A masking and protective film for automotive painting and its preparation method

Abstract

This invention relates to the field of automotive masking and protective film technology, and discloses a masking and protective film for automotive painting and its preparation method. Preparation steps: Take a polyamide composition, polyethylene, a modifier, stearic acid, an antioxidant, and an initiator; melt-blend them; extrude and granulate to obtain a masterbatch; process the masterbatch to obtain a masking and protective film; the polyamide composition includes modified polyamide, PA6, and PA11; the preparation steps of the modified polyamide: take terminal amino hyperbranched polyamide, add it to dimethyl sulfoxide and stir evenly, add acryloyl chloride to obtain modified polyamide; the preparation steps of the modifier: take 2H-1,4-benzoxazine-6-amine, diallylamine, methyl(3,3,3-trifluoropropyl)silanediol, and sodium hydroxide; add dimethyl sulfoxide under nitrogen protection; cool and stir evenly; slowly add N-phenyltetrachlorophthalimide; stir for 1-2 hours; remove the solvent; post-process to obtain the modifier.

Description

Technical Field

[0001] This invention relates to the field of automotive masking and protective film technology, and discloses a masking and protective film for automotive painting and its preparation method. Background Technology

[0002] To enhance the overall appearance of a vehicle, it is painted. Two-tone painting allows for a wider variety of colors for the exterior and has broad applications. During two-tone painting, a masking film is used to protect the parts of the car that do not need to be painted, ensuring an aesthetically pleasing finish.

[0003] In existing technologies, commonly used materials for automotive paint masking films include polyamide (PA), polyethylene (PE), and polypropylene (PP). Using a combination of polyamide and polyethylene as a protective film material offers significant advantages, such as high mechanical strength, good abrasion resistance, and good chemical resistance. However, its insufficient ductility and high-temperature resistance easily lead to problems such as film damage during use, high-temperature warping, shrinkage, and residue during peeling, affecting the vehicle's appearance. Therefore, researching a masking protective film for automotive paint with good ductility, high-temperature resistance, and no residue, and its preparation method, is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a masking and protective film for automotive painting and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a masking and protective film for automotive painting, comprising the following steps: S1: taking a polyamide composition, polyethylene, modifier, stearic acid, antioxidant, and initiator, melting and blending them at 230~240℃, extruding and granulating them to obtain a masterbatch; S2: adding the masterbatch to a casting film machine, casting and processing it into a film at 220~230℃ to obtain a masking and protective film;

[0006] The polyamide composition includes at least two of modified polyamide, PA6, and PA11.

[0007] In a more optimized manner, high-density polyethylene is selected as the polyethylene; the initiator is selected as a peroxide initiator, including one or more of dicumyl peroxide, di-tert-butylperoxyisopropylbenzene, and benzoyl peroxide; the antioxidant includes one or more of antioxidant 1076, antioxidant 164, antioxidant TNP, and antioxidant MB.

[0008] In a more optimized manner, the initiator is selected as di-tert-butylperoxyisopropylbenzene; the antioxidant is selected as antioxidant 1076.

[0009] More preferably, the masterbatch comprises the following raw materials in parts by weight: 50-60 parts polyamide composition, 30-40 parts polyethylene, 10-15 parts modifier, 1-2 parts stearic acid, 0.5-1 part antioxidant, and 0.05-0.1 parts initiator.

[0010] More preferably, the polyamide composition comprises modified polyamide, PA6, and PA11 in a mass ratio of (4~5):(1~2):1.

[0011] In a more optimized manner, the preparation of the modified polyamide includes the following steps: taking terminal amino hyperbranched polyamide, adding it to dimethyl sulfoxide and stirring evenly, adding acryloyl chloride, stirring at 25~30℃ for 6~10h, adding triethylamine to adjust the pH during the reaction, post-treatment, removing the solvent, and obtaining the modified polyamide.

[0012] In a more optimized manner, the modified polyamide comprises the following raw materials, by mass parts: 10-15 parts of terminal amino hyperbranched polyamide, 40-60 parts of dimethyl sulfoxide, 0.05-0.15 parts of acryloyl chloride, and 0.05-0.15 parts of triethylamine.

