Preparation and pasting method of self-adhesive loop label

Abstract

The invention discloses a preparation method and a pasting method of a self-adhesive loop label, and belongs to the technical field of packaging labels, the self-adhesive loop label comprises a release layer, a base material layer, a priming coat, a printing layer and a self-adhesive layer which are stacked in sequence, and the self-adhesive layer is made of a water-based acrylic emulsion pressure-sensitive adhesive; the self-adhesive layer is divided into a plurality of independent sections, hollow-out areas without glue exist in the adjacent sections, and the width of the hollow-out areas without glue is larger than the thickness of the cut-off knife; and then drying and curing are carried out, the coated label is cut into strip-shaped labels, then rolling is carried out, and the loop label is formed. According to the scheme, through material innovation, structural design and process optimization, leap-type upgrading of label production from high pollution and low efficiency to greenization and intellectualization is achieved.

Description

Technical Field

[0001] This invention relates to the field of packaging label technology, specifically to the preparation of self-adhesive ring labels and their application method. Background Technology

[0002] Traditional ring labels are generally applied using hot melt adhesive, but their production process has many problems.

[0003] First, traditional hot melt adhesive labels require heating to a high temperature of around 150°C during the application process, which not only consumes a lot of electricity but also produces harmful fumes, causing environmental pollution and health risks to operators. In addition, hot melt adhesive equipment requires regular cleaning and maintenance, further increasing costs and pollution.

[0004] Secondly, existing pressure-sensitive adhesive labels are prone to adhesive layer adhesion during unwinding, leading to reduced production efficiency and even machine downtime.

[0005] Third, the label has insufficient adhesion to the container surface, and it is prone to falling off, especially in humid or temperature-changing environments, which affects product reliability.

[0006] Fourth, the cutting blades wear out quickly during the cutting process due to direct contact with the self-adhesive layer, resulting in a short service life and increased equipment maintenance costs and production interruption frequency.

[0007] Finally, the overall production process is complex, involving multiple procedures and specialized equipment, resulting in high costs and making it difficult to meet the demands of efficient and environmentally friendly large-scale production.

[0008] These shortcomings collectively constrain the further development of labeling technology, necessitating innovative solutions. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a method for preparing and applying self-adhesive ring tags.

[0010] One of the objectives of this invention is to provide a method for preparing a self-adhesive ring tag.

[0011] Another object of the present invention is to provide a method for applying a self-adhesive ring label.

[0012] The present invention employs the following technical means.

[0013] The method for preparing self-adhesive loop labels includes a release layer, a substrate layer, a primer layer, a printing layer, and a self-adhesive layer stacked sequentially. The self-adhesive layer uses a water-based acrylic emulsion pressure-sensitive adhesive. The self-adhesive layer is divided into several independent sections, with adjacent sections having adhesive-free cutout areas, the width of which is greater than the thickness of the cutter. The labels are then dried and cured. The coated labels are cut into strips and then wound up to form loop labels.

[0014] Step 1, apply release layer to the back; First, octadecyl isocyanate is heated to 60°C and maintained at a constant temperature to completely melt it into a homogeneous liquid phase. Then, chlorooctadecane is added at a mass ratio of 3-6 parts, and mechanically stirred at a speed of 200-300 r / min for 20-30 minutes to ensure thorough mixing. Finally, polyethylene powder is slowly added at a mass ratio of 1-3 parts, with the feeding rate controlled at 5-10 g / min, while the stirring speed is increased to 400-500 r / min, and stirring is continued for 40-60 minutes. The above mixture was uniformly coated onto the back side of the substrate layer using a microgravure coating device at a coating speed of 15-20 m / min, with the coating amount precisely controlled at 2.5 g / m. 2 The thickness fluctuation range is ≤±0.1μm; after coating, the substrate layer enters an 80℃ hot air circulation drying tunnel with a wind speed of 2~3m / s and a drying time of 30~45 seconds, finally forming a release layer with a thickness of 0.5~1.0μm.

[0015] Step 2, varnishing and primer treatment; this step adopts an integrated process of online plasma corona treatment and water-based primer coating. First, the front side of the substrate layer is pretreated; biaxially oriented polypropylene film is selected as the substrate, and its thickness is controlled within the range of 20~30μm; during the pretreatment stage, surface contaminants are removed by an electrostatic dust removal device to ensure that the surface cleanliness of the substrate meets the ISO 8 standard. The substrate layer was then subjected to online plasma corona treatment; an atmospheric pressure plasma treatment system was used, with a high-frequency power supply output of 5kW, an operating frequency of 13.56MHz, and a power density maintained at 5W / cm². 2 During the process, the film transmission speed is precisely controlled at 200 m / min, and the electrode spacing is set to 1.0~1.5 mm. The plasma working gas is a mixture of nitrogen, argon and oxygen with a volume ratio of 85:10:5, and the processing temperature is stabilized in the range of 40~60℃.

