Lignin maleate, styrene-acrylic emulsion and preparation method thereof

Abstract

The application provides a preparation method of a styrene-acrylic emulsion, comprising the following steps: (1) monomer purification: respectively purifying styrene and butyl acrylate to obtain purified styrene / butyl acrylate; (2) solution preparation: a first component, a second component, a third component, a fourth component and a fifth component; (3) emulsion polymerization: a, pouring part of the third component into a reaction container, and setting a stirring speed as a first preset rotating speed; b, when the temperature reaches a first preset temperature, adding part of the fourth component under constant temperature; c, increasing the temperature to a second preset temperature, adjusting the stirring speed to a second preset rotating speed, and adding the remaining third component and fourth component drop by drop through a dropping funnel; d, after the third component and the fourth component are added drop by drop, constant temperature reaction is carried out, then the second component and the fifth component are added drop by drop through the dropping funnel, and constant temperature reaction is carried out for 1.8-2.2 hours to obtain a reaction solution; e, pouring the reaction solution into a sixth container, adding sodium hydroxide to adjust the pH to 8, and obtaining the styrene-acrylic emulsion.

Description

Technical Field

[0001] This invention relates to a lignin maleate, a styrene-acrylic emulsion, and a method for preparing the same. Background Technology

[0002] Currently, styrene-acrylic emulsions are primarily synthesized from petrochemical raw materials. However, with the development of modern industry, petroleum resources are becoming increasingly scarce due to their non-renewable nature. Seeking new renewable materials to replace petrochemical raw materials has become an inevitable path for the future development of the chemical industry. Summary of the Invention

[0003] The purpose of this invention is to provide a styrene-acrylic emulsion and its preparation method, which uses lignin maleate ester to replace styrene to obtain the styrene-acrylic emulsion, thereby reducing the amount of styrene used.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] This invention provides a method for preparing a styrene-acrylic emulsion, comprising the following steps:

[0006] (1) Monomer purification: Styrene and butyl acrylate were purified separately to obtain purified styrene / butyl acrylate.

[0007] (2) Solution preparation:

[0008] First component: Add emulsifier NP-40, sodium dodecyl sulfate and deionized water to the first container in sequence, stir until completely dissolved, let stand to defoam, and obtain the first component;

[0009] Second component: Add purified styrene, purified butyl acrylate, and part of the first component to the second container in sequence, and stir until no layering occurs to obtain the second component;

[0010] Third component: Lignomethyl maleate, acrylic acid, and the remaining first component are added sequentially to the third container, and then ultrasonic treatment is performed to obtain the third component;

[0011] Fourth component: Add a portion of ammonium persulfate and deionized water sequentially to the fourth container to completely dissolve the solid and obtain the fourth component;

[0012] Fifth component: Add the remaining ammonium persulfate and deionized water to the fifth container in sequence to completely dissolve the solid and obtain the fifth component;

[0013] (3) Emulsion polymerization:

[0014] a. Install the four-necked flask, condenser, and stirring rod. Pour part of the third component directly into the reaction vessel, turn on the stirrer, set the stirring speed to the first preset speed, and heat up.

[0015] b. Once the temperature reaches the first preset temperature, add a portion of the fourth component while maintaining a constant temperature, and continue heating.

[0016] c. Heat to the second preset temperature, adjust the stirring speed to the second preset speed, and add the remaining third and fourth components dropwise using a dropping funnel;

[0017] d. After adding the third and fourth components, maintain the reaction temperature at a constant temperature. Then, add the second and fifth components dropwise using a dropping funnel. After adding the second and fifth components, maintain the reaction temperature at a constant temperature for another 1.8-2.2 hours to obtain the reaction solution.

[0018] e. Stop the reaction, pour the reaction solution into the sixth container, add sodium hydroxide solution to adjust the pH to 8, and obtain the styrene-acrylic emulsion.

[0019] Furthermore, the monomer purification specifically involves:

[0020] Wash styrene / butyl acrylate once with a 10% sodium hydroxide solution in a separatory funnel, separate the layers, release the lower alkaline solution, and the upper liquid is the monomer;

[0021] Add an appropriate amount of deionized water to the upper liquid, then wash with water, separate the liquid, and release the lower wastewater. Repeat the water washing operation until the pH of the wastewater is 7-8 to obtain the purified styrene / butyl acrylate.

[0022] Furthermore, the ultrasonic treatment involves placing the third container containing the mixture of lignin maleate, acrylic acid, and the first component into an ultrasonic vibrator and ultrasonically treating it for 1-3 minutes.

