Preparation method of modified hydroxyethyl cellulose and application of modified hydroxyethyl cellulose in coating

Abstract

The invention provides a preparation method of modified hydroxyethyl cellulose and application of the modified hydroxyethyl cellulose in a coating, and belongs to the field of modified hydroxyethyl cellulose. The preparation method comprises the steps of alkalization, etherification and modification. Adding ethylene oxide into the alkalized liquid for the first time, heating to 57-62 DEG C at the rate of 1.8-2.2 DEG C / min, carrying out heat preservation reaction for 58-63 minutes, after the reaction is finished, reducing the temperature to 38-42 DEG C, adding an acetic acid solution to adjust the pH to be neutral, then adding ethylene oxide for the second time, uniformly stirring, heating to 73-76 DEG C at the rate of 0.8-1.2 DEG C / min, carrying out heat preservation reaction for 48-52 minutes, after the reaction is finished, adding an acetic acid solution to adjust the pH to be neutral, and carrying out heat preservation reaction for 48-52 minutes; filtering, washing and drying to obtain etherate; the modified hydroxyethyl cellulose prepared by the method disclosed by the invention has higher surface activity, high viscosity and excellent salt tolerance, and has better stability when being applied to a coating.

Description

Technical Field

[0001] The invention belongs to the field of modified hydroxyethyl cellulose, and particularly relates to a preparation method of modified hydroxyethyl cellulose and application of the modified hydroxyethyl cellulose in coatings. Background Art

[0002] Hydroxyethyl cellulose is a white or light yellow, non-toxic and odorless fibrous or powdered solid. It is prepared by etherification reaction of alkaline cellulose and ethylene oxide (or chloroethanol). It belongs to non-ionic soluble cellulose ethers. It has good thickening, suspension, dispersion, emulsification, adhesion, film-forming, moisture protection and colloid protection properties. It has been widely used in oil extraction, coatings, construction, medicine, food, textiles, papermaking and polymer polymerization.

[0003] Hydroxyethyl cellulose has a large molecular weight and contains more hydrophilic groups, especially the side chain hydroxyl groups which can undergo chain polymerization and have good water solubility. However, its macromolecular chain lacks hydrophobic groups that match the hydrophilic groups, making it difficult to improve its surface activity. In addition, hydroxyethyl cellulose has low stability and transmittance, resulting in poor use effect.

[0004] Modified hydroxyethyl cellulose is obtained by introducing a new type of hydrophobic modification group into the molecular structure of hydroxyethyl cellulose, which makes the modified hydroxyethyl cellulose show hydrophobic effect and viscosity-increasing effect, thereby showing significant viscosity-increasing property, stability and salt resistance. As an important and promising variety among new dispersants, modified hydroxyethyl cellulose has high added value and broad market prospects. It is used as a thickener and dispersant in high-end fields, which is of great significance to the transformation of cellulose ether products, the updating of technology and the enhancement of international market competitiveness.

[0005] (Synthesis and Characterization of Hydrophobically Associating Hydroxyethyl Cellulose, Shao Ziqiang) discloses the preparation of hydrophobically associating hydroxyethyl cellulose using halogenated alkanes as hydrophobizing agents, and the addition of borate modifiers during the preparation process. A large number of hydroxyl groups in hydroxyethyl cellulose and its modified molecules are easily complexed with the boron atoms in the borate to form a cross-linking and thickening effect; however, the modified hydroxyethyl cellulose obtained by this method still has the defect of poor stability when used in coatings.

[0006] With the development of modification technology, the prior art generally introduces anhydride groups into the molecular chain of hydroxyethyl cellulose, and improves its surface activity through the esterification reaction of the anhydride groups; for example, CN117700568A discloses a preparation method of hydroxyethyl cellulose modified with dodecyl succinic anhydride, and the preparation method comprises the steps of activation reaction of cellulose, hydroxyethylation reaction, esterification reaction of a modifier and hydroxyethyl cellulose, secondary hydroxyethylation reaction, neutralization, washing, and drying; specifically, based on the different reactivity of the three active hydroxyl groups C2, C3 and C6 on the glucose unit of cellulose, the more active hydroxyl groups are first subjected to hydroxyethylation reaction, then subjected to esterification reaction with the modifier dodecyl succinic anhydride, and then subjected to hydroxyethylation reaction of the other hydroxyl groups, thereby obtaining uniformly substituted dodecyl succinic anhydride modified hydroxyethyl cellulose; The modified hydroxyethyl cellulose obtained by this method still has a low viscosity and poor stability when used in coatings. Summary of the invention

[0007] In order to solve the technical problems existing in the prior art, the present invention provides a method for preparing modified hydroxyethyl cellulose and its application in coatings. The prepared modified hydroxyethyl cellulose has high surface activity, high viscosity, good salt resistance, and good stability when used in coatings.

