Method for rapidly determining hydrolysis degree of acrylamide polymer

Abstract

The invention discloses a method for rapidly determining the hydrolysis degree of an acrylamide polymer, which comprises the following steps: preparing a polymer solution from a to-be-determined polymer, dropwise adding acid into the polymer solution, and determining the hydrolysis degree of the acrylamide polymer according to an ionization constant expression and the pH change of the polymer solution after dropwise adding the acid under the condition that the ionization constant of the polymer tends to be stable. The amount of sodium carboxylate groups in the polymer solution is determined, the ratio of the sodium carboxylate groups to the total number of polymer chain links is calculated according to the amount of the sodium carboxylate groups, and the hydrolysis degree of the to-be-measured polymer is obtained; the problems that a specific pH value is approximately used as a judgment basis for reaching a titration end point in an existing hydrolysis degree detection method, but the actual situation is that the pH values are different when polymers with different hydrolysis degrees reach the titration end point, so that measurement errors are caused are effectively solved.

Description

Technical Field

[0001] This disclosure relates to the field of tertiary oil recovery in the oil and gas industry, and particularly to a method for determining the degree of hydrolysis of acrylamide polymers. Background Technology

[0002] The degree of hydrolysis is a crucial indicator for the quality control of polymers used in oil displacement, affecting properties such as solubility, rheological behavior, and chemical stability of the polymer solution. Polymers with excessively high hydrolysis levels are prone to interacting with divalent cations in formation water, leading to precipitation and impacting polymer mobility control. Accurate and efficient determination of the degree of hydrolysis is beneficial for controlling polymer product quality and performance, understanding the relationship between polymer molecular structure and properties, and thus playing a positive role in improving the recovery rate of chemical flooding.

[0003] Currently, the most widely used methods for determining the degree of hydrolysis are the mixed indicator method and the pH determination method. These two methods utilize the color change of an indicator and the measurement of the solution's pH value, respectively, to determine whether the solution's pH has reached a specific value, and thus whether the titration endpoint has been reached. However, the pH value at the titration endpoint differs for polymers with different degrees of hydrolysis. Approximating a specific pH value as the criterion for reaching the titration endpoint introduces measurement errors that are difficult to eliminate. Therefore, how to rapidly and accurately determine the degree of hydrolysis of acrylamide polymers remains a pressing technical problem that needs to be solved. Summary of the Invention

[0004] In view of this, this disclosure provides a method for rapidly determining the degree of hydrolysis of acrylamide polymers, which solves the problem that current methods for detecting the degree of hydrolysis approximate a specific pH value as the criterion for reaching the titration endpoint. However, in reality, polymers with different degrees of hydrolysis reach different pH values ​​at the titration endpoint, leading to measurement errors.

[0005] The inventive concept of this method is: under the condition that the polymer ionization constant tends to be stable, the degree of polymer hydrolysis is calculated based on the expression of the ionization constant and the pH change of the solution after adding acid.

[0006] Based on the above-mentioned inventive concept, the method for rapidly determining the degree of hydrolysis of acrylamide polymers provided in this disclosure includes:

[0007] The polymer to be tested is prepared into a polymer solution, and acid is added dropwise to the polymer solution. When the polymer ionization equilibrium constant tends to stabilize, the amount of sodium carboxylate groups in the polymer solution is determined according to the expression of the ionization equilibrium constant and the pH change of the polymer solution after adding acid. The ratio of sodium carboxylate groups to the total number of polymer segments is calculated using the amount of sodium carboxylate groups to obtain the degree of hydrolysis of the polymer to be tested.

[0008] In this disclosure and possible embodiments, the method for determining the amount of sodium carboxylate groups in the polymer solution includes:

[0009] The polymer to be tested was prepared into a polymer solution with a volume of V0 and a mass concentration of m0 using simulated water with a pH of p0. A standard hydrochloric acid solution with a concentration of c was then added dropwise to the polymer solution.

[0010] When the pH value of the added system decreases to the set range, record the pH value p1 of the system and the corresponding volume V1 of hydrochloric acid standard solution added.

