PBT release film and preparation method thereof

Abstract

The invention belongs to the technical field of release films, and relates to a PBT release film and a preparation method thereof.The PBT release film is composed of an A layer, a B layer and a A layer, the A layer is a release layer, and the B layer is a glue blocking layer; the raw materials of the release layer comprise PBT resin, toughening resin, a release modifier and an antioxidant, and the release modifier is a non-polar long olefin chain with one end containing an ester group and comprises one or more of ethyl myristate, ethyl laurate, ethyl palmitate and ethyl stearate. The invention also discloses a preparation method of the PBT release film. After the PBT release film and an FPC (Flexible Printed Circuit) board are heated and pressed, the A layer can realize self-release property and has no undesirable phenomena such as small molecule residues and wrinkles, and the B layer can be fully filled into the surface structure of the FPC board to prevent 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 increasingly being used in the flexible circuit board (FPC) market, and are gradually replacing TPX (poly-4-methyl-1-pentene) resin release films. However, due to its chemical structure, PBT resin has problems such as high surface tension and insufficient toughness, which leads to problems such as insufficient release and PBT film residue on the FPC during the FPC board lamination process for downstream customers. At present, the release properties of PBT release films are usually improved by adding some Si-containing and F-containing release modifiers, but the Si-containing and F-containing small molecule components in the modifiers are unstable in structure and will be transferred to the FPC during the high-temperature lamination process, causing contamination. Summary of the invention

[0003] The purpose of the present invention is to solve the above problems in the prior art and to provide 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 by the following technical solutions: 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; The raw materials of the release layer include 70-90 parts of PBT resin, 10-30 parts of toughening resin, 0.1-20 parts of release modifier and 0.1-10 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 myristic acid, ethyl laurate, ethyl palmitate and ethyl stearate.

[0005] Preferably, the melt index of the PBT resin is 10-20 g / 10 min at 250° C. and 2.16 kg.

[0006] 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).

[0007] Preferably, the mass ratio of PBT resin to toughening resin in the raw materials of the release layer is (2.1-6):1.

[0008] 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.

[0009] 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.

[0010] More preferably, the mass ratio of the PBT resin to the adhesive resistance resin is (1.1-2):1.

[0011] More preferably, the melt index of the PBT resin is measured at 250° C. and 2.16 kg and is 10 to 20 g / 10 min.

[0012] 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.

[0013] More preferably, the adhesive-blocking resin is polyethylene.

[0014] More preferably, the compatibilizer is selected from one or more of maleic anhydride, silane coupling agent, nylon, polyurethane, and polyether.

[0015] More preferably, the antioxidant is selected from one or more of antioxidant 1076, antioxidant 168, and antioxidant 1010.

[0016] 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.

[0017] Preferably, the PBT release film has a thickness of 100-200 μm.

[0018] Preferably, the total thickness of the A layer is 30-60 μm, and the thickness of the B layer is 70-140 μm.

[0019] More preferably, the thickness of the A layer is 15-30 μm.

[0020] Preferably, the release layer has a crystallinity of 23-28%.

[0021] More preferably, the release layer has a crystallinity of 24-25%.

[0022] Preferably, the PBT release film has a TD direction elongation at break of ≥240%, an MD direction elongation at break of ≥300%, and a resistance test value of <90 μm.

[0023] More preferably, the PBT release film has a TD direction elongation at break of ≥300%, an MD direction elongation at break of ≥320%, and a resistance test value of <85 μm.

[0024] 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.

[0025] A method for preparing a PBT release film, comprising: (1) Weigh the raw materials of the release layer, including 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 into a twin-screw granulator, melt-extrude, cool and shape them into pellets, and obtain a release layer masterbatch; (2) Weigh the raw materials of the adhesive barrier layer, including 50-70 parts by weight 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 a 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 laminated and cast into films at the die head.

[0026] Preferably, the moisture content of the release layer masterbatch and the adhesive barrier layer masterbatch is lower than 0.02%.

