Application of BOPP (biaxially-oriented polypropylene) film in preparation of draw-bar box shell

Abstract

The invention discloses an application of a BOPP (Biaxially-oriented Polypropylene) film in preparation of a draw-bar box shell, and the draw-bar box shell with a multi-layer composite structure is formed by compounding a multi-layer BOPP film serving as a main body layer and a lining layer through a hot press molding process. According to the invention, the BOPP film commonly used in the packaging field is creatively applied to the box body structural member, the BOPP film lamination hot press molding replaces the traditional PP injection molding process, and the modular design of the combined layer structure and the collaborative innovation of the hot press process are combined, so that the prepared draw-bar box shell realizes the balance of high strength and light weight, and has no cracking phenomenon when falling at a low temperature of-30 DEG C, and the service life of the draw-bar box shell is prolonged. The low-temperature performance is excellent, and meanwhile, the production suitability and the color control precision are improved.

Description

Technical Field

[0001] This invention belongs to the field of luggage manufacturing, specifically relating to the application of BOPP film in the manufacture of trolley case shells. Background Technology

[0002] As an essential piece of equipment for daily travel, the performance of a suitcase's shell directly determines its lifespan, portability, and applicable scenarios. Currently, most mainstream suitcase shells on the market are made of PP material through injection molding. This type of product has significant performance bottlenecks: on the one hand, to ensure sufficient load-bearing strength, the amount of material used or the material density needs to be increased, resulting in a heavier suitcase that contradicts the consumer demand for lightweight design; on the other hand, traditional PP injection-molded shells have limited tensile strength, and the material is prone to brittleness in low-temperature environments. When exposed to temperatures below -12°C, the suitcase is highly susceptible to cracking upon impact or drop, failing to meet the needs of use in cold regions.

[0003] Meanwhile, traditional injection molding processes lack flexibility in controlling the color of the housing. They usually require adding color masterbatch to the injection molding raw materials. Once the color is determined, it is difficult to adjust it quickly, and the color uniformity is easily affected by the injection molding parameters.

[0004] BOPP (biaxially oriented polypropylene) film is a polypropylene film prepared by biaxial stretching process. It has excellent properties such as lightweight, high strength, tear resistance, water and moisture resistance, and strong processing adaptability. It is currently widely used in packaging, printing, electronic packaging and other fields. However, there are no literature reports on the application of BOPP film in the preparation of trolley case shells. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a new application of BOPP film in the preparation of trolley case shells, breaking through the application limitation of BOPP film mainly used in the packaging field. The trolley case shells prepared by it achieve a balance of high strength, lightweight and low temperature resistance, while improving production adaptability and color control accuracy.

[0006] This invention is achieved through the following technical solution: An application of BOPP film in the preparation of trolley case shells involves using multi-layer BOPP film as the main layer, which is then laminated with an inner lining layer through a hot-pressing process to form a multi-layer composite structure trolley case shell.

[0007] The BOPP film described in this invention is readily available through commercial purchases, has low raw material costs, and a simple processing technology.

[0008] As a preferred embodiment of the present invention, the BOPP film is tested according to GB / T 1040.3-2006 and has a longitudinal tensile strength >120MPa, a transverse tensile strength >270MPa, a longitudinal nominal strain at break >130%, and a transverse nominal strain at break >45%.

[0009] The BOPP film of this invention includes transparent film and colored film (black, red, blue, green, gray, etc.). The colored film is located in the middle of the multilayer composite structure.

[0010] In a preferred embodiment of the present invention, the specifications and performance of the transparent film and the colored film are consistent.

[0011] In a preferred embodiment of the present invention, the total thickness of the suitcase shell is 0.8-1.5 mm.

[0012] The present invention also provides a high-strength lightweight trolley case shell, comprising a main body layer and an inner lining layer (m4 layer) laminated inside the main body layer. The main body layer is formed by hot pressing and laminating layers of BOPP film. The main body layer is provided with an m1 layer, a group A film, a m2 layer, a group B film, a m3 layer, and a group C film in sequence along the thickness direction of the shell. The number of layers of the group A film, group B film, and group C film is ≥5. The m1 layer, group A film, group B film, and group C film are all transparent BOPP films, and the m2 layer and m3 layer are colored BOPP films of the same color.

[0013] In the case shell of the present invention, the strength of the shell is improved by the synergistic layering structure of the A group film, the B group film and the C group film. The independent m2 layer and m3 layer colored film are used for color fixing, so that the color of the case is uniform and full, avoiding the problem of uneven color in traditional masterbatch injection molding. Moreover, the color switching is flexible, only the corresponding film layer needs to be replaced, and the accuracy is high.

