A high temperature resistant modified polypropylene film and its preparation method and container liner bag

Abstract

The invention discloses a kind of high temperature resistant modified polypropylene film and its preparation method and container liner bag, belong to the technical field of preparation of packaging film, it includes film body, characterised in that: film body is composed of outermost layer, sub-outer layer, middle layer, sub-inner layer and innermost layer from outside to inside in sequence; outermost layer and innermost layer are both made of 32-40 parts by mass of homopolymerised polypropylene, 8-10 parts by mass of ethylene-propylene-1-butene block copolymer, 8-10 parts by mass of hydrogenated styrene-butadiene block copolymer and 5-7 parts by mass of ethylene-high alpha-olefin copolymer, sub-outer layer and sub-inner layer are both made of 13-17 parts by mass of homopolymerised polypropylene, 8-10 parts by mass of metallocene polyethylene and 5-7 parts by mass of ethylene-propylene-1-butene block copolymer, and middle layer is made of 18-22 parts by mass of linear low density polyethylene. This film can improve the strength and flexibility of film body, and enhance the connection strength of heat sealing at high temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging film preparation, and specifically relates to a high-temperature resistant modified polypropylene film and a preparation method thereof, and a container liner bag. Background Art

[0002] With the increase in logistics and transportation needs, container transportation has a growing share in modern logistics and transportation due to its certain protection strength and the convenience of replacing transportation tools in the middle of the journey. In order to reduce the cleaning costs of containers and increase the available time of containers, most containers are lined with liner bags, and the materials are placed in the liner bags so that they do not come into direct contact with the containers. After transporting one material, the liner bags are replaced to avoid contamination between different materials.

[0003] At present, the liner bags are basically made of polyethylene film, and the temperature resistance of polyethylene is generally 70-90℃. The production temperature of some industrial materials is relatively high, even up to 120℃ or above, which requires the high-temperature materials to be cooled first and then packed into containers after cooling to a safe temperature range. This not only increases the cooling equipment and space, but also increases the transfer operations caused by cooling, which increases the labor cost. Therefore, it is desired to have a high-temperature resistant container liner bag that can directly load the high-temperature materials produced into the container.

[0004] Polypropylene has higher temperature resistance than polyethylene because it has more molecular branches than polyethylene, but polypropylene film has the disadvantages of poor toughness, hard texture and low sealing strength when heat-sealed into bags. The invention patent with publication number CN110065284A discloses a cold-resistant and tear-resistant high-temperature cooking packaging material and a preparation method. The film layer structure of the packaging material is biaxially oriented polyester film, aluminum foil and modified polypropylene film in sequence; the modified polypropylene film includes a corona layer, an intermediate layer and a heat-sealing layer, wherein the corona layer is composed of ternary random copolymer polypropylene, the intermediate layer is composed of random copolymer polypropylene and hydrogenated styrene-butadiene block copolymer in a mass ratio of (83-87):(13-17), and the heat-sealing layer is composed of ternary random copolymer polypropylene and hydrogenated styrene-butadiene block copolymer in a mass ratio of (93-97):(4-6):(0.8-1.2):(0.8-1.2):(0.1-0.3), a lubricant, an opening masterbatch and a processing aid. Although this packaging material meets the requirements of high-temperature cooking resistance, on the one hand, it is used for food packaging and is very small, and is not in the same volume class as bulk bags; on the other hand, it uses aluminum foil, which increases aluminum consumption and increases costs, and the strength and flexibility of the modified polypropylene film are still not high, and it mainly relies on the reinforcement effect of the biaxially oriented polyester film and aluminum foil. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a high temperature resistant modified polypropylene film and a preparation method thereof and a container liner bag, which can improve the strength and flexibility of the film body.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: design a high temperature resistant modified polypropylene film, including a film body, characterized in that: the film body is composed of an outermost layer, a second outermost layer, a middle layer, a second inner layer and an innermost layer from the outside to the inside;

[0007] The outermost layer and the innermost layer are made of the following raw materials in parts by weight:

[0008] Homopolymer polypropylene 32-40 parts

[0009] 8-10 parts of ethylene-propylene-1-butene block copolymer

[0010] 8-10 parts of hydrogenated styrene-butadiene block copolymer

[0011] Ethylene-higher α-olefin copolymer 5-7 parts

[0012] The sub-outer layer and the sub-inner layer are made of the following raw materials in parts by weight:

[0013] Homopolymer polypropylene 13-17 parts

[0014] Metallocene polyethylene 8-10 parts

[0015] 5-7 parts of ethylene-propylene-1-butene block copolymer

[0016] The middle layer is made of 18 to 22 parts by weight of linear low-density polyethylene.

