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‘Chromatografting' imparts barrier to paper

‘Chromatografting' imparts barrier to paper
BT3 Molecules

BT3 Molecules


BT3 Technologies' self-coined chromatografting (see sidebar at end) technology imparts a barrier to paper substrates using "green chemistry," taking its inspiration from aquatic birds like ducks and swans that can glide through water without getting soaked. You may never have considered that the secret to waterfowls' water repellency is hydrophobic ("water hating") waxes in the form of esters between long-chain alcohols and long-chain fatty acids.

 

Now the start-up company wants to see its technology take flight with the development and commercialization of products and processes of green chemistry dedicated to cellulosic materials with these unique properties:

• Water repellence

• Grease repellence

• Gas barrier properties

• Remain recyclable and biodegradable.

 

The company's main targeted markets are papers and corrugated cases, food packaging and textiles.
What the company's researchers saw several years ago was a pressing need for the development of new technological solutions that would allow the production of papers and boards with good barrier properties that did not hamper their sustainability characteristics. To this end, the BT3 team has been working for some time on the potential of molecular grafting to achieve barrier properties using cellulosic substrates.

 

In 2010, Cleantech was formed in Grenoble, France, with a six-person staff and backed by 15 years of R&D from the CNRS-CERMAV (www.cermav.cnrs.fr) and with a five year partnership with the French pulp and paper technical center, Centre du Papier Technique (CTP, www.webctp.com). BT3 was formed to develop and sell products and processes of green chemistry dedicated to cellulosic materials.

 

Update at TAPPI symposium

 

What has come out of that group is summarized in an abstract for a technical paper that BT3 presented last September at the 12th Technical Assn. of the Pulp and Paper Industry (TAPPI) Advanced Coating Fundamentals Symposium that provides a good overview into what their development is about: "Cellulose-based products such as papers and boards are exceptionally versatile and attractive materials notably from the point of view of sustainability.

 

"Compared to their plastic film competitors, their application potential is however hampered by their lack of barrier resistance to water, grease and gases. Composite multilayer structures have then to be [developed and produced], with an obvious, strong negative impact on sustainability. Chromatografting (or chromatogeny) has been shown to be able to provide a partial answer to this problem. It involves the molecular grafting of long-chain natural fatty acids upon the external OH groups of cellulosic fibers. The resulting hydrophobic effect provides excellent barrier properties to liquid water while being fully compatible with paper sustainability.

 

"We show that the application potential of chromatografting may be extended to grease and gases barrier thanks to the prior coating of specific polyvinyl alcohol (PVOH or PVA) layers. We further show that the barrier properties of chromatografted PVOH layers may be enhanced through the addition of PVOH coated particles that are coined smart reacto­chromatogenic particles."

 

What this all means is that the company's basic technology can produce water-resistant paper substrates and, by employing a PVOH-treated substrates preprocess, can add grease and gas barriers to the finished products. Furthermore, using specialized PVOH-coated particles yields even higher barriers.

BT3 is developing three levels of barrier materials that are being developed in the following priority order with ascending barrier properties:

 

1. Fatty acids chromatografted using conventional paper renders it water-resistant;

2. Fatty acids chromatografted using PVOH paper adds grease and gas barriers;

3. Fatty acids chromatografted using PVOH paper "predecorated" with smart reacto-chromatografting nano/micro particles such as clays, talc or calcium carbonate provide high-barrier protection.

 

 Ambient pressure, high-speed process

 

Fundamental to the whole process is the control of the vapor pressure, which makes it possible to deposit on the surface of paper, at very high speed, an extremely thin layer of molecules of plant origin (fatty acids) and also triggers a reaction to render the paper hydrophobic. BT3's prototype processing system at the CTP uses a web width of up to 240mm (9 1/2 inches) at a speed to 400 m/min. (1,312 ft/min) to treat a paper weight of 30 to 400 g/m² and a reel diameter of 1,200mm (47 inches). The reaction occurs at ambient pressure at temperatures from 120 to 180° C (248 to 356° F) over a period of one second.

 

Olivier Muquet, BT3 Technologies' marketing and sales manager, compares the process to printing. "Basically, the process is similar to a printing process: We apply fatty chlorhyde acids in a liquid state onto paper; then we increase the temperature to bring it to a gaseous state. That allows the entire surface of papers to be protected from water because of the direct chemical bond between surface hydroxyls and fatty acids."

 

The grafting occurs in three dimensions and somewhere between "onto" and "into" the paper substrate, he adds.
Muquet reports that what they are seeing with the technology is the increased performance of cellulosic materials and the reduction in the amount of material (fibers) used: "Our technology protects boards from water and humidity and reduces their thickness. The technology, which can be applied both on roll-to-roll material and also on three-dimensional objects such as molded [pulp], appears very promising."

 

These sustainable chromatografted materials may also help offset a growing trend toward carbon taxes and related "eco taxes" aimed at complex materials that are difficult to recycle or are non-biodegradable.
Muquet acknowledges that one of the challenges they face is to depose (remove) the PVOH layers without creating pinholes in the high barrier applications.

 

The company has a general strategy related to geography. "Our target markets are first Europe and the U.S., and then we will look to expand worldwide," he says. "We are looking for local industrial partners for all those markets. To accelerate our growth, we are currently in a fundraising process and are open to discuss U.S. venture capital opportunities."

 

Muquet tells Packaging Digest the company is currently involved in about 20 developments with industrial partners in different fields including corrugated board packaging.

 

BT3 Technologies, +33 458 001 273.

www.bt3technologies.com

 

TAPPI, 800-332-8686.
www.tappi.org

 

SIDEBAR: Chromatografting: A hybrid of two techniques
As defined by Wikipedia, chromatography is the collective term for a set of laboratory techniques for the separation of mixtures. The mixture is dissolved in a fluid called the mobile phase, which carries it through a structure holding another material called the stationary phase. The various constituents of the mixture travel at different speeds, causing them to separate. The separation is based on differential partitioning between the mobile and stationary phases. A subtle difference in a compound's partition coefficient result in different retention on the stationary phase thus changing the separation.


Another source puts it far more succinctly: A method to separate the components of a substance for analytical purposes.


Grafting is a horticultural technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together.


BT3's hybrid version combines these two scientific methods using heat and vapor pressure to graft biosourced fatty acids onto (or into) paper substrates to provide the barrier properties desired. The company claims the solvent-free method maintains the recyclable and biodegradable behavior of the new material.

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