阅读说明：本技术 一种聚丙烯腈纺丝液氨离子置换率的检测方法 (Detection method for polyacrylonitrile spinning liquid ammonia ion replacement rate ) 是由 丁正南 连峰 李果 王芬 张克勤 于 2019-10-17 设计创作，主要内容包括：本发明属于有机物检测领域,具体涉及一种聚丙烯腈纺丝液氨离子置换率的检测方法。所述方法称取定量纺丝液至干燥玻璃表面中心位置处,利用玻璃棒涂抹成膜,分别以定量的盐酸溶液和水润洗并浸泡薄膜,将润洗水以氢氧化钠标准溶液进行滴定,来计算纺丝液中氨离子置换率。本发明提供的方法,通过标准液的滴定,实现聚合液在氨化改性中的用量及停留时间准确控制。(The invention belongs to the field of organic matter detection, and particularly relates to a method for detecting the ion replacement rate of polyacrylonitrile spinning liquid ammonia. Weighing quantitative spinning solution to the center of the surface of dry glass, coating a glass rod to form a film, respectively rinsing and soaking the film with quantitative hydrochloric acid solution and water, and titrating the rinsing water with sodium hydroxide standard solution to calculate the displacement rate of ammonia ions in the spinning solution. The method provided by the invention realizes accurate control of the dosage and the retention time of the polymerization liquid in the ammonification modification through titration of the standard liquid.)

1. A method for detecting the ammonia ion replacement rate of polyacrylonitrile spinning is characterized in that quantitative spinning liquid is weighed to the center of the surface of dry glass, a glass rod is used for smearing a film, a film is rinsed and soaked by quantitative hydrochloric acid solution, and the rinsing water is titrated by sodium hydroxide standard solution to calculate the ammonia ion replacement rate of the spinning liquid.

2. The method according to claim 1, characterized in that it comprises in particular the steps of:

step (1): putting the spinning solution to be measured into a weighing bottle, weighing 1-2g of the spinning solution at one end of a glass rod, and marking as m;

step (2): coating the spinning solution on a glass plate by using a glass rod to form a film;

and (3): measuring a certain amount of Vml hydrochloric acid standard solution to rinse spinning solution on a glass plate and a glass rod, and completely collecting rinse water in an iodine measuring flask;

and (4): transferring the V1ml solution from an iodine measuring bottle into a conical flask, adding clear water of V2ml, adding 1-2 drops of methyl red indicator, titrating with a sodium hydroxide standard solution to yellow, and recording the volume of the used sodium hydroxide standard solution as V3 ml;

and (5): adding a neutral formaldehyde solution into the conical flask, shaking uniformly, standing, and continuously titrating with a sodium hydroxide standard solution to yellow, wherein the volume of the sodium hydroxide standard solution is recorded as V4 ml;

and (6): repeating the step (1), and recording the quality of the spinning solution as m 1;

and (7): repeating the step (2);

and (8): measuring a certain amount of Vml of clear water to rinse the spinning solution on the glass plate and the glass rod, and completely collecting rinse water in an iodine measuring flask;

and (9): transferring the V1ml solution from the iodine flask into an erlenmeyer flask, adding the hydrochloric acid solution of V2ml, adding 1-2 drops of methyl red indicator, and titrating with a sodium hydroxide standard solution to yellow, wherein the volume is recorded as V3'; repeating the step (5) and ensuring that the volume is V4';

step (10): and calculating to obtain the ammoniation degree of the polyacrylonitrile spinning solution.

3. The method according to claim 2, wherein the spinning solution weighed in step (1) and step (6) is weighed to the nearest 0.0001g by using a reduction method on a ten-thousand-position balance.

4. The method as claimed in claim 2, wherein the step (2) is implemented by taking the center of the sample-stained end of the glass rod as the center of the circle, slowly rotating the glass rod close to the glass plate, and uniformly smearing the sample into a thin layer.

5. The method according to claim 2, wherein the samples rinsed on the glass plate and the glass rod in the steps (3) and (8) are: completely collecting the rinse water in an iodine measuring flask, wherein the rinse water cannot leak out, a spinning solution sample is contacted with the rinse water to be solidified into a thin film, the thin film is gently taken down to the iodine measuring flask by using a pair of tweezers, the surface of the glass plate is cleaned by using the residual hydrochloric acid solution, and the cleaning water is completely collected into the iodine measuring flask with the rinse water; covering with iodine bottle, shaking, and standing for 3-10 min.

6. The method of claim 2, wherein the step (5) is performed by shaking and standing for 1-5 min.

7. The method of claim 2, wherein the ammoniation degree of the polyacrylonitrile spinning solution is calculated in the step (10) according to the formula:

in the formula: v is the total volume of the rinse water, V1 is the volume removed from the rinse solution, C_NaOHIs the concentration, wt., of a sodium hydroxide standard solution_{Itaconic acid}% is the ratio of the total mass of itaconic acid to the total mass of monomers added during preparation of the spinning solution, C_{Total monomer}Is the ratio of the dry weight of the film obtained after the replacement of the spinning solution by water to the weight of the spinning solution before the replacement, m is the mass of the spinning solution before the acid cleaning₁Is the quality of the spinning solution before washing, V₄Volume of sodium hydroxide consumed after addition of Formaldehyde, V₄' As the volume of sodium hydroxide consumed after formaldehyde addition, 0.065 is one thousandth of one half the molar amount of itaconic acid.