[0016] Step 3, Coating of the Printed Layer; This step uses a precision coating process to prepare the printed layer on the surface of the substrate that has undergone plasma treatment and primer coating. The ink is selected as an alcohol-soluble environmentally friendly printing ink, and its coating amount is precisely controlled within the range of 2~5g / m². The ink viscosity is adjusted to 500~800mPa·s, and the pH value is maintained at 6.5~7.5. Modified high chlorine-containing polypropylene resin is added to the ink formula at a mass percentage of 1.5~3% as an adhesion additive. The printing process is achieved using a high-speed gravure printing machine, with the anilox roller line count set to 150~200 lines / inch and the printing speed controlled at 200~300m / min; the coating uniformity is monitored by an online spectral detection system, with a color difference ΔE≤1.5; the hot air temperature is 60~80℃, the wind speed is 2~3m / s, and the drying time is 20~30 seconds.

[0017] The ink comprises the following components by weight percentage: 60-70% water-based UV acrylic resin; 1.5~3% modified high-chlorine chlorinated polypropylene resin; 5% dodecyl acetate; 5% propylene glycol monopropyl ether; 5-8% edible alcohol; The remainder is deionized water.

[0018] Step 4, Localized application of self-adhesive layer; This step uses precision localized coating technology to prepare a segmented self-adhesive layer on the surface of the printed layer; The self-adhesive layer is divided into several independent sections by a laser-engraved stencil. The surface of the stencil is laser-engraved to form a micro-cell structure with a cell depth controlled at 20-50 μm and a line count set at 150-200 lines per inch. In areas where adhesive segments need to be formed, the cells are arranged regularly. In areas corresponding to the stencil, the cells are completely ground flat to form cell-free areas. During operation, the adhesive remains only in the cells. When the stencil comes into contact with the film substrate, the adhesive is transferred through a pressure contact device, ultimately forming an array of adhesive segments with predetermined gaps on the substrate surface.

[0019] In step 4, the self-adhesive layer also needs to be dried and cured using a three-stage hot air circulating oven: The first stage, with a temperature of 65~70℃, allows for the initial evaporation of moisture, and the time is controlled at 3~5 seconds; The second stage involves a temperature of 75-80℃ to promote cross-linking of the adhesive layer, with a time control of 5-8 seconds. The third stage involves a temperature of 70-75℃ to complete the final curing process, with a time control of 3-5 seconds. The total length of the hot air circulating oven is 6~10m, and the ventilation system is equipped with a high-pressure centrifugal fan with an exhaust volume of 12.0~18.0m³. 3 / h, exhaust volume 8.0~14.0m³ 3 / h.

[0020] The self-adhesive layer comprises the following components by weight percentage: 20% butyl acrylate; 25-30% methyl methacrylate; 5% styrene; 2% acrylic acid; 1.5% hydroxyethyl methacrylate; 1% diacetone acrylamide; 0.8% adipic acid dihydrazide; 0.8% sodium dodecyl sulfate; 1.2% alkylphenol polyoxyethylene ether; 0.5% sodium allyl hydroxypropyl sulfonate; 0.2% n-dodecyl mercaptan; 0.5% ammonium sulfate; The balance is 2-ethylhexyl acrylate.

[0021] The method for applying self-adhesive ring labels includes the following steps: Step 1, Automatic Can Import: The cans to be labeled are continuously imported into the labeling station through an automated conveyor system; Step 2, precise label cutting: The cutting blade of the labeling machine cuts at the preset glue-free gap between the self-adhesive layers of the ring label; Step 3, Positioning and Alignment: The cut label is picked up by a robotic arm or vacuum suction cup system and precisely positioned at the preset labeling position on the can to ensure the alignment accuracy of the label when it surrounds the container; Step 4, Loop Application: The label automatically wraps around the container surface thanks to its pre-applied pressure-sensitive adhesive; one side of the self-adhesive layer adheres directly to the container, and the other side is pasted onto the label, forming a strong loop structure. Step 5, Press and Fix: Finally, apply uniform pressure to the attached label using a pressure roller or pressure plate device to ensure that the self-adhesive layer is in full contact with the surface of the can.

[0022] This invention provides a method for preparing and applying a self-adhesive ring label, which has the following advantages: 1. Significantly improved production efficiency: The self-adhesive layer on the ring label eliminates the need for traditional hot melt adhesive spraying during subsequent label application, increasing the labeling speed to 220~230m / min, which is more than 22% more efficient than the traditional process.

