 5), the temperature of the color development reaction is 20-30°C; And, the reaction time is 10 to 40 minutes. The optical path of the cuvette is 5 to 30 mm; Furthermore, the test wavelength of the visible light spectrophotometry is 640 nm.