Starch adhesive bonding

A method and apparatus for starch adhesive bonding of paper, paperboard, and natural cellulosic-fiber materials, especially liner and fluted corrugating medium, into manufactured items, particularly corrugated board. The method includes applying an adhesive coating, comprising starch and water, to a first substrate (e.g. tips of flutes of a corrugated medium), contacting the applied coating with another substrate (e.g. liner) and while so positioned contacting an exterior surface of at least one of the substrates with an ultrasonic energy generating means so as to transmit ultrasonic energy to the adhesive coating to increase coating adhesion to the substrates. The apparatus includes ultrasound means (10, or 37,37', or 43,43', or 55,55', or 61,61') forming a nip with an anvil 16, or roll 35 or 44, or drive means 57 or 62, with the nip including therebetween paper 17/ starch adhesive 19/ paper 18, or liner 30 or 50/ starch adhesive 32/corrugated medium 31 or 51, or liner 40 or 60/ starch adhesive 32'/ single faced corrugated board 34' or 52'.

FIELD 
This invention relates to method and apparatus for adhesive bonding of 
paper, paperboard, and like natural cellulosic-fiber materials. More 
particularly, it has to do with ultrasonic energy used for a starch 
adhesive bonding of these materials together. Most particularly, the 
invention concerns using ultrasonic energy with such materials as liner 
and fluted corrugating medium being adhesively starch bonded to provide 
corrugated board. 
BACKGROUND 
Ultrasonic energy has been taught as useful for fiber liberation, 
disintegration, and the like and for other purposes in the making of 
paper, paperboard, and like natural cellulosic-fiber materials. However, 
conventionally when fabricating such materials into various items of 
manufacture, such as corrugated board, laminated paper products, 
convoluted cardboard tubing, paper bags, and numerous other useful items, 
the fabrication methods and techniques depend on adhesive bonding of the 
materials. With the just-mentioned materials and a starch adhesive bonding 
thereof, it is believed to be unknown to employ ultrasonic energy as 
taught herein. 
Some studies have been made of the effect of ultrasonic energy on starch 
and starch paste. Illustrative thereof are teachings of: "Sonification 
Effect on Potato Starch and Sweet Potato Powder", A. Azhar and K. Hamdy, 
Journal of Food Science, Vol. 44 (1979) p. 801-804; "The Effects of 
Ultrasound on Starch Grains", M. DeGrois, D. Gallant, P. Baldo, and 
Guilbot, Ultrasonics, May 1974, p. 129-131; and "Starch and Its 
Derivatives", J. A. Radley, Vol. One, 3rd Edition, (1953), paragraph 
bridging p. 112-113. In general, those teachings report the effect of 
ultrasound on starch to be starch degradation and deterioration. 
Illustrative of the present-day status of the making of corrugated board is 
a descriptive review in Chapter 26 "Corrugating" by A. J. Didominicis and 
G. H. Klein in the text of "Pulp and Paper Chemistry and Chemical 
Technology" , Vol. IV, Third Edition, (1983), James P. Casey - Editor, 
John Wiley & Sons. 
As taught in the just-mentioned text, in corrugated board production, 
starch adhesive is used to bond the liner(s) to the fluted medium. In a 
typical adhesive formulation, a major portion of the starch is uncooked to 
maintain reasonable viscosity levels prior to application to the tips of 
the flutes. Heat is applied to the starch mixture to achieve 
gelatinization of the starch so that it acts as an adhesive. Typically, 
the heat is applied to the starch during passage between pressure rolls by 
thermal conduction through the preheated fluted medium contacting a heated 
roll and/or by thermal conduction through the preheated liner contacting a 
heated roll. Problems with this process include the following: (1) poor 
quality, low strength, bonds frequently result from non-uniform heating of 
the adhesive; (2) non-uniform heating of the liner or fluted medium often 
distorts the resultant corrugated board; and (3) inefficient use of 
thermal energy in heating those portions of the liner and fluted medium 
that do not require bonding. 
The invention described herein minimizes these problems and achieves better 
bonding at higher production rates while reducing energy consumption. 