[0008] In view of the above technical problems, the present invention adopts the following technical solutions: A method for preparing modified hydroxyethyl cellulose includes alkalization, etherification and modification steps, and the specific operations are as follows: 1. Alkalization The refined cotton is crushed to a particle size of 120-140 nm, and then placed in an alkali solution for ultrasonic treatment, the ultrasonic time is 20-25 minutes, the ultrasonic power is 125-135W, and the ultrasonic frequency is 32-38kHz. After the ultrasonic treatment, the temperature is controlled to be 18-22°C, vacuum is replaced 4 times, nitrogen is filled, the pressure is controlled to be 0.13-0.18MPa, and the temperature is kept for 47-52 minutes for alkalization. After the alkalization is completed, an alkalized liquid is obtained; The mass ratio of the refined cotton powder to the alkali solution is 9.8-10.2:96-105; The alkali solution is prepared by stirring deionized water, sodium hydroxide and isopropanol at 56-60° C. for 0.8-1.2 hours; The mass ratio of the deionized water, sodium hydroxide and isopropanol is 9.7-10.2:2.0-2.5:86.5-87.3.

[0009] 2. Etherification Add ethylene oxide to the alkalized liquid for the first time, heat it to 57-62°C at a rate of 1.8-2.2°C / min, keep it warm for 58-63min, lower the temperature to 38-42°C after the reaction, add acetic acid solution to adjust the pH to neutral, then add ethylene oxide for the second time, stir evenly, heat it to 73-76°C at a rate of 0.8-1.2°C / min, keep it warm for 48-52min, add acetic acid solution to adjust the pH to neutral after the reaction, filter, wash and dry to obtain an etherified product; The mass ratio of the alkalizing liquid, the first addition amount of ethylene oxide, and the second addition amount of ethylene oxide is 106-114:4.3-4.6:5.8-6.2; The mass concentration of the acetic acid solution is 90-94%.

[0010] 3. Modification The etherified product is placed in dimethyl sulfoxide, stirred evenly, and then oleic acid is added, the temperature is raised to 45-50°C, and the mixture is stirred for 28-32 minutes. After the stirring is completed, a modifier is added, and the addition rate is controlled to be 0.03-0.05 g / min. After the addition is completed, the temperature is continued to be raised to 83-87°C, and the mixture is stirred for 1.8-2.2 hours. After the stirring is completed, the mixture is naturally cooled to room temperature, filtered and washed, and dried at 58-62°C for 23.0-25.0 hours to obtain modified hydroxyethyl cellulose; The mass volume ratio of the etherified product, dimethyl sulfoxide, oleic acid and modifier is 9.6-10.3 g:1000 mL:0.50-0.53 g:0.60-0.65 g; The preparation method of the modifier comprises the following steps: placing fumed silica in a mixed acid solution, stirring it evenly, raising the temperature to 64-68° C., and heat-treating it for 0.8-1.2 hours. After the heat-treating is completed, filtering, washing, and drying to obtain acidified fumed silica; adding toluene to the acidified fumed silica, stirring it evenly, adding thionyl chloride, raising the temperature to 40-44° C. in a nitrogen atmosphere, and heat-treating it for 58-62 minutes. After the reaction is completed, filtering, washing, and drying to obtain chlorinated fumed silica; placing chlorinated fumed silica in toluene, adding 1,6-hexanediamine and diethylenetriamine, The temperature is raised to 72-75° C., and the reaction is kept warm for 19.5-20.6 hours. After the reaction is finished, the primary modifier is obtained after filtering, washing, and drying. The primary modifier is added to dimethyl sulfoxide, and after stirring, 3,3′,4,4′-dibenzophenone tetraacid dianhydride and concentrated sulfuric acid are added for ultrasonic dispersion. The ultrasonic time is 13-18 minutes, the ultrasonic power is 105-114W, and the ultrasonic frequency is 22-25kHz. After the ultrasonic treatment is finished, the temperature is raised to 88-92° C. in a nitrogen atmosphere, and the reaction is stirred for 13-15 hours. After the reaction is finished, the modifier is obtained after filtering, washing, and drying. The mass ratio of the fumed silica to the mixed acid solution is 1:6-10; The mixed acid solution is a mixture of concentrated sulfuric acid and concentrated nitric acid, the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1.8-2.3:1, the mass concentration of the concentrated sulfuric acid is 95-98%, and the mass concentration of the concentrated nitric acid is 63-67%; The mass volume ratio of the acidified fumed silica, toluene and thionyl chloride is 5.8-6.2 g: 590-610 mL: 10.7-11.2 g; The mass volume ratio of the chlorinated silicon dioxide, toluene, 1,6-hexanediamine and diethylenetriamine is 1.4-1.6 g:780-830 mL:2.4-2.6 g:3.5-4.0 g; The volume mass ratio of the dimethyl sulfoxide, the primary modifier, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and concentrated sulfuric acid is 490-510 mL: 2.5-2.7 g: 6.3-6.5 g: 12-15 mL; The mass concentration of the concentrated sulfuric acid is 93-96%.