[0013] In a more optimized manner, the preparation of the modifier includes the following steps: taking aminobenzoxazine (selecting 2H-1,4-benzoxazine-6-amine (9ci)), diallylamine, methyl (3,3,3-trifluoropropyl)silanediol, and sodium hydroxide, adding dimethyl sulfoxide under nitrogen protection, cooling to 5~10℃ and stirring evenly, slowly adding N-phenyltetrachlorophthalimide over 1.5~2h, stirring for 1~2h, removing the solvent, and post-processing to obtain the modifier.

[0014] More preferably, the modifier comprises the following raw materials, in parts by mass: 6-8 parts of 2H-1,4-benzoxazine-6-amine (9ci), 4-6 parts of diallylamine, 7-10 parts of methyl(3,3,3-trifluoropropyl)silanediol, 10-15 parts of sodium hydroxide, 300-600 parts of dimethyl sulfoxide, and 17-20 parts of N-phenyltetrachlorophthalimide.

[0015] Ideally, the thickness of the shielding protective film is 0.03~0.05mm.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: A polyamide composition is used, comprising a certain mass ratio of modified polyamide, PA6, and PA11. PA6 has excellent toughness and heat resistance, but its high polarity leads to high water absorption. Therefore, PA11 is introduced. The introduction of PA11 reduces the overall polarity, decreases swelling deformation caused by environmental humidity factors, and improves dimensional stability. The modified polyamide is an acryloyl chloride-modified terminal amino hyperbranched polyamide. Its hyperbranched structure can improve the material elongation and reduce the shrinkage rate. After modification with acryloyl chloride, the overall polarity is reduced, and double bonds are introduced, improving compatibility with polyethylene. It can also be crosslinked in subsequent steps, further enhancing overall performance. The amount of raw materials added to this composition needs to be controlled. Excessive addition of PA6 can easily lead to excessive polarity; excessive addition of PA11 can lead to increased shrinkage and decreased tensile properties; excessive addition of modified polyamide can lead to excessive subsequent crosslinking, making the material brittle.

[0017] This invention also incorporates a modifier, using N-phenyltetrachlorophthalimide as a matrix, grafting a certain mass ratio of aminobenzoxazine, diallylamine, and methyl(3,3,3-trifluoropropyl)silanediol onto its -Cl group. In the matrix, the imide structure exhibits high thermal stability and can reduce the material's thermal shrinkage rate. The grafted benzoxazine structure also possesses excellent thermal stability and mechanical properties, while reducing overall water absorption. The diallylamine introduces double bonds, enabling it to participate in subsequent crosslinking steps, improving the compatibility between the modifier and the polyamide composition, and reducing adhesion loss and residue caused by additive migration. The introduction of fluorine and silicon elements into methyl(3,3,3-trifluoropropyl)silanediol improves temperature resistance and reduces residue by lowering surface energy. The amount of these raw materials added needs to be controlled; a large amount of benzoxazine structure introduction increases the difficulty of the melt blending process; a large amount of diallylamine introduction leads to excessive crosslinking and increased material brittleness; a large amount of methyl(3,3,3-trifluoropropyl)silanediol introduction leads to decreased film adhesion. In summary, this modifier grafts multiple functional compounds, increases molecular weight, and improves compatibility with polyamide compositions, thereby improving performance and mitigating the problem of residue. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that there are no special restrictions on the suppliers of any of the raw materials involved in this invention. Exemplary examples include: high-density polyethylene (HDPE 7200E, TAISOX); stearic acid (CAS: 57-11-4); antioxidant 1076 (CAS: 2082-79-3); di-tert-butylperoxyisopropylbenzene (CAS: 2212-81-9); PA6 (PA6 B3WG6, BASF); PA11 (PA11 AZM30 (Arkema); amino-terminated hyperbranched polyamide (JD181120094032 (Gardel); dimethyl sulfoxide (CAS: 67-68-5); acryloyl chloride (CAS: 814-68-6); 2H-1,4-benzoxazine-6-amine (9ci) (CAS: 575472-93-4); diallylamine (CAS: 124-02-7); methyl (3,3,3-trifluoropropyl)silanediol (CAS: 660-78-6); N-phenyltetrachlorophthalimide (CAS: 31039-74-4);

[0020] Unless otherwise specified, all figures below are parts by weight or mass ratios.

