Phenolic Resin Adhesive in the Plvwood Industrv J
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Development of phenolic resin adhesives and the technic for using them in the manufacture of plywood has made possible a water-proof bond for plywood. The most recent of a series of developments in the use of phenolic resin adhesives for plywood is the new method of applying the resin through the medium of a colloidal suspension of the adhesive in water. Courtesy, Haskelite Manufacturing C o m p a n y
DISPLAY BACKGROUNDS OF HASKELITE, A PHEAOLICRESIN-BONDED M4TERI4L, AT THE GENER4L MOTORS SALON,1933 L. 4. SONT.4G AND A. J. NORTON i n t r o d u c t ion of new a 11d improved in the manufacture of General Plastics, Inc., adhesives. phenol-formaldehyde Plywood is made by two general proNorth Tonawanda, N. Y. resins and in the methods (6, 22) of apcedures-cold pressing and hot pressing. plying them as adhesives make possible The cold press process consists of spreadthe practical use of thermosetting resins in the manufacture ing the adhesive on both sides of the alternate inner plie. of plywood. It has long been known that resins of this type and laying the other veneers in place. Usually a large numgive mater-proof, vermin-proof, and weather-proof bonds (1, ber of panels are assembled in this way into a bundle, placed 2, 14, l 5 ) , but the cost of the resins and expeneive methods in a hydraulic press, clamped, and allowed to set from a few of application prohibited their exploitation. Dent’s method hours to a day, after which the panels are stickered and dried. (5, 6) of spreading from water emulsions makes it possible to In hot pressing, the panels are cured and pressed simultaneobtain good bonds a t a reasonable cost. This, in turn, makes ously between heated platens. Hot pressing is not generally available a new material of construction for the architect, used for ordinary adhesives, but with thermosetting adhesives engineer, and designer. It is now possible to produce large it is necessary in order to develop the inertness and resistance uniform panels as strong and durable as lumber and mlth the of the adhesive. In Europe the hot pressing of panels with ease of erection and the beauty of wood. casein and blood albumin glues has long been practiced. The term “plywood” as used here means a material of There may be three, five, seven, or some other number ut construction which consists of several relatively thin layers plies in a panel, but it is usually an odd number, frequently of wood bonded together or bonded to a lumber core by meanq five. The core may be made up of a single qheet of veneer of some suitable adhesive such that the grain of or may be built of pieces of lumber glued together any one ply is a t right angles to the adjacent ply edgewise. Various kinds of wood are employed, or plies. Plywood construction has been employed but conservation demands that figured woods of for over thirty-five centuries by furniture makers s u b s t a n t i a l v a l u e should be used chiefly for who early recognized the advantages of cutting artistic results and that the less valuable wood valuable wood into thin veneers, thus multiplying should be used for purposes of strength. In the construction of the familiar five-ply (face, crosthe visible s u r f a c e of rare and beautiful grain patterns so attractive in furniture. iilthough for band, core, crossband, back) panel, the grain of furniture making, strength and lasting quality were the crossbands runs perpendicular to the grain of the face and the back, and the grain of the core run5 probably subordinate t o beautiful appearance, the plywood parallel to the face and the back. This alternation of the construction, resisting warping and checking as it does, has grain direction balances the stresses and is the standard preserved many beautiful pieces of antique furniture. Today construction which gives plywood its strength advantage plywood is still important in furniture, but its field of apover solid lumber. plication has widened t o include many other uses through
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ECEST developments
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History of OIde,r l?wnis of Adhesivc
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Prior to the develogineut oE the ~~lietiol-for~nuldeliyde resin glue, the eotnnton adhesives used in the numufactwe of plywood were aninia~,vegetabie, caseill, arid h i i d albuinin glues and several others of less importance. T h o fast t l a t notie oE thcsi?glues is entirely watcr- or rerniiti-prooS has beeit ii serious liandicap t.o ply~~-ood frt,tri aii engineeriirg poiiit of viex. The idea o l uiiiig plienol-forrniildefiy~lc resins to overcome this serious liandicap is not new, hit only rcxeiitly has it heamre econoniieal and Iiractical. 1)arirrg tlie early rlevekqiineut oE ~ ~ l i e ~ i o l - f u r t n a l ~ l ~ ~ ~ y d ~ : resins, their use as u water-pwf h i d for glywoud was suhgestcd (1, 2) bot the high ClJSt of raw riiaterisl ;irid tlw inetliod d application h J n i .wlut,ioris preveuted c x t e i i s i w irniiinercial expluitrrtic~rrat that, time. Yereral gears Inter, tlie dry "film-gliic" rnetlwd (14, 15) of applicathitr was developed. J l c f ~ r ethttt time, pliotioi-foniinldeli~~deresin hail i,eoii dissvlved in alcoliol and applied in the s:ame ~ a y a .tiw ? iiiore c o i m i n i i glues. T b e alcohol was allinred to ev:qair:~tc i d o r e the paiicl was pressed. The ~ o l u t i o t ~had s the rlisiidrantage of soakirig deep iirto the rvood wliicli u . miounts {if resin, stained tlirougir tile wood, and, together li-itli t,Im cost of the a l ~ o h ~made l , it, 8 w r y expensive iiiethod. The film-glue ~rietliodof MeClain eliiitittated tlie woiid stainf a w veneer dinrird after e x i m u i o tor Uo ioinatos. iiig rtnd tile excessivt: use of resin encountered in tiic soltition I i i y l i t : Oidiiiaiy veiiocisd dour panel of standard tliickeem: renter process, and has today becime otic of the succe!,qsfitl ways of completely dcxLrDYed after ClpOBure f"r a0 minutcs. . ~~... .. . ~~. . ___ . . .~ applying pirenol-fortnaldeliyde rosin as a boiid for piyaoid. The cost, OS preparing the film is the chief iiariclicap. lri the film process a piece ol paper is saturat.ed with ail alcoliol roluDevelopment of New Method tion of phenol-foriiraldetlydr resin and then passed tiiriitigh a drier iii which the aicoiiol evaporate&, leaving a sheet of Alter due consideration of tire various inetliods, it appeared film-glue. lii tile construction of a patiel, a sheet oE filtnt,liat a much better process could be developed by meairs of N iulloidal suspension of a rihenol-formaldehyde resin in water. glue or impregnated paper is placed between each of the plies arid tlie asserribly is pressed hetmeen heated platens in a The chief merits of t,liis inetliod are the low cost of ti~anuSai:tiiring tlie glue and the ease rtnd low- cost of application. Iir hydraulic press. Filtn-glue has been largely developed in general, this rriethod coli of dispersing a pheiiol-forriialEurope arid wittiin the last f e v years has been used in tliis ilelryde resin in water, foriniiig a colloid wliicli is tllen spread oount.ry to some extent. iiii botli side.; of the crossbands or core, depending on wliat Several years ago a new process was developed iiiwliicti tlw tlir coiistructioti tiray lie, by means of a glue spreader similar dry powdered resin was sprinkled uniforrrily over the into the one cmnmonly used in spreading animal and yegetable dividual plies of the pnnel wliicli had been wet witlr alcoliol glues. Tlie water, being used merely as a veliiele ti) spread before and alter the resin KRP applied, in le tr
