A thermoplastic film with a multi-layer structure that does not weaken and a preparation method thereof

Abstract

This application belongs to the technical field of automotive interior trim skins. This application discloses a non-weakening thermoplastic film with a multi-layer structure. The non-weakening thermoplastic film with a multi-layer structure in this application includes a surface layer and a TPO layer connected in sequence from top to bottom; the surface layer is a surface paint treatment layer; the TPO layer includes a first TPO functional layer, a second TPO functional layer, and a PP foam sponge connected in sequence from top to bottom; alternatively, the TPO layer includes a first TPO functional layer, a TPO foam layer, and a PP foam sponge connected in sequence from top to bottom; alternatively, the TPO layer includes a first TPO functional layer, a TPO foam layer, a polyurethane polar layer, and a polyurethane foam; the raw materials of the first TPO functional layer include: modified ethylene propylene diene monomer rubber, modified polypropylene, antioxidant, light stabilizer, and masterbatch. The non-weakening thermoplastic film with a multi-layer structure prepared in this application can expand the thickness of the TPO layer skin, and at the same time innovatively introduce a functional layer or a foam layer to expand the existing application scenarios, and at the same time optimize the touch of the non-weakening TPO skin, reduce the plastic feeling, and enhance the luxury feeling of the interior trim.

Description

Technical Field

[0001] This application relates to the technical field of automotive interior skin, and particularly to a non-weakening thermoplastic film with a multi-layer structure and a preparation method thereof. Background Art

[0002] With the development of the automotive industry and the needs of people's lives, the production of automobiles has increased year by year. And with the continuous improvement of road conditions, the driving speed of automobiles has also become faster and faster, resulting in an increase in the probability of road traffic accidents. How to reduce the casualties of drivers and passengers when a car collision occurs has attracted more and more attention. In order to reduce the loss of life and property caused by traffic accidents, technicians have developed an automotive airbag system to buffer the impact generated by the collision and protect the driver and passengers. On the basis of automotive safety, people have higher and higher requirements for beauty and comfort. In recent years, a variety of instrument panels have been designed as integral airbag instrument panels, using a non-weakening explosive skin, so that the TPO instrument panel has better tensile strength and is more likely to break under the explosive impact, ensuring the normal opening of the airbag. The thickness of the existing non-weakening TPO material TPO layer generally does not exceed 0.6 mm at most, and the structure has certain limitations. Some actual instrument panels use the technology of die transfer patterns when adsorbing TPO skin materials, and generally use a one-mold-two-cavity die design for high-efficiency forming processing, resulting in higher requirements for the elongation at break of the TPO skin material, which is contrary to the low elongation at break required by the non-weakening skin. When the stretching is large, the thickness of the skin layer also needs to be increased to meet the actual processing requirements. Therefore, the thickness of the non-weakening TPO skin layer in the existing technical solution is limited by 0.6 mm, and its application has certain limitations. Summary of the Invention

[0003] In order to solve at least one of the above technical problems, develop a thermoplastic film that can expand the thickness of the TPO layer skin, and at the same time innovatively introduce a functional layer or a foaming layer to expand the existing application scenarios, and at the same time optimize the touch of the non-weakening TPO skin, reduce the plastic feeling, and enhance the luxury feeling of the interior. This application provides a non-weakening thermoplastic film with a multi-layer structure and a preparation method thereof.

[0004] On the one hand, the present application provides a non-weakening thermoplastic film with a multi-layer structure, including a surface layer and a TPO layer connected successively from top to bottom; the surface layer is a surface paint treatment layer; the TPO layer includes a first TPO functional layer, a second TPO functional layer and a PP foam sponge connected successively from top to bottom; or, the TPO layer includes a first TPO functional layer, a TPO foam layer and a PP foam sponge connected successively from top to bottom; or, the TPO layer includes a first TPO functional layer, a TPO foam layer, a polyurethane polar layer and a polyurethane foam connected successively from top to bottom; the first TPO functional layer includes the following raw materials in parts by weight: 60-85 parts of modified ethylene propylene diene monomer rubber, 15-25 parts of modified polypropylene, 1-2 parts of antioxidant, 1.5-2 parts of light stabilizer, 1-5 parts of masterbatch; the raw materials of the modified ethylene propylene diene monomer rubber include, by weight ratio: 80-100:18-25:12-16:20-30:5-8 of ethylene propylene diene monomer rubber, polypropylene, ethylene-acrylate copolymer, paraffin oil and talcum powder; the raw materials of the modified polypropylene include, by weight ratio: 65-85:1.5-3:4-9:8-15 of polypropylene, nano calcium carbonate, ethylene-octene copolymer and ethylene-acrylate copolymer.

