Polypropylene film and its applications

Abstract

The present invention relates to the field of films, specifically to a polypropylene film and its applications. The polypropylene film is characterized by having a multilayer structure comprising a corona layer, a core layer, and a heat-sealing layer stacked in sequence; wherein the corona layer is made from a corona layer composition comprising a multiphase polymer a; the core layer is made from a core layer composition comprising a multiphase polymer a and a multiphase polymer b; and the heat-sealing layer is made from a heat-sealing layer composition comprising a multiphase polymer a; and the multiphase polymer a and the multiphase polymer b each independently comprise a continuous phase provided by polypropylene and a dispersed phase provided by a copolymer rubber. The film produced by the above method exhibits excellent mechanical and heat-sealing properties while maintaining good transparency.

Description

Technical Field

[0001] The present invention relates to the field of films, in particular to a polypropylene film and applications thereof. Background Art

[0002] Polypropylene film is widely used in food packaging due to its excellent optical and mechanical properties and packaging adaptability. Polypropylene film can be produced through a unidirectional cast film process. Both during the film production process and during its use as a packaging material, it is desirable for the film to have excellent toughness, optical properties, and low odor volatility. Furthermore, it is desirable for the film to not deform or produce odor even at a sterilization temperature of 131°C.

[0003] CN102453180A discloses a film made from a butene-propylene copolymer, which exhibits good transparency and a low soluble content. However, due to the use of a relatively high amount of the butene-propylene copolymer, the film's soluble content, packaging transparency, and stiffness are still unsatisfactory. Furthermore, it is uncertain whether the film can withstand sterilization at 131°C. Summary of the Invention

[0004] The present invention aims to overcome the problems of poor transparency, low pendulum impact strength, and poor high-temperature resistance in existing films. A polypropylene film and its application are provided. The film can be used in sterilization environments with a sterilization temperature of up to 131°C and has good transparency and good pendulum impact strength.

[0005] In order to achieve the above object, the first aspect of the present invention provides a polypropylene film, characterized in that the film is a multi-layer structure, wherein the film is a corona layer, a core layer and a heat sealing layer stacked in sequence;

[0006] Wherein, the corona layer is made of a corona layer composition comprising a multiphase polymer a; the core layer is made of a core layer composition comprising a multiphase polymer a and a multiphase polymer b; the heat seal layer is made of a heat seal layer composition comprising a multiphase polymer a;

[0007] The multiphase polymer a and the multiphase polymer b each independently comprise a continuous phase provided by polypropylene and a dispersed phase provided by a copolymer rubber;

[0008] Based on the total weight of the multiphase polymer a, the content of the dispersed phase provided by the copolymer rubber is 5-20wt%;

[0009] Based on the total weight of the multiphase polymer b, the content of the dispersed phase provided by the copolymer rubber is 30-50 wt%.

[0010] A second aspect of the present invention provides an application of the polypropylene film in the field of packaging.

[0011] Through the above technical solution, the polypropylene film provided by the present invention and its application have the following beneficial effects:

[0012] The film of the present invention utilizes a corona layer, a core layer, and a heat-seal layer. Each layer comprises at least one of a multiphase polymer (a) and a multiphase polymer (b), each comprising a continuous phase of polypropylene and a dispersed phase of a copolymer rubber. This multiphase polymer structure improves the film's high-temperature resistance and pendulum impact strength while maintaining excellent transparency and exhibiting superior heat-sealing properties. DETAILED DESCRIPTION

[0013] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0014] The first aspect of the present invention provides a polypropylene film, characterized in that: the film is a multi-layer structure, the film is a corona layer, a core layer and a heat sealing layer stacked in sequence;

[0015] Wherein, the corona layer is made of a corona layer composition comprising a multiphase polymer a; the core layer is made of a core layer composition comprising a multiphase polymer a and a multiphase polymer b; the heat seal layer is made of a heat seal layer composition comprising a multiphase polymer a;

[0016] The multiphase polymer a and the multiphase polymer b each independently comprise a continuous phase provided by polypropylene and a dispersed phase provided by a copolymer rubber;

[0017] Based on the total weight of the multiphase polymer a, the content of the dispersed phase provided by the copolymer rubber is 5-20wt%;

[0018] Based on the total weight of the multiphase polymer b, the content of the dispersed phase provided by the copolymer rubber is 30-50 wt%.

