Method and apparatus for preconditioning laminated paper for recycling

Disclosed is method and apparatus including a tank in which shredded corrugate is immersed and shuffled in a solvent fluid capable of attacking and weakening the adhesive bonding the core ply from the liner plies; said corrugate being advanced from its entry point into the tank to an exit point therefrom at a timed rate to limit its absorption of the solvent fluid prior to its transfer to delaminating apparatus.

The invention relates to method and means for conditioning corrugate paper 
bond preliminary to its separation or delamination into its respective 
constituents for recycling. 
BACKGROUND OF THE INVENTION 
It is now well known that significant economic advantages may be gained 
from the recycling of paper waste, (including corrugate) and if the waste 
to be recycled--i.e. the "furnish"--is comprised of mixed papers, it is 
further known that such economic advantages may be enhanced, often to a 
considerable extent, by sorting the various papers comprising the furnish 
according to their respective qualitative categories insofar and to the 
extent it is feasible and possible to do so preliminary to the actual 
recycling thereof. 
This expedient avoids or minimizes admixture of various paper grades in any 
one recycling operation which would usually relegate the recovered product 
to a relatively inferior and, hence, cheaper re-use. Conversely, 
pre-sorting of the paper makes it possible for the better grades to be 
separated and recycled separately from the lesser grades and, hence, 
thereafter used in superior and resultantly more valuable applications. 
RELATED APPLICATION 
Machinery for sorting waste papers in known and one such machine is 
disclosed in U.S. Pat. No. 4,124,168, issued to the Assignee of the 
present Applicant. Such machinery is, however, most useful in the sorting 
of uncomplicated papers and is largely ineffective in the sorting of 
laminated papers of differing qualities which may required to be 
delaminated prior to the actual sorting operation. 
FIELD OF THE INVENTION 
The laminated paper product of present concern is corrugate paper board, 
often simply termed "corrugate", which is used quite extensively, for 
example, in shipping boxes or containers. 
In its commonest form, corrugate comprises a core ply or medium which is 
formed of stiff, crush-resistant, paper which is fluted or rippled 
providing it with upper and lower crests and is substantially receptive to 
water. This core ply is sandwiched between plies of linerboard or liners, 
so-called, of another paper grade, normally less receptive to water and 
tightly bonded to the crests of the core ply, usually by a starchy 
adhesive. 
Recycling the corrugate in its original composite or laminated form and 
without prior delamination would yield a product comprising a mixture of 
the core ply material and the linerboard material; such product being 
usually of relatively low value and useful only in, so called, "low-end" 
applications. Conversely, separate recycling of the liner board on the one 
hand and the core ply on the other, after delamination of the board, will 
upgrade the potential uses and, hence, the value of each of the recovered 
products; conceivably, even imparting to the core ply, which is the 
cheaper component, a greater value at times than that of the waste 
corrugate as a whole. 
The separation of its constituents being thus shown to be desirable, the 
corrugate is subjected to pre-conditioning treatment to undermine, at 
least, the adhesive bonds between its several plies whereby to facilitate 
the ultimate rupture of the bonds and, hence, the separation of the 
respective plies in an ensuing sorting operation thus conducing to the 
subsequent segregation of the paper grades from each other in the actual 
recycling operation. 
DESCRIPTION OF THE PRIOR ART 
The only prior patent known to the Applicant having specific relevance to 
the delamination of corrugate is that issued to IANNAZZI--U.S. Pat. No. 
3,833,460 in the United States in which is described a so-called "dry" 
technique; the present invention being contradistinctively describable as 
involving a "wet" technique. 
SUMMARY OF THE INVENTION 
Theoretically, delamination of corrugate may be accomplished by soaking the 
boad in a suitable "solvent"--e.g. water--with or without additives and, 
while possibly effective to achieve delamination, indiscriminate soaking 
is not commercially practicable or feasible for several reasons. For 
example, it presents a problem in harvesting the respective delaminated 
plies. The plies would be soaked through, hence, less manageable for 
sorting purposes and, of course, prone to disintegration and premature 
repulping before segregation; thus defeating, at least partly, the purpose 
of the delamination and pre-conditioning operations. 
It should be emphasized that the word "solvent" and its variations is used 
rather loosely herein for want of better terminology to define a substance 
which is able to attack and weaken or undermine adhesive which bind 
together the several laminae of the corrugate whether or not by actually 
dissolving the adhesive. Starch, for example, is a very common adhesive in 
corrugate and while not truly soluble in water--which is the preferred 
"solvent" for starchy bonds--it is certainly susceptible thereto and 
capable of absorbing the water; becoming spongy and inclined to lose its 
adhesive tenacity in consequence. 
