A protective film for window frames and its preparation method

Abstract

This invention discloses a protective film for window frames, which is a co-extruded film comprising an outer layer, an anti-aging core layer, and an inner layer, wherein the inner layer is connected to an adhesive layer. The outer layer comprises LDPE, LLDPE, mLLDPE, ethylene vinyl acetate copolymer, silicone, and a first masterbatch. The anti-aging core layer comprises LDPE, LLDPE, silicone, an antioxidant, and the first masterbatch. The inner layer comprises LDPE, LLDPE, oleamide, and a second masterbatch. This protective film for window frames has a reasonable structure and can be used for a long time outdoors and in areas with prolonged sunlight exposure. The masterbatch added to the outer surface and the anti-aging core layer improves the reflection of sunlight, while the masterbatch added to the inner layer blocks sunlight from penetrating into the protective film, thus playing a positive role in the adhesion of the adhesive layer and the durability of the protective film. The dispersibility of the masterbatch is optimized by adding ethylene vinyl acetate copolymer, silicone, silicone, and oleamide to each layer, thereby improving the stability of the protective film in use and its structure.

Description

Technical Field

[0001] This invention relates to the field of protective film technology, specifically to a protective film for window frames and its preparation method. Background Technology

[0002] Protective film for window frames is mainly used to protect window frames from damage during construction, product transportation, installation, and daily use.

[0003] While existing PVC protective films and OPP composite aluminized PET protective films can prevent window frames from suffering physical damage such as scratches, wear, and collisions during transportation, installation, and construction, the former has environmental problems and may release harmful substances. It is also prone to aging and decomposition when exposed to the outdoor environment for a long time, which has a negative impact on the environment. The latter, due to the different resilience of the two layers of film, may cause the protective film to peel up after being pasted onto the profile.

[0004] The prior art, CN104788774A, discloses a protective film formulation for brushed aluminum sheets, comprising low-density polyethylene, linear low-density polyethylene, SEBS, antioxidants, oleamide, and oleic acid amide. While the protective film exhibits anti-aging, scratch resistance, and easy peeling properties, the addition of oleamide during the blown film co-extrusion process generates a large number of small molecules, affecting the quality of the protective film.

[0005] Therefore, it is necessary to improve the protective film in the existing technology. Summary of the Invention

[0006] One of the objectives of this invention is to overcome the deficiencies in the prior art and provide a protective film for window frames that can be used outdoors and in areas with prolonged sunlight for extended periods. The dispersibility of the masterbatch is optimized by adding ethylene vinyl acetate copolymer, silicone, oleamide, and other additives to each layer, thereby improving the stability of the protective film in use and its structure.

[0007] To achieve the above-mentioned process effects, the technical solution of the present invention is as follows: a protective film for window frames, which is a co-extruded film, comprising an outer outer layer, an anti-aging core layer and an inner surface layer, wherein the inner surface layer is connected to an adhesive layer; The outer layer comprises LDPE, LLDPE, mLLDPE, ethylene vinyl acetate copolymer, silicone, and a first masterbatch; The anti-aging core layer includes LDPE, LLDPE, silicone, antioxidant, and a first masterbatch; The inner surface layer comprises LDPE, LLDPE, oleamide, and a second masterbatch.

[0008] The preferred technical solution is that, by mass parts, the outer layer consists of 15-25 parts of LDPE, 65-75 parts of LLDPE, 8-15 parts of mLLDPE, 3-5 parts of ethylene-vinyl acetate copolymer, 0.2-0.5 parts of silicone, and 2-4 parts of the first masterbatch.

[0009] The preferred technical solution is that, by weight, the anti-aging core layer comprises 20-30 parts of LDPE, 70-80 parts of LLDPE, 0.2-0.5 parts of silicone, 5-10 parts of antioxidant, and 1-1.8 parts of first masterbatch.

[0010] The preferred technical solution is that, by mass parts, the inner surface layer comprises 20-30 parts of LDPE, 70-80 parts of LLDPE, 0.2-0.3 parts of oleamide, and 1.5-2 parts of the second masterbatch.

