CN115991908A

CN115991908A - Polypropylene composite film and preparation method and application thereof

Info

Publication number: CN115991908A
Application number: CN202111221982.3A
Authority: CN
Inventors: 张琦; 徐萌; 张师军; 高达利; 尹华; 邵清; 吕芸; 徐凯; 权慧; 袁浩
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: 2023-04-21

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 polypropylene a and an optional polyolefin elastomer B, and the polypropylene composition B comprises random polypropylene x, a polyolefin elastomer y and a polypropylene graft z; the polypropylene graft z comprises structural units derived from a copolymerized polypropylene and structural units derived from an alkenyl-containing silane-based 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 is used as a polymer plastic with a simple structure, has excellent electrical insulation performance and higher melting point, and a polypropylene film is expected to adapt to a more severe working environment as an insulating film packaging material. 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. Methods for improving the impact properties of polypropylene films may use block impact polypropylene to make films or polyolefin elastomers may be added to polypropylene, but films made by the above methods generally have higher haze. The nucleating agent can be added into the film at the same time, and the haze of the film is reduced by thinning crystals in the film, but the method can lead to the reduction of impact performance, and meanwhile, part of nucleating agents can reduce the electrical insulation performance of materials in a high-temperature application environment.

In order to improve the impact resistance and toughness of the film, the film can be prepared by a multilayer coextrusion method, for example, CN101913279A adopts a three-layer coextrusion method to prepare a composite film, the middle layer of the film is an elastomer and PP blended according to the proportion of 1:10-1:3, and the elastomer provides better impact resistance, but the method has the possibility of being difficult to uniformly disperse under the condition of higher elastomer content, and in the multilayer coextrusion process, the uniformity of the film is often influenced by different rheological properties of raw materials between layers, and then the optical and mechanical properties of the film are influenced.

Therefore, it is required to develop a film having electrical insulating 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 polypropylene a and optionally a polyolefin elastomer B, and the polypropylene composition B comprises a random polypropylene x, a polyolefin elastomer y and a polypropylene graft z; the polypropylene graft z comprises structural units derived from a copolymerized polypropylene and structural units derived from an alkenyl-containing silane-based 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 5.5 percent, preferably less than or equal to 2.7 percent; the impact strength of the pendulum bob is more than or equal to 0.8J, and preferably the impact strength of the pendulum bob is more than or equal to 1.8J; the heat sealing strength at 150 ℃ is more than or equal to 17N/15mm, and the heat sealing strength at 150 ℃ is more than or equal to 20N/15mm; volume resistivity is more than or equal to 1.8X10 ¹⁵ Omega.m, preferably volume resistivity not less than 1.9X10 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 polypropylene a and an optional polyolefin elastomer B, and the polypropylene composition B comprises atactic polypropylene x, a polyolefin elastomer y and a polypropylene graft z; the polypropylene graft z comprises structural units derived from a copolymerized polypropylene and structural units derived from an alkenyl-containing silane-based 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, preferablyThe tensile strength in the Machine Direction (MD) is more than or equal to 55MPa; the film haze is less than or equal to 5.5 percent, preferably less than or equal to 2.7 percent; the impact strength of the pendulum bob is more than or equal to 0.8J, and preferably the impact strength of the pendulum bob is more than or equal to 1.8J; the heat sealing strength at 150 ℃ is more than or equal to 17N/15mm, and the heat sealing strength at 150 ℃ is more than or equal to 20N/15mm; volume resistivity is more than or equal to 1.8X10 ¹⁵ Omega.m, preferably volume resistivity not less than 1.9X10 ¹⁵ Ω·m。

According to some embodiments of the invention, the polypropylene a may be a homo-polypropylene and/or a polypropylene graft z. Preferably, the melt mass flow rate of the homo-polypropylene a at 230 ℃ under a load of 2.16kg is 2-15g/10min, the isotacticity is more than 97%, and the molecular weight distribution Mw/Mn is 4.5-7.0. Homo-polypropylene meeting the above characteristics is commercially available. Such as the polypropylene homopolymer with the brand name of PPH-FA 03. Or may be prepared by methods conventional in the art.

According to a preferred embodiment of the invention, the content of structural units derived from alkenyl-containing silane-based monomers in the grafted state in the polypropylene graft z is from 0.2 to 6% by weight, preferably from 0.2 to 2.5% by weight, based on the weight of the polypropylene graft z.

