PH26826A - Latently curable binder compositions which contain cure enhancing agents - Google Patents

Description

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BACKGROUND OF THE INVENTION

I'ield of the Invention

The present invention relates to latently cur-~ able binder compositicns for bonding a network of so- lide including: refractory materials such as in the manufacture of foundry molds and cores and the like; lignocellulosic materials such as in the manufacture of plywood, hardboard, particleboard, fiberboard, waferboard, oriented strandboard and the like; and other solids, including glass fibers, metal filings, ceramic powders and the like. The invention is also directed to processes for producing these binder com- positions and processes which put these binder com- positions to use. lore particularly, the latently curable binder composition containe e curing agent with ester functionality for enhancing the cure speed of phenolic resins conventiomally used in bonding solid materisls. The curing agent is incorporated into the reen in suall, effective quantities with rapid agitation. The stable binder compositions of the present invention permit the bonding of high moisture lignocellulosic starting materials,

Background of the Invention

Phenolic resins are widely used ans athesives - 2 -

BAD ORIGINAL 9 pd and binders in many products, jncluding foundry molds, grictional elements (brake shoeB)e filter papers ceramice. {fiber nats and structural wood pro= ducts guch 88 plywoods particleborrds giverboards ner dboards wafervoard and oriented gtrand poarde

The production of most manufacturing processes ntiliz- ing 1iquid Shenol-formaldebyae resole (PF) binders is often 1imited py the cure speed of the pinders This 4s true pacauset of the inherently slow tharnal cure of these produc tis compared to other commonly used pinders, and becnuse of the need to eliminate molis- ture from the system during curinge it is known that phenolic resin cure can be accelerated by adding form-= aldehyde donorss nexame thylene tetrasmine or various organic and ynorganic acids. These wethods are not well guited to the current purposess hovwevels vecauss nexame thylene tetraamine is relatively sneffectual with resole8 and acids cause problems with corrosion of processint equipment and metal fastenerss

In 1957 orth et al. gisclosed that lactone curing agents could be used to harden PF binders suitable for wood gluing (DAS 106546057 ¢ The use of 1mactoned as curing agents to harden pF binders gui table for use yn foundry molds are disclosed by

Quist et nle iP U.S. patent NOe I, v2641467 wd =

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In these processes, the lactone and PF binders are maintained as two separate components just prior to use since these lactones provide cure (or gelas tion) of the I} binder at amhient temperature. Such a two component cyctem is disadvantageous to the end user of the binder compositions in that he must pro- vide for adequate mixing by processes and equipment which are separate from the manufacturing procedure,

Copending application Serial No. 903,253, filed

September 3, 1986, nnd assigned to Borden, Inc., des cribes a process for combining curing agents with phenolic resins in-line with the manufacturing pro= cess, thus avoiding separate process steps.

This invention provides binder compositions wherein the curing agent is added to the phenolic resin solution well in advance of use. Therefore, the end user need not admix the two components. Prior to the present invention, the addition of curing agents to phenolic resins without immediate cure was dif ficult. Adding highly reactive curing agents, such as plkylene carbonntes, was particularly diffie cult in that colloid particles often formed in the binder composition, as disclosed by Cherubim et al, in U.S. Patent 3,949,149, The procees of the pre= sent invention provides for rapid distribution of the ob — —_

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¢" yb curing agent without formation of colloids. The distribution of curing agent obtained is sufficient to provide a binder composition of high stability.

Phenolic resin solutions modified with ester curing agents are known to be useful in the manuface ture of plywood, compoaition board, particleboard, hardboard, f{iberboard, weferbonard, oriented strand board and the like.

Plywood is a glued-wood panel thet is composed of relatively thin luycras, or plies, with the grain of adjacent layers at an odd number of plies to provide a balanced construction. I{ thick layers of wood are used as plies, often two corresponding layers with ‘ the grain directions parallel to each other are used;

Co 15 plywood that is so constructed cften is called four ply or six ply. The outer pieces are fzces or face and back plies, the inner plies are cores or centers . and the plies between the inner and outer plies are crossbands. The core may be veneer, lumber or parti- cle boerd, with total panel thickness typically being less than one-eighth inch and no more than two inches.

In general, the plywood panels ure dried to remove moisture to = level which is compatible for gluing. The panels are coated with a liquid glue, front and/or back ns appropriate, with =a glue spreader. «5 . - f

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Heat and pressure are applied in a hot press to cure the glve and bond the panels together to form the plywood. The process of the present invention pro- vides for the use of veneers with higher moisture levels, permitting the manufacturer to prepare higher volumes of veneer from existing dryers,

SUMHARY OF THI INVENT ION

The invention provides a latently curable binder composition which rontains a curing agent - 10 having ester functionality and which is sufficiently stable to permit storage for periods in excess of 24 hours. The term "latently curable'', as used herein, is intended to mean curable after & sufficient time for storage, transportstion and application to sow lids.

These stable binder compoeitions comprise a phenolic resin solution capamble of binding a network of fibers upon cure. This phenolic resin solution is sufficiently stable to permit storage in excess of 24 hours.

The latently curable binder composition also contains a curing agent having ester functionality.

This curing egent is soluble in the phenolic resin solutions The quantity of curing agent used is sufe ficiently high to enhance the cure speed of the ale 6 = pr—

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Lo wy 4 yb kaline condensed phenolic resin yet sufficiently low to prevent pelntion within the binder composi-~ tion for a period in excess of 24 hours so as to remain in a liquid form.

Also provided hy the present invention is n method for makini- n latently curable binder cowpoki- tion containing » curing arent with ester functiona= lity. By this process, the curing sgent is introe= duced to an alksli-condeused phenol=formnldehyde resin solution hnving a viscosity below about 500 cps. and st a temperature belou about 10°C. at a re- gion of rapid apitertion, The curing agent is charged into the resin solution at a rate sufficiently high to prevent the formation of gels or colloids upon addition.

Another embodiment of the present invention is a method for the bonding of lignocellulosic materials in the manufacture of structural wood products which can use high moisture starting materials.

DETAILED DESCRIFILGN OF THE PREFERRED EMBODIMENLS

The present invention relates to a latently curable binder composition which comprises an alka= line condensed phenolic resin solution capable of binding a network of sclids. The solids which can be bound upon gelation (or cure) of the resin include . -7e Ree —— dT og

. } Se g a those in the form of granules, fibers, strands, wafers, flakes, veneors and powdern., The solids may be refractory materials, such as alumina, magnesia, zircon, silica sand, quartz, chromite sand, zircon sand or oliviur «r+. In addition, lignocellulosic materials such as wood may also be used either in wood fiber, wood flanke,wood chip, wood shaving, wood wafer, or wood particle form or as a veneer. Other solids may include plnres fibers, carbon fibers, nylon fibers, rayon fibers, ceramics such as calcium oxide and metal filings such as iron or copper used in fric- tional elements.

