A low-moisture-absorbing epoxy film and its preparation method

Abstract

This invention discloses a low-moisture-absorbing epoxy film and its preparation method. The technical solution includes a protective film, an epoxy adhesive layer, and a base film arranged layer by layer. The epoxy adhesive layer is disposed between the protective film and the base film. The epoxy adhesive layer includes the following components by weight: epoxy resin, 100 parts; curing agent, 60-125 parts; accelerator, 0.5-1 part; inorganic filler, 200-800 parts; pigment, 2-3 parts; coupling agent, 2-6 parts. The preparation method includes step 1, mixing: according to the ratio, the epoxy resin and curing agent are first stirred and mixed evenly, and the inorganic filler and pigment are mixed evenly using a homogenizer; then the epoxy resin and curing agent mixture, the filler and pigment mixture, and the coupling agent are stirred and mixed; finally, the accelerator is added and stirred and mixed. Step 2, coating; Step 3, surface drying; Step 4, lamination. Through component optimization, it has good flexibility and pot life before curing, and after curing, it has high Tg, low moisture absorption, and also exhibits a low coefficient of thermal expansion.

Description

Technical Field

[0001] This invention relates to the field of epoxy film preparation technology, and in particular to a low-hygroscopic epoxy film and its preparation method. Background Technology

[0002] Epoxy film is a single-component epoxy adhesive. When heated to a certain temperature, the curing agent and resin cross-link and polymerize, with the degree of cross-linking gradually increasing until it is fully cured and molded, providing adhesion and protection. Because epoxy film possesses the inherent advantages of epoxy adhesives, such as high bonding strength, low curing shrinkage, dimensional stability, excellent electrical properties, and excellent resistance to chemical media, and because it offers unique advantages in ease of use compared to liquid adhesives, it has a very broad application prospect in many fields such as electronics, communications, automotive, aerospace, machinery, shipbuilding, rail transportation, wind power generation, and construction, and is highly favored by the industry.

[0003] In recent years, the focus of attention on epoxy films has mainly been on properties such as high bonding strength, resistance to high / low temperatures, high mechanical properties, and flame retardancy, with few reports on low water absorption and low moisture absorption. CN101845287A discloses a medium-temperature curing epoxy adhesive for flexible printed circuit board encapsulation films and its preparation method. The main components of this epoxy film include: 1-15 parts of liquid epoxy resin CYD-128, 25-40 parts of solid epoxy resin CYD-014, 3-10 parts of liquid carboxylated nitrile rubber CTBN, 5-20 parts of solid carboxylated nitrile rubber 1072, 1-15 parts of low-molecular-weight polyamide medium-temperature curing agent, and 15-30 parts of inorganic filler. This invention utilizes a curing agent with medium-temperature curing characteristics, which can cure at 135-145℃. The moisture absorption rate of this epoxy film is at the level of 3.5%-4%.

[0004] However, as the application environment of epoxy films becomes increasingly harsh, the requirements for the moisture absorption of epoxy films are also becoming higher. Currently, the moisture absorption rate of epoxy films is 3.5% to 4%, which can no longer meet the requirements. Excessive moisture absorption rate can easily cause reliability problems such as decreased bonding strength, decreased aging resistance, delamination, and short circuits. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention aims to provide a low-moisture-absorbing epoxy film and its preparation method. Its advantages lie in that, through component optimization, it not only has excellent flexibility and pot life before curing, but also exhibits high Tg, low moisture absorption rate, and a low coefficient of thermal expansion after curing.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] A low-moisture-absorbing epoxy film, characterized in that it comprises a protective film, an epoxy adhesive layer, and a base film arranged in layers, wherein the epoxy adhesive layer is disposed between the protective film and the base film, and the epoxy adhesive layer comprises the following components by weight: epoxy resin, 100 parts; curing agent, 60-125 parts; accelerator, 0.5-1 part; inorganic filler, 200-800 parts; pigment, 2-3 parts; coupling agent, 2-6 parts.

