PHENOLIC RESIN GLUES FOR PLYWOOD FREDERICK G. S=IWYER lssociate
i n collaboration with
7'. S. HODGIXS m u J. H. ZELLER Keirh h old Chemicals. l n c . . S m ttle. R ash.
Editor
HETIC H E S I \ S
Synrhc.tiv i ~ s i t i glues hecanie roriimt~rrially availabli~ ahout 1835. Their cost, availability, and duraliility ai'c such that thry are likely to displace ot,hcr gluw in oprratioiis \l-hwp volume production justifies thcx installation of the necewarv equipment. In gi.neral, thernioplastic reqins are unsuited for plywood hecau,st: of softrning at high temperatures; therefore, the present discussion is limitctl t o thwe resins that are thermosett,ing in nature. .\Iost of thwe are niadr h y the reaction, under controlled coiiditioris, of forinaldehyde with phriiol, urea, resorcinol, or nic~laiiiine. The: reaction is ai tcd hc>fowit has gonv to (>omplrtiori. The iriteriiirdiate prod , umally an ayucous solution, niay 1 x 3 spray-dried tu a po\vtii.r, concentrated to a viscous liquid, or made into a filni tiy imprrgiiating pap"' (.?). .In idealized vc~ision ui the phenol-ior~iialdeliydertwtioii is giv('ii here as an csample of the rheni-try iiivolrcd i n some of thi. synthetic resin pi~c~l)aratioris.The exact chcnii obsc,ure and controvt=r>ial. Catal! uch as sodium hpdroside or aninioniuni hydroside arv neccassary for the condelisat ion reartiori because of the necessity for a controlled pI3, but structural forniulas cannot be drawn to show esactly how they function. It is known that phenol reacts with formaldehyde under the influence of an alkaline catal>-st to form ort,ho- or para-substituted methplol derivative9 ( 2 ) . For esample, this reaction ma)takr place initially at thcs ortho position of the aromatic ring.
H phenol
Catalyst,
Formaldehyde
OH
Ssligeniti
Control
t'.ttrt.!
Cor T w o Resin Reactors
INDUSTRIAL AND ENGINEERING CHEMISTRY
1012
plywood. l h e molecular structure postulated for this condition involves a thiee-dimensional network ( 2 ) which may bc idealized as follows: I
CH: I
or
The chemistry of phenol-formaldehyde formation may lie summarized as folloivs: The initial reaction of phenols and formaldehyde results in the formation of phenol alcohols, resols of short-chain length, or a rombination of both. These compounds react further to form larger niolecules JThich map be regarded as phenol alcohol joined by methylene linkages. These chains, particularlx in the presence of some slight es-
Vol. 40, No. 6
cess of formaldehyde and a basic catalyst, can be transformed irreversibly into insoluble, infusible material, most probably by condensation ( 1 - 5 ) . Phenolic glues that require temperatures above 210" F. to effect their cure in a reasonable length of time are considered to be high temperature setting. These are usually set by an alkaline hardener. Internicdiate temperature setting phenolic glues (between 80" and 210" F.) are cured by either alkaline or acidic hardeners. However, the nearly neutral or niildly alkaline glues are more common and arc usually preferred bccausc of the poesibility of wood weakehing by strongly acid glues (8). Urea-formaldehyde glues are invariably catalyzed by acids or acid-forming salts. The intermediate temperature setting melamine-formaldehyde glues are catalyzed by acid, but t8he hot press melamine resins usually are neutral. The setting of resorcinol-formaldehyde glues is obtained by adding formaldehyde or paraformaldehydes. These are not cat,alyst,sreally but resinforming ingredients ( 6 ) . FILLERS
The working properties and performance of glues may be modified or improved by adding fillers. Walnut-shell flour is the most commonly used filler, but wheat or rye flour, starch, finely ground resins, Douglas fir bark, vegetable and animal proteins, and inorganic materials have also been used. Although there is no sharp line of distinction between fillers and extenders, it is generally considered that a material is a filler when used as
TABLE I. PROPERTIES OF PLYWOOD ADHESIVES~ Bonding Classification Solvents SR IT
3Iaterial Animal glue
Tater
P
Resistance Ratings Solvents Heat Cold
Fungus
Effectiveness of Bond with Wood
G
31
G
P
E
Starch d u e
dR
TV
P
31
P
P
SR
TV
P
G
AI
31
P P
P
Casein glue Soybean plrir
SR
IT7
P
31
I'
P
P
F
Blood alhuniin glue
31
If-
1\1
G
AI
hI
P
G
Phenol-for inaldehyde
R
A,
K,TT
G
E
G
G
E
1RI
AI H
A , K. TT
E E
E E
E E
E E
E E
E
.i,Ii.Yi.
