A method for preparing bio-based epoxy resin

Abstract

The invention discloses a method for preparing a bio-based epoxy resin, and belongs to the technical field of epoxy resin preparation. After dissolving enzymatic lignin in an alkaline solution, sodium sulfite is added, and the mixture is dried after stirring and heating to obtain demethylated enzymatic lignin; demethylated enzymatic lignin and renewable salicyl alcohol are added to deionized water and continued to be heated and stirred, and then cooled to room temperature, and the reactant is washed with deionized water to obtain highly active polyhydroxy enzymatic lignin; highly active polyhydroxy enzymatic lignin and epichlorohydrin are added to an alkaline solution and heated and stirred, and then washed several times with distilled water, and water and epichlorohydrin are removed by reduced pressure distillation, and the bio-based epoxy resin is obtained after drying. The enzymatic lignin used in the present invention is extracted from the residue of preparing biofuels from straw and corn cobs. During extraction, the enzymatic lignin is not boiled with acid or alkali, and a large number of in-situ active groups can be well retained, and the bio-based epoxy resin has a certain degree of chemical activity.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy resin preparation, and specifically relates to a method for preparing a bio-based epoxy resin. Background Art

[0002] Petroleum-based epoxy resins have the advantages of high strength, high rigidity, and excellent bonding strength, so they are widely used in my country's aerospace, road construction, electronic devices and other fields. In particular, petroleum-based epoxy resins prepared with bisphenol A as a synthetic monomer have occupied more than 90% of the market share. However, bisphenol A petroleum-based epoxy resins are expensive and are non-renewable resources. The synthetic raw material bisphenol A comes from petroleum, which has pain points such as unsustainability and potential physiological toxicity. These problems have restricted the use of epoxy resins to a certain extent, and are not conducive to the sustainable development concept currently advocated.

[0003] As one of the varieties of lignin, enzymatic lignin is the only green and sustainable source of aromatic skeletons in nature, and can be obtained from the residues of energy fuels prepared from non-food biomass waste. Compared with other types of lignin such as lignin sulfonate and alkaline lignin, enzymatic lignin has not been cooked with acid or alkali, and retains a large number of in-situ active groups, providing a basis for the preparation of bio-based epoxy resins. Therefore, the preparation of bio-based epoxy resins has important practical significance for alleviating fossil energy and promoting the development of bio-based materials.

[0004] However, the existing technology of synthesizing bio-based epoxy resin using lignin has the following problems: 1. The extraction of high-boiling alcohol lignin requires a large amount of alcohol solution, which is costly and not conducive to green environmental protection; 2. Conventional modification has limited improvement on the hydroxyl activity and content of enzymatic lignin, resulting in inability to fully carry out epoxidation reaction; 3. The epoxy value of the synthesized bio-based epoxy resin is insufficient, which is difficult to meet the use in various fields. Therefore, it is of great practical significance to develop a new method for preparing bio-based epoxy resin. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing a bio-based epoxy resin to solve the technical problems that the existing bio-based epoxy resin is not environmentally friendly and has insufficient epoxy value.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a bio-based epoxy resin, comprising the following steps:

[0007] S1, dissolving the enzymatic lignin in an alkaline solution, adding sodium sulfite, stirring, heating, and then drying to obtain demethylated enzymatic lignin;

[0008] S2, adding demethylated enzymatic lignin and renewable salicyl alcohol to deionized water and continuing heating and stirring, cooling to room temperature and washing the reactants with deionized water to obtain highly active polyhydroxylated enzymatic lignin;

[0009] S3. Add the highly active polyhydroxy enzymatic lignin to the alkaline solution and stir until dissolved, then add epichlorohydrin and heat and stir, wash the stirred product with distilled water for several times, then distill under reduced pressure to remove water and unreacted epichlorohydrin, and dry to obtain the bio-based epoxy resin.

[0010] Furthermore, the mass ratio of the enzymatically hydrolyzed lignin, sodium sulfite and renewable salicyl alcohol is 100:5-20:60-90.

[0011] Furthermore, the alkaline solution is a hydroxide salt solution, and the hydroxide salt solution is one or a combination of three of sodium hydroxide, magnesium hydroxide and potassium hydroxide.

[0012] Furthermore, the alkaline solution is 15%-30% of the quality of the enzymatically hydrolyzed lignin.

[0013] Furthermore, the mass ratio of epichlorohydrin to high-activity polyhydroxy enzymatically hydrolyzed lignin is 10-60:5-80.

[0014] Furthermore, the heating temperature of step S1 is 60°C-90°C, and the stirring time is 20min-80min; the heating temperature of step S2 is 100°C-120°C, and the stirring time is 30min-60min; the heating temperature of step S3 is 60°C-80°C, and the stirring time is 3h-8h,

[0015] The beneficial effects of the present invention are:

[0016] 1. The enzymatic lignin used in the present invention is extracted from the residue of preparing biofuel from straw and corn cobs. During the extraction, the enzymatic lignin is not boiled with acid or alkali, and can better retain a large number of in-situ active groups and has a certain degree of chemical activity. Therefore, the enzymatic lignin has a low ash content and high purity, and the lignin content in the enzymatic lignin is as high as 90%, which can provide a basis for the preparation of bio-based epoxy resin.