[0011] Continue adding the hydrochloric acid standard solution to the system until the ionization equilibrium constant of the polymer tends to stabilize, and record the pH value p2 of the system and the corresponding volume V2 of hydrochloric acid standard solution added;

[0012] The amount of sodium carboxylate groups was determined based on the principle of ionization equilibrium constant.

[0013] In this disclosure and possible embodiments, the difference between the set range and the pH range of the system when the polymer ionization equilibrium constant tends to stabilize is greater than 0.2.

[0014] In this disclosure and possible embodiments, the pH value of the set range is 3.7 to 3.9; the pH value of the system is 3.3 to 3.5 when the polymer ionization equilibrium constant tends to stabilize.

[0015] In this disclosure and possible embodiments, the formula for calculating the degree of hydrolysis of the polymer to be tested is:

[0016]

[0017] In the formula: H is the degree of polymer hydrolysis; x is the amount of sodium carboxylate group.

[0018] In this disclosure and possible embodiments, the method for calculating the amount of the sodium carboxylate group includes:

[0019] When the volumes of the hydrochloric acid standard solution added to the system are V1 and V2, respectively, the ionization constants of the system are k1 and k2, respectively. Based on k1 = k2, the formula for calculating the amount of sodium carboxylate group is:

[0020] In the formula: b1 and b2 are the concentrations of carboxylic acid groups in the system when the volumes V1 and V2 of the hydrochloric acid standard solution are added to the system, respectively.

[0021] In this disclosure and possible embodiments, the calculation formulas for b1 and b2 are:

[0022]

[0023] In this disclosure and possible embodiments, the ionization constants k1 and k2 of the system are calculated using the following formulas:

[0024]

[0025] In this disclosure and possible embodiments, the mineralization of the polymer solution is greater than 20000 mg / L; the hydrochloric acid standard solution has a hydrochloric acid concentration of 0.10 mol / L and is calibrated using anhydrous sodium carbonate as a reference.

[0026] This disclosure has the following beneficial effects:

[0027] The method disclosed herein for rapidly determining the degree of hydrolysis of acrylamide polymers involves preparing the polymer to be tested into a polymer solution. Under conditions where the polymer ionization constant tends to be stable, the degree of hydrolysis of the polymer is calculated based on the expression for the ionization constant and the pH change of the polymer solution after adding hydrochloric acid. The measurement process is relatively simple and has good accuracy. At the same time, the method of this invention has low requirements for measuring equipment, is easy to operate, and has high measurement accuracy, making it promising for widespread application. Detailed Implementation

[0028] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.

[0029] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0030] To address the problems described in the background art, the present invention discloses a method for rapidly determining the degree of hydrolysis of acrylamide polymers, which is summarized as follows:

[0031] The polymer to be tested is prepared into a polymer solution, and hydrochloric acid is added dropwise to the polymer solution. When the polymer ionization equilibrium constant tends to stabilize, the amount of sodium carboxylate groups in the polymer solution is determined according to the expression of the ionization equilibrium constant and the pH change of the polymer solution after adding hydrochloric acid. The ratio of sodium carboxylate groups to the total number of polymer segments is calculated using the amount of sodium carboxylate groups to obtain the degree of hydrolysis of the polymer to be tested.

[0032] To provide a more detailed description of the general method for rapid determination of the degree of hydrolysis of acrylamide polymers, this disclosure further provides a specific implementation scheme, which includes the following steps:

[0033] (1) Based on the solid content of the polymer sample, prepare a polymer solution with a total mineralization greater than 20000 mg / L, a volume of V0, and a mass concentration of m0.

[0034] Polymer dry powder usually contains a certain amount of moisture. Preparing a test solution of the required concentration based on the solid content of the polymer sample is equivalent to preparing a solution based on the effective content of the sample, which can ensure that the actual concentration of the test solution is consistent with the required concentration.

[0035] Method for determining the solid content of polymer samples: Weigh a certain mass of sample and place it in a constant temperature oven at 120℃. Dry for 2 hours to fully remove the moisture from the sample. Weigh the sample again and calculate the percentage of the sample mass after drying to the initial sample mass, which is the solid content of the sample.

