CN114414558B - Method for measuring acid value content of water-based fluorocarbon resin - Google Patents
Method for measuring acid value content of water-based fluorocarbon resin Download PDFInfo
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Abstract
The invention belongs to the technical field of analytical chemistry, and particularly relates to a method for measuring the acid value content of water-based fluorocarbon resin. The measuring method comprises the following steps: (1) pretreatment of aqueous fluorocarbon resin emulsion; (2) calculating the solids content of the aqueous fluorocarbon resin solids; (3) azeotropic dehydration; (4) dissolving; (5) titration; (6) blank titration; (7) calculating the acid value. The method can be used for efficiently measuring the acid value in the aqueous fluorocarbon resin, and improves the accuracy of the acid value test.
Description
Technical Field
The invention belongs to the technical field of analytical chemistry, and particularly relates to a method for measuring the acid value content of water-based fluorocarbon resin.
Background
The acid value is one of the important indexes of the aqueous fluorocarbon resin, and the affinity of the aqueous fluorocarbon resin for the pigment can be generally judged according to the acid value of the aqueous fluorocarbon resin.
The acid value test method comprises an acid-base indicator method and a potentiometric titration method, wherein the acid-base indicator method judges the endpoint according to the visual observation of the color change of the indicator; the potentiometric titration method determines the end point according to the potential change, wherein an automatic potentiometric titration instrument adopted by the potentiometric titration method is a common analysis instrument designed according to the principle of the potentiometric method and used for capacity analysis, the cost is high, an electrode is extremely easy to damage in an organic solvent, frequent maintenance is needed, and the fluctuation of data is high. The acid-base titration method has the advantages that the price of an instrument used is low, the operation is convenient, the restriction of geographical positions is avoided, the titration endpoint can be easily observed by adopting the indicator color-changing method, and the numerical stability is good.
The acid-base indicator method adopted in the current determination of the acid value of the aqueous fluorocarbon resin is mostly a single-solvent method, however, the aqueous fluorocarbon resin is formed by polymerizing fluoroolefin, alkyl vinyl ether/alkyl vinyl ester and other functional monomers, the main framework adopts fluoroolefin as a comonomer, the polarity of the aqueous fluorocarbon resin is small compared with that of unsaturated polyester resin due to the existence of C-F bonds, so that the aqueous fluorocarbon resin is difficult to dissolve, and fresh solvents can be completely dissolved. Because the single solvent can not completely dissolve the aqueous fluorocarbon resin, the test solution generates a certain turbidity, thereby influencing the observation end point of the color change of the observation indicator, resulting in delay of the titration end point and larger titration result.
CN102495059a discloses a method for measuring the acid value of an unsaturated polyester resin, which adopts anhydrous acetone to dissolve the unsaturated polyester resin. However, due to the structural specificity of the aqueous fluorocarbon resin, the acetone as a single solvent cannot completely dissolve the aqueous fluorocarbon resin.
The national standard GB/T6743-2008 "determination of partial acid value and total acid value of polyester resin for plastics, binder for color paint and varnish" shows that a toluene and ethanol mixed solution system or a pyridine, methyl ethyl ketone and water mixed solvent system is used, but these mixed solvent systems cannot dissolve an aqueous fluorocarbon resin having a multi-branched structure such as C-F bond to a transparent and uniform state, and therefore are not suitable for dissolving the aqueous fluorocarbon resin.
Disclosure of Invention
The invention aims to provide a method for measuring the acid value content of an aqueous fluorocarbon resin, aiming at the defect that the aqueous fluorocarbon resin is difficult to dissolve completely and the problem that the turbidity of a solution after titration is too large for the aqueous fluorocarbon resin to observe the reaction end point correctly in the conventional acid value measuring method. The method can be used for efficiently measuring the acid value in the aqueous fluorocarbon resin, and improves the accuracy of the acid value test.