[0027] Preferably, the melt extrusion temperature in (1) is 260-280°C.

[0028] Preferably, the melt extrusion temperature in (2) is 250-270°C.

[0029] Preferably, the processing temperature of the extruder in (3) is 240-300°C, and the die head temperature is 240-300°C.

[0030] More preferably, the processing temperature of the extruder is 260-280°C, and the die head temperature is 260-280°C.

[0031] 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 rolled.

[0032] 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.

[0033] 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.

[0034] Preferably, the release layer has a crystallinity of 23-28%.

[0035] More preferably, the release layer has a crystallinity of 24-25%.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Compared with the prior art, the present invention has the following beneficial effects: 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, the A layer can achieve self-release, no small molecule residue, no wrinkles and other undesirable phenomena, and the B layer can be fully filled into the surface structure of the FPC board to prevent the overflow of glue; 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 the PBT resin, and the other end is a non-polar long olefin chain with a stable structure 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 the PBT resin. 3. The present invention preferably uses PBAT as a 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 being brittle after lamination or remaining on the FPC board during peeling; 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 the adhesive resistance; while too little crystallinity will cause the film to completely soften and embed into the FPC board after lamination, affecting the release property; 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

[0040] Figure 1It is a schematic diagram of the structure of the PBT release film of the present invention and a schematic diagram of the release principle of the release layer A in Example 1 under normal temperature and high temperature pressing states. DETAILED DESCRIPTION

[0041] 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.

[0042] Unless otherwise specified, the materials used in the present invention are conventional commercial products, and the methods used are conventional technical means.

[0043] In this paper, PBT resin: BASF, model B4500, melt index is 19g / 10min (250℃, 2.16kg); PBT resin: BASF, model B4520, melt index 19g / 10min (250℃, 2.16kg); PBT resin: Mitsubishi, model 5510S, melt index 33g / 10min (250℃, 2.16kg); Ethyl myristate: CAS: 124-06-1; Ethyl laurate: CAS: 106-33-2; PBAT resin: BASF, model C1200, melt index 4g / 10min (190℃, 2.16kg); Polyethylene resin: Shanghai Petrochemical, model Q281, melt index is 3g / 10min (190℃, 2.16kg).

[0044] The structural schematic diagram of the PBT release film of the present invention is shown in Figure 1 . Example 1

[0045] 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.

[0046] The preparation method of the PBT release film comprises: (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 masterbatch of the release layer; (2) Weigh the raw materials of the adhesive barrier layer, including 50 parts by weight of PBT resin (B4500), 40 parts of adhesive 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 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 laminated 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 rubber rollers and steel rollers, cooled and shaped, and annealed by tempering rollers, wherein the temperature of the rubber rollers is set to 25℃, the temperature of the steel rollers is set to 45℃, and the temperature of the tempering rollers is set to 65℃, and finally it is pulled and rolled into a PBT release film product, wherein the pulling ratio is set to 0.98.

[0047] The schematic diagram of the release principle of the release layer A in the present embodiment 1 under the normal temperature and high temperature pressing state is shown in Figure 1 It can be seen that during the high-temperature pressing process, the non-polar long olefin chain of ethyl myristic acid will migrate to the vicinity of the release film surface, reducing the surface energy of the release film to achieve a self-release effect.

[0048] The properties of the PBT release film prepared in this example are shown in Table 1. Example 2

[0049] 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.

[0050] The preparation method of the PBT release film comprises: (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; (2) Weigh the raw materials of the adhesive barrier layer, including 60 parts by weight of PBT resin (B4500), 35 parts of adhesive 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 them into pellets, and obtain the masterbatch of the adhesive barrier layer; (3) Prepare a PBT release film according to the method in Example 1.

[0051] The properties of the PBT release film prepared in this example are shown in Table 1. Example 3

[0052] 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.