[0017] Furthermore, the outermost layer and the innermost layer are made of the following raw materials in parts by weight:

[0018] Homopolymer polypropylene 36 parts

[0019] 9 parts of ethylene-propylene-1-butene block copolymer

[0020] 9 parts of hydrogenated styrene-butadiene block copolymer

[0021] Ethylene-higher α-olefin copolymer 6 parts

[0022] The sub-outer layer and the sub-inner layer are made of the following raw materials in parts by weight:

[0023] Homopolymer polypropylene 15 parts

[0024] Metallocene polyethylene 9 parts

[0025] 6 parts of ethylene-propylene-1-butene block copolymer

[0026] The middle layer was made of 20 parts by mass of linear low-density polyethylene.

[0027] Furthermore, the thickness of the membrane body is 130-150 μm.

[0028] The present invention also provides a method for preparing a high temperature resistant modified polypropylene film, which is characterized by comprising the following steps:

[0029] (1) preparing a first special material: dry-mixing 32 to 40 parts by weight of homopolypropylene, 8 to 10 parts by weight of ethylene-propylene-1-butene block copolymer, 8 to 10 parts by weight of hydrogenated styrene-butadiene block copolymer and 5 to 7 parts by weight of ethylene-higher α-olefin copolymer to obtain a first mixed material, and granulating the first mixed material to obtain a first special material;

[0030] (2) preparing a second special material: dry-mixing 13 to 17 parts by weight of homopolypropylene, 8 to 10 parts by weight of metallocene polyethylene and 5 to 7 parts by weight of ethylene-propylene-1-butene block copolymer to obtain a second mixed material, and granulating the second mixed material to obtain a second special material;

[0031] (3) Co-extrusion film formation: The first special material prepared in step (1), the second special material prepared in step (2), the linear low-density polyethylene, the second special material prepared in step (2) and the first special material prepared in step (1) are subjected to multi-layer co-extrusion blow molding to form a polypropylene film having an outermost layer, a second outermost layer, a middle layer, a second innermost layer and a third innermost layer arranged in sequence from the outside to the inside.

[0032] Furthermore, in step (1), the first mixed material is composed of 36 parts by mass of homopolypropylene, 9 parts by mass of ethylene-propylene-1-butene block copolymer, 9 parts by mass of hydrogenated styrene-butadiene block copolymer and 6 parts by mass of ethylene-higher α-olefin copolymer;

[0033] In step (2), the second mixture is composed of 15 parts by mass of homopolypropylene, 9 parts by mass of metallocene polyethylene and 6 parts by mass of ethylene-propylene-1-butene block copolymer.

[0034] Furthermore, the extrusion temperature of the outermost layer and the innermost layer is 220-230°C, the extrusion temperature of the second inner layer and the second outer layer is 200-210°C, and the extrusion temperature of the middle layer is 175-185°C.

[0035] Furthermore, the granulation temperature of the first special material in step (1) is 210-230°C, and the granulation temperature of the second special material in step (2) is 210-230°C.

[0036] Furthermore, in step (3), the thickness of the prepared packaging film is 130 to 150 μm.

[0037] Furthermore, in step (3), the thickness ratios of the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the innermost layer are 3:1.5:1:1.5:3 respectively.

[0038] The present invention also provides a container liner bag, comprising a bag body, wherein the bag body is made by heat-sealing a polypropylene film, and is characterized in that the polypropylene film is the above-mentioned high-temperature resistant modified polypropylene film, or the high-temperature resistant modified polypropylene film made by the above-mentioned preparation method.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The raw material ratio of each layer of the present invention not only enhances the flexibility and strength of the polypropylene film, but also enhances the connection strength of the heat seal at high temperature, so that the container bag made of the modified film can receive materials at 135°C, so that the high-temperature materials produced can be directly packed.

[0041] 2. The present invention can enhance the compatibility between the materials, allowing the layers to be thermally fused together, thereby enhancing the overall performance of the film.

[0042] 3. The present invention has a unique concept. By improving the raw material formula, the membrane can directly contact the produced high-temperature materials, which broadens the application conditions and facilitates promotion and application in the industry. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with specific implementation modes.

