High-toughness label film and preparation method thereof

Abstract

The invention discloses a high-toughness label film and a preparation method thereof, and relates to the technical field of label films. The high-toughness label film is composed of a base film layer, a bonding layer and a surface coating, the base film layer is prepared from the following components in parts by mass: 60-70 parts of polyester resin, 12-20 parts of polypropylene resin, 8-15 parts of a toughening agent, 3-6 parts of nano silicon dioxide and 0.5-1.5 parts of an ultraviolet absorption antioxidant; the bonding layer is prepared from the following components in parts by mass: 20 to 30 parts of acrylate adhesive and 5 to 8 parts of tackifying resin; the surface coating is prepared from the following components in parts by mass: 10 to 15 parts of fluorine-containing polymer and 2 to 4 parts of ultraviolet absorption antioxidant. The label film has excellent tear resistance, ultraviolet aging resistance and weather resistance, has outstanding surface hydrophobic and antifouling properties, can maintain high bonding strength and low haze characteristics in a complex environment for a long time, and is suitable for identification requirements of outdoor equipment, cold-chain logistics and other harsh scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of label films, and in particular to a high-toughness label film and a preparation method thereof. Background Art

[0002] In the application scenarios of label films, toughness and UV resistance are two key indicators. Traditional label films face many challenges in actual use. On the one hand, the problem of insufficient toughness is more prominent. For example, during logistics transportation and warehousing, label films may be subjected to frequent mechanical shocks, repeated bending and friction on different surfaces. If the toughness of the label film is poor, it is easy to crack, fall off, and even wrinkle or break during labeling, which not only affects the appearance quality of the product, but may also cause incomplete label information, thereby affecting product identification, traceability and sales. Especially in some special environments, such as labels for low-temperature frozen foods or labels for industrial equipment in outdoor high-temperature environments, the toughness requirements for label films are more stringent.

[0003] On the other hand, UV oxidation is also a significant concern. UV light, with its high energy content, can break chemical bonds and alter the molecular structure of label film materials. Prolonged exposure to UV light can cause the polymers in the label film to undergo photooxidative degradation, leading to a gradual deterioration in the material's performance. This degradation manifests itself in yellowing, reduced surface gloss, increased hardness, and increased brittleness. This degradation weakens the bond between the label film and the object being applied, ultimately causing the label to fall off or become insecurely adhered. Furthermore, UV oxidation can damage printed images and text on the label, reducing readability and recognition, and causing significant inconvenience in product use and management.

[0004] In summary, the label film in the existing technology has obvious deficiencies in toughness and anti-ultraviolet oxidation performance, which makes it difficult to meet the needs of increasingly complex and diverse application scenarios. It is urgent to develop a label film with both high toughness and good anti-ultraviolet oxidation performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a label film with high toughness and resistance to ultraviolet oxidation in order to meet the application requirements of complex environments and long-term use in view of the problems existing in the prior art.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a high-toughness label film, the label film is composed of a base film layer, an adhesive layer and a surface coating; The base film layer is composed of the following components in parts by mass: 60-70 parts of polyester resin, 12-20 parts of polypropylene resin, 8-15 parts of toughening agent, 3-6 parts of nano-silicon dioxide, and 0.5-1.5 parts of ultraviolet absorbing antioxidant; The adhesive layer is composed of the following components in parts by mass: 20-30 parts of acrylic adhesive and 5-8 parts of tackifying resin; The surface coating is composed of the following components in parts by mass: 10-15 parts of fluoropolymer and 2-4 parts of ultraviolet absorbing antioxidant; The toughening agent is a compound of styrene-ethylene-butylene-styrene copolymer and ethylene-vinyl acetate copolymer in a mass ratio of 3-5:1; The ultraviolet absorbing antioxidant has a structure shown in Formula 1: Formula 1 Said Z1 is selected from: O, S, N(R2), C(CH3)2, C(CD3)2; R1 is selected from the group consisting of: H, methyl, tert-butyl, phenyl, deuterated methyl, deuterated tert-butyl, and deuterated phenyl; R2 is selected from the group consisting of: D, methyl, tert-butyl, deuterated methyl, deuterated tert-butyl; The D is deuterium.

[0007] Furthermore, the thickness of the base film layer is 25-50 μm, the thickness of the adhesive layer is 10-30 μm, and the thickness of the surface coating is 2-8 μm.

[0008] Furthermore, the ultraviolet absorbing antioxidant is any one of the compounds shown in the following structures: ; ; ; ; .

