A PBT release film and preparation method thereof

Abstract

The present invention relates to the technical field of release films, specifically a PBT release film and its preparation method. The present invention discloses a PBT release film comprising an ABA three-layer structure, wherein layer A is a release layer and layer B is an adhesive barrier layer. The raw materials for the release layer include PBT resin, a toughening resin, a release modifier, and an antioxidant. The release modifier is a non-polar, long olefin chain containing an ester group at one end, including one or more of ethyl myristate, ethyl laurate, ethyl palmitate, and ethyl stearate. The present invention also discloses a method for preparing the PBT release film. After the PBT release film of the present invention is heated and pressed onto an FPC board, layer A can achieve self-release properties, is free of small molecule residues, and exhibits no undesirable wrinkles. Layer B can fully fill the surface structure of the FPC board, preventing glue from overflowing.

Description

Technical Field

[0001] The invention belongs to the technical field of release films and relates to a PBT release film and a preparation method thereof. Background Art

[0002] PBT (polybutylene terephthalate) resin release films are becoming increasingly popular in the flexible circuit board (FPC) market, gradually replacing TPX (poly-4-methylpentene-1-ene) resin release films. However, due to its chemical structure, PBT resin exhibits high surface tension and insufficient toughness, leading downstream customers to experience issues such as insufficient release properties and PBT film residue on the FPC during the lamination process. Currently, the release properties of PBT release films are typically improved by adding release modifiers containing Si and F. However, the small molecules of Si and F in these modifiers are structurally unstable and can transfer to the FPC during high-temperature lamination, causing contamination. Summary of the Invention

[0003] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to propose a PBT release film with self-release and high adhesive resistance properties which is prepared by adding a release modifier with a stable structure.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A PBT release film, which consists of an ABA three-layer structure, wherein layer A is a release layer and layer B is a glue barrier layer;

[0006] The raw materials of the release layer include 70 to 90 parts of PBT resin, 10 to 30 parts of toughening resin, 0.1 to 20 parts of release modifier and 0.1 to 10 parts of antioxidant. The release modifier is a non-polar long olefin chain containing an ester group at one end, including one or more of ethyl myristate, ethyl laurate, ethyl palmitate and ethyl stearate.

[0007] Preferably, the melt index of the PBT resin is 10-20 g / 10 min when measured at 250° C. and 2.16 kg.

[0008] Preferably, the toughening resin is selected from one or more of PBAT resin (polybutylene adipate / terephthalate), PBA resin (polybutyl acrylate), and ABS resin (acrylonitrile-styrene-butadiene copolymer).

[0009] Preferably, the mass ratio of PBT resin to toughening resin in the raw materials of the release layer is (2.1-6):1.

[0010] Preferably, the raw materials of the release layer include, by weight, 70-80 parts of PBT resin, 15-25 parts of PBAT, 5-10 parts of ethyl myristate and 0.5-1 part of antioxidant.

[0011] Preferably, the raw materials of the adhesive resistance layer include, by weight, 50-70 parts of PBT resin, 30-50 parts of adhesive resistance resin, 1-20 parts of compatibilizer and 0.1-10 parts of antioxidant.

[0012] More preferably, the mass ratio of the PBT resin to the adhesive resistance resin is (1.1-2):1.

[0013] More preferably, the melt index of the PBT resin is measured at 250° C. and 2.16 kg and is 10-20 g / 10 min.

[0014] More preferably, the adhesive-blocking resin is selected from one or more of polyethylene, polypropylene, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate copolymer, polyvinyl alcohol, and ethylene acrylic acid copolymer.

[0015] More preferably, the adhesive-blocking resin is polyethylene.

[0016] More preferably, the compatibilizer is selected from one or more of maleic anhydride, silane coupling agent, nylon, polyurethane, and polyether.

[0017] More preferably, the antioxidant is selected from one or more of antioxidant 1076, antioxidant 168, and antioxidant 1010.

[0018] Preferably, the raw materials of the adhesive barrier layer include, by weight, 50-60 parts of PBT resin, 35-45 parts of polyethylene, 5-10 parts of polyurethane and 1-2 parts of antioxidant.

[0019] Preferably, the thickness of the PBT release film is 100-200 μm.

[0020] Preferably, the total thickness of the A layer is 30-60 μm, and the thickness of the B layer is 70-140 μm.

[0021] More preferably, the thickness of the A layer is 15-30 μm.

