Preparation method of recyclable epoxy resin material, obtained material and its application

Abstract

The present invention discloses a preparation method of a recyclable epoxy resin material, which relates to the technical field of adhesives and comprises the following steps: (1) mixing sulfur powder and unsaturated organic acid and heating them for reaction to obtain a polythio high molecular intermediate; (2) heating and mixing the polythio high molecular intermediate in step (1) with epoxy resin to obtain a recyclable adhesive. The present invention also provides an epoxy resin material prepared by the above method and its application. The beneficial effects of the present invention are as follows: the preparation method of the invention has the advantages of simple process, environmental friendliness, no solvent participation, and quick operation; the prepared epoxy resin has excellent mechanical properties. At the same time, due to the existence of the polythio main chain structure in the crosslinked network, under heating conditions, there is a dynamic sulfur-sulfur bond exchange process inside the material, which can promote the reprocessing and molding utilization of the epoxy resin, has a good application prospect, can reduce the environmental pollution of thermosetting epoxy resin, and avoid the waste of resources.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resins, and specifically relates to a preparation method of a recyclable epoxy resin material, the obtained material and its application. Background Art

[0002] Thermosetting resins are widely used in various fields. Due to their stable chemical cross-linked network structure, thermosetting materials cannot be recycled, which may lead to further environmental pollution and waste of resources.

[0003] By introducing a dynamic chemical structure network, the chemical bonds in the chemical network can be broken and recombined under certain external stimuli, or the metathesis process between chemical bonds can be realized. For example, by controlling the ratio of carboxyl groups and hydroxyl groups in epoxy resins, a large number of β-hydroxy ester groups are introduced, and the metathesis reaction between imine groups and the metathesis process of disulfide bonds.

[0004] However, while realizing the recycling of materials, the introduction of a large number of β-hydroxy ester groups reduces the cross-linking density of the system, which in turn leads to a decrease in the mechanical properties of the materials. Other specific functional groups (imine, disulfide, etc.) require complex chemical synthesis processes, resulting in an increase in material costs. For example, the patent application with the publication number CN113087872A discloses a recyclable eugenol-based epoxy resin Vitrimer material and its preparation method. After mixing a eugenol-based epoxy resin matrix similar to DGEBA with a binary carboxylic acid curing agent system containing dynamic bonds and without dynamic bonds, it is cured by a gradient heating method to obtain a recyclable eugenol-based epoxy resin Vitrimer material with both dynamic reversible ester exchange bonds and disulfide bonds. Therefore, it is very necessary to develop a method with controllable cost to achieve the recycling performance of the epoxy resin system and maintain the mechanical properties of the materials as much as possible. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the methods for realizing the recyclability of epoxy resins in the prior art are complex and it is difficult to maintain the mechanical properties of the materials while achieving recyclability. The present invention provides a preparation method of a simple and recyclable epoxy resin material, the obtained epoxy resin material and its application.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] A preparation method of a recyclable epoxy resin material, comprising the following steps:

[0008] (1) Mix sulfur powder and unsaturated organic acid and heat them for reaction to obtain a polythio polymer intermediate;

[0009] (2) Heat the polysulfide polymer intermediate in step (1) and epoxy resin and mix them.

[0010] Principle: Sulfur powder is a chemical raw material with a wide range of sources and low price. It can be melted into a liquid when heated to 120 °C, and its eight-membered ring structure can be opened at 159 °C to generate sulfur free radicals. By reacting with the carbon-carbon double bond, the sulfur free radicals can be stabilized, thereby preventing the reverse formation of octasulfur with an eight-membered ring. The polysulfide main chain formed in the process has a dynamic exchange function under heating conditions.

[0011] In the present invention, by reacting an organic acid containing a double bond with cheap and easily available sulfur powder under high temperature conditions, a liquid polysulfide polymer that can flow at room temperature is first prepared. Since this novel polysulfide polymer contains multiple carboxyl groups, it can be used as a crosslinking agent for traditional commercial epoxy resins and novel epoxy resins, and the epoxy resin can be cured under heating conditions to prepare an epoxy resin with a crosslinked network structure at room temperature.

[0012] In step (1) of the present invention, the heating process is accompanied by the melting of sulfur powder and the process of homolytic cleavage of free radicals. The sulfur atom free radicals react with the double bonds of unsaturated organic acids to obtain a polysulfide polymer intermediate.

