A sealing strip with a bidirectional-stretching nylon-EVOH composite film as a base material and a preparation method thereof

Abstract

The application provides a sealing strip with a bidirectional stretching nylon-EVOH composite film as a base material and a preparation method, the sealing strip comprising a first nylon layer, a first composite layer, an EVOH barrier layer, a second composite layer and a second nylon layer; wherein the first composite layer and the second composite layer are EVOH and nylon 6 composite layers; and the first nylon layer and the second nylon layer are silica and long carbon chain nylon composite layers. The EVOH and the nylon 6 are melt blended first, then the obtained composite layer is subjected to multilayer co-extrusion with the EVOH barrier layer and the nylon layer to obtain the bidirectional stretching nylon-EVOH composite film, and the sealing strip is prepared with the bidirectional stretching nylon-EVOH composite film as the base material, so that the barrier property and the mechanical property of the sealing strip are improved.

Description

A sealing strip based on biaxially oriented nylon-EVOH composite film and its preparation method Technical Field

[0001] This application relates to the field of food packaging technology, and in particular to a sealing strip based on biaxially oriented nylon-EVOH composite film and its preparation method. Background Technology

[0002] With the continuous improvement of living standards, people have increasingly higher requirements for food packaging materials. Biaxially oriented nylon film has good barrier properties, excellent flexibility, high strength, impact resistance, and is non-toxic and harmless, and is widely used in daily necessities, electronic products, food, and pharmaceuticals. However, conventional nylon film still does not meet the barrier properties required for food packaging, which has extremely high requirements for freshness and sterility. Therefore, further improvements to the barrier properties of nylon film are needed.

[0003] Ethylene-vinyl alcohol copolymer (EVOH) is a crystalline polymer with a chain molecular structure. It possesses high tensile strength and mechanical strength, comparable to nylon films. Furthermore, EVOH films effectively prevent the permeation of oxygen, carbon dioxide, and other gases, exhibiting significantly higher barrier properties than other materials. Therefore, it is increasingly widely used in high-barrier-performance applications such as food packaging. However, EVOH is hygroscopic, and its barrier properties decrease in high-humidity environments. Additionally, at lower temperatures, the hardness of EVOH increases, leading to increased brittleness in the EVOH film.

[0004] Therefore, it is necessary to modify biaxially oriented nylon films and EVOH films to improve their barrier properties, antibacterial properties, and mechanical properties in order to overcome the problems in the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a sealing strip with biaxially oriented nylon-EVOH composite film as the substrate and a method for its preparation, so as to solve the above-mentioned technical problems.

[0006] To solve the above-mentioned technical problems, the present invention can be implemented using the following technical solutions:

[0007] In a first aspect, embodiments of the present invention provide a sealing strip with a biaxially oriented nylon-EVOH composite film as the substrate, comprising a first nylon layer, a first composite layer, an EVOH barrier layer, a second composite layer, and a second nylon layer;

[0008] Among them, the first composite layer and the second composite layer are composite layers of EVOH and nylon 6;

[0009] The first and second nylon layers are composite layers of silicon dioxide and long-chain carbon nylon.

[0010] In this invention, the biaxially oriented nylon-EVOH composite film used as the substrate has a five-layer composite structure, including a first nylon layer, a first composite layer, an EVOH barrier layer, a second composite layer, and a second nylon layer. The first and second composite layers are EVOH and nylon 6 composite layers. EVOH is often used in combination with nylon 6, and a common practice is to prepare multilayer films using a multilayer co-extrusion method, which can also improve the barrier properties of the film to a certain extent. In this invention, EVOH and nylon 6 are first melt-blended and then extruded to form an EVOH and nylon 6 composite film. The amide bonds in nylon 6 can combine with the hydroxyl groups in EVOH to form hydrogen bonds, thus tightly binding the two and effectively improving the barrier and mechanical properties of the film. Based on this, a multilayer co-extrusion method is used to stack multiple layers of EVOH and nylon 6 composite layers, as well as EVOH barrier layers and nylon layers, which can further improve the barrier and mechanical properties of the material. At the same time, the preparation method is simple and easy to implement, and can be well applied to actual production.

[0011] In some embodiments, the first composite layer and the second composite layer, by weight, comprise 10-25 parts of EVOH and 75-90 parts of nylon 6.

[0012] In some embodiments, the first nylon layer and the second nylon layer, by weight, comprise 2-5 parts of nano-sized silica, 0.5-1 parts of micron-sized silica, and 94-97.5 parts of long-chain nylon.

