Heat-resistant PET (polyethylene terephthalate) base film for MLCC (multilayer ceramic capacitor) release film and preparation method of heat-resistant PET base film

Abstract

The invention relates to a heat-resistant PET (polyethylene terephthalate) base film for an MLCC (multilayer ceramic capacitor) release film and a preparation method of the heat-resistant PET base film. The PET base film is formed by compounding a surface layer and a core layer through a co-extrusion process, the surface layer contains a multifunctional composite filler, the filler takes Na-montmorillonite as a matrix, a composite cationic intercalator is adopted for intercalation modification, then an amino-terminated RAFT reagent is adopted for surface functionalization, finally, methyl methacrylate and an aromatic monomer are initiated to be subjected to controllable free radical polymerization, and the heat-resistant polymer brush is formed on the surface through grafting. Through molecular design, a polymer brush is grafted on a montmorillonite sheet layer, so that the formed composite functional filler integrates heat resistance and smoothness, meanwhile, the compatibility of montmorillonite and a PET substrate is improved, and surface bulge caused by agglomeration is avoided, so that the finally prepared PET base film has relatively low roughness and low thermal shrinkage rate, and the service life of the PET base film is prolonged. Meanwhile, the adhesive force with the silicone oil release agent is excellent, and the aging resistance is excellent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical film, in particular to a heat-resistant PET base film for MLCC release film and a preparation method thereof. BACKGROUND

[0002] Chip capacitors, also known as multilayer chip ceramic capacitors (MLCC), are a kind of basic passive electronic components, belonging to the category of ceramic dielectric capacitors, and are widely used in mobile communication devices, computer boards, home appliance remote controls, AI servers, new energy vehicles and other fields. MLCC has a wide application prospect and a huge demand, and a large amount of MLCC release film will be consumed in its production process. The area of release film consumed in the production of single-layer MLCC is roughly equal to the area of MLCC. More than 300,000 tons of high-end BOPET film needs to be imported every year in China. In order to save costs, domestic enterprises are also increasing their investment in independent research and development in related fields.

[0003] MLCC release film usually uses polyethylene terephthalate (PET) base film as the basic material, and the PET film needs to have low surface roughness, certain anti-sticking and surface smoothness, and ultra-low thermal shrinkage. At present, the modification of PET base film is mainly by selecting inorganic fillers with smaller particle size as opening agents to reduce the surface roughness of polyester film and improve the flatness. However, the type of opening agent and the addition method of opening agent have a significant impact on the surface roughness of the MLCC release film base film. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application prepares a composite filler which has heat-resistant enhancement and surface functionalization ability by molecular design, and selectively introduces it into the surface layer of the PET base film, effectively solving the problems of thermal shrinkage, surface roughness and release stability.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: A heat-resistant PET base film for MLCC release film, the PET base film is composed of a surface layer and a core layer by co-extrusion process; the surface layer contains a multifunctional composite filler, and the preparation process is as follows: S1, sodium-based montmorillonite is dispersed in deionized water, and a cationic intercalation agent is added for intercalation reaction to obtain organically intercalated modified montmorillonite; S2, the organically intercalated modified montmorillonite is dispersed in an organic solvent, and an amino-terminated RAFT reagent is added, and stirred at 25-40℃ overnight to obtain RAFT functionalized montmorillonite; S3, the RAFT functionalized montmorillonite is re-dispersed in an organic solvent, then methyl methacrylate, styrene, 2-methyl methacrylate biphenyl-4-ester, and initiator AIBN are added, under nitrogen protection, the temperature is raised to 70℃, and the reaction is carried out for 2-6h, after the reaction, centrifugal separation is carried out, anhydrous ethanol is used for washing, and vacuum drying is carried out to obtain the product; The cationic intercalating agent comprises a mixture of erucamide trimethyl ammonium chloride, glycidyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride in a mass ratio of 2-4:4-7:1. The amino-terminated RAFT agent has a structural formula as shown in the following formula (I): .

