Application of NFC by foam coating technique

Transcription

1 Application of NFC by foam coating technique Karita Kinnunen, Tuomo Hjelt, Eija Kenttä, VTT SUNPAP Workshop

2 Foam

3 Outline Benefits of foam coating Foam coating principles Role of foam, foam formation, foam killing Requirements of the foam for foam coating Foam coating facilities Results Conclusions

4 Foam coating in paper industry A well-known technique in the textile, non-woven industry and in plastic film production In paper applications the first patents of the technology date back to the beginning of the 20 th century, but still foam coating technology has not gained ground in paper industry However, some applications are found in paper making industry

5 Foam coating benefits Non-contact application No side streams Allows very thin coatings, e.g. 0.5 gm -2 Even application of small quantities on large areas Less tendency to migrate into the substrate For nanomaterials no binders required Versatile process Compatible with a wide range of materials Higher concentrations possible, e.g. compared to spraying Simple Occupationally safe method

6 Foam coating principles Foam used as a carrier phase to transfer the coating material onto the substrate vertex Liquid containing foaming agents is mixed with air using a foam generator Air content greater than 80%, preferably 90-95% 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

7 Requirements of the foam for foam coating Average bubble size < 100 µm Bubble size remains constant during the coating process Foaming agents compatible with the coating material 2000 µm 2000 µm Air content 66% Air content 94%

8 Foam coating facilities at VTT(KCL co-operation) IR-dryers KCL pilot coater The foam generator The foam applicator

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

10 RESULTS Application of nanoparticles and nanofibrillar cellulose

11 Foam stability in the process Influence of ambient temperature and hose length on foam stability VTT Masuko ground NFC Analyzed by: magnifying high-speed camera monitoring of foam coming from the applicator Turbiscan Online measurement device (light scattering method) installed between the foam generator and the foam applicator cold (16.5 o C), hot (55 o C) water.

12 Testing of foam stability

13 Foam stability in the process Influence of ambient temperature and hose length on foam stability VTT Masuko ground NFC Analyzed by: magnifying high-speed camera monitoring of foam coming from the applicator Turbiscan Online measurement device (light scattering method) installed between the foam generator and the foam applicator cold (16.5 o C), hot (55 o C) water.

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

15 Application of nanofibrillar cellulose NFC foaming NFC, solids content 2.98% Foamed NFC, 90% air

16 Nanoparticle coated paper Coating layer thickness below 1 µm Coated paper Uncoated paper a) b) SEM images Coated paper Uncoated paper 1 µm SEM cross section image Element maps

17 Application of nanofibrillar cellulose SEM x50 SE images from uncalendered paper surfaces Base paper NFC coated paper

18 contact angle [ ] contact angle [ ] Application of nanofibrillar cellulose Contact angle Water Diiodomethane time [s] time [s] Base paper Pure foam NFC-CTP/VTT NFC-TE/VTT NFC-TiO2 Water and DIM (~offset ink): More hydrophilic and oleophobic surface with NFC-TE/VTT and NFC-CTP/VTT

19 Air permeance, PPS20, μm/pa*s Opacity, % Application of nanofibrillar cellulose Air permeance, opacity 9,0 8,0 7,0 6,0 5,0 4,0 3,0 2,0 1,0 0,0 91,0 90,5 90,0 89,5 89,0 88,5 88,0 87,5 87,0 86,5 86,0 85,5 85,0 NFC-TE/VTT sealed the surface No influence on optical properties

20 Print Density Cyan 50%, GretagMacbeth D196 Application of nanofibrillar cellulose Inkjet printing, KCL Versamark2000 Print Density Cyan 50% GretagMacbeth D196 0,90 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,10 0,00 Droplet size : 11 pl 3 pl NFC-TE/VTT sealed the surface -> Decrease in print density

21 Summary of results Thin, uniform coating layer Foam coating enables application of undiluted NFC Different NFC grades have different influences on contact angle values Nanofibrillar cellulose applied to the paper surface decreases air permeance For nano-scale materials no binders are needed

22 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

23 Cooperation partners KCL, Oy Keskuslaboratorio - Centrallaboratorium Ab, Finland All pilot services for paper industry under one roof Hansa Industrie-Mixer GmbH & Co. KG, Germany Heiligenrode (near Bremen) A centre for foam technology: Research, development and manufacturing J. Zimmer Maschinenbau GmbH Klagenfurt, Austria Digital textile printing and coating machine sector

24 Funding Scale-up Nanoparticles in Modern Papermaking, SUNPAP The research leading to these results has received funding from the European Community's 7th Frame work Programme under grant agreement no

25 Foam coating team at VTT Karita Kinnunen Tuomo Hjelt Eija Kenttä

26 Thank you for your attention!