The technical scheme of the invention is as follows: a method for determining the acid value content of an aqueous fluorocarbon resin comprising the steps of:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing a certain amount of the water-containing fluorocarbon resin solid pretreated in the step (1), drying, cooling, weighing, and calculating the solid content;
(3) Azeotropic water removal: weighing a certain amount of the water-containing fluorocarbon resin solid obtained in the step (1), adding an entrainer which forms an azeotropic substance with water, distilling to remove water in the water-containing fluorocarbon resin solid, and calculating the residual quantity of the entrainer according to the addition quantity of the entrainer, the entrainer and the distilled water removal quantity; the water-containing fluorocarbon resin obtained after centrifugation is in a milky pasty state, contains excessive water and needs to be dehydrated, if a molecular sieve, a crystallization salt and other water removing modes are adopted, unnecessary consumption of the fluorocarbon resin can be generated, and impurities can be introduced; if a direct drying and dewatering mode is adopted, the dewatered fluorocarbon resin is in a dry blocky solid, which is not beneficial to subsequent dissolution; the azeotropic agent is adopted to remove water, so that the problem that the acid value measurement error is caused by incapability of timely observing the titration end point due to turbidity of the liquid to be titrated caused by the existence of the water is solved, the use amount of the solvent is reduced, the titration end point is easy to observe, the consumption of the resin is avoided, and other impurities are not introduced;
(4) Dissolving: adopting a mixed double-solvent system consisting of an aromatic solvent and a ketone solvent to dissolve fluorocarbon resin solids subjected to azeotropic dehydration in the step (3) to obtain a uniform and transparent solution; the mixed double-solvent system adopted by the invention is designed for the aqueous fluorocarbon resin with a multi-branched structure such as C-F bond, and the like, so that the aqueous fluorocarbon resin can be completely dissolved to form uniform and transparent solution, and the problem that the reaction end point cannot be accurately observed due to overlarge turbidity of the titration solution is avoided; after the dissolution is completed, the potassium hydroxide alcohol solution is adopted for titration, and finally the content of acidic substances in the aqueous fluorocarbon resin is obtained through calculation by consuming the potassium hydroxide, so that the accuracy of testing the acid value is improved;
(5) Titration: adding an indicator into the solution obtained in the step (4), titrating by adopting a potassium hydroxide alcohol solution, and recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and does not fade within 20-30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) And (3) calculating: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
And (2) in the method for determining the acid value content of the aqueous fluorocarbon resin, the temperature is kept at 110 ℃ for 1h, and the moisture is dried.
The azeotropic agent in the step (3) of the method for measuring the acid value content of the aqueous fluorocarbon resin is acetonitrile, an aromatic hydrocarbon solvent or a ketone solvent.
The entrainer in the method for measuring the acid value content of the aqueous fluorocarbon resin is at least one of toluene, acetonitrile, dimethylbenzene, butanone and ethylbenzene.
The method for measuring the acid value content of the aqueous fluorocarbon resin comprises the step (3) that the solid content of the aqueous fluorocarbon resin is 0.3 g-2.5 g; the distillation is carried out at 40-80 ℃ under negative pressure.
The method for measuring the acid value content of the aqueous fluorocarbon resin comprises the following steps of (4) mixing an aromatic hydrocarbon solvent in a double-solvent system according to mass ratio: the ketone solvent is 0.5-2: 1. the mixed double-solvent system formed by the aromatic hydrocarbon solvent and the ketone solvent in the ratio range can completely dissolve the water-based fluorocarbon resin to form uniform and transparent solution, and provides conditions for accurately judging the titration end point in the subsequent titration.
The method for measuring the acid value content of the aqueous fluorocarbon resin comprises the following steps of (4) mixing the water content of an aromatic hydrocarbon solvent in a double-solvent system to be less than or equal to 0.01 percent, and the water content of a ketone solvent to be less than or equal to 0.01 percent; the water content of the solution obtained was dissolved <0.5%. Further reducing the effect of water on the turbidity of the titration solution.
The aromatic hydrocarbon solvent in the mixed double-solvent system in the step (4) of the method for measuring the acid value content of the aqueous fluorocarbon resin is toluene or xylene; the ketone solvent is butanone, acetone, methyl isobutyl ketone or cyclohexanone.
The method for measuring the acid value content of the water-based fluorocarbon resin adopts ultrasonic oscillation for 5-80 min when in dissolution in the step (4); the dissolution temperature is controlled between 15 and 50 ℃.
