Composite flour packaging bag based on single material

Abstract

The invention relates to the technical field of food packaging, and discloses a flour packaging bag based on single material compositing, which comprises a middle-sealed folding bag and an eight-edge-sealed folding packaging bag, and comprises a first bag body and a first bag side applied to the middle-sealed folding bag, one side edge of the bag body is connected end to end and then is sealed to form a middle sealing part, and the other side edge of the bag body is sealed to form an eight-edge-sealed folding packaging bag. The first bag body and one end face of the bag side are connected and then are subjected to edge sealing to form a transverse sealing part, the position, located on the transverse sealing part, of the first bag body is coated with an adhesive tape, and after middle sealing is completed, the middle sealing part is attached to the adhesive tape. By adopting the unstretched PE film composite design, the tensile strength, the heat sealing performance and the tear resistance of the packaging bag are remarkably improved, the heat sealing temperature is as low as 120 DEG C or below, and the bag breaking risk is reduced; the method is suitable for complex bag shape processing; through the environment-friendly solvent-free adhesive and the dry type compound technology, the production efficiency is improved, the cost is reduced, meanwhile, efficient recycling and environment-friendly performance are achieved, and the packaging requirement of heavy objects is met.

Description

Technical Field

[0001] The invention relates to the technical field of food packaging, in particular to a flour packaging bag based on a single material composite. Background Art

[0002] With the rapid development of the food packaging industry, the packaging demand for bulk commodities such as flour and rice bags has continued to increase, and the market has put forward higher requirements for the strength, environmental protection and processing adaptability of packaging bags. However, the existing packaging technology mainly relies on multi-material composite film structures, such as the composite of polyethylene (PE) with polyethylene terephthalate (PET), polypropylene (PP) or aluminum foil. This type of traditional packaging bag has significant technical defects in practical applications.

[0003] First, the mechanical properties of traditional packaging bags are insufficient, especially when filling heavy objects such as flour and rice or during transportation, they are prone to tearing or breaking due to external forces. This not only increases logistics and storage costs, but also affects the safety and integrity of the product. Secondly, the structure of multi-material composite films is complex and the separation of materials is difficult, resulting in high recycling costs and low efficiency, poor resource recycling, and does not meet the current green environmental protection policy requirements.

[0004] In addition, the heat sealing performance of traditional packaging bags is unstable. The heat sealing area often suffers film damage due to insufficient welding strength or improper welding temperature control, further increasing the risk of package breakage. This problem is particularly prominent in logistics and transportation, and it is difficult to meet the high strength and sealing requirements of heavy packaging. At the same time, the bag-making process of complex bag types (such as center-seal folding bags, eight-side seal bags, etc.) places high demands on the adaptability of materials, but traditional packaging materials are insufficient in terms of welding seal firmness and folding neatness, which affects the practicality and aesthetics of the bag type.

[0005] Although current industry research is gradually applying environmentally friendly single-material structures to the preparation of packaging bags to replace traditional multi-material composite films, the existing technology still has problems such as insufficient bonding strength between composite film layers, poor heat sealing performance, and limited processing adaptability. It is difficult to meet the high performance and high reliability requirements of bulk commodity packaging such as flour. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a flour packaging bag based on a single material composite, which solves the problems of insufficient mechanical properties, poor heat sealing performance, poor adaptability to complex bag processing and difficulty in recycling of existing multi-material composite packaging bags.

[0007] To achieve the above objectives, the present invention is implemented through the following technical scheme: a flour packaging bag based on a single material composite, applied to center-seal folding edge bags and eight-side-seal folding edge packaging bags, including a bag body 1 and a bag side 1 applied to the center-seal folding edge bag, the side edge of the bag body is connected end to end and then sealed to form a center-seal portion, the end faces of the bag body 1 and the bag side 1 are connected and then sealed to form a transverse seal portion, the bag body 1 is coated with a rubber strip at the transverse seal position, after the center seal is completed, the center seal and the rubber strip are fitted, and the center seal and the middle of the transverse seal are coated with sealing glue 1 and sealing glue 2.

[0008] Preferably, the bag body 1 is formed by compounding a substrate 1 and a substrate 2, the composite part of the ends of the substrate 1 and the substrate 2 is coated with a sealing glue 1, and a sealing edge of the bag body is coated with a sealing glue 2.

[0009] Preferably, it also includes bag body 2, bag side 2 and bag bottom applied to the eight-side sealed folded edge bag, and the side edges of the bag body 2, bag side 2 and bag bottom are connected by sealing to form a side sealing part.

