Preparation method of modified hydroxyethyl cellulose and its application in coatings

Abstract

The present invention provides a preparation method of modified hydroxyethyl cellulose and its application in coatings, belonging to the field of modified hydroxyethyl cellulose; the preparation method includes an alkalization step, an etherification step and a modification step; ethylene oxide is added to the alkalization solution for the first time, and the temperature is raised to 57-62 °C at a rate of 1.8-2.2 °C / min, and the reaction is kept for 58-63 min. After the reaction is completed, the temperature is lowered to 38-42 °C, and an acetic acid solution is added to adjust the pH to neutral. Then ethylene oxide is added for the second time. After stirring evenly, the temperature is raised to 73-76 °C at a rate of 0.8-1.2 °C / min, and the reaction is kept for 48-52 min. After the reaction is completed, an acetic acid solution is added to adjust the pH to neutral, and after filtration, washing and drying, an etherified product is obtained; the modified hydroxyethyl cellulose prepared by the method of the present invention has high surface activity, high viscosity and good salt tolerance, and has good stability when applied to coatings.

Description

Technical Field

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

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

[0003] Hydroxyethyl cellulose has a relatively large molecular weight and has many hydrophilic groups. In particular, the side-chain hydroxyl groups can undergo chain polymerization, and it has good water solubility. However, the macromolecular chain lacks hydrophobic groups that match the hydrophilic groups, making it difficult to improve its surface activity. Moreover, the stability and light transmittance of hydroxyethyl cellulose are relatively low, and the use effect is not good.

[0004] Modified hydroxyethyl cellulose introduces a new hydrophobic modification group into the molecular structure of hydroxyethyl cellulose, so that the modified hydroxyethyl cellulose exhibits a hydrophobic effect and a viscosity-increasing effect, and thus shows significant thickening property, stability and salt tolerance; as an important variety with development prospects in new dispersants, modified hydroxyethyl cellulose has a high added value and a broad market prospect. Its use as a thickening agent and dispersant in high-end fields is of great significance for the transformation of cellulose ether products, the update of technology and the enhancement of international market competitiveness.

[0005] (Synthesis and Performance Characterization of Hydrophobically Associating Hydroxyethyl Cellulose, Shao Ziqiang) discloses the preparation of hydrophobically associating hydroxyethyl cellulose using haloalkanes as hydrophobizing agents, and a borate modifier is also added during the preparation process. A large number of hydroxyl groups in hydroxyethyl cellulose and its modified molecules are prone to complex with boron atoms in borates to form complexes, which play a role in cross-linking thickening; 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 technologies, the existing technologies usually introduce acid anhydride groups onto the molecular chains of hydroxyethyl cellulose to improve its surface activity through the esterification reaction of acid anhydride groups. For example, CN117700568A discloses a preparation method of dodecyl succinic anhydride modified hydroxyethyl cellulose. The preparation method includes steps of cellulose activation reaction, hydroxyethylation reaction, esterification reaction of modifier and hydroxyethyl cellulose, secondary hydroxyethylation reaction, neutralization, washing, and drying. Specifically, based on the different reaction activities of the three active hydroxyl groups on the glucose unit of cellulose, the hydroxyl group with stronger activity is first subjected to hydroxyethylation reaction, then esterification reaction with the modifier dodecyl succinic anhydride, and then other hydroxyl groups are subjected to hydroxyethylation reaction to obtain uniformly substituted dodecyl succinic anhydride modified hydroxyethyl cellulose.

[0007] The modified hydroxyethyl cellulose obtained by this method still has a relatively low viscosity and poor stability when used in coatings. Summary of the Invention

[0008] In order to solve the technical problems existing in the prior art, the present invention provides a preparation method of modified hydroxyethyl cellulose and its application in coatings. The prepared modified hydroxyethyl cellulose has high surface activity, high viscosity, good salt tolerance, and good stability when used in coatings.