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 alkenyl-containing silane-based monomers" refers to products formed from alkenyl-containing silane-based monomers, including both "radical" forms and "monomer" forms and also "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 silane-based monomer "in a grafted state" means a structural unit derived from the alkenyl group-containing silane-based monomer forming a covalent bond (grafting) with the copolymer.

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 z is prepared by solid phase grafting of a copolymer polypropylene and an alkenyl group-containing silane-based 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 silane-based monomer may polymerize to form a certain amount of ungrafted polymer. The polypropylene graft z of the invention not only comprises a product (crude product) directly prepared by grafting reaction of copolymerized polypropylene and silane 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 z 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 2.16kg load.

The alkenyl-containing silane monomer can be any monomer silane compound capable of being polymerized by free radicals, can be selected from at least one of monomers with a structure shown in a formula I,

Wherein R is ₁ Is C ₂ -C ₁₂ Alkenyl groups of (a), preferably monounsaturated alkenyl groups; r is R ₂ 、R ₃ 、R ₄ Each independently selected from substituted or unsubstituted C ₁ -C ₁₂ Straight-chain alkyl, substituted or unsubstituted C ₃ -C ₁₂ Branched alkyl, substituted or unsubstituted C ₁ -C ₁₂ Alkoxy, substituted or unsubstituted C ₁ -C ₁₂ An acyloxy group of (a); preferably, R ₁ Is C ₂ -C ₆ Alkenyl groups of (2), preferably monounsaturated alkenyl groupsA base; r is R ₂ 、R ₃ 、R ₄ Each independently selected from substituted or unsubstituted C ₁ -C ₆ Straight-chain alkyl, substituted or unsubstituted C ₃ -C ₆ Branched alkyl, substituted or unsubstituted C ₁ -C ₆ Alkoxy, substituted or unsubstituted C ₁ -C ₆ Is an acyloxy group.

More preferably, the alkenyl-containing silane-based monomer is at least one selected from the group consisting of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriisopropoxysilane, vinyltri-t-butoxysilane, vinyltriacetoxysilane, methylvinyldimethoxysilane, ethylvinyldiethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, allyltriisopropoxysilane, vinyltris (β -methoxyethoxy) silane, allyltris (β -methoxyethoxy) silane, allyltri-t-butoxysilane, allyltriacetoxysilane, methallyldimethoxysilane, and ethylallyldiethoxysilane.

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 C other than propylene ₂ -C ₈ At least one of the alpha-olefins of (a). Said C other than propylene ₂ -C ₈ The alpha-olefins of (a) 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; at 230℃under a load of 2.16kgThe melt mass flow rate of (2) 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 ℃; weight average molecular weight of 20X 10 ⁴ -60×10 ⁴ g/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. For example as described with reference to CN101679557A, CN101058654 a.

The polypropylene graft z 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 alkenyl-containing silane monomer 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 may 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 silane-based monomer may be 0.1 to 10:100, preferably 0.5 to 6:100. The mass ratio of the alkenyl-containing silane monomer to the copolymerized polypropylene is 0.5-12:100, preferably 0.8-9:100, and more preferably 1-6:100.

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, C ₆ The alkane or cycloalkane, benzene, C ₁ -C ₄ Alkyl-substituted benzene, C ₂ -C ₆ Fatty ethers, C ₃ -C ₆ Aliphatic ketones, decalin; further preferred are the following organic solvents At least one of: 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 according to the invention may also comprise an organic solvent, preferably comprising C, as solvent for dissolving the solid free-radical initiator ₂ -C ₅ Alcohols, C ₂ -C ₄ Ethers and C ₃ -C ₅ At least one of the ketones, more preferably comprising C ₂ -C ₄ Alcohols, C ₂ -C ₃ Ethers and C ₃ -C ₅ At least one of the ketones, most preferably at least one of ethanol, diethyl ether and acetone. The mass content of the organic solvent is preferably 1-35% of the mass of the polypropylene copolymer.