[0022] Preferably, the release layer has a crystallinity of 23-28%.

[0023] More preferably, the release layer has a crystallinity of 24-25%.

[0024] Preferably, the PBT release film has a TD break elongation of ≥240%, an MD break elongation of ≥300%, and an adhesive resistance test value of <90 μm.

[0025] More preferably, the PBT release film has a TD break elongation of ≥300%, an MD break elongation of ≥320%, and an adhesive resistance test value of <85 μm.

[0026] Preferably, the PBT release film and the FPC board are heated and pressed at 170-190° C., and the release film is not damaged after being peeled off.

[0027] A method for preparing a PBT release film, comprising:

[0028] (1) Weigh the raw materials of the release layer, which include 70-90 parts by weight of PBT resin, 10-30 parts of toughening resin, 0.1-20 parts of release modifier and 0.1-10 parts of antioxidant, wherein the release modifier is a non-polar long olefin chain containing an ester group at one end. Mix the raw materials and add them to a twin-screw pelletizer. Melt, extrude, cool, shape and pelletize to obtain a release layer masterbatch;

[0029] (2) Weigh the raw materials of the adhesive barrier layer, including 50-70 parts of PBT resin, 30-50 parts of adhesive barrier resin, 1-20 parts of compatibilizer and 0.1-10 parts of antioxidant, mix the raw materials and add them into a twin-screw granulator, melt-extrude, cool and shape them into pellets, and obtain the masterbatch of the adhesive barrier layer;

[0030] (3) The release layer masterbatch and the adhesive layer masterbatch are respectively put into two extruders, and after melt extrusion, they are coated and cast into films at the die head.

[0031] Preferably, the moisture content of the release layer masterbatch and the adhesive layer masterbatch is lower than 0.02%.

[0032] Preferably, the melt extrusion temperature in (1) is 260-280°C.

[0033] Preferably, the melt extrusion temperature in (2) is 250-270°C.

[0034] Preferably, the processing temperature of the extruder in (3) is 240-300°C, and the die head temperature is 240-300°C.

[0035] More preferably, the processing temperature of the extruder is 260-280°C, and the die head temperature is 260-280°C.

[0036] Preferably, after the film is cast, it is pressed by a rubber roller and a steel roller, cooled and shaped, annealed by a tempering roller, and then pulled and wound.

[0037] More preferably, the temperature of the rubber roller is 0-60°C, the temperature of the steel roller is 30-80°C, the temperature of the tempering roller is 50-100°C, and the traction ratio in traction winding is 0.8-1.

[0038] More preferably, the temperature of the rubber roller is 10-30°C, the temperature of the steel roller is 30-70°C, the temperature of the tempering roller is 60-80°C, and the traction ratio in traction winding is 0.95-1.

[0039] Preferably, the release layer has a crystallinity of 23-28%.

[0040] More preferably, the release layer has a crystallinity of 24-25%.

[0041] Preferably, the PBT release film has an elongation at break in the TD direction of ≥240%; an elongation at break in the MD direction of ≥300%, and a resistance test value of <90 μm.

[0042] More preferably, the PBT release film has an elongation at break in the TD direction of ≥300%; an elongation at break in the MD direction of ≥320%, and an adhesive resistance test value of <85 μm.

[0043] Preferably, the PBT release film and the FPC board are heated and pressed at 170-190° C., and the release film is not damaged after being peeled off.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The PBT release film of the present invention has an ABA three-layer structure. After the PBT release film and the FPC board are heated and pressed together, the A layer can achieve self-release properties, no small molecule residue, no wrinkles and other undesirable phenomena, and the B layer can fully fill the surface structure of the FPC board to prevent glue overflow;

[0046] 2. The present invention uses a non-polar long olefin chain compound containing an ester group at one end as a release modifier. The ester group at one end has good compatibility with PBT resin, while the other end is a non-polar long olefin chain, which is structurally stable at high temperatures. During the lamination process, the non-polar long olefin chain will migrate to the vicinity of the release film surface, reducing the surface energy of the release film to achieve a self-release effect, thereby solving the problem of high surface tension of PBT resin.