Technical Field

The invention belongs to the field of organic matter detection, and particularly relates to a method for detecting the ion replacement rate of polyacrylonitrile spinning liquid ammonia.

Background

Because of its excellent mechanical properties, polyacrylonitrile carbon fiber has been widely used in many fields as a high-performance reinforcing material, and is an important strategic basic material and a typical new material for civil and military use. At present, the preparation and control technology of high-quality precursor has become one of the main reasons for restricting the improvement of the performance of carbon fiber.

The polyacrylonitrile carbon fiber is prepared by a series of processes of free radical reaction polymerization, spinning, carbonization and the like of polyacrylonitrile and a comonomer, wherein itaconic acid is used as the most common comonomer at present, and the cyclization reaction efficiency of polyacrylonitrile protofilament in the carbonization pre-oxidation process is increased. The polymerization solution formed by copolymerization is subjected to ammoniation modification, so that unreacted free radicals can be stopped, and the polymerization solution can react with the comonomer itaconic acid to generate ammonium salt, thereby improving the hydrophilicity of the polymer and inhibiting the formation of macropores in the spinning process.

However, the controllability of the ammoniation degree is difficult to realize in the actual production process, and at present, only a detection method for dissolved ammonia in a polymerization solution is available, and the detection for the ammonium itaconate ion replacement rate in a polymer is not reported.

Disclosure of Invention

The invention aims to provide a method for detecting the polyacrylonitrile spinning liquid ammonia ion replacement rate. .

The technical solution for realizing the purpose of the invention is as follows:

a method for detecting the ammonia ion replacement rate of polyacrylonitrile spinning comprises the steps of weighing quantitative spinning liquid to the central position of the surface of dry glass, smearing a glass rod to form a film, rinsing and soaking the film by using quantitative hydrochloric acid solution, and titrating rinsing water by using sodium hydroxide standard solution to calculate the ammonia ion replacement rate of the spinning liquid.

Further, the method specifically comprises the following steps:

step (1): putting the spinning solution to be measured into a weighing bottle, weighing 1-2g of the spinning solution at one end of a glass rod, and marking as m;

step (2): coating the spinning solution on a glass plate by using a glass rod to form a film;

and (3): measuring a certain amount of Vml hydrochloric acid standard solution to rinse spinning solution on a glass plate and a glass rod, and completely collecting rinse water in an iodine measuring flask;

and (4): transferring the V1ml solution from an iodine measuring bottle into a conical flask, adding clear water of V2ml, adding 1-2 drops of methyl red indicator, titrating with a sodium hydroxide standard solution to yellow, and recording the volume of the used sodium hydroxide standard solution as V3 ml;

and (5): adding a neutral formaldehyde solution into the conical flask, shaking uniformly, standing, and continuously titrating with a sodium hydroxide standard solution to yellow, wherein the volume of the sodium hydroxide standard solution is recorded as V4 ml;

and (6): repeating the step (1), and recording the quality of the spinning solution as m 1;

and (7): repeating the step (2);

and (8): measuring a certain amount of Vml of clear water to rinse the spinning solution on the glass plate and the glass rod, and completely collecting rinse water in an iodine measuring flask;

and (9): transferring the V1ml solution from the iodine flask into an erlenmeyer flask, adding the hydrochloric acid solution of V2ml, adding 1-2 drops of methyl red indicator, and titrating with a sodium hydroxide standard solution to yellow, wherein the volume is recorded as V3'; repeating the step (5) and ensuring that the volume is V4';

step (10): and calculating to obtain the ammoniation degree of the polyacrylonitrile spinning solution.

Further, the spinning solution weighed in the step (1) and the step (6) is weighed on a universal balance by a subtraction method to be accurate to 0.0001 g.

Further, the step (2) is that the end of the glass rod, which is stained with the sample, is tightly attached to the glass plate to rotate slowly by taking the center of the glass plate as the center of a circle, and the sample is uniformly coated into a thin layer.

Further, the washing of the samples on the glass plate and the glass rod in the step (3) and the step (8) is specifically as follows: completely collecting the rinse water in an iodine measuring flask, wherein the rinse water cannot leak out, a spinning solution sample is contacted with the rinse water to be solidified into a thin film, the thin film is gently taken down to the iodine measuring flask by using a pair of tweezers, the surface of the glass plate is cleaned by using the residual hydrochloric acid solution, and the cleaning water is completely collected into the iodine measuring flask with the rinse water; covering with iodine bottle, shaking, and standing for 3-10 min.