[0011] A preferred technical solution is that the density of the LDPE is 0.920~0.926 g / cm³. 3 The melt flow index is 1.7~2.2 g / 10min; the density of the LLDPE is 0.915~0.925 g / cm³. 3 The melt flow index is 1.6~2.3 g / 10 min; the density of the mLLDPE is 0.915~0.925 g / cm³. 3 The melt flow index is 1.8~2.0 g / 10 min.

[0012] The preferred technical solution is that the grade of LDPE is Yangba 2426H, the grade of LLDPE is DFDA-7042, and the grade of mLLDPE is sp2320.

[0013] The preferred technical solution is that the layer thickness ratio of the outer outer layer, the anti-aging core layer and the inner outer layer is (10~20):(35~45):(20~30).

[0014] The second objective of this invention is to overcome the defects in the prior art and provide a method for preparing a protective film for window frames, comprising: feeding the raw materials for preparing an outer surface layer, an anti-aging core layer, and an inner surface layer into three extruders respectively, plasticizing them in the three extruders respectively, and then feeding them into the same three-layer blown film die head, and sequentially thermally bonding the first surface layer, the core layer, and the second surface layer together.

[0015] The preferred technical solution is that the extrusion temperature of the outer surface layer, the anti-aging core layer and the inner surface layer are all 150~160℃, and the die head temperature is all 150~160℃.

[0016] The advantages and beneficial effects of this invention are as follows: The protective film structure of this window frame is reasonable and can be used for a long time outdoors and in areas with prolonged sunlight. The outer layer is optimized by adding ethylene vinyl acetate copolymer and silicone to improve the dispersibility of the masterbatch and enhance adhesion to the ink layer. The anti-aging core layer is optimized by adding silicone to improve the dispersibility of antioxidants and masterbatch, thereby improving the mechanical properties and stability of the protective film. The inner surface layer is optimized by adding oleamide to improve the dispersibility of the masterbatch and promotes the formation of micropores to improve adhesion to the adhesive layer. The masterbatch added to the outer surface and anti-aging core layer enhances the reflection of sunlight, while the masterbatch added to the inner surface layer blocks sunlight from penetrating into the protective film, thus playing a positive role in the adhesion strength of the adhesive layer and the durability of the protective film. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0018] definition In this disclosure, the term "LDPE" refers to low-density polyethylene.

[0019] In this disclosure, the term "LLDPE" refers to linear low-density polyethylene, which differs structurally from conventional low-density polyethylene because it lacks long branches.

[0020] In this disclosure, the term "mLLDPE" refers to a polymer produced by ethylene polymerization using a metallocene coordination compound as a catalyst.

[0021] In this disclosure, the term "EVA" refers to ethylene-vinyl acetate copolymer, a thermoplastic material obtained by copolymerization of ethylene and vinyl acetate.

[0022] model

[0023] LDPE is manufactured by BASF Yangtze Company, with the trade name 2426H.

[0024] LLDPE is produced by Sinopec Zhenhai Company, with the trade name DFDA-7042.

[0025] mLLDPE is manufactured by Primavis Co., Ltd. of Japan, with the trade name SP2320.

[0026] The ethylene-vinyl acetate copolymer is manufactured by Mitsui Chemicals of Japan, with the trade name 3190.

[0027] The silicone is produced by Guangzhou Tengshun Chemical Technology Co., Ltd., with the trade name H-Si 6441 P.

[0028] The antioxidant was produced by Jiangsu Praxair Red Plum Masterbatch Co., Ltd.

[0029] The first masterbatch was produced by Jiangsu Puleike Red Plum Masterbatch Co., Ltd., with the trade name 8170.

[0030] The second masterbatch was produced by Jiangsu Praxair Red Plum Masterbatch Co., Ltd., with the trade name 0005C.

[0031] Adhesive layer The resin used is model TH-7053 manufactured by Tianhe Resin Co., Ltd.

[0032] outer surface Including LDPE, LLDPE, mLLDPE, ethylene vinyl acetate copolymer, silicone and first masterbatch.

[0033] Among them, the LDPE selected by BASF Yangzi 2426 H can control the crystal point and has high applicability. It contains an opening agent to facilitate film separation and avoid adhesion during winding and unwinding.