[0006] Further, the surface layer comprises optical grade PET chips and multifunctional composite fillers accounting for 2-8 wt% of the optical grade PET chips; and the core layer is a pure optical grade PET chip layer.

[0007] Further, the specific process of the step S1 is as follows: 10 parts by weight of sodium-based montmorillonite is ultrasonically dispersed in deionized water, and then high-speed stirring is carried out for 2h to form a stable suspension; 10 parts by weight of the cationic intercalating agent is mixed and dissolved in 100 parts by weight of hot water, and then the mixture is slowly added dropwise into the montmorillonite suspension under stirring, low-speed stirring is carried out at 80℃ overnight, the temperature is cooled to room temperature, centrifugal separation is carried out, water and ethanol are used for washing for multiple times, vacuum drying is carried out, and grinding is carried out to obtain the organic intercalation modified montmorillonite.

[0008] Further, in the step S2, the mass ratio of the organic intercalation modified montmorillonite to the amino-terminated RAFT agent is 5:1-2.

[0009] Further, in the step S3, the molar ratio of methyl methacrylate, styrene and 2-methyl methacrylate biphenyl-4-ester is 4-6:1-3:1-3; and the mass ratio of the total mass of the monomers to the RAFT functionalized montmorillonite is 5-10:1.

[0010] Further, the amino-terminated RAFT agent is obtained by acyl chloride reaction of 2-[dodecylsulfanyl(thiocarbonyl)thio]-2-methylpropanoic acid, and then acylamide reaction with excess ethylenediamine.

[0011] The application further provides a method for preparing the heat-resistant PET base film for the MLCC release film, which comprises the following steps: 1) a metered amount of PET chips and multifunctional composite fillers are dried respectively and then added into a mixer to obtain surface layer materials; 2) The pure PET is used as the core material, and the surface layer material is put into the main extruder and the auxiliary extruder respectively, the temperature of the auxiliary extruder is adjusted to 270-290 ℃, the temperature of the main extruder is 255-270 ℃, after melting, the extrusion is filtered, and the surface layer-core layer-surface layer three-layer composite casting piece is prepared through the multi-layer co-extrusion process; 3) The casting piece is preheated at 65-85 ℃, and is longitudinally stretched by 3.2-3.8 times at 90-120 ℃ to obtain a longitudinal stretched piece; and is transversely stretched by 3.5-4.2 times at 100-130 ℃; after the stretching is completed, heat setting is carried out, and then cooling traction is carried out, and the longitudinal stretched piece is obtained.

[0012] Further, the mass ratio of the extrusion amount of the surface layer-core layer-surface layer three layers is 1-3:4-8:1-3.

[0013] Compared with the prior art, the present application has the following beneficial effects: through molecular design, the sodium-based montmorillonite with smoothness is first introduced into the epoxy group through intercalation reaction, and then reacts with the amino-terminated RAFT reagent to introduce active free radicals, and initiates the copolymerization of acrylate monomers to "anchor" the subsequently generated polymer brush on the montmorillonite layer, thereby forming a composite functional filler which integrates heat resistance and smoothness, improves the compatibility of montmorillonite and PET matrix, avoids surface protrusions caused by agglomeration, and makes the finally prepared PET-based film have low roughness and low heat shrinkage rate, has excellent adhesion with silicone release agent, has excellent aging resistance, the filler is added in the form of masterbatch, is easy to industrialize, and can be used as an MLCC release film base film. DETAILED DESCRIPTION

[0014] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0015] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0016] The raw materials used in the present application are mostly bulk products, which can be purchased in the market, such as Sinopharm Group, Aladdin, Sigma-Aldrich, etc., and the PET chip selected is an optical grade with a specific viscosity of 0.65 dl / g, which needs to be dried before use.

