Metal sealing high-temperature-cooking-resistant easy-to-uncover film, composite film, preparation method and application

Abstract

The invention relates to the technical field of composite films, and provides a metal sealing high-temperature-cooking-resistant easy-to-tear film, a composite film, a preparation method and application. According to the invention, high-temperature-resistant modified easy-to-tear resin is adopted as the raw material of the inner layer, and meanwhile, the type and dosage proportion of polypropylene used by the outer layer and the middle layer are strictly controlled, so that the high-temperature-resistant cooking easy-to-tear film for sealing metal is obtained; the metal sealing film resistant to high-temperature cooking and easy to uncover serves as a heat sealing layer, the heat sealing layer, a printing layer and a blocking layer form a composite film, and the obtained composite film has high sealing performance and certain pressure resistance, is easy to uncover, sanitary, safe, convenient and rapid when being used in a sealing cover of a metal package, and improves the customer experience; compared with a can cover of a traditional metal packaging can, the composite film has the advantages of being easy to uncover, free of residues and wiredrawing, resistant to high-temperature steaming and boiling, free of hurting hands after being uncovered, exquisite in appearance and the like, and has wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of composite membrane technology, and in particular to a metal-sealed, high-temperature resistant, easy-to-remove, and easily peelable composite membrane, its preparation method, and its application. Background Technology

[0002] Metal cans are widely used in the food, beverage, and daily necessities industries due to their excellent sealing, pressure resistance, and shelf-life properties. Traditional metal can packaging typically uses a metal cap with a pull ring. Consumers need to pull the ring to separate the metal piece from the cap and open the can. However, this opening method poses a significant safety hazard. The edges of the metal piece are extremely sharp, easily cutting fingers during use, causing consumer insecurity and negatively impacting the user experience.

[0003] Although there are some improvements to the opening method of metal can packaging in existing technologies, such as optimizing the pull ring structure and adding protective design, these improvements have not fundamentally solved the problem of sharp iron pieces, and have increased production costs and packaging complexity, making them difficult to apply widely in actual production. Summary of the Invention

[0004] In view of this, the present invention provides a heat-resistant, retortable, easy-open film for sealing metal containers, a composite film, a preparation method, and applications. The heat-resistant, retortable, easy-open film for sealing metal containers provided by the present invention can be heat-sealed with metal cans and is resistant to high-temperature retorting. When the heat-resistant, retortable, easy-open film for sealing metal containers is prepared into a composite film and used as a sealing cap for metal packaging containers, it has advantages such as easy opening, high-temperature resistance, and gentle opening, fundamentally solving the safety problems of traditional iron caps used in metal packaging.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A metal-sealing, high-temperature resistant, easy-to-remove film for boiling includes an outer layer, a middle layer, and an inner layer arranged sequentially.

[0007] The raw materials for preparing the outer layer, by weight, include 25-85 parts of first polypropylene, 10-55 parts of second polypropylene, and 0.5-1 parts of processing aids.

[0008] By weight, the raw materials for preparing the middle layer include 20-70 parts of third polypropylene, 10-50 parts of fourth polypropylene, and 0.5-1.5 parts of processing aids.

[0009] The raw materials for preparing the inner layer, by weight, include 100 parts of high-temperature resistant modified easy-to-peel resin and 0.5 to 1 part of processing aids;

[0010] The first polypropylene is homopolymer polypropylene, the second polypropylene is random copolymer polypropylene, and the third and fourth polypropylenes are block copolymer polypropylene;

[0011] The melt index of the first polypropylene is 7-9 g / 10 min; the melt index of the second polypropylene is 1.8-2.5 g / 10 min; the melt index of the third polypropylene is 3.8-5.5 g / 10 min; the melt index of the fourth polypropylene is 4-6 g / 10 min; and the melt index of the high-temperature resistant modified easy-peel resin is 6.5-8.5 g / 10 min.

[0012] Preferably, the density of the first polypropylene is 0.890–0.910 g / cm³. 3 The density of the second polypropylene is 0.890–0.910 g / cm³. 3 The density of the third polypropylene is 0.890–0.910 g / cm³. 3 The density of the fourth type of polypropylene is 0.890–0.910 g / cm³. 3 ;

[0013] The density of the high-temperature resistant modified easy-peel resin is 0.900–0.925 g / cm³. 3 The processing aid has a melt index of 5.0–7.0 g / 10 min and a density of 0.890–0.910 g / cm³. 3 .

[0014] Preferably, the first polypropylene is HP510M; the second polypropylene is RC124H; the third polypropylene is J410F; the fourth polypropylene is BI305; the high-temperature resistant modified easy-peel resin is EPR6215; and the processing aid is PA0833PPR.

[0015] Preferably, based on the total mass of the raw materials used in the preparation of the outer layer, middle layer and inner layer, the mass fraction of the raw materials used in the preparation of the outer layer is 20-35%, the mass fraction of the raw materials used in the preparation of the middle layer is 40-60%, and the mass fraction of the raw materials used in the preparation of the inner layer is 20-35%.

[0016] The present invention also provides a method for preparing the high-temperature resistant, easy-to-remove metal sealing film described above, comprising the following steps:

[0017] The raw materials for the outer, middle, and inner layers are co-extruded in three layers to obtain the sealing metal high-temperature resistant and easy-to-remove film.