DISCLOSURE SUMMARY 
The present invention generally stated is a method of adhering substrates 
of paper, paperboard, and like cellulosic-fiber materials to each other by 
means of adhesive composition there-between, which method comprises the 
steps of (a) applying a coating of an adhesive composition, which 
comprises starch and water, to a surface area of a first substrate; (b) 
positioning an uncoated surface area of another substrate in contact with 
the applied coating; (c) contacting an output horn of an ultrasonic energy 
generating means with one or the other or both of the first or another 
positioned substrate at an exterior surface area thereof juxtapositional 
to the applied coating between the positioned substrates; (d) generating 
ultrasonic energy with the ultrasonic energy generating means so as to 
transmit from the output horn into the coating the ultrasonic energy of a 
frequency and for a time duration so as to increase adhesiveness of the 
coating to the positioned substrates. 
Generally and as illustrated herein, the substrates to be adhered are in 
the form of sheet or web-like lengths, such as relatively 
continuously-formed lengths of paper, paperboard and the like natural 
cellulosic-fiber materials. For purposes of illustrating the invention 
with specificity, the invention is described by employing liner, 
corrugating medium, etc. and the making of corrugated board. With 
reference to the description which follows and contents of the 
aforementioned text chapter entitled "Corrugating", it is believed 
apparent how to retrofit conventional practices and apparatus for making 
of corrugating board using the ultrasonic application procedures and 
components taught herein by adding, supplementing, deleting and/or 
replacing conventional rollers, belts, etc. along with incorporating 
requisite ultrasonic energy means. 
The present invention also includes apparatus useful for its practice. An 
appropriate useful apparatus, for adhering substrates of paper, 
paperboard, and like cellulosic-fiber materials to each other by means of 
an adhesive composition therebetween, comprises the following components: 
(a) means for applying a coating of an adhesive composition, which 
comprises starch and water, to a surface area of a first substrate; (b) 
means for positioning an uncoated surface area of another substrate in 
contact with the applied coating; and (c) means for applying ultrasonic 
energy to one or the other or both of the first or another positioned 
substrates at an exterior surface area thereof juxtapositional to the 
applied coating between the positioned substrates. 
The foregoing apparatus also may comprise (d) one or more means for 
preheating either or both of the first and the other substrates to a 
temperature less than the gelatinization temperature of the adhesive 
composition prior to applying of the coating to the first substrate and 
prior to contact of another substrate with the applied coating. 
Additionally the apparatus generally includes: (e) one or more roll means 
provided with flutes thereon for forming of a fluted corrugating medium to 
function as the first substrate, and with the (c) means for applying 
ultrasonic energy positioned in relation to other components so as to 
provide, between an output horn of the means for applying ultrasonic 
energy and a flute on a roll means, a nip space less than the combined 
thickness of the first substrate, the coating and the other substrate.

DETAILED DISCLOSURE AND CARRYING OUT THE INVENTION 
Referring to FIG. 1, experimental apparatus 10 for demonstrating the 
feasibility of ultrasonic bonding according to this invention is shown 
schematically. The test specimen 15 was a lap joint formed by overlapping 
porous paper 17,18 with an intervening layer of adhesive 19. An ultrasonic 
transducer 11 produced high frequency (e.g. 20 kHz) vibratory motion 12 of 
0.025 mm amplitude when energized by an electrical generator 13. The 
vibratory motion 12 was transferred via the horn 14 to the test specimen 
15 compressed between an anvil 16 and the horn 14. A controlled force for 
compression was provided in an axial direction 20 by movement of the 
transducer 11 and horn 14 toward the metal anvil 16 resting on the 
stationary surface 21. The ultrasonic transducer was energized prior to 
contact of the horn 14 with the test specimen and deenergized a fraction 
of second after a steady-state peak pressure was attained to produce an 
adhesive bond. Control experiments were conducted in a similar manner 
except that the transducer 11 was not energized and no ultrasound was 
applied. 
A tensile testing machine (Instron Company) was used to determine the 
strength of the adhesive bond at the lap joint of the test specimen 15. 
The bond strength of the lap joint was calculated as the force in newtons 
(N) applied to the ends of the porous paper 17,18, held in the jaws of the 
tensile testing machine divided by the area in square meters (m.sup.2) of 
the lap joint parallel to the paper 17,18. The bond strength of the lap 
joint measured in the above manner often exceeded the force that could be 
applied in a direction parallel to the paper 17, 18, and the paper 17 or 
18 broke at other than the lap-joint bond area. 
