CN114395216B - Bio-based hyperbranched polymer epoxy resin and preparation method thereof - Google Patents

Abstract

The invention discloses a bio-based hyperbranched polymer epoxy resin, which is prepared from ferulic acid hyperbranched epoxy resin and citric acid hyperbranched polyester through dynamic crosslinking. The invention also discloses a preparation method of the resin. The epoxy resin prepared by the invention is obtained by dynamically crosslinking ferulic acid hyperbranched epoxy resin and citric acid hyperbranched polyester, and a large number of interface covalent bonds are formed in a crosslinked network structure, so that the epoxy resin is endowed with a repeatable processing function; the ferulic acid and the citric acid hyperbranched polyester can be controllably degraded into the ferulic acid and the citric acid hyperbranched polyester under the action of the sodium hydroxide aqueous solution, and the degradation products of the ferulic acid and the citric acid hyperbranched polyester can be used for preparing the full-bio-based epoxy resin again, so that the green closed-loop recovery of the epoxy resin is realized. The resin prepared by the method has excellent mechanical property, heat resistance, solvent resistance, hydrolysis resistance, creep resistance and corrosion resistance, can replace petroleum-based epoxy resin, and is applied to the fields of electronic packaging, insulating materials, printed circuit boards and the like.

Description

Bio-based hyperbranched polymer epoxy resin and preparation method thereof

Technical Field

The invention relates to the technical field of high-performance polymer resins, and in particular to a bio-based hyperbranched polymer epoxy resin and a preparation method thereof.

Background Art

Epoxy resin has the advantages of high strength, good solvent resistance, water resistance and corrosion resistance, and good insulation, so epoxy resin is widely used. Due to the irreversible cross-linking network of epoxy resin, it is very difficult to degrade and recycle it. Most of them are incinerated or landfilled, which not only wastes resources but also pollutes the environment. Therefore, it is of great significance to design high-performance and green recyclable epoxy resin.

Epoxy resins constructed based on dynamic covalent bonds undergo cross-linking network structure rearrangement under external stimulation, thus giving them self-healing and reproducible processing characteristics, providing an effective way for the green recycling of epoxy resins and their composites. Since Leible proposed the concept of Vitrimer based on the dynamic exchange network of epoxy resin/anhydride in 2011, researchers have constructed a variety of epoxy resin systems based on β-hydroxy ester exchange, D-A reaction, disulfide exchange and dynamic imine bond exchange, realizing the self-healing and reproducible processing of epoxy resins. However, the self-healing properties of epoxy resins containing dynamic covalent bonds are contradictory to the mechanical strength. The introduction of dynamic covalent bonds reduces the cross-linking density, strength and modulus of epoxy resins. It has been reported that epoxy resins containing dynamic covalent bonds usually do not have strong thermal and mechanical properties. Therefore, it is necessary to design a high-performance reproducible epoxy resin. In addition, a large amount of organic solvents are required in the current chemical degradation process of epoxy resins, and only part of the degradation products can be reused, which is easy to cause secondary environmental pollution.

Hyperbranched polymers have the characteristics of highly branched structure, molecular shape close to spherical, large number of active end groups available for modification on the outer surface, and unique microporous structure inside. Compared with linear polymers, they show less molecular chain entanglement, less crystallization, low viscosity, good solubility and higher chemical reactivity, and more functional materials can be obtained through end group modification. These excellent properties make hyperbranched polymers show broad application prospects in many aspects such as polymer blending modification, coatings, drug release, self-assembled membranes, etc. Hyperbranched polymer toughening epoxy resin has been a research hotspot in recent years. The unique structure and properties of hyperbranched polymers make it have a modification effect significantly different from that of linear polymers as a toughening agent for epoxy resin. The use of bio-based hyperbranched epoxy resin to dynamically crosslink epoxy resin is expected to solve the problem of difficult recycling of high-performance epoxy resin.

Summary of the invention

A technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a bio-based hyperbranched polymer epoxy resin constructed based on dynamic covalent bonds.

Another technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned bio-based hyperbranched polymer epoxy resin.

