Note: Descriptions are shown in the official language in which they were submitted.
~57Ç6~
M&G 219.396-~S-01
MOISTURE-RESISTANT CORR~GATED BOARD ADHESIVE
HAVING EXTENDED POT LIFE
Field of the Invention
The invention relates to an adhesive composition
that can be used to form a moisture-resistant bond for
corrugated board construction.
Bac~ground of the Invention
The sensitivity of corrugated board structural adhe-
sives to moisture continues to be a difficult problem for
those using shipping or storage containers made of corru-
gated board. Corrugated board is made by gluing papermembers with starch based adhesive compositions. The
resulting corrugated board product can lose strength in the
presence of high humidity, mist, rain or standing water
since both the starch and the paper members are hydrophilic
or water sensitive.
Starch-based adhesives are generally applied by coating
starch or a starch suspension on corrugated board and
heating the starch, resulting in a hydrophilic partly
hydrolyzed film of starch. The starch molecules bond the
paper members through hydrogen bonds between the starch
polysaccharides and the polysaccharides in the paper mem-
bers. However, the adhesive remains hydrophilic and can
absorb substantial amounts of water. The starch in the
presence of such water can become a gummy suspension or
emulsion of starch in water and can rapidly lose bond
strength.
The paper used in making corrugated board is generally
formed from a water slurry of cellulose derived from wood or
other plant sources which is made into a sheet by removing
water from the sheeted slurry. The sheet is commonly rolled
and dried to remove residual water resulting in finished
paper. The resulting paper remains water sensitive since
its component parts are hydrophilic and can tend to revert
partly, in the presence of water, to the dispersion of
~3g
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cellulose particles in water from which it was prepared.
The degree of water resistance engineered into corru-
- gated board varies according to the functional use of a
container made from the corrugated board. The lowest
degree of rnoisture resistance can be found in containers
made from paper members and unmodified starch adhesives.
In comparison, waterproofed boards that must survive immer-
sion in water without delamination are V board or "top iced
poltry board" where components having exceedingly high
levels of wet strength are made by fully impregnating the
board with microcrystalline/paraffin wax on the corrugator
and later curtain coated with a hard wax/polymer blend. In
these instances and all variations between them it is
important to note that water resistance requirements vary
depending on the amount of water resistance required.
Many adhesives for preparing corrugated board have
been proposed in the past including starch-based adhesives,
thermoplastic adhesives, string-like adhesives, adhesives
comprising emulsions of synthetic polymers, and others in
both acidic and basic media. Starch based adhesives have
been made in a variety of formulations including high
amylose starch adhesives, resorcinol-formaldehyde adhesives~
calcium cyanamide-formaldehyde resins, urea-formaldehyde
resins, and ketone-formaldehyde resins.
One type of starch adhesive can contain ketone-form-
aldehyde resins. These resins are useful in starch based
adhesives but are generally so chemically reactive that only
limited amounts have been used in the past in corrugating
adhesives. Starch-based ketone-formaldehyde resins can
prematurely insolubilize raw starch and can prevent or
interfere with starch gelatinization. Addition levels of 25
to 50 lbs. (12-23 kilograms) of dry resin solids (2.5 to 4~
of resin based on the starch) to a 700 gallon batch of
standard adhesive are common. Further, it is believed that
the ketone formaldehyde resin can only provide limited
moisture resistance on non-wet strength components and the
effective pot life of such adhesives is limited to a
.,. . _ .
~;~25~63 '
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few hours. Accordingly, a substantial need exists to
provide a corrugated board adhesive that can provide water
resistance to both the adhesive liner and the paper members,
long pot life and effective corrugated board construction.
Brief Description of the Invention
We have found that a starch based carrier, no carrier,
or carrier/no carrier adhesive composition comprising
a suspension or emulsion of either or both gelatinized or
hydrated and ungelatinized or nonhydrated starch, a cross-
linking resin, a wax, a strong alkali metal hydroxide and a
boric acid compound can have a useful pot life in the
range of 4 to 48 hours, and can be used in the manufacture
of corrugated board providing strong, water-resistant
bonds. The starch in the starch composition can combine
with water upon heating in the corrugator after application
to the corrugated board components, can swell to form
gelatinized or partly hydrated starch particles which
can react with the crosslinking resin, forming a more
insoluble crosslinked polysaccharide mass. The cross]inked
starch in combination with the corrugating board paper
forms the adhesive bond. Upon further heating the starch
can be dehydrated to form the fully cured bond line. The
basic reacting ketone-aldehyde resin crosslinks the starch
molecules of the adhesive, rendering them more water resist-
ant.
