A high-transparency, high-barrier, anti-condensation easy-to-remove cover film and preparation method thereof

Abstract

The present invention belongs to the technical field of packaging materials, in particular to a highly transparent, high barrier, anti-condensation easy-to-remove cover film and a preparation method thereof. The easy-to-remove cover film of the present invention comprises a CPE-EVA-POE co-extruded film, a glue layer and a PET-ALOx layer connected in sequence, and the CPE-EVA-POE co-extruded film is made by a three-layer co-extrusion process of a corona layer, an intermediate layer and a heat-sealing layer, the corona layer is composed of a linear polyethylene and a low-density polyethylene with a mass ratio of 3:1, the intermediate layer is composed of a linear polyethylene, a low-density polyethylene and an anti-fog masterbatch with a mass ratio of 63:25:12, and the heat-sealing layer is composed of an EVA resin, an anti-fog masterbatch, a vinyl POE and an opening agent with a mass ratio of 77:10:10:3. The easy-to-remove cover film prepared by the present invention can continuously prevent condensation, and anti-fog can be achieved whether it is refrigerated or heated; and it has good transparency and excellent barrier properties, and it has excellent sealing with a PP tray and can be easily opened, and it is clean and does not produce silk or residue.

Description

Technical Field

[0001] The invention relates to the technical field of packaging materials, in particular to a highly transparent, high-barrier, anti-condensation easy-to-peel cover film and a preparation method thereof. Background Art

[0002] Prepared food requires packaging materials to have not only good packaging performance, but also multifunctionality, especially for some foods that are stored in a refrigerator and ready to eat after heating. In addition, some packaging that requires trays with cover films to display the contents generally requires the packaging materials to have the following functionalities: high transparency, high barrier, anti-condensation, and easy to open. Currently, most of these cover films on the market are incomplete in functionality, or some of their functionality is not good.

[0003] The specific problems are as follows:

[0004] 1) Condensation occurs when refrigerated or easily condensed when heated;

[0005] 2) Poor transparency and barrier properties;

[0006] 3) Difficult to peel off, or it will fray when peeled off.

[0007] Therefore, there is an urgent need for a highly transparent, high barrier, anti-condensation and easy-to-remove cover film to solve the above problems. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a highly transparent, high barrier, anti-condensation easy-to-peel cover film and a preparation method thereof. The cover film of the present invention has high transparency, good barrier properties, and continuous anti-condensation. The cover film and a PP tray can be easily peeled off and opened. When opening, no silk is left on the PP tray, and it can be peeled off cleanly, which satisfies consumers' needs for easy opening.

[0009] In order to achieve one of the purposes of the present invention, the present invention adopts the following technical solutions:

[0010] A highly transparent, high barrier, anti-condensation easy-to-peel cover film, the easy-to-peel cover film comprises a CPE-EVA-POE co-extruded film, a glue layer and a PET-ALOx layer connected in sequence, the CPE-EVA-POE co-extruded film is made by a three-layer co-extrusion process of a corona layer, an intermediate layer and a heat-sealing layer, the corona layer is composed of a linear polyethylene and a low-density polyethylene in a mass ratio of 3:1, the intermediate layer is composed of a linear polyethylene, a low-density polyethylene and an anti-fog masterbatch in a mass ratio of 63:25:12, and the heat-sealing layer is composed of an EVA resin, an anti-fog masterbatch, vinyl POE and an opening agent in a mass ratio of 77:10:10:3. Among them, POE refers to a polyolefin elastomer; EVA refers to ethylene vinyl acetate; CPE refers to chlorinated polyethylene; the corona layer is connected to the glue layer; and the PET-ALOx layer is made by vacuum aluminum plating of a PET film.

[0011] Preferably, the brand of linear polyethylene is 4533 produced by Sinopec, the brand of low-density polyethylene is L420 produced by TPC, the brand of anti-fog masterbatch is 1000048-KR produced by Anse Color Company, the brand of EVA resin is 53007 produced by DuPont, the brand of vinyl POE is 8200 produced by DowDuPont, and the brand of anti-blocking agent is AB-20LD produced by Aaron.