[0023] 2. Significantly improved environmental performance: The hot melt adhesive process is completely eliminated, avoiding energy consumption and environmental pollution caused by high-temperature operations. The all-water-based process system brings VOC emissions close to zero, meeting the requirements of green manufacturing.

[0024] 3. Enhanced Quality Stability: Through plasma surface treatment (dyne value ≥38mN / m), adhesion additives (MCCPP), and layered coating process, the adhesion of the printed layer reaches ASTM D3359 Grade 0, with no peeling in the cross-cut adhesion test. After accelerated aging test (85℃ / 85%RH, 1000h), the adhesion retention rate is >95%, ensuring long-term product reliability.

[0025] 4. The perforated coating extends the tool life by up to 3 times.

[0026] 5. Improved operational safety: The entire process is carried out at a low temperature (maximum temperature 80℃), avoiding the risk of burns from high temperatures and improving the working environment.

[0027] This solution achieves a leapfrog upgrade in label production from high pollution and low efficiency to green and intelligent production through material innovation (such as MCCPP modified resin), structural design (segmented hollow coating), and process optimization (low-temperature curing). Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Self-adhesive ring tags, including: The release layer uses a special formulation containing 50% octadecyl isocyanate, 30% octadecyl chloride, and 20% polyethylene by mass, at a dosage of 2-3 g / m². This formulation forms a fatty acid amide block structure, effectively preventing adhesive layer adhesion. The release layer coating is applied using microgravure printing technology, with the coating speed controlled at 15-20 m / min and the drying temperature at 60-80℃, resulting in a release layer thickness of 0.5-1.0 μm.

[0030] The substrate layer is made of BOPP film with a thickness of 20~30μm, and the surface is corona treated with a dyne value ≥38mN / m. This treatment ensures that the substrate has good printability and adhesion.

[0031] The base coating was applied using an online plasma corona treatment process with a power of 5 kW and a speed of 200 m / min. This process significantly improved the adhesion of the base coating. The plasma treatment used atmospheric pressure plasma equipment at a frequency of 13.56 MHz and a power density of 5 W / cm³. 2 This improves the surface roughness of the substrate to Ra0.8~1.2μm.

[0032] The printing layer uses alcohol-soluble environmentally friendly printing ink and adds 1.5~3% modified high-chlorine chlorinated polypropylene resin as an adhesion additive to ensure the firmness of the printed pattern.

[0033] The self-adhesive layer uses a water-based acrylic emulsion pressure-sensitive adhesive with a thickness of 0.05~0.1mm. The self-adhesive layer features a partially perforated design, with a gap at the seam between adjacent labels. The width of this gap is greater than the thickness of the cutter. Preferably, the gap width at the seam between adjacent labels is equal to the cutter thickness plus 0.2mm. For example, when using a 0.5mm thick cutter, the gap is set to 0.7mm.

[0034] The preparation method of self-adhesive ring tags includes: Step 1: Apply release layer to the back.

[0035] The substrate layer is made of biaxially oriented polypropylene film (BOPP) with a thickness of 20-30 micrometers.

[0036] First, octadecyl isocyanate is heated to 60°C and maintained at a constant temperature until it is completely melted into a homogeneous liquid phase. Then, 3-6 parts by mass of chlorooctadecane are added, and the mixture is mechanically stirred at 200-300 rpm for 20-30 minutes to ensure thorough mixing and the formation of a transparent solution. Finally, 1-3 parts by mass of polyethylene powder are slowly added at a rate of 5-10 g / min, while simultaneously increasing the stirring speed to 400-500 rpm and continuing stirring for 40-60 minutes until the system presents a homogeneous, milky-white, viscous liquid.

[0037] The above mixture was uniformly coated onto the back side of the substrate layer using a microgravure coating device at a coating speed of 15-20 m / min, with the coating amount precisely controlled at 2.5 g / m. 2 The thickness fluctuation range is ≤±0.1μm. The coated substrate layer is then placed in an 80℃ hot air circulating drying tunnel with an air velocity of 2~3m / s and a drying time of 30~45 seconds, ultimately forming a release layer with a thickness of 0.5~1.0μm. Fourier transform infrared spectroscopy (FTIR) analysis of this release layer shows that it has a typical fatty acid amide block structure, with a polyurethane-grafted acrylic acid crosslinking density of 85%~90%.