[0036] (2) Measure the pH value of the simulated water used to prepare the polymer solution and record it as p0.

[0037] In the various embodiments of this disclosure, the pH value of the solution needs to be measured to an accuracy of 0.01 or 0.001.

[0038] (3) Add a standard hydrochloric acid solution with a molar concentration of c to the polymer solution to be tested, and measure the pH value of the polymer solution at the same time; when titrating the polymer solution to be tested with the standard hydrochloric acid solution, a microburette with a minimum scale of 0.01 mL can be used to titrate the solution.

[0039] (4) When the pH value of the polymer solution decreases to a certain value, preferably when the pH value is 3.7 to 3.9, record the total amount of hydrochloric acid standard solution added at this time as V1, and the corresponding pH value of the polymer solution is p1;

[0040] (5) Continue to add hydrochloric acid standard solution. When the pH value of the polymer solution to be tested is lower than a certain value, preferably 3.3 to 3.5, record the total amount of hydrochloric acid standard solution added at this time as V2, and the corresponding pH value of the polymer solution is p2.

[0041] (6) The reaction equation of sodium carboxylate ions with hydrogen ions in the added standard hydrochloric acid solution is obtained:

[0042] COO - +H3 + O = COOH + H₂O

[0043] Initial concentrations of each substance in the solution

[0044]

[0045] The molar concentration of hydrogen ions in the polymer solution can be calculated based on the pH value.

[0046]

[0047]

[0048] In the formula, c(H3) + O)1 represents the volume of hydrochloric acid added initially, and the hydrogen ion concentration in the solution after ionization equilibrium, c(H3) + O)2 represents the volume of hydrochloric acid added for the second time, and the hydrogen ion concentration in the solution after ionization equilibrium.

[0049] Therefore, when the volumes of hydrochloric acid standard solution added are V1 and V2, after the solution reaches ionization equilibrium, the concentrations b1 and b2 of carboxylic acid groups (-COOH) in the polymer solution to be tested are:

[0050]

[0051] (7) Based on the above expressions for the concentration of each substance, the expression for the ionization equilibrium constant of the solution after adding hydrochloric acid can be obtained from known quantities such as the volume, concentration, and pH value of the solution to be tested.

[0052] When the volumes of hydrochloric acid standard solution added are V1 and V2, let the amount of sodium carboxylate (-COONa) groups in the polymer solution be x, and the ionization constants K1 and K2 of the polymer solution be:

[0053]

[0054] In the formula, c(-COO) - )1、c(H + c(COOH)1 and c(COOH)1 represent the concentrations of carboxylate groups, hydrogen ions, and carboxylate groups in the polymer solution when the pH value of the polymer solution is p1, respectively; c(-COO)1 represents the concentrations of carboxylate groups, hydrogen ions, and carboxylate groups in the polymer solution. - )2、c(H + c(COOH)2 and c(COOH)2 represent the concentrations of carboxylate groups, hydrogen ions, and carboxylate groups in the polymer solution when the pH value of the polymer solution is p2, respectively.

[0055] (8) Partially hydrolyzed acrylamide polymers are polyelectrolytes. Factors such as the mutual attraction of positive and negative charges and changes in macromolecular conformation will affect the combination of hydrogen ions and carboxylate ions. Therefore, the polymer ionization constant will change with the addition of hydrochloric acid.

[0056] As the pH of the solution approaches the titration endpoint, the combination of hydrogen ions and carboxylate ions tends to stabilize, and the change in the polymer ionization constant with the addition of hydrogen ions becomes negligible. The polymer ionization constant tends to stabilize, and it can be assumed that the ionization equilibrium constant remains unchanged at this point. Therefore, K1 = K2, and the initial amount of sodium carboxylate in the polymer solution, x, can be obtained.

[0057]

[0058] (9) Substitute the amount of sodium carboxylate group x into the following formula to calculate the ratio of sodium carboxylate group to the total number of polymer chain segments, i.e., the degree of polymer hydrolysis H:

[0059]

[0060] In the formula, m0 is the polymer mass concentration, V0 is the volume of the solution to be tested, 71 is the relative molecular mass of the acrylamide repeating unit, and 23 is the difference in mass between the sodium acrylate and the acrylamide repeating unit.

