Surface treatment equipment

The treatment with flames is one of the oldest technologies for the activation of polymer surfaces. The flames are used to produce highly reactive chemical species which are able to oxidize polymer surfaces. This technology has found wide spread application on large scale in polypropylene industry in particular.

We cooperate with the company EsseCI s.r.l. in Narni (Italy) to develop flame treatment technologies of the future. A treatment head with a width of 30 cm is installed in our film converting machine.

For lab-scale developments and in preparation for roll-to-roll treatments in the converting machine the burner can be mounted into a linear motion system. The linear system can be run at speeds of up to 8 m/ s (480 m/ min) and moves sheet materials through the flame. Polymer films are mounted on an aluminium cooling block allowing the treatment of very thin films with minimum thermal impact. This kind of experiments is very quick and well suited for a parameter screening before running experiments on the converting equipment.

The machine can convert films with a width of up to 30 cm with a variable configuration. The web speed can range from 0.5 m/min to 80 m/min. The equipment comprises

• Vetaphone corona treater
• EsseCI flame treater
• various printing stations
• spray unit
  
• hot air drier
• laminator
• edge control
• heating/ chilling rolls
• steam generator

The stainless steel chamber is pumped by a turbomolecular pump and a rotary backing pump. A base pressure of 1e-6 mbar can be realized. The pressure in the chamber can be controlled by a butterfly throttle valve. The system can be equipped alternatively with a pulsable microwave (MW) electron cyclotron resonance (ECR) plasma source (Roth & Rau, Germany; 1200 W) or with a down stream radio frequency (RF) source (Fraunhofer IAP, 13.56 MHz, 1200W). In both cases the substrate holder can be biased by a DC or RF voltage. All the system parameters including pressure, gas flow, and plasma power are controlled by a computer.

With a continuous treatment add-on web materials (films or textiles) can be exposed to the plasma. The material can be up to 30 cm wide. The maximum roll diameter is 26 cm. Both rolls are placed in a separately pumped compartment which allows a better control of the outgassing and drying of the material. The roll compartment is pumped by a rotary pumps and a roots pump.

The reactor was designed to minimize memory effects which are often observed when different types of plasma treatments are done in one reactor. This system is made of exchangeable parts. The heart of it is a pyrex tube with 16 cm inner diameter. For every type of process a tube is used which is dedicated only to this particular treatment type. All other parts can be cleaned easily by sand paper. 

The RF power is coupled into the glass tube via two copper ring electrodes. The sample holder hangs down to the bottom in order to avoid the deposition of powdery product from the plasma. It can be placed at different position in the system.

The lamp is a Xenon Excimer double tube system with a length (= treatment width) of 30 cm. It emits at 172 nm. The sample chamber can be pumped for treatments in vacuum or it can be filled or flushed with a gas. In a stationary treatment we can irradiate samples with a maximum size of 50 mm x 300 mm. A web can have a maximum width of 300 mm and it can be moved in a programmable regime with a maximum speed of 80 m/min. With this equipment the web can also be exposed to gaseous and liquid agents.

Plasma treatments often require specialized equipment for a particular object to be treated. On the other hand parts of the equipment are the same such as a vacuum pump, an energy source for igniting the plasma, gas supplies including flow controllers, sensors e.g. for pressure measurement, a computer for controlling the equipment and for monitoring the status of the equipment, the sample, the process etc.

To be able to set up a special plasma treatment quickly we designed a framework with all this generic equipment and with space for the actual reactor for this particular kind of process. For example, the reactor can be a small chamber adjusted to the shape of the object to be treated, a fluidized bed reactor for the treatment of powders or a simple pot-like chamber with a port for a transport lock allowing the vacuum transfer of treated samples to the XPS analysis.

The linear transport system is used to move samples through one or more treatment zones. The speed can be varied along the path with a maximum of 6 m/ s (360 m/ min). The speed range allows simulating roll-to-roll treatments in a rather simple, time and cost efficient way. This is useful for narrowing down the range of treatment parameters before doing the actual R2R experiments for the final adjustments.

The system can be equipped with a flame treater as it is used in the film converting machine. Instead of the flame treater various plasma sources can be used for activation. These processes can be combined with various other treatments as gas or aerosol treatments or coating processes.

The system can be complemented with 2 more moving axes for carrying equipment. For example, flame treatments can be “written” on a surface with a capillary feeding the burning gases.