[0005] By adopting the above technical solution, for the non-weakening thermoplastic film with a multi-layer structure in the present application, a multi-layer structure TPO film product is designed and developed. The surface layer is a traditional surface paint treatment layer, and the TPO layer adopts a unique multi-layer structure, which can be composed of 2 layers of TPO functional layers, or can be designed with 1 functional layer compounded with a TPO foam layer. The purpose of such material design is to combine through special structural collocations to achieve a functional TPO product layer with adjustable strength and controllable modulus, and then compound it with a polypropylene sponge to prepare a non-weakening film with a multi-layer structure. Among them, the introduction of the TPO foam layer can further reduce the mechanical properties of the multi-layer material structure relative to the TPO functional layer and expand the influence scenarios under different airbag shapes.

[0006] In some embodiments, when the TPO multi-layer structure of the non-weakening thermoplastic film is a first TPO functional layer, a second TPO functional layer and a PP foam sponge connected successively from top to bottom, the prepared non-weakening thermoplastic film is applicable to airbags with a Y-shaped or H-shaped skeleton expansion shape.

[0007] In some embodiments, when the TPO multi-layer structure of the non-weakening thermoplastic film is a first TPO functional layer, a TPO foam layer and a PP foam sponge connected successively from top to bottom, the prepared non-weakening thermoplastic film is applicable to airbags with a Y-shaped, H-shaped or U-shaped skeleton expansion shape.

[0008] In some embodiments, when the TPO multi-layer structure of the non-weakening thermoplastic film is a first TPO functional layer, a TPO foaming layer, a polyurethane polar layer, and a polyurethane foam that are connected in sequence from top to bottom, the prepared non-weakening thermoplastic film is suitable for airbags with a frame expansion shape of Y-shaped, H-shaped, or U-shaped.

[0009] In some embodiments, the ethylene-acrylate copolymer includes one or more of ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-propyl acrylate copolymer, ethylene-propyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, and ethylene-n-butyl methacrylate copolymer.

[0010] In some preferred embodiments, the ethylene-acrylate copolymer is one or more of ethylene-methyl methacrylate copolymer and ethylene-methyl acrylate copolymer.

[0011] By adopting the above technical solution, an ethylene-acrylate copolymer is introduced into the modified ethylene propylene diene monomer rubber and modified polypropylene. Compared with ordinary elastomer-modified polypropylene materials, it has good polarity, improves the surface tension of the material, and makes the adhesion between TPO functional layers and between the TPO layer and the surface layer higher. At the same time, due to the good polarity of the material, it has better bonding strength when bonded with an adhesive, expanding the application range of the TPO functional layer or the TPO foaming layer.

[0012] In some embodiments, the light stabilizer is one of light stabilizer 3808, light stabilizer 770, and light stabilizer 944.

[0013] In some embodiments, the second TPO functional layer comprises the following raw materials in parts by weight: 60-85 parts of modified ethylene propylene diene monomer rubber, 15-25 parts of modified polypropylene, 24-35 parts of linear low density polyethylene, 0.5-1.5 parts of foaming agent, and 1-5 parts of masterbatch.

[0014] In some embodiments, the TPO foaming layer comprises the following raw materials in parts by weight: 60-85 parts of modified ethylene propylene diene monomer rubber, 15-25 parts of modified polypropylene, 24-35 parts of linear low density polyethylene, 1.5-3 parts of ethylene-octene copolymer, 2-3 parts of foaming agent, and 1-5 parts of masterbatch.