In order to solve the above-mentioned first technical problem, the bio-based hyperbranched polymer epoxy resin provided by the present invention is prepared by dynamic crosslinking of ferulic acid hyperbranched epoxy resin and citric acid hyperbranched polyester, wherein the ferulic acid hyperbranched epoxy resin is a compound including but not limited to the following structure:

(1)

in

(2)

in

(3)

The citric acid hyperbranched polyester has the following structure:

in

In order to solve the above second technical problem, the bio-based hyperbranched polymer epoxy resin provided by the present invention is prepared by the following method:

(1) After ferulic acid and epichlorohydrin are uniformly mixed, the mixture is stirred and reacted at 80-120° C. for 1-4 hours, and then a 10 wt % to 40 wt % aqueous sodium hydroxide solution is added and the mixture is reacted at 20-40° C. for 1-6 hours. After the reaction is completed, the mixture is filtered, washed with water, separated, and distilled under reduced pressure to obtain a linear ferulic acid epoxy resin FEP.

(2) FEP, a trivalent hydroxy compound and an ionic liquid are stirred and reacted at 60 to 140° C. for 1 to 12 hours to obtain a ferulic acid hyperbranched epoxy resin FEHBP.

(3) Stirring citric acid and acid anhydride at 100-160° C. for 1-6 hours to obtain citric acid hyperbranched polyester CHBP.

(4) FEP, FEHBP and CHBP are mixed and stirred evenly, poured into a mold, and cured at 80°C-120°C for 4-8h to obtain a fully bio-based epoxy resin.

The all-bio-based epoxy resin is heated and degraded at 60°C to 100°C in a 10% to 40% sodium hydroxide aqueous solution for 30 to 60 minutes, and then the pH value of the degradation solution is adjusted to neutral (pH=7) with 0.5 mol/L to 2 mol/L organic acid, and then the water layer and the organic layer are respectively subjected to reduced pressure distillation to obtain closed-loop recovered ferulic acid (r-FA) and closed-loop recovered citric acid hyperbranched polyester (r-CHBP). The organic acid is one or more of hydrochloric acid, formic acid, phosphoric acid, and oxalic acid. The molar ratio of the all-bio-based epoxy resin, sodium hydroxide, and organic acid is 1:(0.55-0.65):(0.50-0.60).

After r-FA and epichlorohydrin are uniformly mixed, stirred and reacted at 80-120° C. for 1-4 hours, 10wt%-40wt% sodium hydroxide aqueous solution is added at 20-40° C. and the reaction is continued for 1-6 hours. After the reaction is completed, the linear ferulic acid epoxy resin FEP is obtained by filtering, washing, separating, and distilling under reduced pressure. The molar ratio of r-FA, epichlorohydrin and sodium hydroxide is 1.0:(10.0-20.0):(2.0-4.0).

r-FEP, a trivalent hydroxyl compound and an ionic liquid are stirred and reacted at 60-140° C. for 1-6 hours to obtain a ferulic acid hyperbranched epoxy resin FEHBP. The molar ratio of the FEP, the trivalent hydroxyl compound and the ionic liquid is 1:0.33:(0.005-0.01), the trivalent hydroxyl compound is one or more of trimethylolpropane, trihydroxyethyl isocyanurate and glycerol, and the ionic liquid is one or more of tributylmethylammonium bis(trifluoromethanesulfonyl)imide, N-methoxyethyl-N-methyldiethylammonium tetrafluoroborate and tetrabutylammonium hexafluorophosphate.

(6) Mixing r-FEP, r-FEHBP and r-CHBP and then pouring them into a mold, and curing them at 80°C to 120°C for 4 to 8 hours to obtain a closed-loop recycled all-biobased epoxy resin. The molar ratio of r-FEP, r-FEHBP and r-CHBP is 1.0:(1.0 to 1.5):(1.0 to 5.0).