[0014] The A-group membrane, B-group membrane, and C-group membrane of the present invention have ≥5 layers, and the m1 layer, m2 layer, and m3 layer can be 1-3 layers.

[0015] In a preferred embodiment of the present invention, the number of layers in group A, group B and group C are equal or substantially equal, which ensures both the uniformity of stress on the laminated structure and the linear control of thickness.

[0016] In a preferred embodiment of the present invention, the thickness of the BOPP film is 0.01-0.08 mm (for example, it can be 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm or any range between the above values).

[0017] This invention allows for flexible adaptation to various product sizes by adjusting the number of layers in the three film groups (A, B, and C), thus meeting the thickness requirements of different sized enclosures and improving production versatility. Typically, the thickness of a 20-inch enclosure is 0.8mm-1.1mm; a 24-inch enclosure is 0.9mm-1.2mm; and a 28-inch enclosure is 1.0mm-1.4mm.

[0018] In a preferred embodiment of the present invention, the inner lining layer (m4 layer) is PP woven fabric or PP mesh fabric. The inner lining layer of the present invention has a basis weight of 200-300 g / m². 2 The use of PP textile or PP mesh fabric mainly increases the internal texture and reduces the amount of internal materials used in the final box shell product. While further achieving the goal of lightweighting, it avoids the introduction of non-PP materials to facilitate the recycling of the box shell.

[0019] The tensile strength of the trolley case shell of the present invention is ≥40 MPa (according to ASTM D638, test conditions are 50 mm / min, 23℃), and no cracking is observed after drop test at -30℃.

[0020] The present invention also provides a method for preparing the above-mentioned high-strength lightweight trolley case shell, comprising the following steps: (1) Cutting: Cut the BOPP film into rectangular pieces that match the front facade of the suitcase; (2) Laying out layers: Lay out layers in the order of inner liner layer → C group film → m3 layer → B group film → m2 layer → A group film → m1 layer. The number of A group film, B group film and C group film is ≥ 5 layers. The BOPP film is set along the short side of the rectangular film in the longitudinal direction and along the long side of the rectangular film in the transverse direction. (3) Preheating: Place the laminated film assembly into a hot press to preheat the press plate; (4) Hot pressing: The preheated sheet is placed into a hot pressing mold for hot pressing; (5) Pressure holding and mold opening: After hot pressing, pressure is held until the mold temperature drops below 60°C, then the mold is opened to obtain the trolley case shell.

[0021] This invention replaces the traditional PP injection molding process with BOPP film lamination and hot pressing. Based on the tensile deformation characteristics during hot pressing and the fact that the longitudinal nominal strain at break of BOPP film is greater than that in the transverse direction, a lamination pattern is designed to align the longitudinal direction (the direction of high nominal strain at break) of the BOPP film with the shorter side of the rectangle requiring large stretching. This structurally avoids the cracking problem during hot pressing. The flexibility of the film layers and the stress release from the hot pressing process allow the shell to maintain good toughness even at -30℃.

[0022] In a preferred embodiment of the present invention, in step (3), the preheating pressure is 0.2-0.5 MPa; the pressurization time is 3-5 min; and the preheating temperature is 140-160℃.

[0023] In a preferred embodiment of the present invention, in step (4), the hot pressing pressure is 2-5 MPa, the temperature is 150-165°C, and the pressing time is 30-80 s. Within this range of hot pressing parameters, the adhesion of the surface layers between BOPP films can be guaranteed, while the disorientation of the core layer can be avoided.

[0024] Compared with the prior art, the present invention has the following beneficial effects: This invention creatively applies BOPP film, commonly used in the packaging industry, to box structural components. By replacing the traditional PP injection molding process with BOPP film lamination and hot pressing, and combining the modular design of the layer structure with the synergistic innovation of the hot pressing process, the problem of existing trolley case shells being "high strength necessarily means heavy, prone to brittleness at low temperatures, and poor production flexibility" is solved. The resulting trolley case shell achieves a balance between high strength and lightweight, and exhibits excellent low-temperature performance without cracking when dropped at -30℃.

[0025] This invention uses an independent colored film layer for color fixing. Color switching only requires replacing the m2 / m3 layer film, without the need to clean the injection molding equipment or replace the color masterbatch. Color control is flexible and efficient, and can quickly respond to personalized customization needs.

[0026] This invention uses BOPP film to integrally mold, which requires no additional adhesives and the inner lining does not need to be spliced ​​separately, resulting in high production efficiency, low energy consumption, and low processing cost. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the trolley case housing of the present invention. Detailed Implementation

[0028] The present invention will be further illustrated below through specific embodiments. The following embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments.