The alkaline phenolic resin solution must also be sufficiently strbLle to remain liquid at ambient temperature for pcriods in excess of 2h hours from synthesis and be sufficiently reactive to gel upon heating to a temperature above about 100%C., and preferably above nbout 150°C. A me jority of the com- monly used alkaline condensed phenolic resins satisfy these criteria. Alkaline condensed phanolic resin solutions nre often not completely stahle at ambient temperatures in that polymerization ccntinues result- ing in an increase in the solution viscosity. Re- action is slow under ambient conditions and, often, the viscosity will increase about 30 to 40 centipoise eo 8 » yr—

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$v ls per day. Although the viscosity of these phenolic resin solmtions may increase, they remain liquids and do not experience gelation for n period in ex~ cess of 24 hours from aynthesis. For most alkaline phenolic resine. gelotion does not occur until well beyond the oh hoon Lovied smd Tor nome, irreversible gelation at embient conditions may never occur until desired, peruilling the addition of solvent to re- duce viscosity cfter prolonged storage.

The alkaline condensed phenolic resin must also be sufficiently reactive to gel upon heating to a temperature of at least mbout 100°C. The majority ©... -:of the common alkaline condensed phenolic resine may. gel at temperotures significantly below 100°¢, as well as at temperatures above 100°C.

A large number of alkaline condensed phenolic resins provide adequate bond strengths to bind solids in a network. ‘those which are most commonly used have a weight average molecular weight preferably greater than 700, more preferably greater than 1,000 and most preferably within the range of about 1,000 to 2,200 as determined by a solution method.

Suitable alkaline materials used to condense the phenolic resins include sodium, potassium, calcium and magnesum hydroxides, with potassium and sodium hy= “0 = r

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= A ——————— —_— - I . _ n eo

SF droxides being most preferred. The phenolic resins may be obtained by the reaction of phenol, cresole, resorcinol, 3,5-xylenol, bicphenol A, other substi= tuted phenols, or mixtures thereof with aldehydes such as formnoldehyde, acetaldehyde, or furfuraldee hyde. The inferred ropetants are phenol ond formnle dehyde utiliznd in n molar ratio of phenol to formale- dehyde in the venge of 1:1 to 1:3.1, and more pre= ferably 1:2.1 to 1:2.8 for bonding lignocellulosic material.

The phenolic resin snlutions have sn alkalie nity content, i.e., contain a base, in the range of about 1.» to ahout 15%, preferably 2.5% to 7%, based on the weipht of the resin solution, when the base is sodium hydroxide. Yhen a different basa is utilized, the alkalinity content is proportionately equivalent.

As used herein, "alkalinity content’ will mean pers cent of solution according to equivalent sodium hy- droxide weirht unless expressly stated according to base. For example, an alkalinity content of 6.4% potassium hydroxide would be equivalent to an alkelie nity content of about 9%, bessed on the equivalent weight of sodium hydroxide. Additional base can be added to a commercial resin to bring it to the de= sired concentrntion. The hase nay be san alkall metal = 10 « r

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Loo v # . or alkaline earth metal compound such as & hydroxide.

The more commonly used phenolic resins which satisfy the criteria given above have a solids cone tent of sbout 40 tc 75% by weight, preferably nbout 80 to 60» by weight. Such compositions are typicale ly sufficiently low in viscosity to permit a more simplified nddition of the curing rgent., The vise comity of these phenolic resin solutions generally range from about 200 to 1,500 centipoise, as detere mined by an Lvl Brookfield Viscometer, using number 2 spindle, at 30 rpm, nt 25%. Preferably, the vis- cosity is below about 500 centipoise and most prefer- ably about 200 to 400 centipcise. , The curing agent for the phenol-formaldehyde resin has an ester functicnal group and must be dis- persible in the phenolic resin solution. By "dis- persible" is meant either soluble, miscible or other= wise distributeble. FPreferably, the curing agent is soluble in the resin solution. The curing agent may be selected from the group consisting of lactones, organic carbonates, carboxylic acid esters or mixe tures thereof. ‘ienerally, it is preferred to use curing agents wiih from 4 to 12 carbon atoms. It is most preferable to use a curing agent with a reacti- vity less than or equal to thet of propylene carbon- - 11 = : — ~

ED

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— - —_— ee 0" (Yl yv ate to simplify its addition into the resin solu- tion. Although a curing agent mery be dispersible in the resin solution, special equipment may be re- quired to prevent the formation of gel and colloids upon addition. “cir penta with a higher mole cular weight then propylene carbonate often have lower reactivitic:, bxamples of lactones which accelerate the cure of phenolic r=asins include, but are not limited to, gamma-butyrol~ctone, valerolactone, caprolactone, beta-proniolactons, beta-butyrolsctone, beta-isobuty- rolactone, bebtn-iropentylactone, gamma-isopentyl=- actone end dello pentylectone., Where a lactone is used, it is preferable to use gamma-butyrolactone, which is lower in reactivity than propylene carbone ate.

Examples of organic carbonates which accele- rate the cure of phenolic resins include, but are not limited to, propylene cerbonnte, ethylene glycol care bonate, glycerol carbonate, 1,2-butenediol carbonate, 1,3-butnnediol carbonate, 1,2-pentanediol carbonate and 1l,3%-pentanediol corbonate. If an organic car- bomate ie utilized, it is preferable to use propy~ lene carbonate. CUnrhoxylic acid esters which accee lerate the cure of phenolic resins include, but are - 12 = !

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¢" ‘fv not limited to, n-butyl acetate, ethylene glycol diacetate and triacetin (glycerol trincetate). If a carboxylic acid aster is u=ed, triacetin is pre-~ ferred. Triascctin har a lower reactivity then pro- pylene carbone!

Other nliyph~tie monnesters may be suitable, such ar propionate, bhutyestes or pentanates, nnd tho like. Additions} nliphntic nvitiesters which may be suitable include iferunte, dincetate, or higher di esters of ethylene lycol, diethylene glycol, pro-~ pylene glycol, hntylinne Flycol, glycerol, l,3-pro- penediol, 1,3-butrredinl, and 1,ltl-butarediol. Fur=- thermore, diesters of dicarborylie acids, such as die . methyl malonate, dimethyl glutarate, dimethyl adipate, and dimethyl suceinnte, are suitable.

