阅读说明：本技术 一种基于香草醛的低粘度生物基环氧树脂及其制备方法 (Low-viscosity bio-based epoxy resin based on vanillin and preparation method thereof ) 是由 敖玉辉 郭宗伟 尚垒 庄海林 刘浏 杜巍峰 迟至远 于 2019-11-20 设计创作，主要内容包括：本发明提供一种基于香草醛的低粘度生物基环氧树脂及其制备方法,属于环氧树脂领域。该环氧树脂具有式(1)所示的结构。本发明还提供了一种基于香草醛的低粘度生物基环氧树脂的制备方法。该结构为一种树枝状分子结构,增加了空间自由体积,降低了生物基环氧树脂单体的粘度,提高树脂的加工性能；同时环氧单体环氧基团较多,提高了环氧树脂的交联密度,芳香结构也有助于材料热稳定性能、机械性能的提高。另外,本发明的主要原料来源于可再生资源,廉价环保节能,整个反应过程简单低毒；不需要太苛刻的反应条件,由于其低粘度且优良的热力学性能、机械性能,具有很好的工业应用价值。(The invention provides a low-viscosity bio-based epoxy resin based on vanillin and a preparation method thereof, belonging to the field of epoxy resin. The epoxy resin has a structure represented by formula (1). The invention also provides a preparation method of the low-viscosity bio-based epoxy resin based on the vanillin. The structure is a dendritic molecular structure, increases the space free volume, reduces the viscosity of a bio-based epoxy resin monomer, and improves the processability of the resin; meanwhile, the epoxy monomer has more epoxy groups, the crosslinking density of the epoxy resin is improved, and the aromatic structure is also beneficial to the improvement of the thermal stability and the mechanical property of the material. In addition, the main raw materials of the invention are derived from renewable resources, the invention has the advantages of low price, environmental protection and energy saving, and the whole reaction process is simple and low in toxicity; does not need too harsh reaction conditions, and has good industrial application value due to low viscosity, excellent thermodynamic property and mechanical property.)

1. A vanillin-based low viscosity bio-based epoxy resin, characterized in that it has a structure represented by formula (1):

2. the method for preparing a vanillin-based low viscosity bio-based epoxy resin as claimed in claim 1, comprising the steps of:

step one, under the protection of nitrogen, adding a solvent, glycerol, itaconic acid and methanesulfonic acid into a reaction vessel, and then reacting at the temperature of 140-;

step two: adding the product 1, a solvent and DMF (dimethyl formamide) into a reaction container, placing the mixture in an ice water bath at 0 ℃ for stirring, then dripping oxalyl chloride, slowly heating the reaction mixture, and reacting at 20-70 ℃ for 3-5 hours to obtain a product 2;

step three: adding vanillin and triethylamine into a reaction container, dissolving in a solvent, placing in an ice water bath, stirring, dissolving the product 2 obtained in the step two in ethyl acetate to obtain a solution, dripping the solution into the reaction container, and keeping the temperature of the reaction container at 20-50 ℃ for 20-60min to obtain a product 3;

step four: adding the product 3 and hot phenol into a reaction vessel at 60-80 ℃ to obtain a uniform solution, then adding p-toluenesulfonic acid and zinc chloride, and keeping the temperature at 30-70 ℃ for reaction for 12-36 hours to obtain a product 4;

step five: adding the product 4 and epichlorohydrin into a reaction vessel, stirring and heating to 90-120 ℃, adding tetrabutylammonium bromide after the product 4 is completely dissolved, reacting the mixture at 90-120 ℃ for 4-6 hours, cooling the mixture to 30-60 ℃, then dropwise adding NaOH solution within 1-2 hours, keeping the obtained mixture at 30-70 ℃ for 3-6 hours, and performing post-treatment to obtain the low-viscosity bio-based epoxy resin based on vanillin.

3. The method for preparing a vanillin-based low viscosity bio-based epoxy resin according to claim 2, wherein the molar ratio of glycerol to itaconic acid in the first step is 1: 3-5.

4. The method for preparing a vanillin-based low viscosity bio-based epoxy resin as claimed in claim 2, wherein the solvent in the first step is toluene.