[0019] In the present invention, the content of the dispersed phase provided by the copolymer rubber in the multiphase polymer has a great influence on the transparency and high temperature resistance of the film. By using a multiphase polymer with the above characteristics, the obtained film has both good transparency and good high temperature resistance.

[0020] According to the present invention, based on the total weight of the multiphase polymer a, the content of the dispersed phase provided by the copolymer rubber is 5-16 wt%;

[0021] And / or, based on the total weight of the multiphase polymer b, the content of the dispersed phase provided by the copolymer rubber is 30-40 wt%.

[0022] According to the present invention, the copolymer rubber is a copolymer of propylene and ethylene and / or butene.

[0023] According to the present invention, the copolymer rubber is a propylene-ethylene copolymer rubber.

[0024] According to the present invention, the multiphase polymer a has a melt mass flow rate of 2-8 g / 10 min measured at 230° C. and a load of 2.16 kg.

[0025] According to the present invention, the multiphase polymer b has a melt mass flow rate of 2-8 g / 10 min measured at 230° C. and a load of 2.16 kg.

[0026] In the present invention, the multiphase polymer can be purchased commercially, for example, multiphase polymer a-1 with the brand F8303-GD from Yanshan Petrochemical; and multiphase polymer b-1 with the brand F8801-GD from Yanshan Petrochemical. The multiphase polymer a and the multiphase polymer b can also be prepared according to the following steps:

[0027] First, the reaction raw materials are introduced into kettle No. 1, and polypropylene is homopolymerized in kettle No. 1 to prepare a polypropylene continuous phase; then, the prepared polypropylene continuous phase is added to kettle No. 2, and reaction raw materials such as propylene and ethylene are introduced into kettle No. 2. While the copolymer rubber dispersed phase is prepared in kettle No. 2, it is mixed into the polypropylene continuous phase to prepare a multiphase polymer.

[0028] In the present invention, a multiphase polymer can also be obtained by directly mechanically mixing the continuous phase provided by polypropylene and the dispersed phase provided by the copolymer rubber.

[0029] According to the present invention, the weight average molecular weight of the copolymer rubber is 400,000-600,000 g / mol.

[0030] In the present invention, the propylene-ethylene copolymer having the above characteristics is used, which has the characteristic of high impact strength.

[0031] According to the present invention, the corona layer composition further comprises an ethylene copolymer, which is a copolymer of ethylene and a monomer B selected from at least one of α,β-unsaturated carboxylic acid, α,β-unsaturated carboxylic acid ester and carboxylic acid vinyl ester (vinyl acetate).

[0032] In the present invention, in order to improve the interfacial interaction between the film and the substrate material, such as aluminum foil, and to enhance the strength of the film-substrate composite material, an ethylene copolymer with polar groups is added to the corona layer composition. By using a corona layer having the above-mentioned characteristics, the composite strength of the film and the substrate is enhanced while the film has better high-temperature resistance.

[0033] According to the present invention, the content of the structural unit provided by the monomer B is 1-10 wt % based on the total weight of the ethylene copolymer.

[0034] According to the present invention, based on the total weight of the corona layer composition, the content of the multiphase polymer a is 90-99 wt%, and the content of the ethylene copolymer is 1-10 wt%.

[0035] Furthermore, based on the total weight of the corona layer composition, the content of the multiphase polymer a is 92-99 wt %, and the content of the ethylene copolymer is 1-8 wt %.

[0036] Furthermore, based on the total weight of the corona layer composition, the content of the multiphase polymer a is 95-99 wt %, and the content of the ethylene copolymer is 1-5 wt %.

[0037] According to the present invention, the ethylene copolymer has a melt mass flow rate of 2-8 g / 10 min measured at 230° C. and a load of 2.16 kg.

