Note: Descriptions are shown in the official language in which they were submitted.
20~2~87
ToM~n ~MULSIONS US~D ~S DUST CONTRO~
ADDITIV~8 IN ~NTI-SKID COMPOSITXON~
The present invention relates generally to a unique
anti-skid composition which includes a colloidal silica and
a water-based elastomer emulsion. This anti-skid
composition is particularly effective in controlling dust
produced during treatment of cellulosic fibers in alkaline
papermaking proce~ses, esp~cially when higher dosages of the
anti-skid composition are required to maintain a
satisfactory slide angle. It is particularly useful in
imparting anti-skid properties to linerboard, fine paper and
newsprint.
BACKGROUND OF THE: INVEN'rION
Paper articles fabricated from Kraft paper, cardboard
and other types of cellulosic fiber material have a tendency
to slip and slide against each other, especially during
transporting or stocking. This tendency is undesirable and
in many cases harmful.
Various attempts have been made to overcome this
slipping and sliding problem. For example, containers
fabricated from crepe paper or containers treated with a
form of an adhesive have been employed. Such containers
have not been entirely satisfactory for reasons including
2072~87
economy, poor printing characteristics, in~uff:icient slip
resistance, unpleasant or uncomfortable handling
characteristics, cleanability factors and excessive amount
of material required.
The problems of slippiny and sliding are exacerbated
when recycled fiber is us~d in the cellulosic mater;al. As
a consequence of extra processing, when compared with virgin
fiber, tha fiber length of the recycled material is less
than that of the virgin fiber. The tendency to slip and
slide increases as the amount of recycled fiber increases.
In recent years there has been a tendency to increase the
proportion of recycled fiber in cellulosic material, so that
the problem of slipping and sliding is increased.
Furthermore, the use of recycled fiber in the finished
paper has led to increasing problems in the handling of the
paper, both in the mill and at converters, because oE its
increased slipperiness. This loss in the coefficient of
friction is due to the shorter fibers, as well as from
contaminants introduced with the recycled paper. These
contaminants include dirt, wax, cold and hot melt adhesives,
water proo~ing, and other special coatings, etc.
The problem of slipping and sliding has also been
overcome by coating the cellulosic fibrous material with an
~7268~
anti-skid product, such as colloldal silica. See Charles c.
Payne, "coating Paper with Colloidal Silicas Helps stop
Slippage of Containers," Puln & Pa~er, August 1989, pp. 90-
sl. The colloidal silica is normally applied just before
the takeup reel on a paper machine to take advantage o~ the
"reel building" properties of the product. Without silica,
telescoping ef~ects often occur at that point.
The colloidal silica is typically applied by any of a
number of conventional applicatiorl methods. In lower speed
machines, a water box application has been successfully
used. In high spee~ machines, the colloidal silica has been
applied as a surface coating by the "size" press in the
paper mill. More commonly, however, a series of low
pressure sprays apply the material to the sheet as it is
being wound on its final reel.
Slide angles in paper products are preferably above
20. This slide angla can be determined by positioning two
paper surfaces (i.e., boxes coated with colloidal silica)
one on top of the other, such -that colloidal silica
particles from one surface rub against particles on the
second surface and create friction. 5ideways foxce is
required to cause the two boxes to slide against each other.
If the two boxes are placed on an inclined plane, the angle
where the two surfaces slide against each other is the
"slide angle" or "coefficient of friction". The coefficient
2072~7
of friction is equal to the tangent of the slide angle.
Surface treatment with colloidal silica increases the sk~tic
friction of linerboard~
Slide angles of less than 20O are the cause of several
paper handling problems. First, in the paper mill itself it
may be difficult to rewind the sheet as it would tend to
wander along the reel. Additionally, when clamp trucks
attempt to lift finished rolls of paper for shipping, the
center of the reel may telescope out.
Slide angle retention with repeated slides is an
important and practical factor of anti-skid material. To be
effective, the coatin~ of colloidal silica must remain on
the surface. Total removal or loss of the silica particles
reduces effectiveness against slippage, resulting in
increased breakage of packaged goods. Conversely, problems
have arisen when the colloidal silica adheres to strongly to
machinery, application equipment, floor surfaces, etc. when
overspray occurs. Recently, commercial colloidal silica sol
products containing urea have appeared on the market. (See
Canadian Patent No. 1,156,803 (Carstens)). Those materials
tend to eliminate this adherence problem in the formation of
a water washable material.