[0011] The modified hydroxyethyl cellulose prepared by the preparation method is used in coatings.

[0012] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The present invention adopts a specific method to prepare modified hydroxyethyl cellulose, specifically, firstly alkalize the refined cotton powder to activate the hydroxyl group of cellulose and ensure the full swelling of cellulose, and ultrasonic treatment is combined to help accelerate the alkalization reaction, improve the reaction uniformity, and make the hydroxyl group of cellulose have higher reaction activity; in the etherification step, ethylene oxide is used as an etherifying agent, and ethylene oxide introduces hydroxyethyl groups through a ring-opening reaction to convert alkali cellulose into hydroxyethyl cellulose, and a two-stage etherification is adopted to ensure the sufficiency of the reaction and improve the degree of substitution of hydroxyethoxy groups; in the modification step, the addition of oleic acid can improve the wettability and dispersibility of the etherified product, and the carboxyl group at one end of the oleic acid can be combined with the hydroxyl group of hydroxyethyl cellulose, and the long-chain alkane at the other end extends out, thereby enhancing the hydrophobic property of hydroxyethyl cellulose, and the modifier is prepared by a specific method, specifically, gas phase dioxide With silicon as a modified matrix, fumed silica can significantly improve the fluidity and viscosity of hydroxyethyl cellulose. First, the fumed silica is acidified and chlorinated so that the surface of the fumed silica contains more acyl chloride groups and the dispersibility of the fumed silica is enhanced. Then, an amino compound is introduced to form a product containing amino groups on the surface. Then, an acid anhydride compound is introduced, and the surface of the modifier contains more acid anhydride groups through the reaction between the acid anhydride and the amino group. In the modification step, the acid anhydride group of the modifier can be esterified with the etherified product so that it has both excellent hydrophilicity and hydrophobicity, further increasing the crosslinking degree and stability of the modified hydroxyethyl cellulose, and finally improving the stability and salt resistance of the product, so that it has better application performance in coatings. When the modified hydroxyethyl cellulose is used in coatings, the viscosity of the coating decreases less with the increase of dilution, and the stability is stronger. 2. The modified hydroxyethyl cellulose prepared by the method of the present invention has a light transmittance of 96.1-96.7% and a hydroxyethoxy substitution degree of 2.29-2.34; 3. The modified hydroxyethyl cellulose prepared by the method of the present invention has a viscosity of 2968-2974 mpa·s in aqueous solution at 25°C; 4. The modified hydroxyethyl cellulose prepared by the method of the present invention has a viscosity of 4018-4155 mpa·s in a 3.0 wt% sodium chloride solution at 25°C; 5. The modified hydroxyethyl cellulose prepared by the method of the present invention is applied to coatings. When the dilution degree of the coating is 0, the viscosity at a rotation speed of 3 rpm is 14793-14806 mpa·s, the viscosity at a rotation speed of 10 rpm is 10624-10635 mpa·s, the viscosity at a rotation speed of 20 rpm is 6265-6274 mpa·s, and the viscosity at a rotation speed of 40 rpm is 4182-4193 mpa·s; When the paint dilution is 20%, the viscosity at 3rpm is 2506-2518mpa·s, the viscosity at 10rpm is 1824-1832mpa·s, the viscosity at 20rpm is 1117-1125mpa·s, and the viscosity at 40rpm is 814-822mpa·s; When the paint dilution is 20%, the viscosity at 3rpm is 1263-1274mpa·s, the viscosity at 10rpm is 974-987mpa·s, the viscosity at 20rpm is 614-622mpa·s, and the viscosity at 40rpm is 556-561mpa·s. DETAILED DESCRIPTION

[0013] In order to more clearly understand the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described.