[0021] Example 1: S1: Take 10 parts of terminal amino hyperbranched polyamide, add it to 50 parts of dimethyl sulfoxide and stir evenly, add 0.1 parts of acryloyl chloride, stir at 30°C for 8 hours, add 0.1 parts of triethylamine during the reaction, and after post-treatment, remove the solvent to obtain modified polyamide;

[0022] S2: Take 7 parts of 2H-1,4-benzoxazine-6-amine (9ci), 5 parts of diallylamine, 8 parts of methyl (3,3,3-trifluoropropyl)silanediol, and 14 parts of sodium hydroxide. Under nitrogen protection, add 500 parts of dimethyl sulfoxide, cool to 6°C, stir evenly, and keep stirring for 2 hours. Slowly add 18 parts of N-phenyltetrachlorophthalimide, stir for 1 hour, remove the solvent, and perform post-treatment to obtain the modifier.

[0023] S3: Take modified polyamide, PA6, and PA11 in a mass ratio of 4:1:1 and mix them to obtain a polyamide composition; take 55 parts of the polyamide composition, 35 parts of high-density polyethylene, 12 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and extrude and granulate them to obtain masterbatch;

[0024] S4: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0025] Example 2: S1: Take 10 parts of amino-terminated hyperbranched polyamide, add it to 50 parts of dimethyl sulfoxide and stir evenly, add 0.05 parts of acryloyl chloride, stir at 30°C for 6 hours, add 0.05 parts of triethylamine during the reaction, and after post-treatment, remove the solvent to obtain modified polyamide;

[0026] S2: Take 6 parts of 2H-1,4-benzoxazine-6-amine (9ci), 4 parts of diallylamine, 7 parts of methyl (3,3,3-trifluoropropyl)silanediol, and 14 parts of sodium hydroxide. Under nitrogen protection, add 500 parts of dimethyl sulfoxide, cool to 6°C, stir evenly, and keep stirring for 1.5 h. Slowly add 18 parts of N-phenyltetrachlorophthalimide, stir for 1 h, remove the solvent, and perform post-treatment to obtain the modifier.

[0027] S3: Take modified polyamide, PA6, and PA11 in a mass ratio of 5:1:1 and mix them to obtain a polyamide composition; take 50 parts of the polyamide composition, 30 parts of high-density polyethylene, 10 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and then extrude and granulate them to obtain masterbatch;

[0028] S4: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0029] Example 3: S1: Take 15 parts of amino-terminated hyperbranched polyamide, add it to 50 parts of dimethyl sulfoxide and stir evenly, add 0.15 parts of acryloyl chloride, stir at 30°C for 10 h, add 0.15 parts of triethylamine during the reaction, and after post-treatment, remove the solvent to obtain modified polyamide;

[0030] S2: Take 8 parts of 2H-1,4-benzoxazine-6-amine (9ci), 6 parts of diallylamine, 7 parts of methyl (3,3,3-trifluoropropyl)silanediol, and 14 parts of sodium hydroxide. Under nitrogen protection, add 500 parts of dimethyl sulfoxide, cool to 6°C, stir evenly, and keep stirring for 1.5 h. Slowly add 20 parts of N-phenyltetrachlorophthalimide, stir for 2 h, remove the solvent, and perform post-treatment to obtain the modifier.