11
Remarks Very fast s e t ; ease of application; no longer used in plywood; expensive; poor resistance t o water, fungus Weak film; poor x a t e r resistance; no longer used in plywood Poor resistance t o water a n d fungus; abrasive glue line; erratic price and supply Poor resistance t o water a n d fungur: stains thin hardwood veneers; weak joints with dense hardwoods Poor resistance t o fungus; stains thin hardwood veneers: used with phenolics in softwood ulvwood; disaeree. _ able odor Ease of application: acid catalyst corrodes wood; stains thin hardwood \-e"PPPI
E
R
A , TT
E
E
E
E
E
E
31
4,\v
E
E
E
E
E
E
Resnrcinol-phenolfornraldehyde
R. R I
A, E;,J T
E
E
E
E
E
E
Resorcinol-furfural
R
A , \I-
E
E
17
E
E
E
Furfuryl alcohol
R
A
E
E
E
E
E
G
Urea-formaldehyde
H R H
E
E E E
E 31
E E
E E
E
E E E
E
E
Resorcinol-f orinaldehyde
11
G
G
Urea-furfural-fornialdeliyde R
E
11 31
E E
E
E
Nelamine-for nialdehyde
31, H
A , JT
E
E
E
Phenolic-elasto iller
H
CI,
K
E
E
31
G
E
G
Krea-resorcinol
R,31 R ,31. H
G
E
G
G
E
G
E
E
E
E
E
E
Urea-melamine
Code for Bonding Classification SR = Solvent released R = Cured a t rooui ternperaturr (70° to 80° I;.) 31 = Cured a t moderate temperature (1.50' to 200' F.) H = Cured a t elex-ated temperature (27'3' to 310c I..) a
Based on "Adhesives Chart-l94i,"
Code for Solvents
h
= hlcoholr C I = Chlorinated hydrocarbons I< = Ketones
TY
=
Plastics CaraloE Corporation. Y v i \ T o r k (91).
T\-ater Reprinted by permission.
Sta&thin hardnxod veneers Excellent bond strength; requires high heat, stains thin hardwood veneers N o heat o r acid required: high cost limits use in softwood plywood Moderate heat required; n o acid used; high cost limits Lse in softwood plyWood E a w of anolication: stains thin hard-
Good adhesion; acid catalyst deteriorates wood Good adhesion: inert Ease of application; nonstaining Sonstaining; limited neather re4stance Craze resistant low pressure bonding; Iiniited rveather rrsirtance Colorlew: u-ater resistant: relatively high cost limits use in softwood plywood Moderate heat re&tance; excellent for bonding with metals but not used in plywood Better water resistance than urea-for maldehyde, b u t higher cost Better water resistance than urea-for maldehpde. b u t higher cost Code for Rating
E G
= Excellent
F
= Fair
31
P
= = =
Good Moderate Poor
June 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
such and only in a quantity which will improve the quality of the glue joints n-ithout sacrificing durability. The addition of 10 t o 15% of walnut-shell flour to a phenol or resorcinol glue to improve its consistency is an example of the use of fillers ( 5 ) . The current cost of walnut-shell flour in the Pacific Northwest is $63.00 a ton, f.o b. Los Angeles, Calif. (26). Extenders are primarily intended to reduce glue costs: they normally make u p a larger percentage of the glue than fillers. For example, extended urea glues are made by adding 25 to 100yo of cereal flour based on \\eight of dry resin. Sodium bisulfite is sometimes added to the extent of 1 to 2% of the flour weight, to reduce the viscosity by peptizing the gluten, in order to help overcome the differences in flours and reduce the water requirements of the glues (9). Solvents are incorporated, by the manufacturer, in glues marketed in liquid form and are added during the mixing of glues marketed as powders. Water is the most common solvent used. Some glues, however, contain either alcohol or acetone as a solvent or these solvents must be added (usually with water) in preparing the glue for use (6). Figure 1. The fortified urea resin glues were developed to imorove the resistance of the hot press urea resins'to boiling water and to a combination of high temperature and high humidity. This was accomplished by adding melamine or resorcinol resin fortifiers. There appears to be a close correlation between the boil-resistance of the glued joints and the amount of fortifier added. When 40 to 50% of the total weight of glue solids consists of a fortifier, the boil resistance may approach that of melamine, resorcinol, and phenol glues. RESIN GLUE PROPERTIES
