Lipoic acid modified epoxy resin capable of being upgraded and recycled and preparation method thereof

Abstract

The invention provides lipoic acid modified epoxy resin capable of being upgraded and recycled, which comprises the following raw materials in parts by weight: 50-100 parts of epoxy resin; 10-100 parts by weight of a curing agent; 0-20 parts by weight of a functional filler; the curing agent is selected from lipoic acid and / or lipoic acid derivatives. Compared with the prior art, a dynamic disulfide bond network, a functional group and non-covalent bond interaction sites (hydrogen bonds, lithium bonds, coordination bonds and the like) can be introduced into the epoxy resin by taking the lipoic acid and the derivative thereof as the curing agent, so that modification including but not limited to curing, toughening, modification binding site introduction and function endowing is realized; moreover, the mutual compounding of the lipoic acid and the derivative thereof can perform multifunctional integration on the epoxy resin on the basis of ensuring the mechanical property, so that the epoxy resin shows special technical effects in the aspects of dielectrics, heat conduction, wave absorption, flexible electricity and the like; furthermore, the epoxy resin is endowed with remodeling and repairing functions by the thioctic acid and derivative curing agent thereof.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy resins, and in particular relates to an upgraded and recyclable lipoic acid-modified epoxy resin and a preparation method thereof. Background Art

[0002] Epoxy resin is one of the most widely used and largest volume thermosetting resins, with the characteristics of strong adhesion, small shrinkage, corrosion resistance, good durability, excellent electrical insulation performance, and easy modification. With the further development of science and technology, the application field of epoxy resin is also constantly expanding and extending, which constantly puts forward new requirements for the functionalization and high performance of epoxy resin.

[0003] At present, the modification and improvement of epoxy resin mainly revolves around toughening, functionalization, recyclability and green environmental protection. The main goals of functionalization are high temperature resistance, metal corrosion resistance, flame retardancy, wear resistance, insulation, thermal conductivity, electromagnetic shielding, etc., so as to meet the special needs of aviation, aerospace, automobiles, machinery, construction, electronics, electrical appliances, transportation and other fields. However, the large-scale use of epoxy resin has also led to certain green economic problems, such as the toxicity of curing agents and the recycling of waste materials. Therefore, it is also a general trend to develop environmentally friendly curing agents, realize the recycling, upgrading, recycling and regeneration of epoxy resins, and extend their carbon cycle life cycle. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide an upgraded and recyclable lipoic acid-modified epoxy resin and a preparation method thereof, wherein the lipoic acid-modified epoxy resin can achieve toughening, functional integration, green environmental protection and upgraded recycling.

[0005] The present invention provides an upgraded and recyclable lipoic acid modified epoxy resin, which comprises, based on raw materials:

[0006] Epoxy resin 50-100 parts by weight;

[0007] 10 to 100 parts by weight of curing agent;

[0008] Functional filler 0-20 parts by weight;

[0009] The curing agent is selected from lipoic acid and / or lipoic acid derivatives;

[0010] The lipoic acid derivative is shown in formula (I):

[0011]

[0012] The R 1 Selected from substituted or unsubstituted amino, substituted hydroxyl;

[0013] The substituent in the substituted amino group is selected from an amino group, a substituted or unsubstituted C1-C10 alkyl group, a succinimide-substituted ester group, a fatty acid group containing an amide bond, a C1-C10 heteroalkyl group, a substituted or unsubstituted C5-C10 cycloalkyl group, and a substituted or unsubstituted C6-C20 aryl group;

[0014] The substituent in the substituted hydroxyl group is selected from succinimide group, alkali metal ion, substituted or unsubstituted C1-C10 alkyl group, C1-C10 heteroalkyl group, substituted or unsubstituted C5-C10 cycloalkyl group, substituted or unsubstituted C6-C20 aryl group;

[0015] The substituents in the substituted C1-C10 alkyl, substituted C5-C10 epoxy and substituted C6-C20 aryl are each independently selected from one or more of C1-C10 alkyl, hydroxyl, C1-C10 alkoxy and alkoxyazophenyl;

[0016] The R 2 A group selected from substituted or unsubstituted C1-C10 alkylene groups, polycalcium carbonate groups or groups represented by formula (III);

[0017]

[0018] The R 3 is selected from furanyl, fused furanyl or alkoxybenzoic acid benzyl ester;

[0019] The substituent in the substituted C1-C10 alkylene group is selected from lipoic acid ester group.

[0020] Preferably, the epoxy resin is selected from one or more of epoxidized olefin compounds, heterocyclic epoxy resins, mixed epoxy resins, polyphenol glycidyl ether epoxy resins, aliphatic glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins and furan-containing epoxy resin monomers.

[0021] Preferably, the furan-containing epoxy resin monomer is selected from one or more of the following formulas (1) to (11):

[0022]

[0023]

[0024] Preferably, the lipoic acid derivative is selected from one or more of the following formulae:

[0025]

[0026] Here, x is an integer greater than or equal to 0.

[0027] Preferably, the functional filler is selected from one or more of metal fillers, metal oxides, metal salts, carbon-based fillers and ceramic fillers.

