A hot bending stamping protective film and a preparation method and application thereof

Abstract

The present application relates to the technical field of protective film, and provides a hot bending stamping protective film, a preparation method and application thereof.The preparation raw material of the outer layer of the hot bending stamping protective film comprises metallocene low-density polyethylene and polyolefin plasticizer, the preparation raw material of the middle layer comprises first polypropylene and low-density polyethylene, and the preparation raw material of the inner layer comprises second polypropylene and third polypropylene.The present application strictly controls the preparation raw material and ratio of the outer layer, the middle layer and the inner layer of the hot bending stamping protective film, can improve the high-temperature resistance of the hot bending stamping protective film, and improve the viscosity stability and mechanical strength.The protective film of the present application is applied to the PET hot bending stamping forming process, and the phenomena such as film tearing difficulty, melting at high temperature and stamping breakage do not occur.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of protective film, in particular to a hot bending stamping protective film and a preparation method and application thereof. BACKGROUND

[0002] Polyethylene terephthalate (PET) has good chemical stability and is widely used in packaging, electronic appliances and household products industries.

[0003] The hot bending stamping forming process of PET is to stamp and form a PET substrate after heating to prepare a product with a certain curvature. For example, in the current preparation process of electronic device housings, a 2D plate is formed into a 3D plate with a curved surface through the hot bending stamping forming process to meet different design and functional requirements. In addition, the preparation of food or medicine packaging boxes and various lamps and lampshades also involves the hot bending stamping process of PET.

[0004] In order to avoid damage to the PET plate during the hot bending stamping forming process, the plate needs to be protected by film coating before forming. However, the hot bending stamping forming needs to be carried out under high temperature conditions. The viscosity of the existing protective film increases under high temperature conditions, making it difficult to tear off the film. Some even melt at high temperatures and stick to the surface of the product. SUMMARY

[0005] Therefore, the present application provides a hot bending stamping protective film and a preparation method and application thereof. The hot bending stamping protective film provided by the present application has good high temperature resistance, stable viscosity, high strength and elongation at break, and does not break during stamping.

[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0007] A hot bending stamping protective film, comprising an outer layer, a middle layer and an inner layer; the preparation raw materials of the outer layer comprise, in terms of weight fraction: metallocene low-density polyethylene 40-80 parts, polyolefin plasticizer 20-60 parts;

[0008] The preparation raw materials of the middle layer comprise, in terms of weight fraction: first polypropylene 30-90 parts, low-density polyethylene 10-60 parts;

[0009] The preparation raw materials of the inner layer comprise, in terms of weight fraction: second polypropylene 30-80 parts, third polypropylene 20-50 parts;

[0010] The melt index of the first polypropylene and the second polypropylene is 1-3 g / 10 min, and the density is 0.89-0.91 g / cm 3 The melt index of the third polypropylene is 0.5-1 g / 10 min, and the density is 0.89-0.91 g / cm 3.

[0011] Preferably, the melt index of the metallocene low density polyethylene is 2-4 g / 10 min, and the density is 0.915-0.920 g / cm 3 ; the melt index of the polyolefin plastomer is 3-4 g / 10 min, and the density is 0.870-0.900 g / cm 3 .

[0012] Preferably, the melt index of the low density polyethylene is 1.5-3.0 g / 10 min, and the density is 0.920-0.930 g / cm 3 .

[0013] Preferably, the grade of the metallocene low density polyethylene is 3518CB; and the grade of the polyolefin plastomer is KC8852G.

[0014] The grade of the first polypropylene and the second polypropylene is RB707CF; the grade of the low density polyethylene is 450E; and the grade of the third polypropylene is HJ340F.

[0015] Preferably, the mass fraction of the outer layer is 10-30%, the mass fraction of the middle layer is 40-80%, and the mass fraction of the inner layer is 10-50%, based on the total mass of the outer layer, the middle layer and the inner layer being 100%.

[0016] The application further provides a preparation method of the hot bending stamping protective film.

[0017] The preparation raw materials of the outer layer, the middle layer and the inner layer are co-extruded in three layers to obtain the hot bending stamping protective film.

[0018] Preferably, the co-extrusion in three layers comprises: the preparation raw materials of the outer layer, the middle layer and the inner layer are respectively fed into the outer layer extruder, the middle layer extruder and the inner layer extruder for melt plasticization, the obtained glue solution is transported to a die head, a bubble is extruded and blown to obtain a film bubble, the film bubble is air-cooled and cooled, and then is guided to an upper traction rotation through a stabilizing ring and a herringbone row, the film bubble is pressed flat and then is detected, edge cut, static electricity removed and wound to obtain the hot bending stamping protective film.