[0014] Example 1 1. Alkalization 10.0 g of refined cotton was crushed to a particle size of 130 nm, and then placed in 100 g of alkali solution for ultrasonic treatment. The ultrasonic time was 23 min, the ultrasonic power was 130 W, and the ultrasonic frequency was 36 kHz. After the ultrasonic treatment, the temperature was controlled to 20 ° C, vacuumed and replaced 4 times, nitrogen was filled, the pressure was controlled to 0.15 MPa, and the temperature was kept for alkalization for 50 min. After the alkalization was completed, an alkalized solution was obtained; The alkali solution is prepared by stirring 10.0 g of deionized water, 2.2 g of sodium hydroxide and 87.0 g of isopropanol at 58° C. for 1.0 h.

[0015] 2. Etherification Add 4.5 g of ethylene oxide to 110 g of the alkalized liquid, heat to 60 ° C at a rate of 2.0 ° C / min, keep warm for 60 minutes, after the reaction is completed, lower the temperature to 40 ° C, add 92 wt% acetic acid solution to adjust the pH to neutral, then add 6.0 g of ethylene oxide, stir evenly, heat to 75 ° C at a rate of 1.0 ° C / min, keep warm for 50 minutes, after the reaction is completed, add 92 wt% acetic acid solution to adjust the pH to neutral, filter, wash and dry to obtain an etherified product.

[0016] 3. Modification 10.0 g of the etherified product was placed in 1000 mL of dimethyl sulfoxide, and after being stirred evenly, 0.51 g of oleic acid was added, and the temperature was raised to 47°C, and the mixture was stirred for 30 min. After the stirring was completed, 0.63 g of the modifier was added, and the addition rate was controlled to be 0.04 g / min. After the addition was completed, the temperature was continued to be raised to 85°C, and the mixture was stirred for 2.0 h. After the stirring was completed, the mixture was cooled to room temperature naturally, filtered and washed, and dried at 60°C for 24.0 h to obtain modified hydroxyethyl cellulose; The preparation method of the modifier is as follows: placing fumed silica in a mixed acid solution of 8 times the mass, stirring evenly, raising the temperature to 66°C, and heat-treating for 1.0h. After the heat-treating is completed, filtering, washing, and drying to obtain acidified fumed silica; adding 600mL of toluene to 6.0g of acidified fumed silica, stirring evenly, adding 11.0g of thionyl chloride, raising the temperature to 42°C in a nitrogen atmosphere, heat-retaining for 60min, filtering, washing, and drying after the reaction is completed to obtain chlorinated fumed silica; putting 1.5g of chlorinated fumed silica into 800mL of toluene, adding 2.5g of 1,6-hexanediamine and 3.7g of diethylenetriamine, raising the temperature to 74°C, heat-retaining for 20.0h, filtering, washing, and drying after the heat-retaining reaction is completed to obtain a primary modifier; adding 2.6g of the primary modifier to 500mL of dimethyl sulfoxide, stirring evenly, and adding 6.4g 3,3′,4,4′-dibenzophenone tetracarboxylic dianhydride and 14 mL of 95 wt% concentrated sulfuric acid were subjected to ultrasonic dispersion, the ultrasonic time was 15 min, the ultrasonic power was 110 W, and the ultrasonic frequency was 23 kHz. After the ultrasonic treatment, the temperature was raised to 90° C. in a nitrogen atmosphere, and the reaction was stirred for 14 h. After the reaction was completed, the modified agent was filtered, washed, and dried. The mixed acid solution is a mixture of concentrated sulfuric acid and concentrated nitric acid, the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 2:1, the mass concentration of the concentrated sulfuric acid is 96%, and the mass concentration of the concentrated nitric acid is 65%.