[0038] Preferably, the mass ratio of octadecyl isocyanate, octadecyl chloride, and polyethylene powder is 5:3:2. The isocyanate group of octadecyl isocyanate forms an urethane bond with the hydroxyl group of polyethylene, and the hydrophobic long chain of octadecyl chloride fills the gaps in the network. The three components work together to construct a stable three-dimensional network structure. At this ratio, a uniform nanoscale uneven structure (Ra=0.2~0.3μm) is formed on the surface of the release layer, with a contact angle of 105°~110°.

[0039] Accelerated aging tests showed that after 6 months of storage at 40℃ and 75% relative humidity, the release layer still maintained a separation success rate of over 99.2%. Its anti-adhesion mechanism stems from two aspects: the fatty acid amide block reduces the surface energy to 22~25 mN / m, decreasing van der Waals forces with the adhesive; and the polyurethane-grafted acrylic provides mechanical support with a tensile strength ≥15 MPa, preventing interlayer damage.

[0040] Step 2: Apply varnish and base coat.

[0041] This step employs an integrated process of online plasma corona treatment and water-based primer coating. The specific implementation flow is as follows: First, the front side of the substrate layer is pretreated. Biaxially oriented polypropylene film is selected as the substrate, with its thickness controlled within the range of 20~30μm. During the pretreatment stage, surface contaminants are removed using an electrostatic dust removal device to ensure that the surface cleanliness of the substrate meets the ISO Class 8 standard.

[0042] The substrate layer was then subjected to online plasma corona treatment. An atmospheric pressure plasma treatment system was used, with the following core parameters: 5kW high-frequency power output, 13.56MHz operating frequency, and power density maintained at 5W / cm³. 2 During the process, the film transport speed was precisely controlled at 200 m / min, and the electrode spacing was set to 1.0~1.5 mm. The plasma working gas was a mixture of nitrogen, argon, and oxygen, with an optimized volume ratio of 85:10:5, and the processing temperature was stabilized in the range of 40~60℃.

[0043] The plasma modification mechanism involves both physical etching and chemical modification effects: Physical etching: High-energy electrons (30~100eV) at a rate of 10 15 ~10 16 The surface of the thin film is bombarded with collisions at a frequency of / s, which increases the surface roughness from the initial Ra 0.2~0.3μm to Ra 0.8~1.2μm, forming a uniformly distributed nanoscale pit structure (50~200nm in diameter and 10~50nm in depth).

[0044] Chemical modification: Plasma opens the CH bonds in the polymer chain, introducing polar functional groups such as carboxyl and hydroxyl groups. X-ray photoelectron spectroscopy analysis shows that the concentration of polar groups significantly increases from 3-5 atomic percent before treatment to 15-20 atomic percent.

[0045] The treatment effect is quality controlled through a real-time monitoring system: Surface energy testing: The surface energy of the treated film reached 38~42mN / m, and the water contact angle decreased from 102° to 52°~55°.

[0046] Adhesion test: The peel strength from the base coating increased from 2.5~3.5 N / cm to 4.5~6.0 N / cm, an increase of over 50%.

[0047] Morphological characterization: The surface is scanned to form a three-dimensional network microstructure, which establishes mechanical interlocking anchor points for the base coating.

[0048] Immediately after plasma treatment, an aqueous primer coating is applied. A microgravure coating device is used, with the coating speed synchronized with the plasma treatment speed at 200 m / min, and the coating amount precisely adjusted to 2~ g / m³. 2 The primer coating material is an acrylic water-based resin with a glass transition temperature (Tg) controlled between -10 and 0°C and a viscosity adjusted to 500~800 mPa·s.

[0049] The effectiveness of this process step was verified by the following experimental data: The adhesion test using the cross-cut adhesion test achieves ASTM D3359 standard grade 0; the water resistance test (immersion in distilled water at 40℃ for 24 hours) shows no peeling; and the adhesion retention rate is >95% after the accelerated aging test (85℃ / 85%RH, 1000 hours).

[0050] This step ensures that the primer layer and the substrate layer form a strong chemical bond and mechanical interlock, providing ideal interface conditions for subsequent printing processes.

[0051] Step 3, coating the printing layer.

[0052] This step employs a precision coating process to prepare a printing layer on the surface of a substrate that has undergone plasma treatment and primer coating.

[0053] Alcohol-soluble, environmentally friendly reverse-coating inks are selected, with the coating amount precisely controlled within the range of 2-5 g / m². The ink viscosity is adjusted to 500-800 mPa·s, and the pH value is maintained at 6.5-7.5 to ensure leveling and stability. To significantly improve the adhesion between the ink and the base coat, 1.5-3% by weight of modified high-chlorine-content chlorinated polypropylene resin is added to the ink formulation as an adhesion additive. This adhesion additive forms coordination bonds between the chlorine atoms in its molecule and the polar groups of the base coat, while its long-chain structure is embedded in the ink resin network, enhancing interfacial bonding.

