A Comprehensive Analysis of Four Main Film Lamination Processes: Dry, Wet, Solventless, Extrusion Lamination—Which to Choose?

Choosing the wrong lamination process may lead to substandard peel strength at best, and excessive solvent residue and constant customer complaints at worst. This article breaks down four mainstream lamination processes in detail to help you make the right choice for your flexible packaging production.

Film lamination is the core process in flexible packaging manufacturing.

What is Film Lamination?

Film lamination is the process of bonding two or more layers of films together with adhesives or hot-melt methods, enabling the composite film to combine the advantages of each layer of material.

Why laminate? Because no single-layer film can meet all application requirements at once:

Requirement	Suitable Materials
Printability	BOPET, BOPP
Oxygen Barrier Property	EVOH, PVDC, Aluminum
Water Vapor Barrier Property	PE, PP, Aluminum Foil
Heat Sealablity	PE, CPP
Machanical Strength	BOPET, BOPA
Retort Resistance	BOPET, BOPA, CPP

Lamination allows us to "learn from each other's strengths to offset weaknesses" and design packaging structures that meet specific requirements.

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Comparison of Four Main Lamination Processes

Different lamination processes are suitable for different product needs.

Process 1: Dry Lamination

Principle: Apply solvent-based adhesive on one film, evaporate the solvent in an oven, bond it with another film between hot pressure rollers, and complete lamination after curing.

Process Flow: Unwinding Film A → Adhesive Coating → Oven Drying (Solvent Evaporation) → Lamination Pressure Rollers ← Unwinding Film B → Winding → Curing Room (40–50°C, 24–72h)

Parameter	Typical Range	Description
Coating Weight	2.5-4.5 gsm (dry basis)	Adjusted by structure and application
Oven Temperature	60-80℃ (3-stage increasing)	Source: Henkel Liofol Application Guide
Lamination Pressure	0.3-0.6 MPa	-
Lamination Speed	150-300 m/min	-
Curing Temperature	40-50℃	-
Curing Time	24-72 hours	Depends on adhesive system

Adhesive System

1. Two-component polyurethane adhesive (most commonly used): Main agent (polyol) + Curing agent (isocyanate)
2. Common solvent: Ethyl acetate
3. Typical products: Henkel Liofol Series, Dow ADCOTE Series, Beijing Gaomeng Series

Advantages

1. Widest application range, compatible with almost all material combinations
2. High lamination strength (peel strength usually >2.0 N/15mm)
3. Retort resistant (when using retort-resistant adhesives)
4. Mature technology and high equipment popularity

Disadvantages

1. Use of organic solvents (ethyl acetate) leads to VOCs emission and solvent residue risks
2. Solvent residue control is a key challenge (national standard requires ≤5 mg/m²)
3. Need for solvent recovery system with high environmental protection investment
4. Long curing time occupies inventory space

Application Scenarios

High-end food packaging, retort packaging, aluminum foil lamination, high-barrier structures.

Process 2: Solventless Lamination

Principle: Apply 100% solid content solventless adhesive (no solvent contained) on the film with precision metering rollers, and directly bond it with another film.

Process Flow: Unwinding Film A → Precision Adhesive Coating (No Oven) → Lamination Pressure Rollers ← Unwinding Film B → Winding → Curing Room (35–45°C, 24–48h)

Parameter	Typical Range	Description
Coating Weight	1.2-2.5 gsm (100% solid content)	40% - 50% les than dry lamination
Lamination Temperature	40-60℃	Adhesive needs heating to reduce viscosity
Lamination Speed	200-450 m/min	Faster than dry lamination
Curing Temperature	35-45℃	-
Curing Time	24-48 hours	Slightly shorter than dry lamination

Adhesive System

1. Two-component solventless polyurethane adhesive: Main agent (polyol, viscosity 500–3000 mPa·s@40°C) + Curing agent (isocyanate)
2. Typical products: Henkel Liofol Solventless Series, Dow SYMBIEX Series, Coim Series

Advantages

1. Solvent-free, no VOCs emission, environmentally friendly
2. No solvent residue issue
3. Less coating weight with lower cost
4. Faster speed and higher production capacity
5. No oven required with low energy consumption

Disadvantages

1. Not suitable for aluminum foil lamination (low surface energy and poor wettability of aluminum foil)
2. Not suitable for retort packaging (inferior lamination strength and temperature resistance compared with dry lamination)
3. Extremely high requirement for adhesive metering precision (coating weight deviation <±0.1 g/m²)
4. Low initial tack, requiring careful handling after lamination

Application Scenarios 

General food packaging, daily chemical packaging, film/film lamination structures

Process 3: Wet Lamination

Principle: Apply water-based adhesive on one film, bond it with another film in the uncured ("wet") state of the adhesive, and then dry it in an oven.

Process Flow: Unwinding Film A → Adhesive Coating (Water-based Adhesive) → Lamination Pressure Rollers ← Unwinding Film B → Oven Drying → Winding

Parameter	Typical Range	Description
Coating Weight	2-5 gsm (dry basis)	-
Oven Temperature	70-100℃	Evaporate water
Lamination Speed	100-200 m/min	Limited by drying speed

Adhesive System

1. Water-based acrylic adhesive
2. Water-based polyurethane adhesive
3. Casein adhesive (traditional)

Advantages

1. Use of water-based adhesive, environmentally friendly
2. Low cost
3. Simple process

Disadvantages

1. Low lamination strength (usually <1.5 N/15mm)
2. At least one layer of material needs to be breathable (for water evaporation), not suitable for aluminum foil/aluminum foil or fully sealed film/film structures
3. Poor water resistance
4. Not suitable for high-requirement food packaging

Application Scenarios

Paper/film lamination, labels, low-requirement packaging

Process 4: Extrusion Lamination/Coating

Principle: Melt thermoplastic resins such as PE or PP through an extruder, coat them on the substrate surface in the form of a film, and bond with another film at the same time.

