A CPP membrane and its manufacturing process

Abstract

This invention relates to the field of thin film manufacturing technology, and proposes a CPP film and its manufacturing process. The CPP film includes a corona layer, an adhesive layer, and a heat-sealing layer arranged sequentially from top to bottom. The adhesive layer comprises the following components by weight: 18-46 parts of first polypropylene, 1-35 parts of polylactic acid, and 10-16 parts of nano-silicon carbide. The corona layer comprises the following components by weight: 18-46 parts of second polypropylene and 4-16 parts of polyhydroxybutyrate. This technical solution solves the problem of poor low-temperature resistance of existing CPP films.

Description

Technical Field

[0001] This invention relates to the field of thin film production technology, specifically to a CPP film and its production process. Background Technology

[0002] CPP film, also known as polypropylene cast film, is a widely used thin film material in daily life. It possesses unique performance characteristics, such as excellent transparency, moisture barrier properties, heat resistance, stiffness, and gloss, making it valuable in various fields including optical and electronic products, food packaging, and pharmaceuticals. Especially in the food industry, CPP film is widely used in the design of various packaging bags. Although CPP film has good heat resistance, its low-temperature resistance is poor, making it unsuitable for the storage of some products in low-temperature environments. Therefore, developing a CPP film with better low-temperature resistance is of great significance for people's daily lives. Summary of the Invention

[0003] This invention proposes a CPP membrane and its production process, which solves the problem of poor low-temperature resistance of CPP membranes in related technologies.

[0004] The technical solution of the present invention is as follows:

[0005] This invention proposes a CPP film, comprising a corona layer, an adhesive layer and a heat-sealing layer arranged sequentially from top to bottom. The adhesive layer comprises the following components in parts by weight: 18-46 parts of first polypropylene, 1-35 parts of polylactic acid, and 10-16 parts of nano-silicon carbide.

[0006] The corona layer comprises the following components in parts by weight: 18-46 parts of second polypropylene and 4-16 parts of polyhydroxybutyrate.

[0007] As a further technical solution, the nano-silicon carbide is ethylene-methyl acrylate copolymer modified nano-silicon carbide.

[0008] Surface treatment of nano-silicon carbide with ethylene-methyl acrylate copolymer can improve the dispersion performance of nano-silicon carbide in the adhesive layer, and can also form hydrogen bonds with polylactic acid in the adhesive layer and polyhydroxybutyrate in the corona layer, respectively, thereby enhancing the bonding ability of the adhesive layer and the corona layer and further improving the low temperature resistance of CPP film.

[0009] As a further technical solution, the preparation method of the ethylene-methyl acrylate copolymer modified nano-silicon carbide includes the following steps: adding ethylene-methyl acrylate copolymer to ethyl acetate, stirring to obtain an ethylene-methyl acrylate copolymer solution, adding nano-silicon carbide to the ethylene-methyl acrylate copolymer solution, mixing evenly, and drying to obtain the ethylene-methyl acrylate copolymer modified nano-silicon carbide.

[0010] As a further technical solution, the weight ratio of the nano-silicon carbide and the ethylene-methyl acrylate copolymer is 3~7:1.

[0011] As a further technical solution, the mass fraction of the ethylene-methyl acrylate copolymer solution is 8%~16%.

[0012] As a further technical solution, the heat-sealing layer includes the following components in parts by weight: 18-46 parts of third polypropylene and 1-3 parts of slip agent.

[0013] As a further technical solution, the first polypropylene, the second polypropylene, and the third polypropylene are each independently one or two of homopolymer polypropylene and copolymer polypropylene.

[0014] As a further technical solution, the slip agent is one or more of oleamide, erucamide, and glyceryl stearate.

[0015] This invention also proposes a CPP membrane manufacturing process, comprising the following steps:

[0016] S1. Mix the components of the corona layer evenly to obtain a corona layer mixture;

[0017] S2. Mix the components of the adhesive layer evenly to obtain the adhesive layer mixture;

[0018] S3. Mix the components of the heat-sealing layer evenly to obtain the heat-sealing layer mixture;

[0019] S4. The corona layer mixture, adhesive layer mixture and heat-sealing layer mixture are melted and extruded in the order of corona layer, adhesive layer and heat-sealing layer from top to bottom, cast and cooled to obtain cast film;

[0020] S5. Perform corona treatment on the corona layer in the cast film to obtain a CPP film.

[0021] As a further technical solution, in step S5, the corona treatment value is 38~40 dynes.