The fully bio-based epoxy resin is crushed and then hot-pressed at 80°C to 160°C and 2 to 10 MPa for 30 to 60 minutes to obtain a reproducible fully bio-based epoxy resin. The ferulic acid hyperbranched polymer containing dynamic covalent bonds prepared by the present invention has the advantages of low viscosity, enhanced toughness and degradation, and the epoxy resin prepared by the ferulic acid hyperbranched polymer can form a dynamic cross-linked network containing a large amount of β-hydroxy esters, and has high strength and high toughness while also obtaining reproducible processing ability and closed-loop recycling and degradation performance.

Preferably, the molar ratio of ferulic acid, epichlorohydrin and sodium hydroxide is 1.0:(10.0-20.0):(2.0-4.0).

Preferably, the molar ratio of the FEP, the trivalent hydroxy compound and the ionic liquid is 1:0.33:(0.005-0.01), and the trivalent hydroxy compound is one or more of trimethylolpropane, tris(hydroxyethyl)isocyanurate and glycerol.

Preferably, the ionic liquid is one or more of tributyl methyl ammonium bis(trifluoromethanesulfonyl)imide, N-methoxyethyl-N-methyldiethylammonium tetrafluoroborate, and tetrabutylammonium hexafluorophosphate.

Preferably, the acid anhydride is one or more of itaconic anhydride and phthalic anhydride, and the molar ratio of citric acid to the acid anhydride is (2.0-80.0):1.0

The molar ratio of the FEP, FEHBP and CHBP is 1:(0.003-0.009):(0.04-0.05).

Compared with the prior art, the technical solution of the present invention has the following advantages and beneficial effects:

1. The ferulic acid hyperbranched epoxy resin and citric acid hyperbranched polyester prepared by the present invention can form a large number of interfacial covalent bonds in the cross-linked network structure when dynamically cross-linking the epoxy resin, thereby giving the epoxy resin a reproducible processing function.

2. The epoxy resin dynamically cross-linked with ferulic acid hyperbranched polymer and citric acid hyperbranched polyester prepared by the present invention can be controllably degraded into ferulic acid and citric acid hyperbranched polyester under the action of sodium hydroxide aqueous solution. The degradation products ferulic acid and citric acid hyperbranched polyester can be used to re-prepare all-biobased epoxy resin, thereby realizing green closed-loop recycling of epoxy resin.

3. The ferulic acid hyperbranched polymer and citric acid hyperbranched polyester prepared by the present invention can significantly improve the mechanical properties, heat resistance, solvent resistance, hydrolysis resistance, creep resistance and corrosion resistance of bio-based epoxy resins, and can replace traditional petroleum-based epoxy resins. The ferulic acid hyperbranched polymer of the present invention has a simple preparation process, low raw material cost, and is suitable for industrial production.

4. The ferulic acid hyperbranched polymer of the present invention has the effect of significantly reducing the viscosity and curing shrinkage of all-biobased epoxy resins, and is expected to be applied to electronic and electrical fields such as electronic packaging, insulating materials and printed circuit boards.

DETAILED DESCRIPTION

The present invention will be described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited to these embodiments, and any equivalent changes or modifications made based on the principle and essence of the technical solution of the present invention should be included in the protection scope of the present invention.

Example 1

194.0g of ferulic acid (FA) and 1295.0g of epichlorohydrin (ECH) were mixed evenly, stirred and reacted at 80°C for 4h, and then 300.0g of 40wt.% sodium hydroxide aqueous solution was added and continued to react at 30°C for 2h. After the reaction, the mixture was filtered, washed with water, and separated. The organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain linear ferulic acid epoxy resin (FEP), with a yield of about 86.6% and an epoxide value of 0.53mol/100g.

300.0 g FEP and 43.7 g trimethylolpropane were stirred and reacted at 110° C. for 6 h to obtain ferulic acid hyperbranched epoxy resin FEHBP. GPC test showed that the number average molecular weight was 4887 g/mol and the epoxy value was 0.29 mol/100 g.

153.6 g of citric acid and 11.2 g of itaconic anhydride were stirred and reacted at 100° C. for 6 h to obtain a citric acid-based hyperbranched epoxy resin CHBP. The GPC test showed that the number average molecular weight was 1504 g/mol and the acid value was 671 mgKOH/g.

