High-crystallinity paper-based multi-dimensional composite food packaging material and preparation method thereof

Abstract

The invention relates to the field of paper-based packaging materials, and discloses a high-crystallinity paper-based multi-dimensional composite food packaging material. The high-crystallinity paper-based multi-dimensional composite food packaging material comprises a back coating, a direct aluminum plating layer, a first barrier coating, a base paper layer, a second barrier coating, an adhesive layer, a transfer aluminum layer, a transfer release layer and a heat sealing coating which are sequentially arranged from bottom to top. The preparation method comprises the following steps: coating a PET (Polyethylene Terephthalate) film with the transfer release layer to form a pre-coating film, and after drying, aluminizing the coating side of the pre-coating film to form a transfer aluminized film; respectively coating two surfaces of the base paper layer with the first barrier coating and the second barrier coating to form backing paper, and after drying, plating aluminum on the first barrier coating side of the backing paper to form direct plating backing paper; adhering the second barrier coating surface of the direct plating bottom paper with the aluminum surface of the transfer aluminum plating film by using an adhesive layer, drying, and stripping off the PET film on line; and the back coating and the heat sealing coating are respectively coated on the direct aluminum plating layer surface and the transfer release layer surface. The material has a multi-dimensional barrier function and is high in damage resistance.

Description

Technical Field

[0001] The invention relates to the field of paper-based packaging materials, and in particular to a high-crystallinity paper-based multi-dimensional composite food packaging material and a preparation method thereof. Background Art

[0002] Plastic packaging has always been favored for its advantages such as lightness, durability, low cost and excellent barrier properties. However, plastic packaging materials generally have the difficulties of high recycling costs, difficulty in natural degradation and dependence on non-renewable resources such as petroleum. Years of abuse have also caused considerable pollution to the environment. In contrast, paper-based materials have significant advantages in environmental protection. The main materials of paper-based packaging materials are mostly from renewable resources, which shows that paper-based packaging materials are naturally renewable, degradable and recyclable. Environmentally friendly properties, at the same time, the fiber structure of paper-based materials also makes its surface suitable for printing without too much secondary surface treatment. This situation has prompted the public to increasingly prefer paper-based materials to replace plastic packaging materials. However, the porous fiber structure of paper gives paper strong hygroscopicity and gas permeability, which makes the barrier properties of conventional paper-based packaging materials poor. Therefore, the development of environmentally friendly paper-based materials with excellent barrier properties has become a hot research topic in the packaging materials industry.

[0003] The mainstream products of paper-based packaging materials at present include aluminum foil barrier paper, paper-plastic composite paper, transfer barrier paper and conventional direct-plated paper. Aluminum foil barrier paper requires a large amount of aluminum, which has high production costs and is difficult to recycle later; the production of paper-plastic composite paper requires the use of plastic substrates, and plastic materials are difficult to degrade naturally in the environment, have a long degradation cycle, and are prone to environmental pollution. Conventional direct-plated paper and transfer aluminum-plated paper can meet cost and environmental protection requirements, but both are not foldable and the aluminum layer is easily damaged, which will lead to a decrease in the barrier properties of the product. Summary of the invention

[0004] In view of the above-mentioned shortcomings that currently exist, the present invention provides a high-crystallinity paper-based multi-dimensional composite food packaging material and a preparation method thereof, which can enable the paper-based packaging material to have a multi-dimensional barrier function, greatly improving the damage resistance of the paper-based packaging material. The material has the characteristics of being plastic-free, high-barrier, heat-sealable, degradable, and directly contactable with food, meeting the requirements of green and environmentally friendly design. The material has high moisture and oxygen barrier properties, can effectively extend the shelf life of the packaged products, and has high production efficiency.

[0005] To achieve the above object, the embodiments of the present invention adopt the following technical solutions: A high-crystallinity paper-based multi-dimensional composite food packaging material comprises a back coating, a direct aluminum plating layer, a first barrier coating, a base paper layer, a second barrier coating, an adhesive layer, a transfer aluminum layer, a transfer release layer, and a heat-sealing coating which are arranged in sequence from bottom to top.

[0006] According to one aspect of the present invention, the first barrier coating and the second barrier coating are both made of water-based acrylic paint, with a solid content of 39%, a viscosity of 20s, and a sizing amount of 3.5g / m 2 ~4g / m 2 .

[0007] According to one aspect of the present invention, the direct-plated aluminum layer and the transferred aluminum layer are both formed by vapor deposition technology, and the thickness of both is 48nm-52nm.