[0022] As a further technical solution, in step S4, during the melt extrusion, the extrusion temperature of the corona layer is 210~220℃, the extrusion temperature of the adhesive layer is 220~230℃, the extrusion temperature of the heat-sealing layer is 228~236℃, and the casting cooling temperature is 24~32℃.

[0023] The working principle and beneficial effects of this invention are as follows:

[0024] In this invention, the adhesive layer includes polylactic acid (PLA), and the corona layer includes polyhydroxybutyrate (PHB). The synergistic effect of PLA and PHB enhances the bonding ability between the adhesive layer and the corona layer, thereby improving the impact resistance of the CPP film at low temperatures and resulting in better low-temperature performance. Furthermore, the addition of nano-silicon carbide to the adhesive layer can also improve the low-temperature resistance of the CPP film. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] In the following examples and comparative examples, the polypropylene is copolymer polypropylene with the grade R700M; the polylactic acid has the grade 4060D; the nano-silicon carbide has a particle size of 50nm; the polyhydroxybutyrate has the grade 1006; and the ethylene-methyl acrylate copolymer has the grade 1224 AC.

[0027] Example 1

[0028] A CPP film includes a corona layer, an adhesive layer and a heat-sealing layer arranged sequentially from top to bottom. The adhesive layer includes the following components in parts by weight: 18 parts copolymer polypropylene, 1 part polylactic acid and 10 parts nano silicon carbide.

[0029] The corona layer comprises the following components in parts by weight: 18 parts copolymer polypropylene and 4 parts polyhydroxybutyrate;

[0030] The heat-sealing layer comprises the following components in parts by weight: 18 parts copolymer polypropylene and 1 part glyceryl stearate;

[0031] Its production process includes the following steps:

[0032] S1. Mix the components of the corona layer evenly to obtain the corona layer mixture;

[0033] S2. Mix the components of the adhesive layer evenly to obtain the adhesive layer mixture;

[0034] S3. Mix the components of the heat-sealing layer evenly to obtain the heat-sealing layer mixture;

[0035] S4. From top to bottom, in the order of corona layer, adhesive layer and heat seal layer, the corona layer mixture is melted and extruded at 210°C, the adhesive layer mixture at 220°C and the heat seal layer mixture at 228°C, and then cast and cooled at 32°C to obtain a cast film.

[0036] S5. The corona layer in the cast film is corona treated at a corona value of 38 dynes to obtain a CPP film.

[0037] Example 2

[0038] A CPP film includes a corona layer, an adhesive layer and a heat-sealing layer arranged sequentially from top to bottom. The adhesive layer includes the following components in parts by weight: 32 parts copolymer polypropylene, 21 parts polylactic acid and 14 parts nano silicon carbide.

[0039] The corona layer comprises the following components in parts by weight: 32 parts copolymer polypropylene and 10 parts polyhydroxybutyrate;

[0040] The heat-sealing layer comprises the following components in parts by weight: 32 parts copolymer polypropylene and 2 parts glyceryl stearate;

[0041] Its production process includes the following steps:

[0042] S1. Mix the components of the corona layer evenly to obtain the corona layer mixture;

[0043] S2. Mix the components of the adhesive layer evenly to obtain the adhesive layer mixture;

[0044] S3. Mix the components of the heat-sealing layer evenly to obtain the heat-sealing layer mixture;

[0045] S4. From top to bottom, in the order of corona layer, adhesive layer and heat seal layer, the corona layer mixture is melted and extruded at 215°C, the adhesive layer mixture at 225°C and the heat seal layer mixture at 233°C, and then cast and cooled at 28°C to obtain a cast film.

[0046] S5. The corona layer in the cast film is corona treated at a corona value of 39 dynes to obtain a CPP film.

[0047] Example 3

[0048] A CPP film includes a corona layer, an adhesive layer and a heat-sealing layer arranged sequentially from top to bottom. The adhesive layer includes the following components in parts by weight: 46 parts copolymer polypropylene, 35 parts polylactic acid and 16 parts nano silicon carbide.

