Modified materials for aluminum coating of multi-layer co-extruded polyethylene aluminum substrate films

Abstract

The invention discloses a modified material for an aluminum coating layer of a multi-layer co-extruded polyethylene aluminum-coated substrate film, belonging to the field of thin film polymer materials. The material is used for the aluminum coating layer of a polyethylene aluminum-coated substrate film, and the aluminum coating layer material is a modified polar polyethylene modified material. The invention uses the modified polar polyethylene modified material as the aluminum coating layer material of the multi-layer co-extruded polyethylene material, thereby effectively improving the aluminum coating adhesion of the polyethylene co-extruded substrate. The invention uses the polar material as a main component to perform polarity modification on polyethylene, thereby obtaining the modified polar polyethylene modified material, which has strong versatility. In the invention, the polar material is the main component for changing the polarity of polyethylene, and the ionic polymer is used as an auxiliary material, which has low crystallinity, good transparency, very strong anti-pollution property, can promote aluminum coating adhesion, and has good film optical properties. The leveling processing aid helps the film surface to be more microscopically flat.

Description

Technical Field

[0001] The invention belongs to the field of film polymer materials and relates to a modified material for an aluminum-plated layer of a multi-layer co-extruded polyethylene aluminum-plated substrate film. Background Art

[0002] In composite packaging, in order to block water, oxygen and light, aluminized materials are preferred as cost-effective materials. Aluminized basic materials include PET, CPP, BOPP and PE. The aluminized functional layers of PET, CPP and BOPP have corresponding functional materials, which make the aluminized fastness and gloss good after aluminization. However, polyethylene (PE) cannot be directly applied to the aluminizing process because it is a non-polar material and has poor aluminized adhesion. Summary of the invention

[0003] The purpose of the present invention is to provide a modified material for the aluminum layer of a multi-layer co-extruded polyethylene aluminum-plated substrate film, which solves the problem that the polyethylene (PE) aluminum plating has poor adhesion in the polyethylene substrate composite packaging and cannot be directly applied to the aluminum plating process. The technical solution adopted by the present invention is as follows:

[0004] The modified material for the aluminum coating layer of the multi-layer co-extruded polyethylene aluminum-coated substrate film comprises a modified polar polyethylene modified material, wherein the modified polar polyethylene modified material is the aluminum coating layer material of the polyethylene aluminum-coated substrate film.

[0005] The present invention uses the modified polar polyethylene modified material as the aluminum-plated layer of the multi-layer co-extruded polyethylene aluminum-plated substrate film, which effectively improves the aluminum-plated adhesion of the polyethylene substrate.

[0006] At present, the preparation method of aluminum-plated polyethylene substrate film includes polar modification and polar coating. The methods of polar modification and coating process are existing technologies and will not be explained in detail here.

[0007] Furthermore, the modified polar polyethylene modified material comprises the following components: polyethylene, ion polymer, polar material, and leveling processing aid.

[0008] Polar coating is very expensive and has been used in certain high-end applications, but it is difficult to popularize; therefore, the present invention preferably uses polar materials as the main component to modify the polarity of polyethylene, thereby obtaining a modified polar polyethylene modified material. In the present invention, the polar material is the main component for changing the polarity of polyethylene, and the ionic polymer is used as an auxiliary material, which has low crystallinity, good transparency, and very strong anti-pollution properties, and can promote aluminum plating fastness and good film optical properties; the leveling processing aid helps the film surface to be more microscopically flat.

[0009] Furthermore, the modified polar polyethylene modified material comprises the following components in mass ratio: 57.5-67.5% polyethylene, 2-6% ion polymer, 25-40% polar material, and 0.5-1.5% leveling processing aid.

[0010] In order to obtain an aluminum-plated film with high adhesion, the present invention optimizes the ratio of each component.

[0011] Furthermore, the polyethylene is one of linear polyethylene, low-density polyethylene and metallocene polyethylene.

[0012] The main chain of linear polyethylene has no long side chains, but only short side chains. Linear polyethylene has the characteristics of high strength, high flexibility, high transparency, and anti-oxidation. It has low density and good chemical resistance. It is not easy to decompose under high temperature for a long time. At the same time, its low temperature performance is also very good, and it can withstand temperatures below -70°C. In addition, linear polyethylene can resist the erosion of various corrosive substances such as acids and alkalis, and has a high surface gloss.