5. The method for preparing low viscosity bio-based epoxy resin based on vanillin of claim 2, wherein the ratio of the product 1 of the second step to oxalyl chloride is 1: 3-4.

6. The method as claimed in claim 2, wherein the stirring rate in step two is 300-400 r/min.

7. The method for preparing a vanillin-based low viscosity bio-based epoxy resin as claimed in claim 2, wherein the molar ratio of the product 2, vanillin and triethylamine in the third step is 1: 3-4: 3-4.

8. The method for preparing a vanillin-based low viscosity bio-based epoxy resin as claimed in claim 2, wherein the molar ratio of the product 3 to the thermal phenol in the fourth step is 1: 6-12; the molar ratio of p-toluenesulfonic acid, zinc chloride and product 3 was 4: 4: 1.

9. the process for the preparation of low viscosity bio-based epoxy resin based on vanillin of claim 2, wherein the molar ratio of product 4 and epichlorohydrin in step five is 1: 50 to 66.

10. The method for preparing a vanillin-based low viscosity bio-based epoxy resin as claimed in claim 2, wherein the tetrabutylammonium bromide is added in an amount of 2 to 6 wt% of the product 4 in the step five.

Technical Field

The invention belongs to the field of epoxy resin, and particularly relates to low-viscosity bio-based epoxy resin based on vanillin and a preparation method thereof.

Background

The epoxy resin is a high molecular oligomer which contains two or more epoxy groups, takes aliphatic or aromatic as a framework, and can generate a thermosetting product through the reaction of the epoxy groups and other active groups. The epoxy resin has a large amount of active and polar groups, and as a thermosetting resin, the epoxy resin is widely applied to the fields of coatings, composite materials, adhesives, electronic packaging materials, engineering plastics, civil engineering and building materials and the like due to excellent comprehensive performance, good cohesiveness, excellent mechanical property, small curing shrinkage, good manufacturability, excellent electric insulation property and corrosion resistance.

However, at present, most of epoxy resins are derived from petroleum resources, particularly bisphenol a epoxy resins, and petroleum resources are non-renewable resources, and the cost of polymer materials derived from petroleum resources is increased along with the gradual reduction of reserves of the petroleum resources. In addition, bisphenol a is suspected of having physiological toxicity and has been restricted in use in many countries such as europe, and therefore, under the current situation of increasingly depleted petroleum resources, there is an urgent need to use raw materials from other sources to produce epoxy resins, and reduce dependence on petroleum resources. The search for sustainable, high-quality, inexpensive, non-toxic alternatives to petroleum is a key to the existence and development of the polymer industry, and it is particularly important to develop alternatives with renewable resources and possessing comparable properties. The vigorous development of the bio-based renewable monomer has good development prospect and conforms to the green sustainable development strategy of the polymer industry.

The bio-based epoxy resin takes renewable resources as a main raw material, reduces the consumption of petrochemical products in the plastic industry, reduces the pollution to the environment in the production process of petroleum-based raw materials, is an important development direction of current high polymer materials, and has important actual value and wide development space. Lignin is the second largest natural renewable resource next to cellulose and is considered a promising biomass source for large-scale extraction of phenylcyclic compounds. Due to the large and complex molecular structure of lignin, the resin directly obtained from lignin has poor processability and unstable performance, and is difficult to apply. While the degradation of lignin into small molecule compounds of specific structure remains a great challenge, it is desirable that processes for the preparation of vanillin from lignin are used commercially. Vanillin has shown great potential in the polymer field as a single benzene ring compound from lignin which is currently produced on a large scale. Itaconic acid, also known as itaconic acid, is an important bio-based raw material, can be prepared from agricultural and sideline products such as biologically fermented starch, sucrose, molasses, wood chips, straw and the like at low cost, and has huge potential and development space in the aspect of replacing bisphenol A to synthesize epoxy resin. Because of its wide application prospect and low price, it has been selected as one of the most potential species of bio-based platform compounds by the U.S. department of energy. The itaconic acid molecule contains two active carboxyl groups and a double bond inside, and the double bond and the carboxyl group form a conjugate structure, so that the itaconic acid molecule has very active chemical properties, and can be widely applied to the fields of ion exchange resin, coating, high-efficiency deodorant, chemical fiber, synthetic resin and the like as industrial raw materials.

