A recycling method for epoxy molding compound waste and its application

Abstract

The present invention relates to the technical field of epoxy molding compounds, and more particularly to a method for recycling epoxy molding compound waste and its application. The recycling method comprises re-solidifying the waste material using an amino curing agent, then crushing the waste material and performing surface pretreatment to obtain recycled epoxy molding compound waste material. The recycled epoxy molding compound waste material prepared using the recycling method of the present invention can be used as a filler in epoxy molding compound, has good dispersibility in the epoxy molding compound, and does not affect the curing system of the epoxy molding compound.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy molding compounds, and in particular to a recycling method and application of epoxy molding compound waste. Background Art

[0002] Epoxy molding compounds are made from inorganic fillers, epoxy resins, phenolic resins, and other additives. Currently, many epoxy molding compounds are unsuitable for client applications, have passed their shelf life, and have been stored at high temperatures for extended periods, leaving some of the resin in a pre-cured state. This prevents direct recycling and reuse, and ultimately becomes waste.

[0003] Since thermosetting resins form a highly cross-linked three-dimensional network structure after complete curing, the energy required to break the covalent bonds in most three-dimensional networks is relatively high, making their recycling challenging. Current methods for recycling waste materials include: pyrolysis recovery, dissolution recovery, and mechanical recovery. However, these methods are not ideal, waste resources, and also introduce toxic substances produced by recycling into the environment, causing serious environmental pollution. Therefore, it is necessary to provide a reasonable and pollution-free method for recycling epoxy molding compound waste.

[0004] Patent document CN111471214A provides a waste recycling method that primarily uses a supercritical solvent dissociation and cross-linking process under certain temperature and pressure conditions to remove resin and extract silica from epoxy molding compound waste. However, this method results in the inability to recover the solvent, polluting the environment and being complex to operate. Summary of the Invention

[0005] Aiming at the waste of semi-cured / partially cured epoxy molding compound with low cross-linking density, the present invention provides a recycling method and application of the waste of epoxy molding compound, so as to use the waste of epoxy molding compound as a filler in the epoxy molding compound.

[0006] Based on the above purpose, the present invention provides a method for recycling epoxy molding compound waste, comprising the following steps:

[0007] (1) curing the epoxy molding compound waste by a curing agent to obtain cured epoxy molding compound waste;

[0008] (2) crushing the solidified epoxy molding compound waste to obtain solidified epoxy molding compound waste powder;

[0009] (3) The surface of the solidified epoxy molding compound waste powder is pretreated to obtain recycled epoxy molding compound waste.

[0010] Preferably, the curing agent is an amino curing agent.

[0011] Preferably, the amino curing agent is one of aromatic amines, fatty amines, polyamides, alicyclic amines, polyether amines, and imidazoles.

[0012] More preferably, the amino curing agent is an aromatic amine curing agent.

[0013] Preferably, the aromatic amine curing agent is diaminodiphenyl sulfone.

[0014] Preferably, the method of curing the epoxy molding compound waste by a curing agent in step (1) is: crushing the epoxy molding compound waste to a particle size D50 of 125 μm, adding 2%-5% of the weight of the epoxy molding compound waste amino curing agent at a temperature of 110-130° C., and reacting for 4-6 hours to obtain cured epoxy molding compound waste.

[0015] Preferably, the particle size distribution D50 of the cured epoxy molding compound waste powder in step (3) is 35-45 μm, 10-15 μm and 2-5 μm respectively.

[0016] Preferably, the surface pretreatment method is: drying the cured epoxy molding compound waste powder at 100-120°C for 5 hours, then preheating to 140°C at a speed of 1000 rpm, increasing the stirring speed to 2000-3000 rpm, spraying a silane coupling agent, and cooling to room temperature after 5-6 hours.

[0017] Preferably, the coupling agent is one of alkyl silane, amino silane, phenyl silane, mercapto silane, epoxy silane and silicate.

[0018] More preferably, the coupling agent is epoxysilane.

[0019] Furthermore, the present invention also provides an application of a method for recycling waste epoxy molding compound, characterized in that the recycled material of the waste epoxy molding compound is used as a filler in the epoxy molding compound.