[0009] In view of the above technical problems, the present invention adopts the following technical solutions:

[0010] A preparation method of modified hydroxyethyl cellulose, including an alkalization step, an etherification step, and a modification step. The specific operations are as follows:

[0011] 1. Alkalization

[0012] Crush refined cotton to a particle size of 120 - 140 nm, then place it in an alkali solution for ultrasonic treatment. The ultrasonic treatment time is 20 - 25 min, the ultrasonic power is 125 - 135 W, the ultrasonic frequency is 32 - 38 kHz. After the ultrasonic treatment, control the temperature at 18 - 22 °C, evacuate and replace the gas 4 times, fill in nitrogen, control the pressure at 0.13 - 0.18 MPa, keep warm and alkalize for 47 - 52 min. After the alkalization is completed, obtain an alkalized solution;

[0013] The mass ratio of the refined cotton powder to the alkali solution is 9.8 - 10.2:96 - 105;

[0014] The alkali solution is prepared by keeping deionized water, sodium hydroxide, and isopropanol at 56 - 60 °C and stirring for 0.8 - 1.2 h;

[0015] The mass ratio of deionized water, sodium hydroxide, and isopropanol is 9.7 - 10.2:2.0 - 2.5:86.5 - 87.3.

[0016] 2. Etherification

[0017] Ethylene oxide is first added to the alkalized solution, and the temperature is raised to 57 - 62 °C at a rate of 1.8 - 2.2 °C / min. After holding for a reaction for 58 - 63 min, after the reaction ends, the temperature is lowered to 38 - 42 °C, and an acetic acid solution is added to adjust the pH to neutral. Then, ethylene oxide is added for the second time. After stirring evenly, the temperature is raised to 73 - 76 °C at a rate of 0.8 - 1.2 °C / min, and the reaction is held for 48 - 52 min. After the reaction ends, an acetic acid solution is added to adjust the pH to neutral. After filtration, washing, and drying, an etherified product is obtained;

[0018] The mass ratio of the alkalized solution, 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;

[0019] The mass concentration of the acetic acid solution is 90 - 94%.

[0020] 3. Modification

[0021] The etherified product is placed in dimethyl sulfoxide and stirred evenly. Then, oleic acid is added, and the temperature is raised to 45 - 50 °C, and stirring is continued for 28 - 32 min. After stirring ends, a modifier is added, and the addition rate is controlled at 0.03 - 0.05 g / min. After the addition is completed, the temperature is further raised to 83 - 87 °C, and the reaction is held for 1.8 - 2.2 h. After the holding reaction ends, after naturally cooling to room temperature, after filtration and washing, it is dried at 58 - 62 °C for 23.0 - 25.0 h to obtain modified hydroxyethyl cellulose;

[0022] The mass - volume ratio of the etherified product, dimethyl sulfoxide, oleic acid, and the modifier is 9.6 - 10.3 g:1000 mL:0.50 - 0.53 g:0.60 - 0.65 g;

[0023] The preparation method of the modifier is as follows: Put fumed silica into a mixed acid solution, stir evenly, then raise the temperature to 64 - 68 °C, keep warm for 0.8 - 1.2 h. After the heat preservation treatment, filter, wash and dry to obtain acidified fumed silica; Add toluene to the acidified fumed silica, stir evenly, then add thionyl chloride, raise the temperature to 40 - 44 °C under a nitrogen atmosphere, keep warm and react for 58 - 62 min. After the reaction, filter, wash and dry to obtain acyl chloride fumed silica; Put the acyl chloride fumed silica into toluene, add 1,6 - hexanediamine and diethylenetriamine, raise the temperature to 72 - 75 °C, keep warm and react for 19.5 - 20.6 h. After the heat preservation reaction, filter, wash and dry to obtain the primary modifier; Add the primary modifier to dimethyl sulfoxide, stir evenly, then add 3,3′,4,4′ - benzophenone tetracarboxylic dianhydride and concentrated sulfuric acid, and perform ultrasonic dispersion. The ultrasonic time is 13 - 18 min, the ultrasonic power is 105 - 114 W, and the ultrasonic frequency is 22 - 25 kHz. After the ultrasonic treatment, raise the temperature to 88 - 92 °C under a nitrogen atmosphere, stir and react for 13 - 15 h. After the reaction, filter, wash and dry to obtain the modifier;

[0024] The mass ratio of the fumed silica to the mixed acid solution is 1:6 - 10;

[0025] 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%;

[0026] 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;

[0027] The mass - volume ratio of the acyl chloride silica, 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;

[0028] The volume - mass ratio of the dimethyl sulfoxide, 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;

[0029] The mass concentration of the concentrated sulfuric acid is 93 - 96%.