The indicator in the step (5) of the method for measuring the acid value content of the aqueous fluorocarbon resin is bromothymol blue or phenolphthalein; the dosage of the indicator is as follows: the mixed double solvent system is 1: 100-1000; the concentration of the potassium hydroxide alcohol solution is 0.002-0.02 mol/L.
The beneficial effects of the invention are as follows: the method for measuring the acid value of the aqueous fluorocarbon resin emulsion provided by the invention aims at the characteristics of the aqueous fluorocarbon resin, creatively designs an azeotropic water removal and mixed double-solvent system for dissolution, and solves the problems that the turbidity of the solution to be titrated influences the judgment of the titration end point, and the measurement accuracy is reduced. The method has the advantages of high sensitivity, good accuracy, simple operation, capability of rapidly and efficiently determining the acid value content of the fluorocarbon resin, avoiding the influence of water, reducing the dosage of the solvent and better observing the titration end point.
Drawings
FIG. 1 is a schematic diagram of an aqueous fluorocarbon resin stock solution of the present invention.
FIG. 2 is a graph of a solution of fluorocarbon resin dissolved in a mixed bi-solvent system of example 2 of the present invention.
Detailed Description
The technical scheme of the invention is described in detail below with reference to the accompanying drawings.
Example 1
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer dimethylbenzene, carrying out negative pressure distillation at 40-80 ℃, and extracting the dimethylbenzene and water to 15g in total; the water content in the water-containing fluorocarbon resin is very small and can be ignored, so that the xylene residue of the entrainer is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 10g of dimethylbenzene and 30g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution; because the entrainer is xylene and 5g of the entrainer remains after azeotropic dehydration, the actual xylene in the mixed double-solvent system is 15g and the acetone is 30g; the entrainer is the same as one component in the solvent system, so that the introduction of other solvents is avoided, interference factors are further reduced, and the measurement accuracy is improved;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Example 2
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer dimethylbenzene, carrying out negative pressure distillation at 40-80 ℃, and extracting the dimethylbenzene and water to 15g in total; the water content in the water-containing fluorocarbon resin is very small and can be ignored, so that the xylene residue of the entrainer is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 25g of dimethylbenzene and 30g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution; because the entrainer is xylene and 5g of the entrainer remains after azeotropic dehydration, the actual xylene in the mixed double-solvent system is 30g and the acetone is 30g; the entrainer is the same as one component in the solvent system, so that the introduction of other solvents is avoided, interference factors are further reduced, and the measurement accuracy is improved;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Example 3
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer dimethylbenzene, carrying out negative pressure distillation at 40-80 ℃, and extracting the dimethylbenzene and water to 15g in total; the water content in the water-containing fluorocarbon resin is very small and can be ignored, so that the xylene residue of the entrainer is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 25g of dimethylbenzene and 15g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution; because the entrainer is xylene and 5g of the entrainer remains after azeotropic dehydration, the actual xylene in the mixed double-solvent system is 30g and the acetone is 15g; the entrainer is the same as one component in the solvent system, so that the introduction of other solvents is avoided, interference factors are further reduced, and the measurement accuracy is improved;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Example 4
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer toluene, carrying out negative pressure distillation at 40-80 ℃, and extracting 15g of toluene and water in total; because the water content in the water-containing fluorocarbon resin is extremely small and can be ignored, the toluene residual quantity of the entrainer is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 30g of dimethylbenzene and 30g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Example 5
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of an entrainer acetonitrile, carrying out negative pressure distillation at 40-80 ℃, and extracting 15g of acetonitrile and water in total; because the water content in the water-containing fluorocarbon resin is extremely small and can be ignored, the acetonitrile residual quantity of the entrainer is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 30g of dimethylbenzene and 30g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Example 6
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer toluene, carrying out negative pressure distillation at 40-80 ℃, and extracting 15g of toluene and water in total; because the water content in the water-containing fluorocarbon resin is extremely small and can be ignored, the toluene residual quantity of the entrainer is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 25g of toluene and 30g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution; because toluene is adopted as the entrainer and 5g of residual water is removed by azeotropy, the actual toluene in the mixed double-solvent system is 30g and the acetone is 30g; the entrainer is the same as one component in the solvent system, so that the introduction of other solvents is avoided, interference factors are further reduced, and the measurement accuracy is improved;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Example 7
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer butanone, carrying out negative pressure distillation at 40-80 ℃, and extracting 15g of butanone and water in total; because the water content in the water-containing fluorocarbon resin is extremely small and can be ignored, the residual quantity of the entrainer butanone is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 30g of dimethylbenzene and 25g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Example 8