[0010] Preferably, the bag body 2 is composed of a composite of substrate 3 and substrate 4, the bag bottom is composed of a composite of substrate 5 and substrate 6, the substrate 3, substrate 4 and the composite part of substrate 5 and substrate 6 are all coated with sealing glue 1, and the bag body 2 and the edge sealing part of the bag bottom are coated with sealing glue 2.

[0011] A method for preparing a flour packaging bag based on a single material composite comprises the following steps:

[0012] S1. Preparation of unstretched PE film for printing layer: low-density polyethylene is used as the base material, high temperature resistant additives, antioxidants and antistatic agents are added, and a printing layer film is formed by extrusion and cast molding;

[0013] S2. Preparation of unstretched PE film for heat-sealing layer: using linear low-density polyethylene as substrate, adding low-temperature heat-sealing additive and toughening material, and forming heat-sealing layer film by extrusion and casting;

[0014] S3. Using a dry lamination process, the printed layer unstretched PE film and the heat-sealed layer unstretched PE film are laminated to form a PE / PE composite film;

[0015] S4. Processing of the PE / PE composite film for the middle-seal folded edge bag, including transverse seal welding and gluing reinforcement of the folded edge area;

[0016] S5. Carry out performance tests on the manufactured flour packaging bags, including tensile strength test, heat seal strength test and tear resistance test, to ensure that they meet the high-strength packaging requirements.

[0017] Preferably, in the preparation of the unstretched PE film of the printing layer:

[0018] The high temperature resistant additive is silicon oxide filler, and the addition ratio is 5%-8%;

[0019] The addition ratios of antioxidant and antistatic agent are 0.1%-0.3% and 0.05%-0.1% respectively;

[0020] The film thickness is controlled at 30μm-50μm.

[0021] Preferably, in the preparation of the unstretched PE film of the heat-sealing layer:

[0022] The low-temperature heat-sealing aid is ethylene-vinyl acetate copolymer, and the addition ratio is 10%-15%;

[0023] The toughening material is polyolefin elastomer, and the addition ratio is 5%-8%;

[0024] The surface of the film is coated with a low-temperature heat-sealing coating with a coating thickness of 1-3 μm.

[0025] Preferably, the dry compounding process comprises the following steps:

[0026] S31. Apply environmentally friendly solvent-free polyurethane adhesive on the non-printing surface of the unstretched PE film of the printed layer, with a coating amount of 2g / m 2 -4g / m 2 ;

[0027] S32. The lamination is completed at a lamination temperature of 80°C-100°C and a lamination pressure of 0.4MPa-0.8MPa;

[0028] S33. Curing in an environment of 40°C-60°C for 24h-48h to form a final PE / PE composite film.

[0029] Preferably, the bag making process of the center-seal folding bag comprises the following steps:

[0030] S41. Perform welding in the transverse sealing area of ​​the composite film, the welding temperature is 110°C-120°C, the welding time is 0.8s-1.5s, and the welding pressure is 0.3MPa-0.6MPa;

[0031] S42. Glue reinforcement is applied to the folded edge area of ​​the bag body, the folded edge width is 10mm-15mm, and the volume of the glue application point is determined by the glue application radius and height to ensure the strength and stability of the folded edge structure.

[0032] Preferably, the performance of the flour packaging bag meets the following indicators:

[0033] Tensile strength σ≥25MPa;

[0034] Heat seal strength S h ≥6N / mm;

[0035] Tear strength T s ≥0.35N / mm.

[0036] The present invention provides a flour packaging bag based on a single material composite, which has the following beneficial effects:

[0037] 1. The present invention significantly improves the tensile strength and tear resistance of the packaging bag through the single material structure design of the composite of unstretched PE film and unstretched PE film (PE / PE). The unstretched PE film of the printing layer provides the tensile resistance of the outer layer, and the unstretched PE film of the heat-sealing layer enhances the toughness and impact resistance of the inner layer. The reasonable composite of the two layers of film has excellent bonding strength, so that the packaging bag can better disperse stress when carrying heavy objects such as flour and reduce the breakage rate, especially showing high reliability in logistics transportation and stacking storage.

[0038] 2. The present invention optimizes the low-temperature heat-sealing performance by formula design and surface coating treatment of the unstretched PE film of the heat-sealing layer. Using EVA as a low-temperature heat-sealing aid and POE as a toughening agent, the heat-sealing temperature of the packaging bag is reduced to below 120°C, and a high heat-sealing strength is ensured. This low-temperature and high-strength heat-sealing characteristic can reduce film fatigue in the transverse and longitudinal sealing areas, improve the tear resistance and air tightness of the seal, and thus effectively reduce the risk of package breakage.