[0047] 3. The present invention preferably uses PBAT as the toughening resin. PBAT has excellent ductility and elongation at break, and has good compatibility with PBT. It can greatly improve the toughness of the PBT surface layer and prevent the surface layer from cracking after lamination or breaking and remaining on the FPC board during peeling;

[0048] 4. The present invention controls the crystallinity of the A layer in the PBT release film within 23-28%. Too much crystallinity will make the film surface too hard and lack adhesive resistance; while too little crystallinity will cause the film to completely soften after lamination and embed into the FPC board, affecting the release performance;

[0049] 5. The PBT release film of the present invention has excellent release and adhesive resistance properties, and the release film is not damaged after heating, pressing, and peeling off. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the structure of the PBT release film of the present invention and schematic diagram of the release principle of the release layer A in Example 1 under normal temperature and high temperature pressing states. DETAILED DESCRIPTION

[0051] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0052] Unless otherwise specified, the materials used in the present invention are conventional commercial products, and the methods used are conventional technical means.

[0053] In this paper, PBT resin: BASF, model B4500, melt index is 19g / 10min (250℃, 2.16kg);

[0054] PBT resin: BASF, model B4520, melt index 19 g / 10 min (250°C, 2.16 kg);

[0055] PBT resin: Mitsubishi, model 5510S, melt index 33g / 10min (250℃, 2.16kg);

[0056] Ethyl myristate: CAS: 124-06-1;

[0057] Ethyl laurate: CAS: 106-33-2;

[0058] PBAT resin: BASF, model C1200, melt index 4 g / 10 min (190°C, 2.16 kg);

[0059] Polyethylene resin: Shanghai Petrochemical, model Q281, melt index 3g / 10min (190℃, 2.16kg).

[0060] The structural diagram of the PBT release film of the present invention is shown in FIG. Figure 1 . Example 1

[0061] In this embodiment, the thickness of the PBT release film is 120 μm, the thickness of the A layer is 20 μm, and the thickness of the B layer is 80 μm.

[0062] The preparation method of PBT release film includes:

[0063] (1) Weigh the raw materials of the release layer, including 80 parts by weight of PBT resin (B4500), 15 parts of toughening resin (PBAT resin), 5 parts of release modifier (ethyl myristate) and 1 part of antioxidant (antioxidant 1076), mix the raw materials and add them into a twin-screw granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0064] (2) Weigh the raw materials of the rubber barrier layer, including 50 parts by weight of PBT resin (B4500), 40 parts of rubber barrier resin (polyethylene resin), 10 parts of compatibilizer (polyurethane) and 1 part of antioxidant (antioxidant 1076), mix the raw materials and add them into a twin-screw granulator, melt extrude at 265°C, cool and shape into pellets, and obtain the rubber barrier layer masterbatch;

[0065] (3) The release layer masterbatch and the adhesive layer masterbatch are respectively put into two extruders, and after melt extrusion, they are coated and cast into films at the die head; layer A is the surface layer of the film, layer B is the core layer of the film, the processing temperature of the extruder is 265~275℃, and the die head temperature is set to 270℃; then it is pressed by the rubber roller and the steel roller, cooled and shaped, and annealed by the tempering roller, where the rubber roller temperature is set to 25℃, the steel roller temperature is set to 45℃, and the tempering roller temperature is set to 65℃, and finally it is pulled and rolled into a PBT release film product, where the pulling ratio is set to 0.98.

[0066] The schematic diagram of the release principle of the release layer A in the embodiment 1 under the normal temperature and high temperature pressing state is shown in FIG. Figure 1 It can be seen that during the high-temperature pressing process, the non-polar long olefin chain of ethyl myristate will migrate to the vicinity of the release film surface, reducing the surface energy of the release film to achieve a self-release effect.

[0067] The properties of the PBT release film prepared in this example are shown in Table 1. Example 2

[0068] In this embodiment, the thickness of the PBT release film is 120 μm, the thickness of the A layer is 20 μm, and the thickness of the B layer is 80 μm.

[0069] The preparation method of PBT release film includes:

[0070] (1) Weigh the raw materials of the release layer, including 70 parts by weight of PBT resin (B4500), 25 parts of toughening resin (PBAT resin), 5 parts of release modifier (ethyl myristate) and 0.5 parts of antioxidant (antioxidant 168), mix the raw materials and add them into a twin-screw granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0071] (2) Weigh the raw materials of the rubber barrier layer, including 60 parts by weight of PBT resin (B4500), 35 parts of rubber barrier resin (polyethylene resin), 5 parts of compatibilizer (polyurethane) and 1 part of antioxidant (antioxidant 168), mix the raw materials and add them into a twin-screw granulator, melt extrude at 265°C, cool and shape into pellets, and obtain the rubber barrier layer masterbatch;

[0072] (3) Prepare a PBT release film according to the method in Example 1.

