The Dow Chemical Company

2531 Technology Drive, Suite 301, Elgin, IL 60124 Phone: 847-649-3800 Fax: 847-649-3760

100% SOLIDS LAMINATING 

Michael L. Leib

Technical Service Manager

Packaging and Converting

The Dow Chemical Company

Midwest Technical Center

Elgin, IL 60123

INTRODUCTION

100% solids laminating adhesives were developed in the mid-1970's to meet converters’ 

need to cut their solvent cost, energy cost, and to meet environmental regulations. Their 

choices to reduce emissions included: running high solids adhesives, solvent incineration, 

solvent recovery, aqueous adhesives or 100% solids adhesives. 100% solids adhesives 

were the only alterative which not only eliminates solvent emissions from the adhesive, 

but also lowered the converters’ energy cost. It eliminated the cost associated with the 

solvent recovery and incineration equipment.

Additional benefits to the converter include:

~lower adhesive coating weight

~no use of solvent diluents

~no retain solvents due to the adhesive

~faster line speeds

~favorable health and safety characteristics

100% solids adhesives are an extension of urethane chemistry which is well known for 

packaging adhesives. The primary difference between 100% solids adhesives and resins 

used in traditional solvent based dry bond adhesives is the adhesive molecular weight. 

The molecular weight of the 100% solids adhesives is significantly lower. Due to the 

lower molecular weights, initial bonds are significantly lower than those obtained with 

the solvent-based analogs. Therefore, laminating equipment with sensitive tension control 

and rewind systems are required to apply and laminate 100% solids adhesives. 

Furthermore, due to the reactivity of the two-component reactive 100% solids adhesive 

systems, meter, mix and dispense (MMD) equipment is required to handle the adhesive.

Guidelines for making successful laminates with 100% solids adhesives will be discussed 

in this paper.
The Dow Chemical Company

2531 Technology Drive, Suite 301, Elgin, IL 60124 Phone: 847-649-3800 Fax: 847-649-3760

THE ADHESIVES

100% solids adhesives are analogs to one and two-component solvent-based adhesives.

Traditional one and two-component solvent-based adhesives are medium to high 

molecular weight resins which are solubilized in an organic solvent. The solvent is 

present for many reasons: it may be used as a polymerization medium, solubilizing agent 

for the resins, viscosity control, adhesive application weight control, substrate wetting, 

and the adhesive film forming properties.

100% solids adhesives have good flow and film forming properties without the aide of 

solvents. In addition to having good runnability, they quickly develop bonds bond 

strength and the laminate can often be slit after 24 hours cure. Full cure is usually 

achieved in 7-10 days depending on the storage conditions and the adhesive used.

100% solids adhesives are supplied as both single-component and two-component 

systems. Some are applied at room temperature while others require heating.

SINGLE-COMPONENT ADHESIVES

Single-component adhesive systems are generally polyether urethane based on aromatic 

isocyanate and are commonly used in low performance applications. They need to be 

heated to 60-90C to reduce their viscosity for application. They require moisture to 

cure. The moisture enters the adhesive from atmospheric moisture, the film surfaces or 

that which is resident in the film (i.e. Nylon and PVOH film). A minimum amount of 

ambient moisture must be present for complete cure. This is not a concern in a warmer 

humid climate. For consistent performance humidification at the laminating nip is 

recommended to assure adequate moisture is present to complete the cure. 

Humidification is accomplished by introducing humidity as a very fine water spray or 

steam. The humidification system is usually directed at the secondary web. Do not spray 

directly on the adhesive. Care has to be taken so that water droplets are not sprayed or 

dropped onto the web.

TWO-COMPONENT ADHESIVES

The two-component adhesive systems can be either polyether and/or polyester urethane 

which is based on either aromatic or aliphatic isocyanate. These adhesives are targeted to 

replace two-component solvent-based adhesives which would be used in median and 

some higher performance applications. The two-component systems generally have 

better heat and chemical resistance that the single-component adhesives. Some of the 

adhesives are room temperature applied while others require heating to lower the 
The Dow Chemical Company

2531 Technology Drive, Suite 301, Elgin, IL 60124 Phone: 847-649-3800 Fax: 847-649-3760

application viscosity and to improve their flow. The two-component systems are designed 

so that their cure is mostly chemical and are not dependant on atmospheric moisture. 

Therefore, humidification is not required.

