Plastic composite sheet and method for producing the same
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGYIN BAOBO NEW TYPE PACKAGING MATERIAL
- Filing Date
- 2026-03-17
- Publication Date
- 2026-06-05
Smart Images
Figure CN122143432A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of daily chemical packaging technology, specifically to a plastic composite sheet and its preparation method. Background Technology
[0002] Tube packaging, due to its convenience and excellent sealing properties, has been widely used in cosmetics, skincare products, ointments, and food additives. Currently, the main materials used in tube packaging on the market are single-material PE and thin aluminum foil composite PE. Single-material PE tubes have advantages in production cost and processing convenience, but because of their high elasticity, they tend to rebound noticeably after being pressed, preventing the material inside from being squeezed out smoothly and completely. Consumers often need to apply pressure repeatedly, affecting the user experience.
[0003] To address the springback issue, the industry has widely adopted a structure using thin aluminum foil composite PE material. This type of material reduces the springback rate to some extent by utilizing the rigidity of the aluminum foil; however, because the aluminum foil used is typically thin, its structural support is limited and cannot completely eliminate springback. Furthermore, after prolonged use under pressure, the thin aluminum foil is prone to breakage due to repeated bending, severely affecting the water and oxygen barrier properties of the hose.
[0004] In recent years, to further meet the needs of users with low rebound rates, the industry has gradually shifted to using aluminum-plastic composite sheets to manufacture hoses. This type of material provides robust mechanical support through the aluminum foil layer, which theoretically can effectively suppress hose rebound. The problem is that if the aluminum foil is too thin, the support is insufficient, failing to achieve the desired non-rebound effect; if it is too thick, it reduces the overall flexibility of the sheet, leading to numerous difficulties in subsequent processing such as punching and folding, and increasing production costs. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite sheet material with low resilience and good processability.
[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows.
[0007] In a first aspect, the present invention provides a plastic composite sheet, the composite sheet comprising an aluminum foil, wherein transition layers are provided on both the upper and lower sides of the aluminum foil by means of a coating, and an outer surface layer and an inner surface layer are respectively provided on the side of the two transition layers away from the aluminum foil; The aluminum foil has a thickness of 40-50 μm, and according to GB / T 228.1-2021, its tensile strength is 10-15 MPa, and its elongation after fracture is ≥30%; the thickness of the aluminum foil accounts for 15%-20% of the total thickness of the composite sheet. The raw materials for the transition layer include ethylene-vinyl acetate copolymer and maleic anhydride-grafted polyethylene, and the melt index of the transition layer at 190°C and 2.16 kg load is 2.0~5.0 g / 10 min.
[0008] As a preferred technical solution, the raw material of the transition layer further includes an interface synergist, which is prepared by reacting cyclohexane-1,3,5-tricarboxyl chloride with a compound containing both amino and phosphonate groups.
[0009] As a preferred technical solution, the compound containing both amino and phosphonate groups includes at least one of aminoethylphosphonate diethyl ester, aminopropylphosphonate diethyl ester, aminopropylphosphonate dimethyl ester, bis(2-aminoethyl)-aminomethylphosphonate triethyl ester or N-(2-aminoethyl)-2-aminoethylphosphonate diethyl ester.
[0010] As a preferred technical solution, the raw materials in the transition layer, by mass, include 85-95 parts of linear low-density polyethylene; 5-15 parts of ethylene-vinyl acetate copolymer; 3-6 parts of maleic anhydride-grafted polyethylene; 1-3 parts of interface synergist; and 0.2-2 parts of processing aid.
[0011] As a preferred technical solution, the raw materials of the outer layer, by weight, include 70-80 parts of high-density polyethylene, 15-25 parts of low-density polyethylene, 0.5-1.0 parts of anti-aging agent, 0.3-0.5 parts of slip agent, and 1-3 parts of color masterbatch; the density of the outer layer is 0.940-0.965 g / cm³. 3 The outer surface layer has a melt flow index of 0.3-0.8 g / 10min at 190°C and a load of 2.16 kg.
[0012] As a preferred technical solution, the raw material of the inner surface layer, by weight, includes 60-70 parts of low-density polyethylene, 25-35 parts of linear low-density polyethylene, 0.3-0.6 parts of food-grade antioxidant, and 0.2-0.4 parts of antibacterial agent; the density of the inner surface layer is 0.910-0.920 g / cm³. 3 The inner surface layer has a melt flow index of 0.8-1.5 g / 10 min at 190°C and a load of 2.16 kg.
[0013] As a preferred technical solution, the thickness of the outer surface layer is 50-60 μm, the thickness of each of the two transition layers is 20-25 μm, and the thickness of the inner surface layer is 100-140 μm.
[0014] As a preferred technical solution, the raw materials of the outer and / or inner surface layers, by mass, further include 0.5-1 parts of the esterification product of pentaerythritol and 3,3'-dithiodipropionic acid.
[0015] As a preferred technical solution, the plastic composite sheet is released after a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s. The rebound displacement is measured, and the calculated rebound rate is ≤3%.