[0054] The ink comprises the following components by weight percentage: 60-70% water-based UV acrylic resin provides a crosslinking skeleton and solvent resistance, forming a rigid network after curing (crosslinking density ≥85%). 1.5~3% modified high-chlorine chlorinated polypropylene resin (MCCPP), with a dual anchoring mechanism (chemical bonding + mechanical interlocking). 5% dodecyl ester reduces surface tension (γ_c < 35 mN / m) and improves wettability; 5% propylene glycol monopropyl ether is added to regulate the evaporation rate and balance the drying speed and adhesion strength. 5-8% edible alcohol evaporates quickly, reducing residue and meeting food packaging safety standards; The remainder is deionized water, which serves as a dispersion medium and enhances the interfacial bonding between the resin and the substrate through hydrogen bonding.

[0055] The ink incorporates modified high-chlorine chlorinated polypropylene resin (MCCPP), whose molecular chain is modified by chloromethylation, resulting in a chlorine content controlled at 18-22%. MCCPP enhances adhesion through the following dual mechanisms: Chemical bonding: The chloromethyl group (-CH2Cl) undergoes a nucleophilic substitution reaction with the hydroxyl group (-OH) of the zinc sulfide meson layer in the transfer adhesive layer to form a Zn-OC covalent bond; Physical interlocking: long-chain alkyl structure (C 18 H 37 Cl) Embedded into the ink resin network, forming a mechanical interlocking energy ≥0.5J / m 2 .

[0056] The printing process is achieved using a high-speed gravure printing press, with the anilox roller line count set to 150-200 lines / inch and the printing speed controlled at 200-300 m / min. Coating uniformity is monitored using an online spectral detection system, with a color difference ΔE ≤ 1.5. Drying parameters are: hot air temperature 60-80℃, air velocity 2-3 m / s, and drying time 20-30 seconds. The adhesion additive's mechanism of action includes: firstly, forming ionic bonds with the carboxyl groups of the base coating through chlorinated groups; and secondly, modifying the flexible segments of the resin to relieve internal stress and prevent cracking.

[0057] Performance testing shows that this process achieves ASTM D3359 standard grade 0 adhesion for the printed layer, with no peeling observed in the cross-cut adhesion test. After accelerated aging testing (85℃ / 85%RH, 1000h), the adhesion retention rate is >95%. The printed layer thickness is 1~2μm, and the surface gloss (60°) is ≥85%, forming a durable and clear visual identifier.

[0058] Step 4: Apply self-adhesive coating to localized areas.

[0059] This step employs a precision local coating technique to prepare a self-adhesive layer with a segmented structure on the surface of the printed layer.

[0060] The self-adhesive layer uses a water-based acrylic emulsion pressure-sensitive adhesive with a surface tension of 30~35 mN / m. Before coating, the adhesive viscosity is monitored in real-time using an online viscometer to ensure it remains within the range of 2700±700 mPa·s, and the pH value is stabilized at 6.5~7.5 using an automatic dosing system. Precision gravure coating equipment is employed, with an anilox roller count of 150~200 lines / inch, coating pressure controlled at 0.3~0.5 MPa, and adhesive application amount precisely controlled at 5~12 g / m² using a weight sensor. 2 .

[0061] The adhesive coating process employs a unique partial hollowing technique. Its core technology lies in achieving patterned deposition of the self-adhesive layer through a high-precision laser-engraved hollow mold. This mold is made of wear-resistant steel or ceramic material, and its working surface is laser-engraved to form precise geometric patterns, with key feature dimensional tolerances strictly controlled within ±0.02mm.

[0062] The self-adhesive layer is divided into several independent sections using a laser-engraved die. Adhesive-free cutout areas exist between adjacent sections, and the width of these areas is slightly larger than the thickness of the cutting blade. Preferably, the width of the adhesive-free cutout area equals the cutting blade thickness plus 0.2mm. For example, when using a 0.5mm cutting blade, the width of the adhesive-free cutout area is 0.7mm. This design ensures that the cutting blade always cuts within the adhesive-free area, significantly reducing blade wear.

[0063] The die-cutting mold has a surface laser-engraved to create a micro-cellular structure, with cell depth controlled at 20-50 μm and a line count of 150-200 lines / inch. In areas where adhesive is needed, the cells are regularly arranged, and their depth and density are optimized using fluid dynamics calculations to ensure adhesive load-bearing capacity and transfer rate. In areas corresponding to the cutout sections, the cells are completely smoothed to create cell-free regions. During operation, adhesive remains only within the cells. When the die-cutting mold contacts the film substrate, a pressure contact device (pressure zone pressure 1.5-2.5 kg / cm²) is used. 2 This achieves precise transfer of adhesive, ultimately forming an array of adhesive segments with predetermined gaps on the substrate surface.

