CA1045263A - Thermosetting adhesive compositions extended with cellulosic paper mill sludges (aminoplasts) - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Thermosetting resinous adhesives, useful particularly as plywood or lumber laminating adhesives, comprise a phenol-, resor-cinal-, urea-, or melamine-formaldehyde resin and an extender there-for. The extender comprises an aqueous cellulosic pulp used in relative proportions of from about 1-50 parts by weight extender for each 100 parts by weight resin, dry solids basis. Water is included in amount sufficient to impart to the compositions a vis-cosity of 1,000-12,000 centipoises. The cellulosic pulp extender preferably comprises the pulp mill paper making waste sludges con-taining the discarded cellulosic fines separated from the pulp products of the mill. Its inclusion has the effect of holding the water at the glue line and accordingly of improving significant-ly the assembly time characteristics of the adhesive.

Description

" ~045Z63 . , THERMOSETTING ADHESIVE COMPOSITIONS EXTENDED WITH
CELLULOSIC PAPER MILL SLUDGES
-Aminoplasts-This invention pertains to thermosetting resinous adhesives of use particularly a~ plywood and lumber-laminating ~ adhesives.
; The present invention concerns itself with both the wood-laminating and paper making industries. This application is related to co-pending application serial no. 229,788. -~
In the wood laminating industry, specifically in the manufacture of plywood, wood veneers are coated with an aqueous ~ thermosetting resinous adhesive and then assembled or laid up $ into plywood assemblies each comprising a plurality of veneers.
A large number of these assemblies is stacked, pre-pressed, and then hot pressed to develop the adhesive bonds and form the finished plywood product.
Although the manufacture of plywood is a well established industry, a problem attending its use of the aqueous thermosetting resinous adhesives stems from the fact that when such adhesives are spread on wood, the water content of the -adhesives tends to migrate into the porous structure of the wood.
If such migration takes place to too great an extent before the adhecives set, the ability of the adhesives to develop strong ~ bonds is severely diminished, or destroyed altogether. This -~ effect in turn imposes a severe operating restriction on the use of the adhesives, since it obviously restricts the time available for assembling the veneers, stacking the assemblies and transferring them to the press. Accordingly, it is advantageous to have available adhesives characterized by retention of their water content at the glue line for A substantial period of time, i.e. for long "assembly times~.

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~O~SZ63 In the paper making industry, it is routine practice to reduce wood to chips, and to pulp the chips by either chemical or mechanical procedures. In chemical pulping the wood lignin is dissoived and a cellulosic fiber product obtained which is converted to paper. In mechanical pulping, the wood is reduced mechanically to the form of small lignocellulosic pieces which are the subject matter of the paper making operation.

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In both procedures, the cellulosic content of the wood is highly refined bybeating or abrading in the presence of water.
This has the well known effect of fibrillating the cellulosic fibers and hydrating them so that they contain a large proportion ; of water.
During the paper making operation there is produced a large quantity of "white water" which contains a substantial proportion of fines, i.e. of cellulosic particles so short that they pass through the forming wire. After processing the white water to re-cover the fiber fraction of longer fiber length, there remains a fines residue which is not suitable for paper making and comprises 'A a waste product of little value.
The present invention is predicated upon the discovery that hydrated cellulosic particles, and in particular those contained ` in paper making pulp mill sludges, have inherent properties which 4 make them highly useful as extenders for thermosetting resinous ~; adhesives in the manufacture of plywood and other glues. In parti-'I
cular, the cellulosic particles have a high content of water bound ; to the cellulose in such a fashion that it is not readily released.
~, 20 Accordingly, the hydrated cellulosic fibers, when included in resinous adhesives, hold the water content thereof and prevent its migration into porous wood surfaces when the adhesives are applied ~ -to the latter. This in turn imparts to the adhesives desirable assembly time characteristics which render the adhesives highly superior in this important property.
Accordingly the present invention has for its objects the preparation of thermosetting resinous adhesive compositions which ~ have exceptionally long assembly time properties, which are stable $~ in storage, which are versatile in their application to the manu-facture of both plywood and laminated lumber products and which ' possess a relatively high water content at given working viscos-~ ities, thus enabling using resinous adhesives having a reduced j resin solids content without loss of performance.

