Note: Descriptions are shown in the official language in which they were submitted.
~076730
LIQUID ADHESIVE FOR USE IN CURTAIN-COATING
ADHESIVE APPLICATORS
This invention relates to liquid adhesives, In particular,
it pertains to liquid phenol-aldehyde adhesives adapted for use in
adhesive applicators of the curtain-coating class. The compositions
are of special applicability in the coating with adhesives of wood
veneers to be used in the manufacture of plywood. They are describ-
ed herein with particular reference to this application, although
no limitation thereby is intended.
The liquid phenol-aldehyde resinous adhesives are widely
used in the plywood and other industries because of the high de-
gree of strength and water resistance which their use imparts tothe products in which they are contained. The phenol-formaldehyde
resinous adhesives are of particular value because of their effect-
iveness, commercial availability and relatively low cost. These
adhesives are sold commercially in the form of their water solu-
tions containing from 3-10% of caustic soda or other alkali and
having a total solids content of from about 40-50% by weight.
In the plywood manufacturing plant the resinous adhesives
are compounded into plywood glues by the addition of suitable
amounts of extenders such as ground corn cobs or ground bark fract-
ions9 and of thickeners such as wheat flour, blood or other pro-
tein and starch containing materials. Also added may be additional
quantities of water and alkali, principally caustic soda or soda
ash. The resulting adhesive compositions contain about 20-35%
resin solids and have a pH of from about 9-13.5. A typical phen-
olic adhesive for use in the manufacture of plywood is prepared
by mixing in sequence the following constituents:
Pounds
Water 585
Ground corn cob filler 250
Wheat flour thickener 95
50% caustic soda 105
Soda ash 46
Liquid, alkaline, phenol-
formaldehyde resin con-
taining 40=50% by weight
solids 1600
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10767;~0
In their use, the li~uid, phenol-aldehyde resinous ad-
hesives conventionally have been applied to the wood veneers by
means of the roll-type glue spreaders included in the classic ply-
wood veneer lay-up line. In such lines the wood veneers are fed by
hand between glue-coated rolls which transfer the glue to the ven-
eers. Because of the large amount of manual labor involved, the
trend lately has been toward the introduction and use of automat-
ed plywood veneer assembly lines in which roll-type glue spreaders
cannot be used to best advantage. In their place, liquid adhesive
applicators of the curtain-coating class preferably are used.
An adhesive applicator of the curtain-coating class, or
"curtain-coater", simply considered, comprises a reservoir contain-
ing liquid adhesive, a circulating system which circulates the
liquid adhesive to a curtain-coating head, a collection pan posi~
tioned a spaced vertical distance beneath the curtain-coating head,
and a conduit conveying surplus unused adhesive from the collection
pan back to the reservoir.
I The curtain-coating head comprises in effect a trough hav-
i ing a longitudinal slot in the bottom. The trough is at least as
wide as the work and is arranged transversely to the path of trav-
el of the latter. It delivers the liquid adhesive either gravita-
tionally or under pressure. Upon delivery, the adhesive forms a
vertical sheet or curtain which hopefully is continuous and with-
out breaks along its entire length.
The work is conveyed continuously through this curtain,
whereupon its upper surface is coated with liquid adhesive in
amounts determined by such factors as the width of the slot in
the curtain-coating head, the pressure applied to the adhesive,
and the lineal rate of travel of the work as it passes through
i 30 the curtain. Any overflow of adhesive is caught in the collection
pan, which is situated beneath the work, and returned to the res-
ervoir.
When the conventional phenolic resin glue is applied in
a curtain-coater, the application of the adhesive to the work
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- 1076'730
tends to be non-uniform and the glued product accordingly defect- -
ive. This undesirable result is attrlbutable to two principal fact-
ors.
In ~he first place, when using conventional phenolic ad-
hesives in curtain-coating apparatus, it is difficult to establish
a uniform curtain and maintain it over long periods of continuous
operation. The curtain tends to break. The breaks in turn cause
discontinuities in the adhesive film applied to the surface of the
work. This results in inadequate bonding.
In the second place, the surfaces of wood veneers invari-
ably are characterized by the presence of spaced ridges. These are
of sufficient height to be bridged over by a film of the conven-
tional phenolic adhesives as the veneers pass through the curtain. ~ ~-
After leaving the curtain, the bridging portion of the adhesive
coalesces, leaving a bare, uncoated area. This also results in in-
adequate bonding.
It accordingly is the principal object of the present in-
vention to provide a liquid, phenol-aldehyde composition designed
for use particularly in curtain-coating apparatus and which when
so used provides a smooth, break-free curtain which persists over
long operating periods and which upon contacting the wood wets the
wood surface readily and uniformly.
