Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUN~ OF THE NVENTION
This inventLon relates to starch-based corrugaLing adh~sLves and
methods for their prepartion. The invention ls also concerned with ~lethods
of uniting articles, particularly laminated articles of fibrous, cellulosic
webs, and more particularly, with the production of paperboard Eor use in
the production of corrugated containers. The invention is also concerned
with articles produced through the use of the new adhesive compositions.
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One usual method of making corrugated board consists of corrugating
a strip of paper by means of a corrugated roller,applying an adhesive to the
tips of the flutes of the corrugations on one side and adhering another strip
of paper called a "liner", to the flute tips by use of heat and under high
pressure.
This product, called "single face'l corrugated board may be used as
is. However, it is usual to make "double face", also called "double back"
board by sending the single face board into the second stage of the corrugating
machine called the l'double backer" stage. The term "singlefacer"generally
refers to the first stage of the machine. An adhesive is applied to the opposite
flute tips, and a second liner of paper is adhered to said opposite side by
the use of heat and under a relatively small amount of pressure. The fact that
2Q the use of a great amaunt of pressure in the adherence of the second strip of
paper would tend to crush the corrugations makes the adhesive prohlem in the
second step quite difficult.
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Starch-based corrugating adhesive formulations have been -in wide
use since the advent of the Stein-Hall technology, as diSclosed in U.S. Patent
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No. 2~05l,025, granted ~ugust L8, l936, to J. V. Bauer, and U.S. I'~tt~llt No.
2~102,937, granted Decemher 2L, l~37, also to J. V. Ba~ler.
A Stein-Hall type adhesive is a two component aqueous system. One
component in this system is generally Eormed from a cooked, or gelatlnized
starch material, which serves as a carrier phase. Qther materials which can
form relatively viscous aqueous slurries, such as carboxymethyl cellulose,
may also be used as a carrier phase.
The second component or phase is formed from a raw, ungelatinized
starch material. This second phase is a latent or po~ential adhesive phase.
That is, the adhesive characteristics of such a formulation are not fully
developed until after the adhesive has been applied to the tips of the flutes
' of the corrugated web, the liner has been pressed against the adhesive~
coated flutes, and heat and pressure have been applied; the heat causing the
granular starch material to gelatinize and develop structure.
.
The swelling and gelatinization of the latent adhesive phase takes
place as the newly assembled corrugated board is passed through a hot plate-
dryer system that is associated with a corrugating machine. This system also
partially dries the corrugated board and sets the adhesive sufficiently so that
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` it can be sub~ected to subsequent operations, such as trimming, slitting, and
sheeting withouit delamination.
The initial degree of cohesiveness in the bond oE the corrugated
board is referred to as the green bond strength. This characteristic detel~ines
the ability of the newly formed corrugated board ~o resist the ins-tantaneous
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high shec~r ~orces tha-t are developed during subsequen-t process-
ing operations, such as the -tri~ming. sli-t-ting, and shee-ting
operations, and is not necessarily an indica-tion of the ~inal
bond strength.
Green bond s-treng-th, or ~or brevi-ty3 green s-trength,
is a major limi-ting factor which controls the operating speed at
which corrugated board may be manu~actured on a given machine.
An experienced machine operator o~ten will operate a machine
a-t the maximum speed of which it is capable without having the
board delaminate during the trimming, slitting, and sheeting
operations. Since the resistance to delamination is a charact-
eristic that is directly dependent on green strength, the
characteristics of the corrugating adhesive play a direct role
in machine e~ficiency9 which in turn determines the rate of
return on -the fixed investment represented by -the machine.
A~ter corrugated board has been trimmed, slit, and
sheeted, it is stacked and sent to storage, where the adhesive
cures to a full strength. Un-til the bond is dry and ~ull~
cured, the corrugated board may be delaminated by slowly and
firmly pulling the liner away from -the corrugated sheet.
Since the middle thirties 9 one of the major advances
in corrugating adhesive technology is that disclosed in U.S.
Patent 3,355,307, granted November 28, 1967, to John J.
Schoenberger and Raymond P. Citko. This patent discloses a
single phase corrugating adhesive re~erred to as a "no-carrier'
system, in which partially swollen starch gr~lules are present
as a homogeneous phase, suspended in an aqueous, alkaline
vehicle. The elimination of the carrier phase permit-ted sub-
stantial operating economies. The no-carrier type corrugating
adhesive disclosed and claimed in the Schoenberger-Cit~so patent
was applied and cured in the same manner as the Stein-~lall type
adhesive formulations.
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()ther advances in the corrugating adhesive EieId reLate(I prim3riIy
to building in moistur~ resistance, generally through the addition o~
syn~hetic resins, such as urea-Eormaldehyde, phenol-formaldehyde, and re-
sorcino:L-formaldehyde resins.
S The Bauer patents represented a significant advance in the art,
for their time. Bauer reported that the use of his adhesive systems permitted
corrugated board machines to be operated up to 20~ faster than would have
been possible utilizing prior art adhesive compositions. The prior art
~; compositions included preparations based on sodium silicate and adhesive
preparations based on the use of gelatinized starches or modified starches
such as dextrins.
