A composite film bag and a method of making the same

Abstract

This invention discloses a composite film bag and its preparation method, relating to the field of composite film bag manufacturing technology. The invention discloses a composite film bag, including a bag body; the bag body is divided into an upper gas chamber and a lower liquid storage chamber by a heat-sealing section; a liquid outlet is provided on one side of the gas chamber; a first heat-sealing rib is provided at the top of the gas chamber and opposite the liquid outlet; a second heat-sealing rib is provided on both sides of the liquid storage chamber; the bag body is made of a composite film layer; the composite film layer includes an outer printing layer, a middle barrier layer, and an inner heat-sealing layer arranged sequentially. This invention improves the ease of operation of the composite film bag by employing a multi-layer composite film structure, double-sided heat-sealing ribs, a wedge-shaped flow guide, and an integrated design with a sloping bottom and no residual corners, combined with a segmented heat-sealing bag-making process.

Description

Technical Field

[0001] This invention relates to the field of composite film bag preparation technology, specifically to a composite film bag and its preparation method. Background Technology

[0002] Traditional composite film bags often employ flat-mouth heat-sealing or easy-tear opening structures. In practical use, they generally require both hands to open and squeeze out the material, making them inconvenient for outdoor, cooking, or commuting scenarios where only one hand can operate. The opening of traditional composite film bags is a one-time destruction structure; once opened, it cannot be closed again, lacking resealing capability. This makes the contents prone to spillage, moisture absorption, contamination, or spoilage. The bag body lacks rigid support, making it prone to wrinkling, collapse, and tipping over when squeezed with one hand, resulting in poor material flow and difficulty in controlling the amount of material dispensed. The opening lacks a flow guide design, leading to splashing and overflow during squeezing. Material easily accumulates at the bottom and corners of the bag, resulting in large residues and low utilization. Some bags with sealing structures have complex and costly designs, making them unsuitable for high-speed bag production lines. The lack of rigid support and the tendency for the bag to wrinkle, tip over, or collapse when squeezed with one hand lead to poor material flow, splashing, or uncontrolled usage.

[0003] Traditional pure CPP heat-sealable film has a single homogeneous polyolefin structure. During the heat-sealing process, the molecular chains of the two film layers fully melt and diffuse, and become highly entangled. The bonding strength at the heat-sealing interface is close to the strength of the film body itself. This results in excessively high heat-sealing strength for the composite film bag, making it impossible to open by hand. Forced tearing easily causes problems such as bag tearing, irregular opening, and severe stringing, seriously affecting the product user experience. Summary of the Invention

[0004] The purpose of this invention is to provide a composite film bag and its preparation method, thereby solving the following technical problems: Existing composite film bags suffer from difficulties in opening, and cannot simultaneously address issues such as material discharge control, bag protection, and insufficient heat resistance and mechanical properties during the manufacturing process.

[0005] The objective of this invention can be achieved through the following technical solutions: A composite film bag includes a bag body and heat-sealing ribs disposed on both sides of the bag body; The bag body is divided into a liquid storage chamber and a gas chamber by a heat-sealing section; A liquid outlet is provided on one side of the gas chamber, and a one-time opening is provided at the end of the liquid outlet; a heat-sealing rib is provided on the top of the gas chamber and on the opposite side of the liquid outlet. A wedge-shaped guide is provided on the opposite side of the liquid outlet of the gas chamber; The liquid storage cavity is provided with two heat-sealing ribs on both sides; The bag body is a bag material made of composite film layer; The composite film layer includes an outer printed layer, an intermediate barrier layer, and an inner heat-sealing layer arranged sequentially. The inner heat-sealing layer comprises the following raw materials in parts by weight: 60-70 parts of random copolymer PP, 15-25 parts of ethylene-acrylic acid copolymer, 6-8 parts of PP elastomer, and 1-2 parts of fumed silica.

[0006] As a further aspect of the present invention, the hot-melt section is configured as a wave shape.

[0007] As a further aspect of the present invention: the heat-sealing width of both the first and second heat-sealing ribs is 3mm-8mm.

[0008] As a further aspect of the present invention: a wedge-shaped guide is also provided in the gas chamber, and its bottom is obliquely transitioned with an angle of 30°-60°; the channel width of the gas chamber is 3mm-10mm.