[0019] Preferably, the outer layer extruder, the middle layer extruder and the inner layer extruder are each provided with 5 heating zones, which are sequentially recorded as zone 1~zone 5 according to the passing order of raw materials; the temperature of zone 1 of the outer layer extruder is 170~180℃, the temperature of zone 2 is 185~195℃, the temperature of zone 3 is 185~195℃, the temperature of zone 4 is 185~195℃, and the temperature of zone 5 is 185~195℃; the temperature of zone 1 of the middle layer extruder is 180~190℃, the temperature of zone 2 is 190~210℃, the temperature of zone 3 is 190~210℃, the temperature of zone 4 is 190~210℃, and the temperature of zone 5 is 190~210℃; the temperature of zone 1 of the inner layer extruder is 190~200℃, the temperature of zone 2 is 200~220℃, the temperature of zone 3 is 200~220℃, the temperature of zone 4 is 200~220℃, and the temperature of zone 5 is 200~220℃.

[0020] The die head is provided with 4 heating zones, which are sequentially recorded as zone 1~zone 4 according to the passing order of raw materials; the temperature of zone 1 of the die head is 190~210℃, the temperature of zone 2 is 200~220℃, the temperature of zone 3 is 200~220℃, and the temperature of zone 4 is 200~220℃.

[0021] Preferably, the extrusion pressure of the outer layer extruder is 250~600bar, the extrusion pressure of the middle layer extruder is 250~600bar, and the extrusion pressure of the inner layer extruder is 250~600bar.

[0022] The application further provides application of the hot-bending stamping protective film prepared by the preparation method in the above scheme in PET hot-bending stamping forming.

[0023] The application provides a hot-bending stamping protective film, which comprises an outer layer, a middle layer and an inner layer; preparation raw materials of the outer layer comprise, in weight parts, 40~80 parts of metallocene low-density polyethylene and 20~60 parts of polyolefin plasticizer; preparation raw materials of the middle layer comprise, in weight parts, 30~90 parts of first polypropylene and 10~60 parts of low-density polyethylene; and preparation raw materials of the inner layer comprise, in weight parts, 30~80 parts of second polypropylene and 20~50 parts of third polypropylene; the first polypropylene and the second polypropylene have a melt index of 1~3g / 10min and a density of 0.89~0.91g / cm 3 ; and the third polypropylene has a melt index of 0.5~1g / 10min and a density of 0.89~0.91g / cm 3The present application strictly controls the preparation raw materials and the ratio of the outer layer, the middle layer and the inner layer of the hot bending stamping protective film, wherein the outer layer can provide stable adhesion, the middle layer provides higher strength and elongation at break, and the inner layer provides better temperature resistance, thereby obtaining a hot bending stamping protective film with high temperature resistance, good viscosity stability, high strength and high elongation at break. The protective film of the present application is applied in the PET hot bending and stamping forming process, and does not have the phenomena of film tearing difficulty, melting at high temperature and the like, and the stamping is not broken. DETAILED DESCRIPTION

[0024] The present application provides a hot bending stamping protective film, comprising an outer layer, a middle layer and an inner layer; the preparation raw materials of the outer layer comprise, in parts by weight: metallocene low density polyethylene 40-80 parts, polyolefin plasticizer 20-60 parts;

[0025] The preparation raw materials of the middle layer comprise, in parts by weight: first polypropylene 30-90 parts, low density polyethylene 10-60 parts;

[0026] The preparation raw materials of the inner layer comprise, in parts by weight: second polypropylene 30-80 parts, third polypropylene 20-50 parts;

[0027] The melt index of the first polypropylene and the second polypropylene is 1-3 g / 10 min, and the density is 0.89-0.91 g / cm 3 The melt index of the third polypropylene is 0.5-1 g / 10 min, and the density is 0.89-0.91 g / cm 3 .