[0023] Furthermore, the ultrasonic treatment needs to be repeated three times, and after each ultrasonic treatment, the particles on the wall of the third container need to be cleaned with a glass rod.

[0024] Furthermore, the speed ratio of the second preset speed to the first preset speed is 1:1.5-2.

[0025] Furthermore, the first preset temperature is 55-65℃;

[0026] The second preset temperature is 75-85℃.

[0027] Furthermore, in step e, the concentration of the sodium hydroxide solution is 4.5-5.5 mol / L.

[0028] Furthermore, in step c, the third and fourth components are added dropwise over a period of 0.8-1.2 hours.

[0029] In step d, the second and fifth components are added dropwise over 1.8-2.2 hours.

[0030] Furthermore, the lignin maleate is obtained through the following steps:

[0031] Add ethylene glycol dimethyl ether to the sixth container containing a thermometer and a condenser, heat it, set the temperature to the third preset temperature, and stir.

[0032] Acidic lignin and maleic anhydride are added sequentially to the ethylene glycol dimethyl ether. When the temperature inside the sixth container reaches the third preset temperature, the reaction is carried out for 5-7 hours.

[0033] After the reaction is cooled to room temperature, the reactants are poured into a seventh container containing deionized water, thereby precipitating a solid.

[0034] The solid was filtered, then washed with water until the pH of the filtrate was 5-6, and dried to obtain the lignin maleate.

[0035] Furthermore, the acidic lignin is obtained by the following steps: boiling and stirring the crude acidic lignin in hot water, filtering and washing it while it is hot, and then drying it.

[0036] The ratio of crude acidic lignin to water is (0-10)g:100ml.

[0037] The present invention also provides a styrene-acrylic emulsion, which is prepared by the above preparation method.

[0038] This invention also provides a method for modifying lignin into lignin maleate, namely, a method for preparing lignin maleate, comprising the following steps:

[0039] Add ethylene glycol dimethyl ether to the sixth container containing a thermometer and a condenser, heat it, set the temperature to the third preset temperature, and stir.

[0040] Acidic lignin and maleic anhydride are added sequentially to the ethylene glycol dimethyl ether. When the temperature inside the sixth container reaches the third preset temperature, the reaction is carried out for 5-7 hours.

[0041] After the reaction is cooled to room temperature, the reactants are poured into a seventh container containing deionized water, thereby precipitating a solid.

[0042] The solid was filtered, then washed with water until the pH of the filtrate was 5-6, and dried to obtain the lignin maleate.

[0043] Furthermore, the acidic lignin is obtained by the following steps: boiling and stirring the crude acidic lignin in hot water, filtering and washing it while it is hot, and then drying it.

[0044] The ratio of crude acidic lignin to water is (0-10)g:100ml.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. This invention provides a styrene-acrylic emulsion and its preparation method, which obtains lignin maleate by modifying lignin, and replaces part of the styrene with lignin maleate, thereby reducing the amount of styrene used.

[0047] 2. Styrene is a petrochemical raw material, while lignin maleate is biomass-based. Replacing some styrene with lignin maleate and using biomass-based materials instead of petrochemical raw materials makes the raw materials used more environmentally friendly.

[0048] 3. Applying lignin maleate to the embodiments of the present invention, and using its lignin maleate to finally produce styrene-acrylic emulsion through chemical reaction, can increase the glass transition temperature of styrene-acrylic emulsion and improve its performance.

[0049] 4. Compared with styrene, lignin maleate contains more polar groups. Applying lignin maleate to the embodiments of the present invention can improve the adhesion of styrene-acrylic emulsion.

[0050] 5. After lignin is modified into lignin maleate, it gains double bonds that participate in free radical reactions, and its oiliness is enhanced, resulting in better compatibility with other components and making the reaction more favorable. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 Photograph of the styrene-acrylic emulsion product prepared in Example 1 of this invention;

[0053] Figure 2 Photograph of the styrene-acrylic emulsion product obtained in Example 2 of this invention;

[0054] Figure 3 This is a photograph of the styrene-acrylic emulsion product prepared in Example 3 of the present invention. Detailed Implementation

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] The inventors of this invention have discovered that lignin, a renewable biomass material with a benzene ring structure, is an ideal substitute for styrene. Therefore, using lignin to partially replace styrene in the preparation of styrene-acrylic emulsions is one way to address the gradual depletion of petroleum resources.