[0073] The properties of the PBT release film prepared in this example are shown in Table 1. Example 3

[0074] In this embodiment, the thickness of the PBT release film is 120 μm, the thickness of the A layer is 20 μm, and the thickness of the B layer is 80 μm.

[0075] The preparation method of PBT release film includes:

[0076] (1) Weigh the raw materials of the release layer, including 70 parts by weight of PBT resin (B4500), 20 parts of toughening resin (PBAT resin), 10 parts of release modifier (ethyl myristate) and 1 part of antioxidant (antioxidant 1010), mix the raw materials and add them into a twin-screw granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0077] (2) Weigh the raw materials of the rubber barrier layer, including 50 parts of PBT resin (B4500), 45 parts of rubber barrier resin (polyethylene resin), 5 parts of compatibilizer (polyurethane) and 2 parts of antioxidant (antioxidant 1010) by weight, mix the raw materials and add them into a twin-screw granulator, melt extrude at 265℃, cool and shape into pellets, and obtain the rubber barrier layer masterbatch;

[0078] (3) Prepare a PBT release film according to the method in Example 1.

[0079] The properties of the PBT release film prepared in this example are shown in Table 1. Example 4

[0080] In this embodiment, the thickness of the PBT release film is 160 μm, the thickness of the A layer is 30 μm, and the thickness of the B layer is 100 μm.

[0081] The preparation method of PBT release film includes:

[0082] (1) Weigh the raw materials of the release layer, including 75 parts by weight of PBT resin (B4520), 18 parts of toughening resin (PBAT resin), 7 parts of release modifier (ethyl myristate) and 1 part of antioxidant (antioxidant 1010), mix the raw materials and add them into a twin-screw granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0083] (2) Weigh the raw materials of the rubber barrier layer, including 55 parts of PBT resin (B4520), 40 parts of rubber barrier resin (polyethylene resin), 5 parts of compatibilizer (polyurethane) and 1 part of antioxidant (antioxidant 1010) by weight, mix the raw materials and add them into a twin-screw granulator, melt extrude at 265℃, cool and shape into pellets, and obtain the rubber barrier layer masterbatch;

[0084] (3) The release layer masterbatch and the adhesive layer masterbatch are respectively put into two extruders, and after melt extrusion, they are coated and cast into films at the die head; layer A is the surface layer of the film, layer B is the core layer of the film, the processing temperature of the extruder is in the range of 265~275℃, and the die head temperature is set to 270℃; then it is pressed by the rubber roller and the steel roller, cooled and shaped, and annealed by the tempering roller, where the rubber roller temperature is set to 30℃, the steel roller temperature is set to 50℃, and the tempering roller temperature is set to 75℃, and finally it is pulled and rolled into a PBT release film product, where the pulling ratio is set to 0.95.

[0085] The properties of the PBT release film prepared in this example are shown in Table 1. Example 5

[0086] In this embodiment, the thickness of the PBT release film is 180 μm, the thickness of the A layer is 30 μm, and the thickness of the B layer is 120 μm.

[0087] The preparation method of PBT release film includes:

[0088] (1) Weigh the raw materials of the release layer, including 80 parts by weight of PBT resin (B4520), 15 parts of toughening resin (PBAT), 5 parts of release modifier (ethyl laurate) and 1 part of antioxidant (antioxidant 168), mix the raw materials and add them into a twin-screw granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0089] (2) Weigh the raw materials of the adhesive barrier layer, including 55 parts by weight of PBT resin (B4520), 40 parts by weight of adhesive barrier resin (ethylene-vinyl acetate copolymer), 5 parts by weight of compatibilizer (maleic anhydride) and 1 part by weight of antioxidant (antioxidant 168), mix the raw materials and add them into a twin-screw pelletizer, melt-extrude at 265°C, cool and shape them into pellets, and obtain the adhesive barrier layer masterbatch;

[0090] (3) Prepare a PBT release film according to the method in Example 1.

[0091] The properties of the PBT release film prepared in this example are shown in Table 1. Comparative Example 1

[0092] In this comparative example, the thickness of the PBT release film is 120 μm, the thickness of the A layer is 20 μm, and the thickness of the B layer is 80 μm.