[0029] Unless otherwise specified, all materials used in this invention can be purchased commercially or prepared using conventional methods.

[0030] The materials used in this invention are sourced from the following sources: BOPP film: 120cm wide, 40µm thick, longitudinal tensile strength 128 MPa, transverse tensile strength 271 MPa, longitudinal breaking nominal strain 133%, transverse breaking nominal strain 48% (testing standard: GB / T 1040.3-2006), purchased from Qingdao Xinguangheng Packaging Materials Co., Ltd.

[0031] Example 1: Preparation of a 20-inch trolley case shell like Figure 1 As shown, a high-strength, lightweight trolley case shell includes a main body layer and an inner lining composited within the main body layer. The lining (m4 layer) is formed by hot pressing and laminating layers of BOPP film. Along the thickness direction of the shell, the main body layer consists of layers m1, A-group film, m2, B-group film, m3, and C-group film. Each of the A-group, B-group, and C-group films has seven layers. Layers m1, A-group, B-group, and C are transparent BOPP films, while layers m2 and m3 are red BOPP films. Layer m4 uses PP mesh fabric. The total thickness of the suitcase shell is 0.96 mm. Its preparation process includes the following steps: (1) Cutting: Cut the BOPP film and PP mesh into rectangular film pieces that match the front facade of the suitcase; (2) Lay the membrane / mesh sheet in the following order: inner lining layer (m4 layers) → C group membrane (7 layers of transparent BOPP film) → m3 layer (1 layer of red BOPP film) → B group membrane (7 layers of transparent BOPP film) → m2 layer (1 layer of red BOPP film) → A group membrane (7 layers of transparent BOPP film) → m1 layer (1 layer of transparent BOPP film) (see Figure 1 Furthermore, the BOPP film is arranged longitudinally along the short side of the rectangular film and transversely along the long side of the rectangular film. (3) Preheating: Place the laminated membrane assembly into the hot press to preheat the press plate. Preheating pressure: 0.3 MPa; pressurization time: 4 min; preheating temperature: 140℃. (4) Hot pressing: The preheated sheet is placed into a hot pressing mold for hot pressing. The hot pressing temperature is 158℃, the pressure is 4.5 MPa, and the pressing time is 80s. (5) Pressure holding and mold opening: After hot pressing, pressure is held until the mold temperature drops below 60°C, then the mold is opened to obtain the trolley case shell.

[0032] Example 2: Preparation of a 24-inch trolley case shell The structure of the suitcase shell is the same as in Example 1, wherein the number of layers of film A, film B and film C are set to 9, 8 and 8 respectively. The m1 layer, film A, film B and film C are all transparent BOPP films, the m2 layer and m3 layer are blue BOPP films, and the m4 layer uses PP mesh cloth; the total thickness of the suitcase shell is 1.12mm.

[0033] Its preparation process includes the following steps: The steps are the same as in Example 1 (1); (2) Lay the membrane / mesh sheet in the following order: inner liner layer → C group membrane (8 layers of transparent BOPP film) → m3 layer (1 layer of blue BOPP film) → B group membrane (8 layers of transparent BOPP film) → m2 layer (1 layer of blue BOPP film) → A group membrane (9 layers of transparent BOPP film) → m1 layer (1 layer of transparent BOPP film). The BOPP film is set longitudinally along the short side of the rectangular membrane sheet and transversely along the long side of the rectangular membrane sheet. See [reference needed] Figure 1 ; (3) Preheating: Place the laminated membrane assembly into the hot press to preheat the press plate. Preheating pressure: 0.2 MPa; pressurization time: 3 min; preheating temperature: 150℃; (4) Hot pressing: The preheated sheet is placed into a hot pressing mold for hot pressing. The hot pressing temperature is 160℃, the pressure is 3.0 MPa, and the pressing time is 60s. (5) Pressure holding and mold opening: After hot pressing, pressure is held until the mold temperature drops below 60°C, then the mold is opened to obtain the trolley case shell.

[0034] Example 3: Preparation of a 28-inch trolley case shell The structure of the suitcase shell is the same as in Example 1, wherein the number of layers of film group A, film group B and film group C are 8, 9 and 10 respectively, the m1 layer, film group A, film group B and film group C are transparent BOPP film, and the m2 layer and m3 layer are blue BOPP film; the total thickness of the suitcase shell is 1.2 mm.