The use of urea with an aqueous sol or suspension of
colloidal silica provides a dual benefit in achieving better
~7~7
slide angles. First, the presence of urea provides the
surface of a material coaked with khe anti-skid composition
with a more permanent and constant coefficient of friction.
Secondly, the urea serves to "blindl' or "encapsulate" wax
particles which accompany recycled paper and contribute to
ts sli eriness
L pp
Although ability to impart a high slide angle and
washability are important, there are other desirable
characteristics of an anti-skid composition. It should be
stable over a period of at least several weeks at
temperatures up to 50 C or higherO It should also be non-
dusting. The magnitude of any dusting problem depends to
some extent on the speed at which machinery handling the
cellulosic material operates; the faster the machine
operates the greater it~ tendency to throw dust in the air.
Hence, as machine speeds increase this problem also
increases.
One attempt at satisfying all of the requirements for
an anti-skid composition, i.e., washability, slide angle,
stability and dust control, is set forth in U.S. Patent
Application, Serial No. 07/493,1~0, filsd March 15, 1990.
This application provides an anti-skid composition for use
on cellulosic fibrous material which comprises wate~,
colloidal silica having a particle size in the range 10 to
150nm, a wat~r soluble acrylamide polymer and, preferably, a
~0~2~87
compatible amphoteric, anionic or nonionic surfactant. This
anti-skid composition is applied to the cellulosic fibrous
material in a known manner. For example, when applied to
linerboard the composition may be added to water sprayed
from a spray bar onto a roll which is part of the machine on
which the linerboard is formed. The amount of the
composition added to the water is usually about 5~ by
volume. In a typical machine this may require supply of the
anti-skid composition at a rate of about 135 to 140 mL/min.
In non-alkaline papermaking processes, the use of the
aforementioned anti-skid composition comprising water,
colloidal sil~.a having a particle size in the range 10 to
150nm and a water soluble acrylamide polymer, and rosin size
provides satisfactory anti-skid results. However, many
papermaking processes have been converted to alkaline
processes and the rosin replaced with an alkyl ketene dimer
sizing. Unfortunately, these alkaline papermaking processes
have been experiencing increased slipperiness in thelr paper
products. The anti-skid composition of colloidal silica and
crosslinked polyacrylamide binder did not provide sufficient
performance, as it reached a perEormance plateau far sooner
than the requirements demand. Another drawback of the
colloidal silica and crosslinked polyacrylamide anti-skid
composition was the increased dusting generated at higher
dosages. It was believed that maybe the crosslinked
polyacrylamide did not have enough binding force for the
2~72f.~7
colloidal silica. Attempts at adding more crosslinked
polyacrylamide blnder resulted in a destabilized product.
The present invention provides a unique antl-skid
composition which is capable of meeting all slide angle,
washability, stability and dust control performanc~
requirements when added to an alkaline paper product,
especially linerboard, fine paper or newsprint~ Moreover,
the unique dust control additive of the present invention
permits substantial increases to the feed rate of the anti-
skid composition without dusting.
The present invention also provides many additional
advantages which shall become apparent as described below.
SUMMARY OF TH~ INVF.NTION
An anti-skid composition for use on cellulosic Eibrous
material. The anti-skid composition includes water,
colloidal silica and a water-based elastomer emulsion. It
is particularly useful in overcoming slipperiness and
dusting problems associated with the production of alkaline
paper products~ e.g., linerboard, fine paper and newsprirlt.
The colloidal silica used in this anti-skid composition
typically has a mean particle size in the range from about
10 to about 150 nm. One preferred colloidal silica has a
2~72~8~
particle size in the range from about 15 to abou-t 25 nm, a
pH in the range from about 8.0 -to about 9.5, a surface area
in the range from about 120 to about 176 m2/gram, and a
viscosity at 77F of less than about 70 centipoise.
The water~based elastomer emulsion is preferably a
film-forming rubber polymer resistant to heat, light and
ozone, e.g. an elastomeric terpolymer~ A preferred
elastomeric terpolymer has 50.5% total solids, pH of 8.4,
surface tension of 40 dynes/cmj BrookPield viscosity of 200
centipoise, and a particle si2e of 0.2 microns.
Another object of the present invention is an article
comprising a substrate having adhered to at least one
surface thereof an effec-tive amount of anti-skid composition
according to the present invention.
Still another object of the present invention is a
process for improving the anti-skid properties of cellulosic
fibrous material, as determined by the slide angle, which
process comprises applying to the cellulosic fibrous
material an anti-skid composition which comprises water,
colloidal silica and a water-based elastomer emulsion;
whereby the dusting tendency of the colloidal sillca during
application is satisfactorily controlled.