[0012] Preferably, the glue used in the glue layer is 7728 solvent-free glue produced by Henkel.

[0013] Preferably, the thickness of the CPE-EVA-POE co-extruded film is 25-55 μm; the thickness of the PET-ALOx layer is 12 μm.

[0014] Preferably, the thickness ratio of the corona layer, the intermediate layer and the heat-sealing layer is 1:2:1.

[0015] The second object of the present invention is to provide a method for preparing a highly transparent, high barrier, anti-condensation and easy-to-remove cover film, the preparation method comprising the following steps:

[0016] S1, casting process: according to the resin raw material formula, corona layer resin raw material, middle layer resin raw material and heat sealing layer resin raw material are added to the three barrels of the extruder respectively; the raw materials in the three barrels are co-extruded and then enter the casting station for cooling and shaping, and then the surface of the corona layer of the film after casting and shaping is corona treated to obtain CPE-EVA-POE co-extruded film;

[0017] S2, aluminum plating process: vacuum aluminum plating is performed on the surface of the PET film, that is, a layer of aluminum oxide (ALOx) is deposited on the surface of the PET film to obtain a PET-ALOx layer;

[0018] S3, composite process: use solvent-free glue to solvent-free composite CPE-EVA-POE co-extruded film and PET-ALOx, and then sequentially perform aging and slitting to obtain an easy-to-peel cover film.

[0019] Preferably, in step S1, the extrusion temperature of the extruder is 235-245°C; the die processing temperature of the extruder is 235-245°C; and the casting roll processing temperature of the extruder is 20±3°C.

[0020] Preferably, oxygen and argon are introduced into the PET film during vacuum aluminum plating in step S2, that is, oxygen and argon are introduced when the aluminum wire evaporates into aluminum atomic vapor, and the amount of oxygen introduced, the amount of argon introduced and the amount of aluminum vapor introduced are all matched with the linear speed of the PET film.

[0021] Preferably, the amount of glue applied in step S3 is 1.2-1.8 g / m 2 .

[0022] Preferably, the compounding speed of the compounding process in step S3 is 300-350 m / min; the aging temperature is 40-45° C., and the aging time is 48-36 h.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The easy-to-peel cover film prepared by the present invention can continuously prevent condensation and can achieve anti-fogging regardless of whether it is refrigerated or heated; it has good transparency and excellent barrier properties, and in addition, it has excellent sealing properties with the PP tray and can be easily peeled off and opened, and it is clean without silk or residue.

[0025] 2) The easy-to-peel cover film of the present invention uses a blend of linear polyethylene with very low small molecule content in the resin and low-density polyethylene as the corona layer and the middle layer of the film. The brand of the linear polyethylene is 4533 produced by Sinopec. The density of the linear polyethylene is higher than that of ordinary linear polyethylene (0.918 g / cm 3 ) is higher, so after being processed into a film, the film has high mechanical strength; the brand of low-density polyethylene is L420 produced by TPC, which has very good processability, good molten resin fluidity and compatibility, less water marks when processed into a film, and high transparency; the brand of anti-fog masterbatch is 1000048-KR produced by Anpaise Company. The carrier resin of the masterbatch is a blend of EVA and LDPE, so the masterbatch has very good compatibility with EVA and PE, and the processed film has high transparency. In addition, the anti-fog masterbatch is usually only added to the anti-fog layer (i.e., the heat sealing layer), and The present invention also adds 12% anti-fog masterbatch in the middle layer to continuously improve the anti-fog effect of the film; the EVA resin is 53007 produced by DuPont, which has good heat-sealing sealing performance with PP material and can be opened, but the present invention reduces the bonding strength with PP by adding vinyl POE (8200 produced by DowDuPont), and can reduce the heat-sealing temperature, improve the heat-sealing appearance of the film, and reduce the heat-sealing energy consumption; the opening agent is AB-20LD produced by Aaron, which can prevent the adhesion of the film. The selected L420 and 53007 resins are usually used for extrusion coating, while the present invention is applied to the cast film processing technology to obtain a highly transparent film, which meets the functional requirements of fully displaying internal and external objects.