[0013] In some embodiments, the first composite layer and the second composite layer, by weight, comprise 15-18 parts of EVOH and 82-85 parts of nylon 6.

[0014] In some embodiments, the first composite layer and the second composite layer, by weight, comprise 16 parts EVOH and 84 parts nylon 6.

[0015] In some embodiments, the first nylon layer and the second nylon layer, by weight, comprise 4 parts of nanoscale silica, 0.6 parts of micrometer-scale silica, and 95.4 parts of long-chain nylon.

[0016] In some embodiments, the particle size of the above-mentioned nanoscale silica is 50-200 nm.

[0017] In some embodiments, the particle size of the micron-sized silica is 2-4 μm.

[0018] In some embodiments, the thickness of the EVOH barrier layer is 4-6 μm, and the total thickness is 15-30 μm.

[0019] In some embodiments, the long carbon chain nylon in the first nylon layer and the second nylon layer is one or a combination of several of nylon 11, nylon 12, nylon 510, nylon 512, nylon 610, nylon 612, nylon 1010, nylon 1012, and nylon 1212.

[0020] Secondly, embodiments of the present invention provide a method for preparing a sealing strip using a biaxially oriented nylon-EVOH composite film as a substrate, comprising the following steps:

[0021] S1. According to the formula, dry EVOH and nylon 6 are mixed evenly, melted, blended, extruded, granulated and dried by a twin-screw extruder, and the dried masterbatch is added to an extrusion casting machine to obtain the first composite layer and the second composite layer.

[0022] S2. According to the formula, dry nano-sized silica, micron-sized silica and long carbon chain nylon are mixed evenly, melted, blended, extruded, granulated and dried by a twin-screw extruder, and the dried masterbatch is added to an extrusion casting machine to obtain the first nylon layer and the second nylon layer.

[0023] S3. The first composite layer and the second composite layer obtained in step S1, the first nylon layer and the second nylon layer obtained in step S2, and the EVOH barrier layer are co-extruded using an extruder, then rapidly cooled and cast into sheets. After the cast sheets are conditioned and dried, they are stretched and shaped on both sides to obtain a biaxially oriented nylon-EVOH composite film.

[0024] S4. Cut the biaxially oriented nylon-EVOH composite film obtained in step S3 into strips of a specific width, and then wind them into disc-shaped film strips of a specific specification to make a sealing strip with the biaxially oriented nylon-EVOH composite film as the substrate.

[0025] In some embodiments, in the aforementioned method,

[0026] The extrusion casting temperature in step S1 is 250-270℃;

[0027] The extrusion casting temperature in step S2 is 230-250℃;

[0028] The stretching ratio in step S3 is 3×3.

[0029] Beneficial effects

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1. EVOH was composited with nylon 6 by melt blending to obtain a composite film of EVOH and nylon 6, which improved the barrier properties and mechanical properties of the single nylon layer and improved the sealing performance of the sealing strip.

[0032] 2. The long carbon chain nylon layer incorporates nano-sized and micron-sized silica, which further reduces the moisture absorption rate of the outermost long carbon chain nylon layer and improves the water-blocking performance of the sealing strip.

[0033] 3. The preparation process is simple, easy to operate, and easy to industrialize. Detailed Implementation

[0034] The embodiments of this disclosure will be described in further detail below with reference to examples. The detailed description of the following embodiments is used to illustrate the principles of this disclosure, but should not be used to limit the scope of this disclosure. This disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0035] These embodiments are provided to make the disclosure thorough and complete, and to fully express the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as exemplary only and not as limiting.

[0036] It should be noted that, in the description of this disclosure, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationship, are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0037] All terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0038] Example 1

[0039] S1. Mix 16 parts of dried EVOH and 84 parts of nylon 6 evenly, melt, blend, extrude, granulate and dry them through a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 260℃ to obtain the first composite layer and the second composite layer.

[0040] S2. Mix 4 parts of dried nano-sized silica, 0.6 parts of micron-sized silica and 95.4 parts of nylon 11 evenly, melt, blend, extrude, granulate and dry them through a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 240℃ to obtain the first nylon layer and the second nylon layer.

[0041] S3. The first composite layer and the second composite layer obtained in step S1, the first nylon layer and the second nylon layer obtained in step S2, and the EVOH barrier layer are co-extruded using an extruder, then rapidly cooled and cast into sheets. After the cast sheets are conditioned and dried, they are stretched and shaped on both sides with a stretching ratio of 3×3 to obtain a biaxially stretched nylon-EVOH composite film.