The wax emulsion particles included in the adhesiveperform a number of functions. First the wax particles can
migrate from the adhesive composition into the paper
fibers in contact with the adhesive. The wax particles
interact with the paper fibers changing the fibers from
substantially hydrophilic to substantially hydrophobic,
reducing the sensitivity of the fibers to the presence of
moisture. Secondly the wax blooms to ~he surface of the
cured and noncured glue line. Before curing the wax tends
to prevent evaporation of water from the adhesive which
makes the adhesive very convenient to use. The control of
moisture evaporation or release insures latent curing of
.... ... . . . .. .. .. .
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corrugated board. The corrugated board having cured glue
line made from the adhesive of this invention can withstand
the effects of temporary contact with substantial amounts of
liquid water. The wax layer which forms during application
on the surface of the glue line repels water from the
surface of the glue line over ~he short term. The wax
prevents water from rehydrating starch and weakening the
bonds. Further the starch prevents ~ater from soaking
through ~he paper fibers to weaken the bond line. The
utility of the starch is very sensitive to wax content.
Below a certain quantity of wax insufficient water repel-
lency is present in the uncured and cured bond line.
More than~a certain amount of wax results in wax particles
interfering in curing of the adhesive.
The starch based adhesives of this invention are
commonly characterized as being either a carrier adhesive, a
no carrier adhesive, or a carrier/no carrier adhesive. The
term carrier adhesive implies the presence of a thin base of
gelatinized starch in which ungelatinized or nonhydrated
starch particles are emulsified or suspended. The term no
carrier adhesive implies the substantial absence of gelatin-
ized or hydrated starch in the adhesive emulsion. The term
carrier/no carrier adhesive implies that the distinction
between gelatinized starch and ungelatinized starch is not
distinct in the adhesive composition. Generally carrier/no
carrier adhesives are prepared in a way that a substantial
amount of partly hydrated or partly gelatinized starch is
formed. These terms are inprecise since during the prepara-
tion of the starch based adhesives some starch inherently
becomes gelatinized during processing at any temperature and
some starch remains ungelatinized and nonhydrated during
preparation and use. The important characteristics of the
invention are that the starch is crosslinked and dehydrated
during curing, the wax particles in the adhesive emulsion
provide moisture resistance to corrugated board material,
and the glue line, the strong base and boric acid compound
provide low cure temperatures and strong high quality bonds
~%25~63
after curing.
Surprisingly, we have found that the components of the
novel adhesive composition of the invention cooperate to
produce a useful pot life of greater tha~ about 4 hours and
can have a pot life up to 48 h~urs. Pot life is generally
considered to be the time durins which the adhesive can be
maintained in the co~rugating machine at an elevated appli-
cation temperaturel can maintain viscosity and can form
useful bonds. During the time the adhesive is maintained at
elevated temperature, both mechanical agitation, chemical
action and heat can degrade starch molecules substantially
reducing molecular weight, resulting solution viscosity,
applicability, and potential bond strength. As ~he adhesive
nears the end of its pot life, viscosity, applicability,
curing time, and resulting bond strength between corrugated
board paper members drops rapidly.
A first aspect of this invention is the novel corru-
gated board adhesiv~. A second aspect of the invention is a
process for making corrugated board which comprises forming
a glue line between corrugated board paper members using the
novel adhesive composition of the invention. A third aspect
of the invention comprises a method for the manufacture of
the novel adhesive of the invention. A fourth aspect is the
corrugated board product.
Thus the present invention provides
an aqueous adhesive composition for assembling
corrugated board by adhesively bonding a corrugated medium
to at least one liner, that when cured is resistant to
water, which comprises in an aqueous emulsion having a pH
of greater than about 8, a major proportion of water,
about 5 to 75 parts starch, about 0.1 to 5 parts of a
basically reacting polymeric ketonealdehyde resin cross-
linking agent, about 0.1 to 10 parts of an alkali metal
hydroxide, about 0.1 to 5 parts of a boric acid compound,
about 0.1 to 5 parts wax, and an effective amount of an
emulsifier each per 100 parts of the water, wherein the
'~1 i
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adhesiYe composition can ~aintain a viscosity of at least
8 ~5 zahn cup seconds for at least 24 hours at a temperature
greater than about 32C. (90F.).
