Bisphenol curing agent containing spiro biborate group, vegetable oil-based epoxy resin, and preparation method and application of bisphenol curing agent and vegetable oil-based epoxy resin

Abstract

The invention provides a bisphenol curing agent containing a spirobiborate group, vegetable oil-based epoxy resin as well as a preparation method and application of the bisphenol curing agent and the vegetable oil-based epoxy resin, and belongs to the technical field of fine chemical engineering. According to the method designed on the basis of a cross-linked network structure, 4-hydroxyphenylboronic acid and pentaerythritol are subjected to dehydration condensation to prepare spiro borate diphenol in one step, and the spiro borate diphenol is used for improving the structural performance of the epoxy adhesive. According to the plant oil-based epoxy resin, both spiroborate diphenol and bisphenol F contain double-benzene-ring structures, so that the molecular structure rigidity of the epoxy adhesive is improved, the cohesion strength of a contribution structure is improved, meanwhile, a B-O bond has high bond binding energy and associative reversible crosslinking characteristics, the bonding strength and reprocessing performance of the plant oil-based epoxy resin can be improved, and the plant oil-based epoxy resin can be applied to the field of adhesive materials. The plant oil-based epoxy resin can significantly improve the structure of an epoxy adhesive, and the prepared plant oil-based epoxy resin not only has better bonding strength, but also has good degradation performance and reprocessing performance.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemicals, and in particular to a bisphenol curing agent containing a spirocyclic biboric acid ester group, a vegetable oil-based epoxy resin, and a preparation method and application thereof. Background Art

[0002] Epoxy adhesive is one of the most widely used adhesive materials. Due to its excellent performance, adjustable structure, simple preparation and other advantages, it is used in a variety of fields such as aerospace, automobile manufacturing, wind power fan blades, structural high-performance resins, etc. According to the different needs of the application scenarios, the current research on epoxy adhesives is mainly to improve the application performance of adhesives by modifying and curing the cross-linking network, mainly including epoxy adhesive reinforcement and toughening modification, high-strength epoxy adhesive preparation, low-temperature / fast curing high-strength epoxy adhesive preparation, high-temperature resistant epoxy adhesive preparation, water-resistant epoxy adhesive preparation, etc. According to the demand for materials in various fields, lightweight and high-strength standards have received more and more attention, so adhesives are required to have excellent bonding strength to meet the structural requirements of materials.

[0003] At present, the performance modification of epoxy adhesives mainly focuses on the following aspects: (1) cross-linking network modification, which is to improve the structural properties of epoxy adhesives and thus improve the bonding performance by designing the structure of epoxy monomers or curing agents, such as introducing hyperbranched structures; (2) blending modification, which is to blend epoxy adhesives with other adhesives with specific excellent properties to improve the shortcomings of epoxy adhesives and improve the bonding performance of epoxy adhesives; (3) nano-hybrid modification, which is to use nano-fillers as reinforcing elements to improve the structural properties of epoxy adhesives and achieve improved bonding performance.

[0004] Patent CN202211122212.8 "A high-strength single-component epoxy adhesive composition and its preparation method" obtains a high-strength epoxy adhesive by designing a toughening agent and then compounding a curing agent, a diluent, a filler and other synergistic modified epoxy resin cross-linking system. However, most of the methods currently disclosed have complex processes and complex additives, which are not conducive to industrial applications, and epoxy resins are mainly petroleum-based products, which do not meet the current "dual carbon" requirements (or such as CN201310675056.2 "A high-strength adhesive and its preparation method and its use"). At the same time, in adhesives prepared from bio-based environmentally friendly materials such as epoxy vegetable oil, the bonding strength is much different from that of petroleum-based epoxy adhesives (such as CN202410260521.4 "A plasma-modified chitosan-cured epoxy soybean oil wood adhesive and its preparation method and application"). In addition, with the increase in the application of epoxy adhesives, after the product completes its service life, the high bonding strength makes it impossible to degrade and remove the colloid, making it difficult to reprocess and reapply, making it impossible to achieve the recycling of the material.

