Method for improving viscosity stability of slow-dissolving methyl cellulose ether

Abstract

The invention discloses a method for improving the viscosity stability of slow-dissolving methyl cellulose ether, and belongs to the technical field of fine chemical industry of polymer materials. The invention uses a specially prepared neutral glyoxal solution, controls the ratio of methyl cellulose ether and glyoxal by metering in the granulation stage of methyl cellulose ether, performs cross-linking treatment on the semi-finished product without affecting the normal cross-linking reaction of glyoxal, improves the effect of cross-linking, reduces the influence of excessive free glyoxal on the viscosity of the slow-dissolving product, ensures the stability of the viscosity of the slow-dissolving methyl cellulose ether product during use, and ensures the use performance of the product.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material fine chemical industry, and in particular relates to a method for improving the viscosity stability of slow-dissolving methyl cellulose ether. Background Art

[0002] At present, domestic methyl cellulose ether increases the slow dissolution time of the product by surface treatment, that is, during the production process, glyoxal solution is sprayed on the surface of methyl cellulose ether for cross-linking treatment, so that the methyl cellulose ether can be quickly dispersed when entering the water, and wait for the cross-linking to open before dissolving, thereby reducing the dissolution center and improving the uniformity of the solution. At present, most cross-linking processes are to directly dilute 40% of industrial glyoxal with water, use ordinary liquid nozzles and conventional cage spirals as cross-linking equipment, and the distribution of glyoxal is uneven, the cross-linking effect is uneven, and there is a lot of free glyoxal residue, which causes the excessive glyoxal in the methyl cellulose ether to slowly oxidize into oxalic acid. In the subsequent storage and application process of the methyl cellulose ether solution, the viscosity of the product drops greatly, resulting in the product being unable to meet the use requirements.

[0003] Therefore, it is necessary to find a method that can ensure the stability of the viscosity of instant products. Summary of the invention

[0004] The technical problem to be solved by the present invention is to develop a treatment process for improving the viscosity stability of a slow-dissolving methyl cellulose ether product.

[0005] In order to solve the above technical problems, the present invention provides a method for improving the viscosity stability of slow-soluble methyl cellulose ether, which comprises the following steps:

[0006] The methyl cellulose ether and the neutral glyoxal aqueous solution are uniformly mixed, crushed, dried and cross-linked to obtain the slow-soluble methyl cellulose ether; the neutral glyoxal solution is prepared by the following method: glyoxal is diluted with water to a glyoxal aqueous solution with a mass concentration of 1-20%, and an alkali and a buffer component are added to the system to adjust the pH of the glyoxal aqueous solution to 7±0.5; the alkali is at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide; the buffer component is at least one of sodium monohydrogen phosphate, potassium monohydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium trihydrogen phosphate and potassium trihydrogen phosphate.

[0007] Preferably, in the above method for improving the viscosity stability of slow-soluble methyl cellulose ether, glyoxal is diluted with water to a mass concentration of 1 to 12%.

[0008] More preferably, in the above method for improving the viscosity stability of slow-dissolving methyl cellulose ether, when producing slow-dissolving methyl cellulose ether with a slow dissolving time of 3 to 5 minutes, the mass concentration is diluted to 3.5 to 5.5%; when producing slow-dissolving methyl cellulose ether with a slow dissolving time of 5 to 10 minutes, the mass concentration is diluted to 3.5 to 5.5%; when producing slow-dissolving methyl cellulose ether with a slow dissolving time ≥15 minutes, the mass concentration is diluted to 7.5 to 9.5%.

[0009] Among them, in the above method for improving the viscosity stability of slow-soluble methyl cellulose ether, the amount of the alkali is controlled to control the mass percentage of the alkali in the neutral glyoxal aqueous solution to be 0.1-3%, and the amount of the buffer component is controlled to control the mass percentage of the buffer component in the neutral glyoxal aqueous solution to be 0.25-5%.