[0015] In some preferred embodiments, the thickness specification of the formed first TPO functional layer is 0.5-1 mm, such as 0.5, 0.6, 0.7, 0.75, or 1 mm, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0016] In some preferred embodiments, the formed thickness specification of the second TPO functional layer is 0.5 - 0.8 mm, such as 0.5, 0.6, 0.7 or 0.8 mm, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0017] In some preferred embodiments, the formed thickness specification of the TPO foaming layer is 0.5 - 0.8 mm, such as 0.5, 0.6, 0.7 or 0.8 mm, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0018] In some preferred embodiments, the formed thickness specification of the PP sponge or the polyurethane foam is 1.5 - 3 mm, such as 1.5, 1.8, 2.0, 2.3, 2.5 or 3 mm, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0019] In some embodiments, the preparation method of the modified ethylene propylene diene monomer rubber comprises: mixing ethylene propylene diene monomer rubber, polypropylene, ethylene - acrylate copolymer, paraffin oil and talcum powder, extruding and pelletizing to obtain the modified ethylene propylene diene monomer rubber.

[0020] In some embodiments, the preparation method of the modified polypropylene comprises: mixing polypropylene, nano calcium carbonate, ethylene - octene copolymer and ethylene - acrylate copolymer, extruding and pelletizing to obtain the modified polypropylene.

[0021] In a second aspect, the present application provides a preparation method of the above - mentioned multi - layer - structured non - weakening thermoplastic film, comprising the following steps:

[0022] S1. Mix the raw materials, co - extrude the first TPO functional layer and the second TPO functional layer in a double - layer manner on an extruder and perform hot - pressing and compounding with the PP foamed sponge to obtain the TPO layer; or, mix the raw materials, co - extrude the first TPO functional layer and the TPO foaming layer in a double - layer manner on an extruder and perform hot - pressing and compounding with the PP foamed sponge to obtain the TPO layer; or, co - extrude the first TPO functional layer and the TPO foaming layer in a double - layer manner, and sequentially form a polyurethane polar layer on the surface of the TPO foaming layer and perform hot - pressing and compounding with the polyurethane foam to obtain the TPO layer;

[0023] S2. Coat paint on the surface of the first TPO functional layer of the TPO layer to produce a surface paint treatment layer, obtaining a semi - finished product;

[0024] S3. Place the semi - finished product obtained in step S3 under the condition of 195 - 210 °C for high - temperature foaming to obtain the multi - layer - structured non - weakening thermoplastic film.

[0025] In some embodiments, in step S1, the preparation process of the polyurethane polar layer is as follows: Dissolve the aqueous polyurethane resin in a polar solvent to obtain a polyurethane adhesive solution, coat the polyurethane adhesive solution on the surface of the TPO foam layer, and dry it at a low temperature to obtain the polyurethane polar layer; the viscosity of the polyurethane adhesive solution is 5 - 30 poises, and the solid content is 5 - 20 wt%.

[0026] By adopting the above technical solution, through the multi-layer structure design of the polyurethane polar layer, it can bond with the polyurethane foam layer to achieve a TPO skin with a touch comparable to that of slush-molded PVC without weakening.

[0027] In summary, the present invention includes at least one of the following beneficial technical effects:

[0028] 1. The introduction of the TPO foam layer in this application can further reduce the mechanical properties of the multi-layer material structure relative to the TPO functional layer, and expand the influence scenarios under different airbag forms.

[0029] 2. The solution design in this application can expand the skin thickness of the TPO layer, innovatively introduce a functional layer or a foam layer to expand the existing application scenarios, while optimizing the touch of the non-weakening TPO skin, reducing the plastic feeling, and enhancing the interior luxury feeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A non-weakening thermoplastic film with a multi-layer structure, where the TPO layer is, from top to bottom, a first TPO functional layer, a second TPO functional layer, and a PP foam sponge.

[0031] Figure 2 A non-weakening thermoplastic film with a multi-layer structure, where the TPO layer is, from top to bottom, a first TPO functional layer, a TPO foam layer, and a PP foam sponge.

[0032] Figure 3 A non-weakening thermoplastic film with a multi-layer structure, where the TPO layer is, from top to bottom, a first TPO functional layer, a TPO foam layer, a polyurethane polar layer, and a polyurethane foam.

[0033] Description of the reference numerals: 1, surface paint treatment layer; 2, first TPO functional layer; 3, second TPO functional layer; 4, PP foam sponge; 5, TPO foam layer; 6, polyurethane polar layer; 7, polyurethane foam. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following further describes the present application in detail with reference to the drawings and embodiments.