[0009] As a further aspect of the present invention: the intermediate barrier layer is made of aluminum or vacuum-metallized polyester film material with a thickness of 7μm-12μm; it blocks oxygen, moisture, light, and aroma, prevents the contents from oxidizing and deteriorating, and meets the food packaging safety requirements.

[0010] As a further aspect of the present invention: the thickness of the inner heat-sealing layer is 35μm-60μm; it provides heat-sealing strength, is hygienic and non-toxic, resistant to corrosion of contents, and ensures reliable sealing of the bag.

[0011] As a further aspect of the present invention: the fumed silica is hydrophobic fumed silica.

[0012] A method for preparing a composite film bag includes the following steps: S1. Random copolymer PP, ethylene-acrylic acid copolymer, PP elastomer and fumed silica are mixed and fed into a twin-screw extruder for granulation, and then fed into a single-screw casting extruder. The extrusion temperature is 200-230℃ and the die temperature is 210-225℃. The mixture is melt-cast and extruded to obtain a heat-sealing film layer with a thickness of 35-60μm. The inner heat-sealing layer is obtained by corona treatment of the composite heat-sealing film layer and the intermediate barrier layer. S2. After corona treatment of the outer printed layer, it is laminated with the aluminum barrier layer using water-based polyurethane adhesive and cured, and then laminated with the inner heat-sealing layer and cured to obtain a three-layer composite film. S3. Feed the three-layer composite film into the bag-making machine, with the inner heat-sealing layer facing inwards. Set the temperature to 120-160℃, the pressure to 0.15-0.25MPa, and hold the pressure for 0.2-0.5 seconds. Figure 1The three-layer composite membrane is hot-pressed at a distance of 3mm-10mm from the top to obtain the heat-fused part. Then, the liquid outlet end of the gas chamber is hot-pressed to obtain a one-time opening. Subsequently, the temperature is raised to 140-180℃, the pressure is 0.3-0.4MPa, and the pressure holding time is 0.2-0.5s. The two sides of the three-layer composite membrane are hot-pressed to form a shaping heat-sealing rib. After cutting, the composite membrane bag is obtained.

[0013] As a further aspect of the present invention: the drying and thermal crosslinking includes: placing the wet film in a ventilated environment for 12-14 hours, then placing it in an oven at 40-50°C for 2-4 hours to dry. After drying, the oven is heated to 80-85°C for 90-120 minutes to obtain the outer printed layer.

[0014] The beneficial effects of this invention are: 1. This invention provides rigid support to the composite film bag by setting double-sided shaping heat-sealing ribs on both sides of the bag body. The bag does not collapse, wrinkle, or tip over when squeezed by one hand, maintaining the stability of the discharge chamber. The gas chamber uses a wedge-shaped directional flow channel to constrain the discharge direction and prevent pastes, liquids, and sauces from splashing or overflowing. The discharge is concentrated and controllable. The bottom of the gas chamber uses an angled transition, and the contents automatically converge to the opening when squeezed, resulting in a low residue rate inside the bag and cleaner use. Combined with a segmented heat-sealing bag making process, it achieves stable one-handed opening, smooth one-handed squeezing, directional and controllable discharge, and low residue use without zippers, nozzles, or any repeated sealing structures. The overall structure is simple, low-cost, and suitable for industrial mass production.

