Shin PublishedSept2017 PDF
Shin PublishedSept2017 PDF
Shin PublishedSept2017 PDF
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1
Researcher and corresponding author (jaeshin12@ snu.ac.kr)
Research Institute of Agriculture and Life Sciences,
Seoul National University, Seoul, South Korea;
Adjunct Professor, 3Professor
2
SUMMARY
This paper builds upon the findings of previous work on the rheological properties and dynamic water retention
properties of starch latex-containing coating colours. The previous work showed that the rheological performance
of starch latex and dynamic water retention of starch latex are different from conventional cooked coating starches.
In this paper, the basic nature of water-swollen starch nanoparticles and their colloidal behaviour are investigated
using serum replacement.
Serum replacement experiments showed that starch latexes are complex systems of particles and a minor
fraction of soluble polymers. Increasing the degree of crosslinking decreased the soluble fraction and lowered
the dispersion viscosity. Coatings applied using a cylindrical laboratory coater showed the plasticity of SB
latexes acted as a lubricant during calendering and aided to improve gloss. Crosslinked biobased latexes and
hydroxyethylated starch (graft polymers) improved water retention, but the use of low crosslinked Bio-A was found
to lower gloss.
KEYWORDS
Biobased latex, Styrene-Butadiene latex, Hydroxyethylated starch, Serum replacement, Particle size
INTRODUCTION The resulting product from the extruder consists of nearly dry
agglomerates of crosslinked starch nanoparticles, which are
Biobased latexes were developed in the early 2000’s for industrial
subsequently pulverized into a final powder product. These
applications (1,2). They provide an alternative binder system
pulverized agglomerates are either dispersed in water to form
to petroleum-based binders used in the paper and paperboard
stable starch nanoparticle dispersions or mixed with coating
industry. Biobased latexes consist of crosslinked water-swollen
pigment slurries during paper coating make-up for use as paper
starch nanoparticles. They have unique wet properties under
coating binders.
high shear, unlike hard sphere particles. Their discrete particles
While crosslinks within the same starch polymer chain also
are not water soluble, but form a colloid dispersion in water.
occur, it is the intermolecular crosslinks between two different
Thus coating viscosity is much lower in coatings containing
starch polymer chains that are critical to the morphology of the
biobased latex than in those containing conventional starch. The
nanoparticles (3)
(3). Although the exact submicroscopic structure
products can be added directly to mixers or dispersed in line
is not known at this point, based upon the chemistry of starch
without cooking. Currently starch latexes are manufactured by
polysaccharide polymers and an understanding of the twin-screw
a continuous reactive extrusion process comprising solubilizing
extrusion manufacturing process, a biobased latex nanoparticle
starch granules, i.e. converting the very high-solids starch paste
can be thought of as one crosslinked macromolecular unit, as is
into a thermoplastic melt phase, and then crosslinking and sizing
illustrated in Figure 1.
the solubilized starch molecules into nanoparticles.
that a biobased
othesis that a biobased latex nanoparticle latex Swell nanoparticle can be can
Ratio of Biobased
thought be thought
Latex
of as a crosslinked
the flow times between two demarcations of a glass Ubbelohde
viscometer forof the asstarchananoparticle
crosslinked dispersion (η) and for its
us of gyrationFig.1of
he radius of gyration a randomly coiled
The swell ratio linear polymer
(effective
linearvolume, molecule C) was (4); note
determined that
(4);bynote theother
Thesame types
method
equation previously re
as aof aARTICLE
randomly coiled polymer molecule that other types
Illustration of the hypothesis that a biobased latex nanoparticle can dispersion medium (η ), which was water. Einstein
o
bePEER-REVIEWED
thought ofPEER-REVIEWED
crosslinked macromolecular
ARTICLE unit, rg is the radius of (8) with a simple modification was used to obtain the effective
ist. relative viscosity (η
gyration of a randomly coiled linear polymer molecule (4); note that other r = η/η o ) of the starch latex binders were obtained by measuring the flo
volume factor (C) which is equal to the maximum volume
types of crosslinked structures
obtain obtain the effective two
the effective demarcations
PEER-REVIEWED
exist.
volumevolume of
ARTICLE
factor factor a
(C) which glass
(C) whichUbbelohde
is equal
swelling of viscometer
to the
is starch
equal tomaximum for
the maximum
nanoparticles thevolume
with their starch nanoparticle
swelling
volume
protective shells atof starch
swelling dispersio
of starch
nanoparticlesnanoparticles dispersion
with their with their medium
protective shells
protective (η at
o ), which
very
shells atlow was
very
very water.
concentrations.
low
low The
concentrations.
concentrations. Einstein equation (8) with a simple modific
obased latex are
s of biobased
related to the molecular
The unique characteristics of obtain
latex are related
structure
to the molecular of the of
biobased the
structure nanoparticles,
latex effective which which
are related tovolume
the nanoparticles,
the
=1 + 2.5
factor (C) which is equal to the maximum volume swe
=1 C + 2.5 C [1] [1]
molecular structure of the nanoparticles withconsist
their protective shells at very low concentrations.