[0028] Preferably, the metal filler is selected from one or more of silver, copper and aluminum;

[0029] The metal oxide is selected from one or more of aluminum oxide, iron oxide and copper oxide;

[0030] The metal salt is selected from one or more of ferric chloride, calcium chloride, zinc chloride, zinc acetate and zinc sulfate;

[0031] The carbon-based filler is selected from one or more of carbon nanotubes, carbon fibers and graphene;

[0032] The ceramic filler is selected from one or more of aluminum oxide, aluminum nitride and boron nitride.

[0033] Preferably, based on raw materials, it includes:

[0034] Epoxy resin 50-100 parts by weight;

[0035] 20 to 100 parts by weight of curing agent;

[0036] Functional filler 0-20 parts by weight.

[0037] The present invention also provides a method for preparing the above-mentioned lipoic acid-modified epoxy resin that can be upgraded and recycled, comprising the following steps:

[0038] S1) mixing epoxy resin, curing agent and functional filler to obtain a prepolymer;

[0039] S2) heating and curing the prepolymer to obtain a zinc sulfate modified epoxy resin.

[0040] Preferably, the step S1) specifically comprises: mixing the epoxy resin, the curing agent and the functional filler in an organic solvent, removing the solvent, and drying to obtain a prepolymer;

[0041] Alternatively, the curing agent is heated and melted, and then epoxy resin and functional filler are added and mixed to obtain a prepolymer;

[0042] Alternatively, the epoxy resin and the curing agent are mixed under heating conditions, and then a functional filler is added to obtain a prepolymer;

[0043] The heating and curing in step S2) is specifically step-by-step heating and curing; the step-by-step heating and curing includes a first stage heating and curing and a second stage heating and curing; the temperature of the first stage heating and curing is 70°C to 120°C; the time of the first stage heating and curing is 1 to 2 hours; the temperature of the second stage heating and curing is 130°C to 150°C; the time of the second stage heating and curing is 2 to 4 hours;

[0044] Alternatively, the heating curing is specifically step-by-step heating curing; the step-by-step heating curing includes a first stage heating curing, a second stage heating curing and a third stage heating curing; the temperature of the first stage heating curing is 70°C to 120°C; the time of the first stage heating curing is 1 to 2 hours; the temperature of the second stage heating curing is 130°C to 150°C; the time of the second stage heating curing is 2 to 8 hours; the temperature of the third stage heating curing is 150°C to 170°C; the time of the third stage heating curing is 1 to 3 hours;

[0045] Alternatively, the heating and curing is carried out under pressurized conditions; the temperature of the heating and curing is 120° C. to 180° C.; and the pressurized conditions are 15 to 25 tons of pressure.

[0046] The present invention also provides a method for recovering the lipoic acid modified epoxy resin, comprising the following steps:

[0047] A1) soaking the lipoic acid-modified epoxy resin in polyethylene glycol under heating to obtain a degradation solution;

[0048] A2) mixing the degradation liquid, water, polyamine, silicone oil, catalyst and isocyanate component to obtain polyurethane foam;

[0049] or,

[0050] B1) soaking the lipoic acid modified epoxy resin in an alkaline solution to obtain a degradation solution;

[0051] B2) subjecting the degradation solution to reduction and acidification treatment to obtain polymer fragments containing thiol units.

[0052] The present invention provides an upgraded and recyclable lipoic acid modified epoxy resin, which includes, in terms of raw materials, 50 to 100 parts by weight of epoxy resin; 10 to 100 parts by weight of curing agent; 0 to 20 parts by weight of functional filler; the curing agent is selected from lipoic acid and / or lipoic acid derivatives. Compared with the prior art, the present invention uses lipoic acid and its derivatives as curing agents to introduce dynamic disulfide bond networks, functional groups, and non-covalent bond interaction sites (hydrogen bonds, lithium bonds, coordination bonds, etc.) into epoxy resins, thereby achieving modifications including but not limited to curing, toughening, introduction of modified binding sites, and function-endowed modifications; and the mutual compounding of lipoic acid and its derivatives can perform multifunctional integration of epoxy resins on the basis of ensuring mechanical properties, so that it exhibits special technical effects in terms of dielectric, thermal conductivity, wave absorption, and flexible electricity; furthermore, lipoic acid and its derivative curing agents endow epoxy resins with remodeling and repair functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a tensile curve diagram of the epoxy resin material obtained in Example 1 of the present invention;

[0054] Figure 2 This is a graph showing the thermal remodeling (recycling) capability of the epoxy resin material obtained in Example 1 of the present invention;

[0055] Figure 3 This is a graph showing the self-healing ability of the epoxy resin material obtained in Example 1 of the present invention;

[0056] Figure 4 This is a tensile curve diagram of the epoxy resin obtained in Example 2 of the present invention;

[0057] Figure 5 This is a photoresponse behavior diagram of the epoxy resin obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0058] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0059] The present invention provides an upgraded and recyclable lipoic acid modified epoxy resin, which comprises, based on raw materials, 50 to 100 parts by weight of epoxy resin; 10 to 100 parts by weight of curing agent; 0 to 20 parts by weight of functional filler; the curing agent is selected from lipoic acid and / or lipoic acid derivatives;

[0060] The lipoic acid derivative is shown in formula (I):

[0061]

[0062] The R 1 is a substituted or unsubstituted amino group or a substituted hydroxy group;

[0063] The substituent in the substituted amino group is an amino group, a substituted or unsubstituted C1-C10 alkyl group, a succinimide-substituted ester group, a fatty acid group containing an amide bond, a C1-C10 heteroalkyl group, a substituted or unsubstituted C5-C10 cycloalkyl group, or a substituted or unsubstituted C6-C20 aryl group.