[0005] Moreover, there is a contradiction between high bonding strength and degradability and reprocessability, and the existing technology cannot achieve the integration of the above-mentioned properties through structural design modification. At present, there is a technology for realizing the reprocessing of epoxy adhesives by constructing epoxy hot melt adhesives, such as CN112877014B "An epoxy resin hot melt adhesive and its preparation method", which uses urea-pyrimidone as a functional structure to achieve repeated bonding. However, there are no relevant reports on the unified integration of high bonding strength, reprocessability and degradability of bio-based epoxy resin adhesives. Therefore, how to take into account the high bonding strength, rapid degradation and repeated bonding performance of adhesives is the focus and difficulty of the current development of the adhesive industry. Summary of the invention

[0006] The purpose of the present invention is to provide a bisphenol curing agent containing a spirocyclic biboric acid ester group, a vegetable oil-based epoxy resin, and a preparation method and application thereof, in view of the current background that high-strength epoxy cross-linking network cannot be balanced with degradation performance and reprocessing performance, a bio-based epoxy resin adhesive with high bonding strength, rapid degradation, and repeated bonding (reprocessing) performance is prepared.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a bisphenol curing agent containing a spirocyclic biboric acid ester group. The bisphenol curing agent containing a spirocyclic biboric acid ester group is prepared from 4-hydroxyphenylboric acid and pentaerythritol in a molar ratio of 2-2.2:1. The structure of the bisphenol curing agent containing a spirocyclic biboric acid ester group is shown in formula (I):

[0009]

[0010] The present invention also provides a method for preparing a bisphenol curing agent containing a spirocyclic biboric acid ester group, comprising the following steps:

[0011] 4-Hydroxyphenylboric acid, pentaerythritol and anhydrous ethanol are mixed, heated for reaction, and rotary evaporated to obtain a bisphenol curing agent containing a spirocyclic biboric acid ester group.

[0012] Preferably, the molar volume ratio of pentaerythritol to anhydrous ethanol is 1 mol:0.5-1L; the temperature of the heating reaction is 50-70° C., and the heating reaction time is 12-24 h.

[0013] The present invention also provides a method for preparing a plant oil-based epoxy resin using a bisphenol curing agent containing a spirocyclic biboric acid ester group, comprising the following steps:

[0014] The epoxy soybean oil, the bisphenol curing agent containing the spirocyclic biboric acid ester group, the curing agent, the catalyst and the anhydrous ethanol are stirred and mixed, heated to react under negative pressure, degassed and hot-dried to obtain the vegetable oil-based epoxy resin.

[0015] Preferably, the curing agent includes one of bisphenol F, bisphenol A and bisphenol S; the catalyst includes one of imidazole, acrylic anhydride, aniline, benzyldimethylamine and phenol.

[0016] Preferably, the molar volume ratio of the epoxidized soybean oil, the bisphenol curing agent containing spirocyclic biboric acid ester groups, the curing agent, and anhydrous ethanol is: epoxidized soybean oil: bisphenol curing agent containing spirocyclic biboric acid ester groups: curing agent: anhydrous ethanol = 1 mol: 0-2 mol: 0-2 mol: 1-1.5 L; the amount of the catalyst used is 0-20% of the weight of the epoxidized soybean oil.

[0017] Preferably, the pressure of the heating reaction under the negative pressure condition is 0.1-0.5 MPa; the heating reaction temperature is 70-100° C., and the heating reaction time is 30-60 min.

[0018] Preferably, the temperature of the heat drying is 120-160° C. and the time is 6 hours.

[0019] The present invention also provides a plant oil-based epoxy resin prepared by the method for preparing the plant oil-based epoxy resin.

[0020] The invention also provides an application of a vegetable oil-based epoxy resin as an adhesive.

