Multilayer film for manufacturing containers and containers manufactured therefrom

Abstract

The present invention provides a multilayer film for manufacturing a container, the multilayer film comprising an outer layer, an inner layer and an intermediate layer between the inner layer and the outer layer, the inner layer facing a content to be filled in the container relative to the outer layer, wherein the outer layer is composed of an outer blend comprising 0-20 wt% of a hydrogenated ethylene aromatic block copolymer, 74-99 wt% of a polypropylene resin; and 1-6 wt% of polymethyl methacrylate; the intermediate layer is composed of an intermediate blend comprising 60-85 wt% of the hydrogenated ethylene aromatic block copolymer and 15-40 wt% of the polypropylene resin; and the inner layer is composed of an inner blend comprising 10-20 wt% of the hydrogenated ethylene aromatic block copolymer and 80-90 wt% of the polypropylene resin.

Description

Technical Field

[0001] This invention relates to the technical field of packaging films, specifically to a multilayer film for manufacturing containers, particularly a multilayer film made with hydrogenated ethylene aromatic block copolymer as an admixture. Background Technology

[0002] In the packaging film industry, it is well known to package medical and other products, such as medical devices; enteric, parenteral, and topical drugs and fluids, as well as food (such as meat, fish, cheese) and liquid foods (such as milk or juice), in packages made of polymer materials, often multilayer film materials.

[0003] Currently, medical packaging films are mainly made of PVC and non-PVC materials. PVC contains free monomers that pose health risks to humans. During PVC processing, plasticizers such as DOP and DEHP are added to weaken the aggregation between large molecular chains in the polymer, thereby improving processing fluidity and helping to reduce extrusion back pressure for smooth molding. However, when DOP and DEHP come into contact with solvents, small molecules may migrate and dissolve in the liquid, causing contamination. Furthermore, DOP and DEHP release estrogen, potentially affecting the human reproductive system and posing a significant health risk. Additionally, PVC has limited heat resistance; the sterilization temperature for general medical materials must be controlled below 110℃, otherwise high temperatures can easily cause cracking and deformation. Due to this limitation, PVC materials are difficult to meet the sterilization standards stipulated in the Chinese Pharmacopoeia (sterility assurance requirement F0 < 12), thus easily leading to drug contamination and pyrogenic reactions between patients. In medical applications, if PVC medical packaging film undergoes a migration reaction with the packaged liquid medicine, the medicine will deteriorate, affecting its efficacy and even rendering it unusable. From an environmental perspective, PVC materials, when not fully combusted, can easily produce substances such as dioxins, which have a detrimental effect on the human body and can cause genetic mutations and deformities in infants.

[0004] In the application of non-PVC materials for medical packaging films, thermoplastic elastomer styrene-ethylene-butene-styrene block copolymer has been recognized by the U.S. Food and Drug Administration (FDA) as a non-toxic material. In addition to not causing allergies, mutations or other rejection reactions in the human body, it also has excellent properties such as high temperature resistance and resistance to ultraviolet aging. It is suitable for necessary sterilization processes such as high-temperature cooking and ultraviolet irradiation of medical packaging materials, and meets the food and medical standards issued by the FDA.

[0005] However, thermoplastic elastomers are generally not easy to process directly due to their large molecular weight and low melt flowability. A small amount of processing oil needs to be added to expand their molecular chains and reduce the back pressure of the granulator. This makes it possible for processing oil to leach out and migrate during the high-temperature sterilization process of medical packaging films, which may affect or contaminate the medicine solution. Summary of the Invention

[0006] This invention has discovered that while existing technologies produce film packaging materials made from thermoplastic elastomers such as styrene-ethylene-butene-styrene block copolymers without added processing oils, they have various other drawbacks. For example, single-layer film packaging materials often add a large amount of polypropylene to achieve rigidity, resulting in poor puncture resistance and elongation. To address this problem, existing technologies have developed multilayer films; however, containers made from these multilayer films suffer from unwinding defects. Unwinding defects refer to the self-adhesion phenomenon between the inner and outer surfaces of the film during the fabrication of thin containers from multilayer films, causing process instability and affecting continuous production yield and stability.