[0064] Then, drying and curing are carried out using a three-stage hot air circulating oven: The first stage, with a temperature of 65~70℃, allows for the initial evaporation of moisture, and the time is controlled at 3~5 seconds; The second stage involves a temperature of 75-80℃ to promote cross-linking of the adhesive layer, with a time control of 5-8 seconds. The third stage involves a temperature of 70-75℃ to complete the final curing process, with a time control of 3-5 seconds.

[0065] The total length of the hot air circulating oven is 6~10m, and the ventilation system is equipped with a high-pressure centrifugal fan with an exhaust volume of 12.0~18.0m³. 3 / h, exhaust volume 8.0~14.0m³ 3 / h, ensuring timely removal of volatile organic compounds. Temperature sensors (accuracy ±0.5℃) monitor the status of each temperature zone in real time, and automatically adjust the heating power through a PID algorithm.

[0066] Quality inspection shows that this process achieves a glue layer thickness uniformity deviation of ≤±0.01mm, initial tack ≥5N / 25mm, and holding power ≥24h. Cutting tests indicate that tool life is increased to 3 times that of traditional processes, and glue consumption is reduced by more than 20%.

[0067] The partially hollowed-out structure ensures that the cutter works in the glue-free area, providing a reliable guarantee for subsequent cutting and labeling processes.

[0068] Furthermore, for the self-adhesive layer, a water-based acrylic emulsion pressure-sensitive adhesive is selected, comprising the following components by weight percentage: 20% butyl acrylate (BA) works synergistically with 2-ethylhexyl acrylate (2-EHA) to further optimize viscosity and improve the film-forming properties of the emulsion. 25-30% methyl methacrylate (MMA) provides rigidity and cohesive strength, preventing residue or peeling after labeling; 5% styrene (St) introduces a benzene ring structure, which significantly enhances the heat resistance and creep resistance of the adhesive layer, enabling it to withstand drying temperatures of 65~80℃ without becoming tacky. 2% acrylic acid (AA) provides emulsion stability and active sites for crosslinking; 1.5% hydroxyethyl methacrylate (HEMA) participates in the cross-linking reaction, enhancing cohesion; 1% diacetone acrylamide (DAAM), together with the subsequently added adipic dihydrazide (ADH), constitutes a room temperature latent crosslinking system, which allows the adhesive to have good flowability in the early stage of coating and drying, making it easy to form cutouts, and to slowly crosslink during later storage or use, continuously improving heat resistance. 0.8% adipic acid dihydrazide (ADH) is used as a post-crosslinking agent, which reacts with DAAM during the drying process to form a network structure; 0.8% sodium dodecyl sulfate (SDS), anionic: provides initial emulsifying ability; 1.2% alkylphenol polyoxyethylene ether (OP-10), nonionic: improves the electrolyte stability of the emulsion; 0.5% sodium allyl hydroxypropyl sulfonate (COPS-1), a reactive emulsifier: participates in copolymerization, bonds to the polymer chain, fundamentally reduces emulsifier migration, and improves water resistance and adhesion stability; 0.2% n-dodecyl mercaptan (n-DDM) is used as a chain transfer agent to precisely control the molecular weight and distribution of the polymer, giving the adhesive suitable rheological properties and facilitating stencil coating. 0.5% ammonium sulfate (APS) is used as an initiator, and a semi-continuous dripping process is adopted to ensure that the monomer conversion rate is >99%, the residual monomer content is extremely low, and it is environmentally friendly and harmless. The balance is 2-ethylhexyl acrylate (2-EHA), which provides excellent initial tack and segmental flexibility, ensuring that the adhesive can quickly wet the surface to be bonded (such as glass bottles and plastic bottles) at room temperature.

[0069] Pressure-sensitive adhesives, through the synergistic effect of monomer blending, functional monomers, and emulsifiers, achieve fidelity, high initial tack, and long-term durability of perforated patterns under high-speed coating. They possess the following characteristics: 1. Unique monomer combination: Through the compounding of 2-EHA / BA / MMA / St, the optimal balance is achieved between initial tack, cohesive strength and heat resistance.

[0070] 2. Composite crosslinking system: AA / HEMA / DAAM and post-crosslinking agent ADH form a room temperature latent crosslinking network, giving the adhesive both good coating applicability and end-use performance.