[0016] In a second aspect, the present invention provides a method for preparing a plastic composite sheet having any of the above-mentioned technical features, comprising the following steps: S1. Prepare mixed raw materials for outer surface layer, inner surface layer and transition layer according to the formula; react cyclohexane-1,3,5-tricarboxyl chloride with compounds containing amino and phosphonate groups at 60-80℃ for 1-3 hours to obtain interface synergist. S2. The raw materials of each layer are melt-blended, extruded, cooled and pelletized by a twin-screw extruder to obtain the corresponding outer surface layer masterbatch, inner surface layer masterbatch and transition layer masterbatch. S3. The outer layer masterbatch and the transition layer masterbatch are fed into a co-extrusion extruder, melted, and extruded through the same die. At the same time, aluminum foil is drawn through the die so that the molten first transition layer is coated on one side of the aluminum foil, and the outer layer is simultaneously laminated on the outside of the first transition layer. After cooling, an intermediate is obtained. S4. Turn the intermediate over so that the uncomposite side of the aluminum foil faces upward; feed the inner surface layer masterbatch and the second transition layer masterbatch into a co-extrusion extruder, melt them, and extrude them through the same die; pull the intermediate through the die so that the molten second transition layer is coated on the other side of the aluminum foil, and the inner surface layer is simultaneously composited on the outside of the second transition layer. After cooling, a composite sheet is obtained. S5. Curing the composite sheet at 40-50℃ for 24-48 hours, then slitting and winding it up, yields the finished product.
[0017] The advantages and beneficial effects of this invention are as follows: This invention uses aluminum foil of a specific thickness as a support layer, ensuring shape retention to resist elastic recovery after pressing while maintaining the overall flexibility of the sheet. This invention introduces a maleic anhydride-grafted polyethylene and ethylene-vinyl acetate copolymer into the transition layer, and, in conjunction with an interface synergist, forms a chemically bonded layer at the aluminum foil-polymer interface through the coordination of phosphonate groups with the aluminum foil surface and the covalent reaction of amino groups with acid anhydrides. This improves interlayer peel strength and encapsulates the aluminum foil, avoiding the risk of delamination and tearing.
[0018] Furthermore, the outer and inner layers are blended with polyethylene systems of different melt indices and densities, balancing the stiffness of the outer layer with the flexibility of the inner layer. Adding the esterification product of pentaerythritol and 3,3'-dithiodipropionic acid to either the inner or outer layer allows for the reversible exchange of disulfide bonds to dissipate energy under stress, suppressing rebound. The resulting sheet exhibits a rebound rate of no more than 3% in simulated compression tests, demonstrating strong interlayer bonding and excellent processing adaptability and content safety. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the composite sheet structure shown in this invention. Detailed Implementation
[0020] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.
[0021] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.
[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly or implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0023] This invention provides a plastic composite sheet, comprising an aluminum foil layer, with transition layers formed by coating on both the upper and lower sides of the aluminum foil layer. An outer surface layer and an inner surface layer are respectively disposed on the side of the two transition layers furthest from the aluminum foil layer. The aluminum foil layer has a thickness of 40-50 μm, and according to GB / T 228.1-2021, its tensile strength is 10-15 MPa, and its elongation after fracture is ≥30%. The thickness of the aluminum foil layer accounts for 15%-20% of the total thickness of the plastic composite sheet. The transition layers are made of ethylene-vinyl acetate copolymer and maleic anhydride-grafted polyethylene, and the melt flow index of the transition layers at 190℃ and a load of 2.16 kg is 2.0-5.0 g / 10 min.
[0024] In this composite sheet, the aluminum foil layer serves as a rigid support, with its thickness controlled within the range of 40-50 μm. When the aluminum foil thickness is less than 40 μm, its flexural modulus is insufficient, making it difficult to effectively resist the elastic recovery force generated after pressing the composite sheet, resulting in a noticeable springback phenomenon. When the thickness exceeds 50 μm, although the springback resistance is enhanced, the overall flexibility of the sheet decreases sharply. During subsequent processing such as hose coiling and sealing, the aluminum foil is prone to irreversible micro-cracks or even breakage due to stress concentration during bending. This invention limits the thickness of the aluminum foil layer to 15%~20% of the total thickness of the composite sheet. This proportion ensures that the rigidity contribution of the aluminum foil plays a dominant but not absolute role in the total thickness. If the proportion is too low, the rigidity effect of the aluminum foil is masked by the excessively thick polymer layer, and the overall composite material tends to exhibit the viscoelasticity of the polymer, resulting in ineffective springback control. If the proportion is too high, the composite material becomes too rigid, losing the flexible feel and processing performance required for the hose. Meanwhile, the specific combination of tensile strength and elongation after fracture of the aluminum foil ensures that while providing rigidity, the aluminum foil itself has good ductility and can undergo plastic deformation along with the polymer layer rather than brittle failure.
[0025] The transition layer, applied via a coating process, is a crucial interface engineering element for achieving a strong bond between the aluminum foil and the inner and outer PE layers. A blend of ethylene-vinyl acetate copolymer (EVA) and maleic anhydride-grafted polyethylene (MAH-g-PE) is selected. The vinyl acetate segments in EVA possess polarity and flexibility, exhibiting good compatibility with the non-polar PE matrix and acting as a toughening phase to enhance the toughness of the transition layer. The introduction of MAH-g-PE allows the maleic anhydride groups on the MAH-g-PE molecular chains to chemically interact with the aluminum foil surface, optionally through corona treatment to form alumina / hydroxylated surfaces, during the melt coating process. This interaction creates ester or coordination bonds, establishing a chemical anchor between the aluminum foil and the polymer.
[0026] The polyethylene backbone of MAH-g-PE can undergo sufficient molecular chain entanglement and co-crystallization with the EVA in the transition layer and the subsequent outer and inner PE matrix, thereby bridging the aluminum foil and PE at the interface. If the melt index of the transition layer is too low, the melt viscosity is too high, and the fluidity is poor, it is difficult to form a uniform and dense thin layer during coating, and the wettability of the aluminum foil is poor, affecting the initial adhesion. If the melt index is too high, the melt strength is too low, and drooling or cracking is likely to occur during extrusion coating, resulting in uneven thickness, and the cohesion of the interface layer may be insufficient after cooling and setting.
[0027] In some embodiments, in order to improve the interfacial bonding between the transition layer and the aluminum foil layer and to impart excellent resistance to damp heat aging, the raw material of the transition layer also contains an interfacial synergist, which is prepared by reacting cyclohexane-1,3,5-tricarboxyl chloride with a compound containing amino and phosphonate groups.
