CN110835402B

CN110835402B - Low-viscosity bio-based epoxy resin based on vanillin and preparation method thereof

Info

Publication number: CN110835402B
Application number: CN201911139270.XA
Authority: CN
Inventors: 敖玉辉; 郭宗伟; 尚垒; 庄海林; 刘浏; 杜巍峰; 迟至远
Original assignee: Changchun University of Technology
Current assignee: Changchun University of Technology
Priority date: 2019-11-20
Filing date: 2019-11-20
Publication date: 2022-02-11
Anticipated expiration: 2039-11-20
Also published as: CN110835402A

Abstract

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.

Description

Low-viscosity bio-based epoxy resin based on vanillin and preparation method thereof

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

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.

Example 1

Step 1, 0.3mol of powdery itaconic acid, 0.1mol of glycerol, 50ml of toluene, 5 wt% of catalyst methanesulfonic acid were charged into a three-necked round-bottomed flask equipped with a stirrer in one neck, a nitrogen flow in the other neck, a toluene reflux and azeotropic distillation apparatus in the third neck, the internal temperature was set at 150 ℃ and the reaction was continued for 10 hours. The condensed liberated water (1.5mol) was gradually extracted from toluene; continuously refluxing anhydrous toluene to the reactor to obtain a product 1; the nuclear magnetic spectrum is shown in FIG. 2.

Step 2, a mixture of product 1(0.1mol), THF (100ml) and DMF (catalyst, 0.05ml) was added to a round-bottomed flask, and oxalyl chloride (0.3mol) was added dropwise over 20min in an ice-water bath at 0 ℃. The reaction mixture was slowly heated and reacted at 50 ℃ for 4 hours until the solid was completely dissolved. Then, carrying out rotary evaporation on the obtained solution to obtain a product 2;

and 3, adding the product 2(0.1mol) into 100ml of ethyl acetate to dissolve to obtain a solution A. Vanillin (0.3mol) and triethylamine (0.36mol) were dissolved in ethyl acetate (200mL) with stirring to give solution B, and solution A was added dropwise in an ice-water bath at 0 ℃ for 20min and then kept at 40 ℃ for 1 hour. The reaction solution was then filtered, the solvent removed by rotary evaporation, boiled in water, extracted with dichloromethane, rotary evaporated and dried under vacuum at 90 ℃ for 5 hours. The product 3 is obtained. The nuclear magnetic spectrum is shown in FIG. 3.

Step 4, adding the product 3(0.1mol) and hot phenol (1.2mol, 80 ℃) into a round-bottom flask, strongly stirring to obtain a uniform solution, adding p-toluenesulfonic acid (0.4mol) and zinc chloride (0.4mol), and reacting for 24 hours at the temperature of 60 ℃. After the reaction, the mixture was washed 5 times with hot water (>70 ℃) to remove residual salts. Most of the unreacted phenol was removed by distillation at 150 ℃ under reduced pressure. The crude product obtained was dissolved in ethanol and precipitated into water with vigorous stirring. The precipitate was collected and dried under vacuum at 100 ℃ to give product 4 as a red solid. The nuclear magnetic spectrum is shown in FIG. 4.

Step 5, adding product 4(0.1mol) and epichlorohydrin (6mol) into a round-bottom flask, stirring and heating to 90 ℃, after the product 4 is completely dissolved, adding tetrabutylammonium bromide (6.8g), and reacting the mixture at 110 ℃ for 5 hours. When the mixture was cooled to 30 ℃, then a NaOH solution (28 g NaOH, 90g water) was added dropwise over 5 hours and the resulting mixture was kept at 30 ℃ for another 5 hours. After cooling to room temperature, the mixture was washed 5 times with water to remove residual salts. Most of the unreacted epichlorohydrin was removed by rotary evaporation at 90 ℃ and dried under vacuum at 90 ℃. Finally, a dark red liquid product 5 of low viscosity is obtained. The nuclear magnetic spectrum is shown in FIG. 5.