Phenol-formaldehyde glues are boilproof, can be soaked indefinitely, and in weather exposure will outlast the wood. The boilproof quality permits steaming of the phenolic bonded plywood to soften i t for bending and forming operations. Extreme resistance to the action of mold and fungi is another important property. These adhesives are easy to apply; complex plywood shapes can be made using phenolic films, sirups, and dry powders. Their cost is lon-for example, phenolic resin in sirup form (40 to 50TCsolids) sells for 10 cents a pound (liquid basis) in tank car quantities delivered to all northwest points. .Idisadvantage of phenolic glues is that they atain thin veneers. Most liquid phenolic glues, which are alkaline in reaction, are applied to the wood plies by means of mechanical spreaders with rubber-covered rolls. On a dry glue weight basis, the glue spreads are normally within the range of 10 to 20 pounds per 1000 square feet of single glue line. These liquid phenolic glues can be used on veneers that have a moisture content as loiv as 1 to 370. Difficulty is likely to be encountered viith blistering of Douglas fir heartwood if the moisture content of the veneer is above 5 to 6% ( 7 ) . The phenolic film glues, because they add no moisture to the wood, give good adhesion on wood containing 8 to 12% moisture ( 6 ) . I n general, when using phenolic glues it is important t o condition the veneers carefully. -1slight residual moisture is necessary to assist in the initial floiv of resin just as it is esposed to the simultaneous action of heat and pressure. With the development of the hot press technique and the increasing use of phenol-formaldehyde resins as plytvood adhesives, there was an insistent demand for a resin glue that could be used to make thin veneers without staining. Urea-formaldehyde glues do not stain because they are light in color. They are available in both liquid and dry powder forms and can be used for hot press or room temperature applications L-rea resin sirups vary in price between 12 and 18 cents per pound in drum or less than carload quantities depending on the solids content and type. Melamine resin adhesives are of recent origin; most of their development has taken place since 1940. The durability of mela-
1013
Exterior Type Douglas Fir Plywood Production in the United States, 1934 through 1947
mine glue joints is similar to that of joints made with phenol resins. Well made melamine glue joint's show excellent resistance to high temperatures, high relative humidity, continuous soaking, cyclic soaking and drying, and to most chemicals, including wood preservatives, fire retardants, and oils. Plies of t,his type of pl., wood do not separate Jvhen exposed to fire (6). Glues based on resorcinol-formaldehyde or resorcinol-paraformaldehyde are developments of the past 5 or 6 years. The limited data available indicate that well made glue joints of this material resemble those made n i t h the phenols and melamines in their resistance to deterioration by moisture, shrinking and swelling stresses, high temperatures, chemicals, and microorganisms. Because of their indicated durability and low setting temperatures, these glues are promising where high curing t'emperaturcs cannot be used but where glue joints resist,act to most' deteriorating factors are desired (10). DOUGLAS FIR PLYWOOD
The vast forests of Douglas fir on the %vestslopes of the Cascades and coastal plains of the Pacific attracted the first plyxvood manufacturer in 1905 (4). Douglas fir plywood now comprises about 95% of the softwood plywood production ( 4 ) , of which 99% (3) comes from 38 plywood plants in Washington, Oregon, and northern California. The growing Canadian industry consists of four large ply1vood mills in British Columbia. It is beyond the scope of this article to discuss the hardwood plyivood industry which is located in southern and southeastern United States. There are two basic types of Douglas fir plywood: the exterior type, commonly referred to as waterproof, or outdoor type, and the interior, or moisture-resistant type intended for indoor applications. There are several appearance grades in each type and except for the grade marking there is little or no difference in the appearance of t.he t,wo basic types. Hovever, there is a vast difference in properties: ext,erior panels are made with phenol-formaldehyde resin adhesives that are completely tvaterproof; t'hey will withstand water, n.eather, boiling, and other environmental abuses. These adhesives are stronger than the viood itself and are, a t least, as durable. Bs phenglic resins must be set under heat and pressure, ~ i i ct..stc,rior type plywood is bonded only in hot' presses, whereas t t i P interior panels may be pressed either hot or cold. The moisture-resistant or interior type of plywood employs any