300.0 g FEP, 30.0 g FEHBP and 205.3 g CHBP were mixed evenly and poured into a silicone rubber mold, and cured at 100 °C for 4 h to obtain a fully bio-based epoxy resin.

100.0g of all-biobased epoxy resin was heated and degraded at 80°C in 200ml of 30.0wt.% sodium hydroxide aqueous solution for 40min, and the pH value of the degradation solution was adjusted to neutral (pH=7) with about 500ml of 3mol/L hydrochloric acid and then filtered. The obtained solid was dried at 80°C for 12h to obtain closed-loop recovered ferulic acid (r-FA), and the filtrate was distilled under reduced pressure and extracted with ethanol to obtain closed-loop recovered citric acid hyperbranched polyester (r-CHBP).

194.0g r-FA, 1295.0g ECH and 1.94g TBAB were mixed evenly, stirred and reacted at 80°C for 4h, and then 300.0g 40wt.% sodium hydroxide aqueous solution was added and the reaction was continued for 2h. After the reaction was completed, the mixture was filtered and washed with water, and the organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain closed-loop recycled linear ferulic acid epoxy resin (r-FEP), with a yield of 85.9% and an epoxide value of 0.53mol/100g.

300.0 g r-FEP and 43.7 g trimethylolpropane (TMP) were stirred and reacted at 110° C. for 6 h to obtain a closed-loop recycled ferulic acid hyperbranched epoxy resin r-FEHBP. The number average molecular weight thereof was 4858 g/mol and the epoxy value was 0.28 mol/100 g.

300.0 g r-FEP, 30.0 g r-FEHBP and 205.3 g r-CHBP were heated and stirred at 120 °C and mixed evenly, then poured into a mold and cured at 100 °C for 4 h to obtain a closed-loop recycled all-biobased epoxy resin.

The all-biobased epoxy resin was crushed and hot-pressed at 120°C and 5MPa for 30 min to obtain a reprocessed all-biobased epoxy resin.

Example 2

194.0g of ferulic acid (FA) and 1104.0g of epichlorohydrin (ECH) were mixed evenly, stirred and reacted at 100°C for 3h, then cooled to room temperature and 320.0g of 30wt.% sodium hydroxide aqueous solution was added to continue the reaction for 3h. After the reaction was completed, the mixture was filtered and washed with water, and the organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain linear ferulic acid epoxy resin (FEP), with a yield of about 84.6% and an epoxide value of 0.52mol/100g.

300.0 g FEP and 81.2 g trihydroxyethyl isocyanurate were stirred and reacted at 120° C. for 4 h to obtain ferulic acid hyperbranched epoxy resin FEHBP. GPC test showed that the number average molecular weight thereof was 5458 g/mol and the epoxy value was 0.20 mol/100 g.

499.2 g of citric acid and 11.2 g of itaconic anhydride were heated and mixed at 120° C. for 6 hours to obtain a citric acid-based hyperbranched epoxy resin CHBP. The GPC test showed that the number average molecular weight was 4672 g/mol and the acid value was 648 mgKOH/g.

300.0 g FEP, 30.0 g FEHBP and 207.2 g CHBP were mixed evenly and poured into a mold, and cured at 120 °C for 3 h to obtain a fully bio-based epoxy resin.

100.0g of all-biobased epoxy resin was heated and degraded at 80°C in 200ml of 30.0wt.% sodium hydroxide aqueous solution for 40min, and the pH value of the degradation solution was adjusted to neutral (pH=7) with about 500ml of 3mol/L hydrochloric acid and then filtered. The obtained solid was dried at 80°C for 12h to obtain closed-loop recovered ferulic acid (r-FA), and the filtrate was distilled under reduced pressure and extracted with ethanol to obtain closed-loop recovered citric acid hyperbranched polyester (r-CHBP).