[0018] Preferably, the three-layer co-extrusion includes: the raw materials for preparing the outer layer, middle layer and inner layer are melted and plasticized by the outer layer extruder, the middle layer extruder and the inner layer extruder respectively, and the resulting adhesive solution is transported to the die head for extrusion blown film;

[0019] The outer, middle, and inner extruders are each equipped with five heating zones, numbered 1 to 5 sequentially from the feed end to the discharge end. The outer extruder has zone 1 with a temperature of 195–205°C, zone 2 with 200–210°C, zone 3 with 205–215°C, zone 4 with 203–213°C, and zone 5 with 201–211°C. The middle extruder has zone 1 with a temperature of… The temperatures in zones 1, 2, 3, 4, and 5 are as follows: Zone 1: 200–210℃; Zone 2: 205–215℃; Zone 3: 210–220℃; Zone 4: 205–215℃; Zone 5: 200–210℃. The temperatures in zones 1 and 5 of the inner extruder are as follows: Zone 1: 190–200℃; Zone 2: 195–205℃; Zone 3: 205–215℃; Zone 4: 200–210℃; Zone 5: 192–212℃.

[0020] The die head is provided with 4 heating zones, which are numbered 1 to 4 in order from the feed end to the discharge end; the temperature of zone 1 of the die head is 205 to 215°C, the temperature of zone 2 is 210 to 220°C, the temperature of zone 3 is 210 to 220°C, and the temperature of zone 4 is 205 to 215°C.

[0021] The present invention also provides a composite film comprising a printing layer, a barrier layer and a heat-sealing layer arranged sequentially; wherein the heat-sealing layer is the metal-sealed high-temperature resistant retort easy-to-peel film described in the above scheme or the metal-sealed high-temperature resistant retort easy-to-peel film prepared by the preparation method described in the above scheme.

[0022] Preferably, the printed layer is a polyester film and the barrier layer is an Al foil.

[0023] The present invention also provides a method for preparing the composite membrane described above, comprising the following steps:

[0024] After laminating the printed layer and the barrier layer with an adhesive, a first curing process is performed to obtain a printed layer / barrier layer composite film.

[0025] The composite film is obtained by bonding the printed layer / barrier layer composite film and the metal sealing high temperature resistant retort easy-to-remove film with an adhesive and then subjecting them to a second curing process.

[0026] The present invention also provides the application of the metal-sealing high-temperature resistant, easy-to-peel film or the composite film described above in the sealing caps of metal packaging cans.

[0027] This invention provides a high-temperature resistant, easy-to-peel metal sealing film, comprising an outer layer, a middle layer, and an inner layer arranged sequentially. By weight, the outer layer is prepared from 25-85 parts of a first polypropylene, 10-55 parts of a second polypropylene, and 0.5-1 part of a processing aid. By weight, the middle layer is prepared from 20-70 parts of a third polypropylene, 10-50 parts of a fourth polypropylene, and 0.5-1.5 parts of a processing aid. By weight, the inner layer is prepared from 100 parts of a high-temperature resistant modified easy-to-peel resin and 0.5-1.5 parts of a processing aid. One part; the first polypropylene is homopolymer polypropylene, the second polypropylene is random copolymer polypropylene, and the third and fourth polypropylenes are block copolymer polypropylene; the melt index of the first polypropylene is 7-9 g / 10 min; the melt index of the second polypropylene is 1.8-2.5 g / 10 min; the melt index of the third polypropylene is 3.8-5.5 g / 10 min; the melt index of the fourth polypropylene is 4-6 g / 10 min; the melt index of the high-temperature modified easy-open resin is 6.5-8.5 g / 10 min. This invention uses a high-temperature modified easy-open resin as the inner layer raw material, while strictly controlling the type and proportion of polypropylene used in the outer and middle layers. The resulting film has good high-temperature retortability and good heat-sealing performance with metal, and also has the advantage of being easy to open, showing broad application prospects in the field of metal packaging.

[0028] This invention also provides a composite film, comprising a printed layer, a barrier layer, and a heat-sealing layer arranged sequentially; the heat-sealing layer is the metal-sealed high-temperature retort-resistant easy-open film described in the above-described scheme or the metal-sealed high-temperature retort-resistant easy-open film prepared by the preparation method described in the above-described scheme. This invention uses the metal-sealed high-temperature retort-resistant easy-open film as the heat-sealing layer, forming a composite film with the printed layer and the barrier layer. The resulting composite film has high sealing performance and certain pressure resistance characteristics. When used in the sealing caps of metal packaging, it is easy to open, hygienic, safe, convenient, and quick, improving the customer experience. Compared with traditional metal packaging can lids, the composite film provided by this invention has many advantages such as easy opening, no residue, no stringing, high-temperature retort resistance, gentle opening, and beautiful appearance. It can be used in the packaging of food and beverages such as bird's nest, porridge, fish, meat, and pet food, and has broad application prospects. Detailed Implementation

[0029] This invention provides a metal-sealing, high-temperature resistant, easy-to-remove film, comprising an outer layer, a middle layer, and an inner layer arranged sequentially.

[0030] The raw materials for preparing the outer layer, by weight, include 25-85 parts of first polypropylene, 10-55 parts of second polypropylene, and 0.5-1 parts of processing aids.

[0031] By weight, the raw materials for preparing the middle layer include 20-70 parts of third polypropylene, 10-50 parts of fourth polypropylene, and 0.5-1.5 parts of processing aids.