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-Another obj ect of the invention is the provision of thermo-setting resinous adhesive compositions which are relatively easy to prepare and which, in contradistinction to the manufacture of resinous adhesives using other cellulosic extenders, do not re-quire digestion in order to develop suitable rheological properties in the exte~der.
Still a further object of this invention is the provision of an extender for thermosetting resinous adhesives which can be used with a wide spectrum of synthetic resins of both acid and alkaline types, in the production of glues having pH values varying over a wide range, as required to produce glues suitable for use in a wide variety of industrial applications.
The thermosetting resinous adhesive compositions of the pres-ent invention comprise at least one thermosetting resin and an ex-tender for the resin comprising an aqueous cellulosic pulp hydrated ;to a freeness of not over 400 cc. C.S.F. (Canadian Standard Free-ness identified hereinafter) and having a content of cellulosic fibers a preponderant proportion of which have maximum lengths of not over about 1/8", preferably not over about 1/16". Water is included in the compositions in amount sufficient to impart there-to a viscosity of from about 1,000 to about 12,000 centipoises.
~ The measure of pulp freeness is identified herein as Canadian `; Standard Freeness (C.S.F.). It is determined by an empirical test procedure which gives an arbitrary measure of the rate at which a suspension of three grams of pulp in one liter of water may be drained. The test procedure is detailed in TAPPI Standard Test Method ~ 227m-58.
The thermosetting resins which may be employed in the for-mulation of the adhesives comprise the thermosetting phenol-, phenol-resorcinol-, resorcinol-, urea-, and melamine-formaldehyde resins. The resins and extender are used in relative proportions of from about 1 to about 50, preferably from about 3 to about 30 parts by weight extender for each 100 parts by weight resin, dry solids basis.

~ , ., : ~ , ~ ~ , In the preparation of the adhesives, the foregoing constit- -uents are simply mixed together, without the necessity of includ-ing a separate digestion step, into adhesive products which when applied to porous surfaces such as wood, and by virtue of the hydrated character of their content of cellulosic pulp extender, retain the water on the glue line for assembly times of 45 minutes or more, thereby materially increasing the facility with which the adhesives may be employed in the manufacture of plywood and other products.
As noted above, the thermosetting resinous adhesive composi-tions of the invention comprise 1-50, preferably 3-30 parts by weL~ht of hydrated cellulosic pulp extender for each lO0 parts by weight thermosetting resin, dry solids basis. Sufficient water is included to provide in the finished adhesive compositions a working or glue spreading viscosity of from about 1,000 to 12,000 centipoises.
With respect to the thermosetting resin, it is a particular feature of the invention that it is applicable to the use of a wide range of such resins. The useful resins fall into three prin-cipal classes: The highly alkaline resins, having a pH of from 10 1 20 to 13; the moderately alkaline resins having a pH of 8 to 10; and '~ the substantially neutral or slightly acidic resins having a pH
of from 5 to 8.
The resins of the first class comprise the resinous condensa-tion products of phenol and formaldehyde; those of the second class comprise the resinous condensation products of resorcinol and formaldehyde, and in particular the resinous condensation products of a phenol-resorcinol mixture and formaldehyde, the mixture containing less than about 50%by weight phenol; those of the thirdclass comprise the aminoplasts, in particular the resin-ous condensation products of urea and formaldehyde and melamine and formaldehyde.
Such thermosetting resins are readily available as resinous products, useful in the formulation of plywood and lumber laminat-ing glues. They have the above indicated pH values and a solids content usually falling within the broad range of from 35-65% by weight, dry solids basis.
Tne foregoing resins are well known and are used with well known catalysts, the working content of which is included in the adhesive formulations set forth above.
The the highly alkaline phenol-formaldehyde resins are cat-`~ alyzed by the presence of alkali, usually by the addition of , caustic soda.
The mildly alkaline resorcinol formaldehyde and phenol-resor-cinol formaldehyde resins are hardened by the presence of aldehydedonors such as liquidformaldehyde, paraformaldehyde and resins con-taining excess formaldehyde or methylol functionality.
The substantially neutral or weakly acid resins require acid catalysts. Representative are ammonium chloride, aluminum sulfate and citric acid used in amount of from 0.3 to 3% by weight, based - on the weight of the resin solids.
The hydrated cellulosic pulp extender for the resin, which comprises another major constituent of the hereindescribed thermo- ;
setting resinous adhesives, may~e derived from a wide variety of lignocellulosic or woody sources. Although it may be derived from ~ . .
d~ annual plants such as.grasses, str~, corn stalks, corn cobs and the like, it preferably is derived from the woods of various spe-cies of trees, both hardwood and softwood. In particular, it may i be derived from the woods of the trees conventionally employed in ¦ the manufacture of papermaking pulps, for example western hemlock, Dou~las Elr, jack pine, loblolly pine, spruce and aspen.
These and other lignocellulosic materials are prepared for the purposes of the invention by pulping them by any of the con-ventional commercially employed procedures, either chemical or mechanical, used for the manufacture of papermaking pulps. Thus they may be produced in the form of a full chemical pulp resulting from the application of conventional sulfite, Kraft, or soda pulp-; ping procedures, followed by refining in conventional refiners such as the Jordan, Claflin, Bauer, Morden and Disco refiners.

