Low-temperature-resistant liquid bag for long-distance railway transportation

Abstract

A low-temperature-resistant liquid bag for long-distance transportation, wherein four layers of PE films are used in the liquid bag, the inner two layers are made of low-temperature PE materials, and the outer two layers are made of high-density PE materials; the inner two layers of low-temperature PE materials are firstly heat-sealed and processed into a sealed cavity, the innermost layer of PE material is in direct contact with liquid cargo, the outer two layers of PE materials are wrapped around the low-temperature PE materials, and all the four layers of PE films are fixed together by means of heat-sealing to form a multi-layer sealed cavity. The liquid bag uses two heat-sealed structures, and a certain distance is reserved between the two heat-sealed structures, so that stress concentration at the seals can be reduced, effectively reducing liquid bag damage caused by tensile impact.

Description

A low-temperature resistant liquid bag for long-distance railway transportation Technical Field

[0001] The invention relates to a low-temperature resistant liquid bag used for long-distance railway transportation, belonging to the field of container transportation. Background Art

[0002] Liquid container bags are a new type of packaging primarily used for transporting non-hazardous liquids and related chemicals. This technology has seen widespread adoption and significant growth in global logistics and transportation in recent years, primarily due to advances in materials and manufacturing technology for large, flexible liquid bags, as well as the development of containerized transportation technology. Compared to canned goods, liquid bags offer advantages such as no emptying, no need for cleaning, low cost, and easy loading and unloading. They are widely used in the food, petroleum, and chemical industries.

[0003] With the increasing prevalence of containerized liquid bags in liquid packaging and transportation, the environments in which they are used are becoming increasingly diverse. With the widespread adoption of containerized liquid bag packaging and transportation in international container transport, this technology has also penetrated into inland onward transportation, especially international rail transport. Winter temperatures in Russia are extremely low, with outdoor temperatures dropping below -40°C. Russia also spans a vast east-west region, stretching from the western region to the eastern coast. Bulk cargo must be transported by rail, over distances of over 5,000 kilometers. When transporting liquid bags by rail, the train generates high-frequency vibrations, causing the bag to vibrate along with the train. The PE film used in liquid bags gradually hardens and loses its flexibility as the temperature drops. Under these high-frequency vibrations, the edges and corners of the bag are prone to developing pinhole-like holes, leading to cargo leakage.

[0004] The materials used in container flexitanks have evolved from cloth-and-rubber to polyurethane, polyvinyl chloride, and polyethylene composites. Currently, to meet increasingly stringent environmental regulations, container flexitanks are primarily made of environmentally friendly polyethylene and are primarily disposable. These flexitanks are available in either multi-layer or single-layer configurations. Multi-layer structures typically utilize four layers of polyethylene for the inner layer and a woven polypropylene outer layer; single-layer structures utilize polyethylene. Current flexitank configurations can develop small holes in corners during transportation, leading to cargo leakage, environmental pollution, and a significant increase in accident handling costs.

[0005] CN102756523A discloses a flexible liquid packaging bag film for containers. The film is produced using a small three-layer co-extrusion unit using a blend of olefin-based specialty elastomers, mLLDPE, and DLPE. The film exhibits enhanced tensile strength, puncture resistance, ductility, flexural strength, and bending resistance, improving the safety of liquid bags. It is less likely to rupture at low temperatures and reduces transportation costs.

[0006] Due to the obvious defects of the liquid bags used in the prior art, it is necessary to improve the design and manufacture of the existing liquid bags to reduce the accident rate, thereby ensuring transportation safety and reducing related processing costs.

[0007] Summary of the Invention

[0008] The present invention discloses a low-temperature resistant liquid bag for long-distance transportation. The liquid bag uses four layers of PE film; the two inner layers are made of low-temperature PE material, and the two outer layers are made of high-density PE material; the two inner layers of low-temperature PE material are first heat-sealed and sealed to form a closed cavity, and the innermost layer of low-temperature PE material directly contacts liquid cargo; the two outer layers are wrapped around the outside of the low-temperature resistant PE, and all four layers of PE film are fixed together by heat sealing to form a multi-layer sealed cavity.