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer butanone, carrying out negative pressure distillation at 40-80 ℃, and extracting 15g of butanone and water in total; because the water content in the water-containing fluorocarbon resin is extremely small and can be ignored, the residual quantity of the entrainer butanone is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 30g of dimethylbenzene and 25g of butanone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution; because the entrainer is butanone and 5g of residual water is removed by azeotropy, the actual dimethylbenzene in the mixed double-solvent system is 30g and the butanone is 30g; the entrainer is the same as one component in the solvent system, so that the introduction of other solvents is avoided, interference factors are further reduced, and the measurement accuracy is improved;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Example 9
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer butanone, carrying out negative pressure distillation at 40-80 ℃, and extracting 15g of butanone and water in total; because the water content in the water-containing fluorocarbon resin is extremely small and can be ignored, the residual quantity of the entrainer butanone is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 30g of dimethylbenzene and 30g of methyl isobutyl ketone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Example 10
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of an entrainer ethylbenzene, carrying out negative pressure distillation at 40-80 ℃, and extracting the total of 15g of ethylbenzene and water; the residual quantity of the azeotropic agent ethylbenzene is 5g because the water content in the water-containing fluorocarbon resin is very small and can be ignored;
(4) Dissolving: adding a mixed double-solvent system consisting of 30g of dimethylbenzene and 30g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Comparative example 1
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 30g of entrainer dimethylbenzene, carrying out negative pressure distillation at 40-80 ℃, and extracting the dimethylbenzene and water to 15g in total; the water content in the water-containing fluorocarbon resin is very small and can be ignored, so that the xylene residue of the entrainer is 15g;
(4) Dissolving: adding 45g of dimethylbenzene into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a solution;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, 60g of dimethylbenzene is weighed to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Comparative example 2
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer butanone, carrying out negative pressure distillation at 40-80 ℃, and extracting 15g of butanone and water in total; because the water content in the water-containing fluorocarbon resin is extremely small and can be ignored, the residual quantity of the entrainer butanone is 5g;
(4) Dissolving: adding 55g of butanone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a solution;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing 60g of butanone to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Comparative example 3
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Dissolving: adding a mixed double-solvent system consisting of 40g of dimethylbenzene and 40g of butanone into the fluorocarbon resin dried in the step (2), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a solution;
(4) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(5) Blank titration: firstly, weighing 40g of dimethylbenzene and 40g of butanone, and mixing to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(6) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Comparative example 4
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer dimethylbenzene, carrying out negative pressure distillation at 40-80 ℃, and extracting the dimethylbenzene and water to 15g in total; the water content in the water-containing fluorocarbon resin is very small and can be ignored, so that the xylene residue of the entrainer is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 5g of dimethylbenzene and 30g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution; because the entrainer is xylene and 5g of the entrainer remains after azeotropic dehydration, the actual xylene in the mixed double-solvent system is 10g and the acetone is 30g; the entrainer is the same as one component in the solvent system, so that the introduction of other solvents is avoided, interference factors are further reduced, and the measurement accuracy is improved;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
Comparative example 5
The method for determining the acid value content of the aqueous fluorocarbon resin comprises the following steps:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing 30g of aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing 1g of the water-containing fluorocarbon resin solid obtained by pretreatment in the step (1), preserving heat at 110 ℃ for 1h, drying the water, placing the water in a drying bottle, cooling the water, weighing the water, and calculating the solid content;
(3) Azeotropic water removal: weighing 1g of the aqueous fluorocarbon resin solid obtained in the step (1) with the estimated acid value of 2mgKOH/g, placing the aqueous fluorocarbon resin solid in a flask, adding 20g of entrainer dimethylbenzene, carrying out negative pressure distillation at 40-80 ℃, and extracting the dimethylbenzene and water to 15g in total; the water content in the water-containing fluorocarbon resin is very small and can be ignored, so that the xylene residue of the entrainer is 5g;
(4) Dissolving: adding a mixed double-solvent system consisting of 25g of dimethylbenzene and 10g of acetone into the distilled flask in the step (3), dissolving the fluorocarbon resin subjected to azeotropic dehydration at 25 ℃, and carrying out ultrasonic oscillation for 40min to obtain a uniform and transparent solution; because the entrainer is xylene and 5g of the entrainer remains after azeotropic dehydration, the actual xylene in the mixed double-solvent system is 30g and the acetone is 10g; the entrainer is the same as one component in the solvent system, so that the introduction of other solvents is avoided, interference factors are further reduced, and the measurement accuracy is improved;
(5) Titration: adding a phenolphthalein indicator into the solution obtained in the step (4), and stirring for 3min; titrating by adopting 0.002mol/L potassium hydroxide alcohol solution, recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and the indicator does not fade within 30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g.