[0026] 3) The present invention selects the cast film forming process and adopts the innovative process of "high temperature processing and low temperature quenching" to make the film have low crystallinity and small crystal particle size, so that the film obtains a high transparency effect; specifically, high temperature processing and low temperature quenching refer to increasing the processing temperature of the extruder and the die head by 5-15°C and reducing the temperature of the cast roller by 5-10°C, so that the temperature of the molten resin flowing out is high, and when it is quickly cooled at low temperature into a film, the film crystallinity is reduced and the crystal particle size is reduced, thereby obtaining a high transparency effect.

[0027] 4) Oxygen and argon are introduced into the PET film of the present invention during vacuum aluminum plating, and the amount of oxygen, argon and aluminum vapor needs to be controlled to match the linear speed of the film, so that a layer of aluminum oxide (ALOx) is deposited on the surface of the PET film, and the PET-ALOx layer has a high barrier property to water vapor and oxygen, good transparency, and PET has good heat resistance. The present invention selects this film not only as the outer layer of the contact heat sealing module, but also plays a barrier function.

[0028] 5) The present invention uses Henkel's 7728 solvent-free glue for solvent-free lamination, with a glue amount of 1.2-1.8 g / m 2 , the amount of glue applied is reduced by 50% compared with dry coating, which can improve the transparency of the film.

[0029] 6) The present invention designs a co-extruded film formula and innovates the casting process, selects PET-ALOx film as a transparent barrier, and adopts a solvent-free composite process to bond, thereby preparing a highly transparent, high-barrier, anti-condensation and easy-to-peel cover film. The composite cover film is heat-sealed with the PP tray, with good sealing effect and clean opening. During the entire packaging cycle, condensation can be prevented throughout the entire process, and the contents can be displayed transparently and clearly, which is convenient for end consumers to choose. In terms of barrier, the moisture in the contents can be kept from evaporating out of the package, and the entry of external oxygen can be well blocked, thereby preventing the contents from undergoing chemical changes such as deterioration and discoloration during the shelf life. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the composite membrane structure of the present invention;

[0031] Figure 2 It is a production process flow chart of the present invention;

[0032] Figure 3 Schematic diagram of heat sealing curve of the present invention;

[0033] Figure 4 It is a graph of anti-fog test data of the film of the present invention.

[0034] The meanings of the symbols in the accompanying drawings are as follows:

[0035] 1. PET-ALOx layer; 2. Glue layer; 3. CPE-EVA-POE co-extruded film. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0037] The invention discloses a highly transparent, high-barrier, anti-condensation easy-to-peel cover film, which comprises a CPE-EVA-POE co-extruded film 3, a glue layer 2 and a PET-ALOx layer 1 which are connected in sequence. The CPE-EVA-POE co-extruded film 3 is made of a corona layer, an intermediate layer and a heat-sealing layer through a three-layer co-extrusion process. The corona layer is composed of linear polyethylene and low-density polyethylene in a mass ratio of 3:1, the intermediate layer is composed of linear polyethylene, low-density polyethylene and anti-fog masterbatch in a mass ratio of 63:25:12, and the heat-sealing layer is composed of EVA resin, anti-fog masterbatch, vinyl POE and an anti-blocking agent in a mass ratio of 77:10:10:3; and the corona layer is connected to the glue layer 2.

[0038] The brand of linear polyethylene is 4533 produced by Sinopec, the brand of low-density polyethylene is L420 produced by TPC, the brand of anti-fog masterbatch is 1000048-KR produced by Anse Co., the brand of EVA resin is 53007 produced by DuPont, the brand of vinyl POE is 8200 produced by DowDuPont, and the brand of anti-blocking agent is AB-20LD produced by Aron. The glue used in glue layer 2 is 7728 solvent-free glue produced by Henkel. The thickness of CPE-EVA-POE co-extruded film 3 is 25-55μm; the thickness ratio of corona layer, middle layer and heat sealing layer is 1:2:1; the thickness of PET-ALOx layer 1 is 12μm.