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-- 1045263 _ ~_ In addition, they m~y comprise mechanical pulps, such as newsprint furnish produced by grinding lignocellulose on pulping stones or in refiners. If ~sired, mixtures of chemical and mechan-ical papermaking pulps may be employed.
As is well known, the pulping and the refining procedures not only reduce the woody materials to the form of fibers or small particles, they also achieve the hydration of the cellulosic mater-ial. This effect includes the fibrillation of the fibers and their swelling with substantial amounts of hydrating water.
The amount of hydration of the cellulosic pulp which should be achieved to suit the purposes of the present invention is widely variable. In general, any degree of hydration is beneficial, since it creates a pulp which when included in the glue mix holds the water, keeps it on the glue line, and prevents it from migrating into porous wood surfaces thereby increasing the assembly time of the glue.
Practically speaking, the degree of hydration should be equal to that produced in a cellulosic pulp by processing in a commer-cial papermaking refiner. Since the degree of hydration of the pulp determines at least in part its freeness, the freeness values ; of the pulp may be used to define the degree of hydration. For present purposes, the pùlp should have a freeness of not over 400 cc. C.S.F.
In addition to providing a hydrated cellulosic pulp, it is important for present purposes to provide one in which the cellu-losic fibers or particles do not exceed a certain length. If a ~ -major proportion of the fibers, e.g. more than about 10% by weight thereof, have a length of more than 1/8", they interfere with the application of the adhesives in which they are incorporated. Spe-cifically, in the case of plywood adhesives, they tend to aggre-gate in spreader hoppers and spray orifices and form in effect a multiplicity of filtering units which filter out and involve the shorter fibers and thus clog the equipment. Accordingly, the cel-lulosic fibers or particles should have maximum lengths of about 1/8". A preferred maximum length is about 1/16".

~ 10 45 26 3 _ 7_ ; It is apparent from the foregoing that the hydrated cellulo~sic pulp which is useful in the hereindescribed adhesive composi-tions may be derived in several manners. If desired, it may be m~de by pulping raw chips specifically for the purpose of producing a pulp for use in the adhesive compositions. Alternatively, the var-ious commercial pulps may be diverted from a papermaking purpose and applied to the purpose of formulating the adhesive compositions.
Principally and preferably, however, the pulps may be derived from the waste sludges produced as a necessary byproduct o~ paper manufacture As noted, such sludges are produced in very large quantities such that their disposal may be a problem. Consequently they are of very low cost and their application to a useful commer-cial purpose such as the formulation of plywood glues would be of substantial economic benefit to the paper mill.
Pulp mill papermaking waste sludges are obtained principally from the white water which is recovered from the forming wire of the ` paper machine. They also may be derived, however, from the waste : liquors of the bleach plant or other processing units of the mill.All of these effluents conventionally are consolidated and processed together. Their compositions accordingly are quite heter-` ogenous.
` Thus, in addition to cellulosic fibers, the sludges may con-tain large amounts of paper fillers including ~lay, titanium dioxide and calcium carbonate. They also may contain preservatives, wetting agents, starch, sizes, flocculating agents, pigments and organic dyes.
Substantial amounts of such non-cellulosic components may be present. Thus a typical pulp mill sludge may contain from 0 to 60%
by weight, dry solids basis, of such extraneous solid materials and be suitable for the present purposes. However, it should not con-tain more than about 75% by weight thereof.
It is to be noted that the extraneous solid components of the sludges contribute little or nothing to the water-holdirgproperties of the glue. Neither do they interfere appreciably with the water-. ` ' ,. ,.` ~ ~, . -.

~ 10~5263 -8- ~
holding propertîes of the hydrated cellulosic pulp component of the sludges. They are present merely as bulk fillers, the presenceof which neither adds nor detracts substantially from the properties of the glue as long as the glue contains adequate amounts of the ` active ingredients, i.e. of thermosetting resin adhesive and hy-drated cellulosic pulp filler.
Typically to prepare a sludge suitable for the purposes in-` tended herein, the white water from the forming wire, or a~ueous sludge residues from other papermill sources are led to a conven-10 tional clarifier or settling tan~. Here the white water is permit-ted to settle, and the supernatent liquor is drawn off, leaving a sludge containing 2-3% by weight solids. This is passed through a processing unit such as a "DSM" screen, or other separator which separates any remaining useful papermaking fibers from the sludge.
The liquor from the screen, which may contain as little as 1% by weight solids, is passed through a second clarifier which concen- ~`
trates the solids to about 7% by weight. These solids then are passed through a dewatering device such as a filter press which presses out excess water, leaving a slush or semi-solid contain-20 ing from 15-75% sludge solids.
For the present purposes, the degree of concentration of such solids should be such as to provide them in a useful concen-tration for formulation of the adhesives. However, if they are con- ;~
;centrated to a level of more than about 75% by weight solids, they become difficult to disperse in the l~id glues.
If the pulp mill sludge contains an unduly large proportion ~ of fibers having a length greater than 1/8", it is desirable to `j! process the sludge to adjust the proportion of long fibers to il within acceptable limits,i.e. less than 10% by weight. Because of the swollen, hydrated character of the material, it is not feas-ible, or at least not practical to achieve this result by a simple screening operation. Accordingly, it is achieved by passing the sludge through a fiber recovering device such as a "DSM" screen `¦ which effectuates a selective separation of the longer fibers. In ~,.