The quantity of curing agent within the latent- ly curable binder composition is sufficiently high to accelerate the cure ~f the alkaline condensed phenolic resin. Very small quantities of curing apents are effective in enhnncing the cure of such resins. Quan-~ tities as low as N.0) wt, I of » highly reactive cur- ing agent based on total solids of the binder com- position will provide detectnhle results. Actually, the larger the auantity of curing agent, the greater the enhancement of cure speed. However, the quantity «13 = r A)

BAD ORIGINAL gy a8" of curing agent must be sufficiently low to main tain the binder composition in a liquid form at am- bient temperature for at least 24 hours, and pre= ferably at lenst » week. By "liquid" is meant that the composition in fluid or flowsble, and is subs- tantinlly free of rel or colloids. In such a con- dition, the Linder composition of the present inven- tion has e pot life of at least 24 hours, nnd pre- ferably ont least p week. quantities of propylene carbonate curing agent equal to about 5 wt. ®» of thas total binder composi- tion (about 11% based on solids) have been found to provide an unstsahle binder composition which cures within minutes at ambient temperature. 1t is preferable to maintain the concentration of curing agent below about 5% by weight beaed on solids. Most preferably, the quantity of curing agent is selected to fn}! within the renge of about O.1 wt. % to 1.0 wte » hrsed on total aolids of the binder composition. Such compositions will be relatively stable and will remein in a liquid form for a period in excess of three weeks without gelation.

The viscosity of the binder composition does increase where there quantities are introduced to a phe nolic rrsinsolution and, in fact, increases at a «lh =» ~~

BAD ORIGINAL 9d i —

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We faster rate than esin solutions which do not cone tain curing agent. However, the rate of viscosity increase is sufficiently low to permit short term storage, transportation and application of the binder compositions. Preferred binder compositims of the present invention will exhibit a viscosity bee low about 1,000 centipoise at 25°. even after one week from production.

It ie important to note that the binder com- positions of the present invention may contain other components, modifiers, extenders, etc. For example, cornstarch extenders may be added without deleterious effect of the present invention and urea may also be aded without effecting the cure rate of the phenolic rescle resin.

The addition of curing agent to the phenolic resole resin will not inhibit cure and upon the application of heat, particularly at temperatures well above ambient temperature, the binder composi= tion will cure rapidly. UGelation times of about 10 to 20 minutes are common for binder compositions of the present invention which are maintained at 100°C.

Also provided by the present invention is a process for preparing a latently curable binder ' composition described above. The binder composie

J — -_— _ (WW tions prepared by this process exhibit stability at ambient temperature and reactivity upon heating.

The initial step of the process incorporates conventional techniques for the manufacture of phe nol-formaldehyde resin condensed by alkaline mate- rials. The resin obtained must be capable of binde ing a network of solids upon gelation and the resin solution must have a viscosity below about S00 cen ti- poise at 25? C. The phenol-formeldehyde resin so- lution is cooled to a temperature below about 40° c. to retard the activity of the curing agent when in- troduced. Preferably, the temperature of the ree sin solution is maintained below about 30%.

The phenol-formaldehyde resin solution is agitated rapidly prior to the addition of the cure ing agent. Agitation is necessary to prevent the formation of colloids or gel upon the addition of curing agent. An impeller operating at about 80 to 100 r.p.m. within a baffled vessel has been found to provide adequate agitation for the addition of propylene carbonate curing agent.

The curing agent is added to the phenol-form- - aldehyde resin solution in a region of rapid agite~ tion to obtain rapii, uniform dispersion. In a conventional reactor, the curing agent is introduced

) Lv at the bottom, in close proximity to a high speed impellers

The curing agent is introduced at a rate suf- ficiently high to prevent the formation of gel or colloids upon addition. This can generally be accom-= plished by injecting the charge of curing agent with air pressure of about 30 to 40 psi. It is prefer- able for the entire charge of curing agent tobe ine troduced within about 20 to 45 seconds, even where a charge of as much es 1 wt. % of curing egent based on the weight of the resin solution is required. . The curing agents used contain at least one ester functional group and are soluble in the phe= nol-formaldehyde resin solution. preferred curing agents are selected from propylene carbonate, gamma= butyrolactone and triacetin. The quantity of curing agent introduced to the resin solution must be eufe ficiently high to accelerate the cure of the alkae line condensed phencl-formaldehyde resin and at the same time, must be sufficiently low to maintain the binder composition in liquid form at ambient teme perature. As discussed previously, quantities vhich provide these results fall below about 5 wt. %e based on the weight of total solids of gaid binder composition. The referred range is about 0.01 wte % eo 17 ® to 1 wt. of based on the weight of total solids of said binder composition.

To obtain a binder composition of adequate stability, it is preferable that the phenoleforme aldehyde resin solution have a viscosity of from about 200 to 400 centipoise at 25%. for a resin having a phenol-formaldehyde mole ratio of 1:1 to 1:3.1. To further insure stability, it is prefer- able to maintain the phenol-formaldehyde resin at a temperature below about 30° C. To provide the rapid agitation necessary, it is helpful to use equipment such as baffled vessels, high speed impellers and subsurface feedlinese.

It is recognized the process of the present invention may comprise additional steps, such as those which provide for the addition of cornstarch or other extenders.

The latently curable binder composition of the present invention can be applied to solids with any form of conventional equipment currently in use,

Such equipment includes spray nozzles, atomizing wheels, roll coaters, curtain coaters, foam applie cators, mixers, roll mills, dip tanks, and the like,

Also provided by this invention is a method for bonding lignocellulosic material (wood) with an - 18 w

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SV adhenive mixture containing binder compositions of the present invention. The process comprises apply- ing the adhesive mixture tn a lignocellulose mate- rial, consolidating the lignocellulosic material and curing the binder composition within the adhe- sive mixture. The preferred binder compositions uti- lize rropylene carbonate, gamma butyrolactone or tri- acetin curing agents,

Boards made from homogeneous lignocellulose materisl or from mixtures of different kinde of such material can be produced by this procesa. A board may be made, for example, completely from wood parti- cles, or completely from wood flakes, or from wood fibers, shavings or the like, or from mixtures of 1% these. Similarly, a board may be formed with multi ple layers, with fine surface flakes and a core of : coarse flakes, or it may have a conrse-flaked core with an overlay of fibers on each of its surfaces.

Other combinations may also be produced.

It ie preferable to manufacture plywood from the process of this invention for bonding lignocel- lulosic materials, Plywood in a board composed of multiple layers of wood veneers. The veneers are usually arrsenged so that the wood grain direction is nerpeadicular tn adjacent veneers.

vs %

The plywood process requires straight logs cut to length, and conditioned in heated vats con- taining water and surfactants to increase the heat- ing efficiency of the vats. The heated logs are

S then ''peeled” wherein a veneer of predetermined thickness is removed continuously until the log dia- meter is reduced to a certain point, usually 3 to 6 inches. The veneer is then clipped into strips, sorted and dried. In conventional bonding processes, the moisture content of the veneer is reduced to 10% or less. Higher moisture contents are permitted by this inventisn,

After drying, the veneers are graded and as- sembled into plywood panels. The adhesive is applied to the veneers at this stage of manufacture, The adhesive is vsually composed of phenol-formaldehyde resin, water, n basic material such as sodium hy=- droxide, and fillers that include inorganic and or= ganic flours, svch as wheat flours, wood flours, and clays. The rdhesives are specially formulated for individual user mills depending on manufacturing equipment, type of wood to be glued, type of product to be made, and ambient environment conditions at the time of panel manufacture. The adhesive is usual- ly applied to the veneers by roll coater, curtain - 20 w

Ju GH coater, sprayline or foam extruder. The adhesive usually containe phenol-formaldehyde resin at a level of 20 to ho¥ resin solids by weight. The ad~ hesive is normally used with spread levels of SO to 110 lbs. of adhesive per 1000 square feet of gluelines, when the veneer is spread on both aides, or 25 to 55 1lbn., when spread or onc side.

