CN115991020B

CN115991020B - Polypropylene composite film and preparation method and application thereof

Info

Publication number: CN115991020B
Application number: CN202111221948.6A
Authority: CN
Inventors: 张琦; 徐萌; 高达利; 尹华; 张师军; 袁浩; 徐耀辉; 侴白舸
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2021-10-20
Filing date: 2021-10-20
Publication date: 2024-09-17
Anticipated expiration: 2041-10-20
Also published as: CN115991020A

Abstract

The invention belongs to the field of films, and relates to a polypropylene composite film, and a preparation method and application thereof. The polypropylene composite film comprises at least one film layer A formed by a polypropylene composition A and at least one film layer B formed by a polypropylene composition B, wherein the polypropylene composition A comprises homopolypropylene a, a polypropylene graft B and a polyolefin elastomer c, and the polypropylene composition B comprises atactic polypropylene x and optionally a polyolefin elastomer y; the polypropylene graft b comprises structural units derived from a copolymerized polypropylene and structural units derived from an alkenyl-containing heterocyclic monomer. The polypropylene composite film prepared by the invention has good electrical insulation property, impact resistance, optical property and tensile property, and has good heat sealing strength at a lower heat sealing temperature.

Description

Polypropylene composite film and preparation method and application thereof

Technical Field

The invention belongs to the field of films, and particularly relates to a polypropylene composite film, and a preparation method and application thereof.

Background

Polypropylene films are typically produced by casting, biaxially oriented drawing, and the like, but polypropylene films produced from homopolymerized polypropylene materials typically have lower impact strength. Polypropylene films are commonly used in packaging applications where high impact properties are required, while good optical properties are also desired for the film for visual and aesthetic purposes of the contents. The method for improving the impact property of the polypropylene film can be used for preparing the film by using the block impact polypropylene or adding the polyolefin elastomer into the polypropylene, but the film prepared by the method generally has higher haze and poorer optical properties such as transparency and the like. It is also possible to add a nucleating agent to the film at the same time to reduce the haze of the film by thinning the crystals in the film, but this method results in a decrease in impact properties.

In order to improve the impact resistance and toughness of the film, the film can also be prepared by a multilayer coextrusion method, for example, a three-layer coextrusion method is adopted for preparing a composite film by CN101913279A, and the middle layer of the film is prepared according to the following ratio of 1:10-1: the elastomer and PP blended in proportion of 3 provide better impact resistance by the elastomer, but the method has the problem that the elastomer is difficult to disperse uniformly under the condition of higher elastomer content, and the film with better optical performance is still difficult to obtain, and the addition amount of the elastomer has certain limit because the problem of phase separation occurs when the addition amount is up to a certain level, thereby limiting the further improvement of the impact performance. Moreover, when the film is used for packaging purposes, it is generally desirable to have better heat seal properties at lower heat seal temperatures.

In addition to mechanical properties and optical properties, electrical insulation is also an important index for film applications in the electrical related fields, and thus, it is required to develop a film having electrical insulation properties, mechanical properties and optical properties.

Disclosure of Invention

The invention aims to solve the problem that the existing polypropylene film is difficult to have better optical performance, impact resistance and electrical insulation performance at the same time, and provides a polypropylene composite film and a preparation method thereof. The polypropylene film of the invention has good impact resistance, optical property, tensile property and insulating resistance, and has good heat sealing strength at lower heat sealing temperature.

A first aspect of the present invention provides a polypropylene composite film comprising at least one film layer a formed from a polypropylene composition a and at least one film layer B formed from a polypropylene composition B, wherein the polypropylene composition a comprises a homo-polypropylene a, a polypropylene graft B and a polyolefin elastomer c, and the polypropylene composition B comprises a random polypropylene x and optionally a polyolefin elastomer y; the polypropylene graft b comprises structural units derived from a copolymerized polypropylene and structural units derived from an alkenyl-containing heterocyclic monomer.

A second aspect of the present invention provides a method for preparing the polypropylene composite film, comprising: the raw material composition for forming each layer is extrusion-cast after an optional granulating process to form the composite film.

A third aspect of the present invention provides the use of the polypropylene composite film described above in the field of packaging materials.

The polypropylene composite film prepared by the invention has good electrical insulation property, impact resistance, optical property and tensile property, and has good heat sealing strength at a lower heat sealing temperature. The tensile strength of the film in the Machine Direction (MD) is more than or equal to 40MPa, and preferably the tensile strength of the film in the Machine Direction (MD) is more than or equal to 55MPa; the film haze is less than or equal to 6.5 percent, preferably less than or equal to 3.5 percent; the impact strength of the pendulum bob is more than or equal to 0.5J, preferably, the impact strength of the pendulum bob is more than or equal to 1.1J; the heat sealing strength at 150 ℃ is more than or equal to 16N/15mm, and the heat sealing strength at 150 ℃ is more than or equal to 21N/15mm; the volume resistivity is not less than 1.8X10 ¹⁵ Ω.m, preferably not less than 2.0X10 ¹⁵ Ω.m.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Detailed Description

The following describes specific embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.

The invention provides a polypropylene composite film, which comprises at least one film layer A formed by a polypropylene composition A and at least one film layer B formed by a polypropylene composition B, wherein the polypropylene composition A comprises homopolypropylene a, a polypropylene graft B and a polyolefin elastomer c, and the polypropylene composition B comprises atactic polypropylene x and optional polyolefin elastomer y; the polypropylene graft b comprises structural units derived from a copolymerized polypropylene and structural units derived from an alkenyl-containing heterocyclic monomer.

According to some embodiments of the invention, the polypropylene composite film has at least one of the following features: the tensile strength in the Machine Direction (MD) is more than or equal to 40MPa, and preferably the tensile strength in the Machine Direction (MD) is more than or equal to 55MPa; the film haze is less than or equal to 6.5 percent, preferably less than or equal to 3.5 percent; the impact strength of the pendulum bob is more than or equal to 0.5J, preferably, the impact strength of the pendulum bob is more than or equal to 1.1J; the heat sealing strength at 150 ℃ is more than or equal to 16N/15mm, and the heat sealing strength at 150 ℃ is more than or equal to 21N/15mm; the volume resistivity is not less than 1.8X10 ¹⁵ Ω.m, preferably not less than 2.0X10 ¹⁵ Ω.m.

According to some embodiments of the invention, the melt mass flow rate of the homo-polypropylene a at 230℃under a load of 2.16kg is from 2 to 15g/10min, the isotacticity is greater than 97% and the molecular weight distribution Mw/Mn is from 4.5 to 7.0. Homo-polypropylene meeting the above characteristics is commercially available. Such as the homopolypropylene with the PPH-FA03 of Qingdao brand, the homopolypropylene with the PPH-FA03 of China petrochemical brand and the homopolypropylene with the FC801 of Shanghai petrochemical brand. Or may be prepared by methods conventional in the art.

According to a preferred embodiment of the present invention, the content of structural units derived from the alkenyl group-containing heterocyclic monomer in the grafted state in the polypropylene graft b is 0.5 to 6wt%, preferably 0.5 to 4wt%, based on the weight of the polypropylene graft b.

In the present invention, the "structural unit" means that it is a part of a polypropylene graft, and the form thereof is not limited. In particular, "structural units derived from a copolymerized polypropylene" refers to products formed from the copolymerized polypropylene, including both "radical" forms and "polymeric" forms. "structural units derived from an alkenyl-containing heterocyclic monomer" refers to products formed from an alkenyl-containing heterocyclic monomer, which include both "radical" forms and "monomer" forms, as well as "polymer" forms. The "structural units" may be repeating units or may be non-repeating independent units.

In the present invention, the structural unit derived from the alkenyl group-containing heterocyclic monomer "in a grafted state" means a structural unit derived from the alkenyl group-containing heterocyclic monomer forming a covalent bond (grafting) with the copolymer polypropylene.

In the present invention, the meaning of "comonomer" of the polypropylene copolymer is known to the person skilled in the art and refers to a monomer copolymerized with propylene.