[0017] 2. The sodium sulfite used in the present invention can be used to demethylate the enzymatically hydrolyzed lignin under normal temperature and pressure. Secondly, the renewable salicyl alcohol raw material is used to graft and modify the demethylated enzymatically hydrolyzed lignin, which is green and environmentally friendly and conforms to the current concept of advocating sustainable development.

[0018] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. DETAILED DESCRIPTION

[0019] Example 1

[0020] S1. Extracting enzymatic lignin from the residue of biofuel preparation from straw and corn cobs, weighing 100g of enzymatic lignin and dissolving it in 5% sodium hydroxide solution, then adding 5g of sodium sulfite to the sodium hydroxide solution, heating it to 60 degrees Celsius and stirring it for 30 minutes, then washing, filtering and drying to obtain demethylated enzymatic lignin;

[0021] S2, take 40g of demethylated enzymatic lignin and 60g of renewable salicyl alcohol and add them to deionized water, raise the temperature to 100 degrees Celsius and stir for 30 minutes, cool to room temperature, wash with deionized water 5 times, filter and dry to obtain highly active polyhydroxylated enzymatic lignin;

[0022] S3. Dissolve 10g of highly active polyhydroxy enzymatic lignin in 5% sodium hydroxide solution. After it is completely dissolved, add 20g of epichlorohydrin. Raise the temperature to 60 degrees Celsius and stir for 3 hours. After the reaction is completed, wash it repeatedly with distilled water for 3 times to remove the sodium hydroxide and the generated NaCl solution. Then, distill under reduced pressure to remove water and unreacted epichlorohydrin, and dry it to obtain a bio-based epoxy resin.

[0023] Example 2

[0024] S1. Extracting enzymatic lignin from the residue of biofuel preparation from straw and corn cobs, weighing 100g of enzymatic lignin and dissolving it in 10% sodium hydroxide solution, then adding 10g of sodium sulfite to the mixed solution of sodium hydroxide and magnesium hydroxide, raising the temperature to 70 degrees Celsius and stirring for 40 minutes, then washing, filtering and drying to obtain demethylated enzymatic lignin;

[0025] S2, adding 30g of demethylated enzymatic lignin and 70g of renewable salicyl alcohol into deionized water, raising the temperature to 110 degrees Celsius and stirring for 50 minutes, cooling to room temperature and washing with deionized water for 5 times, filtering and drying to obtain highly active polyhydroxylated enzymatic lignin;

[0026] S3. Dissolve 15g of highly active polyhydroxy enzymatic lignin in 10% sodium hydroxide solution. After it is completely dissolved, add 40g of epichlorohydrin. Raise the temperature to 60 degrees Celsius and stir for 5 hours. After the reaction is completed, wash it repeatedly with distilled water for 3 times to remove the sodium hydroxide and the generated NaCl solution. Then, distill under reduced pressure to remove water and unreacted epichlorohydrin, and dry it to obtain a bio-based epoxy resin.

[0027] Example 3

[0028] S1. Extracting enzymatic lignin from the residue of biofuel preparation from straw and corn cobs, weighing 100g of enzymatic lignin and dissolving it in 15% sodium hydroxide solution, then adding 15g of sodium sulfite to potassium hydroxide, raising the temperature to 80 degrees Celsius and stirring for 40 minutes, then washing, filtering and drying to obtain demethylated enzymatic lignin;

[0029] S2, then add 20g of demethylated enzymatic lignin and 80g of regenerated salicyl alcohol into deionized water, raise the temperature to 120 degrees Celsius and stir for 60 minutes, cool to room temperature and wash with deionized water 5 times, filter and dry to obtain highly active polyhydroxy enzymatic lignin;

[0030] S3. Dissolve 5g of highly active polyhydroxy enzymatic lignin in 15% sodium hydroxide solution. After it is completely dissolved, add 30g of epichlorohydrin. Raise the temperature to 70 degrees Celsius and stir for 6 hours. After the reaction is completed, wash it repeatedly with distilled water for 3 times to remove the sodium hydroxide and the generated NaCl solution. Then, distill under reduced pressure to remove water and unreacted epichlorohydrin, and dry it to obtain a bio-based epoxy resin.