Recognizing the desirability in many circumstances of initiating 
delamination of the corrugate by soaking and so softening the adhesive 
bonds uniting its plies, the invention seeks, broadly, to provide method 
and means for achieving this result without seriously risking or conducing 
to wholesale premature repulping of the corrugate. 
As a further and important object, the invention seeks to provide method 
and means for pre-conditioning corrugate for recycling by controlled 
exposure thereof to a solvent capable of attacking the adhesive bonds to 
weaken them and thereby render them susceptible to other forces 
subsequently applied to the corrugate to complete the actual delamination 
thereof and, at the same time, to separate its respective plies from each 
other for recycling. 
More specifically, the invention seeks to provide method and means for 
undermining the adhesive bonds as aforesaid by introducing the corrugate 
into a suitable solvent as herein defined and by simultaneously applying 
mechanical forces to the corrugate to procure maximum exposure of its 
adhesive bonds to the solvent whereby to attack the bonds and effectively 
weaken them before the paper components of the corrugate absorb too much 
of the solvent and begin repulping. 
The invention achieves its foregoing objectives by the provision of method 
and means for introducing the corrugate duly cleaned and shredded (as 
hereinafter described) into fluid solvent--for example, a water bath; 
shuffling the corrugate therein promoting flushing of the solvent between 
its outer plies or liners and otherwise conducing to exposure of the 
adhesive bonds to the solvent; maintaining the shuffling of the corrugate 
for a brief period of time sufficient in duration to enable the solvent to 
reach, attack, soften and undermine said adhesive bonds but insufficient 
to initiate active repulping of the corrugate; withdrawing the corrugate 
from the bath aforesaid, draining it of free solvent, before subjecting it 
virtually immediately thereafter to stresses in sorting apparatus 
rupturing said softened bonds and separating the respective plies of the 
corrugate while at the same time segregating or isolating them from each 
other for subsequent re-cycling. 
For a better understanding of the invention at this juncture it is deemed 
useful to observe that the corrugate furnish is usually provided in, 
so-called "shredded" form, i.e.--chopped-up fragments rarely exceeding 100 
sq. inches in plane dimension and with the corrugate core plies thereof 
usually crushed in consequence of having been previously compressed by a 
baling press into a tightly compacted bale; yielding fragments or shreds 
as aforesaid of diverse sizes, profiles and conditions when the bale is 
unbound. 
It is further noteworthy that, despite any cleaning necessary for the 
removal of contraries or the like entrained in the furnish, the components 
of the corrugate may still remain somewhat impure in comparison to their 
original virginal state owing to various "treatments" which the latter may 
have undergone in and for its original use whereby it may have been loaded 
with relatively irremovable contaminants such as coatings, adhesives, 
printing materials and the like. 
Moreover, while the invention has proven most effective in enabling 
adequate separation of the several plies of the corrugate with minimal 
effort and with minimal premature repulping, some incidental repulping is 
virtually inescapable which also tends to degrade the recycled products in 
comparison to their virginal state. Finally, it should be noted that, 
while highly desirable, totally "clean" delamination is not alway feasible 
for a variety of reasons which may stem from the composition of the 
respective plies; from the specific adhesives used for their lamination; 
from coatings and the like specifically applied to one or more of the 
plies, and so forth. 
A selected embodiment of the invention exemplary of its elements, parts and 
principles will now be described with reference to the accompanying 
drawings wherein:

DESCRIPTION OF THE PREFERRED EMBODIMENT 
It need scarcely be pointed out that the drawings are presented in 
schematic form in the interest of clarity and for the sake of better 
comprehension of the inventive concepts as distinguished from the manner 
in which the illustrated apparatus would be engineered for industrial or 
commercial purposes. 
In the following description of the invention method and apparatus aspects 
thereof have been intermingled for better comprehension whereby the method 
will sometimes be obvious from the description of the apparatus which 
will, in turn, be sometimes better apparent from the described method. 
Keeping in mind the wide variations therein which are not only possible but 
reasonably common, the corrugate C selected for the purpose of this 
description is visualized as the simple, familiar, variety in which the 
core ply 2 is commonly formed of semi-chemical fibres and is laminated to 
linerboard skins or liners 4--4 of unbleached kraft fibre by a starchy, 
water-susceptible adhesive forming bonds 6 at which the liners 4--4 
contact and are secured to the crests 6' of the corrugations 8. 