As described above, the polypropylene graft z of the present invention includes both a product (crude product) directly obtained by grafting reaction of a copolymerized polypropylene and a grafting monomer and a pure product of a 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 5 to 100%, more preferably 5 to 60%. 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 b is an elastomeric copolymer of ethylene and an alpha olefin, wherein the alpha olefin is preferably C ₃ -C ₁₂ More preferably selected from alpha olefinsAt least one of 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 C ₃ -C ₁₂ More preferably at least one selected from the group consisting of 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 100wt% of polypropylene a and 0 to 50wt% of polyolefin elastomer b, based on the total weight of the polypropylene composition a.

According to a preferred embodiment of the present invention, the polypropylene composition A comprises 75 to 95 wt.% polypropylene a and 5 to 25 wt.% polyolefin elastomer b, based on the total weight of the polypropylene composition A.

The elastomer or polypropylene graft in the composition contains a rubber phase, so that good impact performance is provided for the film, and meanwhile, as the homo-polymer phase part macromolecular chain segments of the homo-polymer polypropylene are relatively regular, crystallization and orientation occur in the film preparation process, and good mechanical performance is provided for the film. According to the composition provided by the invention, rubber phases can be uniformly distributed in the film, and the size of the rubber phases can meet the refractive index requirement, so that the film with good optical performance can be obtained, and the film has good impact performance and optical performance; meanwhile, under the proportion, the film has good mechanical properties. 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 50 to 90wt% of random polypropylene x, 5 to 40wt% of polyolefin elastomer y and 2 to 40wt% of polypropylene graft z, based on the total weight of the polypropylene composition B.

According to a preferred embodiment of the present invention, the polypropylene composition B comprises from 60 to 85wt% of atactic polypropylene x, from 5 to 20wt% of polyolefin elastomer y and from 5 to 20wt% of polypropylene graft z, based on the total weight of the polypropylene composition B.

According to the research of the inventor, when the polypropylene composition B adopts the proportion, and the surface layer in the composite film is manufactured by the polypropylene composition B, the impact property of the film can be greatly improved, the optical property can be further improved, and meanwhile, the film can have good heat sealing property.

According to some embodiments of the invention, the weight parts of the polyolefin elastomer B are Wb based on 100 weight parts of the total weight of the polypropylene composition A, the weight parts of the polyolefin elastomer y are Wy based on 100 weight parts of the total weight of the polypropylene composition B, the ratio of Wb to Wy is 6:1-1:4, for example, may be 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 Wb to Wy is 4:1 to 1:4.

As a result of the study of the present inventors, when the ratio of Wb 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 when the double-layer or multi-layer film is co-extruded.

According to some embodiments of the invention, the melt mass flow rate of the polypropylene composition A is 2-10g/10min, preferably 3-8g/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 3-10g/10min, preferably 4-8g/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 B is preferably used as a surface 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 basis of quantification ¹³ The method of calibrating the results obtained by C-NMR spectroscopy is performed according to a conventional method 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 using a CRYST-EX instrument 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 gel permeation chromatography (PL-GPC 220 type of Polymer Laboratory) and the concentration was 1.0mg/ml, as measured by high temperature GPC. 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, 5-10 mg of samples are measured by adopting a three-stage temperature rise and fall measuring method from 20 ℃ to 200 ℃, 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 acetone, 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 alkenyl-containing silane-based monomers in the polypropylene graft z, 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 (w) ₁ Is the quality of grafted products in advance; w (w) ₂ Is the quality of the grafted product after extraction; w (w) ₃ Is the mass of the silane monomer containing alkenyl.

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

(12) Degree of isotacticity: by passing through ¹³ C NMR measurement, nuclear magnetic carbon Spectrometry of propylene Polymer at 400MHz was measured by Nuclear magnetic resonance spectrometer (NMR) of model AVANCE III of Bruker, switzerland ¹³ C-NMR), wherein the solvent was deuterated o-dichlorobenzene 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. Dissolving the sample at 140 ℃ and collecting ¹³ C-NMR, test temperature 125 ℃, probe gauge 10 mm, 90 pulse, sampling time AQ 5 seconds, delay time D1 seconds, number of scans 6000. Isotatic with two sets of units [ mm]The content of (2) is taken as isotacticity.

(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 UK Polymer Laboratories, wherein the gel permeation chromatograph comprises 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 the well-suited calibration was performed using EasiCal PS-1 narrow distribution polystyrene standard produced by PL.