INDUSTRIAL AND ENGINEERING CHEMISTRY
1014
TABLE 11. I ) O ~ G L A FIR S PLYWOOD PKODT-CTIOS - 1025
Itr~iclitiold ('hc~niirals, Inc.., a syiithcitie rc,sin iiianuI'artiii,(,r 11126, ha., supplird wsin adhrsivc~sto the Pacific S o i , t h i v t ~ t ~ilyn-oc~tl indubtry sinre 1940. The company mairitairitd a s:rltss ttli. and .Gliippcd thta rcxsins from its c~astt~rii pixit,.. 1)ouglas fir ply\vootl demand \vas iricre lleiclilioltl t l v c i t l t d t o iiiiprovr its custom' resin plaiit iii thc iiiicitilr of the ply\vood 1016, the company signet1 il lcast. oii a S:t~ittle,\Yaali,, tvai' p l m ~ t which had pi,rviously turrietl out, ac*tivatrdcarhori. Building of facilitic+ for wsin nianui'acturca on the 16-acr~plot, started i n Sovcnihrr 1046: thr first batrh of rcvin \\-as iiiatltl March 5 , 1947. The present total availahle flooi, -pact' is 34,0111) square fwt: of this area, production occupiw 4347 syuaIt i'tvt : lahoratory 4440; machine shop and niaintonauce 2760: o f i c ~ ~ 3105; scrvicci 1815: and covered storag" 17,332 squaw ! ' ~ ~ ~ ~ t . Figure 2 s h o w plant layout and Figurci 3 is a flon- ,shwt 01' tlrc. production process.
T H R O ~ L H1947
siiivv
(In millions of square feet) 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 193G
153 173 206 276
358 305 233 200 390 384 480 700
1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947
Vol. 40, No. 6
72.5 650 1000 1200 1600
'
1800 1433 1440 117; 1390 1698
.Ilthough Reichhold makes over 600 differcirit r t 4 r i s in all its iiistallations, the Seattle plant makes uuly thoet: nredr~lby I h c t clominant northnest activity-wood processing T a h k TV stioii 3 thew products. \\%~revc~rj)ossiIilt~,tlic raiv riiatci,ials u s ( d i i t iliaking t I I I ' ~ ( \ re ohtaincd froni \vctstthrn soui . Tab113 1- sho\vs t l i t p r t i i i t ~ i i traw mattxrials data for. thr. Stsatt It. plant,
, linrdc~iers,v t c . , a w not inc*lutlcdi i i Ttii)li>\Imause of small quantities involvtd. -111 clir~niical i'aw materials ai,rive rail shipment I)>, t t i ( & Korthcrn Pacific Railroad. There is iiclin,o space for 10 railroad cars. Four cni,.: of diffrrent materials can he unloadrstl TABLE111. DOCGLAS FIRPLYWOOD PRODUCTIOS .\SEI l'i,y\voori .IDHESIVE ivliilr tlvo aria loaded. Three-inch pipi' lines for each liquid are connected to tht, CONRUJIPTIOX-IR~~ tank car and rsplosionproof centrifugal Douglas Fir Plywood Produced phenolic pumps transfer the rnakrial to storagc. Exterior Resin Soybeail Ca>c,iri Other tanks. Insulated steam-traced linea a w Total. type, hdhesire Adhesive.; Adhesives .Idheai\-c+ used for transferring phenol, formaldl>million nullion Consumed. Conannicd. Consumed, Consumed, $9. f t . sq. ft. Million Million Million lIillion hyde, and sodium hydroxide from heatecl i l l , 23) (11, 2 4 ) Lh. ( I I ) 1.h. ( 1 1 ) Lb. ! I f ) Lb. i 1 1 ) tank car to heated insulated storage tanks. Knitrd State, 1698 j84 36,: 23.8 3 9 2.9 The formaldehyde-carrying pipe is mad(, Canada 275 110 J ,0 3,3" O U 1, 0" of aluminum; connections and valves arc Pacific Sort1in.c.t rubber-lined. The storage facilities whi,rh Total 1978 604 41 . 6 27.1" 3 9'h 3 !4" are diked for fire protection, comprist. E-riinared, eleven 25,000-gallon, two 10,000-gallon, and two 5000-gallon tanks. Those uscd for ,
I
production i i i 1917 is sho\vn i n Tahle 111. To eiisurt' quality c.cintro1, all Ihuglas fir I.ly\rood ir made and niarketcd i n a c ~ ~ i i ~ d a i\vith i c i ~ gradtv set forth by t h t b Sational Bureau of Standards ( f ; ) . Iiispcaors in t h e various fact orivs carcfully guard tht' quality of each pawl. In addit ion, the plyivood industi,y through its t r a d r association, Douglas Fir Ply\vootI ;\rsociatiori, niaintairis an inspection and tcxsting depnitnir,nt intt~nded not only t I J ~ S S U I ' I 'thr, pui~c~liasc~r uniform high quality of thr product, but also to w r k with supc'rvisory personnt.1 at each plant t o pi,rfect methods whivli will facilitatci quality as n-cll a. quantity production. Industry i l l spclctors gather random saniplrh i o l i v t w t d in the association 1ahor:itory i n Tacvina, \Vash. ( 1 2 ) .