[0021] The beneficial effects of the present invention compared with the prior art are:

[0022] (1) The present invention synthesizes a novel spiro borate structure that can be used as a curing agent based on a cross-linked network structure design method to improve the structural properties of epoxy adhesives. Spiro borate-based diphenol is prepared in one step by dehydrating and condensing 4-hydroxyphenylboronic acid and pentaerythritol. The compound is the main functional unit for structural modification.

[0023] (2) The present invention modifies epoxy soybean oil by compounding spiroborate-based diphenol with bisphenol F. The spiroborate-based diphenol and bisphenol F curing agent are beneficial to significantly improve the bonding strength. First, both materials contain a double benzene ring structure, which is beneficial to improve the molecular structural rigidity of the epoxy adhesive and contribute to the structural cohesive strength. Secondly, the spiroborate group in the spiroborate-based diphenol is a double six-membered ring structure, which has a structural strength gain effect similar to that of the benzene ring, further improving the cohesive strength. At the same time, the electron-deficient boron atoms in the spiroborate-based diphenol tend to combine with various substrate-rich donor groups and nucleophiles, thereby improving the interfacial bonding activity and contributing to the interfacial bonding performance. The simultaneous optimization of cohesive strength and interfacial bonding performance synergistically shares excellent bonding strength.

[0024] In addition to the above-mentioned adhesive strength enhancement effect, the BO bond also has associative reversible cross-linking properties, which gives the three-dimensional cross-linked network the ability to be reprocessed, and the adhesive exhibits repeated bonding properties. In addition, the BO bond has a high bond binding energy (809 kJ / mol), which avoids the defects of other dynamic bonding groups that reduce structural strength. The dynamic reversible cross-linking properties of BO enable it to undergo structural degradation under acidic conditions, achieving degradation and removal of colloidal materials.

[0025] (3) The present invention achieves significant improvement in the structure of epoxy adhesive based on the spirocyclic borate group, and the prepared plant oil-based epoxy resin not only has better bonding strength, but also has good degradation performance and reprocessing performance. DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0028] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0029] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] The present invention prepares a plant oil-based epoxy resin with good bonding strength, degradation performance and reprocessing performance. The preparation is mainly divided into two steps. The specific method is as follows:

[0032] (1) Preparation of bisphenol curing agent containing spirocyclic bisboronic acid ester group:

[0033] After mixing 4-hydroxyphenylboric acid, pentaerythritol and anhydrous ethanol, heating for reaction, and rotary evaporation, a bisphenol curing agent containing a spirocyclic biboric acid ester group is obtained;

[0034] (2) The method of vegetable oil-based epoxy resin comprises the following steps:

[0035] The epoxy soybean oil, the bisphenol curing agent containing the spirocyclic biboric acid ester group, the curing agent, the catalyst and the anhydrous ethanol are stirred and mixed, heated to react under negative pressure, degassed and hot-dried to obtain the vegetable oil-based epoxy resin.

[0036] The structure of bisphenol F used in the following examples is shown below:

[0037]

[0038] Example 1

[0039] Embodiment 1 of the present invention provides a method for preparing a bisphenol curing agent containing a spirocyclic biboric acid ester group, which specifically comprises the following steps:

[0040] 2 mol of 4-hydroxyphenylboric acid, 1 mol of pentaerythritol and 1 L of anhydrous ethanol were mixed, reacted at 50° C. for 24 h, and rotary evaporated to obtain a bisphenol curing agent containing a spirocyclic bisboronic acid ester group.

[0041] Example 2

[0042] Embodiment 2 of the present invention provides a method for preparing a plant oil-based epoxy resin using a bisphenol curing agent containing a spirocyclic biboric acid ester group, which specifically comprises the following steps:

[0043] 1 mol of epoxidized soybean oil (calculated here as containing 4 epoxy groups in one structure), 0.8 mol of bisphenol curing agent containing spirocyclic biboric acid ester group, 1.2 mol of bisphenol F, 20% imidazole by weight of epoxidized soybean oil, and 1.5 L of anhydrous ethanol were stirred and mixed, reacted at 100 ° C for 60 min under negative pressure of 0.1 MPa, degassed, and heated at 120 ° C for 6 h to obtain a vegetable oil-based epoxy resin.