[0008] Furthermore, the epoxy resin is selected from one or more combinations of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type, bisphenol AF type, phenolic varnish type epoxy resin, bisphenol A phenolic epoxy resin, o-cresol phenolic varnish type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, silicon-containing epoxy resin, and epoxy resin in which some hydrogen atoms are replaced by halogens.

[0009] Furthermore, the curing agent is a latent curing agent, and the curing agent is any one or a combination of at least two of acid anhydrides, amines, and phenols.

[0010] Furthermore, the accelerator is any one or a combination of at least two of imidazoles and their derivatives, organophosphorus compounds, amines, and quaternary ammonium salts.

[0011] Furthermore, the inorganic filler is any one or a combination of at least two of the following: aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium carbonate, magnesium carbonate, magnesium silicate, aluminum silicate, calcium oxide, magnesium oxide, aluminum oxide, titanium oxide, aluminum borate, zinc borate, calcium borate, sodium borate, aluminum nitride, boron nitride, silicon nitride, silicon dioxide, titanium dioxide, talc, and mica; wherein the silicon dioxide includes modified silicon dioxide, surface-modified silicon dioxide, crystalline silicon dioxide, or fused silicon dioxide.

[0012] Furthermore, the pigment is one of carbon black and titanium dioxide.

[0013] Furthermore, the coupling agent is any one or a combination of at least two of alkane coupling agents, aluminate coupling agents, and titanate coupling agents.

[0014] Furthermore, the base film is one or more of PET and PI films, and the protective film is a release film, which is one or more of PET release film, PE release film, OPP release film, and composite release film; the thickness ratio of the base film to the protective film is (6-10):(6-10); and the light release force of the protective film is 1-20g / 25mm.

[0015] A method for preparing a low-hygroscopic epoxy film includes the following steps:

[0016] Step 1, Ingredient Mixing: According to the formula, first stir and mix the epoxy resin and curing agent evenly, and use a homogenizer to mix the inorganic filler and pigment evenly; then stir and mix the epoxy resin and curing agent mixture, the filler and pigment mixture, and the coupling agent, and use a screw press or kneader to fully disperse the filler; finally, add the accelerator, and use a homogenizer to fully disperse the overall formula while it is hot, and then vacuum degas it to obtain the epoxy resin composition;

[0017] Step 2: Apply the epoxy resin composition onto the base film, controlling the coating thickness to be 1.0 to 1.2 times the required thickness of the adhesive film after surface drying;

[0018] Step 3, Surface drying: Use a tunnel-type forced-air drying oven to dry the epoxy resin wet film at 80℃ for 0.5-1 min, and then dry it at room temperature for 0.5-1 min;

[0019] Step 4: Composite the surface of the epoxy resin film dried in Step 3 with the protective film to obtain a low-hygroscopic epoxy film.

[0020] Furthermore, in step 1, the epoxy resin and curing agent are stirred and mixed evenly at 70-120°C, and the epoxy resin and curing agent mixture, filler and pigment mixture, and coupling agent are stirred and mixed at 100-120°C; in step 4, the composite temperature is 50-120°C, the composite pressure is 0.5-2MPa, and the composite speed is 2.5-5m / s.

[0021] In summary, the present invention has the following beneficial effects:

[0022] 1. Through component optimization, it not only has good flexibility and pot life before curing, but also has high Tg and low moisture absorption after curing, while also showing a low coefficient of thermal expansion.

[0023] 2. By strictly controlling the equivalent ratio of reactive groups and through the screening / adjustment of components, the moisture absorption rate in the resin system is controlled at a very low level, which improves the aging resistance and reliability of the epoxy film.

[0024] 3. During the preparation of epoxy film, the epoxy resin and curing agent are mixed at 70-120℃. Under this condition, the epoxy resin and curing agent maintain good fluidity and avoid premature polymerization. The filler and pigment mixture and coupling agent are stirred and mixed at 100-120℃ to ensure that the components have good fluidity and that all components are fully mixed. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a low-hygroscopic epoxy film.