According to a preferred embodiment of the present invention, the polypropylene graft b is prepared by solid phase grafting reaction of a copolymerized polypropylene and an alkenyl group-containing heterocyclic monomer. The grafting reaction of the present invention is a radical polymerization reaction, and thus, the "in a grafted state" means a state in which a reactant forms a connection with another reactant after radical polymerization. The connection includes both direct and indirect connections.

During the grafting reaction, the alkenyl-containing heterocyclic monomer may polymerize to form a certain amount of ungrafted polymer. The polypropylene graft b of the invention not only comprises a product (crude product) directly prepared by grafting reaction of the copolymerized polypropylene and the heterocyclic monomer containing alkenyl, but also comprises a grafted modified polypropylene pure product obtained by further purifying the product.

According to a preferred embodiment of the invention, the polypropylene graft b has a melt mass flow rate of 0.01 to 30g/10min, preferably 0.05 to 20g/10min, further preferably 0.1 to 10g/10min, more preferably 0.2 to 8g/10min at 230℃under a load of 2.16 kg.

The heterocyclic monomer containing alkenyl can be any heterocyclic compound containing alkenyl capable of being polymerized by free radicals, and can be at least one selected from imidazole containing alkenyl substituent, pyrazole containing alkenyl substituent, carbazole containing alkenyl substituent, pyrrolidone containing alkenyl substituent, pyridine or pyridine salt containing alkenyl substituent, piperidine containing alkenyl substituent, caprolactam containing alkenyl substituent, pyrazine containing alkenyl substituent, thiazole containing alkenyl substituent, purine containing alkenyl substituent, morpholine containing alkenyl substituent and oxazoline containing alkenyl substituent; preferably, the heterocyclic monomer containing alkenyl is a heterocyclic monomer containing mono alkenyl.

Specifically, the alkenyl-containing heterocyclic monomer may be selected from: at least one of 1-vinylimidazole, 2-methyl-1-vinylimidazole, N-allylimidazole, 1-vinylpyrazole, 3-methyl-1-vinylpyrazole, vinylcarbazole, N-vinylpyrrolidone, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, vinylpyridine N-oxide, vinylpyridine salt, vinylpiperidine, N-vinylcaprolactam, 2-vinylpyrazine, N-vinylpiperazine, 4-methyl-5-vinylthiazole, N-vinylpurine, vinylmorpholine and vinyloxazoline.

According to the present invention, the copolymerized polypropylene is a propylene copolymer containing ethylene or higher alpha-olefins or a mixture thereof. Specifically, the comonomer of the copolymerized polypropylene is selected from at least one of C ₂-C₈ alpha-olefins other than propylene. The alpha-olefins of C ₂-C₈ other than propylene include, but are not limited to: at least one of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene, preferably ethylene and/or 1-butene, further preferably the copolymerized polypropylene consists of propylene and ethylene.

According to the invention, the copolymer polypropylene has, in addition to the above-mentioned compositional features, at least one of the following features: the comonomer content is 0.5 to 30mol%, preferably 4 to 25mol%; the xylene solubles content is 2-80wt%, preferably 18-75wt%, further preferably 30-70wt%; the comonomer content in the solubles is 10-70wt%, preferably 10-50wt%, further preferably 20-35wt%; the intrinsic viscosity ratio of the soluble substance to the polypropylene is 0.3 to 5, preferably 0.5 to 3, more preferably 0.8 to 1.3; the melt mass flow rate under a load of 2.16kg at 230℃is 0.01-60g/10min, preferably 0.05-35g/10min, further preferably 0.5-15g/10min; the melting temperature Tm is 100℃or higher, preferably 110 to 180℃and more preferably 120 to 170 ℃; the weight average molecular weight is 20X 104-60X 104g/mol.

The polypropylene copolymer of the present invention may be any commercially available polypropylene powder suitable for the present invention, and may also be produced by the usual polymerization processes described in the literature. Such as described with reference to CN101679557A, CN101058654 a.

The polypropylene graft b of the present invention can be prepared by a process comprising the steps of: and (3) carrying out solid-phase grafting reaction on a reaction mixture comprising the copolymerized polypropylene and the heterocyclic monomer containing alkenyl in the presence of inert gas to obtain the polypropylene graft.

The solid phase grafting reaction of the present invention can be carried out by referring to various methods conventional in the art, for example, forming active grafting sites on the polypropylene copolymer in the presence of a grafting monomer, or forming active grafting sites on the polypropylene copolymer followed by treatment with a grafting monomer. The grafting sites may be formed by treatment with a free radical initiator or by treatment with high energy ionizing radiation or microwaves. The free radicals in the polymer, which are generated as a result of the chemical or radiation treatment, form grafting sites on the polymer and initiate the polymerization of the monomers at these sites.

Preferably, the grafting sites are initiated by a free radical initiator and the grafting reaction is further carried out. In this case, the reaction mixture further comprises a free radical initiator; further preferably, the radical initiator is selected from peroxide-based radical initiators and/or azo-based radical initiators.

Wherein the peroxide radical initiator is preferably at least one selected from dibenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, diisopropyl peroxydicarbonate, t-butyl peroxy2-ethylhexanoate and dicyclohexyl peroxydicarbonate; the azo-based free radical initiator is preferably azobisisobutyronitrile and/or azobisisoheptonitrile.

More preferably, the grafting sites are initiated by peroxide-based free radical initiators and the grafting reaction is further carried out.

Furthermore, the grafting reaction of the present invention can also be carried out by the methods described in CN106543369A, CN104499281A, CN102108112A, CN109251270A, CN1884326a and CN 101492517B.

The amount of each component used in the grafting reaction of the present invention is not particularly limited on the premise of satisfying the above-mentioned product characteristics, and specifically, the mass ratio of the radical initiator to the alkenyl group-containing heterocyclic monomer may be 0.1 to 10:100, preferably 0.5 to 5:100. The mass ratio of the alkenyl group-containing heterocyclic monomer to the copolymerized polypropylene may be 0.3 to 12:100, preferably 0.5 to 10:100.

The process conditions of the grafting reaction are not particularly limited either, and specifically, the temperature of the grafting reaction may be 30 to 130 ℃, preferably 60 to 120 ℃; the time may be 0.5 to 10 hours, preferably 1 to 5 hours.

In the present invention, the "reaction mixture" includes all materials added to the grafting reaction system, and the materials may be added at one time or at different stages of the reaction.

The reaction mixture of the present invention may also include a dispersant, preferably water or an aqueous solution of sodium chloride. The mass amount of the dispersant is preferably 50 to 300% of the mass of the polypropylene copolymer.

The reaction mixture of the present invention may further comprise an interfacial agent which is an organic solvent having a swelling effect on polyolefin, preferably at least one of the following organic solvents having a swelling effect on copolymerized polypropylene: ether solvents, ketone solvents, aromatic hydrocarbon solvents, and alkane solvents; more preferably at least one of the following organic solvents: chlorobenzene, polychlorinated benzene, alkane or cycloalkane with more than C ₆, benzene, C ₁-C₄ alkyl substituted benzene, C ₂-C₆ aliphatic ether, C ₃-C₆ aliphatic ketone, decalin; further preferred is at least one of the following organic solvents: benzene, toluene, xylene, chlorobenzene, tetrahydrofuran, diethyl ether, acetone, hexane, cyclohexane, decalin, heptane. The mass content of the interfacial agent is preferably 1 to 30% by mass, more preferably 10 to 25% by mass of the polypropylene copolymer.

The reaction mixture of the present invention may further comprise an organic solvent, preferably at least one of C ₂-C₅ alcohols, C ₂-C₄ ethers and C ₃-C₅ ketones, more preferably at least one of C ₂-C₄ alcohols, C ₂-C₃ ethers and C ₃-C₅ ketones, and most preferably at least one of ethanol, diethyl ether and acetone, as a solvent for dissolving the solid free radical initiator. The mass content of the organic solvent is preferably 1-35% of the mass of the polypropylene copolymer.

