Preparation method of environment-friendly foaming ratio-controllable epoxy polystyrene foam

Abstract

The invention discloses a preparation method of environment-friendly epoxy polystyrene foam with controllable foaming ratio. A foaming agent and a surfactant are premixed to form an activation system with the Zeta potential larger than or equal to 30 mV, then the activation system is mixed with an epoxy resin matrix in stages, and the epoxy polystyrene foam is prepared by combining the delayed curing agent adding time and the vacuum defoaming technology. The foaming ratio is accurately controlled by 3-5 times, the foam size is 50-200 [mu] m, meanwhile, the VOCs emission is smaller than or equal to 50 [mu] g / g, the curing time is 1-3 h, and the bonding strength is larger than or equal to 12 MPa. The adhesive is suitable for high-performance light-weight bonding requirements in the fields of electronic packaging, automobile manufacturing and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and specifically relates to a method for preparing epoxy foam adhesive, and more particularly to a method for preparing epoxy foam adhesive with environmentally friendly characteristics and a precisely controllable foaming ratio. Background Art

[0002] Epoxy foams, with their excellent bonding properties, mechanical strength, and controllable foam structure, are widely used in building sealing, electronic device packaging, and automotive lightweighting. However, existing technologies generally have the following key issues that need to be addressed:

[0003] 1. Foaming uniformity control defects: In traditional processes, the compatibility between the foaming agent and the resin matrix is ​​poor, which easily leads to uneven foaming. For example, Chinese patent CN111499532B discloses the preparation and application of an epoxy resin foaming agent. The foaming agent and curing agent are added simultaneously. During the high-temperature mixing process, the foaming agent tends to decompose prematurely, resulting in a cell size distribution dispersion exceeding 40% (refer to the data in the patent example) and large fluctuations in product density (±15%). This makes it difficult to meet the requirements of application scenarios such as precision electronic packaging that require high material uniformity.

[0004] 2. VOC emissions and environmental issues: Existing technologies often use high-boiling-point organic solvents (such as xylene) as dispersion media to reduce system viscosity. The mixing process typically requires heating to above 80°C, resulting in the release of large amounts of volatile organic compounds (VOCs). For example, Japanese Patent Application Publication No. 2019-045678A reports VOC emissions as high as 150-200 μg / g, which not only causes environmental pollution but also increases subsequent purification costs.

[0005] 3. Cure-foaming kinetics conflict: When the foaming reaction and curing reaction proceed simultaneously (as described in US Patent Application Publication No. US20200071321A1), the two are in a competitive relationship. A too rapid cure rate can inhibit the full decomposition of the foaming agent, resulting in an insufficient expansion ratio (e.g., <2x). Excessive use of foaming agent or premature release of decomposition gases can disrupt the forming curing network structure, significantly reducing bond strength (comparative examples show a reduction of up to 30%-50%).

[0006] The above problems cause existing epoxy foam products to easily produce defects such as large holes, depressions, pinholes or surface unevenness on the surface or inside of the foam, limiting their application in high-performance fields. Summary of the Invention

[0007] The purpose of the present invention is to provide an environmentally friendly method for preparing epoxy foam with controllable foaming ratio. Through a staged mixing process and interfacial activity control technology, the problem that initial bubbles will leave large holes, depressions, pinholes or surface unevenness on the surface or inside of the foam after curing, resulting in poor foaming uniformity, high VOCs emissions, and mismatch between curing and foaming rates, is solved.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing an environmentally friendly epoxy foam with controllable foaming ratio, characterized by comprising the following steps:

[0010] (1) Raw material preparation: Prepare the following components by weight: 100-150 parts of epoxy resin, 20-50 parts of curing agent, 10-30 parts of foaming agent, 5-15 parts of surfactant, 20-50 parts of filler, and 10-20 parts of toughening agent;

[0011] (2) Premixing: Add epoxy resin, toughening agent and filler to a reaction vessel, stir and mix at 50-80°C and 200-500 rpm for 30-60 minutes to allow the toughening agent to fully graft with the epoxy resin (grafting rate ≥85%) to form a network precursor mixture A with elastic segments;

