Epoxy monomer based on bicyclic acetal structure, preparation method and application thereof

Abstract

The present invention discloses an epoxy monomer based on a bicyclic acetal structure, its preparation method and applications. The structure of the epoxy monomer based on the bicyclic acetal structure is shown in the following formula: #imgabs0# wherein, R1 is any one or more of -H, -CH3, -OCH3, -OC2H5. The preparation method of the epoxy monomer provided by the present invention has a simple process and is easy to be industrially produced. The obtained epoxy resin product has excellent mechanical properties and heat resistance, and at the same time has a high glass transition temperature, thermal stability, tensile strength, and good degradation and recycling performance. It can be applied to fields such as degradable plastics, coatings, adhesives, and composite materials, and has good economic applicability and industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the field of degradable polymer materials, and particularly to an epoxy monomer based on a bicyclic acetal structure, a preparation method thereof, and an application thereof in thermosetting resins. Background Art

[0002] Thermosetting plastics have excellent thermal properties, mechanical properties, dimensional stability, solvent resistance, and insulation properties, etc., and are widely used in daily household, aerospace, transportation, and construction chemical industries, etc., playing an irreplaceable role in the national economy and daily life. However, since they will form a permanent cross-linked network after curing, being insoluble and infusible, it is difficult to reprocess them by extrusion or injection molding like traditional thermoplastic plastics. Therefore, when thermosetting plastics are used up, they are usually post-treated by incineration or landfill, which will undoubtedly cause serious waste of resources and environmental pollution.

[0003] Developing new degradable thermosetting plastics helps to solve this problem. At present, the widely adopted strategy is to introduce dynamic covalent bonds such as ester bonds, imine bonds, borate bonds, disulfide bonds, etc. into the network of thermosetting resins to achieve the degradation of thermosetting resins and even the recycling of raw materials under certain stimuli. In existing degradable thermosetting resins, dynamic covalent bonds usually exist in monomers or cross-linking agents, or exist in the form of cross-linking points. When dynamic covalent bonds exist in monomers or cross-linking agents, most of the degradation products of the resin are complex oligomers or small molecules, making it difficult to reuse the degradation products; while when structures such as imine bonds, borate bonds, and hexahydro-s-triazine exist in the form of cross-linking points, small molecules such as water will be released during re-curing, which has strict requirements for the curing process. Summary of the Invention

[0004] The main object of the present invention is to provide an epoxy monomer based on a bicyclic acetal structure and a preparation method thereof to overcome the deficiencies of the prior art.

[0005] Another object of the present invention is to provide an application of the aforementioned epoxy monomer based on a bicyclic acetal structure.

[0006] To achieve the aforementioned invention objects, the technical solutions adopted by the present invention include:

[0007] Some embodiments of the present invention provide an epoxy monomer based on a bicyclic acetal structure, and the structural formula of the epoxy monomer is shown as formula (I):

[0008]

[0009] Wherein, R1 is any one or more of -H, -CH3, -OCH3, -OC2H5, etc.

[0010] Some embodiments of the present invention also provide a diphenol intermediate based on a bicyclic acetal structure, and the structural formula of the diphenol intermediate is shown in Formula (II):

[0011]

[0012] Wherein, R1 is any one or more of -H, -CH3, -OCH3, -OC2H5, etc.

[0013] Some embodiments of the present invention also provide a preparation method of an epoxy monomer based on a bicyclic acetal structure, which includes:

[0014] Carrying out a first reaction on a first homogeneous mixed reaction system containing a hydroxybenzaldehyde compound, dipentaerythritol, a first catalyst, a first solvent and a second solvent to obtain a diphenol intermediate based on a bicyclic acetal structure;

[0015] Carrying out a second reaction on a second mixed reaction system containing the diphenol intermediate based on a bicyclic acetal structure, a second catalyst, epichlorohydrin and an aqueous solution of a strong basic substance to obtain an epoxy monomer based on a bicyclic acetal structure.

[0016] Embodiments of the present invention also provide an epoxy monomer based on a bicyclic acetal structure prepared by the foregoing preparation method.

[0017] Embodiments of the present invention also provide an epoxy resin, which is obtained by curing and crosslinking the foregoing epoxy monomer based on a bicyclic acetal structure.