197.0g r-FA, 1104.0g ECH and 1.552g TBAB were mixed evenly, stirred at 100°C for 3h, and then 320.0g 30wt.% sodium hydroxide aqueous solution was added to continue the reaction for 3h. After the reaction was completed, the mixture was filtered and washed with water, and the organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain closed-loop recycled linear ferulic acid epoxy resin (r-FEP), with a yield of 84.9% and an epoxy value of 0.51mol/100g.

300.0 g r-FEP and 81.2 g trihydroxyethyl isocyanurate were stirred and reacted at 120° C. for 4 h to obtain closed-loop recycled ferulic acid hyperbranched epoxy resin r-FEHBP. The number average molecular weight thereof was 5387 g/mol and the epoxy value was 0.15 mol/100 g.

300.0 g r-FEP, 30.0 g r-FEHBP and 207.2 g r-CHBP were mixed evenly and poured into a mold, and cured at 120 °C for 3 h to obtain a closed-loop recycled all-biobased epoxy resin.

The all-biobased epoxy resin was crushed and hot-pressed at 140°C and 5 MPa for 20 min to obtain a reprocessed all-biobased epoxy resin.

Example 3

194.0g of ferulic acid (FA) and 1472.0g of epichlorohydrin (ECH) were mixed evenly, stirred and reacted at 80°C for 4h, then cooled to room temperature and 600.0g of 20wt.% sodium hydroxide aqueous solution was added to continue the reaction for 4h. After the reaction was completed, the mixture was filtered and washed with water, and the organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain linear ferulic acid epoxy resin (FEP), with a yield of 82.1% and an epoxide value of 0.54mol/100g.

300.0 g FEP and 30.0 g propylene glycol were stirred and reacted at 120° C. for 4 h to obtain a citric acid-based hyperbranched epoxy resin CHBP. GPC test showed that the number average molecular weight was 5799 g/mol and the epoxy value was 0.19 mol/100 g.

384 g of citric acid and 112 g of itaconic anhydride were heated and mixed at 120° C. for 6 hours to obtain a citric acid-based hyperbranched epoxy resin CHBP. The GPC test showed that the number average molecular weight was 458 g/mol and the acid value was 735 mgKOH/g.

300.0 g FEP, 30.0 g FEHBP and 202.3 g CHBP were mixed evenly and poured into a mold, and cured at 140 °C for 2 h to obtain a fully bio-based epoxy resin.

100.0g of all-biobased epoxy resin was heated and degraded at 90°C in 200ml of 30.0wt.% sodium hydroxide aqueous solution for 20min, and the pH value of the degradation solution was adjusted to neutral (pH=7) with 500ml of 1mol/L phosphoric acid and then filtered. The solid was dried at 80°C for 12h to obtain closed-loop recovered ferulic acid (r-FA), and the filtrate was distilled under reduced pressure and extracted with ethanol to obtain closed-loop recovered citric acid hyperbranched polyester (r-CHBP).

194.0g r-FA, 1472.0g ECH and 2.328g TBAB were mixed evenly, stirred at 80°C for 4h, and then 600.0g 20wt.% sodium hydroxide aqueous solution was added to continue the reaction for 4h. After the reaction was completed, the mixture was filtered and washed with water, and the organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain a closed-loop linear ferulic acid epoxy resin (r-FEP) with a yield of about 82.3% and an epoxy value of 0.53mol/100g.

300.0 g r-FEP and 30.0 g propylene glycol were stirred and reacted at 120° C. for 4 h to obtain a closed-loop recycled ferulic acid hyperbranched epoxy resin r-FEHBP. The number average molecular weight thereof was 5759 g/mol and the epoxy value was 0.19 mol/100 g.

300.0 g r-FEP, 30.0 g r-FEHBP and 202.3 g r-CHBP were heated and stirred at 120 °C and mixed evenly, then poured into a mold and cured at 140 °C for 4 h to obtain a closed-loop recycled all-biobased epoxy resin.

The all-biobased epoxy resin was crushed and then hot-pressed at 100°C and 10 MPa for 30 min to obtain a reproducibly processed all-biobased epoxy resin.