[0057] Embodiments of the present invention:

[0058] The instruments required for preparing styrene-acrylic emulsion in this embodiment of the invention are: stirrer, water bath, condenser, dropping funnel, 250mL three-necked flask, thermometer, beaker, glass rod, rubber stopper, glass stopper, and separatory funnel.

[0059] This invention provides a method for preparing a styrene-acrylic emulsion, comprising the following steps:

[0060] (1) Monomer purification: Styrene and butyl acrylate were purified separately to obtain purified styrene / butyl acrylate.

[0061] The styrene purification process specifically involves:

[0062] Styrene was washed once with a 10% sodium hydroxide solution in a separatory funnel, and the mixture was separated. The lower alkaline layer was discharged, and the upper liquid was the monomer.

[0063] Add an appropriate amount of deionized water to the upper liquid, then wash with water, separate the liquid, and release the lower wastewater. Repeat the water washing operation until the pH of the wastewater is 7-8 to obtain the purified styrene.

[0064] The purification of butyl acrylate specifically involves:

[0065] Wash butyl acrylate once with a 10% sodium hydroxide solution in a separatory funnel, separate the layers, release the lower alkaline solution, and the upper liquid is the monomer.

[0066] Add an appropriate amount of deionized water to the upper liquid, then wash with water, separate the liquid, and release the lower wastewater. Repeat the water washing operation until the pH of the wastewater is 7-8 to obtain the purified butyl acrylate.

[0067] (2) Solution preparation: (Theoretical solid content: 50%)

[0068] First component: Add emulsifier NP-40, sodium dodecyl sulfate and deionized water to the first container in sequence, stir until completely dissolved, let stand to defoam, and obtain the first component;

[0069] Second component: Add purified styrene, purified butyl acrylate, and part of the first component to the second container in sequence, and stir until no layering occurs to obtain the second component;

[0070] Third component: Add lignin maleate, acrylic acid, and the remaining first component to the third container in sequence, and then perform ultrasonic treatment. The ultrasonic treatment needs to be repeated 3 times, and after each ultrasonic treatment, the particles on the wall of the third container need to be cleaned with a glass rod to obtain the third component.

[0071] The ultrasonic treatment is performed by placing the third container containing the mixture of lignin maleate, acrylic acid, and the first component into an ultrasonic vibrator and ultrasonically treating it for 1-3 minutes.

[0072] Fourth component: Add a portion of ammonium persulfate and an appropriate amount of deionized water to the fourth container in sequence to completely dissolve the solid and obtain the fourth component;

[0073] Fifth component: Add the remaining ammonium persulfate and an appropriate amount of deionized water to the fifth container in sequence to completely dissolve the solid and obtain the fifth component;

[0074] (3) Emulsion polymerization:

[0075] a. Install the four-necked flask, condenser, and stirring rod. Pour part of the third component directly into the reaction vessel, turn on the electric stirrer (electric stirring is carried out throughout the emulsion polymerization process), set the stirring speed to the first preset speed of 400 RPM, and heat up.

[0076] b. Once the temperature reaches the first preset temperature of 55-65℃, add part of the fourth component under constant temperature and continue to heat up;

[0077] c. Heat to the second preset temperature of 75-85℃, adjust the stirring speed to the second preset speed of 600RPM, and add the remaining third and fourth components dropwise using a dropping funnel. The third and fourth components are added dropwise within 0.8-1.2 hours.

[0078] d. After the third and fourth components are added, the reaction is kept at a constant temperature. Then, the second and fifth components are added dropwise using a dropping funnel. The second and fifth components are added dropwise over 1.8-2.2 hours. After the second and fifth components are added, the reaction is kept at a constant temperature for another 1.8-2.2 hours to obtain the reaction solution.

[0079] e. Stop the reaction, pour the reaction solution into the sixth container, add sodium hydroxide solution to adjust the pH to 8, and obtain the styrene-acrylic emulsion. The concentration of the sodium hydroxide solution added is 4.5-5.5 mol / L.

[0080] Specifically, the raw materials for preparing the styrene-acrylic emulsion include the following components in parts by weight: 9-10.62 parts styrene, 0.18-1.8 parts lignin maleate, 7.2-18 parts butyl acrylate, 7.2-18 parts acrylic acid, 0.11-0.9 parts ammonium persulfate, 0.72-1.8 parts emulsifier NP-40, and 0.7-1.8 parts sodium dodecyl sulfate.