[0032] The raw materials for preparing the inner layer, by weight, include 100 parts of high-temperature resistant modified easy-to-peel resin and 0.5 to 1 part of processing aids;

[0033] The first polypropylene is homopolymer polypropylene, the second polypropylene is random copolymer polypropylene, and the third and fourth polypropylenes are block copolymer polypropylene;

[0034] The melt index of the first polypropylene is 7-9 g / 10 min; the melt index of the second polypropylene is 1.8-2.5 g / 10 min; the melt index of the third polypropylene is 3.8-5.5 g / 10 min; the melt index of the fourth polypropylene is 4-6 g / 10 min; and the melt index of the high-temperature resistant modified easy-peel resin is 6.5-8.5 g / 10 min.

[0035] By weight, the raw materials for preparing the outer layer include 25-85 parts of a first polypropylene, specifically 30 parts, 38 parts, 43 parts, 55 parts, 62 parts, or 85 parts; the first polypropylene is homopolymer polypropylene; the melt index of the first polypropylene is 7-9 g / 10 min, preferably 8-8.5 g / 10 min; the density of the first polypropylene is preferably 0.890-0.910 g / cm³. 3 Specifically, it can be 0.895–0.9 g / cm³. 3 In a specific embodiment of the present invention, the first polypropylene is grade HP510M, with a melt index of 8 g / 10 min, a density of 0.9 g / cm3, and is manufactured by CNOOC Shell. The first polypropylene used in the present invention has the characteristics of good temperature resistance, high adhesion to aluminum foil, and few crystal points.

[0036] Based on the mass fraction of the first polypropylene used in the outer layer, the raw materials for preparing the outer layer include 10 to 55 parts of a second polypropylene, specifically 12, 18, 22, 35, 48, or 55 parts; the second polypropylene is a random copolymer polypropylene; the melt index of the second polypropylene is 1.8 to 2.5 g / 10 min, preferably 2 to 2.2 g / 10 min, and the density of the second polypropylene is preferably 0.890 to 0.910 g / cm³. 3 Specifically, it can be 0.895–0.9 g / cm³. 3 In a specific embodiment of the present invention, the second polypropylene is grade RC124H, with a melt index of 2.2 g / 10 min and a density of 0.9 g / cm³. 3 The manufacturer is Basel; the second polypropylene used in this invention has the characteristics of good temperature resistance, few crystal points, and easy processing.

[0037] Based on the mass fraction of the first polypropylene used in the outer layer, the raw materials for preparing the outer layer include 0.5 to 1 part of processing aids, specifically 0.8 parts; the melt index of the processing aids is preferably 5.0 to 7.0 g / 10 min, more preferably 6 to 6.5 g / 10 min, and the density is preferably 0.890 to 0.910 g / cm³. 3 More preferably 0.9 g / cm³ 3 In a specific embodiment of the present invention, the preferred grade of the processing aid is PA0833PPR, which has a melt index of 6 g / 10 min and a density of 0.9 g / cm3, and is manufactured by Suzhou Constance Engineering Plastics Co., Ltd. The processing aid used in the present invention has high temperature resistance, which can effectively reduce die accumulation, reduce crystal points, lower extrusion pressure, and improve production efficiency.

[0038] By weight, the raw materials for preparing the middle layer include 20-70 parts of third polypropylene, specifically 23 parts, 35 parts, 45 parts, 54 parts, 62 parts, or 70 parts; the third polypropylene is a block copolymer polypropylene; the melt index of the third polypropylene is 3.8-5.5 g / 10 min, preferably 4.5-5 g / 10 min, and the density of the third polypropylene is preferably 0.890-0.910 g / cm³. 3 Specifically, it can be 0.895–0.9 g / cm³. 3 In a specific embodiment of the present invention, the grade of the third polypropylene is J410F, with a melt index of 4.5 g / 10 min and a density of 0.9 g / cm3, and the manufacturer is Hyosung of South Korea; the third polypropylene used in the present invention has the characteristics of good temperature resistance, high stiffness and few crystal points.

[0039] Based on the mass fraction of the third polypropylene used in the middle layer, the raw materials for preparing the middle layer include 10 to 50 parts of a fourth polypropylene, specifically 12, 20, 25, 33, 42, or 48 parts; the fourth polypropylene is a block copolymer polypropylene; the melt index of the fourth polypropylene is 4 to 6 g / 10 min, preferably 5 to 5.5 g / 10 min; the density of the fourth polypropylene is preferably 0.890 to 0.910 g / cm³. 3 Specifically, it can be 0.895–0.9 g / cm³. 3 In a specific embodiment of the present invention, the fourth polypropylene is grade BI305, with a melt index of 5 g / 10 min and a density of 0.9 g / cm³. 3 The manufacturer is Samsung of South Korea; the fourth type of polypropylene used in this invention has the characteristics of good temperature resistance, high stiffness, few crystal points and good processing.

[0040] Based on the mass fraction of the third polypropylene used in the middle layer, the raw materials for preparing the middle layer include 0.5 to 1.5 parts of processing aids, specifically 0.7 parts; the types and brands of processing aids used in the middle layer are the same as those in the outer layer, and will not be repeated here.

