Epoxy adduct of polysilazane and preparation method thereof, recyclable epoxy resin and recycling method and application thereof

Abstract

The present invention provides an epoxy adduct of polysilazane and a preparation method thereof, a recyclable epoxy resin and a recycling method and application thereof. The epoxy adduct of polysilazane has a structure as shown in Formula I. By applying the technical scheme of the present invention, the epoxy adduct of polysilazane is cured together with epoxy resin and curing agent to form a thermosetting three-dimensional network structure polymer, and the three-dimensional network structure of the polymer can be gradually dissociated and broken in an acidic proton solvent, so that the infusible and insoluble epoxy cured product is decomposed to achieve the purpose of recycling. Due to the presence of polysilazane, the epoxy adduct of polysilazane has higher heat resistance than general epoxy resin.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resin materials, and in particular to an epoxy adduct of polysilazane and a preparation method thereof, a recyclable epoxy resin and a recycling method and application thereof. Background Art

[0002] Epoxy resin is one of the three major thermosetting resins. Due to its excellent adhesion, mechanical properties, weather resistance and other characteristics, it has been widely used in adhesives, composite materials and electronic packaging materials. According to statistics, in 2017, the global annual production capacity of epoxy resin was close to 5 million tons, my country's epoxy resin production capacity reached 2.3 million tons, production reached 1.3 million tons, and consumption was about 1.5 million tons. China has become the world's largest epoxy resin production country, production country and consumer market. Among commercial resins, more than 90% of epoxy resins are bisphenol A glycidyl ethers. This resin has an irreversible covalent cross-linking network and exhibits insoluble and infusible characteristics. It is difficult to reprocess and reuse like thermoplastic resins. Therefore, once cured, the cross-linking points are difficult to open. After use, the resin is difficult to recycle. The large amount of waste epoxy resins and their composite materials causes irreversible environmental pollution and waste of resources, which is one of the key issues restricting the future application and development of epoxy resins and their composite materials. With the increasing attention of human beings to environmental protection and sustainable development, the recycling, degradation and reuse of epoxy resins have become a widely concerned issue in various countries.

[0003] At present, the main treatment method for thermosetting resins is landfilling. However, according to the Solid Waste Management Guidelines (1989) of the Environmental Protection Agency (EPA), landfilling is the least recommended waste treatment method. There is also a method of recycling through incineration, where part of the energy in the resin is converted into heat / electricity, but this will cause problems such as resource waste and environmental pollution; physical crushing recovery method, using a simple process to crush thermosetting epoxy resins and their composites, applied to low-end application fields such as construction or road filling; chemical recycling method uses high temperature environment, high-heat air flow, super / subcritical fluid, solvation, etc. to unlock the cross-linked structure of epoxy resin, so that the resin molecular chain is decomposed into volatile or soluble small molecules, and the fiber reinforcement with higher added value in epoxy resin composites is recycled. However, according to research results, chemical recycling requires harsh reaction conditions to achieve degradation and recycling, and the degradation products are uncontrollable and inefficient, and the performance, structure, and orderliness of the recycled fiber reinforcement are significantly reduced. These treatment methods are actually just processing rather than recycling thermosetting epoxy resins. Summary of the invention

[0004] The main purpose of the present invention is to provide an epoxy adduct of polysilazane and a preparation method thereof, a recyclable epoxy resin and a recycling method and application thereof, so as to solve the problem that epoxy resin is difficult to recycle in the prior art.

[0005] In order to achieve the above object, according to one aspect of the present invention, there is provided an epoxy adduct of polysilazane, wherein the epoxy adduct of polysilazane has a structure as shown in Formula I:

[0006]

[0007] In Formula I, m is an integer of 3 to 20, and the m R1s are independently selected from hydrogen and C1 to C 10 m R2 are independently selected from substituted or unsubstituted C1 to C 50 Alkyl, substituted or unsubstituted C1~C 60 Alkyl ether group, substituted or unsubstituted C1~C 50 Alkyl sulfide group, substituted or unsubstituted C1~C 50 Siloxane, substituted or unsubstituted C6~C 50 Aryl, substituted or unsubstituted C7~C 50 R3 and R4 are each independently selected from substituted or unsubstituted C1 to C 50 Alkylene, substituted or unsubstituted C1~C 60 Alkylene ether group, substituted or unsubstituted C1~C 50 Alkylene sulfide group, substituted or unsubstituted C1~C 50 Siloxane, substituted or unsubstituted C6~C 60 Arylene, substituted or unsubstituted C7~C 60 Any one of the aralkylene groups.

[0008] Furthermore, m R1s are independently selected from any one of hydrogen and C1-C6 alkyl, and m R2s are independently selected from substituted or unsubstituted C1-C 30 Alkyl, substituted or unsubstituted C1~C 30 Alkyl ether group, substituted or unsubstituted C1~C 30 Alkyl sulfide group, substituted or unsubstituted C1~C 20 Siloxane, substituted or unsubstituted C6~C 30 Aryl, substituted or unsubstituted C7~C 30 any one of the arylalkyl groups of 30 Alkylene, substituted or unsubstituted C1~C 20 Alkylene ether group, substituted or unsubstituted C1~C 30 Alkylene sulfide group, substituted or unsubstituted C1~C 20 Siloxane, substituted or unsubstituted C6~C 30Arylene, substituted or unsubstituted C7~C 30 Any one of the aralkylene groups;

[0009] Preferably, the m R1s are independently selected from any one of hydrogen and C1-C3 alkyl, and R3 and R4 are independently selected from substituted or unsubstituted C6-C 30 Arylene, substituted or unsubstituted C7~C 30 Any one of the aralkylene groups;

[0010] More preferably, R1 is methyl, and R3 and R4 are each independently selected from any one of -ph-C(CH3)2-ph-, or -ph-CH2-ph-.