[0009] Furthermore, the tackifying resin is a hydrogenated rosin resin with a degree of hydrogenation of ≥90% and an acid value of ≤10 mg KOH / g.

[0010] Furthermore, the fluorine-containing polymer is at least one of polytetrafluoroethylene, polyvinylidene fluoride or perfluoroethylene propylene copolymer.

[0011] Furthermore, the particle size of the nano-silicon dioxide is 20-40 nm.

[0012] A method for preparing a high-toughness label film comprises the following steps: S1. Preparation of base film layer: The polyester resin and polypropylene resin were dried at 80-100 ° C for 4 h, mixed with the toughening agent, nano-silica, and ultraviolet absorbing antioxidant, melt blended at 240-280 ° C, and cast to obtain a base film; S2. Adhesive layer coating: The acrylic adhesive and the tackifying resin are mixed evenly at 50-60 ° C, and coated on one side of the base film layer prepared in S1 by micro-gravure coating, with a coating amount of 8-12g / m 2 , curing at 80℃ for 20min; S3 surface coating treatment: by magnetron sputtering on the other side of the base film layer prepared in S1 deposited a composite coating containing the fluoropolymer and the UV absorbing antioxidant, sputtering power 80-120W, vacuum 0.1-0.5Pa, deposition time 30-60s, to obtain a film treated with a surface coating; S4 aging: aging the membrane material treated with the surface coating in S3 in an environment of 40-50° C. and relative humidity ≤30% for 24-48 hours.

[0013] Furthermore, the melt blending in S1 is carried out using a twin-screw extruder with a screw speed of 200-400 rpm and a melt pressure of 8-12 MPa.

[0014] Furthermore, the line count of the anilox roller for the micro gravure coating in S2 is 200-300 lines per inch, and the coating speed is 15-25 m / min.

[0015] Furthermore, the magnetron sputtering in S3 uses argon as the working gas, the gas flow rate is 50-80 sccm, and the temperature of the base film layer is controlled at -10°C to 10°C.

[0016] Furthermore, the aging is carried out for 48 hours at 50° C. and relative humidity ≤ 30%.

[0017] The structure of the ultraviolet absorbing antioxidant described in the present invention contains a conjugated aromatic ring system and a hydrogen bond network. The conjugated system absorbs ultraviolet rays (200-400nm) through π→π* electronic transitions, converting light energy into heat energy and releasing it. The heteroatoms (such as O / S / N in Z1) and substituents (such as R1 / R2) in the molecule can adjust the absorption wavelength range and enhance the coverage of the ultraviolet band. The hydrogen bond network captures free radicals (such as ROO·) through a hydrogen donation mechanism, and oxidizes itself to a stable quinone structure, interrupting the chain oxidation reaction. Deuterated substituents (such as C(CD3)2, deuterated phenyl) extend the life of the antioxidant active site through the isotope effect. The CD bond energy is higher than that of the CH bond, requiring higher energy to break, significantly improving the photostability and thermal stability of the molecule. Deuteration reduces the quantum tunneling effect involving hydrogen atoms, reduces photodegradation side reactions, and extends the durability of the antioxidant in outdoor environments (such as high temperature and strong UV).

[0018] Styrene-ethylene-butylene-styrene copolymer (SEBS) of the present invention, its styrene hard segment provides physical crosslinking point, and ethylene-butylene soft segment then gives it high elasticity, can absorb impact energy and disperse stress.By the polarity matching of styrene unit and polyester resin and polypropylene resin, reduced phase separation phenomenon.The vinyl acetate segment in ethylene-vinyl acetate copolymer (EVA) strengthens the adhesion between SEBS and polyester resin and polypropylene resin interface, promotes stress transmission, thus improves the pliability of material.In melt blending process, SEBS and EVA form interpenetrating network structure, and synergistic effect improves the tear resistance and bending fatigue strength of basement membrane.

[0019] In the base film layer described in the present invention, the polyester resin provides a rigid skeleton and dimensional stability to resist tensile deformation. The polypropylene resin has balanced processing fluidity and chemical resistance, and synergistically inhibits brittle fracture with the toughening agent. Nano-silica can fill the resin voids, improve tensile strength, and form a light scattering layer with its nano-scale dispersion to assist in anti-ultraviolet function. In the adhesive layer described in the present invention, the acrylate adhesive forms a chemical bond with the base film through polar groups. The hydrogenated rosin resin has a low acid value, which reduces corrosion to the base film layer and improves the initial adhesion. In the surface coating described in the present invention, the fluorocarbon chains in the fluoropolymer (such as polytetrafluoroethylene) form a low surface energy layer to block the penetration of water vapor and pollutants. High-hardness fluoropolymers (such as polyvinylidene fluoride) reduce the damage to the ultraviolet protection layer caused by mechanical damage. The antioxidants in the base film layer and the surface coating form a gradient protection to deal with ultraviolet radiation in the deep and surface layers respectively.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. Significantly improved toughness: Through the synergistic effect of the compound toughening system of SEBS and EVA, an interpenetrating network structure is formed, which greatly improves the tear resistance and bending fatigue strength of the base film layer and effectively inhibits the brittle fracture trend.