- ~045263 ~h~ alternative, it may be achieved by passing the sludge through a papermaking pulp refiner of the conventional classes listed a-bove as many times as is necessary to reduce the fiber lengths to acceptable values.
In addition to the thermosetting resin and the hydrated cellu-losic pulp components, the herendescribed thermosetting resinous adhesive compositions may include suitable amounts of variou~-sup-plemental materials. Such materials comprise, for example, the con-ventional glue additives such as defoamers, colorants, tackifiers, ~;
etc. In particular, they often may include to advantage a suitable !~ ~
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proportion of wheat flour or other amylaceous material as a tack-ifier.
Still further, the adhesives of our invention include water in amount sufficient to impart to the final adhesive compositions j~
viscosities suitable for spreading and for establishing the desired glue line between the veneers or lumber pieces to be glued together.
The amount of water added for these purposes is widely variable, as determined by the intended use of the glue, the substrate to which it is to be applied, the physical conditions of application, and the identify of the other components. In general, a suitable viscosity for the resinous adhesive lies within the broad range from about 1,000 to about 12,000 centipoises, as determined in a conventional viscosimeter, for example a Brookield viscosimeter operating at 25C. and 20 RPM.
It is a particular feature of the present invention that the ;
resinous adhesive compositions which are its subject matter are prepared easily and quickly using a minimum of equipment. Thus, in contradistinction to compositions including "FURAFIL" extend-ers comprising the residue remaining after the acid hydrolysis of ~ i oat hulls and corn cobs, a separate treatment with alkali is not I -necessary in order to develop appropriate rheological properties in the extender. All that is required is to mix in the extender, preferably at the time of making the glue, using a high shear or ~Trademar~

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counter-rotating mixer of high capacity and efficiency. A stable adhesive results which, as noted, may be applied to advantage in the fabrication of plywood, laminated beams, and other glued pro-ducts.
The adhesive products of the invention are illustrated by the following examples wherein parts are expressed as parts by w~ight on a dry solids basis, and wood failure values are given in per cent, 85% or better being an acceptable level in the tests em-ployed.
The examples fall in three groups. Examples 1 to 5 illustrate the application of the dehydrated cellulosic pulp extenders of the invention to thermosetting resinous adhesives containing phenol-formaldehyde resins; example 6 illustrates the application of the extenders to adhesives containing phenol-resorcinol formaldehyde resins; and example 7 illustrates the application of the extenders to adhesives containing aminoplasts, specifically urea-formalde-hyde resins.
EXAMPLE
To test the adhesive capabilities of a typical phenol-form-20 aldehyde resin-full chemical pulp mill cellulosic sludge of the invention, there was prepared a mixture of 1,000 grams of aqueous alkaline phenol-formaldehyde resin, and 150 grams of papermill sulfite sludge. The resin (Monsanto "PF 541") contained 41% re~n solids and had a pH of 11.2. The sludge was a sulfite pulp sludge refined to a fiber length of at least 90% less than 1/8'i by 15 passes through a Morden papermaking refiner. It contained 31% sol- I
!~ ids of which about 60% comprised cellulosic fibers.
The foregoing mixture was mixed until homogeneous. One hun-dred grams of water than was added and the mixing continued until a homogeneous mixture again was obtained. The mixing was carried ~ out in a Hamilton Beach high speed mixer j The resulting plywood glue contained 32% pheno-formaldehyde resin solids. Its pH was about 11.5. It was spread in an amount of 60 pounds MDGL on Douglas fir plywood veneers which then were ,~
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- ' 1045263 laid up into three-ply assemblies using assembly times varying between three minutes and forty-five minutes. The assemblies were pressed for 2 1/2 minutes at 285 F. and 200 psi.
The resulting 5/16" plywood panels then were subjected to the standard American Plywood A~Dcia~ion vacuum pressùre test for glue bond streng~h as measured by wood failure on shear. As indi-cated in the test data given below, all samples passed the test with significantly high values of wood failure, even at the ex-treme limits of assembly time.
Avera~e of 10 Panels Assembly Time (Min.) Load (PSI~ Wood Failure(%) Average at 4 assembly times 173 98 EXAMPLE II
The procedure of Example I was followed, but using a some-what less advanced phenol-formaldehyde resin, i.e. Monsanto "PF
544" containing 41% resin solids, dry solids basis, and having a pH of 11. The same sulfite-full chemical sludge was emplo~ed as in Example I, but at a solids content of 32%. The sludge was refined by ten passes through a Morden papermaking refiner.
The results were as follows:
Avera~e of 10 Panels Assembly Time (Min.) Load (PSI) Wood Failure (%) Average at 4 assembly times 211 93 -.: . .- . . . : .~