[0041] The inner layer is prepared from 100 parts by weight of a high-temperature resistant modified easy-peel resin. In this invention, the melt index of the high-temperature resistant modified easy-peel resin is 6.5–8.5 g / 10 min, preferably 7.5–8 g / 10 min, and the density of the high-temperature resistant modified easy-peel resin is preferably 0.900–0.925 g / cm³. 3 More preferably, it is 0.915–0.920 g / cm³. 3 In a specific embodiment of the present invention, the high-temperature resistant modified easy-peel resin is grade EPR6215, with a melt index of 7.5 g / 10 min and a density of 0.915 g / cm3. It was purchased from Shanghai Mozhong Industrial Co., Ltd., and the manufacturer is Anhui Baike New Material Technology Co., Ltd. The high-temperature resistant modified easy-peel resin used in the present invention has excellent heat resistance and easy-peel performance, and peels off smoothly without delamination or stringing.

[0042] Based on the mass fraction of the high-temperature resistant modified easy-to-peel resin used in the inner layer, the raw materials for preparing the inner layer include 0.5 to 1 part of processing aids, specifically 1 part; the types and brands of processing aids used in the inner layer are the same as those in the outer layer, and will not be repeated here.

[0043] In this invention, taking the total mass of the raw materials used in the preparation of the outer layer, middle layer, and inner layer as 100%, the mass fraction of the raw materials used in the preparation of the outer layer is 20-35%, specifically 20%, 25%, 30%, or 35%; the mass fraction of the raw materials used in the preparation of the middle layer is 40-60%, specifically 45%, 50%, or 60%; and the mass fraction of the raw materials used in the preparation of the inner layer is 20-35%, specifically 20%, 25%, 30%, or 35%.

[0044] In this invention, the thickness of the heat-resistant, easy-to-remove metal sealing film is preferably 35-80 μm, more preferably 50 μm.

[0045] In this invention, the longitudinal tensile strength of the heat-resistant, easy-to-peel metal sealing film is preferably 44-46.5%, the transverse tensile strength is preferably 40-42%, the longitudinal elongation at break is preferably 625-650%, the transverse elongation at break is preferably 715-730%, the longitudinal modulus of elasticity is preferably 430-455 MPa, the transverse modulus of elasticity is preferably 430-465 MPa, and the wetting tension is preferably 45-50 mN / 15 mm.

[0046] This invention also provides a method for preparing the high-temperature resistant, easy-to-remove metal sealing film described above, comprising the following steps:

[0047] The raw materials for the outer, middle, and inner layers are co-extruded in three layers to obtain the sealing metal high-temperature resistant and easy-to-remove film.

[0048] In this invention, the three-layer co-extrusion preferably includes: the raw materials for preparing the outer layer, middle layer and inner layer are melted and plasticized by the outer layer extruder, the middle layer extruder and the inner layer extruder respectively, and the resulting adhesive liquid is transported to the die head for extrusion blown film.

[0049] In this invention, the outer extruder, middle extruder, and inner extruder are each equipped with five heating zones, which are sequentially designated as zones 1 to 5 from the feed end to the discharge end. The preferred temperature for zone 1 of the outer extruder is 195–205°C, more preferably 200°C; the preferred temperature for zone 2 is 200–210°C, more preferably 205°C; the preferred temperature for zone 3 is 205–215°C, more preferably 210°C; the preferred temperature for zone 4 is 203–213°C, more preferably 208°C; and the preferred temperature for zone 5 is 201–211°C, more preferably 206°C. Similarly, the preferred temperature for zone 1 of the middle extruder is 200–210°C, more preferably 205°C; and the preferred temperature for zone 2 is... The preferred temperatures are 205–215°C, more preferably 210°C; the preferred temperatures for zone 3 are 210–220°C, more preferably 215°C; the preferred temperatures for zone 4 are 205–215°C, more preferably 210°C; and the preferred temperatures for zone 5 are 200–210°C, more preferably 205°C. The preferred temperatures for zone 1 of the inner extruder are 190–200°C, more preferably 195°C; the preferred temperatures for zone 2 are 195–205°C, more preferably 200°C; the preferred temperatures for zone 3 are 205–215°C, more preferably 210°C; the preferred temperatures for zone 4 are 200–210°C, more preferably 205°C; and the preferred temperatures for zone 5 are 192–212°C, more preferably 197°C.

[0050] In this invention, the die head preferably has four heating zones, which are sequentially labeled as zones 1 to 4 from the feed end to the discharge end. The temperature of zone 1 of the die head is preferably 205-215°C, more preferably 210°C; the temperature of zone 2 is preferably 210-220°C, more preferably 215°C; the temperature of zone 3 is preferably 210-220°C, more preferably 215°C; and the temperature of zone 4 is preferably 205-215°C, more preferably 210°C.

[0051] In this invention, the extrusion pressure of the outer extruder is preferably 205-265 bar, more preferably 248 bar; the extrusion pressure of the middle extruder is preferably 280-345 bar, more preferably 315 bar; and the extrusion pressure of the inner extruder is preferably 255-325 bar, more preferably 265 bar.

[0052] In this invention, the extrusion blown film preferably adopts an upward blowing process; the extrusion blown film obtains a film bubble, which is preferably cooled by air and then traction-rotated by a stabilizing ring and a herringbone pattern to flatten the film bubble, followed by corona treatment, edge trimming and winding to obtain the metal-sealing high-temperature resistant and easy-to-peel film.

[0053] The present invention also provides a composite film comprising a printing layer, a barrier layer and a heat-sealing layer arranged sequentially from the outside to the inside; the heat-sealing layer is the metal-sealed high-temperature resistant retort easy-to-peel film described in the above scheme or the metal-sealed high-temperature resistant retort easy-to-peel film prepared by the preparation method described in the above scheme.