[0021] 2. Enhanced anti-ultraviolet oxidation ability: The use of deuterated ultraviolet absorbers and gradient protection structure (double protection of base film layer + surface coating) achieves wider ultraviolet absorption band coverage and free radical capture efficiency, significantly delaying the photooxidative degradation of the material.

[0022] 3. Excellent environmental tolerance: The collaborative design of fluoropolymer surface coating and low acid value tackifying resin can maintain stable bonding performance and hydrophobic protection effect under extreme temperature and humidity conditions, reducing the impact of environmental erosion.

[0023] 4. Optimization of process adaptability: By combining magnetron sputtering low-temperature deposition with micro-gravure coating technology, the coating uniformity and base film structural integrity are simultaneously improved, reducing the thermal stress damage defects in traditional processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The UV absorption spectra of the compounds prepared in Synthesis Examples 1 to 6 of the present invention are shown. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Synthesis example 1 Synthesis of UV-absorbing antioxidant 1:

[0027] Step 1: Under a nitrogen atmosphere, 20 g of raw material 1, 11.09 g of raw material 2, 1.46 g of tetrakis(triphenylphosphine)palladium, and 11.06 g of anhydrous potassium carbonate were added to the phase system in sequence, and dissolved in a mixed solution of 200 g of toluene, ethanol, and water (volume ratio 2:1:1). The mixture was heated at 75°C and refluxed for 10 hours. The heating was turned off, the mixture was cooled to room temperature, and the mixture was allowed to stand for separation. The aqueous phase was extracted twice with ethyl acetate, the organic phases were combined, washed three times with water, dried, and subjected to column chromatography using a mixture of petroleum ether and dichloromethane as the eluent to obtain 17.28 g of intermediate 1. MS [MS+H + ]:568.

[0028] Step 2: Under a nitrogen atmosphere, 17.28 g of intermediate 1, 6.85 g of raw material 3, 16.19 g of potassium phosphate trihydrate, 0.04 g of pyridine-2-carboxylic acid, 0.3 g of CuI, and 180 g of DMSO were added to the phase system in sequence, and heated at 85°C for 16 h; after cooling, the reaction mixture was extracted with aqueous ammonia solution and methyl tert-butyl ether, and the organic phase was washed five times with water and then twice with saturated NaCl solution; finally, the combined organic phase was dried over anhydrous Na2SO4, spin-dried, and column chromatography was performed using a mixture of petroleum ether and dichloromethane as eluent to obtain 16.09 g of intermediate 2. MS [MS+H + ]:676.

[0029] Step 3: Under nitrogen atmosphere, 16.09 g of intermediate 2, 12.06 g of raw material 4 and 170 g of toluene were added to the phase system in sequence, and heated at 85°C for 6 h; cooled and then spin-dried, and column chromatography was performed using a mixture of petroleum ether and dichloromethane as eluent to obtain 16.59 g of ultraviolet absorbing antioxidant 1. MS [MS+H + ]:1083.

[0030] UV absorbing antioxidant 11 HNMR (deuterated chloroform) δ8.12-8.09 (m, 1H), 7.88-7.76 (m, 3H), 7.48-7.28 (m, 7H), 6.85-6.78 (m, 2H), 6.62 (dd, 1H), 3.56 (d, 8H), 3.09-2.93 (m, 3H), 1.90-1.70 (m, 3H), 1.65-1.30 (m, 9H), 0.93 (dd, 9H).

[0031] Synthesis Example 2-Synthesis Example 6 The ultraviolet absorbing antioxidants prepared in Synthesis Examples 2 to 6 were prepared by referring to the synthesis method of Synthesis Example 1, replacing the raw material 2 therein, and the rest remained the same as Synthesis Example 1. The details are shown in the table below.

[0032]

[0033] UV maximum absorption peak test: The UV absorbing antioxidants prepared in Synthesis Examples 1 to 6 were prepared into 10 -5 M tetrahydrofuran solution, and measure its maximum UV absorption peak at 200-450nm. Figure 1 .