[0026] In the diagram, 1 is the epoxy adhesive layer; 2 is the protective film; and 3 is the base film. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, will further illustrate the solutions proposed by this invention. The advantages and features of this invention will become clearer from the following description.

[0028] Example 1:

[0029] A type of low-moisture-absorbing epoxy film, such as Figure 1 As shown, it includes a protective film, an epoxy adhesive layer, and a base film arranged in layers. The epoxy adhesive layer is disposed between the protective film and the base film. The epoxy adhesive layer includes components counted by weight as follows:

[0030]

[0031] The method for preparing the low-hygroscopic epoxy film described in Example 1 includes the following steps:

[0032] Step 1: Ingredient Mixing: Prepare the components according to the formula. First, mix the epoxy resin composition and curing agent evenly at 80°C. Mix the inorganic filler and pigment evenly using a homogenizer. Then, mix the epoxy resin and curing agent mixture, the filler and pigment mixture, and the coupling agent at 100°C. Use a screw press or kneader to fully disperse the filler (screw speed approximately 120 rpm, temperature in each zone between 70 and 110°C; kneader fast and slow paddle speed approximately 40 / 25 (r / min), temperature controlled at 100°C). Finally, add the accelerator and use a homogenizer to fully disperse the overall formula while it is still hot (homogenizer speed 1200 r / min, time 3 min). Vacuum degassing is then performed.

[0033] Step 2: Coat the epoxy resin composition obtained in Step 1 onto the base film, controlling the coating thickness to be 1.1 times the required thickness of the adhesive film after surface drying.

[0034] Step 3: Using a tunnel-type forced-air drying oven, dry the epoxy resin wet film obtained in Step 2 at 80°C for 1 minute, and then at room temperature for 1 minute.

[0035] Step 4: Composite the epoxy resin film obtained in Step 3 with the protective film. The composite temperature is 50℃, the composite pressure is 1MPa, and the composite speed is 5m / s to obtain a low moisture absorption epoxy film.

[0036] Example 2:

[0037] A low-moisture-absorbing epoxy film includes a protective film, an epoxy adhesive layer, and a base film arranged in layers. The epoxy adhesive layer is disposed between the protective film and the base film. The epoxy adhesive layer includes components in parts by weight:

[0038]

[0039] The method for preparing the low-hygroscopic epoxy film described in Example 2 includes the following steps:

[0040] Step 1: Ingredient Mixing: Prepare the components according to the formula. First, mix the epoxy resin composition and curing agent evenly at 80°C. Mix the inorganic filler and pigment evenly using a homogenizer. Then, mix the epoxy resin and curing agent mixture, the filler and pigment mixture, and the coupling agent at 100°C. Use a screw press or kneader to fully disperse the filler (screw speed approximately 120 rpm, temperature in each zone between 70 and 110°C; kneader fast and slow paddle speed approximately 40 / 25 (r / min), temperature controlled at 100°C). Finally, add the accelerator and use a homogenizer to fully disperse the overall formula while it is still hot (homogenizer speed 1200 r / min, time 3 min). Vacuum degassing is then performed.

[0041] Step 2: Apply the epoxy resin composition obtained in Step 1 onto the base film at 80°C, controlling the coating thickness to be 1.1 times the required thickness of the adhesive film after surface drying.

[0042] Step 3: Using a tunnel-type forced-air drying oven, dry the epoxy resin wet film obtained in Step 2 at 80°C for 1 minute, and then at room temperature for 1 minute.

[0043] Step 4: Composite the epoxy resin film obtained in Step 3 with the protective film. The composite temperature is 50℃, the composite pressure is 1.1MPa, and the composite speed is 5m / s to obtain a low moisture absorption epoxy film.