[0010] Preferably, in the above method for improving the viscosity stability of slow-soluble methyl cellulose ether, the amount of the alkali is controlled to control the mass percentage of the alkali in the neutral glyoxal aqueous solution to be 0.2-2.5%, and the amount of the buffer component is controlled to control the mass percentage of the buffer component in the neutral glyoxal aqueous solution to be 0.5-4.5%.

[0011] More preferably, in the above method for improving the viscosity stability of slow-soluble methyl cellulose ether, the amount of the alkali is controlled to have a mass percentage of 0.3-2% in the neutral glyoxal aqueous solution, and the amount of the buffer component is controlled to have a mass percentage of 0.75-4% in the neutral glyoxal aqueous solution.

[0012] Preferably, in the above method for improving the viscosity stability of slow-soluble methyl cellulose ether, the alkali is sodium hydroxide.

[0013] Preferably, in the above method for improving the viscosity stability of slow-soluble methyl cellulose ether, the buffer component is sodium dihydrogen phosphate.

[0014] Wherein, in the above method for improving the viscosity stability of slow-dissolving methyl cellulose ether, the dosage of the methyl cellulose ether and the neutral glyoxal aqueous solution is controlled as follows: when producing the slow-dissolving methyl cellulose ether with a slow dissolution time of 3 to 5 minutes, the mass ratio of the methyl cellulose ether to the neutral glyoxal aqueous solution is controlled to be 120 to 100:1; when producing the slow-dissolving methyl cellulose ether with a slow dissolution time of 5 to 10 minutes, the mass ratio of the methyl cellulose ether to the neutral glyoxal aqueous solution is controlled to be 100 to 60:1; when producing the slow-dissolving methyl cellulose ether with a slow dissolution time of ≥15 minutes, the mass ratio of the methyl cellulose ether to the neutral glyoxal aqueous solution is controlled to be 60 to 37.5:1.

[0015] Among them, in the above method for improving the viscosity stability of slow-soluble methyl cellulose ether, a granulator is used, and compressed air is used to keep the neutral glyoxal aqueous solution in a mist form and evenly sprayed to mix with the methyl cellulose ether through 2 to 5 anti-blocking atomizing nozzles in the granulator.

[0016] Among them, in the above method for improving the viscosity stability of slow-soluble methyl cellulose ether, during spray mixing, the pressure of compressed air is 0.3-0.6MPa, the speed of the granulator is 1000-1500r.pm, the operating frequency of the granulator is 30-55HZ, and the pressure in the granulator is -0.02-0.01Mpa.

[0017] In the above method for improving the viscosity stability of slow-dissolving methyl cellulose ether, during spray mixing, the flow rate of the methyl cellulose ether is controlled to be 18 to 20 m / s. 3 / h, the flow rate of the neutral glyoxal aqueous solution is controlled as follows: when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 3 to 5 minutes, the flow rate of the neutral glyoxal aqueous solution is 45 to 55 L / h; when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 5 to 10 minutes, the flow rate of the neutral glyoxal aqueous solution is 55 to 95 L / h; when producing slow-dissolving methyl cellulose ether with a slow dissolution time of ≥15 minutes, the flow rate of the neutral glyoxal aqueous solution is 95 to 150 L / h.

[0018] Wherein, in the above method for improving the viscosity stability of slow-soluble methyl cellulose ether, the temperature of drying and cross-linking is 80°C to 120°C.

[0019] Beneficial effects of the present invention:

[0020] The invention uses a specially prepared neutral glyoxal aqueous solution, strictly controls the ratio of methyl cellulose ether to glyoxal by metering in the methyl cellulose ether granulation stage, improves the cross-linking effect and reduces the influence of excessive free glyoxal on the viscosity of the slow-dissolving product without affecting the normal cross-linking reaction of glyoxal, and uses a special atomizing nozzle to perform cross-linking treatment on the semi-finished product in a plowshare granulator, thereby ensuring the stability of the viscosity of the product when the terminal customer uses the product, and ensuring the use performance of the product. DETAILED DESCRIPTION

[0021] Specifically, the method for improving the viscosity stability of slow-dissolving methyl cellulose ether comprises the following steps:

[0022] The methyl cellulose ether and the neutral glyoxal aqueous solution are uniformly mixed, crushed, dried and cross-linked to obtain the slow-soluble methyl cellulose ether; the neutral glyoxal solution is prepared by the following method: glyoxal is diluted with water to a glyoxal aqueous solution with a mass concentration of 1-20%, and an alkali and a buffer component are added to the system to adjust the pH of the glyoxal aqueous solution to 7±0.5; the alkali is at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide; the buffer component is at least one of sodium monohydrogen phosphate, potassium monohydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium trihydrogen phosphate and potassium trihydrogen phosphate.

[0023] In the present invention, the initial methyl cellulose ether can be obtained by alkalizing and etherifying (cotton, wood pulp) cellulose, sizing, and washing using conventional techniques available in the art.

[0024] When producing slow-dissolving products, water is used to dilute glyoxal to a glyoxal aqueous solution with a mass concentration of 1 to 20% (in actual production, commercially available 40% glyoxal is generally diluted), and the pH value of the solution is tested (the traditional dilution preparation method only does this step); then, alkalis such as sodium hydroxide and buffer components such as sodium dihydrogen phosphate are added to the aqueous solution to adjust the pH of the glyoxal aqueous solution to 7±0.5. After testing, the neutral glyoxal aqueous solution does not affect the normal cross-linking reaction of glyoxal. In order to further improve the viscosity stability of the slow-dissolving methylcellulose ether, the present invention preferably uses water to dilute glyoxal to a glyoxal aqueous solution with a mass concentration of 1 to 12%. In order to further improve the viscosity stability, the present invention further optimizes products of different brands or slow dissolution times: when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 3 to 5 minutes, the mass concentration is diluted to 3.5 to 5.5%; when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 5 to 10 minutes, the mass concentration is diluted to 3.5 to 5.5%; when producing slow-dissolving methyl cellulose ether with a slow dissolution time of ≥15 minutes, the mass concentration is diluted to 7.5 to 9.5%.

[0025] When water is used to dilute glyoxal to a glyoxal aqueous solution with a mass concentration of 1 to 20%, the pH of the solution is acidic. According to the test, the mass percentage of the alkali in the neutral glyoxal aqueous solution is controlled to be 0.1 to 3%, and the mass percentage of the buffer component in the neutral glyoxal aqueous solution is controlled to be 0.25 to 5%, and a neutral glyoxal solution with a pH of 7 ± 0.5 can be obtained. Preferably, the mass percentage of the alkali in the neutral glyoxal aqueous solution is controlled to be 0.2 to 2.5%, and the mass percentage of the buffer component in the neutral glyoxal aqueous solution is controlled to be 0.5 to 4.5%; more preferably, the mass percentage of the alkali in the neutral glyoxal aqueous solution is controlled to be 0.3 to 2%, and the mass percentage of the buffer component in the neutral glyoxal aqueous solution is controlled to be 0.75 to 4%. In order to further improve the viscosity stability of the slow-dissolving methyl cellulose ether, the preferred alkali of the present invention is sodium hydroxide and the buffer component is sodium dihydrogen phosphate.

[0026] At the same time, according to the different dissolution time requirements of different products and the different degrees of glyoxal cross-linking, different ratios of cellulose ether and glyoxal are required to achieve this. The specific dosage control is as follows: when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 3 to 5 minutes, the mass dosage ratio of methyl cellulose ether to neutral glyoxal aqueous solution is controlled to be 120 to 100:1; when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 5 to 10 minutes, the mass dosage ratio of methyl cellulose ether to neutral glyoxal aqueous solution is controlled to be 100 to 60:1; when producing slow-dissolving methyl cellulose ether with a slow dissolution time ≥15 minutes, the mass dosage ratio of methyl cellulose ether to neutral glyoxal aqueous solution is controlled to be 60 to 37.5:1. The amount of methyl cellulose ether entering the granulator is controlled by the on-site flow meter, and the amount of glyoxal added is accurately adjusted by the on-site metering pump, so as to accurately control the ratio of cellulose ether and glyoxal, and realize the ratio control of the cross-linking reaction.