[0064] The substituent in the substituted hydroxyl group is a succinimide group, an alkali metal ion, a substituted or unsubstituted C1-C10 alkyl group, a C1-C10 heteroalkyl group, a substituted or unsubstituted C5-C10 cycloalkyl group, or a substituted or unsubstituted C6-C20 aryl group.

[0065] The substituents in the substituted C1-C10 alkyl, substituted C5-C10 epoxy and substituted C6-C20 aryl are each independently preferably one or more of C1-C10 alkyl, hydroxy, C1-C10 alkoxy and alkoxyazophenyl, and more preferably one or more of C1-C5 alkyl, hydroxy, C1-C5 alkoxy and alkoxyazophenyl.

[0066] The R 2 is a substituted or unsubstituted C1-C10 alkylene group, a polycalcium carbonate group or a group represented by formula (III);

[0067]

[0068] The R 3 is a furanyl group, a condensed furanyl group or an alkoxybenzoic acid benzoyl ester group; and the substituent in the substituted C1-C10 alkylene group is a lipoic acid ester group.

[0069] According to the present invention, optionally, the content of the epoxy resin in the lipoic acid-modified epoxy resin is 50 parts by weight, 60 parts by weight, 70 parts by weight, 80 parts by weight, 90 parts by weight, 100 parts by weight or a range between any two of the above values.

[0070] In a specific embodiment provided by the present invention, the epoxy resin is preferably one or more of epoxidized olefin compounds, heterocyclic epoxy resins, mixed epoxy resins, polyphenol glycidyl ether epoxy resins, aliphatic glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins and furan-containing epoxy resin monomers.

[0071] In a specific embodiment provided by the present invention, the glycidyl ester epoxy resin is preferably diglycidyl terephthalate.

[0072] In a specific embodiment provided by the present invention, the double A-type epoxy resin is preferably E20 epoxy resin.

[0073] In a specific embodiment provided by the present invention, the glycidylamine-type epoxy resin is preferably triglycidyl p-aminophenol.

[0074] In a specific embodiment provided by the present invention, the furan-containing epoxy resin monomer is preferably one or more of the following:

[0075]

[0076] According to the present invention, optionally, the content of the curing agent in the thioctic acid modified epoxy resin is 1 weight part, 4 weight parts, 5 weight parts, 10 weight parts, 20 weight parts, 30 weight parts, 40 weight parts, 50 weight parts, 60 weight parts, 70 weight parts, 80 weight parts, 90 weight parts, 100 weight parts or a range between any two of the above values.

[0077] According to the present invention, the curing agent is lipoic acid and / or lipoic acid derivatives.

[0078] Wherein, the structure of described lipoic acid is as follows:

[0079]

[0080] In a specific embodiment provided by the present invention, the lipoic acid derivative is selected from one or more of the following formulae:

[0081]

[0082] Here, x is an integer greater than or equal to 0.

[0083] In a specific embodiment provided by the present invention, x is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0084] In a specific embodiment provided by the present invention, the curing agent is thioctic acid and thioctic acid derivatives; the mass ratio of thioctic acid to thioctic acid derivatives is preferably 1:(0.5-2); optionally, the mass ratio of thioctic acid to thioctic acid derivatives is 1:0.5, 1:1, 1:1.5, 1:2 or a range between any two of the above ratios.

[0085] According to the present invention, optionally, the content of the functional filler in the lipoic acid-modified epoxy resin is 0 parts by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight or a range between any two of the above values.

[0086] In a specific embodiment provided by the present invention, the functional filler is preferably one or more of a metal filler, a metal oxide, a metal salt, a carbon-based filler and a ceramic filler.

[0087] In a specific embodiment provided by the present invention, the metal filler is preferably one or more of silver, copper and aluminum.

[0088] In a specific embodiment provided by the present invention, the metal oxide is preferably one or more of aluminum oxide, iron oxide and copper oxide.

[0089] In a specific embodiment provided by the present invention, the metal salt is preferably one or more of ferric chloride, calcium chloride, zinc chloride, zinc acetate and zinc sulfate.

[0090] In a specific embodiment provided by the present invention, the carbon-based filler is preferably one or more of carbon nanotubes, carbon fibers and graphene.

[0091] In a specific embodiment provided by the present invention, the ceramic filler is preferably one or more of aluminum oxide, aluminum nitride and boron nitride.

[0092] According to the present invention, the particle size of the functional filler is preferably 2 to 100 nm; optionally, the particle size of the functional filler is 2 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or a range between any two of the above values.

[0093] In a specific embodiment provided by the present invention, the lipoic acid modified epoxy resin, calculated on the basis of raw materials, comprises:

[0094] Epoxy resin 50-100 parts by weight;

[0095] 20 to 100 parts by weight of curing agent;

[0096] Functional filler 0-20 parts by weight.

[0097] In a specific embodiment provided by the present invention, the lipoic acid modified epoxy resin, calculated on the basis of raw materials, comprises:

[0098] Epoxy resin 50-100 parts by weight;

[0099] 20 to 100 parts by weight of curing agent;

[0100] 1 to 10 parts by weight of functional filler.

