Innovative surface treatment with foam coating technology Final Conference 20.6.2012 Karita Kinnunen, Tuomo Hjelt, Eija Kenttä VTT Technical Research Centre of Finland

Foam

Outline • Principles of foam coating • Benefits of foam coating • Foam coating facilities at VTT • Applications • Results • Conclusions

Foam coating intriguing surface treatment method Material development

?

Novel application methods

Foam coating

• Material properties • Price • Etc.

Conventional application methods

Novel products

Principles of foam coating vertex

•

Foam used as a carrier phase to transfer the coating material onto the substrate 2000 µm

•

2000 µm

Liquid containing foaming agents is mixed with air using a foam generator • Air content greater than 80%, preferably 90-95% Air content 66%

•

Application onto the moving web using a narrow slot type applicator

•

On the web the bubbles collapse due to absorption, leaving the coating material on the web surface

Air content 94%

Benefits of foam coating •

Non-contact application

•

No side streams

•

Allows very thin coatings, e.g. 0.5 gm-2 • Even application of small quantities on large areas • Air 90% -> instead of 1 µm layer 10 µm layer is applied • Less tendency to migrate into the substrate

•

Enables application of gel like material, e.g. NFC

•

For nanomaterials no binders required

•

Using modified materials possible to create activities to the substrate surface Versatile process

•

• Compatible with a wide range of materials • Higher concentrations possible, e.g. compared to spraying

• Occupationally safe method, no airborne particles

Foam coating facilities • Foam generators, capacities: • 12-120 l/h, 6-60 l/h, 2-10 l/h

• Foam applicators, narrow slot type: • Application width 300-500 mm • Application width 160-200 mm o Available summer 2012

• Research environment available: • VTT SUORA, Jyväskylä • VTT KISU, Jyväskylä • VTT SUTCO, Espoo • KCL pilot coater, Espoo KCL pilot coater

Foam generator Hansa Industrie-Mixer GmbH & Co. KG, Germany

Magnojet – foam applicator J. Zimmer Maschinenbau GmbH Klagenfurt, Austria

Applications

Nanoparticle coated paper Coating layer thickness below 1 µm, coat weight 0.5 g/m2 SEM images Coated paper a)

Uncoated paper b)

SEM cross section image

1 µm

Element maps Coated paper

Uncoated paper

Application of nanofibrillar cellulose NFC foaming

NFC, solids content 2.98%

Foamed NFC, 90% air

Higher concentrations possible e.g. compared to spraying

Application of unmodified nanofibrillar cellulose (NFC) Topographic images (SE-SEM) 100x: base paper NFC-TE/CTP double coated paper Base paper

NFC-TE/PTS 2*

NFC coating has evened out paper surface and reduced the surface porosity.

Application of nanofibrillar cellulose (NFC) (SE-SEM) 500x Base paper

NFC-TE/PTS 2*

Application of nanofibrillar cellulose (NFC) (SE-SEM) 5000x and 10 000x NFC-TE/PTS 2*

NFC-TE/PTS 2*

Effects of NFC surfaces Thin layer of NFC on the paper, below 1 g/m2 ´

Roughness, PPS10

µm

SEM x50 SE

Base paper

5,2 5,0 4,8 4,6 4,4 4,2 4,0 3,8

NFC coated paper

Air Permeance

3,0 2,5 2,0 1,5 1,0 0,5 0,0

2 g/m2

Once coated

Douple coated

µm/Pas

Calculated coat weight, g/m2 7,0 6,0 5,0 4,0 3,0 2,0 1,0 0,0

Once coated

Douple coated

Contact angle, water Once and double coated samples NFC-CTP, NFC-TE/CTP, NFC-TE/PTS Double coated

Once coated 50 Contact angle

Contact angle

40 30 20 10 0 0

0,5

Base paper NFC-CTP NFC-TE/CTP NFC-TE/PTS

1 time, s

1,5

2

35 30 25 20 15 10 5 0 0

0,5

1 time, s

1,5

2

• All unmodified NFC surfaces increase hydrophilicity • Strongest influence with NFC-TE/CTP and NFC-TE/PTS

Application of functionalized NFC NFC-ZnO, NFC-TiO2, cationic NFC

TiO2 and ZnO inorganic nanoparticles applied for NFC functionalization TiO 2

TEM images of TiO2 and ZnO nanoparticles, dimensions: 40 and 45 nm respectively.