[0028] The preparation raw materials of the outer layer comprise metallocene low density polyethylene 40-80 parts, specifically 50 parts, 60 parts or 70 parts; the melt index of the metallocene low density polyethylene is preferably 2-4 g / 10 min, more preferably 3-3.5 g / 10 min, and the density is preferably 0.915-0.920 g / cm 3 , more preferably 0.916-0.918 g / cm 3 ; in the specific embodiments of the present application, the grade of the metallocene low density polyethylene is 3518CB, the manufacturer is Exxon, the melt index is 3.5 g / 10 min, and the density is 0.918 g / cm 3 ; the metallocene low density polyethylene used in the present application is a metallocene ethylene-ethane copolymer, which has excellent tensile properties, impact resistance and puncture resistance.

[0029] The raw materials for preparing the outer layer include 20-60 parts of polyolefin plastomer (POP) by weight, specifically 30 parts, 40 parts or 50 parts; the melt index of the polyolefin plastomer is preferably 3-4 g / 10 min, more preferably 3.5-3.8 g / 10 min, and the density is preferably 0.870-0.900 g / cm 3 , more preferably 0.875-0.880 g / cm 3 ; in a specific embodiment of the application, the POP has a trade name of KC8852G, is produced by Dow Chemical, has a melt index of 3.5 g / 10 min and a density of 0.875 g / cm 3 The POP used in the application has high self-adhesion and excellent toughness.

[0030] The raw materials for preparing the middle layer include 30-90 parts of first polypropylene by weight, specifically 40 parts, 50 parts, 60 parts, 70 parts, 80 parts or 90 parts; the melt index of the first polypropylene is 1-3 g / 10 min, preferably 1.5-2 g / 10 min, and the density is 0.89-0.91 g / cm 3 , preferably 0.9-0.905 g / cm 3 ; in a specific embodiment of the application, the first polypropylene has a trade name of RB707CF, is produced by Boppl Chemical, has a melt index of 1.5 g / 10 min and a density of 0.9 g / cm 3 The first polypropylene used in the application has good processability.

[0031] The raw materials for preparing the middle layer include 10-60 parts of low-density polyethylene by weight of the first polypropylene used in the middle layer, specifically 10 parts, 30 parts, 40 parts or 50 parts; the melt index of the low-density polyethylene is preferably 1.5-3.0 g / 10 min, more preferably 2-2.5 g / 10 min, and the density is preferably 0.920-0.930 g / cm 3 , more preferably 0.923-0.925 g / cm 3 ; in a specific embodiment of the application, the low-density polyethylene has a trade name of 450E, is produced by Dow Chemical, has a melt index of 2 g / 10 min and a density of 0.923 g / cm 3 The low-density polyethylene used in the application has the characteristics of low crystallization points and easy processability.

[0032] The preparation raw materials of the inner layer include 30-80 parts of the second polypropylene by weight, and specifically can be 40 parts, 50 parts, 60 parts, 70 parts or 80 parts. In the present application, the melt index of the second polypropylene is 1-3 g / 10 min, preferably 1.5-2 g / 10 min, and the density is 0.89-0.91 g / cm 3 , preferably 0.9-0.905 g / cm 3 ; in a specific embodiment of the present application, the trade name of the second polypropylene is RB707CF, the manufacturer is Bopu Chemical, the melt index is 1.5 g / 10 min, and the density is 0.9 g / cm 3 . The second polypropylene used in the present application has good processability.

[0033] The preparation raw materials of the inner layer include 30-80 parts of the second polypropylene by weight, and specifically can be 40 parts, 50 parts, 60 parts, 70 parts or 80 parts. In the present application, the melt index of the second polypropylene is 1-3 g / 10 min, preferably 1.5-2 g / 10 min, and the density is 0.89-0.91 g / cm 3 , preferably 0.9-0.905 g / cm 3 ; in a specific embodiment of the present application, the trade name of the second polypropylene is RB707CF, the manufacturer is Bopu Chemical, the melt index is 1.5 g / 10 min, and the density is 0.9 g / cm 3 . The third polypropylene used in the present application is a specially designed polypropylene block copolymer, which has very high impact strength and excellent optical properties.

[0034] In the present application, the mass fraction of the outer layer is preferably 10-30%, more preferably 20%, the mass fraction of the middle layer is 40-80%, more preferably 60%, and the mass fraction of the inner layer is 10-50%, more preferably 20%, based on the total mass of the outer layer, the middle layer and the inner layer being 100%.

[0035] In the present application, the longitudinal tensile strength of the hot bending stamping protective film is 36-50 MPa, the transverse tensile strength is 28-30 MPa, the longitudinal elongation at break is 440-580%, the transverse elongation at break is 710-720%, the room temperature viscosity is 0.075-0.088 N, and the viscosity at 120°C is 0.096-0.11 N.