[0030] Application of the modified hydroxyethyl cellulose prepared by the above - mentioned preparation method in coatings.

[0031] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0032] 1. The present invention prepares modified hydroxyethyl cellulose by a specific method. Specifically, refined cotton powder is alkalized first to activate the hydroxyl groups of cellulose, ensuring the full swelling of cellulose. Combining ultrasonic treatment helps to accelerate the alkalization reaction and improve the reaction uniformity, making the hydroxyl groups of cellulose have higher reaction activity. In the etherification step, ethylene oxide is used as the etherifying agent. Ethylene oxide introduces hydroxyethyl groups through ring-opening reaction, converting 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. Moreover, the carboxyl group at one end of oleic acid can combine with the hydroxyl groups of hydroxyethyl cellulose, and the long-chain alkane at the other end stretches out, enhancing the hydrophobic property of hydroxyethyl cellulose. And the modifier is prepared by a specific method. Specifically, fumed silica is used as the modification matrix. Fumed silica can significantly improve the fluidity and viscosity of hydroxyethyl cellulose. First, fumed silica is acidified and acyl chlorinated to make the surface of fumed silica contain more acyl chloride groups and enhance the dispersibility of fumed silica. Then, an amino compound is introduced to form a product with amino groups on the surface. Finally, an acid anhydride compound is introduced, and through the reaction of the acid anhydride and the amino group, the surface of the modifier finally contains more acid anhydride groups. In the modification step, the acid anhydride groups of the modifier can be esterified with the etherified product, making it have both excellent hydrophilicity and hydrophobicity, further increasing the crosslinking degree and stability of the modified hydroxyethyl cellulose, and finally improving the stability and salt tolerance of the product, so that it has good application performance in coatings. When the modified hydroxyethyl cellulose is used in coatings, with the increase of the dilution degree, the viscosity of the coating decreases less and the stability is stronger;

[0033] 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;

[0034] 3. The modified hydroxyethyl cellulose prepared by the method of the present invention has a viscosity of 2968 - 2974 mPa·s in an aqueous solution at 25°C;

[0035] 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;

[0036] 5. The modified hydroxyethyl cellulose prepared by the method of the present invention is applied to coatings. When the coating dilution 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;

[0037] When the coating dilution is 20%, the viscosity at a rotation speed of 3 rpm is 2506 - 2518 mPa·s, the viscosity at a rotation speed of 10 rpm is 1824 - 1832 mPa·s, the viscosity at a rotation speed of 20 rpm is 1117 - 1125 mPa·s, and the viscosity at a rotation speed of 40 rpm is 814 - 822 mPa·s;

[0038] When the coating dilution is 20%, the viscosity at a rotation speed of 3 rpm is 1263 - 1274 mPa·s, the viscosity at a rotation speed of 10 rpm is 974 - 987 mPa·s, the viscosity at a rotation speed of 20 rpm is 614 - 622 mPa·s, and the viscosity at a rotation speed of 40 rpm is 556 - 561 mPa·s. Detailed implementation manners

[0039] For a clearer understanding of the technical features, objectives, and effects of the present invention, the detailed implementation manners of the present invention are now described.

[0040] Example 1

[0041] 1. Alkalization

[0042] 10.0 g of refined cotton is crushed to a particle size of 130 nm, and then placed in 100 g of an alkali solution for ultrasonic treatment. The ultrasonic treatment time is 23 min, the ultrasonic power is 130 W, the ultrasonic frequency is 36 kHz. After the ultrasonic treatment, the temperature is controlled at 20°C, evacuated and replaced 4 times, filled with nitrogen, and the pressure is controlled at 0.15 MPa. Keep warm and alkalize for 50 min. After the alkalization is completed, an alkalized solution is obtained;

[0043] The alkali solution is prepared by keeping 10.0 g of deionized water, 2.2 g of sodium hydroxide, and 87.0 g of isopropanol at 58°C and stirring for 1.0 h.