Figure 2.
Layout of Seattle Plant
June 1948
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
.I,K 1'1, \ST
1015
Phenol
.500.000
T a n k rar
Lrra
?oo,ooo
i'ape r IIR g
\Vatt.r
.5i0.000 c i i . i t . , oc, 100 c u . f t . 10.44 c ~ i . i t . Ib. resin iiiadrr 270.000 a t 7 % 1000 l h .
Cit?
1'tlODl~I''l'~ r.1.
]'I>-nuoil adhe*i\-e:
8000
6002
V-board for paper hose,.: lionding \Vet s t r r n p t h p i a i m I'Iy~vood adhesiT-e Paper and fabric laiiiinatiori.: ivitli wa.3te wood for softhoard and h a r d h o a r d l'alier a n d fabric lainination.: lionding ijaper overlays on p l y r r o o d ; plyiwod adhesix-? Catalyst used with rirea-fornia l l e h y d e for nluinc. don.el ulna. other door part. Catalyst used 11i t t i uren-forinaldehyde f o r e Tata1y.t used w i t h resorciriolc,aral?.>t foriiialdehyde for cold ;erring laininations
Figure 3.
Flow Sheet of Phenolic Resin Glue Process
Iliain-
INDUSTRIAL AND ENGINEERING CHEMISTRY
1016
gages (IS) are used to measure the quantit,ies of reactant,s. This type of gage measures the hydrostatic head of tank liquid by means of a U-tube manometer. One manometer leg is attached to the top of the tank which is vented to the atmosphere; the other leg is connected to a down pipe extending to within 6 inches of the tank bottom. A small pump maintains sufficient air pressure in this pipe just to equal the hydrostatic head. The manometer reading is calibrated to read directly in pounds of liquid, regardless of liquid density. I n the ratio of about 1 mole of phenol to 2 moles of formaldehyde, the materials are then pumped to a reactor. This is a vertical unlined mild steel vessel, 14 feet high on the straight side and 10.5 feet in diameter. The reactor has a capacity of 10,000 gallons and is designed to withstand a pressure range between 45 pounds and complete vacuum. Two of these reactors, which are believed to be the largest in the resin industry, are arranged in parallel so that, different resins can be cooked simultaneously. Cooling or heating within the reactor is obtained by passing water or steam through 300 feet of 3-inch extra heavy steel pipe divided into four parts and manifolded with outlet and inlet. This manifold arrangement, is designed so that there is a h a y s a heating element beneath the liquid surface. This eliminates the polymerization of resin on the coil surfaces during cooking of small batches, or during dehydration of certain urea resins. The uppermost coil is 11 feet above the dished bottom of t,he reactor. Agitation of the resin mix is provided by two 20-inch diameter square pitch propellers located on opposite sides of the reactor and 24 inches off-center. Each is equipped with a 15 h.p. motor. Safety devices on the reactor include a 4-inch vent, 4-inch safety valve, and two 6-inch Monel metal rupture disks. During resin preparation lirge quantities of water are evaporated. A condenser connected to the top of the reactor consists of a 6-pass, u-ater-through-t.ube unit with a condensing area of 1500 square feet. A 6-inch return line permits total reflux of the condensate. MAKING A PHENOLIC RESIN
-1typical phenol-formaldehyde resin for adhesives comprises the following materials, based on an 8000-gallon batch: Phenol, lb. Formaldehyde, 37% s o h , Ib. Sodium hydroxide, 50% soln., lb.