[0035] This application designs a multi-layered non-weakening thermoplastic film, which includes a surface layer and a TPO layer connected in sequence from top to bottom; the surface layer is a surface paint treatment layer; the TPO layer includes a first TPO functional layer, a second TPO functional layer, and a PP foam sponge connected in sequence from top to bottom; or, the TPO layer includes a first TPO functional layer, a TPO foam layer, and a PP foam sponge connected in sequence from top to bottom; or, the TPO layer includes a first TPO functional layer, a TPO foam layer, a polyurethane polar layer, and a polyurethane foam connected in sequence from top to bottom; the first TPO functional layer includes the following raw materials in parts by weight: 60-85 parts of modified ethylene propylene diene monomer rubber, 15-25 parts of modified polypropylene, 1-2 parts of antioxidant, 1.5-2 parts of light stabilizer, and 1-5 parts of masterbatch; the raw materials of the modified ethylene propylene diene monomer rubber include, by weight ratio: 80-100:18-25:12-16:20-30:5-8 of ethylene propylene diene monomer rubber, polypropylene, ethylene-acrylate copolymer, paraffin oil, and talcum powder; the raw materials of the modified polypropylene include, by weight ratio: 65-85:1.5-3:4-9:8-15 of polypropylene, nano calcium carbonate, ethylene-octene copolymer, and ethylene-acrylate copolymer.

[0036] The second TPO functional layer includes the following raw materials in parts by weight: 60-85 parts of modified ethylene propylene diene monomer rubber, 15-25 parts of modified polypropylene, 24-35 parts of linear low density polyethylene, 0.5-1.5 parts of foaming agent, and 1-5 parts of masterbatch.

[0037] The TPO foam layer includes the following raw materials in parts by weight: 60-85 parts of modified ethylene propylene diene monomer rubber, 15-25 parts of modified polypropylene, 24-35 parts of linear low density polyethylene, 1.5-3 parts of ethylene-octene copolymer, 2-3 parts of foaming agent, and 1-5 parts of masterbatch.

[0038] The multi-layered non-weakening thermoplastic film of this application is prepared by the following method, including the following steps:

[0039] S1. Knead the raw materials, double-extrude the first TPO functional layer and the second TPO functional layer on an extruder and perform hot pressing and compounding with the PP foam sponge to obtain the TPO layer; or, knead the raw materials, double-extrude the first TPO functional layer and the TPO foam layer on an extruder and perform hot pressing and compounding with the PP foam sponge to obtain the TPO layer; or, double-extrude the first TPO functional layer and the TPO foam layer, and sequentially form a polyurethane polar layer on the surface of the TPO foam layer and perform hot pressing and compounding with the polyurethane foam to obtain the TPO layer;

[0040] S2. Coat paint on the surface of the first TPO functional layer of the TPO layer to make a surface paint treatment layer to obtain a semi-finished product;

[0041] S3. Place the semi-finished product obtained in step S3 under the condition of 195 - 210 °C for high-temperature foaming to obtain the non-weakening thermoplastic film with a multi-layer structure.

[0042] The technical problem solved by this application is that the thickness of the TPO skin layer in the existing non-weakening blasting skin is limited to 0.6 mm, resulting in limited application scenarios. At the same time, after the existing non-weakening blasting skin is compounded with PP sponge and formed, its pressing touch still has a certain touch disadvantage compared with the traditional slush-molded PVC skin. In this application, a functional TPO product layer with adjustable strength and controllable modulus is combined through special structural collocations, and then it is compounded with polypropylene sponge to prepare a non-weakening film with a multi-layer structure. Among them, the introduction of the TPO foam layer can further reduce the mechanical properties of the multi-layer material structure relative to the TPO functional layer, and expand the influence scenarios under different airbag morphologies. Innovatively introduce a functional layer or a foam layer to expand the existing application scenarios, optimize the touch of the non-weakening TPO skin, reduce the plastic feeling, and enhance the interior luxury feeling.

[0043] The raw materials used in the examples of this application are all commercially available, and the sources are as follows:

[0044] Ethylene propylene diene monomer rubber, Nanjing Bermuda Biotechnology Co., Ltd.

[0045] Ethylene-octene copolymer, grade 8150, Dow Chemical Company

[0046] Ethylene-methyl acrylate copolymer, Nanjing Bermuda Biotechnology Co., Ltd.