~2~87
The anti-skid composition according to the present
invention is particularly effecting in controlling dust and
slipperin~ss when used to treat alkaline cellulosic ~ibrous
material comprising alkyl ketene dimer siæing.
Other and further objects, advantages and features of
the present invention will be understood by reference to the
following specification.
D13SCRIPTIO~ OF THE~ PRE~FBRR:E:D EMEIODIM~3NTS
The use of a low cost elastomer emulsion as a binding
agent in the anti-skid composition according to the present
invention is extremely effective in controlling the dusting
tendency of the colloidal silica also contained therein,
especially in alkaline papermaking processes. It has also
proved to be effective in preventing slipperiness in the
resultant paper product which can have a slide angle of 28
and above.
The water-based elastomer emulsion may be combined with
a colloidal silica in any convenient manner. Thus, the
elastomer emulsion may be combined with the colloidal silica
and the concentrations of the components adjusted by proper
dilution with water. The normal anti-skid treatmen~
employed by many paper mills consists of spraying a dilu-te
2~72~7
dispersion of collo.idal silica on the surface of the paper
product.
The anti-skid composition according to the present
in~ention and used on cellulosic fibrous material comprises
water, colloidal silica and a water-based elastomer
emulsion. While various combinations of colloidal silica
and water-based elastom~.r emulsion have proved suitable, it
has been found that a ratio of colloidal silica to elastomer
emulsion of about 40 to 1 is most effective.
The anti-skid composition preferably has a pH value in
the range between about 7 to 10, more preferably in the
range between about 8.5 to 9.5.
When applied to linerboard the anti-skid composition
may be added to water sprayed from a spray bar onto a roll
which is part of the machine on which the linerboard is
formed. The amount o~ the composition added -to the water is
usually about 5~ by volume. In a typical machine this may
require supply of the anti-skid composition at a rate of
about 135 to 140 mL/min. However, in alkaline papermaking
processes this rate may be substantially increased to
approximately 380 mL/min. The quantity can of course be
metered and varied in accordance with need.
2 0 7 2 ~ ~ r~
COLLOIDAL SII-ICA
The mean particle size of the colloidal silica should
fall within the range of about lo to about 150 nm. An
example of a suitable colloidal silica used herein is one
having a particle size in the range from about 15 -to about
25 nm, a pH in the range from about ~.0 to about 9.5, a
surface area in the range from about 120 to about 176
m2/gram, and a viscosity at 77F of less than about 70
centipoise.
The colloidal silica is typically present in the range
of approximately 5 to 50~ by weight, based on the total
weight of the anti-skid compositio~. Preferably, the
colloidal silica shoùld be present in concentrations of
approximately 30 to 50% by weight, based on the total weight
of the composition. However, the precise concentration of
colloidal silica can be varied on an ever wider scale
depending upon particular application methods and conditions
within the skill of the artisan.
WAT~R-BAS~D ~LASTOM~R EMULSION
The water-based elastomer emulsion is typically a film-
forming rubber polymer resistant to heat, light and ozone,
e.g., an elastomeric terpolymer sold under the trademark
HyStretchTM V-43 by The B.F. Goodrich Company. Thel
HyStretchTM latex V-43 is an elastomeric terpolymer having
50.5~ total solids, pH of 8.4, surface tension of 40
2~2~87
dynes/cm, Brookfield viscosity of 200 centipoise, ancl a
particle size of 0.2 microns. HyStretchTM elastomer
emulsions are sprayable, foamable and heat sensitizable.
The elastomer i5 preferably present in the anti-skid
composition in the range between about 0~1 to about 5%, as
active material. Concentrations above 5% tended to reduce
the slide angle of the papPr product.
This anti-skid composition is preferably adhered to at
least one surface of an article comprising a suhstrate. The
substrate is typically a paper product such as linerboard,
fine paper, or newsprint. The substrate may be formed from
either virgin fibers, recycled fibers or any combination
thereof.
The anti-skid composition of the present invention is
particularly useful for improving the anti-skid properties
of cellulosic fibrous material, as determined by the slide
angle, which process comprises applying to the cellulosic
fibrous material the anti-skid composition which comprises
water, colloidal silica and a water~based elastomer
emulsion; whereby the dusting tendency of the colloidal
silica during application is satisfactorily controlled.
