Protective film for automobile panel production and method for manufacturing the same

Abstract

This invention relates to the field of protective film technology, and provides a protective film for automotive panel production and its preparation method. The protective film for automotive panel production provided by this invention comprises an outer layer, a middle layer, and an inner layer arranged sequentially. The outer layer is prepared from metallocene low-density polyethylene and KN resin; the middle layer is prepared from a first polypropylene and metallocene polyethylene; and the inner layer is prepared from a first polypropylene and a second polypropylene. The protective film provided by this invention exhibits good high-temperature resistance, stable adhesion at high temperatures, leaves no adhesive residue after peeling, and has good puncture resistance, enabling protection throughout the entire automotive panel production process.

Description

Technical Field

[0001] This invention relates to the field of protective film technology, and in particular to a protective film for automotive panel production and its preparation method. Background Technology

[0002] In the industrialized production process of automotive interior and exterior parts, automotive panels, as core decorative and functional components, are highly susceptible to surface scratches, bumps, dust contamination, high-temperature baking residue, and processing stress damage throughout the entire process, including injection molding, painting, baking, assembly, transportation, and warehousing. These issues directly affect product appearance yield and assembly accuracy. To ensure the surface quality of automotive panels, process protective films have become an indispensable protective consumable in the production process. These films must simultaneously meet multiple requirements, including adhesion protection, high-temperature stability, no adhesive residue after peeling, and puncture and breakage resistance.

[0003] Currently, most protective films used in the production of conventional automotive panels are made primarily of ordinary polyethylene and polypropylene. These protective films have poor high-temperature resistance, making them difficult to peel off. Some films may even melt at high temperatures and stick to the mold surface. In addition, existing protective films have poor puncture resistance, making them prone to damage during production and failing to provide protection. Summary of the Invention

[0004] In view of this, the present invention provides a protective film for automotive panel production and a method for preparing the same. The protective film for automotive panel production provided by the present invention has good high-temperature resistance, stable adhesion at high temperatures, leaves no adhesive residue after peeling, and has good puncture resistance, enabling protection throughout the entire process.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A protective film for automotive panel production includes an outer layer, a middle layer, and an inner layer arranged sequentially. The raw materials for preparing the outer layer, by weight, include: 20-50 parts of metallocene low-density polyethylene and 40-80 parts of KN resin; The raw materials for preparing the middle layer, by weight, include: 50-90 parts of first polypropylene and 20-60 parts of metallocene polyethylene; The raw materials for preparing the inner layer, by weight, include: 40-80 parts of first polypropylene and 30-60 parts of second polypropylene; The first polypropylene used in the middle and inner layers has a melt index of 1~3 g / 10 min and a density of 0.89~0.91 g / cm³. 3 The second polypropylene used in the inner layer has a melt index of 0.5~1 g / 10 min and a density of 0.89~0.91 g / cm³. 3 .

[0006] Preferably, the outer layer is made of metallocene low-density polyethylene with a melt index of 2-4 g / 10 min and a density of 0.915-0.920 g / cm³. 3 The outer layer uses KN resin with a melt index of 3-4 g / 10 min and a density of 0.880-0.900 g / cm³. 3 .

[0007] Preferably, the metallocene polyethylene used in the middle layer has a melt index of 0.2~1.0 g / 10 min and a density of 0.920~0.940 g / cm³. 3 .

[0008] Preferably, the outer layer is made of metallocene low-density polyethylene grade 3518CB; and the KN resin grade is KF360T.

[0009] Preferably, the metallocene polyethylene used in the middle layer is grade 3505MC.

[0010] Preferably, the first polypropylene used in the middle and inner layers is RB707CF; and the second polypropylene used in the inner layer is HJ340F.

[0011] The present invention also provides a method for preparing the protective film for automotive panel production described in the above-described scheme, comprising the following steps: The raw materials for the preparation of the outer, middle and inner layers are co-extruded and blown into a film to obtain a protective film for automotive panel production.

[0012] Preferably, the raw materials for preparing the outer layer, middle layer and inner layer are melted and plasticized by the outer layer extruder, the middle layer extruder and the inner layer extruder, respectively, and the resulting adhesive liquid is transported to the die head for extrusion blown film.

[0013] Preferably, the outer extruder, middle extruder, and inner extruder are each equipped with five heating zones, numbered 1 to 5 according to the order in which the raw materials pass through. The temperature of zone 1 of the outer extruder is 170-180℃, zone 2 is 180-190℃, zone 3 is 180-190℃, zone 4 is 180-190℃, and zone 5 is 180-190℃. The temperature of zone 1 of the middle extruder is... The temperatures in zones 1, 2, 3, 4, and 5 of the inner extruder are 190-200℃, 200-220℃, 220-240℃, 220-240℃, and 220-240℃ respectively.