An experimental procedure was developed which simulated conventional 
adhesive bonding as determined by the bond strength of specimens in 
control experiments in which no ultrasound was used. The procedure for 
control experiments will be described first. The anvil 16 which could be 
heated to any temperature up to 200 C. was maintained at the desired test 
temperature (typically room ambient temperature of 26 C., 93 C., or 149 
C.). The lap-joint test specimen 15 was placed on the anvil 16 as shown in 
FIG. 1 and simultaneously the hydraulic feed mechanism of the experiment 
apparatus 10 was activated. From the initial starting position, the horn 
typically contacted the test specimen in 2 seconds and compressed the test 
specimen 15 over a typical period of 2.5 seconds to a peak pressure of 
1,400,000 N/m.sup.2 (200 lb/in.sup.2) which was then maintained for 1 
second after which the hydraulic feed mechanism was deactivated and 
compression reduced over a typical period of 4 seconds after which the 
test specimen 15 was removed from the anvil 16. The adhesively-bonded test 
specimens 15 were set aside for subsequent determination of bond strength. 
The above procedure used in control experiments was followed by comparative 
experiments using ultrasound in which the transducer 11 was energized 
simultaneously with activation of the hydraulic feed mechanism at the 
beginning of the experiment. In comparable experiments, the time from the 
beginning of the experiment until the peak pressure level was reached was 
reproducible. In experiments with ultrasound applied, the transducer was 
deenergized after various time periods at the steady-state pressure of 
1,400,000 N/m.sup.2 such as 0.300, 0.150, and 0.075 seconds with 
compression maintained the full 1 second as in the control experiments. 
In experiments in which the materials of the test specimen 15 were a liner 
and medium typically used in making corrugated board, the bond produced by 
use of ultrasound greatly exceeded the breaking strength of the medium. 
Corrugating medium is made from low strength materials (e.g. straw, waste 
paper, or semichemical pulp). Standard liner is made from high strength 
materials (e.g. heavy weight kraft or jute paper) and has much higher 
tensile strength than corrugated medium. Thus, to obtain comparative 
quantitative data on adhesive bond stength, experimental test specimens 15 
were made from two samples of liner typically used in making corrugated 
board. A test specimen in which liner 17 was bonded to another liner 18 
allowed quantitative measurement of the adhesive bond strength up to the 
breaking strength of the liners 17 or 18. 
Samples of typical paper liner 17,18, approximately 75 mm.times.50 
mm.times.0.46 mm, were overlapped about 6 mm. One sample of liner 18 was 
precoated on its surface being overlapped with a starch adhesive 19 to a 
thickness of 0.25 mm using a Baker blade. The horn 14 had dimensions of 
150 mm.times.19 mm which exceeded the lap-joint area (50 mm.times.6 mm). 
The hydraulic force in the vertical direction 20 over the area of the lap 
joint of the test specimen 15 produced a compression of liners 17,18, of 
1,400,000 N/m.sup.2 which is a typical pressure in the nip of conventional 
pressure rolls used to bond single facer liner to corrugated medium. The 
compression was the minimum attainable with the experimental set up. Lower 
compression in the range of 3000 to 100,000 N/m.sup.2, depending on web 
thickness, would be adequate to insure good contact of liner 17 with liner 
18 and adhesive 19. 
The starch adhesive 19 was a sample of a conventional corrugating starch 
adhesive formulation prepared as follows: 
______________________________________ 
Primary mixer (carrier starch) 
Step 1 Add water 378.5 liter 
Step 2 Add corn starch 90.9 kg 
Step 3 Add caustic soda dissolved in 
13.6 kg 
about 37.9 liters of water 
Step 4 Heat to 66 to 71.degree. C. 
Step 5 Hold under agitation 15 min 
Step 6 Add cooling water 227.1 liters 
Secondary mixer (raw starch) 
Step 7 Add water 1514 liters 
Step 8 Heat to 27 to 32.degree. C. 