[0008] According to one aspect of the present invention, the transfer release layer is made of food-grade transfer coating material with a solid content of 15%, a viscosity of 25s, and a coating dry weight of 1.15g / m 2 , thermal efficiency 74.

[0009] According to one aspect of the present invention, the back coating layer is a water-based environmentally friendly coating with a solid content of 21.1%, a viscosity of 11s, and a sizing amount of 3.5g / m 2 ~4g / m 2 The heat seal coating adopts water-based acrylic heat seal coating, with a solid content of 36±2%, a viscosity of 12±3s, and a sizing amount of 5.5g / m 2 ~6g / m 2 .

[0010] According to one aspect of the present invention, the adhesive layer is made of water-based acrylic glue with a solid content of 45%, a viscosity of 35s, and a composite glue application amount of 5.5g / m 2 ~6g / m 2 .

[0011] According to one aspect of the present invention, the base paper layer is a single-sided coated food grade glassine paper with a grammage range of 30 g / m 2 ~100g / m 2 .

[0012] A method for preparing a high-crystallinity paper-based multi-dimensional composite food packaging material comprises the following steps: The transfer release layer is coated on the PET film to form a pre-coated film, and after drying, the coating side of the pre-coated film is aluminum plated to form a transfer aluminum-plated film; The first barrier coating and the second barrier coating are respectively coated on both sides of the base paper layer to form a base paper, and after drying, the first barrier coating side of the base paper is aluminum plated to form a direct-plated base paper; Use the adhesive layer to adhere the second barrier coating surface of the direct-plated base paper to the aluminum surface of the transfer aluminum-plated film, and peel off the PET film in-line after drying; The back coating and heat-sealing coating are coated on the direct aluminum plating layer and the transfer release layer respectively.

[0013] According to one aspect of the present invention, the PET film is a biaxially oriented polyester film, the pre-coated film is placed in a vacuum aluminum coating machine after drying to aluminum-coat the coating side to form a transfer aluminum-coated film, the base paper is placed in a vacuum aluminum coating machine after drying to aluminum-coat the first barrier coating side to form a direct-coated base paper, and the adhesive layer is bonded by a wet laminating machine.

[0014] According to one aspect of the present invention, the dry coating weight of the transfer release layer is 1.15 g / m 2 , thermal efficiency 74, the thickness of the aluminum layer of the transfer aluminum film and the direct-plated base paper is 48nm-52nm, and the amount of glue applied to the adhesive layer is 5.5g / m 2 ~6g / m 2 The sizing amount of the back coating is 3.5 g / m 2 ~4g / m 2 The glue amount of the heat seal coating is 5.5g / m 2 ~6g / m 2 .

[0015] Advantages of the implementation of the present invention: Through the composite design of the direct-plated aluminum layer, the transferred aluminum layer and the barrier coating, the material has a multi-dimensional barrier function, which greatly improves the damage resistance of the paper-based packaging material. The material has the characteristics of being plastic-free, high-barrier, heat-sealable, degradable, and directly contactable with food, meeting the requirements of green and environmentally friendly design; the material has high moisture and oxygen barrier properties, and can effectively extend the shelf life of the packaged products; step one and step two of the production of the material can be carried out simultaneously, which reduces the waiting time for working hours and has high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 This is a schematic structural diagram of the high crystallinity paper-based multi-dimensional composite food packaging material of the present invention.

[0018] The names corresponding to the serial numbers in the figure are as follows: 1. Back coating; 2. Direct aluminum plating layer; 3. First barrier coating; 4. Base paper layer; 5. Second barrier coating; 6. Adhesive layer; 7. Transfer aluminum layer; 8. Transfer release layer; 9. Heat seal coating. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "top", "bottom", "one side", "the other side", "front", "back", "middle part", "inside", "top", "bottom", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0020] Embodiment 1

[0021] like Figure 1 As shown, a high-crystallinity paper-based multi-dimensional composite food packaging material comprises a back coating 1, a direct aluminum plating layer 2, a first barrier coating 3, a base paper layer 4, a second barrier coating 5, an adhesive layer 6, a transfer aluminum layer 7, a transfer release layer 8, and a heat-sealing coating 9, which are arranged in sequence from bottom to top. The preparation method of the high-crystallinity paper-based multi-dimensional composite food packaging material comprises the following steps: The transfer release layer 8 is coated on the PET film to form a pre-coated film, and after drying, the coating side of the pre-coated film is aluminum plated to form a transfer aluminum-plated film; The first barrier coating 3 and the second barrier coating 5 are respectively coated on both sides of the base paper layer 4 to form a base paper, and after drying, the first barrier coating 3 side of the base paper is aluminum plated to form a direct-plated base paper; The second barrier coating 5 of the direct-plated base paper is adhered to the aluminum surface of the transfer aluminum-plated film using the adhesive layer 6, and the PET film is peeled off inline after drying; The back coating layer 1 and the heat-sealing coating layer are coated on the direct aluminum plating layer 2 and the transfer release layer 8 respectively.