As described above, the polypropylene graft b of the present invention includes both a product (crude product) directly obtained by grafting reaction of the copolymerized polypropylene and the grafting monomer and a pure product of the graft-modified polypropylene obtained by further purifying the product, and thus, in the preparation method of the present invention, a step of purifying the crude product may be optionally included. The purification may be carried out by various methods conventional in the art, such as extraction.

The grafting efficiency of the grafting reaction is not particularly limited, but the higher grafting efficiency is more beneficial to obtaining the polypropylene graft with the required performance through one-step grafting reaction. Therefore, the grafting efficiency of the grafting reaction is preferably controlled to be 30 to 100%, more preferably 35 to 80%. The concept of grafting efficiency is well known to the person skilled in the art and refers to the amount of grafting monomer grafted on/total amount of grafting monomer fed in the reaction.

The inert gas of the present invention may be various inert gases commonly used in the art, including but not limited to nitrogen, argon.

According to some embodiments of the invention, the polyolefin elastomer C is an elastomeric copolymer of ethylene and an alpha olefin, wherein the alpha olefin is preferably an alpha olefin of C ₃-C₁₂, more preferably at least one selected from propylene, 1-butene, 1-hexene and 1-octene.

According to some embodiments of the invention, the polyolefin elastomer y is an elastomeric copolymer of ethylene and an alpha olefin, wherein the alpha olefin is preferably a C ₃-C₁₂ alpha olefin, more preferably at least one selected from propylene, 1-butene, 1-hexene and 1-octene.

Polyolefin elastomers meeting the above characteristics are commercially available. For example, the polyolefin elastomer of Exxon brand 6102, the polyolefin elastomer of Santa Clay brand DF640, and the polyolefin elastomer of ExACT 3139. Or may be prepared by methods conventional in the art.

According to some embodiments of the present invention, the random polypropylene x is a copolymer of propylene and ethylene and/or butene, that is, at least one of a copolymer of propylene and ethylene, a copolymer of propylene and butene, and a copolymer of propylene and ethylene and butene, preferably at least one selected from an ethylene-propylene-butene ternary random copolymer, a propylene-ethylene binary random copolymer, and a propylene-butene binary random copolymer.

The melt mass flow rate of the atactic polypropylene x at 230℃under a load of 2.16kg is preferably 2-10g/10min.

Random polypropylene meeting the above characteristics is commercially available. Such as atactic polypropylene with the brand of F5006, atactic polypropylene with the brand of F500EPS, and atactic polypropylene with the brand of F800 EPS. Or may be prepared by methods conventional in the art.

According to some embodiments of the invention, the polypropylene composition a comprises 50 to 90wt% of the homo-polypropylene a, 5 to 45wt% of the polypropylene graft b and 2 to 40wt% of the polyolefin elastomer c, based on the total weight of the polypropylene composition a.

According to a preferred embodiment of the present invention, the polypropylene composition A comprises 55 to 75wt% of the homo-polypropylene a, 10 to 30wt% of the polypropylene graft b and 5 to 20wt% of the polyolefin elastomer c, based on the total weight of the polypropylene composition A.

Because the homo-polypropylene contains larger spherulites, the polypropylene grafts and the polyolefin elastomer contain rubber phases with different sizes, and the refractive indexes of the components are different and can be influenced together. According to the composition provided by the invention, the size of the rubber phase in the composition can meet the requirement of refractive index, so that a film with good optical performance can be obtained, impact energy can be well absorbed, the requirement of impact performance is met, and the film has good impact performance and optical performance. Meanwhile, as the macromolecular chain segments of the homo-polymer phase are more regular, crystallization occurs in the film preparation process, so that the film also has better tensile property. The polypropylene graft has obviously improved electrical insulation performance due to graft modification, excellent electrical insulation property, and excellent electrical insulation performance or antistatic performance of the film can be realized by matching with different processing aids.

According to some embodiments of the invention, the polypropylene composition B comprises from 40 to 100wt% of the random polypropylene x and from 0 to 60wt% of the polyolefin elastomer y, based on the total weight of the polypropylene composition B.

According to a preferred embodiment of the present invention, the polypropylene composition B comprises 70 to 90wt% of atactic polypropylene x and 10 to 30wt% of polyolefin elastomer y, based on the total weight of the polypropylene composition B.

The polyolefin elastomer can play a role in improving the impact property of the film, but can be separated from the matrix under the condition of larger addition amount, so that the mechanical property and the optical property are reduced. According to the composition B provided by the invention, the optical performance of the film can be ensured, and the heat sealing strength of the film can be improved.

According to some embodiments of the invention, the polyolefin elastomer c is present in parts by weight Wc based on 100 parts by weight of the total weight of the polypropylene composition a, based on 100 parts by weight of the total weight of the polypropylene composition B, the weight fraction of the polyolefin elastomer y is Wy, and the ratio of Wc to Wy is 6:1-1:4, and may be, for example, 5.5:1, 5:1, 4.5:1, 4:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, and any value therebetween.

According to a preferred embodiment of the invention, the ratio of Wc to Wy is 1:1-1:2.

As a result of the study of the present inventors, when the ratio of Wc to Wy is within the range of the present invention, the impact properties and optical properties of the film can be further improved and at the same time the extrusion process can be more stable.

According to some embodiments of the invention, the melt mass flow rate of the polypropylene composition A is in the range of 2-10g/10min, preferably 2-7g/10min, at 230℃under a load of 2.16 kg.

According to some embodiments of the invention, the melt mass flow rate of the polypropylene composition B is 2-10g/10min, preferably 3-8g/10min, at 230℃under a load of 2.16 kg.

When the melt mass flow rates of the polypropylene composition A and the polypropylene composition B are within the above ranges, the film preparation process can be made more stable, thereby ensuring that the film has better uniformity, mechanical properties and optical properties.

The composite film can be of a double-layer structure, can also be of a three-layer or more than three-layer film structure, and other layers can be the same as the film layer A or the film layer B in composition, can also be different from the film layer A or the film layer B in composition, and can also be formed by mixing a polypropylene composition A and a polypropylene composition B. When the polypropylene composite film has a structure with more than three layers, the film layer A is preferably used as an intermediate layer, such as a three-layer film comprising a film layer A, a film layer B and a film layer C, wherein the layer B and the layer C can be respectively positioned at two sides of the layer A.

According to some embodiments of the invention, the ratio of the sum of the thicknesses of the other film layers to the thickness of the film layer a is 1:4-2:1, for example, 1:4, 1:3.5, 1:3, 1:2.5, 1:2, 1:1.5, 1:1, 1.5:1, 2:1 and any value therebetween.

According to a preferred embodiment of the present invention, in the polypropylene composite film, the ratio of the sum of the thicknesses of the other film layers to the thickness of the film layer A is 1:2 to 1:1. At this ratio, the composite film has good mechanical properties.

In the present invention, in order to improve the performance of the composite film during processing, it is preferable that the composite film further contains an antioxidant and/or a lubricant.

In the present invention, the antioxidant may be various antioxidants commonly used in the art, and is not particularly limited. For example, antioxidant 1076, antioxidant 1010, antioxidant 168, and thioester antioxidants (such as DLTP and DSTP) can be used. The antioxidant may be contained in an amount of 0.1 to 0.8 parts by weight, preferably 0.2 to 0.4 parts by weight, based on 100 parts by weight of the total amount of the polypropylene composition A or the polypropylene composition B.

In the present invention, the lubricant is preferably a PEG-based lubricant and/or a mono Gan Zhilei lubricant. The lubricant is contained in an amount of 0.01 to 0.5 parts by weight, preferably 0.05 to 0.2 parts by weight, based on 100 parts by weight of the total amount of the polypropylene composition A or the polypropylene composition B.