[0044] 2. Etherification

[0045] Add 4.5 g of ethylene oxide to 110 g of alkalized solution, heat it up to 60 °C at a rate of 2.0 °C / min, keep the temperature for 60 min. 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 it up to 75 °C at a rate of 1.0 °C / min, keep the temperature for 50 min. After the reaction is completed, add 92 wt% acetic acid solution to adjust the pH to neutral, and obtain the etherified product after filtration, washing and drying.

[0046] 3. Modification

[0047] Place 10.0 g of the etherified product in 1000 mL of dimethyl sulfoxide, stir evenly, add 0.51 g of oleic acid, raise the temperature to 47 °C, keep stirring for 30 min. After stirring is completed, add 0.63 g of the modifier, control the addition rate to be 0.04 g / min. After the addition is completed, continue to raise the temperature to 85 °C, keep the temperature for 2.0 h. After the heat preservation reaction is completed, wait for it to naturally cool to room temperature, and obtain the modified hydroxyethyl cellulose after filtration, washing and drying at 60 °C for 24.0 h;

[0048] The preparation method of the modifier is as follows: place fumed silica in 8 times its mass of mixed acid solution, stir evenly, raise the temperature to 66 °C, keep the temperature for 1.0 h. After the heat preservation treatment is completed, obtain acidified fumed silica after filtration, washing and drying; add 600 mL of toluene to 6.0 g of acidified fumed silica, stir evenly and then add 11.0 g of thionyl chloride, raise the temperature to 42 °C under a nitrogen atmosphere, keep the temperature for 60 min. After the reaction is completed, obtain acyl chloride fumed silica after filtration, washing and drying; put 1.5 g of acyl chloride fumed silica into 800 mL of toluene, add 2.5 g of 1,6-hexanediamine and 3.7 g of diethylenetriamine, raise the temperature to 74 °C, keep the temperature for 20.0 h. After the heat preservation reaction is completed, obtain the primary modifier after filtration, washing and drying; add 2.6 g of the primary modifier to 500 mL of dimethyl sulfoxide, stir evenly, add 6.4 g of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and 14 mL of 95 wt% concentrated sulfuric acid, carry out ultrasonic dispersion, the ultrasonic time is 15 min, the ultrasonic power is 110 W, the ultrasonic frequency is 23 kHz. After the ultrasonic treatment is completed, raise the temperature to 90 °C under a nitrogen atmosphere, stir and react for 14 h. After the reaction is completed, obtain the modifier after filtration, washing and drying;

[0049] The mixed acid solution is a mixture of concentrated sulfuric acid and concentrated nitric acid, the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 2:1, the mass concentration of concentrated sulfuric acid is 96%, and the mass concentration of concentrated nitric acid is 65%.

[0050] Example 2

[0051] 1. Alkalization

[0052] Crush 9.8 g of refined cotton to a particle size of 120 nm, then place it in 96 g of lye and perform ultrasonic treatment. The ultrasonic time is 20 min, the ultrasonic power is 125 W, the ultrasonic frequency is 32 kHz. After the ultrasonic treatment, control the temperature at 18 °C, evacuate and replace 4 times, fill with nitrogen, control the pressure at 0.13 MPa, and keep the temperature for alkalization for 47 min. After the alkalization is completed, obtain the alkalized solution;

[0053] The lye is prepared by keeping 9.7 g of deionized water, 2.0 g of sodium hydroxide and 86.5 g of isopropanol at 56 °C and stirring for 0.8 h.

[0054] 2. Etherification

[0055] Add 4.3 g of ethylene oxide to 106 g of the alkalized solution, heat it up to 57 °C at a rate of 1.8 °C / min, keep the temperature for reaction for 58 min. After the reaction is completed, lower the temperature to 38 °C, add 90 wt% acetic acid solution to adjust the pH to neutral, then add 5.8 g of ethylene oxide, stir evenly, heat it up to 73 °C at a rate of 0.8 °C / min, keep the temperature for reaction for 48 min. After the reaction is completed, add 90 wt% acetic acid solution to adjust the pH to neutral, filter, wash and dry to obtain the etherified product.