[0038] In the present invention, the use of the ethylene copolymer having the above characteristics can further increase the peel strength.

[0039] According to the present invention, the heat-sealing layer composition further comprises random copolymerized polypropylene of propylene and comonomers.

[0040] According to the present invention, the comonomer is selected from ethylene and / or α-olefins.

[0041] According to the present invention, the α-olefin is C4-C 12 of α-olefins.

[0042] Furthermore, the α-olefin is selected from at least one of 1-butene, 1-hexene and 1-octene.

[0043] According to the present invention, based on the total weight of the random copolymerized polypropylene, the content of the structural units provided by the comonomer is 1-8 wt%.

[0044] According to the present invention, based on the total weight of the heat-sealing layer composition, the content of the multiphase polymer a is 80-99 wt%, and the content of the random copolymer polypropylene is 1-20 wt%.

[0045] In the present invention, adding random copolymer polypropylene to the heat-sealing layer can reduce the heat-sealing temperature of the film. Adding the random copolymer polypropylene of the specific composition and content to the heat-sealing layer composition effectively avoids the poor high-temperature resistance of the film caused by an excessively high random copolymer polypropylene content, while also effectively avoiding the inability of the random copolymer polypropylene to reduce the heat-sealing temperature of the film caused by an excessively low random copolymer polypropylene content.

[0046] Furthermore, based on the total weight of the heat-sealing layer composition, the content of the multiphase polymer a is 85-99 wt %, and the content of the random copolymer polypropylene is 1-15 wt %.

[0047] Furthermore, based on the total weight of the heat-sealing layer composition, the content of the multiphase polymer a is 90-99 wt %, and the content of the random copolymer polypropylene is 1-10 wt %.

[0048] According to the present invention, the random copolymer polypropylene has a melt mass flow rate of 2-8 g / 10 min measured at 230° C. and a load of 2.16 kg.

[0049] In the present invention, the random copolymer polypropylene having the above characteristics is used, which has the characteristic of good processing performance.

[0050] According to the present invention, based on the total weight of the core layer composition, the content of the multiphase polymer a is 70-90 wt %, and the content of the multiphase polymer b is 10-30 wt %.

[0051] Furthermore, based on the total weight of the core layer composition, the content of the multiphase polymer a is 70-85 wt %, and the content of the multiphase polymer b is 15-30 wt %.

[0052] Furthermore, based on the total weight of the core layer composition, the content of the multiphase polymer a is 80-85 wt %, and the content of the multiphase polymer b is 15-20 wt %.

[0053] In the present invention, the core layer having the above characteristics is adopted, which has the characteristics of high impact strength and good tear resistance.

[0054] According to the present invention, the film has a three-layer structure.

[0055] According to the present invention, the thickness ratio of the corona layer, the core layer and the heat sealing layer is 1:2-4:1.

[0056] In the present invention, the film having the above characteristics has the advantages of high impact strength, high temperature resistance and tear resistance.

[0057] The polypropylene film preparation method of the present invention comprises: melting a mixture of a corona layer, a core layer, and a heat-seal layer in three extruders, and extruding the melt through a slit (slit gap of 0.4-0.65 mm) on a T-shaped die to form a three-layer film. The extruded film is then applied to a chill roll using compressed air from an air knife. As the extruded film passes through the chill roll, the final thickness of each layer is controlled by controlling the extruder feed rate and pull-off speed.

[0058] A second aspect of the present invention provides an application of the polypropylene film in the field of packaging.

[0059] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, all raw materials used can be obtained from commercial channels.

[0060] The multiphase polymer a-1 was purchased from Yanshan Petrochemical with the brand name F8303-GD. The melt mass flow rate measured at 230° C. and a load of 2.16 kg was 3.5 g / 10 min, and the copolymer rubber content was 16 wt%.

[0061] The multiphase polymer b-1 was purchased from Yanshan Petrochemical with the brand name F8801-GD. The melt mass flow rate measured at 230° C. and a load of 2.16 kg was 4.6 g / 10 min, and the copolymer rubber content was 39 wt%.