[0011] According to another aspect of the present application, a method for preparing the epoxy adduct of polysilazane as described above is provided, the method comprising: step S1, reacting a polysilazane having a structure of formula II with a primary amine under the action of a first catalyst to obtain a secondary amine having a structure of formula III;

[0012]

[0013] In the formula, m is an integer of 3 to 20, and the m R1s are independently selected from hydrogen and C1 to C 10 any one or more of the alkyl groups of 50 Alkyl, substituted or unsubstituted C1~C 60 Alkyl ether group, substituted or unsubstituted C1~C 50 Alkyl sulfide group, substituted or unsubstituted C1~C 50 Siloxane, substituted or unsubstituted C6~C 50 Aryl, substituted or unsubstituted C7~C 50 Any one of the aralkyl groups;

[0014] Step S2, mixing a secondary amine having a structure of Formula III with a multifunctional epoxy resin at a weight ratio of 1:5 to 50, and performing a ring-opening addition reaction to obtain an epoxy adduct of polysilazane.

[0015] Furthermore, the first catalyst is a quaternary ammonium salt,

[0016] Preferably, in step S1, the ratio of the molar number of Si-H functional groups to the molar number of primary amines in the polysilazane having the structure of formula II is 1:1 to 1:2;

[0017] Preferably, the primary amine is selected from any one or more of aliphatic amines, alicyclic amines and aromatic amines.

[0018] Further, in step S2, the reaction temperature is 60-180°C, and the preferred reaction time is 4-24h;

[0019] Preferably, the molar ratio of the secondary amine having the structure of formula III to the epoxy group of the multifunctional epoxy resin is 1:10-100.

[0020] According to another aspect of the present application, a recyclable epoxy resin is provided. The recyclable epoxy resin is obtained by curing a recyclable epoxy resin composition.

[0021] The recyclable resin composition comprises an epoxy resin, a curing agent and the epoxy adduct of the above-mentioned polysilazane.

[0022] Furthermore, the content of the epoxy adduct of polysilazane in the recyclable resin composition is 0.1 to 20 wt %, preferably 0.1 to 15 wt %.

[0023] Preferably, the epoxy resin is selected from any one or more of E51 and E44;

[0024] Preferably, the recyclable resin composition also includes an epoxy diluent. Preferably, the epoxy diluent includes any one or more of butanediol diglycidyl ether, pentaerythritol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol triglycidyl ether and n-butyl glycidyl ether.

[0025] Furthermore, the recyclable resin composition also includes fibers.

[0026] According to another aspect of the present application, a method for recycling any of the above-mentioned recyclable epoxy resins is provided. The recycling method comprises soaking any of the above-mentioned recyclable epoxy resins in an acidic protic solvent at 0 to 70° C.

[0027] Further, the acidic protic solvent is selected from one of formic acid, acetic acid, propionic acid, propionic acid, acrylic acid, propionic acid, hypochlorous acid, dichloroacetic acid, trifluoroacetic acid, methanesulfonic acid, hydrobromic acid, hydrofluoric acid, lactic acid, perchloric acid, hydrobromic acid, chloric acid, oxalic acid, sulfurous acid, phosphoric acid, pyruvic acid, nitrous acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, citric acid, p-toluenesulfonic acid, benzoic acid, salicylic acid, and phthalic acid, or a mixture of several thereof. Preferably, it is any one or more of formic acid, acetic acid, propionic acid, propionic acid, acrylic acid, propionic acid, hypochlorous acid, dichloroacetic acid, methanesulfonic acid, hydrobromic acid, lactic acid, hydrobromic acid, chloric acid, oxalic acid, sulfurous acid, phosphoric acid, pyruvic acid, nitrous acid, sulfuric acid, hydrochloric acid, nitric acid, p-toluenesulfonic acid, benzoic acid, salicylic acid, and phthalic acid;

[0028] Preferably, the pH value of the acidic protic solvent is controlled to be 1-3.

[0029] According to another aspect of the present application, there is provided a use of any of the above-mentioned recyclable epoxy resins in composite materials or prepregs for wind turbine blades and automobiles.

[0030] Applying the technical scheme of the present invention, the epoxy adduct of the above-mentioned polysilazane is cured together with epoxy resin and curing agent to form a thermosetting three-dimensional network structure polymer, and the three-dimensional network structure of the polymer can be gradually dissociated and broken in an acidic proton solvent, so that the insoluble epoxy cured product is decomposed to achieve the purpose of recovery. The epoxy adduct of the above-mentioned polysilazane, due to the presence of polysilazane, has higher heat resistance than general epoxy resin. The epoxy adduct of the polysilazane can be used to prepare recyclable thermosetting epoxy resin and fiber-reinforced recyclable epoxy resin composite materials, prepregs, etc., containing the fiber-reinforced recyclable epoxy resin composite material of the epoxy adduct of the polysilazane of the present application, can realize the separation of epoxy resin matrix and fiber, realize the recovery and reuse of fiber reinforcement, and facilitate the waste parts processing and material recovery of epoxy resin materials of larger volume; It is particularly suitable for wind power, automotive recyclable composite materials and prepreg fields, and has great application prospects. DETAILED DESCRIPTION

[0031] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0032] In the present application, the term "substituted or unsubstituted" refers to substitution by one or more substituents selected from the following: deuterium; halogen group; nitrile group; nitro group; hydroxyl group; carbonyl group; ester group; imide group; amino group; phosphine oxide group; alkoxy group; aryloxy group; alkylthio group; arylthio group; alkylsulfonyl group; silyl group; boron group; alkyl group; cycloalkyl group; epoxy group; alkenyl group; aryl group; aralkyl group; aralkenyl group; alkylaryl group; alkylamino group; aralkylamino group; heteroarylamino group; arylamino group; arylphosphino group; or a heterocyclic group containing at least one of N, O and S, or no substituent, or substituted by substituents connected by two or more substituents among the exemplified substituents, or no substituent. For example, the term "substituents connected by two or more substituents" can be biphenyl. That is, the biphenyl group can be an aryl group, or it can be interpreted as a substituent connected by two phenyl groups.

