CN-121973528-A - Hot-coating high-barrier re-wrapping film and preparation method thereof

CN121973528ACN 121973528 ACN121973528 ACN 121973528ACN-121973528-A

Abstract

The invention discloses a hot-coating high-barrier repackaging film and a preparation method thereof. Belongs to the technical field of packaging materials. The rolled film sequentially comprises an outer layer substrate film, a middle barrier layer and an inner layer heat-sealing film. The middle barrier layer is formed by drying and solidifying nano composite barrier liquid coated on the inner surface of the outer substrate film, wherein the nano composite barrier liquid comprises polyvinyl alcohol, inorganic nano material dispersion liquid subjected to surface modification, polymer emulsion, a cross-linking agent and a wetting agent. The barrier liquid is preheated and then coated by adopting a micro gravure, and is dried in three stages of rapid shaping, deep crosslinking and high-temperature densification in sequence, and finally is solvent-free composite with the inner layer heat sealing film. Through the synergistic effect among specific components and the precise coupling of the multistage drying process, the coiled film has excellent initial oxygen barrier property, water vapor barrier property, excellent stability in high-temperature and high-humidity environment and high barrier stability after simulating dynamic mechanical load of heavy package transportation.

Inventors

HUANG LIANG
HU JICHAO
FANG WEIMIN
WANG FANGMIAO
JIANG JUNJIE

Assignees

黄山源点新材料科技有限公司

Dates

Publication Date: 20260505
Application Date: 20251217

Claims (9)

1. The hot-coating high-barrier re-wrapping film is characterized by sequentially comprising an outer-layer substrate film, a middle barrier layer and an inner-layer heat-sealing film, wherein the middle barrier layer is formed by drying and solidifying a nano composite barrier liquid coated on the inner surface of the outer-layer substrate film, and the nano composite barrier liquid comprises the following components in parts by weight according to the solid content: a) 60-80 parts of polyvinyl alcohol aqueous solution based on solid content; b) 15-25 parts of surface modified inorganic nano material dispersion liquid based on solid content; c) 5-15 parts of polymer emulsion based on solid content; d) 0.5-2 parts of cross-linking agent; e) 0.1-0.5 part of wetting agent.
2. The hot-glued high-barrier re-wrap film according to claim 1, characterized in that the surface-modified inorganic nanomaterial is a silane coupling agent modified platelet-shaped or particulate inorganic nanomaterial.
3. The hot-coated high-barrier re-wrapping film according to claim 2, wherein the inorganic nano material is at least one selected from nano silicon dioxide, nano kaolin and montmorillonite, and the silane coupling agent is an amino or epoxy group-containing silane coupling agent.
4. A thermally coated high barrier re-wrap film according to claim 3, characterized in that the surface modified inorganic nanomaterial is a nanosilica modified with gamma-aminopropyl triethoxysilane or gamma-2, 3-glycidoxypropyl trimethoxysilane with an average particle size of 20-50nm.
5. The heat-applied high barrier re-wrap film according to claim 1, wherein the polymer emulsion is one of a styrene-acrylic polymer emulsion, a pure acrylic polymer emulsion or an acerbate acrylic polymer emulsion, and has a glass transition temperature of-10 ℃ to 25 ℃.
6. The heat-applied high barrier re-wrap film according to claim 5, wherein the polymer emulsion is a styrene-acrylic polymer emulsion.
7. The hot-coated high-barrier re-wrapping film according to claim 1, wherein the cross-linking agent is at least one selected from boric acid, polycarboxylic acid compounds, adipic dihydrazide and aziridine, and the wetting agent is polyether modified polysiloxane.
8. The hot-coated high-barrier repackaging film according to claim 1, wherein the outer layer substrate film is a biaxially oriented polyamide film or a biaxially oriented polyester film with a thickness of 12-25 μm, and the inner layer heat-seal film is a cast polypropylene film, a linear low-density polyethylene film or a co-extrusion film thereof with a thickness of 40-80 μm.
9. A process for preparing a heat-applied high barrier re-wrap film according to any one of claims 1 to 8, comprising the steps of: S1, corona treatment, namely carrying out corona treatment on the inner surface of an outer substrate film to enable the surface tension of the outer substrate film to reach 40-44 dynes; S2, preparing and preprocessing a barrier liquid, namely preheating a polyvinyl alcohol aqueous solution to 70-80 ℃, sequentially adding a surface-modified inorganic nano material dispersion liquid, a polymer emulsion, a cross-linking agent and a wetting agent under stirring, uniformly mixing, and then defoaming for 30-60 minutes at a constant temperature of 70-80 ℃ to obtain the nano composite barrier liquid; S3, heating the nano composite barrier liquid obtained in the step S2 to 40-50 ℃, coating the nano composite barrier liquid on the surface of the outer layer substrate film treated in the step S1 in a micro gravure coating mode, wherein the wet coating weight is 2.5-4.0g/m 2 , and then performing multi-stage program drying: the first stage is to treat the surface of the coating for 3 to 5 seconds at the temperature of 70 to 80 ℃ and the wind speed of 8 to 12m/s so as to form a porous framework rapidly; the second stage is to treat the mixture for 5 to 8 seconds at the temperature of between 90 and 100 ℃ and the wind speed of between 5 and 8m/s so as to promote the deep evaporation of the internal water and the initiation of the crosslinking reaction; the third stage is to treat the polymer emulsion particles for 2 to 4 seconds at the temperature of 110 to 120 ℃ and the wind speed of 2 to 4m/s so as to fully soften and flow the polymer emulsion particles, densify the coating and completely crosslink the coating; cooling to room temperature after drying to form an outer layer substrate film with an intermediate barrier layer; s4, compounding and curing, namely coating a solvent-free polyurethane adhesive on the surface of the inner heat-sealing film, compounding the solvent-free polyurethane adhesive with the outer substrate film with the middle barrier layer obtained in the step S3, wherein the compounding pressure is 0.3-0.6MPa, the compounding speed is 150-250m/min, rolling after compounding, and curing for 36-72h at 45-55 ℃ to obtain the hot-coating high-barrier re-wrapping film.

