EVOH / polyamide regenerated composite film containing regenerated material and preparation method of EVOH / polyamide regenerated composite film

Abstract

The invention belongs to the technical field of film packaging, and particularly discloses an EVOH / polyamide regenerated composite film containing a regenerated material and a preparation method thereof.The EVOH / polyamide regenerated composite film comprises a five-layer structure which sequentially comprises a first polyamide surface layer, a first polyamide regenerated layer, an EVOH barrier layer, a second polyamide regenerated layer and a second polyamide surface layer from top to bottom; wherein the components of the first polyamide surface layer and the second polyamide surface layer comprise 95-97 wt% of polyamide and 3-5 wt% of polyamide anti-sticking master batch; the components of the first polyamide regeneration layer and the second polyamide regeneration layer comprise 60-90 wt% of polyamide and 10-40 wt% of an EVOH / polyamide regeneration material; and the EVOH barrier layer comprises the following components in percentage by weight: 100% of EVOH resin. According to the invention, the polyamide / EVOH regenerated material generated in the production process of the film can be received under the condition that the barrier, surface printing and compounding of the film are not influenced.

Description

Technical Field

[0001] The invention belongs to the technical field of film packaging, and in particular relates to an EVOH / polyamide recycled composite film containing recycled materials and a preparation method thereof. Background Art

[0002] Ethylene-vinyl alcohol copolymer (EVOH) is a new type of polymer synthetic material that combines the processability of ethylene polymers with the gas barrier properties of vinyl alcohol polymers. It has excellent gas barrier, water resistance, oil resistance and other properties. In the 1950s, DuPont of the United States first produced EVOH resin by copolymerization and alcoholysis of ethylene and vinyl acetate (VAc). The oxygen permeability of polyvinyl alcohol in dry state is less than 10cc / m -2 ﹒ d﹒ 0.1Mpa, which is a typical high barrier material. However, EVOH is a material that is difficult to process by thermoplastics, because its decomposition point and melting point are very close, its melting point is 220-240℃, and its decomposition temperature is about 200℃, that is, it is decomposed and carbonized and turns yellow before it is melted. A certain amount of lubricant is added to commercial EVOH during the polymerization process to make its melting point around 160-180℃, so that it can meet the requirements of thermoplastic processing, but the mechanical properties of single-layer EVOH film are poor, which is difficult to meet the application requirements of packaging film.

[0003] BOPA film is made of polyamide 6 (nylon 6) as raw material. Compared with other films, BOPA film has higher strength than PE and BOPP films. At the same time, polyamide has good compatibility with ethylene-vinyl alcohol copolymer, so PA / EVOH / PA biaxially oriented co-extruded film came into being on the market. PA / EVOH / PA biaxially oriented co-extruded film is melted by different extruders at their respective processing temperatures, briefly converged at the T-type die, melt-bonded, rapidly cooled, and then biaxially stretched. In this production process, it is inevitable to produce edge materials and waste films, and the melting point of polyamide 6 is about 220°C, and the processing temperature is usually as high as 250°C. EVOH is very easy to decompose and carbonize at this processing temperature, which makes it difficult to regenerate edge materials and waste films into PA / EVOH / PA biaxially oriented co-extruded films, and the cost is greatly increased. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide an EVOH / polyamide recycled composite film containing recycled materials and a preparation method thereof.

[0005] In order to achieve the above objectives, the technical solution of the present invention is: an EVOH / polyamide recycled composite film containing recycled materials, including a five-layer structure, from top to bottom, a first polyamide surface layer, a first polyamide recycled layer, an EVOH barrier layer, a second polyamide recycled layer, and a second polyamide surface layer; wherein the components of the first polyamide surface layer and the second polyamide surface layer include 95-97wt% of polyamide and 3-5wt% of polyamide anti-sticking masterbatch; the components of the first polyamide recycled layer and the second polyamide recycled layer include 60-90wt% of polyamide and 10-40wt% of EVOH / polyamide recycled materials; the components of the EVOH barrier layer include 100wt% EVOH resin.

[0006] In a preferred embodiment of the present invention, the polyamide is polyamide 6.