[0020] Preferably, the epoxy molding compound is prepared from 6-12 parts of epoxy resin, 2-8 parts of phenolic resin, 70-85 parts of inorganic filler, 1-15 parts of recycled epoxy molding compound waste and 1-3 parts of other additives in parts by weight.

[0021] Preferably, the epoxy resin is a mixture of one or more of multifunctional epoxy resin, phenolic epoxy resin, biphenyl epoxy resin, aliphatic epoxy resin, polyaromatic epoxy resin, dicyclopentadiene epoxy resin, dicyclopentadiene epoxy resin, and o-cresol epoxy resin.

[0022] Preferably, the phenolic resin is a mixture of one or more of multifunctional phenolic resin, biphenyl phenolic resin, biphenyl-phenol phenolic resin, linear phenolic resin, and phenol aralkyl phenolic resin.

[0023] More preferably, the phenolic resin is a linear phenolic resin.

[0024] Preferably, the inorganic filler is silicon dioxide.

[0025] Preferably, the auxiliary agent is a mixture of one or more of a accelerator, a coupling agent, an adhesion agent, a stress relief agent, a flame retardant, and carbon black.

[0026] Beneficial effects of the present invention:

[0027] (1) The amino curing agent used in the present invention is used to re-solidify the waste material. Compared with the phenol curing agent, the amino curing agent has not only a curing effect but also an effect of promoting its curing due to the presence of amino groups.

[0028] (2) The present invention further adopts diaminodiphenyl sulfone (DDS) as a curing agent. The DDS molecule contains a relatively stable benzene ring structure, which makes the cured product have high heat resistance and water resistance. In addition, diaminodiphenyl sulfone contains SO 2- The introduction of polar groups makes the molecular structure of the curing system more compact, resulting in a higher physical density. Regarding non-bonded energy, the van der Waals energy of DDS is negative, while the electrostatic energy of DDS is positive, indicating that the DDS system has a higher packing density.

[0029] (3) In addition, the molecular spatial configuration is another factor that affects the free volume of the curing system. For example, the dihedral angle between the two benzene rings in the DDS system is larger, which makes the molecular spatial configuration larger, and thus makes the free volume of the curing system larger, making it easier for the molecular chain segments in the curing system to move, and making it easier for the organic matter in the waste to be dispersed in the matrix system when it is reused.

[0030] (4) The present invention crushes the waste into particles of different sizes and adds them in a certain proportion to improve the dispersion of the waste in the matrix while preventing the waste from agglomerating in the matrix due to its small particles. At the same time, the crushed waste particles are pretreated, the main benefit of which is to improve the dispersibility of the waste in the matrix. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0032] The epoxy molding compound waste used in the specific embodiment of the present invention has exceeded its shelf life and was retested. Its conventional data is not within its specifications. The specific data are shown in Table 1.

[0033] Table 1 General data of epoxy molding compound waste

[0034] Test items Specification Measured value Spiral flow length / cm 110±20 75 Gelation time / s 30±5 20 Flash (5μm) / mm ≤3.0 3.6 Flash (10μm) / mm ≤3.0 3.8

[0035] (1) 1000 g of epoxy molding compound waste was crushed to a particle size D50 of 125 μm. 30 g of diaminodiphenyl sulfone was added at a temperature of 120° C. The reaction time was 5 h to obtain cured epoxy molding compound waste.

[0036] (2) crushing the solidified epoxy molding compound waste and classifying it according to particle size to obtain solidified epoxy molding compound waste powder 1, solidified epoxy molding compound waste powder 2, and solidified epoxy molding compound waste powder 3;

[0037] (3) respectively drying the solidified epoxy molding material waste powder 1, solidified epoxy molding material waste powder 2 and solidified epoxy molding material waste powder 3 at 110° C. for 5 h, then preheating to 140° C. at a rotation speed of 1000 rpm, increasing the stirring speed to 3000 rpm, spraying silane coupling agent KH-560, spraying silane coupling agent aqueous solution (KH-560: deionized water are mixed according to a ratio of 4:1), the spraying amount is 1-2% of the weight of the waste powder, and after 5-6 h, cooling to room temperature to obtain recycled epoxy molding material waste 1, recycled epoxy molding material waste 2 and recycled epoxy molding material waste 3;

[0038] Among them, the particle size distribution D50 of the recycled material 1 of the epoxy molding compound is 35-45 μm; the particle size distribution D50 of the recycled material 2 of the epoxy molding compound is 10-15 μm; and the particle size distribution D50 of the recycled material 3 of the epoxy molding compound is 2-5 μm.