[0049] The corona layer comprises the following components in parts by weight: 46 parts copolymer polypropylene and 16 parts polyhydroxybutyrate;

[0050] The heat-sealing layer comprises the following components in parts by weight: 46 parts copolymer polypropylene and 3 parts glyceryl stearate;

[0051] Its production process includes the following steps:

[0052] S1. Mix the components of the corona layer evenly to obtain the corona layer mixture;

[0053] S2. Mix the components of the adhesive layer evenly to obtain the adhesive layer mixture;

[0054] S3. Mix the components of the heat-sealing layer evenly to obtain the heat-sealing layer mixture;

[0055] S4. From top to bottom, in the order of corona layer, adhesive layer and heat seal layer, the corona layer mixture is melted and extruded at 220°C, the adhesive layer mixture at 230°C and the heat seal layer mixture at 236°C, and then cast and cooled at 24°C to obtain a cast film.

[0056] S5. The corona layer in the cast film is subjected to corona treatment at a corona value of 40 dynes to obtain a CPP film.

[0057] Example 4

[0058] The only difference between this embodiment and Example 3 is that the nano-silicon carbide is ethylene-methyl acrylate copolymer modified nano-silicon carbide. The preparation method of ethylene-methyl acrylate copolymer modified nano-silicon carbide is as follows: 5 parts of ethylene-methyl acrylate copolymer are added to ethyl acetate and stirred to obtain an ethylene-methyl acrylate copolymer solution with a mass fraction of 15%. 11 parts of nano-silicon carbide are added to the ethylene-methyl acrylate copolymer solution, mixed evenly, and dried to obtain ethylene-methyl acrylate copolymer modified nano-silicon carbide.

[0059] Example 5

[0060] The only difference between this embodiment and Example 3 is that the nano-silicon carbide is ethylene-methyl acrylate copolymer modified nano-silicon carbide. The preparation method of ethylene-methyl acrylate copolymer modified nano-silicon carbide is as follows: 1 part of ethylene-methyl acrylate copolymer is added to ethyl acetate and stirred to obtain an ethylene-methyl acrylate copolymer solution with a mass fraction of 15%. 15 parts of nano-silicon carbide are added to the ethylene-methyl acrylate copolymer solution, mixed evenly, and dried to obtain ethylene-methyl acrylate copolymer modified nano-silicon carbide.

[0061] Example 6

[0062] The only difference between this embodiment and Example 3 is that the nano-silicon carbide is ethylene-methyl acrylate copolymer modified nano-silicon carbide. The preparation method of ethylene-methyl acrylate copolymer modified nano-silicon carbide is as follows: 4 parts of ethylene-methyl acrylate copolymer are added to ethyl acetate and stirred to obtain an ethylene-methyl acrylate copolymer solution with a mass fraction of 15%. 12 parts of nano-silicon carbide are added to the ethylene-methyl acrylate copolymer solution, mixed evenly, and dried to obtain ethylene-methyl acrylate copolymer modified nano-silicon carbide.

[0063] Example 7

[0064] The only difference between this embodiment and Example 3 is that the nano-silicon carbide is ethylene-methyl acrylate copolymer modified nano-silicon carbide. The preparation method of ethylene-methyl acrylate copolymer modified nano-silicon carbide is as follows: 2 parts of ethylene-methyl acrylate copolymer are added to ethyl acetate and stirred to obtain an ethylene-methyl acrylate copolymer solution with a mass fraction of 15%. 14 parts of nano-silicon carbide are added to the ethylene-methyl acrylate copolymer solution, mixed evenly, and dried to obtain ethylene-methyl acrylate copolymer modified nano-silicon carbide.

[0065] Comparative Example 1

[0066] The only difference between this comparative example and Example 1 is that polylactic acid was not added to the adhesive layer, and the amount of added copolymer polypropylene was 19 parts by weight.

[0067] Comparative Example 2

[0068] The only difference between this comparative example and Example 1 is that no polyhydroxybutyrate was added to the corona layer, and the amount of added copolymer polypropylene was 22 parts by weight.

[0069] Comparative Example 3

[0070] The only difference between this comparative example and Example 1 is that polylactic acid was not added to the adhesive layer, and 19 parts of copolymer polypropylene were added; polyhydroxybutyrate was not added to the corona layer, and 22 parts of copolymer polypropylene were added.

[0071] Comparative Example 4

[0072] The only difference between this comparative example and Example 1 is that no nano-silicon carbide was added to the adhesive layer.

[0073] The CPP films produced by the production processes of Examples 1-7 and Comparative Examples 1-4 were placed at -50℃ for 5 hours and then subjected to the following performance tests according to GB / T 9639.1-2008 "Test methods for impact resistance of plastic films and sheets - Free fall dart method - Part 1: Stepwise method":

[0074] Impact fracture quality after cryogenic treatment: The A method was used for testing. The electromagnet was energized, the round handle of the dart was vertically inserted into the magnetic connector, the falling height was adjusted to 0.66m, the electromagnet was de-energized, and the dart fell. The impact fracture quality after cryogenic treatment was recorded.