[0061] To make the objectives, technical solutions, and advantages of this invention clearer, the following uses specific embodiments and application examples, combined with some conventional technical means in the field involved in this technical solution, taking common polymers as examples, to describe in detail the method of rapidly determining the degree of hydrolysis of acrylamide polymers according to this invention.

[0062] Example 1

[0063] The degree of hydrolysis of a 25-30 million salt-resistant oil displacement polymer was determined according to the method of the present invention and the pH value determination method. The specific steps of the determination using the method of the present invention are as follows:

[0064] (1) According to SY / T5862 "Technical Requirements for Polymers for Oil Displacement", the solid content of the above polymer was determined and recorded as S.

[0065] (2) Weigh (1 / S)g of the sample, accurate to 0.0001g, and weigh (200-1 / S)g of simulated water with a mineralization of 30000mg / L prepared by NaCl reagent and deionized water into a 500mL beaker, accurate to 0.01g.

[0066] (3) Adjust the speed of the mechanical stirrer to (400±20) r / min to make the simulated water in the beaker form a vortex. Slowly and evenly sprinkle the sample into the vortex wall and stir for 2 hours until the sample is completely dissolved to prepare a polymer solution with a mass concentration of 0.5%.

[0067] (4) Add 6.00g of polymer solution with a mass concentration of 0.5% and 94.00g of simulated water to three beakers respectively, stir with a vertical stirrer for 15min to prepare a polymer solution with a mass concentration of 0.03% to be tested, and obtain three parallel samples.

[0068] (5) The pH of the simulated water used to prepare the polymer solution was determined to be 7.002.

[0069] (6) Prepare a standard hydrochloric acid solution with a molar concentration of 0.10 mol / L according to GB / T 601, and calibrate it with anhydrous sodium carbonate to obtain a hydrochloric acid concentration of 0.1006 mol / L.

[0070] The standard solution of hydrochloric acid can be calibrated using bromocresol green-methyl red indicator. When the titration reaches the endpoint, the solution color will change from green to dark red.

[0071] (7) Use a 0.1006 mol / L hydrochloric acid standard solution to titrate three 0.03% polymer solutions to be tested, and use a precision pH meter to measure the pH change of the solutions.

[0072] (8) When the pH of the solution drops to 3.7-3.9, the amounts of hydrogen ions and carboxylate groups added are close, and the polymer ionization constant is little affected by the addition of hydrochloric acid. Three measurement points are selected, and the total amount of hydrochloric acid standard solution added and the pH of the solution are recorded (see Table 1).

[0073] (9) When the pH value of the solution drops to 3.3-3.5, three measurement points are selected again, and the total amount of hydrochloric acid standard solution added and the pH value of the solution are recorded (see Table 1). When the pH value is below 3.3, the pH value of the solution changes little with the addition of hydrochloric acid. When the pH value is above 3.5, the pH value of the solution is close to that in step (8), which is not conducive to improving the accuracy of the measurement results.

[0074] (10) The degree of hydrolysis of the sample was obtained based on the measurement results and calculation formula, as shown in Table 1 below:

[0075] Table 1. Hydrolysis Degree Measurement Data from Example 1

[0076]

[0077] (11) The degree of hydrolysis of the sample was determined by pH value determination method, and the result was 19.3%. Since the acceptable range of degree of hydrolysis of salt-resistant polymers is 16-27%, excessive hydrochloric acid needs to be added to make polymers with lower degree of hydrolysis reach the specified titration endpoint, which leads to the measurement result being too high.

[0078] In Embodiment 1 of this disclosure, the method of the present invention simplifies the process of adding hydrochloric acid to a specific pH value and further improves the accuracy of the measurement results, playing an important role in accurately verifying the quality of samples with hydrolysis values ​​close to the qualified range.

[0079] Example 2

[0080] The determination of the degree of hydrolysis of a polymer for general oil displacement with a strength of 25-30 million KJ / m³ includes the following steps:

[0081] (1) According to Q / SY17119 "Technical Specification for Partially Hydrolyzed Polyacrylamide for Oil Displacement", the polymer solid content was determined and recorded as S.