In the normal, uncrushed state of the corrugate C, its corrugations 8 
provide flutes or channels 10 through which bonds 6 can readily be reached 
by fluid in which it is immersed. Commonly, however, the corrugations 8 
will be crushed in the baling of the furnish and, while that may well 
restrict access to the bonds 6, the general disruption of the corrugate C, 
which is also a concommitant of baling, will tend to increase its exposure 
or receptivity to the solvent and thus compensate to a greater or lesser 
degree for the constrictions resulting from the collapse of the channels 
10. 
It having already been explained that the core ply 2 is more readily 
saturable than the liners 4--4, the invention seeks to concentrate upon 
maximum wetting of the bonds 6 within the least time whereby to minimize 
soaking of the liners 4--4 and, hence, so to retard the repulping thereof. 
Thus, the invention visualizes the introduction of precleaned corrugate C, 
in its shredded form, into a solvent fluid to be more particularly 
described and of shuffling the corrugate in the solvent to flex it, tilt 
it, reorient it, tumble it and generally move it around not only to expose 
new areas thereof to the solvent, but also to gain maximum accessability 
of the adhesive bonds 6 thereto. 
One convenient and very simple expedient for carrying out this step is to 
provide the solvent in an elongated, axially horizontal container such as 
a tank, shown for example in FIG. 2 and other views of the drawings. A 
tank as aforesaid may be constituted by the tubular, rotatable, drum 20 
shown in FIG. 2 and other views, which is provided with bulkheads 22--22 
at its ends; there being central apertures 24-26 in the bulkheads 22--22 
for the introduction and removal of corrugate C into and out of drum 20. 
Said drum 20 is intended to provide an environment in which the corrugate C 
may be conveniently bathed in the solvent fluid whose nature and character 
depend necessarily on and are most appropriate to the specific adhesive 
used in the lamination of the particular corrugate C under treatment. 
As previously stated, common starch is a very popular adhesive used for 
this purpose and is also susceptible to an aqueous solvent which tends to 
soften it and diminish its adhesive tenacity. As is well known, the 
effects of such aqueous solvent on the starch may, of course, be enhanced 
under certain conditions by the admixture therewith of a wetting agent 
such as, for example, urea or poly alkoxylated alkyl phenol available on 
the market under the trademark TRITON X-100. 
Thus, in the present embodiment, the solvent fluid S contained in drum 20 
between its bulkheads 22--22 consists of water (with or without additives) 
which is replenishable from time to time when required as at 28 through an 
aperture aforesaid in one of the bulkheads 22 or into fill chute 30, if 
preferred. 
It should be re-emphasized at this juncture, that the effectiveness of the 
present process is dependent upon several factors to a greater or lesser 
degree according to the specific corrugate C being pre-conditioned. 
Thus, not only should the solvent S utilized be that most appropriate to 
the adhesive used in the lamination of the corrugate C but, in addition, 
the temperature thereof may also be varied according to prevailing 
conditions as may be the exposure of the corrugate C thereto--i.e. its 
residence time in the solvent. 
Other factors may also be relevant e.g. the shred size; the vigor of the 
shuffling, and so forth. However, these parameters are not quite as 
important as the solvent, its temperature, and the residence time. 
In the present example, fill chute 30 is disposed to empty into drum 20 
through aperture 24 in one of the bulkheads 22; this being the entry point 
for the shredded corrugate C into drum 20; the exit point thereof being 
the discharge aperture 26 in the opposite bulkhead 22. 
The residence time of the corrugate C is that spent in its transit from its 
point of entry to the point of its exit from drum 20 and recourse may, of 
course, be had to various expedients for advancing the corrugate C between 
these two points. 
For example, the residence time may be governed by the rate at which the 
corrugate C is introduced into drum 20 as well as the rate of rotation of 
the latter as will appear. 
As will be apparent from FIG. 6 corrugate C fed rapidly into drum 20 tends 
to pile up adjacent aperture 24 where it is first dropped by fill chute 
30. However, the pile up understandably tends to level off as drum 20 is 
rotated whereby several other beneficial results are collaterally 
achieved. 
That is to say, rotation of the drum 20 will tend to carry and lift the 
lowermost layers of corrugate C out of the fluid solvent bath at the 
bottom of drum 20 and drop them again on top of the pile thereby making 
room for the upper strata of the pile to be accomodated and immersed in 
the solvent substantially as shown in FIG. 3. 
Likewise, the rotation will shuffle and reorient the corrugate shreds 
exposing new surfaces thereof to the solvent and will move them about to 
promote flushing of the solvent S through the channels 10 of core ply 2. 
Thus, in general, the rotation of drum 20 will have the effect of 
shuffling the corrugate C contained therein to impart to it a variety of 
movements such as flexing, tilting, tumbling, up-setting and so forth 
causing the solvent to flush back and forth in channels 10 and thereby 
maximize its access to the adhesive bonds 6. 
