A method for determining the gel point of delayed dissolution cellulose ether

Abstract

The present invention relates to a method for determining the gel point of a delayed dissolution type cellulose ether, comprising the following steps: (1) preparing a suspending agent, wherein the suspending agent is prepared by granulating a 50% to 80% ethanol solution with a non-ionic cellulose ether; (2) mixing a sample to be tested, the suspending agent, and water in a mass ratio of 2:100 to 1:100, stirring for t x After a certain time, the test solution is prepared; wherein a is the material-water ratio of the suspension agent to water, which corresponds to a viscosity of 20 to 40 mPa·s at room temperature after the suspension prepared by mixing the suspension agent with water is completely dissolved; t x is the time required for the suspension to completely dissolve; (3) measuring the viscosity-time curve of the solution to be tested, and calculating the gel point using the difference average method. The present invention achieves accurate and rapid determination of the gel points of different delayed-dissolution cellulose ethers by preparing a suspending agent and sieving it for different particle sizes to form a low-viscosity solution with a certain viscosity.

Description

Technical Field

[0001] The invention belongs to the technical field of cellulose ether testing methods, and particularly relates to a method for determining the gel point of delayed-dissolution cellulose ether. Background Art

[0002] Cellulose ethers are water-soluble polymers with excellent water solubility, viscosity deformability, and biodegradability, making them widely used in industries such as construction, medicine, food, daily chemicals, and energy. To address the solubility problem of cellulose ethers in cold water, industrial cellulose ethers are typically surface treated (using glyoxal) to rapidly disperse in water, where they gradually dissolve to form a homogeneous gel system. The gel point of a delayed-dissolution cellulose ether is a key indicator of the initial swelling process of the cellulose ether in water. Different usage environments have different requirements for its gel point. Therefore, accurately determining the gel point of a delayed-dissolution cellulose ether is of great significance for scientifically selecting the delay time, the amount of surface treatment agent added, and the development of functional materials. Currently, the dissolution time of delayed-dissolution cellulose ethers is mainly determined by visual observation and hand feeling of the solution viscosity change, or by plotting a viscosity-time curve by measuring the solution viscosity change. The turning point in the curve where the viscosity no longer increases is used as the initial and final dissolution times of the cellulose ether.

[0003] Currently, the gel point of delayed-dissolution cellulose ethers is mainly determined by testing the turning point of the viscosity-time curve during stirring in distilled water. However, since the slurry formed during the dispersion of cellulose ether in water is a granular slurry, it is easily subjected to gravity and sedimentation, resulting in the separation of water and gel during the gel formation process, making it difficult to measure its gel point. At the same time, to prevent the cellulose ether from sinking during the dissolution process, it must be continuously stirred, and the stirring process will affect the accurate determination of its gel point, resulting in large errors in the measurement results, making it difficult to truly reflect the accurate performance parameters of the test target. Therefore, developing a convenient, fast, and accurate gel point test method for delayed-dissolution cellulose ethers is of great significance for the development of cellulose ether products with different delayed dissolution times. Summary of the Invention

[0004] In order to solve the technical problems existing in the related art, an embodiment of the present invention provides a method for measuring the gel point of delayed dissolution type cellulose ether.

[0005] The embodiment of the present invention provides a method for determining the gel point of a delayed dissolution type cellulose ether, comprising the following steps:

[0006] (1) preparing a suspension concentrate, wherein the suspension concentrate is prepared by granulating a 50% to 80% ethanol solution with a nonionic cellulose ether, and the particle size is one or a combination of two or more of 40 to 50 mesh, 50 to 60 mesh, 60 to 70 mesh, 70 to 80 mesh, and 80 to 100 mesh;

[0007] (2) The sample to be tested (delayed dissolution type cellulose ether), suspending agent and water are mixed in a mass ratio of 2:100 to 1:100 and stirred for t x After a certain time, the test solution is prepared;

[0008] Where a is the material-water ratio of the suspending agent to water, which corresponds to a viscosity of 20-40 mPa·s at room temperature (20-25°C) after the suspension prepared by mixing the suspending agent with water is completely dissolved; t x is the complete dissolution time of the suspension, the complete dissolution time t x The change rate of the measured suspension viscosity value shall not exceed 5%;

[0009] (3) Measure the viscosity-time curve of the solution to be tested and calculate the gel point using the difference average method.