[0018] Embodiments of the present invention also provide the application of the epoxy resin in the fields of preparing degradable and recyclable plastics, coatings, adhesives, composite materials or aerospace materials, etc.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1) The epoxy resin prepared by the present invention has excellent thermal properties and mechanical properties, including a relatively high glass transition temperature (>160 °C) and heat distortion temperature, as well as good thermal stability (initial thermal degradation temperature >300 °C). At the same time, the obtained epoxy resin has a high tensile strength (>65 MPa), modulus (>2 GPa) and elongation at break (>5), which can meet various application requirements;

[0021] 2) The epoxy monomer provided by the present invention contains two cyclic acetal structures and can be degraded under acidic conditions after curing. The degradation products include the starting material dipentaerythritol and a new tetrafunctional aldehyde compound (which can be used for the preparation of polyimide thermosetting resins), realizing the effective utilization of the degradation products, and can be further extended to curing agents and other thermosetting resins, which has positive significance for promoting the development of thermosetting resins;

[0022] 3) The preparation process of the epoxy monomer provided by the present invention is simple, easy to operate, has good controllability, is easy to implement, is suitable for large-scale industrial production, and can be applied to fields such as degradable and recyclable plastics, coatings, adhesives, and composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is the nuclear magnetic resonance hydrogen spectrum of the diphenol intermediate obtained in Example 1 of the present invention.

[0025] Figure 2 It is the nuclear magnetic resonance hydrogen spectrum of the epoxy monomer obtained in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] As mentioned above, in view of the deficiencies of the prior art, the inventors of this case have conducted extensive and in-depth research and have been able to propose the technical solution of the present invention. The epoxy monomer can be obtained by the acetal reaction and epoxidation reaction of hydroxybenzaldehyde compounds and dipentaerythritol. It can be mass-produced using existing chemical equipment, and has the advantages of high yield and simple process. The polymer prepared from this epoxy monomer has excellent properties in terms of strength, modulus, and creep resistance, and also has a relatively high glass transition temperature and heat distortion temperature. At the same time, the two cyclic acetal structures enable the polymer to have the property of degradation and recycling.

[0027] In the present invention, by utilizing the characteristic that the acetal bond can be hydrolyzed under acidic conditions, it is introduced into the thermosetting plastic through structural design to achieve controllable degradation and recycling under acidic conditions. Hydroxybenzaldehyde substances are reacted with dipentaerythritol to prepare a diphenol compound with two six-membered cyclic acetal structures in its structure. Further reaction with epichlorohydrin, etc. can synthesize a new type of epoxy resin. At the same time, due to the connection of the benzene ring with the cyclic acetal and the high-density hydrogen bonds brought by the hydroxyl groups in the monomer structure, the obtained material has good thermal and mechanical properties. At the same time, due to the presence of two six-membered cyclic acetal structures in its structure, after curing, it can be degraded and recycled to obtain dipentaerythritol and the corresponding tetrafunctional aldehyde compounds. Among them, dipentaerythritol can be used again for the synthesis of epoxy monomers, while the tetrafunctional aldehyde compounds can be cross-linked with diamines / triamines to prepare polyimide thermosetting resins and other uses, realizing the closed-loop recycling of thermosetting resins.

[0028] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] First, it should be noted that the interpretations of the terms described in the specification of the present invention are well-known to those skilled in the art.

[0030] A structural formula of an epoxy monomer based on a bicyclic acetal structure provided by one aspect of the embodiments of the present invention is shown in Formula (I):

[0031]

[0032] In Formula (I), R1 is any one or more of -H, -CH3, -OCH3, -OC2H5, etc.

[0033] The above epoxy monomer based on the bicyclic acetal structure contains two bicyclic acetal structures and can be degraded after curing to obtain a reusable product. By introducing the bicyclic acetal structure, the present invention endows epoxy polymers with more excellent mechanical properties and heat resistance, and enables the material to have a higher glass transition temperature and heat distortion temperature. At the same time, the bicyclic acetal structure can be broken under acidic conditions, making the polymer have degradation and recycling properties.

[0034] Another aspect of the embodiments of the present invention provides a diphenol intermediate based on a bicyclic acetal structure, characterized in that the structural formula of the diphenol intermediate based on the bicyclic acetal structure is shown in Formula (II):

[0035]

[0036] In Formula (II), R1 is any one or more of -H, -CH3, -OCH3, -OC2H5, etc.

[0037] Another aspect of the embodiments of the present invention also provides a preparation method of an epoxy monomer (shown in Formula (I)) based on a bicyclic acetal structure, which includes:

[0038] Carrying out a first reaction on a first homogeneous mixed reaction system containing a hydroxybenzaldehyde compound, dipentaerythritol, a first catalyst (also referred to as "Catalyst A"), a first solvent (also referred to as "Solvent B") and a second solvent (also referred to as "Solvent C") to obtain a diphenol intermediate based on a bicyclic acetal structure (abbreviated as "diphenol intermediate");

[0039] Subject the second reaction mixture system containing the diphenol intermediate, a second catalyst (also referred to as "Catalyst D"), epichlorohydrin, and an aqueous solution of a strong base to a second reaction to obtain an epoxy monomer based on a bicyclic acetal structure.