[0054] In this invention, the printed layer is preferably a polyester (PET) film, and the barrier layer is preferably an Al foil.

[0055] In this invention, the thickness of the polyester film is preferably 12 μm, and the corona value of the printed surface of the polyester film is preferably greater than 52 dynes; the use of the above-mentioned polyester film in this invention can improve the composite strength; the thickness of the Al foil is preferably 60 μm, and the Al foil is preferably Grade A Al foil; the use of the above-mentioned Al foil in this invention can improve the barrier properties.

[0056] The present invention also provides a method for preparing the composite membrane described above, comprising the following steps:

[0057] After laminating the printed layer and the barrier layer with an adhesive, a first curing process is performed to obtain a printed layer / barrier layer composite film.

[0058] The composite film is obtained by bonding the printed layer / barrier layer composite film and the metal sealing high temperature resistant retort easy-to-remove film with an adhesive and then subjecting them to a second curing process.

[0059] This invention involves bonding a printed layer and a barrier layer with an adhesive (referred to as the first bonding) followed by a first curing process to obtain a printed layer / barrier layer composite film. In this invention, the printed layer is preferably printed before bonding with the barrier layer, according to requirements. This invention does not have special requirements for the printing method; gravure printing, a process well-known to those skilled in the art, is sufficient. The ink used for printing is preferably a retort-resistant ink. In this invention, the first bonding is preferably a dry bonding process. The adhesive used in the first bonding preferably includes a polyurethane adhesive and a curing agent. In a specific embodiment of this invention, the polyurethane adhesive is preferably Dow Chemical's high-performance retort polyurethane adhesive 811A with a solid content of 60%, and the curing agent is preferably 9L10 with a solid content of 75%. When using, it is preferable to mix the polyurethane adhesive and the curing agent, with a preferred mixing mass ratio of 100:8. The amount of adhesive applied in the first bonding is preferably 4-5 g / m³. 2 In a specific embodiment of the present invention, the first composite is preferably performed by a composite heating roller, the temperature of which is preferably 70-75°C and the composite speed is preferably 110-120 m / min; the temperature of the first curing is preferably 45-55°C, more preferably 50°C, and the curing time is preferably 36-48 h.

[0060] After obtaining the printed layer / barrier layer composite film, the present invention further combines the printed layer / barrier layer composite film and the PE gasket film with an adhesive (denoted as the second composite) and then performs a second curing to obtain the composite film. In the present invention, the second composite is preferably a dry composite; the adhesive used in the second composite is preferably the same as that used in the first composite, and will not be described again here; the adhesive application amount in the second composite is preferably 3.5-4.5 g / m³. 2 In a specific embodiment of the present invention, the second composite is preferably performed by a composite heating roller, the temperature of which is preferably 70-75°C and the composite speed is preferably 110-120 m / min; in the present invention, the temperature of the second curing is preferably 45-55°C, more preferably 50°C, and the time is preferably 72 h; after the second curing is completed, the resulting composite film is preferably cooled at room temperature for 24 h and then cut.

[0061] This invention also provides the application of the high-temperature resistant, easy-to-peel metal sealing film or the composite film described above in the sealing caps of metal packaging cans. In an embodiment of this invention, the composite film is specifically heat-sealed with the metal packaging can to serve as a sealing cap. This invention does not have special requirements for the specific material of the metal packaging can; any commonly used metal packaging can in the art is acceptable, specifically aluminum. The preferred heat-sealing temperature is 121°C, the preferred pressure is 3 kg, and the preferred time is 1 second.

[0062] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0063] The manufacturers, melt index, and density of the raw materials used in the following examples are shown in Table 1.

[0064] Table 1. Manufacturers, melt indexes, and densities of the raw materials used in the examples.

[0065]

[0066]

[0067] Example 1

[0068] 1. Preparation of a high-temperature resistant, easy-to-remove metal sealing film

[0069] The metal-sealing, high-temperature resistant, easy-to-remove film provided by this invention has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each of the three layers are as follows: 30% for the outer layer, 50% for the middle layer, and 20% for the inner layer.

[0070] The raw materials for the preparation of the outer layer, by mass, are: 30 parts of homopolymer polypropylene HP510M, 55 parts of random copolymer polypropylene RC124H, and 0.8 parts of processing aid PA0833PPR.

[0071] By weight, the raw materials for preparing the middle layer are: 45 parts of block copolymer polypropylene J410F, 25 parts of block copolymer polypropylene BI305, and 0.7 parts of processing aid PA0833PPR.

[0072] By weight, the raw materials for preparing the inner layer are: 100 parts of high-temperature resistant modified easy-to-peel resin EPR6215 and 1 part of processing aid PA0833PPR.

[0073] The preparation method of the metal-sealed high-temperature retort-resistant easy-peel film is as follows: The raw materials for the outer, middle, and inner layers are mixed in proportion using an automatic batching system and then fed into the outer, middle, and inner layer extruders. After melting and plasticizing, the raw materials are fed into the die head for extrusion and top blowing. Following air cooling, the film passes through a stabilizing ring and a herringbone pattern, then is traction-rotated to flatten the cylinder. It then enters a corona treatment device via guide rollers for corona treatment. Finally, the edges are trimmed, and the film is wound forward and backward via lower traction clamping rollers into a front and rear winding device to obtain a 50μm metal-sealed high-temperature retort-resistant easy-peel film. The temperatures and pressures of the outer, middle, and inner layer extruders, as well as the die head temperature, are shown in Table 2.