In another aspect the invention provides
a method for forming an aqueous adhesive composi-
tion for assembling corrugated board by adhesively bonding
a corrugated medium to at least one liner, which comprises
forming an aqueous emulsion of a major proportion of watex,
about lO to 75 parts of starch, about 0.1 to 5 parts of a
basically reacting polymeric ketone-aldehyde resin cross-
linking agent, about 0.1 to lO parts of an alkali metal
hydroxide, about 0.1 to 5 parts of a boric acid compound,
about 0.1 to 5 parts of wax and an effective amount of an
emulsifier, each per lO0 parts of the water, wherein the
adhesive composition has a pH of greater than about 8 andwherein the adhesive composition can maintain a viscosity
of at least 8 #5 zahn cup seconds for at least 24 hours at
a temperature greater than about 32C. (90F.).
In still a further aspect, the invention provides
a method of forming a substantially water
resistant corrugated product which comprises applying to
the flutes of a corrugated medium an aqueous adhesive
composition, comprising in an aqueous emulsion having a
pH of greater than about 8, a major proportion of water,
about 6 to 75 parts starch, about 0.1 to 5 parts of a
basically reacting polymeric resin crosslinking agent,
about 0.1 to lO parts of an alkali metal hydroxide, about
0.1 to 5 parts of a boric acid compound, about 0.1 to
5 parts wax, and an effective amount of an emulsifier
each per 100 parts of water, wherein the adhesive com-
position prior to application can maintain a viscosity
of at least 8 #5 zahn cup seconds for at least 24 hours
at a temperature greater than about 32C., to form a
glue line on each flute, and contacting the glue line
with a liner sheet.
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Detailed Descri tion of the Invention
p
Briefly, the novel water-resistant corrugated board
adhesives of this invention are prepared by forming an
aqueous emulsion, having a pH greater than about 8, of
starch in the form of an ungelatinized starch or gelatinized
starch, a basically reacting crosslinking resin, a wax, a
strong alkali metal hydroxide base and a boric acid com-
pound. The corrugated paper board adhesive of this inven-
tion is preferably formed from a suspension of ungelatinized
starch particles in a thin paste of gelatinized starch,
called the carrier phase. The viscosity and solids content
of the paste are important factors influencing the speed
with which the pa~er board machine can be operated and also
,~,
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3L2~57~i3
effects the quality of the finished paper board. The
suspending paste or carrier medium must be sufficiently
viscous to maintain a smooth suspension of the nongelatin-
ized starch particles, but not so viscous as to interfere
with the application of the adhesive to the paper board.
The nature and proportion of dissolved solids in the
carrier medium influences both pot life and the speed with
which a given paper stock absorbs water from the applied
adhesive. The water content of the adhesive efects adhesive
propertieS. A small degree of water absorption from the
adhesive to the paper is desirable in forming strong
bonds between the paper plies. Absorption of water beyond
that required to give good bonding is undesirable slnce it
robs the adhesive of water needed to complete the gelatini-
zation of the suspended starch upon heating in the corruga-
tor and leads to inferior bonding.
Starch
The starch used in both the carrier phase and suspend-
ed starch phase is a commodity chemical produced from a
number of plant root, stem or fruit sources. Starch is a
high molecular weight polymeric carbohydrate polysaccharide,
most commonly composed of six carbon monosaccharide units
joined by alpha-glycan linkages having an approximate
molecular formula of (C6Hloos)nt wherein n equals
102 to 106. Starch occurs naturally in the form of
white granules and comprise linear and branched polysaccha-
ride polyrners. Starch is commonly manufactured by first
soaking and grinding the plant starch source, and separating
the starch from waste matter. The starch is commonly
reslurried and processed into a finished dried starch
product. Commercial starch often has the form of a pearl
starch, powdered starch, high amylose starch, precooked or
gelatinized starch, etc. Preferably pearl starch is used in
making both the carrier phase and the particulate starch
suspended in the carrier.
Crosslinking Resins
Resins that can be used in the novel adhesive composi-
~L2Z5~763
-- 7 --tions of this invention include resins that upon heating in
basic media generate crosslinking species that react with
and crosslink the hydroxyls in adjacent starch molecules.