After the adhesive is applied to the wood veneers and the panels are arsemhled, they are con- golidated under heat and pressure. This is usually dona in a steam hot-press using platen temperatures of about 240° to 250°F. and pressures of about 75 to 250 psi.

In producing plywood, the most critical glue- line for cure is the innermost one. This glueline ig the most difficult to cure under present condi tions. That is, often the innermost glueline is not fully cured when the other gluelines are. It is necessary, then, to apply additional hot pressing to the board to cure this glueline. One additional use of the binder composition of the present inven= tion is that they can be applied to the innermost glueline and a conventional resin applied at the other gluelines. The accelerated resin is then able to provide a complete cure at the innermost glueline w 21 = ve ad in the same time period as it takes to cure the other gluelines.

It has been discovered that several advant- ages are obtained by utilizing the binder composi ~ tions of the present invention, i.e., a resin con- taining the curing agent, in the manufacture of structural wood products. One advantage is that cure time can be decreased. For example, in the prepara- ' tion of 4 ply-1/2" thick plywood by conventional pro- cesses, a 3.5 minute cycle cure time (press and heat) is utilized when the resin does not contain a curing agent. The time can be reduced to a 2.5 minute cy~- cle with binder composition having a propylene car- bonate curing agent in a quantity of about 0.35 to 1 wt. %, based on the weight of solids, without losa in durability and other important properties. A second, significant advantage is that the addition of the curing agent increases the tolerance to moig~ ture in the system, Thus, where plywood formed by conventional processes has a moisture content for the face sheets of 1 to 9 wte ¥ pnd a moisture con- tent of 0 to 6 wt. % for the core sheets, if a cur= ing agent is used, the moisture content for the core can be up to 12 wt. ¥ and up to 25 wt. % moisture for the face sheets,

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Even when a higher moisture content is used, a minimal number of blows result, and board properties such as thickness, swell and durability are good with no effect on the test for wood failure, After press- ing and heating, j.e, curing the resin, the moisture content of the rroduct is also generally higher,

Since the system can withatand more moisture when the binder compositions of the present invention are used, it is possible to produce more on-grade panels. It has been found thnt the thicker the heard, the more effective this invention, and the more significant the advantages. 1t is recognized that the compositions of the present invention may be used in preparing products requiring an adhesive or binder other than structural wood products. For example, the compositions may be used as binders for foundry molds or cores.

The invention will be demonstrated by the following examples. In these examples and elsewhere throughout the specification, parts and parcentages are by weight and temperatures are in degrees Celsius unless expressly indicated otherwise. The term "molar ratio" refers to the molar ratio of formal=- dehyde to phenol unless indicated otherwire. All

Brookfield viscosity values recited hereinabove and ad in the appended claims are made with reference to an LVF Brookfield Viecometer using a #2 spindle at 30 rpm and at 25°, unless otherwise specified.

A Method for Making Binder Compositions of

High Stability With A Guring Agent Therein

Example 1

To a 5 gal, reactor equipped with baffles and an impeller powered by a motor were added about 4680 gms of phenol 2nd about 3285 gms of formaldehyde (50% aquecus solution), with stirring at about 80 up to 100 r.p.m. fhe refractive index of the mixture was deter- mined in order to confirm molar ratios. The value was fourd to fall within the renge of about 1.4840 to 1.4860,

About 3240 gms of water were subsequently added and the refractive index redetermined to con- firm the molar ratio, which was found to fall with- in the range of about 1.4350 to 1.4360.

Thereafter, about 540 gms of a 50% sodium hy- droxide solution ware added with stirring and the temperature of the mixture was allowed to increase to about 95% by exotherm. Tha viscosity during reaction of the solution was monitored by comparison wd" to Gardner-Holt bubble standards. About 20 minutes after the addition of NaOH, the mixture had an A-l rating, corresponding to about 30 centipoise.

About 1 hour after the additicn of NaOH, the viscosity inererred to an A-rating (40 centipoise), at which time the mixture was ccoled to ebout 80°¢c. end a second chorre of about 1080 gms a 50% NaOH so- jution was added. The temperature was maintained at about 80°C. during tha exothermic resction. Imme- : 10 diately after the addition of NaOH, nhout 3285 gms. of formaldehyde (50% solution) ware added over about 30 minutes. The refractive index was again measured and found to fall in the renge of 1.4700 to 1.4730.

The temperature of the mixture vas allowed to rise by the heat of exothermic reaction to about 90% near the end of the formaldehyde addition.

Upon completing the addition of formaldehyde, the temperature of the reaction was maintained at 90°C. , providing an increase in viscosity which corres- ponded to an F-rating (140 centipoise). The mixture was then cooled to about 85°¢. and the reaction pro- ceeded at that temperature until a viscosity core responding to en M-rating (320 centipoise) was at- tained.

The addition of about 990 gms of water fol- - 25 =

BAD ORIGINAL 9 vi lowed and the mixture wos allcwed to cool to about 22°. The reaction proceeded at 72°C. providing an increase in viscosity to a P-rating (400 centi- poise).

Phe wicture was then further cooled to 67°C. and an addition-l charge of about 540 gms of S0%

NaOH solution was added. The remction proceeded at about 67°C. The viscosity decreased with tiie addi tion of NaOH to sn H-rating (240 centipoise) with reaction, when & J~rating was obtained, the mixture wag cooled to about 50°C. and about 90 gms of corns- tarch ertender ond about 90 gms of urea were added,

Upon cooling to about 30°C, about 180 gms of propylene carbuunte were injected through the bottom of the 5 gellon reactor, under vacuum, in close proximity to thr impeller, The mixture was allowed to cool to 25°C. nnd the batch was characterized as having & refractive index of about 1.4693, a speci- fic gravity of about 1.204 and a Brookfield vise cosity of about 450 centipoise at 25%. and as de~ termined by a RVF Brookfield Viscometer with a #3 spindle at 20 rpm. A sample of the batch was cured at 100%, snd gelled to a solid in about 13.2 minutes,

After about 40 minutes, about 156 gms of urea - 26 «

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(1% solution) were added. The refractive index vas redetermined to be 1.4700 and the viscosity was about 450 centipoiase as determined above.