[0074] Table 2 Extruder temperature and pressure, and die temperature

[0075] temperature Zone 1 Zone 2 Zone 3 4th District District 5 Pressure (bar) outer layer 200 205 210 208 206 248 Middle layer 205 210 215 210 205 315 Inner layer 195 200 210 205 197 265 mold head 210 215 215 210 / /

[0076] 2. Preparation of composite membranes

[0077] The composite film is prepared using the above-mentioned metal-sealed, high-temperature resistant, easy-to-remove film. The specific steps are as follows:

[0078] The polyester film (PET) used was purchased from Anhui Guofeng. The corona value of the printed surface of the polyester film was greater than 52 dynes, and the thickness was 12μm. The aluminum foil used was purchased from Shanghai Shenhuo Aluminum Foil Co., Ltd., and it was a grade A aluminum foil with a thickness of 60μm.

[0079] The printing layer of the polyester film is printed using gravure printing, and the ink used must be a retort-resistant ink. The printed polyester film is then laminated with aluminum foil using a dry lamination process. The adhesive used is Dow Chemical's high-performance retort polyurethane adhesive 811A (60% solids content), and the curing agent is 9L10 (75% solids content). The mixing ratio of the functional retort polyurethane adhesive to the curing agent is 100:8. The temperature of the lamination heating roller is controlled at 75℃, the lamination speed is 110 m / min, and the adhesive application rate is 4.8 g / m². 2 After lamination, the film is placed in a curing room at 50℃±5℃ for 48 hours to obtain a PET / AL composite film.

[0080] The PET / AL composite film was laminated with a metal-sealed, high-temperature retortable, easy-peel film using a dry lamination process. The adhesive used was Dow Chemical's high-performance retortable polyurethane adhesive 811A (60% solids content), and the curing agent was 9L10 (75% solids content). The mixing ratio of the high-performance retortable polyurethane adhesive to the curing agent was 100:8. The coating solids content was 35%. The temperature of the lamination heating roller was controlled at 70℃, the lamination speed was 120 m / min, and the adhesive application rate was 4.0 g / m³. 2 After lamination, the composite film is placed in a curing room at 50℃±5℃ for 72 hours and then cut to obtain the composite film.

[0081] Example 2

[0082] 1. Preparation of a high-temperature resistant, easy-to-remove metal sealing film

[0083] The metal-sealing, high-temperature resistant, easy-to-remove film provided by this invention has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each of the three layers are as follows: outer layer 25%, middle layer 50%, and inner layer 25%.

[0084] By weight, the raw materials for the preparation of the outer layer are: 55 parts of homopolymer polypropylene HP510M, 22 parts of random copolymer polypropylene RC124H, and 0.8 parts of processing aid PA0833PPR.

[0085] By weight, the raw materials for preparing the middle layer are: 70 parts of block copolymer polypropylene J410F, 12 parts of block copolymer polypropylene BI305, and 0.7 parts of processing aid PA0833PPR.

[0086] By weight, the raw materials for preparing the inner layer are: 100 parts of high-temperature resistant modified easy-to-peel resin EPR6215 and 1 part of processing aid PA0833PPR.

[0087] The preparation method is the same as in Example 1.

[0088] 2. A composite film was prepared using the metal-sealing, high-temperature resistant, easy-to-remove film prepared in Example 2. The preparation method was the same as in Example 1.

[0089] Example 3

[0090] 1. Preparation of a high-temperature resistant, easy-to-remove metal sealing film

[0091] The metal-sealing, high-temperature resistant, easy-to-remove film provided by this invention has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each of the three layers are as follows: outer layer 20%, middle layer 60%, and inner layer 20%.

[0092] The raw materials for the preparation of the outer layer, by mass, are: 38 parts of homopolymer polypropylene HP510M, 48 parts of random copolymer polypropylene RC124H, and 0.8 parts of processing aid PA0833PPR.

[0093] By weight, the raw materials for preparing the middle layer are: 23 parts of block copolymer polypropylene J410F, 48 parts of block copolymer polypropylene BI305, and 0.7 parts of processing aid PA0833PPR.

[0094] By weight, the raw materials for preparing the inner layer are: 100 parts of high-temperature resistant modified easy-to-peel resin EPR6215 and 1 part of processing aid PA0833PPR.

[0095] The preparation method is the same as in Example 1.

[0096] 2. A composite film was prepared using the metal-sealing, high-temperature resistant, easy-to-remove film prepared in Example 3. The preparation method was the same as in Example 1.

[0097] Example 4

[0098] 1. Preparation of a high-temperature resistant, easy-to-remove metal sealing film

[0099] The metal-sealing, high-temperature resistant, easy-to-remove film provided by this invention has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each of the three layers are as follows: outer layer 25%, middle layer 45%, and inner layer 30%.

[0100] The raw materials for the preparation of the outer layer, by mass, are: 85 parts of homopolymer polypropylene HP510M, 12 parts of random copolymer polypropylene RC124H, and 0.8 parts of processing aid PA0833PPR.

[0101] By weight, the raw materials for preparing the middle layer are: 35 parts of block copolymer polypropylene J410F, 33 parts of block copolymer polypropylene BI305, and 0.7 parts of processing aid PA0833PPR.

