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Author:Jokinen, Mikko Sakari
Title:Effect of bimodal binder system on coating color immobilization and holdout
Bimodaalisen sideaineen vaikutus päällystyspastan immobilisaatioon ja peittoon
Publication type:Master's thesis
Publication year:2012
Pages:97 + [6]      Language:   eng
Department/School:Puunjalostustekniikan laitos
Main subject:Paperi- ja painatustekniikka   (Puu-21)
Supervisor:Paltakari, Jouni
Instructor:Ojanen, Mari
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  2188   | Archive
Keywords:coating
binder
rheology
immobilization
päällystys
sideaine
reologia
immobilisaatio
Abstract (eng): The effect of bimodal particle size distribution of latex binder on coating colour performance and properties was studied.
A novel, small particle size, high specific surface area styrene-acrylate (SA) emulsion was used to replace specific amount of conventional styrene-butadiene (SB) latex in a coating colour to create bimodal binder system containing smaller amount of total latex.

The effect of increasing SA latex content in coating colour was studied, as well as the impact of increasing the SBISA replacement ratio from 2: I to 3: 1.
Other variables in the study were particle size of SB latex, use synthetic thickener instead of carboxymethyl cellulose (CMC) and solids content of the colour.
Furthermore, a case of weakened colloidal stability of coating colour was introduced with addition of calcium chloride on series of colours.
Properties of prepared coating colours were examined by determining viscosity, thixotropy, water retention, immobilization time and immobilization solids content of the colours.
In addition, a pilot trial was employed to study the effects on pilot scale.

Bimodal binder system enhanced water retention in comparison to monomodal binder containing colours simultaneously fastening the immobilization.
Decreased particle size of SB latex enhanced water retention and slowed down the immobilization remarkably.
Increase of replacement ratio slightly increased immobilization time when CMC was used as thickener.
Use of synthetic thickener affected coating colour rheology and slowed the immobilization.
Solids content of the coating colour had effect on rheology and immobilization of colour.
Addition of calcium chloride caused flocculation in coating colour but the effects on immobilization were negligible.

Pilot trial coating colours had differences in rheological behaviour and immobilization times in comparison to laboratory colours.
Run ability of all pilot trial points was good, as all colours produced stable films and blade pressures remained fairly low.
Differences in optical properties of the coated sheets were relatively small.
Increase of replacement ratio had increasing effect on porosity of the pilot trial sheets.
Moreover, increasing immobilization solids content decreased both average pore volume and pore size.
According to pilot results, the increase of replacement ratio does not deteriorate the paper properties.

Burnouts were used to evaluate coating colour holdout.
All trial points proved to have very similar, thoroughly covered burnout images, indicating that the impact of base paper pore structure had dominating effect on coating holdout.
Abstract (fin): Tässä työssä tutkittiin sideaineen bimodaalisen partikkelikokojakauman vaikutusta päällystyspastan toimintaan ja ominaisuuksiin.
Uudenlaista, pienipartikkelikokoista korkean ominaispinta-alan styreeniakrylaattilateksia muistuttavaa emulsiota käytettiin korvaamaan tietty määrä tavanomaista styreenibutadieenilateksia, jolloin lateksin kokonaismäärää voidaan vähentää.

Kokeellisessa osassa tutkittiin lisääntyvän SA-emulsiomäärän vaikutusta päällystyspastojen ominaisuuksiin.
Lisäksi SB/SA korvaussuhdetta nostettiin alkuperäisestä 2:1 suhteesta korvaussuhteeseen 3:1.
Muita muuttujia työssä olivat SB-lateksin partikkelikoko, synteettisen paksuntajan käyttö, pastan kuiva-ainepitoisuuden vaikutus sekä pastan stabiiliuden heikennys kalsiumkloridin avulla.
Valmistetuista päällystyspastoista määritettiin viskositeetti, tiksotropia, vesiretentio sekä immobilisaatioaika.
Pilot-koeajolla tutkittiin bimodaalisen sideaineen vaikutuksia suuremmassa mittakaavassa.

Bimodaalinen sideaine paransi pastojen vesiretentiota verrattuna monomodaalisiin sideaineisiin ja samalla immobilisaatio nopeutui hiukan.
SB-lateksin partikkelikoon pieneneminen hidasti immobilisaatiota merkittävästi.
Korvaussuhteen nosto pidensi immobilisaatioaikoja, kun sideaineena käytettiin karboksyylimetyyliselluloosaa (CMC).
Synteettisen paksuntaja aiheutti immobilisaation hidastumista.
Päällystyspastan kuiva-ainepitoisuuden muuttaminen vaikutti pastan reologiaan ja immobilisaatioon.
Kalsiumkloridin lisäys aiheutti flokkaantumista, mutta vaikutukset immobilisaation olivat pieniä.

Pilot-pastat erosivat laboratoriossa valmistetuista pastoista reologisilta ominaisuuksiltaan sekä immobilisaatioajoiltaan.
Kaikkien pilot-pastojen ajettavuus osoittautui hyväksi, päällystefilmit olivat tasaisia ja terapaineet hyväksyttävällä tasolla.
Päällystetyt paperit erosivat optisilta ominaisuuksiltaan vain vahan.
Korvaussuhteen nosto nosti paperin huokoisuutta ja immobilisaatiopisteen kuiva-ainepitoisuuden nousu laski sekä huokoistilavuutta että -kokoa.
Pilot-koeajon perusteella korvaussuhteen nousu ei heikennä päällystetyn paperin ominaisuuksia.

Päällysteen peittoa tutkittiin burnoutien avulla.
Kaikkien pilot-koepisteiden burnoutit olivat hyvin samankaltaisia osoittaen, että pohjapaperin huokoisrakenne on määräävä tekijä arvioitaessa päällystekerroksen peittokykyä.
ED:2012-11-09
INSSI record number: 45409
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