In accordance with the present invention, the composite film preferably further comprises a film forming aid in order to enhance other properties of the composite film (e.g., stability, antistatic properties, etc.). The film forming aid may be at least one selected from the group consisting of an anti-halogen agent, a light stabilizer, a heat stabilizer, a colorant, a filler, a slip agent, an anti-sticking agent (anti-blocking agent), and an antistatic agent. The specific kind of the film forming aid may be selected conventionally in the art, and the present invention is not particularly limited thereto.

In the present invention, the content of the film forming aid may be 0.01 to 0.5 parts by weight, preferably 0.05 to 0.3 parts by weight, based on 100 parts by weight of the total amount of the polypropylene composition a or the polypropylene composition B.

The invention also provides a preparation method of the polypropylene composite film, which comprises the following steps: the raw material composition for forming each layer is extrusion-cast after an optional granulating process to form the composite film.

In the preparation method of the present invention, the process of granulating the pellets may generally include: and uniformly mixing the components of the polypropylene composition, an optional antioxidant, a lubricant and a film forming auxiliary agent in a high-speed stirrer, adding the uniformly mixed materials into a double-screw extruder, performing melt mixing, uniformly extruding, granulating and drying to obtain granules. Wherein, the processing temperature of the double-screw extruder can be controlled to be 170-230 ℃.

According to some embodiments of the invention, the pellets may be processed using extrusion casting. The process of the extrusion casting method can comprise the steps of respectively conveying the granules of different compositions into a plurality of extruders, enabling the granules to flow out through coextrusion compounding of die openings of the extruders, sequentially passing through a casting roller, a traction roller, cutting edges and rolling, and thus obtaining the composite film. Wherein the temperature of the extrusion casting may be controlled to 170-230 ℃ and the temperature of the casting roll may be 10-50 ℃. The specific process of preparing the film by the extrusion casting method is a common choice in the field, and will not be described herein.

The resulting composite film may be stretched in a subsequent process, such as biaxially stretching, to advantageously further improve the mechanical properties of the composite film.

According to one embodiment of the present invention, the polypropylene composite film is produced by extrusion casting and optionally stretching the polypropylene composition a and the polypropylene composition B after pelletization.

The polypropylene composite film of the present invention can be used in the field of packaging materials, such as in the field of high-end packaging where the film has high requirements for impact resistance, optical properties and electrical insulation properties, including but not limited to battery packaging, electronic product packaging or food, especially high-end food packaging.

Specific embodiments of the present invention will be described in detail below by way of examples. It should be understood that the examples described below are illustrative and explanatory only and are not restrictive of the invention.

In the following examples and comparative examples:

the film casting apparatus was purchased from Labtech, sweden under the model LCR400.

The polypropylene composition and film properties were tested according to the following methods, the film test results are shown in table 1:

(1) Melt Mass Flow Rate (MFR): the measurement was carried out according to the method specified in GB/T3682-2000, wherein the test temperature was 230℃and the load was 2.16kg.

(2) Film tensile strength: the measurement was carried out according to the method specified in GB/T1040.3-2006.

(3) Film pendulum impact strength: the measurement was performed according to the method specified in GB/T8809-2015.

(4) Film haze: the measurement was carried out according to the method specified in GB/T2410-2008.

(5) Film heat seal strength: the measurement was performed according to the method specified in QB/T2358. When the sample is prepared, the heat sealing temperature is 150 ℃, the heat sealing pressure is 0.2MPa, and the heat sealing time is 3s.

(6) Comonomer content in the copolymer polypropylene: comonomer content was determined by quantitative Fourier Transform Infrared (FTIR) spectroscopy. The correlation of the determined comonomer content is calibrated by quantitative Nuclear Magnetic Resonance (NMR) spectroscopy. The calibration method based on the results obtained by quantitative ¹³ C-NMR spectroscopy is performed according to the conventional methods in the art.

(7) Xylene solubles content in the copolymer polypropylene, comonomer content in the solubles, and intrinsic viscosity ratio of the solubles/copolymer polypropylene: the test was performed by means of CRYST-EX equipment from Polymer Char. Dissolving with trichlorobenzene solvent at 150deg.C, maintaining the temperature for 90min, sampling, cooling to 35deg.C, maintaining the temperature for 70min, and sampling.

(8) Weight average molecular weight of the copolymer polypropylene: the sample was dissolved in 1,2, 4-trichlorobenzene by using PL-GPC 220 type gel permeation chromatography (Polymer Laboratory) under high temperature GPC measurement, and the concentration was 1.0mg/ml. The test temperature was 150℃and the solution flow rate was 1.0ml/min. The molecular weight of polystyrene is used as an internal reference to make a standard curve, and the molecular weight and molecular weight distribution of the sample are calculated according to the outflow time.

(9) Melting temperature Tm: the melting process and crystallization process of the material were analyzed using a differential scanning calorimeter. The specific operation is as follows: under the protection of nitrogen, 5-10mg of samples are measured from 20 ℃ to 200 ℃ by adopting a three-stage temperature-rise and drop measurement method, and the melting and crystallization processes of the materials are reflected by the change of heat flow, so that the melting temperature Tm is calculated.

(10) Grafting efficiency GE, parameter M1: 2-4g of the grafted product is put into a Soxhlet extractor, extracted for 24 hours by ethyl acetate, unreacted monomers and homopolymers thereof are removed, and the pure grafted product is obtained, dried and weighed, and parameters M1 and grafting efficiency GE are calculated.

The parameter M1 represents the content of structural units derived from heterocyclic monomers in the polypropylene graft b, and in the invention, the calculation formulas of M1 and GE are as follows:

In the above formula, w ₀ is the mass of the PP matrix; w ₁ is the mass of grafted product drawn forward; w ₂ is the mass of the grafted product after extraction; w ₃ is the mass of the heterocyclic monomer added.

(11) Volume resistivity: the measurement was carried out according to the method specified in GB/T1410-2006.

(12) Degree of isotacticity: nuclear magnetic resonance spectrum (¹³ C-NMR) of propylene polymer at 400MHz was measured by ¹³ C NMR using a nuclear magnetic resonance spectrometer (NMR) model AVANCE III from Bruker, switzerland, wherein the solvent was deuterated orthodichlorobenzene and the sample concentration was 250mg sample/2.5 mL solvent. To prevent oxidative degradation of the sample during dissolution and data collection, 2mg of 2, 6-di-tert-butyl-4-methylphenol antioxidant (BHT for short) was added to the sample. The sample was dissolved at 140℃and collected ¹³ C-NMR, the test temperature was 125℃and the probe had a gauge of 10mm, 90℃pulses, the sampling time AQ was 5 seconds, the delay time D1 was 1 second, and the number of scans was 6000. The isotacticity is the content of isotacticity [ mm ] of the two-unit group.

(13) Molecular weight distribution (Mw/Mn): the gel permeation chromatograph was used in combination with an IR5 type infrared detector, and the gel permeation chromatograph was used as a model PL-GPC 220 by the company Polymer Laboratories in the United kingdom, wherein the column in the gel permeation chromatograph was 3 columns of Plgel 10 μm MIXED-B connected in series, the solvent and mobile phase were 1,2, 4-trichlorobenzene (containing 0.3g/1000mL of antioxidant 2, 6-di-tert-butyl-p-cresol), the column temperature was 150℃and the flow rate was 1.0mL/min, and a narrow-distribution polystyrene standard of EASICAL PS-1 was produced by the company PL for universal calibration.

Preparation example 1

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 18.1wt%, xylene solubles content 48.7wt%, comonomer content 31.9wt% in the solubles, solubles/copolymerized polypropylene intrinsic viscosity ratio 0.89, weight average molecular weight 34.3X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load 1.21g/10min, tm=143.4 ℃, sieving to remove fines less than 40 mesh. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 1.2g of dibenzoyl peroxide and 40g of 4-vinylpyridine are added, stirred and mixed for 30min, swelled for 30min at 50 ℃, heated to 90 ℃ and reacted for 4 hours. After the reaction is finished, nitrogen is purged and cooled to obtain polypropylene-g-4-vinyl pyridine C1, wherein the melt mass flow rate is 0.89g/10min, M1 is 0.92%, and the grafting efficiency is 47%.