(5). A(5).
r
networks balance exists exists
between the osmotic pressure
nanoparticles, which
in eachinparticle of r
cle
2 [1]
the
e in
esure the change
acterize in
Fig.2 Schematic representation of serum replacement apparatus.
he Fig.2 Schematic representation of serum replacement apparatus.
as used to characterize
and
eating colour, the
Particle Size Measurement
ork
ents during theA NICOM 370 DLS Particle Sizing Systems submicron analyzer
om (10,11) was used to measure the particle size distribution of the
biobased latex suspensions. Solutions were diluted to obtain the
mer afrom a
gy·Innovation·Manufacturing·Environment
appropriate intensity between 200 to 400 counts. Data analysis 3
sion
dispersion was undertaken
orbed emulsifier from a using two methods: Gaussian Distribution
om
o-B,
-A, Bio-B,latex dispersion
a starch Analysis (unimodal distribution) and NICOMP Distribution
rum
ugh serum(Bio-A,
and
densities
Analysis (multimodal distribution) (11).
Bio-B, was 3determined
The best-fitFig. The colour intensities
by minimizing the of
Fig. 3 The colour intensities of biobased latexes (solid 1%)
biobased
deviation latexes (solid 1%) Left: Bio C (heavy brown), Middle: Bi
Left: Bio C (heavy brown), Middle: Bio B (brown) Right: Bio A (light brown).
acterized through serum
will
the the
which between the Ameasured
(light brown).
autocorrelation function and those
from the model function (11). This deviation was measured by
gium
aa container
sodium in which the called chi-squared (χ2). If the value of χ2 is larger As starch polymers are crosslinked, they are converted to form
the quantity
two
ween two
o pH 8.0 using a sodium the
than 3, then AsGaussian
starch polymers
Analysis result wasare crosslinked,
considered they
to be higher are weight
molecular converted
insoluble to form
polymer higher
networks, molecular weigh
or starch
nate
cell held between two networks, or starch particles. Depending on the degree of crosslinking, the
ycarbonate inappropriate, and so the analysis was changed to the NICOMP particles. Depending on the degree of crosslinking, the final final starch la
was
brane was polycarbonate mixture of insoluble starch particles, with some soluble starch polymers as shown
Nuclepore Analysis for accuracy. starch latex will consist of a mixture of insoluble starch particles,
ion.
lseduration. with some soluble starch polymers as shown in Figure 4. After
Cylindrical
to the membrane was Lab Coater (CLC) Trial and Coated crosslinking, a certain amount of starch molecules are converted
arch
hy the starch
experimentalPaper Properties
duration. to starch particles and some colour bodies form during the
om
rder to replace Coating
the the
ogging
the starch
trials were undertaken using a CLC coater at Western
Michigan University on 63 gsm paper, using a rigid blade at 609
extrusion manufacturing processes as suggested in Figure 4.
As shown in Figure 5, a highly crosslinked starch latex (e.g.
, no
with no Appita Technology·Innovation·Manufacturing·Environment
m/min, with a drying time of 15 to 25 s at 100 % power. The Bio C) has fewer swellable particles and fewer solubles, so its
4
ch particles clogging the
ane
membrane
factory
coated paper was calendered using two passes over a chrome- viscosity is low, but a less crosslinked starch latex (e.g. Bio A)
results,finished
with heated
no metal roll (mated up to the coated paper surface)
uent
ofpass
effluent
through membrane
has more swellable particles and more soluble starch molecules,
and a cotton roll (uncoated side) at 131 N/mm impression so its viscosity is high.
were
eeks were
oncentrations ofpressure
effluent
at 60 °C. The target gloss of the control was 72.
the of the
lage
ximately 1-2 weeks were
avoid the spoilage of the
Vol 70 No 3 July - September 2017 253
ARTICLE
ARTICLE
certain amount
amount of
of starch
starch molecules
molecules are
are converted
converted totostarch
starchparticles
particlesand
andsome
somecolour
colourbodies
certain
PEER REVIEW
e extrusion manufacturing processes as suggested in Figure 4.
e extrusion manufacturing processes as suggested in Figure 4.
bodies
igure 5, a highly crosslinked starch latex (e.g. Bio C) has fewer swellable particles and fewer
igure 5, a highly crosslinked starch latex (e.g. Bio C) has fewer swellable particles and fewer
viscosity is low, but a less crosslinked starch latex (e.g. Bio A) has more swellable particles
viscosity is low, but a less crosslinked starch latex (e.g. Bio A) has more swellable particles
ble starch molecules, so its viscosity is high.
ble starch molecules, so its viscosity is high.