Example 4

194.0g of ferulic acid (FA) and 1295.0g of epichlorohydrin (ECH) were mixed evenly, stirred and reacted at 120°C for 2h, then cooled to room temperature and 300.0g of 40wt.% sodium hydroxide aqueous solution was added to continue the reaction for 2h. After the reaction was completed, the mixture was filtered and washed with water, and the organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain linear ferulic acid epoxy resin (FEP), with a yield of about 81.6% and an epoxide value of 0.51mol/100g.

300g FEP and 81.2g trihydroxyethyl isocyanurate were stirred and reacted at 140°C for 4h to obtain ferulic acid hyperbranched epoxy resin FEHBP. GPC test showed that the number average molecular weight was 6158g/mol and the epoxy value was 0.13mol/100g.

153.6 g of citric acid and 10.0 g of succinic anhydride were heated and mixed at 120° C. for 6 hours to obtain a citric acid-based hyperbranched epoxy resin CHBP. The GPC test showed that the number average molecular weight was 1492 g/mol and the acid value was 677 mgKOH/g.

300.0 g FEP, 30.0 g FEHBP and 197.8 g CHBP were mixed evenly and poured into a mold, and cured at 160 °C for 1 h to obtain a fully bio-based epoxy resin.

100.0g of all-biobased epoxy resin was heated and degraded at 90°C in 200ml of 30.0% sodium hydroxide aqueous solution for 20min, and the pH value of the degradation solution was adjusted to neutral (pH=7) with 500ml of 3mol/L formic acid and then filtered. The solid was dried at 80°C for 12h to obtain closed-loop recovered ferulic acid (r-FA), and the filtrate was distilled under reduced pressure and extracted with ethanol to obtain closed-loop recovered citric acid hyperbranched polyester (r-CHBP).

194.0g r-FA, 1295.0g ECH and 1.97g TEBA were mixed evenly, stirred and reacted at 120°C for 2h, and then 300.0g 40wt.% sodium hydroxide aqueous solution was added to continue the reaction for 2h. After the reaction was completed, the mixture was filtered and washed with water, and the organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain closed-loop recycled linear ferulic acid epoxy resin (r-FEP), with a yield of 80.9% and an epoxide value of 0.51mol/100g.

300.0 g r-FEP and 81.2 g trihydroxyethyl isocyanurate were stirred and reacted at 140° C. for 3 h to obtain a closed-loop recycled ferulic acid hyperbranched epoxy resin r-FEHBP. GPC test showed that its number average molecular weight was 5912 g/mol and its epoxy value was 0.13 mol/100 g.

300.0 g r-FEP, 30.0 g r-FEHBP and 197.8 g r-CHBP were mixed evenly and poured into a mold, and cured at 160 °C for 1 h to obtain a closed-loop recycled all-biobased epoxy resin.

The all-biobased epoxy resin was crushed and hot-pressed at 120°C and 5MPa for 30 min to obtain a reprocessed all-biobased epoxy resin.

Example 5

194.0g of ferulic acid (FA) and 1295.0g of epichlorohydrin (ECH) were mixed evenly, stirred and reacted at 120°C for 2h, then cooled to room temperature and 300.0g of 40wt.% sodium hydroxide aqueous solution was added to continue the reaction for 2h. After the reaction was completed, the mixture was filtered and washed with water, and the organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain linear ferulic acid epoxy resin (FEP), with a yield of about 82.6% and an epoxide value of 0.54mol/100g.

300.0 g r-FEP and 81.2 g trihydroxyethyl isocyanurate were stirred and reacted at 140° C. for 3 h to obtain ferulic acid hyperbranched epoxy resin FEHBP. GPC test showed that the number average molecular weight was 4987 g/mol and the epoxy value was 0.29 mol/100 g.

499.2 g of citric acid and 10.0 g of succinic anhydride were heated and mixed at 120° C. for 6 h to obtain a citric acid-based hyperbranched epoxy resin CHBP. The GPC test showed that the number average molecular weight was 1478 g/mol and the acid value was 648 mgKOH/g.

300.0 g FEP, 30.0 g FEHBP and 172.7 g CHBP were mixed evenly and poured into a mold, and cured at 100 °C for 4 h to obtain a fully bio-based epoxy resin.

