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CN-121991622-A - Solvent-free adhesive for flexible package printing and preparation method thereof

CN121991622ACN 121991622 ACN121991622 ACN 121991622ACN-121991622-A

Abstract

The invention belongs to the technical field of solvent-free adhesives, and discloses a solvent-free adhesive for flexible package printing and a preparation method thereof, wherein the adhesive comprises a component A and a component B, wherein the component A comprises prepolymer polyisocyanate, fluorine modified chain segments and hydroxyl-containing reactive diluents; the B component comprises a multifunctional polyether polyol, an epoxy modified polyester polyol, and an adhesion promoter with hydrogen bond donor/acceptor groups. The invention ensures gradual release under the curing condition of 40-50 ℃ through a unique slow release mechanism, thereby avoiding insufficient leveling caused by over-fast initial reaction and shortening the whole curing period to 12-24 hours. Meanwhile, the nano hybrid filler with the surface modified by isocyanate or epoxy groups can strengthen the chemical combination with a polyurethane matrix to form a compact three-dimensional crosslinked network, further accelerate the curing process and improve the mechanical property, and the synergistic effect fundamentally solves the bottleneck of production efficiency.

Inventors

  • WENG YUSHAN
  • WEI HUA

Assignees

  • 浙江顺阳新材料科技有限公司

Dates

Publication Date
20260508
Application Date
20260119

Claims (10)

  1. 1. The solvent-free adhesive for flexible package printing is characterized by comprising a component A and a component B: the component A comprises prepolymer polyisocyanate, fluorine modified chain segments and hydroxyl-containing reactive diluents; the component B comprises a multifunctional polyether polyol, an epoxy modified polyester polyol and an adhesion promoter with hydrogen bond donor/acceptor groups; The A/B component is mixed and then forms a three-dimensional cross-linked network through the synergistic reaction of the nano hybrid filler and the slow-release catalyst, so that the rapid solidification and high initial adhesion are realized.
  2. 2. The solvent-free adhesive for flexible package printing as claimed in claim 1, wherein the fluorine modified chain segment is fluorine-containing end isocyanate or fluorine-containing polyether polyol, and the introduced amount of the fluorine modified chain segment is 2-10% of the total mass of the component A, so as to improve the heat resistance and the dielectric resistance of the composite film.
  3. 3. The solvent-free adhesive for flexible package printing as claimed in claim 1, wherein the reactive diluent is a hydroxyl-containing low molecular polyol or carbonate compound with a molecular weight of 100-500 g/mol, and is used for regulating the viscosity of the system and providing a quick reaction site.
  4. 4. The solvent-free adhesive for flexible package printing as claimed in claim 1, wherein the adhesion promoter is selected from amide group, urea group or phenolic hydroxyl group-containing compounds to form reversible force with the surface of the substrate through hydrogen bond at the initial stage of compounding, thereby remarkably improving initial tackiness.
  5. 5. The solvent-free adhesive for flexible package printing as claimed in claim 1, wherein the nano hybrid filler is selected from nano silicon dioxide, graphene oxide or organic montmorillonite, and the surface of the nano hybrid filler is modified by isocyanate or epoxy groups so as to enhance chemical combination with a polyurethane matrix and improve coating uniformity and mechanical properties.
  6. 6. The solvent-free adhesive for flexible package printing as claimed in claim 1, wherein the slow-release catalyst is formed by compounding a metal organic catalyst and a microporous carrier, can realize gradual release under the curing condition of 40-50 ℃, avoids insufficient leveling caused by over-fast initial reaction, and shortens the overall curing period to 12-24 hours.
  7. 7. The solvent-free adhesive for flexible package printing according to any one of claims 1 to 6, wherein the preparation method comprises the following steps: 1) Preparing a component A, namely reacting polyisocyanate with a fluorine modified chain segment in an inert atmosphere to obtain a prepolymer, and then adding a reactive diluent and a surface modified nano filler to uniformly disperse; 2) The component B is prepared by mixing polyether polyol and epoxy modified polyester polyol, and adding an adhesion promoter and a stabilizer; 3) Pre-dispersing a slow-release catalyst in the component B; 4) And (3) dynamically mixing the component A and the component B according to the mass ratio of 100 (80-120) by using solvent-free compounding equipment, coating, compounding, rolling, and curing for 12-24 hours at 40-50 ℃.
  8. 8. The solvent-free adhesive for flexible package printing as claimed in claim 7, wherein the nanofiller in the step 1 is treated by a dual process of ultrasonic dispersion and high shear mixing to ensure that the nanofiller is in a stable dispersion state in the A component.
  9. 9. The solvent-free adhesive for flexible package printing as claimed in claim 7, wherein the epoxy modified polyester polyol in the step 2 is further crosslinked with isocyanate in the curing process, so that the compactness and migration resistance of the adhesive layer are improved.
  10. 10. The solvent-free adhesive for flexible package printing as claimed in claim 7, wherein the peel strength of the finally prepared composite film is not lower than 1N/15 mm in 2 hours, the peel strength reaches not less than 3N/15 mm after curing for 24 hours, and the finally prepared composite film can resist boiling at 121 ℃ for 30 minutes without delamination or tack-free.