[0028] In this interfacial synergist, cyclohexane-1,3,5-tricarboxyl chloride provides a rigid, trifunctional core. During the reaction, its three highly reactive acyl chloride groups undergo amidation with the primary amino groups on compounds containing amino and phosphonate groups, forming a star-shaped or network-like prepolymer with cyclohexane as the core. The phosphonate groups introduced onto this prepolymer have a strong affinity for the surfaces of metal oxides such as aluminum and iron. Its P=O and P-OH groups can form stable coordination bonds and even covalent PO-Al bonds with the Al-OH on the aluminum foil surface; this binding force is far stronger than physical adsorption or hydrogen bonding.
[0029] Meanwhile, the polar groups such as amide bonds and carboxyl groups remaining on the prepolymer or generated by the reaction, as well as the potential sites in their molecular structure that may further react with the anhydride groups in MAH-g-PE, together constitute a complex mechanism that tightly binds with the polymer matrix. This constructs a dense transition region with strong energy dissipation capacity in the interface area, which can effectively prevent small molecules such as moisture from penetrating along the interface, thereby improving the adhesion durability under humid and hot conditions.
[0030] Furthermore, the compounds containing amino and phosphonate groups can be selected from at least one of aminoethylphosphonate, aminopropylphosphonate, aminopropylphosphonate, bis(2-aminoethyl)-aminomethylphosphonate, or N-(2-aminoethyl)-2-aminoethylphosphonate. These compounds all possess one or more highly reactive primary amino groups and one or more phosphonate groups, potentially forming a higher crosslinking density interfacial network, thereby providing stronger anchoring force. However, the increased molecular weight may also have some impact on diffusion and migration in the polymer melt. Therefore, the specific compound selection can be adjusted based on the comprehensive requirements of interfacial strength, processing technology, and cost.
[0031] In some embodiments, the transition layer comprises, by weight, 85-95 parts of linear low-density polyethylene (LLDPE), 5-15 parts of EVA, 3-6 parts of MAH-g-PE, 1-3 parts of interfacial synergist, and 0.2-2 parts of processing aid.
[0032] LLDPE, as the continuous phase, provides excellent flexibility, processability, and mechanical strength. EVA, as a polar modifier and toughening agent, improves initial wettability with aluminum foil. The introduction of vinyl acetate segments also reduces crystallinity, increases segment mobility, and facilitates stress relaxation. The amount of MAH-g-PE needs to be coordinated with the interfacial synergist. Too little MAH-g-PE results in insufficient bonding at the basic interface; too much may cause it to aggregate and affect the dispersion of other components. The interfacial synergist, at a low addition of 1-3 parts, can improve peel strength through its efficient multi-point anchoring effect. Processing aids (such as silica) ensure process stability during masterbatch processing and sheet winding.
[0033] In some embodiments, to achieve the required stiffness, abrasion resistance, printability and anti-aging properties of the outer surface layer, the outer surface layer comprises, by weight of total raw materials: 70-80 parts of high-density polyethylene (HDPE), 15-25 parts of low-density polyethylene (LDPE), 0.5-1.0 parts of anti-aging agent, 0.3-0.5 parts of slip agent, and 1-3 parts of color masterbatch.
[0034] The outer layer is a blend of HDPE and LDPE, utilizing the complementary properties resulting from the different chain structures of the two PEs. HDPE, with its high crystallinity, density, and rigidity, provides the outer layer with excellent compressive strength, scratch resistance, and dimensional stability, which is fundamental for maintaining the hose's shape during stacking and transportation. The introduction of LDPE, with its long-branched structure, improves the blend's melt elasticity, processing flowability, and impact resistance, preventing the brittleness that pure HDPE might exhibit. The addition of anti-aging agents (such as hindered phenols) effectively delays the degradation of PE molecular chains caused by ultraviolet radiation and heat-oxidation, ensuring the hose maintains its appearance and performance throughout its shelf life and service life. Lubricants (such as stearamide) reduce the surface friction coefficient, facilitating smooth hose transport on the production line and improving the user experience.
[0035] In some embodiments, to ensure the safety, excellent flexibility, sealing performance and certain puncture resistance of the inner surface layer in contact with the contents, the inner surface layer comprises, by weight of the total raw materials: 60-70 parts of LDPE, 25-35 parts of linear low-density polyethylene (LLDPE), 0.3-0.6 parts of antioxidant, and 0.2-0.4 parts of antibacterial agent.
[0036] The inner layer formulation is primarily based on LDPE, fully utilizing its long-chain structure to provide high melt strength, excellent flexibility, low-temperature flexibility, and heat-sealing properties, ensuring the inner layer tightly adheres to the contents and can be successfully extruded. The short-chain structure of LLDPE provides higher tensile strength, puncture resistance, and resistance to environmental stress cracking, compensating for LDPE's strength deficiencies and preventing hose breakage and leakage during folding or localized compression. The inner layer has a lower density than the outer layer, corresponding to lower crystallinity and higher flexibility, making the hose easier to deflate. The melt index is slightly higher than the outer layer, ensuring good flowability during lamination and forming a smooth, defect-free sealing surface.
[0037] In some embodiments, the outer surface layer has a thickness of 50-60 μm, the two transition layers each have an independent thickness of 20-25 μm, and the inner surface layer has a thickness of 100-140 μm. The outer surface layer provides necessary protection and stiffness; the transition layers, acting as bonding bridges, need to be thick enough to form a continuous, defect-free interface layer. If too thin, uneven coverage may occur, resulting in weak bonding; if too thick, it increases cost and may introduce additional internal stress due to differences in thermal expansion coefficients. The inner surface layer is the thickest, providing sufficient material to ensure excellent heat-sealing performance and sealing reliability. Secondly, when pressed, the thicker inner surface layer undergoes large deformation to absorb energy, while the aluminum foil layer restricts recovery. Together, they achieve low rebound, improving the overall internal pressure resistance and drop impact resistance of the hose.