[0101] The present invention uses lipoic acid and its derivatives as curing agents to introduce dynamic disulfide bond networks, functional groups, and non-covalent bond interaction sites (hydrogen bonds, lithium bonds, coordination bonds, etc.) into epoxy resins, thereby achieving modifications including but not limited to curing, toughening, introduction of modified binding sites, and function imparting; and the mutual compounding of lipoic acid and its derivatives can perform multifunctional integration of epoxy resins on the basis of ensuring mechanical properties, so that it exhibits special technical effects in dielectric, thermal conductivity, wave absorption, and flexible electricity. Furthermore, lipoic acid and its derivative curing agents impart remodeling and repair functions to epoxy resins.

[0102] The present invention also provides a method for preparing the above-mentioned lipoic acid modified epoxy resin that can be upgraded and recycled, comprising the following steps: S1) mixing epoxy resin, curing agent and functional filler to obtain a prepolymer; S2) heating and curing the prepolymer to obtain zinc sulfate modified epoxy resin.

[0103] The present invention uses thioctic acid and its functional derivatives as curing agents, which can not only reduce the toxicity and irritation in the production process, but also can prepare modified epoxy resin with epoxy resin through a one-step method, the process is simple, and it is suitable for industrial production; and the thioctic acid and its derivatives used can introduce dynamic disulfide bond networks, functional groups, non-covalent bond interaction sites (hydrogen bonds, lithium bonds, coordination bonds, etc.) into the epoxy resin, thereby realizing modifications including but not limited to curing, toughening, introduction of modified binding sites and function imparting, and the mutual compounding of thioctic acid and its derivatives can perform multifunctional integration on the epoxy resin on the basis of ensuring mechanical properties, so that the epoxy resin can show special technical effects in terms of dielectric, thermal conductivity, wave absorption, flexible electricity, etc.; in addition, the introduction of fillers can further expand and enhance the functionality of the epoxy resin; furthermore, the thioctic acid modified epoxy resin obtained by the present invention can be easily reshaped and repaired by means of a dynamic network, and can also be slightly degraded and upgraded to polyurethane foam and modified rubber through in-situ foaming.

[0104] The present invention has no particular limitation on the sources of all raw materials, and any raw materials available on the market can be used.

[0105] The epoxy resin, the curing agent and the functional filler are mixed to obtain a prepolymer; the mixing method is a method well known to those skilled in the art and is not particularly limited.

[0106] In a specific embodiment provided by the present invention, the step S1) is specifically: mixing an epoxy resin, a curing agent and a functional filler in an organic solvent, removing the solvent, and drying to obtain a prepolymer; further specifically, mixing the epoxy resin with an organic solvent, then adding a curing agent and a functional filler to mix, removing the solvent, and drying to obtain a prepolymer; the organic solvent can be an organic solvent well known to those skilled in the art, and there is no special restriction. In the present invention, dichloromethane is preferably used; the method for removing the solvent can be a method well known to those skilled in the art, and there is no special restriction. In the present invention, the solvent is preferably removed by heating under low vacuum conditions; the heating temperature is preferably 40°C to 60°C, more preferably 50°C; the heating time is preferably 2 to 6h, more preferably 3 to 5h, and more preferably 4h; the drying temperature is preferably 70°C to 90°C, more preferably 80°C; further preferably, air is preferably removed by reducing pressure during the drying process.

[0107] In a specific embodiment provided by the present invention, the step S1) is specifically: heating and melting the curing agent, and then adding epoxy resin and functional filler to mix to obtain a prepolymer; the heating and melting temperature is preferably 120°C to 160°C, more preferably 130°C to 150°C, and more preferably 140°C.

[0108] In a specific embodiment provided by the present invention, the step S1) is specifically: mixing the epoxy resin and the curing agent under heating conditions, and then adding the functional filler to obtain a prepolymer; the heating temperature is preferably 60°C to 90°C; the mixing time is preferably 1 to 10 minutes, more preferably 3 to 8 minutes, more preferably 4 to 6 minutes, and most preferably 5 minutes.

[0109] In a specific embodiment provided by the present invention, the step S1) is specifically: thoroughly mixing the epoxy resin, the curing agent and the functional filler by a rapid mixer to obtain a prepolymer; the mixing time is preferably 1 to 5 minutes, more preferably 3 minutes.

[0110] In a specific embodiment provided by the present invention, the heating and curing in the step S2) is specifically step-by-step heating and curing; the step-by-step heating and curing includes a first-stage heating and curing and a second-stage heating and curing; the temperature of the first-stage heating and curing is preferably 70°C to 120°C, more preferably 70°C to 100°C; the time of the first-stage heating and curing is preferably 1 to 2 hours; the temperature of the second-stage heating and curing is preferably 130°C to 150°C, more preferably 130°C to 140°C; the time of the second-stage heating and curing is preferably 2 to 4 hours.

[0111] In a specific embodiment provided by the present invention, the step S2) is specifically: curing the prepolymer at 70° C. for 1 hour and at 140° C. for 3 hours to obtain a zinc sulfate-modified epoxy resin.