1a

•

TiO2 6% water suspension

•

ZnO 1% diethylene glycol suspension.

1b

Physico-chemical characterisation of inorganic nanopartcles.

Concentration (%w/w) Density (g/cm3) Viscosity (25 C) (mPa/sec)

TiO2

ZnO

0.5

6.0

1.0

0.05

1.20

1.12

0.1

2.00

ND

40.0

45.0

0.05

0.25

0.20

0.5

1.0

ND

0.05

0.1

-

Particles Dimension (nm) (DLS Malvern Instruments) Polidispersity Index pH Cationic surfactant (%w/w)

• Patrizia Sadocco(*), Jessica Causio(*), Giovanni Baldi(**) • (*) Innovhub-SSCCP, (**) Centro Ricerche Colorobbia Italia

Application of modified nanofibrillar cellulose NFC-ZnO S. aureus *) Standard solar light lamp (6 h)

K. pneumoniae **) 15 h room light

7,00 6,00

*)

**)

8,00

untreated paper (control)

5,00

*)

**)

untreated paper (control)

7,00 6,00

4,00

5,00

3,00

Inhibition of grow 3,00 *) **) killing of bacteria

4,00

2,00

Inhibition of grow killing of bacteria *) **) *) **)

2,00

1,00

*)

**)

0,00

1,00 0,00

after contact (log CFU T18h)

Bacteriostatic activity (log reduction)

Bactericidal activity (log reduction)

after contact (log CFU T18h)

Bacteriostatic activity (log reduction)

Bactericidal activity (log reduction)

 NFC-ZnO has significant antibacterial activity against S. aureus and K. pneumoniae. • Patrizia Sadocco(*), Jessica Causio(*), Giovanni Baldi(**) (*) Innovhub-SSCCP, (**) Centro Ricerche Colorobbia Italia

Kinetic of NOx photodegradation in gaseous phase by NFC-TiO2 foam coated paper Test Point 182

NO NOx NO2

500

abbattimento NOx 110 100 90

80 NOTE: coat weight below 1 g/m2

abbattimento NOx (%)

Concentrazione (ppbv)

400

300

200

100

70 60 50 40 30 20 10

0

0 0

20

40

60

80

100

Tempo (min)

0

1

2

3

4

5

6

7

8

tempo (ore)

Around 70% NOx oxidation within 100 min

NFC-TiO2 has significant activity for the oxidation of NO and NOx • Patrizia Sadocco(*), Jessica Causio(*), Giovanni Baldi(**)(*) Innovhub-SSCCP, (**) Centro Ricerche Colorobbia Italia

Laboratory foam coating tests: Cationic modification improves inkjet print density (pigment based ink, droplet 1.5 pl, EPSON stylus photo R800) Printed base paper

Printed foam coated surface Ink density higher

•

prepared by mixing NFC with a cationic polyelectrolyte (PDDA+PSS+PDDA) University Aveiro, Portugal

Summary of NFC results  Foam coating enables application of undiluted NFC  Unmodified NFC:  Increases hydrophilicity  Decreases air permeability  Smoothens surfaces; influence on small scale roughness (PPS S10)  Using modified NFC possible to create activities to paper surface  Antimicrobiological influence; NFC-ZnO  Photo activity; NFC-TiO2  Improvement in ink jet print quality; cationic NFC

Conclusions  Foam coating enables very thin coatings of nanomaterials  Foam coating method has been proven at pilot scale  A large variety of materials possible  Higher concentrations possible e.g. compared to spraying  For nano-scale materials no binders are needed

 Occupational healthy method – no air born particles

Cooperation partners  KCL, Oy Keskuslaboratorio Centrallaboratorium Ab, Finland • •

All pilot services for paper industry under one roof www.kcl.fi

 Hansa Industrie-Mixer GmbH & Co. KG, Germany • Heiligenrode (near Bremen) • A centre for foam technology: Research, development and manufacturing • www.hansamixer.de

 J. Zimmer Maschinenbau GmbH Klagenfurt, Austria • •

Digital textile printing and coating machine sector www.zimmer-austria.com

Thank you for your attention! For further questions, please contact: [email protected]

Acknowledgement • The research leading to these results received funding from the European Community’s Seventh Framework Programme under Grant Agreement No 228802.