[0015] 2. The inner heat-sealing layer of this invention is achieved by blending random copolymer PP, ethylene-acrylic acid copolymer, PP elastomer, and fumed silica. Easy peeling is achieved by relying on the controllable interface formed by the phase separation of the random copolymer PP and ethylene-acrylic acid copolymer. The PP elastomer has excellent compatibility with the PP matrix and also possesses a certain degree of compatibility with the ethylene-acrylic acid copolymer, buffering the interfacial stress between the two phases, preventing brittle fracture and stringing during peeling, refining the size of the ethylene-acrylic acid copolymer island dispersed phase, making the dispersed phase particles more uniform, and reducing peel strength fluctuations. The fumed silica further homogenizes the dispersed phase size, providing appropriate stress concentration sites, ensuring uniform distribution of the two-phase interface throughout the film, and reducing the dispersion of peel strength at different locations. The synergistic effect of each component enables easy peeling at the interface in the low-temperature heat-sealing melt section and high-strength sealing at the high-temperature heat-sealing rib positions, while simultaneously ensuring reliable adhesion between the composite film layers. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the structure of the extrusion composite film bag in the embodiment; In the picture: 1. Bag body; 2. Heat-sealing section; 3. Gas chamber; 4. Liquid storage chamber; 5. Wedge-shaped guide section; 6. One-time opening; 7. Shaping heat-sealing rib one; 8. Shaping heat-sealing rib two. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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] In this application, the random copolymer PP was selected from Shanghai Weikena Plastics Co., Ltd.; purity 100%; In this application, the ethylene-acrylic acid copolymer is selected from Ningbo Rongsu New Materials Co., Ltd., brand name 2002; In this application, the PP elastomer is selected from Dongguan Jincan Plastics Technology Co., Ltd., grade 9500; In this application, the fumed silica is selected from Shandong Kason New Materials Co., Ltd., model KS-8150.

[0020] Example 1

[0021] like Figure 1 As shown: A method for preparing a composite film bag includes the following steps: S1. Preparation of the inner heat-sealing layer Random copolymer PP, ethylene-acrylic acid copolymer, PP elastomer and fumed silica are mixed and fed into a twin-screw extruder for granulation, and then fed into a single-screw casting extruder. The extrusion temperature is 200℃ and the die temperature is 210℃. The melt casting extrusion yields a heat-sealing film layer with a thickness of 35μm. The inner heat-sealing layer is obtained by corona treatment of the composite heat-sealing film layer and the intermediate barrier layer.

[0022] S2. Preparation of composite membrane bags

[0023] After corona treatment of the outer printed layer, it is laminated with the aluminum barrier layer using water-based polyurethane adhesive and cured, and then laminated with the inner heat-sealing layer and cured to obtain a three-layer composite film. The three-layer composite film is fed into the bag making machine with the inner heat-sealing layer facing the inside of the bag. The temperature is set to 120℃, the pressure to 0.15MPa, and the pressure holding time to 0.2s. The middle of the three-layer composite film is heat-pressed 3mm from the top to obtain the heat-sealed part 2. Then, the liquid outlet end of the gas chamber 3 is heat-pressed to obtain the one-time opening 6. Subsequently, the temperature is raised to 140℃, the pressure is 0.3MPa, and the pressure holding time is 0.2s. The top and sides of the three-layer composite film are heat-pressed to form the liquid storage chamber 4 in the middle, the first heat-sealing rib 7 on the top, and the second heat-sealing rib 8 on both sides. The opposite side of the liquid outlet of the gas chamber 3 is heat-pressed to form a wedge-shaped guide part 5. After cutting, the bag body 1, i.e., the composite film bag, is obtained.

[0024] Example 2

[0025] like Figure 1 As shown: A method for preparing a composite film bag includes the following steps: S1. Preparation of the inner heat-sealing layer Random copolymer PP, ethylene-acrylic acid copolymer, PP elastomer and fumed silica are mixed and fed into a twin-screw extruder for granulation, and then fed into a single-screw casting extruder. The extrusion temperature is 215℃ and the die temperature is 219℃. The melt casting extrusion yields a heat-sealing film layer with a thickness of 50μm. The inner heat-sealing layer is obtained by corona treatment of the composite heat-sealing film layer and the intermediate barrier layer.

[0026] S2. Preparation of composite membrane bags

[0027] After corona treatment of the outer printed layer, it is laminated with the aluminum barrier layer using water-based polyurethane adhesive and cured, and then laminated with the inner heat-sealing layer and cured to obtain a three-layer composite film. The three-layer composite film is fed into the bag making machine with the inner heat-sealing layer facing the inside of the bag. The temperature is set to 140℃, the pressure to 0.2MPa, and the pressure holding time to 0.3s. The middle of the three-layer composite film is heat-pressed 6mm from the top to obtain the heat-sealed part 2. Then, the liquid outlet end of the gas chamber 3 is heat-pressed to obtain the one-time opening 6. Subsequently, the temperature is raised to 160℃, the pressure is 0.35MPa, and the pressure holding time is 0.3s. The top and sides of the three-layer composite film are heat-pressed to form the liquid storage chamber 4 in the middle, the first heat-sealing rib 7 on the top, and the second heat-sealing rib 8 on both sides. The opposite side of the liquid outlet of the gas chamber 3 is heat-pressed to form a wedge-shaped guide part 5. After cutting, the bag body 1, i.e., the composite film bag, is obtained.