The amount of unaccounted losses was then determined using the
following equation:
PEER-REVIEWED
PEER-REVIEWED
ARTICLE ARTICLE
V1 - V2
Loss or Gain % = x 100 [2]
V1
where V1 is the theoretical amount and V2 is the actual amount Table 3. TheT
of starch latex in the container after replacement. For Bio-A
the theoretical amount is 4.69 g (V1: 5.17 – 0.48 = 4.69 g), but
the actual amount of starch latex was 4.32 g (V2: 5.17 – 0.85 =
4.32 g). The unaccounted amount, using equation 2, was 7.88%
((4.69-4.32)/4.69*100). It is likely that this loss is due to the
adsorption of starch latex particles onto the container wall or
pipes of the apparatus.
As starch in solution can spoil at room temperature, a biocide
was added to the starch latex dispersions and water reservoir.
As starch inAssolution
starch in
cansolution
spoil atcan
ro
Fig. 4 The new concept of biobased latex dispersions. Similarly, to control the pH of the solution, a Na2CO3 buffer was
Fig. 4 The new concept of biobased latex
Fig. 4 The new concept of biobased latex dispersions. dispersions. water reservoir.
water Similarly,
reservoir. to
Similarl
contro
PEER-REVIEWED added to the reservoir. However, the amount of these components
ARTICLE
However, theHowever,
amount the
of these
amountcomp
of
added was minimal relative to the total water volume, thus their
masses weremasses
neglected
werewithin
neglected
the we
w
masses
Table 2. The filtrate were
flow neglected
rates (gram within
perthe weight
day) of calculations.
biobased latex dispersions by seru
To assess the
To molecular
assess the structure
molecularo
Bio-B, and Bio-C at 1% solid). Table 4. The
Table
composite
4. The (or
composite
average)(
Table 2. then calculated
thenaccording Equatio
calculatedtoaccording
The filtrate flow 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶
rates (gram per day) where A is where
the starch
A isvolume
the starch
of eac
vol
of biobased latex swell ratio. swell ratio.
dispersions by
serum replacement If the massIfbalance
the mass is correct,
balance theis co
o
(Bio-A, Bio-B, and Also, the swell
Also,ratio
the swell
(SR) ofratio
each
(SR
The new conceptFig.
of Bio-C (heavy brown), Bio-B (brown), and
5 The new concept of Bio-C (heavy brown), Bio-B (brown), Bio-A (light brown) dispersions.
Bio-C at 1% solid). materials that
materials
passed that
through
passedthethro
m
The new conceptand
of Bio-A
Bio-C (heavy
(light brown), Bio-B (brown), and Bio-A (light brown) dispersions.
brown) dispersions. SR, before SR,replacement
before replacement
were quite
Table 2, biobased latexes showed different filtrate flow rates, because each starch latex has its balance calculations.
balance calculations.
Each of theEaf
able 2, biobased Aslatexes showed different filtrate Unfortunately,
Unfortunately,
all filtrates all
of Bio-B
filtrate
which is related to its incrosslinked
shown Table 2, biobased density.
latexes The flow
showed rates,
filtrate
different flow because
filtrate rate ofeach
eachstarch
starchlatex
latexhas
wasits characteristics
characteristics
swell ratios.swell ratio
which is flow
related rates,
to its because each
crosslinked starch latex
density. has its own
The viscosity,
filtrate which
nt, indicating that there was little or no clogging of the surface of the membrane. As shown was
flow rate of each starch latex in
is related to its crosslinked density. The filtrate flow rate of each
Each starchEach
latexstarch
is a mixture
latex isofa low
mi
t, indicating
entire that
container there
volume was(400 littlemL)or nowas clogging
replaced of the surface
within of the membrane.
a two-week period for As the
shownlowin particles, soparticles,
the original
so the
swell
original
ratio
starch latex was almost constant, indicating that there was little or
entire
rch, container
Bio-A no volume
sample. clogging of (400
The filtrate mL)
flow
the surface was
ofrate
the replaced
is inversely
membrane. within
related
As shown toa the
in Figure two-week
viscosityperiod for the low
of the solution, so and particles.
andEach
particles.
of theEacheffluents
of the
s
rch,viscosity
on Bio-A sample.