[0056] 3. Modification

[0057] Place 9.6 g of the etherified product in 1000 mL of dimethyl sulfoxide, stir evenly, add 0.50 g of oleic acid, raise the temperature to 45 °C, keep the temperature and stir for 28 min. After the stirring is completed, add 0.60 g of the modifier, control the addition rate at 0.03 g / min. After the addition is completed, continue to raise the temperature to 83 °C, keep the temperature for reaction for 1.8 h. After the heat preservation reaction is completed, wait for it to naturally cool to room temperature, filter and wash, and dry at 58 °C for 23.0 h to obtain the modified hydroxyethyl cellulose;

[0058] The preparation method of the modifier is as follows: Put fumed silica into a mixed acid solution with a mass 6 times that of the fumed silica. After stirring evenly, raise the temperature to 64 °C and keep it warm for 0.8 h. After the heat preservation treatment is completed, filter, wash and dry to obtain acidified fumed silica; Add 590 mL of toluene to 5.8 g of acidified fumed silica. After stirring evenly, add 10.7 g of thionyl chloride. Raise the temperature to 40 °C under a nitrogen atmosphere and keep it warm for reaction for 58 min. After the reaction is completed, filter, wash and dry to obtain acyl chloride fumed silica; Put 1.4 g of acyl chloride fumed silica into 780 mL of toluene, add 2.4 g of 1,6 - hexanediamine and 3.5 g of diethylenetriamine, raise the temperature to 72 °C and keep it warm for reaction for 19.5 h. After the heat preservation reaction is completed, filter, wash and dry to obtain the primary modifier; Add 2.5 g of the primary modifier to 490 mL of dimethyl sulfoxide. After stirring evenly, add 6.3 g of 3,3′,4,4′ - benzophenonetetracarboxylic dianhydride and 12 mL of 93 wt% concentrated sulfuric acid, and perform ultrasonic dispersion. The ultrasonic time is 13 min, the ultrasonic power is 105 W, and the ultrasonic frequency is 22 kHz. After the ultrasonic treatment is completed, raise the temperature to 88 °C under a nitrogen atmosphere and stir for reaction for 13 h. After the reaction is completed, filter, wash and dry to obtain the modifier;

[0059] The mixed acid solution is a mixture of concentrated sulfuric acid and concentrated nitric acid. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 2.3:1. The mass concentration of concentrated sulfuric acid is 95%, and the mass concentration of concentrated nitric acid is 63%.

[0060] Example 3

[0061] 1. Alkalization

[0062] Crush 10.2 g of refined cotton to a particle size of 140 nm, then put it into 105 g of an alkali solution for ultrasonic treatment. The ultrasonic time is 25 min, the ultrasonic power is 135 W, and the ultrasonic frequency is 38 kHz. After the ultrasonic treatment is completed, control the temperature at 22 °C, evacuate and replace 4 times, fill with nitrogen, control the pressure at 0.18 MPa, and keep it warm for alkalization for 52 min. After the alkalization is completed, obtain the alkalized solution;

[0063] The alkali solution is prepared by keeping 10.2 g of deionized water, 2.5 g of sodium hydroxide and 87.3 g of isopropanol at 60 °C and stirring for 1.2 h.

[0064] 2. Etherification

[0065] Add 4.6 g of ethylene oxide to 114 g of alkalized solution, heat it up to 62 °C at a rate of 2.2 °C / min, keep the temperature for 63 min for the reaction. 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. After stirring evenly, heat it up to 76 °C at a rate of 1.2 °C / min, keep the temperature for 52 min for the reaction. After the reaction is completed, add 94 wt% acetic acid solution to adjust the pH to neutral, and after filtration, washing and drying, an etherified product is obtained.

[0066] 3. Modification

[0067] Place 10.3 g of the etherified product in 1000 mL of dimethyl sulfoxide, stir evenly, add 0.53 g of oleic acid, raise the temperature to 50 °C, keep stirring for 32 min. After stirring is completed, add 0.65 g of the modifier, control the addition rate at 0.05 g / min. After the addition is completed, continue to raise the temperature to 87 °C, keep the temperature for 2.2 h for the reaction. After the heat preservation reaction is completed, wait for it to naturally cool down to room temperature, and after filtration and washing, dry it at 62 °C for 25.0 h to obtain modified hydroxyethyl cellulose;