[0028] Example 3

[0029] like Figure 1 As shown: A method for preparing a composite film bag includes the following steps: S1. Preparation of the inner heat-sealing layer Random copolymer PP, ethylene-acrylic acid copolymer, PP elastomer and fumed silica are mixed and fed into a twin-screw extruder for granulation, and then fed into a single-screw casting extruder. The extrusion temperature is 230℃ and the die temperature is 225℃. The melt casting extrusion yields a heat-sealing film layer with a thickness of 60μm. The inner heat-sealing layer is obtained by corona treatment of the composite heat-sealing film layer and the intermediate barrier layer.

[0030] S2. Preparation of composite membrane bags

[0031] After corona treatment of the outer printed layer, it is laminated with the aluminum barrier layer using water-based polyurethane adhesive and cured, and then laminated with the inner heat-sealing layer and cured to obtain a three-layer composite film. After corona treatment of the outer printed layer, it is laminated with the aluminum barrier layer using water-based polyurethane adhesive and cured, and then laminated with the PE heat-sealing layer and cured to obtain a three-layer composite film. The three-layer composite film is fed into the bag making machine with the inner heat-sealing layer facing the inside of the bag. The temperature is set to 160℃, the pressure to 0.25MPa, and the pressure holding time to 0.5s. The middle of the three-layer composite film is heat-pressed 10mm from the top to obtain the heat-sealed part 2. Then, the liquid outlet end of the gas chamber 3 is heat-pressed to obtain the one-time opening 6. Subsequently, the temperature is raised to 180℃, the pressure is 0.4MPa, and the pressure holding time is 0.5s. The top and sides of the three-layer composite film are heat-pressed to form the liquid storage chamber 4 in the middle, the first heat-sealing rib 7 on the top, and the second heat-sealing rib 8 on both sides. The opposite side of the liquid outlet of the gas chamber 3 is heat-pressed to form a wedge-shaped guide part 5. After cutting, the bag body 1, i.e., the composite film bag, is obtained.

[0032] Comparative Example 1

[0033] Compared with Example 3, step S1 was omitted in this comparative example, and the inner heat-sealing layer prepared in step S1 was replaced with random copolymer PP film.

[0034] Comparative Example 2

[0035] Compared with Example 3, steps S1 and S2 remain unchanged in this comparative example. The three-layer composite film obtained in step S3 is fed into a bag making machine with the inner heat-sealing layer facing the inside of the bag. The temperature is set to 180°C, the pressure to 0.4MPa, and the pressure holding time to 0.5s. The three-layer composite film is heat-pressed at the middle part 6mm from the top and on both sides. After cutting, a composite film bag is obtained.

[0036] Performance testing

[0037] The heat resistance of the composite film bags prepared in Examples 1-3 and Comparative Examples 1-2 was determined in accordance with the standard GB / T 10004-2008 "Dry lamination and extrusion lamination of plastic composite films and bags for packaging". The heat resistance results are expressed as no deformation, interlayer peeling, and peeling at the heat-sealed area. The mechanical properties of the composite film bags prepared in Examples 1-3 and Comparative Examples 1-2 were determined in accordance with the standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The peel strength at the hot-melt section and the peel strength at the heat-sealing rib of the composite film bags prepared in Examples 1-3 and Comparative Examples 1-2 were determined in accordance with the standard GB / T 8808-2026 "Peel Test Method for Flexible Composite Plastic Materials". The composite film bags prepared in Examples 1-3 and Comparative Examples 1-2 were tested by single-handed squeezing to determine whether the material flow was smooth and whether the bag body was intact.