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In the Stein-Hall type system, according to the teachings of
Bauer~ the time required to form an adhesive bond between the corrugated
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interliner and a liner or facer sheet is substantially independent of the
rate at which the moisture in the adhesive is driven off by heat or absorbed
by the paper. According to Bauer, the time required to form the adhesive bond
` depended mainly on the time required to cause gelatinization of the granular
starch particles suspended in the gelatinized starch carrier phase. As this
granular starch gelatinized, water was taken up, and the viscosity of the
adhesive was raised rapidly~ to form an immediate green bond. Bauer considered
that tapioca, rye and potato starches were inherently superior to corn,
wheat, and rlce starches for making corrugating adhesives in accordcmce with
his developments.
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i Bauer described four prlncipal factors that he considered to
'1, 25 determine the sultability of the starch for use as the latent adhesi~e
component in his system. These four factors were:
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1. the tirne required for complete gelatiniza-tion of the
granular starch by m~ans of the heat input on the
corrugating machine.
2. The temperature at which the starch gelatinizes.
3~ The viscosity developed a-fter gelatinization.
. The degree oE tackiness developed after gelatinization.
However, subsequent developments indicate that the green
bond strength depends significantly on the evaporation oE moisture
from the bond site: Thayer & Thomas Analysis of the Glue Lines
in Corru~ated Board, TAPPI; 22nd Corrugated Containers Con-
ference, May 1971.
- It has now been discovered that a select class of starch
materials, when used as the adhesive component in a corrugating
adhesive composition, demonstrate superior properties. One way
to take advantage of these properties is by the use of machine
speeds that are ordinarily from 5~/O to 100% higher than had
been considered possible with conventional Stein-Hall type
corrugating adhesive compositions, or with the more recently
introduced no-carrier corrugating adhesive compositions, at
generally the same levels of adhesive usage.
According to the invention in one aspect there is
provided a composition suitable for use as a corrugating
adhesive including at least two phases, comprising a carrier
phase and a la~ent adhesive phase that is dispersed in tha
carrier phase; the latent adhesive phase comprising an
ungelatinized, granular saponifiable starch ester and a
quantity of alkali sufficient to substantially completely
~ saponify the saponifiable starch ester, the composition
< being tractable on a corrugating machine.
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In another aspect of the invention there is provided
a process for uniting at least two items of materia:L comprising
applying between the items a composition of the invention,
and activating the composition to form an adhesive bond.
Still further the invention provides in another
aspect an article of manufacture comprising a plurality of
items of material joined with an adhesive boncl comprised of
a composition of the invention.
` In yet another asp2ct of the invention there is
provided an improvement in a process for the preparation
of a corrugating adhesive of the no-carrier type, which
consists in replacing at least a portion of the starch
material with a saponifiable starch ester.
- Stated in another way, superior results have been
obtained when the primary active adhesive component in a
corrugating adhesive formulation is a saponifiable starch
ester material which exhibits at Least about a 3~/O greater
area under anInstron force-time heating curve and at least
about a 30/0 greater area under an Instron force-time cooling
curve, compared with unmodified corn starch under the same
test conditionsO
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Preferred adhesive compositions of the present
invention are based on the use of primary adhesive components
which are saponifiable starch esters having a saponifiable
degree of substi-tution (D.S.) o~ at least about 0.015.
As used herein, "saponifiable degree of subs-titution" means
the total D,S, of all saponifiable ester groups on the starch
moleculeO Particularly preferred starch lester materials are
starch acetate, starch succinate and starch acetate succinate.
One or more of these active adhesive components can be used
10 to advantage either in a Stein-Hall type formulation or in a
no-carrier type formulation, with equally superior improvements
over the prior art.
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The most ~reEerred aclhesive component is a stclrcil acetate su(clnate
having a saponifiable degree of substitution (D.S ) in the range ~rom abouL
0.025 to about 0.045. Thase D.S. levels represent ranges that are appLicable
to starch acetate succinate. Other derivatives that are usef~ll in accordance
with the invention will have their own preferred D.S. ranges. Gener~lly, if
the D.S. level is too low, the derivatized material will not exhibit significant
improvement over unmodified corn starch when used in a corrugating adhesive
formulation. If the D.S. level is too high, the gelatinization temperature
may be unworkable.
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The specific materials that have been identified, for use in
accordance with the invention~ are starch derivatives identified above. These
starch derivatives may be prepared immediately prior to use, i.e., in situ
at the corrugating machin~, or they may be prepared in advance, and may be
formulated into corrugating adhesive compositions as with other starch
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materials that are to be used for such purposes in accordance with prior art
practices.
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It is also possible to utilize modified starch materials which
~ may be produced from the aforementioned starch esters. These modified
;~ starch materials are produced by substantially completely saponifying the
2Q starch esters and removing the salts formed thereby. The resulting modi~ied
, starch material may then be drled. Although the derivative has been sub-
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stantially completely removed from the starch material, the modified starch
` ~ retains the beneficial properties of the ester materialO
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- Wh:ile we do not fully understand the reason l~hy the speclclL
materials identi~ied hy our invention are superior Eor use in corrugating
adhesives in partlcular, it can be theorized that they not on]y develop
unusually high viscosity upon gelatinization, but in addition, provide a
hlgh green strength without the necessity oE solvent evaporation.