[0009] Preferably, the width of the heat-sealed portion of the two layers of low-temperature PE film is 1-5 cm, preferably 2-4 cm.

[0010] Preferably, the width of the heat-sealed portion of all four PE films is 2-8 cm, preferably 3-6 cm.

[0011] Preferably, the distance between the heat-sealed portion of the two-layer low-temperature PE film and the heat-sealed portion of the four-layer PE film is 5-15 cm, preferably 8-10 cm.

[0012] The thickness of the PE film material is 100-150 μm, preferably 120-140 μm.

[0013] The high-density PE material has a number average molecular weight of 200,000-500,000, preferably 300,000-350,000; the low-temperature PE material is metallocene-catalyzed polyethylene, with a number average molecular weight of 10,000-30,000, preferably 20,000-25,000.

[0014] The liquid bag can be used for railway transportation at a minimum temperature of -30°C for at least 30 days, and more preferably can be used for railway transportation at a minimum temperature of -40°C for at least 30 days.

[0015] The long-distance low-temperature resistant liquid bag disclosed in the present invention comprises a multi-layer film, wherein the inner layer of the low-temperature film ensures the sealing of the liquid bag and prevents leakage, and the outer layer of the high-density PE film increases the strength of the bag body and improves transportation safety. When the liquid bag is being formed, the low-temperature PE film is first processed into a closed cavity, which contacts the goods with the inner layer and will not be damaged in a low-temperature, high-frequency vibration environment, thereby ensuring the sealing of the bag body; two layers of high-density PE film are wrapped around the outside of the low-temperature PE film and heat-sealed with the low-temperature PE film to form a multi-layer sealed cavity, which increases the overall tensile strength of the liquid bag and prevents the liquid bag from being damaged by impact and stretching during transportation, while achieving multi-layer sealing of the liquid in the bag to prevent leakage. The liquid bag described in the present invention adopts a unique double heat-sealing structure and leaves a certain distance between the two heat-sealing structures, which can more efficiently reduce stress concentration at the sealing point and effectively reduce damage to the liquid bag caused by tensile impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the structure of a fluid bag;

[0017] Figure 2 is a schematic diagram of the heat-sealed structure of the liquid bag. DETAILED DESCRIPTION

[0018] Flexitanks were manufactured according to the method of the present invention and the manufacturing method not described in the present invention, and the flexitanks were filled with crude oil at -30°C. Simulated transportation experiments were conducted on a simulated motion platform, where the maximum acceleration of the simulated motion platform was 5 m / s. 2 , to simulate the acceleration condition of or, and provide a vibration with an amplitude of 5cm to simulate the vibration of the train. The simulation experiment is carried out for 30 days to examine the performance of the liquid bag.

[0019] Example 1

[0020] The volume is 24m 3 The flexitank had dimensions of 5700 mm × 2300 mm × 1950 mm and a filling ratio of 0.72. It used four layers of PE film, each 120 μm thick. The two inner layers were low-temperature PE, and the two outer layers were high-density PE. The heat-sealed portion between the two layers was 4 cm wide, while the heat-sealed portion between all four layers was 6 cm wide. The distance between the two layers was 10 cm. No rupture occurred during the 30-day test.

[0021] Example 2

[0022] The volume is 22m 3The flexitank had dimensions of 5700mm × 2300mm × 1950mm and a filling ratio of 0.67. It used four layers of PE film, each 120μm thick. The two inner layers were low-temperature PE, and the two outer layers were high-density PE. The heat-sealed portion between the two layers was 4cm wide, while the heat-sealed portion between all four layers was 6cm wide. The distance between the heat-sealed portions of the two layers was 10cm. No rupture occurred during the 30-day test.

[0023] Example 3

[0024] Volume is 20m 3 The flexitank had dimensions of 5700 mm × 2300 mm × 1950 mm and a filling ratio of 0.61. It used four layers of PE film, each 120 μm thick. The two inner layers were low-temperature PE, and the two outer layers were high-density PE. The heat-sealed portion between the two layers was 4 cm wide, while the heat-sealed portion between all four layers was 6 cm wide. The distance between the two layers was 10 cm. No rupture occurred during the 30-day test.