[0031] S3: Take modified polyamide, PA6, and PA11 in a mass ratio of 5:2:1 and mix them to obtain a polyamide composition; take 60 parts of the polyamide composition, 40 parts of high-density polyethylene, 15 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and extrude and granulate them to obtain masterbatch;

[0032] S4: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0033] Example 4: S1: Take 14 parts of terminal amino hyperbranched polyamide, add it to 50 parts of dimethyl sulfoxide and stir evenly, add 0.1 parts of acryloyl chloride, stir at 30°C for 8 hours, add 0.1 parts of triethylamine during the reaction, and after post-treatment, remove the solvent to obtain modified polyamide;

[0034] S2: Take 6 parts of 2H-1,4-benzoxazine-6-amine (9ci), 6 parts of diallylamine, 8 parts of methyl (3,3,3-trifluoropropyl)silanediol, and 14 parts of sodium hydroxide. Under nitrogen protection, add 500 parts of dimethyl sulfoxide, cool to 6°C, stir evenly, and keep stirring for 2 hours. Slowly add 17 parts of N-phenyltetrachlorophthalimide, stir for 1 hour, remove the solvent, and then perform post-treatment to obtain the modifier.

[0035] S3: Take modified polyamide, PA6, and PA11 in a mass ratio of 4:1:1 and mix them to obtain a polyamide composition; take 60 parts of the polyamide composition, 40 parts of high-density polyethylene, 15 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and then extrude and granulate them to obtain masterbatch;

[0036] S4: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0037] Example 5: S1: Take 10 parts of terminal amino hyperbranched polyamide, add it to 50 parts of dimethyl sulfoxide and stir evenly, add 0.05 parts of acryloyl chloride, stir at 30°C for 10 h, add 0.05 parts of triethylamine during the reaction, and after post-treatment, remove the solvent to obtain modified polyamide;

[0038] S2: Take 8 parts of 2H-1,4-benzoxazine-6-amine (9ci), 4 parts of diallylamine, 7 parts of methyl (3,3,3-trifluoropropyl)silanediol, and 14 parts of sodium hydroxide. Under nitrogen protection, add 500 parts of dimethyl sulfoxide, cool to 6°C, stir evenly, and keep stirring for 2 hours. Slowly add 20 parts of N-phenyltetrachlorophthalimide, stir for 2 hours, remove the solvent, and then perform post-treatment to obtain the modifier.

[0039] S3: Take modified polyamide, PA6, and PA11 in a mass ratio of 4:1:1 and mix them to obtain a polyamide composition; take 50 parts of the polyamide composition, 30 parts of high-density polyethylene, 10 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and then extrude and granulate them to obtain masterbatch;

[0040] S4: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0041] Comparative Example 1 (the ratio of raw materials in the polyamide composition was changed, and the remaining methods and steps were the same as in Example 1): S1: Take 10 parts of terminal amino hyperbranched polyamide, add it to 50 parts of dimethyl sulfoxide and stir evenly, add 0.1 parts of acryloyl chloride, stir at 30°C for 8 hours, add 0.1 parts of triethylamine during the reaction, and after post-treatment, remove the solvent to obtain modified polyamide.

[0042] S2: Take 7 parts of 2H-1,4-benzoxazine-6-amine (9ci), 5 parts of diallylamine, 8 parts of methyl (3,3,3-trifluoropropyl)silanediol, and 14 parts of sodium hydroxide. Under nitrogen protection, add 500 parts of dimethyl sulfoxide, cool to 6°C, stir evenly, and keep stirring for 2 hours. Slowly add 18 parts of N-phenyltetrachlorophthalimide, stir for 1 hour, remove the solvent, and perform post-treatment to obtain the modifier.

[0043] S3: Take modified polyamide and PA6 in a mass ratio of 1:1 and mix them to obtain a polyamide composition; take 55 parts of the polyamide composition, 35 parts of high-density polyethylene, 12 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and then extrude and granulate them to obtain masterbatch;

[0044] S4: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0045] Comparative Example 2 (the raw material ratio of the polyamide composition was changed, and the remaining methods and steps were the same as in Example 1): S1: Take 10 parts of terminal amino hyperbranched polyamide, add it to 50 parts of dimethyl sulfoxide and stir evenly, add 0.1 parts of acryloyl chloride, stir at 30°C for 8 hours, add 0.1 parts of triethylamine during the reaction, and after post-treatment, remove the solvent to obtain modified polyamide.

