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Abstract(s)
A colagem superficial tem como principal objectivo melhorar as propriedades de superfície do
papel, uma vez que a aparência do papel é um factor determinante no seu consumo. Uma das
propriedades de superfície do papel com maior peso na sua comercialização é a brancura. Daí
surgirem vários estudos no sentido de melhorar essa mesma propriedade óptica.
Um dos interesses que está continuamente na actualidade da investigação do papel de impressão é
o de aumentar os valores de brancura, uma vez que, este é um dos parâmetros de venda mais
importante. Uma das formas de abordar este assunto é usar determinados produtos químicos no
tratamento de superfície da colagem superficial.
Um aumento da brancura do papel pode ser alcançado usando agentes branqueadores ópticos,
vulgarmente denominados por OBA’s. Esses branqueadores, para terem maior eficácia devem ser
usados em conjunto com determinados polímeros, conhecidos por transportadores. Os
transportadores têm como principal função fixar o OBA às suas longas cadeias poliméricas ao mesmo
tempo que se fixam com maior eficácia à superfície da folha de papel, melhorando a sua brancura.
Os transportadores usados com mais frequência são o Álcool polivínilico (PVA), a
Carboximetilcelulose (CMC). O PVA é referido por muitos investigadores como sendo o mais
eficiente de todos os transportadores estudados (Kuraray Specialities Europe , 2008).
O presente trabalho tem como objectivo principal estudar as variações de brancura do papel quando
usados diferentes OBA’s e também diferentes transportadores no tratamento de superfície.
Pretendendo verificar quais os OBA’s mais eficientes na colagem superficial, assim como, averiguar
quais os melhores transportadores, isto é, aqueles que associados aos OBA’s conseguem originar
melhores níveis de brancura.
Os OBA’s derivados do estilbeno, são os mais utilizados na indústria papeleira e estão divididos em
três tipos; dissulfónicos, tetrassulfónicos e hexassulfónicos. Neste trabalho foram testados os vários
tipos de OBA’s usando sempre o mesmo papel base. O OBA do tipo dissulfónico testado foi o Tinopal
UP, do tipo tetrassulfónico, foram usados o Tinopal ABP-Z e o Leucophor FTS, por último, do tipo
hexassulfónico foram usados o Blankophor UWS e o Neucoblanc PSP. Verificou-se que o OBA que
apresenta melhor desempenho na colagem superficial é do tipo hexassulfónico.
Posteriormente foram testados vários transportadores conjuntamente com os OBA´s que produziram
os papéis com melhores resultados de brancura após a colagem superficial. Os transportadores
testados foram PVA, a CMC, o Agar e o Viviprint. Dos resultados obtidos com estes transportadores
conclui-se que aquele que apresenta melhor eficiência na colagem superficial é o PVA. Pode igualmente verificar-se a eficiência do Agar como transportador, mas apenas a baixas concentrações
devido á sua elevada viscosidade.
Surface sizing main objective is the paper surface properties improvement, as paper appearance is a key factor for its consumption. Whiteness is one of the most important paper surface properties for its marketing. Hence, various studies were made to improve this optical property. One of the concerns continuously present in paper printing research is whiteness values increase, as this is one of the most important sales parameter. One way of addressing this is the use of certain chemicals in surface sizing treatment. An increase in paper whiteness may be achieved using optical bleaching agents, commonly referred to as OBAs. These whiteners, in order to attain greater efficacy, should be used in conjunction with certain polymers known as carriers. The carriers have as its main function linking OBA to their long polymer chains while binding more effectively to the paper surface, thus improving its whiteness. The carriers most frequently used are polyvinyl alcohol (PVA) and carboxymethylcellulose (CMC). PVA is reported by many researchers as the most efficient amongst all the studied carriers (Kuraray Specialities Europe, 2008). This work main goal is to study paper whiteness variations using different OBAs and also different carriers in surface treatment, in order to ascertain which OBAs are more efficient in surface sizing, as well as selecting what are the best carriers, i.e., those that when associated with the OBAs can lead to better brightness levels. The stilbene derivatives OBAs are frequently used in paper industry and are divided in three main types: disulfonic, tetrasulfonic and hexasulfonic. In this work we tested different types of OBAs, using always the same base paper. Tinopal UP was tested for the disulfonic type OBA, Tinopal ABP-Z and Leucophores FTS were tested for the tetrasulfonic type and, finally, UWS Blankophor Neucoblanc PSP was used for the hexassulfonic type. It was found that the OBA that performs best in surface sizing is the hexassulfonic type. Subsequently several carriers were tested with OBAs, which produced papers with the best whiteness results after surface sizing. The tested carriers were PVA, CMC, Agar and Viviprint. It was concluded, from the obtained results with these carriers, that the one showing better efficiency in surface sizing is PVA. Agar efficiency as a carrier was also tested, but only at low concentrations due to its high viscosity.
Surface sizing main objective is the paper surface properties improvement, as paper appearance is a key factor for its consumption. Whiteness is one of the most important paper surface properties for its marketing. Hence, various studies were made to improve this optical property. One of the concerns continuously present in paper printing research is whiteness values increase, as this is one of the most important sales parameter. One way of addressing this is the use of certain chemicals in surface sizing treatment. An increase in paper whiteness may be achieved using optical bleaching agents, commonly referred to as OBAs. These whiteners, in order to attain greater efficacy, should be used in conjunction with certain polymers known as carriers. The carriers have as its main function linking OBA to their long polymer chains while binding more effectively to the paper surface, thus improving its whiteness. The carriers most frequently used are polyvinyl alcohol (PVA) and carboxymethylcellulose (CMC). PVA is reported by many researchers as the most efficient amongst all the studied carriers (Kuraray Specialities Europe, 2008). This work main goal is to study paper whiteness variations using different OBAs and also different carriers in surface treatment, in order to ascertain which OBAs are more efficient in surface sizing, as well as selecting what are the best carriers, i.e., those that when associated with the OBAs can lead to better brightness levels. The stilbene derivatives OBAs are frequently used in paper industry and are divided in three main types: disulfonic, tetrasulfonic and hexasulfonic. In this work we tested different types of OBAs, using always the same base paper. Tinopal UP was tested for the disulfonic type OBA, Tinopal ABP-Z and Leucophores FTS were tested for the tetrasulfonic type and, finally, UWS Blankophor Neucoblanc PSP was used for the hexassulfonic type. It was found that the OBA that performs best in surface sizing is the hexassulfonic type. Subsequently several carriers were tested with OBAs, which produced papers with the best whiteness results after surface sizing. The tested carriers were PVA, CMC, Agar and Viviprint. It was concluded, from the obtained results with these carriers, that the one showing better efficiency in surface sizing is PVA. Agar efficiency as a carrier was also tested, but only at low concentrations due to its high viscosity.
Description
Keywords
Branqueadores ópticos Branqueadores ópticos - Colagem superficial Tratamento de superficial - Colagem superficial OBA'S - Transportadores - Polímeros