[0039] 3. The present invention is successfully applied to the bag-making process of complex bag types such as center-seal folding bags and eight-side-seal bags through the high bonding strength and processing adaptability of the composite film. The horizontal seal, vertical seal and folding welding area of ​​the bag are reasonably designed, combined with the high tensile strength and flexibility of the composite film, to maintain good dimensional stability during the processing, and the welded seal part is firm and flat, thereby improving the aesthetics and structural integrity of the packaging bag in actual use.

[0040] 4. The present invention adopts a single material structure formed by a composite of unstretched PE film, so that the packaging bag of the present invention has excellent recyclability and environmental friendliness. Traditional multi-layer composite packaging bags are difficult to recycle due to mixed materials, while the PE / PE structure of the present invention avoids the problem of material separation and greatly simplifies the recycling process.

[0041] 5. The present invention uses environmentally friendly solvent-free polyurethane adhesive and optimized dry compounding process in the coating, compounding and curing process, which reduces the solvent volatilization process and improves the compounding efficiency; in the bag making process, the welding and folding technology are improved to reduce material waste and increase the welding speed. The optimization of the overall manufacturing process significantly improves production efficiency and reduces the production cost of each packaging bag. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A three-dimensional diagram of a center-sealed gusseted bag in the present invention;

[0043] Figure 2 Schematic diagram of the unfolding of the center-sealed gusseted bag of the present invention;

[0044] Figure 3 Schematic diagram of the edge sealing of the center-sealed folding bag of the present invention;

[0045] Figure 4 It is a three-dimensional diagram of the eight-side sealed folding bag of the present invention;

[0046] Figure 5 Schematic diagram of the sealing edge of the eight-side sealed folding bag of the present invention;

[0047] Figure 6 The figure is a schematic flow chart of the steps for preparing the packaging bag in the present invention.

[0048] Among them, 11, bag body one; 111, substrate one; 112, substrate two; 12, bag side one; 13, middle sealing part; 14, transverse sealing part; 15, rubber strip; 21, sealing glue one; 22, sealing glue two; 31, bag body two; 311, substrate three; 312, substrate four; 32, bag side two; 33, bag bottom; 331, substrate five; 332, substrate six; 34, side sealing part. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Embodiment 1:

[0051] Please see attached Figure 1 -Attached Figure 3The embodiment of the present invention provides a flour packaging bag based on a single material composite, which includes a bag body 11 and a bag side 12 used for a center-seal folding bag. The sides of the bag body 11 are connected end to end and then sealed to form a center-seal portion 13. After the sides of the bag body 11 are connected end to end and sealed, the bag body 11 and the bag side 12 form a ring structure to produce the packaging bag. The end faces of the bag body 11 and the bag side 12 are connected and then sealed to form a transverse seal portion 14. The bag body 11 is coated with a rubber strip 15 at the position of the transverse seal portion 14 for structural reinforcement. After the center seal is completed, the center seal portion 13 and the rubber strip 15 are fitted together. The center seal portion 13 and the middle of the transverse seal portion 14 are coated with a sealant 21 and a sealant 22. The sealant 21 and the sealant 22 are both environmentally friendly solvent-free polyurethane adhesives to provide adhesion performance. The bag body 11 is composited by a substrate 111 and a substrate 2 112, the composite portion at the ends of the substrate 111 and the substrate 2 112 is coated with a sealing glue 21, the substrate 111 and the substrate 2 112 are respectively the printing layer and the heat-sealing layer of the bag body 11, the sealing edge of the bag body 11 is coated with a sealing glue 22, and the sealing glue 22 is connected to the rubber strip 15, so that the welding seams of the bag side 12 and the bag body 11 are in a straight line to form an integral weld seal, so as to eliminate the stress at the 90° intersection formed by the transverse seal and the longitudinal fold when the packaging bag is subjected to stress, so that the packaging bag can withstand greater external forces.

[0052] Please see attached Figure 4 -Attached Figure 5 A flour packaging bag based on a single material composite also includes a bag body 2 31, a bag side 2 32 and a bag bottom 33 applied to an eight-side sealed folding bag. The side connection parts of the bag body 2 31, the bag side 2 32 and the bag bottom 33 are sealed to form a side sealing part 34. The bag body 2 31 is composited by a base material 3 311 and a base material 4 312. The bag bottom 33 is composited by a base material 5 331 and a base material 6 332. The base material 3 311, the base material 4 312 and the composite part of the base material 5 331 and the base material 6 332 are all coated with a sealing glue 1 21. The sealing parts of the bag body 2 31 and the bag bottom 33 are coated with a sealing glue 22.