[0033] As analyzed in the background technology of the present application, there is a problem in the prior art that epoxy resins are prone to cause irreversible environmental pollution and waste of resources after being discarded, and are difficult to recycle. In order to solve this problem, the present application provides an epoxy adduct of polysilazane and a preparation method thereof, a recyclable epoxy resin and a recycling method and application thereof.

[0034] According to a typical embodiment of the present application, an epoxy adduct of polysilazane is provided. The epoxy adduct of polysilazane has a structure as shown in Formula I.

[0035]

[0036] In Formula I, m is an integer of 3 to 20, and the m R1s are independently selected from hydrogen and C1 to C 10 m R2 are independently selected from substituted or unsubstituted C1 to C 50 Alkyl, substituted or unsubstituted C1~C 60 Alkyl ether group, substituted or unsubstituted C1~C 50 Alkyl sulfide group, substituted or unsubstituted C1~C 50 Siloxane, substituted or unsubstituted C6~C 50 Aryl, substituted or unsubstituted C7~C 50 R3 and R4 are each independently selected from substituted or unsubstituted C1 to C 50 Alkylene, substituted or unsubstituted C1~C 60 Alkylene ether group, substituted or unsubstituted C1~C 50 Alkylene sulfide group, substituted or unsubstituted C1~C 50 Siloxane, substituted or unsubstituted C6~C 60 Arylene, substituted or unsubstituted C7~C 60 Any one of the aralkylene groups.

[0037] The epoxy adduct of the above-mentioned polysilazane is cured together with epoxy resin and curing agent to form a thermosetting three-dimensional network structure polymer, and the three-dimensional network structure of the polymer can be gradually dissociated and broken in an acidic proton solvent, so that the insoluble epoxy cured product is decomposed to achieve the purpose of recovery. The epoxy adduct of the above-mentioned polysilazane has higher heat resistance than general epoxy resin due to the presence of polysilazane. The epoxy adduct of the polysilazane can be used to prepare recyclable thermosetting epoxy resin and fiber-reinforced recyclable epoxy resin composite materials, prepregs, etc., and the fiber-reinforced recyclable epoxy resin composite materials containing the epoxy adduct of the polysilazane of the present application can realize the separation of epoxy resin matrix and fiber, realize the recovery and reuse of fiber reinforcement, and facilitate the waste parts processing and material recovery of epoxy resin materials with a larger volume; It is particularly suitable for wind power, automotive recyclable composite materials and prepreg fields, and has great application prospects.

[0038] In some preferred embodiments of the present application, m R1s are independently selected from any one of hydrogen and C1-C6 alkyl, and m R2s are independently selected from substituted or unsubstituted C1-C30 Alkyl, substituted or unsubstituted C1~C 30 Alkyl ether group, substituted or unsubstituted C1~C 30 Alkyl sulfide group, substituted or unsubstituted C1~C 20 Siloxane, substituted or unsubstituted C6~C 30 Aryl, substituted or unsubstituted C7~C 30 any one of the arylalkyl groups of 30 Alkylene, substituted or unsubstituted C1~C 20 Alkylene ether group, substituted or unsubstituted C1~C 30 Alkylene sulfide group, substituted or unsubstituted C1~C 20 Siloxane, substituted or unsubstituted C6~C 30 Arylene, substituted or unsubstituted C7~C 30 In order to further improve the comprehensive properties of the epoxy adduct of polysilazane, the m R1s are independently selected from any one or more of hydrogen and C1-C3 alkyl, and R3 and R4 are independently selected from substituted or unsubstituted C6-C 30 Arylene, substituted or unsubstituted C7~C 30 When R1 is methyl, and R3 and R4 are independently selected from -ph-C(CH3)2-ph-, or -ph-CH2-ph-, the comprehensive properties of the epoxy adduct of polysilazane are significantly improved, and the raw materials for preparation are cheaper and more readily available, making it easier to produce.

[0039] According to another typical embodiment of the present application, a method for preparing the epoxy adduct of the above-mentioned polysilazane is provided, and the preparation method comprises: step S1, reacting a polysilazane having a structure of formula II with a primary amine under the action of a first catalyst to obtain a secondary amine having a structure of formula III;

[0040]

[0041] In the formula, m is an integer of 3 to 20, and the m R1s are independently selected from hydrogen and C1 to C 10 any one of the alkyl groups of 50 Alkyl, substituted or unsubstituted C1~C 60 Alkyl ether group, substituted or unsubstituted C1~C 50 Alkyl sulfide group, substituted or unsubstituted C1~C 50 Siloxane, substituted or unsubstituted C6~C 50Aryl, substituted or unsubstituted C7~C 50 Any one of the aralkyl groups;

[0042] Step S2, mixing a secondary amine having a structure of Formula III with a multifunctional epoxy resin at a weight ratio of 1:5 to 50, and performing a ring-opening addition reaction to obtain an epoxy adduct of polysilazane.