A sample of this composition was cured at 100° c.

S and gelled in about 13.6 minutes to form a solid.

The remaining portion of the composition stayed in liquid form for over several hours.

The second addition of urea in this example demonstrated that it is not urea which enhances cure speed.

Urea loes Not gnhance Cure Speed

Example 2

This example demonstrates that when urea is present, cure speeds are not affected. The proce- dure of Example 1 was repeated except that the ini- : tial mixture of phenol, formaldehyde and water was found to have » refractive index of 1.4394, The mixture mfter addition of the second charge of form= aldehyde had a refractive index of about 1l.473h. ’ 20 The process of Example 1 was modified by cooling the mixture to 50°C after a Gardner-Holt viscosity rating of "I" was obtained (220 centipoiee)s

After cooling to 50°C, the quantities of cornstarch, uren and propylene carbonate added were the same,

a ——_— (r 8

The batch was characterized as having a re- fractive index of about 1.4695, a mpecific gravity of 1.204 and a Brookfield viscosity of 440 at 25%. as measured in Example 1, A sarple of the batch gelled to a solid in 13.1 minutes at 100%,

An additional charge of urea (about 1% by weight or about 156 gms) was added to the batch with mixing, A sample of thie composition was gelled to 8 s0lid in shout 13.4 minutes at 100%,

The cemposition remained liquid after seversl hours,

The Presence of Ester-Functionalized

Curing Agents Enhances Cure Speeds

Example 3

This example demonstrates the effectiveness of the curing agents having este. functionality in enhancing cure speed,

The procedure of Example 1 was repeated uti=- lizing the same equipment except that about 4320 gms of phenol were used with 3240 gms of formalde~ hyde to make the initial mixture followed by addje tion of about 3420 Ems of water. The first charge of

NaOH vas 558 gms (50% solution) and the second charge was about 1260 gms. The second charge of formaldehyde -- "28. ko omc, 9

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7 (about 3076 gms of a 50% solution) was added over 20 minutes as in Example le The second charge of water was about 1566 gms and the third charge of

NaOH, SHO gmse

After the desired viscosity of about 240 centipoire uno obtained (J-rating) the mixture wag cooled to abont 30°C. and propylene carbonate (about sh gms, 0.36 wte » pased on total renin) was added.

A specific gravity of 1.198, = refractive index of 1.4610 and 2 Brookfield viscosity of 250 centipoise at 25° Ce were notede A sample Was found to gel in 22.1 minutes . at 100°C. oo Additional propylene carbonate was added to > this mixture (about sh gos) to double the concentra- tion of the original mixture (about 0e73 wt percent based on the total mixture, oT about 1.2 wte percent vased on solids). The Brookfizlf viecosity vas 410 centipcise at 25°c. as measured in Exemple le The specific gravity was 1.196 and the refractive index 1.4635. A sample was gelled in 17.1 minutes at 100°C.

Thier Armonatrates that the ester-functionalized species is an affective curing agent for enhancing cure speedr. - 29 = / 220 omaina g)

EY

Production of Binder Compositions on a

Commercial Scale

The following components were added through the top of an 11,700 gallon reactor equipped with baffles, cooling coils for temperature ccntrol and an impeller powerrd by a 25 h.p. motor, with stirre ing at about 100 r.p.me.! phenol -~ about 2684 gallons} formaldehyde (50% aqueous solution) ~ about 1817 gal- lone. lhe refractive index of the mixture was deter- mined in order to confirm molar ratios. Recycled water (about 215% gnllenn) was then added through the top and the refractive index redetermined.

Thereafter, about 2628 lbs. of NaOH (50% so- lution) were added through the top and an exothermic reaction continued. The temperature was maintained at about 93° to 95°c, by the cooling coils. A Gard- ner=ilolt viscority rating of about "A" was obtained (about 40 centipoise) for the mixture after about 1.5 hours. The raactor contents were cooled to 80°c. and a second charge of about 6614 lbs. of NaOH (50% aqueous solution) was added. Immediately following the addition of HaUH, 1737 gallons of formaldehyde (50% solution) were added. The refractive index wae measured for quality control. The temperature was - 3 - Co oo

BAD ORIGINAL 9 —_ 4 pe allowed to rise to about 90°C. with exothermic re- action until a viscosity rating of "D" was obtained (about 100 centipoise). The mixture was cooled to about 85°C. and the reaction continued. when a viscosity rating of "L" (about 300 centipoise) was obtained, sn mdditional cherge of 987 gallons of water was added and the mixture was cooled further to about 80%:., ‘leaction continued within the mixture to provide a P-rating for the viscosity (about h0O centipoine), after which the mixture was cooled to about 70°C. and additional RaCH (50% golution) was added (mbout 2832 1lbe.), The viscosity decreased to less than an H-rating on the addition of NaOH and, after shout 1 hour, the viscosity approached an

J-rating (270 centipoise), The mixture was cooled to about %0°¢. and cornstarch wes added (about 700 1bs.) followed by prorylene carbonate (about 700 1bs).

The propylene carbonate was injected through the bot- tom of the 11,000 gallon reactor near the impeller with the aid of air pressure (30-40 pei). The entire charging time wan lese than 30 seconds.

The mixture was then cooled to about 25° Ce ‘ and the batch characterized as having a refractive index of about 1.4590, a specific gravity of about 1.194 and a Breokfisld viscority of 345 centipoise [~ Ce - - “» 31 (3AD ORIGINAL 9

Te—— FL

OV i at 2s5%., as determined by an LVF Brookfield Visco- meter with a #2 spindle at 30 rpm. A sample of the batch was cured by heating to 100°C. and galled to a solid in about 17,1 minute,

The remaining batch was transported to a storage tank and rerained in liquid form for over 72 hours.

Uniformity of Product

Example

This example is a repeat of the process used for the production of the stable binder compositions of the present invention on a large scale, and illus- trates the uniformity of product.

The quantilies of reactants snd the equipe ment used in this nxample are the srme as in Example 4 except that about 2724 gallons of phenol ware used instead of the 2634 gallons of Example 4, and the phenol: formaldehyde mixture had e refractive index of about 1.4850. 1n addition, the 2154 gallons of water comnrised 30° recycled water snd 50% fresh water and the refractive index for this mixture was 1.4455.

The procedural variations from Example 4 were as follows. After the first addition of NaOH, the - 32a [SAD ORIGINAL 9) ia >

Lo wt viscosity was allowed to reach slightly higher than an A-rating (Gardner-Holt) and after the second addition of NaOH, formaldehyde was added over a 20 minute period (Refractive Index = 1.470%) and reacted at 90°¢. until an F-reting for viscosity {about 140 centipoine) wars attained.