[0081] In this embodiment of the invention, lignin maleate is obtained through the following steps:

[0082] The crude acidic lignin is stirred in hot water at 70-90℃ for 1-2 hours, filtered while hot, washed, and dried to obtain acidic lignin; the ratio of crude acidic lignin to water is (0-10)g:100ml.

[0083] Add 120-180 mL of ethylene glycol dimethyl ether to a three-necked flask equipped with a thermometer and a condenser. Heat the flask to a preset temperature (90-110°C) and stir. Add 25-35 g of acidic lignin and 10-15 g of maleic anhydride sequentially. When the temperature inside the flask reaches the preset temperature, react for 5-7 hours. After the reaction is complete, the flask contains a black liquid and a black viscous solid. Cool the black liquid to room temperature and then pour it into a beaker containing 0.8-1.2 L of deionized water while stirring, thereby precipitating a solid. Filter the precipitated solid and wash it with water 2-3 times until the pH of the filtrate is 5-6. Dry the filtrate to obtain the lignin maleate ester.

[0084] The following provides specific embodiments.

[0085] The instruments required for this invention embodiment include: stirrer, water bath, condenser, dropping funnel, 250mL three-necked flask, thermometer, beaker, glass rod, rubber stopper, glass stopper, and separatory funnel.

[0086] Example 1

[0087] Example 1 of this invention provides a method for preparing a styrene-acrylic emulsion, comprising the following steps:

[0088] (1) Monomer purification:

[0089] Styrene was purified to:

[0090] Styrene was washed once with a 10% sodium hydroxide solution in a separatory funnel, separated, and the lower alkaline layer was discharged, while the upper liquid was monomer. An appropriate amount of deionized water was added to the upper liquid, followed by washing, separation, and discharge of the lower wastewater. The washing operation was repeated until the pH of the wastewater was 7-8 to obtain the purified styrene.

[0091] Butyl acrylate was purified to:

[0092] The butyl acrylate was washed once with a 10% sodium hydroxide solution in a separatory funnel, separated, and the lower alkaline layer was discharged, while the upper liquid was the monomer. An appropriate amount of deionized water was added to the upper liquid, and then the mixture was washed with water, separated, and the lower wastewater was discharged. The water washing operation was repeated until the pH of the wastewater was 7-8 to obtain the purified butyl acrylate.

[0093] (2) Solution preparation:

[0094] First component: Add 0.72g of emulsifier NP-40, 1.08g of sodium dodecyl sulfate, and 21g of deionized water to the first beaker in sequence, stir with a glass rod until the solid is completely dissolved, let stand to defoam, and obtain the first component;

[0095] Second component: Add 10.62g of purified styrene, 7.2g of purified butyl acrylate and 10.7g of the first component to the second beaker in sequence, stir with a magnetic stirrer at 450 rpm until no layering is formed, and the second component is obtained.

[0096] Third component: Add 0.18g of lignin maleate, 18g of acrylic acid, and 12.1g of the first component to the third beaker in sequence, and then sonicate for 2 minutes. The sonication needs to be repeated 3 times, and after each sonication, the particles on the wall of the third container need to be cleaned with a glass rod to obtain the third component.

[0097] The ultrasonic treatment is performed by placing the third container, which contains a mixture of lignin maleate, acrylic acid, and the first component, into an ultrasonic vibrator and ultrasonically treating it for 2 minutes.

[0098] Fourth component: Add 0.06g of ammonium persulfate and 1.5g of deionized water to the fourth beaker in sequence to completely dissolve the solid and obtain the fourth component;

[0099] Fifth component: Add 0.05 g of ammonium persulfate and 1.5 g of deionized water to the fifth beaker in sequence, shake the beaker to completely dissolve the solid, and obtain the fifth component;

[0100] (3) Emulsion polymerization:

[0101] a. Install the four-necked flask, condenser, and stir bar. Pour half of the third component directly into the reaction flask, turn on the electric stirrer (electric stirring is carried out throughout the emulsion polymerization process), set the stirring speed to the first preset speed of 400 RPM, and heat up.

[0102] b. Once the temperature reaches the first preset temperature of 60℃, add half of the fourth component into the titration funnel under constant temperature. After the addition is complete, continue to raise the temperature.

[0103] c. Heat to the second preset temperature of 78℃, adjust the stirring speed to the second preset speed of 600RPM, and add the remaining third and fourth components dropwise using a dropping funnel. The addition of the third and fourth components is completed in about 1 hour.