[0112] In a specific embodiment provided by the present invention, the heating and curing in the step S2) is specifically step-by-step heating and curing; the step-by-step heating and curing includes a first stage heating and curing, a second stage heating and curing and a third stage heating and curing; the temperature of the first stage heating and curing is preferably 70°C to 120°C, more preferably 80°C to 100°C; the time of the first stage heating and curing is preferably 1 to 2 hours, more preferably 2 hours; the temperature of the second stage heating and curing is preferably 130°C to 150°C; the time of the second stage heating and curing is preferably 2 to 8 hours; the temperature of the third stage heating and curing is preferably 150°C to 170°C; the time of the third stage heating and curing is preferably 1 to 3 hours.

[0113] In a specific embodiment provided by the present invention, the step S2) is specifically: heating the prepolymer to 100° C. and maintaining it for 2 hours, 130° C. and maintaining it for 2 hours, and 150° C. and maintaining it for 2 hours.

[0114] In a specific embodiment provided by the present invention, the step S2) is specifically: curing the prepolymer at 80° C. for 2 hours, curing at 150° C. for 8 hours, and post-curing at 170° C. for 1 hour.

[0115] In a specific embodiment provided by the present invention, the heating and curing in step S2) is carried out under pressurized conditions; the temperature of the heating and curing is preferably 120°C to 180°C; the pressurized conditions are preferably 15 to 25 tons of pressure, more preferably 18 to 22 tons of pressure, and even more preferably 20 tons of pressure.

[0116] The present invention also provides a method for recovering the thioctic acid modified epoxy resin, comprising the following steps: A1) soaking the thioctic acid modified epoxy resin in polyethylene glycol under heating conditions to obtain a degradation solution; A2) mixing the degradation solution, water, polyamine, silicone oil, a catalyst and an isocyanate component to obtain a polyurethane foam; or, B1) soaking the thioctic acid modified epoxy resin in an alkaline solution to obtain a degradation solution; B2) subjecting the degradation solution to reduction and acidification treatment to obtain polymer fragments containing thiol units.

[0117] The lipoic acid modified epoxy resin provided by the invention can be upgraded and recycled into polyurethane foam through in-situ foaming after being slightly degraded.

[0118] In a specific embodiment provided by the present invention, the heating temperature in the step A1) is preferably 180°C to 220°C, more preferably 200°C; the polyethylene glycol is preferably polyethylene glycol-600; the soaking time is preferably 15 to 25 hours, more preferably 18 to 22 hours, and even more preferably 20 hours.

[0119] In a specific embodiment provided by the present invention, the polyamine is preferably triethylenediamine; the catalyst is any catalyst well known to those skilled in the art without any special limitation, and in the present invention, dibutyltin diacid is preferably used; the isocyanate component is preferably polymethylene polyphenylene isocyanate, and more preferably polyphenyl polymethylene polyisocyanate PAPI.

[0120] In a specific embodiment provided by the present invention, the degradation liquid, water, polyamine, silicone oil and catalyst are first mixed and stirred until emulsified and whitened, and then the isocyanate component is quickly added and mixed and stirred; the mass of the water is preferably 1% to 10% of the mass of the polyethylene glycol, more preferably 2% to 6%, and more preferably 4%; the mass of the polyamine is preferably 1% to 10% of the mass of the lipoic acid-modified epoxy resin, more preferably 2% to 6%, and more preferably 4%; the mass of the silicone oil is preferably 50% to 100% of the mass of the lipoic acid-modified epoxy resin, more preferably 50% to 100% of the mass of the lipoic acid-modified epoxy resin. 60% to 80%, more preferably 70%; the mass of the catalyst is preferably 1% to 10% of the mass of the thioctic acid modified epoxy resin, more preferably 2% to 6%, and more preferably 4%; the mass ratio of the isocyanate component to the thioctic acid modified epoxy resin is preferably (4 to 10):1, more preferably (5 to 8):1, more preferably (6 to 7):1, and most preferably (6 to 6.2):1; the mixing and stirring time is preferably 1 to 10s, more preferably 5s; after mixing and stirring, stopping stirring, foaming, and cooling to room temperature to obtain polyurethane foam.

[0121] The lipoic acid modified epoxy resin provided by the invention can be upgraded and recycled into modified rubber after being slightly degraded.

[0122] In a specific embodiment provided by the present invention, the alkaline solution in step B1) is preferably an alkali metal hydroxide solution; the concentration of the alkaline solution is preferably 0.1-1 mol / L, more preferably 0.3-0.8 mol / L, and even more preferably 0.5 mol / L; and the immersion time is preferably 6-24 h.

[0123] In a specific embodiment provided by the present invention, the reduction in step B2) is preferably carried out using sodium borohydride; the amount of sodium borohydride added is based on the curing agent in the lipoic acid-modified epoxy resin, 6 to 8 g of sodium borohydride is added per 10 g of curing agent, preferably 6.5 to 8 g of sodium borohydride is added per 10 g of curing agent, more preferably 7 to 7.5 g of sodium borohydride is added per 10 g of curing agent, and more preferably 7.3 g of sodium borohydride is added per 10 g of curing agent; the reduction is preferably carried out in a protective atmosphere; the protective atmosphere can be a protective atmosphere well known to those skilled in the art, and there is no special limitation, and in the present invention, nitrogen is preferably used; the reduction time is preferably 1 to 3 hours, more preferably 1.2 to 2.5 hours, and more preferably 2 hours.