[0075] Impact breakage quality retention rate: The impact breakage quality before cryogenic treatment was tested using the A method. The impact breakage quality retention rate was calculated using the following formula: Impact breakage quality retention rate (%) = Impact breakage quality after cryogenic treatment / Impact breakage quality before cryogenic treatment × 100.

[0076] The test results are shown in Table 1 below:

[0077] Table 1 Test Results

[0078]

[0079] Compared with Comparative Examples 1-3, the impact breakage quality and impact breakage quality retention rate of Example 1 after low-temperature treatment were significantly improved, indicating that the polylactic acid in the adhesive layer and the polyhydroxybutyrate in the corona layer have a synergistic effect, enhancing the bonding ability between the adhesive layer and the corona layer, thereby improving the impact resistance of the CPP film at low temperatures and giving the CPP film better low-temperature resistance. Compared with Comparative Example 4, the impact breakage quality and impact breakage quality retention rate of Example 1 after low-temperature treatment were significantly improved, indicating that the addition of nano-silicon carbide to the adhesive layer can also improve the low-temperature resistance of the CPP film.

[0080] Compared to Example 3, the impact breakage quality and impact breakage quality retention rate after low-temperature treatment in Examples 4-7 are improved, indicating that modification of the nano-silicon carbide in the adhesive layer can further improve the low-temperature resistance of the CPP film. Furthermore, compared to Examples 4-5, the impact breakage quality and impact breakage quality retention rate after low-temperature treatment in Examples 6-7 are improved, indicating that when the weight ratio of nano-silicon carbide to ethylene-methyl acrylate copolymer is 3-7:1, the low-temperature resistance of the CPP film can be further improved.

[0081] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A CPP film comprising a corona layer, an adhesive layer and a heat seal layer disposed in order from top to bottom, characterized in that, The adhesive layer comprises the following components by weight: 18-46 parts of first polypropylene, 1-35 parts of polylactic acid, and 10-16 parts of nano-silicon carbide; The corona layer comprises the following components by weight: 18-46 parts of second polypropylene and 4-16 parts of polyhydroxybutyrate; The nano-silicon carbide is an ethylene-methyl acrylate copolymer modified nano-silicon carbide; The preparation method of the ethylene-methyl acrylate copolymer modified nano-silicon carbide comprises the following steps: adding ethylene-methyl acrylate copolymer into ethyl acetate, stirring to obtain an ethylene-methyl acrylate copolymer solution, adding nano-silicon carbide into the ethylene-methyl acrylate copolymer solution, uniformly mixing, and drying to obtain the ethylene-methyl acrylate copolymer modified nano-silicon carbide.

2. The CPP film according to claim 1, characterized in that, The weight ratio of the nano-silicon carbide and the ethylene-methyl acrylate copolymer is 3-7:

1.

3. The CPP film according to claim 1, characterized in that, The mass fraction of the ethylene-methyl acrylate copolymer solution is 8%-16%.

4. The CPP film according to claim 1, characterized in that, The heat-sealing layer comprises the following components by weight: 18-46 parts of third polypropylene and 1-3 parts of a slip agent.

5. The CPP film according to claim 4, characterized in that, The first polypropylene, the second polypropylene, and the third polypropylene are each independently one or both of a homopolymer polypropylene and a copolymer polypropylene.

6. The CPP film according to claim 4, characterized in that, The slip agent is one or more of oleic acid amide, erucic acid amide, and glyceryl stearate.

7. The process for producing a CPP film according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1, uniformly mixing the components of the corona layer to obtain a corona layer mixture; S2, uniformly mixing the components of the adhesive layer to obtain an adhesive layer mixture; S3, uniformly mixing the components of the heat-sealing layer to obtain a heat-sealing layer mixture; S4, sequentially melt-extruding the corona layer mixture, the adhesive layer mixture, and the heat-sealing layer mixture from top to bottom in the order of the corona layer, the adhesive layer, and the heat-sealing layer, and casting and cooling to obtain a cast film; S5, performing corona treatment on the corona layer in the cast film to obtain a CPP film.

8. The process for producing a CPP film according to claim 7, characterized in that, In step S5, the corona treatment is performed at a corona value of 38-40 dynes.

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