[0104] d. After adding the third and fourth components, maintain the temperature for 1 hour. Then, add the second and fifth components dropwise using a dropping funnel. The second and fifth components are added in about 2 hours. After the second and fifth components are added, maintain the temperature for another 2 hours to obtain the reaction solution.

[0105] e. Stop the reaction, pour the reaction solution into the sixth container, add 5 mol / L sodium hydroxide solution to adjust the pH to 8, and obtain the styrene-acrylic emulsion. Measure the solid content.

[0106] The preparation method of lignin maleate in Example 1 is as follows:

[0107] (1) Boil crude acidic lignin in hot water at 80℃ for 1.5 hours, filter while hot, wash and dry to obtain purified acidic lignin; the concentration of crude acidic lignin in water is 5g / 100ml.

[0108] (2) Add 150 mL of ethylene glycol dimethyl ether to a 250 mL three-necked flask equipped with a thermometer and a condenser, heat to the preset temperature (90 °C), stir, and add 30 g of acidic lignin and 12 g of maleic anhydride in sequence. When the temperature inside the flask reaches the preset temperature of 90 °C, react for 6 h. After the reaction is completed, cool the above reaction solution to room temperature, and then pour it into a beaker containing 1 L of deionized water while stirring, so that a solid is precipitated. Filter the precipitated solid, wash it with water twice until the pH of the filtrate is 5-6, and dry it to obtain the lignin maleate ester.

[0109] Example 2

[0110] Example 2 was prepared using the same method as Example 1, the only difference being the proportion of raw materials used.

[0111] Example 2 of the present invention provides a method for preparing a styrene-acrylic emulsion, comprising the following steps:

[0112] (1) Monomer purification:

[0113] Styrene was purified to:

[0114] Styrene was washed once with a 10% sodium hydroxide solution in a separatory funnel, separated, and the lower alkaline layer was discharged, while the upper liquid was monomer. An appropriate amount of deionized water was added to the upper liquid, followed by washing, separation, and discharge of the lower wastewater. The washing operation was repeated until the pH of the wastewater was 7-8 to obtain the purified styrene.

[0115] Butyl acrylate was purified to:

[0116] The butyl acrylate was washed once with a 10% sodium hydroxide solution in a separatory funnel, separated, and the lower alkaline layer was discharged, while the upper liquid was the monomer. An appropriate amount of deionized water was added to the upper liquid, and then the mixture was washed with water, separated, and the lower wastewater was discharged. The water washing operation was repeated until the pH of the wastewater was 7-8 to obtain the purified butyl acrylate.

[0117] (2) Solution preparation:

[0118] First component: Add 0.72g of emulsifier NP-40, 1.08g of sodium dodecyl sulfate, and 21g of deionized water to the first beaker in sequence, stir with a glass rod until the solid is completely dissolved, let stand to defoam, and obtain the first component;

[0119] Second component: Add 9.72g of purified styrene, 7.2g of purified butyl acrylate and 10.7g of the first component to the second beaker in sequence, stir with a magnetic stirrer at 450 rpm until no layering is formed, and the second component is obtained.

[0120] Third component: Add 1.08g of lignin maleate, 18.0g of acrylic acid and 12.1g of the first component to the third beaker in sequence, and then sonicate for 2 minutes. The sonication needs to be repeated 3 times. After each sonication, the particles on the wall of the third container need to be cleaned with a glass rod to obtain the third component.

[0121] The ultrasonic treatment is performed by placing the third container, which contains a mixture of lignin maleate, acrylic acid, and the first component, into an ultrasonic vibrator and ultrasonically treating it for 2 minutes.

[0122] Fourth component: Add 0.29g of ammonium persulfate and 7.5g of deionized water to the fourth beaker in sequence to completely dissolve the solid and obtain the fourth component;

[0123] Fifth component: Add 0.25g of ammonium persulfate and 7.5g of deionized water to the fifth beaker in sequence, shake the beaker to completely dissolve the solid, and obtain the fifth component;

[0124] (3) Emulsion polymerization:

[0125] a. Install the four-necked flask, condenser, and stirring rod. Pour half of the third component directly into the reaction flask, turn on the electric stirrer (electric stirring is carried out throughout the emulsion polymerization process), set the stirring speed to the first preset speed of 400 RPM, and heat up.

[0126] b. Once the temperature reaches the first preset temperature of 60℃, add half of the fourth component into the titration funnel under constant temperature. After the addition is complete, continue to raise the temperature.