[0044] When the present invention is in use, the side close to the packaged object is defined as the inner side, and the other side away from the packaged object is defined as the outer side. Embodiment 1

[0045] The high temperature resistant modified polypropylene film is prepared by the following steps:

[0046] (1) preparing a first special material: dry-mixing 32 parts by weight of homopolypropylene, 8 parts by weight of ethylene-propylene-1-butene block copolymer, 8 parts by weight of hydrogenated styrene-butadiene block copolymer and 5 parts by weight of ethylene-higher α-olefin copolymer to obtain a first mixed material, and granulating the first mixed material to obtain a first special material, wherein the granulation temperature of the first special material is 210° C.;

[0047] (2) preparing a second special material: dry-mixing 13 parts by weight of homopolypropylene, 8 parts by weight of metallocene polyethylene and 5 parts by weight of ethylene-propylene-1-butene block copolymer to obtain a second mixed material, and granulating the second mixed material to obtain a second special material. The granulation temperature of the second special material is 210° C.;

[0048] (3) Co-extrusion film forming: The first special material prepared in step (1), the second special material prepared in step (2), the linear low-density polyethylene, the second special material prepared in step (2) and the first special material prepared in step (1) are subjected to multi-layer co-extrusion blow molding to form a modified polypropylene film having an outermost layer, a second outermost layer, a middle layer, a second inner layer and an innermost layer arranged in sequence from the outside to the inside, the extrusion temperature of the outermost layer and the innermost layer is 220° C., the extrusion temperature of the second inner layer and the second outer layer is 200° C., and the extrusion temperature of the middle layer is 175° C. The thickness of the obtained modified polypropylene film is 130 μm, and the thickness ratio of the outermost layer, the second outermost layer, the middle layer, the second inner layer and the inner layer is 3:1.5:1:1.5:3 in sequence. Embodiment 2

[0049] The difference between this embodiment and the first embodiment is that:

[0050] In step (1), the first mixed material is composed of 40 parts by weight of homopolypropylene, 10 parts by weight of ethylene-propylene-1-butene block copolymer, 10 parts by weight of hydrogenated styrene-butadiene block copolymer and 7 parts by weight of ethylene-higher α-olefin copolymer, and the granulation temperature of the first special material is 230° C.;

[0051] In step (2), the second mixed material is composed of 17 parts by weight of homopolypropylene, 10 parts by weight of metallocene polyethylene and 7 parts by weight of ethylene-propylene-1-butene block copolymer, and the granulation temperature of the second special material is 230° C.;

[0052] In step (3), the extrusion temperature of the outermost layer and the innermost layer is 230°C, the extrusion temperature of the second inner layer and the second outer layer is 210°C, and the extrusion temperature of the middle layer is 185°C. The thickness of the obtained modified polypropylene film is 150 μm.

[0053] The rest is the same as in Example 1. Embodiment 3

[0054] The difference between this embodiment and the first embodiment is that:

[0055] In step (1), the first mixed material is composed of 36 parts by weight of homopolypropylene, 9 parts by weight of ethylene-propylene-1-butene block copolymer, 9 parts by weight of hydrogenated styrene-butadiene block copolymer and 6 parts by weight of ethylene-higher α-olefin copolymer, and the granulation temperature of the first special material is 220°C;

[0056] In step (2), the second mixed material is composed of 15 parts by weight of homopolypropylene, 9 parts by weight of metallocene polyethylene and 6 parts by weight of ethylene-propylene-1-butene block copolymer, and the granulation temperature of the second special material is 220° C.;

[0057] In step (3), the extrusion temperature of the outermost layer and the innermost layer is 225°C, the extrusion temperature of the second inner layer and the second outer layer is 205°C, and the extrusion temperature of the middle layer is 180°C. The thickness of the obtained modified polypropylene film is 140 μm.

[0058] The rest is the same as in Example 1. Embodiment 4

[0059] The difference between this embodiment and the first embodiment is that:

[0060] In step (1), the first mixed material is composed of 40 parts by weight of homopolypropylene, 8 parts by weight of ethylene-propylene-1-butene block copolymer, 8 parts by weight of hydrogenated styrene-butadiene block copolymer and 7 parts by weight of ethylene-higher α-olefin copolymer, and the granulation temperature of the first special material is 230° C.;

[0061] In step (2), the second mixture is composed of 13 parts by mass of homopolypropylene, 10 parts by mass of metallocene polyethylene and 7 parts by mass of ethylene-propylene-1-butene block copolymer.

[0062] In step (3), the extrusion temperature of the outermost layer and the innermost layer is 230°C, the extrusion temperature of the second inner layer and the second outer layer is 200°C, and the extrusion temperature of the middle layer is 185°C. The thickness of the obtained modified polypropylene film is 150 μm.