[0044] Example 3

[0045] Example 3 of the present invention provides a method for preparing a vegetable oil-based epoxy resin using a bisphenol curing agent containing a spirocyclic bisborate group. The difference from Example 2 is that in Example 3, the amount of the bisphenol curing agent containing a spirocyclic bisborate group is 2 mol, and the amount of bisphenol F is 0 mol.

[0046] Example 4

[0047] Example 4 of the present invention provides a method for preparing a vegetable oil-based epoxy resin using a bisphenol curing agent containing a spirocyclic bisborate group. The difference from Example 2 is that in Example 4, the amount of the bisphenol curing agent containing a spirocyclic bisborate group is 0.4 mol, and the amount of bisphenol F is 1.6 mol.

[0048] Example 5

[0049] Example 5 of the present invention provides a method for preparing a vegetable oil-based epoxy resin using a bisphenol curing agent containing a spirocyclic bisborate group. The difference from Example 2 is that in Example 5, the amount of the bisphenol curing agent containing a spirocyclic bisborate group is 1.2 mol, and the amount of bisphenol F is 1.4 mol.

[0050] Example 6

[0051] Example 6 of the present invention provides a method for preparing a vegetable oil-based epoxy resin using a bisphenol curing agent containing a spirocyclic bisborate group. The difference from Example 2 is that in Example 6, the amount of the bisphenol curing agent containing a spirocyclic bisborate group is 1.6 mol, and the amount of bisphenol F is 2 mol.

[0052] Comparative Example 1

[0053] Comparative Example 1 of the present invention provides a method for preparing a vegetable oil-based epoxy resin, which is different from Example 2 in that the amount of the bisphenol curing agent containing a spirocyclic biboric acid ester group in Comparative Example 1 is 0 mol, and the amount of bisphenol F is 2 mol.

[0054] Test Example 1

[0055] Test Example 1 of the present invention detects the bonding strength performance of the vegetable oil-based epoxy resins prepared in Examples 2 to 6 and Comparative Example 1. The prepared vegetable oil-based epoxy resins are coated on the surface of the substrate, and another substrate is covered on it. After clamping, the adhesive is cured at 120° C. and 140° C. for 2 hours each to test the shear bonding strength of the cured adhesive. The specific results are shown in Table 1.

[0056] Table 1 Bonding strength properties of different vegetable oil-based epoxy resins

[0057] Grouping Bonding strength Example 2 16.24±0.81MPa Example 3 10.57±1.68MPa Example 4 12.96±0.90MPa Example 5 14.03±0.15MPa Example 6 12.84±1.47MPa Comparative Example 1 8.33±0.64MPa

[0058] It can be seen from Table 1 that when a bisphenol curing agent containing a spirocyclic biboric acid ester group is added, the bonding strength of the vegetable oil-based epoxy resin prepared by the present invention as an adhesive is significantly improved.

[0059] Test Example 2

[0060] Test Example 2 of the present invention detects the repeated bonding performance of the vegetable oil-based epoxy resins prepared in Examples 2 to 6 and Comparative Example 1. The bonded specimens that were broken in the tensile strength test of Test Example 1 were stacked in their original positions, and the broken specimens were re-bonded using a hot press at 140°C and 3MPa for 1h. The strength test was carried out according to the method of Test Example 1. The results are shown in Table 2.

[0061]

[0062] It can be seen from Table 2 that after adding the bisphenol curing agent containing the spirocyclic biboric acid ester group, the vegetable oil-based epoxy resin prepared by the present invention can be used as an adhesive for repeated bonding, and the reprocessing performance is significantly improved.

[0063] Test Example 3

[0064] Test Example 3 of the present invention tests the repeated bonding performance of the plant oil-based epoxy resins prepared in Examples 2 to 6 and Comparative Example 1, and the specific method is as follows:

[0065] 2 volumes of water were added to 8 volumes of tetrahydrofuran solvent, HCl was added to make the final concentration of the solution 0.1, 0.5, and 1.0 M, respectively. At temperatures of 20 and 50° C., the vegetable oil-based epoxy resins prepared in Examples 2 to 6 and Comparative Example 1 were added, and the time for complete degradation of the epoxy resin was recorded. The results are shown in Table 3.