The room temperature systems are applied at slightly above the hottest ambient 

conditions (i.e. Room temperature is defined as the hottest ambient temperature) and can 

be pumped at ambient conditions. These systems are lower molecular weight than the 

single-component systems and are typically applied at 40-50C. The actual running 

temperature is dependant on the adhesive and line speed of the laminator.

The heated systems are higher molecular weight than the room temperature applied 

products. They are applied above 50C. Due to their high viscosity, they must be 

preheated to facilitate transfer to the MMD pump and to completely empty the containers.

The room temperature and heated two-component adhesive systems require the use of 

MMD equipment to ensure that the adhesive is properly and uniformly mixed. Most twocomponent systems are designed to have a mixed working time of 15-20 minutes. Batch 

mixing, as done with the solvent-based systems, is not recommended due to the high 

reactivity of the adhesive system. The 15-20 minute working time allows the machine 

operator time to make machine adjustments, web changes, etc., without having to 

completely clean the application unit when the laminator is restarted. Laminator 

stoppages of greater than 15-20 minutes would necessitate complete cleaning of the 

adhesive application unit and flushing of the adhesive meter, mix and dispense unit from 

the mixing head on.

SUBSTRATES

Most laminations currently made using dry bond adhesives can be made using 100% 

solids adhesive technology. The adhesive supplier should be contacted to determine the 

best adhesive for the application. As with dry bond adhesive technology the more stable 

substrate is generally coated. Often, this is the printed web. The secondary web is 

typically the sealant film.

EXAMPLES OF COMMERCIAL APPLICATIONS

~ Polyethylene / Polyethylene for personal care products, potting soil

~ Metalized Polyester / High Slip Polyethylene for coffee portion packaging

~ Polypropylene / Polypropylene for beverage bottle label, salty snacks

~ Polypropylene / Metalized Polypropylene for dry snack filling

~ Polypropylene / Polystyrene for beverage bottle labels
The Dow Chemical Company

2531 Technology Drive, Suite 301, Elgin, IL 60124 Phone: 847-649-3800 Fax: 847-649-3760

~ Polypropylene / Polyethylene for fresh produce

~ Polyester / Aluminum Foil / Polyethylene for coffee

~ PVDC coated Nylon / Polyethylene for meat and cheese

~ Nylon / Coextruded sealant film for thermoformed webs, meats

~ Polyester / Aluminum Foil / Coextruded sealant film for retort applications

~ Polyester / Polyethylene for hot fill

~ Many others

CORONA TREATMENT

Surface tension control of the substrates to be laminated is critical. Some film will be 

treated to the appropriate level prior to laminating, while others films will need additional 

treatment at the laminator to promote adhesion. In-line corona treatment at the laminator 

is recommended to raise the surface energy and to clean the film surfaces of film 

additives or other contaminates which may hinder adhesion. For example, on high slip 

polyethylene, the slip additive will migrate to the film surface over time and it will 

adversely affect adhesion. Polyethylene and polypropylene films have to be treated to a 

minimum surface energy level of 38 dynes/cm. When in-line treating films, care has to 

be taken to assure that you do not get backside treatment of the sealant film to avoid 

sealing problems.

Nylon and polyester films should be in-line corona treated to assure good adhesion. 

Zippery bonds may occur, depending on the adhesive, without retreatment.

PRINTING

Both Flexographic and Gravure printing processes are used to print substrates which are 

laminated with 100% solids adhesives. The inks which are used must be suitable for 

laminating. Complete drying of the inks is vital, especially with inks which contain 

alcohol diluents. Retain alcohols will react with the adhesive and alter the cure. CG 

analyses for retain solvents is recommended to ensure that the printing has been 

adequately dried. If the printed ink contains a high level of retain alcohol, the adhesive 

will not cure properly. It will have poorer heat resistance. It will have poorer product 

resistance. It will have and lower bond strengths in the printed areas. In contrast, 

adhesive performance in the non-printed areas will be largely unaffected because there is 

no retain in these areas to alter the adhesive cure. In addition, ink components which 

contain hydroxyl (-OH) groups or other functional groups which will react with the 

adhesive will alter the adhesive cure in a manner similar to that noted with alcohols.
The Dow Chemical Company

2531 Technology Drive, Suite 301, Elgin, IL 60124 Phone: 847-649-3800 Fax: 847-649-3760

ADHESIVE HANDLING

The adhesive should be stored in their original containers at 20±10C in a dry 

environment.

Depending on the adhesive system, one of the components will contain isocyanate groups. 