[0036] The present application also provides a preparation method of the hot bending stamping protective film described in the above-mentioned scheme, which comprises the following steps:

[0037] The preparation raw materials of the outer layer, the middle layer and the inner layer are co-extruded in three layers to obtain the hot bending stamping protective film.

[0038] In the present application, the three-layer co-extrusion preferably comprises: feeding the raw materials for preparing the outer layer, the middle layer and the inner layer into the outer layer, middle layer and inner layer extruders respectively for melt plasticization, conveying the obtained glue liquid to a die head, extruding and blowing a film bubble, air cooling the film bubble, and then passing the film bubble through a stabilizing ring and a herringbone arrangement to an upper traction rotation, flattening the film bubble, and then detecting, trimming, removing static electricity and winding to obtain the hot bending stamping protective film.

[0039] In the present application, the outer layer extruder, the middle layer extruder and the inner layer extruder are each preferably provided with 5 heating zones, which are sequentially recorded as zone 1 to zone 5 according to the passing order of the raw materials; the temperature of zone 1 of the outer layer extruder is preferably 170-180℃, more preferably 175℃, the temperature of zone 2 is preferably 185-195℃, more preferably 190℃, the temperature of zone 3 is preferably 185-195℃, more preferably 190℃, the temperature of zone 4 is preferably 185-195℃, more preferably 190℃, and the temperature of zone 5 is preferably 185-195℃, more preferably 190℃; the temperature of zone 1 of the middle layer extruder is preferably 180-190℃, more preferably 185℃, the temperature of zone 2 is preferably 190-210℃, more preferably 200℃, the temperature of zone 3 is preferably 190-210℃, more preferably 200℃, the temperature of zone 4 is preferably 190-210℃, more preferably 200℃, and the temperature of zone 5 is preferably 190-210℃, more preferably 200℃; the temperature of zone 1 of the inner layer extruder is preferably 190-200℃, more preferably 195℃, the temperature of zone 2 is preferably 200-220℃, more preferably 210℃, the temperature of zone 3 is preferably 200-220℃, more preferably 210℃, the temperature of zone 4 is preferably 200-220℃, more preferably 210℃, and the temperature of zone 5 is preferably 200-220℃, more preferably 210℃.

[0040] In the present application, the die head is preferably provided with 4 heating zones, which are sequentially recorded as zone 1 to zone 4 according to the passing order of the raw materials; the temperature of zone 1 of the die head is preferably 190-210℃, more preferably 200℃, the temperature of zone 2 is preferably 200-220℃, more preferably 210℃, the temperature of zone 3 is preferably 200-220℃, more preferably 210℃, and the temperature of zone 4 is preferably 200-220℃, more preferably 210℃.

[0041] In the present application, the extrusion pressure of the outer layer extruder is preferably 250-600bar, more preferably 300-355bar, the extrusion pressure of the middle layer extruder is preferably 250-600bar, more preferably 300-330bar, and the extrusion pressure of the inner layer extruder is preferably 250-600bar, more preferably 400-425bar.

[0042] In the present application, the detection is preferably the detection of the appearance and crystal points of the film by a crystal point flaw detector; after the detection, the edges are cut, then the single sheet is separated by the lower traction clamp roller, enters the static electricity removing device for static electricity removing, and then is wound by the front and rear winding devices to obtain the hot bending stamping protective film of the present application.

[0043] The present application also provides the application of the hot bending stamping protective film in the PET hot bending stamping forming.

[0044] The technical solutions in the present application will be clearly and completely described below with the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0045] Embodiment 1

[0046] A hot bending stamping protective film is made of three layers of co-extrusion blown film, i.e. an outer layer, a middle layer and an inner layer, and the weight percentages of the raw materials of the outer layer, the middle layer and the inner layer are respectively: 20% for the outer layer, 60% for the middle layer and 20% for the inner layer, and the raw material dosages of the layers are shown in Table 1.