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%, solubles/copolymerized polypropylene intrinsic viscosity ratio 0.89, weight average molecular weight 34.3X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load of 1.21g/10min, tm=143.4 ℃, sieving to remove fines smaller 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. 2.5g of lauroyl peroxide and 50g of vinyltriethoxysilane were added, stirred and mixed for 30min, swollen for 1 hour at 40 ℃, heated to 90℃and reacted for 4 hours. After the reaction is finished, nitrogen purging and cooling are carried out to obtain the polypropylene-g-vinyl triethoxysilane C1, wherein the melt mass flow rate is 1.15g/10min, the M1 is 1.03%, and the grafting efficiency is 42%.

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 29.2×10 ⁴ g/mol, MFR at 230 ℃,2.16kg load of 5.37g/10min, tm=163.3 ℃, sieving to remove fines smaller 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. 3.7g of lauroyl peroxide is dissolved in 70g of acetone, the obtained acetone solution is added into a reaction system, the temperature is raised to 40 ℃, the acetone is removed by nitrogen purging for 30min, 75g of vinyltriethoxysilane is added, stirring and mixing are carried out for 30min, the temperature is raised to 85 ℃, and the reaction is carried out for 4 hours. After the reaction is finished, nitrogen purging, cooling and cooling to obtain polypropyleneG-vinyltriethoxysilane C2, having a melt mass flow rate of 4.77g/10min, M1 of 1.24% and a grafting efficiency of 34%.

Preparation example 3

Selecting basic copolymerized polypropylene powder with the following characteristics: 9.3wt% of comonomer ethylene, 21.0wt% of xylene solubles, 35.4wt% of comonomer in the solubles, an intrinsic viscosity ratio of the solubles/the copolymerized polypropylene of 1.68, a weight average molecular weight of 30.4X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load of 5.69g/10min, tm= 163.0 ℃, and sieving to remove fines smaller 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. 4.5g of tert-butyl peroxy (2-ethylhexanoate) and 120g of vinyltriisopropoxysilane were added, stirred and mixed for 60min, heated to 100℃and reacted for 1.5 hours. After the reaction is finished, nitrogen purging and cooling are carried out to obtain the polypropylene-g-vinyl triisopropoxy silane C3, wherein the melt mass flow rate is 8.51g/10min, the M1 is 2.11%, and the grafting efficiency is 37%.

Preparation example 4

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 of 8.46g/10min, tm=162.0 ℃, sieving to remove fines smaller 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. 5.0g of lauroyl peroxide was dissolved in 100g of vinyltrimethoxysilane and 50g of toluene as an interface agent to form a solution, the solution was stirred and mixed for 30 minutes, the temperature was raised to 95 ℃, 4kg of dispersant water at 95 ℃ was added, and the reaction was carried out for 0.75 hours. After the reaction is finished, cooling, filtering to remove dispersant water, and vacuum drying at 70 ℃ for 10 hours to obtain polypropylene-g-vinyl trimethoxy silane C4 with a melt mass flow rate of 8.31g/10 min, M1 was 1.42% and grafting efficiency was 29%.

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 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 80 weight parts, and the weight part Wb of the component b is 20 weight parts. Adding lubricant (PEG lubricant manufactured by Swiss Corp., molecular weight 10000, and the addition amount of lubricant is 0.1 weight part based on 100 weight parts of the sum of the weight of the component a and the weight of the component b), adding the mixture into a high-speed stirrer, mixing uniformly, and adding the mixed material into W&In a feeder of a double-screw extruder manufactured by P company, materials enter a double screw through the feeder, the temperature of the screw is kept between 160 ℃ and 230 ℃ in the processing process, and the materials are evenly mixed by melting the screw, extruded, granulated and dried to obtain polypropylene composition A granules, and the melt mass flow rate MFR of the polypropylene composition A granules is detected _A ＝3.5g/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; the component y is a polyolefin elastomer with the trade name 6102, which is purchased from the Ekken company and is an ethylene-propylene copolymer, and the content of ethylene structural units is 16wt%; component z is polypropylene-g-vinyltriethoxysilane C2. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wx of the component x is 85 weight parts, the weight part Wy of the component y is 5 weight parts, and the weight part Wz of the component z is 10 weight parts. Wb: wy is 4:1. Other steps are the same as the step (1) to finally obtainTo polypropylene composition B pellets, the melt mass flow rate MFR thereof was measured _B ＝4.68g/10min。