EXAMPLE III
This example illustrates the application to the formulation of the adhesives of the invention of another commercial phenol-formaldehyde resin~ (Borden's "Cascophen W166"), in sharply re-duced amount.
The procedure of Example I was repeated, employing 1,000 ~~ grams of the resin, 500 grams of full chemical bleached kraft pulp, and 270 grams of water. Mixing was accomplished in a "Cowles" dis-solver. The phenol-formaldehyde resin had a solids content of 41%
10 and a pH of 11.5. 1 -The sludge was separated in a " DSM" papermaking fiber sep-arator to a concentration of fines having a content of about 90%
cellulosic fibers less than 1/16" long. The refined sludge contain-ed 28% solids, of which about 50% by weight comprised clay. The final glue contained only 22.6% phenol-formaldehyde resin solids, dry solids basis.
The glue was applied to wood veneers which were laid up into plywood assemblies, pressed and tested as set forth in Example I
except that the glue spread was 65-70 pounds MDGL and the press time was 3 minutes. The test applied was American Plywood Associa-'~ tion's standard plywood dry shear test.
Avera~e of 10 Panels Assembly Time (Min.) Load (PSI) Wood Failure (%~

Average at 4 assembly times 264 93 EXAMPLE IV
This example illustrates the application in the adhesives of the invention of a phenol-formaldehyde resin of particularly high alkalinity.
The procedure of Example I was repeated using 1500 grams of ~radem~rk ..... .

- ~ 1045Z63 - /3 ,phenol-formaldehyde liquid resin, 350 grams of pulpmill sludge and 250 grams o~ water. The resin (Borden's "Cascophen W156-V") was highly advanced, contained 41% resin solids, and had a pH of ` 12. The pulp sludge was predominantly a bleached kraft sludge, refined by four passes through a Jordan refiner to a C.S.F. free-ness of 85cc. It contained 30% solids of which 65 comprised Doug-las fir and Ponderosa pine cellulosic fibers having a fiber length of about 1/16" or less.
The resultant adhesive was applied in spreads of 67-68 pounds MDGL to 1/8" mixed Western soft wood veneers which were laid up ,~ into five ply plywood assemblies. The assemblies were pressed five minutes at 300F. and 175 PSI after which the plywood panels were tested for wood failure by the American Plywood Association standard vacuum pressure test. The results are given below:
Avera~e of 10 Panels AssemblY Time (Min.) Load (PSI) Wood Failure(%) 180 78 ~, Average at 4-assembly times 209 91 EXAMPLE V
This group of tests illustrates the app~ication of yet an- ,-~ .
other phenol-formaldehyde resin together with various cellulosic , pulp sludges and an amylaceous tackifier in the formulation of the , t hereindescribed compositions. The following plywood glues were ~, formulated: ,, Y . .
Glue #l ` 30 2000 gm. Phenol-formaldehyde Resin , 475 gm. Water { 375 gm. Cellulosic Pulp Sludge (Jordan-refined, 4-pass, 30% solids) Mix 5 minutes ~,~ ., ~! loo gm. Wheat Flour '~ Mix 3 minutes '`I .
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- 1045Z63 - 14_ 75 gm. 50% Sodium Hydroxide Mix 10 minutes

2 gm. Borax Mix 5 minutes Immediate Viscosity 7500 cps at 81F.
28.5% Resin solids Glue #2 1500 gm. Phenol-formaldehyde Resin 100 gm. Water 400 gm. Cellulosic sludge (17% solids) Mix 5 minutes 50 gm. Wheat Flour Mix 3 minutes 50 gm. 50% Sodium Hydroxide Mix 10 minutes Immediate Viscosity 6000 cps at 81F.
30.7% Resin Solids Glue #3 ` 1500 gm. Phenol-formaldehyde Resin 150 gm. Water 400 gm. Cellulosic Pulp Sludge (16.5% Solids) Mix 5 minutes 50 gm. Wheat Flour Mix 3 minutes 50 gm. 50% Sodium Hydroxide Mix 10 minutes Immediate Viscosity 11,250 cps at 79F. ~ -30% Resin Solids Glue #4 1500 gm. Phenol-formaldehyde Resin 400 gm. Cellulosic Pulp Sludge ,~
Mix until homogeneous 34% Resin Solids In all of Glues #1, 2, 3 and 4 t~e same phenol-formaldehyde resin was used, i.e. Pacific Resins "AMRES 5581"~ having a resin solids of 43% and a pH of 11.5. The mixing in all cases was car-ried out in a laboratory model "Dispersator" high shear mixer.
In Glue #l the same full chemical bleached kraft pulp was employed as was employed in Example IV. In Glue #2 there was em-ployed a clarifier sludge comprising approximately 75% Western hem-lock groundwood and 25% mixed Western woods kraft pulp, no filler :
being present. It had a C.S.F. freeness of 100 cc.
In Glues #3 and 4 the cellulosic sludge was of the same sour-ce as Glue #2, but comprised a "Saveall" sludge, i.e. one from which the longer fibers had been separated and recycle~ and the fines accordingly concentrated. It had a C.S.F. freeness of 265 cc.
All of the foregoing plywood adhesives were applied to the production of test samples of plywood by spreading them on Douglas fir veneers in spreads of from 65-68 pounds MDGL. The coated ven-eers were laid up into three ply assemblies which were prèssed at 6, various assembly times using a pre-cure time of 30 seconds, a press time of 2 l/2 minutes, a temperature of 285F and a pressure of 175 psi.
The resulting panels then were tested for wood failure by the American Plywood Association's standard vacuum pressure test with results as follows:
i Glue #l Average of 10 Panels AssemblY Time (Min.) Load (PSI) Wood Failure (%~

4~ 240 94 ,~
Glue #2 . ;
` . Average of lO Panels ~ --s Assembly Time (Min.) Load (PSI) Wood Failure (Z)

3 315 89 320 lO0 ~Trade~ark : ~' . .

