CN104132868A - Cellulose polymerization degree determination method - Google Patents

Abstract

The invention relates to a cellulose polymerization degree determination method. The cellulose polymerization degree determination method comprises the following steps of 1, stirring dimethyl sulfoxide and 1-ethyl-3-methylimidazolium acetate to obtain a uniform mixed solvent, 2, putting the mixed solvent into an Ubbelohde viscometer and measuring flowing time t0 of the mixed solvent in the Ubbelohde viscometer, 3, drying cellulose to be measured until weight is constant and adding the cellulose into the mixed solvent to obtain a cellulose solution having a concentration c, 4, putting the cellulose solution obtained by the step 3 into the Ubbelohde viscometer, putting the Ubbelohde viscometer with the cellulose solution into a thermostatic water bath having a temperature of 25 DEG C, carrying out thermostatic treatment for 20-30min, and determining flowing time t0 of the cellulose solution in the Ubbelohde viscometer, 5, calculating h<sp>/c according to the formula (I) and calculating an [Eta] value according to the formula (II), and 6, calculating a DP value according to the formula (III). The cellulose polymerization degree determination method has simple and easy processes, is free of expensive equipment, has a low cost, is convenient for use, has short determination time and produces accurate test data.

Description

A kind of assay method of cellulose polymerization degree

technical field

The invention relates to the technical field of measuring the degree of polymerization, in particular to a method for measuring the degree of polymerization of cellulose.

Background technique

The cellulose molecules of cellulosic materials are extremely long chain molecules consisting of D-glucopyranosyl groups (C ₆ H ₁₀ O ₅ , anhydroglucose). The number of glucose groups in a cellulose molecule is called the degree of polymerization (DP) of cellulose. The degree of polymerization of cellulose represents the length of cellulose molecular chains and the strength of cellulose. The degree of polymerization of cellulose can objectively and quantitatively reflect the degree of damage to fibers in the actual processing of spinning, weaving and dyeing, and is also an important indicator to measure fiber quality.

Methods for determining the degree of cellulose polymerization include end-group chemical titration, boiling point rise method, osmotic pressure method, ultracentrifugal sedimentation method, diffusion method, light scattering method, and viscosity method. The most widely used and relatively simple method is the viscosity method. When using the viscosity method to measure the degree of polymerization of cellulose, it is necessary to dissolve the cellulose in a solvent to prepare a certain concentration of cellulose solution. So far, the solvents used to dissolve cellulose include copper ammonia solution, copper ethylenediamine solution and cadmium ethylenediamine solution. Both cuproammonia solution and copper ethylenediamine solution easily lead to severe oxidative degradation of cellulose, and are extremely unstable and difficult to store; moreover, the reagents used to prepare these two solutions are many, the preparation process is complicated, and the preparation cycle is long; in addition, due to In the process of dissolving cellulose, it is necessary to add copper particles or copper sheets, and the cellulose will be sandwiched between copper particles or copper sheets, resulting in insufficient dissolution. In contrast, the cadmium ethylenediamine solution is more stable, but also causes mild oxidative degradation of cellulose. Obviously, using these solvents to dissolve cellulose to measure the degree of cellulose polymerization, in addition to the disadvantages of appeal, will also cause relatively large errors, which will eventually affect the accuracy of the measurement data. Despite their shortcomings, these solvents have been used to date because there are no alternatives with better solubility and more stable performance.

Contents of the invention

The purpose of the present invention is to provide a kind of assay method of cellulose polymerization degree for solving the deficiency of above-mentioned technical problem, use new alternative solvent (1-ethyl-3-methylimidazole acetate/dimethyl sulfoxide (EmimAc/DMSO)) dissolves cellulose without additional solid co-solvent, which is beneficial to the complete dissolution of cellulose, and the accuracy of the measurement data is high.

The present invention is to solve the deficiencies of the above-mentioned technical problems, and the technical scheme adopted is: a kind of assay method of cellulose polymerization degree, comprises the following steps:

(1) Take dimethyl sulfoxide and 1-ethyl-3-methylimidazole acetate in a weight ratio of 3:1, and add 1-ethyl-3-methylimidazole acetate to dimethyl sulfoxide After stirring evenly, a mixed solvent is obtained;

(2) Take part of the mixed solvent obtained in step (1) and put it into the Ubbelohde viscometer, and then place it in a constant temperature water tank at 25°C for 20-30 minutes, and measure the flow time t ₀ of the mixed solvent in the Ubbelohde viscometer;

(3) Take the cellulose to be tested and dry it to constant weight, then add the cellulose to the mixed solvent in different ratios of cellulose and mixed solvent, stir at 25-30°C for 0.5-1h, and obtain fibers with different concentrations of c prime solution;

(4) Put the cellulose solutions with different concentrations obtained in step (3) into the Ubbelohde viscometer respectively, and then place them in a constant temperature water tank at 25°C for 20 to 30 minutes, and measure the Ubbelohde's viscosity of the cellulose solutions with different concentrations. flow time t in the viscometer;

(5) According to the formula (I), calculate the reduced viscosity values h _sp / c of different concentrations of cellulose solutions, and then according to the formula (II), use η _sp / c to plot c to obtain a fitting straight line equation, the straight line The intercept of the equation is the intrinsic viscosity value [ η ];

Formula (I) is as follows:

,

Formula (II) is as follows:

;

(6) Calculate the degree of polymerization DP of the cellulose solution according to the formula (Ⅲ), and the formula (Ⅲ) is as follows:

.