[0040] In some embodiments, the structural formula of the diphenol intermediate based on a bicyclic acetal structure is as shown in Formula (II):

[0041]

[0042] Wherein, R1 is any one or more of -H, -CH3, -OCH3, -OC2H5, etc.

[0043] In some embodiments, the hydroxybenzaldehyde compounds include p-hydroxybenzaldehyde, 2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, 4-hydroxy-3-methylbenzaldehyde, 4-hydroxy-2-methylbenzaldehyde, 2-hydroxy-3-methylbenzaldehyde, 2-hydroxy-4-methylbenzaldehyde, 3-hydroxy-4-methylbenzaldehyde, 4-hydroxy-3,5-dimethylbenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 4-hydroxy-2-methoxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde, 3-hydroxy-4-methoxybenzaldehyde, 4-hydroxy-3,5-dimethoxybenzaldehyde, 4-hydroxy-3-ethoxybenzaldehyde, 4-hydroxy-2-ethoxybenzaldehyde, 2-hydroxy-3-ethoxybenzaldehyde, 2-hydroxy-4-ethoxybenzaldehyde, 3-hydroxy-4-ethoxybenzaldehyde, 4-hydroxy-3,5-diethoxybenzaldehyde, etc., and any one or a combination of two or more thereof, but not limited thereto.

[0044] In some embodiments, the molar ratio of the hydroxybenzaldehyde compounds to dipentaerythritol is 2 to 20:1.

[0045] In some embodiments, the first catalyst (also referred to as "Catalyst A") includes any one or a combination of two or more of p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, citric acid, etc., but not limited thereto.

[0046] In some embodiments, the mass ratio of the first catalyst to the hydroxybenzaldehyde compounds is 1:5 to 100.

[0047] In some embodiments, the first solvent (also referred to as "Solvent B") is an organic solvent, and its function is to dissolve reactants, such as (hydroxybenzaldehyde compounds, dipentaerythritol, Catalyst A, etc.). Solvent B may specifically include any one or a combination of two or more of tetrahydrofuran, dioxane, acetone, butanone, N,N-dimethylformamide, dimethyl sulfoxide, etc., but not limited thereto.

[0048] Furthermore, the mass ratio of the first solvent to the hydroxybenzaldehyde compound is 1 to 20:1.

[0049] In some other preferred embodiments, the first homogeneous mixing reaction system further includes a second solvent, also known as "solvent C", which is an organic solvent and functions to carry out the water generated in the acetalization reaction.

[0050] Furthermore, solvent C may specifically include any one or a combination of two or more of petroleum ether, n-hexane, cyclohexane, toluene, benzene, etc., but is not limited thereto.

[0051] Furthermore, the mass ratio of the second solvent to the hydroxybenzaldehyde compound is 1 to 20:1.

[0052] In some embodiments, the temperature of the first reaction is 50 to 120 °C and the time is 0.5 to 72 h.

[0053] In some embodiments, the second catalyst (also known as "catalyst D") includes any one or a combination of two or more of tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltriethylammonium chloride, tetrabutylammonium hydrogensulfate, etc., but is not limited thereto.

[0054] Furthermore, the strong basic substance contained in the aqueous solution of the strong basic substance includes any one or a combination of two or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, etc., but is not limited thereto.

[0055] Furthermore, the mass ratio of the second catalyst to the diphenol intermediate is 1:5 to 100.

[0056] In some embodiments, the mass ratio of epichlorohydrin to the diphenol intermediate is 1 to 30:1.

[0057] Furthermore, the mass fraction of the aqueous solution of the strong basic substance is 5% to 50%.

[0058] Furthermore, the mass ratio of the strong basic substance in the aqueous solution of the strong basic substance to the diphenol intermediate is 1 to 20:1.

[0059] In some embodiments, the second reaction is divided into two steps (pre-reaction and reaction after adding the aqueous solution of the strong basic substance), and the overall temperature range is 0 °C to 110 °C, and the reaction time is 0.5 h to 72 h.

[0060] Furthermore, in the present invention, a second catalyst and epichlorohydrin can be first added to the diphenol intermediate for a preliminary reaction at a temperature of 50 to 110° C. for a reaction time of 0.5 h to 36 h, and then a strong alkaline substance aqueous solution is added for a reaction at a temperature of 0 to 50° C. for a reaction time of 0.5 h to 72 h, thereby reducing by-products and improving the yield of epoxy monomers.