Preparation example 2

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 4.8wt%, xylene solubles content 19.2wt%, comonomer content 17.6wt% in the solubles, solubles/copolymerized polypropylene intrinsic viscosity ratio 1.04, weight average molecular weight 29.2X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load 5.37g/10min, tm=163.3 ℃, sieving to remove fines less than 40 mesh. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 3g of dibenzoyl peroxide is dissolved in 100g of acetone, the obtained acetone solution is added into a reaction system, the temperature is raised to 40 ℃, nitrogen is purged for 30min to remove acetone, 60g of N-vinyl pyrrolidone is added, stirring and mixing are carried out for 30min, the temperature is raised to 100 ℃, and the reaction is carried out for 1 hour. After the reaction, cooling to obtain polypropylene-g-N-vinyl pyrrolidone C2, wherein the melt mass flow rate is 5.07g/10min, the M1 is 1.09%, and the grafting efficiency is 37%.

Preparation example 3

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 12.6wt%, xylene solubles content 30.6wt%, comonomer content 43.6wt% in the solubles, solubles/copolymerized polypropylene intrinsic viscosity ratio 1.84, weight average molecular weight 27.1X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load 8.46g/10min, tm=162.0 ℃, sieving to remove fines less than 40 mesh. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 7g of lauroyl peroxide and 160g of N-vinylcarbazole are dissolved in 500g of interfacial agent toluene to form a solution, the solution is added into a reaction kettle, stirred and mixed for 30min, the temperature is raised to 95 ℃, 3kg of dispersant water at 95 ℃ is added, and the reaction is carried out for 3 hours. After the reaction is finished, cooling, filtering to remove dispersant water, and vacuum drying at 70 ℃ for 10 hours to obtain polypropylene-g-N-vinylcarbazole C3, wherein the melt mass flow rate is 7.98g/10min, the M1 is 3.45%, and the grafting efficiency is 46%.

Preparation example 4

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 9.3wt%, xylene solubles content 21.0wt%, comonomer content 35.4wt% in the solubles, solubles/copolymerized polypropylene intrinsic viscosity ratio 1.68, weight average molecular weight 30.4x ⁴ g/mol, MFR at 230 ℃,2.16kg load 5.69g/10min, tm= 163.0 ℃, and sieving to remove fines less than 40 mesh. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 2g of tert-butyl peroxy (2-ethylhexanoate) and 40g of 1-vinylimidazole were added, stirred and mixed for 30min, swollen for 2 hours at 55 ℃, heated to 95 ℃ and reacted for 4 hours. After the reaction is finished, nitrogen is purged and cooled to obtain polypropylene-g-1-vinylimidazole C4, wherein the melt mass flow rate is 6.56g/10min, M1 is 0.75%, and the grafting efficiency is 38%.

Example 1

This example is used to illustrate the preparation of the polypropylene composite film provided by the present invention.

(1) Preparation of polypropylene composition A:

The component a is homopolymerized polypropylene with the brand name of PPH-FA03, and is purchased from Qingdao refining, the mass flow rate of a melt is 3.1g/10min, the isotacticity is 98%, and the molecular weight distribution Mw/Mn is 4.7; component b is polypropylene-g-4-vinylpyridine C1; component c was a polyolefin elastomer having a trade designation 6102, available from Exxon, and was an ethylene-propylene copolymer having an ethylene structural unit content of 16% by weight. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wa of the component a is 75 weight parts, the weight part Wb of the component b is 10 weight parts, and the weight part Wc of the component c is 15 weight parts. Adding a lubricant (the lubricant is PEG lubricant produced by Swiss Clariant company, the molecular weight is 10000, the adding amount of the lubricant is 0.1 part by weight based on 100 parts by weight of the sum of the mass of the component a, the mass of the component b and the mass of the component c), adding the mixture into a high-speed stirrer, uniformly mixing, adding the mixed material into a feeder of a double-screw extruder manufactured by W & P company, feeding the material into the double-screw extruder through the feeder, keeping the temperature of the screw between 160 ℃ and 230 ℃ in the processing process, uniformly mixing, extruding, granulating and drying through the screw to obtain polypropylene composition granules, and detecting the melt mass flow rate MFR _A = 3.1g/10min.

(2) Preparation of polypropylene composition B:

The component x is random polypropylene with the brand number of F5006, is purchased from the petrifaction of Yanshan and is an ethylene-propylene-butene terpolymer, and the melt mass flow rate is 5.2g/10min; component y was a polyolefin elastomer having a trade designation 6102, available from Exxon and was an ethylene-propylene copolymer having an ethylene structural unit content of 16% by weight. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wx of the component x is 75 weight parts, and the weight part Wy of the component y is 25 weight parts. Wc: wy is 3:5. The other steps are the same as in step (1), and pellets of the polypropylene composition B are finally obtained, and the melt mass flow rate MFR _B =3.2 g/10min is detected.

(3) Preparation of a composite film:

drying the polypropylene composition A and the polypropylene composition B pellets obtained in the step (1) and the step (2), and then adding the polypropylene composition A into a core layer extruder of a multilayer extrusion casting machine, and adding the polypropylene composition B into an upper surface layer extruder of the multilayer extrusion casting machine, wherein an inorganic anti-sticking agent (silicon dioxide, the same applies below) is added into the upper surface layer extruder, and the weight ratio of the anti-sticking agent to the polypropylene composition pellets is 0.2:100. In the casting process, the casting chill roll temperature was set to 30 ℃, and wound up to produce a composite film consisting of an upper skin layer (film layer B) and a core layer (film layer a). The film thickness was 50 μm, with a thickness ratio of film layer B to film layer A of 1:2.

Example 2

(1) Preparation of polypropylene composition A:

The component a is homopolymerized polypropylene with the brand name of PPH-FA03, and is purchased from original petrochemical industry, the mass flow rate of a melt is 3.0g/10min, the isotacticity is 98%, and the molecular weight distribution Mw/Mn is 4.6; component b is polypropylene-g-N-vinyl pyrrolidone C2; component c was a polyolefin elastomer, commercially available from Sanjing, as an ethylene-1-butene copolymer, having a butene structural unit content of 32% by weight, under the designation DF 640. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wa of the component a is 65 weight parts, the weight part Wb of the component b is 30 weight parts, and the weight part Wc of the component c is5 weight parts. Adding a lubricant (the lubricant is PEG lubricant produced by Swiss Clariant company, the molecular weight is 10000, the adding amount of the lubricant is 0.1 part by weight based on 100 parts by weight of the sum of the mass of the component a, the mass of the component b and the mass of the component c), adding the mixture into a high-speed stirrer, uniformly mixing, adding the mixed material into a feeder of a double-screw extruder manufactured by W & P company, feeding the material into the double-screw extruder through the feeder, keeping the temperature of the screw between 160 ℃ and 230 ℃ in the processing process, uniformly mixing by melting through the screw, extruding, granulating and drying to obtain polypropylene composition A granules, and detecting the melt mass flow rate MFR _A = 3.7g/10min.

(2) Preparation of polypropylene composition B:

The component x is random polypropylene with the brand of F500EPS, is purchased from Shanghai petrochemical industry, is an ethylene-propylene-butene terpolymer, and has a melt mass flow rate of 5.3g/10min; the component y is a polyolefin elastomer with the brand DF640, which is purchased from Sanjing corporation and is an ethylene-1-butene copolymer, and the butene structural unit content is 32 weight percent. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wx of the component x is 90 weight parts, and the weight part Wy of the component y is 10 weight parts. Wc: wy is 1:2. The other steps are the same as in step (1), and pellets of the polypropylene composition B are finally obtained, and the melt mass flow rate MFR _B =5.2 g/10min is detected.