[0007] In view of the above, the present invention provides a multilayer film that simultaneously possesses puncture resistance, low haze, and easy unwinding properties for manufacturing containers. According to a preferred embodiment, the present invention provides a three-layer co-extruded film, each of which individually contains the same type of hydrogenated ethylene aromatic block copolymer, but the content of each layer is different, wherein the inner and outer layers contain less hydrogenated ethylene aromatic block copolymer, while the middle layer contains more.

[0008] The present invention unexpectedly discovered that by adding polymethyl methacrylate to the outer layer and simultaneously controlling the hydrogenated ethylene aromatic block copolymer in the middle layer within a specific range, a multilayer film that simultaneously achieves puncture resistance, low haze, and easy unwinding properties can be produced. Details of various aspects of the present invention will be described in detail below. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of the three-layer thin film of the present invention.

[0010] Explanation of reference numerals in the attached figures:

[0011] 100+ layer thin film

[0012] 110 Outer layer

[0013] 120 Intermediate Layer

[0014] 130 Inner Layer Detailed Implementation

[0015] The following will illustrate the implementation of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. It should be understood that these different embodiments or examples are merely illustrative and not intended to limit the present invention. The present invention can be implemented or applied through other different embodiments. Those skilled in the art can modify and / or change the specific embodiments based on different implementation methods and applications to carry out the present invention without departing from its spirit and scope.

[0016] Methods for measuring physical properties

[0017] Weight-average molecular weight (Mw) of hydrogenated ethylene aromatic block copolymers: gel permeation chromatography is a method commonly used by those skilled in the art.

[0018] Vinyl aromatic bond content (wt%) of hydrogenated ethylene aromatic block copolymers: measured using a nuclear magnetic resonance analyzer, a measurement method well known to those skilled in the art.

[0019] Vinyl structure content (wt%) of hydrogenated ethylene aromatic block copolymer: measured using a nuclear magnetic resonance analyzer, a measurement method well known to those skilled in the art.

[0020] Melt flow index (MFI, g / 10 min, 2.16 kg at 190°C): Place particles in a melt flow indexing machine, test specification: ASTM D1238.

[0021] Melting point (°C): The peak temperature of the endothermic peak was measured using a differential scanning calorimeter (DSC) "TGA / DSC1 Star System" (manufactured by Mettler Toledo). The sample was heated from 30°C to 250°C at a heating rate of 10°C / min until it melted. Then, it was cooled from 250°C to 30°C at a cooling rate of 10°C / min. Finally, the sample was heated from 30°C to 250°C again at a heating rate of 10°C / min.

[0022] Puncture elongation (mm): The puncture elongation of the film was determined using the ASTM F1306 test method for low-velocity penetration resistance of flexible barrier films and laminates. This test method uses a hemispherical probe with a 3.2 mm diameter puncture probe and a 34.9 mm diameter test window. The film was cut into 76 mm x 76 mm specimens. After measuring the thickness of the film specimen, the specimen was clamped in a fixture, which was positioned below the puncture probe, aligning it with the center of the specimen and moving it as low as possible without contacting the specimen. This position is the starting position of the puncture probe. The testing machine was started, causing the puncture probe to descend at a speed of 25 mm / min until the specimen was punctured. The probe then returned to its starting position, and the distance (mm) traveled by the probe from the starting position was recorded as the puncture elongation data.

[0023] Peel strength (gf / inch): The test method for peel strength of adhesive tapes (GB / T 2792-2014) was used to simulate the self-adhesive unwinding force between the outer and inner layers of the wound film. First, the film was manually unwound, and six film samples (25mm wide x 350mm long) were prepared. One outer layer was overlapped on top of the area of ​​another inner layer, resulting in three sets of film samples. The overlapping film samples were then pressed against a steel cylindrical roller. The roller was covered with approximately 6mm thick rubber with a hardness of 80±5 Shore A and a mass of 2±0.1kg. The roller speed was fixed at 300mm / min. Each set of film samples underwent two back-and-forth roller presses. After 3 hours, a peel tester clamped both ends of the film sample, with a peel angle of 180° and a machine speed set to 300mm / min. The test was then started, and the peel strength data of the film sample was read by the instrument software. Haze (%): The transmittance and haze optical properties of the thin film were measured using a Hangzhou Yuanfang Optoelectronics HAM-200 luminance meter. The test light source type was D65. Five 80mm x 80mm samples were cut for each type of sample. Before the test, the light source of the HAM-200 luminance meter was turned on. The baseline zeroing test was performed first without any sample. After the sample was placed in the light source, the transmittance and haze tests were performed. The test results were read from the instrument display screen. The average value of the five sets of data was taken.