[0063] The rest is the same as in Example 1. Embodiment 5

[0064] The difference between this embodiment and the first embodiment is that:

[0065] In step (1), the first mixture is composed of 32 parts by mass of homopolypropylene, 10 parts by mass of ethylene-propylene-1-butene block copolymer, 10 parts by mass of hydrogenated styrene-butadiene block copolymer and 5 parts by mass of ethylene-higher α-olefin copolymer.

[0066] In step (2), the second mixed material is composed of 17 parts by weight of homopolypropylene, 8 parts by weight of metallocene polyethylene and 5 parts by weight of ethylene-propylene-1-butene block copolymer, and the granulation temperature of the second special material is 230° C.;

[0067] In step (3), the extrusion temperature of the outermost layer and the innermost layer is 225°C, the extrusion temperature of the second inner layer and the second outer layer is 205°C, and the extrusion temperature of the middle layer is 180°C. The thickness of the obtained modified polypropylene film is 145 μm.

[0068] The rest is the same as in Example 1.

[0069] Comparative Example

[0070] The difference between this embodiment and the first embodiment is that:

[0071] In step (1), 32 parts by weight of homopolymer polypropylene and 8 parts by weight of hydrogenated styrene-butadiene block copolymer are prepared;

[0072] In step (3), the first special material obtained in step (1) is co-extruded and blown to form a modified polypropylene film, wherein the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the innermost layer are arranged in sequence from the outside to the inside, and the extrusion temperature of each layer is 200°C.

[0073] The rest is the same as in Example 1.

[0074] The olefin film obtained in the above embodiment was subjected to performance tests in terms of tensile strength, tear strength, puncture resistance, elongation, flat dart impact and heat deformation temperature, and heat seal strength tests were performed at room temperature 20°C and high temperature 130°C, respectively, and compared with the comparative example. Among them, the tensile strength test was carried out in accordance with the ASTM standard "D 882-02 Test method for tensile properties of plastic thin sheets", the tear strength test was carried out in accordance with the ASTM standard "D 1004-13 American Materials and Testing Standards", the puncture resistance test was carried out in accordance with the national standard "GB / T37841-2019 Test method for puncture resistance of plastic films and sheets", the flat dart impact test was carried out in accordance with the national standard "GB / T 9639.1-2008 Test method for impact resistance of plastic films and sheets Free falling dart method", and the heat seal strength was carried out in accordance with the industry standard "QB / T 2358-1998 Test method for heat seal strength of plastic film packaging bags". The test results are shown in Table 1:

[0075] Table 1 Performance indicators of each membrane

[0076]

[0077] It can be seen that compared with the comparative example, the modified polypropylene film prepared by the present invention has obvious advantages in tensile strength, tear strength, puncture resistance, elongation, dart drop and heat sealing strength under the premise of the same thickness, number of layers and thickness of each layer, and is more suitable for direct contact with materials with a temperature of less than 140°C.

[0078] The modified polypropylene film can also be thermally synthesized into container liner bags for easy packaging.

[0079] The above-mentioned ethylene-propylene-1-butene block copolymer is a product of block polymerization of ethylene, 1-butene and propylene, and is a compound with the structural formula [-CH2-CH2-CH(CH3)-CH2-CH2-CH2-CH2-CH(CH3)-CH2-] n, the raw material is purchased from Kraton, USA, and the invention patent with publication number CN107921763A also involves the raw material. Ethylene-high-grade α-olefin copolymer is referred to as POE, which is mainly composed of repeating units of isotactic polypropylene and randomly distributed ethylene. It is an externally purchased raw material, such as Vistamaxx POE 6102 from ExxonMobil. Linear low-density polyethylene is abbreviated as LLDPE. It uses ethylene as the main raw material and adds a small amount of α-olefins (such as 1-butene, 1-octene, etc.). It is polymerized in a low-pressure gas-phase fluidized bed under the action of a catalyst. The structural formula is [-CH2-CH2-] n , which is a purchased raw material, can be seen as Wanhua Chemical's LLDPE.

[0080] The raw material composition of the closed expression in the present invention refers to the main raw material, that is, the raw material accounting for more than 98.5% of the total weight of the raw materials, and may also include other trace auxiliary materials. That is to say, based on the raw material composition of the closed expression of the present invention, if the proportion of the added auxiliary materials in the total weight of the raw materials does not exceed 1.5%, it still falls within the scope of protection of the present invention.