Disclosure of Invention

The invention aims to provide a low-viscosity bio-based epoxy resin based on vanillin and a preparation method thereof, wherein the epoxy resin has low viscosity and good thermodynamic and mechanical properties.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:

the invention firstly provides a low-viscosity bio-based epoxy resin based on vanillin, which has a structure shown in a formula (1):

the invention also provides a preparation method of the low-viscosity bio-based epoxy resin based on the vanillin, which comprises the following steps:

step one, under the protection of nitrogen, adding a solvent, glycerol, itaconic acid and methanesulfonic acid into a reaction vessel, and then reacting at the temperature of 140-;

step two: adding the product 1, a solvent and DMF (dimethyl formamide) into a reaction container, placing the mixture in an ice water bath at 0 ℃ for stirring, then dripping oxalyl chloride, slowly heating the reaction mixture, and reacting at 20-70 ℃ for 3-5 hours to obtain a product 2;

step three: adding vanillin and triethylamine into a reaction container, dissolving in a solvent, placing in an ice water bath, stirring, dissolving the product 2 obtained in the step two in ethyl acetate to obtain a solution, dripping the solution into the reaction container, and keeping the temperature of the reaction container at 20-50 ℃ for 20-60min to obtain a product 3;

step four: adding the product 3 and hot phenol into a reaction vessel at 60-80 ℃ to obtain a uniform solution, then adding p-toluenesulfonic acid and zinc chloride, and keeping the temperature at 30-70 ℃ for reaction for 12-36 hours to obtain a product 4;

step five: adding the product 4 and epichlorohydrin into a reaction vessel, stirring and heating to 90-120 ℃, adding tetrabutylammonium bromide after the product 4 is completely dissolved, reacting the mixture at 90-120 ℃ for 4-6 hours, cooling the mixture to 30-60 ℃, then dropwise adding NaOH solution within 1-2 hours, keeping the obtained mixture at 30-70 ℃ for 3-6 hours, and performing post-treatment to obtain the low-viscosity bio-based epoxy resin based on vanillin.

Preferably, the molar ratio of the glycerol to the itaconic acid in the step one is 1: 3-5.

Preferably, the solvent in the first step is toluene.

Preferably, the ratio relationship between the product 1 of the second step and the oxalyl chloride is 1: 3-4.

Preferably, the stirring speed in the second step is 300-400 r/min.

Preferably, the molar ratio of the product 2, vanillin and triethylamine in the third step is 1: 3-4: 3-4.

Preferably, the molar ratio of the product 3 to the hot phenol in the fourth step is 1: 6-12; the molar ratio of p-toluenesulfonic acid, zinc chloride and product 3 was 4: 4: 1.

preferably, the molar ratio of the product 4 to the epichlorohydrin in the step five is 1: 50 to 66.

Preferably, the addition amount of tetrabutylammonium bromide in the step five is 2-6 wt% of the product 4.

The invention has the advantages of

The invention provides a low-viscosity bio-based epoxy resin based on vanillin and a preparation method thereof, wherein the bio-based epoxy resin has a structure shown in a formula (1), and the structure is a dendritic molecular structure, so that the space free volume is increased, the viscosity of a bio-based epoxy resin monomer is reduced, and the processing performance of the resin is improved; meanwhile, the epoxy monomer has more epoxy groups, the crosslinking density of the epoxy resin is improved, and the aromatic structure is also beneficial to the improvement of the thermal stability and the mechanical property of the material.

In addition, the main raw materials of the invention are derived from renewable resources, the invention has the advantages of low price, environmental protection and energy saving, and the whole reaction process is simple and low in toxicity; does not need too harsh reaction conditions, and has good industrial application value due to low viscosity, excellent thermodynamic property and mechanical property.

Drawings

FIG. 1 is a chart of the infrared spectra of various products of the preparation of example 1 according to the invention;

FIG. 2 is a NMR spectrum of product 1 of example 1;

FIG. 3 is a NMR spectrum of product 3 of example 1;

FIG. 4 is a NMR spectrum of product 4 of example 1;

FIG. 5 is a NMR spectrum of product 5 of example 1;

FIG. 6 is a viscosity temperature curve of the low viscosity bio-based epoxy resin prepared in example 1.