[0017] Embodiment: A heat-resistant PET base film for MLCC release film, which is composed of a surface layer and a core layer by a co-extrusion process; the surface layer contains multifunctional composite fillers, and the preparation process is as follows: S1, 10 parts by weight of sodium-based montmorillonite (Zhejiang Fenghong, DK1) was ultrasonically dispersed in deionized water, and then high-speed stirring was carried out for 2 h to form a stable suspension; 10 parts by weight of cationic intercalation agent was mixed in 100 parts by weight of hot water, and was slowly added to the montmorillonite suspension under stirring, and was stirred at low speed at 80℃ overnight, and was cooled to room temperature, and was centrifuged, and was washed with water and ethanol for several times, and was vacuum dried, and was ground to obtain organic intercalation modified montmorillonite (OMMT).

[0018] S2, 5g OMMT was dispersed in 150mL anhydrous DMF, and was ultrasonically treated for 2 hours. 3g amino-terminated RAFT agent and 1mL triethylamine were added, and were stirred at 40℃ under nitrogen protection overnight. After the reaction was completed, centrifugal separation was carried out, and washing with DMF and ethanol was carried out in sequence until the washing liquid was colorless, and vacuum drying was carried out at 60℃ to obtain a light yellow powder of RAFT functionalized montmorillonite (OMMT-RAFT).

[0019] S3, OMMT-RAFT was redispersed in anhydrous DMF, and then methyl methacrylate, styrene, 2-methyl methacrylate biphenyl-4-ester, and initiator AIBN were added, and were heated to 70℃ under nitrogen protection, and were reacted for 2~6h. After the reaction was completed, centrifugal separation was carried out, and anhydrous ethanol was washed, and vacuum drying was carried out to obtain the product.

[0020] The structure of the amino-terminated RAFT agent is The preparation process is as follows: 5g 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid (CAS: 461642-78-4, purchased from Jiangsu Puleisi Biological Technology Co., Ltd.), 10mL thionyl chloride (SOCl2) and 2 drops of DMF were mixed, and were refluxed at 70℃ for 3 hours. Excess SOCl2 was evaporated to obtain trithio acyl chloride. The acyl chloride was dissolved in 50 mL anhydrous THF, and was slowly added to a solution of excess ethylenediamine (20mL) in 100mL THF under ice bath and stirring. After the addition was completed, the reaction was carried out at room temperature for 12 hours. The solvent was removed under reduced pressure, and the residue was dissolved in dichloromethane, and was washed with dilute hydrochloric acid, water and saturated brine in sequence, and was dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure to obtain a yellow oil, which was recorded as CTA-NH2 (yield about 75%).

[0021] In the above reaction, the cationic intercalating agent comprises a mixture of erucamide trimethylammonium chloride, glycidyltrimethylammonium chloride, and octadecyltrimethylammonium chloride in a mass ratio of 2-4:4-7:1; the molar ratio of methyl methacrylate, styrene, and biphenyl-4-methacrylate is 4-6:1-3:1-3; and the mass ratio of the total monomer mass to the RAFT-functionalized montmorillonite is 5-10:1. Different samples can be obtained by controlling different feed ratios. Table 1 lists the sample numbers and corresponding parameters for different feed ratios. In the table, the cationic intercalating agent is the mass ratio of erucamide trimethylammonium chloride, glycidyltrimethylammonium chloride, and octadecyltrimethylammonium chloride; n is the molar ratio of methyl methacrylate, styrene, and biphenyl-4-methacrylate; and m is the mass ratio of the total monomer mass to the RAFT-functionalized montmorillonite.