[0061] Among them, in some more specific implementation cases, the preparation method of the epoxy monomer based on the bicyclic acetal structure comprises the following steps:

[0062] a) fully mixing a hydroxybenzaldehyde compound, dipentaerythritol, a catalyst A, an organic solvent B, and an organic solvent C, and reacting to obtain a diphenol intermediate based on a bicyclic acetal structure;

[0063] b) The diphenol intermediate, catalyst D and epichlorohydrin are mixed for pre-reaction, and then a strong alkaline aqueous solution is added dropwise to obtain an epoxy monomer based on a bicyclic acetal structure after the reaction.

[0064] In summary, the preparation method of the epoxy monomer of the present invention is simple in process and easy for industrial production. The prepared product has excellent mechanical properties and heat resistance, as well as a high glass transition temperature and thermal stability, tensile strength and good degradation and recycling performance. It can be applied to the fields of degradable plastics, coatings, adhesives and composite materials, and has good economic applicability and industrial application prospects.

[0065] Another aspect of the embodiments of the present invention further provides an epoxy monomer based on a bicyclic acetal structure prepared by the aforementioned preparation method, and its structural formula is also shown in formula (I):

[0066]

[0067] In formula (I), R1 is any one or more of -H, -CH3, -OCH3, -OC2H5, etc.

[0068] Correspondingly, another aspect of an embodiment of the present invention further provides an epoxy resin, which is obtained by curing and cross-linking the aforementioned epoxy monomer based on the bicyclic acetal structure.

[0069] Another aspect of the embodiments of the present invention further provides the use of the aforementioned epoxy resin in the preparation of degradable and recyclable plastics, coatings, adhesives, composite materials or aerospace materials.

[0070] Correspondingly, another aspect of the embodiments of the present invention further provides a composite material, which uses the aforementioned epoxy resin as a base resin.

[0071] With the above technical solutions, the preparation method of the epoxy monomer of the present invention has a simple process and is easy to industrialize. The prepared product has excellent mechanical properties and heat resistance, as well as a relatively high glass transition temperature, heat distortion temperature, good degradation performance and recycling performance. It can be applied to the fields of degradable plastics, coatings, adhesives and composite materials, and has good economic applicability and industrial application prospects.

[0072] To further understand the present invention, the present invention will be further elaborated below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Non-essential improvements and adjustments made by those skilled in the art under the core guiding ideology of the present invention still fall within the protection scope of the present invention. The experimental methods with specific conditions in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0073] The experimental materials used in the following embodiments can be obtained from conventional biochemical reagent stores if not otherwise specified.

[0074] In the following embodiments, nuclear magnetic resonance hydrogen spectrum 1 1H-NMR was measured using a 400AVANCE III spectrometer from Bruker Corporation, 400 MHz, with deuterated dimethyl sulfoxide (DMSO-d6) as the deuterated reagent.

[0075] Example 1

[0076] (1) Take 25.4 g (0.1 mol) of dipentaerythritol, 24.4 g (0.2 mol) of p-hydroxybenzaldehyde, and 0.488 g of p-toluenesulfonic acid and dissolve them in 60 g of N,N-dimethylformamide. Add 50 g of petroleum ether and react at 90 °C for 12 h. Cool to room temperature, separate the petroleum ether by liquid separation, carry out sedimentation with a 5 wt% aqueous sodium bicarbonate solution, precipitate a white precipitate, filter by suction, wash it several times with a small amount of deionized water, and then dry it to obtain a diphenol intermediate 1 based on a cyclic acetal structure, the structural formula of which is shown in the following formula (II-I), and the yield is 90.5%. Its 1 1H-NMR is as Figure 1 shown, and the number, position and integral of the peaks in the figure correspond one by one to formula II-I.

[0077]

[0078] (2) 9.24 g of cyclic acetal diol intermediate 1 and 0.0924 g of tetrabutylammonium bromide were dissolved in 30 g of epichlorohydrin, and the reaction was carried out at 80 °C for 2 h. Then the temperature was lowered to below 5 °C, and 50 g of 40 wt% sodium hydroxide solution was added dropwise, and the reaction was carried out for 5 h. After the reaction was completed, petroleum ether was used for sedimentation, a white precipitate was precipitated, filtered by suction, washed with a small amount of ethanol, and dried to obtain an epoxy monomer, the structural formula of which is shown in the following formula (I-I), and the yield was 91.6%. Its 1 H-NMR is as Figure 2 shown.