Step 9 Add corn starch 454.5 kg 
Step 10 Add borax (10 mole) 13.6 kg 
Step 11 Transfer primary to secondary 
in about 30 min 
______________________________________ 
Additional details and description for preparation of the above starch 
adhesive formulation can be found on pages 2388-2392 in the aforementioned 
Chapter 26 "Corrugating" of the text "Pulp and Paper Chemistry and 
Chemical Technology". The above starch adhesive 19 was at room temperature 
(26 C.) when applied to the liner 18. In the control experiments in which 
the anvil 16 was heated, heat transfer from the anvil 16 to the starch 19 
occurred through the liner 18 after the lap joint 15 was positioned on the 
anvil 16. 
The above experimental conditions provided a simulation of conventional 
adhesive bonding of corrugated board for control experiments in which no 
ultrasound was applied based on the experimental results discussed next. 
The results of comparative experiments conducted to demonstrate the 
beneficial effect of use of ultrasonics in bonding liner materials with 
starch adhesive are summarized in FIG. 2. In control experiments, in which 
no ultrasonic energy was used, essentially no bonding was obtained at room 
temperature (.about.26 C.) with peak pressure maintained for 1 second in 
all experiments. As shown in FIG. 2, bond strength in the range of 220,000 
and 350,000 N/m.sup.2 was obtained for lap-joint specimens with the anvil 
16 at a temperature of 93 C. At an anvil temperature of 149 C., the bond 
strength was above the breaking strength of the paper liners 17,18 and 
quantitatively indeterminate. The latter result is typical of conventional 
bonding on paper machines in which the single-facer pressure roll is 
typically maintained at 188 C. and the resultant bonds with starch 
adhesive are stronger than the liner. 
In similar experiments in which ultrasonic energy at 20 kHz was applied for 
a time of 0.150 seconds of the total time of 1 second at peak pressure, 
good bonds were obtained above the breaking strength of the liner 17,18 at 
all temperatures tested of 26 C., 93 C., and 149 C. as shown in FIG. 2. 
The results with the anvil 16 at room ambient temperature (26 C.) clearly 
show the beneficial effect of ultrasonic bonding (i.e. good bond with 
ultrasonics and no significant bond in the absence of ultrasonic energy 
input). Thus, the use of ultrasonics can produce a good bond at room 
temperature without the need for inefficient heating of the corrugated 
board materials by heat transfer rolls at temperatures above 150 C. as 
presently required in conventional starch bonding processes of the prior 
art that do not use ultrasonic energy. 
Additional experiments were conducted with the time of application of 
ultrasound energy at peak pressure reduced from 0.150 second to 0.075 
second. As shown in FIG. 2, experiments with ultrasound for 0.075 second 
produced good bonds at 93 C. which were at least twice as strong as 
comparable bonds in the absence of ultrasound. At room ambient 
temperature, the shorter period of application of ultrasound still 
produced a significant bond strength, as good as achievable with samples 
in control experiments at 93 C. which did not use ultrasound. 
Other experiments conducted with a time of application of ultrasound energy 
of 0.300 second at peak pressure produced results similar to those for 
0.150 seconds as shown in FIG. 2. 
The exact mechanism by which application of ultrasound improves the bonds 
achieved with starch adhesive is not known. It is expected that ultrasound 
applied to the lap joint of test specimen 15 produced heat sufficient to 
raise the temperature of the starch adhesive above the gelatinization 
temperature of approximatel 60 C. of the employed starch adhesive 19. 
However, other factors than heat may be involved. It is well known that 
ultrasound promotes fluid flow into porous materials and can increase 
wetability. Ultrasound might promote adsorption of heat and water into the 
raw starch granules to cause gelatinization to occur at lower temperature 
than in the absence of ultrasound. There may be other factors involved 
which lead to improved bonds by use of ultrasonic energy at much lower 
anvil temperature than expected based on the prior art. The results with 
the anvil at room ambient temperature as shown in FIG. 2 clearly 
demonstrates the beneficial effect of application of ultrasound. The 
negligible bond obtained in the control experiments with the anvil at 26 
C. would be expected since the starch adhesive would not reach the 
gelatinization temperature of about 60 C. In contrast, use of ultrasound 
for 0.075 second to 0.300 seconds at peak pressure achieved bonds 
comparable to bonds requiring anvil temperatures of 93 C. to 149 C. in the 
absence of ultrasound. 