[0022] In this embodiment, the back coating 1 is made of water-based environmentally friendly paint, with a solid content of 21.1%, a viscosity of 11s (apply 4 cups, room temperature), and a sizing amount of 3.5g / m 2 ~4g / m 2 The back coating 1 can provide a certain degree of protection for the direct-plated aluminum layer 2, reduce scratches and wear, and at the same time increase the surface tension of the direct-plated aluminum layer 2, making it more printable.

[0023] In this embodiment, the direct-plated aluminum layer 2 and the transferred aluminum layer 7 are both formed by vapor deposition technology, so that they have excellent air tightness and can effectively block the penetration of oxygen and moisture; the thickness of the two aluminum layers is 48nm to 52nm.

[0024] In this embodiment, the first barrier coating 3 and the second barrier coating 5 are the same barrier coating, the structural materials of the two are the same, both are water-based acrylic paint, the solid content is 39%, the viscosity is 20s (apply 4 cups, room temperature), and the glue amount is 3.5g / m 2 ~4g / m 2 ; The barrier coating ensures excellent moisture and oxygen barrier properties. After the barrier coating penetrates into the base paper layer 4, it can effectively improve the molecular crystallinity of paper fibers and increase the ordered micro-region space of the paper, significantly reducing the adsorption of water molecules on hydroxyl groups and the transfer of oxygen molecules in the fiber structure of the paper, and has excellent moisture and oxygen barrier properties; at the same time, after being filled with the first barrier coating 3, the surface of the base paper layer 4 can become smoother, which is conducive to the formation of the direct aluminum plating layer 2.

[0025] In this embodiment, the base paper layer 4 is made of single-sided coated food-grade glassine paper, which has a higher cohesive energy density and a lower fiber structure pore diameter after overpressure treatment, which can effectively prevent the transfer of oxygen molecules in the paper. At the same time, a flatter and smoother paper surface is also conducive to the formation of the direct aluminum plating layer 2; the optional gram weight range of the base paper layer 4 is 30g / m 2 ~100g / m 2 .

[0026] In this embodiment, the adhesive layer 6 is made of water-based acrylic glue with a solid content of 45% and a viscosity of 35s (apply 4 cups at room temperature). It is used to connect the base paper layer 4 and the transfer aluminum layer 7. The composite glue application amount is 5.5g / m 2 ~6g / m 2 .

[0027] In this embodiment, the transfer release layer 8 is made of food-grade transfer coating material, with a solid content of 15%, a viscosity of 25s (coating 4 cups, room temperature), and a coating dry weight of 1.15g / m 2 , thermal efficiency 74.

[0028] In this embodiment, the heat seal coating is a water-based acrylic heat seal coating with a solid content of 36±2%, a viscosity of 12±3s, and a sizing amount of 5.5g / m 2 ~6g / m 2 The heat-sealing coating can provide the material of the present invention with stable heat-sealing performance, and the material is safe and non-toxic and can be directly in contact with food.

[0029] The beneficial effects of this embodiment are: through the composite design of the direct-plated aluminum layer 2, the transferred aluminum layer 7 and the barrier coating, the material has a multi-dimensional barrier function, which greatly improves the damage resistance of the paper-based packaging material. The material has the characteristics of plastic-free, high barrier, heat-sealable, degradable, and directly contactable with food, meeting the requirements of green and environmentally friendly design; the material has high moisture and oxygen barrier properties, and can effectively extend the shelf life of the packaged products; step one and step two of the production of the material can be carried out simultaneously, reducing working hours and waiting time, and the production efficiency is high.

[0030] Embodiment 2

[0031] This embodiment provides a method for preparing a high-crystallinity paper-based multi-dimensional composite food packaging material. The method for preparing a high-crystallinity paper-based multi-dimensional composite food packaging material comprises the following steps: Step 1: Coat the transfer release layer 8 on the PET film, i.e., the biaxially oriented polyester film (BOPET), to form a pre-coated film, with a coating dry weight of 1.15 g / m 2 , thermal efficiency 74, after sufficient drying, the pre-coated film is placed in a vacuum aluminum coating machine for aluminum coating on its coating side to form a transfer aluminum coating film, and the thickness of the aluminum layer (transfer aluminum layer 7) is 48nm.