Beneficial effect

1. The solvent used in the present invention will not cause oxidative degradation of cellulose, is stable and does not decompose during storage, is non-corrosive, and is quick and easy to prepare the solvent, and has a strong ability to dissolve cellulose;

2. In the process of dissolving cellulose, the assay method of the present invention does not need to add solid co-solvent, which is beneficial to the complete dissolving of cellulose, thereby improving the accuracy of assay data;

3. The measurement method of the present invention is simple and easy to operate, does not require expensive equipment, is low in cost, easy to use, short in measurement time, accurate in test data, and strong in practicability. Determination of the degree of polymerization of raw materials.

Detailed ways

A method for measuring the degree of polymerization of cellulose, comprising the following steps:

(1) Take dimethyl sulfoxide and 1-ethyl-3-methylimidazole acetate in a weight ratio of 3:1, and add 1-ethyl-3-methylimidazole acetate to dimethyl sulfoxide After stirring evenly, a mixed solvent is obtained;

(2) Take 20ml of the mixed solvent obtained in step (1) and put it into an Ubbelohde viscometer (0.77mm Ubbelohde viscometer), and then place it in a constant temperature water tank at 25°C for 25 minutes to measure the mixed solvent in the Ubbelohde viscometer. flow time t ₀ ;

When measuring, first carefully suck the mixed solvent into the sphere at the upper end of the capillary of the viscometer with the ear washing ball, release the ear washing ball when the liquid level exceeds the upper marking line of the sphere, and start timing when the liquid level falls to the upper marking line. When the liquid surface flows out of the sphere and reaches the lower mark line, stop the watch, measure the outflow time t ₀ , repeat it three times, and take the average value.

(3) Take 1 g of fiber raw material, cut it into pieces (the length does not exceed 1 mm), put it in a constant temperature drying oven, and dry it to constant weight at 102-105 ° C, then take the fiber raw material after constant weight and mixed solvent, Stirring at 25°C for 0.5h, the cellulose solution A, 0.24g/100mL cellulose solution B, 0.18g/100mL cellulose solution C, 0.12g/100mL cellulose solution C, 0.12g/100mL 100 mL of cellulose solution D and 0.06 g/100 mL of cellulose solution E;

(4) Put the five different concentrations of cellulose solutions (AE) obtained in step (3) into the Ubbelohde viscometer respectively, and then place them in a constant temperature water tank at 25°C for 20-30min to measure the cellulose solution Flow time t ₀ in the Ubbelohde viscometer;

When measuring, first carefully suck the cellulose solution into the sphere at the upper end of the capillary of the viscometer with the ear washing ball, release the ear washing ball when the liquid level exceeds the upper marking line of the sphere, and start timing when the liquid level falls to the upper marking line , Stop the watch when the liquid surface flows out of the sphere and reaches the lower mark line, measure the outflow time t, repeat three times, and take the average value.

(5) Calculate the reduced viscosity value h _sp / c according to the formula (I), the formula (I) is as follows:

,

The results are shown in the table below:

 

Then according to the formula (II), the formula (II) is as follows:

; Obtain a fitting straight line equation with η _sp / c to c plotting, and the intercept of straight line equation is intrinsic viscosity value [ η ], and [ η ] is 1.7321;

(6) Calculate the degree of polymerization DP of the cellulose solution according to the formula (Ⅲ), and the formula (Ⅲ) is as follows:

; Be 1.7321 by [ η ], calculate DP to be 437.

Claims (1)

1. an assay method for cellulosic degree of polymerization, is characterized in that: comprise the following steps:

(1) according to weight ratio 3:1, get dimethyl sulfoxide (DMSO) and 1-ethyl-3-methylimidazole acetate, 1-ethyl-3-methylimidazole acetate is added in dimethyl sulfoxide (DMSO), after stirring, obtain mixed solvent;

(2) get the mixed solvent that a part of step (1) obtains and pack in Ubbelohde viscometer, be then placed in the Water Tank with Temp.-controlled constant temperature 20～30min of 25 ℃, measure the flowing time t of mixed solvent in Ubbelohde viscometer ₀;

(3) get cellulose to be measured and be dried to constant weight, then with cellulose proportionings different from mixed solvent, cellulose is added in mixed solvent, under 25～30 ℃ of conditions, stir 0.5～1h, obtain respectively the cellulose solution of variable concentrations c;

(4) cellulose solution that step (3) is obtained to variable concentrations is respectively charged in Ubbelohde viscometer, be then placed in 25 ℃ ℃ Water Tank with Temp.-controlled constant temperature 20～30min, the flowing time t of the cellulose solution of measuring variable concentrations in Ubbelohde viscometer;

(5) according to formula (I), calculate respectively the reduced viscosity value of variable concentrations cellulose solution η _sp/ c,according to formula (II), use again η _sp/ cc mapping is obtained to a fitting a straight line equation, the intercept of straight-line equation be inherent viscosity [ η];

Formula (I) is as follows:

，

Formula (II) is as follows:

；

According to formula (III), calculate the degree of polymerization DP of cellulose solution, formula (III) is as follows:

。