[0039] Example 1: 3 g of biphenyl-type epoxy resin, 3 g of biphenyl-phenol-type epoxy resin, 3 g of biphenyl-phenol-formaldehyde resin, recycled material 1: recycled material 2: recycled material 3 is 60:20:20, the addition amount is 8 g, 80 g of silica, 0.3 g of triphenylphosphine-1,2-methylimidazole, 0.25 g of carbon black, 0.3 g of palm wax, and 0.5 g of silicone oil are added to a high-speed stirrer in sequence, mixed evenly, melt-kneaded on an open rubber mixer at 95°C, the evenly mixed material is removed from the open rubber mixer, cooled and crushed to obtain a powdery material, and finally preformed into a cake material to obtain an epoxy resin composition.

[0040] Example 2: 3g of biphenyl-type epoxy resin, 3g of biphenyl-phenol-type epoxy resin, 3g of biphenyl-phenol-formaldehyde resin, recycled material 1: recycled material 2: recycled material 3 is 65:15:20, the addition amount is 8g, 80g of silica, 0.3g of triphenylphosphine-1,2-methylimidazole, 0.25g of carbon black, 0.3g of palm wax, and 0.5g of silicone oil are added to a high-speed stirrer in sequence, mixed evenly, melt-kneaded on an open rubber mixer at 95°C, the evenly mixed material is removed from the open rubber mixer, cooled and crushed to obtain a powdery material, and finally preformed into a cake material to obtain an epoxy resin composition.

[0041] Example 3: The addition amount of biphenyl type epoxy resin is 3g, the biphenyl phenol type epoxy resin is 3g, the biphenyl phenol type phenolic resin is 3g, the recycled material 1: recycled material 2: recycled material 3 is 60:15:25, the addition amount is 8g, silica is 80g, triphenylphosphine-1,2-methylimidazole is 0.3g, carbon black is 0.25g, palm wax is 0.3g, and silicone oil is 0.5g. They are added to a high-speed stirrer in sequence, mixed evenly, and melt-kneaded on an open rubber mixer at 95°C. The evenly mixed material is removed from the open rubber mixer, cooled and crushed to obtain a powdery material, and finally preformed into a cake material to obtain an epoxy resin composition.

[0042] Comparative Example 1: 3 g of biphenyl epoxy resin, 3 g of biphenyl phenol epoxy resin, 3 g of biphenyl phenol phenolic resin, 88 g of silica, 0.3 g of triphenylphosphine-1,2-methylimidazole, 0.25 g of carbon black, 0.3 g of palm wax, and 0.5 g of silicone oil are added to a high-speed stirrer in sequence, mixed evenly, and melt-kneaded on an open rubber mixer at 95°C. The evenly mixed material is removed from the open rubber mixer, cooled and crushed to obtain a powdery material, and finally preformed into a cake material to obtain an epoxy resin composition.

[0043] Comparative Example 2: 3 g of biphenyl-type epoxy resin, 3 g of biphenyl-phenol-type epoxy resin, 3 g of biphenyl-phenol-formaldehyde resin, 8 g of recycled material 1, 80 g of silica, 0.3 g of triphenylphosphine-1,2-methylimidazole, 0.25 g of carbon black, 0.3 g of palm wax, and 0.5 g of silicone oil are added to a high-speed stirrer in sequence, mixed evenly, and melt-kneaded on an open rubber mixer at 95°C. The evenly mixed material is removed from the open rubber mixer, cooled and crushed to obtain a powdery material, and finally preformed into a cake material to obtain an epoxy resin composition.

[0044] Comparative Example 3: 3 g of biphenyl-type epoxy resin, 3 g of biphenyl-phenol-type epoxy resin, 3 g of biphenyl-phenol-formaldehyde resin, 8 g of recycled material 2, 80 g of silica, 0.3 g of triphenylphosphine-1,2-methylimidazole, 0.25 g of carbon black, 0.3 g of palm wax, and 0.5 g of silicone oil are added to a high-speed stirrer in sequence, mixed evenly, and melt-kneaded on an open rubber mixer at 95°C. The evenly mixed material is removed from the open rubber mixer, cooled and crushed to obtain a powdery material, and finally preformed into a cake material to obtain an epoxy resin composition.