I~hile the flnal form of the useful starch materials of this
invention is not known, it is known that the esters materials saponiEy
substantially completely in a short period of time in the environment
present in the mixing apparatus on the corrugating machine.
The invention will be better understood by a more detailed
explanation of several specific embodiments thereof. All parts and
percentages are by weight, on a commercial basis, unless express'y stated
to be otherwise~ The commercial basis for the starch materials includes
about 12r moisture.
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I)l`'l`AILI~I) DESCRIP'I`10~ OF TtlE PREFERRED EMBODIMEN'rS
The proper selection of the primary active aclhes-Lve component
is of great importance Eor the proper practice of the present invention.
In preparing saponifiable starch esters for use as the primary active
adhesive components, the starting starch material may be derived from
any vegetable source. Starches derived from non waxy grain sources,
such as, for example, corn, wheat, rice, and grain sorghum are preferred.
The ~erm "starch" is used broadly herein and encompasses flour, un-
modified starch and tailings. Corn starch is a preferred starting starch
~ 10 material.
- The initial starcll is esterified, as will be described presently,
to produce the primary active adhesive component that has the desired
characteristics in accordance with the invention.
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In a typical corrugating adhesive formulation, it is usual to
add bora~ and caustic to increase the adhesive strength and tack, and to ad-
~ust the gelatiniæation temperature. When using either a carrier-type
or a no-carrier type adhesive formulation, the Stein-Hall viscosity of
the formulation must be within the conve.ntional range to permit an
adequate amount of adhesive to be applied to the flute tips at all machine
, 20 speedsO Generally, to be tractable on a corrugating machine, an adhesive
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~orDlation should have a Stein~Hall viscosity in the range of about
' 20 sec. to about 100 sec. The optimum Stein-Hall viscosity of the formu-
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lation will depend on the particular corrugating machine.
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Unless otherwise speciEied, the materiaLs ~escribed an~l
claimed herein are those ~hich are to be added to ~orm the adhesive
formulation. In the particular environment of the adhestve formula-
tion, the form of certain materials may be altered. For example, the
starch ester will saponify in a typical corrugating adhesive formulation.
This will reduce the actual amount of alkali present. The borax may be
present in any of several species, or as an equilibrium mixture of
these species, depending prilDarily on the pH of the formulation.
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As previously described, it is standard practice in the
corrugating industry to add alkali and borax to the adhesive formulations.
While formulations ~hich do not include these materials may be used
as corrugating adhesives, it is preferred to include both of these
materials to the formulations of this invention.
The borax is generally utilized to increase the gel structure
of the adhesive paste. However, an excess of borax may have an adverse
effect on the cured bond strength. In addition, borax has the tendency
to increase the gel tempe~ature of the formulation. Generally, up
to about 5% borax (10 mol) may be incorporated into the formulations.
A more usual quantity would be about 2% to about 3%. The percentages
are based on the total starch material present in the formulation,
including both the primary active adhesive material and the carrier
material. If 5 mol borax is to be used instead of 10 mol, it is necessary
to compensate for the reduced water of hydration. In no-carrier systems,
` boric acid may be utilized as a reaction stopper. The boric acid will
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~uicklv be conver~ed to a horate and is tllen able to serve as a substL-
tute for added borax. As used herein, the term "borax" will include
those borates which are present due to the addition of boric acid.
Any standard alkali may be used. However, for economic reasons,
S sodium hydroxide is most commonly utili~ed. The aLkali serves to reduce
the gel temperature of the adhesive formulation to a readily tractable
point. Generally this will be in the range of frorn about 145~F to about
150F, but may in some applications range from about 140F to about 160F.
It is important that large amounts of alkali not be used in any corru-
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gating adhesive formulation, whether conventional or in accordance with
- this invention, as alkali tends to reduce gel structure format:Lon.
Generally up to about 5% alkali (calculated as sodlum hydroxide) may be
used, based on total starch material in the system. More usual amounts
would be from about 3% to about 3.5%.
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~--` 15 It is of critical importance to the practice of this invention
that at least enough alkali to substantially completely saponify the
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~ starch ester be used. Tha amounts of alkali referred to above are
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~ the quantity of alkali in excess of this minimum amount.
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The particular starch ester to be used in the practice of this
invention is not critical, as long as it will saponify in the environ-
ment of a corrugating adhesive formulation. Consequently, inexpensive and
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" ~ simple starch esters, such as starch acetate are preferred. Particularly
;l~ preferred is the mixed ester, starch acetate succinate.
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The starch esters may be obtained commercially, or
may be made by any conven-tional method, such as by reacting
unmodified starch with acid anhydrides 3 acid halides, vinyl
esters and -the like. The same reagents may be used when util-
izing the 1n situ method of this invention. I-t is necessary
however that the esterification be carried out at a temperature
which is below -the ac-tual gelatiniza-tion -temperature of both
the unmodified starch and the starch es-ter.
In addition, the water conten-t of an adhesive form-
ulation should be adjus-ted so -that an extremely -tacky adhesive
characteristic is obtained immediately after gelatinization.
This implies that sufficient water is present for complete ~-
gelatinization. It is most desirable that rapid developmen-t
;~ of tack is obtained upon the application of heat in the
corrugating equipment.