[0079]

[0080] Example 2

[0081] (1) 25.4 g (0.1 mol) of dipentaerythritol, 304 g (2 mol) of vanillin (4-hydroxy-3-methoxybenzaldehyde), and 3.04 g of citric acid were dissolved in 600 g of N,N-dimethylformamide, 500 g of n-hexane was added, and the reaction was carried out at 120 °C for 0.5 h. After cooling to room temperature, the n-hexane was separated by liquid separation, and 5 wt% aqueous sodium bicarbonate solution was used for sedimentation, a white precipitate was precipitated, filtered by suction, washed with a small amount of deionized water for several times, and then dried to obtain cyclic acetal diol intermediate 2. Its structural formula is shown in the following formula (II-II), and the yield was 91.6%.

[0082]

[0083] (2) 10.44 g of cyclic acetal diol intermediate 2 and 0.104 g of tetrabutylammonium chloride were dissolved in 50 g of epichlorohydrin, and the reaction was carried out at 50 °C for 36 h. Then the temperature was lowered to below 5 °C, and 100 g of 40 wt% potassium hydroxide aqueous solution was added dropwise, and the reaction was carried out for 8 h. After the reaction was completed, petroleum ether was used for sedimentation, a white precipitate was precipitated, filtered by suction, washed with a small amount of ethanol, and dried to obtain an epoxy monomer, the structural formula of which is shown in the following formula (I-II), and the yield was 90.4%.

[0084]

[0085] Example 3

[0086] (1) 25.4 g (0.1 mol) of dipentaerythritol, 54.6 g (0.3 mol) of syringaldehyde (4-hydroxy-3,5-dimethoxybenzaldehyde), and 0.546 g of sulfuric acid were dissolved in 80 g of dimethyl sulfoxide, 55 g of petroleum ether was added, and the reaction was carried out at 120 °C for 0.5 h. After cooling to room temperature, the petroleum ether was separated by liquid separation, and 5 wt% aqueous sodium bicarbonate solution was used for sedimentation, a white precipitate was precipitated, filtered by suction, washed with a small amount of deionized water for several times, and then dried to obtain bicyclic acetal diol intermediate 3, the structural formula of which is shown in the following formula (II-III), and the yield was 91.5%.

[0087]

[0088] (2) Take 11.64 g of the bicyclic acetal diol intermediate 3 and 0.582 g of tetrabutylammonium bromide and dissolve them in 300 g of epichlorohydrin. React at 110 °C for 0.5 h, then cool to 0 °C and dropwise add 30 g of a 40 wt% calcium hydroxide solution. React for 8 h. After the reaction is completed, carry out sedimentation with petroleum ether to precipitate a white solid. Filter by suction, wash with a small amount of ethanol, and dry to obtain the epoxy monomer, the structural formula of which is shown as the following formula (I-III), and the yield is 90.9%.

[0089]

[0090] Example 4

[0091] (1) Take 25.4 g (0.1 mol) of dipentaerythritol, 54.4 g (0.4 mol) of 4-hydroxy-3-methylbenzaldehyde, and 0.554 g of p-toluenesulfonic acid and dissolve them in 100 g of dioxane. Add 100 g of petroleum ether and react at 100 °C for 5 h. Cool to room temperature, separate the petroleum ether by liquid separation, carry out sedimentation with a 5 wt% aqueous sodium bicarbonate solution to precipitate a white solid. Filter by suction, wash with a small amount of deionized water multiple times, and then dry to obtain the cyclic acetal diol intermediate 4, the structural formula of which is shown as the following formula (II-IV), and the yield is 90.8%.

[0092]

[0093] (2) Take 9.81 g of the cyclic acetal diol intermediate 4 and 0.15 g of benzyltriethylammonium chloride and dissolve them in 100 g of epichlorohydrin. React at 90 °C for 1 h, then cool to below 20 °C and dropwise add 25 g of a 40 wt% lithium hydroxide solution. React for 1 h. After the reaction is completed, carry out sedimentation with petroleum ether to precipitate a white solid. Filter by suction, wash with a small amount of ethanol, and dry to obtain the epoxy monomer, the structural formula of which is shown as the following formula (I-IV), and the yield is 90.9%.