Description

Hot-coating high-barrier re-wrapping film and preparation method thereof Technical Field The invention belongs to the technical field of packaging materials, and particularly relates to a hot-coating high-barrier re-wrapping film and a preparation method thereof. Background The high-barrier packaging material is a key for guaranteeing the shelf life and the quality safety of products. With the development of electronic commerce and global logistics, heavy packaging puts higher demands on film materials beyond static barrier properties, namely that the barrier function cannot be significantly attenuated after repeated vibration, impact and extrusion during transportation, handling and stacking. The existing mainstream high-barrier technical routes all have obvious short plates in this respect. Although the ethylene-vinyl alcohol copolymer (EVOH) co-extruded film has excellent barrier property, when the multi-layer co-extruded structure is subjected to external bending or impact, stress concentration easily occurs between layers to cause invisible microcracks of the barrier layer, the barrier property is rapidly reduced, and the raw material and processing cost are high. The aluminum plating film or aluminum foil composite material has poor ductility of a metal layer, is extremely easy to generate pinholes when being bent and dropped, causes barrier failure, is opaque, can not be heated by microwaves and is difficult to recover. The wet coating technology based on polyvinyl alcohol (PVA) is regarded as an environment-friendly and economical alternative, but has two inherent defects that firstly, the barrier property of the PVA coating is extremely sensitive to humidity and is greatly reduced due to moisture absorption and swelling under high-temperature and high-humidity environments, and secondly, the brittleness and insufficient toughness of the pure PVA or common PVA/nanocomposite coating are more critical, and a microcrack network is easily generated in the coating due to stress in the process of subsequent compounding, slitting and bagging, especially in the process of transportation and dropping of terminal packaging pieces. These micro-or even nano-scale cracks will become a rapid path for gas permeation, leading to premature, invisible failure of the barrier function of the package in a dynamic use scenario, which failure is difficult to find in conventional factory inspection, with a huge quality risk. In order to improve the brittleness and the humidity sensitivity of PVA, the prior art discloses a method for adding nano silicon dioxide or montmorillonite into PVA, which improves the hardness and the humidity stability to a certain extent, but has limited improvement on flexibility and impact resistance, and the interface bonding strength of nano particles and a PVA matrix is insufficient, so that the interface is easy to be debonded under dynamic load to form defects. The prior art also discloses that the addition of acrylate emulsion to PVA for toughening, while improving the flexibility of the coating, often at the expense of barrier properties, as the introduction of ordinary emulsion particles may destroy the compactness of the coating. In addition, the existing coating process adopts single-stage or simple two-stage drying, and is difficult to simultaneously realize rapid shaping of the surface of the coating, uniform formation of an internal structure, interfacial fusion of a nano component and a polymer matrix and densification of a final coating, so that stress or micro defects possibly exist in the coating, and hidden danger is buried for performance attenuation under dynamic load. Therefore, a novel high-barrier re-wrapping film which is designed cooperatively from a formula to a process, aims to obtain the balance of initial barrier property, environmental stability and dynamic mechanical durability and is excellent is developed, and has urgent market demands and important technical values. Disclosure of Invention The invention aims at overcoming the defects of easy attenuation of barrier performance and insufficient environmental stability of the existing high-barrier packaging film, in particular to a coating type high-barrier film under dynamic mechanical load (mainly referring to impact and continuous pressure born by packaging in transportation and stacking), and providing a nano composite barrier re-wrapping film with reasonable structural design and excellent comprehensive performance. The invention further aims to provide the preparation method of the coiled film, which realizes controllable construction of a coating microstructure through the accurate matching of the formula design of the nano composite barrier liquid and a multi-stage program drying process, so that excellent processing efficiency, initial performance and use durability are synchronously obtained. In order to achieve the above purpose, the invention adopts the following technical scheme: The hot-coating high-ba