[0017] Example 2 1. Alkalization 9.8 g of refined cotton was crushed to a particle size of 120 nm, and then placed in 96 g of alkali solution for ultrasonic treatment. The ultrasonic time was 20 min, the ultrasonic power was 125 W, and the ultrasonic frequency was 32 kHz. After the ultrasonic treatment, the temperature was controlled to 18 ° C, and the vacuum was replaced 4 times. Nitrogen was filled and the pressure was controlled to 0.13 MPa. The temperature was kept for 47 min for alkalization. After the alkalization was completed, an alkalized solution was obtained; The alkali solution is prepared by stirring 9.7 g of deionized water, 2.0 g of sodium hydroxide and 86.5 g of isopropanol at 56° C. for 0.8 h.

[0018] 2. Etherification To 106 g of the alkalized liquid, 4.3 g of ethylene oxide was added, the temperature was raised to 57 ° C at a rate of 1.8 ° C / min, and the reaction was kept warm for 58 minutes. After the reaction was completed, the temperature was lowered to 38 ° C, and a 90 wt% acetic acid solution was added to adjust the pH to neutral, and then 5.8 g of ethylene oxide was added. After stirring, the temperature was raised to 73 ° C at a rate of 0.8 ° C / min, and the reaction was kept warm for 48 minutes. After the reaction was completed, a 90 wt% acetic acid solution was added to adjust the pH to neutral, and the etherified product was obtained by filtration, washing and drying.

[0019] 3. Modification 9.6 g of the etherified product was placed in 1000 mL of dimethyl sulfoxide, and after being stirred evenly, 0.50 g of oleic acid was added, and the temperature was raised to 45°C, and the mixture was stirred for 28 minutes. After the stirring was completed, 0.60 g of the modifier was added, and the addition rate was controlled to be 0.03 g / min. After the addition was completed, the temperature was continued to be raised to 83°C, and the mixture was stirred for 1.8 hours. After the stirring was completed, the mixture was naturally cooled to room temperature, filtered and washed, and dried at 58°C for 23.0 hours to obtain modified hydroxyethyl cellulose; The preparation method of the modifier is as follows: placing fumed silica in a mixed acid solution of 6 times the mass, stirring evenly, raising the temperature to 64°C, and heat-treating for 0.8h. After the heat-treating is completed, filtering, washing, and drying to obtain acidified fumed silica; adding 590mL of toluene to 5.8g of acidified fumed silica, stirring evenly, adding 10.7g of thionyl chloride, raising the temperature to 40°C in a nitrogen atmosphere, and heat-retaining for 58min. After the reaction is completed, filtering, washing, and drying to obtain chlorinated fumed silica; putting 1.4g of chlorinated fumed silica into 780mL of toluene, adding 2.4g of 1,6-hexanediamine and 3.5g of diethylenetriamine, raising the temperature to 72°C, and heat-retaining for 19.5h. After the heat-retaining reaction is completed, filtering, washing, and drying to obtain a primary modifier; adding 2.5g of the primary modifier to 490mL of dimethyl sulfoxide, stirring evenly, and adding 6.3g 3,3′,4,4′-dibenzophenone tetracarboxylic dianhydride and 12 mL of 93 wt% concentrated sulfuric acid were subjected to ultrasonic dispersion, the ultrasonic time was 13 min, the ultrasonic power was 105 W, and the ultrasonic frequency was 22 kHz. After the ultrasonic treatment, the temperature was raised to 88° C. in a nitrogen atmosphere, and the reaction was stirred for 13 h. After the reaction was completed, the modified agent was filtered, washed, and dried. The mixed acid solution is a mixture of concentrated sulfuric acid and concentrated nitric acid, the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 2.3:1, the mass concentration of the concentrated sulfuric acid is 95%, and the mass concentration of the concentrated nitric acid is 63%.

[0020] Example 3 1. Alkalization 10.2 g of refined cotton was crushed to a particle size of 140 nm, and then placed in 105 g of alkali solution for ultrasonic treatment. The ultrasonic time was 25 min, the ultrasonic power was 135 W, and the ultrasonic frequency was 38 kHz. After the ultrasonic treatment, the temperature was controlled to 22 ° C, and the vacuum was replaced 4 times. Nitrogen was filled and the pressure was controlled to 0.18 MPa. The temperature was kept for alkalization for 52 min. After the alkalization was completed, an alkalized solution was obtained; The alkali solution is prepared by stirring 10.2 g of deionized water, 2.5 g of sodium hydroxide and 87.3 g of isopropanol at 60° C. for 1.2 h.