[0047] Paraffin oil, Hubei Yongkuo Technology Co., Ltd.

[0048] Talc powder, Changxing Qingsheng Calcium Industry Co., Ltd.

[0049] Polypropylene, Nanjing Bermuda Biotechnology Co., Ltd.

[0050] PP foam sponge, Xiamen Chenyu Rubber and Plastic Products Co., Ltd.

[0051] Waterborne polyurethane resin, Guangzhou Difen New Materials Co., Ltd.

[0052] Polyurethane foam, Changzhou Daye Tengfei Sponge Factory.

[0053] Preparation Examples 1 - 5

[0054] Preparation Examples 1 - 5 are modified ethylene propylene diene monomer rubbers prepared with different raw material ratios, and the specific raw material ratios are shown in Table 1.

[0055] Table 1

[0056]

[0057] The preparation process of the modified ethylene propylene diene monomer (EPDM) in Preparation Examples 1 - 5 is as follows:

[0058] Plasticize ethylene propylene diene monomer (EPDM), polypropylene, ethylene - acrylate copolymer, paraffin oil and talcum powder at a roll temperature of 75 °C with a plasticizing speed of 2 min / kg, then refine and sheet out at a refining temperature of 60 °C with a refining speed of 2 min / kg, and then granulate to obtain the modified ethylene propylene diene monomer (EPDM).

[0059] The ethylene - acrylate copolymer used in Preparation Examples 1 - 5 is ethylene - methyl acrylate copolymer.

[0060] Preparation Examples 6 - 10

[0061] Preparation Examples 6 - 10 are modified polypropylenes prepared with different raw material ratios. The specific raw material ratios are shown in Table 2.

[0062] Table 2

[0063]

[0064]

[0065] The preparation process of the modified polypropylene in Preparation Examples 6 - 10 is as follows:

[0066] Put polypropylene, nano - calcium carbonate, ethylene - octene copolymer, and ethylene - acrylate copolymer into a mixer and knead at 180 °C for 10 min, extrude at 180 °C, and granulate to obtain the modified polypropylene.

[0067] The ethylene - acrylate copolymer used in Preparation Examples 6 - 10 is ethylene - methyl acrylate copolymer.

[0068] The average particle size of the nano - calcium carbonate in Preparation Examples 6 - 10 is 300 nm.

[0069] Preparation Examples 11 - 15

[0070] Preparation Examples 11 - 15 are different raw material ratios of the first TPO functional layer. The specific raw material ratios are shown in Table 3.

[0071] Table 3

[0072]

[0073] Among them, the antioxidant used in Preparation Examples 11 - 15 is antioxidant 168; the light stabilizer used in Preparation Examples 11 - 15 is light stabilizer 770.

[0074] Preparation Example 16

[0075] Preparation Example 16 is the raw material formula for the second TPO functional layer, specifically: 21 kg of modified polypropylene, 75 kg of modified ethylene-propylene-diene monomer rubber, 28 kg of linear low-density polyethylene, 1.2 kg of foaming agent, and 2 kg of masterbatch.

[0076] The foaming agent used in Preparation Example 16 is AC foaming agent.

[0077] Preparation Example 17

[0078] Preparation Example 17 is the raw material formula for the TPO foaming layer, specifically: 21 kg of modified polypropylene, 70 kg of modified ethylene-propylene-diene monomer rubber, 27 kg of linear low-density polyethylene, 11 kg of polyolefin thermoplastic elastomer, 2.5 kg of foaming agent, and 2 kg of masterbatch.

[0079] The foaming agent used in Preparation Example 17 is AC foaming agent.

[0080] Examples 1-13

[0081] Examples 1-13 are non-weakening thermoplastic films with a multi-layer structure prepared with different raw material ratios. The specific raw material ratios are shown in Table 4. The TPO layers in Examples 1-13 are the first TPO functional layer, the second TPO functional layer, and the PP foaming sponge connected in sequence from top to bottom.