It is a further purpose of the present invention to pro-
vide an adhesive composition of the foregoing class which is read-
ily compatible with the other constituents of the glue mix, which
- is non-staining, and which does not affect adversely the pot life
of the adhesive mix in which it is incorporated.
Broadly stated, the foregoing and other objects of the in-
vention are achieved by the provision of a liquid, alkaline, phenol-
aldehyde resinous adhesive which contains as a curtain-improving
additive a small but effective proportion of 2,4,7,9-tetramethyl-
~` 5-decyne-4,7-diol or of the ethylene glycol-, propylene glycol-,
and butylene glycol-ethers thereof having from 1-10 mols of glycol
per mol of diol.
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107~o730
Considering the compositions of the invention in greater
detail:
As noted above, the adhesive compositions of the invention
broadly comprise a liquid, alkaline phenol-aldehyde resin, water,
a filler or extender, a thickening agent, and a novel curtain-im-
proving additive.
The first named of the foregoing constituents broadly com-
prise any of the adhesive, water soluble alkaline resinous conden-
sation products of a phenol and an aldehyde. They are commercially
available as water solutions having a pH of about 9-13.5 and a
total solids content of from 40-50%.
They are manufactured by the reaction in alkaline medium
occurring between a selected phenol and a selected aldehyde. Typ-
ical of the phenols which may be employed are phenol itself, the
cresols, the xylenols, and resorcinol. Typical of aldehydes
which may be condensed with the phenols in the production of the
hereindescribed resinous adhesives are formaldehyde itself, ace-
taldehyde, and furfural.
Typical condensation products of these starting materials
which are useful for the present purpose comprise the resinous
condensation products of phenol and formaldehyde, phenol and fur-
fural, and resorcinol and formaldehyde.
In the present state of the art the phenol-formaldehyde
resins are of primary importance for the present purposes. How-
ever, for certain applications they may be modified by the inclu-
sion of a proportion of one or the other of the phenol-aldehyde
resins, for example from 1-20% by weight of such a resin, based
on the total resin solids content.
Fillers or extenders which are employed for the herein-
described purpose are well known and serve the purpose of extend-
ing, or increasing the efficient use of, the adhesive use of the
adhesive component of the mix. Typical of them are ground corn
cobs, ground oat hulls, and ground fractions of bark or wood,etc.
The thickening agents employed in the compositions of my
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1076~730
invention comprise the well known materials added to resinous ply-
wood glues for the purpose of giving additional body to the glue.
Typical of such agents are wheat flour and dried blood.
In addition to the foregoing, there may be employed addi-
tional caustic soda, soda ash or other alkaline materials as requir-
ed to establish a desired pH. Rot proofing, mildew proofing, and
fire preventive chemicals may also be included.
All of the foregoing constituents are conventionally used
in phenol-aldehyde resinous adhesives, and in particular in phenol-
aldehyde resinous plywood adhesives. The novel constituent of thehereindescribed compositions which distinguishes them from the
resinous adhesive compositions of the prior art and which imparts
to them the desired curtain-improving qualities, making them of
particular value for use in curtain-coaters, is a selected acety-
lenic diol or certain of its ether derivatives.
The diol in question is 2,4,7,9-tetramethyl-5-decyne-4,7-
diol. This has the following formula:
CH3-cH(cH3)-cH2-c(cH3)(OH)-C-C-C(CH3)(oH)-cH2~cH(cH3)-cH3-
Its ether derivatives are ethylene glycol-, propylene glycol-,
20 and butylene glycol- ethers having from 1-10 mols of glycol per
mol of diol. These chemicals are available commercially as products
of Air Products and Chemicals, Inc., the diol being sold under the
B trade ~m~ of SURFYNOL 104 and the ethylene glycol ether of the
~ o,~
diol being sold under the trade ~*~e of SURFYNOL 440 (Air Products
and Chemicals Technical Bulletin S-3 of April, 1969 and Technical
Bulletin S-5 of June, 1967).
The ether derivatives of the diol are manufactured by con-
densation of the diol with predetermined molar ratios of ethylene
oxide, propylene oxide or butylene oxide. As is well known, such
oxides condense with the hydroxyl groups of the diol to form ethers
which also contain functional hydroxyl groups. These have the cap-
acity of condensing further with additional alkylene oxide to form
high molecular weight products.
