Hints For Using A Roller Laminator

Helpful Hints

Practical Hints for Using A Roller Laminator

Dr. Hans Schuurmans

President and Technical Director

Purpose and Essence

Roller laminators are used to form multilayer structures of film and foils or can be used to put flexible flat goods on rigid substrates (mounting). They can use either a pressure sensitive or heat activated adhesive. The essential part is a nip formed by two rollers that are usually rubber clad. This rubber is frequently a silicone based material to prevent sticking of adhesive to the rollers. The rollers can be cold (room temperature) or heated.

Adhesives and Substrates

Adhesives can be applied during the process of laminating or they are pre-applied to the films or foils used. If they are pre-applied, giving some tackiness to the carrier film, frequently a removable liner (release liner) is used that is discarded after processing.

Adhesives come in numerous chemical varieties. They form a chemical bond with their substrates, bond through physical affinity or plain depend on penetration into the webs to bond, which webs then must be porous. To bond well, the adhesives must not only grab the surfaces they intend to bond, but also have internal strength (good cohesive and peel strength). If the finished sandwich is subject to physical deformation, the properties of the adhesive must be elastic, but have good resistance to breakage (high tensile strength and good sheer strength). An adhesive that resists deformation has a high modulus.

It is important to select an adhesive that has good affinity to the surfaces to be bonded and the right internal properties. Generally knowing the surface energy of surfaces to be bonded is a good guide in selecting the correct adhesive. Most adhesive manufacturers will indicate if their product is to be used on high or low surface energy surfaces. Bonding a low surface energy material (such as a polyolefin) to a high surface energy product generally dictates using a two or more layered adhesive. This can be accomplished by putting two different adhesives on a carrier that has been primed differently on each side.

Application Variables

The variables of importance during laminating are:

temperature
time (speed of operation)
nip pressure
hardness of the roll surface
tension on web

Generally, a better appearing bond can be made by running slowly at elevated temperatures, although temperatures should not be so high that the adhesive becomes too fluid. With uneven surfaces, a soft surface roller is the best, but deformation of sandwich structures that are pliable could become a problem with such rollers, especially when high pressure is applied. To prevent deformation and yet get the best results with most commonly used surfaces in laminating graphics, the rubber used in cladding the nip rollers has a shore hardness of somewhere around 80. Tension should be even across the width of the roll and not so high that the web has a tendency to neck-in.

Preparation

Before starting:

Make sure the nip rollers are clean and parallel and that speed dials are set to lowest speed.

There should be no obstructing material in the path of the work to be processed.

Have tools handy that you might need..

Surface of feed and receive tables should be slick (not sticking to adhesive) by covering with old liner or Teflon coat.

When applying volatile liquid adhesives, work in a well ventilated atmosphere and use precautions listed by vendor.

Running

Set-up for film laminating:

Make sure adhesive on rolls are facing the right way.

Position adhesive film taut on both sides with help of a leader board. Organize systematic take-up of used liner where applicable and adjust pressure to desired level.

When putting a laminate on un-mounted print, be sure print is positioned on slick board (e.g. board covered with old liner).

Operations When Applying Adhesive Films:

Place work to which adhesive surface has to be applied against leader board and start machine slowly. Make sure no flukes appear in the middle of the web (lower tension if they do) and that no wrinkles form in the web at the edge (lower pressure if they do).

Prepare the next piece of work and butt it against the preceding one, like the first piece of work was butted against the leader board. If there is time left over, increase speed gradually until a steady state is reached, whereby new work can be prepared for processing and corrections in operating conditions can be made "on the fly" without getting into a time bind.

Do not stop the machine in the middle of a laminating job since that will most surely leave a mark, especially on foam and when over-laminating.

Make sure that someone is collecting the finished work on the trailing end of the machine and cuts it loose from the following pieces of work.

Wipe print surface clean with special dirt removing rags.

Handle cutting tools with care so as not to injure individuals or damage the rubber surface of nip rollers.
Trim finished work on self-healing rubber mat.