[0094]

[0095] Example 5

[0096] (1) Take 25.4 g (0.1 mol) of dipentaerythritol, 90.09 g (0.6 mol) of 4-hydroxy-3,5-dimethylbenzaldehyde, and 1.8 g of phosphoric acid, dissolve them in 90 g of dimethyl sulfoxide, add 90 g of n-hexane, react at 50 °C for 30 h, cool to room temperature, separate and remove petroleum ether by liquid separation, carry out sedimentation using a 5 wt% aqueous sodium bicarbonate solution, precipitate a white solid, perform suction filtration, wash it several times with a small amount of deionized water, and then dry it to obtain the bicyclic acetal diol intermediate 5, whose structural formula is shown as the following formula (II-V), and the yield is 90.8%.

[0097]

[0098] (2) Take 10.372 g of the cyclic acetal diol intermediate 5 and 0.3 g of tetrabutylammonium hydrogen sulfate, dissolve them in 30 g of epichlorohydrin, react at 60 °C for 8 h, then cool to below 10 °C, dropwise add 50 g of a 40 wt% sodium hydroxide solution, and react for 8 h. After the reaction is completed, carry out sedimentation using petroleum ether, precipitate a white solid, perform suction filtration, wash it with a small amount of ethanol, and dry it to obtain the epoxy monomer, whose structural formula is shown as the following formula (I-IV), and the yield is 90.9%.

[0099]

[0100] Example 6

[0101] (1) Take 25.4 g of dipentaerythritol, 33.24 g of 4-hydroxy-3-ethoxybenzaldehyde, and 0.33 g of p-toluenesulfonic acid, dissolve them in 120 g of tetrahydrofuran, add 60 g of toluene, react at 50 °C for 30 h, cool to room temperature, separate and remove petroleum ether by liquid separation, carry out sedimentation using a 5 wt% aqueous sodium bicarbonate solution, precipitate a white solid, perform suction filtration, wash it several times with a small amount of deionized water, and then dry it to obtain the bicyclic acetal diol intermediate 6, whose structural formula is shown as the following formula (II-VI), and the yield is 91.5%.

[0102]

[0103] (2) Take 13.25 g of the bicyclic acetal diol intermediate 6 and 0.5 g of tetrabutylammonium bromide, dissolve them in 150 g of epichlorohydrin, react at 85 °C for 2 h, then cool to below 20 °C, dropwise add 35 g of a 40 wt% sodium hydroxide solution, and react for 2 h. After the reaction is completed, carry out sedimentation using petroleum ether, precipitate a white solid, perform suction filtration, wash it with a small amount of ethanol, and dry it to obtain the epoxy monomer, whose structural formula is shown as the following formula (I-VI), and the yield is 90.9%.

[0104]

[0105] Example 7

[0106] (1) Take 25.4 g (0.1 mol) of dipentaerythritol, 84.04 g (0.4 mol) of 4-hydroxy-3,5-diethoxybenzaldehyde, and 4.202 g of p-toluenesulfonic acid and dissolve them in 500 g of acetone. Add 500 g of cyclohexane and react at 60 °C for 24 h. Cool to room temperature, separate the petroleum ether by liquid separation, carry out sedimentation using a 5 wt% aqueous sodium bicarbonate solution, precipitate a white solid, filter by suction, wash several times with a small amount of deionized water, and then dry it to obtain the bicyclic acetal diol intermediate 7, whose structural formula is shown as the following formula (II-VII), and the yield is 90.8%.

[0107]

[0108] (2) Take 13.77 g of the bicyclic acetal diol intermediate 7 and 2.754 g of tetrabutylammonium bromide and dissolve them in 13.77 g of epichlorohydrin. React at 110 °C for 0.5 h, then cool to below 15 °C, and dropwise add 70 g of a 20 wt% lithium hydroxide solution and react for 6 h. After the reaction is completed, carry out sedimentation using petroleum ether, precipitate a white solid, filter by suction, wash with a small amount of ethanol, and dry to obtain the epoxy monomer, whose structural formula is shown as the following formula (I-VII), and the yield is 90.9%.

[0109]

[0110] Example 8

[0111] (1) Take 25.4 g (0.1 mol) of dipentaerythritol, 61.05 g (0.5 mol) of 3-hydroxybenzaldehyde, and 0.996 g of p-toluenesulfonic acid and dissolve them in 90 g of dimethyl sulfoxide. Add 70 g of n-hexane and react at 100 °C for 8 h. Cool to room temperature, separate the petroleum ether by liquid separation, carry out sedimentation using a 5 wt% aqueous sodium bicarbonate solution, precipitate a white solid, filter by suction, wash several times with a small amount of deionized water, and then dry it to obtain the cyclic acetal diol intermediate 8, whose structural formula is shown as the following formula (II-VIII), and the yield is 90.8%.