(higher The filtrate
crosslink flow
density) rate is inversely
resulted in
6 the entire container volume (400 mL) was replaced within a a related
faster to the viscosity
replacement of of
thethe solution,
serum. The so
fontheviscosity (higher
Bio-A solution
two-week crosslink
was longer
period density)
than
for the low the resulted
other starch,
crosslinked in Bio-A
samples, a faster
due toreplacement
sample. of the serum.
its higher viscosity. The totalThe
flaced starch solution
the Bio-A after
Thetwo-weeks
wasflow
filtrate longerwasisthan
rate 9.28%. The
othermedium
the related
inversely tosamples, crosslinked
the viscositydue to itsstarch,
of the higherBio-B, had The
viscosity. the full
total
me
acedreplaced
starch aftersolution,
twice within
two-weeksso a twelve
lowerwassolution
days. viscosity
9.28%. AtThe (higher
the endcrosslink
medium density)33.17starch,
of 12crosslinked
days, % of the
Bio-B,original
had starch
the full
resulted in a faster replacement of the serum. The replacement of
Thereplaced
me high crosslinked
twice withinstarch Bio-C
twelve had At
days. the the
fullendcontainer
of 12 volume
days, replaced
33.17 % of twice
the withinstarch
original just
the Bio-A solution was longer than the other samples, due to its
52 %high
The of the original
higher starch
crosslinked starch
viscosity.wasThe replaced
Bio-C had within
total amount the this
full
of replaced period.
container
PEER-REVIEWED
starch aftervolume
ARTICLE
two- replaced twice within just
52 % of the original starch was replaced within this period.
weeks was 9.28%. The medium crosslinked starch, Bio-B, had Table 3.3.The Table The mass balance of serum replacement experiments.
mass balance of serum replacement experiments.
the full container volume replaced twice within twelve days. At
the end of 12 days, 33.17 % of the original starch was replaced.
The high crosslinked starch Bio-C had the full container volume
replaced twice within just nine days, and 52 % of the original
starch was replaced within this period.
Table 3 presents the mass balance of the system undertaken
to verify the amounts of replaced starch. The theoretical
amount of starch latex (V1) in the container was determined
from the difference in the original weight of the starch
ogy·Innovation·Manufacturing·Environment
latex before replacement (eg 5.17 g As for starch
Bio-A)in solution
5
and the can spoil at room temperature, a biocide was added to the starch latex dispersion
Appita Technology·Innovation·Manu
Appita Technology·Innov
ogy·Innovation·Manufacturing·Environment water
total amount of starch in the filtrate (eg 0.48 g for Bio-A). reservoir. Similarly, 5
to control the pH of the solution, a Na 2CO3 buffer was added to the res
However, the amount of these components added was minimal relative to the total water volume, thu
Fig.6.The daily change amounts of starch passed through the 30 nm membrane.
masses were neglected within the weight calculations.
To assess the molecular structure of materials in each filtrate, the swell ratio was determined as sho
TableTable
4. The3 presents
composite the mass balance
(or average) of of
swell ratio theallsystem undertaken
the filtrates to verify
and the material the amounts
remaining in the con
254 Appita TECHNOLOGY • INNOVATION • MANUFACTURING • ENVIRONMENT
then theoretical amount of
calculated according starch latex
to Equation 3. (V1) in container was determined from the differenc
of the starch latex before𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶
replacement (eg∑𝑛𝑛𝑛𝑛𝑖𝑖𝑖𝑖=5.17
𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 = g𝑖𝑖𝑖𝑖 +(𝐵𝐵𝐵𝐵
1(𝐴𝐴𝐴𝐴 ×𝐶𝐶𝐶𝐶) for×𝐶𝐶𝐶𝐶)
Bio-A) and the total amount
[3] of
∑𝑛𝑛𝑛𝑛
0.48 g for Bio-A). The amount of unaccounted 𝑖𝑖𝑖𝑖=1 losses
𝐴𝐴𝐴𝐴𝑖𝑖𝑖𝑖 + 𝐵𝐵𝐵𝐵
was then determined using the
where A is the starch volume of each filtrate, B is the starch𝑉𝑉𝑉𝑉volume
1 −𝑉𝑉𝑉𝑉2
remaining in the container, and C
PEER REVIEW
ARTICLE
able 3. The
Table
mass3.balance
The mass
of serum
balance
replacement
of serum replacement
experiments.
experiments.
