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CN-121989538-A - Low-gas-yield heat-shrinkable film and manufacturing method thereof

CN121989538ACN 121989538 ACN121989538 ACN 121989538ACN-121989538-A

Abstract

The invention discloses a low-gas-yield heat-shrinkable film and a manufacturing method thereof, relating to the technical field of high-end packaging materials, wherein the heat-shrinkable film comprises an outer layer, an intermediate layer and an inner layer which are sequentially laminated, the heat-shrinkable film has a free volume gradient from outside to inside when being heated and shrunk, the outer layer and the inner layer are high-rigidity compact layers, the heat-shrinkable film consists of metallocene polyethylene, cycloolefin copolymer, a smooth opening agent with molecular weight not less than 500 and a macromolecular antioxidant, the intermediate layer is a high free volume adsorption layer, the invention is composed of polyolefin elastomer, metallocene polyethylene and hydrophobic modified ZIF-8 volatile adsorption master batch, the traditional static physical separation route is abandoned, the glass transition temperature drop of cycloolefin copolymer and polyolefin elastomer is skillfully utilized, free volatile in the film is reversely pumped to the middle layer at the moment of thermal contraction, and the nano ZIF-8 with the one-way valve resistance effect is utilized to permanently lock the film, so that the problem of volatile pollution in the package of precision electronic and optical devices is solved.

Inventors

  • GUO BIWEI
  • YE XIAOBIN
  • YIN HONGFEI

Assignees

  • 黄山永创科技包装有限公司

Dates

Publication Date
20260508
Application Date
20260323

Claims (10)

  1. 1. The low-gas-production heat-shrinkable film is characterized by comprising an outer layer, an intermediate layer and an inner layer which are sequentially laminated, wherein the heat-shrinkable film has a free volume gradient from outside to inside when being heated and shrunk; The outer layer and the inner layer are high-rigidity compact layers, and the raw materials comprise, by weight, 60-75 parts of metallocene polyethylene, 15-30 parts of cycloolefin copolymer COC, 2-5 parts of smooth opening agent with molecular weight not lower than 500 and 0.1-0.3 part of macromolecular antioxidant; The middle layer is a high free volume adsorption layer, and comprises, by weight, 50-70 parts of polyolefin elastomer POE, 15-25 parts of metallocene polyethylene and 5-15 parts of volatile adsorption master batch; wherein the glass transition temperature of the cycloolefin copolymer COC is greater than that of the polyolefin elastomer POE to induce densification of the outer layer when the film is shrunk by heating and form an extrusion stress driving the reverse migration of the free volatiles toward the intermediate layer.
  2. 2. The low-gassing heat shrinkable film of claim 1 wherein said volatile adsorption master batch is prepared by a process comprising: Dispersing a ZIF-8 porous material with the average particle size of 50-150nm in a solvent, and adding octyl triethoxysilane to carry out surface grafting modification to coat long-chain alkyl on the micropore port of the ZIF-8; And (3) carrying out melt blending granulation on the modified ZIF-8 porous material and a polyolefin elastomer POE carrier to obtain the volatile adsorption master batch.
  3. 3. The low-gassing heat shrinkable film according to claim 2, wherein the cycloolefin copolymer COC has a glass transition temperature of 65-80 ℃ and the polyolefin elastomer POE has a glass transition temperature of not higher than-40 ℃.
  4. 4. The low-gassing heat shrinkable film according to claim 1 wherein the slip opening agent is specifically selected from at least one of ultra-high molecular weight polysiloxane masterbatches, ethylene bis stearamide EBS, ethylene bis oleamide EBO or stearyl stearamide SS.
  5. 5. The low-gas-production heat-shrinkable film according to claim 1, wherein the outer layer, the middle layer and the inner layer do not contain mono-fatty acid amide substances with molecular weight lower than 500, and the macromolecular antioxidant is a compound of hindered phenol antioxidant Irganox1330 and phosphite antioxidant Irgafos 168.
  6. 6. The low-gas-production heat-shrinkable film according to claim 1, wherein the ZIF-8 porous material has an average particle diameter of 50-150nm and a specific surface area of more than 1200m2/g, and the thickness ratio of the outer layer, the intermediate layer and the inner layer is 1 (2.5-4): 1.
  7. 7. The low-gas-generating heat shrinkable film according to claim 1, wherein the raw materials of the outer layer and the inner layer further comprise 0.1 to 0.5 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer PPA, and the PPA has an average particle diameter of less than 2 μm dispersed in a matrix.
  8. 8. A method of manufacturing a low-gas-production heat-shrinkable film according to any one of claims 1 to 7, characterized by using a three-layer co-extrusion double-bubble tube method, comprising the steps of: treating the thick plate tube blank by quenching water of a first bubble tube, wherein the temperature of the quenching water is controlled to be 10-15 ℃ so as to inhibit crystallization of a polyolefin matrix; and (3) reheating the cooled tube blank to 105-115 ℃ and performing inflation biaxial stretching on the second tube blank, wherein the stretching multiplying power is 3-5 times of that of the longitudinal direction and 3-5 times of that of the transverse direction.
  9. 9. The method of manufacturing a low-gassing heat shrinkable film according to claim 8, further comprising an annealing setting step of: and introducing the biaxially oriented tube film into a third bubble tube for annealing treatment, wherein the annealing temperature is controlled to be 50-60 ℃, and the inside of the tube film is kept at micro positive pressure in the annealing process, so that the transverse heat shrinkage pre-release amount of the tube film is controlled to be 2-5%.
  10. 10. The method for producing a low-gassing heat shrinkable film according to claim 8, wherein the annealing time is controlled to 1.5 to 3.0 seconds, and then the film is wound after being rapidly cooled to room temperature by a cooling roll.