[0021] 2. Etherification To 114 g of the alkalized liquid, add 4.6 g of ethylene oxide, heat to 62 ° C at a rate of 2.2 ° C / min, keep warm for 63 minutes, after the reaction is completed, lower the temperature to 42 ° C, add 94 wt% acetic acid solution to adjust the pH to neutral, then add 6.2 g of ethylene oxide, stir evenly, heat to 76 ° C at a rate of 1.2 ° C / min, keep warm for 52 minutes, after the reaction is completed, add 94 wt% acetic acid solution to adjust the pH to neutral, filter, wash and dry to obtain an etherified product.

[0022] 3. Modification 10.3 g of the etherified product was placed in 1000 mL of dimethyl sulfoxide, and after stirring evenly, 0.53 g of oleic acid was added, and the temperature was raised to 50°C, and the mixture was stirred for 32 minutes. After the stirring was completed, 0.65 g of the modifier was added, and the addition rate was controlled to be 0.05 g / min. After the addition was completed, the temperature was continued to be raised to 87°C, and the mixture was stirred for 2.2 hours. After the stirring was completed, the mixture was cooled to room temperature naturally, filtered and washed, and dried at 62°C for 25.0 hours to obtain modified hydroxyethyl cellulose; The preparation method of the modifier is as follows: placing fumed silica in a mixed acid solution with a mass of 10 times the mass, stirring evenly, raising the temperature to 68°C, and heat-treating for 1.2 hours. After the heat-treating is completed, filtering, washing, and drying are performed to obtain acidified fumed silica; adding 610 mL of toluene to 6.2 g of acidified fumed silica, stirring evenly, adding 11.2 g of thionyl chloride, raising the temperature to 44°C in a nitrogen atmosphere, and heat-retaining for 62 minutes. After the reaction is completed, filtering, washing, and drying are performed to obtain chlorinated fumed silica; putting 1.6 g of chlorinated fumed silica into 830 mL of toluene, adding 2.6 g of 1,6-hexanediamine and 4.0 g of diethylenetriamine, raising the temperature to 75°C, and heat-retaining for 20.6 hours. After the heat-retaining reaction is completed, filtering, washing, and drying are performed to obtain a primary modifier; adding 2.7 g of the primary modifier to 510 mL of dimethyl sulfoxide, stirring evenly, and adding 6.5 g 3,3′,4,4′-dibenzophenone tetracarboxylic dianhydride and 15 mL of 96 wt% concentrated sulfuric acid were subjected to ultrasonic dispersion, the ultrasonic time was 18 min, the ultrasonic power was 114 W, and the ultrasonic frequency was 25 kHz. After the ultrasonic treatment, the temperature was raised to 92° C. in a nitrogen atmosphere, and the reaction was stirred for 15 h. After the reaction was completed, the modified agent was filtered, washed, and dried. The mixed acid solution is a mixture of concentrated sulfuric acid and concentrated nitric acid, the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1.8:1, the mass concentration of the concentrated sulfuric acid is 98%, and the mass concentration of the concentrated nitric acid is 67%.

[0023] Comparative Example 1 Based on Example 1, the changes are as follows: In the etherification step, ethylene oxide is added at one time; the etherification step is to add 10.5g of ethylene oxide to 110g of the alkaline solution, heat to 75°C at a rate of 2.0°C / min, keep warm for 110min, add 92wt% acetic acid solution after the reaction to adjust the pH to neutral, filter, wash and dry to obtain an etherified product; In the modification step, the modifier is replaced in equal amounts with fumed silica without any treatment; The rest of the operations are the same.

[0024] Comparative Example 2 Based on Example 1, the changes are as follows: In the modification step, the oleic acid component is replaced by dimethyl sulfoxide in equal amounts, and the modifier is replaced by chlorinated fumed silica in equal amounts; The rest of the operations are the same.

[0025] Performance Testing 1. Basic performance The modified hydroxyethyl cellulose obtained in Examples 1-3 and Comparative Examples 1-2 was subjected to performance tests, and the test results are as follows:

[0026] In the viscosity test, the mass concentration of the modified hydroxyethyl cellulose product in the aqueous solution and the 3.0wt% sodium chloride solution was 0.1%, and the test temperature was 25°C.

