Preparation method of cellulose ether with high thickening time

Abstract

A preparation method of cellulose ether with high thickening time comprises the following steps: 1) taking a glyoxal solution and citric acid, adding the glyoxal solution and the citric acid into water, uniformly stirring and mixing to obtain a diluent, the mass ratio of glyoxal to water in the glyoxal solution is 1: 8, and the mass ratio of the diluent to the glyoxal solution to the citric acid is 2640-2660: 226-230: 129-131 for later use; 2) taking cellulose, crushing, alkalizing, etherifying and neutralizing to obtain slurry; 3) centrifuging the slurry to obtain a wet material with the moisture content of 45-55 wt%; (4) the diluent prepared in the step (1) is sprayed to the wet material, the wet material and the diluent are mixed to be uniform, the mass ratio of the wet material to the diluent is 550-600: 264-266, and a treated wet material is obtained; and 5) granulating and drying the treated wet material to obtain a target product. The method is simple in process, convenient to operate and low in treatment cost, and the prepared cellulose ether can effectively prolong the construction time of the water-based paint.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, and in particular to a method for preparing cellulose ether with high thickening time. Background Art

[0002] In recent years, China's environmental protection industry has continued to develop, and there are strict controls on solvent-based paints that produce pollution. Water-based paint is an environmentally friendly paint that mainly uses water as a solvent. Water-based paint has been widely recognized by the market for its excellent environmental performance. It has excellent properties such as reducing pollution, saving resources, safety and environmental protection, good adaptability to material surfaces, strong coating adhesion, and corrosion resistance.

[0003] In the application of water-based coatings, high performance requirements are placed on cellulose ethers, which need to have good dispersing and thickening properties to meet usage requirements.

[0004] Therefore, how to produce cellulose ether products with a high thickening time at a lower cost based on the existing process is one of the research and development directions of those skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing cellulose ether with a long thickening time in view of the deficiencies in the prior art. The method has a simple process, is easy to operate, and has a low processing cost. The prepared cellulose ether has a long viscosity time and can be used in water-based coatings to effectively avoid clumping and stratification in a short period of time, thereby extending the construction time of the water-based coating.

[0006] The technical solution of the present invention is: a method for preparing cellulose ether with high thickening time, comprising the following steps:

[0007] 1) adding glyoxal solution and citric acid into water, and stirring to obtain a diluent, wherein the mass ratio of glyoxal to water in the glyoxal solution is 1:8, and the mass ratio of the diluent, glyoxal solution, and citric acid is 2640-2660:226-230:129-131, and the mixture is set aside;

[0008] 2) crushing, alkalizing, etherifying and neutralizing cellulose to obtain slurry;

[0009] 3) The slurry is centrifuged to obtain a wet material, wherein the moisture content of the wet material is 45-55wt%;

[0010] 4) spraying the diluent prepared in step 1) onto the wet material and mixing well, wherein the mass ratio of the wet material to the diluent is 550-600:264-266, to obtain a treated wet material;

[0011] 5) The wet material is granulated and dried to obtain the target product.

[0012] Preferably, in step 1), the mass ratio of the diluent, the glyoxal solution and the citric acid is 2650:228:130.

[0013] Preferably, the cellulose in step 2) is refined cotton and / or coniferous pulp.

[0014] Preferably, the alkalization and etherification in step 2) are both carried out under vacuum, and the pH of the slurry is 7-8.

[0015] Preferably, the moisture content of the wet material in step 3) is 50 wt%.

[0016] Preferably, in step 4), the mass ratio of the wet material to the diluent is 570:265.

[0017] Preferably, in step 5), the 80-mesh screening rate of the target product is ≥95%.

[0018] The present invention also provides a cellulose ether with a high thickening time, which is prepared by any of the above-mentioned preparation methods.

[0019] The present invention also provides the use of the cellulose ether with a high thickening time as an additive for water-based coatings.

[0020] The above technical solution has the following beneficial effects:

[0021] 1. The preparation method of the present invention comprises the following steps: the cellulose raw material is crushed, alkalized, etherified and neutralized to obtain a slurry containing cellulose ether; the slurry is centrifuged to obtain a wet cellulose ether material; the prepared diluent is sprayed on the wet cellulose ether material and mixed to make the surface of the cellulose ether adhere to citric acid and glyoxal; after the cellulose ether product is added to the water-based coating, the glyoxal therein can promote the cellulose ether to fully dissolve and disperse in a water (ambient temperature) environment, thereby ensuring that the cellulose ether is evenly distributed in the water-based coating system; the citric acid adhered to the surface of the cellulose ether can reduce the pH of the surrounding environment of the cellulose ether to form a weakly acidic environment, prolong the swelling and tackification time of the cellulose ether, ensure that the cellulose ether is evenly dispersed in the water-based coating system before tackification, avoid the water-based coating from agglomerating and stratifying in a short time, ensure the coating and leveling properties of the coating during construction, and enhance the stability of the coating system to avoid particle sedimentation or precipitation.

[0022] 2. The present invention controls the mass ratio of the diluent, the glyoxal solution (the mass ratio of glyoxal to water is 1:8) and the citric acid in the diluent to be 2640-2660:226-230:129-131. The diluent with such a ratio is mixed with the wet material with a water content of 45-55wt% in a ratio of (264-266:550-600), so that the prepared cellulose ether has the advantages of high thickening time and high dispersibility. If the added amount is larger, the amount of citric acid and glyoxal used will increase, which is not conducive to cost control.