[0007] In a preferred embodiment of the present invention, the components of the EVOH / polyamide recycled material include 97-98.8wt% of EVOH / polyamide recycled composite film crushed material, 1-2wt% of lubricant, 0.1-0.5wt% of hydroxyl end-capping agent and 0.1-0.5wt% of antioxidant.

[0008] Further preferably, the EVOH content in the EVOH / polyamide recycled composite film crushed material is ≤30wt%.

[0009] Further preferably, the lubricant is one or a combination of dicarboxylic acid esters, fatty acid esters of glycerol and other short-chain alcohols, oligomeric fatty acid esters, polar polyolefin waxes and their derivatives, non-polar polyolefin waxes, and natural and synthetic paraffin waxes.

[0010] Further preferably, the hydroxyl end-capping agent is one or a combination of fatty acids, fatty acid amides, montanic acid and metal salts thereof.

[0011] More preferably, the antioxidant is one or a combination of phenolic antioxidants, organophosphorus antioxidants and sulfate antioxidants.

[0012] In a preferred embodiment of the present invention, the total thickness of the EVOH / polyamide recycled composite film layer is 15-35 μm, the thickness of the EVOH barrier layer is 3-6 μm, the thickness of the first polyamide surface layer and the second polyamide surface layer is 1-2 μm, and the thickness of the first polyamide recycled layer and the second polyamide recycled layer is 2.5-15 μm.

[0013] A method for preparing an EVOH / polyamide recycled composite film containing recycled materials comprises the following steps:

[0014] (1) Preparation of EVOH / polyamide recycled material: The scraps and waste films generated in the production process of EVOH / polyamide recycled composite film are crushed to obtain the crushed material of EVOH / polyamide recycled composite film, and then the crushed material is evenly mixed with lubricant, hydroxyl end-capping agent and antioxidant according to the component ratio, and granulated by a twin-screw extruder to obtain EVOH / polyamide recycled material;

[0015] (2) Preparation of each film layer of the EVOH / polyamide recycled composite film: polyamide and polyamide anti-sticking masterbatch are put into an extruder according to a component ratio to prepare a first amide surface layer and a second polyamide surface layer respectively; the EVOH / polyamide recycled material and polyamide obtained in step (1) are put into an extruder according to a component ratio to prepare a first polyamide recycled layer and a second polyamide recycled layer respectively; EVOH resin is put into an extruder to prepare an EVOH barrier layer;

[0016] (3) Preparation of EVOH / polyamide recycled composite film: The film layers prepared in step (2) are rapidly cooled, and then humidified, cleaned, and surface evaporated, and then biaxially stretched using the LISIM synchronous stretching method to obtain an EVOH / polyamide recycled composite film.

[0017] In a preferred embodiment of the present invention, the temperature of the twin-screw extruder in step (1) is controlled between 165-185° C., and the rotation speed is controlled between 150-300 r / min.

[0018] In a preferred embodiment of the present invention, in step (2), the extruder temperature of the first polyamide surface layer and the second polyamide surface layer and the temperature of the T-die thereof are controlled between 210-250°C, the extruder temperature of the first polyamide regenerated layer and the second polyamide regenerated layer and the temperature of the T-die thereof are controlled between 180-220°C, and the extruder temperature of the EVOH barrier layer and the temperature of the T-die thereof are controlled between 160-190°C.

[0019] In a preferred embodiment of the present invention, in step (3), the humidity adjustment temperature is 60-80°C, the stretching temperature is 160-190°C, the shaping temperature is 180-210°C, and the stretching ratio is 3.0*3.0-3.8*3.8.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. A relatively high content of lubricant is added to the EVOH / polyamide recycled material of the present invention to prevent the EVOH from being melted and decomposed and carbonized and yellowed due to the high processing temperature during the regeneration and backfilling process; a hydroxyl end-capping agent is added to end-cap the hydroxyl groups of EVOH and the terminal amino groups and terminal carboxyl groups of polyamide in a molten state to avoid the cross-linking of the hydroxyl groups with the terminal amino groups and carboxyl groups by hot melt reaction; an antioxidant is added to prevent the EVOH and polyamide from being thermally degraded during multiple processing processes, thereby affecting the processing and later application of the film;

[0022] 2. The present invention can receive polyamide / EVOH recycled materials generated in the film production process without affecting the barrier, surface printing and lamination of the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the layer structure of the EVOH / polyamide recycled composite film of Example 1-4;

[0024] Among them, 10 is the first polyamide surface layer, 20 is the first polyamide recycled layer, 30 is the EVOH barrier layer, 40 is the second polyamide recycled layer, and 50 is the second polyamide surface layer. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is described in more detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0026] The terms "upper" and "lower" are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0027] It should be noted that, if no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used, and the reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained commercially.