The shuffling of corrugate C as well as its advancement within drum 20 may 
also be enhanced or achieved entirely by lengthwise disposition of spaced 
apart fins or vanes 32 on its interior walls 34 so as to be co-rotatable 
therewith. As will be obvious, corrugate C in drum 20 will be periodically 
lifted by the rotating vanes 32 and dropped back thus constantly shuffling 
and re-shuffling it. Moreover, a somewhat diagonal or spiral inclination 
of vanes 32 on drum walls 34 in an appropriate orientation will 
co-incidentally procure the required advancement of corrugate C while it 
is being shuffled as aforesaid (not illustrated). 
Accordingly, all corrugate C introduced into rotating drum 20 will 
ultimately be duly immersed in the solvent fluid S contained therein as 
and while it is being advanced from the point of its entry to the point of 
its exit from drum 20. 
The rotation of drum 20 will therefore be seen to serve as an effective 
expedient not only for enhancing exposure of corrugate C to the solvent 
fluid S but also for procuring its advance between the two points 
aforesaid. However, while quite effective for these purposes a rotatable 
drum is not the only expedient available for shuffling the corrugate C and 
advancing it in a bath of solvent fluid S. 
That is to say, equivalent purposes may be served by the relay system 
illustrated schematically in FIG. 5 of the drawing which is shown as 
comprising a non-rotatable tank 120 for a pool P of solvent and a train of 
communicating paddle wheels 40 installed therein to extend between fill 
chute 130 and the point of exit 126 from tank 120. In a manner which will 
be quite obvious, the entering corrugate C is received by the first paddle 
wheel 40 in the train and is relayed by it to the next and so on until it 
reaches exit point 126. In this embodiment, the paddles 42 of each said 
paddle wheel are carried through an arcuate path which lies partly in the 
pool P contained in tank 120 whereby said corrugate C is not only 
constantly re-shuffled but is, from time to time immersed and re-immersed 
in the solvent as it is being received and relayed as aforesaid. 
The structures illustrated and described disclose various expedients 
whereby corrugate C may be shuffled and advanced in a bath of solvent in 
order to provide access of the solvent to the bonds 6 joining the liners 
4--4 to the core plies 2 of shreds of corrugate C and to control the 
residence time; it being appreciated that the residence is also variable 
according to the distance to be traversed by the corrugate between its 
points of entry and exit as well as by the speed of the specific advancing 
mechanisms. 
Usually, any free solvent S or most of it remaining trapped in channels 10 
of core ply 2 will be drained therefrom in the course of such incidental 
stirring as the corrugate C may receive in its removal from the solvent S 
and its transfer to delaminating and sorting apparatus. However, positive 
drainage may be achieved by subjecting the corrugate C to a mechanical 
draining treatment such as rotating cage 50 which is shown in schematic 
section in FIG. 6 of the drawing in receiving relation to drum 20. 
Said cage 50 may or may not be equipped with vanes 132 corresponding to 
vanes 32 in drum 20; the cage being broken in FIG. 6 with the respective 
portions thereof shown as vaned and unvaned. 
Cage 50 may be rotated to shuffle the corrugate C deivered thereto by the 
soaking apparatus; the free solvent being drained therefrom during such 
shuffling while the corrugate moves in cage 50 from the discharge end of 
drum 20 to the output end 52 of cage 50. 
An alternate expedient for drainage is represented by the bucket chain 
transport 60 mounting scoops 62 and positioned at the exit end of tank 120 
to scoop corrugate C from the last paddle wheel 40 in the train and to 
carry it upwardly out of the fluid solvent S to a point outboard of tank 
120 and there to drop it; the fluid solvent S entrained in the corrugate C 
being allowed to drain back through the bucket chain transport 60 either 
into tank 120 or into sump 64 where it may be collected and re-circulated. 
The dredging device 70 in tank 220 (FIG. 7) may, in appropriate 
circumstances, substitute for the paddle wheel train of FIG. 5 being 
similarly equipped with paddles 72 to which corrugate C is delivered by 
fill chute 230 and by which it is then pushed through fluid solvent S both 
in tank 220 to the exit end 226. 
Although perhaps not as vigorous as the rotating drum 20 or the relay 
system of FIG. 5, the bucket chain transport 60 in FIG'S. 5 and 7 and 
dredge device 70 in FIG. 7 will nevertheless stir the corrugate C in its 
transit through and out of tanks 120 and 220 to a degree more or less 
sufficient to achieve the objects of the invention depending on various 
factors such as the average size of the corrugate shreds. 