The crosslinking reagent tends to reduce the hydrophilic
nature and the water solubility of the starch molecules by
effectively removing the availability of hydroxyl groups to
water and by introducing aliphatic alkylene-type crosslink-
ing moieties.
A preferred class of crosslinking resins comprise
well known condensation products of the reaction of a ketone
and an aldehyde compound. These resins are characterized as
a polyether polymer but can contain a variety of other
monomers such as urea, melamine, etc. In the presence of
heat and base, they commonly decompose to produce species
that effectively crosslink the starch molecules. Preferred
resins are acetone-formaldehyde resins, acetone-urea-form-
aldehyde resins, acetone-melamine-formaldehyde resins
comprising 15 to 30 wt-~ acetone, about 5 to 50 wt-% form-
aldehyde and 0 to 15 wt-% of third monomer. One example of
the preferred crosslinking resin embodiment of this inven-
tion comprises the Ketack*series of resins manufacture~ by
American Cyanamide.
Wax
The term wax is used very broadly and is applied to
a wide variety of materials. The materials can have proper-
ties resembling certain well known waxes or can be used to
provide physical properties similar to those associated with
well known properties of wax such as sealing, polishing,
candle making, etc. Many waxy substances have been found in
nature and have been known to be useful for many years.
Historically waxes include substances that are natural
products. Chemically natural waxes are esters of fatty
acids and monohydric fatty alcohols. Physicall~ waxes
are water repellant solids having a useful degree of plastic
character. However, modern waxes include various synthetic
substances that can replace natural waxes in many prepara-
tions. The composition of natural waxes generally comprise
-i *Trade Mark
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an ester of a saturated fatty acid and a long chain mono-
hydric alcohol. Long chain fatty acids often include
acids having greater than 16 carbon atoms and most commonly
about 26 carbon atoms. The aliphatic monohydric alcohol
commonly has at least 14 and can range as high as 36 carbon
atoms. Petroleum, mineral or other synthetic waxes often
consist of saturated hydrocarbons having aliphatic or open
chain structures with relatively low branching or side
chains.
Particularly preferable waxes for the water resistant
corrugated board adhesive are waxes such as petroleum waxes,
candelilla wax, beeswax, etc. Particularly preferred
waxes are the petroleum waxes such as microcrystalline
waxes, slack waxes and paraffin waxes.
Base
The novel adhesive composi-tions of the invention con-
tain a strong base which promotes the production of cross-
linking species from the resin and acts to cure the adhe-
sive. Essentially any strong base can be used, however
preferred bases are alkali metal hydroxides. The most
preferred strong bases include sodium and potassium hydrox-
ide. The strong base also lowers the gel point of the
starch, which increases the rate of hydration of the starch
during curing of the glue line.
Boric Acid Compound
The novel adhesive compositions of the invention
include a boric acid compound which cooperates with the
gelatinized and nongelatinized starch during heating and
curing by reacting with available hydroxyl groups of the
starch, forming a starch borax complex which aids in gelling
the carrier starch molecules and the suspended starch
molecules. The cooperative reaction increases the tack of
the adhesive and produces strong bonds. Any boric acid
compound having free hydroxyl groups attached to the boron
atom can be used, however commercial boric acid (orthoboric
acid, H3BO3 and its hydrated forms) and borax (sodium
tetraborate decahydrate, Na2B4O7 10H2O and other hydrate
9 ~225~3
and anhydrous forms) are commonly used. For a discussion of
boric acid compounds such as boron oxides, boric acicls and
borates, see Kirk-Othmer Encyclopedia of Chemical Technolo-
gy, 2nd Edition, Vol. 3, pp. 608-652. The boric acid
compound increases the tackiness, viscosity, and cohesive
strength of the adhesive. As the adhesive cures in the glue
line, a gel structure forms between the boric acid compound
hydroxyl group and the hydroxyl groups of the polysaccha-
ride. The exact mechanism of the reaction between the boric
acid compound and the starch is unknown. Further7 the borax
buffers the caustic nature of the base used in the adhesive
stabilizing the adhesive to the hydrolytic effect of the
base.
In somewhat greater detail, the novel adhesives of this
invention are made by first combining water and starch and
then adding the balance of the components. PreEerably the
adhesive is made by first forming the carrier phase compris-
ing water, gelatinized starch and strong base. The carrier
phase is made by mixing water with about 1 to about 25 parts
Of starch and about 0.1 to about 10 parts of strong base.