[0028] Example 1

[0029] A recycled EVOH / polyamide composite film containing recycled materials, comprising a five-layer structure, which comprises, from top to bottom, a first polyamide surface layer 10, a first polyamide recycled layer 20, an EVOH barrier layer 30, a second polyamide recycled layer 40, and a second polyamide surface layer 50; wherein the components of the first polyamide surface layer 10 and the second polyamide surface layer 50 include 696wt% polyamide and 4wt% polyamide anti-sticking masterbatch; the components of the first polyamide recycled layer 20 and the second polyamide recycled layer 40 include 670wt% polyamide and EVOH / polyamide recycled material 30wt%; the components of the EVOH barrier layer 30 include 100wt% EVOH resin; the components of the EVOH / polyamide recycled material include 98wt% EVOH / polyamide recycled composite film crushed material (wherein the EVOH content is 26.67wt%), 1.5wt% polyethylene wax, 0.3wt% stearic acid and 1680.2wt% antioxidant, including EVOH content in the EVOH / polyamide recycled composite film crushed material is 26.67wt%.

[0030] The method comprises the following steps:

[0031] (1) Preparation of EVOH / polyamide recycled material: The scraps and waste films generated in the production process of EVOH / polyamide recycled composite film are crushed to obtain the crushed material of EVOH / polyamide recycled composite film, and then the crushed material is evenly mixed with lubricant, hydroxyl end-capping agent and antioxidant according to the component ratio, and granulated by a twin-screw extruder to obtain EVOH / polyamide recycled material;

[0032] (2) Preparation of each film layer of EVOH / polyamide recycled composite film: polyamide and polyamide anti-sticking masterbatch are put into an extruder according to a component ratio to prepare a first amide surface layer and a second polyamide surface layer respectively; the EVOH / polyamide recycled material and polyamide obtained in step (1) are put into an extruder according to a component ratio to prepare a first polyamide recycled layer and a second polyamide recycled layer respectively; EVOH resin is put into an extruder to prepare an EVOH barrier layer; wherein the extruder temperature of the first polyamide surface layer and the second polyamide surface layer and the temperature of the T-die thereof are controlled between 210-250°C, the extruder temperature of the first polyamide recycled layer and the second polyamide recycled layer and the temperature of the T-die thereof are controlled between 180-220°C, and the extruder temperature of the EVOH barrier layer and the temperature of the T-die thereof are controlled between 160-190°C;

[0033] (3) Preparation of EVOH / polyamide recycled composite film: The film layers prepared in step (2) are rapidly cooled, and then humidified and cleaned in a 60°C hot steamer. After removing the surface evaporation with hot air, the film is biaxially stretched by the LISIM synchronous stretching method at a stretching temperature of 185°C, a setting temperature of 205°C, and a stretching ratio of 3.0*3.1 to obtain an EVOH / polyamide recycled composite film.

[0034] Example 2

[0035] A recycled EVOH / polyamide composite film containing recycled materials, comprising a five-layer structure, which is sequentially a first polyamide surface layer 10, a first polyamide recycled layer 20, an EVOH barrier layer 30, a second polyamide recycled layer 40, and a second polyamide surface layer 50 from top to bottom; wherein the components of the first polyamide surface layer 10 and the second polyamide surface layer 50 include 95wt% polyamide 6 and 5wt% polyamide anti-sticking masterbatch; the components of the first polyamide recycled layer 20 and the second polyamide recycled layer 40 include 60wt% polyamide and 40wt% EVOH / polyamide recycled materials; the components of the EVOH barrier layer 30 include 100wt% EVOH resin; the components of the recycled materials of the EVOH / polyamide composite film include 97wt% EVOH / polyamide composite film crushed materials (wherein the EVOH content is 26.67wt%), 2wt% polypropylene wax, 0.5wt% erucic acid amide, and 0.5wt% antioxidant 10. The preparation method is the same as that of Example 1.