[0102] By weight, the raw materials for preparing the inner layer are: 100 parts of high-temperature resistant modified easy-to-peel resin EPR6215 and 1 part of processing aid PA0833PPR.

[0103] The preparation method is the same as in Example 1.

[0104] 2. A composite membrane was prepared using the metal-sealing, high-temperature resistant, easy-to-remove film prepared in Example 4. The preparation method was the same as in Example 1.

[0105] Example 5

[0106] 1. Preparation of a high-temperature resistant, easy-to-remove metal sealing film

[0107] The metal-sealing, high-temperature resistant, easy-to-remove film provided by this invention has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each of the three layers are as follows: outer layer 20%, middle layer 45%, and inner layer 35%.

[0108] The raw materials for the preparation of the outer layer, by mass, are: 62 parts of homopolymer polypropylene HP510M, 18 parts of random copolymer polypropylene RC124H, and 0.8 parts of processing aid PA0833PPR.

[0109] By weight, the raw materials for preparing the middle layer are: 54 parts of block copolymer polypropylene J410F, 54 parts of block copolymer polypropylene BI30, and 0.7 parts of processing aid PA0833PPR.

[0110] By weight, the raw materials for preparing the inner layer are: 100 parts of high-temperature resistant modified easy-to-peel resin EPR6215 and 1 part of processing aid PA0833PPR.

[0111] The preparation method is the same as in Example 1.

[0112] 2. A composite membrane was prepared using the metal-sealing, high-temperature resistant, easy-to-remove film prepared in Example 5. The preparation method was the same as in Example 1.

[0113] Example 6

[0114] 1. Preparation of a high-temperature resistant, easy-to-remove metal sealing film

[0115] The metal-sealing, high-temperature resistant, easy-to-remove film provided by this invention has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each of the three layers are as follows: 30% for the outer layer, 45% for the middle layer, and 25% for the inner layer.

[0116] The raw materials for the preparation of the outer layer, by mass, are: 43 parts of homopolymer polypropylene HP510M, 35 parts of random copolymer polypropylene RC124H, and 0.8 parts of processing aid PA0833PPR.

[0117] By weight, the raw materials for preparing the middle layer are: 62 parts of block copolymer polypropylene J410F, 20 parts of block copolymer polypropylene BI305, and 0.7 parts of processing aid PA0833PPR.

[0118] By weight, the raw materials for preparing the inner layer are: 100 parts of high-temperature resistant modified easy-to-peel resin EPR6215 and 1 part of processing aid PA0833PPR.

[0119] The preparation method is the same as in Example 1.

[0120] 2. A composite film was prepared using the metal-sealing, high-temperature resistant, easy-to-remove film prepared in Example 6, and the preparation method was the same as in Example 1.

[0121] Comparative Example 1

[0122] The polypropylene film provided by this invention has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each of the three layers are as follows: 25% for the outer layer, 50% for the middle layer, and 25% for the inner layer.

[0123] By weight, the raw materials for the preparation of the outer layer are: 20 parts of homopolymer polypropylene HP510M, 75 parts of random copolymer polypropylene RC124H, and 0.8 parts of processing aid PA0833PPR.

[0124] By weight, the raw materials for preparing the middle layer are: 70 parts of block copolymer polypropylene J410F, 12 parts of block copolymer polypropylene BI305, and 0.7 parts of processing aid PA0833PPR.

[0125] By weight, the raw materials for preparing the inner layer are: 100 parts of high-temperature resistant modified easy-to-peel resin EPR6215 and 1 part of processing aid PA0833PPR.

[0126] The preparation method is the same as in Example 1.

[0127] 2. A composite membrane was prepared using the polypropylene membrane prepared in Comparative Example 1, and the preparation method was the same as in Example 1.

[0128] Performance testing

[0129] The mechanical properties and wetting tension of the metal-sealing, high-temperature-resistant, easy-to-peel films prepared in Examples 1-6 and Comparative Example 1 were tested. The test methods and results are shown in Table 3.

[0130] Table 3. Test Results of High-Temperature Resistant and Easy-Removable Metal Sealing Film

[0131]

[0132]

[0133] As can be seen from the results in Table 1, the metal-sealing, high-temperature resistant, easy-to-remove film provided by the present invention has excellent mechanical and wetting properties.

[0134] The mechanical properties, boiling resistance, permeability, sealing properties, and ease of peeling of the composite films prepared in Examples 1-6 and Comparative Example 1 were tested. The test methods and results are shown in Table 4. Specifically, the heat seal strength was tested after heat sealing the composite film of the present invention with aluminum (the most common material for aluminum cans).

[0135] Table 4 Performance test results of composite membranes

[0136]

[0137]

[0138] As can be seen from the results in Table 4, the composite film provided by this invention has good mechanical properties, and the peel strength and heat seal strength do not change much before and after cooking, proving that it has excellent cooking resistance. At the same time, the water vapor transmission and oxygen transmission of the composite film are low, indicating good sealing performance. Moreover, the sealing material does not break when opened, the handle is intact, and it is easy to open and has reliable opening. In contrast, the proportion of polypropylene used in the outer layer of Comparative Example 1 was changed, and the peel strength and heat seal strength of the resulting composite film decreased significantly. At the same time, the sealing was not tight, and the sealing material did not break when opened, which could not meet the requirements for the use of metal packaging can sealing caps.