[0027] 2. Application performance The modified hydroxyethyl cellulose products prepared in Examples 1-3 and Comparative Examples 1-2 were used in coatings, wherein the coating had a formula of 42.0% deionized water, 0.2% modified hydroxyethyl cellulose, 23% titanium dioxide, 34% acrylic emulsion, 0.3% sodium hexametaphosphate, 0.3% octylphenol polyoxyethylene ether, and 0.2% polydimethylsiloxane; The viscosity of the coating was tested at different dilutions, as follows: (1) When the dilution is 0

[0028] (2) When the dilution is 20%, the dilution = water mass / (water mass+coating mass) × 100%. The viscosity of the diluted coating is tested again, as follows:

[0029] (3) When the dilution is 30%, the dilution = water mass / (water mass+coating mass) × 100%. The viscosity of the diluted coating is tested again, as follows:

[0030] The invention adopts a specific method to prepare modified hydroxyethyl cellulose, specifically, firstly alkalizes refined cotton powder to activate the hydroxyl group of cellulose and ensure the full swelling of cellulose, and combines with ultrasonic treatment to help accelerate the alkalization reaction, improve the reaction uniformity, and make the hydroxyl group of cellulose have higher reaction activity; in the etherification step, ethylene oxide is used as an etherifying agent, and ethylene oxide introduces hydroxyethyl groups through a ring-opening reaction to convert alkali cellulose into hydroxyethyl cellulose, and a two-stage etherification is adopted to ensure the sufficiency of the reaction and improve the substitution degree of hydroxyethoxy groups; in the modification step, the addition of oleic acid can improve the wettability and dispersibility of the etherified product, and the carboxyl group at one end of the oleic acid can be combined with the hydroxyl group of the hydroxyethyl cellulose, and the long-chain alkane at the other end extends out, thereby enhancing the hydrophobic property of the hydroxyethyl cellulose, and the modifier is prepared by a specific method, specifically, fumed silica. As a modified matrix, fumed silica can significantly improve the fluidity and viscosity of hydroxyethyl cellulose. The fumed silica is firstly acidified and chlorinated so that the surface of the fumed silica contains more acyl chloride groups and the dispersion performance of the fumed silica can be enhanced. Then, an amino compound is introduced to form a product containing amino groups on the surface. Then, an acid anhydride compound is introduced and the surface of the modifier finally contains more acid anhydride groups through the reaction between the acid anhydride and the amino group. In the modification step, the acid anhydride group of the modifier can be esterified with the etherified product so that it has both excellent hydrophilicity and hydrophobicity, further increasing the crosslinking degree and stability of the modified hydroxyethyl cellulose, and finally improving the stability and salt resistance of the product, so that it has better application performance in coatings. When the modified hydroxyethyl cellulose is used in coatings, the viscosity of the coating decreases less with the increase of dilution and the stability is stronger.

[0031] In Comparative Example 1, in the etherification step, ethylene oxide is added at one time, resulting in incomplete reaction and reducing the degree of substitution of the hydroxyethoxy group. In the modification step, the modifier is replaced by fumed silica without any treatment. The fumed silica is unevenly dispersed with oleic acid and etherified products, and the combination is not strong, and a stable structure cannot be formed, which ultimately reduces the stability of the modified hydroxyethyl cellulose. The viscosity of the modified hydroxyethyl cellulose increases greatly in the salt solution, and the salt resistance is poor. When it is used in the coating, the dilution resistance is unstable. With the increase of the dilution degree, the viscosity of the coating is greatly reduced, which affects the application of the modified hydroxyethyl cellulose. In Comparative Example 2, in the modification step, the oleic acid component is replaced by dimethyl sulfoxide in equal amounts, resulting in poor wettability and dispersibility of the etherified product, and the modifier is replaced by chlorinated fumed silica in equal amounts, which omits the amino compound and the acid anhydride compound, and cannot make the modified hydroxyethyl cellulose have both excellent hydrophilicity and hydrophobicity, and also reduces the salt resistance and the stability of the modified hydroxyethyl cellulose product, resulting in poor application performance in coatings.

[0032] Unless otherwise specified, all percentages used in the present invention are by mass.