[0093] The preparation method of PBT release film includes:

[0094] (1) Weigh the raw materials of the release layer, including 60 parts by weight of PBT resin (B4520), 40 parts of toughening resin (PBAT resin), 10 parts of release modifier (ethyl myristate) and 1 part of antioxidant (antioxidant 1076), mix the raw materials and add them into a twin-screw granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0095] (2) Weigh the raw materials of the rubber barrier layer, including 50 parts of PBT resin (B4520), 45 parts of rubber barrier resin (polyethylene resin), 5 parts of compatibilizer (polyurethane) and 2 parts of antioxidant (antioxidant 1076) by weight, mix the raw materials and add them into a twin-screw granulator, melt extrude at 265°C, cool and shape into pellets, and obtain the rubber barrier layer masterbatch;

[0096] (3) Prepare a PBT release film according to the method in Example 1.

[0097] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 2

[0098] In this comparative example, the thickness of the PBT release film is 120 μm, the thickness of the A layer is 20 μm, and the thickness of the B layer is 80 μm.

[0099] The preparation method of PBT release film includes:

[0100] (1) Weigh the raw materials of the release layer, including 70 parts by weight of PBT resin (B4520), 20 parts of toughening resin (PBAT resin), 10 parts of release modifier (ethyl myristate) and 1 part of antioxidant (antioxidant 168), mix the raw materials and add them into a twin-screw granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0101] (2) Weigh the raw materials of the rubber barrier layer, including 40 parts by weight of PBT resin (B4520), 55 parts of rubber barrier resin (polyethylene resin), 5 parts of compatibilizer (polyurethane) and 2 parts of antioxidant (antioxidant 168), mix the raw materials and add them into a twin-screw pelletizer, melt extrude at 265°C, cool and shape into pellets, and obtain the rubber barrier layer masterbatch;

[0102] (3) Prepare a PBT release film according to the method in Example 1.

[0103] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 3

[0104] In this comparative example, the thickness of the PBT release film is 120 μm, the thickness of the A layer is 20 μm, and the thickness of the B layer is 80 μm.

[0105] The preparation method of PBT release film includes:

[0106] (1) Weigh the raw materials of the release layer, including 90 parts by weight of PBT resin (B4520), 5 parts of toughening resin (PBAT resin), 5 parts of release modifier (ethyl myristate) and 1 part of antioxidant (antioxidant 1076), mix the raw materials and add them into a twin-screw granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0107] (2) Weigh the raw materials of the rubber barrier layer, including 50 parts by weight of PBT resin (B4520), 45 parts of rubber barrier resin (polyethylene resin), 5 parts of compatibilizer (polyurethane) and 1 part of antioxidant (antioxidant 1076), mix the raw materials and add them into a twin-screw granulator, melt extrude at 265°C, cool and shape into pellets, and obtain the rubber barrier layer masterbatch;

[0108] (3) Prepare a PBT release film according to the method in Example 1.

[0109] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 4

[0110] In this comparative example, the thickness of the PBT release film is 120 μm, the thickness of the A layer is 20 μm, and the thickness of the B layer is 80 μm.

[0111] The preparation method of PBT release film includes:

[0112] (1) Weigh the raw materials of the release layer, including 80 parts by weight of PBT resin (B4520), 15 parts of toughening resin (PBAT resin), 5 parts of release modifier decene and 1 part of antioxidant (antioxidant 1076), mix the raw materials and add them into a twin-screw pelletizer, melt extrude at 275°C, cool and shape into pellets, and obtain a release layer masterbatch;

[0113] (2) Weigh the raw materials of the rubber barrier layer, including 50 parts by weight of PBT resin (B4520), 40 parts of rubber barrier resin (polyethylene resin), 10 parts of compatibilizer (polyurethane) and 1 part of antioxidant (antioxidant 1076), mix the raw materials and add them into a twin-screw granulator, melt extrude at 265°C, cool and shape into pellets, and obtain the rubber barrier layer masterbatch;

[0114] (3) Prepare a PBT release film according to the method in Example 1.

[0115] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 5

[0116] In this comparative example, the thickness of the PBT release film is 120 μm, the thickness of the A layer is 20 μm, and the thickness of the B layer is 80 μm.