[0034] LLDPE and LDPE possess a certain degree of elasticity and cushioning, absorbing minor impacts or vibrations that may occur during transportation or processing, protecting window frames from physical damage. mLLDPE exhibits excellent flexibility and tear resistance; when compounded with LDPE and LLDPE, it further enhances the mechanical strength of the film, making it more wear-resistant and tear-resistant. The addition of EVA makes the outer layer more flexible, thereby improving the softness and elasticity of the outer surface, suitable for bonding to the bending parts of the window frame; EVA also has excellent low-temperature resistance, maintaining good flexibility even in low-temperature environments, enhancing the application of the protective film in low-temperature environments; due to the polarity of EVA, this helps improve the adhesion between the outer layer and the ink layer; the addition of EVA can improve the dispersion of the first masterbatch and the processing performance between the mixed raw materials in this layer, such as reducing melt viscosity, making the processing smoother, and further improving processing stability. Silicone has very low surface tension and low friction, resulting in good sliding between mixed raw materials. This further disperses the first masterbatch and effectively prevents precipitation due to uneven masterbatch dispersion. Silicone also has good thermal stability, low foaming, and strong anti-foaming properties. Combined with its low friction, it effectively solves the problem of a large number of air bubbles generated during the processing of the outer layer raw materials, making the surface of the outer layer smoother and improving the flatness of the ink layer. For film products, the addition of silicone can effectively reduce adhesion between films, making processing easier and avoiding adhesion or static electricity problems during winding and unwinding. The addition of silicone can improve the wear resistance and scratch resistance of the protective film and extend its service life. During blown film or extrusion processes, silicone can reduce or eliminate surface defects such as fisheyes and floating fibers, making the surface of the protective film more uniform and beautiful.

[0035] Inner surface Including LDPE, LLDPE, oleamide, and second masterbatch.

[0036] LLDPE and LDPE exhibit good flexibility and adhesion to various surfaces. When combined with acrylate adhesive layers, they ensure a firm bond between the protective film and the window frame surface, preventing detachment and maintaining good adhesion even on complex-shaped or curved window frames. Oleamide reduces internal friction during PE resin processing, decreasing friction between the protective film and processing equipment. This helps improve production efficiency, reduce energy consumption, and improve the surface quality of the product, reducing fisheyes and streaks. It also effectively prevents film adhesion and improves opening properties. Oleamide enhances the antistatic properties of the protective film, reducing dust adsorption and facilitating the application of adhesive coatings on this surface. Oleamide also improves the dispersibility of the second masterbatch. The oleamide molecule contains an unsaturated double bond and a polar amide group, giving it both oleophilic and hydrophilic properties. This allows it to act as a bridge between different polar or non-polar materials, promoting interfacial interactions and enhancing adhesion.

[0037] LLDPE and LDPE In the outer layer, anti-aging core layer, and inner surface layer, LLDPE exhibits better melt flowability than LDPE, attributed to its narrower molecular weight distribution and linear structure. In blend systems, increasing the proportion of LLDPE improves melt flowability and facilitates masterbatch dispersion in the melt. The higher shear sensitivity of LLDPE also benefits the better dispersion of solid particles in the masterbatch under high shear conditions. The long-branched structure of LDPE leads to heterogeneous crystallization, potentially forming larger crystalline regions in the film and affecting the uniformity of masterbatch dispersion. In contrast, the more uniform crystallization of LLDPE contributes to the formation of a finer microstructure, which is beneficial for the uniform distribution of pigment particles in the masterbatch. The melting point and crystallization temperature of LLDPE are typically higher than those of LDPE, influencing the selection of processing temperature and the width of the processing window. An appropriate LDPE / LLDPE ratio can regulate the processing temperature, optimize the dispersion performance of the masterbatch in the molten state, and prevent excessively high processing temperatures from causing degradation of pigments or additives in the masterbatch.

[0038] LDPE has a lower crystallinity and a branched structure that makes it softer, with better extensibility and flexibility, thus optimizing the bending performance of the protective film. However, adding too much not only reduces the mechanical strength of the protective film (such as tensile strength and puncture resistance), but also makes it more prone to defects such as melt cracking and sharkskin texture during blown film or cast film processes.