[0035] Its preparation process includes the following steps: (1) Same as step (1) in Example 1; (2) Laying out layers, the same as in Example 1, wherein 8, 9 and 10 layers of transparent BOPP film are laid out for groups A / B / C respectively, and 1 layer each for m1 / m2 / m3. (3) Preheating: Place the laminated membrane assembly into the hot press to preheat the press plate. Preheating pressure: 0.4 MPa; pressurization time: 5 min; preheating temperature: 155℃. (4) Hot pressing: The preheated sheet is placed into a hot pressing mold for hot pressing. The hot pressing temperature is 165℃, the pressure is 2.5 MPa, and the pressing time is 30s. (5) Pressure holding and mold opening: After hot pressing, pressure is held until the mold temperature drops below 60°C, then the mold is opened to obtain the trolley case shell.

[0036] Comparative Example 1: PP Injection Molded Box Shell Molten modified PP was directly injected into 20-inch, 24-inch, and 28-inch mold cavities using an injection molding machine to obtain three different sizes of box shells.

[0037] Comparative Example 2: The difference from Example 1 is that in step (1), the longitudinal direction of each BOPP film is set along the long side of the rectangular film, and the transverse direction is set along the short side of the rectangular film; the rest is the same as in Example 1.

[0038] When the hot press chamber shell is in step (4) of Example 1, the shell will crack longitudinally. This is because the pull rod is external and the pull rod groove causes the overall transverse dimension of the shell to increase, exceeding the nominal transverse fracture strain value of the BOPP film.

[0039] Table 1 Performance test results of the examples and comparative examples

[0040] * Take samples vertically on the left or right side of the enclosure; ** Take samples horizontally above or below the enclosure.

[0041] As shown in Table 1, under the condition that the specific gravity is basically the same, compared with the traditional PP injection molded box shell of Comparative Example 1, the tensile strength of the trolley box shell prepared by the present invention is more than 3 times higher and the weight is more than 30% lighter, achieving a balance between lightweight and strength. Moreover, it does not crack when dropped at a low temperature of -30℃, and has excellent low temperature performance.

Claims

1. The application of a BOPP film in the manufacture of a suitcase shell, characterized in that, The case shell is made of multi-layer BOPP film as the main layer and is combined with the inner lining layer through a hot pressing process to form a multi-layer composite structure.

2. The application according to claim 1, characterized in that, The BOPP film was tested according to GB / T 1040.3-2006, with longitudinal tensile strength > 120 MPa, transverse tensile strength > 270 MPa, longitudinal nominal strain at break > 130%, and transverse nominal strain at break > 45%.

3. The application according to claim 1, characterized in that, The BOPP film includes a transparent film and a colored film, with the colored film disposed in the middle of the multilayer composite structure.

4. The application according to claim 1, characterized in that, The total thickness of the suitcase shell is 0.8-1.5 mm.

5. A high-strength, lightweight trolley case shell, characterized in that, The system includes a main body layer and an inner liner layer laminated inside the main body layer. The main body layer is formed by laminating BOPP films and then laminating them together using a hot-pressing process. The main body layer has, along the thickness direction of the shell, layers m1, A, m2, B, m3, and C. The number of layers of A, B, and C is ≥ 5. Layers m1, A, B, and C are all transparent BOPP films, while layers m2 and m3 are colored BOPP films of the same color.

6. The high-strength lightweight trolley case shell according to claim 5, characterized in that, The thickness of the BOPP film is 0.01-0.08 mm.

7. The high-strength lightweight trolley case shell according to claim 5, characterized in that, The inner lining is made of PP textile fabric or PP mesh fabric.

8. The method for preparing a high-strength, lightweight trolley case shell according to any one of claims 5 to 7, characterized in that, Includes the following steps: (1) Cutting: Cut the BOPP film into rectangular pieces that match the front facade of the suitcase; (2) Laying out layers: Lay out layers in the order of inner liner layer → C group film → m3 layer → B group film → m2 layer → A group film → m1 layer. The number of A group film, B group film and C group film is ≥ 5 layers. The BOPP film is set along the short side of the rectangular film in the longitudinal direction and along the long side of the rectangular film in the transverse direction. (3) Preheating: Place the laminated film assembly into a hot press to preheat the press plate; (4) Hot pressing: The preheated sheet is placed into a hot pressing mold for hot pressing; (5) Pressure holding and mold opening: After hot pressing, pressure is held until the mold temperature drops below 60°C, then the mold is opened to obtain the trolley case shell.

9. The preparation method according to claim 8, characterized in that, In step (3), the preheating pressure is 0.2-0.5 MPa; the pressurization time is 3-5 min; and the preheating temperature is 140-160℃.

10. The preparation method according to claim 8, characterized in that, In step (4), the pressure of hot pressing is 2-5 MPa, the temperature is 150-165℃, and the pressing time is 30-80s.

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