The ultrasonic apparatus 10 used in the experiments had an input rating of 
about 1 kW. However, the exact amount of ultrasonic energy coupled to the 
lap joint of the test specimen 15 is not known. In the experiments, 
ultrasound was coupled to the materials of the lap joint of the test 
specimen 15 when the horn 14 made contact with the liner 17 and the 
pressure began to increase. The ultrasound coupling was probably very 
inefficient at first and increased with compression reaching maximum 
efficiency of coupling at some unknown compression level below peak 
pressure. It is believed that a significant portion of the ultrasound 
energy input to the lap joint of the test specimen 15 occurred during the 
time period at steady-state peak pressure since reduction of the latter 
time period from 0.150 second to 0.075 second affected the bond strength 
in experiments at room temperature (26 C.) as shown in FIG. 2. 
No direct measurement of temperature of the starch adhesive 19 could be 
conveniently made during application of ultrasound. However, test 
specimens that had been subjected to ultrasound at 20 kHz for 0.300 second 
at peak pressure with the anvil 16 at room temperature (26 C.) were 
prepared for examination by scanning electron microscope. There was no 
evidence of raw starch granules from the original applied coating left in 
the area of the lap joint bond which suggests that the gelatinization 
temperature of about 60 C. had been exceeded in the starch adhesive 19 by 
application of ultrasound. The ultrasound might have coupled directly to 
the starch adhesive producing heat in-situ. It is also probable that the 
ultrasound coupled efficiently to the liner 17 in contact with the horn 14 
and also coupled to the liner 18 to produce heat in situ within the liners 
17,18 which would be conducted to the starch adhesive 19 to increase its 
temperature. In-situ generation of heat within the lap joint of test 
specimen 15 would be more efficient in raising the starch temperature to 
the gelatinization temperature in a finite time than by thermal conduction 
from the anvil 16 through the liner 18 required in the control 
experiments. Regardless of the exact mechanism by which use of ultrasound 
achieves good bonds at low anvil temperature, ultrasound has beneficial 
effects that can be practically applied to bonding with starch adhesive of 
porous paper products such as corrugated board. 
In typical embodiments of this invention, as shown schematically in FIGS. 3 
and 4, ultrasonic apparatus can be added to conventional production 
machines for starch bonding of corrugated board. FIG. 3 shows a typical 
embodiment of this invention for production of corrugated board of the 
type referred to as single-faced 34. A typical rotating metal roll 35 with 
a surface containing metal flutes 36 carries a fluted medium 31 that has 
been prepasted with starch adhesive 32 at the tips of the flutes. An 
ultrasound horn 37 or a plurality of similar horns 37' is oriented in an 
essentially radial position relative to the roll 35 (i.e. horn 37 is 
juxtapositionally positioned with respect to adhesive 32 at the tips) and 
fixedly positioned such that a pressure nip is formed between the horn 37 
of the ultrasound apparatus and the flutes 36 of the roll 35. Liner 30 
moving in direction 38 passes into the nip of the first horn 37' 
contacting the adhesive 32 and is compressed against the fluted medium 31 
when rotation of the roll 35 brings a metal flute 36 and the fixedly 
positioned horn 37' to their minimum spacing. The spacing between the horn 
37,37' and metal flute 36 on the roll 35 is adjusted to slightly less than 
the combined thickness of the liner 30, adhesive 32 and fluted medium 31 
to produce the desired compression in the nip. Ultrasonic energy is 
applied via the horn 37,37' to one side of the liner 30 to provide high 
frequency vibration 12 in an axial direction to produce a bond 33 in the 
single-faced corrugated board 34 that subsequently detaches from the roll 
35 and continues in the direction 39. The horn 37,37' or multiple segments 
(not illustrated) of horns extend the width of the roll 35 (direction 
perpendicular to plane of FIG. 3). 
FIG. 4 shows a typical embodiment of the invention for producing corrugated 
board of the type referred to as double-backed 42. The apparatus and 
process of FIG. 4 differ from FIG. 3 in that the roll 44 has a smooth 
surface 45 and carries a single-faced board 34' coated with adhesive 32' 
at the flute tips into contact with the double-backer liner 40 moving in 
direction 46. The process differs in that the spacing between the fixedly 
positioned horns 43,43' and the surface 45 of the roll 44 is adjusted to 
slightly less than the caliper of the resultant double-faced board 42 so 
as to produce compression of the liner 40 and single-faced board 34' in 
the nip between the horn 43,43' and single faced board 34' without 
exceeding the compressive strength of the single-faced board 34'. 