PEER-REVIEWED ARTICLE
olution
spoil atcan
room Fig.6.The
spoil at room daily
temperature, change
temperature,
a biocide was added Fig.6
a amounts
biocide ofthe
to
was The daily to
starch
added
starch
Table
change
passed
latex
the amounts
through
4. starch
of starch
dispersions
The latex
swell the passed
nmthrough
30(SR)
dispersions
and
ratios and
of
the 30 nm membrane.
membrane.
filtrates, original samples, and composites: Bio-A (low cross
y,
ir. to
Similarly,
control the
to control
pH of the the solution, Na2CO3 buffer
pH of thea solution, a Na2CO was 3 buffer
added was
crosslinked). to theadded
reservoir.
to the reservoir.
these
amount components
of these components
added
Table
To was
the minimal
3 presents
assess added was
the
molecular relative
minimal
mass
structure to
ofthe
relative
balance totalof
materials to
water
the
eachtotal
inthe volume,
systemwater
filtrate, thus
the volume,
their
Table thus
undertaken 4. totheir verify the amounts of replaced starch. The
neglected
ithin the weight
within calculations.
the weight calculations.
ns by serum theoretical amount
swell
replacementratio was
(Bio-A, of starch latex (V1) in container wasThe
determined as shown in Table 4. The composite (or determined from the difference in the original weight
molecular
structure ofstructure
materials ofinmaterials
average) each
swelllatexin of
ratio each
filtrate, all filtrate,
thethe
swell theandswell
ratio
filtrates was ratio was
the determined
material as shown inasswell
determined
remaining shownratiosin
or average)(or
composite of
swell the
ratio
average) starch before replacement (eg 5.17 g for Bio-A) filtrates, total amount of starch in the filtrate (eg
and the
in theof all the
swell ratiofiltrates
container of then
was and
all the the material
filtrates
calculated and the
accordingremaining
material
to Equationin the
3. container
remaining in(SR)
theofcontainer
0.48 g for
Equationto3.Equation
dtoaccording 3. Bio-A). The amount of unaccounted losses was then
original determined
samples, and using the following equation:
∑𝑛𝑛𝑛𝑛 (𝐴𝐴𝐴𝐴 ×𝐶𝐶𝐶𝐶) +(𝐵𝐵𝐵𝐵
∑𝑛𝑛𝑛𝑛 ×𝐶𝐶𝐶𝐶) 𝑉𝑉𝑉𝑉 −𝑉𝑉𝑉𝑉2 composites: Bio-A (low
𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶
𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 = 𝑖𝑖𝑖𝑖=𝐶𝐶𝐶𝐶1𝐶𝐶𝐶𝐶∑𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆
(𝐴𝐴𝐴𝐴 ×𝐶𝐶𝐶𝐶)𝑖𝑖𝑖𝑖 +(𝐵𝐵𝐵𝐵 ×𝐶𝐶𝐶𝐶)
𝑖𝑖𝑖𝑖
𝑛𝑛𝑛𝑛 𝐴𝐴𝐴𝐴=
𝑖𝑖𝑖𝑖=1 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 𝐿𝐿𝐿𝐿𝑜𝑜𝑜𝑜 𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺 % =[3]1𝑉𝑉𝑉𝑉 × 100
[3] [2]
𝑖𝑖𝑖𝑖=1 𝑖𝑖𝑖𝑖 + 𝐵𝐵𝐵𝐵 ∑𝑛𝑛𝑛𝑛
crosslinked) and Bio-C
𝑖𝑖𝑖𝑖=1 𝐴𝐴𝐴𝐴𝑖𝑖𝑖𝑖 + 𝐵𝐵𝐵𝐵 1
eume
starch
of each
volume where
filtrate,
of eachVfiltrate,
B is is starch
1the theB theoretical
isvolume
the starch
remaining
volume V2 is
amountinremaining
and in theand
the container, actual amount
container,
C is (high
the C isofthe
starch
andcrosslinked). latex in container after replacement.
where A is the starch volume of each filtrate, B is the starch
Forvolume
Bio-A the theoretical amount is 4.69 g (V1: 5.17 – 0.48 = 4.69 g), but the actual amount of starch latex
remaining in the container, and C is the swell ratio.
wasIf4.32the massg (V 2: 5.17
balance – 0.85
is correct, = 4.32sample g). The unaccounted amount, using equation 2, was 7.88% ((4.69-
alance
rrect, the
is correct,
originalthe sample
originalswellsample
ratio swell
should be the
ratio equal original
should tobe theequal toswell
composite ratio
the swell
composite
ratio. swell ratio.