[0010] The present invention prepares a suspending agent (non-delayed dissolution neutral cellulose ether particles) and sieves different particle sizes thereof. By utilizing the different dispersion and dissolution times of the suspending agent in water, a low-viscosity solution with a certain viscosity is formed to achieve accurate and rapid determination of the gel points of different delayed dissolution cellulose ethers.

[0011] In some embodiments, the method further comprises: determining the complete dissolution time t of the suspension formed by mixing the suspending agent with different particle sizes and distilled water according to different material-water ratios. x and the viscosity value after complete dissolution; the complete dissolution time is based on the measured suspension viscosity value change rate not exceeding 5%, which provides a reference for the later selection of appropriate suspending agents (selection of particle size and selection of cellulose ether type) and their material-water ratio.

[0012] In some embodiments, the method further comprises estimating the gel point according to conventional methods, and the estimated gel point is t a ; and the suspending agent selected in step (1) satisfies the following conditions: t x <t a More preferably, the suspending agent selected in step (1) satisfies the following conditions: x <t a .

[0013] In some embodiments, the estimation of the gel point comprises the following steps: mixing the sample to be tested with distilled water, measuring the viscosity-time curve under stirring, and the turning point is the estimated gel point t a .

[0014] In some embodiments, the viscosity of the solution to be tested is measured by a digital viscometer, with rotor No. 1 selected and a rotation speed of 60 rpm.

[0015] In some embodiments, the measurement in step (3) is stopped when the viscosity of the test solution reaches 2 to 2.3 times the viscosity of the suspension.

[0016] In some embodiments, the calculation method of the difference average method is: the viscosity values corresponding to adjacent detection time points are calculated, and when η i+1 -η i ≥0.5, where η i t i The viscosity of the solution to be tested is measured by time, η i+1 t i+1 The viscosity of the solution to be tested is measured by time, t i+1 and t i is the adjacent detection time, record time t i+1 , when η appears for the first time n+1 -η n ≥1, where η n t n The viscosity of the solution to be tested is measured by time, η n+1 t n+1 The viscosity of the solution to be tested is measured by time, t n+1 and t n is the adjacent detection time, record time t n+1 , the gel point of the sample to be tested is t=t x+ (t i+1 +t n+1 ) / 2.

[0017] In some embodiments, the difference average method is processed using numerical software such as EXCEL or MATLAB.

[0018] In some embodiments, the suspending agent is prepared by wetting a non-ionic cellulose ether with a 50%-80% ethanol solution, followed by film formation, drying, crushing, and sieving. The non-ionic cellulose ether is one or a combination of hydroxyethyl cellulose (HEC) and hydroxypropyl methylcellulose (HPMC).

[0019] In some embodiments, the nonionic cellulose ether is one or a combination of hydroxyethyl cellulose (HEC) and hydroxypropyl methyl cellulose (HPMC) that is not surface treated (surface treated with glyoxal) and has a 1% viscosity (aqueous solution, at room temperature (20-25° C.)) greater than 1000 mPa·s.

[0020] The advantages and beneficial effects of the present invention are:

[0021] The present invention relates to a method for determining the gel point of a delayed-dissolving cellulose ether. The method can accurately test the gel point of the delayed-dissolving cellulose ether within different threshold values, avoiding errors caused by reading and / or stirring processes in traditional testing methods. After the suspension is prepared, the testing process is simple, rapid and accurate, and the surface treatment degree of the cellulose ether can be effectively evaluated, thereby providing a scientific basis for setting and accurately controlling the gel point of the delayed-dissolving cellulose ether. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the viscosity-time test curve of the suspension agent mixed with water (material-water ratio 3:1000);

[0023] Figure 2 It is the viscosity-time test curve of the test solution (test sample, suspension and water). DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0025] The embodiment of the present invention provides a method for determining the gel point of a delayed dissolution type cellulose ether, comprising the following steps:

[0026] (1) preparing a suspension concentrate, wherein the suspension concentrate is prepared by granulating a 50% to 80% ethanol solution with a nonionic cellulose ether, and the particle size is one or a combination of two or more of 40 to 50 mesh, 50 to 60 mesh, 60 to 70 mesh, 70 to 80 mesh, and 80 to 100 mesh;