[0036] Example 3

[0037] A recycled EVOH / polyamide composite film containing recycled materials, comprising a five-layer structure, which is sequentially composed of a first polyamide surface layer 10, a first polyamide recycled layer 20, an EVOH barrier layer 30, a second polyamide recycled layer 40, and a second polyamide surface layer 50 from top to bottom; wherein the components of the first polyamide surface layer 10 and the second polyamide surface layer 50 include 697wt% polyamide and 3wt% polyamide anti-sticking masterbatch; the components of the first polyamide recycled layer 20 and the second polyamide recycled layer 40 include 690wt% polyamide and 10wt% EVOH / polyamide recycled materials; the components of the EVOH barrier layer 30 include 100wt% EVOH resin; the components of the recycled materials of the EVOH / polyamide composite film include 97-98.8wt% EVOH / polyamide composite film crushed materials (wherein the EVOH content is 26.67wt%), 1wt% paraffin, 0.1wt% montanic acid, and 2640.1wt% antioxidant. The preparation method is the same as that of Example 1.

[0038] Comparative Example 1

[0039] Commercially available 15μm biaxially oriented EVOH / nylon co-extruded film.

[0040] Comparative Example 2

[0041] An EVOH / polyamide recycled composite film containing recycled materials includes a five-layer structure, which is sequentially composed of a first polyamide surface layer 10, a first polyamide recycled layer 20, an EVOH barrier layer 30, a second polyamide recycled layer 40, and a second polyamide surface layer 50 from top to bottom; wherein the components of the first polyamide surface layer 10 and the second polyamide surface layer 50 include 96% polyamide and 4wt% polyamide anti-sticking masterbatch; the components of the first polyamide recycled layer and the second polyamide recycled layer include 670wt% polyamide and 30wt% EVOH / polyamide recycled materials; the components of the EVOH barrier layer 30 include 100wt% EVOH resin; the components of the EVOH / polyamide composite film recycled materials include 100wt% EVOH / polyamide composite film crushed materials (wherein the EVOH content is 26.67wt%). The preparation method is the same as that of Example 1.

[0042] The films of Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the test standards were as follows:

[0043] (1) Thickness: GB / T20220-2006 Average thickness of plastic film and sheet samples, average thickness of rolls and unit mass area;

[0044] (2) Surface tension: Test the film surface tension according to GB / T 14216-2008;

[0045] (3) Hygroscopic elongation: The initial size of the film is L0. After being placed in a 23°C / 50% humidity environment for 48 hours, the size becomes L1. The film size unchanged rate is measured as [(L1-L0) / L0]*100%;

[0046] (4) Thermal shrinkage: GB / T12027-2004 Test method for dimensional change rate of plastic film and sheet under heating;

[0047] (5) Oxygen barrier: Test with reference to GB / T19789-2005 “Oxygen permeability test for plastic films and sheets for packaging materials - Coulometric test method”.

[0048] (6) Nucleated crystal points: Use a 10cm*10cm thick slice and count the number of points with an outer diameter greater than 1mm under the oblique illumination of a flashlight.

[0049] The film performance test evaluation results are shown in Table 1:

[0050] Table 1 Test results of film properties of Examples 1-3 and Comparative Examples 1-2

[0051]

[0052] It can be seen from Table 1 that the EVOH / polyamide recycled composite films prepared in Examples 1-3 have good oxygen barrier properties, and their dimensional stability and apparent quality are comparable to those of the film in Comparative Example 1 without adding recycled materials.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An EVOH / polyamide recycled composite film containing recycled materials, characterized in that: The invention comprises a five-layer structure, which comprises, from top to bottom, a first polyamide surface layer, a first polyamide recycled layer, an EVOH barrier layer, a second polyamide recycled layer and a second polyamide surface layer; wherein, components of the first polyamide surface layer and the second polyamide surface layer comprise 95-97wt% of polyamide and 3-5wt% of polyamide anti-sticking masterbatch; components of the first polyamide recycled layer and the second polyamide recycled layer comprise 60-90wt% of polyamide and 10-40wt% of EVOH / polyamide recycled material; components of the EVOH barrier layer comprise 100wt% of EVOH resin.