Description

Low-gas-yield heat-shrinkable film and manufacturing method thereof Technical Field The invention mainly relates to the technical field of high-end packaging materials, in particular to a low-gas-yield heat-shrinkable film and a manufacturing method thereof. Background The heat-shrinkable film has been dominant in the fields of electronic components, precision optical instruments, medicines, high-end food packaging and the like due to its excellent physical and mechanical properties such as adhesion, high transparency and tear resistance. However, in practical heat shrink packaging processes (heated environments typically up to 120 ℃ to 150 ℃), conventional heat shrink films of the polyolefin (e.g., PE) type are very prone to "gassing" or "oil out" phenomena. From physical and chemical analysis, the pollution phenomenon mainly originates from two dimensions, namely that one dimension is the release of oligomers on the resin matrix level, the common polyolefin resin contains oligomers with wider molecular weight distribution, the oligomers are extremely easy to generate phase transition and escape outwards under high-temperature excitation, and the other dimension is the dynamic migration and volatilization of an auxiliary agent system, so that the processing and opening performance are met, and single fatty acid amide substances (such as erucic acid amide and oleic acid amide) with lower molecular weight (about 300) are commonly added in the industry. These small molecular substances migrate to the surface at normal temperature, but rapidly gasify to form tiny Volatile Organic Compounds (VOCs) "oil mist" when heated at high temperature, adhere to the surface of a precision semiconductor or optical lens after condensation, and cause irreversible electrical performance failure or serious pollution such as optical diffraction. In the face of the above technical pain, the prior art mostly adopts modified logic blocked by dynamic and static states. For example, by blending inorganic platelet materials such as montmorillonite into the resin, attempts have been made to increase the physical tortuosity of the out-diffusion of gas molecules. However, this strategy has the obvious limitation that the mechanical extrusion force generated inside the film is very easy to forcefully discharge the gas in the dynamic process of violent disorientation and volume shrinkage of the heat-shrinkable film, and the static barrier shape is similar to that of the dummy. More deadly, the conventional inorganic powder is extremely easy to agglomerate in the nonpolar polymer melt, the particle size of the conventional inorganic powder is far beyond the wavelength of visible light, so that serious Rayleigh scattering is caused, the haze of the film is increased sharply, and the optical-grade transparency and the code scanning recognition rate which are necessary for high-end packaging are completely lost. Therefore, there is a need in the industry for a new heat shrink film structure that can jump out of the prior art nest, cut off the pollution from the source, and actively capture free molecules during the heat shrink dynamics. Disclosure of Invention The technical scheme of the invention aims at the technical problem that the prior art is too single, provides a solution which is obviously different from the prior art, and mainly provides a low-gas-yield heat-shrinkable film and a manufacturing method thereof, which are used for solving the technical problem in the prior art. The technical scheme adopted for solving the technical problems is as follows: a low-gas-production heat-shrinkable film comprises an outer layer, an intermediate layer and an inner layer which are sequentially laminated; The raw materials of the outer layer and the inner layer are the same, and the raw materials comprise, by weight, 60-75 parts of metallocene polyethylene mPE, 15-30 parts of cycloolefin copolymer COC, 2-5 parts of ultrahigh molecular weight silicone master batch and 0.1-0.3 part of antioxidant; the intermediate layer comprises, by weight, 50-70 parts of linear low density polyethylene, 15-25 parts of metallocene polyethylene mPE and 5-15 parts of volatile adsorption master batch. Further, the preparation method of the volatile adsorption master batch comprises the following steps: Dispersing the ZIF-8 porous material in absolute ethyl alcohol, adding octyl triethoxysilane for surface modification reaction, filtering and drying to obtain hydrophobically modified ZIF-8 particles; And (3) carrying out melt blending, extrusion granulation and obtaining the volatile adsorption master batch by using 15-25 parts by weight of the hydrophobically modified ZIF-8 particles and 75-85 parts by weight of polyolefin elastomer POE in a double screw extruder. Further, the ZIF-8 porous material has an average particle size of 50-150nm and a specific surface area of more than 1200m < 2 >/g. Further, the antioxidant is a compound of hindered phenol antioxidant Irga