Motor M shown in FIG. 2 drives wheels W which rotate drum 20 and may also 
power the mobile structures of FIG'S. 5 and 7. Either said motor M or the 
transmissions (not shown) normally and conventionally associated therewith 
or may be regulatable to govern the speed of the equipment and so to 
control the residence time of the corrugate C in solvent S. 
Certain operating parameters relating to the conditioning of corrugate were 
investigated under model conditions using the following test procedure: 
Single wall corrugate board (basis weight 42-26-42) adhered with a starch 
base adhesive was cut into strips 150 mm perpendicular to flute channels 
by 15 mm. The strips were immersed in the conditioning solvent for a given 
time and delaminated on an Instron Tester within 11/2 min. of recovery 
from the solvent. The resistance to delamination was measured as an 
average force required to rupture the bond between the crests of the 
medium and linerboard. Each value represents testing of at least five 
strips and 8-10 readings per strip. Moisture content of strips was 
determined immediately after testing by oven drying. "Control" conditions 
are defined as employing as the conditioning solvent water at 20.degree. 
C. with no additive thereto. 
Values for the resistance to delamination of corrugate under various 
treatment conditions are shown in FIG. 8. With reference thereto, curve 1 
shows the variation of the resistance to delamination as a function of 
time under control treatment conditions. At zero time, the resistance to 
delamination considerably exceeds the strength of the individual laminae 
comprising the corrugate, and tearing of the laminae takes place. "Easy 
delamination" is considered to occur when the resistance drops to an 
arbitrary value of 60 grams in the above described test procedure, as 
conditioned corrugate will normally be subject to a force of at least this 
magnitude in subsequent fibre classifying apparatus. Under control 
conditions of treatment, easy delamination occurs after some 50 seconds of 
immersion (Point A). 
The moisture content of the conditioned corrugate is shown in FIG. 9. Under 
standard conditions it may be seen that the moisture content increases 
moderately rapidly over the time period at about which easy delamination 
is reached (Curve 1, Point A'). Although not shown in the accompanying 
data, it will be appreciated that the wet strength of the individual 
laminae decreases both as the water content thereof increases and also as 
a function of time. Under control conditions it is found that the wet 
strength of the laminae may approach zero, as evidenced by the 
disintegration of the laminae, after about 5 minutes immersion. There is 
then a differential between the time required for "easy delamination" and 
that which disintegration of the corrugate laminae occurs. 
In practice this differential may be increased by removing the corrugate 
from the treatment bath prior to the time at which easy delamination 
occurs. Solvent entrained with the corrugate continues to attack the 
adhesive bond between the laminae and reduce the resistance to 
delamination. Part of the entrained solvent will drain from the corrugate 
by the described means provided for this purpose. A portion thereof will 
be imbibed into the corrugate to increase the moisture content thereof and 
thus to decrease the wet strength thereof. However, whilst the resistance 
to delamination is quickly reduced to below the easy delamination value, 
the quantity of solvent available for imbibition may generally be 
controlled so as to be less than that which will completely saturate the 
laminae and lead to their disintegration. 
The time differential may also be affected by the temperature of operation 
of the conditioning bath and the solvent employed. In FIGS. 8 and 9 values 
obtained where the temperature of operation is reduced to 10.degree. C. 
are shown as curve 2. Predictably, the time for easy delamination was 
increased, a value of 1.3 minutes being obtained (Point B) (FIG. 9). 
Surprisingly, the moisture content of the corrugate at the time for easy 
separation (Point B') (FIG. 8) was significantly less than that which 
obtains for the control, pointing to an increased time differential. It 
may also be remarked that it is advantageous to reduce the amount of 
solvent passing into the fibre classifying apparatus with which the 
instant conditioning apparatus will generally be employed. 
The control conditions were further varied by using as solvent water 
containing 0.004% by volume of a non-ionic surfactant (Triton X-100, 
trademark for a poly alkoxylated alkyl phenol), whilst maintaining the 
temperature of the bath at 20.degree. C. The values obtained are shown in 
FIGS. 8 and 9 in curve 3. The time for easy separation was reduced, (Point 
C) in comparison to the control. Whilst the rate of moisture pick up of 
the corrugate essentially duplicated that found for the control, the 
moisture content of the corrugate at easy separation time (Point C') was 
significantly lower than that for the control, again pointing to an 
increased time differential. 
The foregoing being the best form of the invention presently known to the 
inventors, it is by no means inconceivable that means other than those 
specifically enumerated may be resorted for carrying out the inventive 
concepts described without departing from the true scope of the invention 
as defined in the following claims.