Note: Descriptions are shown in the official language in which they were submitted.
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RAPIDLY-FOAMABLE, ~ST-SETTING
PHENOLIC RESIN PLY~OOD GLUE
This invention relates to liquid glues of the class used in
the manufacture of plywood. It pertains particularly to liquid glues
comprising phenolic resins and dried animal blood, which are rapidly
foamable and fast setting and which accordingly in the manu~acture
of plywood are applicable to the in-line application of foamed glues
to wood veneers.
The application of phenolic resin glues in foamed condition
is well known and has been practiced commercially from time to time
over a period of several years. Their application has been attended
by many significant advantages, including more uniform coverage per
unit weight of glue; satisfactory coverage of rough surfaces with
less glue; minimum penetration into the substrate; faster drying;
the use of lower viscosity glues; the elimination of the necessity
of using solid extenders; and, in some instances, lower unit glue i:
weight and therefore lower glue costs while still producing satis-
factory bonding.
This application of the phenolic resin glues prçsupposes,of
course, that they are foamable. In the past, it has been possible
to foam such glues adequately since relatively low molecular weight ~;
phenolic resins were used in their manufacture. However, the use of
phenolic resins o~ low molecular weight created an economic problem
in that a relatively long press time was required to cure them in
the plywood hot presses. This in turn delayed production and increas-
ed costs.
In an effort to overcome this problem, the plywood industry
has turned to the use of more highly advanced resins which cure fast~
er in the press. Such resins, being less soluble in alkaline solu-
tions than are the less highly advanced resins, presently are sup- :-
plied to the market in aqueous alkaline solutions containing about
~o% by weight resin solids, as opposed to the solutions containing
about 50% resin solids, formerly used extensively.
A serious problem attending the use of the present day more
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highly advanaed phenolic resin glues is that using conventional
foaming techniques, they are not foamable at all, or at least `
with sufficient speed to be useful in the commercial production
of plywood using foamed glue.
In accordance with the Cone procedure, phenolic resin
glue is passed continuously from a reservoir to an in-line
foamer where it is converted to foam. The resulting foam then
is passed continuously to an applicator head which applies it to
wood veneer surfaces in the plywood production line. Since the
volume requirements of foam are high and the capacity of an
in-line foamer necessariiy is restricted, it is essential, ~;~
~ for the successful application of this procedure, that the
foaming of the liquid phenolic resin glue occur very rapidly,
i.e. in a few seconds. Up to the present time this has not been
possible, using the highly advanced phenolic resin glues of
present day commerce.
A possible soiution to the problem is the inclusion in
the glue mix of a suitable foaming agent for phenolic resin glues.
Menger et al, U.S. Patent 2,323,831, for example, suggests a
large number of foaming agents which may be used to assist in
the foaming of phenolic resin glues.
Listed as foaming agents in this patent are such
materials as casein, hide glue, bone glue, blood, blood albumen r ~',i
saponins, the salts of diisopropyl naphthalene sulfonic acid,
the salts of sulfonated tar oils or of sulfonated fatty acids,
the ammonium salts of high molecular weight aliphatic carboxylic
acids such as fatty acids, wax acids, rosin acids and montanic
acid. This reference does not indicate, however, the
applicability of these foaming agents to the foaming of highly
advanced phenolic resin glues, nor could it, since such glues
were not commercially available nor in use at the time the Menger
et al work was done.
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Neither does the Menger et al disclosure recognize
that, of all the foaming agents listed, dried blood when added
to a phenolic resin glue will convert it to a product which can
be foamed successfully in a matter of a few seconds in an in-line
plywood plant glue foaming unit to produce a uniform, stable
foamed glue which can be applied to advantage in the commercial
manufacture of plywood.
Applicants have discovered that this is the case. In -
accordance with the present invention rapidly foamable, fast
setting phenolic resin plywood glue is made by forming an aqueous
alkaline solution of a highly advanced resinous condensation
product of a phenol and an aldehyde, particularly phenol and
formaldehyde, having a resin solids content of from 30-45% by -~
weight. The degree of advancement of the resin is such as to
impart to the aqueous resin solution a viscosity of from 3-30
poises.
Mixed with this is a dried, powdered animal blood
product used in amount sufficient to render the liquid glue
convertible upon agitation in a gas and in 12ss than 30 seconds
preferably less than 15 seconds to a foam having a density of
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less than 0.5 and more preferably, in less than 15 seconds to a
foam having a density of less than 0.3.
Water is included in the glue mix in amount sufficient
o impart to the adhesive a viscosity of from 1-50 poises.