[0024] Hydrogenated ethylene aromatic block copolymer

[0025] Hydrogenated ethylene aromatic block copolymers refer to hydrogenated block copolymers containing ethylene aromatic monomers and conjugated diene monomers. Specific examples of ethylene aromatic monomers suitable for use in this invention include styrene, 4-tert-butylstyrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, vinylnaphthalene, N,N-dimethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene, and mixtures thereof. Styrene is a preferred choice.

[0026] The conjugated diene monomers suitable for use in this invention can be conjugated dienes containing 4 to 12 carbon atoms, and specific examples include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, and mixtures thereof, wherein 1,3-butadiene and isoprene are preferred choices.

[0027] Preferred examples of various hydrogenated ethylene aromatic block copolymers are hydrogenated styrene-butadiene-styrene triblock copolymers (styrene-ethylene-butene-styrene block copolymers, SEBS), hydrogenated styrene-isoprene-styrene triblock copolymers (styrene-ethylene-propylene-styrene block copolymers, SEPS), and hydrogenated styrene-isoprene / butadiene-styrene triblock copolymers (styrene-[ethylene-(ethylene-propylene)]-styrene block copolymers, SEEPS). A more preferred example is the styrene-ethylene-butene-styrene block copolymer (SEBS) obtained by hydrogenating the styrene-butadiene-styrene triblock copolymer. According to a preferred embodiment, the weight-average molecular weight of this hydrogenated ethylene aromatic block copolymer ranges from 180,000 to 210,000. According to a preferred embodiment, the vinyl aromatic bond content of this hydrogenated ethylene aromatic block copolymer is 10 wt% to 15 wt%. According to a preferred embodiment, the vinyl content in the conjugated diene monomer content of the hydrogenated ethylene aromatic block copolymer before hydrogenation is 75 wt% or more. According to a preferred embodiment, the melt flow index of the hydrogenated ethylene aromatic block copolymer is 2-5 g / 10 min (190°C, 2.16 kg).

[0028] Polypropylene resins refer to polypropylene resins with a propylene monomer content exceeding 50 wt%. The monomers in polypropylene resins, besides propylene, can be α-olefin structural units such as ethylene, 1-butene, 1-hexene, 1-heptene, and 1-octene. Specific examples of polypropylene resins include homopolymer polypropylene, propylene-ethylene random copolymers, propylene-ethylene block copolymers, propylene-butene random copolymers, propylene-ethylene-butene random copolymers, propylene-pentene random copolymers, propylene-hexene random copolymers, propylene-octene random copolymers, propylene-ethylene-pentene random copolymers, propylene-ethylene-hexene random copolymers, and at least one of the above groups. In a preferred embodiment, the polypropylene resin is a propylene-ethylene random copolymer, with a preferred melting point of [missing information]. Better The polypropylene resin used in the multilayer film of the present invention can be a single type, or two or more types can be used in combination. In a preferred embodiment, the polypropylene resin in the multilayer film of the present invention comprises a first polypropylene resin and a second polypropylene resin different from the first polypropylene resin, for example, the two may have different melting points. In a more preferred embodiment of the present invention, commercially available polypropylene resins, such as PPST612 or PP SFC750D, are used.

[0029] polymethyl methacrylate

[0030] Polymethyl methacrylate (PMMA) refers to a polymer whose monomer is primarily methyl methacrylate (MMA). A preferred embodiment of the present invention uses commercially available polymethyl methacrylate microspheres, such as PMMA-MB. The morphology of the polymethyl methacrylate microspheres is preferably spherical, semi-spherical, or similar. The average particle size of the polymethyl methacrylate was determined based on scanning electron microscopy (SEM) images. In one preferred embodiment, the polymethyl methacrylate microspheres have an average particle size of 0.5–20 μm. In another preferred embodiment, the polymethyl methacrylate microspheres have an average particle size of 0.5–10 μm.