[0068] The preparation method of the modifier is as follows: place fumed silica in a mixed acid solution with 10 times its mass, stir evenly, raise the temperature to 68 °C, keep the temperature for 1.2 h for the treatment. After the treatment is completed, filter, wash and dry to obtain acidified fumed silica; add 610 mL of toluene to 6.2 g of acidified fumed silica, stir evenly and then add 11.2 g of thionyl chloride, raise the temperature to 44 °C under a nitrogen atmosphere, keep the temperature for 62 min for the reaction. After the reaction is completed, filter, wash and dry to obtain acylated fumed silica; put 1.6 g of acylated fumed silica into 830 mL of toluene, add 2.6 g of 1,6-hexanediamine and 4.0 g of diethylenetriamine, raise the temperature to 75 °C, keep the temperature for 20.6 h for the reaction. After the reaction is completed, filter, wash and dry to obtain a primary modifier; add 2.7 g of the primary modifier to 510 mL of dimethyl sulfoxide, stir evenly, add 6.5 g of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 15 mL of 96 wt% concentrated sulfuric acid, carry out ultrasonic dispersion, the ultrasonic time is 18 min, the ultrasonic power is 114 W, the ultrasonic frequency is 25 kHz. After the ultrasonic treatment is completed, raise the temperature to 92 °C under a nitrogen atmosphere, stir and react for 15 h. After the reaction is completed, filter, wash and dry to obtain the modifier;

[0069] The mixed acid solution is a mixture of concentrated sulfuric acid and concentrated nitric acid, the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1.8:1, the mass concentration of concentrated sulfuric acid is 98%, and the mass concentration of concentrated nitric acid is 67%.

[0070] Comparative Example 1

[0071] Based on Example 1, the changes are as follows:

[0072] 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;

[0073] In the modification step, the modifier is replaced in equal amounts with fumed silica without any treatment;

[0074] The rest of the operations are the same.

[0075] Comparative Example 2

[0076] Based on Example 1, the changes are as follows:

[0077] 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;

[0078] The rest of the operations are the same.

[0079] Performance Testing

[0080] 1. Basic performance

[0081] 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:

[0082]

[0083] 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.

[0084] 2. Application performance

[0085] 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;

[0086] The viscosity of the coating was tested at different dilutions, as follows:

[0087] (1) When the dilution is 0

[0088]

[0089] (2)When the dilution is 20%, the dilution = mass of water / (mass of water + mass of coating) × 100%, and the viscosity of the diluted coating is tested again, specifically as follows:

[0090]

[0091] (3)When the dilution is 30%, the dilution = mass of water / (mass of water + mass of coating) × 100%, and the viscosity of the diluted coating is tested again, specifically as follows:

[0092]

[0093] The present invention prepares modified hydroxyethyl cellulose by a specific method. Specifically, refined cotton powder is alkalized first to activate the hydroxyl groups of cellulose, ensuring the full swelling of cellulose. Combining ultrasonic treatment helps to accelerate the alkalization reaction and improve the reaction uniformity, making the hydroxyl groups of cellulose have high reactivity; in the etherification step, ethylene oxide is used as the 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 oleic acid can combine with the hydroxyl group of hydroxyethyl cellulose, and the long-chain alkane at the other end extends out, enhancing the hydrophobic property of hydroxyethyl cellulose. The modifier is prepared by a specific method. Specifically, fumed silica is used as the modification matrix, and fumed silica can significantly improve the fluidity and viscosity of hydroxyethyl cellulose. First, fumed silica is acidified and acyl chlorinated to make the surface of fumed silica contain more acyl chloride groups and enhance the dispersion performance of fumed silica, then an amino compound is introduced to form a product with amino groups on the surface, and then an acid anhydride compound is introduced. Through the reaction of the acid anhydride and the amino group, finally, the surface of the modifier contains more acid anhydride groups; in the modification step, the acid anhydride groups of the modifier can be esterified with the etherified product, making it have both excellent hydrophilicity and hydrophobicity, further increasing the crosslinking degree and stability of the modified hydroxyethyl cellulose, and ultimately improving the stability and salt tolerance of the product, so that it has good application performance in coatings. When the modified hydroxyethyl cellulose is used in coatings, as the dilution increases, the viscosity of the coating decreases less and the stability is stronger.

[0094] 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.

[0095] 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.

[0096] Unless otherwise specified, all percentages used in the present invention are by mass.

[0097] 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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