[0013] In step (2) of the mixing process, one or more epoxy resins can be used, including glycidyl ether type, glycidyl ester type, glycidyl amine type, linear aliphatic epoxy resin, etc.

[0014] Beneficial effects: The preparation method of the present invention has the advantages of simple process, environmental friendliness and fast operation; the prepared epoxy resin has excellent mechanical properties. At the same time, due to the existence of the polysulfide main chain structure in the crosslinked network, under heating conditions, there is a dynamic sulfur-sulfur bond exchange process inside the material, which can promote the reprocessing and forming utilization of the epoxy resin, has good application prospects, can reduce the environmental pollution of thermosetting epoxy resin, and avoid waste of resources.

[0015] The epoxy resin in the present invention can achieve adhesion between metal interfaces and other interfaces when heated to a temperature above 120 °C. This adhesion can maintain a stable structure at room temperature and conventional use temperature conditions, and can be disassembled when heated to above 180 °C.

[0016] Preferably, the mass ratio of sulfur powder to unsaturated organic acid in step (1) is 1-2:1-5.

[0017] Beneficial effects: By adjusting the mass ratio of sulfur powder to unsaturated organic acid, a carboxyl-functionalized polysulfide polymer containing a polysulfide main chain with a sulfur content between 16.7% and 67% is obtained. Too high or too low content is not conducive to the formation of a dynamic crosslinked structure with epoxy resin in the later stage.

[0018] Preferably, the unsaturated organic acid includes an organic acid containing 1 to 3 carbon-carbon double bonds or an organic acid containing 1 to 3 carboxyl groups.

[0019] Preferably, the position of the carbon-carbon double bond in the unsaturated organic acid is at the molecular end or in the middle.

[0020] Preferably, the unsaturated organic acid includes oleic acid or undecylenic acid.

[0021] Preferably, the heating temperature in step (1) is 160 - 200 °C.

[0022] Beneficial effect: The temperature during the reaction process can be selected between 160 - 200 °C, which helps to complete the reaction as soon as possible.

[0023] Preferably, a catalyst is added during the mixing process of sulfur powder and unsaturated organic acid in step (1).

[0024] Preferably, the addition amount of the catalyst is 0.1 - 10% of the sulfur powder content.

[0025] Preferably, the catalyst is a metal diethyldithiocarbamate catalyst.

[0026] Preferably, the metal diethyldithiocarbamate catalyst is zinc diethyldithiocarbamate, zinc dimethyldithiocarbamate, sodium diethyldithiocarbamate, silver diethyldithiocarbamate, iron diethyldithiocarbamate, ammonium diethyldithiocarbamate, ferrous diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, zinc dihydroxydithiocarbamate or manganese diethyldithiocarbamate.

[0027] Preferably, the heating and mixing temperature in step (2) is 80 °C.

[0028] Preferably, an epoxy resin crosslinking agent is further added in step (2), including acid anhydride-based, organic acid-based, organic amine-based and polyamide-based crosslinking agents, etc.

[0029] Preferably, an epoxy resin curing catalyst is further added in step (2).

[0030] Preferably, the epoxy resin curing catalyst is a metal diethyldithiocarbamate catalyst.

[0031] Preferably, the metal diethyldithiocarbamate catalyst is zinc diethyldithiocarbamate, zinc dimethyldithiocarbamate, sodium diethyldithiocarbamate, silver diethyldithiocarbamate, iron diethyldithiocarbamate, ammonium diethyldithiocarbamate, ferrous diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, zinc dihydroxydithiocarbamate or manganese diethyldithiocarbamate.

[0032] In the mixing process of step (2), cross-linking agents of other epoxy resins and catalysts for the curing process of epoxy resins can also be added in appropriate proportions.

[0033] Preferably, the prepared epoxy resin is heated to 120°C to 200°C and cooled to room temperature after curing.

[0034] Beneficial effect: Bonding between the metal interface and other interfaces can be achieved under the temperature condition of heating above 120°C.

[0035] Preferably, the bonded epoxy resin is heated to above 180°C.

[0036] Beneficial effect: Demolition can be achieved by heating above 180°C, and the epoxy resin can be recycled.

