Thermosetting epoxy resin accelerated degradation method and device based on popcorn effect

Abstract

The invention belongs to the technical field of degradation, and particularly relates to a thermosetting epoxy resin accelerated degradation method and device based on a popcorn effect. The method comprises the following specific steps: S1, granulation pretreatment: crushing thermosetting epoxy resin into thermosetting epoxy resin particles by using a crushing mechanism; and S2, the thermosetting epoxy resin particles are placed in a sealed container to be heated, the rotating container drives the thermosetting epoxy resin particles to turn over, heating is stopped when the pressure in the container is larger than or equal to 3.0 MPa, and the expanded and burst thermosetting epoxy resin particles are poured out after pressure relief is completed. According to the method, the degradation difficulty of the thermosetting epoxy resin material is greatly reduced, the chemical degradation efficiency of the epoxy resin material is improved, and the method has good universality and practicability.

Description

Technical Field

[0001] The invention belongs to the technical field of degradation, and in particular relates to a method and a device for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect. Background Art

[0002] Epoxy resin is a high-performance thermosetting material with excellent thermal stability, excellent mechanical properties and electrical insulation properties. It has been widely used in many fields related to the national economy, such as power transmission, civil construction, and aerospace. However, it is precisely because of the highly stable three-dimensional network structure of epoxy resin materials after cross-linking that the degradation and recycling of thermosetting epoxy resin materials is hindered. The environmental pollution and waste of resources caused by the retirement or disposal of materials have become a great challenge restricting their development and application. Therefore, based on the degradation and recycling of thermosetting epoxy resin materials, developing a method to accelerate the degradation of materials is the key to resolving this challenge.

[0003] At present, research on the degradation of epoxy resin materials is mainly focused on the design of network structure, such as introducing functional groups that respond to external stimuli into the epoxy cross-linked network, designing photosensitive or thermosensitive epoxy resins (such as: Chem. Mater. 2022, 34, 10, 4732-4740), and using functional group response strategies to achieve the degradation of thermosetting epoxy resin materials; However, this type of epoxy resin material requires special functional groups for degradation, and the degradation efficiency is low, and the degradation conditions are relatively harsh. At the same time, some scholars have studied the biodegradation characteristics of epoxy resin materials, which mainly use microorganisms to break chemical bonds in the epoxy cross-linked network (such as: ACS Macro Letters, 2023, 12, 54-58), and then deconstruct the epoxy cross-linked network. However, this microbial degradation method is aimed at epoxy resins containing biomacromolecules, which is a specific selective degradation of microorganisms, so the use conditions are more harsh, making it difficult to become a universal method for degrading thermosetting epoxy resin materials.

[0004] Therefore, there is an urgent need for a method and device for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect. Summary of the invention

[0005] In order to overcome the defects in the above-mentioned prior art, the present invention provides a method and device for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect. The present invention greatly reduces the difficulty of degradation of thermosetting epoxy resin materials and improves the chemical degradation efficiency of epoxy resin materials, and has good universality and practicality.

[0006] To achieve one of the above purposes, the present invention adopts the following technical solution: A method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect, the specific steps are as follows: S1. Granulation pretreatment: using a crushing mechanism (such as a wall-breaking crusher) to crush the thermosetting epoxy resin into thermosetting epoxy resin particles; S2. Heat the thermosetting epoxy resin particles in a sealed container. The rotating container drives the thermosetting epoxy resin particles to flip. When the pressure in the container is ≥3.0 MPa, stop heating. After the pressure is released, pour out the expanded and exploded thermosetting epoxy resin particles.

[0007] Preferably, in step S1, the thermosetting epoxy resin is crushed in a wall-breaking pulverizer at a rotation speed of 30,000 r / min, and after crushing, the thermosetting epoxy resin particles are gradually screened using a sieve with an aperture of 0.1-15 mm to select thermosetting epoxy resin particles with a particle size of 1-5 mm.

[0008] Preferably, the filling volume of the thermosetting epoxy resin particles in the container is 30-60% of the volume of the container cavity.

[0009] Preferably, in step S2, the heating temperature of the container is 100-300°C, and the internal pressure limit of the container is 10Mpa. When the internal pressure of the container reaches the upper limit under continuous high-temperature heating, the pressure relief valve on the container will automatically release the pressure, thereby ensuring the safety of the experimental process.

[0010] Preferably, the thermosetting epoxy resin is any one or more of glycidyl epoxy resin (including glycidyl ether, glycidyl ester, glycidyl amine), aliphatic epoxy resin and alicyclic epoxy resin.