[0038] In some embodiments, in order to further dissipate the elastic potential energy generated during pressing from the perspective of material intrinsics and suppress rebound, the raw materials of the outer and / or inner layers, by mass, also include 0.5-1 parts of the reaction esterification product of pentaerythritol and 3,3'-dithiodipropionic acid.
[0039] The esterification product of this reaction is a functional additive containing dynamic disulfide bonds. Its mechanism of action differs from traditional plasticizers or elastomers. When the hose is subjected to rapid pressure, micro-stress concentration occurs within the material. At this time, the disulfide bonds on the additive molecules dispersed in the PE matrix may undergo reversible homolytic cleavage or exchange reactions under shear force. This process of bond breaking and reforming actively dissipates some of the mechanical energy that causes the material's elastic recovery, converting it into irreversible energy forms such as heat.
[0040] In some embodiments, to objectively quantify the core performance characteristics of the present invention, the plastic composite sheet is released after a pressing stroke of 10 mm, a pressing pressure of 50 N, and a holding pressure of 10 s. The rebound displacement is measured, and the calculated rebound rate is ≤3%. This test method simulates the typical working condition of a human hand actually squeezing a flexible tube. A rebound rate (rebound displacement / pressing stroke × 100%) ≤3% means that the rebound is almost imperceptible, achieving the ideal effect of "pressing out immediately and stopping immediately upon release". The preparation method of the plastic composite sheet of the present invention includes the following steps: S1. Prepare mixed raw materials for outer surface layer, inner surface layer and transition layer according to the formula; react cyclohexane-1,3,5-tricarboxyl chloride with compounds containing amino and phosphonate groups at 60-80℃ for 1-3 hours to obtain interface synergist. S2. The raw materials of each layer are melt-blended, extruded, cooled and pelletized by a twin-screw extruder to obtain the corresponding outer surface layer masterbatch, inner surface layer masterbatch and transition layer masterbatch. S3. The outer layer masterbatch and the transition layer masterbatch are fed into a co-extrusion extruder, melted, and extruded through the same die. At the same time, aluminum foil is drawn through the die so that the molten first transition layer is coated on one side of the aluminum foil, and the outer layer is simultaneously laminated on the outside of the first transition layer. After cooling, an intermediate is obtained. S4. Turn the intermediate over so that the uncomposite side of the aluminum foil faces upward; feed the inner surface layer masterbatch and the second transition layer masterbatch into a co-extrusion extruder, melt them, and extrude them through the same die; pull the intermediate through the die so that the molten second transition layer is coated on the other side of the aluminum foil, and the inner surface layer is simultaneously composited on the outside of the second transition layer. After cooling, a composite sheet is obtained. S5. Curing the composite sheet at 40-50℃ for 24-48 hours, then slitting and winding it up, yields the finished product.
[0041] In this preparation method, the pre-synthesis of the interfacial synergist in step S1 ensures the controllability of its chemical structure and the completeness of the reaction, avoiding side reactions or uneven dispersion that may occur with direct feeding. The masterbatch process in step S2 is crucial for achieving highly uniform mixing of raw materials in each layer and avoiding metering errors or dispersion problems caused by subsequent direct feeding, thus ensuring the stability and consistency of mass production. Steps S3 and S4 use two independent co-extrusion coating operations, rather than laminating all layers at once. This adapts to the physical characteristics of aluminum foil as a solid substrate, which cannot merge with other molten layers within a single die. Furthermore, the step-by-step operation allows for independent optimization and precise control of the lamination process parameters for each side, ensuring strong and uniform interfacial bonding on each side. For example, after the first lamination, the resulting "outer layer / first transition layer / aluminum foil" intermediate has a certain rigidity, facilitating stable traction during the second lamination and preventing wrinkles.
[0042] The present invention will now be explained and described in detail with reference to specific embodiments and comparative examples.
[0043] Example 1 A manufacturing process for a plastic composite sheet includes the following steps: S1. Prepare the mixed raw materials for the outer surface layer, inner surface layer, and transition layer according to the formula: The raw materials for the transition layer are: 90 parts LLDPE, 8 parts EVA, 4 parts MAG-g-PE, and 0.5 parts processing aid (silica).
[0044] The raw materials for the outer layer are: 75 parts HDPE, 20 parts LDPE, 0.8 parts anti-aging agent (hindered phenol), 0.4 parts slip agent (stearamide), and 2 parts color masterbatch.
[0045] The raw materials for the inner surface layer are: 65 parts LDPE, 30 parts LLDPE, 0.5 parts food-grade antioxidant, and 0.3 parts antibacterial agent.
[0046] Separately, cyclohexane-1,3,5-tricarboxylic acid chloride and diethyl aminoethylphosphonate were reacted at 70°C for 2 hours to prepare an interfacial synergist. 1.5 parts of this interfacial synergist were added to the transition layer mixture based on the total mass of the transition layer raw materials.
[0047] S2. The prepared outer surface layer, inner surface layer and transition layer mixed raw materials are melt-blended, extruded, cooled and pelletized by a twin-screw extruder to obtain the corresponding outer surface layer masterbatch, inner surface layer masterbatch and transition layer masterbatch.