From 0.1 to 10% by weight, based on the dry weight of the ;
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blood, of glyoxal or other aldehyde may be included in the
blend to lower its viscosity to working levels.
The resulting glue mix upon introduction into an in-line
continuous foamer may be foamed in a few seconds to a uniform
foam having a density of less than 0.5, specifically a~out 0.2
grams/cc., and accordingly is well adapted to continuous
application to traveling plywood veneers in a plywood mill
production line. ;
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In accordance with one broad aspect, the invention
relates to a rapidly foamable, fast setting phenolic resin
liquid plywood glue comprising: `
a) an aqueous alkalin~ solution of a resinous . :
condensation product of a phenol and an aldehyde having a resin
solids content of from 30-45% by weight, the resinous
condensation product having a degree of advancement such as to
impart to the aqueous resin solution a viscosity of from 3-30
poises, ;
b) dried animal blood having a water solubility not
exceeding 90% by weight used in amount sufficient to render the
- liquid glue convertible upon agitation in a gas and in less
than 30 seconds, to a foam having a density of less than 0.5
grams~cc~
. c) from 0.1 to 10% by weight, based on the dried
weight of the blood, of an aldehyde glue viscosity lowering
agent, and .
d) water used in amount sufficient to impart to the
liquid glue a viscosity of from 1-50 poises.
20. The hereindescribed glue compositions when foamed ~;
are also characteri~ed by the following important advantages:
They are substantially faster curing than those not
including blood. This decreases press time and increases
production.
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They have a substantially longer assembly time tolerance, corres-
pondingly facilitating plant schedules. They require less heat for
curing, thereby lowering required press temperatures and further
decre~sing press times.
They do not require the presence of a filler such as clay,
walnu~ shell flour, oat hull flour, wood ~lour, ground bark, or
ground corn cobs, which normally are used with conventional plywood
glues with accompanying well known pro~lems. Accordingly, it is pos~
sible to reduce the amount of water in the glue mix. This in turn
10 reduces the likelihood of blistering in the press.
Considering the foregoing in greater detail:
As noted above, the hereindescribed phenolic resin plywood
glues comprise essentially an aqueous alkaline solution of a highly -
~advanced resinous condensation product of a phenol and an aldehyde;
a quantity of dried animal blood foaming agent; water; and, option-
ally, an aldehyde type viscosity-lowering agent.
The resinous condensation product of a phenol and an alde- i
hyde used in the glues of the invention may comprise any of those -
suitable for use in the production of plywood-type glue~. Typical
20 phenols employed in the manufacture of such products comprise phenol
itself, the cresols, and resorcinol. Typi~al aldehydes employed in
the manufacture of such products include formaldehyde, acetaldehyde,
and furura1. The commonest of such products, and the one with re~er-
ence to which the present invention is described, comprises the
resinous condensation product of phenol and formaldehyde.
Whatever its identity, the phenolic resin adhesive employed ;
in the present formulation is characterized by having a relatively
high degree of advancement so that it will set rapidly in the ply-
wood press, i.e. in a matter of five minutes or so under the usual
30 press conditions, as compared with six or seven minutes for the for-
merly used phenolic resins having a lesser degree of advancement
The degree of advancement of such resins is a dif~icult
property to characterize. However~ for the present purposes the phen-
olic resins are contemplated which have a resin solids content of
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1~ 5~from 30-45% by weight, but have a degree of advancemen't such as
to impart to the aqueous resin solutions in which they are contain
ed a viscosity of from 3-30 poises. When incorporated in a plywood
glue the resulting glue is capable oE producing plywood association
'lexterior grade" quality glue bonds when two 7/16 inch three ply
panels are pressed per plywood press opening for a period of 6 1/2
minutes with press plates at 300F.
Such phenolic resins normally are supplied to ~he plywood
trade in the form of their aqueous alkaline solutions having a suf-
ficient content of caustic soda or other alkaline material to im-
part to them a pH of from 9-12.
The blood which is the second major component of the present-
ly described plywood adhesives comprises the dried blood of com-
merce available in powdered form. This product is manufactured by
collecting beef, hog or sheep blood from the slaughter house floor
and dehydrating it under controlled conditions to a dry powder form.
In one successfully operated commercial process, the blood `;
is sprayed into a cyclone separator containing hot air under care-
fully controlled conditions of temperature and time to produce a
spray dried blood product of desired properties. By controlling
the operating variables the degree of water solubility of the dry
blood may be varied over a range of from completely soluble to com-
pletely insoluble iIl waterO
Although it is possible to use any of the solubility grades ~ i
of blood, from completel~ soluble to completely insoluble, it is
preferred to use a blood product having a water solubility of from
30-90% by weight. Blood products having a solubility of less than
30% are not quite as efficient as foaming agents as are those hav-
ing a greater degree of water solubility. On the other hand, blood
products having a water solubility of more than 90% tend to cause
gelation of the compositions.