[0044] Example 3:

[0045] A low-moisture-absorbing epoxy film includes a protective film, an epoxy adhesive layer, and a base film arranged in layers. The epoxy adhesive layer is disposed between the protective film and the base film. The epoxy adhesive layer includes components in parts by weight:

[0046]

[0047] The method for preparing the low-hygroscopic epoxy film described in Example 3 includes the following steps:

[0048] Step 1: Ingredient Mixing: Prepare the components according to the formula. First, mix the epoxy resin composition and curing agent evenly at 80°C. Mix the inorganic filler and pigment evenly using a homogenizer. Then, mix the epoxy resin and curing agent mixture, the filler and pigment mixture, and the coupling agent at 100°C. Use a screw press or kneader to fully disperse the filler (screw speed approximately 120 rpm, temperature in each zone between 70 and 110°C; kneader fast and slow paddle speed approximately 40 / 25 (r / min), temperature controlled at 100°C). Finally, add the accelerator and use a homogenizer to fully disperse the overall formula while it is still hot (homogenizer speed 1200 r / min, time 3 min). Vacuum degassing is then performed.

[0049] Step 2: Apply the epoxy resin composition obtained in Step 1 onto the base film at 80°C, controlling the coating thickness to be 1.1 times the required thickness of the adhesive film after surface drying.

[0050] Step 3: Using a tunnel-type forced-air drying oven, dry the epoxy resin wet film obtained in Step 2 at 80°C for 1 minute, and then at room temperature for 1 minute.

[0051] Step 4: Composite the epoxy resin film obtained in Step 3 with the protective film. The composite temperature is 50℃, the composite pressure is 1.0MPa, and the composite speed is 5m / s to obtain a low moisture absorption epoxy film.

[0052] Comparative Example 1:

[0053] A type of low-moisture-absorbing epoxy film, such as Figure 1 As shown, it includes a protective film, an epoxy adhesive layer, and a base film arranged in layers. The epoxy adhesive layer is disposed between the protective film and the base film. The epoxy adhesive layer includes components counted by weight as follows:

[0054]

[0055] The method for preparing the low-hygroscopic epoxy film described in Example 1 includes the following steps:

[0056] Step 1: Ingredient Mixing: Prepare the components according to the formula. First, mix the epoxy resin composition and curing agent evenly at 80°C. Mix the inorganic filler and pigment evenly using a homogenizer. Then, mix the epoxy resin and curing agent mixture, the filler and pigment mixture, and the coupling agent at 100°C. Use a screw press or kneader to fully disperse the filler (screw speed approximately 120 rpm, temperature in each zone between 70 and 110°C; kneader fast and slow paddle speed approximately 40 / 25 (r / min), temperature controlled at 100°C). Finally, add the accelerator and use a homogenizer to fully disperse the overall formula while it is still hot (homogenizer speed 1200 r / min, time 3 min). Vacuum degassing is then performed.

[0057] Step 2: Coat the epoxy resin composition obtained in Step 1 onto the base film, controlling the coating thickness to be 1.1 times the required thickness of the adhesive film after surface drying.

[0058] Step 3: Using a tunnel-type forced-air drying oven, dry the epoxy resin wet film obtained in Step 2 at 80°C for 1 minute, and then at room temperature for 1 minute.

[0059] Step 4: Composite the epoxy resin film obtained in Step 3 with the protective film. The composite temperature is 50℃, the composite pressure is 1MPa, and the composite speed is 5m / s to obtain a low moisture absorption epoxy film.

[0060] Performance testing:

[0061] Relevant testing methods:

[0062] Glass transition temperature (Tg) and coefficient of thermal expansion (CTE): The Tg of the epoxy film in this invention is determined according to the test method of GB / T36800.2-2018 Plastics Thermomechanical Analysis Method, which can be achieved through dynamic mechanical analysis (DMA) or thermomechanical analysis (TMA). The coefficient of thermal expansion (CTE) is determined using the coefficient of thermal expansion method. The epoxy film is first cured at 135℃ for 1 hour in a hydraulic press, and then cured at 180℃ for 0.5 hours to form sample strips / sheets. The sample size for TMA testing is 2*2*1mm (length*width*thickness); the sample size for DMA testing is 40mm*5mm*1mm (length*width*thickness).