Detailed Description

The invention firstly provides a low-viscosity bio-based epoxy resin based on vanillin, which has a structure shown in a formula (1):

the invention also provides a preparation method of the low-viscosity bio-based epoxy resin based on the vanillin, which comprises the following steps:

step one, adding a solvent, glycerol, itaconic acid and methanesulfonic acid into a reaction vessel under the protection of nitrogen, and then reacting for 5-10 hours at the temperature of 140-160 ℃, wherein the molar ratio of the glycerol to the itaconic acid is preferably 1:3-5, and the mass of a catalyst methanesulfonic acid is 0.15 wt%; the selected solvent is preferably toluene, and the reaction route is as follows:

step two: adding the product 1, a solvent and DMF into a reaction vessel, placing the mixture in an ice water bath at 0 ℃ for stirring, wherein the stirring speed is preferably 300-400r/min, then dripping oxalyl chloride, slowly heating the reaction mixture, reacting at 20-70 ℃ for 3-5 hours until the solid is completely dissolved, and then performing rotary evaporation on the obtained solution at preferably 40-60 ℃ to obtain a product 2; the mol ratio of the product 1 to the oxalyl chloride is preferably 1: 3-4; the solvent is preferably one of anhydrous tetrahydrofuran or anhydrous dichloromethane;

step three: adding vanillin and triethylamine into a reaction vessel to be dissolved in a solvent, placing the mixture into an ice water bath to be stirred, wherein the stirring speed is preferably 300-400r/min, then dissolving the product 2 obtained in the step two into ethyl acetate to obtain a solution, dripping the solution into the reaction vessel within 10-20min, keeping the reaction vessel at 20-50 ℃ for 20-60min, preferably filtering the reaction solution after the reaction, removing the solvent through a rotary evaporation method, extracting the solution with dichloromethane after the water boiling, removing the solvent through the rotary evaporation method again, and performing vacuum drying at 80-100 ℃ for 3-10 hours to obtain a product 3; the molar ratio of the product 2 to the vanillin to the triethylamine is 1: 3-4: 3-4; the solvent is preferably ethyl acetate: the reaction route is as follows:

step four: after the product 3 and hot phenol are added to a reaction vessel at 60-80 ℃ to obtain a homogeneous solution, p-toluenesulfonic acid and zinc chloride are added and the temperature is maintained at 30-70 ℃ for reaction for 12-36 hours, after which the mixture is preferably washed 3-5 times with hot water (>70 ℃) to remove residual salts. Most of the unreacted phenol was removed by distillation at 100 ℃ and 150 ℃ under reduced pressure. The crude product obtained was dissolved in ethanol and precipitated into water with vigorous stirring. Collecting the precipitate and vacuum drying at 80-110 deg.c to obtain product 4; the molar ratio of the product 3 to the hot phenol is 1: 6-12; the molar ratio of p-toluenesulfonic acid, zinc chloride and product 3 was 4: 1; the reaction route is as follows:

step five: adding the product 4 and epichlorohydrin into a reaction vessel, stirring and heating to 90-120 ℃, adding tetrabutylammonium bromide after the product 4 is completely dissolved, allowing the mixture to react at 90-120 ℃ for 4-6 hours, when the mixture is cooled to 30-60 ℃, then dropwise adding a NaOH solution within 1-2 hours, keeping the obtained mixture at 30-70 ℃ for 3-6 hours, preferably cooling to room temperature, and washing the mixture 3-5 times with water to remove residual salts. Most of the unreacted epichlorohydrin was removed by rotary evaporation at 70-100 ℃ and dried under vacuum at 80-100 ℃ to obtain a low viscosity bio-based epoxy resin based on vanillin. The molar ratio of the product 4 to the epichlorohydrin is preferably 1: 50-66, and the preferable adding amount of the tetrabutylammonium bromide is 2-6 wt% of the product 4. The reaction route is as follows:

the present invention is described in further detail below with reference to specific examples, in which the starting materials are all commercially available.