[0082] (2) Weigh (1 / S)g of the sample, accurate to 0.0001g, and weigh (200-1 / S)g of deionized water into a 500mL beaker, accurate to 0.01g.

[0083] (3) Adjust the speed of the mechanical stirrer to (400±20) r / min to make the simulated water in the beaker form a vortex. Slowly and evenly sprinkle the sample into the vortex wall and stir for 2 hours until the sample is completely dissolved to prepare a polymer solution with a mass concentration of 0.5%.

[0084] (4) Add 6.00g of 0.5% solution, 3.00g of analytical grade NaCl reagent and 94.00g of deionized water to three 250mL beakers respectively, stir with a vertical stirrer for 15min to prepare a polymer solution with a mass concentration of 0.03%, and obtain three parallel samples.

[0085] (5) Weigh 100g of deionized water, add 3.00g of analytical grade NaCl reagent, stir to dissolve evenly, and determine that the pH of the solution is 7.004.

[0086] (6) Prepare a standard hydrochloric acid solution with a molar concentration of 0.10 mol / L according to GB / T 601, and calibrate it with anhydrous sodium carbonate to obtain a hydrochloric acid concentration of 0.1002 mol / L.

[0087] (7) Use a 0.1002 mol / L hydrochloric acid standard solution to titrate three 0.03% polymer solutions respectively, and use a precision pH meter to measure the pH change of the solutions.

[0088] (8) When the pH of the solution drops to 3.7-4.0, select a measurement point and record the total amount of hydrochloric acid standard solution added and the pH value of the solution (see Table 2).

[0089] (9) When the pH of the solution drops to 3.3-3.5, select another measurement point and record the total amount of hydrochloric acid standard solution added and the pH value of the solution (see Table 2).

[0090] (10) The degree of hydrolysis of the sample was obtained based on the measurement results and calculation formula, as shown in Table 2 below:

[0091] Table 2. Hydrolysis Degree Measurement Data from Example 2

[0092]

[0093] Example 3

[0094] The determination of the degree of hydrolysis of a polymer for general oil displacement with a strength of 12-16 million KJ / m³ includes the following steps:

[0095] (1) According to SY / T5862 "Technical Requirements for Polymers for Oil Displacement", determine the solid content of the polymer and record it as S.

[0096] (2) Weigh (1 / S)g of the sample, accurate to 0.0001g, and weigh (200-1 / S)g of deionized water into a 500mL beaker, accurate to 0.01g.

[0097] (3) Adjust the speed of the mechanical stirrer to (400±20) r / min to make the simulated water in the beaker form a vortex. Slowly and evenly sprinkle the sample into the vortex wall and stir for 2 hours until the sample is completely dissolved to prepare a polymer solution with a mass concentration of 0.5%.

[0098] (4) Add 6.00g of 0.5% solution, 3.00g of analytical grade NaCl reagent and 94.00g of deionized water to three 250mL beakers respectively, stir with a vertical stirrer for 15min to prepare a polymer solution with a mass concentration of 0.03%, and obtain three parallel samples.

[0099] (5) Weigh 100g of deionized water, add 3.00g of analytical grade NaCl reagent, stir to dissolve evenly, and determine that the pH of the solution is 7.006.

[0100] (6) Prepare a standard hydrochloric acid solution with a molar concentration of 0.10 mol / L according to GB / T 601, and calibrate it with anhydrous sodium carbonate to obtain a hydrochloric acid concentration of 0.1006 mol / L.

[0101] (7) Use a 0.1002 mol / L hydrochloric acid standard solution to titrate three 0.03% polymer solutions respectively, and use a precision pH meter to measure the pH change of the solutions.

[0102] (8) When the pH value of the solution drops to 3.7-4.0, select a measurement point and record the total amount of hydrochloric acid standard solution added and the pH value of the solution (see Table 3).

[0103] (9) When the pH value of the solution drops to 3.3-3.5, select another measurement point and record the total amount of hydrochloric acid standard solution added and the pH value of the solution (see Table 3).