[0124] In a specific embodiment provided by the present invention, the acidification in step B2) is preferably carried out using an inorganic acid solution, more preferably a hydrochloric acid solution; the concentration of the inorganic acid solution is preferably 0.5-2 mol / L, more preferably 0.5-1.5 mol / L, further preferably 0.8-1.2 mol / L, and most preferably 1-1.2 mol / L; the acidification to a pH value is 3-4.

[0125] In the present invention, the obtained polymer fragments containing mercapto units can be used as a vulcanization crosslinking agent to participate in rubber vulcanization.

[0126] In order to further illustrate the present invention, an upgraded and recyclable lipoic acid-modified epoxy resin and a preparation method thereof provided by the present invention are described in detail below in conjunction with embodiments.

[0127] The reagents used in the following examples are all commercially available.

[0128] Example 1

[0129] 50g of diglycidyl terephthalate, 50g of thioctic acid and 50g of thioctic acid hydrazide were dissolved completely with a small amount of dichloromethane and mixed evenly, then the solvent was removed under low vacuum at 50°C for 4 hours, and then carefully poured into a mold sprayed with a release agent, and the mold filled with the prepolymer was transferred to a vacuum drying oven at 80°C to remove air under reduced pressure. Hot press at 120°C and 20 tons of pressure for 6 hours, cooled to room temperature, and a modified epoxy resin was obtained.

[0130] See attached Figure 1 , Figure 1 The modified epoxy resin provided in Example 1 was cut into dumbbell-shaped strips (the size of the narrow neck was 2×12 mm) and then -1 The results show that the elongation at break can reach 28%, the maximum strength can reach 38MPa, and the toughness and elongation are greatly improved.

[0131] The discarded sample of Example 1 is cut into pieces and hot-pressed at 120° C. and 5 tons of pressure for 30 to 60 minutes to be reshaped into a uniform transparent film, such as Figure 2 As shown, Figure 2 This is a graph showing the thermal remodeling (recycling) ability of the modified epoxy resin obtained in Example 1.

[0132] The modified epoxy resin obtained in Example 1 was prepared into a film, and scratches were cut on the surface of the sample film with a scalpel. The healing of the scar was observed under a microscope and photographed for record. Figure 3 As shown, Figure 3 This is a diagram of the self-healing ability of the modified epoxy resin obtained in Example 1.

[0133] Example 2

[0134] 100g E20 epoxy resin and 50g lipoic acid were stirred at 90℃ for 5-10 minutes to form a prepolymer. The prepolymer was then cast into a stainless steel mold with a size of 50mm×50mm×1.5mm and hot-pressed at 120℃ and 20 tons of pressure for 6 hours. After cooling to room temperature, a uniform and transparent sample was obtained.

[0135] See attached Figure 4 , Figure 4 The modified epoxy resin provided in Example 2 was cut into dumbbell-shaped strips (the size of the narrow neck was 2×12 mm) and then heated at 2 mm·min. -1 The results show that the elongation at break can reach 26%, the breaking strength can reach 22MPa, and the toughness and elongation are greatly improved.

[0136] The lipoic acid-modified epoxy resin waste prepared in Example 2 was soaked in a PEG-600 solution (1g waste and 10g PEG-600) at 200°C for 20 hours until completely degraded. After cooling to room temperature, a degradation solution was obtained. The degradation fragment mixture was mixed with 0.4g water, 0.04g triethylenediamine, 0.7g silicone oil, and 0.04g dibutyltin dilaurate under magnetic stirring until emulsified and whitened. Subsequently, 6.14g of polyphenyl polymethylene polyisocyanate PAPI was quickly added, stirred for 5s, then stirring was stopped, foaming, and cooled to room temperature. The resulting foam has good mechanical flexibility. According to the national standard GB / T 8813-2020 Determination of compression properties of rigid foam plastics, a sample with a size of 10mm×10mm×10mm was used on a universal mechanical testing machine at 10mm min -1 The compression performance of the foam was tested at a compression rate of , and the results showed that the compressive strength was 0.15MPa and the modulus was 0.097MPa.

[0137] The lipoic acid-modified epoxy resin prepared in Example 2 was soaked in a 0.5M sodium hydroxide solution for 10 hours to obtain a degradation solution, and then sodium borohydride was added (based on the lipoic acid in the epoxy resin feed, 7.3g of sodium borohydride was added for every 10g of lipoic acid degradation) and stirred for reaction under nitrogen for 2 hours, and then 1.2M dilute hydrochloric acid (the pH value of the dropwise addition system was 2-3) was added for acidification to obtain polymer fragments containing thiol units.

[0138] 3 g of the fragments were mixed with 100 g of a rubber matrix (styrene-butadiene rubber), and an initiator, azobisisobutyronitrile (AIBN) (1 wt%), was added, and the rubber was swollen after being dissolved in toluene. The rubber was heated at 80° C. for 2 hours to finally form a modified rubber.

[0139] After the modified rubber was cut into dumbbell-shaped specimens (the size of the narrow neck was 2×12 mm), -1 The tensile curve under the rate (refer to the national standard GBT 528-2009 vulcanized rubber or thermoplastic rubber. Determination of tensile stress-strain properties) shows that its tensile strength is 18MPa (better than the 10-15MPa of unmodified rubber) and the elongation at break is 420% (equivalent to the unmodified rubber).