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10'76730
When the diol is reacted with ethylene oxide, an ethoxide
product is formed having the following general formula:
CH~CH~ ~ ~C ~-C(C ~ CH ~ ~Hl~C~C{C(CH~pCH ~ ~ bOH]~C ~CH~ ~-C
In the above formula, the subscript letters a and b indi-
cate the number of mols ~ ethylene oxide which have condensed with
the diol. For the purposes of the invention, the products formed -
in the case of this and the other named ethers are suitable where-
in a+b=from 1 to 10. The limiting factor is primarily the solubility
of the ether product~n water.
When one or a combination of the foregoing acetylenic diols
and its ether derivatives is included in the phenol-aldehyde resin-
ous adhesives of commerce it profoundly affects their curtain-form-
ing qualities in that under the usual conditions of operation the
curtain is rendered uniformly smooth and complete, being without
breaks, over long periods of continuous operation. It also imparts
to the resinous adhesives the ability to wet uniformly and complete-
ly the substrate surfaces to which it is applied. Both of these
factors lead to the production of a glued product of uniformly high
strength and high wood failure values.
A very small amount of the diol or its stated ether deriva-
tives is effective in achieving this result. As little as 0.01%
by weight, based on the weight of the liquid resin component of the -
adhesive, co~ributes a perceptible effect.
The upper limit of use of the curtain-improving additive ;
is determined primarily by cost and mechanical considerations. The
solubility of the additive in the aqueous resin adhesive solutions
is limited. Any excess additive accordingly forms a separate phase
which, in its least significant effect is wasteful, and in its
most significant effect interferes mechanically with the normal
application of the adhesive.
The solubility of the additive obviously is a function of
its molecular weight. In general, however, it may be included in
an amount from about 0.01% to about 5.0% by weight, based on~he
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1 0~ 6~30
weight of the liquid phenol-aldehyde resin content of the adhesive
composition A preferred range of use is from 0.025% to 0.3% by
weight. In the commercial application of an adhesive composition
containing 2,4,7,9-tetramethyl-5-decyne-4,7-diol as the curtain-
improv~ng additive, a diol use of from 0.05 to 0.2% by weight is
indicated by reason of economy and efficient use.
It is of particular interest that the 2,4,7,9-tetramethyl
-5-decyne-4,7-diol and its stated ether derivatives are unique in
their action in improving the curtain-forming properties of the
phenol aldehyde resinous adhesives. In a comprehensive program in-
volving a large number of surface acting materials including phen-
ols, alcohols, polyols, ethers, esters, amines, various polymers,
and even various other acetylenic diols, 2,4,7,9-tetramethyl-5-de-
cyne-4,7-diol and its glycol ethers alone demonstrated significant
and useful activity in improving the curtain-forming properties of
the adhesive composition.
Various procedures may be employed in compositing the here-
in-described curtain-improving additives with the phenol aldehyde
resinous adhesive mixtures.
In one of especial commercial significance, the additive ~
is mixed with the phenol-aldehyde resin at the place of its manu- - --
fac~ure preliminary to shipment to the place of compounding and us-
ing the glue. The solution of additive in resin thus per se is an
article of commerce.
This may be accomplished by melting the diol or its glycol
ether derivative and mixing it directly with the resin. This is
accomplished easily, since the additive is of relatively low melt-
ing point. 2,4,7,9-tetramethyl-5-decyne-4,7-diol, for example, has
a melting point of about 50C.
On bhe other hand, the additive may be introduced in the
form of a solution of the additive in an appropriate solvent. Such
a solvent should, of course, be non-detrimental to, and non-inter-
fering with, the other constituents of the adhesive composition.
10'76'730
Suitable solvents comprise ethylene glycol and the alcohol solve~ts
of intermediate molecular weight. Such alcohol solvents include,
for example, the butanols, the pentanols, and the octanols. A suf-
ficient amount of the solvent is employed to dissolve the diol or
its glycol ether, there being no object in employing a large ex-
cess of solvent.
Alternatively, the curtain-improving additives of the in-
vention may be added to the adhesive composition at the time of
manufacture of the latter. The usual practice in compounding the
adhesive compositions is to place a quantity of water in a commer-
cial mixer, adding the various components stepwise with intermit-
tent mixing until a uniform glue of the desired compo$ition is ob-
tainedO The hereindescribed curtain-forming additives may be in-
corporated in the adhesive compositions manufactured by this pro-
cedure at any suitable stage of the mixing. They preferably are
applied in liquid form, either in the molten condition or in solu-
tion, as above described.
After their formulation, the adhesive compositions may be
applied in curtain-coating apparatus of conventional design with-
out essential modification of apparatus or operating procedure.They do not affect the assembly time values of the glues in which
they are contained, nor the strength of the final bond. In fact,
as noted above, the strength of the glued product is materially
improved by reason of the fact that the use of the additive causes
the production of a smooth, uniform curtain having no breaks and
persisting over long o~erating periods. It also causes uniform wet-
ting of the substrate surface so that a uniform application of the
glue is ensured.