R)
ell ofratio
each
(SR) of4.32)/4.69*100).
filtrate should
each
helps be provide
filtrate
to equal
helpsto toaIt iscomposite
likely
theclearer
provide a that
picture swell
clearerthis
of ratio.
the loss
picture is the
Also,
molecular
of due
the swellto the adsorption
structure
molecular ofstructure ofof starch latex particles onto the container
ough
passedthethrough
membrane wall
ratioor
the filter pipes
(SR)
membrane of of
each
(Tablefilter the
4). (Tableapparatus.
filtrate
As shown helps
4). in to provide
AsTable
shown a
4, in clearer
theTable picture
original
4, theswell of
original
ratios,swell ratios,
were
placement
quite were
similar theto molecular
quite the
similar tostructure
composite the swell of ratios,
composite materials
swell that
whichratios,passed
help to through
which help the
validate to
thevalidate
mass the mass
chlations.
of theEach
filtrates membrane
of theshowed
filtratesfilter (Tableswell-ratios
different
showed 4). As shown
different in Table
swell-ratios
with time 4, the
as original
with time swell
shown inas Table
shown4.in Table 4.
s, all
of Bio-B
filtrateswere ratios,
of Bio-B
lost, but SR,
were before
high
lost,
and replacement
butlowhigh andwere
crosslinkedlow quite similarlatexes
crosslinked
biobased tobiobased
the composite
clearlylatexes
showed
clearly showed
s.swell ratios. swell ratios, which help to validate the mass balance calculations.
xture
tex isofa low
mixture
and ofhighlowmolecular
and highall
Unfortunately, weight
molecular linear
filtrates weight
of and
Bio-B branched
linear
wereand polymer
branched
lost, but high molecules
polymer
and and molecules and
he
swell original
ratio is anAppita
swell average
ratio
low is Technology·Innovation·Manufacturing·Environment
an
swell
average
crosslinked ratio of
swell
biobased the ratio
low
latexesand
of clearly
the
high
lowmolecular
and high
showed weight
molecular
characteristic polymers
weight polymers 6
effluents
Each showed
of the effluentsa different
swell ratios.swell-ratio
showed a different with time aswith
swell-ratio showntimeinasTable
shown 4. in Table 4.
Each starch latex is a mixture of low and high molecular weight
linear and branched polymer molecules and particles, so the
original swell ratio is an average swell ratio of the low and high
molecular weight polymers and particles. Each of the effluents
For Bio-A, the swell ratios of the filtrates were much lower than the average, from d
showed a different swell-ratio with time as shown in Table 4. materials in the filtrates have not been quantitatively analysed,
suggests that the filtrates collected on those days contained very low molecular so
For Bio-A, the swell ratios of the filtrates were much lower their swell ratios suggest that they have both nanoparticles that
appeared to mostly have water-swollen particles larger than 30 nm and large soluble
than the average, from day 2 to day 14, which suggests that the are smaller than 30 nm and low molecular weight soluble starch
filtrates collected on those days contained could very low notmolecular
pass through the 30
molecules nm pore filter, based on the serum replacement measurem
present.
weight soluble starches. Bio-A appeared to mostly have water-For Bio-C, the swell ratios were lower than the average for day 1 to day 3, which can
Particle Size of Biobased Latex
swollen particles larger than 30 nm and crosslinked large soluble starch small particles or very low molecular weight soluble starch. For day 8 to
molecules that could not pass through the 30were nm pore higher than the
filter, based Foraverage
measurementswellof particle
ratio, size distributions,
which can also1%attributed
solid biobased
to high molecular
on the serum replacement measurements. Bio-C appeared to have more nanoparticles smaller than 30 the
latex dispersions were prepared. Before measuring
nm,particle
compared to Bio-A.
For Bio-C, the swell ratios were lower than replaced
the average for day size,
materials
all samples were sonicated, because starch molecules can be
in the filtrates have not been quantitatively analysed, their swell ra
1 to day 3, which can be attributed to highly crosslinked small associated due to hydrogen bonding in water.
have both nanoparticles In that
Table 5, are
all Chismaller than were
squared values 30 nm and low
extremely high (χmolecular
2
> 3), weight sol
particles or very low molecular weight soluble starch. For day 8
present.
to day 9, the swell ratios were higher than the average swell ratio, so all the analysis followed NICOMP Analysis (11). NICOMP
which can also be attributed to high molecular weight soluble 370 DLS has three different types of weighting systems; (a)
Particle Size of Biobased Latex (b) volume-weighted, (c) number-weighted
intensity-weighted,
x dispersions and starch. Bio-C appeared to have more nanoparticles smaller for data analysis. Table 5 presents the intensity weighted data.
ation·Manufacturing·Environment
logy·Innovation·Manufacturing·Environment For
7 measurement7 of particle size distributions, 1% solid biobased latex dispersions w
to the reservoir. than 30 nm, compared to Bio-A. Although the serum-replaced
volume, thus their measuring the particle size, all samples were sonicated, because starch molecules can
hydrogen bonding in water.