The mixture is blended until uniform and heated to
gelatinize or hydrate the starch particles. The carrier
phase is then combined with additional particulate starch,
the boric acid compound, the crosslinking resin, and addi-
tional amounts of water or strong base if needed. About 5to 50 parts of additional starch per 100 parts of water,
about 0.1 to 5.0 parts of boric acid compound per 100 parts
of water, about 0.1 to about 5 parts of basically reacting
resin per 100 parts of water and about 0.1 to 5 parts of wax
~ 30 per 100 parts of water are added. The mixture can be heated
to partly hydrate or gelatinize the starch.
The wax is preferably added in the form of an emulsion
of the wax in water. The wax emulsions preferred in
the invention are commonly made by suspending wax in water
using commonly available emulsifying agents. A particu-
larly advantageous wax emu]sion is prepared by adding about
10 to 40 parts of nonionic slack wax to about 10 parts of
S763
-- 10 --
hot water in the presence of a nonionic surfactant. The
mixture is blended until uniform and abo~t 40 parts of warm
water is added along with about 3.3 parts of urea. The
mixture is blended until uniform and an antifoam agent is
added and additional water is provided until the proper wax
concentration is reached.
The final adhesive composition of the invention con-
tains about 10 to 80 wt-%, preferably 10 to 40 wt-%, and
most preferably 20 to ~0 wt-% solids for reasons of vis-
cosity control and application speed. The pH of theadhesive is greater than about 8, preferably in the range of
9 to 13, and most preferably for reasons of low gel point
and rapid cure of the glue line, about 11 to 12.
The following Examples describe the preparation of
the novel adhesives of this invention and contain a best
mode.
Example I
Into a two-liter container maintained at 100 F. (36
F~) was placed 6.1 parts of water. Into the water is mixed
1.6 parts of cornstarch and a sodium hydroxide solution
prepared by mixing 0.8 parts of sodium hydroxide and 1.3
parts water. The mixture was stirred until blended and
maintained at a temperature of about 35 C. ~100 F.)
until the sta~ch was ~ully gelatinized forming the carrier
phase, a period of about 15 minutes. Once gelatinized the
mixture was placed in a dipping funnel.
In a separate two-liter vessel was mixed 51 parts
of water and 29 parts of pearl corn starch maintained at 32
C. (88 F.)~ Into this suspension of pearl starch and water
was slowly added drop-wise the contents of the dropping
funnel containi~g the carrier phase. After the addition was
complete the r~s~lting mixture of carrier phase and raw
starch was heated until the raw starch had a viscosity of 22
#4 Zahn cup viscosity units. At that point 0.2 parts of
boric acid were added to the mixture and the mixture was
agitated until uniform. Into the mixture was placed a~out
1.2B parts of a premixed emulsion containing a ketone-
J~-,
25i~3
aldehyde resin and wax. The emulsion is formed by combining
equal parts of KETAC 1156, a water solution containing 65
wt-% of the resin and the emulsion of wax of Example III.
Example II
Into a two-liter container immersed in a water bath
maintained at 130 F~, was added 30 parts of water, 6.2
parts of Vinamyl*II (a modified high amylose starch made by
National Starch and Chemical). Into the suspension,
at 130 F., was added a premix of 1.0 part of sodium
hydroxide and 0.5 part of water and the mixure was stirred
until uniform. The mixture was agitated for 15 minutes at
130 F. until the Vinamyl II was fully hydrated and gelatin-
ized. The container was removed to a 100 F. water bath and
into the mixture was added 0.1 part borax (Na2B4O7~5H2O)
and 38.6 parts of water. The mixture was stirred until
uniform and into the mixture was added 23.4 parts of corn-
starch. The mixture was stirred until the suspension was
uniform and an additional 0.2 parts of borax was added. The
mixture was again stirred until uniform and into the uniform
mixture was placed about 1.4 parts of the emulsion of
Example III.
Example III
Into a suitable container was placed 39.35 parts
of plasticrude LMPF*wax (a slack wax), 2.15 parts TWEEN*60,
a polysorbate 60 emulsifier, and 2.15 parts of SPAN 60, a
sorbitan monooleate emulsifier. The mixture was heated with
agitation to 210 F. and into the mixture was added 5.0
parts of water at 185 F. and 0.5 parts urea. The mixture
was stirred until uniform and a solution of 39.25 parts of
warm water and 2.8 parts of urea are added to the mixture.