[0127] c. Heat to the second preset temperature of 85℃, adjust the stirring speed to the second preset speed of 600RPM, and add the remaining third and fourth components dropwise using a dropping funnel. The third and fourth components are added dropwise in about 1 hour.

[0128] d. After adding the third and fourth components, maintain the temperature for 1 hour. Then, add the second and fifth components dropwise using a dropping funnel. The second and fifth components are added in about 2 hours. After the second and fifth components are added, maintain the temperature for another 2 hours to obtain the reaction solution.

[0129] e. Stop the reaction, pour the reaction solution into the sixth container, add 5 mol / L sodium hydroxide solution to adjust the pH to 8, and obtain the styrene-acrylic emulsion. Measure the solid content.

[0130] The preparation method of lignin maleate in Example 2 is as follows:

[0131] (1) Boil crude acidic lignin in hot water at 90℃ for 1 hour, filter while hot, wash and dry to obtain purified acidic lignin; the concentration of crude acidic lignin in water is 10g / 100ml.

[0132] (2) Add 150 mL of ethylene glycol dimethyl ether to a 250 mL three-necked flask equipped with a thermometer and a condenser, heat to the preset temperature (90 °C), stir, and add 30 g of acidic lignin and 12 g of maleic anhydride in sequence. When the temperature inside the flask reaches the preset temperature of 90 °C, react for 6 h. After the reaction is completed, cool the above reaction solution to room temperature, and then pour it into a beaker containing 1 L of deionized water while stirring, so that a solid is precipitated. Filter the precipitated solid, wash it with water twice until the pH of the filtrate is 5-6, and dry it to obtain the lignin maleate ester.

[0133] Example 3

[0134] Example 3 was prepared using the same method as Example 1, the only difference being the proportion of raw materials used.

[0135] Example 3 of the present invention provides a method for preparing a styrene-acrylic emulsion, comprising the following steps:

[0136] (1) Monomer purification:

[0137] Styrene was purified to:

[0138] Styrene was washed once with a 10% sodium hydroxide solution in a separatory funnel, separated, and the lower alkaline layer was discharged, while the upper liquid was monomer. An appropriate amount of deionized water was added to the upper liquid, followed by washing, separation, and discharge of the lower wastewater. The washing operation was repeated until the pH of the wastewater was 7-8 to obtain the purified styrene.

[0139] Butyl acrylate was purified to:

[0140] The butyl acrylate was washed once with a 10% sodium hydroxide solution in a separatory funnel, separated, and the lower alkaline layer was discharged, while the upper liquid was the monomer. An appropriate amount of deionized water was added to the upper liquid, and then the mixture was washed with water, separated, and the lower wastewater was discharged. The water washing operation was repeated until the pH of the wastewater was 7-8 to obtain the purified butyl acrylate.

[0141] (2) Solution preparation:

[0142] First component: Add 0.72g of emulsifier NP-40, 1.08g of sodium dodecyl sulfate, and 21g of deionized water to the first beaker in sequence, stir with a glass rod until the solid is completely dissolved, let stand to defoam, and obtain the first component;

[0143] Second component: Add 9.0g of purified styrene, 7.2g of purified butyl acrylate and 10.7g of the first component to the second beaker in sequence, stir with a magnetic stirrer at 450 rpm until no layering is formed, and the second component is obtained;

[0144] Third component: Add 1.8g of lignin maleate, 18.0g of acrylic acid and 12.1g of the first component to the third beaker in sequence, and then sonicate for 2 minutes. The sonication needs to be repeated 3 times. After each sonication, the particles on the wall of the third container need to be cleaned with a glass rod to obtain the third component.

[0145] The ultrasonic treatment is performed by placing the third container, which contains a mixture of lignin maleate, acrylic acid, and the first component, into an ultrasonic vibrator and ultrasonically treating it for 2 minutes.

[0146] Fourth component: Add 0.50g of ammonium persulfate and 8.00g of deionized water to the fourth beaker in sequence until the solid is completely dissolved to obtain the fourth component;

[0147] Fifth component: Add 0.4g of ammonium persulfate and 8.00g of deionized water to the fifth beaker in sequence, shake the beaker to completely dissolve the solid, and obtain the fifth component;

[0148] (3) Emulsion polymerization:

[0149] a. Install the four-necked flask, condenser, and stirring rod. Pour half of the third component directly into the reaction flask, turn on the electric stirrer (electric stirring is carried out throughout the emulsion polymerization process), set the stirring speed to the first preset speed of 400 RPM, and heat up.