[0048] S3. The outer layer masterbatch and transition layer masterbatch obtained in step S2 are fed into a co-extrusion extruder, melted, and extruded through the same die. Simultaneously, an aluminum foil with a thickness of 42 μm (tested according to GB / T 228.1-2021, tensile strength of 12 MPa, elongation after fracture of 35%) is drawn through the die, so that the molten first transition layer is coated on one side of the aluminum foil, and the outer layer is simultaneously laminated to the outside of the first transition layer. After cooling, an intermediate is obtained. In this intermediate, the outer layer thickness is 55 μm, and the first transition layer thickness is 22 μm.
[0049] S4. Flip the intermediate so that the uncomposite side of the aluminum foil faces upward. Feed the inner surface layer masterbatch and the second transition layer masterbatch obtained in step S2 into another co-extrusion extruder, melt them, and extrude them through the same die. Pull the intermediate through the die so that the molten second transition layer coats the other side of the aluminum foil, and the inner surface layer is simultaneously composited onto the outside of the second transition layer. After cooling, a composite sheet is obtained. The thickness of the inner surface layer is 120 μm, and the thickness of the second transition layer is 22 μm. The total thickness of the resulting composite sheet is 261 μm, and the aluminum foil layer accounts for approximately 16.1% of the total thickness.
[0050] S5. Curing the composite sheet at 45°C for 36 hours, then slitting and winding it up, yields the finished plastic composite sheet.
[0051] The sheet obtained in this embodiment, after being released following a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s, showed a springback rate of 2.4%.
[0052] Example 2 A manufacturing process for a plastic composite sheet includes the following steps: S1. Prepare the mixed raw materials for the outer surface layer, inner surface layer, and transition layer according to the formula: The raw materials for the transition layer are: 88 parts LLDPE, 10 parts EVA, 5 parts MAG-g-PE, and 0.8 parts processing aids.
[0053] The raw materials for the outer layer are: 72 parts HDPE, 23 parts LDPE, 0.6 parts anti-aging agent, 0.45 parts slip agent, and 1.5 parts color masterbatch.
[0054] The raw materials for the inner surface layer are: 68 parts LDPE, 28 parts LLDPE, 0.4 parts food-grade antioxidant, and 0.35 parts antibacterial agent.
[0055] Separately, cyclohexane-1,3,5-tricarboxyl chloride was reacted with diethyl aminopropylphosphonate at 65°C for 2.5 hours to prepare an interfacial synergist. Two parts of this interfacial synergist were added to the transition layer mixture based on the total mass of the transition layer raw materials.
[0056] S2. The prepared outer surface layer, inner surface layer and transition layer mixed raw materials are melt-blended, extruded, cooled and pelletized by a twin-screw extruder to obtain the corresponding outer surface layer masterbatch, inner surface layer masterbatch and transition layer masterbatch.
[0057] S3. The outer layer masterbatch and transition layer masterbatch obtained in step S2 are fed into a co-extrusion extruder, melted, and extruded through the same die. Simultaneously, an aluminum foil with a thickness of 45 μm (tested according to GB / T 228.1-2021, tensile strength of 11 MPa, elongation after fracture of 38%) is drawn through the die, so that the molten first transition layer is coated on one side of the aluminum foil, and the outer layer is simultaneously laminated onto the outside of the first transition layer. After cooling, an intermediate is obtained. In this intermediate, the outer layer thickness is 52 μm, and the first transition layer thickness is 21 μm.
[0058] S4. Flip the intermediate so that the uncomposite side of the aluminum foil faces upward. Feed the inner surface layer masterbatch and the second transition layer masterbatch obtained in step S2 into another co-extrusion extruder, melt them, and extrude them through the same die. Pull the intermediate through the die so that the molten second transition layer coats the other side of the aluminum foil, and the inner surface layer is simultaneously composited onto the outside of the second transition layer. After cooling, a composite sheet is obtained. The thickness of the inner surface layer is 110 μm, and the thickness of the second transition layer is 21 μm. The total thickness of the resulting composite sheet is 249 μm, and the aluminum foil layer accounts for approximately 18.1% of the total thickness.
[0059] S5. Curing the composite sheet at 48°C for 30 hours, then slitting and winding it up, yields the finished plastic composite sheet.
[0060] The sheet obtained in this embodiment was released after a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s. The measured and calculated rebound rate was 2.1%.
[0061] Example 3 A manufacturing process for a plastic composite sheet includes the following steps: S1. Prepare the mixed raw materials for the outer surface layer, inner surface layer, and transition layer according to the formula: The raw materials for the transition layer are: 92 parts LLDPE, 6 parts EVA, 3.5 parts MAG-g-PE, and 1.2 parts processing aids.
[0062] The raw materials for the outer layer are: 78 parts HDPE, 17 parts LDPE, 0.9 parts anti-aging agent, 0.35 parts slip agent, and 2.5 parts color masterbatch. In addition, based on the total mass of the outer layer raw materials, 0.6 parts of the reaction esterification product of pentaerythritol and 3,3'-dithiodipropionic acid are added.
[0063] The raw materials for the inner surface layer are: 62 parts LDPE, 33 parts LLDPE, 0.55 parts food-grade antioxidant, and 0.25 parts antibacterial agent.
[0064] Separately, cyclohexane-1,3,5-tricarboxylic acid chloride was reacted with triethyl bis(2-aminoethyl)-aminomethylphosphonate at 75°C for 1.5 hours to prepare an interfacial synergist. 2.5 parts of this interfacial synergist were added to the transition layer mixture based on the total mass of the transition layer raw materials.
[0065] S2. The prepared outer surface layer, inner surface layer and transition layer mixed raw materials are melt-blended, extruded, cooled and pelletized by a twin-screw extruder to obtain the corresponding outer surface layer masterbatch, inner surface layer masterbatch and transition layer masterbatch.