In the practice of this invention, magnetostrictive and piezoelectric 
transducers are typically used to generate ultrasound at frequencies from 
about 2 to 100 kHz. It is preferred to operate at frequencies in the range 
of 10 to 100 kHz or above the frequency limit for human hearing. The 
ultrasonic horn is designed in accordance with well-known principles for 
efficient coupling and in relation to the bonding application. For example 
in FIG. 3, the surface of the horn 37 in contact with liner 38 would have 
a slight radius corresponding essentially to the radius of the roll 35 at 
the tips of the flutes 36 plus an allowance for the compressed thickness 
of the liner 30 and medium 31. Similarly, in FIG. 4 the surface of the 
horn 43 would have a radius essentially equal to the radius of the roll 44 
plus an allowance for the caliper of the compressed double-backed 
corrugated board. The length of the horn 37 in the direction of rotation 
of roll 35 is selected such that one or more flutes may be subjected to 
ultrasound under a single horn 37. For example, typical corrugated board 
of 128 flutes/meter would have a spacing of 0.78 cm between tips of 
adjacent flutes and the length of the horn in contact with liner 30 could 
be in the range of 0.1 cm to 2 cm. A horn 37 with length of 2 cm might 
have a width of about 30 cm across the width of roll 35 and sufficient 
similar horns 35 would be used across the width of the roll 35 to 
accommodate the width of the single-faced board 34 being produced. 
Typically, ultrasonic vibration in the radial direction 12 would be 
applied continuously and the duration of application for each flute bond 
33 would be related to the length of the horn 37 and the speed of the web 
34. For example, with web speed of 3 m/sec and length of horn of 2 cm, the 
duration of application of ultrasound to a single flute bond 33 would be 
about 0.007 second. Additional horns 43' would be used to increase the 
duration of ultrasound application (e.g. 0.07 second for ten horns) as 
needed depending on such factors as the energy provided by each horn, the 
efficiency of energy coupling, and the temperature of the liner 30, medium 
31, and starch 32 prior to entering the nip (i.e. amount of preheating). 
Apparatus according to this invention for adhering substrates of paper, 
paperboard, and like cellulosic-fiber materials to each other by means of 
an adhesive composition therebetween comprises means for applying 
ultrasonic energy and other means as appropriate to manufacture the 
finished product. For purposes of illustrating the invention, the 
invention is described for making single-faced corrugated board as shown 
schematically in FIG. 5 and double-backed corrugated board as shown in 
FIG. 6. 
Referring to FIG. 5, apparatus according to this invention for production 
of single-faced corrugated board 52 comprises substitution of ultrasonic 
apparatus 55,55' for the conventional pressure bonding roll used in the 
prior art. A moving web of preformed fluted medium 51 is coated with an 
adhesive composition, which comprises starch and water, by a conventional 
starch applicator roll coater 54 which applies a thin layer of starch to 
the surface area at the tip of the flutes. A guide roll 53 guides the 
moving web of single-facer liner 50 into juxtapositional contact with the 
starch coated flute tips of medium 51 in the nip formed between the 
ultrasonic transducer/horn 55,55' and the corrugated drive 57. Ultrasound 
is applied to adhesively bond the webs 50,51 while they pass through the 
nip in the manner as previously described with reference to corresponding 
liner 30 and fluted medium 31 of FIG. 3. A drive means 56 such as a canvas 
belt moves the web of adhesively-bonded single-faced board 52 in the 
direction 58 to subsequent operations such as trimming, slitting and 
cutting if it is the final product or to the subsequent production of 
double-backed corrugated board. The ultrasonic apparatus comprises 
electrical generating means connected to the transducer/horn 55 or a 
plurality of similar transducer/horns 55' as required to impart the 
necessary ultrasound energy for adhesive bonding depending on the web 
speed and other factors such as the temperature of the liner 50, fluted 
medium 51 and starch coating prior to application of ultrasonic energy. 