The mixture was then cooled to about 87° C. and the reaction proceeded to maintain a viscosity corresponding to an M-rating (320 centipoire). The second charge of water wan added (about 987 gallons) the mixture cooled to nbhout 75°, and the reaction proceeded to attain a viscosity slightly higher than an O-rating. The mixture was about 80° Ce. when a a oo rating was ntteired (400 centipoise).

The mixture was then cooled to 67° Ce. followed by addition of the third charge of linGil (50: solu- tion). The reaction then procecded until a viscosity slightly above anu l-rating (220 centipoise) was at- tained.

This mixture was then cooled to 30° Cey 8t which time 700 lbrn. of propylene carbonate were added as described in Example bg

After cooling to 25%¢, the batch was charac- terized as having a refractive index of ahout 1.4595, a specific gravity of about 1.19h and a Brookfield -33 - f (BAD ORIGINAL 9 !

vv vd : viscosity of 400 centipoise at 25%., as measured in Example 4, A sample of the composition was cured and found to pel to a solid in about 17.6 minutes at ahout 100°C. The remaining batch was trannferrved to a storage tank and remained liquid for over 2h hours,

Lff~ciive and Excessive quantities of

Examples 6-9

The {ecllowing examples illustrate that excess quantities of curing agent are unsuitable.

In there examples a resin was prepared in large scale in accordance with the procedures des- cribed in kxnmple 4, A portion of the mixture was removed from the 11,000 gallon reactor and trans- ferred to a 5 gallon reactor equipped as described in Example 1.

For Fxezmples 6 and 7, 18,000 gm samples (about 5 wt. % solids) were removed after the third charge of NaClla These samples were cooled to about 20%. and the viscosity increased to above an N-rating (e2bout 340 centipoise). The mixtures wepe cooled to 30°c. and 63 gme (about 0,35% based on the total weight of resin) of propylene carbonate were added to each mixture in the manner described in Example 1. . ) : gh : cap. oo =

BAD Ria. -— A ( tii - ;

rv 8

For Example 6, the mixture had a Brookfield viscosity of 395 centipoise at 25%., as determined by an RVF Brookfield Viscometer with a #3 spindle at 20 rpm. A specific gravity of 1.198 and a re- fractive index of about 1.470 were determined. A sample gelled in about 21.4 minutes at 100°¢.

For example 7, the mixture had a Brookfield viscosity of 370 centipoise at 25%C., as determined in Example 6, a specific gravity of 1.200 and a re- fractive index of 1.4701. A aample gelled to a so= 14d in 22.0 minutes at 100°C.

About 9,000 gms of the batch from Example 7 was added to a 5 gallon reactor and a second charge of pro- pylene carbonate (about 16 gms) was added, as des= cribed in Example 1, to provide about 0.53 wt. % cure ing agent based on the total weight of resin (about 1.78 wt. % solids). This mixture had a refractive index of 1.4697, a Brookfield viscosity of 550 centi= poise at 25°c., as determined in Example 6, and a specific gravity of 1.153. A sample gelled to a soe 14d in 19.6 minutes at 100°C.

A portion of the mixture (about 250 gms) in the 11,000 gallon reactor was removed just after the addition of the third charge of NaOH and prior to the addition of propylene carbonate. A 95 gm. sample was

- a -__———_—_m—m—mMmnn-—————————————— ee - wu? taken from this 250 gm portion for Example 8 and a second, 99 gm sample was obtained from the 250 gm portion for kxample 9. Each sample was placed withe in a 250 ml beaker and was cooled to about 30° Cc.

Propylene carbonate was added to each with rapid hand-stirring using a wooden spatula. In Example 8, about 5 gms. of propylene carbonate (about 5% by weight based on total resin) was added to the sample of resin and, in Example 9, about 1 gm. of propylene carbonate (about 1% by wt. based on total resin) was added to the rample of resin. After about 30 to 60 sec. of stirring, ench sample was allowed to stand at ame bient temperature (about 25° C)e The sample of Exam- ple 8 had gelled to a solid within less than 3 minutes. At the same time, the sample of Example 9 remained a viscous liquid for several hours.

Long Term Stability

Examples 10-12

These examples demonstrate the long term sta~ bility of the binder compositions of the present in- vention.

The equipment described in Example 4 was used to make the large volumes of binder composition for

Examples 10, 11, and 12.

In each of Examples 10-12, about 2898 gallons -3- en ORIGINAL 9

Lo of phenol were used and about 1867 gallons of forme aldehyde (50% aqueous solution). The refractive in- dex was checked to be between 1.4865 and 1.4855.

About 2074 gallons of fresh water were used in Exam- ples 10 end 11 while the same volume of recycled water was used in Example 12. The refractive index was checked again and about 2880 lbs. of NaOH (50% golution) were added. The reaction proceeded at from 73° to 95°C. to obtain an A-rating for viscosity (Gardner-Holt), after which the reaction mixture was cooled to 80°C. and a second charge of 5760 1bs. NaOH, followed by 1987 gallons of formaldehyde, were added : “to the mixture for each example. Thé refrattiveé index was checked at about 1.4700 to 1.4750, The reaction was allowed to proceed at 90°%¢. A D-rating for vis- cosity was attained for Example 10, a G-rating for

Example 11 and an F-rating for Example 12. The re- action mixture was then cooled to about 85° c. and the viscosity increased to a K-rating for Example 10, an L-rating for Example 11 and a G-rating for Example 12. About 621 gallons of water were added to each re- action mixture. Each mixture was cooled to 80° c and each obtained a p-rating for viscosity. Additional

NaOH (50% ecolution) was added (about 2880 lbs.) after a temperature of 70%. was obtained. Reaction pro-

ceeded in each mixture to a J-rating for viscosity, after which about 240 lbs. of cornstarch and 720 lbs. of urea were added at about 50°C. Each mixe ture was then cooled to 30°C, and about 700 lbs. of propylene carbonate were added to each of ExampleslO4 11 and 12.

Upon cooling to 25°¢, each mixture was cha racterized.

Example 10 showed about a 1.4678 refractive index, a 1,202 specific gravity and an initial sample showed a Brookfield viscosity of 430 centipoise at 25°%C., as determined by an LVF Brookfield Viscometer with a #2 spindle at 30 rpm. A sample gelled in 16 minutes at 100°C. Another sample was retained (about 100 ml). After 8 days, this retained sample was found to have a Brookfield viscosity of about 750 centie poise at 25%. , as determined by an RVF Brookfield viscometer with a #4 spindle at 20 rpms A portion of this sample was cured at 100°C, and found to gel in about 14.4 minutes.

Example 11 showed a 1.4670 refractive index, a 1.200 specific gravity and a Brookfield viscosity of about 345 centipoise at 25%c., as determined for the initial sample of Example 10. A sample was cured at 100°C. and found to gel in 16.6 minutes. Another 38 Co a sample was retained (about 100 ml) for 2 days.

This retained sample had a Brookfield viscosity of about 440 centipoise at 25°C. on the second day, as determined for the retained sample of Examples 10.