[0062] The multiphase polymer a-2 was purchased from Yanshan Petrochemical Company with the designation F8004-GD. The melt mass flow rate measured at 230° C. and a load of 2.16 kg was 4 g / 10 min, and the copolymer rubber content was 20 wt %.

[0063] The multiphase polymer b-2 was purchased from Yanshan Petrochemical Company with the designation F9004-GD. The melt mass flow rate measured at 230° C. and a load of 2.16 kg was 4 g / 10 min, and the copolymer rubber content was 50 wt %.

[0064] The multiphase polymer a-3 was purchased from Yanshan Petrochemical with the brand name F8005-GD. The melt mass flow rate measured at 230° C. and a load of 2.16 kg was 5 g / 10 min, and the copolymer rubber content was 4 wt%.

[0065] The heterogeneous polymer b-3 was purchased from Basel with the brand name C200F. The melt mass flow rate measured at 230°C and a load of 2.16 kg was 6.3 g / 10 min, and the copolymer rubber content was 52 wt%.

[0066] Random copolymer polypropylene was purchased from Yanshan Petrochemical with the designation F4903-GD (abbreviated as d-1). The melt mass flow rate measured at 230° C. and a load of 2.16 kg was 3 g / 10 min, and the content of the structural unit provided by the comonomer ethylene was 3.5 wt%.

[0067] Random copolymer polypropylene, purchased from Yanshan Petrochemical, with the brand name F4904-GD (abbreviated as d-2), has a melt mass flow rate of 4 g / 10 min measured at 230° C. and a load of 2.16 kg, and the content of the structural unit provided by the comonomer ethylene is 7 wt%.

[0068] The ethylene copolymer is EAA, purchased from Exxon, with the brand name EAA5000 (abbreviated as: c-1). The melt mass flow rate measured at 230°C and a load of 2.16 kg is 5.6 g / 10 min, and the content of the structural unit provided by the comonomer ethyl acrylate is 6 wt%.

[0069] The ethylene copolymer is EAA, purchased from Exxon, with the brand name EAA5100 (abbreviated as: c-2). The melt mass flow rate measured at 230°C and a load of 2.16 kg is 8 g / 10 min, and the content of the structural unit provided by the comonomer ethyl acrylate is 3 wt%.

[0070] 1. In the present invention, the melt mass flow rate is measured according to GB / T 3682-2000.

[0071] 2. In the present invention, the method for determining the dispersed phase content of the copolymer rubber in the heterogeneous polymer is as follows: a sample, weighed W1, is added to boiling n-decane and stirred for 1 hour. The sample is then cooled to room temperature for 1 hour, stirred again at room temperature for 1 hour, and filtered. The filtrate contains the rubber phase. The total weight of the filter paper and stirrer is W2. The filtrate is added to 400 ml of acetone while stirring, and stirred for 1 hour. The sample is filtered through filter paper and then dried to obtain the rubber phase. The filter paper, stirrer, and rubber phase are weighed together as W3. The dispersed phase content of the copolymer rubber in the final heterogeneous polymer is calculated as (W3 - W2) / W1 × 100%.

[0072] 3. Film toughness: The film toughness is characterized by pendulum impact strength and tested in accordance with standard GB / T8809-1988.

[0073] 4. Corona layer bonding performance: The film and aluminum foil are heat-sealed at 190°C, 0.3 MPa, and 2 seconds. The heat-sealing strength between the corona layer and the aluminum foil is then tested according to standard QB / T 2358-98 to characterize the bonding performance of the corona layer.

[0074] 5. Heat sealing performance: Heat seal the film itself at 0.3 MPa for 2 seconds according to standard QB / T 2358-98. Record the temperature at which the heat seal strength reaches 7N / 15mm. This temperature is the heat sealing temperature.

[0075] 6. High temperature resistance: Place the film in a sterilizer, set the temperature of the sterilizer to 131°C, take out the film after 15 minutes and observe the state of the film.

[0076] 7. Transparency: Test the film haze according to standard GB / T2410-2008.