(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:

component a is polypropylene-g-vinyltriethoxysilane C1; component b is a polyolefin elastomer, commercially available from Sanjing, as an ethylene-1-butene copolymer, having a butene structural unit content of 32% by weight, having a brand DF 640. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wa of the component a is 95 weight parts, and the weight part Wb of the component b is 5 weight parts. Adding lubricant (PEG lubricant manufactured by Swiss Corp., molecular weight 10000, and the addition amount of lubricant is 0.1 weight part based on 100 weight parts of the sum of the weight of the component a and the weight of the component b), adding the mixture into a high-speed stirrer, mixing uniformly, and adding the mixed material into W&In a feeder of a double-screw extruder manufactured by P company, materials enter a double screw through the feeder, the temperature of the screw is kept between 160 ℃ and 230 ℃ in the processing process, and the materials are evenly mixed by melting the screw, extruded, granulated and dried to obtain polypropylene composition A granules, and the melt mass flow rate MFR of the polypropylene composition A granules is detected _A ＝4.73g/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; component z is polypropylene-g-vinyltriethoxysilane C1. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wx of the component x is 60 weight parts, the weight part Wy of the component y is 20 weight parts, and the weight part Wz of the component z is 20 weight parts. Wb: wy is 1:4. Other steps are the same as in step (1), and pellets of the polypropylene composition B are finally obtained, which are examined for melt mass flow rate MFR _B ＝4.85g/10min。

(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 polypropylene-g-vinyl triisopropoxysilane C3; component b 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 by the method are mixed according to the proportionThe weight and mixing were carried out, wherein the weight part Wa of the component a was 85 parts by weight and the weight part Wb of the component b was 15 parts by weight. Adding lubricant (PEG lubricant manufactured by Swiss Corp., molecular weight 10000, and the addition amount of lubricant is 0.1 weight part based on 100 weight parts of the sum of the weight of the component a and the weight of the component b), adding the mixture into a high-speed stirrer, mixing uniformly, and adding the mixed material into W&In a feeder of a double-screw extruder manufactured by P company, materials enter a double screw through the feeder, the temperature of the screw is kept between 160 ℃ and 230 ℃ in the processing process, and the materials are evenly mixed by melting the screw, extruded, granulated and dried to obtain polypropylene composition A granules, and the melt mass flow rate MFR of the polypropylene composition A granules is detected _A ＝9.18g/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; the component y is a polyolefin elastomer with the brand of EXACT3139, which is purchased from the Ekken company and is an ethylene-1-octene copolymer, and the content of octene structural units is 14wt%; component z is polypropylene-g-vinyltriisopropoxysilane C3. The components prepared above are weighed and mixed according to the proportion, wherein the weight part Wx of the component x is 85 weight parts, the weight part Wy of the component y is 10 weight parts, and the weight part Wz of the component z is 5 weight parts. Wb: wy is 3:2. Other steps are the same as in step (1), and pellets of the polypropylene composition B are finally obtained, which are examined for melt mass flow rate MFR _B ＝8.70g/10min。

(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. Except that the part by weight Wa of the component a was 70 parts by weight and the part by weight Wb of the component b was 30 parts by weight. ObtainingPolypropylene composition A pellets, the melt mass flow rate MFR of which was examined _A ＝3.2g/10min。

(2) Preparation of polypropylene composition B:

the procedure is as in example 1. The difference is that the part by weight Wx of the component x is 90 parts by weight, the part by weight Wy of the component y is 5 parts by weight, and the part by weight Wz of the component z is 5 parts by weight. Wb: wy is 6:1. Other steps are the same as in step (1), and pellets of the polypropylene composition B are finally obtained, which are examined for melt mass flow rate MFR _B ＝4.89g/10min。

(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 Wa, a component a, and Wb, b, were 75 parts by weight and 25 parts by weight, respectively. To obtain pellets of the polypropylene composition A, the melt mass flow rate MFR of which was measured _A ＝9.63g/10min。

(2) Preparation of polypropylene composition B:

the procedure was as in example 3, except that the part by mass Wx of component x was 85 parts by weight, the part by mass Wy of component y was 13 parts by weight, and the part by mass Wz of component z was 2 parts by weight. Wb: wy is 25:13. Finally, pellets of the polypropylene composition B were obtained, the melt mass flow rate MFR of which was examined _B ＝8.83g/10min。

(3) Preparation of a composite film:

the procedure is as in example 2. 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 2:1.