[0012] (3) Foaming agent activation treatment: The foaming agent and surfactant are mixed at a temperature of 20-30°C and a rotation speed of 100-300 rpm for 10-20 minutes, and a stable double-layer structure (Zeta potential absolute value ≥ 30 mV) is formed on the surface of the foaming agent particles by the directional adsorption effect of the surfactant to obtain an activated foaming agent mixture B;

[0013] (4) Main mixing: Add mixture B to mixture A, stir and mix at a temperature of 50-80°C and a speed of 300-600 rpm for 20-40 minutes, and use high shear force to evenly disperse the activated foaming agent in the resin matrix to form a mixture C containing uniform bubble nuclei (the average particle size of the bubble nuclei is 10-50 μm, and the particle size distribution satisfies D90 / D10 ≤ 1.5);

[0014] (5) Curing agent mixing: adding the curing agent to the mixture C, stirring and mixing at a temperature of 30-50° C. and a speed of 150-350 rpm for 10-20 minutes to obtain a curable foaming mixture D;

[0015] (6) Degassing: Place the mixture D in a vacuum environment and degas at a vacuum degree of 0.05-0.1 MPa for 10-30 minutes. This process not only removes macroscopic bubbles (diameter > 100 μm) introduced by stirring, but also precisely controls the expansion rate of the decomposition gas of the foaming agent through the negative pressure environment, ultimately producing the epoxy foam.

[0016] The epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin and novolac epoxy resin.

[0017] The curing agent is selected from at least one of an amine curing agent, an acid anhydride curing agent, and an imidazole curing agent.

[0018] The foaming agent is selected from at least one of azodicarbonamide, sodium bicarbonate, and ammonium carbonate.

[0019] The surfactant is a polyoxyethylene ester surfactant with an HLB value of 8-12, preferably at least one selected from polyoxyethylene sorbitan fatty acid esters (such as Tween series), alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, and fatty alcohol polyoxyethylene ether.

[0020] The filler is selected from at least one of calcium carbonate, talc and silicon dioxide.

[0021] The toughening agent is selected from at least one of carboxyl-terminated nitrile rubber (CTBN), polysulfide rubber, and polyurethane rubber.

[0022] Preferably, in step (2), the stirring temperature is 60-70° C., the stirring speed is 300-400 rpm, and the mixing time is 40-50 minutes.

[0023] Preferably, in step (4), the stirring temperature is 60-70° C., the stirring speed is 400-500 rpm, and the mixing time is 25-35 minutes.

[0024] Preferably, the vacuum degree of vacuum degassing in step (6) is 0.06-0.08 MPa, and the degassing time is 15-25 minutes.

[0025] Preferably, the vacuum degassing in step (6) adopts a gradient pressure reduction mode: the vacuum degree is maintained at 0.06-0.08 MPa for the initial 5-6 minutes, and the vacuum degree is increased to 0.09-0.1 MPa in the subsequent treatment stage and maintained until the degassing is completed. This mode is more conducive to the stepwise removal of bubbles of different sizes and reduces the residual microscopic bubbles.

[0026] Preferably, the grafting rate of the toughening agent and the epoxy resin in step (2) is ≥85%, which can be detected by Fourier transform infrared spectroscopy (FTIR) at 1710 cm -1 The presence or intensity change of the characteristic peak of carbamate or ester carbonyl group at the same position (depending on the type of toughening agent) can be used to confirm the presence or intensity change of the characteristic peak of carbamate or ester carbonyl group at the same position (depending on the type of toughening agent).

[0027] Preferably, the average particle size of the bubble nuclei in the mixture C obtained in step (4) is 10-50 μm, and the uniformity of the particle size distribution satisfies D90 / D10≤1.5.

[0028] The key points of the inventive method are as follows:

[0029] 1. Foaming agent pre-activation mechanism: The foaming agent is pre-mixed with a surfactant of a specific HLB value (8-12) at low temperature (20-30°C) to form a stable dispersion with an absolute zeta potential of ≥30mV. This activation layer significantly slows the decomposition rate of the foaming agent during the subsequent higher-temperature mixing step, decoupling the foaming reaction from the resin curing process and avoiding kinetic conflicts.