[0053] The manufacturing process of eight-side sealed gusset bags is the same as that of center-sealed gusset bags.

[0054] Embodiment 2:

[0055] Please see attached Figure 6 As part of this application, the present invention also provides a method for preparing a flour packaging bag based on a single material composite, comprising the following steps:

[0056] S1. Preparation of unstretched PE film for printing layer: low-density polyethylene is used as the base material, high temperature resistant additives, antioxidants and antistatic agents are added, and a printing layer film is formed by extrusion and cast molding;

[0057] In the preparation of unstretched PE film for printing layer:

[0058] The high temperature resistant additive is silicon oxide filler, and the addition ratio is 5%-8%;

[0059] The addition ratios of antioxidant and antistatic agent are 0.1%-0.3% and 0.05%-0.1% respectively;

[0060] The film thickness is controlled at 30μm-50μm.

[0061] S2. Preparation of unstretched PE film for heat-sealing layer: using linear low-density polyethylene (LLDPE) as substrate, adding low-temperature heat-sealing additive and toughening material, and forming heat-sealing layer film by extrusion and casting;

[0062] In the preparation of the unstretched PE film of the heat sealing layer:

[0063] Linear low-density polyethylene (LLDPE), accounting for 75%-80% of the total formula. LLDPE's low melting point and high flexibility are suitable for heat sealing requirements of heavy packaging;

[0064] The low-temperature heat-sealing aid is ethylene-vinyl acetate copolymer (EVA), and the addition ratio is 10%-15%. The addition of EVA significantly reduces the heat-sealing starting temperature of the film.

[0065] The toughening material is polyolefin elastomer (POE), and the addition ratio is 5%-8%. The molecular chain of POE has high elasticity and good mechanical properties, which can effectively improve the tear resistance of the film;

[0066] The film thickness is controlled at 40μm-60μm;

[0067] The surface of the film is coated with a low-temperature heat-sealing coating with a coating thickness of 1 μm-3 μm.

[0068] The performance indicators of the material formulation are optimized by the following formula:

[0069]

[0070] Among them, C d is the dispersion coefficient of the additive, φ f and φ m are the volume fractions of additive and substrate respectively; by controlling C d ≥0.6, ensuring uniform distribution of heat-sealing additives and toughening materials, and improving the overall performance of the film.

[0071] S3. Using a dry lamination process, the printed layer unstretched PE film and the heat-sealed layer unstretched PE film are laminated to form a PE / PE composite film;

[0072] The dry compounding process comprises the following steps:

[0073] S31. Apply environmentally friendly solvent-free polyurethane adhesive on the non-printing surface of the unstretched PE film of the printed layer, with a coating amount of 2g / m 2 -4g / m 2 ;

[0074] Environmentally friendly solvent-free polyurethane adhesive is used with a viscosity range of 800mPa-1200mPa to ensure fluidity and adhesion performance.

[0075] The adhesive coating amount is calculated according to the following formula:

[0076]

[0077] Among them, Q g is the adhesive coating amount (unit: g / m 2 ), M g is the mass of adhesive applied (unit: g), A is the film coating area (unit: m 2 );

[0078] The coating amount is controlled at 2g / m 2 -4g / m 2 To ensure that the interlayer peeling strength after compounding meets the design requirements.

[0079] Roller coating equipment is used for coating, the roller speed is set to 10m / min-20m / min, and the coating uniformity error is controlled within ±5%.

[0080] S32. The lamination is completed at a lamination temperature of 80°C-100°C and a lamination pressure of 0.4MPa-0.8MPa;

[0081] Laminating temperature control: The laminating temperature is set at 80℃-100℃, the laminating roller adopts a double-sided constant temperature heating structure, and the temperature fluctuation is controlled within ±2℃;

[0082] Lamination pressure control: The lamination pressure is set to 0.4MPa-0.8MPa to ensure full contact between the films and avoid bubbles;

[0083] Laminating speed: The laminating speed is set at 10m / min-20m / min to ensure uniform diffusion and initial bonding of the adhesive during the laminating process.

[0084] S33. Curing in an environment of 40°C-60°C for 24h-48h to form a final PE / PE composite film.