[0082] In Examples 1-13, the modified ethylene-propylene-diene monomer rubber and modified polypropylene used in the first TPO functional layer and the second TPO functional layer correspond to the preparation examples in each group of examples. For example, in Example 1, the modified ethylene-propylene-diene monomer rubber used in the first TPO functional layer and the second TPO functional layer is Preparation Example 1, and the modified polypropylene used is Preparation Example 7; in Example 2, the modified ethylene-propylene-diene monomer rubber used in the first TPO functional layer and the second TPO functional layer is Preparation Example 2, and the modified polypropylene used is Preparation Example 7; and so on for other examples.

[0083] The specific structure of Examples 1-13 is shown in Figure 1 , which is, from top to bottom in sequence, the surface paint treatment layer 1, the first TPO functional layer 2, the second TPO functional layer 3, and the PP foaming sponge 4.

[0084] Table 4

[0085]

[0086] The preparation process of Examples 1-13 is as follows:

[0087] The raw materials of the first TPO functional layer and the second TPO functional layer are respectively kneaded, and the kneading temperature is controlled at 220°C, and the kneading time is 20 minutes; then, the first TPO functional layer and the second TPO functional layer are co-extruded on an extruder and hot-pressed and compounded with PP foamed sponge to obtain a TPO layer; paint is coated on the surface of the first TPO functional layer of the TPO layer to make a surface paint treatment layer, and a semi-finished product is obtained; the obtained semi-finished product is placed at 200°C for high-temperature foaming to obtain a multi-layered non-weakening thermoplastic film.

[0088] In Examples 1-13, the thickness of the first TPO functional layer after molding is controlled at 0.8 mm, the thickness of the second TPO functional layer after molding is controlled at 0.7 mm, and the thickness of the PP foamed sponge after molding is controlled at 2.8 mm.

[0089] Example 14

[0090] In Example 14, the TPO layer is the first TPO functional layer, the TPO foaming layer and the PP foamed sponge connected in sequence from top to bottom. Among them, the first TPO functional layer uses Preparation Example 12, and the TPO foaming layer uses Preparation Example 17; the modified ethylene propylene diene monomer rubber in the raw materials of the first TPO functional layer and the TPO foaming layer uses Preparation Example 2, and the modified polypropylene uses Preparation Example 7.

[0091] The specific structure of Example 14 is shown in Figure 2 , from top to bottom in sequence are the surface paint treatment layer 1, the first TPO functional layer 2, the TPO foaming layer 5, and the PP foamed sponge 4.

[0092] The preparation process of Example 14 is as follows:

[0093] The raw materials of the first TPO functional layer and the TPO foaming layer are respectively kneaded, and the kneading temperature is controlled at 220°C, and the kneading time is 20 minutes; then, the first TPO functional layer and the TPO foaming layer are co-extruded on an extruder and hot-pressed and compounded with PP foamed sponge to obtain a TPO layer; paint is coated on the surface of the first TPO functional layer of the TPO layer to make a surface paint treatment layer, and a semi-finished product is obtained; the obtained semi-finished product is placed at 200°C for high-temperature foaming to obtain a multi-layered non-weakening thermoplastic film.

[0094] In Example 14, the thickness of the first TPO functional layer after molding is controlled at 0.8 mm, the thickness of the TPO foaming layer after molding is controlled at 0.7 mm, and the thickness of the PP foamed sponge after molding is controlled at 2.8 mm.

[0095] Example 15

[0096] In Example 15, the TPO layer is composed of a first TPO functional layer, a TPO foaming layer, a polyurethane polar layer, and a polyurethane foam that are connected in sequence from top to bottom. Among them, the first TPO functional layer uses Preparation Example 12, and the TPO foaming layer uses Preparation Example 17; the modified ethylene-propylene-diene monomer rubber in the raw materials of the first TPO functional layer and the TPO foaming layer uses Preparation Example 2, and the modified polypropylene uses Preparation Example 7.

[0097] The specific structure of Example 15 is shown in Figure 3 , from top to bottom, are a surface paint treatment layer 1, a first TPO functional layer 2, a TPO foaming layer 5, a polyurethane polar layer 6, and a polyurethane foam 7.

[0098] The preparation process of Example 15 is as follows:

[0099] Mix the raw materials of the first TPO functional layer and the TPO foaming layer separately, and control the mixing temperature at 220 °C and the mixing time at 20 min; then, co-extrude the first TPO functional layer and the TPO foaming layer in a double-layer on an extruder, and sequentially form a polyurethane polar layer on the surface of the TPO foaming layer and perform hot pressing and lamination with the polyurethane foam to obtain the TPO layer. Coat paint on the surface of the first TPO functional layer of the TPO layer to make the surface paint treatment layer, and obtain a semi-finished product. Place the obtained semi-finished product at 200 °C for high-temperature foaming to obtain a multi-layered non-weakening thermoplastic film.