[0043] The epoxy adduct of polysilazane prepared by the above-mentioned preparation method is cured together with epoxy resin and curing agent to form a thermosetting three-dimensional network structure polymer, and the three-dimensional network structure of the polymer can be gradually dissociated and broken in an acidic proton solvent, so that the insoluble epoxy cured product is decomposed to achieve the purpose of recovery. The epoxy adduct of the above-mentioned polysilazane prepared, due to the presence of polysilazane, has higher heat resistance than general epoxy resin. The epoxy adduct of the polysilazane can be used to prepare recyclable thermosetting epoxy resin and fiber-reinforced recyclable epoxy resin composite materials, prepregs, etc., containing the fiber-reinforced recyclable epoxy resin composite material of the epoxy adduct of the polysilazane of the present application, can realize the separation of epoxy resin matrix and fiber, realize the recovery and reuse of fiber reinforcement, and facilitate the waste parts processing and material recovery of epoxy resin materials with a larger volume; It is particularly suitable for wind power, automobiles, and transformers. Recyclable composite materials and prepreg fields.

[0044] The above step S1 reacts the polysilazane containing Si-H with the primary amine, and grafts the secondary amine on the side group of the polysilazane. In some embodiments of the present application, in the reaction, the first catalyst used is a quaternary ammonium salt, the reaction rate is suitable, and the reaction conditions are relatively mild. The quaternary ammonium salt can be a monoquaternary ammonium salt or a polyquaternary ammonium salt, and can be selected from existing quaternary ammonium salt compounds. There are no special requirements and no detailed introduction is given here. Exemplarily, the quaternary ammonium salt can be ammonium chloride, ammonium bromide, ammonium sulfate, and ammonium nitrate. The reaction can be carried out in a wide temperature range, such as 10 to 150°C. In some embodiments, the above reaction is carried out at room temperature, such as 15 to 35°C, and the reaction time is 12 to 72h. Increasing the reaction temperature can accelerate the reaction of polysilazane and primary amine, such as at 120°C, the reaction can be completed in 6 to 12h.

[0045] The ratio of polysilazane to primary amine can be determined according to the stoichiometric ratio of the reaction. For example, the ratio of the molar number of Si-H functional groups in the polysilazane having the structure of Formula II to the molar number of primary amine is 1:1 to 1:2. There is no particular limitation on the primary amine to be used in the reaction. Considering the properties of the epoxy adduct of the final product polysilazane, preferably, the primary amine is selected from the group R2 connected to the amino group and is substituted or unsubstituted C1 to C 30 Alkyl, substituted or unsubstituted C1~C 30 Alkyl ether group, substituted or unsubstituted C1~C30 Alkyl sulfide group, substituted or unsubstituted C1~C 20 Siloxane, substituted or unsubstituted C6~C 30 Aryl, substituted or unsubstituted C7~C 30 Any one of the aralkyl groups.

[0046] In some embodiments of the present application, the primary amine is selected from any one or more of aliphatic amines, alicyclic amines and aromatic amines, wherein the aliphatic amine can be selected from diethylenetriamine, triethylenetetramine, tetraethylenepentamine, divinylpropylamine, and polyetheramines; the alicyclic amine can be selected from menthanediamine, isophoronediamine, N-aminoethylpiperazine, bis(4-aminocyclohexyl)methane, and bis(4-amino-3-methylcyclohexyl)methane; the aromatic amine can be selected from meta-phenylenediamine, diaminodiphenylmethane, diaminodiphenyl sulfone, and meta-phenylenediamine. The above reaction with Si-H-containing polysilazane is easier to carry out, and the epoxy adduct of the prepared polysilazane has excellent performance.

[0047] In the above step S2, the polysilazane with the side-grafted secondary amine undergoes a ring-opening addition reaction with an excess of a multifunctional epoxy resin to obtain an epoxy adduct of the polysilazane. In order to further improve the efficiency of the above ring-opening addition reaction, in the preferred step S2, the reaction temperature is 60 to 180°C, and the more preferred reaction time is 4 to 24 hours, and the obtained product has better performance. In some preferred embodiments of the present application, the molar ratio of the secondary amine having the structure of formula III to the epoxy group of the multifunctional epoxy resin is 1:10 to 100, the reaction speed is fast, and the prepared epoxy adduct of the polysilazane has better comprehensive performance.

[0048] According to another typical embodiment of the present application, a recyclable epoxy resin is provided. The recyclable epoxy resin is obtained by curing a recyclable epoxy resin composition, wherein the recyclable resin composition comprises an epoxy resin, a curing agent and the epoxy adduct of the above-mentioned polysilazane.

[0049] The recyclable epoxy resin has higher heat resistance than general epoxy resin due to the epoxy adduct containing the above-mentioned polysilazane, and because it can be gradually dissociated in an acidic proton solvent, the recycling of resin is realized. The epoxy adduct of the polysilazane can be used to prepare recyclable thermosetting epoxy resin and fiber-reinforced recyclable epoxy resin composite materials, prepregs, etc. The fiber-reinforced recyclable epoxy resin composite containing the epoxy adduct of the polysilazane of the present application can realize the separation of epoxy resin matrix and fiber, and realize the recycling and reuse of fiber reinforcement; It is particularly suitable for wind power, automotive recyclable composite materials and prepreg fields.

[0050] In some embodiments of the present application, in order to better coordinate the performance of the recyclable resin in use and the performance after recycling, the content of the epoxy adduct of polysilazane in the recyclable resin composition is 0.1-20wt%, preferably 0.1-15wt%. The epoxy resin in the above-mentioned recyclable epoxy resin composition can be selected from the prior art without special restrictions, for example, the epoxy resin is selected from any one or more of E51 and E44. The specific curing conditions of the composition can be determined according to the type and content of the epoxy resin in the composition, and there is no special restriction in the present application.