[0066] S3. The outer layer masterbatch and transition layer masterbatch obtained in step S2 are fed into a co-extrusion extruder, melted, and extruded through the same die. Simultaneously, an aluminum foil with a thickness of 48 μm (tested according to GB / T 228.1-2021, tensile strength of 13 MPa, elongation after fracture of 32%) is drawn through the die, so that the molten first transition layer is coated on one side of the aluminum foil, and the outer layer is simultaneously laminated on the outside of the first transition layer. After cooling, an intermediate is obtained. In this intermediate, the outer layer thickness is 58 μm, and the first transition layer thickness is 23 μm.
[0067] S4. Flip the intermediate so that the uncomposite side of the aluminum foil faces upward. Feed the inner surface layer masterbatch and the second transition layer masterbatch obtained in step S2 into another co-extrusion extruder, melt them, and extrude them through the same die. Pull the intermediate through the die so that the molten second transition layer coats the other side of the aluminum foil, and the inner surface layer is simultaneously composited onto the outside of the second transition layer. After cooling, a composite sheet is obtained. The thickness of the inner surface layer is 130 μm, and the thickness of the second transition layer is 23 μm. The total thickness of the resulting composite sheet is 282 μm, and the aluminum foil layer accounts for approximately 17.0% of the total thickness.
[0068] S5. The composite sheet is cured at 42°C for 42 hours, then cut and rolled up to obtain the finished plastic composite sheet.
[0069] The sheet obtained in this embodiment, after being released with a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s, had a measured and calculated rebound rate of 1.8%.
[0070] Example 4 A manufacturing process for a plastic composite sheet includes the following steps: S1. Prepare the mixed raw materials for the outer surface layer, inner surface layer, and transition layer according to the formula: The raw materials for the transition layer are: 85 parts LLDPE, 12 parts EVA, 6 parts MAG-g-PE, and 1.8 parts processing aids.
[0071] The raw materials for the outer layer are: 70 parts HDPE, 25 parts LDPE, 0.5 parts anti-aging agent, 0.5 parts slip agent, and 1 part color masterbatch.
[0072] The raw materials for the inner surface layer are: 70 parts LDPE, 25 parts LLDPE, 0.3 parts food-grade antioxidant, and 0.4 parts antibacterial agent. In addition, based on the total mass of the raw materials for the inner surface layer, 0.8 parts of the esterification product of pentaerythritol and 3,3'-dithiodipropionic acid are added.
[0073] Separately, cyclohexane-1,3,5-tricarboxyl chloride and dimethyl aminopropylphosphonate were reacted at 80°C for 1 hour to prepare an interfacial synergist. Three parts of this interfacial synergist were added to the transition layer mixture based on the total mass of the transition layer raw materials.
[0074] S2. The prepared outer surface layer, inner surface layer and transition layer mixed raw materials are melt-blended, extruded, cooled and pelletized by a twin-screw extruder to obtain the corresponding outer surface layer masterbatch, inner surface layer masterbatch and transition layer masterbatch.
[0075] S3. The outer layer masterbatch and transition layer masterbatch obtained in step S2 are fed into a co-extrusion extruder, melted, and extruded through the same die. Simultaneously, an aluminum foil with a thickness of 50 μm (tested according to GB / T 228.1-2021, tensile strength of 14 MPa, elongation after fracture of 31%) is drawn through the die, so that the molten first transition layer is coated on one side of the aluminum foil, and the outer layer is simultaneously laminated to the outside of the first transition layer. After cooling, an intermediate is obtained. In this intermediate, the outer layer thickness is 60 μm, and the first transition layer thickness is 25 μm.
[0076] S4. Flip the intermediate so that the uncomposite side of the aluminum foil faces upward. Feed the inner surface layer masterbatch and the second transition layer masterbatch obtained in step S2 into another co-extrusion extruder, melt them, and extrude them through the same die. Pull the intermediate through the die so that the molten second transition layer coats the other side of the aluminum foil, and the inner surface layer is simultaneously composited onto the outside of the second transition layer. After cooling, a composite sheet is obtained. The thickness of the inner surface layer is 140 μm, and the thickness of the second transition layer is 25 μm. The total thickness of the resulting composite sheet is 300 μm, and the aluminum foil layer accounts for approximately 16.7% of the total thickness.
[0077] S5. Curing the composite sheet at 50°C for 24 hours, then slitting and winding it up, yields the finished plastic composite sheet.
[0078] The sheet obtained in this embodiment, after being released following a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s, had a measured and calculated rebound rate of 2.7%.
[0079] Example 5 A manufacturing process for a plastic composite sheet includes the following steps: S1. Prepare the mixed raw materials for the outer surface layer, inner surface layer, and transition layer according to the formula: The raw materials for the transition layer are: 95 parts LLDPE, 5 parts EVA, 3 parts MAG-g-PE, and 0.2 parts processing aids.
[0080] The raw materials for the outer layer are: 80 parts HDPE, 15 parts LDPE, 1.0 part anti-aging agent, 0.3 parts slip agent, and 3 parts color masterbatch. In addition, based on the total mass of the outer layer raw materials, 0.5 parts of the reaction esterification product of pentaerythritol and 3,3'-dithiodipropionic acid are added.
[0081] The raw materials for the inner surface layer are: 60 parts LDPE, 35 parts LLDPE, 0.6 parts food-grade antioxidant, and 0.2 parts antibacterial agent. In addition, based on the total mass of the raw materials for the inner surface layer, 1 part of the esterification product of pentaerythritol and 3,3'-dithiodipropionic acid is added.
[0082] Separately, cyclohexane-1,3,5-tricarboxylic acid chloride and diethyl N-(2-aminoethyl)-2-aminoethylphosphonate were reacted at 60°C for 3 hours to prepare an interfacial synergist. One part of this interfacial synergist was added to the mixed raw materials of the transition layer based on the total mass of the transition layer raw materials.