100.0g of all-biobased epoxy resin was heated and degraded at 80°C in 200ml of 30.0% sodium hydroxide aqueous solution for 60min, and then the pH value of the degradation solution was adjusted to neutral (pH=7) with 500g of 3mol/L hydrochloric acid and filtered. The solid was dried at 80°C for 12h to obtain closed-loop recovered ferulic acid (r-FA), and the filtrate was distilled under reduced pressure and extracted with ethanol to obtain closed-loop recovered citric acid hyperbranched polyester (r-CHBP).

197.0g r-FA, 1295.0g ECH, 1.97g dodecyltrimethylammonium chloride were mixed evenly, stirred at 120°C for 2h, and then 300.0g 40wt.% sodium hydroxide aqueous solution was added to continue the reaction for 2h. After the reaction was completed, the mixture was filtered and washed with water, and the organic layer was dried with anhydrous sodium sulfate and then distilled under reduced pressure to remove epichlorohydrin to obtain closed-loop recycled linear ferulic acid epoxy resin (r-FEP), with a yield of 82.9% and an epoxide value of 0.54mol/100g.

306.0 g r-FEP and 36.9 g trihydroxyethyl isocyanurate were stirred and reacted at 140° C. for 3 h to obtain closed-loop recycled ferulic acid hyperbranched epoxy resin r-FEHBP. The number average molecular weight thereof was 4967 g/mol and the epoxy value was 0.15 mol/100 g.

300.0 g r-FEP, 30.0 g r-FEHBP and 172.7 g r-CHBP were mixed evenly and poured into a mold, and cured at 100 °C for 4 h to obtain a closed-loop recycled all-biobased epoxy resin.

The all-biobased epoxy resin was crushed and hot-pressed at 120°C and 5MPa for 30 min to obtain all-biobased epoxy resins with different repeated processing times.

Example 6

300.0 g of bisphenol A epoxy resin, 117.5 g of citric acid and 4.17 g of 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed evenly and poured into a mold, and cured at 100° C. for 4 h.

The degradation rate of the epoxy resin obtained by the above curing was 12.6% when heated at 80° C. for 60 min in 200 ml of 30.0% sodium hydroxide aqueous solution.

The epoxy resin obtained by the above curing was crushed and then hot-pressed at 120° C. and 5 MPa for 30 min to obtain epoxy resins with different repeated processing times.

After the epoxy resin obtained in Examples 1 to 6 of this specific implementation method is cured and placed at 25°C for 24 hours, the tensile properties are measured according to ASTM 3039, the unnotched impact strength is measured according to ASTM D256, the fracture toughness of the material is measured according to ASTM D5045, the glass transition temperature is measured according to ASTM_D2863, and the relaxation time is tested using the tensile mode of DMA Q800. The sample maintains a tensile deformation of 1.5% at 140°C, and the time when the stress relaxes to 1/e is recorded as the relaxation time of the sample at 140°C.

The performance indicators of the epoxy resins obtained in each embodiment are shown in Table 1, Table 2 and Table 3.

Table 1 Properties of all bio-based epoxy resins obtained in Examples 1 to 6

performance Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Tensile strength, MPa 128 138 75 127 129 41 Impact strength, kJ/ ^m2 24.5 32.4 12.7 27.9 46.8 7.3 Glass transition temperature, °C 94 113 81 105 124 48 Creep resistance temperature 103 124 83 117 136 47 Relaxation time at 140℃, s 47 45 101 31 19 2623

Table 2 Performance of closed-loop recycled all-biobased epoxy resins obtained in Examples 1 to 5

Table 3 Properties of epoxy resins obtained by repeated processing in Examples 1 to 6

It can be seen from Tables 1, 2 and 3 above that the all-biobased epoxy resin obtained in the present invention has excellent mechanical properties, glass transition temperature and creep resistance temperature, and is expected to replace traditional petroleum-based epoxy resins in the fields of adhesives, carbon fiber composites and high-temperature resistant wind power insulation materials.