[0046] S2: Take 7 parts of 2H-1,4-benzoxazine-6-amine (9ci), 5 parts of diallylamine, 8 parts of methyl (3,3,3-trifluoropropyl)silanediol, and 14 parts of sodium hydroxide. Under nitrogen protection, add 500 parts of dimethyl sulfoxide, cool to 6°C, stir evenly, and keep stirring for 2 hours. Slowly add 18 parts of N-phenyltetrachlorophthalimide, stir for 1 hour, remove the solvent, and perform post-treatment to obtain the modifier.

[0047] S3: Take modified polyamide and PA11 in a mass ratio of 4:1 and mix them to obtain a polyamide composition; take 55 parts of the polyamide composition, 35 parts of high-density polyethylene, 12 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and then extrude and granulate them to obtain masterbatch;

[0048] S4: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0049] Comparative Example 3 (no modification of end-amino hyperbranched polyamide, the remaining methods and steps are the same as in Example 1): S1: Take 7 parts of 2H-1,4-benzoxazine-6-amine (9ci), 5 parts of diallylamine, 8 parts of methyl (3,3,3-trifluoropropyl)silanediol, 14 parts of sodium hydroxide, add 500 parts of dimethyl sulfoxide under nitrogen protection, cool to 6°C, stir evenly, keep stirring for 2 hours, slowly add 18 parts of N-phenyltetrachlorophthalimide, stir for 1 hour, remove the solvent, and perform post-treatment to obtain the modifier;

[0050] S2: Take 4 parts by mass of terminal amino hyperbranched polyamide, PA6, and PA11 in a ratio of 4:1:1 and mix them to obtain a polyamide composition; take 55 parts of the polyamide composition, 35 parts of high-density polyethylene, 12 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and then extrude and granulate them to obtain masterbatch;

[0051] S3: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0052] Comparative Example 4 (the modifier was changed, and the rest of the methods and steps were the same as in Example 1): S1: Take 10 parts of amino-terminated hyperbranched polyamide, add it to 50 parts of dimethyl sulfoxide and stir evenly, add 0.1 parts of acryloyl chloride, stir at 30°C for 8 hours, add 0.1 parts of triethylamine during the reaction, and after post-treatment, remove the solvent to obtain modified polyamide.

[0053] S2: Take 7 parts of 2H-1,4-benzoxazine-6-amine (9ci), 5 parts of diallylamine, 8 parts of dimethoxymethyl(3,3,3-trifluoropropyl)silane, and 18 parts of phthalimide, stir and mix to obtain the modifier;

[0054] S3: Take modified polyamide, PA6, and PA11 in a mass ratio of 4:1:1 and mix them to obtain a polyamide composition; take 55 parts of the polyamide composition, 35 parts of high-density polyethylene, 12 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and extrude and granulate them to obtain masterbatch;

[0055] S4: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0056] Comparative Example 5 (the amount of modifier added is increased, and the rest of the methods and steps are the same as in Example 1): S1: Take 10 parts of terminal amino hyperbranched polyamide, add it to 50 parts of dimethyl sulfoxide and stir evenly, add 0.1 parts of acryloyl chloride, stir at 30°C for 8 hours, add 0.1 parts of triethylamine during the reaction, and after post-treatment, remove the solvent to obtain modified polyamide.

[0057] S2: Take 7 parts of 2H-1,4-benzoxazine-6-amine (9ci), 5 parts of diallylamine, 8 parts of methyl (3,3,3-trifluoropropyl)silanediol, and 14 parts of sodium hydroxide. Under nitrogen protection, add 500 parts of dimethyl sulfoxide, cool to 6°C, stir evenly, and keep stirring for 2 hours. Slowly add 18 parts of N-phenyltetrachlorophthalimide, stir for 1 hour, remove the solvent, and perform post-treatment to obtain the modifier.

[0058] S3: Take modified polyamide, PA6, and PA11 in a mass ratio of 4:1:1 and mix them to obtain a polyamide composition; take 55 parts of the polyamide composition, 35 parts of high-density polyethylene, 18 parts of modifier, 1 part of stearic acid, 0.8 parts of antioxidant, and 0.1 parts of initiator di-tert-butylperoxyisopropylbenzene, add them to a screw extrusion reactor, melt blend them at a temperature of 230°C, and then extrude and granulate them to obtain masterbatch;

[0059] S4: Add the masterbatch to the casting film machine and cast it into a film at a temperature of 230℃. The film thickness is 0.04mm, thus obtaining a shielding protective film.