FIG. 1 is an infrared spectrum of each product obtained in the preparation of example 1 of the present invention, and FIG. 1 shows that bio-based epoxy resin was successfully synthesized in the present invention.

The product obtained in example 1 was tested to determine the epoxyEquivalent W_EEW272g/mol, a viscosity of 5553mpa.s at 20 ℃.

FIG. 6 is a viscosity temperature curve of the low viscosity bio-based epoxy resin prepared in example 1. Figure 6 illustrates that the viscosity of the resin decreases with increasing temperature, but the bio-based epoxy resin prepared at lower temperatures (<60 ℃) has a lower viscosity, demonstrating excellent processability at lower temperatures.

Table 1 shows the viscosity at the characteristic temperature of the low viscosity bio-based epoxy resin of example 1.

TABLE 1

Viscosity (mPa.s)	20℃	30℃	40℃	80℃
					Bisphenol A epoxy resin	29042	6497	1811	82
Synthetic resin of the invention	5553	2023	783	65

Table 1 shows the viscosities of example 1 at different temperatures, and it can be seen from table 1 that bio-based epoxy resin prepared at the same temperature has lower viscosity than bisphenol a epoxy resin, indicating more excellent processability.

Example 2

Step 1, 0.5mol of powdery itaconic acid, 0.1mol of glycerol, 50ml of toluene, 5 wt% of catalyst methanesulfonic acid were charged into a three-necked round-bottomed flask equipped with a stirrer in one neck, a nitrogen flow in the other neck, a toluene reflux and azeotropic distillation device in the third neck, the internal temperature was set to 160 ℃ and the reaction was continued for 5 hours. The condensed liberated water (1.5mol) was gradually extracted from toluene; continuously refluxing anhydrous toluene to the reactor to obtain a product 1;

step 2, a mixture of product 1(0.1mol), THF (100ml) and DMF (catalyst, 0.05ml) was added to a round-bottomed flask, and oxalyl chloride (0.4mol) was added dropwise over 20min in an ice-water bath at 0 ℃. The reaction mixture was slowly heated and reacted at 25 ℃ for 4 hours until the solid was completely dissolved. Then, carrying out rotary evaporation on the obtained solution to obtain a product 2;

and 3, adding the product 2(0.1mol) into 100ml of ethyl acetate to dissolve to obtain a solution A. Dissolving vanillin (0.4mol) and triethylamine (0.4mol) in ethyl acetate (200mL) under stirring to obtain solution B, adding dropwise solution A in ice water bath at 0 deg.C within 20min, and keeping at 30 deg.C for 50 min. The reaction solution was then filtered, the solvent removed by rotary evaporation, boiled in water, extracted with dichloromethane, rotary evaporated and dried under vacuum at 100 ℃ for 3 hours. The product 3 is obtained.

Step 4, adding the product 3(0.1mol) and hot phenol (0.6mol, 80 ℃) into a round-bottom flask, strongly stirring to obtain a uniform solution, adding p-toluenesulfonic acid (0.4mol) and zinc chloride (0.4mol), and reacting for 15 hours at the temperature of 50 ℃. After the reaction, the mixture was washed 5 times with hot water (>70 ℃) to remove residual salts. Most of the unreacted phenol was removed by distillation at 150 ℃ under reduced pressure. The crude product obtained was dissolved in ethanol and precipitated into water with vigorous stirring. The precipitate was collected and dried under vacuum at 100 ℃ to give product 4 as a red solid.

Step 5, adding product 4(0.1mol) and epichlorohydrin (5mol) into a round-bottom flask, stirring and heating to 120 ℃, after the product 4 is completely dissolved, adding tetrabutylammonium bromide (6.8g), and reacting the mixture at 120 ℃ for 6 hours. When the mixture was cooled to 50 ℃, then a NaOH solution (28 g NaOH, 90g water) was added dropwise over 2 hours and the resulting mixture was kept at 50 ℃ for another 6 hours. After cooling to room temperature, the mixture was washed 5 times with water to remove residual salts. Most of the unreacted epichlorohydrin was removed by rotary evaporation at 90 ℃ and dried under vacuum at 90 ℃. Finally, a dark red liquid product 5 of low viscosity is obtained.