The amounts of starch materials utilized in the ad-
hesive formulations of this invention are similar to those
utilized in conventional formulations. Generally, -the granular
starch component of a Stein-Hall type formulation will contain
from about 10% to about 25% starch. The final adhesive mixture
generally has from about 12% to about 25% of its total s-tarch
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in the form of the gelatinized carrier.
; The starch esters of this invention may also be u~ed
as the carrier portion of a Stein-Hall type adhesive. In such
instances, it may be possible to reduce -the quantity of carrier
`!` somewhat due to -the greater thickness of these starch es-ters.
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The desirable clegree of substitution depencls upon the ~lrt i( ular
initiaL starch material selected However, in general, it hcls been ~o~lncl
desirable to utilize a saponifiable D.S. of at least about 0.015. Starch
esters having a saponifiable D.S. of at least about 0.015 have been found
to satisfy the Instron test criteria, discussed infra, and therby permlt
machine speeds at least about 20% greater than those attainable utilizing
unmodified corn starch as the primary active adhesive component.
Generally D.S. levels greater than 0.015 will produce even faster
machine speeds. It has been found preferable to utilize saponifiable
starch esters havlng a saponifiable D~S. in the range of from about 0.025
to about 0.045. The utilization of such materials will generally permit
operation of a corrugating machine at speeds of up to about 100% higher
than those attaînable using conventional adhesives.
The green strength, and the viscosity of ~he gelatinized
corrugating adhesive that produces the green stren~th, cannot conveniently
be sub~ected to direct quantitative measurement at the exact site of the
bond. However, it appears tnat the inherent ability of a corrugating
adhesive to form ~igher green strength, which permits lmproved corru-
gating speeds, may be predicted by a measurement of the area under an
Instron force-time curve of a paste made in a particular manner from the
prlmary active adhesive component that is selected for use in accordance
with the present invention.
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` The Instron force-time curve of a paste of a prlmary active
adhesive component may be determined in accordance with the following
procedure.
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ST~NDARD INSTRON Ml~r[HOD
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An Instron Tensile Tester Model TT is fitted with com~resslon
load cell "CM". A culture tube approximately 22 mm in diameter and 175 mm
high ls fitted into a constant temperature cha~lber This chamber is a
~ 5 metal sleeve approximately 23 mm in diameter and 116 mm hLgh, wrapped
; with about 4 feet of 3/16 inch copper tubing and covered with asbestos
wrap. The copper tubing is connected to constant temperature baths
through appropriate inlets.
The starch slurry to be tested is placed into the culture tube
to a depth of 2.75 inches.
The culture tube is lowered into the sleeve, which has been
preheated by circulating water at a temperature of 210F through the
copper tubing. A thermocouple probe having a diameter of 0.184 inch
is inserted about 1 inch deep into the top surface of the slurry. Simul-
` 15 taneously the machine and recorder are turned on, with the probe being
driven into the slurry at a speed of 0.02 in/min. This heating cycle is
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continued for 14 min. and then the hot water circulation is stopped.
After another minute, lce water is circulated through the tubing and
continued for 15 minutes.
The curve generated on tbe recorder is called a force-tlme
curve. The first 15 minute segment wlll be referred to as the heating
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~ cycle and the second 15 ~inute segment as the cooling cycle.
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The test slurries for use OA the Instron are made as follows.
:, 15
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~ predetermined quantity of unmodified corn starcl~ is slurried ln
110 ml ~ater. A ~redetermined amount oE a 4~ w/v borax (10 mol) soLution
and a ~redetermined amount of a 20~ w/v NaO~I solution are added. Sufficient
water is added to produce a total additional volume of 60 ml. The re-
sulting slurry is heated at a temperature of 212F, with agitation for 5mimltes, and then allowed to stand for 5 minutes. It is then immediately
added to the ~econd slurry which has been previously prepared.
The second slurry is prepared by slurrying 50 gm of the test
starch in 165 ml of water. The first slurry is then mixed with this
slurry and the admixture stirred for 15 min. It is then immediately
tested on the Instron tester.
A sample of unmodified corn starch is run as the test starch
under these standard test conditions. The force-time heating and cooling
curves are generated as described above and the area under each of these
; 15 segments is independently determined.
The identical procedure is then followed for the starch material
to be tested. The areas under the heating curve for the test starch is
compared with the area for unmodified corn starch. The same is done for
the areas under the cooling curve. It must be stressed that the areas
-20 under each of the segments of the curves are treated independently of
each other.
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- The absolute areas determined in this manner are arbitrary
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; values largely determined by the test procedure. The crucial feature
of the test ~s not these absolute values~ but the ratio of the areas
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for the test starch to the areas Eor the unmodified corn starch, ~hcn
performe~ under the same test conditions. This means that the pre-
determined amounts of carrier starch, borax and sodium hydroxicle are
identical.
While the Instron test does not duplicate exactly the viscosity
and gel structure on the glue line, it does give a relative measurement of the
ability of a particular primary adhesive component to develop high green
strength in a corrugating honding environment.