[0104] (10) The degree of hydrolysis of the sample was obtained based on the measurement results and calculation formula, as shown in Table 3 below:

[0105] Table 3. Hydrolysis Degree Measurement Data from Example 3

[0106]

[0107] Example 4

[0108] The determination of the degree of hydrolysis of a polymer with a salt-flooding resistance of 6 million to 12 million KJ includes the following steps:

[0109] (1) According to Q / SY17119 "Technical Specification for Partially Hydrolyzed Polyacrylamide for Oil Displacement", the polymer solid content was determined and recorded as S.

[0110] (2) Weigh (1 / S)g of the sample, accurate to 0.0001g, and weigh (200-1 / S)g of simulated water with a mineralization of 30000mg / L prepared by NaCl reagent and deionized water into a 500mL beaker, accurate to 0.01g.

[0111] (3) Adjust the speed of the mechanical stirrer to (400±20) r / min to make the simulated water in the beaker form a vortex. Slowly and evenly sprinkle the sample into the vortex wall and stir for 2 hours until the sample is completely dissolved to prepare a polymer solution with a mass concentration of 0.5%.

[0112] (4) Add 6.00g of 0.5% solution and 94.00g of simulated water to a beaker, stir with a vertical stirrer for 15min, and prepare a polymer solution with a mass concentration of 0.03%.

[0113] (5) The pH of the water used to prepare the solution was determined to be 7.003.

[0114] (6) Prepare a standard hydrochloric acid solution with a molar concentration of 0.10 mol / L according to GB / T 601, and calibrate it with anhydrous sodium carbonate to obtain a hydrochloric acid concentration of 0.1012 mol / L.

[0115] (7) Titrate the 0.03% polymer solution with a 0.1012 mol / L hydrochloric acid standard solution, and simultaneously measure the pH change of the solution with a precision pH meter.

[0116] (8) When the pH value of the solution drops to 3.7-4.0, select three measurement points and record the total amount of hydrochloric acid standard solution added and the pH value of the solution (see Table 4).

[0117] (9) When the pH of the solution drops to 3.3-3.5, select three measurement points again and record the total amount of hydrochloric acid standard solution added and the pH value of the solution (see Table 4).

[0118] (10) The degree of hydrolysis of the sample was obtained based on the measurement results and calculation formula, as shown in the table below:

[0119] Table 4. Hydrolysis Degree Measurement Data from Example 4

[0120]

[0121] Example 5

[0122] The determination of the degree of hydrolysis of a polymer for general oil displacement with a strength of 16-19 million KJ includes the following steps:

[0123] (1) According to Q / SY17119 "Technical Specification for Partially Hydrolyzed Polyacrylamide for Oil Displacement", the polymer solid content was determined and recorded as S.

[0124] (2) Weigh (1 / S)g of the sample, accurate to 0.0001g, and weigh (200-1 / S)g of deionized water into a 500mL beaker, accurate to 0.01g.

[0125] (3) Adjust the speed of the mechanical stirrer to (400±20) r / min to make the simulated water in the beaker form a vortex. Slowly and evenly sprinkle the sample into the vortex wall and stir for 2 hours until the sample is completely dissolved to prepare a polymer solution with a mass concentration of 0.5%.

[0126] (4) Add 6.00g of 0.5% solution, 3.00g of analytical grade NaCl reagent and 94.00g of deionized water to three 250mL beakers respectively, stir with a vertical stirrer for 15min to prepare a polymer solution with a mass concentration of 0.03%, and obtain three parallel samples.

[0127] (5) Weigh 100g of deionized water, add 3.00g of analytical grade NaCl reagent, stir to dissolve evenly, and determine that the pH of the solution is 7.004.

[0128] (6) Prepare a standard hydrochloric acid solution with a molar concentration of 0.10 mol / L according to GB / T 601, and calibrate it with anhydrous sodium carbonate to obtain a hydrochloric acid concentration of 0.1012 mol / L.

[0129] (7) Use a 0.1012 mol / L hydrochloric acid standard solution to titrate three 0.03% polymer solutions respectively, and use a precision pH meter to measure the pH change of the solutions.