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, 40 265 92 Glue #3 ` Avera~e of 10 P~nels, AssemblY Time (Min.) Load (PSI) Wood Failure (%) ` 10 325 91 ,~ 1030 305 97 ~ Glue #4 i Average of 10 Panels 0, Assembly Time (Min.)Load (PSI) Wood Failure (Z) , t ` 3 285 96 `, 10 255 100 i 30 150 100 -`" 40 280 95 , ~, 20 " It is apparent from the test results on Glues #1, 2 and 3 , that the cellulosic pulp extenders are compatible and useful with ,, conventional tackifiers for phenolic resin adhesives, such as wheat flour. Glue #2 indicates the applicability of the invention ,~ to the use of groundwood sludges derived from the clarifier with .~ , .
`y the fines unconcentrated.
Glue #3 illustrates the applicability of the invention to the use of groundwood sludges in concentrated form, such as are de~
rived from paper mill "Saveall" units. Glue #4 illustrates the sat-isfactory application of such sludges in the absence of an extran-eous tackifier.
EXAMPLE VI
; This group of tests illustrates the use of cellulosic pulpsludges as extenders for the mildly alkaline phenol-resorcinol-., .... . . . .
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- ^~ 1045263 ~ormaldehyde resins in the manufacture of adhesive compositions useful, for example, in laminating lumber.
The following formulations were prepared, using various phenol-resorcinol-formaldehyde resins and cellulosic pulp sludges obtained from various sources:
GLUE #l .~ .
-100 g~. Phenol-resorcinol-formaldehyde Immediate Viscosity resin 3370 cps ` Monsanto "PRF 2915"
15 Minute Viscosity ~ 12.5 gm. Cellulosic Pulp Sludge 3550 cps j Mix until smooth Gel Time 30 Minutes 7.5 gm. Paraformaldehyde Catalyst Mix until smooth GLUE #2 100 gm. Phenol-resorcinol-formaldehyde Immediate Viscosity resin 3150 cps ~i Monsanto "PRF 2915"
-~ 20 Minute Viscosity 5 gm. Cellulosic Pulp Sludge 3400 cps Mix until smooth Gel Time 29 Minutes 7~5 gm. Paraformaldehyde catalyst ;
Mix until smooth -GLUE #3 tControl) a 100 gm. Phenol-resorcinol-formaldehyde IT~nediate Viscosity resin 2710 cps ~ ;
:~ Monsanto "PRF 291511 -15 Minute Viscosity 20 gm. Paraformaldehyde Catalyst 2900 cp Monsanto ~2915 Fll -ca.50% by weight paraformaldehyde Gel Ti~e33 Minutes ' and50% by weight wood flour -; Mix until smooth -GLUE #4 100 gm. Phenol-resorcinol-formaldehyde Immediate Viscosity ~i resin 2750 cps 'i * Monsanto '~14-2911 10 gm. Cellulosic Pulp Sludge 15 Minute Viscosity i~ Mix until smooth 2800 cps '"J 7 gm. Paraformaldehyde catalyst .
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_UE #5 (Control) 100 gm. Phenol-resorcinol-formaldehyde Immediate Viscosity resin 2300 cps Monsanto "M4-29"
15 Minute Viscosity 17 gm. Paraformaldehyde Catalyst 2400 cps Monsanto "M4-28"
Gel Time 28 Minutes ~^ Mix until smooth ? GLUE #6 100 gm. Phenol-resorcinol-formaldehyde Immediate Viscosity resin 2700 cps ;~ * Borden "Cascophen LT75"
45 Minutes Viscosity 12.5 gm. Cellulosic Pulp Sludge 3420 cps Mix until smooth Gel time 24 Minutes ~ .
7.5 gm. Paraformaldehyde Catalyst Mix until smooth GLUE #7 100 gm. Phenol-resorcinol-formaldehyde Immediate Viscosity resin 3750 cps `Borden "Cascophen""LT75"
` 25 Minute Viscosity - 20 7.5 gm. Cellulosic Pulp Sludge 3720 cps .~
i Mix until smooth Gel Time 26 Minutes .j . .
.~î 7 gm.~- lOO~rnesh Paraformaldehyde Catalyst_Glue pH=9.0 . ........................................................................... .
Mix until smooth GLUE #8 (Control) ~;
~3 lOQ gm. Phenol-resorcinol-formaldehyde Immediate Viscosity resin 4440 cps Borden "Cascophen LT 75"
15 Minute Viscosity 15 gm. Paraformaldehyde Catalyst 4000 cps Borden "~282"
Gel Time 50 Minutes Mix until smooth Glue pH 9.0 In formulating the above adhesive compositions, all viscosi-ties were measured at 25C. using a Brookfield Viscosimeter, No.4 , spindle at 20 rpm. All gel times were determined in a 110F. cir-culating water bath according to standard test procedures and endpoint.
The cellulosic pulp sludge employed in Glue #l was a "Saveall"
sludge consisting of about 75% by weight groundwood and 25% by weight kraft having a solids content of 16.4 and a pH of 4.2.
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1045263 ~l9-Those employec~ in glues #2 and 7 were Jordan refined (4-pass) kraf~ pulps having a solids content of 29.4 and a pH of 5.2. That employed in Glue #4 comprised screened clarifier sulfite sludge h~ving a solids content of 32% and a p H of 6.8. That employed in Glue #6 comprised unrefined clarifier mixed groundwood and kraft sludge having a solids content of 20% and a pH of 6.
~` Glues #3, 5 and 8 contained no slu~ge, being controls for -;
; resins Monsanto "PRF 2915", Monsanto '~1 4-29", and Borden "Casco-phen LT75", respectively.
The phenol-resorcinol-formaldehyde resins had the following properties:
Type ViscositY *Solids ~
-^~ Monsanto "PRF 2915" 350 cps 50% 8.8 ~` Monsanto '~4-29" 245 cps 50% 9.2 Borden "Cascophen LT 75" 210 cps 50% 9.0 *Measured at 77F. (25C) by Brookfield (20 rpm, #4 spindle) All three of the ab~ve commercial phenol-resorcinol-formalde-. , . , ~
, hyde resins contained phenol and resorcinol in the proportion offrom 40-50% of the phenol to 50-60% resorcinol, by weight, dry ~1~ 20 solids basis.
- The foregoing glue samples then were subjected to tests of primary interest in evaluating adhesives to be used in gluing up wood laminates: An adhesive "sag" test, and an adhesion test con-;~ sisting of t:he American Institute of Timber Construction (AITC) test No. 110, a variation of the ASTM D-1101-65 cyclic delamination test. 1-The sag test provides a method of determining the capabil-ity of the glue to remain in place on a vertical surface when extruded from orifices of graduated sizes without pulling itself into beads or granules by surface tension or dripping (running) from the applied line of glue. me larger the orifice in which the glue remains in place, the better its consistency and per-formance for lumber laminating and the more uniform the glue cov-erage when pressure is applied. It is of particular significance, .