[0117] The preparation method of PBT release film includes:

[0118] (1) Weigh the raw materials of the release layer, including 80 parts by weight of PBT resin (5510S), 15 parts of toughening resin (PBAT resin), 5 parts of release modifier (ethyl myristate) and 1 part of antioxidant (antioxidant 1010), mix the raw materials and add them into a twin-screw granulator, melt extrude at 265°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0119] (2) Weigh the raw materials of the adhesive barrier layer, including 50 parts by weight of PBT resin (5510S), 40 parts of adhesive barrier resin (polyethylene resin), 10 parts of compatibilizer (polyurethane) and 1 part of antioxidant (antioxidant 1010), mix the raw materials and add them into a twin-screw granulator, melt extrude at 255°C, cool and shape into pellets, and obtain the masterbatch of the adhesive barrier layer;

[0120] (3) Prepare a PBT release film according to the method in Example 1.

[0121] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 6

[0122] In this comparative example, the thickness of the PBT release film is 120 μm, the thickness of the A layer is 20 μm, and the thickness of the B layer is 80 μm.

[0123] The preparation method of PBT release film includes:

[0124] (1) Weigh the raw materials of the release layer, including 80 parts by weight of PBT resin (B4520), 15 parts of toughening resin (PBAT resin), 5 parts of release modifier (ethyl myristate) and 1 part of antioxidant (antioxidant 168), mix the raw materials and add them into a twin-screw granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a release layer masterbatch;

[0125] (2) Weigh the raw materials of the rubber barrier layer, including 50 parts by weight of PBT resin (B4520), 40 parts of rubber barrier resin (polyethylene resin), 10 parts of compatibilizer (polyurethane) and 1 part of antioxidant (antioxidant 168), mix the raw materials and add them into a twin-screw granulator, melt extrude at 265°C, cool and shape into pellets, and obtain the rubber barrier layer masterbatch;

[0126] (3) The release layer masterbatch and the adhesive layer masterbatch are respectively put into two extruders, and after melt extrusion, they are coated and cast into films at the die head; layer A is the surface layer of the film, layer B is the core layer of the film, the processing temperature of the extruder is 265~275℃, and the die head temperature is set to 270℃; then it is pressed by the rubber roller and the steel roller, cooled and shaped, and annealed by the tempering roller, where the rubber roller temperature is set to 75℃, the steel roller temperature is set to 95℃, and the tempering roller temperature is set to 65℃, and finally it is pulled and rolled into a PBT release film product, where the pulling ratio is set to 0.98.

[0127] The properties of the PBT release film prepared in this comparative example are shown in Table 1.

[0128] Table 1. PBT release film performance data

[0129]

[0130] As can be seen from the above table, the PBT release film of the present invention has good elongation at break and adhesive resistance, and the release film is not damaged after being pressed and peeled off from the FPC board.

[0131] In Examples 1 to 4 of the present invention, ethyl myristate is used as a release modifier. One end of the ethyl myristate is an ester group, which has good compatibility with the PBT resin, and the other end is a non-polar long olefin chain. The structure is stable at high temperatures. In addition, during the high-temperature pressing process, the non-polar long olefin chain of ethyl myristate migrates to the vicinity of the release film surface, reducing the surface energy of the release film to achieve a self-release effect, thereby solving the problem of high surface tension of the PBT resin.

[0132] In Comparative Example 1, excessive PBAT inhibits the crystallization of PBT, resulting in too little crystallinity. Excessive PBAT also greatly reduces the melting point of layer A, causing the film to completely soften and embed into the FPC board after lamination, affecting the release property.

[0133] In Comparative Example 2, the amount of the adhesive resistance resin added to the adhesive resistance layer is higher than that of the PBT resin, resulting in a lower melting point of the B layer, which melts and overflows during high-temperature pressing.

[0134] In Comparative Example 3, too little toughening resin was added, resulting in poor mechanical properties of layer A, which resulted in brittle cracking after hot pressing and residual fractures on the FPC board during peeling.

[0135] In Comparative Example 4, decene (a non-polar long olefin chain without an ester group) is used as a release modifier. Although it can meet the mechanical properties and adhesive resistance properties, the release film is tightly bonded to the FPC board after heating and pressing. After being peeled off, the release film is damaged. This is because pure olefin has poor compatibility with PBT and without ester group traction, the olefin migrates irregularly to the film surface, resulting in poor temperature resistance of the film surface.

[0136] Comparative Example 5 uses a high melt index PBT resin, which causes severe softening of the film during high-temperature lamination, resulting in severe board sticking.

[0137] In Comparative Example 6, the temperature during the film formation process was relatively high, resulting in excessive crystallinity, which in turn caused the film surface to be too hard and lacked glue resistance.