[0031] Structure and composition of multilayer thin films

[0032] like Figure 1 As shown, the multilayer film 100 of the present invention includes an outer layer 110, an inner layer 130, and an intermediate layer 120 located between the inner layer 130 and the outer layer 110. The multilayer film 100 of the present invention is used to manufacture containers, such as liquid packaging containers. Relative to the outer layer 110, the inner layer 130 faces the contents to be filled into the container. Taking a medical container as an example, the inner layer 130 may come into contact with medical drugs; therefore, the composition of the inner layer must be relatively simple to avoid contaminating the medical drugs.

[0033] In one preferred embodiment, the outer layer 110 is composed of an external blend comprising 0-20 wt% of a hydrogenated ethylene aromatic block copolymer, 74-99 wt% of a polypropylene resin, and 1-6 wt% of polymethyl methacrylate. In another preferred embodiment, the external blend comprises 1-5 wt% of the polymethyl methacrylate. In yet another preferred embodiment, the external blend comprises 1-3 wt% of the polymethyl methacrylate. In still another preferred embodiment, the external blend comprises 10-20 wt% of the hydrogenated ethylene aromatic block copolymer, 77-89 wt% of the polypropylene resin, and 1-3 wt% of the polymethyl methacrylate.

[0034] The intermediate layer is composed of an intermediate blend comprising 60-85 wt% of the hydrogenated ethylene aromatic block copolymer and 15-40 wt% of the polypropylene resin. In another preferred embodiment, the intermediate blend comprises 60-80 wt% of the hydrogenated ethylene aromatic block copolymer and 20-40 wt% of the polypropylene resin.

[0035] The inner layer is composed of an inner blend comprising 10-20 wt% of the hydrogenated ethylene aromatic block copolymer and 80-90 wt% of the polypropylene resin.

[0036] In another preferred embodiment, the same polypropylene resin (referred to as the first polypropylene resin) is used for both the external blend and the intermediate blend, while a second polypropylene resin different from the first polypropylene resin is used for the internal blend. Preferably, the melting point of the second polypropylene resin is lower than that of the first polypropylene resin, with a difference not exceeding 20°C. More preferably, the melting point of the first polypropylene resin is higher than 145°C, while the melting point of the second polypropylene resin is lower than 135°C. In another even preferred embodiment, the weight content of the first polypropylene resin in the external blend is greater than the weight content of the second polypropylene resin in the internal blend. In yet another preferred embodiment, the difference between the weight content of the first polypropylene resin in the external blend and the weight content of the second polypropylene resin in the internal blend is less than 15 wt%.

[0037] In another preferred embodiment, the weight content of the hydrogenated ethylene aromatic block copolymer in the external blend is less than the weight content of the hydrogenated ethylene aromatic block copolymer in the internal blend. In yet another preferred embodiment, the difference between the weight content of the hydrogenated ethylene aromatic block copolymer in the external blend and the weight content of the hydrogenated ethylene aromatic block copolymer in the internal blend is less than 15 wt%.

[0038] In another preferred embodiment, the multilayer film of the present invention consists only of the outer layer, the inner layer, and the intermediate layer. More preferably, the inner layer does not contain polymethyl methacrylate. In a particularly preferred embodiment, the multilayer film of the present invention does not contain processing oil.

[0039] Applications of multilayer thin films

[0040] The multilayer film of this invention is preferably used as a liquid packaging container. Suitable for medical liquids such as blood, pharmaceutical solutions, and nutritional solutions; and for food liquids such as sterilized foods, mayonnaise, tomato sauce, soft drinks, and ice cream. Specific Implementation

[0042] The following specific embodiments demonstrate that the multilayer film has the following characteristics: puncture resistance elongation greater than 25 mm, peel strength less than 250 gf / inch, and haze less than 12%.