The product obtained in example 2 was tested to determine the epoxy equivalent W_EEW286g/mol, viscosity 5642mPa.s at 20 ℃.

Example 3

Step 1, 0.4mol of powdery itaconic acid, 0.1mol of glycerol, 50ml of toluene, 5 wt% of catalyst methanesulfonic acid were charged into a three-necked round-bottomed flask equipped with a stirrer in one neck, a nitrogen flow in the other neck, a toluene reflux and azeotropic distillation apparatus in the third neck, the internal temperature was set at 140 ℃ and the reaction was continued for 10 hours. The condensed liberated water (1.5mol) was gradually extracted from toluene; continuously refluxing anhydrous toluene to the reactor to obtain a product 1;

step 2, a mixture of product 1(0.1mol), THF (100ml) and DMF (catalyst, 0.05ml) was added to a round-bottomed flask, and oxalyl chloride (0.35mol) was added dropwise over 20min in an ice-water bath at 0 ℃. The reaction mixture was slowly heated and reacted at 25 ℃ for 4 hours until the solid was completely dissolved. Then, carrying out rotary evaporation on the obtained solution to obtain a product 2;

and 3, adding the product 2(0.1mol) into 100ml of ethyl acetate to dissolve to obtain a solution A. Dissolving vanillin (0.5mol) and triethylamine (0.5mol) in ethyl acetate (200mL) under stirring to obtain solution B, adding dropwise solution A in ice water bath at 0 deg.C within 20min, and keeping at 40 deg.C for 40 min. The reaction solution was then filtered, the solvent removed by rotary evaporation, boiled in water, extracted with dichloromethane, rotary evaporated and dried under vacuum at 100 ℃ for 3 hours. The product 3 is obtained.

Step 4, adding the product 3(0.1mol) and hot phenol (0.8mol, 80 ℃) into a round-bottom flask, strongly stirring to obtain a uniform solution, adding p-toluenesulfonic acid (0.4mol) and zinc chloride (0.4mol), and reacting for 12 hours at the temperature of 60 ℃. After the reaction, the mixture was washed 5 times with hot water (>70 ℃) to remove residual salts. Most of the unreacted phenol was removed by distillation at 150 ℃ under reduced pressure. The crude product obtained was dissolved in ethanol and precipitated into water with vigorous stirring. The precipitate was collected and dried under vacuum at 100 ℃ to give product 4 as a red solid.

Step 5, the product 4(0.1mol) and epichlorohydrin (5.5mol) were added to a round-bottom flask, stirred and heated to 90 ℃, and after the product 4 was completely dissolved, tetrabutylammonium bromide (6.8g) was added, and the mixture was reacted at 90 ℃ for 7 hours. When the mixture was cooled to 60 ℃, then a NaOH solution (28 g NaOH, 90g water) was added dropwise over 2 hours and the resulting mixture was kept at 60 ℃ for another 7 hours. After cooling to room temperature, the mixture was washed 5 times with water to remove residual salts. Most of the unreacted epichlorohydrin was removed by rotary evaporation at 90 ℃ and dried under vacuum at 90 ℃. Finally, a dark red liquid product 5 of low viscosity is obtained.

The product obtained in example 3 was tested to determine the epoxy equivalent W_EEW278 g/mol. The viscosity at 20 ℃ was 5411 mPas.

Claims

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 for 5-10 hours at the temperature of 140-;

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

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 a vanillin-based low viscosity bio-based epoxy resin as claimed in claim 2, wherein the molar ratio of the product of step two (1) 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 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.