[0066] Table 3 Degradation properties of vegetable oil epoxy adhesive

[0067] Grouping 0.1M HCl, 20°C 0.5M HCl, 20°C 1M HCl, 20°C 1M HCl, 50°C Example 2 752mins 560mins 325mins 125mins Example 3 488mins 400mins 264mins 88mins Example 4 1020mins 850mins 765mins 690mins Example 5 690mins 490mins 300mins 110mins Example 6 510mins 430mins 286mins 98mins Comparative Example 1 - - - -

[0068] It can be seen from Table 3 that when a bisphenol curing agent containing a spirocyclic biboric acid ester group is added, the vegetable oil-based epoxy resin prepared by the present invention has the characteristic of being rapidly degradable.

[0069] 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. A bisphenol curing agent containing a spirocyclic bisborate group, characterized in that: The bisphenol curing agent containing a spirocyclic biboric acid ester group is prepared from 4-hydroxyphenylboric acid and pentaerythritol in a molar ratio of 2-2.2:1; the structure of the bisphenol curing agent containing a spirocyclic biboric acid ester group is shown in formula (I):

2. A method for preparing the bisphenol curing agent containing spirocyclic bisboronic acid ester groups according to claim 1, characterized in that: The steps include: 4-Hydroxyphenylboric acid, pentaerythritol and anhydrous ethanol are mixed, heated for reaction, and rotary evaporated to obtain a bisphenol curing agent containing a spirocyclic biboric acid ester group.

3. The method for preparing a bisphenol curing agent containing a spirocyclic biboric acid ester group according to claim 2, characterized in that: The molar volume ratio of pentaerythritol to anhydrous ethanol is 1 mol:0.5-1L; the temperature of the heating reaction is 50-70° C., and the heating reaction time is 12-24 hours.

4. A method for preparing a vegetable oil-based epoxy resin using the bisphenol curing agent containing a spirocyclic biboric acid ester group according to claim 1, characterized in that: The steps include: The epoxy soybean oil, the bisphenol curing agent containing the spirocyclic biboric acid ester group, the curing agent, the catalyst and the anhydrous ethanol are stirred and mixed, heated to react under negative pressure, degassed and hot-dried to obtain the vegetable oil-based epoxy resin.

5. The method for preparing a vegetable oil-based epoxy resin according to claim 4, characterized in that: The curing agent includes one of bisphenol F, bisphenol A and bisphenol S; the catalyst includes one of imidazole, acrylic anhydride, aniline, benzyl dimethylamine and phenol.

6. The method for preparing a vegetable oil-based epoxy resin according to claim 4, characterized in that: The molar volume ratio of the epoxidized soybean oil, the bisphenol curing agent containing spirocyclic biboric acid ester groups, the curing agent, and anhydrous ethanol is: epoxidized soybean oil: bisphenol curing agent containing spirocyclic biboric acid ester groups: curing agent: anhydrous ethanol = 1 mol: 0-2 mol: 0-2 mol: 1-1.5 L; the amount of the catalyst used is 0-20% of the weight of the epoxidized soybean oil.

7. The method for preparing a vegetable oil-based epoxy resin according to claim 4, characterized in that: The pressure of the heating reaction under the negative pressure condition is 0.1-0.5 MPa; the heating temperature is 70-100° C., and the heating time is 30-60 min.

8. The method for preparing a vegetable oil-based epoxy resin according to claim 4, characterized in that: The temperature of the heat drying is 120-160° C. and the time is 6 hours.

9. A vegetable oil-based epoxy resin prepared by the method for preparing a vegetable oil-based epoxy resin according to any one of claims 4 to 8.

10. Use of the vegetable oil-based epoxy resin according to claim 9 as an adhesive.

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