[0014] Preferably, the die head is provided with 4 heating zones, which are numbered 1 to 4 according to the order in which the raw materials pass through; 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℃.

[0015] This invention provides a protective film for automotive panel production, comprising an outer layer, a middle layer, and an inner layer arranged sequentially. By weight, the outer layer is prepared from 20-50 parts of metallocene low-density polyethylene and 40-80 parts of KN resin. By weight, the middle layer is prepared from 50-90 parts of first polypropylene and 20-60 parts of metallocene polyethylene. By weight, the inner layer is prepared from 40-80 parts of first polypropylene and 30-60 parts of second polypropylene. The first polypropylene used in the middle and inner layers has a melt index of 1-3 g / 10 min and a density of 0.89-0.91 g / cm³. 3 The second polypropylene used in the inner layer has a melt index of 0.5~1 g / 10 min and a density of 0.89~0.91 g / cm³. 3 This invention employs metallocene low-density polyethylene (MDPE) with excellent tensile and puncture resistance in the outer layer, adds MPE with excellent tensile and puncture resistance in the middle layer, and adds a second polypropylene with high impact resistance in the inner layer, thereby improving the puncture resistance of the protective film. Simultaneously, this invention adds KN resin with good heat resistance to the outer layer, improving the high-temperature resistance of the protective film. In summary, this invention strictly controls the types and proportions of raw materials used in the outer, middle, and inner layers to obtain a protective film with good high-temperature resistance and puncture resistance. The results of the embodiments show that the protective film provided by this invention has stable adhesion at high temperatures, leaves no residue after peeling, and has a puncture force of 4.8~5.0N, enabling protection throughout the entire automotive panel production process. Detailed Implementation

[0016] This invention provides a protective film for automotive panel production, comprising an outer layer, a middle layer, and an inner layer arranged sequentially. The raw materials for preparing the outer layer, by weight, include: 20-50 parts of metallocene low-density polyethylene and 40-80 parts of KN resin; The raw materials for preparing the middle layer, by weight, include: 50-90 parts of first polypropylene and 20-60 parts of metallocene polyethylene; The raw materials for preparing the inner layer, by weight, include: 40-80 parts of first polypropylene and 30-60 parts of second polypropylene; The first polypropylene used in the middle and inner layers has a melt index of 1~3 g / 10 min and a density of 0.89~0.91 g / cm³. 3The second polypropylene used in the inner layer has a melt index of 0.5~1 g / 10 min and a density of 0.89~0.91 g / cm³. 3 .

[0017] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0018] The outer layer is prepared from 20-50 parts by weight of metallocene low-density polyethylene, specifically 30 or 40 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 / cm³. 3 More preferably, it is 0.918~0.920 g / cm³. 3 In a specific embodiment of the present invention, the metallocene low-density polyethylene is grade 3518CB, manufactured by ExxonMobil, with a melt index of 3.5 g / 10 min and a density of 0.918 g / cm³. 3 Specifically, it is a metallocene ethylene-ethane copolymer with excellent tensile properties and puncture resistance.

[0019] Based on the mass fraction of metallocene low-density polyethylene used in the outer layer, the raw materials for preparing the outer layer include 40-80 parts of KN resin, specifically 60 or 70 parts; the melt index of the KN resin is preferably 3-4 g / 10 min, more preferably 3.5-4 g / 10 min, and the density is preferably 0.880-0.900 g / cm³. 3 More preferably, it is 0.895~0.898 g / cm³. 3 In a specific embodiment of the present invention, the KN resin is grade KF360T, manufactured by Mitsubishi Corporation of Japan, with a melt index of 3.5 g / 10 min and a density of 0.898 g / cm³. 3 The KN resin used in this invention has good heat resistance and can maintain stable adhesion at high temperatures.

[0020] By weight, the raw materials for preparing the middle layer include 50-90 parts of first polypropylene, specifically 70 or 80 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 / cm³. 3 The preferred value is 0.9 g / cm³. 3 In a specific embodiment of the present invention, the first polypropylene is grade RB707CF, manufactured by Boluer Chemical, with a melt index of 1.5 g / 10 min and a density of 0.9 g / cm³. 3 The first polypropylene used in this invention has good processability.