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
The measurement was repeated three times, and an average was obtained.
The acid values of the fluorocarbon resins measured by the methods described in examples 1 to 10 and comparative examples 1 to 5 are shown in Table 1.
TABLE 1 acid value and relative standard deviation of fluorocarbon resins of examples 1-10 and comparative examples 1-5
As can be seen from the results in table 1,
(1) The measurement results obtained in examples 1 to 5 are stable and have high accuracy;
(2) Comparative examples 1-2 were found to have large errors and instability in the measurement with a single solvent;
(3) Compared with the comparative example 3 and the example 8, the azeotropic water removal can be seen to greatly improve the accuracy of the measurement result;
(4) Comparing examples 1-3 with comparative examples 4, 5, it can be seen that the results of the determination of the ratio of the mixed double solvent system according to the present invention are accurate and stable, while the accuracy is greatly reduced when the ratio exceeds the range.
In conclusion, the method for testing the acid value content of the aqueous fluorocarbon resin by adopting the measuring method disclosed by the invention is high in accuracy.
Claims (10)
1. A method for determining the acid value content of an aqueous fluorocarbon resin comprising the steps of:
(1) Pretreatment of aqueous fluorocarbon resin emulsion: firstly, weighing aqueous fluorocarbon resin emulsion, and performing centrifugal separation to obtain supernatant and aqueous fluorocarbon resin solid; then washing the aqueous fluorocarbon resin solid by deionized water, repeating the above operation until the conductivity of the supernatant fluid in the last centrifugation is less than 10 mu s/cm;
(2) Calculating the solid content of the aqueous fluorocarbon resin solid: weighing a certain amount of the water-containing fluorocarbon resin solid pretreated in the step (1), drying, cooling, weighing, and calculating the solid content;
(3) Azeotropic water removal: weighing a certain amount of the water-containing fluorocarbon resin solid obtained in the step (1), adding an entrainer which forms an azeotropic substance with water, distilling to remove water in the water-containing fluorocarbon resin solid, and calculating the residual quantity of the entrainer according to the addition quantity of the entrainer, the entrainer and the distilled water removal quantity;
(4) Dissolving: adopting a mixed double-solvent system consisting of an aromatic solvent and a ketone solvent to dissolve fluorocarbon resin solids subjected to azeotropic dehydration in the step (3) to obtain a uniform and transparent solution;
(5) Titration: adding an indicator into the solution obtained in the step (4), titrating by adopting a potassium hydroxide alcohol solution, and recording the consumption volume of the potassium hydroxide alcohol solution after the indicator changes color and does not fade within 20-30 seconds as a titration end point;
(6) Blank titration: firstly, weighing the mixed double-solvent system with the same mass in the step (4), and then adding the same entrainer into the mixed double-solvent system according to the residual quantity of the entrainer calculated in the step (3) to obtain a blank solution; repeating the operation of the step (5), and recording the consumption volume of the potassium hydroxide alcoholic solution;
(7) Acid value was calculated: the acid value content of the aqueous fluorocarbon resin was calculated according to the following formula
Wherein A is the content of acidic substances, mg/gKOH;
V 2 Volume, mL, of potassium hydroxide alcoholic solution consumed for titration of the aqueous fluorocarbon dissolution solution;
V 1 volume of potassium hydroxide alcoholic solution consumed for titration of blank solution, mL;
c is the concentration of potassium hydroxide in the potassium hydroxide alcoholic solution and mol/L;
m is the mass of the water-containing fluorocarbon resin solid obtained by centrifugation, g;
n is the solid content of the water-containing fluorocarbon resin solid obtained by centrifugation,%.