The adhesive compositions of the invention and their manner
of formulation is illustrated in the following examples:
EXAMPLE
This example illustrates the effect on curtain-forming prop-
erties of the incorporation of the hereindescribed diol in a com-
; mercial phenol-formaldehyde resin~
.~ . .
.......
1076'73~ ~e ~, ~
i ~ , A commercial liquid phenol-formaldehyde resin, (~ERAC 312)
containing 6.1% by weight sodium hydroxide and 40% by weight total
solids, and having a T viscosity on the Gardner-Holdt scale, and a
pH of 12.3, was compounded with 0.1% by weight of 2,4,7,9-tetrameth-
yl-5-decyne-4,7-diol based on the weight of the liquid resin. The
resulting mixture was stirred until a clear solution resulted. Its
curtain-forming and veneer-wetting properties were tested by apply-
ing it in conventional manner to plywood veneers using a laboratory
type curtain-coater having a pressure head developing 6-10 psi
10 pressure. As a control, the procedure was repeated using straight
resin (CERAC 312), without the addition of the diol.
The tested composition including the diol formed a curtain
and wetted the veneer. The control composition containing no diol
additive was not curtain-forming and had poor veneer-wetting prop-
erties.
EXAMPLE II
This example illustrates the application of the hereindes-
cribed dioladditive to the formulation of a phenol-formaldehyde
resin plywood glue.
The gluewas compounded from the same liquid phenol-formal-
dehyde resin (CERAC 312) employed in Example I.
First a control glue was prepared which contained no cur-
tain-forming additive. It had the following composition, parts
being expressed as parts by weight:
Phenol-formaldehyde resin 75.86
Water 11.49
Ground corn cob filler 5.75
Wheat flour thickening agent 4.60
50% caustic soda solution 2.30
The foregoing ingredients were compounded in a mixer yield-
ing a glue having a viscosity of 1600 centipoises when measured on
a Brookfield viscometer at 25C., at 20 r.p.m. spindle speed.
This glue has a solids content of 30.4% by weight. When
used in a commercial pressure-type curtain-coater at a head pres-
_g_
1 0 7 6 7 30
sure of 6-10 p.s.i., a breaking, unsatisfactory curtain was formed.
Additionally, the glue did not wet the veneers satisfactorily.
Next a glue of the invention was prepared by adding to the
foregoing plywood glue 0.1% by weight of 2,4,7,9-tetramethyl-5-
decyne-4,7-diol, based on the weight of the phenol-formaldehyde
liquid resin. The resulting compounded glue was tested in the same
commercial coater. It was observed to form an excellent curtain and
to wet the veneer substrate uniformly and effectively.
EXAMPLE III
This example illustrates the composition of the invention
using varying amounts of the 2,4,7,9-tetrameth~1-5-decyne-4,7-diol
additive.
The procedure of Example II was repeated, using in a first
instance 0.025% by weight of the diol and in a second instance ~3%
by weight thereof. In both instances improved curtain-forming and
veneer-wetting properties were demonstrated, although in the second
instance there was incipient separation of the acetylenic diol.
EXAMPLE IV
This example illustrates the composition of the invention
20 used at high viscosity.
The procedure of Example II was followed, with the glue be-
ing mixed until a viscosity value of 8,250 centipoises was reached.
The improved curtain-forming and wetting qualities related in
Example II again were observed.
EXAMPLE V
This sample illustrates the glue of the invention at a 25%
resin solids content as opposed to the 30.4% resin solids content
of Example II.
The procedure of Example II was repeated employing the follow-
30 ing composition:
Parts by weight
Commercial phenol-formaldehyde resin 57.2
Water 22.9
Ground corn cob filler 11.3
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~ . . - . .
1cr76 73U~
Wheat flour thickener 3.2
50% caustic ~e ~o~ k~-3
B The resin employed was CERAC 303,7ra commercial re~in con-
taining 6. l~/o by weight sodium hydroxide and 43% by weight total
solids, and having a T viscosity (Gerdner-Holdt) and a pH of 12.1.
To the foregoing mixture, 0.1% by weight (based on the weight
of the liquid resin), of 2,4,7,9-tetramethy1-5-decyne-4,7-diol was
added and mixed in. Upon applying the composition to plywood ven-
eers in a commercial curtain-coater, the composition again display-
ed the noted superior curtain-forming and veneer-wetting properties.