[0039] Example 1

[0040] The protective film for window frames is a co-extruded film, which includes an outer surface layer, an anti-aging core layer, and an inner surface layer. The inner surface layer is connected to the adhesive layer, and the outer surface layer is connected to the ink layer.

[0041] By mass, the outer layer comprises 20 parts LDPE, 70 parts LLDPE, 10 parts mLLDPE, 4 parts ethylene vinyl acetate copolymer, 0.4 parts silicone, and 2.6 parts first masterbatch.

[0042] By weight, the anti-aging core layer comprises 25 parts LDPE, 75 parts LLDPE, 0.42 parts silicone, 7 parts antioxidant, and 1.4 parts first masterbatch.

[0043] By weight, the inner surface layer comprises 25 parts LDPE, 75 parts LLDPE, 0.26 parts oleamide, and 1.8 parts second masterbatch.

[0044] The preparation method of the protective film for window frames includes: feeding the raw materials for the preparation of the outer surface layer, the anti-aging core layer and the inner surface layer into three extruders respectively, plasticizing them in the three extruders and then feeding them into the same three-layer blown film die head, and sequentially thermally bonding the first surface layer, the core layer and the second surface layer together. The extrusion temperature of the outer surface layer, the anti-aging core layer and the inner surface layer is 155°C and the die head temperature is 155°C.

[0045] The outermost layer has a thickness of 15μm, the anti-aging core layer has a thickness of 40μm, and the innermost layer has a thickness of 25μm.

[0046] Example 2

[0047] Example 2 is based on Example 1, except that, by mass parts, the outer layer includes 15 parts of LDPE, 75 parts of LLDPE, 10 parts of mLLDPE, 4 parts of ethylene vinyl acetate copolymer, 0.4 parts of silicone and 2.6 parts of the first masterbatch.

[0048] Example 3

[0049] Example 1 is based on Example 1, except that, by mass parts, the inner surface layer includes 20 parts of LDPE, 80 parts of LLDPE, 0.26 parts of oleamide, and 1.8 parts of the second masterbatch.

[0050] Comparative Example 1 Comparative Example 1 is based on Example 1, except that the outer surface layer does not include mLLDPE.

[0051] Comparative Example 2 Comparative Example 2 is based on Example 1, except that the outer layer does not include ethylene vinyl acetate copolymer.

[0052] Comparative Example 3 Comparative Example 3 is based on Example 1, except that the inner surface layer includes 100 parts of LLDPE, 0.26 parts of oleamide, and 1.8 parts of the second masterbatch.

[0053] Comparative Example 4 Comparative Example 4 is based on Example 1, except that the inner surface layer does not include oleic acid amide.

[0054] Comparative Example 5 Comparative Example 5 is based on Example 1, except that the inner surface layer includes 20 parts of LDPE, 80 parts of LLDPE, 4 parts of ethylene vinyl acetate copolymer, and 1.8 parts of second masterbatch.

[0055] Comparative Example 6 Comparative Example 6 is based on Example 1, except that the anti-aging core layer does not include silicone.

[0056] Protective film performance test: 1. Determination of tensile strength and elongation at break: according to test standard GB / T1040.3-2006; 2. Ink Layer Adhesion: Cross-cut Test - Use a cross-cut knife to cut 1mm wide squares on the protective film and observe the ink peeling within the squares. The adhesion grade is divided into 0 to 4 levels. Level 0 indicates that there are small pieces of paint peeling off at the cut and intersection, and the actual damage within the squared area is less than 5%. Level 1 indicates that the peeled area at the cut and intersection is 5-15%. Level 2 indicates that there is partial or large-area peeling at the cut and intersection, and the peeled area is 16-35%. Level 3 indicates that some squares are peeled off, and the peeled area is 36-65%. Level 4 indicates that the peeled area is greater than 65%. The lower the adhesion grade, the weaker the ink layer adhesion.