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It has been found that to produce the desired 20% improvement in
machine speed, the ester material must exhibit at least about a 30%
greater area under both the Instron heating and cooling curves compared to
unmodified corn starch. In other words, a saponifiable starch ester
which will exhibit a 30% Instron improvement (greater area) Imder both
`~ heating and cooling curves will produce machine speeds at least about 20%
faster than machine speeds obtainable using unmodified corn starch, on
the same machine.
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The useful starch ester materials may also be defined as having
a total saponifiable degree of substitution (D.S.) of at least about
0.015. The upper limit on saponifiable D.S. is economic and functional.
It is necessary that the material have a gel temperature high ellough so
that it will not gelatini~e prior to use; such as dur:lng manufacture of
the derivative or during formulation of the adhesive composition.
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While the exact upper limit on saponLELable D.S. w-Lll depeQ(I on the ~)lrtl-
cular substituent belng used, in general, for esters oE monocarboxyL-Lc
acids it will be about 0.1 and for mono-esters oE dlc:arboxylic ~I`id9 about
n.o6.
It ls known that in the environment of the adhesive formulation,
the ester will saponify in a relatively short time. This means that the
ester will have substantially completely saponified prior to its appli-
cation to the flute tips. The exact form of the saponified starch
material is not known. It is possibly a complex with either the caustic
or borax which are generally present in the system.
It is believed that a portion of the imp~svement in machine
speed may be ascribed to a reduced alkali ]evel in the formulation. As
the ester material saponifies, some of the alkali is used up.
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Certain of the beneficial properties of the starch esters are
retained in the saponified product. Prior to actually being applied
to the~flute tips, the ester has substantially completely saponified. It
has been found that a modified starch material may be produced by
-~ saponifying the starch ester. The saponification is carried out in the
presence of alkali and may fur~her include borax in the sapon~lfication
medium~ The ~odified material may then be dried. This process, i.e.,
esterification followed by saponification yields a material whi~h is
different from the original unmodified s~arch material. This modified
` material may be used in a corru~ating adhesive formulation in a manner
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similar to the use of the starch esters. Improvecl green bond strengtl
compared with unmodified corn starch is found. The exact mechanism of
the modification is not known, but may be a pllysical disruption of the
granules, or may be a small amount of a complex formed between the
alkali and the starch.
The use of a reduced quantity of alkali in the corrugating
adhesive formulation does not account for all of the machine speed
improvement. When unmodified corn starch and a starch ester in accord-
ance with this invention are run at identical actual alkali levels9
machine speeds are still greatly faster using the starch ester materials.
The starch esters may be formed in sitù at the corrugating
machine when preparing the adhesive formulation. It is merely necessary
to add an ester forming reagent to the formulation. The conditions
are those which wil~ permit very rapid esterificationp followed by
irrever:lble eapDDitication to take
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place. The esterifyillg reagents are the aforementioned conventional materials.
The quantity of reagent to be added is that amount which would, in the absellcc
of saponi~ication, produce a product having a saporlifiable D.S. suitable Eor use
in accordance with this inventionO Generally, a reagent such as acetic anhydride
will have a reaction efficiency of about 50~ to about 70% under the conditions
found in a corrugating adhesive formulation.
The order of addition of the materials to the adhesive formulation is
not critical to the success of the in situ method. It is, of course, necessary
that the esterification reagent not be allowed to remaln in an environment for
any lengthy period of time where it might, at least in part, decompose.
In order to more fully understand the invention the following demon-
strations of specific embodiments of the invention are described. They are
illustrative and informative in nature and in no way are intencled to limit the
scope of the invention.
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E~AMPLE I
Comparative Corrugated Board Production Runs
In order to demonstrate that the corxugating adhesives of the present
$nvention provide improvements over conventional unmodified starch Stein-Hall
adhesive formulations, it was necessary to establish a limit, above which speed,
conventional s~arch adhesives no longer bind the corrugating board sufficiently
to prevent dela~ination during the subsequent operations, and then determine at
what machine speed corrugated board using adhesives prepared ln accordance with
the presen~ invention could be produced before they reached the failure point.
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The corrugatecl board man~lfact~lred in all tests oE th-Ls example wa~ a
double backer board consisting of a 26 pound corrugated sheet positioned between
two 42 pound Kraft liners. A commercial double-backer corrugated paper machine
was used. All hot plate temperatures were set at 300 F. for this trial.
Initially the glue clearance of the adhesive applicator was set at 0.014 in. A
Stein-Hall type conventional corrugating adhesive, for use as a control, and
corrugating adhesive formulations prepared in accordance with the present
inventlon, were made as tabulated below.
Conventional Doub_e Backer Formula
Primary Mixer
Add 10.0 gal. water
Add 20.0 lb. unmodified corn starch
Heat to 150 F.
Add 3.3 lb. NaOH dissolved in 2.0 gal. water
Agitate for 15 min.
Then add 10.0 gal. cooling water
Mix for 10 min. and hold at 110 F.
. .
Seconda~x MixPr
.' .
Add 30 gal. water ancl heat to 90 F.
Add 3.4 lb. 10 mol borax
Add 100 lb. unmodified corn starch
Add primary to secondary over a period of 30 min.
and hold at llO F.
