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Author:Sorsa, Perttu
Title:The effect of binder system on coating color performance and coating structure
Sideaineen vaikutus päällystyspastan toimintaan ja päällystekerroksen rakenteeseen
Publication type:Master's thesis
Publication year:2010
Pages:115 + [13]      Language:   eng
Department/School:Puunjalostustekniikan laitos
Main subject:Paperi- ja painatustekniikka   (Puu-21)
Supervisor:Paltakari, Jouni
Instructor:Huhtala, Kimmo ; Ojanen, Mari
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  2213   | Archive
Keywords:latex
water retention
rheology
immobilization
cnating structure
printability
lateksi
vesiretentio
reologia
immobilisaatio
päällysteen rakenne
painettavuus
Abstract (eng): Binder system has more visible impact on the coating color performance than the coating structure of a double coated fine paper.
In this study, the effect of different binder systems on the coating color performance were examined using several approaches, including static and dynamic water retention, viscosity, thixotropy and immobilization measurements.
Binder variables used in the study were binder level, type of a binder, particle size and particle size distribution (PSD) of a binder.
The structure of a dry coating layer was characterized by means of e.g. optical and physical properties of a coated paper, mercury porosimetry and SF0 printing.
Both laboratory scale and pilot scale studies were pursued and the results were compared to each other.

A novel concept of the binder reduction was employed.
Modified styrene-acrylate (SA) emulsions were used to replace a specific amount of styrene-butadiene (SB) latex, aiming at improved coating color performance and SFO printability of a double coated fine paper at reduced binder level.
Both monomodal and bimodal binder systems were examined.
Binder system was noted to change the rheology and water retention of a coating color.
High-shear viscosity decreased with smaller-sized particles and broad PSD of bimodal binder, and the blade loadings were slightly reduced with the decreasing viscosity.
Bimodal coating colours showed improved colloidal stability but increased immobilization times.
The immobilization times increased when the total binder level and proportional amount of SA emulsion increases.
Small latex particle size and PSD does not increase the immobilization time to a large extent.
The immobilization times of the pilot scale coating colours were higher but there was correlation to the laboratory scale coating colours.

Immobilization times can be used to estimate the formation of the pore sizes.
Increased immobilization time seemed to reduce the pore size.
Larger pores and higher specific surface area of a binder increased the picking strength of a coating to some extent.
Print gloss and optical properties did not change when the binder system was changed.
Bimodal coating with 6 parts of SB latex and 2 parts of SA emulsion gave similar picking strengths with increased porosity as compared to 10 parts of reference SB latex coating.
Smaller-sized bimodal binder slowed down the ink-setting rate but provided a similar print density at lower ink amount.
Monomodal SA emulsion at 4 parts showed poor picking strength and low print quality, and is not suitable for SFO printing.

The binder properties did not explain the changes in the immobilization time as accurately as the rheology and water retention measurements employed within the study.
Changes in the formation of the pore size can be explained through the binder properties.
Abstract (fin): Sideaineella on selkeämpi vaikutus päällystyspastan toimintaan ja rakenteeseen kuin päällystekerroksen rakenteeseen.
Tässä työssä tutkittiin erilaisten sideaineiden vaikutusta pintapäällystyspastaan mittaamalla staattista ja dynaamista vesiretentiota, pastan reologiaa ja päällysteen immobilisaatiota eli asettumista.
Päällystyspastojen muuttujina olivat sideaineen määrä ja tyyppi, sekä partikkelikoko ja partikkelikokojakauma.
Päällystekerroksen rakennetta tutkittiin optisia ja fyysisiä ominaisuuksia vertailemalla.
Elohopeahuokoisuusmittauksilla määritettiin päällysteen huokosrakenne ja IGT-painatuksella havaittiin muutokset painettavuudessa.
Mittauksia tehtiin laboratorio- ja pilot-mittakaavassa ja niiden tuloksia vertailtiin keskenään.

Työssä sovellettiin uudenlaista sideainekonseptia, jossa osa styreenibutadieenilateksista (SB) korvataan styreeniakrylaattilateksia (SA) muistuttavalla emulsiolla.
Työn tavoitteena oli parantaa pintapastan toimintaa ja arkkioffset-painettavuutta matalammalla sideainetasolla hyödyntäen erilaisia sideaineseoksia.
Sideaineen havaittiin muuttavan päällystyspastan reologiaa ja vesiretentiota.
Päällystyspastan ajettavuus parani lateksin partikkelikoon pienetessä ja sideaineseoksen partikkelikokojakauman kasvaessa.
Kokeelliset päällystyspastat olivat kolloidisesti stabiilimpia mutta niiden asettumiseen kulunut aika oli vastaavasti pidempi referenssipäällysteisiin verrattuna.
Päällystyspastan asettumisaika kasvoi sideainemäärän ja SA-emulsion osuuden kasvaessa.
Lateksin partikkelikoko ja partikkelikokojakauma vaikuttivat immobilisaatioon jossain määrin.
Laboratoriomittakaavassa valmistetut päällystyspastat antoivat samansuuntaisia immobilisoitumisaikoja pilot-mittakaavan päällystyspastoihin verrattuna.

Päällysteen asettumisajalla voidaan arvioida päällysteeseen syntyvien huokosten kokoa.
Korkeampi asettumisaika pienentää huokoskokoa.
Suurempien huokosten ja lateksin ominaispinta-alan havaittiin parantavan nukkaantumislujuutta jossain määrin.
Sideaineseos jossa on 6 osaa SB lateksia ja 2 osaa SA-tyypin sideainetta huomattiin antavan samanlaisen painolujuuden huokoisemmalla rakenteella verrattuna 10 osaa SB lateksia sisältävään päällysteeseen.
Erot painokiillossa ja optisten ominaisuuksien välillä olivat pieniä.
Pienipartikkelinen bimodaalinen lateksi hidastaa painovärin asettumista mutta antaa hieman paremman densiteetin samalla määrällä väriä.
Puhdas SA-emulsio antoi matalan pintalujuuden ja painolaatu oli huono.

Muutoksia päällystyspastan asettumisnopeudessa ei pystytty selittämään sideaineiden ominaisuuksilla yhtä hyvin kuin käytetyillä reologia- ja vesiretentiomittauksilla.
Huokoskoon muodostuminen näytti olevan riippuvaisempi sideaineiden ominaisuuksista kuin huokostilavuus.
ED:2010-06-02
INSSI record number: 39713
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