The third major component of the hereindescribed plywood
glues is water. A certain content o water is introduced into ~he
glue mix via the water content of the aqueous resin employed. Addi-
5~ 6~ ~tional water may be added, however, in amount sufficient to produce
a product viscosity of the desired value, broadly from 1-50 poises,
preferably from 1-30 poises.
Under some conditions, combin:ing blood with highly advanced
phenolic resin glue solutions creates a problem in that the result-
ing mixture has a higher viscosity than either of its components.
Furthermore, this viscosity tends to increase rapidly with time to
levels interfering with normal plant procedures.
The degree of viscosity increase may be controlled to some
extent by minimizing the amount of added blood, maximizing the a-
mount of added water, using blood of a lower degree of water solu-
bility, and using a less highly advanced resin.
For practical purpose, it often is not possible to control -
these variables sufficiently to produce the desired result. In
such cases, advantage may be taken of our discovery that the vis-
cosity of the phenolic resin plywood glues of the class described
herein may be controlled rapidly and effectively by the inclusion ;- -
in the compositions of a viscosity-controlling amount of an alipha-
tic or aromatic aldehyde. ~ -
Typical of materials of this class which may be employed are
the lower aliphatic aldehydes including formaldehyde; ~he formalde-
hyde donors, such as paraformaldehyde, sodium sulfite formaldehyde~
and oxyzolidine; glyoxal; glutaraldehyde; pyruvicaldehyde; and the
lower molecular weight aromatic aldehydes such as benzaldehyde.
These aldehydes may be used singly or in combination with each
other. They are used in amount suficient to reduce the viscosity
of the glue to the desired level. Normally this will require from `~
O.YOto 10% by weight of aldehyde, based on the weight of the solid ;-
blood content of the composition.
3~ The viscosity reducing effect of the aldehyde is surprising
in view of the fact that normally aldehydes added to alkaline solu-
tions of blood markedly increase, rather than decrease, the vis-
cosities of the solutions. Furthermore, the addition of the alde-
hydes to the presently described compositions does not impair
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either the foam inducing or the adhesion enhancing properties of
the blood.
The glues of the invention are easily and simply
prepared, usually in two stages.
In the first stage, the predetermined amount of water
and solid dried blood are thoroughIy mixed in a suitable mixer.
From one to three minutes of mixing suffices. Next the
selected phenolic resin is added to the mixture and the mixing
continued for another period of from one to three minutes. The
mixing may be carried out at room temperature and no special
precautions such as cooling of the mix are required.
- In the event that an aldehyde anti-thickener is to be
included, the foregoing procedure is modified by adding the
selected aldehyde in the predetermined amount to the mixer in
the first stage of mixing. To be effective, the aldehyde should
be added to the blood-water mixture before the blood is mixed
with the resin. t
The compositions prepared as above are ready for use in
the manufacture of plywood. Although they may be foamed
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batchwise before application to the veneers, they are
particularly suited or continuous in-line foaming at a high
production rate. Their use is attended by the above noted
advantages of rapid and uniform foaming, even when highly -`
advanced resins are used; long assembly time tolerance;
elimination of the need for filler use with attendant
disadvantages; faster curing in the press; and less heat required ~ -
for curing. `~
The process of the invention is illustrated by the
following examples wherein parts are given in parts by weight ` ;
and percentages are given in percentages by weight.
EXAMPLE 1
This example compares the application of the herein
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described rapidly foamable, fast setting phenolic resin glue .
containing a highly advanced phenolic resin, in both foamed
and unfoamed condition, with a commercial phenolic resin glue ~:
containing phenolic
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resin having a conventiona1 de~ree of advancement, in the manu-
facture o plywood~
The adhesive composition o~ the invention wa~ prep~red as
~ollowsi:
240 Partis water and 50 parts blood having a water solubility
at 72F. of 50% by weight were mixed in a mechanical ~ixer for t~o
minutes. l,000 Parts of aqueou~ alkallne phenol formaldehyde resin
*~"~orden W-166S") having a viscosity of 5 poises, a pH of about 11
and ~ resin solids content of 40% ~y weight were added and the mix-
in~ continued for 2 minutes. The compo~ition then wa~ resdy ~or
applic8tion.