[0011] Preferably, the rotation speed of the container is 30-300 r / min.

[0012] Preferably, the container is tested for air tightness by a soapy water leak detection method before use. The specific detection method is: evenly apply soapy water on the outer surface of the container, turn on the heater to continuously heat the container at a high temperature to generate pressure inside the container, and when the pressure inside the container reaches 0.5MPa, observe whether bubbles appear in the soapy water on the outer surface of the container.

[0013] To achieve the second of the above purposes, the present invention provides a device for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect, the device comprising a rotatable container and a heater for heating the container, the container is placed horizontally, and a pressure relief valve and a pressure gauge are also installed on the container.

[0014] Preferably, the container is a non-welded container, and the volume of the container is 100-500 ml.

[0015] Preferably, the device further comprises a wall-breaking pulverizer for crushing the thermosetting epoxy resin into particles and a screening element for screening the thermosetting epoxy resin particles, and the screening element can be a screen.

[0016] The advantages of the present invention are: (1) The present invention only expands and explodes the thermosetting epoxy resin material to form a porous structure, which is convenient for accelerating the penetration of organic solvents into the epoxy cross-linked network during subsequent degradation, promoting the exchange reaction between polar groups and organic solvents in the epoxy resin cross-linked network, and accelerating the swelling rate of the thermosetting epoxy resin material in the chemical degradation agent and the deconstruction rate of the cross-linked network, thereby improving the problems of low degradation efficiency and harsh degradation conditions of the thermosetting epoxy resin material in the existing methods. At the same time, since the method is simple and easy to operate, and the effects of multiple treatments have good reproducibility, it will help to control the batch stability of thermosetting epoxy resin materials during batch degradation. At the same time, the expansion and explosion treatment does not need to change the original cross-linked network structure of the epoxy material, and also avoids the introduction of new harmful substances in the network and the generation of additional waste after degradation. Therefore, this method also conforms to the environmentally friendly material degradation design principle and meets the development requirements of new green polymer materials.

[0017] (2) In the present invention, as the heater continuously applies heat energy, the temperature inside the container cavity gradually rises, which in turn causes the movement of the gas molecules inside to intensify, causing the gas pressure inside the cavity to continue to increase. At the same time, due to the difference in heat dissipation conditions outside the cavity and inside, the pressure inside and outside is unbalanced, forming an obvious pressure difference. When this pressure difference acts on the granulated thermosetting epoxy resin material, the epoxy resin particles begin to undergo a series of physical changes, as follows: As the temperature continues to rise, the moisture and volatile substances inside the epoxy resin particles begin to evaporate rapidly, forming a large amount of gas, which further increases the pressure inside the particles. When this internal pressure reaches a certain level, the outer shell of the epoxy resin particles cannot withstand the pressure inside them, and tiny cracks begin to appear. These cracks gradually expand as the internal pressure continues to increase, eventually turning the epoxy resin particles into a porous structure.

[0018] When the particle shell breaks, the high-pressure gas and evaporated substances accumulated inside are quickly released, resulting in strong expansion and explosion. This phenomenon not only significantly increases the volume of the epoxy resin particles, but is also accompanied by a huge sound and energy release. Through this process, the epoxy resin material achieves a rapid transition from solid to gaseous state, resulting in expansion and explosion.

[0019] (3) The method of the present invention can play a good role in promoting the chemical degradation of a variety of commercially available thermosetting epoxy resin materials. After being treated by this method, the penetration of organic degradation solvents into epoxy resin materials is significantly improved, and different organic degradation solvents can also directionally break the chemical bonds in the epoxy cross-linked network. Therefore, the method based on the accelerated degradation of epoxy resin materials has a high universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the device of the present invention.

[0021] Figure 2 This is a surface microscopic morphology diagram of Example 1 of the present invention.

[0022] Figure 3 This is a surface microscopic morphology diagram of comparative example 1 of the present invention.

[0023] The meanings of the symbols in the figure are as follows: 1-Container, 2-Heater, 3-Pressure relief valve, 4-Pressure gauge. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0025] A method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect comprises the following steps: Step 1: Air tightness test of the integrated puffing and bursting device; The soapy water leak detection method is adopted. After soapy water is evenly coated on the outer surface of the container 1, the heater 2 is used to continuously heat the container 1 at a high temperature to generate a certain pressure in the cavity of the container 1. When the internal pressure reaches 0.5MPa, the air tightness of the epoxy resin material container 1 is detected by observing whether soapy water bubbles appear on the surface of the container 1.