[0043] Examples of SEBS block copolymers

[0044] 48 kg of cyclohexane and 50 g of ethylene glycol diethyl ether were added to a 100 L reactor. 6 g of NBL (n-butyllithium) was added, followed by 425 g of styrene monomer to initiate the reaction. After the styrene monomer polymerization was complete, 5.7 kg of butadiene monomer was added. After the butadiene monomer polymerization was complete, another 425 g of styrene monomer was added. Once the styrene monomer polymerization was complete, an SBS triblock copolymer was formed. The polymerization of this polymer was terminated with methanol. 1000 g of the polymer solution of the SBS triblock copolymer prepared above was placed in a pressure-resistant hydrogenation reactor and maintained in a nitrogen atmosphere. At room temperature, 0.11 mmol of stabilizer was dissolved in 10 mL of cyclohexane; 0.055 mmol of bis(cyclopentadienyl)titanium dichloride was dispersed in 10 mL of cyclohexane; and 0.33 mmol of triisobutylaluminum was dissolved in 10 mL of cyclohexane. The above solutions were added to an SBS triblock copolymer, and hydrogen was injected at a pressure of 25 kg / cm², followed by hydrogenation at 80 °C until more than 95% of the butadiene double bonds were saturated. The resulting polymer was precipitated in water to form particles, which were then dried.

[0045] The proportions of the components in the above embodiments can be varied to formulate SEBS with various properties that meet the requirements.

[0046] Examples of fabricating multilayer thin films

[0047] Example A:

[0048] Weigh out the outer layer blend, which contains 10 wt% SEBS, 87 wt% PP ST612, and 3 wt% PMMA-MB. The SEBS has a weight-average molecular weight of 180,000, a styrene content of 13 wt%, and a vinyl content of 77 wt% in the unhydrogenated polybutadiene blocks, with a melt flow index of 3 g / 10 min (190°C, 2.16 kg). Weigh out the intermediate layer blend, which contains 60 wt% of the aforementioned SEBS and 40 wt% PP ST612. Weigh out the inner layer blend, which contains 20 wt% of the aforementioned SEBS and 80 wt% PP SFC750D. The weighed materials were poured into the loss-in-weight hopper of the LABTECH three-layer co-extrusion casting extruder. If the remaining material at the bottom was insufficient, the hopper would automatically discharge. The screw temperatures from the feed zone to the die section were set to 175℃ / 230℃ / 230℃ / 230℃ / 230℃ / 230℃, and the screw speeds were 8 RPM for the outer layer, 60 RPM for the middle layer, and 8 RPM for the inner layer. After the granules were heated into a melt in the feed cylinder, the die temperatures were set to 230℃ / 230℃ / 230℃ from left to right. The material was then cast and extruded through the die. The roller traction speed was set to 1.37-1.40 m / min to obtain a film with a thickness of 200±30 μm. The implementation methods of Examples B and C and Comparative Examples 1 to 6 can be referred to Example A, and the differences in component content are shown in Table 1.

[0049] Table 1

[0050]

[0051] Comparative Examples 1 to 3 show that the SEBS content in the intermediate layer is too low, resulting in insufficient puncture elongation. Comparative Examples 4 to 6 show that the SEBS content in the intermediate layer is as high as 100 wt%, and although the puncture elongation meets or exceeds the standard (above 25 mm), the peel strength is significantly too high, causing difficulty in unwinding. Higher peel strength means a higher unwinding force is required. Compared to Comparative Example 4 (without added PMMA-MB), the addition of PMMA-MB to the outer layer in Comparative Examples 5 to 6 reduces the peel strength, but the peel strength is still too high, and when the PMMA-MB addition reaches 9 wt%, excessive haze occurs. Examples A, B, and C have better puncture elongation than Comparative Examples 1 to 3. Examples A, B, and C have significantly lower peel strength (no difficulty in unwinding) than Comparative Examples 4 to 6. Examples A, B, and C also have better transparency (haze below 12%) than Comparative Example 6.

[0052] The above description of specific embodiments is merely illustrative, and various formulations can be modified according to specific needs without departing from the scope of the invention. These specific embodiments are intended to illustrate, and not to limit, the invention disclosed herein. Therefore, it will be apparent to those skilled in the art that certain modifications can be made to the described torso device without departing from the scope of the appended claims.