The mixture was stirred until uniform and 7.0 parts of cold
water and a foam control agent were added to the mixture
along with 0.15 parts formaldehyde as a preservative.
~sing the procedure of Example I the following Tables
set forth the preparation of Examples IV through XXIX.
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~a ,. ~ ~ ~,tcl ~, ~1 ^ ~ ~ ~ ~ O
.. v x ~ ~ ~~ ~_I C E~
~: u) E O m u~ ~ ~ ~
. h ~ J 1~1 ,1 t~ t~ C C~ C~ C
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)~ v ~ v ~ ::~ JJ ~ ~ ~ m ~ ~ ~ x JJ ~ E
t~ ~ O ~ o ~ ~ o oo o a)-- ~ 3 0 a (~
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~L2~7~
-- 15 --
a~
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cn u~ In
H ~ D ~00 0 0 ~ ~ ~
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H H ~ ~D ~0;1 0 O t~l a~
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X ~ U~ ~
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X ~
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~ ~ ~ ~o ~ a~ o o
X ~
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H ~t ~D t~ CCl O O~ el
H . . - . . .
~ ~ ~ ~O ~ o~ O ~ ,_~
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1_1~D ~/ ~1 0 ~ o o 1
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v a~ ~ ~ ~ o -~~ ,~ x -~ ~ ~ ~ -: 1
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~2~763
- 16 -
The corr~gated board whose properties and manufacture
are summarized in Table III were prepared by cutting "C"
flute into 5" x 6" rectangles wherein the flutes are paral-
lel with the 5" side. The facing medium (wet strength sized
liner board) is cut into 6" x 8" rectangles wherein the
grain of the board is parallel with the lengthwise direc-
tion. After the adhesive has aged in the pot for a period
of from about 1/2 to 23 hours after the resin wax is added,
the corrugated b~ard is assembled by first aspirating 20
milliliters of adhesive into a syringe, releasing 10 milli-
liters of the adhesive onto a glass plate and drawing the
adhesive into a 12 mil (0.012 inch) film with a Gardene
knife. Onto the 12 mil film is placed a S" x 6" flute,
flute side down on the adhesive. A smooth application of
the adhesive to the flute was insured by pressing the flute
back with fingertips into the adhesive film~ The coated
flutes are then contacted with the grain side of the liner
board. The combined liner board and flute board are placed
on a platen heated at 350 F. The adhesive is cured by
pressing the board with a glass plate as the glue line is
heated by the platen, commonly for 10 seconds or more. The
glass plate, equipped with a handle, weighed 7.3 pounds.
The board was removed from the platen and allowed to cool
and tested for bond strensth using the "Pin Adhesion Test of
Corrugated Fiber ~oard", established by TAPPI (Technical
Association Paper and Pulp Industry). In this test, the
force required to separate the liner from the flute of the
corrugated board is measured and the mechanism of separa-
tion, whether fiber failure or glue line failure is noted.
In the test a rigid templ~e 4" x 4" square is placed on the
bonded si~e of the board so the liner board is on the top.
Two 2" x 4" corrugated board pieces are cut from the board
with a razor knife and are labeled. The pieces are cut so
that the flutes are parallel with the 2" side. After aging
the board a minimum of 24 hours at ambient temperatures, the
bonded samples are immersed in water at ambient temperature
and allowed to soak for 3 + 1/2 hour. The soaXed sample
.~ ,~,i
~,
~2S763
- 17 -
is inserted onto the pin testing jig making sure that the
pins are inserted between a single face side and the bonded
liner board and not through the single face side alone. The
soaked samples are debonded in an Instron device at a cross
set speed of 2" per minute by using compression to separate
the liner board from the bonded medium. The debonding
strength is noted in pounds per area of the specimen and
the type and percent of failure (fiber failure or glue line
failure) are also recorded.