ined as shown in In Table 5, all Chi squared values were extremely high (χ2 > 3), so all the analys
gamounts of replaced starch. The
in the container Analysis (11). NICOMP 370 DLS has three different
Vol 70 No 3 Julytypes of2017
- September weighting
255 systems; (a) i
e difference in the original weight volume-weighted, (c) number-weighted for data analysis. Table 5 presents the intensity
mount [3] of starch in the filtrate (eg Problems due to aggregation of the starch molecules due to hydrogen bonding durin
using the following equation: consistent and reliable results for the particle sizes of biobased latexes at different co
iner, and C is the
PEER-REVIEWED ARTICLE
PEER REVIEW
PEER-REVIEWED ARTICLE
A CLC coating study was conducted to evaluate the overall performances of biobased latexes. Fi
Table 6. Coating
10 illustrate formulations
the coated with properties
paper 30% XSB replacement.
for all six trials. Except for gloss, all the coated paper
Coating Colours # which
1 were dependent
2 on coat 3 weight, were 4 similar. In Figure
5 9, the gloss
6 of Bio-A was the wors
with the other coated papers, which indicates that the amount of soluble starch in Bio-A and c
Coating Description XSB +CMC affects
density 30%film
Bio-Aformation.
30% Bio-B
Shrinkage 30%leads
Bio-C to rougher
30% Starch XSB Onlysurfaces, which can red
paper coating
Pigment [pph] optical properties,
Fig.8 Coating such as time
immobilization gloss. Conventionalatcooked
characterization (water-soluble) starches
37 °C. (7)
Fig. 9.have
Thebeen
properties o
reporte
GCC upon
70 drying and70lead to a reduction 70 in paper 70 optical properties
70 (especially
70 gloss) relative to petro
Clay SB 30
A CLClatexcoating
bindersstudy
30 (12). was
Therefore,
30
conducted it istobelieved
evaluatethat
30 the the larger
30
overall amount of soluble
30
performances starchlatexes.
of biobased molecule
Fig
Binder [pph]
10 illustrate the coated paper properties for all six trials. Except for gloss, all the coated paper
XSB Latex 10 7 7 7 7 10
Bio-A
which
0
were dependent
3
on coat0 weight, were0 similar. In Figure 0
9, the gloss
0
of Bio-A was the wors
Bio-B with
Appita
0 the other coated papers, which indicates
Technology·Innovation·Manufacturing·Environment
0 3 0 that the amount
0 of soluble
0 starch in 10
Bio-A and cr
Bio-C density
0 affects film0 formation.0 Shrinkage leads 3 to rougher0 paper coating 0 surfaces, which can red
Starch optical
0 properties, 0 such as gloss. 0 Conventional 0 cooked (water-soluble)
3 0starches have been reporte
Additives [pph] upon drying and lead to a reduction in paper optical properties (especially gloss) relative to petrol
CMC 0.5 latex binders0 (12). Therefore,
SB 0 0
it is believed 0
that the larger amount 0of soluble starch molecule
Ca-Stearate 0.25 0.25 0.25 0.25 0.25 0.25
Solid Content, % 66.7 66.7 67.0 66.7 66.7 67.0
pH 8.0 8.0 8.1 8.1 8.1 8.0
Brookfield [mPa.s], 100 rpm Appita
2460 Technology·Innovation·Manufacturing·Environment
1250 560 370 1380 1170 10
Fig. 9. The properties
As shown in Figure 8, all of the six coating formulations studied SB latex binders (12). Therefore, it is believed that the larger
showed clear immobilization times (7). Bio-A (low crosslinked amount of soluble starch molecules in Bio-A, compared with
biobased latex) showed the highest dynamic water retention, Bio-B and C, contributes to the shrinkage. However, the highly
atexes. Figures 9while
andthe all synthetic latex system gave poor water retention. The crosslinked biolatex Bio-C, like hard spheres, is more resistant to
ated paper properties, demonstrated that even the more highly crosslinked Bio-C
results shrinkage during drying.
grade of biobased latex had good water retention performance As shown in Figure 10, the gloss of coated papers containing
s the worst compared
compared to the all-synthetic binder coating formulations with XSB dominated the others, which is caused by plasticizing of
o-A and cross-linking
or without CMC. The temperature was increased to better reflect petroleum based polymers during calendaring. Hydroxyethylated
ch can reduce critical
conditions in a paperpapers
mill by(coat
raisingweight
the sample starch and 1, 3-butadiene and styrene appeared to have good film
roperties
een of uncalendered
reported to shrink coated [g/mchamber
2
]) from
room temperature to 37 °C. Fig. 9. The properties of forming properties
uncalendered as shown
coated in Figures
papers (coat9weight
and 10. [g/m2])
ve to petroleum-basedA CLC coating study was conducted to evaluate the overall The formation of a latex film arises from the coalescence
hatexes.