[0034] DPPH free radical scavenging experiment: DPPH solid was prepared into a 50μM DPPH test solution with an absorbance of 0.45. Sample solution preparation: The sample was dissolved in a suitable solvent to prepare a 20mM solution. Before testing, the 20mM test compound solution was diluted with ethanol to 500μM, and then diluted with ethanol to 40μM for testing. A value measurement (test group): In a 96-well plate, 40μL of the ethanol solution of the test compound was taken with a pipette, and then 160μL of DPPH solution was added. At room temperature for 8 hours, the A519 nm value was measured. A0 value measurement (blank group): 40μL of the ethanol solution was taken with a pipette, and then 160μL of DPPH solution was added. The measured A value is A0.

[0035] The UV maximum absorption peak and DPPH free radical scavenging rate of the UV absorbing antioxidants prepared in Synthesis Examples 1 to 6 are shown in the table below.

[0036]

[0037] Example 1

[0038] Preparation of a high-toughness label film: S1. Preparation of base film layer: Weigh 65 parts by mass of polyester resin (PET) and 16 parts by mass of polypropylene resin (PP), place them in a 90°C oven and dry them for 4 hours. The dried resin is mixed with 11 parts by mass of toughening agent (SEBS and EVA are compounded in a mass ratio of 4:1), 5 parts by mass of nano-silica (particle size 30nm) and 1.0 parts by mass of ultraviolet absorbing antioxidant (prepared in Synthesis Example 1), and added to a twin-screw extruder for melt blending. Process parameters of the twin-screw extruder: extruder zone temperature: zone I 240°C, zone II 260°C, zone III 270°C, die head 280°C, screw speed: 300rpm, melt pressure: 10MPa. A base film layer with a thickness of 35μm is obtained by tape casting. S2. Adhesive Layer Coating: 25 parts by weight of acrylic adhesive and 6 parts by weight of hydrogenated rosin resin (hydrogenation degree 92%, acid value 8 mg KOH / g) were stirred and mixed at 55°C for 1 hour. The mixture was then coated onto one side of the base film layer using a micro-gravure coater. Micro-gravure coater process parameters: anilox roller line count: 250 lines / inch, coating speed: 20 m / min, coating weight: 10 g / m 2 After coating, the coating was cured by hot air at 80°C for 20 minutes to form an adhesive layer with a thickness of 20 μm.

[0039] S3. Surface Coating Treatment: 12 parts by weight of polytetrafluoroethylene (PTFE) and 3 parts by weight of a UV-absorbing antioxidant (compound from Synthesis Example 1) were mixed and deposited on the other side of the base film using a magnetron sputtering device. The magnetron sputtering parameters were: sputtering power: 100 W, argon flow rate: 60 sccm, vacuum: 0.3 Pa, base film temperature: 0°C (controlled by a cooling coil), and deposition time: 45 seconds. A 5 μm thick composite surface coating was formed.

[0040] S4 aging: The obtained film material is placed in a constant temperature and humidity chamber and aged for 48 hours at 50° C. and a relative humidity of 25% to produce a high-toughness label film.

[0041] Example 2-Example 6 Referring to the preparation method of Example 1, the ultraviolet absorbing antioxidant was replaced with the compounds prepared in Synthesis Examples 2 to 6 in sequence, and the rest remained the same as in Example 1.

[0042] Comparative Example 1 Referring to the preparation method of Example 1, the ultraviolet absorbing antioxidant was replaced with the comparative compound 1 in sequence, and the rest remained the same as in Example 1.

[0043] Comparative compound 1: .

[0044] Comparative Example 2 Referring to the preparation method of Example 1, the ultraviolet absorbing antioxidant was replaced by the comparative compound 2 in sequence, and the rest remained the same as in Example 1.

[0045] Comparative compound 2: .

[0046] Comparative Example 3 Referring to the preparation method of Example 1, the ultraviolet absorbing antioxidant was replaced by the comparative compound 3 in sequence, and the rest remained the same as in Example 1.

[0047] Comparative compound 3: .

[0048] Comparative Example 4 Referring to the preparation method of Example 1, the ultraviolet absorbing antioxidant is not added, and the rest remains the same as in Example 1.

[0049] Comparative Example 5 Referring to the preparation method of Example 1, EVA was not added as the toughening agent, and the rest remained the same as in Example 1.

[0050] Performance Testing The tensile strength, surface tension and haze of the high-toughness label films prepared in each embodiment and comparative example were tested respectively. The data are shown in the table below.