~LZ25~
- 18 -
Table III
Test Properties of Corrugated
Board Using Adhesive
Adhe- Bond
sive strength
Film Cur- #4 Hours of Finished
Adhesive Thick- ing Press Zahn Gel Aged Corrugated
of ness Temp. time Visc. Temp. at Board
Example (Mils) (F.) (Sec.) (Sec.) (F.) Ambient lb/8in_)
10 XXIII 12 350 10 28 142 1/2 17.6
23 1-1/2 22.0
2-1/2 17.5
3-1/2 14.8
18 153 22 10.5
15 XXXIV 12 350 10 28 142 1/2 20.6
23 1-1/2 19.9
2-1/2 17.3
3-1/2 16.2
18 153 22 8.5
20 XXXV 12 350 10 28 145 1/2 18.4
1-1/2 15.85
27 2-1/2 14.5
3-1/2 14.0
23 4-1/2 13.7
150 23 7.5
XXXVI 12 350 10 28 145 1/2 19.1
1-1/2 16.2
27 2-1/2 18.5
3-1/2 13.8
23 4-1/2 15.2
- 30 150 23 6.9
XXXVII 12 350 10 25 142 1/2 18.57
1-1/2 18.2
23 3 15.3
4 16.2
15.5
6 13.3
22 152 23 6.26
... .. . .. .
~2~57~
-- 19 --
Adhe- Bond
sive strength
Film Cur- #4 Hours of Finished
Adhesive Thick- ing Press Zahn Gel Aged Corrugated
5 of ness Temp. time Visc. Temp. at Board
Example (Mils) (F.) (Sec.) (Sec.) (F._ Ambient lb/8in2)
XXXVIII 12 350 10 25 142 1/2 18.9
1-1/2 16u9
23 3 17.0
4 19.1
15.97
6 16.1
22 152 23 8.7
.
~2~
- 20 -
Adhe-- Bond
sive strength
Film Cur- ~5 Hours of Finished
Adhesive Thick- ing Press Zahn Gel Aged Corrugated
5 of ness Temp. time Visc. Temp. at Board
Example (Mils) (F.) (Sec.) (Sec.) (F.l Ambient lb/8in_)
XXXIX 12 350 10 20 141 1/2 19.77
1-1/2 18.47
3-1/2 18.10
4-1/2 15.35
5-1/2 14O50
6-1/2 12.00
IV 12 350 10 23 148 1/2 18.75
6 17 1-1/2 9.93
8 1-1/2 13.45
12 1 1/2 18.9
12 18 3-1/2 18.37
6 18 4-1/2 --
8 4-1/2 5.4
12 4-1/2 12.67
12 19 148 5-1/2 10.2
V 12 350 10 23 148 1/2 17.3
6 17 1-1/2 9.5
8 1-1/2 12.8
12 1-1/2 18.5
12 18 3-1/2 14.95
6 18 4-1/2 4.0
8 4-1/2 6.2
12 4-1/2 10.4
12 19 148 5-1/2 6.2
XL 12 350 10 13 145 1 27.5
13 2 24.7
3 22.2
9 4 19.8
9 145 5 21.2
6 15.9
i7~
- 21 -
Adhe- Boncl
sive strength
Film Cur- #5 Hours of Finished
Adhesive Thick- inq Press Zahn Gel Aged Corrugated
5 of ness Temp. time Visc. Temp. at Board
Example (~lils) (F.) (Sec.l (Sec.) (F.) Ambient lb/8in_)
XLI 12 350 10 9 145 1 25.9
9 2 15.1
8 3 22.1
8 4 17.3
8 14~ 5 15 8
6 16.6
XLII 12 350 10 10 145 1/2 25.1
1~1/2 23.5
2-1/2 17.0
3-1/2 18.1
5-1/2 9.8
9 21 7.4
XLIII 12 350 10 11 144 1/2 23.4
9 1-1/2 22.1
9 2-1/2 18.2
9 3-1/2 12.4
- 5-1/2 11.2
21 4.0
An examination of the Tables set out above shows
that the gel temperature, pot life viscosity, and bond
strength are much improved when compared to o-ther starch
based adhesives. The No. 4 and 5 Zahn cup viscosity
of the adhesive over a 22 or 23 hour period remains suffi-
cient for satisfactory machine application of the adhesive
to corrugated board members and sufficient to provide
adequate bond strengths as shown. The gel temperatures
range from 142 to 153 F. which will provide an efficient,
rapid, energy conserving corrugated board manufacture.
While the above description, Examples and data provide
a basis for understanding the invention, since many embodi-
:~25~76~
- 22 -
ments can be made without departing from the spirit and
scope of the invention, the invention resides wholly in the
claims hereinafter appended.