[0021] Based on the mass fraction of the first polypropylene used in the middle layer, the raw materials for preparing the middle layer include 20 to 60 parts of metallocene polyethylene, specifically 20, 30, or 35 parts; the melt index of the metallocene polyethylene is preferably 0.2 to 1.0 g / 10 min, more preferably 0.5 to 0.6 g / 10 min, and the density is preferably 0.920 to 0.940 g / cm³. 3 More preferably, it is 0.93~0.935 g / cm³. 3 In a specific embodiment of the present invention, the metallocene polyethylene is grade 3505MC, manufactured by ExxonMobil, with a melt index of 0.5 g / 10 min and a density of 0.935 g / cm³. 3 Specifically, it is an ethylene-1-hexene copolymer with high tensile strength and excellent puncture resistance.

[0022] By mass, the raw materials for preparing the inner layer include 40 to 80 parts of first polypropylene, specifically 40, 60, or 70 parts; the melt index, density, and grade of the first polypropylene used in the inner layer are the same as those used in the middle layer, and will not be repeated here.

[0023] Based on the mass fraction of the first polypropylene used in the inner layer, the raw materials for preparing the inner layer include 30 to 60 parts of a second polypropylene, specifically 30, 40, or 60 parts; the melt index of the second polypropylene is 0.5 to 1 g / 10 min, preferably 0.8 to 0.9 g / 10 min, and the density is 0.89 to 0.91 g / cm³. 3 The preferred value is 0.9 g / cm³. 3 In a specific embodiment of the present invention, the second polypropylene is grade HJ340F, manufactured by Hyosung of South Korea, with a melt index of 0.9 g / 10 min and a density of 0.9 g / cm³. 3 This grade of polypropylene is a specially designed polypropylene block copolymer with very high impact strength and excellent optical properties.

[0024] In this invention, taking the total mass of the raw materials for the preparation of the outer layer, middle layer and inner layer as 100%, the mass fraction of the raw materials for the preparation of the outer layer is 10~20%, specifically 15%, the mass fraction of the raw materials for the preparation of the middle layer is preferably 40~70%, specifically 55%, and the mass fraction of the raw materials for the preparation of the inner layer is preferably 20~40%, specifically 30%.

[0025] In this invention, the thickness of the protective film used in automotive panel production is 25-50 micrometers, specifically 30 micrometers; the longitudinal tensile strength of the high-temperature resistant, easy-to-peel film used for sealing Tyvek is preferably 80-90 MPa, the transverse tensile strength is preferably 39-42 MPa, the longitudinal elongation at break is preferably 500-730%, the transverse elongation at break is preferably 740-780%, the viscosity at room temperature is 0.053-0.063 N, and the viscosity at 150°C is 0.189-0.207 N.

[0026] The present invention also provides a method for preparing the protective film for automotive panel production described in the above-described scheme, comprising the following steps: The raw materials for the preparation of the outer, middle and inner layers are co-extruded and blown into a film to obtain a protective film for automotive panel production.

[0027] In this invention, the raw materials for preparing the outer layer, middle layer and inner layer are preferably melted and plasticized by an outer layer extruder, a middle layer extruder and an inner layer extruder, respectively, and the resulting adhesive liquid is transported to a die head for extrusion blown film.

[0028] In this invention, the outer extruder, middle extruder, and inner extruder are each equipped with five heating zones, which are sequentially designated as zones 1 to 5 according to the order in which the raw materials pass through. The preferred temperature for zone 1 of the outer extruder is 170-180℃, specifically 180℃; the preferred temperature for zone 2 is 180-190℃, specifically 188℃; the preferred temperature for zone 3 is 180-190℃, specifically 188℃; the preferred temperature for zone 4 is 180-190℃, specifically 185℃; and the preferred temperature for zone 5 is 180-190℃, specifically 185℃. Similarly, the preferred temperature for zone 1 of the middle extruder is 190-200℃, specifically 190℃; the preferred temperature for zone 2 is 2... The temperature ranges from 00 to 220℃, specifically 210℃. The preferred temperatures for zones 3 and 4 are 200 to 220℃, specifically 210℃, and for zones 5 and 5 are 200 to 220℃, specifically 210℃. The preferred temperatures for zones 1, 2, 2, 3, 4, and 5 of the inner extruder are 190 to 200℃, specifically 200℃; the preferred temperatures for zones 2, 2, 3, 4, and 5 of the inner extruder are 220 to 240℃, specifically 230℃.