[0085] Curing temperature: The curing chamber temperature is set at 40℃-60℃, and the temperature uniformity is ensured by segmented temperature control equipment;

[0086] Curing time: The curing time is 24h-48h, ensuring that the solvent in the adhesive is completely volatilized and a stable cross-linking structure is formed;

[0087] Film placement method: The composite film is hung on the curing rack to avoid curling and contact adhesion.

[0088] S4. Processing of the PE / PE composite film for the middle-seal folded edge bag, including transverse seal welding and gluing reinforcement of the folded edge area;

[0089] The bag making process of the center-seal folding bag comprises the following steps:

[0090] S41. Cut and fold the composite film according to the size requirements of the center-seal folded edge bag to form an initial bag shape with folded sides and butt-jointed in the middle. The folding edge width is 10mm-15mm and the folding edge angle is 90° to ensure that the bag body can maintain structural stability when subjected to stress.

[0091] S42. Perform transverse sealing welding at both ends of the bag body, the width of the transverse sealing area is 8mm-12mm, and the welding is completed using heat sealing equipment;

[0092] The horizontal seal welding temperature is controlled according to the following formula:

[0093] T h =T m,h +ΔT

[0094] Among them, T h is the horizontal seal welding temperature, in °C, T m,h is the melting point temperature of the heat-sealing film, ΔT = 10°C-20°C; the welding temperature range is 110°C-120°C, the welding pressure is set to 0.3MPa-0.6MPa, and the welding time is set to 0.8s-1.5s;

[0095] S43. The middle docking area of ​​the bag body is longitudinally welded, and the width of the welded area is 5mm-10mm. The same welding temperature, pressure and time parameters are used to ensure the continuity of the welded area and form a strong longitudinal middle seal structure.

[0096] S44. Apply glue in dots on the folded areas on both sides of the bag body. The volume of each dot of glue is calculated according to the following formula:

[0097] V g =πr 2 h g

[0098] Among them, V g is the volume of glue applied at each point, in m 3 , r is the radius of the glue application point, in mm, h gis the height of the glue coating point, in mm; the distance between the glue coating points is 10mm-15mm, ensuring the stability and durability of the folding structure

[0099] S45. After completing the welding and gluing, the bag body is cooled and shaped to make the bag body flat as a whole, ensuring that it is suitable for packaging heavy objects such as flour.

[0100] S5. Carry out performance tests on the manufactured flour packaging bags, including tensile strength test, heat seal strength test and tear resistance test, to ensure that they meet the high-strength packaging requirements.

[0101] The performance of the flour packaging bag meets the following indicators:

[0102] Tensile strength σ≥25MPa;

[0103] Heat seal strength S h ≥6N / mm;

[0104] Tear strength T s ≥0.35N / mm.

[0105] The thickness and bonding strength of the composite film must meet the following requirements:

[0106] Thickness requirements:

[0107] Printing layer unstretched PE film thickness t p =30μm-50μm;

[0108] Thickness of unstretched PE film of heat sealing layer t h =40μm-60μm;

[0109] Glue layer thickness d g =3μm-5μm.

[0110] Peel strength test:

[0111] Peel strength h Calculated using the following formula:

[0112]

[0113] Among them, S h is the peel strength (unit: N / mm), F p is the peeling force (unit: N), W h is the peeling width (unit: mm);

[0114] The test results require peel strength S h ≥6N / mm to ensure that the composite film does not separate between layers during subsequent processing and use.

[0115] The composite film prepared through the above-mentioned gluing, laminating and curing steps has a stable structure and good interlayer adhesion performance, providing high-quality raw materials for the subsequent processing of center-seal gusseted bags. The thickness uniformity and peel strength of the composite film both meet the expected standards, laying a solid foundation for the reliability and durability of flour packaging bags.

[0116] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A flour packaging bag based on a single material composite, characterized in that: The invention is applied to a center-sealed folded edge bag and an eight-side-sealed folded edge packaging bag, comprising a bag body (11) and a bag side (12) applied to the center-sealed folded edge bag, wherein the side edges of the bag body (11) are connected end to end and then sealed to form a center-sealed portion (13), and the end faces of the bag body (11) and the bag side (12) are connected and then sealed to form a transverse seal portion (14), and a rubber strip (15) is coated on the bag body (11) at the transverse seal portion (14). After the center-sealing is completed, the center-sealed portion (13) and the rubber strip (15) are fitted together, and the middle parts of the center-sealed portion (13) and the transverse seal portion (14) are coated with a sealing glue (21) and a sealing glue (22).