The isocyanate groups are chemically reactive and will react with water, alcohol, amines 

and similar materials which have active hydrogen. Opened containers should be resealed 

and kept tightly closed to maximize the storage life. Nitrogen purging of the containers 

will maximize the storage life after opening. If the adhesive is supplied in drums, a 

desiccant tube should be fitted on the drum to insure the makeup air entering the drum, as 

the adhesive is withdrawn, is dry.

ADHESIVE MIXING

METER, MIX AND DISPENSE EQUIPMENT

Two part 100% solids adhesives require the use of a meter/mix/dispense unit (MMD) to 

supply the adhesive to the laminator.

There are a number of suppliers of MMD equipment for reactive two component 

adhesive systems on the market. Equipment is available which will run both the room 

temperature applied and heated adhesive systems.

Most MMD pumps are variable ratio units which allow for the use of a variety of 

adhesives. The MMD units keep the adhesive components separate until the pump 

receives an electronic signal from the laminator that adhesive is needed. The adhesive is 

then mixed in the mixing block and supplied to the laminator.

ADHESIVE MIX RATIO

Running the adhesive at the recommended ratio is critical to assure that the adhesive 

performs as designed. The mix ratio should be monitored on a regular basis. Some of 

the MMD units are supplied with automatic mix ratio monitoring which will trigger an 

alarm when the pump is out of ratio. Others require manual ratio checks. Regular 

checking of the adhesive mix ratio will verify that the adhesive is properly mixed and 

will identify if an out-of-ratio situation has developed. Regular mix ratio checks will also 

help you identify when the MMD unit needs servicing. This will minimize suspect 

material. The mix ratio tolerance is dependant on the adhesive system being used.
The Dow Chemical Company

2531 Technology Drive, Suite 301, Elgin, IL 60124 Phone: 847-649-3800 Fax: 847-649-3760

IMPLICATION OF USING THE WRONG MIX RATIO

Laminations made using adhesive which contains excess amount of hydroxyl (-OH) 

component will not cure properly. The adhesive may remain tacky. The adhesive will 

exhibit reduced heat resistance, poorer product resistance and poorer bond strengths.

Lamination made with an improperly mixed adhesive which contains an excess amount 

of isocyanate (-NCO) component will be dependant on atmospheric moisture to complete 

the cure and may take a long time to cure, especially in a low humidity environment. The 

adhesive may remain tacky until an adequate amount of moisture has entered the 

laminate to complete the cure. In addition, if the adhesive is MDI (diphenylmethane 

diisocyanate) based, the potential for developing sealing problems due to the extended 

cure time is increased.

THE LAMINATOR

100% solids adhesives are coated by multi-roll differential speed smooth roll coaters. In 

this section I will discuss aspects of the adhesive application unit which will affect the 

quality of the laminate. I will also review the impact that tension control has on laminate 

quality.

THE APPLICATION UNIT

The application unit consists of a series of polished rubber and metal rollers which 

deposit the adhesive on the primary substrate. The roll temperature and quality will 

impact the adhesive flow properties and influence the coating appearance. In addition to 

the application rolls, the application unit also contains an exhaust system to vent vapors. 

There is also an adhesive distribution system with adhesive level control, and a 

laminating nipping station. I will also review adhesive coating weight typically run on 

various structures and aspects of housekeeping.

Roller temperatures

The application rollers are heated to reduce the adhesive viscosity to a suitable level 

which has good flow properties. Maintenance of a constant temperature on the 

application rolls is critical to controlling the adhesive coating weight. Precise 

temperature control is needed for both the hot applied and the room temperature applied 

systems. Temperature control for the heated systems must be very exact. Small changes 

in the temperature will cause larger changes in the viscosity of the heated systems. 

Viscosity changes will alter the adhesive flow, the coating weight, and appearance.
The Dow Chemical Company

2531 Technology Drive, Suite 301, Elgin, IL 60124 Phone: 847-649-3800 Fax: 847-649-3760

Typical temperatures of the heated steel rolls:

~Single component systems -- 60-90C

~Two-component room temperature applied systems -- 40-50C

~Two component heated systems -- >60C

The actual application temperature used to run the adhesive will depend on the adhesive 

system which and the line speed. Higher line speeds typically require higher roll 

temperatures. The rubber rollers on most application units are not directly heated. These 

rolls are heated through roller contact or supplemental IR heating.

Application Roll Quality

The quality of the application rolls will influence the flow of the adhesive onto the 

substrate. Defects in the rolls such as cracks, pits, lumps or hard adhesive residue will be 

seen in the lamination.