[0013] Low-density polyethylene is a type of polyethylene resin. It is prepared by polymerization under high pressure (100-300 MPa) using ethylene monomer and organic peroxide as initiator. Due to the high pressure involved in its preparation process, low-density polyethylene is also called high-pressure polyethylene. Its density is usually between 0.910 and 0.925 g / cm 3 Low-density polyethylene has many excellent physical and chemical properties. It is tasteless, odorless and non-toxic. It has good softness, extensibility, electrical insulation, transparency, easy processing and certain air permeability. In addition, low-density polyethylene also has the characteristics of cold resistance, low temperature resistance and high temperature resistance. Its film can withstand the sterilization process of immersion in 90℃ hot water. At the same time, it has good moisture resistance, stable chemical properties and is insoluble in general solvents.

[0014] Metallocene polyethylene has many unique properties. First, it has greater elongation at break and better impact strength than traditional polyethylene, which is mainly due to its large molecular weight and dense distribution. Second, metallocene polyethylene has a low heat sealing temperature but high strength, which is related to its molecular weight distribution. Some metallocene polyethylene has good transparency and low haze, which makes it advantageous in applications that require high transparency. The diversity of metallocene polyethylene makes it suitable for a wide range of flexible packaging film applications. For example, it can be used for shrink packaging films for bottled water, beverages, canned goods, hand sanitizers, detergents, health products, and skin care products. It can also be used for pallet packaging of bulk goods, multi-layer hand-wrapped packaging films, agricultural greenhouse films, medium and heavy packaging bags, and various composite flexible packaging films for food and non-food. The production of metallocene polyethylene involves the polymerization reaction of metallocene catalysts and ethylene monomers at a certain temperature and pressure. The comonomer is inserted into the polyethylene chain under the action of the metallocene catalyst to produce metallocene polyethylene products.

[0015] The above-mentioned types of polyethylene can all be used for polar modification of polyethylene.

[0016] Furthermore, the ion polymer is a Na ion polymer or a Zn ion polymer.

[0017] Na-ion polymer is a polymer material containing sodium ions, which combines the electrochemical properties of sodium ions with the mechanical properties and processability of polymers. It has excellent chemical stability and adhesion to metals, and can maintain its structure and performance in different environments.

[0018] Zn ion polymer is a polymer material containing zinc ions, which combines the electrochemical properties of zinc ions with the mechanical properties and processability of polymers. It has excellent chemical stability and adhesion to metals, and can maintain its structure and performance in different environments.

[0019] Furthermore, the polar material is one of ethylene-vinyl acetate copolymer, ethylene acrylic acid copolymer, and maleic anhydride grafted polyethylene.

[0020] Ethylene-vinyl acetate copolymer is referred to as EVA. Generally, the content of vinyl acetate (VA) is 5%-40%. Compared with polyethylene, EVA has polarity due to the introduction of vinyl acetate monomer in the molecular chain, which reduces the high crystallinity and improves the toughness, impact resistance, filler compatibility and heat sealing performance. It is widely used in foaming shoe materials, functional shed films, packaging films, hot melt adhesives, wires and cables, toys and other fields.

[0021] Ethylene acrylic acid copolymer, referred to as EAA, is a thermoplastic formed by high-pressure and high-temperature free radical polymerization of ethylene and acrylic acid. It combines the characteristics of ethylene and acrylic acid, and has both the good mechanical strength and heat resistance of ethylene, as well as polarity, good transparency, wear resistance, low-temperature resistance, adhesion, colorability, etc. It has excellent adhesion to polar substrates such as metallized films, paper, iron, steel and glass.

[0022] Maleic anhydride grafted polyethylene is obtained by grafting several maleic anhydride molecules onto the polyethylene molecular chain through chemical reaction. This grafting modification not only allows the product to retain the original good processability of polyethylene, but also gives the maleic anhydride polar molecules the reactivity and strong polarity. Therefore, maleic anhydride grafted polyethylene has many excellent properties, such as heat resistance, strength, corrosion resistance and environmental protection.

[0023] Furthermore, the leveling processing aid is a fluorocarbon resin.

[0024] Fluorocarbon resin is a chemical substance. The low surface energy of fluorocarbon resin makes it non-adhesive, non-wetting and has better leveling properties.

[0025] Furthermore, the polyethylene is a metallocene polyethylene with an MI value of 2, the ion polymer is a Zn ion polymer, the polar material is an ethylene-vinyl acetate copolymer with a VA content of 28% by mass, and the leveling processing aid is a fluorocarbon resin; the modified polar polyethylene modified material includes the following components in a mass ratio: 64% metallocene polyethylene, 5% Zn ion polymer, 30% ethylene-vinyl acetate copolymer with a VA content of 28% by mass, and 1% fluorocarbon resin.