[0022] Table 1 Sample numbers and corresponding parameters under different feed ratios

[0023] Example 1: 1) 100 parts by weight of PET chips and 5 parts by weight of multifunctional composite filler sample 1 were dried and then added to a mixer to mix and obtain the surface material; 2) Using pure PET as the core material, it is fed into the main extruder and auxiliary extruder respectively along with the surface material. The temperature of the auxiliary extruder is adjusted to 280 ℃ and the temperature of the main extruder is 265 ℃. After melting, it is metered, extruded and filtered, and then processed through a multi-layer co-extrusion process to produce a three-layer composite casting sheet with a surface layer-core layer-surface layer. The mass ratio of the extruded amount of the three layers is 1.5:7:1.5. 3) Preheat the cast sheet at 85 ℃, stretch it longitudinally by 3.4 times at 110 ℃ to obtain a longitudinally stretched sheet; and stretch it transversely by 3.8 times at 125 ℃; after stretching, heat set it, then cool and traction roll it up to obtain the final product.

[0024] Example 2: Basically the same as Example 1, except that the multifunctional composite filler is sample 2.

[0025] Example 3: Basically the same as Example 1, except that sample 3 is selected as the multifunctional composite filler.

[0026] Example 4: Basically the same as Example 1, except that sample 4 is selected as the multifunctional composite filler.

[0027] Example 5: Basically the same as Example 4, except that the proportion of multifunctional composite filler is 2 parts by weight.

[0028] Example 6: Basically the same as Example 4, except that the proportion of multifunctional composite filler is 8 parts by weight.

[0029] Comparative Example 1: It is basically the same as Example 1, except that the multifunctional composite filler is selected as control sample 1.

[0030] Comparative Example 2: It is basically the same as Example 1, except that the multifunctional composite filler is selected as control sample 2.

[0031] The performance of the PET base film prepared above was tested, and the results are recorded in Table 2.

[0032] Surface roughness Ra (nm): AFM (5μm×5μm); Heat shrinkage rate (%): 250℃, 10 min; Adhesion: After applying the same silicone oil release agent to the base film surface and curing, the coating adhesion was evaluated by a cross-cut adhesion test (0 is the best, 5 is the worst). Release force: 180° peel after applying silicone oil; Heat aging resistance: Artificial accelerated aging was carried out in hot air at 85°C for 96 hours, and the release force retention rate was tested after cooling to room temperature.

[0033] Table 2 Performance test results of PET base film

[0034] Analysis of the data in Table 2 shows that surface roughness and thermal shrinkage vary with the selection of composite functional fillers in the system. Specifically, higher contents of erucamide trimethylammonium chloride, styrene, and biphenyl-4-methylacrylate in the samples result in lower roughness and thermal shrinkage. This application uses layered montmorillonite as the core, which is itself an excellent thermally stable reinforcing agent and slip agent. Organic modification can effectively enhance its compatibility with the PET matrix. The cationic intercalating agents selected were erucamide trimethylammonium chloride, glycidyltrimethylammonium chloride, and octadecyltrimethylammonium chloride. Erucamide trimethylammonium chloride further provided slip properties, improving the dispersion of montmorillonite in the organic phase during filler preparation. In the base film, its long alkyl segments enriched on the surface, collectively providing low surface energy and slip properties, resulting in ultra-low surface roughness. Glycidyltrimethylammonium chloride provided reaction sites, facilitating the covalent bonding of subsequent RAFT reagents, thus forming RAFT-functionalized montmorillonite. This RAFT-functionalized montmorillonite then underwent free radical polymerization with methyl methacrylate, styrene, and biphenyl-4-methacrylate to form a polymer brush. The rigid styrene structure and the biphenyl structural unit (biphenyl-4-methacrylate) significantly improved the glass transition temperature and thermal stability of the polymer brush. Synergistically with montmorillonite, a stable network structure was formed in the PET matrix, effectively improving the heat resistance of the film. This interface layer, formed by the chemically bonded polymer brushed onto the film surface, has strong adhesion to the PET matrix and provides an ideal substrate for the subsequent coating of silicone oil release agent. It exhibits good adhesion to the silicone oil release agent at level 0-1, good release force, and due to its good heat resistance and stability, the release force retention rate is still above 95% after heat aging.