(3) Preparation of a composite film:

drying the polypropylene composition A and the polypropylene composition B pellets obtained in the step (1) and the step (2), adding the polypropylene composition A into a core layer extruder of a multilayer extrusion casting machine, and adding the polypropylene composition B into an upper surface layer extruder and a lower surface layer extruder of the multilayer extrusion casting machine, wherein inorganic anti-sticking agents (silicon dioxide, the same applies below) are added into the upper surface layer extruder and the lower surface layer extruder, and the weight ratio of the anti-sticking agents to the polypropylene composition pellets is 0.2:100. In the casting process, the casting chill roll temperature was set to 30 ℃ and wound up to produce a composite film consisting of upper and lower skin layers (film layer B) and a core layer (film layer a). The film thickness was 50 μm, wherein the ratio of the sum of the upper and lower skin layers thickness to the core layer thickness was 1:1.

Example 3

(1) Preparation of polypropylene composition A:

Component a is homo-polypropylene with the brand of FC801, which is purchased from Shanghai petrochemical industry, the melt mass flow rate is 7.8g/10min, the isotacticity is 98%, and the molecular weight distribution Mw/Mn is 4.8; the component b is polypropylene-g-N-vinyl carbazole C3; component c was a polyolefin elastomer having the trade designation EXACT3139, available from Exxon and was an ethylene-1-octene copolymer having an octene structural unit content of 14wt%. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wa of the component a is 55 weight parts, the weight part Wb of the component b is 25 weight parts, and the weight part Wc of the component c is 20 weight parts. Adding a lubricant (the lubricant is PEG lubricant produced by Swiss Clariant company, the molecular weight is 10000, the adding amount of the lubricant is 0.1 part by weight based on 100 parts by weight of the sum of the mass of the component a, the mass of the component b and the mass of the component c), adding the mixture into a high-speed stirrer, uniformly mixing, adding the mixed material into a feeder of a double-screw extruder manufactured by W & P company, feeding the material into the double-screw extruder through the feeder, keeping the temperature of the screw between 160 ℃ and 230 ℃ in the processing process, uniformly mixing by melting through the screw, extruding, granulating and drying to obtain polypropylene composition A granules, and detecting the melt mass flow rate MFR _A = 8.9g/10min.

(2) Preparation of polypropylene composition B:

The component x is random polypropylene with the brand of F800EPS, is purchased from Shanghai petrochemical industry, is an ethylene-propylene-butene terpolymer, and has a melt mass flow rate of 8.2g/10min; component y was a polyolefin elastomer having the trade designation EXACT3139, available from Exxon and was an ethylene-1-octene copolymer having an octene structural unit content of 14wt%. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wx of the component x is 80 weight parts, and the weight part Wy of the component y is 20 weight parts. Wc: wy is 1:1. The other steps are the same as in step (1), and pellets of the polypropylene composition B are finally obtained, and the melt mass flow rate MFR _B =7.9 g/10min is detected.

(3) Preparation of a composite film:

The preparation procedure is the same as in step (3) of example 1.

Example 4

(1) Preparation of polypropylene composition A:

The procedure is as in example 1. The difference is that the part by weight Wa of the component a is 80 parts by weight, the part by weight Wb of the component b is 18 parts by weight, and the part by weight Wc of the component c is 2 parts by weight. Pellets of the polypropylene composition a were obtained, which was examined for melt mass flow rate MFR _A =3.0 g/10min.

(2) Preparation of polypropylene composition B:

The procedure is as in example 1. The difference is that the weight part Wx of the component x is 92 weight parts, and the weight part Wy of the component y is 8 weight parts. Wc: wy is 1:4. The other steps are the same as in step (1), and pellets of the polypropylene composition B are finally obtained, and the melt mass flow rate MFR _B =7.7 g/10min is detected.

(3) Preparation of a composite film:

The procedure is as in example 1. The film thickness was 50 μm, with a thickness ratio of film layer B to film layer A of 1:3.

Example 5

(1) Preparation of polypropylene composition A:

The procedure was as in example 3, except that the part by weight Wa of component a was 90 parts by weight, the part by weight Wb of component b was 5 parts by weight, and the part by weight Wc of component c was 5 parts by weight. Pellets of polypropylene composition a were obtained, which was examined for melt mass flow rate MFR _A =8.3 g/10min.

(2) Preparation of polypropylene composition B:

the procedure is as in example 3, except that Wc: wy is 1:4.

(3) Preparation of a composite film:

the procedure is as in example 2. The film thickness was 50 μm, with the upper and lower skin layers having a thickness ratio of 2:1 to the core layer.

Example 6

(1) Preparation of polypropylene composition A:

The procedure was as in example 3, except that Wa, wb, and Wc were 50 parts by weight, 40 parts by weight, and 10 parts by weight, respectively. Pellets of the polypropylene composition a were obtained, which was examined for melt mass flow rate MFR _A =8.4 g/10min.

(2) Preparation of polypropylene composition B:

The procedure is as in example 3, except that the mass fraction Wx of component x is 60 parts by weight and the mass fraction Wy of component y is 40 parts by weight. Wc: wy is 1:4. Pellets of the polypropylene composition B were finally obtained, which were examined for melt mass flow rate MFR _B =9.8 g/10min.

(3) Preparation of a composite film:

The procedure is as in example 3. The film thickness was 50 μm, with the upper skin layer thickness and the thickness ratio to the core layer being 1:4.

Example 7

(1) Preparation of polypropylene composition A:

The procedure is as in example 1. The difference is that the part by weight Wa of the component a is 50 parts by weight, the part by weight Wb of the component b is 20 parts by weight, and the part by weight Wc of the component c is 30 parts by weight. Pellets of the polypropylene composition a were obtained, which was examined for melt mass flow rate MFR _A =3.7 g/10min.

(2) Preparation of polypropylene composition B:

The procedure is as in example 1. The difference is that the weight part Wx of the component x is 85 parts by weight and the weight part Wy of the component y is 15 parts by weight. Wc: wy is 2:1. The other steps are the same as in step (1), and pellets of the polypropylene composition B are finally obtained, and the melt mass flow rate MFR _B =4.5 g/10min is detected.

(3) Preparation of a composite film:

Example 8

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition A, the component a was 40 parts by weight of Wa, the component b was 40 parts by weight of Wb, and the component c was 20 parts by weight of Wc. Wc: wy is 4:5. Pellets of the polypropylene composition a were obtained, which was examined for melt mass flow rate MFR _A =2.3 g/10min.

Example 9

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition A, the component a was 50 parts by weight of Wa, the component b was 45 parts by weight of Wb, and the component c was 5 parts by weight of Wc. Wc: wy is 1:5. Pellets of the polypropylene composition a were obtained, which was examined for melt mass flow rate MFR _A =1.9 g/10min.

Example 10

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition A, the component a was 50 parts by weight of Wa, the component b was 10 parts by weight of Wb, and the component c was 40 parts by weight of Wc. Wc: wy is 8:5. Pellets of the polypropylene composition a were obtained, which was examined for melt mass flow rate MFR _A =3.0 g/10min.

Example 11

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition B, the component x was 50 parts by weight of Wx and the component y was 50 parts by weight of Wy. Wc: wy is 3:10. Pellets of polypropylene composition B were obtained, which were examined for melt mass flow rate MFR _B =4.7 g/10min.

Example 12

A polypropylene composite film was prepared as in example 1. The polypropylene composition B, however, only contains component x.

Example 13

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition B, the component x was 92.5 parts by weight of Wx and the component y was 7.5 parts by weight of Wy. Wc: wy is 2:1. Pellets of the polypropylene composition B were finally obtained, which were examined for melt mass flow rate MFR _B =5.5 g/10min.

Example 14

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition A, the component b is polypropylene-g-1-vinylimidazole C4; pellets of the polypropylene composition a were obtained, which was examined for melt mass flow rate MFR _A =3.4 g/10min. In the preparation of the polypropylene composition B, the mass fraction Wx of the component x was 85 parts by weight and the mass fraction Wy of the component y was 15 parts by weight. Wc: wy is 1:1. Pellets of the polypropylene composition B were finally obtained, which were examined for melt mass flow rate MFR _B =5.1 g/10min.