[0026] In order to obtain an aluminum-plated film with high adhesion, good aluminum-plated gloss, high barrier properties after aluminum-plating, and controllable friction coefficient after composite, the present invention optimizes the ratio of each component.

[0027] The mechanism of polyethylene, Zn ion polymer, ethylene-vinyl acetate copolymer with VA content, and fluorocarbon resin is:

[0028] From a physical point of view: the above components are mixed in a molten state through mechanical shear force and thermal action. Polyethylene, as the main matrix material, has excellent processability and compatibility, and can form a uniform mixture with Zn ion polymer, VA-content ethylene-vinyl acetate copolymer and fluorocarbon resin. In this process, the molecules between the components are physically entangled and interpenetrated to form a relatively stable mixing system.

[0029] From a chemical point of view: Polyethylene (PE) is a long-chain hydrocarbon polymer, mainly polymerized from ethylene monomers, with stable carbon-carbon bonds and fewer active functional groups. Zn ion polymers contain Zn ions and organic ligands. These Zn ions have coordination ability and can coordinate with atoms or groups containing lone pairs of electrons. VA-content ethylene-vinyl acetate copolymer is a monomer containing a certain content of ethylene-vinyl acetate copolymer groups. The oxygen atoms in this group have lone pairs of electrons and can participate in coordination reactions; fluorocarbon resins are known for their non-adhesive properties;

[0030] During the mixing process, the chemical reaction mainly includes coordination reaction and weak chemical bonding; the Zn ions in the Zn ion polymer coordinate with the oxygen atoms in the ethylene-vinyl acetate copolymer groups in the ethylene-vinyl acetate copolymer with VA content to form coordination bonds. This coordination can enhance the interaction between the Zn ion polymer and the ethylene-vinyl acetate copolymer with VA content, and improve the bonding force between the mixture and the metal aluminum.

[0031] In addition, the non-adhesiveness of fluorocarbon resin allows the polyethylene modified material to have better leveling properties on the screw, die head and grinding mouth, making the film surface smoother.

[0032] Since polyethylene is mainly composed of stable carbon-carbon bonds, its activity in chemical reactions is low. Therefore, in mixed reactions, polyethylene mainly plays the role of main support and cost reduction, rather than directly participating in chemical reactions.

[0033] In general, the mixed reaction principle of polyethylene, Zn ion polymer, ethylene-vinyl acetate copolymer with VA content and fluorocarbon resin mainly involves the coordination reaction between Zn ions and ethylene-vinyl acetate copolymer groups with a certain VA content. These chemical reactions enhance the interaction and compatibility between the components, thereby affecting the overall performance of the mixture, and obtaining a modified polar polyethylene modified material with a stronger polarity.

[0034] Furthermore, the polyethylene is a metallocene polyethylene with an MI value of 4, the ion polymer is a Zn ion polymer, the polar material is an ethylene-vinyl acetate copolymer with a VA content of 28% by mass, and the leveling processing aid is a fluorocarbon resin; the modified polar polyethylene modified material includes the following components in a mass ratio: 65% metallocene polyethylene, 4% Zn ion polymer, 30% ethylene-vinyl acetate copolymer with a VA content of 28% by mass, and 1% fluorocarbon resin.

[0035] In order to obtain an aluminum-plated film with high adhesion, good aluminum-plated gloss, high barrier properties after aluminum-plating, and controllable friction coefficient after composite, the present invention optimizes the ratio of each component.

[0036] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0037] 1. Modified materials for the aluminum coating of multi-layer co-extruded polyethylene aluminum-coated substrate films. The modified polar polyethylene modified material is used as the aluminum coating material of the polyethylene aluminum-coated substrate film, which effectively improves the aluminum coating adhesion of the polyethylene aluminum-coated substrate;

[0038] 2. The present invention preferably uses polar materials as the main component to modify the polarity of polyethylene, thereby obtaining a modified polar polyethylene modified material with strong versatility; the polar material in the present invention is the main component for changing the polarity of polyethylene, and the ionic polymer is used as an auxiliary material, which has low crystallinity, good transparency, and very strong anti-pollution property, and can promote the fastness of aluminum plating and good optical properties of the film; the leveling processing aid helps the film surface to be more microscopically smooth;

[0039] 3. The preferred content of ethylene-vinyl acetate copolymer in the present invention is used as a polar material, which has low cost, is easy to obtain and easy to process, thereby significantly reducing the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative work, among which:

[0041] Figure 1 It is a product picture of a modified material for the aluminum layer of a multi-layer co-extruded polyethylene aluminum-coated substrate film. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0044] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0045] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0046] The modified material for the aluminum layer of a multi-layer co-extruded polyethylene aluminum-plated substrate film provided by the present invention includes a modified polar polyethylene modified material, wherein the modified polar polyethylene modified material is the aluminum layer material of the polyethylene aluminum-plated substrate film; the polyethylene aluminum-plated substrate film also includes a core layer material, wherein the core layer material is polyethylene or a modified polar polyethylene modified material, and the core layer material and the aluminum layer material are sequentially stacked from the inside to the outside through a multi-layer co-extrusion blow molding process to form a polyethylene substrate film.