[0138] In summary, the PBT release film of the present invention has an ABA three-layer structure. After the PBT release film and the FPC board are heated and pressed, layer A can achieve self-relevant properties, without small molecule residues, wrinkles and other undesirable phenomena, and layer B can be fully filled into the surface structure of the FPC board to prevent glue from overflowing; the PBT release film of the present invention has excellent release and glue resistance properties, and the release film is not damaged after heating, pressing and peeling off.

[0139] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A PBT release film, characterized in that: It consists of an ABA three-layer structure, where layer A is the release layer and layer B is the adhesive barrier layer; The crystallinity of the release layer is 23-28%; The PBT release film has a TD direction elongation at break of ≥240%; Elongation at break in MD direction ≥300%, adhesive resistance test value <90μm; The preparation method of the PBT release film comprises: (1) weighing raw materials of a release layer, which include 70 to 90 parts by weight of PBT resin, 10 to 30 parts by weight of PBAT toughening resin, 0.1 to 20 parts by weight of a release modifier, and 0.1 to 10 parts by weight of an antioxidant; mixing the raw materials and adding them to a twin-screw pelletizer, and performing melt extrusion, cooling, forming, and pelletizing to obtain a release layer masterbatch; The mass ratio of the PBT resin to the PBAT toughening resin is (2.1-6):1; The release modifier is one or both of ethyl myristate and ethyl laurate; The melt index of the PBT resin is 19 g / 10 min when measured at 250° C. and 2.16 kg. (2) Weigh the raw materials of the adhesive barrier layer, including 50-70 parts of PBT resin, 30-50 parts of adhesive barrier resin, 1-20 parts of compatibilizer and 0.1-10 parts of antioxidant, mix the raw materials and add them into a twin-screw granulator, melt-extrude, cool and shape them into pellets, and obtain the masterbatch of the adhesive barrier layer; (3) The release layer masterbatch and the adhesive layer masterbatch are respectively put into two extruders, and after melt extrusion, they are coated and cast into films at the die head; After the film is cast, it is pressed by a rubber roller and a steel roller, cooled and shaped, annealed by a tempering roller, and then pulled and wound; the temperature of the rubber roller is 0-60°C, the temperature of the steel roller is 30-80°C, the temperature of the tempering roller is 50-100°C, and the traction ratio during traction and winding is 0.8-1.

2. The PBT release film according to claim 1, characterized in that The raw materials of the release layer include, by weight, 70-80 parts of PBT resin, 15-25 parts of PBAT toughening resin, 5-10 parts of ethyl myristate and 0.5-1 part of antioxidant.

3. The PBT release film according to claim 1, characterized in that The mass ratio of the PBT resin to the adhesive resistance resin is (1.1~2):

1.

4. The PBT release film according to claim 1, characterized in that The adhesive-blocking resin is selected from one or more of polyethylene, polypropylene, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate copolymer, polyvinyl alcohol, and ethylene acrylic acid copolymer.

5. A method for preparing a PBT release film according to claim 1, characterized in that: The preparation method comprises: (1) weighing raw materials of a release layer, which include 70 to 90 parts by weight of PBT resin, 10 to 30 parts by weight of PBAT toughening resin, 0.1 to 20 parts by weight of a release modifier, and 0.1 to 10 parts by weight of an antioxidant; mixing the raw materials and adding them to a twin-screw pelletizer, and performing melt extrusion, cooling, forming, and pelletizing to obtain a release layer masterbatch; (2) Weigh the raw materials of the adhesive barrier layer, including 50-70 parts of PBT resin, 30-50 parts of adhesive barrier resin, 1-20 parts of compatibilizer and 0.1-10 parts of antioxidant, mix the raw materials and add them into a twin-screw granulator, melt-extrude, cool and shape them into pellets, and obtain the masterbatch of the adhesive barrier layer; (3) The release layer masterbatch and the adhesive layer masterbatch are respectively put into two extruders, and after melt extrusion, they are coated and cast into films at the die head.

6. The method for preparing a PBT release film according to claim 5, wherein: The melt extrusion temperature in (1) is 260-280°C; the melt extrusion temperature in (2) is 250-270°C; and the processing temperature of the extruder in (3) is 240-300°C, and the die head temperature is 240-300°C.

7. The method for preparing a PBT release film according to claim 5, wherein: The PBT release film and the FPC board are heated and pressed at 170-190° C., and the release film is not damaged after being peeled off.

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