[0130] (8) When the pH value of the solution drops to 3.7-4.0, select a measurement point and record the total amount of hydrochloric acid standard solution added and the pH value of the solution (see Table 5).

[0131] (9) When the pH of the solution drops to 3.3-3.5, select another measurement point and record the total amount of hydrochloric acid standard solution added and the pH value of the solution (see Table 5).

[0132] (10) The degree of hydrolysis of the sample was obtained based on the measurement results and calculation formula, as shown in Table 5 below:

[0133] Table 5. Hydrolysis Degree Measurement Data from Example 5

[0134]

[0135] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. A method for rapidly determining the degree of hydrolysis of acrylamide polymers, characterized in that, include: The polymer to be tested is prepared into a polymer solution, and acid is added dropwise to the polymer solution. When the polymer ionization equilibrium constant tends to stabilize, the amount of sodium carboxylate groups in the polymer solution is determined according to the expression of the ionization equilibrium constant and the pH change of the polymer solution after adding acid. The ratio of sodium carboxylate groups to the total number of polymer segments is calculated using the amount of sodium carboxylate groups to obtain the degree of hydrolysis of the polymer to be tested.

2. The method for rapidly determining the degree of hydrolysis of acrylamide polymers according to claim 1, characterized in that, The method for determining the amount of sodium carboxylate groups in the polymer solution includes: The polymer to be tested was prepared into a polymer solution with a volume of V0 and a mass concentration of m0 using simulated water with a pH of p0, and a hydrochloric acid standard solution with a concentration of c was added dropwise to the polymer solution. When the pH value of the added system decreases to the set range, record the pH value p1 of the system and the corresponding volume V1 of hydrochloric acid standard solution added. Continue adding the hydrochloric acid standard solution to the system until the ionization equilibrium constant of the polymer tends to stabilize, and record the pH value p2 of the system and the corresponding volume V2 of hydrochloric acid standard solution added; The amount of sodium carboxylate group is determined based on the ionization equilibrium constant expression.

3. The method for rapidly determining the degree of hydrolysis of acrylamide polymers according to claim 2, characterized in that: The difference between the set range and the range of pH values ​​of the system when the polymer ionization equilibrium constant tends to stabilize is greater than 0.

2.

4. The method for rapidly determining the degree of hydrolysis of acrylamide polymers according to claim 3, characterized in that: The set range is 3.7 to 3.9; the pH range of the system when the polymer ionization equilibrium constant tends to stabilize is 3.3 to 3.

5.

5. The method for rapid determination of the degree of hydrolysis of acrylamide polymers according to any one of claims 1-4, characterized in that, The formula for calculating the degree of hydrolysis of the polymer to be tested is: In the formula: H is the degree of polymer hydrolysis; x is the amount of sodium carboxylate group.

6. The method for rapidly determining the degree of hydrolysis of acrylamide polymers according to claim 5, characterized in that, The method for calculating the amount of the sodium carboxylate group includes: When the volumes of the hydrochloric acid standard solution added to the system are V1 and V2, respectively, the ionization constants of the system are k1 and k2, respectively. Based on k1 = k2, the formula for calculating the amount of sodium carboxylate groups is: In the formula: b1 and b2 are the concentrations of carboxylic acid groups in the system when the volumes V1 and V2 of the hydrochloric acid standard solution are added to the system, respectively.

7. The method for rapidly determining the degree of hydrolysis of acrylamide polymers according to claim 6, characterized in that, The formulas for calculating b1 and b2 are:

8. The method for rapidly determining the degree of hydrolysis of acrylamide polymers according to claim 7, characterized in that, The formulas for calculating the ionization constants k1 and k2 of the system are as follows:

9. The method for rapid determination of the degree of hydrolysis of acrylamide polymers according to any one of claims 1-4 or 6-8, characterized in that: The mineralization of the polymer solution is greater than 20,000 mg / L.

10. The method for rapidly determining the degree of hydrolysis of acrylamide polymers according to claim 9, characterized in that: The hydrochloric acid standard solution has a hydrochloric acid concentration of 0.10 mol / L and is calibrated using anhydrous sodium carbonate as a reference.

Images