The conventional phenolic reæin ~dhesive compositlon was pre- :
- pared as followQ:
220 Parts water at 70, lO0 parts alder bark filler, and 34
parts wheat flour filler were mixed for f1ve mlnutes. 75 P~ir~s of
aqueous alksline highly advanced phenol form~ldeh~de liquld resin
~"Bord~n W-166S") h~ving a ViRco~ity of 5 poises, a pH o~ ~bou~
ll snd a ~olids content of about 40% wexe added and the mixin~ con~ ~:
tinued for two minute~.
2~ 30 P~rts 50% aqueous C8U8tiC soda then was added and ehe mix-
~n8 con~inued for ~no~her two m~nuees..l5 Parts qoda ~sh wai~ iadded ~.
and ~he m~xing continued for~nother 20 min~tes. 540 P~rts of the
~sme phenol form~ldehyde resin w~ added and ~he mix~ng continued
for 5 minutes. Thi~ gave the finii~hed ~onvention~l adhesive compo- ~;...
sition.
The two ~dhe~ive compo~itions prepared in the fore~o~ng man-
ner then were ~pplied to the ma~ufscture of plywood.
In one te~t prodedure ~i portion of the fidhe~lve composition ~?
of the lnventio~ which cont~ined bl~od ~iS a foaming a8ent wa~ in-
troduced into the in-line contlnuous fo~mer described above and
thereb~ converted i~ a foaming time of ~bout three second~ to B
uniLform foam h~vLn~ a den~ of 0.2 grAm~ p~r c~. Thl~ ~æ e~
truded on~o the ~rfacea of wood vereer~ ~hi~ih then wer~ l~ld up
lneo pl~wo~d asse~lie3.
Trademark
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For purposes of comparison, another portion of the blood-
resin glue o~ the invention was roller spread on wood veneers which
then were laid up into plywood making assemblies in the usual man-
ner.
The conventional phenol-forma:Ldehyde resin glue could not
be foamed in the in-line foaming unit in the dwell time of the unit.
It was rolle~ spread on plywood veneers which then were laid up in-
to plywood assemblies in the usual manner.
In all three cases the assemblies comprised three ply Douglas
fir panels of 7/16" thickness pressed two per press opening in a
hot press with plates at 300~F. for 5 l/4 minutes. Test pieces were
cut from the resulting panels and subjected to the standard Plywood
Association shear test. In each case groups of panels having assem~
bly times of 4, 14 and 32 minutes were tested. This spans the range
of assembly times ordinarily used in the plywood mill. The test re-
sults were averaged. -
The glue spread rate for the blood-resin glues of the inven-
tion was 26 pounds per thousand square ~eet of single glue line,
that for the conventional phenolic resin glueg 34 pounds. The pounds ;
of resin applied per thousand s~uare feet thus was approximately
the same in both cases.
The results of the test are given in Table I. l ;
TABLE I
PLYWOOD SXEAR TEST RESULTS - (AVERAGE)
Load in % Wood
Glue Procedure Lbs.Per Sq. In. Failure
Blood Resin Foamed and Extruded246 - 97
Blood Resin Not Foamed, Roller
Spread 202 - 65
Conventional Not Foamed, Roller
Phenolic Resin Spread 34 - 02
30 ~lue
The foregoing results clearly indicate several things. First,
the hereindescribed blood resin glue is rapidly foamable under con-
ditions in which the conventional phenolic resin glue is not foam-
able a~ all, although both glues contain the same phenolic resin
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o high degree of advancement. Second, the hereindesc~ibed blood
resin glues can be cured adequately in the press at a press time
of only 5 1/4 minutes. The usual press time required for the con-
ventional phenolic resin glue descriked above is 6 1/4 minutes or
longer. This represents a saving in press time of almost 20%. Third,
the blood-resin composition of the invention foamed has a noti~eably
faster cure than does the same blood-resin mixture unfoamed. This
is unexpected and additionally indical~es the unique quality of the
composition.
In a manner similar to the foregoing there are prepared and
applied the glues of the invention using, in place of the phenol-
formaldehyde resin: a cresol formaldehyde resin, a resorcinol or-
maldehyde resin, a phenol acetaldehyde resin, or a phenol furfural
resin.