[0100] Among them, the preparation process of the polyurethane polar layer in Example 15 is as follows: Dissolve the waterborne polyurethane resin in a polar solvent to obtain a polyurethane glue solution, coat the polyurethane glue solution on the surface of the TPO foaming layer, and dry it at 50 °C to obtain the polyurethane polar layer; among them, the polar solvent is acetone, the viscosity of the polyurethane glue solution is 20 poise, and the solid content is 10 wt%.

[0101] In Example 15, the thickness of the first TPO functional layer after molding is controlled at 0.8 mm, the thickness of the TPO foaming layer after molding is controlled at 0.7 mm, the thickness of the polyurethane polar layer after molding is controlled at 0.2 mm, and the thickness of the polyurethane foam after molding is controlled at 2.8 mm.

[0102] Comparative Examples 1-3

[0103] Comparative Example 1 is based on Example 2, and the difference is that: in Comparative Example 1, no ethylene-acrylate copolymer is added to the modified ethylene-propylene-diene monomer rubber and the modified polypropylene used.

[0104] Comparative Example 2 is based on Example 2, and the difference is that: in Comparative Example 2, no ethylene-octene copolymer is added to the modified polypropylene used.

[0105] Comparative Example 3 is based on Example 2, with the difference that: in the TPO layer of Comparative Example 3, the second TPO functional layer is deleted, and only the first TPO functional layer is compounded with the PP foamed sponge.

[0106] Performance Testing

[0107] 1. According to the standard QLQBC-235-2014 "Instrument Panel Test Method", the multi-layered non-weakening thermoplastic film of Examples 1-15 and Comparative Examples 1-3 was subjected to a bursting test. After storing the non-weakening thermoplastic films of Examples 1-15 and Comparative Examples 1-3 at -35 ± 2 °C, 23 ± 4 °C, and 85 ± 2 °C for 6 hours respectively, a static bursting experiment was carried out to observe the bursting situation of the airbag, and the measurement results are shown in Table 5.

[0108] 2. According to the standard Q-320282HET001-2019, the tensile strength and elongation at break of the multi-layered non-weakening thermoplastic film of Examples 1-15 and Comparative Examples 1-3 were tested, and the measurement results are shown in Table 6.

[0109] Table 5

[0110]

[0111]

[0112] Table 6

[0113]

[0114]

[0115] By analyzing the data in Table 5 and Table 6, it can be obtained that by optimizing and adjusting the raw material ratio of the TPO functional layer in the TPO layer, balancing and integrating the various properties of the instrument panel material, and taking into account both mechanical properties and bursting integrity performance, it can be seen that the comprehensive test performance of Example 2 is better, and the tensile strength and tear strength are more balanced. At the same time, on the basis of Example 2, replacing the TPO functional layer with a foamed layer or replacing the PP foamed sponge with a polyurethane foam, the multi-layered non-weakening thermoplastic film prepared also has good comprehensive test performance, and is superior to Example 2 in some aspects. In Table 6, when comparing the examples with Comparative Examples 1-3, the tensile strength and elongation at break in Comparative Examples 1, 2, and 3 are too high, and the non-weakening thermoplastic film cannot burst. Although the elongation at break in Comparative Example 3 has decreased significantly, it has also led to a too large decrease in tensile strength, resulting in the non-weakening thermoplastic film not being able to meet normal use.

[0116] Result analysis The above are all preferred embodiments of this application, and the protection scope of this application is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of this application shall be covered within the protection scope of this application.