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4S~63 since lumber laminates conventionally are laid up on edge with the glue films vertical, and accordingly subject to running.
The glue samples of this example were subjec~ed to the above ;- sag test using orifices of 1/32", 3/64", 2/32", 3/32", 4/32" and 5/32". All of the fully formulated glues, i.e. glues 1, 2, 5, 6 ;~ and 7 passed the sag test satisfactorily, there being no runs when extruded from ~rifices up to and including 3/32" in diameter.
It is of particular interest that control glue #3 which con-tained no cellulosic pulp extender, but rather contained via the ..
catalyst a conventional wood flour extender, performed poorly and demonstrated substantial running with the smaller orifices.
Next lumber laminates were laid up using all eight of ~e ~ test glues under the following conditions:
`~ Glue age: 30 to 45 minutes Glue spread: 80 lbs/MSGL
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-i Stock: l 1/2-inch vertical grain Douglas fir, -~' S4S, 7-8% MC.
Clamp time: 24 hrs. at 80-85F.
Pressure: 100 psi.
All eight of the samples satisfactorily passed the conven- ~`
tional cleavage test, showing wood failures of from 95-100% when knifed at all combinations of both open and closed assembly times, -i.
at 85F. m ey also passed the AITC 110 cyclic delamination ~est, ,~ ~
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one cycle of which is accepted as satisfactory exterior adhesive `~
performance for laminated lumber products.
SAMæLE VII
-- This Example illustrates the application of the hereindes-cribed cellulosic pulp extenders to urea-formaldehyde resinous adhesive mixes.
, A series of glue sarnples was prepared using various ce~h-30 losic pulp sludges in conjunction with a thermosetting urea-for-maldehyde resin. The formulations and the manner in which they --were prepared were as follows: ~