[0042] S4. Cut the biaxially oriented nylon-EVOH composite film obtained in step S3 into strips of a specific width, and then wind them into disc-shaped film strips of a specific specification to make a sealing strip with the biaxially oriented nylon-EVOH composite film as the substrate.

[0043] Example 2

[0044] S1. Mix 10 parts of dried EVOH and 90 parts of nylon 6 evenly, melt, blend, extrude, granulate and dry them through a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 260℃ to obtain the first composite layer and the second composite layer.

[0045] S2. Mix 3 parts of dried nano-sized silica, 0.8 parts of micron-sized silica and 96.2 parts of nylon 1012 evenly, melt, blend, extrude, granulate and dry them through a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 240℃ to obtain the first nylon layer and the second nylon layer.

[0046] S3. The first composite layer and the second composite layer obtained in step S1, the first nylon layer and the second nylon layer obtained in step S2, and the EVOH barrier layer are co-extruded using an extruder, then rapidly cooled and cast into sheets. After the cast sheets are conditioned and dried, they are stretched and shaped on both sides with a stretching ratio of 3×3 to obtain a biaxially stretched nylon-EVOH composite film.

[0047] S4. Cut the biaxially oriented nylon-EVOH composite film obtained in step S3 into strips of a specific width, and then wind them into disc-shaped film strips of a specific specification to make a sealing strip with the biaxially oriented nylon-EVOH composite film as the substrate.

[0048] Example 3

[0049] S1. Mix 25 parts of dried EVOH and 75 parts of nylon 6 evenly, melt, blend, extrude, granulate and dry them through a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 270℃ to obtain the first composite layer and the second composite layer.

[0050] S2. Mix 2 parts of dried nano-sized silica, 0.5 parts of micron-sized silica and 97.5 parts of nylon 612 evenly, melt, blend, extrude, granulate and dry them in a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 245℃ to obtain the first nylon layer and the second nylon layer.

[0051] S3. The first composite layer and the second composite layer obtained in step S1, the first nylon layer and the second nylon layer obtained in step S2, and the EVOH barrier layer are co-extruded using an extruder, then rapidly cooled and cast into sheets. After the cast sheets are conditioned and dried, they are stretched and shaped on both sides with a stretching ratio of 3×3 to obtain a biaxially stretched nylon-EVOH composite film.

[0052] S4. Cut the biaxially oriented nylon-EVOH composite film obtained in step S3 into strips of a specific width, and then wind them into disc-shaped film strips of a specific specification to make a sealing strip with the biaxially oriented nylon-EVOH composite film as the substrate.

[0053] Example 4

[0054] S1. Mix 23 parts of dried EVOH and 77 parts of nylon 6 evenly, melt, blend, extrude, granulate and dry them through a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 260℃ to obtain the first composite layer and the second composite layer.

[0055] S2. Mix 3 parts of dried nano-sized silica, 0.5 parts of micron-sized silica and 96.5 parts of nylon 12 evenly, melt, blend, extrude, granulate and dry them through a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 230℃ to obtain the first nylon layer and the second nylon layer.

[0056] S3. The first composite layer and the second composite layer obtained in step S1, the first nylon layer and the second nylon layer obtained in step S2, and the EVOH barrier layer are co-extruded using an extruder, then rapidly cooled and cast into sheets. After the cast sheets are conditioned and dried, they are stretched and shaped on both sides with a stretching ratio of 3×3 to obtain a biaxially stretched nylon-EVOH composite film.

[0057] S4. Cut the biaxially oriented nylon-EVOH composite film obtained in step S3 into strips of a specific width, and then wind them into disc-shaped film strips of a specific specification to make a sealing strip with the biaxially oriented nylon-EVOH composite film as the substrate.

[0058] Example 5

[0059] S1. Mix 12 parts of dried EVOH and 88 parts of nylon 6 evenly, melt, blend, extrude, granulate and dry them through a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 270℃ to obtain the first composite layer and the second composite layer.

[0060] S2. Mix 4 parts of dried nano-sized silica, 0.5 parts of micron-sized silica and 95.5 parts of nylon 610 evenly, melt, blend, extrude, granulate and dry them through a twin-screw extruder, add the dried masterbatch to an extrusion casting machine, and control the extrusion casting temperature at 245℃ to obtain the first nylon layer and the second nylon layer.