[0083] S2. The prepared outer surface layer, inner surface layer and transition layer mixed raw materials are melt-blended, extruded, cooled and pelletized by a twin-screw extruder to obtain the corresponding outer surface layer masterbatch, inner surface layer masterbatch and transition layer masterbatch.
[0084] S3. The outer layer masterbatch and transition layer masterbatch obtained in step S2 are fed into a co-extrusion extruder, melted, and extruded through the same die. Simultaneously, an aluminum foil with a thickness of 40 μm (tested according to GB / T 228.1-2021, tensile strength of 10 MPa, elongation after fracture of 40%) is drawn through the die, so that the molten first transition layer is coated on one side of the aluminum foil, and the outer layer is simultaneously laminated to the outside of the first transition layer. After cooling, an intermediate is obtained. In this intermediate, the outer layer thickness is 50 μm, and the first transition layer thickness is 20 μm.
[0085] S4. Flip the intermediate so that the uncomposite side of the aluminum foil faces upward. Feed the inner surface layer masterbatch and the second transition layer masterbatch obtained in step S2 into another co-extrusion extruder, melt them, and extrude them through the same die. Pull the intermediate through the die so that the molten second transition layer coats the other side of the aluminum foil, and the inner surface layer is simultaneously composited onto the outside of the second transition layer. After cooling, a composite sheet is obtained. The thickness of the inner surface layer is 100 μm, and the thickness of the second transition layer is 20 μm. The total thickness of the resulting composite sheet is 230 μm, and the aluminum foil layer accounts for approximately 17.4% of the total thickness.
[0086] S5. Curing the composite sheet at 40°C for 48 hours, then slitting and winding it up, yields the finished plastic composite sheet.
[0087] The sheet obtained in this embodiment, after being released following a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s, had a measured and calculated rebound rate of 2.9%.
[0088] Example 6 A manufacturing process for a plastic composite sheet includes the following steps: S1. Prepare the mixed raw materials for the outer surface layer, inner surface layer, and transition layer according to the formula: The raw materials for the transition layer are: 93 parts LLDPE, 7 parts EVA, 4.5 parts MAG-g-PE, and 1.5 parts processing aids. The melt flow index of the transition layer at 190℃ and 2.16kg load is 3.5 g / 10min.
[0089] The outer layer is made of the following raw materials: 76 parts HDPE, 19 parts LDPE, 0.75 parts anti-aging agent, 0.42 parts slip agent, and 2.2 parts color masterbatch. The density of the outer layer is 0.950 g / cm³. 3 The melt flow index at 190℃ and 2.16kg load is 0.5 g / 10min.
[0090] The raw materials for the inner surface layer are: 66 parts LDPE, 29 parts LLDPE, 0.45 parts food-grade antioxidant, and 0.32 parts antibacterial agent. The density of the inner surface layer is 0.915 g / cm³. 3 The melt flow index at 190℃ and 2.16kg load is 1.2 g / 10min.
[0091] Separately, cyclohexane-1,3,5-tricarboxyl chloride was reacted with diethyl aminopropylphosphonate at 72°C for 2.2 hours to prepare an interfacial synergist. 1.8 parts of this interfacial synergist were added to the mixed raw materials of the transition layer based on the total mass of the transition layer materials.
[0092] S2. The prepared outer surface layer, inner surface layer and transition layer mixed raw materials are melt-blended, extruded, cooled and pelletized by a twin-screw extruder to obtain the corresponding outer surface layer masterbatch, inner surface layer masterbatch and transition layer masterbatch.
[0093] S3. The outer layer masterbatch and transition layer masterbatch obtained in step S2 are fed into a co-extrusion extruder, melted, and extruded through the same die. Simultaneously, an aluminum foil with a thickness of 44 μm (tested according to GB / T 228.1-2021, tensile strength of 11.5 MPa, elongation after fracture of 36%) is drawn through the die, so that the molten first transition layer is coated on one side of the aluminum foil, and the outer layer is simultaneously laminated to the outside of the first transition layer. After cooling, an intermediate is obtained. In this intermediate, the outer layer thickness is 53 μm, and the first transition layer thickness is 22 μm.
[0094] S4. Flip the intermediate so that the uncomposite side of the aluminum foil faces upward. Feed the inner surface layer masterbatch and the second transition layer masterbatch obtained in step S2 into another co-extrusion extruder, melt them, and extrude them through the same die. Pull the intermediate through the die so that the molten second transition layer coats the other side of the aluminum foil, and the inner surface layer is simultaneously composited onto the outside of the second transition layer. After cooling, a composite sheet is obtained. The thickness of the inner surface layer is 125 μm, and the thickness of the second transition layer is 22 μm. The total thickness of the resulting composite sheet is 266 μm, and the aluminum foil layer accounts for approximately 16.5% of the total thickness.
[0095] S5. The composite sheet is cured at 46°C for 40 hours, then cut and rolled up to obtain the finished plastic composite sheet.
[0096] The sheet obtained in this embodiment, after being released following a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s, had a measured and calculated rebound rate of 2.0%.
[0097] Comparative Example 1 A commercially available aluminum-plastic composite sheet for flexible tube packaging is used (aluminum foil thickness approximately 30μm, overall structure PE / Ad / AL / Ad / PE, total thickness approximately 220μm). Its manufacturing process is conventional multilayer co-extrusion or dry lamination.
[0098] The comparative sheet was released after a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s. The measured and calculated rebound rate was 8.5%.
[0099] Comparative Example 2 A manufacturing process for a composite sheet is basically the same as that in Example 1, except that: in step S1, when preparing the transition layer raw materials, no interface synergist is added, and the synthesis step of the interface synergist is not performed. The transition layer raw materials are only 90 parts LLDPE, 8 parts EVA, 4 parts MAG-g-PE, and 0.5 parts processing aid.