[0139] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A metal-sealing, high-temperature resistant, easy-to-remove film, characterized in that, This includes an outer layer, a middle layer, and an inner layer arranged sequentially. The raw materials for preparing the outer layer, by weight, include 25-85 parts of first polypropylene, 10-55 parts of second polypropylene, and 0.5-1 parts of processing aids. By weight, the raw materials for preparing the middle layer include 20-70 parts of third polypropylene, 10-50 parts of fourth polypropylene, and 0.5-1.5 parts of processing aids. The raw materials for preparing the inner layer, by weight, include 100 parts of high-temperature resistant modified easy-to-peel resin and 0.5 to 1 part of processing aids; The first polypropylene is homopolymer polypropylene, the second polypropylene is random copolymer polypropylene, and the third and fourth polypropylenes are block copolymer polypropylene; The melt index of the first polypropylene is 7-9 g / 10 min; the melt index of the second polypropylene is 1.8-2.5 g / 10 min; the melt index of the third polypropylene is 3.8-5.5 g / 10 min; the melt index of the fourth polypropylene is 4-6 g / 10 min; and the melt index of the high-temperature resistant modified easy-peel resin is 6.5-8.5 g / 10 min.

2. The metal-sealing, high-temperature resistant, easy-to-remove film according to claim 1, characterized in that, The density of the first polypropylene is 0.890–0.910 g / cm³. 3 The density of the second polypropylene is 0.890–0.910 g / cm³. 3 The density of the third polypropylene is 0.890–0.910 g / cm³. 3 The density of the fourth type of polypropylene is 0.890–0.910 g / cm³. 3 ; The density of the high-temperature resistant modified easy-peel resin is 0.900–0.925 g / cm³. 3 The processing aid has a melt index of 5.0–7.0 g / 10 min and a density of 0.890–0.910 g / cm³. 3 .

3. The metal-sealing, high-temperature resistant, easy-to-remove film according to any one of claims 1 to 2, characterized in that, The first polypropylene is HP510M; the second polypropylene is RC124H; the third polypropylene is J410F; the fourth polypropylene is BI305; the high-temperature resistant modified easy-peel resin is EPR6215; and the processing aid is PA0833PPR.

4. The metal-sealing, high-temperature resistant, easy-to-remove film according to claim 1, characterized in that, Based on the total mass of the raw materials used in the preparation of the outer layer, middle layer and inner layer as 100%, the mass fraction of the raw materials used in the preparation of the outer layer is 20-35%, the mass fraction of the raw materials used in the preparation of the middle layer is 40-60%, and the mass fraction of the raw materials used in the preparation of the inner layer is 20-35%.

5. The method for preparing the high-temperature resistant, easy-to-remove metal sealing film according to any one of claims 1 to 4, characterized in that, Includes the following steps: The raw materials for the outer, middle, and inner layers are co-extruded in three layers to obtain the sealing metal high-temperature resistant and easy-to-remove film.

6. The preparation method according to claim 5, characterized in that, The three-layer co-extrusion includes: the raw materials for the preparation of the outer layer, middle layer and inner layer are melted and plasticized by the outer layer extruder, the middle layer extruder and the inner layer extruder respectively, and the resulting adhesive liquid is transported to the die head for extrusion blown film; The outer, middle, and inner extruders are each equipped with five heating zones, numbered 1 to 5 sequentially from the feed end to the discharge end. The outer extruder has zone 1 with a temperature of 195–205°C, zone 2 with 200–210°C, zone 3 with 205–215°C, zone 4 with 203–213°C, and zone 5 with 201–211°C. The middle extruder has zone 1 with a temperature of… The temperatures in zones 1, 2, 3, 4, and 5 are as follows: Zone 1: 200–210℃; Zone 2: 205–215℃; Zone 3: 210–220℃; Zone 4: 205–215℃; Zone 5: 200–210℃. The temperatures in zones 1 and 5 of the inner extruder are as follows: Zone 1: 190–200℃; Zone 2: 195–205℃; Zone 3: 205–215℃; Zone 4: 200–210℃; Zone 5: 192–212℃. The die head is provided with 4 heating zones, which are numbered 1 to 4 in order from the feed end to the discharge end; the temperature of zone 1 of the die head is 205 to 215°C, the temperature of zone 2 is 210 to 220°C, the temperature of zone 3 is 210 to 220°C, and the temperature of zone 4 is 205 to 215°C.

7. A composite membrane, characterized in that, It includes a printing layer, a barrier layer and a heat-sealing layer arranged in sequence; the heat-sealing layer is the metal-sealing high-temperature resistant retort easy-to-peel film according to any one of claims 1 to 4 or the metal-sealing high-temperature resistant retort easy-to-peel film prepared by the preparation method according to claim 5 or 6.

8. The composite membrane according to claim 7, characterized in that, The printed layer is a polyester film, and the barrier layer is an Al foil.

9. The method for preparing the composite membrane according to claim 7 or 8, characterized in that, Includes the following steps: After laminating the printed layer and the barrier layer with an adhesive, a first curing process is performed to obtain a printed layer / barrier layer composite film. The composite film is obtained by bonding the printed layer / barrier layer composite film and the metal sealing high temperature resistant retort easy-to-remove film with an adhesive and then subjecting them to a second curing process.

10. The application of the metal-sealing high-temperature resistant, easy-to-peel film according to any one of claims 1 to 3 or the composite film according to claim 7 or 8 in the sealing cap of metal packaging cans.

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