34,780 44,540 1,368
Vol. 40, NO. 6,
The resin mix is now cooled to 35 C. by varying the rate of water through the coils and the vacuum is shut off. This requires 1.5 hours. At this point, 838 pounds of sulfuric acid (66' Bb.) are added to neutralize the resin to a pH of 6.9 to 7.2. The resin is next dehydrated at the boiling point (98" C.) by sending steam through the coils until 26,680 pounds of water are removed. The batch is cooled and filtered or settled to remove the precipitated sodium sulfate. .1ir pressure applied to the reactor for 2 hours transfers the resin to storage tanks by a 3-inch steel pipe. Recording temperature and pressure instruments control all phases of the process within narrow limits. Total elapsed time is 12.5 hours; total yield is 53,000 pounds of resin which represents over 90% of theoretical. Xormal handling losses account for 2% and the remainder consists of loss through the vacuum system, loss of phenol in the exit, water, and loss of some monomer during the dehydration step. Figure 4 s h o m the entire 12.5-hour process as a function of time and temperature. The cooking step for the resin just described required 7 hours. -1similar phenolic resin can be prepared in 6 hours. These short reaction periods are the result of constant development work at the Seattle plant. Previous installat,ions, such as the one at Tuscaloosa, -%la,, require 24 hours to make similar resins in 5000-gallon reactors. Several important factors explain thrir difference: Complete and instantaneous control of the resin batch temperature is of prime importance and unliniited quantities of cold, clean water are available in Seattle for this purpose. This control is necessary for maximum efficiency of the heat, transmission in the reactor coils and in t,he condenser tubes. The additional and all important factor of knorv-how enters inti) all operations. UREA RESIN
Between cooks of different types of resin, the reactor systerli 14 cleaned by boiling with a 2 to 370 sodium hydroxide solution for a half hour. I t is then drained and flushed with Tyater. Under the present one shift operation this cleaning procedure requires 1 day. A typical water-soluble urea-formaldehyde resin comprise< the follon ing materials, based on an 8000-gallon batch: Urea, lb. Formaldehyde, 30% soln., lb. Boric acid, Ib.
17,800 59,250 2,960
The order of addition for these components into the reactor is. formaldehyde, boric acid, urea. This order is important because it is necessary to adjust the pH before and after each addition. When all components are in the reactor, the pH is adjusted
The phenol is pumped from storage to a feed tank where by King pneumatic gages, then '(liarwd to the reactor. The foimaIdeh?dc 0'. ~ ~ follows g e the Although the unimportant, s added after wash out any s. Then the solution is auded. A v ri ,m (18inchesof mercury) 1s maintained by meansof tuibMaterejectors operated by two-stage centrifugal pumps. Steam is sent through the reactor coils and the mix brought to a temperature of 60" C. in 1.5 hours. During the uarm-up period, the chemical condensation reaction becomes highly exothermic. At the 60" C. point, heat is liberated at a rate in excess of 45,000 B t u a minute. The batch is held a t 60" C. for 4 5 hours. Maintenance of the temperature within the narrow limits necessary for making a good resin requires the circulation of cooling water through the Figure 4. Phenolic and Urea Resin Production as a Function of Time an reactor coils, as well as total Temperature reflux a t the corresponding boilProcedure for mnking typical phenolic resin (bottom) and urea resin (top) ingpointof all then aterliberated. it 15 measured accurately
June 1948
1017
INDUSTRIAL AND ENGINEERING CHEMISTRY
The severity of the laboratory inspection is indicated by one of the tests for exterior type fir plywood ( l a ): Test specimens 1 inch wide by 3 inches long are sawed so that the testing loads, when subsequently applied, are directly on t h e glue line. T h e s p e c i m e n s are then boiled in water for 4 hours, followed by drying for 20 hours at a temperature of 145' F. After a second 4-hour boiling period and whik still wet, the pieces are placed individually in a , shear-testing machint, where stress is applied until failure. To be a(*ceptable by the Douglas Fir Plywood Sssociat i o n s t a n d a r d s , t h (, average wood f a i l u r c must be above 85%. hll control tests are completed and evaluated within 48 hours after the resin is made. Only after these quality tests have beer1 performed and the product declared satisfactory, will the shipping department be instructed to fill t'ank cars for rail shipment. About 500,000 pounds of resin under test' can be stored.