[0027] In the present invention, when the slow-dissolving methyl cellulose ether is produced on a small scale, the conventional feeding means can be used to achieve a better uniform mixing of the methyl cellulose ether and the neutral glyoxal aqueous solution. However, in industrial production, in order to ensure the mixing effect of large-scale production, the present invention transforms the granulator, opens 2 to 5 atomizing nozzle holes on the side of the horizontal plowshare granulator ZLH-4.8, installs a special anti-blocking atomizing nozzle, and the nozzle uses compressed air for atomization; at the same time, an induced draft fan is used to keep the pressure balance in the equipment at a normal pressure state; 2 to 5 anti-blocking special atomizing nozzles are sprayed in the horizontal plowshare granulator, and the mist is sprayed uniformly in the entire granulator wall, so that the neutral glyoxal aqueous solution and the methyl cellulose ether material are well integrated, which is completely different from the conventional flowing water spraying, and the mixing uniformity of the product in this state is very good. Through experiments, in the present invention, during spray mixing, the pressure of the compressed air is controlled to be 0.3-0.6MPa, the rotation speed of the granulator is 1000-1500r.pm, the operating frequency of the granulator is 30-55HZ, and the pressure in the granulator is -0.02-0.01Mpa, thereby ensuring the atomization effect of the neutral glyoxal aqueous solution and the mixing effect in a very short time.

[0028] In the present invention, when the granulator is used for spray mixing, the flow rate of the methyl cellulose ether is controlled to be 18 to 20 m 3 / h, the flow rate of the neutral glyoxal aqueous solution is controlled as follows: when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 3 to 5 minutes, the flow rate of the neutral glyoxal aqueous solution is 45 to 55 L / h; when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 5 to 10 minutes, the flow rate of the neutral glyoxal aqueous solution is 55 to 95 L / h; when producing slow-dissolving methyl cellulose ether with a slow dissolution time of ≥15 minutes, the flow rate of the neutral glyoxal aqueous solution is 95 to 150 L / h.

[0029] In the present invention, in the drying stage, the drying temperature of the pulverizing system is set to 80-120° C., and the methyl cellulose ether material also completes the cross-linking reaction in this stage (the cross-linking reaction can generally be completed within 30-1 min).

[0030] The present invention is further described in detail below by way of examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0031] Neutral glyoxal aqueous solution preparation:

[0032] 1. Add 2m3 of glyoxal to the glyoxal preparation tank. 3 (about 80%) water, based on the cumulative flow of the on-site flow meter;

[0033] 2. Add 0.2m into the glyoxal preparation tank 3 (1 barrel) 40% glyoxal available on the market, based on the cumulative flow of the on-site flow meter;

[0034] 3. Add 25 kg of solid NaH2PO4, start stirring and continue stirring for 20 minutes;

[0035] 4. Take samples to check whether NaH2PO4 is completely dissolved and whether the solution is transparent and free of impurities;

[0036] 5. Add 8.0-10 kg of caustic soda flakes, stir continuously for 60 min, adjust the pH value to 6.5-7.5, and obtain a 3.5-4.5% neutral glyoxal aqueous solution.

[0037] Neutral glyoxal aqueous solution preparation:

[0038] 1. Add 2m3 of glyoxal to the glyoxal preparation tank. 3 (about 80%) water, based on the cumulative flow of the on-site flow meter;

[0039] 2. Add 0.4m3 of glyoxal into the glyoxal preparation tank. 3 (2 barrels) 40% glyoxal available on the market, based on the cumulative flow of the on-site flow meter;

[0040] 3. Add 50 kg of solid NaH2PO4, start stirring and continue stirring for 20 minutes;

[0041] 4. Take samples to check whether NaH2PO4 is completely dissolved and whether the solution is transparent and free of impurities;

[0042] 5. Add 16-20 kg of caustic soda flakes, stir continuously for 60 minutes, adjust the pH value to 6.5-7.5, and obtain a 7.5%-8.5% neutral glyoxal aqueous solution.