[0150] b. Once the temperature reaches the first preset temperature of 60℃, add half of the fourth component into the titration funnel under constant temperature. After the addition is complete, continue to raise the temperature.

[0151] c. Heat to the second preset temperature of 85℃, adjust the stirring speed to the second preset speed of 600RPM, and add the remaining third and fourth components dropwise using a dropping funnel. The third and fourth components are added dropwise in about 1 hour.

[0152] d. After adding the third and fourth components, maintain the temperature for 1 hour. Then, add the second and fifth components dropwise using a dropping funnel. The second and fifth components are added in about 2 hours. After the second and fifth components are added, maintain the temperature for another 2 hours to obtain the reaction solution.

[0153] e. Stop the reaction, pour the reaction solution into the sixth container, add 5 mol / L sodium hydroxide solution to adjust the pH to 8, and obtain the styrene-acrylic emulsion. Measure the solid content.

[0154] The preparation method of lignin maleate in Example 3 is as follows:

[0155] (1) Boil crude acidic lignin in hot water at 70°C for 2 hours, filter while hot, wash and dry to obtain purified acidic lignin; the ratio of crude acidic lignin to water is 8g / 100ml.

[0156] (2) Add 150 mL of ethylene glycol dimethyl ether to a 250 mL three-necked flask equipped with a thermometer and a condenser, heat to the preset temperature (90 °C), stir, and add 30 g of acidic lignin and 12 g of maleic anhydride in sequence. When the temperature inside the flask reaches the preset temperature of 90 °C, react for 6 h. After the reaction is completed, cool the above reaction solution to room temperature, and then pour it into a beaker containing 1 L of deionized water while stirring, so that a solid is precipitated. Filter the precipitated solid, wash it with water twice until the pH of the filtrate is 5-6, and dry it to obtain the lignin maleate ester.

[0157] Comparative Example 1

[0158] The only difference from Example 1 is that lignin maleate was not used; everything else is the same as in Example 1. Comparative Example 2

[0159] The only difference from Example 1 is that the initiator ammonium persulfate was added all at once; in Example 1, the initiator ammonium persulfate was added in two parts, and Comparative Example 2 is otherwise the same as Example 1.

[0160] Comparative Example 3

[0161] The only difference from Example 1 is that all the raw materials used in the styrene-acrylic emulsion are added at once, while everything else is the same as in Example 1.

[0162] Comparative Example 4

[0163] The only difference from Example 1 is that the lignin maleate in Example 1 is replaced with lignin, and everything else is the same as in Example 1.

[0164] The following is a table showing the amounts of raw materials used in the examples and comparative examples:

[0165]

[0166] The emulsions prepared in the examples and the emulsions prepared in the comparative examples were coated into films, and the adhesion of the samples was tested according to the national standard GB / T9286-1998; the glass transition temperature (T) was measured. g The test method was as follows: nitrogen atmosphere, heating and cooling rate of 10℃ / min; first, the temperature was raised from room temperature to 80℃, held for 5 min, then lowered to -30℃, held for 5 min, and then raised to 80℃ again. The results are shown in Table 1.

[0167] Table 1

[0168]

[0169] As can be seen from the table above, lignin in Comparative Example 4 did not participate in the reaction, the reaction in Comparative Examples 2-3 was incomplete and the glass transition temperature was greatly reduced, and no lignin maleate was added in Comparative Example 1. The glass transition temperature of Comparative Example 1 was also greatly reduced compared to Example 1, and the solid film detached.

[0170] Therefore, it can be seen that the order of raw material feeding in the embodiments of the present invention needs to be strictly controlled, and lignin maleate needs to be added. This not only increases the glass transition temperature and reduces the shedding of the solid film, but also, by increasing the amount of lignin maleate, can even completely prevent the solid film from shedding. Moreover, using a new type of lignin maleate to replace styrene is more environmentally friendly.