[0051] The curing conditions of the above-mentioned recyclable resin composition can be determined according to the types of epoxy resin and curing agent in the recyclable epoxy resin composition. In some embodiments of the present application, when the added amine in the epoxy adduct of polysilazane is a fatty amine, the curing temperature is room temperature to 120°C, and when the added amine is an aromatic amine, the curing is carried out at 150 to 180°C.

[0052] In some embodiments of the present application, the recyclable resin composition also includes an epoxy diluent. Preferably, the epoxy diluent includes any one or more of butanediol diglycidyl ether, pentaerythritol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol triglycidyl ether and n-butyl glycidyl ether.

[0053] In some typical embodiments of the present application, the above-mentioned recyclable resin composition also includes fibers, which further enhance the strength of the recyclable resin and prepare fiber-reinforced recyclable epoxy resin composite materials. Under certain recycling conditions, the epoxy resin matrix and the fibers can be separated, thereby achieving the purpose of recycling and reusing the fiber reinforcement.

[0054] According to another typical embodiment of the present application, a method for recycling a recyclable epoxy resin is provided, that is, the above-mentioned recyclable epoxy resin is immersed in an acidic proton solvent at 0 to 70°C, so that it can be gradually dissociated and crushed to achieve the recycling and reuse of the resin. Similarly, the recycling method can also be used to achieve the separation of the resin matrix and the fiber in the fiber-reinforced recyclable epoxy resin composite material.

[0055] Above-mentioned acidic protic solvent can be selected from prior art, does not have special requirements.In some embodiments of the present application, acidic protic solvent is selected from one or several mixing in formic acid, acetic acid, propionic acid, propyl formic acid, acrylic acid, propionic acid, hypochlorous acid, dichloroacetic acid, trifluoroacetic acid, methanesulfonic acid, hydrobromic acid, hydrofluoric acid, lactic acid, perchloric acid, hydrobromic acid, chloric acid, oxalic acid, sulfurous acid, phosphoric acid, pyruvic acid, nitrous acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, citric acid, p-toluenesulfonic acid, benzoic acid, salicylic acid, phthalic acid.Preferably any one or more in formic acid, acetic acid, propionic acid, propyl formic acid, acrylic acid, propionic acid, hypochlorous acid, dichloroacetic acid, methanesulfonic acid, hydrobromic acid, lactic acid, hydrobromic acid, chloric acid, oxalic acid, sulfurous acid, phosphoric acid, pyruvic acid, nitrous acid, sulfuric acid, hydrochloric acid, nitric acid, p-toluenesulfonic acid, benzoic acid, salicylic acid and phthalic acid. In order to further increase the resin dissociation rate, the pH value of the acidic protic solvent is preferably controlled to be 1-3.

[0056] According to another typical embodiment of the present application, there is provided an application of the above-mentioned recyclable epoxy resin in composite materials or prepregs for wind turbine blades and automobiles. The recyclable epoxy resin has higher heat resistance than general epoxy resins due to the epoxy adducts containing the above-mentioned polysilazane, and because it can be gradually dissociated in acidic proton solvents, the recycling of resins is realized. The epoxy adducts of the polysilazane can be used to prepare recyclable thermosetting epoxy resins and fiber-reinforced recyclable epoxy resin composite materials, prepregs, etc. The fiber-reinforced recyclable epoxy resin composites containing the epoxy adducts of the polysilazane of the present application can realize the separation of epoxy resin matrix and fiber, and realize the recycling and reuse of fiber reinforcement; solve the problem that traditional thermosetting epoxy resins cannot be repeatedly processed and recycled, and are particularly suitable for wind power, automobiles, and transformers. Recyclable composite materials and prepreg fields.

[0057] The beneficial effects that can be achieved by the present application will be further explained below with reference to embodiments.

[0058] Example 1

[0059] A preparation process of recyclable epoxy resin OPSZ-TS51 for wind turbine blades comprises the following steps:

[0060] Step 1, reacting KB8802 polysilazane (OPSZ) and polyetheramine D230 under the action of quaternary ammonium salt catalyst tetramethylammonium fluoride, wherein the mass ratio of KB8802 polysilazane to polyetheramine D230 is 1:2.2, and the amount of tetramethylammonium fluoride is 0.05% of the sum of the mass of the two reaction raw materials, reacting at 80° C. for 24 hours, and grafting secondary amine (OPSZ-N) on the side group of polysilazane;

[0061] Step 2: OPSZ-N and epoxy resin (E51) are mixed at a weight ratio of 1:30, and reacted at 80° C. for 15 hours to produce an epoxy adduct OPSZ-EP51 containing a Si-N structure;

[0062] Step 3: Evenly mix the epoxy resin (E51), E51 curing agent and 4 wt% of OPSZ-EP, and completely cure them at 120°C for 3 hours to generate a polymer with a thermosetting three-dimensional network structure, namely, the recyclable epoxy resin OPSZ-TS51. The tensile strength, flexural strength and glass transition temperature of the epoxy resin are tested. The results are shown in Table 1 below.

[0063] The recycling process of recyclable epoxy resin OPSZ-TS51 is as follows: Propionic acid, hydrochloric acid and sulfuric acid are mixed evenly, and the pH is controlled between 1 and 3 by adding deionized water. OPSZ-TS51 is immersed in the above acidic solution at 50°C. After 0.5 hours, the sample begins to soften and decompose. Within 2 hours, the sample is completely dissolved in the solution.