[0026] Step 2: Particle pretreatment of thermosetting epoxy resin: The thermosetting epoxy resin was broken into pieces the size of corn kernels by a wall-breaking pulverizer at a speed of 30,000 r / min, and the particle size of the thermosetting epoxy resin particles was gradually screened through a sieve with an aperture of 0.1-15 mm, and thermosetting epoxy resin particles with a particle size range of 1-5 mm were selected.

[0027] Step 3: Expansion and bursting test of thermosetting epoxy resin: The thermosetting epoxy resin particles are poured into the cavity of the container 1, and the heater 2 is turned on to continuously heat the container 1 at a temperature of 100°C-300°C, and the container 1 is kept rotating at a speed of 30-300r / min to ensure that the outside of the container 1 is evenly heated. After heating the container 1 for a certain period of time, the indication of the pressure gauge 4 is observed. When the indication of the pressure gauge 4 reaches 3.0MPa or more, the heating is stopped and the pressure is released, and the expanded and exploded thermosetting epoxy resin particles are poured out.

[0028] The filling volume of the thermosetting epoxy resin particles in the container 1 is 30-60% of the volume of the container 1. The thermosetting epoxy resin is any one or more combinations of glycidyl epoxy resins (glycidyl ether, glycidyl ester, glycidyl amine), aliphatic and alicyclic epoxy resins.

[0029] like Figure 1 As shown, a thermosetting epoxy resin accelerated degradation device based on the popcorn effect is an integrated device for expansion and explosion. The container 1 in the integrated device for expansion and explosion of epoxy resin material used in the present invention has a cavity volume of 100-500 ml and an internal pressure limit of 10Mpa. When the container 1 is continuously heated at high temperature and the internal pressure of the cavity reaches the upper limit, the pressure relief valve 3 of the device will automatically release the pressure, thereby ensuring the safety of the experimental process.

[0030] The device includes a non-welded container 1, a heater 2, a wall-breaking pulverizer and a screen. The wall-breaking pulverizer breaks the thermosetting epoxy resin into particles, the screen selects the thermosetting epoxy resin particles with a size of 1-5 mm, and the larger particles continue to be broken. The non-welded container 1 is used to load the broken thermosetting epoxy resin, and the heater 2 is used to heat the container 1; a pressure relief valve 3 and a pressure gauge 4 are installed on the container 1. The container 1 is placed horizontally, and the pressure relief valve 3 and the pressure gauge 4 are also installed on the container 1.

[0031] Example 1 A method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect comprises the following steps: S1. Using a wall-breaking grinder at a speed of 30,000 r / min, the commercially available thermosetting bisphenol A epoxy resin material is broken into pieces the size of corn kernels, and the thermosetting epoxy resin particles with a particle size range of 1-5 mm are screened out through a sieve. The thermosetting epoxy resin particles are poured into a container 1, and the volume filling fraction of the thermosetting epoxy resin particles in the cavity is 50%.

[0032] S2. After sealing the container 1, use the heater 2 to heat the container 1 at a heating temperature of 200°C, and keep the container 1 rotating at a speed of 200r / min, observe the value of the pressure gauge 4 on the container 1, and when the value of the pressure gauge 4 reaches 3.0MPa, stop heating and release the pressure. After the pressure is released, pour out the thermosetting epoxy resin particles that have been expanded and exploded.

[0033] The thermosetting epoxy resin particles were tested by scanning electron microscopy and the Figure 2 The scanning electron microscope image shown in the figure shows Figure 2 A local porous structure is formed on the surface of the thermosetting epoxy resin particles.

[0034] Example 2 The method of this embodiment is different from that of Embodiment 1 in that the volume filling fraction of the epoxy resin particles in the cavity is 30%, and the other steps are the same as those of Embodiment 1, to obtain thermosetting epoxy resin particles II.

[0035] Comparative Example 1 The commercially available thermosetting bisphenol A epoxy resin material was crushed into pieces the size of corn kernels using a wall-breaking mill at a speed of 30,000 r / min, and thermosetting epoxy resin particles with a particle size range of 1-5 mm were screened out using a sieve.

[0036] The thermosetting epoxy resin particles were tested by scanning electron microscope and the Figure 3 The scanning electron microscope image shown in the figure shows Figure 3 The surface of the thermosetting epoxy resin particles in the mold is flat and has no pores.

[0037] Comparative Example 2 The comparative method is different from Example 1 in that the volume filling fraction of the epoxy resin particles in the cavity is 70%, and the other steps are the same as Example 1 to obtain thermosetting epoxy resin particles four.