Adjust viscosity to 60 sec~ with 4.5 gal. water
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.9 L.~ d ~ ~
Double Backer Formula ~ccorclLn~_to the Present [llventio
Primary _ixer
Add 10.0 gal. water
Add 19.0 lb. unmodified corn starch
Heat to 150 F
Add 3.9 lb. NaOH dissolved in 2.0 ~al. water
`~ Agitate for 15 min.
Add 10.0 gal. cooling water and hold at 110 F.
Secondary Mixer
Add 30.0 gal. water and heat to 90 F.
Add 1.5 lb. 10 mol borax
Add 100 lb. starch acetate succinate (0.027 D.S.
acetate, 0.01 D.S. succinate)~
Add primary to secondary over a period of 30 min.
and hold at 110 F.
` Mix 5 min. and add 1.5 lb. 10 mol borax
Add 4.5 gal. water to adjust viscosîty in 60 sec.
The adhesive properties of these formulations were
determined to be as indicated beIo~.
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, Double Backer
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Stein-Hall Temp.
Solids Viscosity Sec. F.
Conventional 19.1 65 110
s~ Acetate/Succinate 20.0 45 110
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- Bo~h of ~hese adheslve formulations were evaluated, successively,
~ on the same corrugati~g machine.
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Using the control adl~esive above, ttle maximum speecl obtal~lab:le On
the corrugating machine, before the corrugated board began to deLamlnate at
the cutting knife, was 450 fpm.
Using the starch acetate succinate as the raw starch portion oE the
Stein Hall double backer adhesive formulation, speeds of 600 feet per minute
were achieved. At this point, the glue clearance on the double backer
applicator was increased from 0.014 inches to 0.016 inches and the corrugating
machine was run at 700 feet per minute, or 55% better than the control, with
excellent double backer green strength. Above this speed the single facer
corrugating machine, which was supplying the single face corrugated paper to
the double backer, would not keep up due to the fact that the adhesive formulation
being used in the single facer stage was a typical conventional unmodified
starch adhesive and not enough heat could be applied by the machine to cause
sufficiently rapld gelatinization of that adhesive.
' ' .
~ owever, wlth the single facer bridge full of board made at lower
machine speeds,the double backer section could be run in brief spurts at speeds
well over 800 feet per minute. The limitation on these spurts occurred when
unbonded single facer sheets would reach the double backer glue machine. It is
apparent, therefore, that the starch acetate succinate adhesive will produce
good double backer corrugated board at corrugator speeds considerably in excess
of 700 feet per minute.
,:
EXAMPI~ II
Corrugated_Board Production Runs
A further test of corrugat~ng was conducted using the same corrugating
- machine, and :ubstantially the same operating conditions, as for the runs in
.
- 23 -
E~ample I. The machine was used for making board usi~g 42 pound llners and a
26 pound corr~ated medium, with glue clearances of 0.013 :Lnches and 0.014 inches.
The starch derivative used as the primary adhesive component was
characterized as follows. It was a starch acetate succinate having a D.S.
acetate = 0.011; D.S. succinate = 0.015. It was found that an adhesive formu-
lation made up as descrlbed below could be run successfully at quite high
machine speeds. The formulation was as follows:
Primary
Water 50 gal.
Unmodified corn starch 90 lbs.
Caustic Soda (dissolved -
in 5 gals. water)20 lbs.
Eleat to 160 F. and
hold 15 minutes
Water 33 gals.
Secondar~
Wa~er 200 gals.
Borax (10 mol) 9 lbs.
Starch Acetate
Z0 Succinate 500 lbs.
Add the primary over a
period of 30 min.
Add additional Borax
(10 mol) 5 lbs.
With the glue settings set a 0.013 inches, the corrugat~r could be
run efficiently at 700 feek per minute. Decreasing the glue clearances to
0.009 inches allowed the attainmen~ of sustained corrugator speedæ of o~er
800 fpm. At this point the corrugating machine had reached its practical
limit and 62 pound liners were then substituted for the 42 pound l:Lners.
. - 2~ -
With the heavier liner, the corrugatlng ~lachlne eEfLcientLy produced
corrugated board at speeds of 650 fpm. at a setting of :350 F. on the corrug~tor
hot plates. Conventional starch adhesives have a limLt of 300-500 fpm. at
300 F. and 350-400 Epm at 350 F. hot plate temperatures when uslng these
liners on this machine. Corrugating efficiency was dramatically superior, using
the Eormulations of the invention.
EXAMPLE III
dditional Production Runs, Stein-Hall Formulations
Additional runs were made on the same machine in accordance with the
last-mentioned procedure of Example II using 62 pound liners with primary ad-
hesive components characterized as follows:
.
- Starch Derivative
-~ Starch acetate succinate
(D.S. acetate = 0.013;
D.S. succinate = 0.016).
S~arch acetate succinate
(D.S. acetate = 0.013;
D.S. succinate = 0.014)
The starch derivative identified as (a) was prepared in an adhesive
formulation as described in Example II, and used on a corrugating machine with
glue clearances of 0.007 inches with the hot plate set at 300 F. Initially
machine speeds of 600 fpm were attained. As the glue clearance was opened up
to 0.010 inches, machine speeds of up to 750 fpm were achieved. When the hot
plate temperatures were raised to 350 F., machine speeds of 775 fpm were
attained, with satisfactory board production.
, .
