TYCEL 7900

• Product Description

TYCEL 7900 adhesive with TYCEL 7283 curing agent is a commercial, two-component, solventbased, polyurethane adhesive for flexible packaging laminating. The cured adhesive is optically clear, odor free and elastic.

• Target Application

Designed for high performance, film/film and film/foil food packaging laminations that require heat and chemical resistance. Its primary use is for laminations exposed to pasteurization, boiling water, sterilization and retort conditions.

Due to the wide variability of film additives, materials, surface conditions, process conditions, and performance criteria, pretesting on your substrates and production equipment is required to determine if this adhesive system will meet all your needs.

• Other Applications

This adhesive also can be used for general-purpose food packaging laminations, health care, pharmaceutical and cosmetic applications.

Adhesive Mixing Instructions

% Running:  Solids Determine the adhesive viscosity based on your application method, cylinder selection and desired coating weight. Typically, a coating weight between 1.5 – 2.0 lbs/ream (2.4-3.3 gm/m2 ) is used for standard laminations. The chart below may be used for reference and is typical for TYCEL 7900/TYCEL 7283 when diluted with Ethyl Acetate. Determine the % running solids required:

% Solids vs. Viscosity for TYCEL 7900 /TYCEL 7283

Solvent Selection: Select a dilution solvent. Urethane grade ethyl acetate is recommended. However, methyl ethyl ketone or acetone may also be used. Using a solvent other than ethyl acetate will change the viscosity curve shown above.

Water content of the selected solvent should not exceed 300 ppm. High water content of the solvent can cause an undesirable reaction with the isocyanate that can alter the final performance of the adhesive mixture.

Dilution: Calculate the amount of solvent required to dilute the adhesive and curing agent to the desired % running solids.

Adhesive Mixing : Weigh the desired amount of adhesive into a clean, dry container. While stirring under slow agitation, add the total amount of solvent calculated based on the desired batch size. Stir slowly for approximately 10 minutes. Slowly add the curing agent to the stirring adhesive mixture. Stir for an additional 10 – 15 minutes. Note: A slight cloudiness of the mixed adhesive during the addition of the curing agent is normal. Cover the container to prevent additional solvent loss.

Processing Information

Application Method: The recommended method of application for this adhesive mix is with a standard gravure roll coater. When using this type of conventional coating equipment, apply the adhesive at 30-45% TSC for best results. Depending upon the film or foil combinations, and the end use of the lamination, apply approximately 1.5 – 2.0 lbs/ream (2.4-3.3 gm/m2 ) coating weight of adhesive. Deep draw applications often require higher coating weights to accommodate the package elongation.

Drying Optimum: drying conditions are dependent on the specific machine speed, coating weight, dwell time, and efficiency of the dryer. A system with good air volume and exhaust is more effective than extremely high temperature to remove the solvents.

Example:

• 50 – 60°C at 165 fpm
• 60 – 80°C at 500 fpm

Dryers with multiple zones should be staged from a lower temperature in the first zone to higher temperatures in successive zones. This will facilitate solvent removal without adhesive skinning. Extremely high temperatures and over-drying the adhesive can result in cure irregularities and lower performance. Caution should be taken to establish the optimum process conditions for your equipment.

Combining Nip: The lamination of the primary and secondary substrates should exhibit excellent initial tack when combined at heated nip temperatures of 122-158°F (50-70°C). Pressure and temperature of the laminating nip may require adjustment based on the appearance, degree of wrap angle, dwell time, and thickness of the substrates.

Pot Life: Typically, this product at 40% solids in a closed container has a working time of 8 – 12 hours without substantial viscosity increase. However, solvent moisture content, relative humidity, temperature, solvent loss, and % running solids can all shorten the pot life of the adhesive mixture. Due to the chemical activity of the material, using material that is older than 8-12 hours is not recommended.

Viscosity Increase of TYCEL 7900 / TYCEL 7283 @ 25°C, 40% Solids

Curing: The laminate can be further processed, rewound and slit after 1-2 days of curing at room temperature. To achieve complete curing, i.e., total resistance to severe environments, allow 7-14 days of storage at room temperature. Cure rate may depend on film combination.

Equipment Clean: Up Clean up of the application station is accomplished with solvents such as ethyl acetate, methyl ethyl ketone, acetone, or toluene. Protective gloves should be worn.