[0037] A recyclable epoxy resin material prepared by the above preparation method.

[0038] Beneficial effect: The epoxy resin material prepared in the present invention can achieve bonding between the metal interface and other interfaces under the temperature condition of heating above 120°C. This bonding can maintain a stable structure at room temperature and conventional use temperature conditions, while being detachable by heating above 180°C.

[0039] Application of the recyclable epoxy resin material prepared by the above preparation method as an adhesive or sealant.

[0040] Beneficial effect: The prepared epoxy resin can achieve bonding between the metal interface and other interfaces. This bonding can maintain a stable structure at room temperature and conventional use temperature conditions, while the removal between metal sheets can be achieved by heating above 180°C, and it can be used as an adhesive or sealant.

[0041] The advantages of the present invention are as follows: The preparation method of the present invention has the advantages of simple process, environmental friendliness and fast operation; the prepared epoxy resin has excellent mechanical properties. At the same time, due to the existence of the polysulfide main chain structure in the cross-linked network, under heating conditions, there is a dynamic sulfur-sulfur bond exchange process inside the material, which can promote the reprocessing and molding utilization of the epoxy resin, has good application prospects, can reduce the environmental pollution of thermosetting epoxy resin, and avoid waste of resources.

[0042] The epoxy resin in the present invention can achieve adhesion between the metal interface and other interfaces under the temperature condition of heating to above 120°C. This adhesion can maintain a stable structure at room temperature and conventional use temperature conditions, and can be disassembled when heated to above 180°C.

[0043] Adjust the mass ratio of sulfur powder and unsaturated organic acid to obtain a carboxyl-functionalized polysulfide polymer containing a dynamic polysulfide main chain structure with sulfur content between 16.7% and 67%. Too high or too low content is not conducive to the formation of a dynamic cross-linked structure.

[0044] The temperature during the reaction process can be selected between 160 - 200°C, which helps to complete the reaction as soon as possible. Description of the Drawings

[0045] Figure 1 It is a picture of the polysulfide polymer intermediate prepared in Example 1 of the present invention;

[0046] Figure 2 It is the NMR diagram of the polysulfide polymer intermediate prepared in Example 1 of the present invention;

[0047] Figure 3 It is the infrared spectrum diagram of the epoxy resin material prepared in Example 1 of the present invention;

[0048] Figure 4 It is the shear stress value after bonding the metal sheet with epoxy resins of different ratios in the examples of the present invention;

[0049] Figure 5 It is the mechanical tensile property diagram of an epoxy resin obtained in Example 1 of the present invention after three cycles of hot pressing processing. Detailed Embodiments

[0050] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] The test materials and reagents used in the following embodiments can be obtained from commercial channels without special instructions.

[0052] For those not specified in the embodiments regarding specific technologies or conditions, they can all be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications.

[0053] Example 1

[0054] Preparation method of recyclable epoxy resin material, specifically including the following steps:

[0055] (1) Mix 15 grams of sulfur powder and 30 grams of oleic acid in a 50 - milliliter flask, and add a magnetic stir bar; place the round - bottom flask in an oil bath at 160 °C and heat - react for 3 hours; cool to room temperature to obtain a polythio - high - molecular intermediate product.

[0056] (2) Add 45 grams of bisphenol - A - based epoxy resin DGEBA to the polythio - high - molecular intermediate product obtained in step (1), and heat - stir at 60 °C to make the epoxy resin and the polythio - high - molecular intermediate product fully mixed evenly to obtain a recyclable binder.

[0057] (3) Pour the binder into a mold and heat - cure in an oven at 120 °C for 3 hours; or coat the binder between metal sheets and heat - cure in an oven at 120 °C for 3 hours to obtain bonded metal sheets.

[0058] Example 2

[0059] The difference between this example and Example 1 is that: the oleic acid used is 37.5 grams, and the content of bisphenol - A - based epoxy DGEBA is 45 grams.

[0060] Example 3

[0061] The difference between this example and Example 1 is that: the oleic acid used is 30 grams, and the content of bisphenol - A - based epoxy DGEBA is 60 grams.

[0062] Example 4

[0063] The difference between this example and Example 1 is that: the sulfur powder used is 22.5 grams, the oleic acid is 30 grams, and the content of bisphenol - A - based epoxy DGEBA is 45 grams.