[0064] Step 4: Evenly mix the epoxy adduct OPSZ-EP51 prepared in step 2 with epoxy resin (E51) and D230 curing agent, and form a resin mixture in the same proportion as step 3. Use vacuum introduction process to introduce glass fiber (Jushi unidirectional glass fiber E7-UD1250-390) into the mold, and cure at 80°C for 6h to prepare a glass fiber composite sheet, wherein the mass ratio of the resin mixture to the glass fiber is 100:32. The prepared glass fiber composite sheet was tested for tensile strength, flexural strength and glass transition temperature, and the test results are shown in Table 1.

[0065] The recycling process of glass fiber composite board is as follows: the cured composite material is dissolved in an acetic acid solution with a pH value of 1 to 3, heated to 50°C, and the resin swelling phenomenon is observed after 5 minutes. After 1.5 hours, it is found that the fiber and resin are completely separated.

[0066] Example 2

[0067] A preparation process of recyclable epoxy resin OPSZ-TS44 for wind turbine blades comprises the following steps:

[0068] Step 1, reacting KB8802 polysilazane (OPSZ) and isophorone diamine under the action of a quaternary ammonium salt catalyst (CH3)3NCH2CH2OH)OH, wherein the mass ratio of KB8802 polysilazane to isophorone diamine is 1:1.6, and the amount of (CH3)3NCH2CH2OH)OH is 0.08% of the mass of the two reaction raw materials, reacting at 80°C for 36h, and grafting a secondary amine (OPSZ-N) on the side group of the polysilazane;

[0069] Step 2: OPSZ-N and epoxy resin (E44) were mixed at a ratio of 1:30 and reacted at 100° C. for 10 h to produce an epoxy adduct OPSZ-EP44 containing a Si-N structure;

[0070] Step 3: Evenly mix epoxy resin (E44), E44 curing agent and 10wt% OPSZ-EP44, and completely cure at 150°C for 3h to generate a thermosetting three-dimensional network structure polymer, which is the recyclable epoxy resin OPSZ-TS44. The tensile strength, flexural strength and glass transition temperature of the polymer were tested, and the results are shown in Table 1 below.

[0071] The recycling process of recyclable epoxy resin OPSZ-TS44 is as follows: Propionic acid and sulfuric acid are mixed evenly, and the pH is controlled between (1 and 3) by adding deionized water. OPSZ-TS44 is immersed in the above acidic solution at 60°C. After 20 minutes, the sample begins to soften and decompose. Within 3 hours, the sample is completely dissolved in the solution.

[0072] Step 4: Evenly mix the epoxy adduct OPSZ-EP51 prepared in step 2 with epoxy resin (E51+622 diluent) and D230 curing agent, and form a resin mixture in the same proportion as step 3. Use vacuum introduction process to introduce glass fiber (Jushi unidirectional glass fiber E7-UD1250-390) into the mold, and cure at 80°C for 6h to prepare a glass fiber composite sheet, wherein the mass ratio of the resin mixture to the glass fiber is 100:35. The prepared glass fiber composite sheet was tested for tensile strength, flexural strength, and glass transition temperature, and the test results are shown in Table 1.

[0073] The recycling process of glass fiber composite board is as follows: the cured composite material is dissolved in an acetic acid solution with a pH value of 1 to 3, heated to 60°C, and the resin swelling phenomenon is observed after 5 minutes. After 2 hours, it is found that the fiber and resin are completely separated.

[0074] Example 3

[0075] The difference from Example 1 is that in step 2, OPSZ-N and epoxy resin (E51) are mixed in a ratio of 1:5; the implementation methods of steps 3 and 4 are the same as those in Example 1, and the corresponding recyclable epoxy resin and glass fiber composite board are obtained.

[0076] The recyclable epoxy resin was recycled under the same conditions as in Example 1. After 0.5 h, the sample began to soften and decompose; within 2 h, the sample was completely dissolved in the solution.

[0077] The glass fiber composite board was heated to 60°C using the same acid solution as in Example 1. Resin swelling was observed after 5 minutes, and the fiber and resin were completely separated after 1 hour.

[0078] Example 4

[0079] The difference from Example 1 is that in steps 3 and 4, the content of epoxy adduct OPSZ-TS51 in the mixture consisting of epoxy resin (E51), E51 curing agent and recyclable epoxy resin OPSZ-TS51 is 0.1wt%;

[0080] The recyclable epoxy resin was recycled under the same conditions as in Example 1. After 1 hour, the sample began to soften and decompose. Within 4 hours, the sample was completely dissolved in the solution.

[0081] The glass fiber composite board was heated to 60° C. using the same mixed acid as in Example 1. Resin swelling was observed after 15 minutes, and the fiber and resin were completely separated after 3 hours.

[0082] Example 5

[0083] The recyclable epoxy resin OPSZ-TS51 was prepared in the manner of Example 1, except that in step 1, the same amount of KB-8804 polysilazane was used to replace KB8802 polysilazane. The implementation methods of steps 2, 3, and 4 were the same as those of Example 1, and the corresponding recyclable epoxy resin and glass fiber composite board was obtained.

[0084] The recyclable epoxy resin was recycled under the same conditions as in Example 1. After 0.5 h, the sample began to soften and decompose. Within 2 h, the sample was completely dissolved in the solution.

[0085] The glass fiber composite board was heated to 60° C. using the same acid solution as in Example 1. Resin swelling was observed after 5 minutes, and the fiber and resin were completely separated after 1.5 hours.