[0027] (2) The sample to be tested (delayed dissolution type cellulose ether), suspending agent and water are mixed in a mass ratio of 2:100 to 1:100 and stirred for t x After a certain time, the test solution is prepared;

[0028] Where a is the material-water ratio of the suspending agent to water, which corresponds to a viscosity of 20-40 mPa·s at room temperature (20-25°C) after the suspension prepared by mixing the suspending agent with water is completely dissolved; t x is the complete dissolution time of the suspension, the complete dissolution time t x The change rate of the measured suspension viscosity value shall not exceed 5%;

[0029] (3) Measure the viscosity-time curve of the solution to be tested and calculate the gel point using the difference average method.

[0030] The present invention prepares a suspending agent (non-delayed dissolution neutral cellulose ether particles) and sieves different particle sizes thereof. By utilizing the different dispersion and dissolution times of the suspending agent in water, a low-viscosity solution with a certain viscosity is formed to achieve accurate and rapid determination of the gel points of different delayed dissolution cellulose ethers.

[0031] In some embodiments, the method further comprises: determining the complete dissolution time t of the suspension formed by mixing the suspending agent with different particle sizes and distilled water according to different material-water ratios. x and the viscosity value after complete dissolution; the complete dissolution time is based on the measured suspension viscosity value change rate not exceeding 5%, which provides a reference for the later selection of appropriate suspending agents (selection of particle size and selection of cellulose ether type) and their material-water ratio.

[0032] In some embodiments, the method further comprises estimating the gel point according to conventional methods, and the estimated gel point is t a ; and the suspending agent selected in step (1) satisfies the following conditions: t x <t a More preferably, the suspending agent selected in step (1) satisfies the following conditions: x <t a .

[0033] In some embodiments, the estimation of the gel point comprises the following steps: mixing the sample to be tested with distilled water, measuring the viscosity-time curve under stirring, and the turning point is the estimated gel point t a .

[0034] In some embodiments, the viscosity of the solution to be tested is measured by a digital viscometer, with rotor No. 1 selected and a rotation speed of 60 rpm.

[0035] In some embodiments, the measurement in step (3) is stopped when the viscosity of the test solution reaches 2 to 2.3 times the viscosity of the suspension.

[0036] In some embodiments, the calculation method of the difference average method is: the viscosity values corresponding to adjacent detection time points are calculated, and when η i+1 -η i ≥0.5, where η i t i The viscosity of the solution to be tested is measured by time, η i+1 t i+1 The viscosity of the solution to be tested is measured by time, t i+1 and t i is the adjacent detection time, record time t i+1 , when η appears for the first time n+1 -η n ≥1, where η n tn The viscosity of the solution to be tested is measured by time, η n+1 t n+1 The viscosity of the solution to be tested is measured by time, t n+1 and t n is the adjacent detection time, record time t n+1 , the gel point of the sample to be tested is t=t x+ (t i+1 +t n+1 ) / 2.

[0037] In some embodiments, the difference average method is processed using numerical software such as EXCEL or MATLAB.

[0038] In some embodiments, the suspending agent is prepared by wetting a non-ionic cellulose ether with a 50%-80% ethanol solution, followed by film formation, drying, crushing, and sieving. The non-ionic cellulose ether is one or a combination of hydroxyethyl cellulose (HEC) and hydroxypropyl methylcellulose (HPMC).

[0039] In some embodiments, the nonionic cellulose ether is one or a combination of hydroxyethyl cellulose (HEC) and hydroxypropyl methyl cellulose (HPMC) that is not surface treated (surface treated with glyoxal) and has a 1% viscosity (aqueous solution, at room temperature (20-25° C.)) greater than 1000 mPa·s.

[0040] The following is a specific example to illustrate the specific steps of the method for measuring the gel point of the delayed dissolution type cellulose ether of the present invention:

[0041] (1) preparing a suspension concentrate (prepared by granulating 60% ethanol solution with cellulose ether (HEC)) with a particle size of 50-60 mesh;

[0042] (2) Prepare a suspension solution with a mass ratio of a=3:1000 (i.e. a=0.003) and measure its viscosity-time curve; (e.g. Figure 1 The complete dissolution time t x The viscosity after complete dissolution is stable at 22.5-23 mPa·s for 5 minutes.