[0171] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0172] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a styrene-acrylic emulsion, characterized in that, Includes the following steps: (1) Monomer purification: Styrene and butyl acrylate were purified separately to obtain purified styrene / butyl acrylate. (2) Solution preparation: First component: Add emulsifier NP-40, sodium dodecyl sulfate and deionized water to the first container in sequence, stir until completely dissolved, let stand to defoam, and obtain the first component; Second component: Add purified styrene, purified butyl acrylate, and part of the first component to the second container in sequence, and stir until no layering occurs to obtain the second component; Third component: Lignomethyl maleate, acrylic acid, and the remaining first component are added sequentially to the third container, and then ultrasonic treatment is performed to obtain the third component; Fourth component: Add a portion of ammonium persulfate and deionized water sequentially to the fourth container to completely dissolve the solid and obtain the fourth component; Fifth component: Add the remaining ammonium persulfate and deionized water to the fifth container in sequence to completely dissolve the solid and obtain the fifth component; (3) Emulsion polymerization: a. Install the four-necked flask, condenser, and stirring rod. Pour part of the third component directly into the reaction vessel, start stirring, set the stirring speed to the first preset speed, and heat up. b. Once the temperature reaches the first preset temperature, add a portion of the fourth component while maintaining a constant temperature, and continue heating. c. Heat to the second preset temperature, adjust the stirring speed to the second preset speed, and add the remaining third and fourth components dropwise using a dropping funnel; d. After adding the third and fourth components, maintain the reaction temperature at a constant temperature. Then, add the second and fifth components dropwise using a dropping funnel. After adding the second and fifth components, maintain the reaction temperature at a constant temperature for another 1.8-2.2 hours to obtain the reaction solution. e. Stop the reaction, pour the reaction solution into the sixth container, add sodium hydroxide solution to adjust the pH to 8, and obtain the styrene-acrylic emulsion.

2. The method for preparing a styrene-acrylic emulsion according to claim 1, characterized in that, The monomer purification specifically involves: Wash styrene / butyl acrylate once with a 10% sodium hydroxide solution in a separatory funnel, separate the layers, release the lower alkaline solution, and the upper liquid is the monomer; Add an appropriate amount of deionized water to the upper liquid, then wash with water, separate the liquid, and release the lower wastewater. Repeat the water washing operation until the pH of the wastewater is 7-8 to obtain the purified styrene / butyl acrylate.

3. The method for preparing a styrene-acrylic emulsion according to claim 1, characterized in that, The ultrasonic treatment is performed by placing the third container containing the mixture of lignin maleate, acrylic acid, and the first component into an ultrasonic vibrator and ultrasonically treating it for 1-3 minutes.

4. The method for preparing a styrene-acrylic emulsion according to claim 3, characterized in that, The ultrasonic treatment needs to be repeated 3 times, and after each ultrasonic treatment, the particles on the wall of the third container need to be cleaned with a glass rod.

5. The method for preparing a styrene-acrylic emulsion according to claim 1, characterized in that, The first preset temperature is 55-65℃; The second preset temperature is 75-85℃.

6. The method for preparing a styrene-acrylic emulsion according to claim 1, characterized in that, In step e, the concentration of the sodium hydroxide solution is 4.5-5.5 mol / L.

7. The method for preparing a styrene-acrylic emulsion according to claim 1, characterized in that, The lignin maleate ester is obtained through the following steps: Add ethylene glycol dimethyl ether to the sixth container containing a thermometer and a condenser, heat it, set the temperature to the third preset temperature, and stir. Acidic lignin and maleic anhydride are added sequentially to the ethylene glycol dimethyl ether. When the temperature inside the sixth container reaches the third preset temperature, the reaction is carried out for 5-7 hours. After the reaction is cooled to room temperature, the reactants are poured into a seventh container containing deionized water, thereby precipitating a solid. The solid was filtered, then washed with water until the pH of the filtrate was 5-6, and dried to obtain the lignin maleate.

8. A styrene-acrylic emulsion, characterized in that, It is prepared by any one of the preparation methods according to claims 1-7.

9. A method for preparing lignin maleate, characterized in that, Includes the following steps: Add ethylene glycol dimethyl ether to the sixth container containing a thermometer and a condenser, heat it, set the temperature to the third preset temperature, and stir. Acidic lignin and maleic anhydride are added sequentially to the ethylene glycol dimethyl ether. When the temperature inside the sixth container reaches the third preset temperature, the reaction is carried out for 5-7 hours. After the reaction is cooled to room temperature, the reactants are poured into a seventh container containing deionized water, thereby precipitating a solid. The solid was filtered, then washed with water until the pH of the filtrate was 5-6, and dried to obtain the lignin maleate.

10. The method for preparing lignin maleate according to claim 9, characterized in that, The acidic lignin is obtained by the following steps: boiling and stirring the crude acidic lignin in hot water, filtering and washing it while it is hot, and then drying it. The ratio of crude acidic lignin to water is (0-10)g:100ml.

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