[0100] The comparative sheet was released after a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s. The measured and calculated rebound rate was 5.2%.
[0101] Comparative Example 3 A manufacturing process for a composite sheet is basically the same as that in Example 1, except that MAG-g-PE is not added when preparing the transition layer raw materials in step S1. The transition layer raw materials are 94 parts LLDPE, 8 parts EVA, 1.5 parts interface synergist, and 0.5 parts processing aid.
[0102] The comparative sheet was released after a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s. The measured and calculated rebound rate was 6.8%.
[0103] Comparative Example 4 A process for producing composite sheets is basically the same as that in Example 3, except that: when preparing the outer layer raw materials in step S1, the reaction esterification product of pentaerythritol and 3,3'-dithiodipropionic acid is not added.
[0104] The comparative sheet was released after a pressing stroke of 10mm, a pressing pressure of 50N, and a holding pressure of 10s. The calculated rebound rate was 2.5%.
[0105] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A plastic composite sheet, characterized in that, It includes an aluminum foil layer, and transition layers are provided on both the upper and lower sides of the aluminum foil layer by coating. An outer surface layer and an inner surface layer are respectively provided on the side of the two transition layers away from the aluminum foil layer. The aluminum foil layer has a thickness of 40~50μm, and according to GB / T 228.1-2021, its tensile strength is 10-15MPa, its elongation after fracture is ≥30%, and the thickness of the aluminum foil layer accounts for 15%~20% of the total thickness of the plastic composite sheet; The raw materials for the transition layer include ethylene-vinyl acetate copolymer and maleic anhydride-grafted polyethylene, and the melt index of the transition layer at 190°C and 2.16 kg load is 2.0~5.0 g / 10 min.
2. The plastic composite sheet according to claim 1, characterized in that, The raw material of the transition layer also includes an interface synergist, which is prepared by reacting cyclohexane-1,3,5-tricarboxyl chloride with a compound containing amino and phosphonate groups.
3. The plastic composite sheet according to claim 2, characterized in that, The compound containing amino and phosphonate groups is at least one of aminoethylphosphonate diethyl ester, aminopropylphosphonate diethyl ester, aminopropylphosphonate dimethyl ester, bis(2-aminoethyl)-aminomethylphosphonate triethyl ester or N-(2-aminoethyl)-2-aminoethylphosphonate diethyl ester.
4. The plastic composite sheet according to claim 2, characterized in that, The transition layer comprises, by weight, 85-95 parts of linear low-density polyethylene, 5-15 parts of ethylene-vinyl acetate copolymer, 3-6 parts of maleic anhydride-grafted polyethylene, 1-3 parts of interface synergist, and 0.2-2 parts of processing aid.
5. The plastic composite sheet according to claim 1, characterized in that, The outermost layer comprises, by weight, 70-80 parts of high-density polyethylene, 15-25 parts of low-density polyethylene, 0.5-1.0 parts of anti-aging agent, 0.3-0.5 parts of slip agent, and 1-3 parts of color masterbatch. The density of the outer layer is 0.940-0.965 g / cm³. 3 Furthermore, the melt flow index at 190℃ and 2.16kg load is 0.3-0.8 g / 10min.
6. The plastic composite sheet according to claim 1, characterized in that, Based on the total mass of the raw materials for the inner surface layer, it includes: 60-70 parts of low-density polyethylene, 25-35 parts of linear low-density polyethylene, 0.3-0.6 parts of food-grade antioxidant, and 0.2-0.4 parts of antibacterial agent; The density of the inner surface layer is 0.910-0.920 g / cm³. 3 Furthermore, the melt flow index at 190℃ and 2.16kg load is 0.8-1.5 g / 10min.
7. The plastic composite sheet according to claim 1, characterized in that, The outermost layer has a thickness of 50-60 μm, the two transition layers each have a thickness of 20-25 μm, and the innermost layer has a thickness of 100-140 μm.
8. The plastic composite sheet according to claim 1, characterized in that, The raw materials of the outer and / or inner surface layers also include, by mass, 0.5-1 parts of the esterification product of pentaerythritol and 3,3'-dithiodipropionic acid.
9. The plastic composite sheet according to claim 1, characterized in that, The plastic composite sheet was pressed with a stroke of 10mm, a pressing pressure of 50N, and held for 10s before being released. The rebound displacement was measured, and the calculated rebound rate was ≤3%.
10. A method for preparing the plastic composite sheet according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Prepare mixed raw materials for outer surface layer, inner surface layer and transition layer according to the formula; react cyclohexane-1,3,5-tricarboxyl chloride with compounds containing amino and phosphonate groups at 60-80℃ for 1-3 hours to obtain interface synergist. S2. The raw materials of each layer are melt-blended, extruded, cooled and pelletized by a twin-screw extruder to obtain the corresponding outer surface layer masterbatch, inner surface layer masterbatch and transition layer masterbatch. S3. The outer layer masterbatch and the transition layer masterbatch are fed into a co-extrusion extruder, melted, and extruded through the same die. At the same time, aluminum foil is drawn through the die so that the molten first transition layer is coated on one side of the aluminum foil, and the outer layer is simultaneously laminated on the outside of the first transition layer. After cooling, an intermediate is obtained. S4. Turn the intermediate over so that the uncomposite side of the aluminum foil faces upward; feed the inner surface layer masterbatch and the second transition layer masterbatch into a co-extrusion extruder, melt them, and extrude them through the same die; pull the intermediate through the die so that the molten second transition layer is coated on the other side of the aluminum foil, and the inner surface layer is simultaneously composited on the outside of the second transition layer. After cooling, a composite sheet is obtained. S5. Curing the composite sheet at 40-50℃ for 24-48 hours, then slitting and winding it up, yields the finished product.