2. A flour packaging bag based on a single material composite according to claim 1, characterized in that: The bag body 1 (11) is composited by a substrate 1 (111) and a substrate 2 (112); the composite end portion of the substrate 1 (111) and the substrate 2 (112) is coated with a sealing glue 1 (21); and the edge sealing of the bag body 1 (11) is coated with a sealing glue 2 (22).

3. A flour packaging bag based on a single material composite according to claim 2, characterized in that: The invention also comprises a bag body 2 (31), a bag side 2 (32) and a bag bottom (33) applied to an eight-side sealed folding bag, wherein the side edges of the bag body 2 (31), the bag side 2 (32) and the bag bottom (33) are connected by sealing to form a side sealing portion (34).

4. A flour packaging bag based on a single material composite according to claim 3, characterized in that: The bag body 2 (31) is composited by substrate 3 (311) and substrate 4 (312), and the bag bottom (33) is composited by substrate 5 (331) and substrate 6 (332). The composite parts of substrate 3 (311), substrate 4 (312) and substrate 5 (331) and substrate 6 (332) are all coated with sealing glue 1 (21), and the edge sealing parts of the bag body 2 (31) and the bag bottom (33) are coated with sealing glue 2 (22).

5. A method for preparing a flour packaging bag based on a single material composite, characterized in that: Using a flour packaging bag based on a single material composite according to any one of claims 1 to 4 comprises the following steps: S1. Preparation of unstretched PE film for printing layer: low-density polyethylene is used as the base material, high temperature resistant additives, antioxidants and antistatic agents are added, and a printing layer film is formed by extrusion and cast molding; S2. Preparation of unstretched PE film for heat-sealing layer: using linear low-density polyethylene as substrate, adding low-temperature heat-sealing additive and toughening material, and forming heat-sealing layer film by extrusion and casting; S3. Using a dry lamination process, the printed layer unstretched PE film and the heat-sealed layer unstretched PE film are laminated to form a PE / PE composite film; S4. Processing of the PE / PE composite film for the production of center-seal folded bags, including transverse seal welding and gluing reinforcement of the folded edge area; S5. Carry out performance tests on the manufactured flour packaging bags, including tensile strength test, heat seal strength test and tear resistance test, to ensure that they meet the high-strength packaging requirements.

6. The method for preparing a flour packaging bag based on a single material composite according to claim 5, characterized in that: In the preparation of the unstretched PE film of the printing layer: The high temperature resistant additive is silicon oxide filler, and the addition ratio is 5%-8%; The addition ratios of antioxidant and antistatic agent are 0.1%-0.3% and 0.05%-0.1% respectively; The film thickness is controlled at 30μm-50μm.

7. The method for preparing a flour packaging bag based on a single material composite according to claim 5, characterized in that: In the preparation of the unstretched PE film of the heat sealing layer: The low-temperature heat-sealing aid is ethylene-vinyl acetate copolymer, and the addition ratio is 10%-15%; The toughening material is polyolefin elastomer, and the addition ratio is 5%-8%; The surface of the film is coated with a low-temperature heat-sealing coating with a coating thickness of 1-3 μm.

8. The method for preparing a flour packaging bag based on a single material composite according to claim 5, characterized in that: The dry compounding process comprises the following steps: S31. Apply environmentally friendly solvent-free polyurethane adhesive on the non-printing surface of the unstretched PE film of the printed layer, with a coating amount of 2g / m 2 -4g / m 2 ; S32. The lamination is completed at a lamination temperature of 80°C-100°C and a lamination pressure of 0.4MPa-0.8MPa; S33. Curing in an environment of 40°C-60°C for 24h-48h to form a final PE / PE composite film.

9. The method for preparing a flour packaging bag based on a single material composite according to claim 5, characterized in that: The bag making process of the center-seal folding bag comprises the following steps: S41. Perform welding in the transverse sealing area of ​​the composite film, the welding temperature is 110°C-120°C, the welding time is 0.8s-1.5s, and the welding pressure is 0.3MPa-0.6MPa; S42. Glue reinforcement is applied to the folded edge area of ​​the bag body, the folded edge width is 10mm-15mm, and the volume of the glue application point is determined by the glue application radius and height to ensure the strength and stability of the folded edge structure.

10. The method for preparing a flour packaging bag based on a single material composite according to claim 5, characterized in that: The performance of the flour packaging bag meets the following indicators: Tensile strength σ≥25MPa; Heat seal strength S h ≥6N / mm; Tear strength T s ≥0.35N / mm.

Images