EXAMPLE VI
This example illustrates an alternate method of manufactur- `
ing the hereindescribed curtain-coating, phenol-formaldehyde resin-
ous composition, wherein the acetylenic diol additive is added to
the phenol-formaldehyde resin before the latter is incorporated in
the glue mix.
The procedure of Example II was repeated except that the
phenol-formaldehyde resin was heated to a temperature of 83~/o C~
and 0.1% by weight, based on the weight of the liquid resin, of
2,4,7,9-tetramethyl-5-decyne-4,7-diol mixed in. Since the melting
point of the diol is 50C., the mixing temperature was above the
melting point of the latter and facilitated its incorp~ ation into
the resin.
Thereafter the resin with its content of acetylenic diol
was added to the other constituents of the glue mix in the manner
recited in Example II, and with similar resultsO
EXAMPLE VII
This example illustrates the compositions of the invention
employing in lieu of the 2,4,7,9-tetramethyl-5-decyne-4-7,diol the
ethylene glycol ether thereof.
The procedure of Example II again was repeated, using in
place of the 2,4,7,9-tetramethyl-5-decyne~4,7-diol the same weight
percent of the ethylene glycol ether of 2,4,7,9-tetramethyl-5-
decyne-4,7-diol having 3.5. mols of glycol per mol of diol. Upon
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1076'730
testing the curtain-forming and veneer-wetting qualities of the
resulting product, the same superior performances were noted.
In a manner similar to the foregoing, there are prepared
compositio~ of the invention containing in lieu of the ethylene
glycol ether of 2,4,7,9-tetramethyl-5-decyne-4,7-diol an equivalent
amount of the propylene glycol-and butylene glycol-ethers thereof
having from 1-10 mols of glycol per mol of diol; and in lieu of
the phenol-formaldehyde resin an equivalent amount of resorcinol
formaldehyde resin, cresol formaldehyde resin and phenol furfural
resin.
EXAMPLE VIII
To illustrate the unique effect of the use of 2,4,7,9-tet-
ramethyl-5-decyne-4,7-diol and its ethylene glycol, propylene gly-
col and butylene glycol ethers, there were prep~red and tested a
large number of compounds of different classes known to act in
varying degree as wetting agents. The compositions were formulated
and tested in the manner set forth in Example II, using the Example
II test mixture with the substitution of the hereinbelow listed
compounds for the 2,4,7,9-tetramethyl-5-decyne-4,7-diol of the lat-
~ ter example. The amounts and procedures were the same as in ExampleII, with the exception that the indicated amount of additive was
employed, by weight, based on the weight of the liquid phenol-for-
maldehyde resin.
WETTING AGENT AMOUNT USED (%)
:
ALCOHOLS
Isopropanol 0.2
n-Amylalcohol 0.2
n-Octanol 0.2
Dimethyl Octanol 0.2
Isononyl alcohol 0.1
Decyl alcohol 0.2
Dodecyl alcohol 0.2
Diacetone alcohol 0.2
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1076730
Wet~in~ A~ent Amount Used (%)
Isostearyl alcohol 0.2
Methyl pentynol 0.2
Hexynol 0.2
Dimethyl Hexynol 0.2
Ethyl octynol 0.2
POLYOLS
1,2,6 Hexane Triol 0~2
Dimethyl hexynediol 0.2
Dimethyl Octynediol 0.2
Dimethyl Hexanediol 0.2
ETHERS
Polyoxyethylene
(12) Tridecyl ether 0.2
Polyoxyethylene
(15) Tridecyl ether 0.2
Polyoxyethylene
(6) Tridecyl ether 0.25
ESTERS
Sodium Dioctyl
sulfosuccinate 0.2
Sodium Heptadecyl sulfate 0.2
Butyl Stearate 0.2
Sorbitan monopalmitate 0.2
Sorbitan monostearate 0.2
Sorbitan monolaurate 0.2
MISCELLANEOUS
N,N-Cetyl ethyl
morpholinium sulfate 0.2
Lecithin 0.2
Methyl isobutyl ketone 0.2
Vinsol resin 0.2
Sodium 2-ethylhexyl-sulfate 0.2
Carboxymethylcellulose 0.2
2 Ethyl hexoic acid 0.2
Decanoic Acid (Capric) 0.2
Octanoic Acid (Caprylic) 0.2
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1076~30
Upon testing the curtain-forming and veneer-wetting prop-
erties of the resulting glue compositions, none of the above noted
additives, even though they are known wetting agents, and even
though some of them are acetylenic derivatives, significantly im-
proved the curtain-forming and veneer-wetting properties of the
compositions in which they were contained.
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