2. The method for determining the acid value content of an aqueous fluorocarbon resin as claimed in claim 1, wherein the step (2) is carried out by heat-preserving for 1 hour at 110 ℃ to dry the moisture.
3. The method for determining the acid value content of an aqueous fluorocarbon resin as claimed in claim 1, wherein the azeotropic agent in step (3) is acetonitrile, an aromatic hydrocarbon solvent or a ketone solvent.
4. The method for determining the acid value content of an aqueous fluorocarbon resin as claimed in claim 3, wherein the entrainer is at least one of toluene, acetonitrile, xylene, butanone and ethylbenzene.
5. The method for determining the acid value content of an aqueous fluorocarbon resin as claimed in claim 1, wherein the aqueous fluorocarbon resin solid in step (3) is 0.3 to 2.5g; the distillation is carried out at 40-80 ℃ under negative pressure.
6. The method for determining the acid value content of the aqueous fluorocarbon resin as set forth in claim 1, wherein the step (4) comprises mixing the aromatic hydrocarbon solvents in a mixed double solvent system according to the mass ratio: the ketone solvent is 0.5-2: 1.
7. the method for determining the acid value content of the aqueous fluorocarbon resin according to claim 1, wherein the water content of the aromatic hydrocarbon solvent in the mixed double solvent system in the step (4) is less than or equal to 0.01%, and the water content of the ketone solvent is less than or equal to 0.01%; the water content of the solution obtained was dissolved <0.5%.
8. The method for determining the acid value content of an aqueous fluorocarbon resin as claimed in claim 1, wherein the aromatic hydrocarbon solvent in the mixed double solvent system of step (4) is toluene or xylene; the ketone solvent is butanone, acetone, methyl isobutyl ketone or cyclohexanone.
9. The method for determining the acid value content of the aqueous fluorocarbon resin as set forth in claim 1, wherein ultrasonic oscillation is adopted for 5 to 80 minutes during the dissolution in the step (4); the dissolution temperature is controlled between 15 and 50 ℃.
10. The method for determining the acid value content of an aqueous fluorocarbon resin of claim 1, wherein the indicator in step (5) is bromothymol blue or phenolphthalein; the dosage of the indicator is as follows: the mixed double solvent system is 1: 100-1000; the concentration of the potassium hydroxide alcohol solution is 0.002-0.02 mol/L.
Applications Claiming Priority (2)
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| CN106324185A (en) * | 2016-08-26 | 2017-01-11 | 巨石集团有限公司 | Measuring method for acid value of unsaturated polyester resin emulsion |
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| CN112098593A (en) * | 2020-09-21 | 2020-12-18 | 山东东岳高分子材料有限公司 | Method for testing acid value content of perfluoropolyether |
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| JP2001153861A (en) * | 1999-11-30 | 2001-06-08 | Chubu Denki Hoan Kyokai | Measuring method of total acid number |
| CN106324185A (en) * | 2016-08-26 | 2017-01-11 | 巨石集团有限公司 | Measuring method for acid value of unsaturated polyester resin emulsion |
| CN107389669A (en) * | 2017-06-22 | 2017-11-24 | 湖北富邦科技股份有限公司 | A kind of dark oil anti-caking agent acid number content assaying method |
| CN112098593A (en) * | 2020-09-21 | 2020-12-18 | 山东东岳高分子材料有限公司 | Method for testing acid value content of perfluoropolyether |
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