TABLE VI.
~
SPECIFICATIOSS FOR RESINS
Diluents Solids content Sp. gr. a t 20' C. Lb./gal. Vficosity
Color Storage life
Phenolic Resin (Plyophen P-398)
Urea Resin (Beckamine P-3G4.k)
\{-at er, ethanol 42 7n 1 171 t o 1 191 9 75 to 9.92 225 to 500 cp. 11.0 to 11.5 Dark red GO days
Water. ethanol 73 t o 77% 1.306 t o 1.320 10.89 to 11.01 330 t o 500 cp. 6.8 t o 7.4 White-opaque 60 days
CoAtrolling Glue Qualitj
TAHLE VII. P-398 tu 7.0 tu 7.8; steam is run through the reactor heating coils; and the mix is heated to 100" C. During this period the pH drops to 4.0 because the condensation reaction removes free urea with formation of di- and trimethylolurea. The mix is refluxed a t atmospheric pressure for 2 hours; then the vacuum is applied to the system until i t attains 28 to 29 inches of mercury. The temperature drops to 40 O C. in less than an hour. These distillation conditions are maintained for about 5 hours until 14,800 pounds of water are removed. The system is shifted to total reflux and cooled to about 30" C.; the pH is adjusted t o 7.2 to 7.4 with 50% sodium hydroxide; and the reactor is vented to atmospheric pressure. Elapsed time is 10 hours; yield is 66,200 pounds of resin sirup (50Oj, solids). Figure 4 also shows the entire 10-hour process as a function of time and temperature. QUALITY CONTROL
Because of the nonhomogeneous nature of a resin product, estensive control testing is necessary to meet esacting specifications. This occupies the full attention of a chemical engineer a t the Seattle plant. Two laborat,ory technicians also test plyn-ood samples t o evaluate the resin glues produced. Current specifications of typical resins are given in Table 1-1. Another sample of the finished resin is processed into a glue and used to make plywood test panels. TJ-pica1 glue formulations are shoxn in Tables VI1 and TTII.
Flus 3Iix Add Mix
Si(:
W-alnut-shell flour (325 mesh) parts
I00
For 3 minutes Water a t 70' F . , p a r t s For 3 minutes
10@ ,
, L.
T.ABLEm I .
INSTRTCTI(I.V.-
P L Y o P i I E N C O L D LIIXIXG
P-398 Plyoulien (phenolic resin) p a r t r
P-364A
BECK.4YIBE LIIXING
.. .
'.
i
I'RCJTIONS
P-364.4 Beckamine (urea resin) parcs
Plus Rlix Add slow-ly Rlix Add
Catalyst ( 5 l h . S H d C l i n 25lb. water) p a r t s
,500
30
For 3 minutes Wheat flour. parts
250
For 5 minutes Water a t 70'
F..p a r t s
230
During an average month's production, 6000 square feet of plywood panels are tested for product evaluation. Bn additional 5000 square feet of plyLYood are submitted for test by Reichhold technical service representatives to determine the effectiveness of the resin glues applied in mills throughout the Sorthwest. Labor requirements for the plant are low. There is only one shift a day. Personnel data are shon-n in Table I S .
I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T.R Y
1018
Vol. 40. No. 6
\v(iods as tops, limbs, bi.olic111niatcsrial, aiid pai,tly defective logs. Of thr, rrmaining two thi1,ds of the log, about one half goes out the wrong end of the processing equipmrnt arid only 35% is utilized ( 2 2 ) . A f r w years ago oiily the large trees were used.
('utting was largely by complt~tcstripping: therefore, the smaller \vvr(~ cut and n-asted. Kecent d(velopments--such as selectivv (nutting, sustaincd 1-ield programs, arid stringent fire previxntioii rulcs-are tiuilding toward a mor(. stahle future supply.