Example 6

(1) Preparation of polypropylene composition A:

the procedure is as in example 3, except that the part by weight Wa of component a is 100 parts by weight. To obtain pellets of the polypropylene composition A, the melt mass flow rate MFR of which was measured _A ＝8.94g/10min。

(2) Preparation of polypropylene composition B:

the procedure was as in example 3, except that the part by mass Wx of component x was 50 parts by weight, the part by mass Wy of component y was 30 parts by weight, and the part by mass Wz of component z was 20 parts by weight. Finally, pellets of the polypropylene composition B were obtained, the melt mass flow rate MFR of which was examined _B ＝9.70g/10min。

(3) Preparation of a composite film:

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

Example 7

(1) Preparation of polypropylene composition A:

the procedure is as in example 1. Except that the part by weight Wa of the component a was 100 parts by weight. To obtain pellets of the polypropylene composition A, the melt mass flow rate MFR of which was measured _A ＝3.1g/10min。

(2) Preparation of polypropylene composition B:

the procedure is as in example 1. The difference is that the part by weight Wx of the component x is 50 parts by weight, the part by weight Wy of the component y is 20 parts by weight, and the part by weight Wz of the component z is 30 parts by weight. Other steps are the same as in step (1), and pellets of the polypropylene composition B are finally obtained, which are examined for melt mass flow rate MFR _B ＝3.55g/10min。

(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 100 parts by weight of Wa. Finally, the polypropylene group is obtainedPellets of Compound A, the melt mass flow rate MFR of which is measured _A ＝3.1g/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 and the component b was 50 parts by weight of Wb. Wb: wy is 10:1. Finally, pellets of the polypropylene composition A were obtained, the melt mass flow rate MFR of which was examined _A ＝3.5g/10min。

Example 10

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, the component y was 30 parts by weight of Wy, and the component z was 30 parts by weight of Wz. Wb: wy is 2:3. To obtain pellets of the polypropylene composition B, the melt mass flow rate MFR of which was measured _B ＝3.33g/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, the component y was 40 parts by weight of Wy, and the component z was 10 parts by weight of Wz. Wb: wy is 1:2. To obtain pellets of the polypropylene composition B, the melt mass flow rate MFR of which was measured _B ＝3.92g/10min。

Example 12

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, the component y was 10 parts by weight of Wy, and the component z was 40 parts by weight of Wz. Wb: wy is 2:1. To obtain pellets of the polypropylene composition B, the melt mass flow rate MFR of which was measured _B ＝3.36g/10min。

Example 13

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition A, the component a was 99 parts by weight of Wa and the component b was 1 part by weight of Wb. Wb: w (W)y is 1:5. Finally, pellets of the polypropylene composition A were obtained, the melt mass flow rate MFR of which was examined _A ＝3.2g/10min。

Example 14

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition A, the component a was 97.5 parts by weight of Wa and the component b was 2.5 parts by weight of Wb. Wb: wy is 1:2. Finally, pellets of the polypropylene composition A were obtained, the melt mass flow rate MFR of which was examined _A ＝3.1g/10min。

Example 15

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition A, the component a was 95 parts by weight of Wa and the component b was 5 parts by weight of Wb. Wb: wy is 1:1. Finally, pellets of the polypropylene composition A were obtained, the melt mass flow rate MFR of which was examined _A ＝3.2g/10min。

Example 16

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition A, the component a was 90 parts by weight of Wa and the component b was 10 parts by weight of Wb. Wb: wy is 2:1. Finally, pellets of the polypropylene composition A were obtained, the melt mass flow rate MFR of which was examined _A =3.3 g/10min; in the preparation of polypropylene composition B, component z was polypropylene-g-vinyltrimethoxysilane C4 to give polypropylene composition B pellets, which were examined for melt mass flow rate MFR _B ＝5.40g/10min。

Example 17

A polypropylene composite film was prepared as in example 1. In the preparation of the polypropylene composition A, the component a was 75 parts by weight of Wa and the component b was 25 parts by weight of Wb. Wb: wy is 5:1. Finally, pellets of the polypropylene composition A were obtained, the melt mass flow rate MFR of which was examined _A ＝3.1g/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. The polypropylene composition B, however, only contains component x.