[0039] A method for preparing a highly transparent, high barrier, anti-condensation and easy-to-remove cover film, the preparation method comprising the following steps:

[0040] S1, casting process: according to the resin raw material formula, corona layer resin raw material, intermediate layer resin raw material and heat sealing layer resin raw material are added to the three barrels of the extruder respectively; the raw materials in the three barrels are co-extruded and then enter the casting station for cooling and shaping, and then the surface of the corona layer of the film after casting and shaping is corona treated to obtain CPE-EVA-POE co-extruded film 3, wherein the extrusion temperature of the extruder is 235-245°C; the die processing temperature of the extruder is 235-245°C; the casting roller processing temperature of the extruder is 20±3°C;

[0041] S2, aluminum plating process: vacuum aluminum plating is performed on the surface of the PET film, oxygen and argon are introduced into the PET film during the vacuum aluminum plating, and the amount of oxygen, argon and aluminum vapor introduced are all matched with the linear speed of the PET film, to obtain a PET-ALOx layer 1;

[0042] S3, composite process: use solvent-free glue to composite the CPE-EVA-POE co-extruded film 3 with the PET-ALOx layer 1 without solvent, the composite speed is 300-350 m / min, and the glue amount is 1.2-1.8 g / m 2, and then ripening and cutting are carried out in sequence, the ripening temperature is 40-45°C, the ripening time is 48-36h, and an easy-to-peel cover film is obtained.

[0043] Example 1

[0044] This embodiment provides a method for preparing a highly transparent, high barrier, anti-condensation and easy-to-remove cover film, which specifically includes the following steps:

[0045] S1, casting process: according to the resin raw material formula, corona layer resin raw material, intermediate layer resin raw material and heat sealing layer resin raw material are added to the three barrels of the extruder respectively; the raw materials in the three barrels are co-extruded and then enter the casting station for cooling and shaping, and then the surface of the corona layer of the film after casting and shaping is corona treated to obtain CPE-EVA-POE co-extruded film 3, wherein the extrusion temperature of the extruder is 235-245°C; the die processing temperature of the extruder is 235-245°C; the casting roller processing temperature of the extruder is 20±3°C;

[0046] S2, aluminum plating process: vacuum aluminum plating is performed on the surface of the PET film, oxygen and argon are introduced into the PET film during the vacuum aluminum plating, and the amount of oxygen, argon and aluminum vapor introduced are all matched with the linear speed of the PET film, to obtain a PET-ALOx layer 1;

[0047] S3, composite process: use solvent-free glue to composite the CPE-EVA-POE co-extruded film 3 with the PET-ALOx layer 1 without solvent, the composite speed is 300-350 m / min, and the glue amount is 1.2-1.8 g / m 2 , and then ripening and cutting are carried out in sequence, the ripening temperature is 40-45°C, the ripening time is 48-36h, and an easy-to-peel cover film is obtained.

[0048] The raw material formula of the co-extruded film 3 is shown in Table 1 below:

[0049] Table 1

[0050] Thickness distribution CPE-EVA-POE co-extrusion film formula 10 Corona layer: 75% 4533 + 25% L420 20 Middle layer: 63% 4533 + 25% L420 + 12% 1000048-KR 10 Heat seal layer: 77% 53007 + 10% 1000048-KR + 10% 8200 + 3% AB-20LD

[0051] The properties of each particle in Table 1 are shown in Table 2 below:

[0052] Table 2

[0053]

[0054] The casting process parameters in step S1 are shown in Table 3 below:

[0055] Table 3

[0056]

[0057]

[0058] Comparative Example 1

[0059] 14μmKPET / 35μmCPP composite film

[0060] The easy-to-peel cover film prepared in Example 1 and the composite film prepared in Comparative Example 1 were heat-sealed with a PP tray, respectively, and the measured heat-seal strength data are shown in Table 4 below:

[0061] Table 4

[0062]

[0063]