Description

Solvent-free adhesive for flexible package printing and preparation method thereof Technical Field The invention belongs to the technical field of solvent-free adhesives, and particularly relates to a solvent-free adhesive for flexible package printing and a preparation method thereof. Background The solvent-free compounding technology is one of the most widely applied and developed compounding technologies in the current flexible packaging field. The solvent-free adhesive adopted by the technology is mainly bi-component reactive polyurethane, and consists of an A component main agent containing isocyanate groups and a B component curing agent containing active hydrogen groups such as hydroxyl groups. The technological process includes mixing main agent and curing agent in certain proportion in special solvent-free compounding equipment, coating the mixture onto the first layer of base material via several heated coating rollers, and compounding with the second layer of base material via hot pressing roller. After winding, the composite film is sent to a curing chamber at a specific temperature, typically forty to fifty degrees celsius, for chemical crosslinking reaction, and finally a strong bond is formed. Compared with the traditional dry-process compounding process, the solvent-free compounding process has the advantages of no organic solvent, no emission of volatile organic compounds, high production speed, low energy consumption and controllable unit cost, and by virtue of the remarkable advantages, the solvent-free compounding process takes the dominant role in the packaging production of foods, medicines, daily chemicals and the like, and is recognized as an environment-friendly and efficient compounding scheme. Although solvent-free compounding techniques offer significant advantages, in actual production, its inherent process sensitivity and initial performance drawbacks also expose a series of substantial problems. One of the most prominent bottlenecks is the inefficiency of production caused by the excessively long curing cycle. The curing of solvent-free adhesives relies on polyurethane chemical addition reactions which are very slow at ambient temperature and must be cured by warming for twenty-four to seventy-two hours or more to achieve the final composite strength required for slitting or bagging. The long waiting time greatly prolongs the production period, occupies a large amount of storage space, causes the overstock of the product stock and the reduction of the fund turnover rate, further causes the product quality to be unable to be immediately judged, and causes huge loss once the problem occurs. Another key problem is the low initial adhesion of the adhesive. The composite film just taken off the machine has extremely low peel strength between two layers of base materials and can be separated almost easily. The low initial viscosity is extremely easy to cause quality defects such as tunnel effect, fold, edge curling and the like when the tension control is improper or the internal stress of the base material is larger, and is particularly serious when processing materials with higher rigidity such as aluminum foil or aluminum plating. At the same time, the control window of the process is very narrow. The final appearance of the adhesive is highly sensitive to parameters such as the mixing proportion of the main agent and the curing agent, the gluing temperature, the compound pressure, the surface tension of the base material, the ambient temperature and humidity and the like, any tiny fluctuation can cause defects such as white spots, crystal spots, orange peel, uneven coating and the like, and the skill of operators and the stability of the production environment form a serious challenge. Besides the challenges of the technological process, the existing solvent-free adhesive has deep hidden troubles in the aspects of final performance and chemical safety of products. First, the food safety risk associated with chemical migration. Since the stoichiometry of the two-component reaction is difficult to be absolutely precise, and the reaction process is susceptible to disturbances and cannot proceed completely, unreacted monomers, such as isocyanates, may remain in the cured glue line. More seriously, these residual monomers hydrolyze under specific conditions to produce primary aromatic amines with potential carcinogenic risk. When the small molecular substances are contacted with the package contents for a long time, the small molecular substances can migrate and permeate into foods, so that serious threat is formed to the health of consumers, and meanwhile, flexible package enterprises face strict regulation and supervision and brand reputation risks. Secondly, the product has insufficient adaptability to special applications. Traditional general solvent-free adhesives have limited heat and medium resistance and are difficult to meet increasing high performance packaging requirements