[0025] Example 4

[0026] The volume is 24m 3 The flexitank had specifications of 5700mm × 2300mm × 1950mm, a liquid filling height of 1400mm, and a liquid filling ratio of 0.72. It used four layers of PE film, each 120μm thick. The two inner layers were low-temperature PE material, and the two outer layers were high-density PE material. The heat-sealed portion between the two low-temperature PE layers was 5cm wide, while the heat-sealed portion between all four layers was 7cm wide. The distance between the heat-sealed portion between the two low-temperature PE layers and the four-layer PE layer was 12cm. No rupture occurred during the 30-day test.

[0027] Comparative Example 1

[0028] The volume is 24m 3 The flexitank had specifications of 5700mm × 2300mm × 1950mm, a liquid filling height of 1400mm, and a liquid filling ratio of 0.72. It used four layers of PE film, each 120μm thick, with the two inner layers made of low-temperature PE material and the two outer layers of high-density PE material. The heat-sealed section of all four layers was 8cm wide. No rupture occurred on the 16th day of the experiment.

[0029] Comparative Example 2

[0030] The volume is 24m 3The flexitank had specifications of 5700mm × 2300mm × 1950mm, a liquid filling height of 1400mm, and a liquid filling ratio of 0.72. It used four layers of PE film, each 120μm thick. The two inner layers were low-temperature PE material, and the two outer layers were high-density PE material. The heat-sealed portion between the two layers of low-temperature PE film was 4cm wide, and the heat-sealed portion between all four layers was 6cm wide. The distance between the heat-sealed portions of the two layers of low-temperature PE film and the four layers of PE film was 4cm. No rupture occurred on the 18th day of the experiment.

[0031] Comparative Example 3

[0032] The volume is 24m 3 The flexitank had specifications of 5700mm × 2300mm × 1950mm, a liquid filling height of 1400mm, and a liquid filling ratio of 0.72. It used four layers of PE film, each 120μm thick, with the two inner layers and the two outer layers made of low-temperature PE material. The heat-sealed portion between the two layers was 4cm wide, and the heat-sealed portion between all four layers was 6cm wide. The distance between the heat-sealed portions of the two layers was 20cm. It ruptured on the 25th day of the experiment.

[0033] The above contents are merely examples and explanations of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the present invention, they should all fall within the scope of protection of the present invention.

Claims

1. A low-temperature resistant liquid bag for long-distance transportation, the liquid bag uses 4 layers of PE film; the inner 2 layers are made of low-temperature PE material, and the outer 2 layers are made of high-density PE material; the inner two layers of low-temperature PE material are first heat-sealed and processed into a closed cavity, and the innermost layer of low-temperature PE material directly contacts the liquid cargo; the outer two layers are wrapped outside the low-temperature resistant PE, and all four layers of PE film are fixed together by heat sealing to form a multi-layer sealed cavity.

2. The liquid bag according to claim 1, characterized in that The width of the heat-sealed portion of the two layers of low-temperature PE film is 1-5 cm, preferably 2-4 cm.

3. The liquid bag according to claim 1, characterized in that The width of the heat-sealed portion of all four PE films is 2-8 cm, preferably 3-6 cm.

4. The liquid bag according to claim 1, characterized in that The distance between the heat-sealed portion of the two-layer low-temperature PE film and the heat-sealed portion of the four-layer PE film is 5-15 cm, preferably 8-10 cm.

5. The liquid bag according to claim 1, characterized in that The thickness of the PE film material is 100-150 μm, preferably 120-140 μm.

6. The liquid bag according to claim 1, characterized in that The high-density PE material has a number average molecular weight of 200,000-500,000, preferably 300,000-350,000; the low-temperature PE material is metallocene-catalyzed polyethylene, with a number average molecular weight of 10,000-30,000, preferably 20,000-25,000.

7. The liquid bag according to claim 1, characterized in that The liquid bag can be used for railway transportation at a minimum temperature of -30°C for at least 30 days, and more preferably can be used for railway transportation at a minimum temperature of -40°C for at least 30 days.

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