[0047] The modified polar polyethylene modified material comprises polyethylene, ion polymer, polar material, and leveling processing aid, and the preparation method is as follows:

[0048] S1. Raw material preparation: Prepare polyethylene, ion polymer, polar material, and leveling processing aid according to a certain ratio to ensure the purity and dryness of polyethylene, ion polymer, polar material, and leveling processing aid to avoid the influence of moisture and impurities on the reaction;

[0049] S2. Premixing: Preliminary mixing of polyethylene, ionomer, polar material and leveling processing aid is performed under low-speed stirring to ensure uniform distribution of each component;

[0050] S3, melt mixing: the pre-mixed materials are fed into a melt mixing device (such as a twin-screw extruder) and melt mixed at an appropriate temperature and pressure. During the melt mixing process, the components are further mixed uniformly under the action of heat and mechanical shear force;

[0051] S4, reaction stage: During melt mixing, polyethylene, as the main matrix material, undergoes physical entanglement and chemical interaction with other components to form a stable mixture.

[0052] In the following examples, the present invention provides a variety of modified polar polyethylene modified material ratios, see Table 1 for specific cases. All the preparation methods provided in the following examples adopt the preparation method of the modified polar polyethylene modified material, except that different components correspond to different melting temperatures and reaction times in the actual processing, and the overall step flow is the same.

[0053] Table 1 Proportions of modified polar polyethylene modified materials in various embodiments

[0054]

[0055]

[0056]

[0057]

[0058] The MI value of polyethylene is the melt index, which is the mass of polyethylene that flows freely from the molten state within 10 minutes under certain conditions, usually in grams. The test conditions are usually 190°C and 2.16kg. The MI value is a common indicator for measuring the molecular weight distribution of polyethylene. The smaller it is, the more concentrated the molecular weight distribution is and the worse the melt fluidity is. On the contrary, the larger the MI value is, the better the melt fluidity is. Different types of polyethylene melt index are suitable for different product processing and quality control under special requirements. For example, the MI value is suitable for the processing control of polyethylene products such as spindles, injection molding, blow molding and recycling processing, and is of great significance for the quality control and quality assurance of polyethylene.

[0059] Examples 1-13 mainly screen the types and addition amounts of polyethylene, ionomers, polar materials, and leveling processing aids; Examples 14-25 are further screened ratios based on Examples 1-13.

[0060] Test example

[0061] First, the modified polar polyethylene modified material prepared according to the ratio of Examples 1-25 was subjected to film-forming processes such as blow molding and cooling to obtain an aluminum-coated polyethylene substrate film. Then, the processability and processing cost of the film-forming process, and the aluminum-coating adhesion, COF (coefficient of friction) stability, and aluminum-coating barrier properties of the aluminum-coated polyethylene substrate film were tested. The test results are shown in Table 2.

[0062] Judgment of the processability of the film-forming process: According to the ratios of Examples 1-25, if the polyethylene modified material with polarity can be successfully prepared, it means that it is processable. If the components cannot react and the polyethylene modified material with polarity cannot be obtained, it means that it is not processable.

[0063] The calculation standard of processing cost is: the total cost is calculated by allocating raw material cost, production process cost, packaging and transportation cost, management cost, and R&D cost. If the cost is twice or more than the current market cost, it means that the processing cost is high; if the cost is within twice (not including twice) of the current market cost, it means that the processing cost is relatively high; if the cost is lower than the current market cost, it means that the cost is low.

[0064] Aluminum coating adhesion: Aluminum-coated polyethylene substrate film is aluminized to obtain an aluminized film, and the aluminized layer is heat-sealed with EAA material to test the aluminized fastness. The higher the heat-sealing strength, the higher the aluminized fastness.

[0065] Determination of COF (friction coefficient) stability: Aluminum-plated polyethylene substrate film is aluminum-plated to obtain an aluminum-plated film. After composite aging, the friction coefficient of the aluminum-plated film is measured using a friction coefficient tester. The sample is fixed on the test instrument and tested according to the instrument's operating instructions. The friction coefficient value of each test is recorded, and the same sample is tested repeatedly for multiple times. The average and standard deviation of the multiple test results are calculated to evaluate the stability of the friction coefficient. The smaller the standard deviation, the better the stability of the friction coefficient; a standard deviation within 0.1 indicates high COF stability, a standard deviation between 0.1-0.2 indicates average COF stability, and a standard deviation above 0.2 indicates poor stability.