[0029] In this invention, the extrusion pressure of the outer extruder is preferably 250-500 bar, specifically 355 bar; the extrusion pressure of the middle extruder is preferably 250-500 bar, specifically 287 bar; and the extrusion pressure of the inner extruder is preferably 250-500 bar, specifically 316 bar.

[0030] In this invention, the die head is provided with four heating zones, which are numbered 1 to 4 according to the order in which the raw materials pass through. The temperature of zone 1 of the die head is preferably 190 to 210°C, specifically 200°C; the temperature of zone 2 is preferably 200 to 220°C, specifically 215°C; the temperature of zone 3 is preferably 200 to 220°C, specifically 215°C; and the temperature of zone 4 is preferably 200 to 220°C, specifically 210°C.

[0031] In this invention, the extrusion blown film is used to obtain a film bubble. The film bubble is preferably cooled by air and then traction-rotated by a stabilizing ring and a herringbone pattern. The film bubble is flattened and then cooled by a guide roller. The film then enters a crystal point defect detector to inspect its appearance and crystal points. After the edges are cut, the film is separated into individual sheets by a lower traction clamping roller and enters an antistatic device. Finally, it is wound up by a front and rear winding device to obtain a protective film for automotive panel production.

[0032] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] Example 1 A protective film for automotive panel production is made of three co-extruded blown film layers: an outer layer, a middle layer, and an inner layer. Based on the total mass of the raw materials used in the preparation of the outer, middle, and inner layers (100%), the weight percentages of each layer are as follows: outer layer 15%, middle layer 55%, and inner layer 30%. The raw material ratios for each layer are shown in Table 1, and the film thickness is 30 μm.

[0034] Table 1 Raw material ratio for each layer

[0035] The preparation method is as follows: The raw materials for the outer, middle, and inner layers are mixed in proportion by an automatic batching system and then fed into the outer, middle, and inner layer extruders. The raw materials for the outer, middle, and inner layers are melted and plasticized and then fed into the die head for extrusion and blown film extrusion. After air cooling, the film is flattened by a stabilizing ring and herringbone-shaped rollers and guided by an upper traction rotating device. After being cooled by guide rollers, the film enters a crystal point defect detector to inspect the appearance and crystal points of the film. Then, the edges are trimmed and separated into individual sheets by a lower traction clamping roller and wound up by a front and rear winding device to obtain the protective film for automotive panel production. The temperatures and pressures of the outer, middle, and inner layer extruders, as well as the die head temperature, are shown in Table 2.

[0036] Table 2. Temperature and pressure of the extruder and temperature of the die head

[0037] Example 2 A protective film for automotive panel production is made of three co-extruded blown film layers: an outer layer, a middle layer, and an inner layer. Based on the total mass of the raw materials used in the preparation of the outer, middle, and inner layers (100%), the weight percentages of each layer are as follows: outer layer 15%, middle layer 55%, and inner layer 30%. The raw material ratios for each layer are shown in Table 3, and the film thickness is 30 μm.

[0038] Table 3 Raw material ratio for each layer

[0039] The preparation method is the same as in Example 1.

[0040] Example 3 A protective film for automotive panel production is made of three co-extruded blown film layers: an outer layer, a middle layer, and an inner layer. Based on the total mass of the raw materials used in the preparation of the outer, middle, and inner layers (100%), the weight percentages of each layer are as follows: outer layer 15%, middle layer 55%, and inner layer 30%. The raw material ratios for each layer are shown in Table 4, and the film thickness is 30 μm.

[0041] Table 4 Raw material ratio for each layer

[0042] The preparation method is the same as in Example 1.

[0043] Comparative Example 1 A protective film for automotive panel production is made of three co-extruded blown film layers: an outer layer, a middle layer, and an inner layer. Based on the total mass of the raw materials used in the preparation of the outer, middle, and inner layers (100%), the weight percentages of each layer are as follows: outer layer 15%, middle layer 55%, and inner layer 30%. The raw material ratios for each layer are shown in Table 5, and the film thickness is 30 μm.

[0044] Table 5 Raw material ratios for each layer

[0045] The preparation method is the same as in Example 1.

[0046] Comparative Example 2 A protective film for automotive panel production is made of three co-extruded blown film layers: an outer layer, a middle layer, and an inner layer. Based on the total mass of the raw materials used in the preparation of the outer, middle, and inner layers (100%), the weight percentages of each layer are as follows: outer layer 15%, middle layer 55%, and inner layer 30%. The raw material ratios for each layer are shown in Table 6, and the film thickness is 30 μm.

[0047] Table 6 Raw material ratios for each layer

[0048] The preparation method is the same as in Example 1.