[0071] Step 5: Cut the coated labels into strips, then roll them up to form loop labels, and then pack them into boxes for storage. After rolling, the adhesive must not transfer to the other side of the material.

[0072] The method for applying self-adhesive ring labels includes the following steps: Step 1, Automatic Can Import: Cans to be labeled (such as glass bottles, plastic bottles or metal cans) are continuously imported into the labeling station through an automated conveyor system to ensure the continuity and efficiency of the process.

[0073] Step 2, Precise Label Cutting: The labeling machine's cutter cuts the label at the pre-set glue-free gap between the self-adhesive layers of the loop label. This gap is designed based on the principle of "gap = cutter thickness + 0.2mm" (for example, when the cutter thickness is 0.5mm, the gap is 0.7mm), ensuring that the cutter only contacts the glue-free area, avoiding glue adhesion and significantly extending the blade's life.

[0074] Step 3, Positioning and Alignment: The cut label is picked up by a robotic arm or vacuum suction cup system and precisely positioned at the preset labeling position on the can to ensure the alignment accuracy of the label when it surrounds the container.

[0075] Step 4, Loop Application: The label automatically wraps around the container surface thanks to its pre-applied pressure-sensitive adhesive (water-based acrylic emulsion). One side of the self-adhesive layer adheres directly to the container, while the other side is pasted onto the label, forming a secure loop structure without the need for additional adhesive.

[0076] Step 5, Pressing and Fixing: Finally, apply uniform pressure to the attached label using a pressure roller or platen device to ensure full contact between the self-adhesive layer and the can surface, improving adhesion strength and durability. During labeling, only slight pressure is needed for the self-adhesive layer to wet the container surface and form initial tack. The self-adhesive layer already possesses complete pressure-sensitive adhesive properties. The labeling machine only needs to complete the "cut-position-apply-press" actions, and the self-adhesive layer can firmly bond to the container surface and the other end of the label under normal temperature and pressure, forming a loop structure.

[0077] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a self-adhesive ring label, characterized in that, Self-adhesive loop labels consist of a release layer, a substrate layer, a primer layer, a printing layer, and a self-adhesive layer stacked sequentially. The self-adhesive layer uses a water-based acrylic emulsion pressure-sensitive adhesive. The self-adhesive layer is divided into several independent sections, with adhesive-free cutouts between adjacent sections, and the width of the adhesive-free cutouts is greater than the thickness of the cutter. After drying and curing, the coated labels are cut into strips and then wound up to form loop labels.

2. The method for preparing the self-adhesive ring label according to claim 1, characterized in that, Includes the following steps: Step 1, apply release layer to the back; First, octadecyl isocyanate is heated to 60°C and maintained at a constant temperature to completely melt it into a homogeneous liquid phase; then, chlorooctadecane is added at a mass ratio of 3-6 parts, and mechanically stirred at a speed of 200-300 r / min for 20-30 minutes to ensure thorough mixing. Finally, slowly add polyethylene powder at a mass ratio of 1 to 3 parts, controlling the feeding rate at 5 to 10 g / min, while increasing the stirring speed to 400 to 500 r / min and continuing to stir for 40 to 60 minutes. The above mixture was uniformly coated onto the back side of the substrate layer using a microgravure coating device at a coating speed of 15-20 m / min, with the coating amount precisely controlled at 2.5 g / m. 2 The thickness fluctuation range is ≤±0.1μm; after coating, the substrate layer enters an 80℃ hot air circulation drying tunnel with a wind speed of 2~3m / s and a drying time of 30~45 seconds, finally forming a release layer with a thickness of 0.5~1.0μm.

3. The method for preparing the self-adhesive ring label according to claim 2, characterized in that, Also includes: Step 2, varnishing and primer treatment; this step adopts an integrated process of online plasma corona treatment and water-based primer coating. First, the front side of the substrate layer is pretreated; biaxially oriented polypropylene film is selected as the substrate, and its thickness is controlled within the range of 20~30μm. During the pretreatment stage, surface contaminants are removed using an electrostatic dust removal device to ensure that the surface cleanliness of the substrate meets the ISO Class 8 standard. The substrate layer was then subjected to online plasma corona treatment; an atmospheric pressure plasma treatment system was used, with a high-frequency power supply output of 5kW, an operating frequency of 13.56MHz, and a power density maintained at 5W / cm². 2 During the process, the film transmission speed is precisely controlled at 200 m / min, and the electrode spacing is set to 1.0~1.5 mm. The plasma working gas is a mixture of nitrogen, argon and oxygen with a volume ratio of 85:10:5, and the processing temperature is stabilized in the range of 40~60℃.