When an adhesive formulation as described in Example II, incorporating
,
~, the starch derivative identiEied above as ~b), was run on the corrugating machine
.
wi~h ~he glue clearance~ at 0.007 inches, and the hot plates set at 350 F.,
corrugated board was made successfully at 800 fpm.
.
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EX~MPLE LV
_-Carrier Type FormuLation
A small-scale demonstration was conducted with an adhesive Eormu:Lation
(IV-l) containing 18-20% of starch acetate succinate (D S. acetate 0.0266;
~.S. succinate 0.018) as the primary adhesive component~ in an aqueous slurry.
This is equivalent, in composition, to a conventional ]l-bag mix in a mill
(i.e., equivalent to a formulation containing 11 bags oE the adhesive compon&nt
in approximately 650 gallons of total adhesive).
A second demonstration was conducted with an adhesive formulation
(IV-2) made of a mixture of unmodified corn starch and the primary adhesive
component, in such proportions that on a mill scale~ 2 of the 11 bags (i.e.,
about 18%) would be unmodified corn starch, the ramainder being the primary
adhesive component.
Stein-Hall viscosity measurements were made on each of these formu-
lations after they were made up ready for use. The make-up procedure was that
described in U. S. 3?355~307~ and was as follows. 250 g of starch material
was slurried in 890 ml of water at 105 F. 275 ml of 4.0% sodium hydroxide
(caustic~ was added to the starch slurry at room temperature over a perlod of
4.5 min. The reaction was then stopped at 60~ cps. with 4.7g boric acid. The
resulting paste consisted in each case of a substantially homogeneous suspension
~ of partially swollen ~ranules.
`~ The Stein-~all viscosity observations were made at once, and then
af~er each formulation had been stored for 24 hours, at 100 F. with mild
agitation. Viscositie~ were similar to those for typical conven~ional formu-
lations.
.
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d.~ ~
VLscoslt-ies of No-Carr-ier Adhe~iv~ Form~lLatio~s
IV-l LV-2Typlcal conven~Lonal
_ _ Eormulation
Stein-Hall Viscos:ity
seconds
` after makeup 21 20 ~1
after overnight
storage 20 20 20
EXAMPLE V
An adhesive composition having the following formulation was prepared.
::
Primary Mixer
Water lOO gal.
Unmodified corn ~tarch 220 lb.
NaOH (dissolved in lO gal.) 40 lb.
Heat to 160 F and hold 15 min.
Water 66 gal.
Secondary Mixer
~, Water 380 gal.
; Borax ~lO mol) 18 lb,
Starch acetate succinate 1000 lb.
Drop primary over 30 minutes
Water 20 gal.
Borax (10 mol~ lO lb.
Thi8 composition was run on a commercial machine using a 90 lb. liner
on the single face side and two 90 lb. liners laminated on the machine on the
double backer side. Good bonding was observed at speeds oE 320 fpm. Conventional
adhesives can normally be run at about 200-250 fpm under the same test conditions.
.
The same composition was used as a laminating adhesive with satisfactory
results. However, no numerical data was obtained as this particular machlne was-~ abl~ to operate at its top speed when using either a conventional fo~mulation or
. ~ ,
~ a eor:ul-tlon in accordance with this lnvention.
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EXAMPL~ VI
Another batch oE adhe~sive was prepare~ using the same starcl~ acetn~e
succinate as in Example V. The amount of carrier starch was 210 lbs; ~he
remainder of the formulation identical to that of Example V. Using the ldentical
90, 90/90 laminate, liners as in Example V, speeds of 420 fpm were achleved. A
further run was made where the double backer liner consisted of a 90 lb. liner
laminated on the machine using this adhesive formulation to a 69 lb. liner.
Speeds of 410 fpm. were obtained. The average speeds for both of these grades
of board was 200 fpm. using conventional adhesives. The machine speed was not
lir.21ted in these two cases by glue line failure, but by the possibility of
drive overload at higher speeds.
`; EXAMPLE VII
~ .
To a slurry of 24.6g of unmodified corn starch in 330 ml water, 25 ml
of a 2.75% (wt/vol~ borax xolution, 45 ml of 3.09% (wt/vol) NaOH and a mixture
of 0.018 mole of succinic anhydride and 0.048 mole of acetic anhydride were added.
A laboratory evaluation of the resulting slurry indicated it to have superior
adhesive properties.
EXAMPLE YIII
Example VII was repeated except that the succinic anhydride was re-
. . .
placed by adipic anhydride. The product was again evaluated as being a superior
, corrugating adhesive.
,~ ~
E~MPLE IX
, ~
Commercial runs were made on a series of products using the following
formula~ions.
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,3 ~ L~ q ?
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Pri~ary Mixer
Water 50 gal.
Unmodified corn starch:LOO lb~s.
NaOH 17 lbs.
Heat to 160 F. and hold 15 min.
Water 33 gal.
Secondary Mixer
Water 200 gal.
Borax (10 mol) 17 lbs.
Test starch 500 lbs.
Drop primary over 30 min.
When using the ester materials, the NaOH was increased to 20 lbs. and
the bora~ to 18 lbs.
~ .
The formulations were run using 60 lb. liners with glue settings of
0.020" on the single facer and 0.018" on the double backer.