[0066] Determination of aluminum barrier properties: Use a water vapor transmission rate tester to determine the water vapor barrier properties of ethylene aluminum-coated films. The determination method of the water vapor transmission rate tester is a prior art and will not be explained in detail here. The smaller the water vapor transmission rate value, the better the barrier properties of the film. Use an oxygen transmission rate tester to determine the oxygen barrier properties of the film. The water vapor transmission rate is 1g / m 2 .day.1atm or less indicates good water barrier and oxygen permeability of 100cc / m 2 .day.Below 1atm indicates good oxygen barrier properties.

[0067] Determination of aluminum-plated gloss: Under a standard light source, visually compare the aluminum-plated film with a standard sample or a reference object of known gloss, and observe the difference in gloss on their surfaces with the human eye; if the difference is large, it means that the aluminum-plated gloss is poor.

[0068] Table 2 Performance test results of aluminized polyethylene substrate film

[0069]

[0070]

[0071] Combined with the above performance test results, it can be seen that the modified polar polyethylene modified materials prepared in Examples 1-25 of the present invention all have certain aluminum plating adhesion, which solves the problem that the existing polyethylene is a non-polar material and has poor aluminum plating adhesion and cannot be directly applied to the aluminum plating process. Combined with the processing cost, COF stability, aluminum plating barrier and aluminum plating gloss, the present invention selects the best two ratios, which are Example 12 and Example 20, respectively. Figure 1 The product picture corresponding to Example 20 shows that the obtained polyethylene aluminized film has high aluminized adhesion, good aluminized gloss, and high barrier properties after aluminizing (water vapor permeability is less than 1g / m 2 .day.1atm, oxygen barrier <10cc / m 2 .day.1atm), high friction coefficient stability, can achieve plastic reduction, simplify product structure, save packaging costs, simplify PET / VMPET / PE to PET / VMPE, and simplify BOPP / VMPET / PE to BOPP / VMPE; it can also achieve high barrier and environmentally friendly single material structure, single PO structure BOPP / VMPE, single PE structure BOPE / VMPE, MDOPE / VMPE, and non-stretched PE / VMPE.

[0072] In addition, some embodiments of the present invention use ethylene-vinyl acetate copolymer with a specific VA content as the polar material, which has low cost, easy acquisition and easy processing, thereby significantly reducing the cost; the high polyethylene content in the optimal embodiment further reduces the cost; therefore, after the present invention uses chemical substances to modify the polarity of polyethylene, the material cost is significantly reduced compared to other polar modified materials, and can be popularized.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made by any technician familiar with the field within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. Modified material for aluminum-plated layer of multi-layer co-extruded polyethylene aluminum-plated substrate film, characterized by: It includes a modified polar polyethylene modified material, wherein the modified polar polyethylene modified material is an aluminum-plated layer material of a polyethylene aluminum-plated substrate film; The modified polar polyethylene modified material comprises the following components: polyethylene, ion polymer, polar material, and leveling processing aid; The polyethylene is a metallocene polyethylene with an MI value of 2, the ion polymer is a Zn ion polymer, the polar material is an ethylene-vinyl acetate copolymer with a VA content of 28% by mass, and the leveling processing aid is a fluorocarbon resin; the modified polar polyethylene modified material includes the following components in a mass ratio: 64% metallocene polyethylene, 5% Zn ion polymer, 30% ethylene-vinyl acetate copolymer with a VA content of 28% by mass, and 1% fluorocarbon resin.

2. Modified material for aluminum-plated layer of multi-layer co-extruded polyethylene aluminum-plated substrate film, characterized by: It includes a modified polar polyethylene modified material, wherein the modified polar polyethylene modified material is an aluminum-plated layer material of a polyethylene aluminum-plated substrate film; The modified polar polyethylene modified material comprises the following components: polyethylene, ion polymer, polar material, and leveling processing aid; The polyethylene is a metallocene polyethylene with an MI value of 4, the ion polymer is a Zn ion polymer, the polar material is an ethylene-vinyl acetate copolymer with a VA content of 28% by mass, and the leveling processing aid is a fluorocarbon resin; the modified polar polyethylene modified material includes the following components in a mass ratio: 65% metallocene polyethylene, 4% Zn ion polymer, 30% ethylene-vinyl acetate copolymer with a VA content of 28% by mass, and 1% fluorocarbon resin.

Images