[0038] The test results are shown in the table below: Performance test results of composite film bags

[0039] As can be seen from the data in the table above, the composite film bag prepared in this application has strong tensile strength, wear resistance, heat resistance and oxidation resistance. Compared with Comparative Example 1, Examples 1-3 use random copolymer PP film as the inner heat-sealing layer. No EAA, PP elastomer and fumed silica phase separation components are added. The pure random copolymer PP film is a homogeneous polyolefin system. After heat sealing, the molecular chains of the two film surfaces are fully diffused and entangled, and a weak interface structure of PP / EAA cannot be formed. The dual temperature gradient heat sealing process alone cannot make up for the lack of easy-to-peel phase separation structure of the material itself. It is necessary to construct a weak island interface by EAA blending in order to achieve the synergy of controllable easy peeling and high-strength sealing.

[0040] Compared with Comparative Example 2, Examples 1-3 use the same high-temperature and high-pressure heat sealing conditions as the sides in the central hot-melt area. The inner PE heat-sealing layer is fully melted to form a permanent high-strength seal, losing the differentiated function of the central part being easy to open and squeeze. When squeezed by one hand, the hot-melt part cannot be squeezed open smoothly, resulting in poor material discharge and damage to the bag.

[0041] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A composite film bag, characterized in that, Including the bag body; The bag body is divided into an upper gas chamber and a lower liquid storage chamber by a heat-sealing section. A liquid outlet is provided on one side of the gas chamber, and the liquid outlet is a one-time opening; a heat-sealing rib is provided on the top of the gas chamber and on the opposite side of the liquid outlet. The liquid storage cavity is provided with two heat-sealing ribs on both sides; The bag body is made of a composite film layer; The composite film layer includes an outer printed layer, an intermediate barrier layer, and an inner heat-sealing layer arranged sequentially. The inner heat-sealing layer comprises the following raw materials in parts by weight: 60-70 parts of random copolymer PP, 15-25 parts of ethylene-acrylic acid copolymer, 6-8 parts of PP elastomer, and 1-2 parts of fumed silica.

2. The composite film bag according to claim 1, characterized in that, The hot-melt section is designed to be wavy.

3. The composite film bag according to claim 1, characterized in that, The heat-sealing width of both the first and second heat-sealing bars is 3mm-8mm.

4. A composite film bag according to claim 1, characterized in that, The gas chamber is also provided with a wedge-shaped guide section, and its bottom is a beveled transition with an angle of 30°-60°; the channel width of the gas chamber is 3mm-10mm.

5. A composite film bag according to claim 1, characterized in that, The outer printed layer is made of PET film with a thickness of 12μm-20μm.

6. A composite film bag according to claim 1, characterized in that, The intermediate barrier layer is made of aluminum or vacuum-metallized polyester film with a thickness of 7μm-12μm.

7. A composite film bag according to claim 1, characterized in that, The thickness of the inner heat-sealing layer is 35μm-60μm.

8. A composite film bag according to claim 1, characterized in that, The fumed silica is hydrophobic fumed silica.

9. A method for preparing a composite film bag according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Random copolymer PP, ethylene-acrylic acid copolymer, PP elastomer and fumed silica are mixed and fed into a twin-screw extruder for granulation, and then fed into a single-screw casting extruder. The extrusion temperature is 200-230℃ and the die temperature is 210-225℃. The mixture is melt-cast and extruded to obtain a heat-sealing film layer with a thickness of 35-60μm. The inner heat-sealing layer is obtained by corona treatment of the composite heat-sealing film layer and the intermediate barrier layer. S2. After corona treatment of the outer printed layer, it is laminated with the aluminum barrier layer using water-based polyurethane adhesive and cured, and then laminated with the inner heat-sealing layer and cured to obtain a three-layer composite film. S3. Feed the three-layer composite film into the bag making machine, with the inner heat-sealing layer facing the inside of the bag. Set the temperature to 120-160℃, the pressure to 0.15-0.25MPa, and hold the pressure for 0.2-0.5s. Heat-press the middle of the three-layer composite film 3mm-10mm from the top to obtain the heat-sealed part. Then heat-press the liquid outlet end of the gas chamber to obtain a one-time opening. Subsequently, raise the temperature to 140-180℃, the pressure to 0.3-0.4MPa, and hold the pressure for 0.2-0.5s. Heat-press the top and sides of the three-layer composite film to form the first and second heat-sealing ribs. After cutting, the composite film bag is obtained.

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