Example 15

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition B, the component x was 70 parts by weight of Wx and the component y was 30 parts by weight of Wy. Wc: wy is 1:2. Pellets of the polypropylene composition B were finally obtained, which were examined for melt mass flow rate MFR _B =4.4 g/10min.

Example 16

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition B, the component x was 40 parts by weight of Wx and the component y was 60 parts by weight of Wy. Wc: wy is 1:4. Pellets of the polypropylene composition B were finally obtained, which were examined for melt mass flow rate MFR _B =2.9 g/10min.

Example 17

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition B, the mass fraction Wx of the component x was 97 parts by weight and the mass fraction Wy of the component y was 3 parts by weight. Wc: wy is 5:1. Pellets of the polypropylene composition B were finally obtained, which were examined for melt mass flow rate MFR _B =6.0 g/10min.

Comparative example 1

A polypropylene composite film was prepared as in example 1. Except that the polypropylene composition A alone was extrusion-cast as a monolayer film having a film thickness of 50. Mu.m.

Comparative example 2

A polypropylene composite film was prepared as in example 2. Except that the polypropylene composition B alone was extrusion cast as a monolayer film having a film thickness of 50. Mu.m.

Comparative example 3

A polypropylene composite film was prepared as in example 1. Except that the polypropylene composition a contains only component b.

Comparative example 4

A polypropylene composite film was prepared as in example 1. The polypropylene composition A, however, contained only the component a and the component b, wherein the component a was 75 parts by weight of Wa and the component b was 25 parts by weight of Wb.

Comparative example 5

A polypropylene composite film was prepared as in example 1. The polypropylene composition A, however, contained only the component a and the component c, wherein the component a was 75 parts by weight of Wa and the component c was 25 parts by weight of Wc.

TABLE 1

As can be seen from the results of the examples in Table 1, the polypropylene composite film of the present invention has good impact resistance, optical properties and tensile properties at the same time, and also has good heat seal strength. The film of the invention has a Machine Direction (MD) tensile strength of not less than 40MPa, a film haze of not more than 6.5%, a pendulum impact strength of not less than 0.5J, a heat seal strength at 150 ℃ of not less than 16N/15mm, and a volume resistivity of not less than 1.8X10 ¹⁵ Ω.m. As can be seen from the preferred examples, the film has a Machine Direction (MD) tensile strength of 55MPa or more, a film haze of 3.5% or less, a pendulum impact strength of 1.1J or more, a heat seal strength at 150℃of 21N/15mm or more, and a volume resistivity of 2.0X10 ¹⁵ Ω.m or more. As can be seen from the comparative examples, it is difficult to achieve a balance of various properties by using only a single film or a change in the composition ratio of the film layers, and it is difficult to obtain a film having a uniform thickness because the film surface is unstable during extrusion casting.

The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described.

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

Claims

1. A polypropylene composite film, characterized in that the polypropylene composite film comprises at least one film layer a formed from a polypropylene composition a and at least one film layer B formed from a polypropylene composition B, wherein the polypropylene composition a comprises a homo-polypropylene a, a polypropylene graft B and a polyolefin elastomer c, and the polypropylene composition B comprises a random polypropylene x and optionally a polyolefin elastomer y; the polypropylene graft b comprises structural units derived from a copolymerized polypropylene and structural units derived from an alkenyl-containing heterocyclic monomer;

The polypropylene composition A comprises 50-90wt% of homo-polypropylene a, 5-45wt% of polypropylene graft b and 2-40wt% of polyolefin elastomer c based on the total weight of the polypropylene composition A; the polypropylene composition B comprises 40 to 100wt% of random polypropylene x and 0 to 60wt% of polyolefin elastomer y based on the total weight of the polypropylene composition B;

When the polypropylene composition B comprises a polyolefin elastomer y, the weight part of the polyolefin elastomer c is Wc based on 100 weight parts of the total weight of the polypropylene composition A, the weight part of the polyolefin elastomer y is Wc based on 100 weight parts of the total weight of the polypropylene composition B, and the ratio of Wc to Wy is 6:1-1:4;

The content of the structural unit which is derived from the heterocyclic monomer containing alkenyl and is in a grafted state in the polypropylene graft b is 0.5-6 wt percent based on the weight of the polypropylene graft b.

2. The polypropylene composite film according to claim 1, wherein the polypropylene composite film has at least one of the following characteristics: the longitudinal tensile strength is more than or equal to 40MPa; the haze of the film is less than or equal to 6.5 percent; the impact strength of the pendulum bob is more than or equal to 0.5J; the heat sealing strength at 150 ℃ is more than or equal to 16N/15mm; the volume resistivity is more than or equal to 1.8X10 ¹⁵ Ω.m.

3. The polypropylene composite film according to claim 2, wherein the longitudinal tensile strength is not less than 55MPa.

4. The polypropylene composite film according to claim 2, wherein the film haze is 3.5% or less.

5. The polypropylene composite film according to claim 2, wherein the pendulum impact strength is not less than 1.1J.

6. The polypropylene composite film according to claim 2, wherein the heat seal strength at 150 ℃ is not less than 21N/15mm.

7. The polypropylene composite film according to claim 2, wherein the volume resistivity is not less than 2.0X10 ¹⁵. OMEGA.m.

8. The polypropylene composite film according to claim 1, wherein the polypropylene composition a has a melt mass flow rate of 2 to 10g/10min at 230 ℃ under a load of 2.16 kg;

the melt mass flow rate of the polypropylene composition B is 2-10 g/10min under the action of a load of 2.16kg at 230 ℃.

9. The polypropylene composite film according to claim 8, wherein the polypropylene composition a has a melt mass flow rate of 2 to 7 g/10min at 230 ℃ under a load of 2.16 kg.

10. The polypropylene composite film according to claim 8, wherein the polypropylene composition B has a melt mass flow rate of 3 to 8g/10min at 230 ℃ under a load of 2.16 kg.

11. The polypropylene composite film according to claim 1, wherein the melt mass flow rate of the homo-polypropylene a at 230 ℃,2.16 kg load is 2-15g/10min, the isotacticity is more than 97%, and the molecular weight distribution Mw/Mn is 4.5-7.0.

12. The polypropylene composite film according to claim 1, wherein the content of the structural unit in the grafted state derived from the alkenyl group-containing heterocyclic monomer in the polypropylene graft b is 0.5 to 4 wt% based on the weight of the polypropylene graft b;

The melt mass flow rate of the polypropylene graft b at 230 ℃ and under the load of 2.16 kg is 0.01-30 g/10min.

13. The polypropylene composite film according to claim 12, wherein the polypropylene graft b has a melt mass flow rate of 0.05-20 g/10min at 230 ℃, under a load of 2.16 kg.

14. The polypropylene composite film according to claim 13, wherein the polypropylene graft b has a melt mass flow rate of 0.1 to 10 g/10min at 230 ℃, under a load of 2.16 kg.

15. The polypropylene composite film according to claim 14, wherein the polypropylene graft b has a melt mass flow rate of 0.2 to 8 g/10min at 230 ℃, under a load of 2.16 kg.

16. The polypropylene composite film according to claim 1, wherein the polypropylene graft b is prepared by solid phase grafting reaction of copolymerized polypropylene and an alkenyl group-containing heterocyclic monomer.

17. The polypropylene composite film according to claim 1, wherein the comonomer of the copolymerized polypropylene is selected from at least one of C ₂-C₈ α -olefins other than propylene;

The copolymerized polypropylene has at least one of the following characteristics: the comonomer content is 0.5-30 mol%; the xylene solubles content is 2-80 wt%; the content of comonomer in the soluble matters is 10-70 wt%; the intrinsic viscosity ratio of the soluble matters to the polypropylene is 0.3-5; melt mass flow rate at 230 ℃,2.16 kg load is 0.01-60 g/10 min; the melting temperature Tm is above 100 ℃; the weight average molecular weight was 20X 10 ⁴-60×10⁴ g/mol.