Further, shaking uniformly and standing for 1-5min in the step (5).

Further, in the step (10), the ammoniation degree of the polyacrylonitrile spinning solution is calculated according to a formula, wherein the formula is as follows:

in the formula: v is the total volume of the rinse water, V1 is the volume removed from the rinse solution, C_NaOHIs the concentration, wt., of a sodium hydroxide standard solution_{Itaconic acid}% is the ratio of the total mass of itaconic acid to the total mass of monomers added during preparation of the spinning solution, C_{Total monomer}Is the ratio of the dry weight of the film obtained after the replacement of the spinning solution by water to the weight of the spinning solution before the replacement, m is the mass of the spinning solution before the acid cleaning₁Is the quality of the spinning solution before washing, V₄Volume of sodium hydroxide consumed after addition of Formaldehyde, V₄' As the volume of sodium hydroxide consumed after formaldehyde addition, 0.065 is one thousandth of one half the molar amount of itaconic acid.

Compared with the prior art, the invention has the remarkable advantages that:

the invention mainly aims to provide a method for rapidly and accurately measuring the ammonium ion replacement rate of polyacrylonitrile polymer liquid, so as to realize accurate control of the dosage and retention time of the polymer liquid in ammoniation modification; the method can solve the problem that the amination degree can not be accurately measured in the ammonification modification of the polyacrylonitrile spinning solution, thereby providing a judgment basis for obtaining the optimal ammonification dosage of the spinning solution.

Detailed Description

The invention mainly aims to provide a method for quickly and accurately measuring the ammonium ion replacement rate of polyacrylonitrile polymer liquid, so as to accurately control the dosage and retention time of the polymer liquid in ammoniation modification.

The method comprises the following steps:

step 1, putting the spinning solution to be measured into a weighing bottle, and weighing 1-2g of the spinning solution at one end of a glass rod on a ten thousand position balance by a subtraction method until the weight is accurate to 0.0001g, and recording the weight as m.

Step 2, taking the center of the glass plate as the center of a circle, enabling one end of the glass rod, which is stained with the sample, to cling to the glass plate to rotate slowly, and uniformly smearing the sample into a thin layer;

and 3, measuring a quantitative V (ml) hydrochloric acid standard solution to rinse samples on the glass plate and the glass rod, completely collecting rinsing water in the iodine measuring flask, paying attention to the fact that the samples cannot leak out, solidifying the samples into a thin film by contacting the rinsing water, gently taking down the thin film to the iodine measuring flask by using tweezers, washing the surface of the glass plate by using the residual hydrochloric acid solution, and completely collecting the washing water in the iodine measuring flask with the rinsing water. Cover the iodine content bottle, shake and stand for 5 min.

Step 4, transferring the V1(ml) solution from the iodine measuring flask into a conical flask, adding the V2(ml) clear water, adding 1-2 drops of methyl red indicator, and titrating the solution to yellow with a sodium hydroxide standard solution, and recording the volume as V3 (ml).

And 5, adding a neutral formaldehyde solution into the conical flask, shaking uniformly, standing for 1min, and continuously titrating with a sodium hydroxide solution to yellow, wherein the volume is recorded as V4(ml).

Step 6, repeating the step 1, and recording as m 1;

step 7, repeating the step 2;

and 8, measuring a certain amount V (ml) of clear water for rinsing the glass plate and the sample on the glass rod, completely collecting rinsing water in the iodine measuring bottle, paying attention to the fact that the rinsing water cannot leak out, solidifying the sample into a thin film by contacting the rinsing water, gently taking down the thin film into the iodine measuring bottle by using tweezers, cleaning the surface of the glass plate by using the residual clear water, and completely collecting the rinsing water into the iodine measuring bottle of the rinsing water. Cover the iodine content bottle, shake and stand for 5 min.

Step 9. transferring the V1(ml) solution from the iodometric flask into the conical flask, adding the V2(ml) hydrochloric acid solution, adding 1-2 drops of methyl red indicator, titrating with sodium hydroxide standard solution to yellow, and recording as volume V3'. Repeat step 5 for a volume of V4'.

Step 10. according to the formula

And calculating to obtain the ammoniation degree of the polyacrylonitrile spinning solution.

In the formula: v is the total volume of the rinse water, V1 is the volume removed from the rinse solution, CNaOH is the concentration, wt., of the sodium hydroxide standard solution_{Itaconic acid}% is the ratio of the total mass of itaconic acid to the total mass of monomers added during preparation of the spinning solution, C_{Total monomer}Is the ratio of the dry weight of the film obtained after the replacement of the spinning solution by water to the weight of the film before the replacement of the spinning solution, m is the mass of the spinning solution before the acid washing, m1 is the spinning solution before the water washingThe mass of the solution, V4 is the volume of sodium hydroxide consumed after formaldehyde is added, V4' is the volume of sodium hydroxide consumed after formaldehyde is added, and 0.065 is one thousandth of one half of the molar amount of itaconic acid.