[0035] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A heat-resistant PET-based film for an MLCC release film, characterized by, The PET base film is composed of a surface layer and a core layer by a co-extrusion process; the surface layer contains multifunctional composite fillers, and the preparation process is as follows: S1, take sodium-based montmorillonite and disperse it in deionized water, add cationic intercalation agent for intercalation reaction, and obtain organic intercalation modified montmorillonite; S2, disperse the organic intercalation modified montmorillonite in an organic solvent, add an amino-terminated RAFT agent, and stir at 25-40 ℃ overnight to obtain RAFT functionalized montmorillonite; S3, disperse the RAFT functionalized montmorillonite in an organic solvent, then add methyl methacrylate, styrene, 2-methyl methacrylate biphenyl-4-ester, and initiator AIBN, heat to 70 ℃ under nitrogen protection, and react for 2-6 h; after the reaction is completed, centrifugal separation, anhydrous ethanol washing, and vacuum drying are performed to obtain the product; The cationic intercalation agent includes a mixture of erucyl amide trimethyl ammonium chloride, glycidyl trimethyl ammonium chloride, and octadecyl trimethyl ammonium chloride in a mass ratio of 2-4:4-7:1; The amino-terminated RAFT agent has the structure .

2. The heat-resistant PET-based film for an MLCC release film according to claim 1, characterized by, The surface layer includes optical grade PET chips and multifunctional composite fillers accounting for 2-8 wt% of the optical grade PET chips; and the core layer is a pure optical grade PET chip layer.

3. The heat-resistant PET-based film for an MLCC release film according to claim 1, characterized by, The specific process of step S1 is as follows: 10 parts by weight of sodium-based montmorillonite is ultrasonically dispersed in deionized water, and then stirred at high speed for 2 h to form a stable suspension; 10 parts by weight of cationic intercalation agent is mixed and dissolved in 100 parts by weight of hot water, and slowly added dropwise to the montmorillonite suspension under stirring, and stirred at low speed at 80 ℃ overnight; after cooling to room temperature, centrifugal separation, water and ethanol washing, and vacuum drying are performed, and the product is obtained by grinding.

4. The heat-resistant PET-based film for an MLCC release film according to claim 1, characterized by, In step S2, the mass ratio of the organic intercalation modified montmorillonite to the amino-terminated RAFT agent is 5:1-2.

5. The heat-resistant PET-based film for an MLCC release film according to claim 1, characterized by, In step S3, the molar ratio of methyl methacrylate, styrene, and 2-methyl methacrylate biphenyl-4-ester is 4-6:1-3:1-3; and the mass ratio of the total mass of the monomers to the RAFT functionalized montmorillonite is 5-10:

1.

6. The heat-resistant PET-based film for an MLCC release film according to claim 1, characterized by, The amino-terminated RAFT agent is obtained by acyl chloride reaction of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, and then amide reaction with excess ethylenediamine.

7. A method for producing the heat-resistant PET-based film for an MLCC release film according to any one of claims 1 to 6, characterized by, The steps include the following: 1) After the metered PET chips and multifunctional composite fillers are dried, they are added to a mixer to obtain surface layer materials; 2) The pure PET is used as the core layer material, and is put into the main extruder and the auxiliary extruder together with the surface layer materials; the temperature of the auxiliary extruder is adjusted to 270-290 ℃, and the temperature of the main extruder is adjusted to 255-270 ℃; after melting, the materials are extruded and filtered, and a three-layer surface-core-surface composite casting sheet is prepared by a multi-layer co-extrusion process; 3) The casting sheet is preheated at 65-85 ℃, and is longitudinally stretched by 3.2-3.8 times at 90-120 ℃ to obtain a longitudinal stretched sheet; and the stretched sheet is transversely stretched by 3.5-4.2 times at 100-130 ℃; after stretching, heat setting is performed, and then the sheet is cooled and drawn to be wound up.

8. The method for preparing heat-resistant PET-based film for MLCC release film according to claim 7, characterized in that, The mass ratio of the extrusion amount of the surface layer-core layer-surface layer three layers is 1-3:4-8:1-3.

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