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)45263 GLUE #l (Control) 200 gm. Urea-formaldehyde Resin Glue pH 6.2 260 gm. Water Immediate Viscosity 3400 cps Mix until smooth 6 hour Viscosity 3000 cps 200 gm. Soft Wheat Flour Resin Solids 19.4%
, Mix until smooth 10 gm. Catalyst Solution Mix until smooth ` GLUE #2 200 gm. Urea-formaldehyde Resin Glue pH 5.8 125 gm. Water Immediate Viscosity 9150 cps - Mix until smooth 1 hour Viscosity 9850 cps (6000 cps with helical path) 100 gm. Cellulosic pulp sludge:
; 75% groundwood, 25% kraft 6 hour Viscosity 9550 cps ~-~ Mix until smooth Resin Solids 29.9% -;. '~ . .
10 gm. Catalyst Solution Mix until smooth GLUE #3 ~ 200 gm. Urea-formaldehyde Resin Glue pH 6.1 ; 20 230 gm. Water Immediate Viscosity 4600 cps :,;
`~ Mix until smooth 1 hour Viscosity 4300 cps !'`'`~ 160 gm. Cellulosic pulp sludge: kraft4 hour Viscosity 4220 cps Mix until smooth Resin Solids 20.3%
40 gm. Soft Wheat Flour Mix until smooth 10 gm. Catalyst solution ~ Mix until smooth ;i GLUE #4 . .1 ; .
200 gm. Urea-formaldehyde Resin Glue pH 5.9 30 gm. Cellulosic Pulp Sludge: Immediate Viscosity 3350 ca 50% groundwood, 50% kraft 3 1 hour Viscosity 3620 cps Mix until smooth 2 hour Viscosity 3670 cps i 10 gm. Catalyst Solution Rein SoIids 54.2%
Mix until smooth ''~' ' al .. ~

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1~4~i263 In all of the above formulations, the urea-formaldehyde resin was Borden "Casco 5 H" having ~5% solids, a viscosity at 77 F. of 810 centipoises and a p H of 7Ø The catalyst comprised, in per cent by weight, 35% ammonium hydroxide, 15% ammonium chlor-ide and 50/~ water. The mixing apparatus was a "DISPERSATOR:" high shear impeller mixer. All glue viscosities were measured at 77F.
on a Brookfield viscosimeter using a No. 4 spindle at 20 rpm after 30 seconds of rotation.
All of the foregoing glues were applied to the manufacture of ~; 10 plywood under the following gluing conditions:
Panel Construction - Three plies of 1/10 inch Spruce veneer Glue Spread - 75 to 80 lbs/MDGL for Glues 1 through 4 45 to 50 lbs/MDGL for Glue 5 Assembly Times - 3 to 120 minutes Press Time - 3 minutes Press Temperature - 260F.
Platen Pressure - 175 psi ` Precure - 30 seconds.
The plywood panels thus produced were subjected to ~e con- ;
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ventional knife test for plywood bonds and the standard American g~ 20 Plywood Association adhesive failure test for interior plywood.
~^ The knife test comprises a vsual estimate of wood failure on each - glue line after knifing. The adhesive failure test comprises a 100F. vacuum soak, oven dry test wherein delamination of the p~es indicates adhesive failure.
All of the sample glues passed both the knife test and the -adhesive failure test, indicating their suitability for use as interior plywood glues.

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Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A thermosetting resinous adhesive composition comprising:
a) at least one thermosetting resin of the class consisting of the thermosetting urea-formaldehyde resins, and melamine-formalde-hyde resin, b) an extender for the resin comprising an aqueous cellulosic pulp hydrated to a freeness of not over 400 cc. Canadian Standard Freeness and having a content of cellulosic fibers a preponder-ant proportion of which have maximum lengths of not over about 1/8", c) the resin and extender being used in relative proportions of from about one to about fifty parts extender for each one hun-dred parts resin, parts being expressed as parts by weight on a dry solids basis, and d) water used in amount sufficient to impart to the composition a viscosity of from about 1,000 to about 12,000 centipoises.

2. The adhesive composition of claim 1 wherein the thermoset-ting resin consists essentially of a urea formaldehyde resin.

3. The adhesive composition of claim 1 wherein the thermoset-ting resin consists essentially of a melamine-formaldehyde resin.

4. The adhesive composition of claim 1 wherein the cellulosic pulp comprises a chemical pulp.

5. The adhesive composition of claim 1 wherein the cellulosic pulp comprises a sulfite pulp.

6. The adhesive composition of claim 1 wherein the cellulosic pulp comprises a kraft pulp.

7. The adhesive composition of claim 1 wherein the cellulosic pulp comprises a soda pulp.

8. The adhesive composition of claim 1 wherein the cellulosic pulp comprises a mechanical pulp.

9. The adhesive composition of claim 1 wherein the cellulosic pulp comprises groundwood pulp.

10. The adhesive composition of claim 1 wherein the pulp com-prises pulp mill papermaking waste sludge containing the discarded cellulosic fines separated from the papermaking pulp products of the mill.

11. The adhesive composition of claim 1 wherein the cellulosic fibers have maximum lengths of not over about 1/16".

12. The adhesive composition of claim 1 wherein the resin and extender are used in relative proportions of from about 3 to about 30 parts extender for each 100 parts resin.

13. The adhesive composition of claim 1 wherein the resin con-sists essentially of a thermosetting urea-formaldehyde resin having a pH of 5-8, the pulp comprises pulp mill papermaking waste sludge containing the discarded cellulosic fines separated from paper-making pulp products of the mill, wherein at least 90% by weight of the fibers have maximum lengths of not over about 1/16", and wherein the resin and extender are used in relative proportions of from about 3 to about 30 parts by weight, dry solids basis.