[0045] Comparative Example 4: 3 g of biphenyl-type epoxy resin, 3 g of biphenyl-phenol-type epoxy resin, 3 g of biphenyl-phenol-formaldehyde resin, 8 g of recycled material 3, 80 g of silica, 0.3 g of triphenylphosphine-1,2-methylimidazole, 0.25 g of carbon black, 0.3 g of palm wax, and 0.5 g of silicone oil are added to a high-speed stirrer in sequence, mixed evenly, and melt-kneaded on an open rubber mixer at 95°C. The evenly mixed material is removed from the open rubber mixer, cooled and crushed to obtain a powdery material, and finally preformed into a cake material to obtain an epoxy resin composition.

[0046] Comparative Example 5: 3 g of biphenyl epoxy resin, 3 g of biphenyl phenol epoxy resin, and 3 g of biphenyl phenol phenolic resin are directly crushed into epoxy molding material waste (without curing process), D50 particle size 35-45 μm: 10-15 μm: 2-5 μm is 60:20:20, the addition amount is 8 g, silica is 80 g, triphenylphosphine-1,2-methylimidazole 0.3 g, carbon black 0.25 g, palm wax 0.3 g, silicone oil 0.5 g, are added to a high-speed stirrer in sequence, mixed evenly, melt-mixed on an open rubber mixer at 95°C, the evenly mixed material is removed from the open rubber mixer, cooled and crushed to obtain a powdery material, and finally preformed into a cake material to obtain an epoxy resin composition.

[0047] Comparative Example 6: 3 g of biphenyl epoxy resin, 3 g of biphenyl phenol epoxy resin, and 3 g of biphenyl phenol phenolic resin are directly added to epoxy molding compound waste (without coupling agent surface treatment), D50 particle size 35-45 μm: 10-15 μm: 2-5 μm is 60:20:20, the addition amount is 8 g, silica is 80 g, triphenylphosphine-1,2-methylimidazole 0.3 g, carbon black 0.25 g, palm wax 0.3 g, and silicone oil 0.5 g are added to a high-speed stirrer in sequence, mixed evenly, and melt-mixed on an open rubber mixer at 95°C. The evenly mixed material is removed from the open rubber mixer, cooled and crushed to obtain a powdery material, and finally preformed into a cake material to obtain an epoxy resin composition.

[0048] Test method:

[0049] Spiral flow: This measurement uses a mold to measure the spiral flow. Under the conditions of a molding temperature of 175°C, an injection mold pressure of less than 6.9 MPa, and a curing time of 120 seconds, the spiral flow length is measured and expressed in cm.

[0050] Gelation time: This method measures the molding and curing characteristics and mixing uniformity of epoxy resin molding materials. Pour the above composition onto the center of a 175±2℃ electric hot plate and immediately spread it out with a tongue depressor to an area of ​​about 5cm2. Start timing from the moment the composition melts. Use the tongue depressor to push the powder at a frequency of 1 time per second. The end point is when the powder gradually changes from a fluid to a gel state. Read the time taken. Repeat the same method twice (the two measured values ​​should not exceed 2s). The gelation time is the average of the two test values.

[0051] Flash: Generally used to characterize the degree of mixing of the components in a molding compound; better mixing results in less flash. This measurement is performed on a molding press using a flash metal mold, with a mold temperature of 175±2°C and a pressure of 70kg±2kg / cm². 20±2g of sample powder is poured into the laminator cavity for molding. After 120 seconds of molding and the mold is opened, the mold is moved to the operating table. Flash Mold measures the length of flash from various grooves, expressed in mm.

[0052] Insoluble Matter Test: This test measures all materials in the epoxy molding compound that cannot be completely dissolved by acetone and remain on the sieve. Take 100g of epoxy resin composition and add a certain amount of acetone (epoxy resin:acetone ratio is 1:1). Stir thoroughly to dissolve the mixture (at 80-100 rpm for 60 minutes). Pass the mixture through a 100-mesh sieve and repeatedly rinse the residue on the sieve with acetone to remove any soluble matter and particles smaller than the sieve aperture. The insoluble matter (UPA) remains on the sieve.