Claims

1. A non-weakening thermoplastic film with a multi-layer structure, characterized in that, It includes a surface layer and a TPO layer connected successively from top to bottom; The surface layer is a surface paint treatment layer; The TPO layer includes a first TPO functional layer, a second TPO functional layer and a PP foamed sponge connected successively from top to bottom; or, the TPO layer includes a first TPO functional layer, a TPO foamed layer and a PP foamed sponge connected successively from top to bottom; or, the TPO layer includes a first TPO functional layer, a TPO foamed layer, a polyurethane polar layer and a polyurethane foam; The first TPO functional layer includes the following raw materials in parts by weight: 60-85 parts of modified ethylene propylene diene monomer rubber, 15-25 parts of modified polypropylene, 1-2 parts of antioxidant, 1.5-2 parts of light stabilizer, 1-5 parts of masterbatch; The raw materials of the modified ethylene propylene diene monomer rubber include, by weight ratio: 80-100:18-25:12-16:20-30:5-8 of ethylene propylene diene monomer rubber, polypropylene, ethylene-acrylate copolymer, paraffin oil and talcum powder; The raw materials of the modified polypropylene include, by weight ratio: 65-85:1.5-3:4-9:8-15 of polypropylene, nano calcium carbonate, ethylene-octene copolymer and ethylene-acrylate copolymer; The ethylene-acrylate copolymer includes one or more of ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-propyl acrylate copolymer, ethylene-propyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer and ethylene-n-butyl methacrylate copolymer.

2. The thermoplastic film with a multi-layer structure according to claim 1, characterized in that, The light stabilizer is one of light stabilizer 3808, light stabilizer 770 and light stabilizer 944.

3. The non-weakening thermoplastic film with a multi-layer structure according to claim 1, characterized in that, The second TPO functional layer includes the following raw materials in parts by weight: 60-85 parts of modified ethylene propylene diene monomer rubber, 15-25 parts of modified polypropylene, 24-35 parts of linear low density polyethylene, 0.5-1.5 parts of foaming agent, 1-5 parts of masterbatch.

4. The thermoplastic film without weakening having a multi-layer structure according to claim 1, characterized in that, The TPO foamed layer includes the following raw materials in parts by weight: 60-85 parts of modified ethylene propylene diene monomer rubber, 15-25 parts of modified polypropylene, 24-35 parts of linear low density polyethylene, 1.5-3 parts of ethylene-octene copolymer, 2-3 parts of foaming agent, 1-5 parts of masterbatch.

5. The thermoplastic film with a multi-layer structure according to claim 1, characterized in that, The preparation method of the modified ethylene propylene diene monomer rubber includes: mixing ethylene propylene diene monomer rubber, polypropylene, ethylene-acrylate copolymer, paraffin oil and talcum powder, extruding and pelletizing to obtain the modified ethylene propylene diene monomer rubber.

6. The non-weakening thermoplastic film with a multi-layer structure according to claim 1, wherein, The preparation method of the modified polypropylene includes: mixing polypropylene, nano calcium carbonate, ethylene-octene copolymer and ethylene-acrylate copolymer, extruding and pelletizing to obtain the modified polypropylene.

7. A method for preparing a thermoplastic film with a multi-layer structure according to any one of claims 1-6, characterized in that It includes the following steps: S1. Knead the raw materials, co-extrude the first TPO functional layer and the second TPO functional layer in a double-layer manner on an extruder and thermally press and laminate them with a PP foamed sponge to obtain the TPO layer; or, knead the raw materials, co-extrude the first TPO functional layer and the TPO foamed layer in a double-layer manner on an extruder and thermally press and laminate them with a PP foamed sponge to obtain the TPO layer; or, co-extrude the first TPO functional layer and the TPO foamed layer in a double-layer manner, and sequentially form a polyurethane polar layer on the surface of the TPO foamed layer and thermally press and laminate it with a polyurethane foam to obtain the TPO layer. S2. Coat paint on the surface of the first TPO functional layer of the TPO layer to make a surface paint treatment layer, and obtain a semi-finished product. S3. Place the semi-finished product obtained in step S3 under the condition of 195 - 210 °C for high-temperature foaming to obtain the multi-layered non-weakening thermoplastic film.

8. The method for preparing a non-weakening thermoplastic film having a multi-layer structure according to claim 7, characterized in that, In step S1, the preparation process of the polyurethane polar layer is as follows: dissolve the waterborne polyurethane resin in a polar solvent to obtain a polyurethane glue solution, coat the polyurethane glue solution on the surface of the TPO foamed layer, and dry it at a low temperature to obtain the polyurethane polar layer; the viscosity of the polyurethane glue solution is 5 - 30 poise, and the solid content is 5 - 20 wt%.

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