[0060] Performance test: Take the protective films prepared in Examples 1-5 and Comparative Examples 1-5; (1) Test the elongation at break according to ASTM D638-22; the stretching rate is 200 mm / min; (2) Place the protective film in an oven and bake it at 180°C for 30 min, then place it at room temperature for 48 h and test the shrinkage rate; see Table 1 for details;

[0061]

[0062] Table 1

[0063] Conclusions: Comparative Example 1 and Comparative Example 2 show significant performance degradation due to changes in the raw material ratio of the polyamide composition. Comparative Example 1 reduced the amount of modified polyamide added and did not introduce PA11, while Comparative Example 2 did not introduce PA6. This demonstrates the importance of the raw materials and their ratio in this composition. Comparative Example 3 did not modify the terminal amino hyperbranched polyamide, resulting in a performance decrease. Comparative Example 4 changed the modifier by directly mixing 2H-1,4-benzoxazine-6-amine (9ci), diallylamine, dimethoxymethyl (3,3,3-trifluoropropyl)silane, and phthalimide, leading to a performance decrease and residue upon peeling. Comparative Example 5 increased the amount of modifier added, resulting in a performance decrease, indicating that the amount of modifier added also needs to be controlled. In summary, the protective film prepared by this invention exhibits good extensibility, high-temperature resistance, and leaves no residue after use.

[0064] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a masking and protective film for automotive painting, characterized in that: Includes the following steps: S1: Take a polyamide composition, polyethylene, modifier, stearic acid, antioxidant, and initiator, melt blend them at 230-240℃, extrude and granulate them to obtain masterbatch; S2: Add the masterbatch to the casting film machine and cast it at 220-230°C to obtain a shielding protective film; the polyamide composition includes modified polyamide, PA6, and PA11 in a mass ratio of (4-5):(1-2):

1. The preparation of the modified polyamide includes the following steps: taking terminal amino hyperbranched polyamide, adding it to dimethyl sulfoxide and stirring evenly, adding acryloyl chloride, stirring at 25-30℃ for 6-10h, adding triethylamine to adjust the pH during the reaction, post-treatment, removing the solvent, and obtaining the modified polyamide. The preparation of the modifier includes the following steps: taking aminobenzoxazine, diallylamine, methyl (3,3,3-trifluoropropyl)silanediol, and sodium hydroxide, adding dimethyl sulfoxide under nitrogen protection, cooling to 5-10°C and stirring evenly, slowly adding N-phenyltetrachlorophthalimide over 1.5-2 hours, stirring for 1-2 hours, removing the solvent, and then performing post-treatment to obtain the modifier; The modifier comprises the following raw materials, in parts by mass: 6-8 parts aminobenzoxazine, 4-6 parts diallylamine, 7-10 parts methyl(3,3,3-trifluoropropyl)silanediol, 10-15 parts sodium hydroxide, 300-600 parts dimethyl sulfoxide, and 17-20 parts N-phenyltetrachlorophthalimide.

2. The method for preparing a masking and protective film for automotive painting according to claim 1, characterized in that: The masterbatch comprises the following raw materials, by mass parts: 50-60 parts polyamide composition, 30-40 parts polyethylene, 10-15 parts modifier, 1-2 parts stearic acid, 0.5-1 part antioxidant, and 0.05-0.1 parts initiator.

3. The method for preparing a masking and protective film for automotive painting according to claim 1, characterized in that: The modified polyamide comprises the following raw materials, in parts by weight: 10-15 parts of amino-terminated hyperbranched polyamide, 40-60 parts of dimethyl sulfoxide, 0.05-0.15 parts of acryloyl chloride, and 0.05-0.15 parts of triethylamine.

4. The method for preparing a masking and protective film for automotive painting according to claim 1, characterized in that: The thickness of the shielding protective film is 0.03 to 0.05 mm.

5. The masking protective film prepared by the method for preparing a masking protective film for automotive painting according to any one of claims 1 to 4.

Images