Effect of Recycling Number on the Fluorescence Reduction of Fluorescent Whitening Agents in White Wastepapers
*OUSPEVDUJPO
tachment from white wastepaper and the distribu- tion change of FWAs in the sheet was investigated. Three types of papers were prepared, dyed with various FWAs, disintegrated, and again made into handsheets. The recycling rounds were repeated up to ten times for D-FWA and five times for T-FWA and H-FWA. After each round of recycling, the CIE whiteness, ISO brightness, and fluorescence index of the handsheet were measured, and the fluorescence reduction was calculated as an indi- cator, which represents the FWA detachment from wastepaper, using the fluorescence indices before recycling and after each round of recycling. Fi- nally, the distribution of FWAs in the cross section of the handsheet was observed using a confocal laser scanning microscope (CLSM).
The most important advantage of paper is its re- cyclability. 1) Paper is recycled as a raw material for the manufacture of other paper products, and re- cycled wastepaper is classified into many groups such as old newspapers (ONPs), old corrugated containers (OCCs), old magazines (OMGs), and mixed office waste (MOW). Paperboard-grade products, including linerboard and white-lined chipboard, have been manufactured from recycled wastepaper, and the production of paperboard grade products accounts for approximately 50% of the paper products produced in South Korea. 2) Therefore, recycled wastepaper is a very important resource for the Korean paper industry. Among all wastepaper, the white varieties, in- cluding OMGs, MOW, and white ledger paper, are widely used to produce white-lined chipboard, which is used for food packaging, pharmaceuticals, detergents, and other products. 3) White wastepaper contains fluorescent whitening agents (FWAs), which are subject to safety regulation in chipboard mills. 4) In addition, costumers worry about the toxicity of FWAs in recycled paper products. Be- cause it is inevitable to use white wastepaper to manufacture paperboard in the Republic of Korea, it is necessary to develop a method to remove or control FWAs originating from white wastepaper. The FWAs used in the paper industry are classi- fied into three groups according to the level of sul- fonic acid present: disulfo-FWA (D-FWA), tetra- sulfo-FWA (T-FWA), and hexasulfo-FWA (H-FWA). 5,6) FWAs are used in the papermaking process because FWAs have their own affinity to cellulosic fibers and wide-ranging solubility in aqueous solutions. 5) Therefore, papermakers should analyze the type of FWA for understanding FWA detachment and distribution change during the re- cycling process. 7) In this study, the effect of recycling on FWA de-
.BUFSJBMTBOE.FUIPET
.BUFSJBMT Three types of FWAs, including disulfo-FWA (D-FWA), tetrasulfo-FWA (T-FWA), and hexas- ulfo-FWA (H-FWA) are commercially available products. Bleached softwood kraft pulp (Sw-BKP) and bleached hardwood kraft pulp (Hw-BKP) were provided by Moorim Paper (Jinju, Republic of Ko- rea), and used to make handsheets that were dyed with D-FWA. Non-sized fine paper with a gram- mage of 95 g/m 2 was used as the base paper for surface sizing with T-FWA or H-FWA. Oxidized starch, which was provided by Daesang (Icheon, Republic of Korea), was used for surface sizing. 4UPDLQSFQBSBUJPOBOENBOVGBDUVSFPG QBQFSEZFEXJUI'8" Sw-BKP and Hw-BKP were beaten to 450±5 mL CSF using a laboratory valley beater (Daeil Ma- chinery Co. Ltd., Daejeon, Republic of Korea). The pulp samples were mixed in a ratio of 2:8 (Sw- BKP:Hw-BKP). The mixed pulp slurry was then
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펄프·종이기술 51(2) 2019
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