[0023] The applicant's experiments have shown that the tackification time of the cellulose ether prepared by the present invention can be extended to 5.5 hours. DETAILED DESCRIPTION

[0024] In the present invention, the cellulose raw materials are refined cotton and coniferous pulp, the weight ratio of refined cotton and coniferous pulp is 15:85, and other reagents are all industrial pure.

[0025] Example 1

[0026] Cellulose ether is produced intermittently. According to existing technical standards, the cellulose raw material is crushed, alkalized, etherified, and hydrochloric acid is added to adjust the pH to 7.98. The resulting slurry is sent to a centrifuge for sharpening and washed with hot water. The moisture content of the obtained filter cake (wet material) is about 50wt%.

[0027] Prepare diluent: prepare glyoxal solution first, the mass ratio of glyoxal to water is 1:8, mix water, glyoxal solution and citric acid in a mass ratio of 2292:228:130, stir for more than half an hour and set aside.

[0028] Spray the prepared diluent into the wet material and mix well. The ratio of the diluent to the wet material is 265:570 to obtain treated wet material.

[0029] The treated wet material is sent to a dryer, and after drying and crushing, a cellulose ether product is obtained, with a fineness of 80 mesh 99.1%, a water content of 3.8wt%, an appearance of white or off-white powder, RV2% wet viscosity of 14200mpa.S, an ash content of 3.1wt%, and a pH of 4.0. According to the standard tack time detection method, the tack time is 5h28min.

[0030] Example 2

[0031] Take the cellulose ether prepared in Example 1;

[0032] Emulsion: acrylic emulsion (solid content 25wt%);

[0033] Powder (per ton):

[0034] 325 white cement 800kg;

[0035] 200kg of heavy calcium limestone powder.

[0036] According to the ratio of 70.24wt% of powder, 29.40wt% of emulsion and 0.36wt% of cellulose ether, first take the emulsion, add the powder under stirring, then add the cellulose ether, continue stirring for 120s, observe the state and test the thickening time.

[0037] After observation, the obtained water-based paint has a uniform and delicate appearance, no obvious agglomeration, and a good dispersion effect.

[0038] Comparative Example 1

[0039] Take Lotte model FMC51502 cellulose ether, its RV2% wet viscosity is 14450mpa.S, ash content is 3.8wt%, water content is 3.4, fineness 80 mesh is 93.0%, pH is 4.2, and standard tack time detection method is used. After testing, its tack time is 5h17min.

[0040] According to the ratio and process of Example 2, a water-based coating was prepared.

[0041] After observation, the obtained water-based coating has a uniform and fine appearance, no obvious agglomeration, and a good dispersion effect, which is worse than the thickening time of the cellulose ether prepared in the present application.

[0042] Comparative Example 2

[0043] Cellulose ether was prepared according to the process of Example 1, omitting the addition of citric acid. The remaining processes were the same. According to the standard tack time detection method, the tack time was tested to be 11 minutes.

[0044] According to the ratio and process of Example 2, a water-based coating was prepared.

[0045] It was observed that the obtained water-based coating had obvious clumping and poor dispersion, which was significantly worse than the dispersion state of the cellulose ether prepared in the present application, and the construction time was greatly reduced.

Claims

1. A method for preparing cellulose ether with a high thickening time, characterized in that: The following steps are involved: 1) adding glyoxal solution and citric acid into water, and stirring to obtain a diluent, wherein the mass ratio of glyoxal to water in the glyoxal solution is 1:8, and the mass ratio of the diluent, glyoxal solution, and citric acid is 2640-2660:226-230:129-131, and the mixture is set aside; 2) crushing, alkalizing, etherifying and neutralizing cellulose to obtain slurry; 3) The slurry is centrifuged to obtain a wet material, wherein the moisture content of the wet material is 45-55wt%; 4) spraying the diluent prepared in step 1) onto the wet material and mixing well, wherein the mass ratio of the wet material to the diluent is 550-600:264-266, to obtain a treated wet material; 5) The wet material is granulated and dried to obtain the target product.

2. The preparation method according to claim 1, characterized in that: Step 1) The mass ratio of the diluent, the glyoxal solution and the citric acid is 2650:228:

130.

3. The preparation method according to claim 1, characterized in that: Step 2) The cellulose is refined cotton and / or coniferous pulp.

4. The preparation method according to claim 1, characterized in that: Step 2) The alkalization and etherification are both carried out under vacuum, and the pH of the slurry is 7-8.

5. The preparation method according to claim 1, characterized in that: Step 3) The moisture content of the wet material is 50wt%.

6. The preparation method according to claim 1, characterized in that: Step 4) The mass ratio of the wet material to the diluent is 570:

265.

7. The preparation method according to claim 1, characterized in that: Step 5) The 80-mesh screening rate of the target product is ≥95%.

8. A cellulose ether with a high thickening time, characterized in that: The product is prepared by any preparation method according to claim 1-7.

9. Use of the high thickening time cellulose ether according to claim 8 as an additive for water-based coatings.