[0043] Example 1

[0044] By specially preparing the glyoxal aqueous solution, the glyoxal solution is neutral and does not affect its normal cross-linking reaction. The slow-dissolving products of other companies and two mainstream slow-dissolving methyl methyl cellulose ether products treated by the method of the present invention are compared and analyzed. The test results are shown in Appendix 1 (simulated storage conditions: the powder is stored in a 50°C oven for 30 consecutive days, which is used to replace the storage for one year under normal conditions. The test conditions are: 2% aqueous solution, kept at 20°C, sealed, and the viscosity is tested using a Brookfield RV viscometer). The results show that the viscosity of the glyoxal cross-linked product that has not been treated by the method of the present invention has a significantly higher drop in dry powder under simulated long-term storage conditions than the methyl cellulose ether treated by the method.

[0045] LH70MR production process: cotton pulp rolls and wood pulp rolls made of cotton linters are selected, crushed by a fine cotton grinder, and the cotton powder crushed to a certain mesh size is put into the reactor, and a certain amount of chemicals are added. After a period of reaction, the generated cellulose ether is slurried and washed, and enters the granulation stage, and the 3.5-4.5% neutral glyoxal aqueous solution is added. The feed amount of methyl cellulose ether is 20m 3 / h, the air compressor pressure of the granulator is 0.5Mpa, three anti-blocking atomizing nozzles are opened on site, the motor speed of the granulator is controlled to be 1250r.pm, the working frequency of the granulator is 42HZ, the internal pressure of the granulator is maintained at 0.01MPa, and compressed air is used to keep the neutral glyoxal aqueous solution in a mist-like and uniform spray and mixed with methyl cellulose ether. The granulator has a single-line neutral glyoxal aqueous solution, and the mass dosage ratio of methyl cellulose ether to neutral glyoxal aqueous solution is controlled to be 110:1, so as to ensure its atomization and mixing effect in a very short time, and then enter the crushing and drying stage. In the drying stage, the drying temperature of the crushing system is set to 105℃, and the material continues to undergo subsequent cross-linking reactions in this stage. The dissolution time of the material produced under this process condition is 3 minutes to 5 minutes.

[0046] LH55RR production process: cotton pulp rolls and wood pulp rolls made of cotton linters are selected, crushed by a fine cotton grinder, and the cotton powder crushed to a certain mesh size is put into the reactor, and a certain amount of chemicals are added. After a period of reaction, the generated cellulose ether is slurried and washed, and enters the granulation stage, and the 7.5-8.5% neutral glyoxal aqueous solution is added. The feed amount of methyl cellulose ether is 18m 3 / h, the air pressure of the granulator on site is 0.6Mpa, three anti-blocking atomizing nozzles are turned on on site, the motor speed of the granulator is controlled to be 1500r.pm, the working frequency of the granulator is 55HZ, the internal pressure of the granulator is maintained at 0MPa, and compressed air is used to keep the neutral glyoxal aqueous solution in a mist-like uniform spray and mixed with methyl cellulose ether. The mass ratio of methyl cellulose ether to neutral glyoxal aqueous solution is controlled to be 50:1, and the atomization and mixing effect is guaranteed in a very short time. The subsequent crushing and drying stage, in the drying stage, the drying temperature of the crushing system is set to 115℃, and the material continues to undergo subsequent cross-linking reactions in this stage. The dissolution time of the material produced under this process condition is more than 15 minutes.

[0047] Table 1 Comparison of viscosity stability of slow-dissolving methyl cellulose ethers

[0048]

[0049] Note: The fluctuation of viscosity is due to the systematic analysis error in viscosity analysis.