18. The polypropylene composite film according to claim 17, wherein the comonomer content of the copolymerized polypropylene is 4 to 25 mol%.

19. The polypropylene composite film according to claim 17, wherein the copolymerized polypropylene has a xylene solubles content of 18 to 75 wt%.

20. The polypropylene composite film according to claim 19, wherein the copolymerized polypropylene has a xylene solubles content of 30 to 70 wt%.

21. The polypropylene composite film according to claim 17, wherein the comonomer content in the soluble fraction of the copolymerized polypropylene is 10 to 50 wt%.

22. The polypropylene composite film according to claim 21, wherein the comonomer content in the soluble fraction of the copolymerized polypropylene is 20 to 35wt%.

23. The polypropylene composite film according to claim 17, wherein the ratio of the intrinsic viscosity of the polypropylene to the solubles of the copolymerized polypropylene is 0.5 to 3.

24. The polypropylene composite film according to claim 23, wherein the intrinsic viscosity ratio of the soluble matter of the copolymerized polypropylene to the polypropylene is 0.8 to 1.3.

25. The polypropylene composite film according to claim 17, wherein the copolymerized polypropylene has a melt mass flow rate of 0.05-35 g/10min at 230 ℃, under a load of 2.16 kg.

26. The polypropylene composite film according to claim 25, wherein the copolymerized polypropylene has a melt mass flow rate of 0.5 to 15 g/10min at 230 ℃ under a load of 2.16 kg.

27. The polypropylene composite film according to claim 17, wherein the copolymerized polypropylene has a melting temperature Tm of 110 to 180 ℃.

28. The polypropylene composite film according to claim 27, wherein the copolymerized polypropylene has a melting temperature Tm of 120 to 170 ℃.

29. The polypropylene composite film according to claim 1, wherein the heterocyclic monomer containing an alkenyl group is at least one selected from the group consisting of imidazole containing an alkenyl group substituent, pyrazole containing an alkenyl group substituent, carbazole containing an alkenyl group substituent, pyrrolidone containing an alkenyl group substituent, pyridine or a pyridine salt containing an alkenyl group substituent, piperidine containing an alkenyl group substituent, caprolactam containing an alkenyl group substituent, pyrazine containing an alkenyl group substituent, thiazole containing an alkenyl group substituent, purine containing an alkenyl group substituent, morpholine containing an alkenyl group substituent and oxazoline containing an alkenyl group substituent.

30. The polypropylene composite film according to claim 29, wherein the alkenyl group-containing heterocyclic monomer is a mono-alkenyl group-containing heterocyclic monomer.

31. The polypropylene composite film according to claim 29, wherein the alkenyl group-containing heterocyclic monomer is selected from the group consisting of: at least one of 1-vinylimidazole, 2-methyl-1-vinylimidazole, N-allylimidazole, 1-vinylpyrazole, 3-methyl-1-vinylpyrazole, vinylcarbazole, N-vinylpyrrolidone, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, vinylpyridine N-oxide, vinylpyridine salt, vinylpiperidine, N-vinylcaprolactam, 2-vinylpyrazine, N-vinylpiperazine, 4-methyl-5-vinylthiazole, N-vinylpurine, vinylmorpholine and vinyloxazoline.

32. The polypropylene composite film according to claim 1, wherein the polyolefin elastomer c and the polyolefin elastomer y are each independently an elastomeric copolymer of ethylene and an alpha olefin.

33. The polypropylene composite film according to claim 32, wherein the alpha olefin is a C ₃-C₁₂ alpha olefin.

34. The polypropylene composite film according to claim 33, wherein the alpha olefin is selected from at least one of propylene, 1-butene, 1-hexene, and 1-octene.

35. The polypropylene composite film according to claim 1, wherein the random polypropylene x is a copolymer of propylene with ethylene and/or butene; the melt mass flow rate of the atactic polypropylene x under the load of 2.16 kg at 230 ℃ is 2-10 g/10min.

36. The polypropylene composite film according to claim 35, wherein the random polypropylene x is at least one selected from the group consisting of ethylene-propylene-butene ternary random copolymer, propylene-ethylene binary random copolymer, and propylene-butene binary random copolymer.

37. The polypropylene composite film according to claim 1, wherein the polypropylene composition a comprises 55 to 75wt% of the homo-polypropylene a, 10 to 30wt% of the polypropylene graft b and 5 to 20wt% of the polyolefin elastomer c based on the total weight of the polypropylene composition a.

38. The polypropylene composite film according to claim 1, wherein the polypropylene composition B comprises 70 to 90wt% of the random polypropylene x and 10 to 30wt% of the polyolefin elastomer y based on the total weight of the polypropylene composition B.

39. The polypropylene composite film according to claim 1, wherein the weight part of the polyolefin elastomer c is Wc based on 100 weight parts of the total weight of the polypropylene composition a, the weight part of the polyolefin elastomer y is Wc based on 100 weight parts of the total weight of the polypropylene composition B, and the ratio of Wc to Wy is 1:1 to 1:2.

40. The polypropylene composite film according to any one of claims 1 to 39, wherein the ratio of the sum of the thicknesses of the other film layers to the thickness of the film layer a is 1:4 to 2:1.

41. The polypropylene composite film according to claim 40, wherein the ratio of the sum of the thicknesses of the other film layers to the thickness of the film layer A is 1:2 to 1:1.

42. The polypropylene composite film according to any one of claims 1 to 39, wherein when the polypropylene composite film has a three-layer or more structure, the film layer a is an intermediate layer.

43. The polypropylene composite film according to any one of claims 1 to 39, wherein the polypropylene composition a and/or the polypropylene composition B further comprises an antioxidant and/or a lubricant.

44. The polypropylene composite film according to claim 43, wherein the antioxidant is at least one selected from the group consisting of antioxidant 1076, antioxidant 1010, antioxidant 168 and a thioester antioxidant.

45. The polypropylene composite film according to claim 43, wherein the antioxidant is contained in an amount of 0.1 to 0.8 parts by weight based on 100 parts by weight of the total amount of the polypropylene composition A or the polypropylene composition B.

46. The polypropylene composite film according to claim 45, wherein the antioxidant is contained in an amount of 0.2 to 0.4 parts by weight based on 100 parts by weight of the total amount of the polypropylene composition A or the polypropylene composition B.

47. The polypropylene composite film according to claim 43, wherein the lubricant is a PEG-based lubricant and/or a mono Gan Zhilei lubricant.

48. The polypropylene composite film according to claim 43, wherein the lubricant is contained in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the total amount of the polypropylene composition A or the polypropylene composition B.

49. The polypropylene composite film according to claim 48, wherein the lubricant is contained in an amount of 0.05 to 0.2 parts by weight based on 100 parts by weight of the total amount of the polypropylene composition A or the polypropylene composition B.

50. The polypropylene composite film according to any one of claims 1 to 39, wherein the polypropylene composition a and/or the polypropylene composition B further comprises a film forming aid.

51. The polypropylene composite film according to claim 50, wherein the film forming aid is at least one selected from the group consisting of an anti-halogen agent, a light stabilizer, a heat stabilizer, a colorant, a filler, a slip agent, an anti-adhesion agent, and an antistatic agent.

52. The polypropylene composite film according to claim 50, wherein the film forming aid is contained in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the total amount of the polypropylene composition A or the polypropylene composition B.

53. The polypropylene composite film according to claim 52, wherein the film-forming aid is contained in an amount of 0.05 to 0.3 parts by weight based on 100 parts by weight of the total amount of the polypropylene composition A or the polypropylene composition B.

54. The process for producing a polypropylene composite film as claimed in any one of claims 1 to 53, comprising: extruding and casting the raw material composition for forming each layer after the granulating process to form the composite film; optionally, the method further comprises stretching the resulting composite film.

55. The method of claim 54, wherein the stretching is bi-directional stretching.

56. The use of the polypropylene composite film according to any one of claims 1 to 53 in the field of packaging materials.

57. The use of claim 56, wherein the package is a battery package, an electronics package, or a food package.