Run Machine sReed 7 fpm
1. Unmodified corn starch 425
2. Starch acetate succinate (DS 0.016~ 525
3. Starch acetate succinate (DS 0.024) 575
4. Starch acetate ~DS 0.020) 625
` EXAMPLE X
Instron force-time curves were produced following the standard method
for the following starch materials.
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. . . - . . - -:
~:
lleat CycleCool Cycle
MaterLal ~ Imp. ~ p. _ I).S.
acetate/succinate40 78 .016 (a)
acetate/succinate53 98 .024
acetate/succinate62 95 .024 (b)
acetate/succinate74 134 .021
acetate 55 113 .020 (c)
acetate/succinate71 163 .039 (d)
acetate/succinate88 170 .02G (e)
acetate/succinate22 75 .024 (f)
~ acetate/succinate44 88 .028 (g)
:~ acetate/succinate68 118 .026 (h)
~ acetate/succinate79 122 .023 (i)
~,~
(a) This is material from Example IX, Run 2.
(b) This is material rom Example IX, Run 3.
(c) This is material from Example I~9 Run 4.
(d) This is material rom Example I.
:
' (e) This is material from Exa~ple V.
(f) This product showed only 13% machine speed lmprovement.
; 20 ~g) This is material from Example III, Run a.
h) This is material from Example III, Run b.
~i (i) This product showed 38% machine speed improvement.
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p~ 3~
EXAMPLE XI
Standard Instron force-time areas were determlned for the follow-
ing starch materials.
Heat CycleCool Cycle
Material 7O Imp. % Imp._ D.S.
Maleate 143 196 .037
Phthalate 138 64 .031
Proprionate 72 147 .035
Butyrate 74 133 .041
Iso-butyrate 75 110 .036
: Acetate 110 337 .102
Acetate 67 101 .033
Succinate 57 46 .014
Succinate 76 174 .044
~; 15 Acet-ate 80 336 .080
,~ .
. ~
Succinate 76 108 .024
ac~t.ate/succinate 86 228 .058
acetate/succinate 63 113 .029
. j :
acetate/succinate 27 25 .014
acetate/succinate 31 20 .009
Proprionate 40 42 .018
~:~ Proprionate 26 35 .009
:
.~;
:i~
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d
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EXA~LE XII
The material from Example I was saponified in the presence of
NaOH and borax. It was then washed with water to remove the caustic,
borax and salts. A standard Instron force-time determination was made.
The material showed 58% heating cycle improvement and 82~ cooling cycle
improvement.
EXAMPLE XIII
Example XII was repeated using the material of Example V. This
showed 58% heating cycle improvement and 102% cooling cycle improvement.
'~
When an acid neutrali~ation step was introduced, no significant
improvement compared with unmodified corn starch was shown.
' , :
While the starch acetate succinate, and the other specific
primary adhesive components identifie~ herein, produce superior results
as compared to formulations based on unmodified corn starch and other
conveDtional materials, generally they may be used in making up
corrugating adhesive formulations in the same general manner and i~ -~
substantially the same proportions as conventional materials~ such
... . .
~l as unmo~ified corn starch, would be used. Generally, the primary
., .
`adhesive components of this in~entlon may be used to replace a portion,
~, 20~ or preferably all, of the conventional primary adhesive components
1 , :
j in both Stein-Hall type and no-carrier type adhesi~e formulations. Specific
variations ln amounts of componen~s and the addition of other components
may be made in the formulations uslng these primary adhesive components
'1 :
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~32
.' . ` '
in the same manner as are made for conventional adhesive -formu-
lations. These variations are well known to those skilled in
the art.
The details of the Stein-Hall type adhesive system
may be found in the aforementioned U.S. Patent Nos. ~,051,025
and 2,102,937. The details of no-carrier type adhesive systems
may be found in the disclosure of U.S. Patent No. 3,3S5,307.
When utilizing the novel compositions in a no-carrier environment,
reaction stoppers such as acid anhydride~ and acid chlorides may
be used. These may be broadly defined as acid or acid producing
materials. Careful selection of the reaction stopper may thus
allow the same material to serve as reaction stopper and ester-
ifying reagent.
It is, of course, necessary that the final bond
strength, ascontrasted with the green bond strength be suffi-
ciently high to permit all conventional use of the product~
,,
Pin adhesion tests have shown that the final bond strengths
using the adhesiv~ formulations of thi~ invention are sub~
~ stantially equal to bond strengths of conventional adhesives,
`~ 20 The adhesive formulations of this invention are also
useful in applications other than producing corrugated paper-
board~ For example, these formulations can find application in
tube winding and manufacturing laminated board and multiwall
paper sacks~
In addition, the conventional additives which will
.~
impart water-resistance to the cured bonds may also be incorpor-
ated into the formulation~
,
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~ 33 _
. . . .
. - - . .
l~hile the inventlon has been described in co[mect:ion with
speciEic embodiments thereof, it will be understood that it :is capable
of further modification, and thls application is intendecl to cover other
variations, uses, or adaptions of the invention :Eollow:Lng, in general,
the principles of the invention and including such departures from the
present disclosure as are within Icnown or customary practice in the art
to ~hich the inventipn pertains and as may be applied to the essential
features hereinbefore set forth, and as are within the scope of the invention.
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