[0140] Example 3

[0141] 70g of bisphenol F type glycidyl ether was completely dissolved with a small amount of dichloromethane, and then 20g of lipoic acid amide and 20g of liquid crystal functionalized lipoic acid shown in formula (A) were added and stirred and mixed evenly. Then the solvent was removed under low vacuum at 50°C for 4 hours, and then carefully poured into a mold (60×60mm) sprayed with a release agent. After the mold was completely filled, it was transferred to a vacuum drying oven at 80°C to decompress and remove air, and then hot pressed at 120°C and 10 tons of pressure for 4 hours, and cooled to room temperature.

[0142]

[0143] The polymer obtained in Example 3 was cut into strip films and exposed to ultraviolet light (365 nm, 50 mW / cm 2 ) induced bending behavior, and recovered to the initial state within 5 seconds after the removal of the illumination. Heating was similar, and deformation occurred at 80°C. Figure 5 The obtained epoxy resin exhibits the light and heat response behavior of liquid crystal.

[0144] Example 4

[0145] 60 g of lipoic acid hydrazide was melted at 140° C., and then 100 g of bisphenol A diglycidyl ether and 50 nm multi-walled carbon nanotubes (the doping amount was 3% of the mass of lipoic acid hydrazide) were added and mixed quickly and evenly, poured into a mold of a specific shape, and cured at 70° C. for 1 h and at 140° C. for 3 h to obtain a modified epoxy resin.

[0146] The thermal conductivity and contact thermal resistance of the modified epoxy resin obtained in Example 4 were tested using a thermal conductivity tester model LW-9389 produced by Taiwan Ruiling Company. 2 The square cutter cuts the sample into three square slices of different thicknesses. The pressure during the test is 10 psi, the heat source temperature is 80°C, and the test results are directly read by the computer. The thermal conductivity tester is designed and manufactured according to ASTM D 5470-06, and its thermal conductivity is greater than or equal to 1.93 W mK -1 , indicating that the modified epoxy resin obtained has good thermal conductivity.

[0147] Example 5

[0148] 50 g of diglycidyl 2,5-furandicarboxylate and 40 g of thioctic acid were stirred at 60° C. to 90° C. for 5 minutes to form a prepolymer, ferric chloride (10 wt% of the mass of thioctic acid) was added and mixed evenly, hot-pressed at 120° C. and 20 tons of pressure for 6 hours, and cooled to room temperature to obtain a modified epoxy resin.

[0149] The mechanical properties of the modified epoxy resin obtained in Example 5 were tested. The modified epoxy resin was cut into dumbbell-shaped specimens (the size of the neck was 2×12 mm) and then heated to 2 mm·min. -1 The tensile curve at a rate of 47% (refer to the national standard GB / T41929-2022 Plastic Epoxy Resin Test Method) shows that its elongation at break is 47% and its fracture strength is 52 MPa, indicating that it has enhanced toughness and strength.

[0150] Example 6

[0151] After 50g of diglycidyl phthalate is completely dissolved in a small amount of dichloromethane, 50g of 2,5-furandicarboxylic acid dithioic acid and flake boron nitride (10% of the mass of 2,5-furandicarboxylic acid dithioic acid) are added and stirred and mixed evenly. Then the solvent is removed under low vacuum at 50°C for 4 hours, and then carefully poured into a mold sprayed with a release agent, and the mold filled with the prepolymer is transferred to a vacuum drying oven at 80°C to remove air under reduced pressure. Hot press at 120°C and 20 tons of pressure for 6 hours, and cool to room temperature to obtain a modified epoxy resin.

[0152] The thermal conductivity and contact thermal resistance of the modified epoxy resin obtained in Example 6 were tested using a thermal conductivity tester model LW-9389 produced by Taiwan Ruiling Company. 2The sample was processed into three square slices of different thicknesses by a square cutter. The pressure during the test was 10 psi, the heat source temperature was 80°C, and the test results were directly read by a computer (the thermal conductivity tester was designed and manufactured according to ASTM D 5470-06), and the thermal conductivity was greater than or equal to 1.87 W mK -1 , indicating that the modified epoxy resin obtained has good thermal conductivity.

[0153] Example 7

[0154] 100 g of triglycidyl p-aminophenol and 100 g of polycalcium carbonate dithioic acid represented by formula (B) were thoroughly mixed at room temperature by a rapid mixer for 3 minutes, and then hot-pressed at 120° C., 150° C. for 2 hours, and 180° C. for 1 hour under a pressure of 20 tons; cooled to room temperature to obtain a modified epoxy resin.

[0155]

[0156] The mechanical properties of the modified epoxy resin obtained in Example 7 were tested. The modified epoxy resin was cut into dumbbell-shaped specimens (the size of the neck was 2×12 mm) and then heated to 2 mm·min. -1 The tensile curve at rate (refer to national standard GB / T41929-2022 plastic epoxy resin test method) shows that its elongation at break is 44% and its breaking strength is 60 MPa, indicating that it has enhanced toughness, elasticity and strength.