[0030] 2. Gradient mixing process:

[0031] Premixing stage: At a moderate temperature (50-80°C), the epoxy resin and toughening agent are fully grafted (grafting rate ≥ 85%) to form a network precursor with elastic buffering effect, thereby improving the toughness and crack resistance of the final foam.

[0032] Main mixing stage: Under moderate temperature (50-80°C) and high shear force (300-600rpm), the pre-activated blowing agent system is evenly dispersed in the pre-mixed resin matrix to ensure the formation of small (10-50μm) and highly uniformly distributed (D90 / D10 ≤ 1.5) bubble nuclei, laying the foundation for the final cell uniformity;

[0033] 3. Delayed curing agent addition strategy: After the resin / activated blowing agent system is thoroughly mixed (i.e., after obtaining mixture C), the curing agent is introduced. This strategy effectively prevents the premature reaction of curing agents (especially amines) with certain blowing agents (such as carbonates) to generate gases (such as CO2) and escape, ensuring that the foaming gas source mainly comes from the controlled decomposition of the blowing agent, thereby improving the controllability of the foaming ratio.

[0034] 4. Coordinated control of vacuum degassing: Degassing is carried out at a relatively low vacuum degree (0.05-0.1MPa), which has a dual effect: (a) efficiently removing large mechanical bubbles (diameter >100μm) introduced during the stirring process; (b) through a precisely controlled negative pressure environment, controlling the expansion behavior of the decomposition gas of the foaming agent, causing the final pore size to be concentrated in the range of 50-200μm (accounting for ≥90%) and improving the closed cell ratio (usually >95%).

[0035] 6. Low VOCs environmental protection characteristics: The entire preparation process is carried out at a low temperature and moderate stirring speed, and no organic solvent is added, which significantly reduces the generation and emission of volatile organic compounds (VOCs). The VOCs content can be controlled at ≤50μg / g, meeting strict environmental protection requirements.

[0036] 7. The selected raw materials and processes enable the epoxy foam to achieve a good balance between curing speed and bonding strength, which can not only meet the needs of rapid construction, but also ensure that the bonding parts have high strength, thus broadening the application range of the product.

[0037] The present invention premixes a foaming agent with a surfactant to form an activated system with a zeta potential ≥ |30mV|. This is then mixed with an epoxy resin matrix in stages. Combined with delayed curing agent addition and vacuum degassing, this method achieves precise control of the foaming ratio by 3-5 times (deviation ≤±5%), a cell size of 50-200μm (uniformity D90 / D10 ≤1.5), VOCs emissions ≤50μg / g, a curing time of 1-3 hours, and a bond strength ≥12MPa. This invention is particularly suitable for bonding and packaging applications in fields such as electronic packaging and automotive manufacturing, where lightweighting, high bond strength, high uniformity, and environmental friendliness are crucial. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a scanning electron microscope (SEM) image of the internal cell structure of the epoxy foam product prepared in Example 1, showing its uniform and fine closed-cell structure. DETAILED DESCRIPTION

[0039] Example 1 Preparation of general medium-density epoxy foam

[0040] (1) Raw material ratio (by weight):

[0041] Bisphenol A epoxy resin: 100 parts

[0042] Amine curing agent (diethylenetriamine): 20 parts

[0043] Foaming agent (azodicarbonamide): 3 parts

[0044] Surfactant (polyoxyethylene sorbitan monostearate, HLB = 9.6): 5 parts

[0045] Filler (calcium carbonate, particle size 2 μm): 20 parts

[0046] Toughener (carboxyl-terminated nitrile rubber, CTBN): 10 parts

[0047] (2) Preparation process:

[0048] 2-1) Premixing: Bisphenol A epoxy resin, CTBN and calcium carbonate were added to a reaction kettle and stirred at 200 rpm for 30 minutes at 50°C to obtain a mixture A (viscosity reduced to about 8500 mPa·s; FTIR detection 1710 cm -1 The characteristic peak of ester carbonyl generated by the reaction of carboxyl and epoxy groups appears nearby, indicating that the grafting reaction occurs);

[0049] 2-2) Activation of the foaming agent: Azodicarbonamide and polyoxyethylene sorbitan monostearate were mixed at 20° C. and 100 rpm for 10 minutes to obtain a mixture B (the zeta potential value was −32 mV, indicating that the dispersion system was stable);

[0050] 2-3) Main mixing: Add mixture B to mixture A, stir and mix at 50°C and 300 rpm for 20 minutes to obtain mixture C (the average bubble nucleus diameter measured by laser particle size analyzer is about 15 μm, D90 / D10 = 1.4);

[0051] 2-4) Curing agent mixing: Diethylenetriamine was slowly added to mixture C, and the mixture was mixed at 30° C. and 150 rpm for 10 minutes (the pH value of the system was stabilized at 8.5-9.0) to obtain mixture D;

[0052] 2-5) Vacuum degassing: The mixture D was placed in a vacuum apparatus and degassed at a vacuum degree of 0.05 MPa for 10 minutes (microscope observation confirmed that the removal rate of bubbles with a diameter of >120 μm was >98%) to obtain an epoxy foam adhesive.

[0053] (3) Performance testing:

[0054] Foaming ratio: 3.0±0.2 times;

[0055] The curing time is 45 min (using differential scanning calorimetry (DSC) at the set curing temperature until the heat flow curve baseline is stable).

[0056] Cell structure: pore size 5-25μm (accounting for 90%), SEM image shows closed cell ratio >98%

[0057] Compression strength: 10.6 MPa (tested according to ASTM D695 standard).

[0058] Cell uniformity: D90 / D10 = 1.4 (D10: 10% of the cell sizes in the foam are smaller than this value, representing the upper limit of the smallest cell population; D90: 90% of the cell sizes in the foam are smaller than this value, representing the lower limit of the largest cell population; the closer the D90 / D10 ratio is to 1, the more concentrated the cell size distribution and the better the uniformity).

[0059] VOCs emissions: 38 μg / g (detected by gas chromatography-mass spectrometry GC-MS, the main component is a trace amount of unreacted epoxy oligomers).

[0060] Bond strength: 12.8MPa (according to relevant ASTM D1002 bond strength test standard).

[0061] Thermal stability: After being placed at 80°C for 24 hours, the collapse rate of the foamed structure is 2.1%.

[0062] Example 2 Preparation of fast-curing high-strength epoxy foam

[0063] (1) Raw material ratio:

[0064] Bisphenol F epoxy resin: 120 parts

[0065] Acid anhydride curing agent (methyltetrahydrophthalic anhydride): 30 parts

[0066] Foaming agent (sodium bicarbonate): 10 parts

[0067] Surfactant (nonylphenol polyoxyethylene ether, HLB = 12.8): 10 parts

[0068] Filler (talc, 1250 mesh): 30 parts

[0069] Toughening agent (liquid polysulfide rubber): 15 parts

[0070] (2) Preparation process:

[0071] 2-1) Premixing: Add bisphenol F epoxy resin, liquid polysulfide rubber, and talc into a reaction kettle and stir at 200 rpm for 30 minutes at 50° C. to obtain a mixture A;

[0072] 2-2) Activating the foaming agent: mixing sodium bicarbonate and nonylphenol polyoxyethylene ether at 20° C. and 100 rpm for 10 minutes to obtain a mixture B);

[0073] 2-3) Main mixing: Add mixture B to mixture A, stir at 50°C and 400 rpm for 20 minutes to obtain mixture C, wherein the diameter of the CO2 bubble nucleus generated by the decomposition of sodium bicarbonate is ≤50 μm;

[0074] 2-4) Curing agent mixing: Slowly add methyltetrahydrophthalic anhydride to mixture C, and mix at 40° C. and 150 rpm for 10 minutes to obtain mixture D;

[0075] 2-5) Vacuum degassing: Degas the mixture D at 0.05 MPa vacuum for 10 minutes to obtain epoxy foaming adhesive.