[0032] Step 2: (simultaneously) use a wet laminating machine to coat the first barrier coating 3 and the second barrier coating 5 on both sides of the base paper layer 4 to form a base paper. After drying, place the base paper in a vacuum aluminum plating machine to aluminum-plate the first barrier coating 3 side to form a direct-plated base paper. The thickness of the aluminum layer (direct-plated aluminum layer 2) is 48nm.

[0033] Step 3: Use adhesive layer 6 to adhere the second barrier coating 5 of the direct-plated base paper to the aluminum surface of the transfer aluminum film on a wet laminating machine, with an adhesive amount of 5.5g / m 2 ~6g / m 2 , and after drying in an oven, the PET film is peeled off online.

[0034] Step 4: Apply the back coating 1 and the heat-sealing coating on the direct aluminum coating 2 and the transfer release layer 8 respectively. The amount of glue applied to the back coating 1 is 3.5 g / m 2 ~4g / m 2 The glue amount of the heat seal coating is 5.5g / m 2 ~6g / m 2 ; The final high crystallinity paper-based multi-dimensional composite food packaging material is obtained.

[0035] In this embodiment, the back coating layer 1 adopts a water-based environmentally friendly coating with a solid content of 21.1% and a viscosity of 11s (coating 4 cups at room temperature); the back coating layer 1 can provide certain protection for the direct-plated aluminum layer 2, reduce scratches and wear, and at the same time increase the surface tension of the direct-plated aluminum layer 2, making it have higher printing adaptability.

[0036] In this embodiment, the direct-plated aluminum layer 2 and the transferred aluminum layer 7 are both formed by vapor deposition technology, so that they have excellent air tightness and can effectively block the penetration of oxygen and moisture; the thickness of the two aluminum layers is 48nm to 52nm.

[0037] In this embodiment, the first barrier coating 3 and the second barrier coating 5 are the same barrier coating, the structural materials of the two are the same, both are water-based acrylic paint, the solid content is 39%, the viscosity is 20s (apply 4 cups, room temperature), and the glue amount is 3.5g / m 2 ~4g / m 2 ; The barrier coating ensures excellent moisture and oxygen barrier properties. After the barrier coating penetrates into the base paper layer 4, it can effectively improve the molecular crystallinity of paper fibers and increase the ordered micro-region space of the paper, significantly reducing the adsorption of water molecules on hydroxyl groups and the transfer of oxygen molecules in the fiber structure of the paper, and has excellent moisture and oxygen barrier properties; at the same time, after being filled with the first barrier coating 3, the surface of the base paper layer 4 can become smoother, which is conducive to the formation of the direct aluminum plating layer 2.

[0038] In this embodiment, the base paper layer 4 is made of single-sided coated food-grade glassine paper, which has a higher cohesive energy density and a lower fiber structure pore diameter after overpressure treatment, which can effectively prevent the transfer of oxygen molecules in the paper. At the same time, a flatter and smoother paper surface is also conducive to the formation of the direct aluminum plating layer 2; the optional gram weight range of the base paper layer 4 is 30g / m 2 ~100g / m 2 .

[0039] In this embodiment, the adhesive layer 6 is made of water-based acrylic glue with a solid content of 45% and a viscosity of 35s (apply 4 cups at room temperature), which is used to connect the base paper layer 4 and the transfer aluminum layer 7. The transfer release layer 8 is made of food-grade transfer coating material with a solid content of 15% and a viscosity of 25s (apply 4 cups at room temperature).

[0040] In this embodiment, the heat-sealing coating uses a water-based acrylic heat-sealing coating with a solid content of 36±2% and a viscosity of 12±3s. The heat-sealing coating can provide stable heat-sealing performance for the material of the present invention, and the material is safe and non-toxic and can directly contact food.

[0041] The beneficial effects of this embodiment are: 1. The composite design of the direct aluminum layer 2, the transfer aluminum layer 7 and the barrier coating enables the material to have a multi-dimensional barrier function, greatly improving the damage resistance of the paper-based packaging material; even if the paper is folded and rubbed many times, the barrier layer of the paper can still maintain the maximum degree of integrity, ensuring that the barrier property of the paper is always within the technical standard range; 2. The material of the present invention has high moisture and oxygen barrier properties. After repeated testing, it was verified that its water vapor transmission rate WVTR < 0.5 (38°C, 90% RH), oxygen transmission rate OTR < 3 (23°C, 50% RH), can effectively extend the shelf life of the packaged products; 3. The combined use of transfer and direct plating processes makes the production process of the present invention not much more complicated than the production processes of conventional transfer paper "coating-aluminum plating-composite + top coating + back glue" and direct plating paper "primer coating-aluminum plating-composite + top coating + back glue", wherein step one and step two can be carried out simultaneously, reducing the waiting time of working hours and improving production efficiency.