[0077] Example 1

[0078] Film preparation process: The mixture of the corona layer, core layer, and heat seal layer is melted separately in three extruders and extruded through a slit in a T-shaped die (the gap is 0.4-0.65mm) to form a three-layer film. The extruded film is applied to a chill roll using compressed air from an air knife. The final thickness of each layer is controlled by controlling the extruder feed and pull-off speeds as the extruded film passes through the chill roll. The total thickness of the polypropylene film is 50μm, with the corona layer being 10μm, the core layer being 30μm, and the heat seal layer being 10μm.

[0079] The specific compositions of the corona layer composition, core layer composition and heat seal layer composition in Example 1 are shown in Table 1.

[0080] Example 2-Example 6, Comparative Example 1

[0081] Films were prepared according to the method of Example 1. The amounts and types of the raw materials used in the different corona layer compositions, core layer compositions and heat seal layer compositions were different. See Table 1 for details.

[0082] Table 1

[0083]

[0084] Example 7

[0085] The film was prepared using the same ratio as in Example 1, except that the rubber content in the multiphase polymer a-2 was 20 wt % and the rubber content in the multiphase polymer b-2 was 50 wt %.

[0086] Example 8

[0087] The film was prepared using the same ratio as in Example 1, except that the content of the structural unit provided by the comonomer in the random copolymerized polypropylene (d-2) was 7 wt%.

[0088] Example 9

[0089] The film was prepared using the same ratio as in Example 1, except that in the ethylene copolymer (c-2), the content of the structural unit provided by the comonomer ethyl acrylate was 3 wt%.

[0090] Comparative Example 2

[0091] The film was prepared using the same ratio as in Example 1, except that the content of the copolymer rubber in the multiphase polymer a-3 was 4 wt %; and the content of the copolymer rubber in the multiphase polymer b-3 was 52 wt %.

[0092] Comparative Example 3

[0093] The film was prepared using the same ratio as in Example 1, except that the content of the copolymer rubber in the multiphase polymer b-3 was within 52 wt%.

[0094] Comparative Example 4

[0095] The film was prepared using the same ratio as in Example 1, except that the content of the copolymer rubber in the multiphase polymer a-3 was within 4 wt%.

[0096] The performance test results of the films prepared in the examples and comparative examples are shown in Table 2.

[0097] Table 2

[0098]

[0099]

[0100] As can be seen from Table 2, the film prepared by adopting the technical solution of the present invention has good pendulum impact strength and heat resistance, while maintaining good transparency and showing good heat sealing performance.

[0101] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A polypropylene film, characterized in that The film has a multi-layer structure, and the film comprises a corona layer, a core layer and a heat-sealing layer stacked in sequence; Wherein, the corona layer is made of a corona layer composition comprising a multiphase polymer a; the core layer is made of a core layer composition comprising a multiphase polymer a and a multiphase polymer b; the heat seal layer is made of a heat seal layer composition comprising a multiphase polymer a; The multiphase polymer a and the multiphase polymer b each independently comprise a continuous phase provided by polypropylene and a dispersed phase provided by a copolymer rubber; Based on the total weight of the multiphase polymer a, the content of the dispersed phase provided by the copolymer rubber is 5-20wt%; Based on the total weight of the multiphase polymer b, the content of the dispersed phase provided by the copolymer rubber is 30-50wt%; Wherein, the copolymer rubber is a copolymer of propylene and ethylene and / or butene; Wherein, the corona layer composition further comprises an ethylene copolymer, which is a copolymer of ethylene and a monomer B, wherein the monomer B is selected from at least one of α,β-unsaturated carboxylic acid, α,β-unsaturated carboxylic acid ester and vinyl carboxylate; Wherein, based on the total weight of the ethylene copolymer, the content of the structural unit provided by the monomer B is 1-10wt%; Wherein, based on the total weight of the corona layer composition, the content of the multiphase polymer a is 90-99wt%, and the content of the ethylene copolymer is 1-10wt%; Wherein, the heat seal layer composition further comprises random copolymerized polypropylene of propylene and comonomer; Wherein, based on the total weight of the heat-sealing layer composition, the content of the multiphase polymer a is 80-99wt%, and the content of the random copolymer polypropylene is 1-20wt%; Based on the total weight of the core layer composition, the content of the multiphase polymer a is 70-90 wt %, and the content of the multiphase polymer b is 10-30 wt %.