Example 12 showed a value of 1.4663 for the refractive index, a 1.200 specific gravity and a

Brookfield viscosity of 340 centipoise at 25°%C., as determined for the initial sample of Example 10. A sample was cured at 100°C. and found to gel in about 17.5 minutes. Another sample was retained (about 100 ml) for 5 days. This retained sample had a Brooke field viscosity of about 560 centipoise at 25° Ce on the fifth day, as determined for the retained sample of Example 10.

These examples demonstrate there is a slight {ncrease in viscosity during storage; however, the liquids had not gelled and were still useful, The . viscosity of these mixtures remains sufficiently low to permit easy handling within conventional equipe ment, even after storage beyond 24 hours,

High Strength Cure for High Moisture Solids

Example 13

This example demonstrates that the binder com- positions of the present invention provide suitable strength for binding high moisture solids.

- wt

An adhesive mix for plywood was made from the binder formulation prepared in accordance with Exam- ple 3 by adding the following ingredients to a high shear (speed) mixer:

Binder composition 1400 gms. 58.8 wt % (based on the total weight of adhesive)

Furafil (at 5% m.c.) extender 200 gms. 8.4 wt, % wheat Flomr (at 11% mec.) extender 1500 gms, 6.3 wt, %

Sodium Hydroxide 80 gms. 3.3 wte % {50% solution) water 550 gms. 23.2 wte ¥ 2380 gms. 100 wt. %

Board Manufacturing

Veneers of about 1/8" were cut into 12" by 12" panels and their moisture content was checked. Faces generally have about a 14% average moisture and cores generally have an 8% average moisture. The adhesive was applied with a roller coater using a standard glue spread commonly used in the manufacture of plywood.

A glue spread of about $8 to 60 1lbs,/1000 £42 of double glue line is generally used,

The panels were laid-up and prepressed for - 40 = or

OV

Le about 4-6 minutes followed by hot-pressing for a time period of from 2 1/2 to 3 1/2 minutes. The following gluing conditions were used

Thickness 1/2 inch

No. of Flies b

Press Temperature 315°F. (157°¢)

Glue Spread 58 to 60 1bs/1000 £12 of double glue line (M.D.G.L.)

Assembly Time 10 to 60 minutes

Mix Solids 58,3% by weight

Resin Solids } in Nix 26.5 wt. % ) Mix Viscosity 3000 to 7000 cps

Applicator Roll Coater

Veneer Moisture

Content:

Faces 14% average moisture, 9-22% range

Cores 8% average moisture, 5-12% range

After the boards were hot pressed, they were cooled to ambient temperature. Adhesion was tested by separating the glued panels with a square knife at the corners of the plys and at the middle of an edge. All glueline separations of veneer plies con- tained at least 85% wood failure.

Plywood boards were made from the large scale - hl -

GW

HU batches of Examples 4 and 5 and all boards tested passed commercial standarde and approval by the

American Plywood Amssociation.

Other Effective Curing Agents

Examples 14 and 15

These examples are presented to demonstrate the efficacy of curing agents other than propylene carbonate,

The procedure of Example 1 is substantially repeated, except that 180 gms of gamma-butyrolactone and of triacctin (glycerol triacetate) (Examples 14 and 15, respectively) are used in lieu of propylene carbonate. Acceptsble results are expected for each parameter measured in Example 1 and the binder com- position is expected to have acceptable stability.

Potassium Phenol-Formaldehyde Resins

EXample 16

This example demonstrates that potassium hy- droxide-condensed resins may be used in connection with this invention,

The procedure of Example 1 is again substantial- ly followed except that three potassium hydroxide charges are omployed in lieu of the sodium hydroxide charges. In each case, approximately 50% more of i 25 potassium hydroxide is used relative to the sodium

¢V"

Tv hydroxide. Propylene cerbonante is again used,

Acceptable valuen for each parameter reassured in

Example 1 and acceptable stability of the binder composition are ngain expected. while the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications. This application is intended to cover any variations, uses or adaptations of the in- vention following, in general, the principles of the {nvention, and including such departures from the

Lo . present disclosure as come within known and customary practice within the art to which the invention per- tains. - hi -

Claims (1)

1. qu WHAT IS CLAIMED IS:

   l. A latently curable alkaline binder com- position sufficiently stable to remain in liquid form at ambient temperature for at least 24 hours and sufficiently reactive to gel upon heating to a temperature above 100°¢. comprising in admixturej (a) an alkaline condensed phenolic resin solution capable of binding a network of soe 1ids upon gelation wherein said resin has a viscosity of less than about 1500 centipoise at 25%. and average molecular weight of from about 700 to about 20003 and 3 (b} an amount of curing agent wherein said curing agent has at least one ester functional group and wherein the amount of said curing agent is from 0.1% up to 5% by weight based on total solids of the binder composition.

   ?. A binder composition as in Claim 1 wherein the alkaline condensed phenolic remin is the reaction product of a phenol and formaldehyde, J

   - 3. A binder composition as in Claim 2 wherein said resin is the condensation product of a phenol bh a and formaldehyde nnd the phenol: formaldehyde molar ratio falls within the range of 1:1 to 1l:3.1. 4, A binder composition as in Claim 3 where~ in the solids content of the phenoli resin solution is from about 40 to 75% by weight and the viscosity of said phenolic resin solution is less than about 1500 centipoise at 25°c. 5, A binder composition as in Claim 1 wherein the phenolic resin is condensed with an alkali selected from the group consisting of potassium hydroxide, so- dium hydroxide and mixtures thereof, and the alkali- nity content, based on sodium hydroxide, is from 1% to 15% by weight of said resin solution.

   6. A binder composition as in Claim 5 wherein the alkaline condensed phenolic resin has a weight average molecular weight of from about 700 to about 2200.

   7. A binder composition as in Claim 1 wherein the alkaline condensed phenolic resin is capable of bonding solids selected from the group consisting of grenular refractory material and lignocellulosic material.

   8. A binder composition as in Claim 7 wherein wr" the granular refractory material is selected from the group consisting of alumina, magnesia, zircon, silice sand, nuartz, chromite sand, zircon sand and olivine sand, and the lignocellulosic material is selected from the group consisting of wood veneer, wood fibers, wood ¥afers, wood shavings, wood chips, wood flekes, mand wood particlea. 9+ A 1lntently curable slkaline binder com= position sufficiently stable to remain in liquid form at ambiant temperature for at leeat 24 hours and sufficiently reactive to gel upon heating to a temperature above about 100°C. comprising in admixe tures (a) sn alkaline condensed phenol-fornme aldehyde resin solution having a phenol: formaldehyde molar ratio within the range of 1 to 1l:3.1, a solids content of from about 40 to 75% by weight, a viscosity of from about 700 to about 1500 centie poise at 25%, an alkalinity content, based on soe dium hydroxide, of from about 1¥ to 15% by weight of said resin solution, an average molecular weight of from about 700 to about 2000 wherein said alkali is selected from the group consisting of potassium hydroxide, sodium hydroxide and mixtures thereof and oo . 46 =

   Vt be (b) an amount of curing agent dispersed in assoid alksline condensed phenol-formaldes hyde resin polution wher-in said curing agent has at lenst one ester functional group and wherein the amount of said curing agent is from about 0.1% up to 5% by weight based on total molids of the binder.