Although this anti-skid composition improves the an~ti-skid
properties and controls dusting in conventional papermaking
processes, it is particularly effective when used to treat
2~2~87
alkaline cellulosic fibrous material comprisiny an alkyl
ketene dimer siæing.
This anti-skid composition is typically added to the
alkaline cellulosic ~ibrous material in a dosage within the
ran~e between about 300 to about 380 mL/min, and *o non-
alkaline cellulosic fibrous material in a dosage within the
range between about 135 to about 140 mL/min.
The properties and effectiveness of the anti-skid
composition in controlling dust and slipperiness in the
manufacturing of linerboard, fine paper and newsprint is
clearly demonstrated in the below examples. Also set forth
below is comparative data demonstrating the increased
effectiveness of the anti-skid composition verses
conventional compositions in treating alkaline paper
products.
~X~MP~ 1
The test procedures for det.ermining slide angle involve
dipping suita~le dimensioned strips of mill paperboard into
a one-day old 5~ solution of formulated product, i.eO, alkyl
ketene dimer (AKD) size, solution~ The lightly wetted
papers were then sandwiched by two blotter papers and dried
by a drum dryer.
2 ~ r~4 2 ~ 8 ~
Anti-skid compositions with various formulations were
prepared as 5% ~olutions. Thereafter, the AKD-coated papers
were treated in the same manner as above with these anti-
skid compositions. The colloidal silica used in samples 3-6
had a particle size of about 20 nm, a pH of about 8.5, a
surface area of about 150 m2/gram, and a viscosity at 77F
of about 15 centipoise. The elastomer in samples 4-6 was an
elastomeric terpolymer having 50.5~ total solids, pH of 8.4,
surface tension of 40 dynes/cm, Brookfield viscosity of 200
centipoise, and a particle size of 0.2 microns sold under
the trademark HyStretchTM V-43 by The B.F. Goodrich Company.
Samples of the treated paper were then mounted on an
adjustable plane wherein an inclined plane tast following
AST~ procedure D3248-73 was used to determine the angle
where two surfaces slide together. Three slide angle
measurements are taken, i.e., right side, middle and leEt
side. The important criterion is the level of angle
achieved and the degree of change between the first and
third mea~urement of any one sample. The results of this
experiment are set forth below in Table 1.
TABL~ 1
91ide Anqles
S~mple Anti-Skid Conlpo~icion Riqht !liddle Lei~
~31~n~ 21' 22' 22
2 C.S. /Ure~l 79' 24 24
3 C.g.~ ~O' 29' 29'
14
.,
~72~
4 C.9. ~ elao~omor 30' ~0' 30'
S C.~. ''/2~ Bln~ton~or 1~ 11 33
6 _ C.q./~ el-~L ~2~ nlvcol~ 2~ ' 27'
C.S. d~rlo~ collol~ IUc~.
' C.S. ~lenotes ~ ~oll~ld~ hlvi~g ~ m~ll p~tlclo ~Izo o~ 2Q
-' ThC 2qr~ C;lyc~ prop~leno ~Iycol.
The sample of colloidal silica and 2% elastomer
emulsion not only gave the highest slide angle but also
exhibited no sign of rubbing off the colloidal silica (i.e.,
dusting~ from the paper surface.
~XAMP~ 2
An alkaline papermaking mill was evaluated using
various anti-skid compositions to determine their effect on
slide angle and dusting. Paper produced from this mill
without any treatment with an anti-skid composition
demonstrated a slide anyle of from about 11 to about 1~'.
When an anti-skid composition having colloidal silica
with a mean particle size of about 20 nm was used -to treat
the papex product at a dosage of about 240 mL/min. (i.e.,
0.24kg/lOOOm2) it produced a slide angle of about 23.
Since a 23 slide angle was determined by the mill op~rators
to be unacceptably low, i.e., a slide angle of at least 28'
is required to take care of base sheet variation, the ~eed
rate was increased to 300 mL/min. At a feed rate of 300
mL/min., the colloidal silica solution was dusting
moderately at the rewinder although no dust was evident at
the lower feed rate of 240 mL/min. Because of the lower
20726~7
active content of this colloidal silica, it was decided to
increase the feed rate to 380 mL/min. which produced even
greater dusting.
Upon addition of an anti-skid composition comprising
colloidal silica, an elastomer emulsion and water, the
dusting problem at the rewinder immediately disappeared.
Fifty minutes later the above anti-skid composition was
replaced with a composition comprising colloidal silica, an
elastomer emulsion, water, and a fumed silica. The purpose
of adding the fumed silica was to access whether the larger
sized fumed silica would result in a higher slide angle. No
appreciable dusting or change in slide angle was noted.