[0112]

[0113] (2) Take 9.24 g of the cyclic acetal diol intermediate 8 and 0.277 g of tetrabutylammonium bromide and dissolve them in 277.2 g of epichlorohydrin. React at 70 °C for 60 h, then cool to 0 °C, and dropwise add 370 g of a 50 wt% calcium hydroxide solution and react for 72 h. After the reaction is completed, carry out sedimentation using petroleum ether, precipitate a white solid, filter by suction, wash with a small amount of ethanol, and dry to obtain the epoxy monomer, whose structural formula is shown as the following formula (I-VIII), and the yield is 90.9%.

[0114]

[0115] Example 9

[0116] (1) 25.4 g (0.1 mol) of dipentaerythritol, 45.6 g (0.3 mol) of 3-hydroxy-4-methoxybenzaldehyde, and 9.12 g of hydrochloric acid were dissolved in 912 g of N,N-dimethylformamide, and 912 g of toluene was added. The mixture was reacted at 80° C. for 10 h, cooled to room temperature, and the petroleum ether was removed by separation. A 5 wt % aqueous solution of sodium bicarbonate was used for precipitation to precipitate a white precipitate. The precipitate was filtered, washed several times with a small amount of deionized water, and then dried to obtain a bicyclic acetal diphenol intermediate 9, whose structural formula is shown in the following formula (II-IX), and the yield is 91.5%.

[0117]

[0118] (2) 10.45 g of the dicyclic acetal diphenol intermediate 9 and 0.3135 g of tetrabutylammonium chloride were dissolved in 160 g of epichlorohydrin, reacted at 90° C. for 1.5 h, then cooled to 50° C., and 250 g of a 5 wt% calcium hydroxide solution was added dropwise, and reacted for 0.5 h. After the reaction was completed, petroleum ether was used for precipitation, a white precipitate was precipitated, filtered, washed with a small amount of ethanol, and dried to obtain an epoxy monomer, the structural formula of which is shown in the following formula (I-IX), and the yield is 90.9%.

[0119]

[0120] Example 10

[0121] 0.741g of isophorone diamine (IPDA, Aladdin) and 5g of the epoxy monomer prepared in Example 1 were dissolved in 10ml of N, N-dimethylformamide, pre-reacted at 100°C for 1h, the solvent was volatilized at 150°C, then pre-cured at 100°C for 2h, transferred to a vacuum oven for curing at 150°C for 2h, and cured at 180°C for 2h to obtain the final cured product. The glass transition temperature of the cured product was 169°C (the cured product was cut into strips with a size of 30mm*5mm*0.5mm, and measured using a dynamic thermomechanical analyzer produced by TA Company of the United States, with a heating rate of 3°C / min and a frequency of 1Hz), the initial thermal degradation temperature was greater than 300°C, the tensile strength was 71.3MPa, the tensile modulus was 2.31GPa, and the elongation at break was 8.09%, and good mechanical properties could still be maintained above 130°C. At the same time, the solidified material can be degraded at pH=1 to obtain tetraaldehyde compounds and dipentaerythritol, one of the starting materials, to achieve closed-loop recycling.

[0122] The inventors of this case also prepared the same epoxy resin as in Example 10 using the epoxy monomers obtained in Examples 2-9, and also conducted performance tests, and the results were basically consistent with those in Example 10.

[0123] In summary, the preparation method of the epoxy monomer of the present invention has a simple process and is easy to be industrially produced. The obtained product has excellent mechanical properties and heat resistance, and at the same time has a relatively high glass transition temperature and heat distortion temperature, as well as good degradation performance and recycling performance. It can be applied to the fields of degradable plastics, coatings, adhesives and composite materials, and has good economic applicability and industrial application prospects.

[0124] In addition, the inventors of this case also carried out experiments in the manner of Examples 1-10 with other raw materials and conditions listed in this specification, and corresponding effects can also be achieved. An epoxy monomer with a bicyclic acetal structure having more excellent mechanical properties and heat resistance, and at the same time having a relatively high glass transition temperature, heat distortion temperature and degradation and recycling performance can be prepared.

[0125] It should be understood that the above embodiments are only for illustrating the technical concept and characteristics of the present invention, and the purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly. It cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An epoxy monomer based on a bicyclic acetal structure, characterized in that, The structural formula of the epoxy monomer based on the bicyclic acetal structure is shown in Formula (Ⅰ): Among them, R1 is any one or more of -H, -CH3, -OCH3, -OC2H5.

2. A diphenol intermediate based on a bicyclic acetal structure, characterized in that, The structural formula of the diphenol intermediate based on the bicyclic acetal structure is shown in Formula (Ⅱ): Among them, R1 is any one or more of -H, -CH3, -OCH3, -OC2H5.