[0043] (3) Weighing 8 g of delayed dissolution type cellulose ether powder having a gel point greater than 10 min and 1.2 g of the suspending agent prepared in step (1), and mixing them with 400 g of distilled water to prepare a test solution;

[0044] (4) Stir the solution to be tested in step (3) for 5 minutes and measure its viscosity data, and draw a viscosity-time curve, such as Figure 2 As shown;

[0045] (5) Process the data in EXCEL or other numerical processing software (MATLAB), select a viscosity value every 1 minute, stop the measurement when the viscosity of the test liquid reaches 50 mPa·s, and calculate the first viscosity value η by interpolation calculation. i+1 -η i ≥0.5 and η n+1 -η n Time t when ≥1 i+1 and t n+1 In this embodiment, t i+1 =27min, t n+1 =37min, the gel point of the delayed dissolution type cellulose ether powder is: t=t x+ (t i+1 +t n+1 ) / 2=5+(27+37) / 2=37min.

[0046] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0047] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for determining the gel point of a delayed dissolution type cellulose ether, characterized in that: The steps include: (1) preparing a suspension concentrate, wherein the suspension concentrate is prepared by granulating a 50% to 80% ethanol solution with a non-ionic cellulose ether, and the particle size is one or a combination of two or more of 40 to 50 mesh, 50 to 60 mesh, 60 to 70 mesh, 70 to 80 mesh, and 80 to 100 mesh; (2) Stir the sample, suspension agent and water in a mass ratio of 2:100a:100 for t x After a certain time, the test solution is prepared; Where a is the material-water ratio of the suspending agent to water, which corresponds to a viscosity of 20-40 mPa·s at room temperature after the suspension is completely dissolved; t x is the complete dissolution time of the suspension, and the complete dissolution time t x The standard is that the change rate of the measured suspension viscosity value does not exceed 5%; It also includes estimating the gel point according to conventional methods, and estimating the gel point is t a ; and the suspending agent selected in step (1) satisfies the following conditions: t x <t a ; (3) Determine the viscosity-time curve of the test solution and calculate the gel point using the difference average method; in step (3), stop the measurement when the viscosity of the test solution reaches 2 to 2.3 times the viscosity value of the suspension; The calculation method of the difference average method is: the viscosity values corresponding to adjacent detection time points are calculated, and when η i+1 -η i ≥0.5, where η i t i The viscosity of the solution to be tested is measured by time, η i+1 t i+1 The viscosity of the solution to be tested is measured by time, t i+1 and t i is the adjacent detection time, record time t i+1 , when η appears for the first time n+1 -η n ≥1, where η n t n The viscosity of the solution to be tested is measured by time, η n+1 t n+1 The viscosity of the solution to be tested is measured by time, t n+1 and t n is the adjacent detection time, record time t n+1 , the gel point of the sample to be tested is t = t x+ (t i+1 +t n+1 ) / 2.

2. The method for determining the gel point of a delayed dissolution type cellulose ether according to claim 1, wherein: In the preparation of the suspending agent, the nonionic cellulose ether is one or a combination of hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

3. The method for determining the gel point of a delayed dissolution type cellulose ether according to claim 1, wherein: The nonionic cellulose ether is one or a combination of hydroxyethyl cellulose and hydroxypropyl methyl cellulose that is not surface treated and has a 1% viscosity greater than 1000 mPa·s at room temperature.

4. The method for determining the gel point of a delayed dissolution type cellulose ether according to claim 1, wherein: The gel point estimation comprises the following steps: mixing the sample to be tested with distilled water, measuring the viscosity-time curve under stirring, and the turning point is the estimated gel point t a .

5. The method for determining the gel point of a delayed dissolution type cellulose ether according to claim 1, wherein: The viscosity of the solution to be tested is measured by a digital viscometer, with rotor No. 1 selected and a rotation speed of 60 rpm.

6. The method for determining the gel point of a delayed dissolution type cellulose ether according to claim 1, wherein: The difference average method is processed using EXCEL table or MATLAB numerical software.

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