[0050] Example 2

[0051] HK200000S production process: select cotton pulp rolls and wood pulp rolls made of cotton linters, crush them in a fine cotton crusher, and put the cotton powder into a reactor after a certain mesh size. Add a certain amount of chemicals. After a period of reaction, the generated cellulose ether is slurried and washed, and enters the granulation stage. Add the configured 3.5-4.5% neutral glyoxal aqueous solution. The feed amount of methyl cellulose ether is 20m 3 / h, the air pressure of the granulator on site is 0.3Mpa, three anti-blocking atomizing nozzles are opened on site, the motor speed of the granulator is controlled to be 1000r.pm, the working frequency of the granulator is 30HZ, the internal pressure of the granulator is maintained at -0.01MPa, and compressed air is used to keep the neutral glyoxal aqueous solution in a mist-like state and spray it evenly to mix with the methyl cellulose ether. The mass ratio of methyl cellulose ether to the neutral glyoxal aqueous solution is controlled to be 110:1, and the atomization and mixing effect is guaranteed in a very short time. The subsequent crushing and drying stage, in the drying stage, the drying temperature of the crushing system is set to 85℃, and the cellulose ether material continues to undergo subsequent cross-linking reactions in this stage. The dissolution time of the material produced under this process condition is 3 minutes to 5 minutes.

[0052] LH55RR production process: cotton pulp rolls and wood pulp rolls made of cotton linters are selected, crushed by a fine cotton grinder, and the cotton powder crushed to a certain mesh size is put into the reactor, and a certain amount of chemicals are added. After a period of reaction, the generated cellulose ether is slurried and washed, and enters the granulation stage, and the 7.5-8.5% neutral glyoxal aqueous solution is added. The feed amount of methyl cellulose ether is 18m 3 / h, the air pressure of the granulator on site is 0.6Mpa, three anti-blocking atomizing nozzles are turned on on site, the motor speed of the granulator is controlled to be 1500r.pm, the working frequency of the granulator is 55HZ, the internal pressure of the granulator is maintained at 0MPa, and compressed air is used to keep the neutral glyoxal aqueous solution in a mist-like state and spray it evenly to mix with the methyl cellulose ether. The mass ratio of methyl cellulose ether to the neutral glyoxal aqueous solution is controlled to be 50:1, and the atomization and mixing effect is guaranteed in a very short time. The subsequent crushing and drying stage, in the drying stage, the drying temperature of the crushing system is set to 115℃, and the cellulose ether material continues to undergo subsequent cross-linking reactions in this stage. The dissolution time of the material produced under this process condition is greater than 15 minutes.

[0053] The above two slow-dissolving products HK200000S and LH55RR were subjected to viscosity stability test, and the test standard was 2% solution of slow-dissolving methyl cellulose ether (distilled water), and the results are shown in Table 2. The results show that whether it is the HPMC HK200000S slow-dissolving product of 3-5 minutes or the HEMC LH55RR slow-dissolving product of more than 15 minutes, the cross-linking treatment by the method of the present invention can well improve its viscosity stability.

[0054] Table 2 Viscosity stability test results of slow-dissolving methyl cellulose ether

[0055]

[0056] Note: The fluctuation of viscosity is due to the systematic analysis error in viscosity analysis.

[0057] Considering the presence of phosphate in the neutral glyoxal aqueous solution, which is a retarder and may affect the setting time of cement, the present invention conducted an application test (the test standard is JC / T547-2017 Ceramic Tile Adhesive), and the results are shown in Table 3.

[0058] Table 3 Application test

[0059]

[0060]

[0061] Combining Table 2 and Table 3, it can be seen that while the present invention improves stability by introducing phosphate, the initial setting time and final setting time of cement vary little and are both within an acceptable range.