[0031] Example 4

[0032] S1. Extracting enzymatic lignin from the residue of biofuel prepared from straw and corn cobs, weighing 100g of enzymatic lignin and dissolving it in 20% sodium hydroxide solution, then adding 20g of sodium sulfite to a mixed solution of sodium hydroxide, magnesium hydroxide and potassium hydroxide, raising the temperature to 90 degrees Celsius and stirring for 80 minutes, then washing, filtering and drying to obtain demethylated enzymatic lignin;

[0033] S2, then add 10g of demethylated enzymatic lignin and 90g of regenerated salicyl alcohol into deionized water, raise the temperature to 120 degrees Celsius and stir for 60 minutes, cool to room temperature and wash with deionized water 5 times, filter and dry to obtain highly active polyhydroxy enzymatic lignin;

[0034] S3. Dissolve 30g of highly active polyhydroxy enzymatic lignin in 20% sodium hydroxide solution. After it is completely dissolved, add 30g of epichlorohydrin. Raise the temperature to 80 degrees Celsius and stir for 8 hours. After the reaction is completed, wash it repeatedly with distilled water for 3 times to remove the sodium hydroxide and the generated NaCl solution. Then, distill under reduced pressure to remove water and unreacted epichlorohydrin, and dry it to obtain a bio-based epoxy resin.

[0035] In order to demonstrate the superiority of the present invention, the present application also provides Comparative Example 1-Comparative Example 2.

[0036] Comparative Example 1

[0037] S1. Take 100g of lignin and dry it in an oven at 80°C, then place the lignin and 25g of epichlorohydrin in a 30% sodium hydroxide solution for reaction, heat to 50°C and stir for 1 hour, then let it stand for 24 hours to obtain a bio-based epoxy resin product. The bio-based epoxy resin is an elastic brown solid, which is brown-yellow after washing, filtering and drying.

[0038] Comparative Example 2

[0039] S1, take 100g lignin and dry it in an oven at 70℃, then dissolve the lignin in a mixed solution of 30ml DMF and 20ml n-dodecyl mercaptan, heat to 100℃ and stir, reflux condensation for 2 hours;

[0040] S2, adding water to terminate the reaction, adjusting the Ph value to 2 with hydrochloric acid, and centrifugally drying to obtain the modified lignin powder;

[0041] S3. Take the modified lignin and 25g of epichlorohydrin and place them in a 20% sodium hydroxide solution for reaction. The temperature is raised to 80°C and stirred for 3 hours. After the reaction is completed, water and unreacted epichlorohydrin are distilled under reduced pressure and dried to obtain a bio-based epoxy resin.

[0042] The epoxy values ​​of the bio-based epoxy resins prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were determined using GB-T1677-1981 “Determination of epoxy value of plasticizer (hydrochloric acid-acetone method)”. The results are shown in Table 1.

[0043] Table 1 shows the epoxy values ​​of the bio-based epoxy resins prepared in various examples.

[0044] Example Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Epoxy value (mol / 100g) 0.335 0.526 0.437 0.228 0.082 0.144

[0045] It can be seen from the above table that the epoxy value of Example 1 of the present application is 0.335, the epoxy value of Example 2 is 0.526, the epoxy value of Example 3 is 0.437, and the epoxy value of Example 4 is 0.228. The epoxy values ​​of the bio-based epoxy resins prepared in Examples 1 to 4 of the present application are improved compared to the bio-based epoxy resins prepared by the traditional method, and the preparation process of the bio-based epoxy resins of the present application is green and environmentally friendly, which meets the current environmental development requirements.

[0046] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a bio-based epoxy resin, characterized in that: The following steps are involved: S1, dissolving the enzymatic lignin in an alkaline solution, adding sodium sulfite, stirring, heating, and then drying to obtain demethylated enzymatic lignin; S2, adding demethylated enzymatic lignin and renewable salicyl alcohol to deionized water and continuing heating and stirring, cooling to room temperature and washing the reactants with deionized water to obtain highly active polyhydroxylated enzymatic lignin; S3, adding the highly active polyhydroxylated enzymatic lignin to the alkaline solution and stirring until dissolved, then adding epichlorohydrin and stirring at a high temperature, washing the stirred product with distilled water for several times, then distilling under reduced pressure to remove water and unreacted epichlorohydrin, and drying to obtain a bio-based epoxy resin; The mass ratio of the enzymatically hydrolyzed lignin, sodium sulfite and renewable salicyl alcohol is 100:5-20:60-90; The alkaline solution is 15%-30% of the quality of the enzymatically hydrolyzed lignin; The mass ratio of epichlorohydrin to high-activity polyhydroxy enzymatic lignin is 10-60:5-80.

2. The method for preparing a bio-based epoxy resin according to claim 1, characterized in that: The alkaline solution is a hydroxide salt solution, and the hydroxide salt solution is one of sodium hydroxide, magnesium hydroxide, and potassium hydroxide, or a combination of the three.

3. The method for preparing a bio-based epoxy resin according to claim 1, characterized in that: The heating temperature of step S1 is 60°C-90°C, and the stirring time is 20min-80min; the heating temperature of step S2 is 100°C-120°C, and the stirring time is 30min-60min; the heating temperature of step S3 is 60°C-80°C, and the stirring time is 3h-8h.