Comparative example 4

A polypropylene composite film was prepared as in example 1. The polypropylene composition B was different in that it contained only the component x and the component y, wherein the component x was 85 parts by weight of Wx and the component y was 15 parts by weight of Wy.

Comparative example 5

A polypropylene composite film was prepared as in example 2. The polypropylene composition B, however, contained only the component x and the component z, wherein the component x has a weight part Wx of 70 parts by weight and the component z has a weight part Wz of 30 parts by weight.

TABLE 1

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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 the tensile strength in the Machine Direction (MD) of more than or equal to 40MPa, the film haze of less than or equal to 5.5 percent, the pendulum impact strength of more than or equal to 0.8J, the heat sealing strength at 150 ℃ of more than or equal to 17N/15mm and the volume resistivity of more than or equal to 1.8X10 ¹⁵ Omega.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 2.7% or less, a pendulum impact strength of 1.8J or more, and a heat at 150 ℃Sealing strength is more than or equal to 20N/15mm, and volume resistivity is more than or equal to 1.9X10 ¹⁵ Omega.m. 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 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 polypropylene a and optionally a polyolefin elastomer B, and the polypropylene composition B comprises a random polypropylene x, a polyolefin elastomer y and a polypropylene graft z; the polypropylene graft z comprises structural units derived from a copolymerized polypropylene and structural units derived from an alkenyl-containing silane-based monomer.

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, preferably the longitudinal tensile strength is more than or equal to 55MPa; the film haze is less than or equal to 5.5 percent, preferably less than or equal to 2.7 percent; the impact strength of the pendulum bob is more than or equal to 0.8J, and preferably the impact strength of the pendulum bob is more than or equal to 1.8J;150The heat sealing strength at the temperature is more than or equal to 17N/15mm, preferably more than or equal to 20N/15mm at 150 ℃; volume resistivity is more than or equal to 1.8X10 ¹⁵ Omega.m, preferably volume resistivity not less than 1.9X10 ¹⁵ Ω·m。

3. The polypropylene composite film according to any one of claims 1 to 2, wherein the melt mass flow rate of the polypropylene composition a is 2-10g/10min, preferably 3-8g/10min, at 230 ℃ under a load of 2.16 kg; and/or

The melt mass flow rate of the polypropylene composition B is 3-10g/10min, preferably 4-8g/10min, at 230℃under a load of 2.16 kg.

4. A polypropylene composite film according to any one of claims 1 to 3, wherein the polypropylene a is homo-polypropylene and/or polypropylene grafts z; preferably, the melt mass flow rate of the homo-polypropylene at 230 ℃ under a load of 2.16kg is 2-15g/10min, the isotacticity is more than 97%, and the molecular weight distribution Mw/Mn is 4.5-7.0.

5. The polypropylene composite film according to any one of claims 1 to 4, wherein the content of structural units in the polypropylene graft z derived from alkenyl group-containing silane monomers in the grafted state is 0.2 to 6wt%, preferably 0.2 to 2.5wt%, based on the weight of the polypropylene graft z; and/or the number of the groups of groups,

the melt mass flow rate of the polypropylene graft z at 230 ℃ under a load of 2.16kg is 0.01-30g/10min, preferably 0.05-20g/10min, more preferably 0.1-10g/10min, and even more preferably 0.2-8g/10min.

6. The polypropylene composite film according to any one of claims 1 to 5, wherein the polypropylene graft z is prepared by solid phase grafting reaction of a copolymerized polypropylene and an alkenyl group-containing silane-based monomer.

7. According to any one of claims 1-6The polypropylene composite film is characterized in that the comonomer of the copolymerized polypropylene is selected from C except propylene ₂ -C ₈ At least one of the alpha-olefins of (a); and/or, the copolymerized polypropylene has at least one of the following characteristics: 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 ℃; weight average molecular weight of 20X 10 ⁴ -60×10 ⁴ g/mol。

8. The polypropylene composite film according to any one of claims 1 to 7, wherein the alkenyl group-containing silane-based monomer is at least one selected from monomers having a structure represented by formula I,