[0064] The heat sealing curves of the easy-to-peel lid film prepared in Example 1 and the composite film in Comparative Example 1 are as follows: Figure 3 As shown in Table 4 and Figure 3 It can be seen that the heat-sealing strength of the easy-to-peel lid film prepared by the present invention and the PP tray is between 8.3-11.8N / 15mm, and the heat-sealing temperature starts from 90°C, the heat-sealing temperature is low, and the heat-sealing temperature window is wide, while the heat-sealing strength of the composite film in Comparative Example 1 at a heat-sealing temperature of 130-150°C is 8.9-14.9N / 15mm. Compared with the easy-to-peel lid film prepared in Example 1, the heat-sealing window of the composite film in Comparative Example 1 is narrow, the heat-sealing temperature is high, and the corresponding heat-sealing strength is also high. The possible reason is that the composite film in Example 1 adopts a heat-sealing film layering method to achieve the peeling ability. By using Co-PP resin as the heat-sealing layer, the middle layer uses PE with poor compatibility, and the heat-sealing layer is very thin, usually 2-4μm. After the composite film is heat-sealed, the heat-sealing layer is easy to adhere to the PP tray; in addition, the PE and Co-PP interfaces are separated, there is a wire-forming phenomenon, and the heat-sealing strength is uncontrollable and uneven and stable.

[0065] The performance of the easy-to-peel cover film prepared in Example 1 and the composite film of Comparative Example 1 was tested, and the results are shown in Table 5 below:

[0066] Table 5

[0067]

[0068] Table 6 below shows the anti-fog performance evaluation method according to the anti-fog effect level:

[0069] Table 6

[0070]

[0071]

[0072] From Table 5 and Figure 4 It can be seen that the moisture permeability of the easy-to-peel cover film prepared in Example 1 is 1.22 gm / m2 24h, oxygen permeability value is 1.89gm / m 2 ·24h, haze is 2.1%, peel strength is 1.51N / 15mm, moisture permeability of the composite film of comparative example 1 is 2.16gm / m 2 24h, oxygen permeability value is 2.32gm / m 2 ·24h, the haze is 3.2%, and the peel strength is 0.85N / 15mm. The moisture permeability, oxygen permeability and haze of the easy-to-peel-off cover film prepared in Example 1 are lower than those of the composite film in Comparative Example 1, and the peel strength is higher than that of the composite film in Comparative Example 1. The easy-to-peel-off cover film prepared in the present invention has better barrier properties and better anti-condensation effect; the higher peel strength indicates that the sealing is excellent; Figure 4 The anti-fog score of the easy-to-peel cover film of the present invention for 60 days is 7-9 points, and the anti-fog effect is excellent.

[0073] In addition, the easy-to-peel cover film of the present invention can continuously prevent condensation. When the product is placed at room temperature and refrigerated at a storage temperature of 4-6°C, the cover film does not condense. After microwave heating to 100°C, the cover film does not condense and still maintains its original transparency; the haze value of the composite film is ≤2.5%, and the moisture permeability is less than ≤2.0gm / m 2 24h, oxygen permeability is less than 2.0cc / m 2 ·24h; after heat-sealing with the PP tray, the easy-to-peel cover film was tested at a negative pressure of 40KPa, and there was no air leakage in the easy-to-peel cover film. The composite heat-sealing strength with the PP tray was 8.3-11.8N / 15mm, and when the cover film was peeled off, it was separated cleanly without any residual threads. Therefore, the experimental results show that the easy-to-peel cover film prepared by the present invention is easier to peel off and open than the composite film of Comparative Example 1, and is opened cleanly without any threads or residues.

[0074] Those skilled in the art should understand that the above are only some specific embodiments of the present invention, rather than all embodiments. It should be noted that for those of ordinary skill in the art, many modifications and improvements can be made, and all modifications or improvements that do not exceed the scope of protection of the present invention should be regarded as the scope of protection of the present invention.