[0076] (3) Performance data:

[0077] Foaming ratio: 4.1±0.3 times

[0078] Cell structure: SEM observations show that the average pore size of the cells is about 80 μm, mainly distributed in the range of 14-40 μm (accounting for 94%), and the closed cell rate is >97%.

[0079] Curing time: 28 minutes

[0080] Compression strength: 14.8 MPa (ASTM D695)

[0081] Pore ​​uniformity: (D90 / D10) = 1.4

[0082] VOCs emissions: 35 μg / g (GC-MS detection, the main component is unreacted epoxy oligomers)

[0083] Bond strength: 13.5MPa

[0084] Thermal stability: After being placed at 80°C for 24 hours, the foam structure collapse rate is 1.8%

[0085] Example 3 Preparation of ultra-low density heat-resistant epoxy foam

[0086] (1) Raw material ratio:

[0087] Novolac epoxy resin (DEN431): 150 parts

[0088] Imidazole curing agent (2-ethyl-4-methylimidazole): 50 parts

[0089] Foaming agent (ammonium carbonate): 15 parts

[0090] Surfactant (lauryl polyoxyethylene ether, HLB = 10.0): 15 parts

[0091] Filler (nanosilica, Aerosil 200): 50 parts

[0092] Toughener (polyurethane rubber, hydroxyl value 56mgKOH / g): 20 parts

[0093] (2) Preparation process:

[0094] 2-1) Premixing: Phenolic epoxy resin, polyurethane rubber and nano-silica were added to a reaction kettle and stirred at 80°C and 400 rpm for 50 minutes to obtain a mixture A (FTIR detection 1710 cm -1 There is an obvious urethane characteristic peak at , indicating that the epoxy group and the hydroxyl group undergo a grafting reaction);

[0095] 2-2) Activation of the foaming agent: Ammonium carbonate and lauryl alcohol polyoxyethylene ether were mixed at 30° C. and 250 rpm for 15 minutes to obtain a mixture B (Zeta potential value -38 mV);

[0096] 2-3) Main mixing: Add mixture B to mixture A, stir and mix at 70°C and 500 rpm for 35 minutes to obtain mixture C (laser particle size analyzer measurement of bubble nucleus D50 = 32 μm, D90 / D10 = 1.5);

[0097] 2-4) Curing agent mixing: 2-ethyl-4-methylimidazole was slowly added to mixture C, and the mixture was mixed at 50° C. and 300 rpm for 15 minutes to obtain mixture D;

[0098] 2-5) Vacuum degassing: The mixture D was subjected to vacuum degassing with a gradient pressure reduction for 30 minutes: the vacuum degree was maintained at 0.08 MPa for the first 5 minutes and then increased to 0.1 MPa and maintained there for the next 25 minutes (microscope observation confirmed that the bubble residual rate was <0.1%) to obtain an epoxy foam adhesive.

[0099] (3) Performance data:

[0100] Foaming ratio: 5.0±0.1 times

[0101] Curing time: 40 minutes

[0102] Cell structure: SEM observations show that the average pore size of the cells is about 60 μm, mainly distributed in the range of 10-35 μm (accounting for 90%), and the closed cell rate is >95%.

[0103] Compression strength: 5.91MPa (ASTM D695, due to low density)

[0104] Pore ​​uniformity: D90 / D10=1.3

[0105] VOCs emissions: 42 μg / g (GC-MS detection, the main component is unreacted epoxy oligomers)

[0106] Bond strength (high temperature): ≥8.0MPa when tested at 150℃

[0107] Thermal stability: After being placed at 80°C for 24 hours, the collapse rate of the foamed structure is 3.2%.