Process Flow: Unwinding Film A → Corona Treatment → Primer Coating (AC Agent) → Extruder T-die → Molten PE Curtain → Cooling Roll ← Unwinding Film B → Winding

Parameter	Typical Range	Description
Extrusion Temperature	280-330℃ (PE)	High temperature ensures oxidation and bonding
Coating Thickness	10-50um	-
Line Speed	100-300 m/min	-
Cooling Roll Temperature	15-30℃	-

Advantages

1. No adhesive used, no solvent residue
2. Extruded layer can serve as heat seal layer or barrier layer itself
3. On-line coating + lamination achievable
4. Suitable for mass production

Disadvantages

1. High equipment investment (extrusion lamination line usually >20 million RMB)
2. High extrusion temperature (280–330°C) limits substrate selection
3. Lamination strength depends on primer (AC agent) and corona treatment effect
4. Not suitable for thin coating (<10μm)

Application Scenarios: Tetra Pak packaging, paper/PE lamination, aluminum foil/PE lamination, mass packaging.

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Overall Comparison of the Four Processes

Comparison Item	Dry Lamination	Solventless Lamination	Wet Lamination	Extrusion Lamination
Adhesive	Solvent-based PU	Solventless PU	Water-based Adhesive	Hot-melt PE/PP
Coating Weight (dry basis)	2.5-4.5 gsm	1.2-2.5 gsm	2-5 gsm	10-50 um
Lamination Speed	150-300 m/min	200-450 m/min	100-200 m/min	100-300 m/min
Peel Strength	＞2.0 N/15mm	＞1.5 N/15mm	＜1.5 N/15mm	1.0 - 3.0 N/15mm
Solvent Residue	Risk exists	None	None	None
VOCs Emission	Exists	None	Extremely Low	Exists (flue gas)
Retort Resistance	√	□	×	□
Aluminum Foil Lamination	√	×	×	√
Equipment investment	☆☆☆	☆☆☆	☆☆	☆☆☆☆☆
Comprehensive Cost	☆☆☆☆	☆☆☆	☆☆	☆☆☆

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Selection Decision Guide

What do your products require?

1. Retort packaging (121°C)? → Dry Lamination (retort-resistant adhesive)
2. Aluminum foil-containing structure? Small batch → Dry Lamination. Mass production → Extrusion Lamination
3. General food packaging (film/film)? Sensitive to solvent residue → Solventless Lamination. General requirement → Dry Lamination or Solventless Lamination
4. Paper/film lamination? Low requirement → Wet Lamination. High requirement → Extrusion Lamination
5. Mass production & low cost? → Extrusion Lamination

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Common Problems and Solutions for Each Process

Problem 1: Bubbles (tunneling) after lamination

Causes:

1. Insufficient or uneven coating weight
2. Low oven temperature leading to incomplete solvent evaporation
3. Insufficient lamination pressure
4. Insufficient substrate surface tension (Source: Henkel Liofol® Troubleshooting Guide)

Solutions:

1. Check the state of coating rollers to ensure uniform coating
2. Increase oven temperature (especially the first stage)
3. Raise lamination pressure
4. Inspect corona treatment effect (surface tension ≥38 dyn/cm)

Problem 2: Excessive solvent residue

Causes:

1. Insufficient oven temperature or air volume
2. Excessive coating weight
3. Overly fast lamination speed
4. Improper adhesive mixing ratio

Solutions:

1. Optimize oven temperature gradient (recommended 60°C→70°C→80°C 3-stage increasing)
2. Control coating weight within the recommended range
3. Appropriately reduce lamination speed
4. Mix adhesive strictly according to ratio

Problem 3: Insufficient peel strength

Causes:

1. Inadequate substrate surface treatment
2. Insufficient coating weight
3. Incomplete curing
4. Improper adhesive selection

Solutions:

1. Ensure corona treatment dyne value ≥38 dyn/cm
2. Appropriately increase coating weight
3. Extend curing time or raise curing temperature
4. Select suitable adhesive according to material combination

Problem 4: Uneven coating weight

Causes:

1. Uneven metering roller gap
2. Adhesive viscosity change due to temperature fluctuation
3. Metering roller surface wear

Solutions:

1. Calibrate metering roller gap (precision requirement ±2μm) (Source: Nordmeccanica Technical Manual)
2. Stabilize adhesive temperature (fluctuation <±1°C)
3. Regularly inspect metering roller surface state

Problem 5: White spots after lamination

Causes:

1. Poor wettability between adhesive and substrate
2. Insufficient coating weight
3. Oil stains or exudates on substrate surface

Solutions:

1. Select adhesive with better wettability
2. Appropriately increase coating weight
3. Clean substrate surface

Problem 6: Severe neck-in

Causes:

1. Excessively large air gap between die and cooling roll
2. Low extrusion temperature
3. Low resin MFR

Solutions:

1. Reduce air gap distance
2. Raise extrusion temperature
3. Select resin with higher MFR

Problem 7: Low lamination strength

Causes:

1. Uneven or insufficient primer (AC agent) coating
2. Poor corona treatment effect
3. Insufficient extrusion temperature (inadequate oxidation)

Solutions:

1. Optimize AC agent coating process
2. Ensure corona treatment dyne value ≥40 dyn/cm
3. Appropriately raise extrusion temperature (avoid excessive temperature causing flue gas and odor)