[0049] Performance testing The tensile strength, elongation at break, and adhesion at room temperature and high temperature (150°C) of the protective films prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested. The test methods and results are shown in Table 7. The method for evaluating the temperature resistance was as follows: the obtained protective film was subjected to a vacuum forming test (vacuum forming conditions: 180°C, 15s). The phenomenon of melting, film breakage, or sticking to the mold during the vacuum forming process was observed. If no such phenomenon occurred, the film was considered to be heat resistant.

[0050] Table 7 Test Results

[0051] As can be seen from the results in Table 7, the protective films prepared in Examples 1-3 have excellent mechanical properties, high puncture strength, stable viscosity at 150°C, no residue after peeling, and good temperature resistance. They do not melt, break, or stick to the mold during the vacuum forming process. In Comparative Example 1, the second polypropylene used in the inner layer was omitted, and the resulting protective film was not heat-resistant and easily stuck to the mold surface during the vacuum forming process, making it difficult to peel off. In Comparative Example 2, the outer KN resin was omitted. Although it was heat-resistant, it had no adhesive properties and could not meet the requirements for protective films used in automotive panel production.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A protective film for automotive panel manufacturing, characterized in that, This includes an outer layer, a middle layer, and an inner layer arranged sequentially. The raw materials for preparing the outer layer, by weight, include: 20-50 parts of metallocene low-density polyethylene and 40-80 parts of KN resin; The raw materials for preparing the middle layer, by weight, include: 50-90 parts of first polypropylene and 20-60 parts of metallocene polyethylene; The raw materials for preparing the inner layer, by weight, include: 40-80 parts of first polypropylene and 30-60 parts of second polypropylene; The first polypropylene used in the middle and inner layers has a melt index of 1~3 g / 10 min and a density of 0.89~0.91 g / cm³. 3 The second polypropylene used in the inner layer has a melt index of 0.5~1 g / 10 min and a density of 0.89~0.91 g / cm³. 3 .

2. The protective film for automotive panel production according to claim 1, characterized in that, The outer layer uses metallocene low-density polyethylene with a melt index of 2-4 g / 10 min and a density of 0.915-0.920 g / cm³. 3 The outer layer uses KN resin with a melt index of 3-4 g / 10 min and a density of 0.880-0.900 g / cm³. 3 .

3. The protective film for automotive panel production according to claim 1, characterized in that, The middle layer uses metallocene polyethylene with a melt index of 0.2~1.0 g / 10 min and a density of 0.920~0.940 g / cm³. 3 .

4. The protective film for automotive panel production according to claim 1, characterized in that, The outer layer uses metallocene low-density polyethylene of grade 3518CB; the KN resin is grade KF360T.

5. The protective film for automotive panel production according to claim 1, characterized in that, The middle layer uses metallocene polyethylene of grade 3505MC.

6. The protective film for automotive panel production according to claim 1, characterized in that, The first polypropylene used in the middle and inner layers is RB707CF; the second polypropylene used in the inner layer is HJ340F.

7. The method for preparing the protective film for automotive panel production according to any one of claims 1 to 6, characterized in that, Includes the following steps: The raw materials for the preparation of the outer, middle and inner layers are co-extruded and blown into a film to obtain a protective film for automotive panel production.

8. The preparation method according to claim 7, characterized in that, The raw materials for the preparation of the outer, middle and inner layers are melted and plasticized by the outer layer extruder, the middle layer extruder and the inner layer extruder, respectively, and the resulting adhesive liquid is transported to the die head for extrusion blown film.

9. The preparation method according to claim 8, characterized in that, The outer, middle, and inner extruders are each equipped with five heating zones, numbered 1 to 5 according to the order in which the raw materials pass through. The outer extruder has zone 1 temperatures of 170-180℃, zone 2 temperatures of 180-190℃, zone 3 temperatures of 180-190℃, zone 4 temperatures of 180-190℃, and zone 5 temperatures of 180-190℃. The middle extruder has zone 1 temperatures of 190℃. The temperatures in zones 1, 2, 3, 4, and 5 of the inner extruder are 0~200℃, 200~220℃, 200~220℃, 200~220℃, and 200~220℃ respectively.

10. The preparation method according to claim 8, characterized in that, The die head is provided with 4 heating zones, which are numbered 1 to 4 according to the order in which the raw materials pass through. The temperature of zone 1 of the die head is 190~210℃, zone 2 is 200~220℃, zone 3 is 200~220℃, and zone 4 is 200~220℃.

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