China’s national standard GB/T 10004-2008, effective August 1, 2009, set a residual solvent limit of 5 mg/m² for laminated flexible packaging films. This regulatory threshold — combined with rising environmental awareness and the clear economic advantages of solventless lamination — has triggered a rapid shift in the Chinese flexible packaging industry. Where only Shanghai Kangda Chemical initially produced domestic solventless laminating adhesives, now multiple Chinese manufacturers have entered the field alongside international suppliers including Henkel and Cromogenia-Units. The technology is evolving along four distinct development paths.
Development Path 1: General-Purpose Solventless Adhesives
General-purpose adhesives are the entry point for most converters new to solventless lamination. The priorities are straightforward: appropriate viscosity for the coating system, adequate open time for the lamination process, sufficient initial tack to hold the laminate during winding, and broad substrate compatibility.
For converters making the transition from solvent-borne to solventless, viscosity is the first operational challenge. Solventless adhesives have significantly higher viscosity than solvent-borne systems. If the viscosity is too high, the adhesive does not spread evenly on the coating roll, producing a non-uniform bond line, streaks, and localized bond failures. A minimum open time of 30 minutes is essential — this is the window between adhesive application and film nip during which the adhesive remains workable. Without adequate open time, the operator cannot complete the web-up and start the run before the adhesive begins to cure on the coating roll.
Equipment cleaning is another practical consideration. A solventless laminator requires 1–2 hours to clean thoroughly when changing adhesive types. For converters running multiple product families, changing between general-purpose and specialty adhesives requires careful scheduling to minimize downtime.
Development Path 2: Retort-Resistant Solventless Adhesives
Retort pouches — flexible packages that withstand steam sterilization at 121°C, 135°C, or even 145°C — have traditionally required solvent-borne adhesives because no solventless system could match the heat and hydrolysis resistance. The three sterilization tiers are:
- 121°C: 20–60 minutes depending on product — sufficient for most foods including meat (60 min), seafood and soy products (20 min)
- 135°C: Up to 20 minutes — achieves commercial sterility for aseptic packaging
- 145°C: 2–5 minutes — flash sterilization that destroys all heat-resistant pathogens including Clostridium botulinum spores
Each tier demands progressively higher bond strength retention after sterilization, resistance to hydrolytic degradation at temperature, and resistance to acid, oil, salt, and sulfur compounds in the food. Third-generation solventless adhesives have now reached 121°C capability for standard retort structures (PET/Al/CPP, PET/PA/CPP). 135°C solventless adhesives are in development but not yet commercially widespread. The gap between solventless and solvent-borne performance is narrowing, but for the most demanding retort applications — particularly those requiring 135°C or aggressive food media — solvent-borne systems remain the safer specification.
Development Path 3: High-Performance and Chemically Resistant Adhesives
As solventless lamination extends beyond standard snack food and dry goods packaging into more demanding applications, the adhesive must resist increasingly aggressive media: acids, alkalis, oils, solvents, surfactants, and pesticides. Chemical resistance requirements include:
- Resistance to DMF (dimethyl formamide) solvent residues below 20%
- Resistance to pesticide formulations containing organic solvents
- Resistance to surfactants in detergent and personal care packaging
- Resistance to essential oils and flavor compounds in food packaging
These applications require specially formulated adhesives with crosslink densities and polymer architectures that resist swelling, plasticization, and hydrolytic attack by the specific chemical environment. Unlike general-purpose adhesives, which can be formulated as a single universal product, chemically resistant adhesives must be tailored to the specific chemical challenge — requiring a product portfolio rather than a single grade.
Development Path 4: Fast-Cure and High-Speed Adhesives
Conventional two-component solventless adhesives require 24–72 hours at 40–50°C in a curing oven to reach full bond strength. For converters serving just-in-time customers with short order-to-delivery windows, this curing time is a production bottleneck. Fast-cure formulations achieve handling strength within 1–3 hours at elevated temperature, enabling same-day slitting and converting.
The trade-off with fast-cure adhesives is shorter pot life — the mixed adhesive has less working time before it becomes too viscous to coat uniformly. This places tighter demands on the metering and mixing system, the coating station temperature control, and the operator’s skill. For converters with high-speed laminators running at 300–600 m/min, the adhesive must be formulated not only for fast cure but also for stable viscosity at application temperature over the extended run duration.
The Chinese Market Transition
The solventless lamination market in China is at an inflection point. The installed base of solventless laminators has grown rapidly since 2009, driven by GB/T 10004-2008 compliance pressure. However, most converters are using general-purpose adhesives for relatively simple structures. The migration to higher-value applications — retort pouches, chemical-resistant packaging, high-speed lines — requires not only adhesive technology advancement but also process knowledge transfer from adhesive suppliers to converters. The adhesive suppliers that invest in technical service, application laboratories (analogous to Henkel’s Liofol lab), and converter training programs will capture the premium segment of the market as it matures.
References
- Wikipedia: Lamination: Dry-bond, solventless, and extrusion lamination processes for flexible packaging — equipment, adhesives, and process parameters.
- Wikipedia: Polyurethane Adhesive: Two-component PU adhesive chemistry, curing mechanisms, and performance tuning for flexible packaging applications.
- Wikipedia: Retort Pouch: Sterilization standards for retortable flexible packaging and the adhesive performance requirements for each temperature tier.
- Wikipedia: VOC: Regulatory limits on residual solvents in flexible packaging — the driving force behind China’s shift to solventless lamination.
- Wikipedia: GB/T 10004-2008: Chinese national standard for laminated flexible packaging films including the 5 mg/m² residual solvent limit.