[0064] Example 5

[0065] The difference between this example and Example 1 is that: the oleic acid used is 30 grams, the content of bisphenol - A - based epoxy DGEBA is 45 grams, and 0.9 grams of zinc diethyldithiocarbamate is added in step (1).

[0066] Example 6

[0067] The difference between this example and Example 1 is that: the undecylenic acid used is 30 grams, the content of bisphenol - A - based epoxy DGEBA is 45 grams, and 0.9 grams of the catalyst zinc diethyldithiocarbamate is added in step (1).

[0068] The present invention is verified by the following tests, and the specific steps are as follows:

[0069] 1. Use a mechanical tensile testing machine to test the mechanical tensile properties of the epoxy resin obtained in the mold.

[0070] 2. Further process the tested fragment materials with scissors to particles smaller than 2 mm in size, and perform hot pressing at 180 °C and 88.4 kPa for 10 minutes using a hot press to verify the cyclic processing performance of the materials, and compare the differences in the mechanical tensile properties between the recycled materials and the original ones.

[0071] 3. Place the above hot-pressed film material between two pieces of metal, and place it in an oven at 120 °C for 30 minutes under pressurized conditions, and then test the shear stress after the metal sheet is adsorbed to prove the recyclability of the material.

[0072] Figure 1 It is a picture of the polysulfide polymer intermediate prepared in Example 1, which is in a flowable state at room temperature. Figure 2 It is the NMR diagram of the polysulfide polymer intermediate prepared in Example 1.

[0073] Figure 3 It is the infrared spectrum diagram of the epoxy resin material prepared corresponding to Example 1. It can be seen that the absorption peak at 1730 is the ester bond absorption peak. The ester bonds formed by the reaction of the carboxyl group in the polysulfide molecular chain and the organic acid with epoxy together constitute the cross-linked network.

[0074] Figure 4 It is the shear stress data after the epoxy resin with different ratios is bonded to the metal sheet. Methods 1 to 5 correspond to Examples 1 to 5. Method 1 is 13.45 MPa, Method 2 is 8.69 Mpa, Method 3 is 17 MPa, Method 4 is 11.06 MPa, and Method 5 is 9 MPa. As the amount of epoxy resin added increases, its mechanical properties are enhanced relative to Method 1; as the amount of sulfur powder, organic unsaturated acid, and catalyst increases or is added, its mechanical properties decrease relative to Method 1.

[0075] Figure 5 It is the mechanical tensile property diagram of the binder after three cycles of hot pressing in Example 2. It can be seen that after three cycles of hot pressing, the mechanical properties of the binder basically remain unchanged.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of a recyclable epoxy resin material, characterized in that: It includes the following steps: (1) Mix sulfur powder and unsaturated organic acid, and heat and react at 160 - 200 °C to obtain a polythio high-molecular intermediate; the unsaturated organic acid includes an organic acid containing 1 - 3 carbon-carbon double bonds, and the position of the carbon-carbon double bond in the unsaturated organic acid is at the molecular end or in the middle; the mass ratio of the sulfur powder to the unsaturated organic acid is 1 - 2:1 - 5; (2) Heat and mix the polythio high-molecular intermediate in step (1) with epoxy resin to obtain a recyclable epoxy resin material.

2. The preparation method of the recyclable epoxy resin material according to claim 1, characterized in that: The unsaturated organic acid includes oleic acid or undecylenic acid.

3. The preparation method of the recyclable epoxy resin material according to claim 1, characterized in that: The heating temperature in step (1) is 160 - 200 °C.

4. The preparation method of the recyclable epoxy resin material according to claim 1, characterized in that: A catalyst is added during the mixing process of the sulfur powder and the unsaturated organic acid in step (1).

5. The preparation method of the recyclable epoxy resin material according to claim 4, characterized in that: The addition amount of the catalyst is 0.1 - 10% of the sulfur powder content.

6. The preparation method of the recyclable epoxy resin material according to claim 1, characterized in that: Heat the prepared binder to 120 - 200 °C, and cool it to room temperature after curing.

7. A recyclable epoxy resin material prepared by the method according to any one of claims 1 - 6.

8. Application of the recyclable epoxy resin material prepared by the method according to any one of claims 1 - 6 as an adhesive or a sealant.

Images