Claims

1. A method for improving the viscosity stability of slow-dissolving methyl cellulose ether, characterized in that: The following steps are involved: The methyl cellulose ether and the neutral glyoxal aqueous solution are uniformly mixed, crushed, dried and cross-linked to obtain the slow-dissolving methyl cellulose ether; the neutral glyoxal solution is prepared by the following method: when producing the slow-dissolving methyl cellulose ether with a slow-dissolving time of 3 to 5 minutes, glyoxal is diluted with water to a glyoxal aqueous solution with a mass concentration of 3.5 to 5.5%; when producing the slow-dissolving methyl cellulose ether with a slow-dissolving time of 5 to 10 minutes, glyoxal is diluted with water to a glyoxal aqueous solution with a mass concentration of 3.5 to 5.5%; when producing the slow-dissolving methyl cellulose ether with a slow-dissolving time of ≥15 minutes, glyoxal is diluted with water to a glyoxal aqueous solution with a mass concentration of 3.5 to 5.5%; The method comprises the following steps: releasing the glyoxal aqueous solution to a mass concentration of 7.5-9.5%; adding an alkali and a buffer component to the system to adjust the pH of the glyoxal aqueous solution to 7±0.5, wherein the alkali is at least one of sodium hydroxide, potassium hydroxide, and calcium hydroxide; the buffer component is at least one of sodium monohydrogen phosphate, potassium monohydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium trihydrogen phosphate, and potassium trihydrogen phosphate; the amount of the alkali is such that the mass percentage of the alkali in the neutral glyoxal aqueous solution is controlled to be 0.1-3%, and the amount of the buffer component is such that the mass percentage of the buffer component in the neutral glyoxal aqueous solution is controlled to be 0.25-5%; The dosage of the methyl cellulose ether and the neutral glyoxal aqueous solution is controlled as follows: when producing a slow-dissolving methyl cellulose ether with a slow-dissolving time of 3 to 5 minutes, the mass ratio of the methyl cellulose ether to the neutral glyoxal aqueous solution is controlled to be 120 to 100:1; when producing a slow-dissolving methyl cellulose ether with a slow-dissolving time of 5 to 10 minutes, the mass ratio of the methyl cellulose ether to the neutral glyoxal aqueous solution is controlled to be 100 to 60:1; when producing a slow-dissolving methyl cellulose ether with a slow-dissolving time of ≥15 minutes, the mass ratio of the methyl cellulose ether to the neutral glyoxal aqueous solution is controlled to be 60 to 37.5:1; A granulator is used, and compressed air is used to keep the neutral glyoxal aqueous solution in a mist-like state and spray it evenly to mix with the methyl cellulose ether through 2 to 5 anti-blocking atomizing nozzles in the granulator; When spraying and mixing, control the flow rate of methyl cellulose ether to 18-20m 3 / h, the flow rate of the neutral glyoxal aqueous solution is controlled as follows: when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 3 to 5 minutes, the flow rate of the neutral glyoxal aqueous solution is 45 to 55 L / h; when producing slow-dissolving methyl cellulose ether with a slow dissolution time of 5 to 10 minutes, the flow rate of the neutral glyoxal aqueous solution is 55 to 95 L / h; when producing slow-dissolving methyl cellulose ether with a slow dissolution time of ≥15 minutes, the flow rate of the neutral glyoxal aqueous solution is 95 to 150 L / h.

2. The method for improving the viscosity stability of slow-dissolving methyl cellulose ether according to claim 1, characterized in that: The alkali content is 0.2-2.5%, and the buffer component content is 0.5-4.5%.

3. The method for improving the viscosity stability of slow-dissolving methyl cellulose ether according to claim 2, characterized in that: The alkali content is 0.3-2%, and the buffer component is 0.75-4%.

4. The method for improving the viscosity stability of slow-dissolving methyl cellulose ether according to claim 1, characterized in that: The base is sodium hydroxide.

5. The method for improving the viscosity stability of slow-dissolving methyl cellulose ether according to claim 1, characterized in that: The buffer component is sodium dihydrogen phosphate.

6. The method for improving the viscosity stability of slow-dissolving methyl cellulose ether according to claim 1, characterized in that: During spray mixing, the pressure of compressed air is 0.3-0.6MPa, the rotation speed of the granulator is 1000-1500r.pm, the operating frequency of the granulator is 30-55HZ, and the pressure inside the granulator is -0.02-0.01Mpa.

7. The method for improving the viscosity stability of slow-dissolving methyl cellulose ether according to any one of claims 1 to 6, characterized in that: The temperature of the drying and cross-linking is 80°C to 120°C.

Images