molecules in Bio-A,
Figures 9performances
and of biobased latexes. Figures 9 and 10 illustrate the (i.e. compaction, deformation, cohesion and polymer chain
ted paper properties,
coated paper properties for all six trials. Except for gloss, all the interdiffusion) of the individual latex particles, as shown in Figure
s the worst compared
coated paper properties, which were dependent on coat weight, 11 (13). The formation of a continuous film (i.e. transparent and
-A and cross-linking
were similar. In Figure 9, the gloss of Bio-A was the worst crack-free) is then dependent on the minimum film formation
compared with the other coated papers, which indicates that
ch can reduce critical temperature (MFFT) of the polymer. If the film is cast above
the amount of soluble starch in Bio-A and cross-linking density
en reported to shrink its MFFT, then deformation and cohesion of the latex particles
affects film formation. Shrinkage leads to rougher paper coating
e to petroleum-based can occur (13). During film formation, SB latex is not subject to
surfaces, which can reduce critical optical properties, such as significant shrinkage upon drying and is known to deliver good
molecules in Bio-A,
gloss. Conventional cooked (water-soluble) starches have been optical properties, such as gloss and roughness (12). However,
reported to shrink upon drying and lead to a reduction in paper the lowest crosslinked Bio-A underwent very severe shrinkage
optical properties (especially gloss) relative to petroleum-based during drying (Figures 8 and 9).
properties of uncalendered coated papers (coat weight [g/m2])
PEER-REVIEWED ARTICLE
The formation of a latex film arises from the coalescence (i.e. compaction, deformation, cohesion an
polymer chain interdiffusion of the individual latex particles, as shown in Figure 11 (13). The formation of
continuous
Fig. 10 film (i.e. transparent
The properties of calenderedand coatedcrack-free) is then
papers (Conditions: 131 dependent
N/mm (2 passes), on 60 the°C,minimum
coat weight film formatio
[g/m2]).
temperature (MFFT) of the polymer. If the film is cast above its MFFT, then deformation and cohesion
Fig. 10 The properties of calendered coated papers (Conditions: 131 N/mm (2 passes), 60 °C, coat weight [g/m ]).
2
the latex particles can occur (13). During film formation, SB latex is not subject to significant shrinka
upon drying and is known to deliver good optical properties, such as gloss and roughness (12). However, t
lowest crosslinked Bio-A underwent very severe shrinkage during drying (Figures 8 and 9).
Fig.11 The illustration of idealized latex film formation as it transitions from a wet latex dispersion (upper) to a dried fi
(lower). Fig.11 The illustration of idealized latex film formation as it transitions from a wet latex dispersion (upper) to a dried film (lower).
CONCLUSIONS
258 Appita TECHNOLOGY • INNOVATION • MANUFACTURING • ENVIRONMENT
The separation of both free and adsorbed low molecular weight solubles and crosslinked small star
particles from starch nanoparticle dispersions was undertaken using serum phase replacement. The resu
PEER REVIEW
CONCLUSIONS
The separation of both free and adsorbed low molecular weight solubles and crosslinked small starch particles from starch nanoparticle
dispersions was undertaken using serum phase replacement. The results obtained from the serum replacement experiment provided
information on the amounts of replaced starch molecules and particles. The amounts of replaced starch were dependent on crosslinked
density (Table 3). The swell ratios of filtrates elucidated the components of starch latex mixed with low and high linear and branched
polymer molecules and particles (Table 4). Bio-A appeared to have mostly large water-swollen particles and large molecular weight
soluble starch, based on the serum replacement measurements. Bio-C appeared to have more nanoparticles smaller than 30 nm,
compared to Bio-A.
Hydrogen bond association of the starch molecules was found to occur during particle size measurements. The resulting aggregation
of the molecules thus prevented consistent particle size measurements to be made of the biobased latexes.
In the CLC trial, the deformation of solid SB latex occurred due to plasticity during calendering, which improved the gloss of all SB
latex coated paper. However, the roughness caused by shrinkage occurred regardless of the better rheological performance and water
retention in coatings containing starch. Hydroxyethylated starch functioned well as a rheology modifier by improving water retention
and showed better film-forming properties than Bio-A. It is expected that the large amount of soluble starch molecules (mostly linear
and branched) in Bio-A caused more shrinkage to occur than the other biolatexes. The grafted and crosslinked polymers (Bio-B and
Bio-C) were durable against shrinkage.
ACKNOWLEDGEMENTS
The authors express appreciation to the Paper Technology Foundation at Western Michigan University and EcoSynthetix Inc. for
partial financial support of this work.
esion and
mation of a
formation REFERENCES
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mall starch
The results
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