Exhaust

Good ventilation around the coating head is needed. It is important to assure that any 

vapors which may develop around the coating head are safely vented. At higher line 

speeds the 100% solid adhesive may exhibit misting in the application unit. Misting is 

atomization of the adhesive caused by adhesive splitting between the rollers. The mist 

must be exhausted when it occurs. It can be easily controlled by increasing the 

application roll temperature or slowing the line speed. If the application roll temperature 

is increased, the coating weight will drop and may have to be brought back into your 

targeted range. The exhaust is also needed while cleaning the application unit to remove 

any solvent vapors which are generated.

Adhesive Distribution and Level Control

The mixed adhesive should be delivered to the adhesive nip by a transverse feed 

mechanism to assure fresh adhesive is supplied to the entire width of the adhesive puddle. 

The application unit should also have a level sensor which is interfaced with the MMD 

unit to automatically supply adhesive as the adhesive level drops. The adhesive level 

should be kept as low as practical, especially for more reactive systems to minimize 

coating variations due to changes in the adhesive viscosity while running.
The Dow Chemical Company

2531 Technology Drive, Suite 301, Elgin, IL 60124 Phone: 847-649-3800 Fax: 847-649-3760

Coating weight control

Differential speed multi-roll coaters are a very good method of precisely applying 

adhesive.. The coating weight is control by a combination of the relative roll gaps and 

roll speeds. The application rolls must have true roundness and very low total indicated 

run out (TIR). Freshly mixed adhesive must be used whenever checking the adhesive 

coating weight. Freshly mixed adhesive will always have lower viscosity than mixed 

adhesive that has aged on the application unit. The lower viscosity material will coat at a 

lower coating weight than higher viscosity adhesive using the same application 

conditions. The coating weight may vary depending on the line speed and rheological 

properties of the adhesive. The coating weight should be check on material which was 

run at the target line speed. Coating weight adjustments are fine tuned by adjusting the 

speed of the applicator rolls. Ideally, the lowest possible coating weight to achieve the 

required laminate performance is desired.

Below are typical coating weights used in laminates:

~Unprinted film/film laminates -- 1.3-1.8 g/m2

~Printed film/film laminates -- 1.5-2.0 g/m2

~Printed film/metalized film laminates -- 1.8-2.5 g/m2

The coating weight used in laminated with high ink coverage is governed by the 

laminates optical appearance.

~Film/Paper -- 2.5-5.0 g/m2

~AF/Paper -- 2.5-5.0 g/m2

The coating weight on paper containing laminates is governed by porosity of the 

paper. More porous papers require higher coating weights.

~Film/AF -- 1.5-2.5 g/m2

The coating weight depends on the laminates’ end use application and adhesive. 

The coating weight has an influence on the cured laminate appearance. High coating 

weights will generally yield a laminate which has an orange skin like appearance in the 

unprinted areas. Low coating weights will have a bubble like appearance in the printed 

areas, especially with metalized film structures. Continuous unprinted areas of a laminate 

oriented in the machine direction are under lower rewind pressure that the unprinted areas 

which are oriented transverse machine direction. Therefore, the unprinted machine 

direction areas may have poorer optical appearance.
The Dow Chemical Company

2531 Technology Drive, Suite 301, Elgin, IL 60124 Phone: 847-649-3800 Fax: 847-649-3760

Nip conditions

The lamination nip will influence the laminate appearance. The actual nip temperature is 

determined by the substrates used in the structure. Optimal appearance is typically 

achieved by using the hottest nip temperature possible. Excessively hot nips may lead to 

tension control problems or laminate curl. Roll hardness and impression pressure also 

influence appearance.

The condition of the lamination nip rollers, like the application nip rollers, will affect the 

laminate appearance. The nip rollers should be clean and free of defects for optimum 

laminate appearance.

Tension Control

Good web tension control is very important in making a laminate with good appearance. 

Because the adhesives have low initial bonds and shear strength, it is critical that the 

laminator is designed to precisely control the tension on the substrates. Tension has to 

be well controlled from the unwinds to the rewind to avoid folds and creases in the 

finished roll. Laminates which are made without good tension control will typically 

exhibit severs curling or tunneling.

FINISHED ROLL STORAGE

It is a good idea to suspend the master rolls while they cure. Finished rolls of laminate 

should be stored at room temperature or above to cure. If the laminate is stored in too 

cold of an environment, the curing rate will be slowed or even stopped in some cases. 

The cure will continue once the roll is warmed. Most laminates can be slits after 2-3 days 

cure and will achieve complete cure in 7 -10 days depending on the storage condition and 

the adhesive used.