[0042] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes, combinations or substitutions that can be easily thought of by any technician familiar with the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A high crystallinity paper-based multi-dimensional composite food packaging material, characterized in that: The invention comprises a back coating layer (1), a direct aluminum plating layer (2), a first barrier coating layer (3), a base paper layer (4), a second barrier coating layer (5), an adhesive layer (6), a transfer aluminum layer (7), a transfer release layer (8), and a heat-sealing coating layer (9) which are arranged in sequence from bottom to top.

2. The high crystallinity paper-based multi-dimensional composite food packaging material according to claim 1, characterized in that: The first barrier coating (3) and the second barrier coating (5) are both made of water-based acrylic paint, with a solid content of 39%, a viscosity of 20s, and a sizing amount of 3.5g / m 2 ~4g / m 2 .

3. The high crystallinity paper-based multi-dimensional composite food packaging material according to claim 1, characterized in that: The direct-plated aluminum layer (2) and the transferred aluminum layer (7) are both formed by vapor deposition technology, and both have a thickness of 48 nm to 52 nm.

4. The high crystallinity paper-based multi-dimensional composite food packaging material according to claim 1, characterized in that: The transfer release layer (8) is made of food-grade transfer coating material with a solid content of 15%, a viscosity of 25s, and a coating dry weight of 1.15g / m 2 , thermal efficiency 74.

5. The high crystallinity paper-based multi-dimensional composite food packaging material according to claim 1, characterized in that: The back coating (1) is a water-based environmentally friendly coating with a solid content of 21.1%, a viscosity of 11s, and a sizing amount of 3.5g / m 2 ~4g / m 2 The heat seal coating adopts water-based acrylic heat seal coating, with a solid content of 36±2%, a viscosity of 12±3s, and a sizing amount of 5.5g / m 2 ~6g / m 2 .

6. The high crystallinity paper-based multi-dimensional composite food packaging material according to claim 1, characterized in that: The adhesive layer (6) is made of water-based acrylic glue with a solid content of 45%, a viscosity of 35s, and a composite glue application amount of 5.5g / m 2 ~6g / m 2 .

7. The high crystallinity paper-based multi-dimensional composite food packaging material according to claim 1, characterized in that: The base paper layer (4) is made of single-sided coated food-grade glassine paper, and its grammage range is 30g / m 2 ~100g / m 2 .

8. A method for preparing a high-crystallinity paper-based multi-dimensional composite food packaging material, characterized in that: The following steps are involved: The transfer release layer (8) is coated on the PET film to form a pre-coated film, and after drying, the coating side of the pre-coated film is aluminum plated to form a transfer aluminum-plated film, i.e., a transfer aluminum layer (7); The first barrier coating (3) and the second barrier coating (5) are respectively coated on both sides of the base paper layer (4) to form a base paper, and after drying, the first barrier coating (3) side of the base paper is aluminum plated to form a direct-plated base paper; Using an adhesive layer (6) to adhere the second barrier coating (5) surface of the direct-plated base paper to the aluminum surface of the transfer aluminum-plated film, and then peeling off the PET film in-line after drying; The back coating (1) and the heat-sealing coating are coated on the surface of the direct aluminum plating layer (2) and the surface of the transfer release layer (8) respectively.

9. The preparation method according to claim 8, characterized in that: The PET film is a biaxially stretched polyester film. After the pre-coating film is dried, it is placed in a vacuum aluminum coating machine to aluminum-coat the coating side to form a transfer aluminum coating film. After the base paper is dried, it is placed in a vacuum aluminum coating machine to aluminum-coat the first barrier coating (3) side to form a direct-coated base paper. The adhesive layer (6) is bonded by a wet laminating machine.

10. The preparation method according to claim 8, characterized in that: The dry coating weight of the transfer release layer (8) is 1.15 g / m 2 , thermal efficiency 74, the thickness of the aluminum layer of the transfer aluminum film and the direct-plated base paper is 48nm-52nm, and the amount of glue applied to the adhesive layer (6) is 5.5g / m 2 ~6g / m 2 The sizing amount of the back coating (1) is 3.5 g / m 2 ~4g / m 2 The glue amount of the heat seal coating is 5.5g / m 2 ~6g / m 2 .

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