3. A preparation method of an epoxy monomer based on a bicyclic acetal structure, characterized in that, It includes: Carrying out a first reaction on a first homogeneous mixed reaction system containing a hydroxybenzaldehyde compound, dipentaerythritol, a first catalyst, a first solvent, and a second solvent to obtain a diphenol intermediate based on the bicyclic acetal structure; Carrying out a second reaction on a second mixed reaction system containing the diphenol intermediate based on the bicyclic acetal structure, a second catalyst, epichlorohydrin, and an aqueous solution of a strong basic substance to obtain an epoxy monomer based on the bicyclic acetal structure; The structural formula of the epoxy monomer based on the bicyclic acetal structure is shown in Formula (Ⅰ): The structural formula of the diphenol intermediate based on the bicyclic acetal structure is shown in Formula (Ⅱ): Among them, R1 is any one or more of -H, -CH3, -OCH3, -OC2H5; The hydroxybenzaldehyde compound is selected from any one or a combination of two or more of p-hydroxybenzaldehyde, 2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, 4-hydroxy-3-methylbenzaldehyde, 4-hydroxy-2-methylbenzaldehyde, 2-hydroxy-3-methylbenzaldehyde, 2-hydroxy-4-methylbenzaldehyde, 3-hydroxy-4-methylbenzaldehyde, 4-hydroxy-3,5-dimethylbenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 4-hydroxy-2-methoxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde, 3-hydroxy-4-methoxybenzaldehyde, 4-hydroxy-3,5-dimethoxybenzaldehyde, 4-hydroxy-3-ethoxybenzaldehyde, 4-hydroxy-2-ethoxybenzaldehyde, 2-hydroxy-3-ethoxybenzaldehyde, 2-hydroxy-4-ethoxybenzaldehyde, 3-hydroxy-4-ethoxybenzaldehyde, 4-hydroxy-3,5-diethoxybenzaldehyde; The first catalyst is selected from any one or a combination of two or more of p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, citric acid; The second catalyst is selected from any one or a combination of two or more of tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltriethylammonium chloride, tetrabutylammonium hydrogensulfate.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the hydroxybenzaldehyde compound to dipentaerythritol is 2 - 20:

1.

5. The preparation method according to claim 3, characterized in that: The mass ratio of the first catalyst to the hydroxybenzaldehyde compound is 1:5 - 100.

6. The preparation method according to claim 3, characterized in that: The first solvent is selected from any one or a combination of two or more of tetrahydrofuran, dioxane, acetone, butanone, N,N-dimethylformamide, dimethyl sulfoxide.

7. The preparation method according to claim 3, characterized in that: The mass ratio of the first solvent to the hydroxybenzaldehyde compound is 1 - 20:

1.

8. The preparation method according to claim 3, characterized in that: The second solvent is selected from any one or a combination of two or more of petroleum ether, n-hexane, cyclohexane, toluene, benzene.

9. The preparation method according to claim 3, characterized in that: The mass ratio of the second solvent to the hydroxybenzaldehyde compound is 1 - 20:

1.

10. The preparation method according to claim 3, characterized in that: The strong basic substance contained in the strong basic substance solution is selected from any one or a combination of two or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and barium hydroxide.

11. The preparation method according to claim 3, characterized in that: The mass ratio of the second catalyst to the diphenol intermediate based on the bicyclic acetal structure is 1:5 to 100.

12. The preparation method according to claim 3, wherein: The mass ratio of epichlorohydrin to the diphenol intermediate based on the bicyclic acetal structure is 1 to 30:

1.

13. The preparation method according to claim 3, characterized in that: The mass fraction of the strong basic substance aqueous solution is 5% to 50%.

14. The preparation method according to claim 3, characterized in that: The mass ratio of the strong basic substance in the strong basic substance aqueous solution to the diphenol intermediate based on the bicyclic acetal structure is 1 to 20:

1.

15. The preparation method according to claim 3, characterized in that: The temperature of the first reaction is 50 to 120 °C, and the time is 0.5 to 72 h.

16. The preparation method according to claim 3, wherein: The temperature of the second reaction is 0 °C to 110 °C, and the reaction time is 0.5 h to 72 h.

17. An epoxy resin, characterized in that, The epoxy resin is obtained by curing and cross-linking the epoxy monomer based on the bicyclic acetal structure described in claim 1.

18. Use of the epoxy resin according to claim 17 in the preparation of degradable and recyclable plastics, coatings, adhesives, composite materials or aerospace materials.

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