Claims

1. A multilayer film for manufacturing a container, the multilayer film comprising an outer layer, an inner layer, and an intermediate layer located between the inner layer and the outer layer, wherein the inner layer is positioned relative to the contents to be filled into the container, relative to the outer layer. The outer layer is composed of an external admixture comprising 0–20 wt% of hydrogenated ethylene aromatic block copolymer, 74–99 wt% of polypropylene resin, and 1–6 wt% of polymethyl methacrylate microspheres. The intermediate layer is composed of an intermediate blend comprising 60–85 wt% of the hydrogenated ethylene aromatic block copolymer and 15–40 wt% of the polypropylene resin; and The inner layer is composed of an internal blend comprising 10-20 wt% of the hydrogenated ethylene aromatic block copolymer and 80-90 wt% of the polypropylene resin, wherein... The hydrogenated ethylene aromatic block copolymer comprises ethylene aromatic blocks polymerized from ethylene aromatic monomers and conjugated diene blocks polymerized from conjugated diene monomers. The content of vinyl aromatic bonds in the hydrogenated ethylene aromatic block copolymer is 10wt% to 15wt%, and the vinyl structure content of the conjugated diene blocks before hydrogenation is more than 75wt%. The weight-average molecular weight of the hydrogenated ethylene aromatic block copolymer is 180,000 to 210,000, and the melt flow index of the hydrogenated ethylene aromatic block copolymer is 2 to 5 g / 10 minutes (190°C, 2.16 kg). The multilayer film has the following characteristics: puncture resistance elongation greater than 25 mm, peel strength less than 250 gf / inch, and haze less than 12%.

2. The multilayer thin film as described in claim 1, characterized in that, The polymethyl methacrylate microspheres have an average particle size of 0.5–20 μm.

3. The multilayer thin film as described in claim 1, characterized in that, The polymethyl methacrylate microspheres have an average particle size of 0.5–10 μm.

4. The multilayer thin film as described in claim 1, characterized in that, The admixture contains 1 to 5 wt% of the polymethyl methacrylate microspheres.

5. The multilayer thin film as described in claim 1, characterized in that, The external admixture comprises 10-20 wt% of the hydrogenated ethylene aromatic block copolymer, 77-89 wt% of the polypropylene resin, and 1-3 wt% of the polymethyl methacrylate microspheres.

6. The multilayer thin film as described in claim 1, characterized in that, This polypropylene resin is a random copolymer of propylene and ethylene.

7. The multilayer thin film as described in claim 1, characterized in that, The polypropylene resin comprises a first polypropylene resin and a second polypropylene resin different from the first polypropylene resin, wherein the first polypropylene resin is used in the external blend and the intermediate blend, and the second polypropylene resin is used in the internal blend.

8. The multilayer thin film as described in claim 7, characterized in that, The melting point of the second polypropylene resin is lower than that of the first polypropylene resin, and the difference is no more than 20°C.

9. The multilayer thin film as described in claim 7, characterized in that, The weight content of the first polypropylene resin in the external admixture is greater than the weight content of the second polypropylene resin in the internal admixture.

10. The multilayer thin film as described in claim 7, characterized in that, The difference between the weight content of the first polypropylene resin in the external admixture and the weight content of the second polypropylene resin in the internal admixture is less than 15 wt%.

11. The multilayer thin film as claimed in claim 1, characterized in that, The weight content of the hydrogenated ethylene aromatic block copolymer in the external admixture is less than the weight content of the hydrogenated ethylene aromatic block copolymer in the internal admixture.

12. The multilayer thin film as described in claim 1, characterized in that, The difference between the weight content of the hydrogenated ethylene aromatic block copolymer in the external blend and the weight content of the hydrogenated ethylene aromatic block copolymer in the internal blend is less than 15 wt%.

13. The multilayer thin film as described in claim 1, characterized in that, The multilayer film consists of only the outer layer, the inner layer, and the intermediate layer.

14. The multilayer thin film as claimed in claim 1, characterized in that, The inner layer does not contain the polymethyl methacrylate microbeads.

15. The multilayer thin film as claimed in claim 1, characterized in that, This multilayer film contains no processing oil.

16. A container made of any one of the multilayer films according to claims 1 to 15.

17. The container as claimed in claim 16, characterized in that, This container is used to package medical products or food.

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