[0061] S3. The first composite layer and the second composite layer obtained in step S1, the first nylon layer and the second nylon layer obtained in step S2, and the EVOH barrier layer are co-extruded using an extruder, then rapidly cooled and cast into sheets. After the cast sheets are conditioned and dried, they are stretched and shaped on both sides with a stretching ratio of 3×3 to obtain a biaxially stretched nylon-EVOH composite film.

[0062] S4. Cut the biaxially oriented nylon-EVOH composite film obtained in step S3 into strips of a specific width, and then wind them into disc-shaped film strips of a specific specification to make a sealing strip with the biaxially oriented nylon-EVOH composite film as the substrate.

[0063] Comparative Example 1

[0064] The difference between Comparative Example 1 and Example 1 is that step S1 is omitted, and the first composite layer and the second composite layer are replaced with a single nylon layer. The remaining steps are the same as in Example 1. The resulting sealing strip consists of a first nylon layer, a single nylon 6 layer, an EVOH barrier layer, a single nylon 6 layer, and a second nylon layer from top to bottom.

[0065] Comparative Example 2

[0066] The difference between Comparative Example 1 and Example 1 is that the micron-sized silica in step S2 is omitted, while the remaining steps are the same as in Example 1, and a sealing strip is obtained.

[0067] Comparative Example 3

[0068] The difference between Comparative Example 1 and Example 1 is that the stretching ratio in step S3 is 3.2 × 3.2, while the rest of the steps are the same as in Example 1, and a sealing strip is obtained.

[0069] The sealing strips prepared in the examples and comparative examples were subjected to performance tests, and the test results are shown in Table 1 below:

[0070] Table 1 Performance Test Results

[0071]

[0072] According to the performance test results of Examples 1-5 and Comparative Examples 1-3 in Table 1, the sealing strip with biaxially oriented nylon-EVOH composite film as the substrate has low oxygen permeability and better oxygen barrier effect; it also has low moisture absorption and can achieve good barrier effect against moisture; it has high tensile strength and good mechanical properties, making it suitable for use as a barrier sealing material in food packaging.

[0073] While specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this disclosure. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any manner.

Claims

1. A sealing strip using a biaxially oriented nylon-EVOH composite film as the substrate, characterized in that, The sealing strip comprises a first nylon layer, a first composite layer, an EVOH barrier layer, a second composite layer, and a second nylon layer; by weight, the first composite layer and the second composite layer each independently comprise 10-25 parts EVOH and 75-90 parts nylon 6; by weight, the first nylon layer and the second nylon layer each independently comprise 2-5 parts nano-sized silica, 0.5-1 part micron-sized silica, and 94-97.5 parts long-chain nylon; wherein the long-chain nylon is one or more of nylon 11, nylon 12, nylon 510, nylon 512, nylon 610, nylon 612, nylon 1010, nylon 1012, and nylon 1212; the preparation method of the sealing strip includes the following steps: S1. According to the formula, dry EVOH and nylon 6 are mixed evenly, melted, blended, extruded, granulated and dried by a twin-screw extruder. The dried masterbatch is added to an extrusion casting machine to obtain the blanks of the first and second composite layers. S2. According to the formula, dry nano-sized silica, micron-sized silica and long carbon chain nylon are mixed evenly, melted, blended, extruded, granulated and dried by a twin-screw extruder. The dried masterbatch is added to an extrusion casting machine to obtain the blanks of the first and second nylon layers. S3. Each layer is co-extruded by an extruder, then rapidly cooled and cast into sheets. After the sheets are conditioned and dried, they are biaxially stretched and shaped with a stretch ratio of 3×3 to obtain a biaxially stretched nylon-EVOH composite film. S4. The biaxially stretched nylon-EVOH composite film obtained in step S3 is cut into strip films and then wound into disc-shaped film strips to make a sealing strip with the biaxially stretched nylon-EVOH composite film as the substrate.

2. The sealing strip according to claim 1, characterized in that, The first composite layer and the second composite layer, by mass, comprise 15-18 parts of EVOH and 82-85 parts of nylon 6.

3. The sealing strip according to claim 1, characterized in that, The nanoscale silica particles have a diameter of 50-200 nm.

4. The sealing strip according to claim 1, characterized in that, The micron-sized silica particles have a diameter of 2-4 μm.

5. The sealing strip according to any one of claims 1-3, characterized in that, The thickness of the EVOH barrier layer is 4-6 μm, and the total thickness of the sealing strip is 15-30 μm.

6. The sealing strip according to claim 1, characterized in that, In the preparation method, the extrusion casting temperature in step S1 is 250-270℃; the extrusion casting temperature in step S2 is 230-250℃.

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