[0157] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An upcyclable lipoic acid modified epoxy resin, characterized in that: In terms of raw materials, it includes: Epoxy resin 50-100 parts by weight; 10 to 100 parts by weight of curing agent; Functional filler 0-20 parts by weight; The curing agent is selected from lipoic acid and / or lipoic acid derivatives; The lipoic acid derivative is shown in formula (I): The R1 is selected from substituted or unsubstituted amino, substituted hydroxyl; The substituent in the substituted amino group is selected from an amino group, a substituted or unsubstituted C1-C10 alkyl group, a succinimide-substituted ester group, a fatty acid group containing an amide bond, a C1-C10 heteroalkyl group, a substituted or unsubstituted C5-C10 cycloalkyl group, and a substituted or unsubstituted C6-C20 aryl group; The substituent in the substituted hydroxyl group is selected from succinimide group, alkali metal ion, substituted or unsubstituted C1-C10 alkyl group, C1-C10 heteroalkyl group, substituted or unsubstituted C5-C10 cycloalkyl group, substituted or unsubstituted C6-C20 aryl group; The substituents in the substituted C1-C10 alkyl, substituted C5-C10 epoxy and substituted C6-C20 aryl are each independently selected from one or more of C1-C10 alkyl, hydroxyl, C1-C10 alkoxy and alkoxyazophenyl; The R2 is selected from a substituted or unsubstituted C1-C10 alkylene group, a polycalcium carbonate group or a group represented by formula (III); The R3 is selected from furanyl, fused furanyl or alkoxybenzoic acid benzyl ester; The substituent in the substituted C1-C10 alkylene group is selected from lipoic acid ester group.

2. The lipoic acid modified epoxy resin according to claim 1, characterized in that The epoxy resin is selected from one or more of epoxidized olefin compounds, heterocyclic epoxy resins, mixed epoxy resins, polyphenol glycidyl ether epoxy resins, aliphatic glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins and furan-containing epoxy resin monomers.

3. The lipoic acid modified epoxy resin according to claim 2, characterized in that The furan-containing epoxy resin monomer is selected from one or more of the following formulas (1) to (11):

4. The lipoic acid modified epoxy resin according to claim 1, characterized in that The lipoic acid derivative is selected from one or more of the following formulas: Here, x is an integer greater than or equal to 0.

5. The lipoic acid modified epoxy resin according to claim 1, characterized in that The functional filler is selected from one or more of metal fillers, metal oxides, metal salts, carbon-based fillers and ceramic fillers.

6. The lipoic acid modified epoxy resin according to claim 5, characterized in that The metal filler is selected from one or more of silver, copper and aluminum; The metal oxide is selected from one or more of aluminum oxide, iron oxide and copper oxide; The metal salt is selected from one or more of ferric chloride, calcium chloride, zinc chloride, zinc acetate and zinc sulfate; The carbon-based filler is selected from one or more of carbon nanotubes, carbon fibers and graphene; The ceramic filler is selected from one or more of aluminum oxide, aluminum nitride and boron nitride.

7. The lipoic acid modified epoxy resin according to claim 1, characterized in that In terms of raw materials, it includes: Epoxy resin 50-100 parts by weight; 20 to 100 parts by weight of curing agent; Functional filler 0-20 parts by weight.

8. A method for preparing the upcyclable lipoic acid-modified epoxy resin according to claim 1, characterized in that: The following steps are involved: S1) mixing epoxy resin, curing agent and functional filler to obtain a prepolymer; S2) heating and curing the prepolymer to obtain a zinc sulfate modified epoxy resin.

9. The preparation method according to claim 8, characterized in that: The step S1) specifically comprises: mixing epoxy resin, curing agent and functional filler in an organic solvent, removing the solvent, and drying to obtain a prepolymer; Alternatively, the curing agent is heated and melted, and then epoxy resin and functional filler are added and mixed to obtain a prepolymer; Alternatively, the epoxy resin and the curing agent are mixed under heating conditions, and then a functional filler is added to obtain a prepolymer; The heating and curing in step S2) is specifically step-by-step heating and curing; the step-by-step heating and curing includes a first stage heating and curing and a second stage heating and curing; the temperature of the first stage heating and curing is 70°C to 120°C; the time of the first stage heating and curing is 1 to 2 hours; the temperature of the second stage heating and curing is 130°C to 150°C; the time of the second stage heating and curing is 2 to 4 hours; Alternatively, the heating curing is specifically step-by-step heating curing; the step-by-step heating curing includes a first stage heating curing, a second stage heating curing and a third stage heating curing; the temperature of the first stage heating curing is 70°C to 120°C; the time of the first stage heating curing is 1 to 2 hours; the temperature of the second stage heating curing is 130°C to 150°C; the time of the second stage heating curing is 2 to 8 hours; the temperature of the third stage heating curing is 150°C to 170°C; the time of the third stage heating curing is 1 to 3 hours; Alternatively, the heating and curing is carried out under pressurized conditions; the temperature of the heating and curing is 120° C. to 180° C.; and the pressurized conditions are 15 to 25 tons of pressure.

10. A method for recovering the lipoic acid modified epoxy resin according to claim 1, characterized in that: The following steps are involved: A1) soaking the lipoic acid-modified epoxy resin in polyethylene glycol under heating to obtain a degradation solution; A2) mixing the degradation liquid, water, polyamine, silicone oil, catalyst and isocyanate component to obtain polyurethane foam; or, B1) soaking the lipoic acid modified epoxy resin in an alkaline solution to obtain a degradation solution; B2) subjecting the degradation solution to reduction and acidification treatment to obtain polymer fragments containing thiol units.

Images