   10. A binder composition as in Claim 1 where- in the curing arent is nelected from the group cone Get faa 10 aisting of lactones, carboxylic acid esters, ore ganic carbonates and mixtures thereof,

   11. A binder composition as in Claim 10 where- in the curing agent hae from 4 to 12 carbon atoms.

   12. A binder composition as in Claim 9 whereine the curing scent hac from & to 12 carbon atoms.

   13. A binder composition as in Claim 11 where- in the reactivity of the curing agent is equal to or lass than the reactivity of propylene carbonate. 14, A birder composition ar in Claim 12 where- in the reactivity of the curing agent is equal to or less than the reactivity of propylene carbonate,

   15. A binder composition as in Claim 1 wheree BA LP ORIGIN, 7 — Lg - 49 - 4

   = — = —_— 8 in the curing agent is selected from the group cone sisting of propylene carbonate, triacetin and gamma butyrolactone.

   16. A binder composition as in Claim 9 where- S in the curing agent is selected from the group cone ~ sisting of propylene carbonate, triacetin and gamma- butyrolactone,

   17. A latently curable binder composition comprising in admixture: . (a) an alkaline condensed phenoleform= aldehyde resin solution having a phenol: forme aldehyde molar ratio in the range of 1:1 to

   1:3.1, colids content in the range of about hox to 75% by weight, an alkalinity content, based on sodium hydroxide, of about 1% to 15% by weight of resin solution, a viscosity of less than about 1500 centipoisge at 25° Ce and an average molecular weight of from about 700 to about 2000 wherein said alkali is selected from the group consisting of sodium hydroxide, potassium hydroxide and mixtures thereof} Lo (b) 2n amount of a curing agent wherein said curing agent has 4 to 12 carbon atoms wherein grid curing agent has a reactivity - hg w

   Yo qu less then or equal to the reactivity propy= lene carbonate, wherein said curing agent is selected from the group consisting of lactones, carboxylic acid eaters, organic carbonates and mixtures thereof} and wherein the amount ofsaid curing agent 1s from O.1% up to 5% by waight based on total solids of the binder solution, 18, A cemposition as in Claim 17 wherein the curing agent is selected from the group coneiating of butyrolactone, triacetin and propylene carbonate, in a quantity falling in the range of sbout 0.1 wt. per= cent to 1.0 wt. percent, based on total solide of the binder compositions

   19. A composition as jn Claim 1 which remains : in a liquid form for at least 72 hours, at a viscosity Jess than 1000 centipoise.

   20. A composition as jn Claim 17 which addie tionally comprises cornstarch and urea.

   21. A process for preparing a latently cure able binder composition which is sufficiently stable to remain in a 1iquid form at ambient temperature for at least 24 hours and which in sufficiently reactive to gel upon hearing to a temperature above about

   8° 100%, comprising the steps of (a) reacting phenol and formaldehyde in . the presence of aqueous alkali to form a resin in solution, the resin solution having a via= cosity below about 500 cps at 25°; {(b) cooling said resin in solution to a temperature of below about 40°C; (c) agitating the resin solution rapidly; and (d) adding to said resin solution, in a \ region of rapid agitation, an amount of curing agent for the resin solution st a rate of addi- tion wherein the addition of said curing agent is completed with 20-45 seconds; wherein said amount of curing agent added is an amount of from 0.1% to 1% based on the weight of resin solids; and wherein said curing agent has at least one erter functional group and is dis- persible in the resin solution. 22, The process of Claim 21 wherein the curing agent is injected into the resin solution at a pres- sure of shout 30 to 40 psi.

   23. The process of Claim 21 wherein rapid agie tation is provided ty an impeller means within a bafe- ;

   ¢ / le 2h, The process of Claim 23 wherein the cur- ing agent is added below the surface of the resin solution to a region of rapid agitation.

   25. The process of Claim 24 wherein the cur= S ing agent is added in close proximity to the impeller . means. 26, The process of Claim 21 wherein the cure ing agent is added over a period of about 20 to 4s seconds,

   27. The nrocess of Clnim 21 wherein the resin } solution is cooled to a temperature of below about 30°C.

   28. The process of Claim 21 wherein phenol and formaldehyde are reacted in the presence of an aqueous alkali to form a resin in solution, the solue tion having a viscosity in range of about 200 to about LOO cps at 25%.

   29. The process according to Claim 21 com=- prising the additional step of adding cornstarch prior to the addition of curing agent.

   30. A procese as in Claim 21 wherein the phe- nol and formaldehyde are reacted to provide a resin w 51 = BAD ORIGINAL ©, boo

   / Wo 9 { having a phenol: formaldehyde molar ratio of from ‘ about 1:1 to 1:3.1, and said solution comprises from about 40% to 75% by weight solids, has a Brooke field viscosity of from about 200 to 400 centipoise at 25° C. and has an alkalinity content, based on sodium hydroxide, of from about 2.5% to 7%, based on the weight of resin solution, and said alkali is selected from potassium hydroxide and sodium hy- droxide. ‘ '

   31. A process as in Claim 21 wherein the cur= ing agent is selected from propylene carbonate, gamma butyrolactone and triacetin.

   32. A process for preparing a latently curable binder composition which is sufficiently stable to remain in a liquid form at ambient temperature for at least 24 hours and which is sufficiently reactive to gel upon heating to a temperature above about 100°C. comprising the steps of: (a) reacting phenol and formaldehyde £n the presence of aqueous alkali selected from potassium hydroxide and sodium hydroxide to form a resin in solution, said resin having a phenol: formaldehyde molar ratio of from about 1:2.1 to 1:2.8, said resin solution hav- ing an alkalinity content, based on sodium hye ge lr droxide, of about 2.5 to 7%, based on the weight eof resin solution, a solids content in the range of 40 to 60% by weight and a vis- cosity of from 250 to 400 centipoise at 25%. (b) cooling said resin solution to a temperature of below about 30%. , (c) agitating the resin solution rapide ly, and (d) addingto the resin solution a cure ing agent selected from the group consisting of propylene carbonate, triacetin and gamma . butyrolactone in a quantity of from about 0.1 ,

   wt. percent to 1 wt. percent, based on the weight of solids in said binder composition, gaid addition of curing agent being completed within about 20 to 45 seconds. RICHARD D. STRATON DAVID A. PERRY Inventors