Many grades of paper have shifted from acid to alkaline production
conditions. This change excludes the usage of traditional alum-rosin
sizing chemistry. In some cases however, rosin sizing could prove
beneficial if it could be used under neutral to alkaline paper making
conditions. One effort toward this goal has been the use of
epi-halohydrin modified polyamine/polyaminoamide in place of alum. The
optimum sizing conditions, as well as the mechanism that modified
polyamines/polyaminoamides use to size rosin, is investigated.
Polyethyleneimine modified with epi-chlorohydrin was used in these studies.
Rosin dosage was found to be the main variable that controlled the
degree of sizing achieved. As the only hydrophobic material added, this
was expected. In addition to rosin dosage, the polymer and pH had
significant impacts on this sizing chemistry.
Laboratory data shows that the synthesis procedure for and structure of
polyethyleneimine-epi-cholohydrin (PEI-epi) impacts the degree of sizing
achieved. Use of different modification techniques and degrees of
modification illustrated several key factory regarding the polymer as a
rosin sizing mordant. Prevention or removal of by-products from
epi-chlorohydrin imporves the sizing efficiency of PEI-epi with rosin. A
critical molecular weight of the PEI-epi was found to be important to
sizing. Higher charge density on PEI-epi provides better the sizing
efficiency. In addition to the polymer, other important factors where
examined.
The pH of the stock impacted the degree of sizing and permanency of the
sizing achieved. Varying stock pH showed changes in sizing that are
consistent with effects seen for rosin retention and of PAE as a wet
strength agent. Low and high pH levels also caused reversion of the
sizing effect.
A pilot trial of the PEI-epi-rosin sizing chemistry was conducted at the
Herty Foundation. The pilot trial shows that PEI-epi-rosin can reach the
required level of sizing for linerboard. Trial results showed that
calcium carbonate filled sheets could be sized by this chemistry. No
significant impact on strength is seen from the sizing chemistry at the
required dosage levels. As would be expected, addition of filler
diminishes sheet strength. No sizing reversion was seen from any samples
of this trial.
Size reversion at low stock pH indicated that acid catalytic cleavage of
an ester bond could have been occurring. Addition of acid or base to
permanently sized sheets showed significant levels of reversion, similar
to that seen for low stock pH sheets. This provides further supporting
eviden ce for the formation and importance of an ester bond between
rosin and PEI-epi.
FTIR spectra were collected for model compounds to further examine the
presence and importance of ester bonds. An ester bond was found to form
at room temperature with aging or immediately with drying. Further, the
ester bonds were found to decrease when the sample was subjected to
acidic or basic environments.
Solid state NMR was run to demonstrate the presence and importance of
ester bonds to sizing in handsheets. Use of a [superscript 13]C labeled
fatty acid showed that the ester bond peak dominated when sizing was
present. After treatment with sodium hydroxide, the sizing disappeared
and much of the ester bond signal shifted to a carboxylic acid or salt.
Further solid state NMR of a non-reactive cationic polymer or a fully
pre-reacted PEI-epi polymer shows retention of the fatty acid, but no
ester bond and no sizing.
The sizing mechanism of PEI-epi-rosin sizing appears to be connected to
an ester bond formed during drying or with aging. While the amount of
rosin retained controls the degree of sizing, retention alone is not
enough to give sizing. The most effective pH for this sizing chemistry
is near neutral, pH 6-8. FTIR and solid state NMR shows that an
epichlorohydrin modified polyamine can form ester bonds with fatty acids
in handsheets under conditions comparable to papermaking. The presence
of residual acid or base in handsheets destroys the sizing effect
achieved. Destruction of the sizing by addition of sodium hydroxide
parallels the cleavage of many of the ester bonds present. PEI-epi
appears to function as a mordant for rosin by creating an ester bond to
anchor and help orient the hydrophobic portion of rosin.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/7032 |
| Date | 13 January 2004 |
| Creators | Hartong, Bradley H. |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
| Format | 3997418 bytes, application/pdf |
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