Claims

1. A highly transparent, high barrier, anti-condensation easy-to-remove cover film, characterized in that: The easy-to-peel cover film comprises a CPE-EVA-POE co-extruded film (3), a glue layer (2) and a PET-ALOx layer (1) which are connected in sequence. The CPE-EVA-POE co-extruded film (3) is made of a corona layer, an intermediate layer and a heat-sealing layer through a three-layer co-extrusion process. The corona layer is composed of linear polyethylene and low-density polyethylene in a mass ratio of 3:1, the intermediate layer is composed of linear polyethylene, low-density polyethylene and anti-fog masterbatch in a mass ratio of 63:25:12, and the heat-sealing layer is composed of EVA resin, anti-fog masterbatch, vinyl POE and an anti-blocking agent in a mass ratio of 77:10:10:3; the corona layer is connected to the glue layer (2); and the PET-ALOx layer (1) is made of a PET film vacuum-plated with aluminum. The highly transparent, high barrier, anti-condensation and easy-to-remove cover film is prepared by the following preparation process, and the preparation method comprises the following steps: S1, casting process: according to the resin raw material formula, corona layer resin raw material, intermediate layer resin raw material and heat sealing layer resin raw material are added to the three barrels of the extruder respectively; the raw materials in the three barrels are co-extruded and then enter the casting station for cooling and shaping, and then the surface of the corona layer of the film after casting and shaping is corona treated to obtain CPE-EVA-POE co-extruded film (3); S2, aluminum plating process: vacuum aluminum plating is performed on the surface of the PET film to obtain a PET-ALOx layer (1); S3, composite process: using solvent-free glue to perform solvent-free composite of CPE-EVA-POE co-extruded film (3) and PET-ALOx, and then sequentially performing aging and slitting to obtain an easy-to-peel cover film.

2. The highly transparent, high barrier, anti-condensation easy-to-peel cover film according to claim 1, characterized in that: The brand of the linear polyethylene is 4533 produced by Sinopec, the brand of the low-density polyethylene is L420 produced by TPC, the brand of the EVA resin is 53007 produced by DuPont, the brand of the vinyl POE is 8200 produced by DowDuPont, and the brand of the antiblocking agent is AB-20LD produced by Aaron.

3. The highly transparent, high barrier, anti-condensation easy-to-peel cover film according to claim 1, characterized in that: The thickness of the CPE-EVA-POE co-extruded film (3) is 25-55 μm; the thickness of the PET-ALOx layer (1) is 12 μm.

4. The highly transparent, high barrier, anti-condensation easy-to-peel cover film according to claim 3, characterized in that: The thickness ratio of the corona layer, the middle layer and the heat sealing layer is 1:2:

1.

5. A method for preparing the highly transparent, high barrier, anti-condensation easy-to-peel cover film according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: S1, casting process: according to the resin raw material formula, corona layer resin raw material, intermediate layer resin raw material and heat sealing layer resin raw material are added to the three barrels of the extruder respectively; the raw materials in the three barrels are co-extruded and then enter the casting station for cooling and shaping, and then the surface of the corona layer of the film after casting and shaping is corona treated to obtain CPE-EVA-POE co-extruded film (3); S2, aluminum plating process: vacuum aluminum plating is performed on the surface of the PET film to obtain a PET-ALOx layer (1); S3, composite process: using solvent-free glue to perform solvent-free composite of CPE-EVA-POE co-extruded film (3) and PET-ALOx, and then sequentially performing aging and slitting to obtain an easy-to-peel cover film.

6. The method for preparing a highly transparent, high barrier, anti-condensation and easy-to-peel cover film according to claim 5, characterized in that: In step S1, the extrusion temperature of the extruder is 235-245°C; the die processing temperature of the extruder is 235-245°C; and the casting roll processing temperature of the extruder is 20±3°C.

7. The method for preparing a highly transparent, high barrier, anti-condensation and easy-to-peel cover film according to claim 5, characterized in that: In step S2, oxygen and argon are introduced into the PET film during vacuum aluminum plating, and the amount of oxygen, the amount of argon and the amount of aluminum vapor introduced are all matched with the linear speed of the PET film.

8. The method for preparing a highly transparent, high barrier, anti-condensation and easy-to-peel cover film according to claim 5, characterized in that: The amount of glue applied in step S3 is 1.2-1.8 g / m 2 .

9. The method for preparing a highly transparent, high barrier, anti-condensation and easy-to-peel cover film according to claim 5, characterized in that: The compounding speed of the compounding process in step S3 is 300-350 m / min; the aging temperature is 40-45° C., and the aging time is 48-36 h.

Images