For example, the guide roll 53 might be a drum-type heater to preheat the 
liner 50. The corrugated drive 57 might also be heated to preheat the 
medium 51. Typically, the corrugated drive/heater is the conventional dual 
purpose corrugating roll on which the medium is formed into flutes prior 
to coating the flute tips of the fluted medium 51 with starch at the 
coater 54. 
Referring to FIG. 6, apparatus according to this invention for production 
of double-backed corrugated board 63 comprises substitution of ultrasonic 
apparatus 61,61' for the conventional heated platens or pressure bonding 
rolls used in the prior art. A moving web of single-faced corrugated board 
52', which is typically a continuation of web 52 of FIG. 5 moving in the 
direction 58, is coated at the flute tips with starch adhesive at a coater 
54'. A guide roll 53' guides the moving web of double-backer liner 60 into 
contact with the starch-coated flute tips of single-faced board 52' in the 
nip formed between the ultrasonic transducer/horn 61,61' and the support 
drive 62. Ultrasound is applied to adhesively bond the webs 60 and 52' 
while they pass through the nip as previously described with reference to 
FIG. 4. Drive means 56,56', such as canvas belts, move the 
adhesively-bonded, double-backed corrugated board in the direction 64 to 
subsequent operations such as slitting, trimming, and cutting. A hot-plate 
section may precede or be combined with the drive 56,56' wherein heat is 
transfered to the surfaces of the combined corrugated web 63 by steam 
heated platens or rolls to further set and develop the ultimate adhesive 
bond strength. The ultrasonic apparatus comprises electric generating 
means connected to the transducer/horn 61 or a plurality of 
transducer/horns 61' as required to accomplish adhesive bonding depending 
on web speed and other factors such as preheat of the double-backer liner 
60 by a drum-type heater 53' or preheat of the single-facer board 52' by a 
rotating drum-type heater 62 with an essentially smooth (non-corrugated) 
surface supporting and driving the web 52'. 
While the invention has been described with particularity and specificity 
as to its employment in manufacture of corrugated board and specifically 
illustrated with respect to single-faced corrugated board and 
double-backed corrugated board, it is contemplated from teachings herein 
also to be useful for manufacture of other corrugated board constructions, 
for example double-wall and triple-wall corrugated board and from 
teachings presented herein for one in the art to so apply the invention. 
Likewise the invention is contemplated to be readily applicable to 
manufacture of other items, whose constructions involve adhesively starch 
bonding together of paper, paperboard, and like natural cellulosic-fiber 
materials. To mention just a few of such items and applications, they 
include: laminated paper products, paper bags, rolled tubing, and 
convoluted tubing, rapid sealing of moistened starch-gummed tapes and 
labels, etc. 
Of essence to the invention is that the applied ultrasonic energy increases 
the adhesiveness of a starch adhesive coating, which contacts the 
to-be-adhered substrates of paper, paperboard, or like cellulosic-fiber 
material. The composition of the starch adhesive coating can vary greatly 
with the invention still being applicable. The starch adhesive, as 
applied, comprises starch and water, but also may contain numerous other 
constituents, and also vary considerable in its formulation. For example, 
instead of the herein described adhesive comprising both cooked starch and 
natural or raw granules of starch, the starch adhesive could be of a 
no-carrier starch adhesive formulation, wherein the starch granules are 
swelled in a controlled manner to a desired viscosity. Water-resistant 
starch adhesive formulations containing synthetic resins and the like also 
should be useful in practicing the invention. Additionally various starch 
formulations containing physically and/or chemically modified starches 
should be useful in practicing the invention. 
While the significant advantages and improvements of the invention 
resulting from its application to corrugated board manufacture as 
illustrated herein may not be of the same magnitude and be greater or less 
with differing starch adhesive compositions in applying the invention to 
manufacturing items other than corrugated board, it still is considered 
that the invention will be useful with such compositions and in such 
manufacturing while remaining within the true spirit of the invention. 
While the forms of the invention herein disclosed constitute presently 
preferred embodiments, many others are possible. It is not intended herein 
to mention all of the possible equivalent forms or ramifications of the 
invention. It is to be understood that the terms used herein are merely 
descriptive rather than limiting, and the various changes may be made 
without departing from the spirit or scope of the invention.