2. The polypropylene film according to claim 1, wherein Based on the total weight of the multiphase polymer a, the content of the dispersed phase provided by the copolymer rubber is 5-16wt%; And / or, based on the total weight of the multiphase polymer b, the content of the dispersed phase provided by the copolymer rubber is 30-40 wt%.

3. The polypropylene film according to claim 1 or 2, wherein The copolymer rubber is propylene-ethylene copolymer rubber.

4. The polypropylene film according to claim 1 or 2, wherein The multiphase polymer a has a melt mass flow rate of 2-8 g / 10 min measured at 230° C. and a load of 2.16 kg; And / or, the multiphase polymer b has a melt mass flow rate of 2-8 g / 10 min measured at 230° C. and a load of 2.16 kg.

5. The polypropylene film according to claim 3, wherein The melt mass flow rate of the multiphase polymer a measured at 230° C. and a load of 2.16 kg is 2-8 g / 10 min.

6. The polypropylene film according to any one of claims 1, 2 or 5, wherein The weight average molecular weight of the copolymer rubber is 400,000-600,000 g / mol.

7. The polypropylene film according to claim 3, wherein The weight average molecular weight of the copolymer rubber is 400,000-600,000 g / mol.

8. The polypropylene film according to claim 4, wherein The weight average molecular weight of the copolymer rubber is 400,000-600,000 g / mol.

9. The polypropylene film according to claim 1, wherein Based on the total weight of the corona layer composition, the content of the multiphase polymer a is 92-99 wt %, and the content of the ethylene copolymer is 1-8 wt %.

10. The polypropylene film according to claim 9, wherein Based on the total weight of the corona layer composition, the content of the multiphase polymer a is 95-99 wt %, and the content of the ethylene copolymer is 1-5 wt %.

11. The polypropylene film according to claim 1, wherein The ethylene copolymer has a melt mass flow rate of 2 to 8 g / 10 min, measured at 230° C. and a load of 2.16 kg.

12. The polypropylene film according to claim 1, wherein The comonomer is selected from ethylene and / or α-olefins.

13. The polypropylene film according to claim 12, wherein The α-olefin is C4-C 12 α-olefins; And / or, based on the total weight of the random copolymerized polypropylene, the content of the structural units provided by the comonomer is 1-8 wt %.

14. The polypropylene film according to claim 13, wherein The α-olefin is at least one of 1-butene, 1-hexene and 1-octene.

15. The polypropylene film according to claim 12, wherein Based on the total weight of the heat-sealing layer composition, the content of the multiphase polymer a is 85-99 wt %, and the content of the random copolymer polypropylene is 1-15 wt %.

16. The polypropylene film according to claim 15, wherein Based on the total weight of the heat-sealing layer composition, the content of the multiphase polymer a is 90-99 wt %, and the content of the random copolymer polypropylene is 1-10 wt %.

17. The polypropylene film according to any one of claims 12 to 16, wherein The random copolymer polypropylene has a melt mass flow rate of 2-8 g / 10 min measured at 230° C. and a load of 2.16 kg.

18. The polypropylene film according to claim 1 or 2, wherein Based on the total weight of the core layer composition, the content of the multiphase polymer a is 70-85 wt %, and the content of the multiphase polymer b is 15-30 wt %.

19. The polypropylene film according to claim 18, wherein Based on the total weight of the core layer composition, the content of the multiphase polymer a is 80-85 wt %, and the content of the multiphase polymer b is 15-20 wt %.

20. The polypropylene film according to claim 1 or 2, wherein The film has a three-layer structure.

21. The polypropylene film according to claim 20, wherein The thickness ratio of the corona layer, the core layer and the heat sealing layer is 1:2-4:

1.

22. Use of the polypropylene film according to any one of claims 1 to 21 in the field of packaging.

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