[0108] Comparative Example 1 Preparation of epoxy foam by conventional one-step mixing method

[0109] (1) Raw material ratio:

[0110] Bisphenol A epoxy resin: 100 parts

[0111] Diethylenetriamine curing agent: 20 parts

[0112] Azodicarbonamide: 5 parts

[0113] Xylene solvent: 30 parts (used to reduce viscosity)

[0114] Calcium carbonate: 20 parts

[0115] No surfactants or toughening agents added

[0116] (2) Preparation process:

[0117] All raw materials (epoxy resin, curing agent, foaming agent, solvent, filler) were added into the reactor at one time, stirred at 600 rpm at 80°C for 30 minutes, and directly injection molded and cured (without vacuum degassing treatment) to obtain epoxy foam samples.

[0118] (3) Performance testing:

[0119] Foaming ratio: 2.1±0.8 times (fluctuation range of ±38%), which is significantly lower than that of the embodiment of the present invention and the fluctuation is much greater.

[0120] Cell structure: SEM observations show that the cell size is extremely uneven, with a pore size range of 30-500 μm, a dispersion of D90 / D10 = 4.2, a closed cell ratio of only about 65%, and a large number of open cells and connected cells.

[0121] Curing time: 60min

[0122] Bond strength: 6.8 MPa, about 47% lower than Example 1 (12.8 MPa)

[0123] VOCs emissions: up to 205 μg / g (GC-MS detection, mainly containing a large amount of xylene solvent residue)

[0124] Thermal stability: After being placed at 80°C for 24 hours, the collapse rate of the foamed structure is 10%.

[0125] Comparative Example 2: Synchronous addition of blowing agent and curing agent (violating the delayed addition strategy of the present invention)

[0126] (1) Raw material ratio (same as Example 1):

[0127] Bisphenol A epoxy resin: 100 parts

[0128] Amine curing agent (diethylenetriamine): 20 parts

[0129] Foaming agent (azodicarbonamide): 3 parts

[0130] Surfactant (polyoxyethylene sorbitan monostearate, HLB = 9.6): 5 parts

[0131] Filler (calcium carbonate, particle size 2 μm): 20 parts

[0132] Toughener (carboxyl-terminated nitrile rubber, CTBN): 10 parts

[0133] (2) Preparation process:

[0134] 2-1) Premixing: Add bisphenol A epoxy resin, CTBN, and calcium carbonate into a reaction kettle and stir at 200 rpm for 30 minutes at 50°C to obtain mixture A (viscosity of approximately 8500 mPa·s);

[0135] 2-2) Mixing: Add azodicarbonamide, polyoxyethylene sorbitan monostearate, and diethylenetriamine curing agent together, and stir at 50° C. and 300 rpm for 30 minutes to obtain a mixture C (different from the order of steps 3 and 5 of the present invention, the curing agent and the foaming agent are mixed in advance)

[0136] 2-5) Vacuum degassing: The mixture C was degassed at a vacuum degree of 0.05 MPa for 10 minutes to obtain an epoxy foam sample.

[0137] (3) Performance testing

[0138] Premature decomposition of the foaming agent: Thermogravimetric analysis (TGA) showed that during the mixing process (50°C, 30 min), the decomposition rate of azodicarbonamide was greater than 50% (the activation stabilization mechanism was destroyed and the foaming agent decomposed in large quantities during mixing), and the foaming ratio was 1.8±0.6 times.

[0139] Thermal stability: After being placed at 80°C for 24 hours, the collapse rate of the foamed structure is 4.3%.

[0140] Interface defects: There are obvious microcracks at the resin-filler interface (due to a serious mismatch between the release of foaming gas (premature or blocked) and the formation of the curing network, resulting in internal stress concentration and interface damage);

[0141] Bond strength: The bond strength was 4.6 MPa, significantly lower than that in Example 1.

[0142] Table 1 Comparative analysis of the embodiments and comparative examples

[0143]

[0144] By comparing Examples 1-3 with Comparative Examples 1-2, the significant advantages of the environmentally friendly controllable expansion ratio epoxy foam preparation method provided by the present invention are fully demonstrated: the expansion ratio is high and precisely controllable (3-5 times ± 5%), the pore structure is highly uniform and fine (50-200μm, D90 / D10≤1.5), the closed cell ratio is high (>95%), and the conflict between curing and foaming dynamics is effectively resolved, VOCs emissions are significantly reduced (≤50μg / g), and environmental protection is good. High bonding strength (≥12MPa) and good comprehensive performance are obtained. The process is stable and reliable, with good repeatability. The method of the present invention has important industrial application value.