[0081] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A high temperature resistant modified polypropylene film, comprising a film body, characterized in that: The membrane body is composed of an outermost layer, a second outermost layer, a middle layer, a second innermost layer and an innermost layer from the outside to the inside; The outermost layer and the innermost layer are made of the following raw materials in parts by weight: Homopolymer polypropylene 32-40 parts 8-10 parts of ethylene-propylene-1-butene block copolymer 8-10 parts of hydrogenated styrene-butadiene block copolymer Ethylene-higher α-olefin copolymer 5-7 parts The sub-outer layer and the sub-inner layer are made of the following raw materials in parts by weight: Homopolymer polypropylene 13-17 parts Metallocene polyethylene 8-10 parts 5-7 parts of ethylene-propylene-1-butene block copolymer The middle layer is made of 18 to 22 parts by weight of linear low-density polyethylene; The thickness ratio of the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the inner layer is 3:1.5:1:1.5:3; The ethylene-higher α-olefin copolymer is POE 6102.

2. The high temperature resistant modified polypropylene film according to claim 1, characterized in that: The outermost layer and the innermost layer are made of the following raw materials in parts by weight: Homopolymer polypropylene 36 parts 9 parts of ethylene-propylene-1-butene block copolymer 9 parts of hydrogenated styrene-butadiene block copolymer Ethylene-higher α-olefin copolymer 6 parts The sub-outer layer and the sub-inner layer are made of the following raw materials in parts by weight: Homopolymer polypropylene 15 parts Metallocene polyethylene 9 parts 6 parts of ethylene-propylene-1-butene block copolymer The middle layer was made of 20 parts by mass of linear low-density polyethylene.

3. The high temperature resistant modified polypropylene film according to claim 1 or 2, characterized in that: The thickness of the membrane body is 130-150 μm.

4. A method for preparing the high temperature resistant modified polypropylene film according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) preparing a first special material: dry-mixing 32 to 40 parts by weight of homopolypropylene, 8 to 10 parts by weight of ethylene-propylene-1-butene block copolymer, 8 to 10 parts by weight of hydrogenated styrene-butadiene block copolymer and 5 to 7 parts by weight of ethylene-higher α-olefin copolymer to obtain a first mixed material, and granulating the first mixed material to obtain a first special material; (2) preparing a second special material: dry-mixing 13 to 17 parts by weight of homopolypropylene, 8 to 10 parts by weight of metallocene polyethylene and 5 to 7 parts by weight of ethylene-propylene-1-butene block copolymer to obtain a second mixed material, and granulating the second mixed material to obtain a second special material; (3) Co-extrusion film formation: The first special material prepared in step (1), the second special material prepared in step (2), the linear low-density polyethylene, the second special material prepared in step (2) and the first special material prepared in step (1) are subjected to multi-layer co-extrusion blow molding to form a polypropylene film, wherein the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the innermost layer are arranged in sequence from the outside to the inside, and the thickness ratio of the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the inner layer is 3:1.5:1:1.5:

3.

5. The method for preparing the high temperature resistant modified polypropylene film according to claim 4, characterized in that: In step (1), the first mixed material is composed of 36 parts by mass of homopolypropylene, 9 parts by mass of ethylene-propylene-1-butene block copolymer, 9 parts by mass of hydrogenated styrene-butadiene block copolymer and 6 parts by mass of ethylene-higher α-olefin copolymer; In step (2), the second mixture is composed of 15 parts by mass of homopolypropylene, 9 parts by mass of metallocene polyethylene and 6 parts by mass of ethylene-propylene-1-butene block copolymer.

6. The method for preparing a high temperature resistant modified polypropylene film according to claim 4 or 5, characterized in that: The extrusion temperature of the outermost layer and the innermost layer is 220-230°C, the extrusion temperature of the second inner layer and the second outer layer is 200-210°C, and the extrusion temperature of the middle layer is 175-185°C.

7. The method for preparing a high temperature resistant modified polypropylene film according to claim 6, characterized in that: The granulation temperature of the first special material in step (1) is 210-230°C, and the granulation temperature of the second special material in step (2) is 210-230°C.

8. The method for preparing a high temperature resistant modified polypropylene film according to claim 7, characterized in that: In step (3), the thickness of the prepared polypropylene film is 130 to 150 μm.

9. A container liner bag, comprising a bag body, wherein the bag body is made by heat-sealing a polypropylene film, and wherein: The polypropylene film is a high temperature resistant modified polypropylene film according to any one of claims 1 to 3, or a high temperature resistant modified polypropylene film prepared by any one of the preparation methods of claims 4 to 8.

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