[0057] 3. High-temperature resistance test: The protective films (including ink layer and adhesive layer) obtained in the examples and comparative examples were placed in ovens set at 60℃ and 80℃ respectively. After being placed at 60℃ for 30 minutes, they were removed and the surface of the protective film was observed for any exudates and delamination. The adhesion between the adhesive layer and the inner surface layer, between the outer surface layer and the anti-aging core layer, and between the anti-aging core layer and the inner surface layer was tested. Similarly, after being placed at 80℃ for 10 minutes, the protective film was removed and the surface of the protective film was observed for any exudates and delamination.

[0058] The performance test results of the protective films in the examples and comparative examples are as follows:

[0059] Compared to Example 1, Examples 2 and 3 show a reduction in the amount of LDPE added to the outer or inner surface layer, requiring a higher processing temperature for successful processing, which negatively impacts the stability of the masterbatch.

[0060] Compared to Example 1, Comparative Example 1 showed reduced durability.

[0061] Compared to Example 1, Comparative Example 2 showed that, under the condition of constant processing temperature, the raw material on the outer surface was difficult to process, which had a negative impact on both high temperature resistance and mechanical properties.

[0062] Compared to Example 1, Comparative Example 3 did not have LDPE added to the inner surface, requiring a higher processing temperature for successful processing, which negatively impacted the stability of the second masterbatch.

[0063] Compared to Example 1, Comparative Example 4 did not include oleic acid amide on the inner surface, which negatively affected the adhesion between the inner surface layer and the adhesive layer and the dispersibility of the second masterbatch.

[0064] Compared to Example 1, in Comparative Example 5, the outer and inner layers of the protective film adhered to each other during winding, making it difficult to process. The use of oleamide easily creates a small number of micropores during production. Although the surface of the inner layer becomes uneven, it increases the contact area with the adhesive layer, further improving the adhesion between the adhesive layer and the inner layer.

[0065] Compared to Example 1, in Comparative Example 6, the antioxidants and first masterbatch of the anti-aging core layer were unevenly dispersed during the processing, which had a negative impact on mechanical properties and high temperature resistance.

[0066] 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 technical principles 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 window frames, characterized in that, The protective film is a co-extruded film composed of an outer outer layer, an anti-aging core layer, and an inner surface layer, wherein the inner surface layer is used to connect with the adhesive layer. By weight, the outer layer consists of 15-25 parts LDPE, 65-75 parts LLDPE, 8-15 parts mLLDPE, 3-5 parts ethylene-vinyl acetate copolymer, 0.2-0.5 parts silicone, and 2-4 parts first masterbatch. By weight, the anti-aging core layer comprises 20-30 parts LDPE, 70-80 parts LLDPE, 0.2-0.5 parts silicone, 5-10 parts antioxidant, and 1-1.8 parts first masterbatch; The inner surface layer comprises, by weight, 20-30 parts LDPE, 70-80 parts LLDPE, 0.2-0.3 parts oleamide, and 1.5-2 parts second masterbatch.

2. The protective film for window frames according to claim 1, characterized in that, The density of the LDPE is 0.920~0.926 g / cm³. 3 The melt flow index is 1.7~2.2 g / 10min; the density of the LLDPE is 0.915~0.925 g / cm³. 3 The melt flow index is 1.6~2.3 g / 10 min; the density of the mLLDPE is 0.915~0.925 g / cm³. 3 The melt flow index is 1.8~2.0 g / 10 min.

3. The protective film for window frames according to claim 1, characterized in that, The grade of LDPE is Yangba 2426H, the grade of LLDPE is DFDA-7042, and the grade of mLLDPE is sp2320.

4. The protective film for window frames according to claim 1, characterized in that, The thickness ratio of the outer outer layer, the anti-aging core layer and the inner outer layer is (10~20):(35~45):(20~30).

5. A method for preparing a protective film for window frames, characterized in that, The protective film for window frames according to any one of claims 1 to 4 includes: conveying the raw materials for preparing the outer surface layer, the anti-aging core layer and the inner surface layer to three extruders respectively, plasticizing them in the three extruders and then conveying them to the same three-layer blown film die head, and sequentially thermally bonding the outer surface layer, the anti-aging core layer and the inner surface layer together.

6. The method for preparing a protective film for window frames according to claim 5, characterized in that, The extrusion temperature of the outer surface layer, the anti-aging core layer, and the inner surface layer is 150~160℃, and the die head temperature is 150~160℃.

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