4. The method for preparing the self-adhesive ring label according to claim 3, characterized in that, Also includes: Step 3, coating the printing layer; This step employs a precision coating process to prepare a printed layer on the surface of a substrate that has undergone plasma treatment and primer coating. The alcohol-soluble, environmentally friendly printing ink is selected, and its coating amount is precisely controlled within the range of 2~5g / m². The ink viscosity is adjusted to 500~800 mPa·s, the pH value is maintained at 6.5~7.5, and 1.5~3% by mass of modified high chlorine-containing chlorinated polypropylene resin is added to the ink formulation as an adhesion additive. The printing process is achieved using a high-speed gravure printing machine, with the anilox roller line count set to 150~200 lines / inch and the printing speed controlled at 200~300m / min; the coating uniformity is monitored by an online spectral detection system, with a color difference ΔE≤1.5; the hot air temperature is 60~80℃, the wind speed is 2~3m / s, and the drying time is 20~30 seconds.

5. The method for preparing a self-adhesive ring label according to claim 4, characterized in that, The ink comprises the following components by weight percentage: 60-70% water-based UV acrylic resin; 1.5~3% modified high-chlorine chlorinated polypropylene resin; 5% dodecyl acetate; 5% propylene glycol monopropyl ether; 5-8% edible alcohol; The remainder is deionized water.

6. The method for preparing a self-adhesive ring label according to claim 4 or 5, characterized in that, It also includes step 4, localized application of the self-adhesive layer; this step uses precision localized coating technology to prepare a self-adhesive layer with a segmented structure on the surface of the printed layer; The self-adhesive layer is divided into several independent sections by laser-engraved hollow molds; The die-cutting mold has a surface laser-engraved to form a micro-cell structure with a cell depth controlled between 20 and 50 μm and a line count of 150 to 200 lines per inch. In areas where adhesive segments need to be formed, the cells are arranged regularly. In areas corresponding to the cutout area, the cells are completely ground flat to form cell-free regions. During operation, the adhesive remains only within the cells. When the die-cutting mold comes into contact with the film substrate, the adhesive is transferred through a pressure contact device, ultimately forming an array of adhesive segments with predetermined gaps on the substrate surface.

7. The method for preparing a self-adhesive ring label according to claim 6, characterized in that, In addition, step 4 requires the self-adhesive layer to be dried and cured using a three-stage hot air circulating oven. The first stage, with a temperature of 65~70℃, allows for the initial evaporation of moisture, and the time is controlled at 3~5 seconds; The second stage involves a temperature of 75-80℃ to promote cross-linking of the adhesive layer, with a time control of 5-8 seconds. The third stage involves a temperature of 70-75℃ to complete the final curing process, with a time control of 3-5 seconds. The total length of the hot air circulating oven is 6~10m, and the ventilation system is equipped with a high-pressure centrifugal fan with an exhaust volume of 12.0~18.0m³. 3 / h, exhaust volume 8.0~14.0m³ 3 / h.

8. The method for preparing a self-adhesive ring label according to claim 7, characterized in that, The self-adhesive layer comprises the following components by weight percentage: 20% butyl acrylate; 25-30% methyl methacrylate; 5% styrene; 2% acrylic acid; 1.5% hydroxyethyl methacrylate; 1% diacetone acrylamide; 0.8% adipic acid dihydrazide; 0.8% sodium dodecyl sulfate; 1.2% alkylphenol polyoxyethylene ether; 0.5% sodium allyl hydroxypropyl sulfonate; 0.2% n-dodecyl mercaptan; 0.5% ammonium sulfate; The balance is 2-ethylhexyl acrylate.

9. A method for applying a self-adhesive ring label, characterized in that, Includes the following steps: Step 1, Automatic Can Import: The cans to be labeled are continuously imported into the labeling station through an automated conveyor system; Step 2, precise label cutting: The cutting blade of the labeling machine cuts at the preset glue-free gap between the self-adhesive layers of the loop label; the loop label is a self-adhesive loop label as described in any one of claims 1 to 8; Step 3, Positioning and Alignment: The cut label is picked up by a robotic arm or vacuum suction cup system and precisely positioned at the preset labeling position on the can to ensure the alignment accuracy of the label when it surrounds the container; Step 4, Loop Application: The label automatically wraps around the container surface thanks to its pre-applied pressure-sensitive adhesive; one side of the self-adhesive layer adheres directly to the container, and the other side is pasted onto the label, forming a strong loop structure. Step 5, Press and Fix: Finally, apply uniform pressure to the attached label using a pressure roller or pressure plate device to ensure that the self-adhesive layer is in full contact with the surface of the can.