[0047] Table 1 Raw material dosages of the hot bending stamping protective film in Embodiment 1

[0048]

[0049] The preparation method is as follows: the outer layer, the middle layer and the inner layer raw materials are mixed by proportion through an automatic batching system, then are sent into the outer layer, the middle layer and the inner layer extruders, the raw materials of the outer layer, the middle layer and the inner layer are melt plasticized, then are sent into a die head, extruded and blown into a film, then are air-cooled, enter a stabilizing ring and a herringbone arrangement, then enter a crystal point flaw detector for detecting the appearance and crystal points of the film, then are cut, separated by a lower traction clamp roller, enter a static electricity removing device, and are wound by front and rear winding devices to obtain the hot bending stamping protective film, the thickness of which is 35 μm; the extrusion pressure of the outer layer, the middle layer and the inner layer extruders and the temperature of each zone are shown in Table 2.

[0050] Table 2 Extrusion pressure of the outer layer, the middle layer and the inner layer extruders and temperature of each zone

[0051] temperature zone 1 zone 2 zone 3 zone 4 zone 5 pressure (bar) outer layer 180 190 190 190 190 355 middle layer 190 200 200 200 200 330 inner layer 200 210 210 210 210 425 die 200 210 210 210 / /

[0052] Embodiment 2

[0053] A hot bending and stamping protective film is made of three layers of co-extrusion blown film, i.e. an outer layer, a middle layer and an inner layer. The weight percentage of the raw materials of the outer layer, the middle layer and the inner layer is respectively: 20% for the outer layer, 60% for the middle layer and 20% for the inner layer. The raw material usage of each layer is shown in Table 3. The thickness of the protective film is 35 μm.

[0054] Table 3 Raw material usage of each layer of the hot bending and stamping protective film in Example 2

[0055]

[0056] The preparation method is the same as that in Example 1.

[0057] Example 3

[0058] A hot bending and stamping protective film is made of three layers of co-extrusion blown film, i.e. an outer layer, a middle layer and an inner layer. The weight percentage of the raw materials of the outer layer, the middle layer and the inner layer is respectively: 20% for the outer layer, 60% for the middle layer and 20% for the inner layer. The raw material usage of each layer is shown in Table 4. The thickness of the protective film is 35 μm.

[0059] Table 4 Raw material usage of each layer of the hot bending and stamping protective film in Example 3

[0060]

[0061] The preparation method is the same as that in Example 1.

[0062] Comparative Example 1

[0063] A hot bending and stamping protective film is made of three layers of co-extrusion blown film, i.e. an outer layer, a middle layer and an inner layer. The weight percentage of the raw materials of the outer layer, the middle layer and the inner layer is respectively: 20% for the outer layer, 60% for the middle layer and 20% for the inner layer. The raw material usage of each layer is shown in Table 5. The thickness of the protective film is 35 μm.

[0064] Table 5 Raw material usage of each layer of the hot bending and stamping protective film in Comparative Example 1

[0065]

[0066]

[0067] The preparation method is the same as that in Example 1.

[0068] Comparative Example 2

[0069] A hot bending and stamping protective film is made of three layers of co-extrusion blown film, i.e. an outer layer, a middle layer and an inner layer. The weight percentage of the raw materials of the outer layer, the middle layer and the inner layer is respectively: 20% for the outer layer, 60% for the middle layer and 20% for the inner layer. The raw material usage of each layer is shown in Table 6. The thickness of the protective film is 35 μm.

[0070] Table 6 Raw material usage of each layer of the hot bending and stamping protective film in Comparative Example 2

[0071]

[0072] The preparation method and example 1 are the same.

[0073] Performance test:

[0074] The tensile strength, elongation at break, viscosity at room temperature and viscosity at 120 DEG C of the protective films prepared in example 1 to example 3 and comparative example 1 to comparative example 3 are tested, the testing method and testing results are shown in table 7, wherein the temperature resistance is tested by hot stamping experiment, the temperature of hot stamping test is 500 DEG C, the hot stamping time is 3s, and the protective film does not melt during the hot stamping process, then it is temperature resistant, otherwise it is not temperature resistant.

[0075] Table 7 performance test results

[0076]

[0077] According to the data in table 1, it can be seen that the tensile strength and elongation at break of the hot bending stamping protective film prepared in the application are high, the higher elongation at break makes it not easy to be broken during stamping process; and the viscosity at high temperature and the viscosity at room temperature of the hot bending stamping protective film prepared in the application change little compared with each other, which shows that it has good viscosity stability, does not melt during hot stamping process, has good temperature resistance, and is suitable for the hot bending stamping forming process of PET; the protective film prepared in comparative example 1 and comparative example 2 is not temperature resistant, and will melt during hot bending stamping process, especially comparative example 2 has serious tackiness at high temperature, and has poor mechanical properties.

