A bio-based epoxy resin and its preparation method and application

Abstract

A bio-based epoxy resin, a preparation method and an application thereof. The present invention belongs to the field of epoxy resins and their preparation. The purpose of the present invention is to provide a bio-based epoxy resin to replace traditional epoxy resins. The method of the present invention is as follows: under the protection of inert gas, a reaction solvent is added to chitosan for swelling, and then diisocyanate and epoxy resin are added for cross-linking reaction. After the reaction is completed, the solvent is removed and vacuum drying is performed to obtain a bio-based epoxy resin. The present invention uses diisocyanate to completely convert the hydroxyl and amino groups on chitosan into a single structure of carbamate and urea. The resin cured sample obtained by DDM curing shows good tensile strength and elongation at break, indicating that the introduction of chitosan greatly improves the mechanical properties of the epoxy resin, and both the strength and elongation at break are improved.

Description

Technical Field

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

[0002] Epoxy resin, one of the most representative thermosetting resins, is widely used in numerous fields due to its excellent properties after curing. However, over 90% of commercial epoxy resins are currently bisphenol A-based, mostly synthesized from petroleum-based compounds and lacking in renewable resources. In recent years, with the increasing demand for natural products in industrial applications, the preparation of bio-based polymers from renewable resources to replace petroleum-based polymers has become a research focus. Bio-based epoxy resins are attracting considerable attention as a replacement for traditional epoxy resins.

[0003] Chitosan, a deacetylated form of chitin, is non-toxic, environmentally friendly, and biocompatible. It also exhibits excellent biodegradability, film-forming properties, and antibacterial and anti-inflammatory properties. It is widely used in a variety of fields, including medicine, food, agriculture, daily chemicals, and environmental protection. However, chitosan's rigid structure and strong intermolecular hydrogen bonding make it insoluble in common organic solvents and water, limiting its application to a certain extent. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a bio-based epoxy resin and a preparation method and application thereof.

[0005] The purpose of the present invention is to achieve through the following technical solutions:

[0006] One of the purposes of the present invention is to provide a bio-based epoxy resin having the general structural formula:

[0007]

[0008] In the formula, R1 is an epoxy resin group, and R is a benzyl group, an isophorone group, a diphenylmethyl group, a dicyclohexylmethyl group or a hexamethylene group.

[0009] A second object of the present invention is to provide a method for preparing a bio-based epoxy resin, which is carried out according to the following steps:

[0010] Under the protection of inert gas, a reaction solvent is added to chitosan for swelling, and then diisocyanate and epoxy resin are added for cross-linking reaction. After the reaction is completed, the solvent is removed and vacuum drying is performed to obtain a bio-based epoxy resin.

[0011] It is further defined that the chitosan is vacuum dried at 60-100° C. for 1-20 h before swelling.

[0012] Furthermore, the chitosan is dried under vacuum at 80° C. for 4-6 h before swelling.

[0013] It is further defined that chitosan is chitosan with a degree of deacetylation greater than 80%.

[0014] It is further defined that the molecular weight of chitosan is 5,000-20,000.

[0015] It is further defined that the reaction solvent is toluene.

[0016] It is further defined that the chitosan concentration in the reaction solvent is 0.025-0.037 g / mL.

[0017] It is further defined that the swelling time is 10-60 hours.

[0018] It is further defined that the swelling time is 20-24 hours.

[0019] It is further defined that the diisocyanate is toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI) or hexamethylene diisocyanate (HDI).

[0020] To further define, toluene diisocyanate (TDI) is specifically one of the following structures:

[0021]

[0022] It is further defined that the molar amount of the diisocyanate is 0.25-1 times the total molar amount of the hydroxyl groups and amino groups in the chitosan.

[0023] It is further defined that the molar amount of the diisocyanate is 0.5-1 times the total molar amount of the hydroxyl groups and amino groups in the chitosan.

[0024] It is further defined that the cross-linking reaction temperature is 40-110° C. and the time is 0.5-24 h.

[0025] It is further defined that the cross-linking reaction temperature is 80-100° C. and the time is 0.5-20 h.

[0026] It is further defined that after the reaction is completed, the vacuum drying temperature is 35-100° C. and the time is 24-60 hours.

[0027] It is further defined that after the reaction is completed, the vacuum drying temperature is 40-80°C and the time is 24-48 hours.

[0028] A third object of the present invention is to provide an application of the above-mentioned bio-based epoxy resin as an anti-corrosion coating.

[0029] A fourth object of the present invention is to provide an application of the above-mentioned bio-based epoxy resin as a substrate in the preparation of engineering plastics.