[0086] Example 6

[0087] The recyclable epoxy resin OPSZ-TS51 was prepared in the manner of Example 1, which differed from Example 1 in that the primary amine was replaced with the same molar amount of isophorone diamine in step 1. The implementation methods of steps 2, 3, and 4 were the same as those of Example 1, and the corresponding recyclable epoxy resin and glass fiber composite board were obtained.

[0088] The recyclable epoxy resin was recycled under the same conditions as in Example 1. After 0.5 h, the sample began to soften and decompose; within 3 h, the sample was completely dissolved in the solution.

[0089] The glass fiber composite board was prepared using the same acid solution as in Example 1, heated to 60°C, and the resin swelling phenomenon was observed after 10 minutes. After 2.5 hours, it was found that the fiber and the resin were completely separated.

[0090] Example 7

[0091] Steps 1 to 3 of this embodiment are exactly the same as those of Example 1, and the only difference between step 4 and Example 1 is that the glass fiber (Jushi unidirectional glass fiber E7-UD1250-390) is replaced by carbon fiber, model Toray T700-12K unidirectional carbon fiber.

[0092] The prepared glass fiber composite plate was subjected to performance tests such as tensile strength, flexural strength and glass transition temperature. The test results are shown in Table 1.

[0093] The recycling process of glass fiber composite board is as follows: the cured composite material is dissolved in an acetic acid solution with a pH value of 1 to 3, heated to 50°C, and the resin swelling phenomenon is observed after 5 minutes. After 1.5 hours, it is found that the fiber and resin are completely separated.

[0094] Comparative Example 1

[0095] The epoxy resin (E51) and the E51 curing agent in the same proportion as in Example 1 were uniformly mixed and completely cured at 120° C. for 3 hours to generate an epoxy resin cured product. The same recycling conditions as in Example 1 were used, but no softening and decomposition phenomenon occurred, and recycling could not be achieved.

[0096] Comparative Example 2

[0097] The difference from Example 1 is that in step 2, OPSZ-N and epoxy resin (E51) are mixed in a mass ratio of 1:2. The implementation methods of steps 3 and 4 are the same as those of Example 1, and the corresponding recyclable epoxy resin and glass fiber composite board is obtained.

[0098] The recyclable epoxy resin was recycled under the same conditions as in Example 1. After 1 hour, the sample began to soften and decompose; within 6 hours, the sample was completely dissolved in the solution.

[0099] The glass fiber composite board was heated to 60° C. using the same mixed acid as in Example 1. Resin swelling was observed after 20 minutes. After 5 hours, it was found that the fiber and the resin were completely separated.

[0100] Comparative Example 3

[0101] The recyclable epoxy resin OPSZ-TS51 was prepared in the same manner as in Example 1, except that the polyetheramine D230 was replaced with the same weight of DMP30 in step 1. The implementation methods of steps 2, 3, and 4 were the same as in Example 1, and the corresponding recyclable epoxy resin and glass fiber composite board was obtained.

[0102] The recyclable epoxy resin and glass fiber composite board were recycled in the same manner as in Example 1, and neither showed any softening, decomposition, or swelling, and could not be recycled.

[0103] The performance of the cured resins of the above embodiments and comparative examples was tested, and the test results are shown in the following table.

[0104] Table 1

[0105]

[0106] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: the epoxy adduct of polysilazane is cured together with epoxy resin and curing agent to form a thermosetting three-dimensional network structure polymer. The polymer can be gradually dissociated and broken in an acidic proton solvent to achieve the purpose of recovery. The epoxy adduct of the above-mentioned polysilazane, due to the presence of polysilazane, has a higher heat resistance than general epoxy resin. The epoxy adduct of the polysilazane can be used to prepare recyclable thermosetting epoxy resins and fiber-reinforced recyclable epoxy resin composite materials, prepregs, etc., and the fiber-reinforced recyclable epoxy resin composite materials containing the epoxy adduct of the polysilazane of the present application can realize the separation of epoxy resin matrix and fiber, and realize the recovery and reuse of fiber reinforcement; It is particularly suitable for wind power, automotive recyclable composite materials and prepreg fields, and has great application prospects.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An epoxy adduct of polysilazane, characterized in that: The epoxy adduct of polysilazane has a structure as shown in Formula I, In Formula I, m is an integer of 3 to 20, and the m R1s are independently selected from hydrogen and C1 to C 10 m R2 are independently selected from substituted or unsubstituted C1 to C 50 Alkyl, substituted or unsubstituted C1~C 60 Alkyl ether group, substituted or unsubstituted C1~C 50 Alkyl sulfide group, substituted or unsubstituted C1~C 50 Siloxane, substituted or unsubstituted C6~C 50 Aryl, substituted or unsubstituted C7~C 50 R3 and R4 are each independently selected from substituted or unsubstituted C1 to C 50 Alkylene, substituted or unsubstituted C1~C 60 Alkylene ether group, substituted or unsubstituted C1~C 50 Alkylene sulfide group, substituted or unsubstituted C1~C 50 Siloxane, substituted or unsubstituted C6~C 60 Arylene, substituted or unsubstituted C7~C 60 Any one of the aralkylene groups.

2. The epoxy adduct of polysilazane according to claim 1, characterized in that The m R1s are independently selected from any one of hydrogen and C1-C6 alkyl, and the m R2s are independently selected from substituted or unsubstituted C1-C 30 Alkyl, substituted or unsubstituted C1~C 30 Alkyl ether group, substituted or unsubstituted C1~C 30 Alkyl sulfide group, substituted or unsubstituted C1~C 20 Siloxane, substituted or unsubstituted C6~C 30 Aryl, substituted or unsubstituted C7~C 30 wherein R3 and R4 are independently selected from substituted or unsubstituted C1 to C 30 Alkylene, substituted or unsubstituted C1~C 20 Alkylene ether group, substituted or unsubstituted C1~C 30 Alkylene sulfide group, substituted or unsubstituted C1~C 20 Siloxane, substituted or unsubstituted C6~C 30 Arylene, substituted or unsubstituted C7~C 30 Any one of the aralkylene groups.