[0038] Comparative Example 3 The comparative method is different from Example 1 in that the sieve screens out thermosetting epoxy resin particles with a particle size range of 5-10 mm for accelerated degradation, and the other steps are the same as Example 1 to obtain thermosetting epoxy resin particles five.

[0039] Comparative Example 4 The comparative method is different from Example 1 in that the sieve screens out thermosetting epoxy resin particles with a particle size range of 10-15 mm for accelerated degradation, and the other steps are the same as Example 1 to obtain thermosetting epoxy resin particles 6.

[0040] The thermosetting epoxy resin particles prepared in the above Examples 1-2 and Comparative Examples 1-4 were subjected to degradation experiments respectively. The specific method is: the thermosetting epoxy resin particles are placed in a mixed solution of 0.1M HCl water and acetone (water: acetone volume ratio is 1:9), and degradation is carried out at 80°C. The degradation of the thermosetting bisphenol A epoxy resin material is observed. The results are shown in Table 1 below: Table 1 ; From Table 1 and Figure 2-3 It can be seen that compared with the unexpanded epoxy resin, the degradation rate of the expanded epoxy resin has been significantly improved, with the degradation rate increased by more than 60%, indicating that the method of the present invention has an outstanding effect on accelerating the degradation rate of thermosetting epoxy resin.

[0041] Secondly, by adjusting the particle size range, the degradation rate of thermosetting epoxy resin fragments with different particle sizes after expansion was explored, and it was found that the degradation rate of the expanded epoxy resin fragments with a particle size range of 1-5 mm was the fastest. At the same time, changing the filling volume fraction in the cavity of container 1 will also affect the chemical degradation rate of the expanded epoxy resin material. The comparison between Example 1 and Example 2 and Comparative Example 2 shows that when the filling volume fraction of the epoxy resin fragments in the cavity is 50%, the epoxy resin material after expansion and explosion treatment has a higher chemical degradation rate.

[0042] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect, characterized in that: The specific steps are as follows: S1. Granulation pretreatment: using a crushing mechanism to crush the thermosetting epoxy resin into thermosetting epoxy resin particles; S2. The thermosetting epoxy resin particles are placed in a sealed container (1) and heated. The rotating container (1) causes the thermosetting epoxy resin particles to flip. When the pressure in the container (1) is ≥3.0 MPa, the heating is stopped. After the pressure is released, the expanded and exploded thermosetting epoxy resin particles are poured out.

2. The method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect according to claim 1, characterized in that: In step S1, the thermosetting epoxy resin is placed in a wall-breaking pulverizer at a rotation speed of 30,000 r / min for crushing. After crushing, the thermosetting epoxy resin particles are screened by particle size using a sieve to select thermosetting epoxy resin particles with a particle size of 1-5 mm.

3. The method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect according to claim 1, characterized in that: The filling volume of the thermosetting epoxy resin particles in the container (1) is 30-60% of the volume of the cavity of the container (1).

4. The method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect according to claim 1, characterized in that: In step S2, the heating temperature of the container (1) is 100-300°C.

5. The method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect according to claim 1, characterized in that: The thermosetting epoxy resin is any one or more of a glycidyl epoxy resin, an aliphatic epoxy resin and an alicyclic epoxy resin.

6. The method for accelerating degradation of thermosetting epoxy resin based on popcorn effect according to claim 1, characterized in that: The rotation speed of the container (1) is 30-300 r / min.

7. The method for accelerating degradation of thermosetting epoxy resin based on popcorn effect according to claim 1, characterized in that: Before use, the container (1) is tested for air tightness using a soapy water leak detection method.

8. A device for implementing the method for accelerating degradation of thermosetting epoxy resin based on popcorn effect as claimed in any one of claims 1 to 7, characterized in that: The device comprises a rotatable container (1) and a heater (2) for heating the container (1); the container (1) is placed horizontally, and a pressure relief valve (3) and a pressure gauge (4) are also installed on the container (1).

9. The device for accelerating degradation of thermosetting epoxy resin based on popcorn effect according to claim 8, characterized in that: The container (1) is a non-welded container (1), and the volume of the container (1) is 100-500 ml.

10. The device for accelerating degradation of thermosetting epoxy resin based on popcorn effect according to claim 8, characterized in that: The device also comprises a wall-breaking pulverizer for breaking the thermosetting epoxy resin into particles and a screening element for screening the thermosetting epoxy resin particles.

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