Claims

1. A method for preparing an environmentally friendly epoxy foam with controllable foaming ratio, characterized in that: The following steps are involved: (1) By weight, take 100-150 parts of epoxy resin, 20-50 parts of curing agent, 10-30 parts of foaming agent, 5-15 parts of surfactant, 20-50 parts of filler, and 10-20 parts of toughening agent; (2) stirring and mixing the epoxy resin, toughening agent and filler at 50-80°C and 200-500 rpm for 30-60 minutes to form a mixture A; (3) mixing the foaming agent and the surfactant at 20-30° C. and 100-300 rpm for 10-20 minutes to form a mixture B; (4) Mixing mixture A and mixture B, stirring the mixture at 50-80° C. and 300-600 rpm for 20-40 minutes to obtain mixture C; (5) Add the curing agent to the mixture C, and stir and mix at 30-50°C and 150-350 rpm for 10-20 minutes to obtain a mixture D; (6) Degassing treatment: Degas the mixture D under a vacuum degree of 0.05-0.1 MPa for 10-30 minutes to obtain epoxy foam.

2. The method for preparing an environmentally friendly epoxy foam with controllable foaming ratio according to claim 1, wherein: The epoxy resin is at least one of bisphenol A epoxy resin, bisphenol F epoxy resin or novolac epoxy resin; the curing agent is at least one of amine curing agent, acid anhydride curing agent or imidazole curing agent; the foaming agent is at least one of azodicarbonamide, sodium bicarbonate or ammonium carbonate.

3. The method for preparing an environmentally friendly epoxy foam with controllable foaming ratio according to claim 1, wherein: The surfactant is at least one of polyoxyethylene sorbitan fatty acid ester, alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether or fatty alcohol polyoxyethylene ether.

4. The method for preparing an environmentally friendly epoxy foam with controllable foaming ratio according to claim 3, wherein: The surfactant is a polyoxyethylene ester with an HLB value of 8-12.

5. The method for preparing an environmentally friendly epoxy foam with controllable foaming ratio according to claim 1, wherein: The filler is at least one of calcium carbonate, talc or silicon dioxide, and the toughening agent is at least one of carboxyl-terminated nitrile rubber, polysulfide rubber or polyurethane rubber.

6. The method for preparing an environmentally friendly epoxy foam with controllable foaming ratio according to claim 1, wherein: In step (2), the stirring temperature is 60-70°C, the stirring speed is 300-400 rpm, and the mixing time is 40-50 minutes; in step (4), the stirring temperature is 60-70°C, the stirring speed is 400-500 rpm, and the mixing time is 25-35 minutes.

7. The method for preparing an environmentally friendly epoxy foam with controllable foaming ratio according to claim 1, characterized in that: The vacuum degree of vacuum degassing in step (6) is 0.06-0.08 MPa, and the degassing time is 15-25 minutes.

8. The method for preparing an environmentally friendly epoxy foam with controllable foaming ratio according to claim 7, characterized in that: The vacuum degassing in step (6) adopts a gradient pressure reduction mode, with the vacuum degree being 0.06-0.08 MPa for the initial 5-6 minutes and rising to 0.09-0.1 MPa in the subsequent treatment stage.

9. The method for preparing an environmentally friendly epoxy foam with controllable foaming ratio according to claim 1, characterized in that: In step (2), the grafting rate of the toughening agent and the epoxy resin is ≥85%.

10. The method for preparing an environmentally friendly epoxy foam with controllable foaming ratio according to claim 1, characterized in that: The average particle size of the bubble nuclei in the mixture C obtained in step (4) is 10-50 μm, and the particle size distribution satisfies D90 / D10≤1.5.

Images