Claims (10)

1. A bio-based hyperbranched polymer epoxy resin is characterized in that: the bio-based hyperbranched polymer epoxy resin is prepared from ferulic acid hyperbranched epoxy resin and citric acid hyperbranched polyester through dynamic crosslinking, and the ferulic acid hyperbranched epoxy resin comprises the following structures:

wherein R is ₁ ＝-CH ₂ -CH ₃ ，

The citric acid hyperbranched polyester has the following structure:

wherein the method comprises the steps of

2. The preparation method of the bio-based hyperbranched polymer epoxy resin is characterized by comprising the following steps:

(1) Uniformly mixing ferulic acid and epichlorohydrin, stirring at 80-120 ℃ for reaction for 1-4 hours, adding 10-40 wt% sodium hydroxide aqueous solution at 20-40 ℃ for continuous reaction for 1-6 hours, washing with water, separating liquid, and distilling under reduced pressure after the reaction is finished to obtain linear ferulic acid epoxy resin FEP;

(2) Stirring FEP, a trihydroxy compound and ionic liquid at 60-140 ℃ for reaction for 1-12 h to obtain ferulic acid hyperbranched epoxy resin FEHBP;

(3) Stirring citric acid and anhydride at 100-160 ℃ for reaction for 1-6h to obtain citric acid hyperbranched polyester CHBP;

(4) FEP, FEHBP and CHBP are mixed and stirred uniformly and poured into a mold, and cured for 4-8 hours at the temperature of 80-120 ℃ to obtain the full bio-based epoxy resin.

3. The preparation method of the bio-based hyperbranched polymer epoxy resin according to claim 2, wherein the molar ratio of the ferulic acid to the epichlorohydrin to the sodium hydroxide is 1.0 (10.0-20.0): 2.0-4.0.

4. The preparation method of the bio-based hyperbranched polymer epoxy resin according to claim 2 or 3, wherein the molar ratio of the FEP to the ternary hydroxyl compound to the ionic liquid is 1:0.33 (0.005-0.01), and the ternary hydroxyl compound is one or more than two of trimethylolpropane, tris (hydroxyethyl) isocyanurate and glycerol.

5. The method for preparing bio-based hyperbranched polymer epoxy resin according to claim 2 or 3, wherein the ionic liquid is one or more of tributyl methyl ammonium bis (trifluoromethanesulfonyl) imide salt, N-methoxyethyl-N-methyldiethyl ammonium tetrafluoroborate and tetrabutyl ammonium hexafluorophosphate.

6. The method for preparing bio-based hyperbranched polymer epoxy resin according to claim 2 or 3, wherein the acid anhydride is one or more than two of itaconic anhydride and phthalic anhydride, and the molar ratio of the citric acid to the acid anhydride is (2.0-80.0): 1.0.

7. The method for preparing bio-based hyperbranched polymer epoxy resin according to claim 2 or 3, wherein the molar ratio of FEP, FEHBP and CHBP is 1 (0.003-0.009) (0.04-0.05).

8. A method for preparing bio-based hyperbranched polymer epoxy resin again using degradation products of the bio-based hyperbranched polymer epoxy resin prepared by the method according to any one of claims 2 to 7, characterized in that the ferulic acid hyperbranched epoxy resin and the citric acid hyperbranched polyester of the method are obtained by degrading the all-bio-based epoxy resin, the degradation method comprising the steps of:

(1) Heating and degrading in 10-40% sodium hydroxide aqua at 60-100 deg.c for 30-60 min;

(2) Then adjusting the pH value of the degradation liquid to be neutral by using 0.5 mol/L-2 mol/L of organic acid;

(3) And then respectively carrying out reduced pressure distillation on the water layer and the organic layer to obtain the ferulic acid and citric acid hyperbranched polyester.

9. The preparation method of claim 8, wherein the organic acid is one or more of hydrochloric acid, formic acid, phosphoric acid and oxalic acid.

10. The preparation method according to claim 8 or 9, wherein the molar ratio of the all bio-based epoxy resin, sodium hydroxide and organic acid is 1 (0.55-0.65): 0.50-0.60.