2. The EVOH / polyamide recycled composite film containing recycled materials according to claim 1, characterized in that: The polyamide is polyamide 6.

3. The EVOH / polyamide recycled composite film containing recycled materials according to claim 1, characterized in that: The components of the EVOH / polyamide recycled material include 97-98.8wt% of EVOH / polyamide recycled composite film crushed material, 1-2wt% of lubricant, 0.1-0.5wt% of hydroxyl end-capping agent and 0.1-0.5wt% of antioxidant.

4. The EVOH / polyamide recycled composite film containing recycled materials according to claim 3, characterized in that: The EVOH content in the EVOH / polyamide recycled composite film crushed material is ≤30wt%.

5. The EVOH / polyamide recycled composite film containing recycled materials according to claim 3, characterized in that: The lubricant is one or a combination of dicarboxylic acid esters, fatty acid esters of glycerol and other short-chain alcohols, oligomeric fatty acid esters, polar polyolefin waxes and their derivatives, non-polar polyolefin waxes, natural and synthetic paraffins; the hydroxyl end-capping agent is one or a combination of fatty acids, fatty acid amides, montanic acid and their metal salts; and the antioxidant is one or a combination of phenolic antioxidants, organophosphorus antioxidants and sulfate antioxidants.

6. The EVOH / polyamide recycled composite film containing recycled materials according to claim 1, characterized in that: The total thickness of the EVOH / polyamide recycled composite film layer is 15-35 μm, the thickness of the EVOH barrier layer is 3-6 μm, the thickness of the first polyamide surface layer and the second polyamide surface layer is 1-2 μm, and the thickness of the first polyamide recycled layer and the second polyamide recycled layer is 2.5-15 μm.

7. A method for preparing the EVOH / polyamide recycled composite film containing recycled materials as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Preparation of EVOH / polyamide recycled material: The scraps and waste films generated in the production process of EVOH / polyamide recycled composite film are crushed to obtain EVOH / polyamide recycled composite film crushed material, which is then mixed evenly with lubricant, hydroxyl end-capping agent and antioxidant according to the component ratio, and granulated by a twin-screw extruder to obtain EVOH / polyamide recycled material; (2) Preparation of each film layer of the EVOH / polyamide recycled composite film: polyamide and polyamide anti-sticking masterbatch are put into an extruder according to a component ratio to prepare a first amide surface layer and a second polyamide surface layer respectively; the EVOH / polyamide recycled material and polyamide obtained in step (1) are put into an extruder according to a component ratio to prepare a first polyamide recycled layer and a second polyamide recycled layer respectively; EVOH resin is put into an extruder to prepare an EVOH barrier layer; (3) Preparation of EVOH / polyamide recycled composite film: The film layers prepared in step (2) are rapidly cooled, and then humidified, cleaned, and surface evaporated, and then biaxially stretched using the LISIM synchronous stretching method to obtain an EVOH / polyamide recycled composite film.

8. The method for preparing the EVOH / polyamide recycled composite film containing recycled materials according to claim 7, characterized in that: In the step (1), the temperature of the twin-screw extruder is controlled between 165-185° C., and the rotation speed is controlled between 150-300 r / min.

9. The method for preparing the EVOH / polyamide recycled composite film containing recycled materials according to claim 7, characterized in that: In the step (2), the extruder temperature of the first polyamide surface layer and the second polyamide surface layer and the temperature of the T-die thereof are controlled between 210-250°C, the extruder temperature of the first polyamide regenerated layer and the second polyamide regenerated layer and the temperature of the T-die thereof are controlled between 180-220°C, and the extruder temperature of the EVOH barrier layer and the temperature of the T-die thereof are controlled between 160-190°C.

10. The method for preparing the EVOH / polyamide recycled composite film containing recycled materials according to claim 7, characterized in that: In the step (3), the humidity adjustment temperature is 60-80°C, the stretching temperature is 160-190°C, the shaping temperature is 180-210°C, and the stretching ratio is 3.0*3.0-3.8*3.8.

Images