[0053] Reliability testing: First, the required components were packaged using a molding machine. The packaged frames were then placed in an oven at 175°C for 6 hours. The frames were removed and analyzed for delamination using a scanning ultrasonic microscope. The results are shown in Table 2.

[0054] Table 2 Performance test results of epoxy resin compositions prepared in Examples and Comparative Examples

[0055]

[0056] Data analysis: Compared with Comparative Example 1, the SF, Flash, UPA and package SOP8 data of Examples 1-3 are equivalent, indicating that the epoxy molding compound waste after treatment can be used as a partial filler. At the same time, compared with Comparative Example 1, the GT of Examples 1-3 and Comparative Example 2-4 are equivalent, indicating that the resin in the waste has been completely cured, and the use of the waste has no effect on the curing system of the new epoxy molding compound system. Compared with Examples 1-3, Comparative Example 2-4 has a lower SF and a longer Flash, indicating that the waste needs to be compounded and used according to a certain particle size ratio after treatment. The small particle size makes the waste well dispersed in the matrix, and compounding reduces the phenomenon of small particle size waste being easy to agglomerate.

[0057] Compared with Example 1, the shorter GT of Comparative Example 5 indicates that the presence of resin in the waste material participates in the curing reaction of the new epoxy molding compound system, resulting in a shorter SF and an underfill of the SOP8 package. Furthermore, the GT and SF of Example 1 are comparable to those of Comparative Example 1, indicating that the addition of an amino curing agent can completely cure the waste material, eliminating free epoxy groups or phenolic hydroxyl groups from participating in the subsequent curing reaction.

[0058] Compared to Example 1, Comparative Example 6 exhibits a shorter SF, comparable GT, and larger Flash, indicating that the waste material, which was not pretreated with a coupling agent, exhibits poor dispersibility. This is primarily due to the high proportion of inorganic fillers in the waste material, which have poor compatibility with the organic matrix. Pretreating the waste material with a coupling agent can improve its dispersibility in the organic matrix.

[0059] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A method for recycling waste epoxy molding compound, characterized in that: The following steps are involved: (1) curing the epoxy molding compound waste with a curing agent to obtain cured epoxy molding compound waste; (2) crushing the solidified epoxy molding compound waste to obtain solidified epoxy molding compound waste powder; (3) performing surface pretreatment on the powder of the solidified epoxy molding compound waste to obtain recycled materials of the epoxy molding compound waste; The curing agent is an amino curing agent; the amino curing agent is an aromatic amine curing agent; the aromatic amine curing agent is diaminodiphenyl sulfone; The method for curing the epoxy molding compound waste by a curing agent in step (1) is as follows: the epoxy molding compound waste is crushed to a particle size D50 of 125 μm, and an amino curing agent of 2% to 5% by weight of the epoxy molding compound waste is added at a temperature of 110 to 130° C. for a reaction time of 4 to 6 hours to obtain cured epoxy molding compound waste; The particle size distribution D50 of the recycled materials of the epoxy molding compound waste in step (3) is 35-45 μm, 10-15 μm and 2-5 μm respectively.

2. The method for recycling waste epoxy molding compound according to claim 1, characterized in that: The surface pretreatment method comprises drying the solidified epoxy molding compound waste powder at 100-120° C. for 5 hours, preheating to 140° C. at a rotation speed of 1000 rpm, increasing the stirring speed to 2000-3000 rpm, spraying a silane coupling agent, and cooling to room temperature after 5-6 hours.

3. The method for recycling waste epoxy molding compound according to claim 2, wherein: The coupling agent is one of alkyl silane, amino silane, phenyl silane, mercapto silane, epoxy silane and silicate.

4. The method for recycling waste epoxy molding compound according to claim 2, wherein: The coupling agent is epoxy silane.

5. An application of the method for recycling waste epoxy molding compound according to any one of claims 1 to 4, characterized in that: The recycled material of the epoxy molding compound waste is used as a filler in the epoxy molding compound.

6. Application of the method for recycling waste epoxy molding compound according to claim 5, characterized in that: The epoxy molding compound is prepared from 6-12 parts of epoxy resin, 2-8 parts of phenolic resin, 70-85 parts of inorganic filler, 1-15 parts of recycled epoxy molding compound waste and 1-3 parts of other additives in parts by weight.

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