[0078] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A heat-bend press protection film, characterized by, The outer layer, the middle layer and the inner layer; the preparation raw materials of the outer layer include: metallocene low density polyethylene 40-80 parts, polyolefin plastomer 20-60 parts by weight; The preparation raw materials of the middle layer include: first polypropylene 30-90 parts, low density polyethylene 10-60 parts by weight; The preparation raw materials of the inner layer include: second polypropylene 30-80 parts, third polypropylene 20-50 parts by weight; The melt index of the first polypropylene and the second polypropylene is 1-3 g / 10 min, and the density is 0.89-0.91 g / cm 3 The melt index of the third polypropylene is 0.5-1 g / 10 min, and the density is 0.89-0.91 g / cm 3 The grade of the first polypropylene and the second polypropylene is RB707CF; and the grade of the third polypropylene is HJ340F.

2. The heat-bend press protection film according to claim 1, characterized by, The melt index of the metallocene low density polyethylene is 2 to 4 g / 10 min and the density is 0.915 to 0.920 g / cm 3 The melt index of the polyolefin plastomer is 3 to 4 g / 10 min and the density is 0.870 to 0.900 g / cm 3 .

3. The heat-bend press protection film according to claim 1, characterized in that, The low-density polyethylene has a melt index of 1.5 to 3.0 g / 10 min and a density of 0.920 to 0.930 g / cm 3 .

4. The heat-bend press protection film according to claim 1, characterized in that, The brand of the metallocene low density polyethylene is 3518CB; the brand of the polyolefin plastomer is KC8852G; The brand of the low density polyethylene is 450E.

5. The heat-bend-stamp protective film according to claim 1, wherein The mass fraction of the outer layer is 10-30%, the mass fraction of the middle layer is 40-80%, and the mass fraction of the inner layer is 10-50% based on the total mass of the outer layer, the middle layer and the inner layer being 100%.

6. The method of producing a hot-bend press protective film according to any one of claims 1 to 5, characterized by, The preparation raw materials of the outer layer, the middle layer and the inner layer are three-layer co-extruded to obtain the hot bending stamping protective film. The three-layer co-extrusion includes: the preparation raw materials of the outer layer, the middle layer and the inner layer are respectively sent into the outer layer, the middle layer and the inner layer extruders for melt plasticization, the obtained glue solution is transported to the die head, the film bubble is extruded and blown to obtain the film bubble, the film bubble is air-cooled and cooled, then is sent to the stabilizing ring, the herringbone row to the upper traction rotation, the film bubble is flattened and then detected, edge cut, static electricity removed and wound to obtain the hot bending stamping protective film.

7. The preparation method according to claim 6, characterized in that, The outer layer extruder, the middle layer extruder and the inner layer extruder are all provided with five heating zones, which are sequentially recorded as zone 1-zone 5 according to the passing order of the raw materials; the temperature of zone 1 of the outer layer extruder is 170-180℃, the temperature of zone 2 is 185-195℃, the temperature of zone 3 is 185-195℃, the temperature of zone 4 is 185-195℃, and the temperature of zone 5 is 185-195℃; the temperature of zone 1 of the middle layer extruder is 180-190℃, the temperature of zone 2 is 190-210℃, the temperature of zone 3 is 190-210℃, the temperature of zone 4 is 190-210℃, and the temperature of zone 5 is 190-210℃; the temperature of zone 1 of the inner layer extruder is 190-200℃, the temperature of zone 2 is 200-220℃, the temperature of zone 3 is 200-220℃, the temperature of zone 4 is 200-220℃, and the temperature of zone 5 is 200-220℃.

8. The preparation method according to claim 7, characterized in that, The die head is provided with four heating zones, which are sequentially recorded as zone 1-zone 4 according to the passing order of the raw materials; the temperature of zone 1 of the die head is 190-210℃, the temperature of zone 2 is 200-220℃, the temperature of zone 3 is 200-220℃, and the temperature of zone 4 is 200-220℃. The extrusion pressure of the outer layer extruder is 250-600bar, the extrusion pressure of the middle layer extruder is 250-600bar, and the extrusion pressure of the inner layer extruder is 250-600bar.

9. The production method according to claim 8, characterized by, 10. The hot bending stamping protective film of any one of claims 1-5 or the hot bending stamping protective film prepared by the preparation method of any one of claims 6-9 is applied in PET hot bending stamping forming. ​

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