The results are set forth in Table 2 below:
~rAEL~ 2
Oos4qo Sl~r3O Allqlo
Produc~ Timo mL/min. Fronc Dsc~ Rewindu~ Obr~ervu~lo
_ _ _ _ _
C8 09~52 240 13' 2D' 23' no dusclm
C9 10:27 ]00 2n' 34' 26' d~lsCinsl
CS li:l2 J00 )2' 30' 1]' d~lscinq
cs/~l~s~ 12:20 380 22 25 31~ no duscillg
CSIE14Y/FS 12:52 3ûO 25 29' 30' no dus~ing
CS 13:59 300 Z3 ~ sclnq
No~c: (l) cs ~kao~ couoltiai ~llrlh~vlng dmcsnpatùcic1lz~ o~app~osin~ z~3
(2) l`hc d3~10mct ~mubloa v~. HySll::lcb'rM V.13.
(3~ FS denole~ ~ iumcd ~Illr~ rold ~ndcr ihc ~ecma~ to~d 2i)0.
lS
2~72~g~
~XAMPL~ 3
The following experiments set forth below in Table 3
demonstrate that the anti-skid composition accord-lng to the
present invention also performs satisfactorily when used to
treat fine paper.
'rABL~ 3
(9LID5 1-80L~ .s~ R397L~9~
Slide Allqle 9heec APr~liC~Lion
Product iliqhc Niddlo ~ Ave~sge Is/sc~m~
~Isnk 17. 4 18.3 IR. I 17 . 9 ~o wa~er
91snk 23.7 24.6 `~.o 24.1 0.11 ~9 w.lcer
CS/AA 30.8 30.3 2q. 1 30. 1 0.79
CS/AA 29. 5 27 . 2 . 9. 1 2a . 3 0. 25
CS/AA 29. 0 29. 0 .16 . q 28 . ] o . 15
CS/AA 27.5 29.5 11.7 28.5 o.oa
Cs (20nm) 27.2 32.0 J2. / 39.6 0.34
CS 120nm) 30.3 32.2 11.7 31.4 0.21
Cs 120nml 2a S 2a.0 28.D 23.4 0.16
Cu 120nml 27.5 28.5 26. 1 27.4 Od~6
CS/AA 32.0 32.3 1 1 12. 3 U.21
CS/AA 31. 3 32.3 ~ 32 . 1 0. 21
CS/AA 31.3 27.0 11. I 30.1
CS/AA 28.7 29.0 ~a. 1 2a. 1 9.0'
CS/iil~3. 3t.5 30.2 . '.S 30.4 0.29
CS/Bk3a.--- 32.0 31.2 .3 (1 30.~ 0.25
C6/~n:l. -- 2~.0 29.0 ~' S 2a.s 0.1~
CS/~ .--- 27.0 28.2 ' ' 27.6 O.oR
CS/FS--- 31.7 32.0 , 32.5 0.25
CS/FS -- 32.a 31.8 ~ ' 33. 1 ~).2a
CS/FS 32.0 30.2 1~ ~ ll.q n.~l
CS/FS 32.0 32.0 .: 30.S o. Io
C3/FS 27.5 26.8 1 . 2a.s 0.0/
Fhl~1~3coc~ 1cionolcollolds3~11ic3h3ving3m~nya~dclcsl~col~llnr~ .s~3~ dv~.ly~r~yl~n3dcllolliol~ oluliolly~l1ync~.Jl~cvc.
7.711J 1~ a oonq70sicion o~ coUold~3 siUc4 h4vlog 3 m30 pllUclc si~o ol 20mD u~3 ~ 1~ Islill~rd yoiy~ylsul8(10 nonioluiC solulioll yolym ~ 49q~ ~cc vo.
'-- 7hl~1~3co~nyo~1Uonotcolloslts3slllc3h4vl~games~r~licdcsi~co~201~ n~3J~In~ r~tmuWoo,41qSaccivs.
~r- Tlll~i~3co~lr~osllionoicolloscL~islUclhavlng3~l/3l~rdrc3clcsl~cvl2u~ mllall~ uvc.
~72~8~
While I have shown and described several embodiments in
accordance with my invention, it is to be clearly understood
that the same are su~ceptible to numerous changes apparent
to one skilled in the art. Therefore, I do not wish to be
limited to the details shown and described but intend to
show all changes and modifications wh.ich come within the
scope of the appended claims.
18