[0053] The preparation method of the PBT release film comprises: (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 masterbatch of the release layer; (2) Weigh the raw materials of the adhesive barrier layer, including 50 parts by weight of PBT resin (B4500), 45 parts of adhesive barrier resin (polyethylene resin), 5 parts of compatibilizer (polyurethane) and 2 parts 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 the masterbatch of the adhesive barrier layer; (3) Prepare a PBT release film according to the method in Example 1.

[0054] The properties of the PBT release film prepared in this example are shown in Table 1. Example 4

[0055] 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.

[0056] The preparation method of the PBT release film comprises: (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; (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 (polyethylene resin), 5 parts by weight of compatibilizer (polyurethane) and 1 part by weight 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 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 laminated 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°C, and the die head temperature is set to 270°C; then, it is pressed by a rubber roller and a steel roller, cooled and shaped, and annealed by a tempering roller, wherein the temperature of the rubber roller is set to 30°C, the temperature of the steel roller is set to 50°C, and the temperature of the tempering roller is set to 75°C, and finally it is pulled and rolled into a PBT release film product, wherein the pulling ratio is set to 0.95.

[0057] The properties of the PBT release film prepared in this example are shown in Table 1. Example 5

[0058] 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.

[0059] The preparation method of the PBT release film comprises: (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; (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 masterbatch of the adhesive barrier layer; (3) Prepare a PBT release film according to the method in Example 1.

[0060] The properties of the PBT release film prepared in this example are shown in Table 1. Comparative Example 1

[0061] 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.

[0062] The preparation method of the PBT release film comprises: (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; (2) Weigh the raw materials of the adhesive barrier layer, including 50 parts by weight of PBT resin (B4520), 45 parts of adhesive barrier resin (polyethylene resin), 5 parts of compatibilizer (polyurethane) and 2 parts of antioxidant (antioxidant 1076), 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 the masterbatch of the adhesive barrier layer; (3) Prepare a PBT release film according to the method in Example 1.

[0063] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 2

[0064] 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.

[0065] The preparation method of the PBT release film comprises: (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; (2) Weigh the raw materials of the adhesive barrier layer, including 40 parts by weight of PBT resin (B4520), 55 parts of adhesive 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 granulator, melt extrude at 265°C, cool and shape them into pellets, and obtain the masterbatch of the adhesive barrier layer; (3) Prepare a PBT release film according to the method in Example 1.

[0066] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 3

[0067] 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.

[0068] The preparation method of the PBT release film comprises: (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; (2) Weigh the raw materials of the adhesive barrier layer, including 50 parts by weight of PBT resin (B4520), 45 parts of adhesive 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 them into pellets, and obtain the masterbatch of the adhesive barrier layer; (3) Prepare a PBT release film according to the method in Example 1.

[0069] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 4

[0070] 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.

[0071] The preparation method of the PBT release film comprises: (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 granulator, melt extrude at 275°C, cool and shape them into pellets, and obtain a masterbatch of the release layer; (2) Weigh the raw materials of the adhesive barrier layer, including 50 parts by weight of PBT resin (B4520), 40 parts of adhesive 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 them into pellets, and obtain the masterbatch of the adhesive barrier layer; (3) Prepare a PBT release film according to the method in Example 1.

[0072] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 5

[0073] 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.

[0074] The preparation method of the PBT release film comprises: (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; (2) Weigh the raw materials of the adhesive barrier layer, including 50 parts by weight of PBT resin (5510S), 40 parts by weight of adhesive barrier resin (polyethylene resin), 10 parts by weight of compatibilizer (polyurethane) and 1 part by weight of antioxidant (antioxidant 1010), mix the raw materials and add them into a twin-screw granulator, melt extrude at 255°C, cool and shape them into pellets, and obtain the masterbatch of the adhesive barrier layer; (3) Prepare a PBT release film according to the method in Example 1.

[0075] The properties of the PBT release film prepared in this comparative example are shown in Table 1. Comparative Example 6

[0076] 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.