[0051]

[0052] The Examples demonstrate significant advantages in longitudinal and transverse tensile strength, surface tension, and haze. Through the synergistic effects of a toughening agent compound, a UV-absorbing antioxidant, and a fluorine-containing coating, the Examples achieve significantly improved tensile strength, lower surface tension (indicating a more hydrophobic coating), and lower haze (higher transparency). In contrast, the Comparative Examples, due to the lack of key components or the use of non-deuterated / non-fluorine materials, exhibit significantly reduced tensile strength, increased surface energy leading to increased contamination, and increased haze reflecting increased internal defects in the material. The overall trend demonstrates that the component design and process control of the present invention play a decisive role in improving the overall performance of the label film.

[0053] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high-toughness label film, characterized in that: The label film is composed of a base film layer, an adhesive layer and a surface coating layer; The base film layer is composed of the following components in parts by mass: 60-70 parts of polyester resin, 12-20 parts of polypropylene resin, 8-15 parts of toughening agent, 3-6 parts of nano-silicon dioxide, and 0.5-1.5 parts of ultraviolet absorbing antioxidant; The adhesive layer is composed of the following components in parts by mass: 20-30 parts of acrylic adhesive and 5-8 parts of tackifying resin; The surface coating is composed of the following components in parts by mass: 10-15 parts of fluoropolymer and 2-4 parts of ultraviolet absorbing antioxidant; The toughening agent is a compound of styrene-ethylene-butylene-styrene copolymer and ethylene-vinyl acetate copolymer in a mass ratio of 3-5:1; The ultraviolet absorbing antioxidant has a structure shown in Formula 1: Formula 1 Said Z1 is selected from: O, S, N(R2), C(CH3)2, C(CD3)2; R1 is selected from the group consisting of: H, methyl, tert-butyl, phenyl, deuterated methyl, deuterated tert-butyl, and deuterated phenyl; R2 is selected from the group consisting of: D, methyl, tert-butyl, deuterated methyl, deuterated tert-butyl; The D is deuterium.

2. The high-toughness label film according to claim 1, characterized in that: The ultraviolet absorbing antioxidant is any one of the compounds shown in the following structures: ； ； ； ； 。 3. The high-toughness label film according to claim 1, characterized in that: The tackifying resin is hydrogenated rosin resin, the degree of hydrogenation of which is ≥90% and the acid value is ≤10mg KOH / g.

4. The high-toughness label film according to claim 1, characterized in that: The fluorine-containing polymer is at least one of polytetrafluoroethylene, polyvinylidene fluoride or perfluoroethylene propylene copolymer.

5. The high-toughness label film according to claim 1, characterized in that: The particle size of the nano-silicon dioxide is 20-40 nm.

6. A method for preparing a high-toughness label film according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Preparation of base film layer: The polyester resin and polypropylene resin were dried at 80-100 ° C for 4 h, mixed with the toughening agent, nano-silica, and ultraviolet absorbing antioxidant, melt blended at 240-280 ° C, and cast to obtain a base film; S2. Adhesive layer coating: The acrylic adhesive and the tackifying resin are mixed evenly at 50-60 ° C, and coated on one side of the base film layer prepared in S1 by micro-gravure coating, with a coating amount of 8-12g / m 2 , curing at 80℃ for 20min; S3 surface coating treatment: by magnetron sputtering on the other side of the base film layer prepared in S1 deposited a composite coating containing the fluoropolymer and the UV absorbing antioxidant, sputtering power 80-120W, vacuum 0.1-0.5Pa, deposition time 30-60s, to obtain a film treated with a surface coating; S4 aging: aging the membrane material treated with the surface coating in S3 in an environment of 40-50° C. and relative humidity ≤30% for 24-48 hours.

7. The method for preparing a high-toughness label film according to claim 6, characterized in that: The melt blending in S1 is carried out using a twin-screw extruder with a screw speed of 200-400 rpm and a melt pressure of 8-12 MPa.

8. The method for preparing a high-toughness label film according to claim 6, characterized in that: The line count of the anilox roller for the micro gravure coating in S2 is 200-300 lines per inch, and the coating speed is 15-25 m / min.

9. The method for preparing a high-toughness label film according to claim 6, characterized in that: The magnetron sputtering described in S3 uses argon as the working gas, the gas flow rate is 50-80 sccm, and the temperature of the base film layer is controlled at -10°C to 10°C.

10. The method for preparing a high-toughness label film according to claim 6, characterized in that: The aging is carried out for 48 hours at 50° C. and relative humidity ≤ 30%.

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