3. The epoxy adduct of polysilazane according to claim 2, characterized in that: The m R1s are independently selected from any one of hydrogen and C1-C3 alkyl, and the R3 and R4 are independently selected from substituted or unsubstituted C6-C 30 Arylene, substituted or unsubstituted C7~C 30 Any one of the aralkylene groups.

4. The epoxy adduct of polysilazane according to claim 2, characterized in that: The R1 is a methyl group, and the R3 and R4 are each independently selected from any one of -ph-C(CH3)2-ph-, or -ph-CH2-ph-.

5. A method for preparing the epoxy adduct of polysilazane according to any one of claims 1 to 4, characterized in that: include: Step S1, reacting a polysilazane having a structure of formula II with a primary amine under the action of a first catalyst to obtain a secondary amine having a structure of formula III; In the formula, m is an integer of 3 to 20, and the m R1s are independently selected from hydrogen and C1 to C 10 any one or more of the alkyl groups of 50 Alkyl, substituted or unsubstituted C1~C 60 Alkyl ether group, substituted or unsubstituted C1~C 50 Alkyl sulfide group, substituted or unsubstituted C1~C 50 Siloxane, substituted or unsubstituted C6~C 50 Aryl, substituted or unsubstituted C7~C 50 Any one of the aralkyl groups; Step S2, mixing the secondary amine having the structure of formula III with a multifunctional epoxy resin in a weight ratio of 1:5 to 50, and performing a ring-opening addition reaction to obtain the epoxy adduct of the polysilazane.

6. The preparation method according to claim 5, characterized in that: The first catalyst is a quaternary ammonium salt.

7. The preparation method according to claim 6, characterized in that: In the step S1, the ratio of the molar number of Si-H functional groups in the polysilazane having the structure of formula II to the molar number of primary amine is 1:1 to 1:

2.

8. The preparation method according to claim 6, characterized in that: The primary amine is selected from any one or more of aliphatic amines, alicyclic amines and aromatic amines.

9. The preparation method according to claim 5, characterized in that: In the step S2, the reaction temperature is 60-180°C.

10. The preparation method according to claim 9, characterized in that: In step S2, the reaction time is 4-24 hours.

11. The preparation method according to claim 9, characterized in that: In the step S2, the molar ratio of the secondary amine having the structure of formula III to the epoxy group of the multifunctional epoxy resin is 1:10-100.

12. A recyclable epoxy resin, characterized in that: The recyclable epoxy resin is obtained by curing a recyclable epoxy resin composition. The recyclable resin composition comprises an epoxy resin, a curing agent and the epoxy adduct of the polysilazane according to any one of claims 1 to 4.

13. The recyclable epoxy resin according to claim 12, characterized in that The content of the epoxy adduct of polysilazane in the recyclable resin composition is 0.1 to 20 wt %.

14. The recyclable epoxy resin according to claim 13, characterized in that The content of the epoxy adduct of polysilazane in the recyclable resin composition is 0.1 to 15 wt %.

15. The recyclable epoxy resin according to claim 13, characterized in that The epoxy resin is selected from any one or more of E51 and E44.

16. The recyclable epoxy resin according to claim 13, characterized in that The recyclable resin composition also includes an epoxy diluent.

17. The recyclable epoxy resin according to claim 16, characterized in that The epoxy diluent includes any one or more of butanediol diglycidyl ether, pentaerythritol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol triglycidyl ether and n-butyl glycidyl ether.

18. The recyclable epoxy resin according to claim 12, characterized in that: The recyclable resin composition also includes fibers.

19. A method for recycling a recyclable epoxy resin according to any one of claims 12 to 18, characterized in that: The recyclable epoxy resin according to any one of claims 12 to 18 is immersed in an acidic protic solvent at 0 to 70°C.

20. The recycling method according to claim 19, characterized in that: The acidic proton solvent is selected from one of formic acid, acetic acid, propionic acid, propionic acid, acrylic acid, propionic acid, hypochlorous acid, dichloroacetic acid, trifluoroacetic acid, methanesulfonic acid, hydrobromic acid, hydrofluoric acid, lactic acid, perchloric acid, hydrobromic acid, chloric acid, oxalic acid, sulfurous acid, phosphoric acid, pyruvic acid, nitrous acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, citric acid, p-toluenesulfonic acid, benzoic acid, salicylic acid, and phthalic acid, or a mixture of several of them.

21. The recycling method according to claim 20, characterized in that: The acidic protic solvent is any one or more of formic acid, acetic acid, propionic acid, propanoic acid, acrylic acid, propionic acid, hypochlorous acid, dichloroacetic acid, methanesulfonic acid, hydrobromic acid, lactic acid, hydrobromic acid, chloric acid, oxalic acid, sulfurous acid, phosphoric acid, pyruvic acid, nitrous acid, sulfuric acid, hydrochloric acid, nitric acid, p-toluenesulfonic acid, benzoic acid, salicylic acid and phthalic acid.

22. The recycling method according to claim 20, characterized in that: The pH value of the acidic protic solvent is controlled to be 1-3.

23. Use of the recyclable epoxy resin according to any one of claims 12 to 18 in composite materials or prepregs for wind turbine blades and automobiles.

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