[0077] The preparation method of the PBT release film comprises: (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; (2) Weigh the raw materials of the adhesive barrier layer, including 50 parts by weight of PBT resin (B4520), 40 parts of adhesive 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 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 laminated 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 rubber rollers and steel rollers, cooled and shaped, and annealed by tempering rollers, wherein the temperature of the rubber rollers is set to 75℃, the temperature of the steel rollers is set to 95℃, and the temperature of the tempering rollers is set to 65℃, and finally it is pulled and rolled into a PBT release film product, wherein the pulling ratio is set to 0.98.

[0078] The properties of the PBT release film prepared in this comparative example are shown in Table 1.

[0079] Table 1. PBT release film performance data

[0080] It can be seen from the above table that 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.

[0081] In Examples 1 to 4 of the present invention, ethyl myristate is used as a release modifier, one end of which is an ester group, which has good compatibility with the PBT resin, and the other end is a non-polar long olefin chain, which has a stable structure at high temperatures. In addition, 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, thereby solving the problem of high surface tension of the PBT resin.

[0082] In Comparative Example 1, excessive PBAT inhibits the crystallization of PBT, resulting in too small a crystallinity, and excessive PBAT greatly reduces the melting point of layer A, thereby causing the film to completely soften and embed into the FPC board after lamination, affecting the release property.

[0083] In Comparative Example 2, the amount of the adhesive resistance resin added to the adhesive resistance layer is higher than the amount of the PBT resin added, resulting in a lower melting point of the B layer, which melts and overflows during high-temperature pressing.

[0084] 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.

[0085] 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 requirements of mechanical properties and adhesive resistance, the release film is tightly bonded to the FPC board after heating and pressing. The release film is damaged after being peeled off. 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.

[0086] In Comparative Example 5, a PBT resin with a high melt index is used, which results in severe softening of the film during high-temperature lamination, thereby causing severe board sticking.

[0087] 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 adhesive resistance.

[0088] 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, the A layer can achieve self-release, no small molecule residue, no wrinkles and other undesirable phenomena, and the B layer can be fully filled into the surface structure of the FPC board to prevent the overflow of glue; 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.

[0089] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A PBT release film, characterized in that: It consists of an ABA three-layer structure, where layer A is a release layer and layer B is a glue barrier layer; The raw materials of the release layer include 70-90 parts of PBT resin, 10-30 parts of toughening resin, 0.1-20 parts of release modifier and 0.1-10 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 myristic acid, ethyl laurate, ethyl palmitate and ethyl stearate.

2. The PBT release film according to claim 1, characterized in that: The melt index of the PBT resin is measured at 250° C. and 2.16 kg and is 10-20 g / 10 min.

3. The PBT release film according to claim 1, characterized in that: The mass ratio of PBT resin to toughening resin in the raw materials of the release layer is (2.1-6):

1.

4. The PBT release film according to claim 1, characterized in that: 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.

5. 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.

6. 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.

7. A method for preparing a PBT release film, characterized in that: The preparation method comprises: (1) weighing raw materials of a release layer, which include 70-90 parts by weight of a PBT resin, 10-30 parts of a toughening resin, 0.1-20 parts of a release modifier and 0.1-10 parts of an antioxidant, wherein the release modifier is a non-polar long olefin chain containing an ester group at one end, mixing the raw materials and adding them to a twin-screw granulator, and performing melt extrusion, cooling, forming and pelletizing to obtain a masterbatch of the release layer; (2) Weigh the raw materials of the adhesive barrier layer, including 50-70 parts by weight 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 a 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 laminated and cast into films at the die head.

8. The method for preparing a PBT release film according to claim 7, characterized in that: 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.

9. The method for preparing a PBT release film according to claim 7, characterized in that: 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 pulled and rolled.

10. The method for preparing a PBT release film according to claim 7, characterized in that: The crystallinity of the release layer is 23-28%; the elongation at break of the PBT release film in the TD direction is ≥240%; the elongation at break in the MD direction is ≥300%, and the adhesive resistance test value is <90 μm; 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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