[0030] Compared with the prior art, the present invention has the following significant effects:

[0031] The present invention cross-links chitosan and epoxy resin by reacting diisocyanate with hydroxyl and amino groups on chitosan and hydroxyl groups on epoxy resin to obtain chitosan-based epoxy resin. The specific advantages are as follows:

[0032] (1) The present invention uses diisocyanate to completely convert the hydroxyl and amino groups on chitosan into a single structure of carbamate and urea. The resin cured with 4,4-diaminodiphenylmethane (DDM) exhibits good tensile strength and elongation at break, indicating that the introduction of chitosan greatly improves the mechanical properties of epoxy resin, with both strength and elongation at break being increased.

[0033] (2) The present invention provides a new approach for synthesizing chitosan-based epoxy resins from biomass resources, further broadens the application of chitosan in the field of epoxy resins, and has a good industrial prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the infrared spectrum of the bio-based epoxy resin prepared in Example 1;

[0035] Figure 2 This is the infrared spectrum of the bio-based epoxy resin prepared in Example 2;

[0036] Figure 3 This is the infrared spectrum of the bio-based epoxy resin prepared in Example 3;

[0037] Figure 4 This is a comparison chart of the tensile properties of the bio-based epoxy resin cured sample prepared in Example 1 and the pure epoxy resin cured sample. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0040] As used in the following examples, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0041] When amount, concentration or other value or parameter are represented with the range of scope, preferred range or a series of upper preferred value and lower preferred value limit, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, and no matter whether this scope is disclosed separately.For example, when disclosing scope "1 to 5", described scope should be interpreted as including scope "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc.When numerical range is described in this article, unless otherwise stated, otherwise this scope is intended to include its end value and all integers and fractions within the scope.In this application specification and claims, range limitation can be combined and / or interchanged, and if these ranges are not otherwise stated, include all subranges contained therein.

[0042] The indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirement (i.e. the number of times they appear). Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the quantity clearly refers to only the singular form.

[0043] The term "one embodiment" or "embodiment" of the present invention refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it necessarily refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0044] The epoxy resin structure used in the following examples is as follows:

[0045]

[0046] Example 1:

[0047] The method for preparing the bio-based epoxy resin of this embodiment is characterized by being carried out according to the following steps:

[0048] First, chitosan (molecular weight 14000) was vacuum dried at 80 °C for 4 h;

[0049] Then, under nitrogen protection, 1.5 g of vacuum-dried deacetylated chitosan was taken, 40 mL of toluene was added thereto, and the mixture was swelled for 24 h;

[0050] Subsequently, under nitrogen protection, 6.8 g of 4,4-methylenediphenylisocyanate (the molar amount was 1.0 times the total molar amount of hydroxyl and amino groups) and 66 g of epoxy resin were added to the swollen chitosan, and the cross-linking reaction was carried out at 80°C for 24 h;

[0051] Finally, after the reaction was completed, the reaction system was poured into an eggplant-shaped flask, the toluene was removed by rotary evaporation on a rotary evaporator, and the product was vacuum-dried at 60°C for 24 hours to obtain a bio-based epoxy resin with a yield of 85.45%.

[0052] The bio-based epoxy resin obtained in Example 1 was subjected to infrared spectroscopy analysis, and the results were as follows: Figure 1 As shown, it can be seen that 3400cm -1 (Stretching vibration peak of NH in carbamate and urea); 1753 cm -1 : (stretching vibration peak of C=O in carbamate and urea); 1582 cm -1 (NH bending vibration characteristic peak of carbamate and urea); 1249 cm -1 (CO stretching vibration peak of carbamate); 918 cm -1 The results show that the hydroxyl and amino groups on chitosan are completely converted into chitosan-based epoxy resin with carbamate and urea groups.

[0053] Example 2:

[0054] The method for preparing the bio-based epoxy resin of this embodiment is characterized by being carried out according to the following steps:

[0055] First, chitosan (molecular weight 14000) was vacuum dried at 80 °C for 4 h;

[0056] Then, under nitrogen protection, 1.5 g of vacuum-dried deacetylated chitosan was taken, 40 mL of toluene was added thereto, and the mixture was swelled for 24 h;

[0057] Subsequently, under nitrogen protection, 3.9 mL of 2,5-toluene diisocyanate (the molar amount was 1.0 times the total molar amount of hydroxyl and amino groups) and 66 g of epoxy resin were added to the swollen chitosan, and the cross-linking reaction was carried out at 80 °C for 24 h;

[0058] Finally, after the reaction was completed, the reaction system was poured into an eggplant-shaped flask, the toluene was removed by rotary evaporation on a rotary evaporator, and the product was vacuum-dried at 60°C for 24 hours to obtain a bio-based epoxy resin with a yield of 90.23%.