EXAMPLE II
This example illustrates the unique suitability of dried ani~
mal blood as a rapid foaming agent for foaming phenolic resin solu- `~
tions containing phenolic resins of a high degree of advancem~
In the preparation of the test compositions, "x" parts of the
20 test agent was mixed with 300 parts of water for two minutes. The re-
sulting mixture then was added to 1,000 parts of aqueous alkaline ;~
phenol-formaldehyde resin having a solids content of 40% by weight,
a viscosity of about 5 poises and a pH of about 11 and mixed for
another two minùtes. `,
The resulting composition then was passed continuously through
an in-line foamer where it was mixed with a stream oE air. In order
to foam the mixture exhaustively, the streams were recirculated un~
til the liquid would take up no more air. This required a time of
up to 3 minutes.
The stream when it emerged from the foamer contained large
bubbles of incorporated air. These bubbles were separated from the
stream and measured v~lume of the foamed material, free of large
bubbles, was weighed to determine its density (grams per cubic ce~ti-
meter).
The results are given ~ ~Table II.
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TABLE II
FOAMING AGENT
Foamed Density
Tes~ No. Kind Amount ~.
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parts by
.- 1 Blood-30% water weight) `:
- soluble 50 193
2 " ll 30. 320
3 B lood ~40% wa t er
soluble 30 . 221
4 Blood-50% water
~oluble 50 .12 1
" " ~0. 172 ~
6 ~l 1. 30 .251 -
7 " " 20.4~7
8 B loo d -7()% wa t er
soluble 30 ,290
9 Bl~od-90% water
soluble 3Q . 301
~Q Blood-water insolubl e 30 . 484
11 .l Soybean f lour 100 . 834
2012 Animal glue 50 , 990
13 Alkyl aryl sulfon~te 30 o712
type foaming agent
~k( 'Ultra T~et 60L")
14 " " 60 . 5~4 -
Sodium ~alt o:E an
alkyl aryl 8ulfona~e
type wet~ing a,~ent ::
( 'Ultra Wet SK ) 3n .780 .~::
16 Ole~:c acid l .
~ Neof~t 9bO4") 30 . 846
17 Stearic acid ~ :
Cheofat 854") 30 1.03 .. :
18 Aliph~t~c amine type ':
wetting a~ent ;::
~ ~"Armeen DM~") 30 1.08
19 Amine t~pe wetting
~gent*( 'Armflow 65") 30 1.05 `
Sodium alkyl aryrl poly-
ether sulfate type wet'cillg
agent~("Trlton 770") 30 .984
1 " " 30 . 9~5 ~`.
~(Triton X200"~
22 Palmc>llve soap 30 ,87fi
The test resule.Q ~et forth in Table II clearly indicate ehe
unique suitability of drled animal blood a9 a foaming agent Xor
highly ~dvanced aqueous alkaline phenol formaldehyd~ resins. Even "~
when exhaustively foamed over a per~od o 8everal mlnute~ 7 the lise-
ed non-blood foaming agen~, which all ~re of recog;nized potencr"
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did not produce a foam having the density of 0.5 or less necessary
for successful application in the in-line application for foamed
glue to plywood production.
The test results further indicate that animal bloods of all
grades of water solubility, i.e. per cent soluble in water at 72F.
in 5 minutes, share this unique property. Thus even blood which has
been heated until it is totally insoluble is a reasonably efficient
foaming agent for the intended purpose. Bloods having solubility in
the range of 30 to 90% by weight are preferred.
`10 EXAMPLE III ;;
This example illustrates the effectiveness of a minor pro-
portion of an aldehyde in lowering the viscosity of the hereindes-
cribed blood-resin adhesive compositions:
The procedure o~ Example I was followed with the exception -~
that the indicated amount of the indicated aldehyde was added to
the water-dry blood mixture preliminary to mixing in the phenolic
resin. The blood employed was dried animal blood having a water ,'J~
solubility of 40-50% by weight~ The resin employed was an aqueous
alkaline solution having a pH of from 9-11, a viscosity of 5 poises,
and a solids content of highly advanced phenol formaldehyde resin
of 40%.
TABLE III
Amount 3 1/2 hr. 22 hr.
Aldehyde Addi~ive (Parts by weight)Viscosity Viscosity
(~oises2 (Poises)
None - (Control) 45.6 260
40% Aqueous Glyoxal 1 9.2 16.3
" " " 3 .5 7.3
37% Aqueous Formaldehyde 1 9 14 ;
" " " 3 4 4.3 ~;
25% Aqueous Glutaraldehyde 3 9 14
45% Aqueous Pyruvic 3 10.1 15.8 -
Aldehyde
100% Benzaldehyde 3 14.8 27.7
Sodium Sulfite Formaldehyde 6 11.2 16
60% Aqueous Oxyzolidine 3 9.7 12.0
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Thus the addition of even a small amount of a wide variety
of aldehydes effectively controls the viscosity of the glues.
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