[0033] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing modified hydroxyethyl cellulose, characterized in that: It includes alkalization, etherification and modification steps; The etherification step comprises adding ethylene oxide to the alkalized liquid for the first time, reacting at 57-62° C. for 58-63 minutes, lowering the temperature to 38-42° C., and then adding ethylene oxide for the second time, reacting at 73-76° C. for 48-52 minutes to obtain an etherified product; The modification step is to place the etherified product in dimethyl sulfoxide, add oleic acid, stir at 45-50° C. for 28-32 minutes, then add the modifier at a rate of 0.03-0.05 g / min, and react at 83-87° C. for 1.8-2.2 hours to obtain modified hydroxyethyl cellulose; The preparation method of the modifier comprises the following steps: adding toluene to acidified fumed silica, adding thionyl chloride after stirring, reacting at 40-44° C. for 58-62 min in a nitrogen atmosphere to obtain chlorinated fumed silica; adding chlorinated fumed silica to toluene, adding 1,6-hexanediamine and diethylenetriamine, reacting at 72-75° C. for 19.5-20.6 h to obtain a primary modifier; adding the primary modifier to dimethyl sulfoxide, stirring, adding 3,3′,4,4′-dibenzophenone tetraacid dianhydride and concentrated sulfuric acid, performing ultrasonic dispersion, and then reacting at 88-92° C. for 13-15 h in a nitrogen atmosphere to obtain the modifier.

2. The method for preparing modified hydroxyethyl cellulose according to claim 1, characterized in that: The alkalization step comprises the following steps: crushing the refined cotton to a particle size of 120-140 nm, and then placing the refined cotton in an alkali solution for ultrasonic treatment, wherein the ultrasonic treatment time is 20-25 min, the ultrasonic power is 125-135 W, and the ultrasonic frequency is 32-38 kHz. After the ultrasonic treatment, the temperature is controlled to be 18-22° C., vacuuming and replacing the cotton 4 times, and nitrogen is introduced to control the pressure to be 0.13-0.18 MPa. The refined cotton is kept warm for 47-52 min. After the alkalization, an alkalized liquid is obtained.

3. The method for preparing modified hydroxyethyl cellulose according to claim 2, characterized in that: The mass ratio of the refined cotton powder to the alkali solution is 9.8-10.2:96-105; The alkali solution is prepared by stirring deionized water, sodium hydroxide and isopropanol at 56-60° C. for 0.8-1.2 hours; The mass ratio of the deionized water, sodium hydroxide and isopropanol is 9.7-10.2:2.0-2.5:86.5-87.

3.

4. The method for preparing modified hydroxyethyl cellulose according to claim 1, characterized in that: In the etherification step, the mass ratio of the alkalizing liquid, the first added amount of ethylene oxide, and the second added amount of ethylene oxide is 106-114:4.3-4.6:5.8-6.

2.

5. The method for preparing modified hydroxyethyl cellulose according to claim 1, characterized in that: In the modification step, the mass volume ratio of the etherified product, dimethyl sulfoxide, oleic acid and modifier is 9.6-10.3 g:1000 mL:0.50-0.53 g:0.60-0.65 g.

6. The method for preparing modified hydroxyethyl cellulose according to claim 1, characterized in that: The preparation method of the acidified fumed silica comprises placing the fumed silica in a mixed acid solution, stirring the solution evenly, raising the temperature to 64-68° C., and heat-treating the solution for 0.8-1.2 hours. After the heat-treating is completed, filtering, washing, and drying the solution to obtain the acidified fumed silica. The mass ratio of the fumed silica to the mixed acid solution is 1:6-10; The mixed acid solution is a mixture of concentrated sulfuric acid and concentrated nitric acid, the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1.8-2.3:1, the mass concentration of the concentrated sulfuric acid is 95-98%, and the mass concentration of the concentrated nitric acid is 63-67%.

7. The method for preparing modified hydroxyethyl cellulose according to claim 1, characterized in that: In the preparation method of the modifier, the mass volume ratio of the acidified fumed silica, toluene, and thionyl chloride is 5.8-6.2 g: 590-610 mL: 10.7-11.2 g; The mass volume ratio of the chlorinated silicon dioxide, toluene, 1,6-hexanediamine and diethylenetriamine is 1.4-1.6 g:780-830 mL:2.4-2.6 g:3.5-4.0 g; The volume mass ratio of the dimethyl sulfoxide, the primary modifier, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and concentrated sulfuric acid is 490-510 mL: 2.5-2.7 g: 6.3-6.5 g: 12-15 mL; The mass concentration of the concentrated sulfuric acid is 93-96%.

8. Use of the modified hydroxyethyl cellulose obtained according to the preparation method according to any one of claims 1 to 7 in coatings.

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