[0059] The bio-based epoxy resin obtained in Example 2 was subjected to infrared spectroscopy analysis, and the results were as follows: Figure 2 As shown, it can be seen that 3300cm-1 (Stretching vibration peak of NH in carbamate and urea); 1735 cm -1 : (stretching vibration peak of C=O in carbamate and urea); 1584 cm -1 (NH bending vibration characteristic peak of carbamate and urea); 1249 cm -1 (CO stretching vibration peak of carbamate); 917 cm -1 The results show that the hydroxyl and amino groups on chitosan are completely converted into chitosan-based epoxy resin with carbamate and urea groups.

[0060] Example 3:

[0061] The method for preparing the bio-based epoxy resin of this embodiment is characterized by being carried out according to the following steps:

[0062] First, chitosan (molecular weight 14000) was vacuum dried at 80 °C for 4 h;

[0063] Then, under nitrogen protection, 1.5 g of vacuum-dried deacetylated chitosan was taken, 40 mL of toluene was added thereto, and the mixture was swelled for 24 h;

[0064] Subsequently, under nitrogen protection, 4.69 g of hexamethylene diisocyanate (the molar amount was 1.0 times the total molar amount of hydroxyl and amino groups) and 66 g of epoxy resin were added to the swollen chitosan, and the cross-linking reaction was carried out at 80 °C for 24 h;

[0065] Finally, after the reaction was completed, the reaction system was poured into an eggplant-shaped flask, the toluene was removed by rotary evaporation on a rotary evaporator, and the product was vacuum-dried at 60°C for 24 hours to obtain a bio-based epoxy resin with a yield of 90.23%.

[0066] The bio-based epoxy resin obtained in Example 3 was subjected to infrared spectroscopy analysis, and the results were as follows: Figure 3 As shown, it can be seen that 3300cm -1 (Stretching vibration peak of NH in carbamate and urea); 1721 cm -1 : (stretching vibration peak of C=O in carbamate and urea); 1579cm -1 (NH bending vibration characteristic peak of carbamate and urea); 1249 cm -1 (CO stretching vibration peak of carbamate); 916 cm -1 The results show that the hydroxyl and amino groups on chitosan are completely converted into chitosan-based epoxy resin with carbamate and urea groups.

[0067] Application examples:

[0068] The bio-based epoxy resin (named CE resin) prepared in Example 1 was cured with 4,4-diaminodiphenylmethane (DDM) to obtain a cured resin sample. At the same time, the unmodified epoxy resin was used as a control group and a tensile test was performed according to the national standard GB / T 2567-2008. The results are as follows: Figure 4 As shown in the figure, the synthetic resin has good tensile strength and elongation at break, which are higher than those of pure epoxy resin cured sample.

[0069] The foregoing are merely preferred embodiments of the present invention. These embodiments are all different implementations based on the overall concept of the present invention. The scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a bio-based epoxy resin, characterized in that: Follow these steps: Under inert gas protection, a reaction solvent is added to chitosan for swelling, and then diisocyanate and epoxy resin are added for cross-linking reaction. After the reaction is completed, the solvent is removed and vacuum drying is performed to obtain a bio-based epoxy resin. The bio-based epoxy resin is characterized in that its general structural formula is: ； In the formula, R1 is an epoxy resin group, R is benzyl, isophorone, diphenylmethylene, dicyclohexylmethylene or hexamethylene, the reaction solvent is toluene, the chitosan concentration in the reaction solvent is 0.025-0.037 g / mL, the swelling time is 10-60 h, and the molar amount of diisocyanate is 0.25-1 times the total molar amount of hydroxyl and amino groups in chitosan.

2. The method according to claim 1, characterized in that The chitosan is vacuum dried at 60-100° C. for 1-20 h before swelling. The chitosan has a deacetylation degree greater than 80% and a molecular weight of 5000-20000.

3. The method according to claim 1, characterized in that The diisocyanate is TDI, IPDI, MDI, HMDI or HDI.

4. The method according to claim 3, characterized in that TDI is specifically one of the following structures: 。 5. The method according to claim 1, wherein The cross-linking reaction temperature is 40-110° C. and the time is 0.5-24 h. After the reaction is completed, the vacuum drying temperature is 35-100° C. and the time is 24-60 h.

6. Use of the bio-based epoxy resin prepared by the method according to claim 1 as an anti-corrosion coating.

7. Use of the bio-based epoxy resin prepared by the method according to claim 1 as a base material in the preparation of engineering plastics.

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