[0063] Water absorption rate: The water absorption rate test was conducted according to the "PCT24" method, with the sample size being 30*30*0.2mm (length*width*thickness), and the test conditions being 121℃, 100RH%, 2atm, and 24h; the water absorption rate was calculated as follows: weight increase of the sample after PCT24 / initial weight of the sample * 100%.

[0064] Test results:

[0065] The low-moisture-absorbing epoxy film of Example 1 has a glass transition temperature (Tg) of 180°C, a moisture absorption rate of 0.37%, and a coefficient of thermal expansion (CTE) of 15 / 50ppm / °C.

[0066] The low-moisture-absorbing epoxy film of Example 2 has a glass transition temperature (Tg) of 180°C, a moisture absorption rate of 0.34%, and a coefficient of thermal expansion (CTE) of 12 / 36ppm / °C.

[0067] The low-moisture-absorbing epoxy film of Example 3 has a glass transition temperature (Tg) of 170°C, a moisture absorption rate of 0.25%, and a coefficient of thermal expansion (CTE) of 10 / 28 ppm / °C.

[0068] The low-moisture-absorbing epoxy film of Comparative Example 1 has a glass transition temperature (Tg) of 179℃, a moisture absorption rate of 2.2%, and a coefficient of thermal expansion (CTE) of 15 / 49ppm / ℃.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A low-moisture-absorbing epoxy film, characterized in that, The invention comprises a protective film, an epoxy adhesive layer, and a base film arranged in layers, wherein the epoxy adhesive layer is disposed between the protective film and the base film. The epoxy adhesive layer comprises, by weight, the following components: phenolic epoxy resin, 100 parts; biphenyl alkylphenol resin, 110 parts; accelerator, 0.5-1 part; hydrophobic modified silica powder, 300-490 parts; pigment, 2-3 parts; and coupling agent, 2-6 parts. The accelerator is any one or a combination of at least two of imidazoles and their derivatives, organophosphorus compounds, amines, and quaternary ammonium salts; The coupling agent is any one or a combination of at least two of the following: silane coupling agent, aluminate coupling agent, and titanate coupling agent. The base film is one or more of PET and PI films; the protective film is a release film, which is one or more of PET release film, PE release film, OPP release film, and composite release film; the thickness ratio of the base film to the protective film is (6~10):(6~10); the light release force of the protective film is 1~20g / 25mm; A method for preparing a low-hygroscopic epoxy film includes the following steps: Step 1, Ingredient Mixing: According to the formula, first stir and mix the phenolic epoxy resin and biphenyl alkylphenol resin evenly, and mix the hydrophobic modified silica powder and pigment evenly using a homogenizer; then stir and mix the mixture of phenolic epoxy resin and biphenyl alkylphenol resin, the mixture of hydrophobic modified silica powder and pigment, and the coupling agent, and use a screw press or kneader to fully disperse the hydrophobic modified silica powder. Finally, add the accelerator, and while hot, use a homogenizer to fully disperse the overall formula. Vacuum degassing is then performed to obtain the epoxy resin composition. Step 2: Coat the epoxy resin composition onto the base film, controlling the coating thickness to be 1.0 to 1.2 times the required thickness of the adhesive film after surface drying; Step 3, Surface drying: Use a tunnel-type forced-air drying oven to dry the epoxy resin wet film at 80℃ for 0.5~1min, and then dry it at room temperature for 0.5~1min; Step 4: Composite the epoxy resin film dried in Step 3 with the protective film to obtain a low-moisture-absorbing epoxy film. In step 1, phenolic epoxy resin and biphenyl alkylphenol resin are stirred and mixed evenly at 70~120℃, and the mixture of phenolic epoxy resin and biphenyl alkylphenol resin, the mixture of hydrophobic modified silica powder and pigment, and the coupling agent are stirred and mixed at 100~120℃; in step 4, the composite temperature is 50~120℃, the composite pressure is 0.5~2MPa, and the composite speed is 2.5~5m / s.

2. The low-moisture-absorbing epoxy film according to claim 1, characterized in that: The pigment is either carbon black or titanium dioxide.

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