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wherein R is ₁ Is C ₂ -C ₁₂ Alkenyl groups of (a), preferably monounsaturated alkenyl groups; r is R ₂ 、R ₃ 、R ₄ Each independently selected from substituted or unsubstituted C ₁ -C ₁₂ Straight-chain alkyl, substituted or unsubstituted C ₃ -C ₁₂ Branched alkyl, substituted or unsubstituted C ₁ -C ₁₂ Alkoxy, substituted or unsubstituted C ₁ -C ₁₂ An acyloxy group of (a); preferably, R ₁ Is C ₂ -C ₆ Alkenyl groups of (a), preferably monounsaturated alkenyl groups; r is R ₂ 、R ₃ 、R ₄ Each independently selected from substituted or unsubstituted C ₁ -C ₆ Straight-chain alkyl, substituted or unsubstituted C ₃ -C ₆ Branched alkyl, substituted or unsubstituted C ₁ -C ₆ Alkoxy, substituted or unsubstituted C ₁ -C ₆ An acyloxy group of (a);

9. The polypropylene composite film according to any one of claims 1 to 8, wherein the polyolefin elastomer b and the polyolefin elastomer y are each independently an elastomeric copolymer of ethylene and an alpha olefin, wherein the alpha olefin is preferably C ₃ -C ₁₂ More preferably at least one selected from the group consisting of propylene, 1-butene, 1-hexene and 1-octene.

10. The polypropylene composite film according to any one of claims 1 to 9, wherein the random polypropylene x is a copolymer of propylene with ethylene and/or butene, preferably at least one selected from the group consisting of ethylene-propylene-butene terpolymers, propylene-ethylene co-random copolymers, propylene-butene co-random copolymers; and/or the melt mass flow rate of the atactic polypropylene x at 230 ℃ under a load of 2.16kg is 2-10g/10min.

11. The polypropylene composite film according to any one of claims 1 to 10, wherein the polypropylene composition a comprises 50 to 100wt% of polypropylene a and 0 to 50wt% of polyolefin elastomer b, based on the total weight of the polypropylene composition a; preferably, the polypropylene composition A comprises 75 to 95wt% of polypropylene a and 5 to 25wt% of polyolefin elastomer b.

12. The polypropylene composite film according to any one of claims 1 to 11, wherein the polypropylene composition B comprises 50 to 90wt% of the random polypropylene x, 5 to 40wt% of the polyolefin elastomer y and 2 to 40wt% of the polypropylene graft z, based on the total weight of the polypropylene composition B; preferably, the polypropylene composition B comprises 60 to 85wt% of random polypropylene x, 5 to 20wt% of polyolefin elastomer y and 5 to 20wt% of polypropylene graft z.

13. The polypropylene composite film according to any one of claims 1 to 12, wherein the weight fraction of the polyolefin elastomer B is Wb based on 100 parts by weight of the total weight of the polypropylene composition a, the weight fraction of the polyolefin elastomer y is Wy based on 100 parts by weight of the total weight of the polypropylene composition B, and the ratio of Wb to Wy is 6:1 to 1:4, preferably 4:1 to 1:4.

14. The polypropylene composite film according to any one of claims 1 to 13, 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, preferably 1:2 to 1:1.

15. The polypropylene composite film according to any one of claims 1 to 14, wherein when the polypropylene composite film has a three-layer or more structure, the film layer B is a skin layer.

16. The polypropylene composite film according to any one of claims 1 to 15, wherein the polypropylene composition a and/or the polypropylene composition B further comprises an antioxidant and/or a lubricant;

preferably, the antioxidant is selected from at least one of antioxidant 1076, antioxidant 1010, antioxidant 168 and a thioester antioxidant;

preferably, the antioxidant is 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;

preferably, the lubricant is a PEG-based lubricant and/or a mono Gan Zhilei lubricant;

preferably, 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.

17. The polypropylene composite film according to any one of claims 1 to 16, wherein the polypropylene composition a and/or the polypropylene composition B further comprises a film forming aid, preferably selected from at least one of halogen-resistant agents, light stabilizers, heat stabilizers, colorants, fillers, slip agents, anti-adhesion agents and antistatic agents; more preferably, the content of the film forming aid is 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.

18. A method for producing the polypropylene composite film according to any one of claims 1 to 17, comprising: extruding and casting the raw material composition for forming each layer after an optional granulating process to form the composite film; optionally, the method further comprises stretching, preferably biaxially stretching, the resulting composite film.

19. Use of the polypropylene composite film according to any one of claims 1 to 17 in the field of packaging materials; the package is preferably a battery package, an electronic product package or a food package.