T H E FL-TUHE
I t ic c,stiniattd that thci Sorth\vc.it \vi11 coiisuiiic 100,000,000 *ynth(stic' w n i i i aclhrsivc.s i n 1950. During I047 thc Srat t lr plant productd 12,000,000 pounds of pht.1101-for~iialdehycif., 3,000,000 pounds of urea-iormaldehydc, and 500,000 pounds t r f ' rcsorcinol-formaldeh?.dc rcisin sirups. Extrapolation of prcst'nt production rate's indicates that tht, figures for 1948 w i l l doubl(. t1i1)s.c~of 1c147. In ordrr to rcac.!i the production ratt' o l 3,000,000 pounds of rrsin sirup p i ~ rmonth, which is e,qtiniatc,d for late 1948, thy plant is esp'cted to switch to 7-daj- operatioil. This irici~cascdout put can he attained with thr presrrit eyuipnic'nt , E:xpansion hyorid 1948 will be accompli$hctl by iiistalling adtiiticinal 10,000-g:nllon reactors, identical with thc' t w o iiii\v ustltl. 1 i 0 ~ i i d cof
1 x 7
1-w of 3 continuous process for making rtsains i. not antii8i;)attd. erxl years ago, thc Detroit plant hnilt and operatid a pilot Iitinuouuly. I3c:lausc rhholtl f t ~ l st h t thii
The plywood industry is doing its share in conserving wood: Hig lathcs arr bcirig supplemented by small ones; smaller logs arc' tieing pecsled : and soon the mills may bc reducing the unused part of the core to a piece no larger than a broom handlr (14). \l-aste wood scraps. formerly burned, are now treatcd with thermosetting resins and pressed, and emerge as soft- or hardboards. Short pieces of wood, also formerly burned, are glued togpt,her with phenolic resins t o make doors. This conserves the niorc valuable long pieces. A host of other developments are making dollar products out of 10-cent wood. Any inrrease in the ralue of wood product$ by using waste as a raiy mntcrial is a consrrration measure. i i . r h oil glues and gluing is of intercast to the coriwrvationist hwiusv it makcs possitilt~more complete use' of forest products.
maiiuiacturer is concerned with adht+Avc, rcwarch hccausc products frrquentiy can hi, uwd to roducc~Tart :ind to improw produci quality. The, consumer is intc ( ' a u ~gluw ( ~ anti gluing makc, availatilr products of superior periomianw, appcwancc., convcnicxncr,, and wonom?- (1 ) . ReThe,
gI:icd
fic~ltlof twnicndoua sropc~and infinitc ramifications. L I T E H 4 TUR E C IT El)
rc&i, i t islessflesihlethan a hatchI;(,ttlrsetup.
Tiit, Iieichhold Detroit plant is pursuing an t~xtctisivc~ 1)rograni ot w s t w c h and developni('nt aimcd at making iieiv rcsiw as w l l as improving the, quality of pi'escnt urea?, phvnolics, rwirciriols,
mid nit~lamines. The Scattlv plant i h conc'c~ applying these data to q)t'cific ?;orth\vrst u lopnicnt prograni stressing wsins used i ckitalyxta, hardcnrrs, fillers, anti extrndcw:. 1'hc.riol-~~sor~inol resins a r hcing ~ prepared \vhic.h roiiiI)iri(~t hc, IvatiJrproot'ntw of t h r phenolic. typp and the cold-strtt ing property iiiied at ir ahout, 30 (wits f i t this rworcinol. The product pri a pound, which is half the pi'rwrit pricr of resorcinol rvsiii. This combination rwiii adhesive i,s ospecteri to find \vide appliratioii for picvtv such a- multi-ply timticr structurrs, h a t I i ( ~ t ~ l * and , cold-pat c h t d ply~s!~od. A phr~riol-iorma!di~hydi~ Iwiii adhwivt, plastirizetl \vi1 11 :t viiiyl conipouiitl is heirig twteti for u5e in facing plyivood Ivith shi aluminum. h r l ifisulating panol made of thi,. material c~iiinbinr~c thc~llrar reflec.tirig quality of the nictal ivith thr ply\vootIqtrurt u r d strength. rhyd(3 adhwivi~sart' twiny c.ompiuiidrd i o plyn-ood that is interniediatc~i t 1 propvr01 aiid urea typt's. Lighter c d i i i , , coldset,ting, and i m p r o v d \\-atci.proofiic~si)vvr urva a r e t l l r . iiiiticipated propntirs. Ioii. 1:. Z . . ('hmzicryic Reprint. Series 12 (.Jan. 15, 1945). T. 11.. "hlodrt~n PIy\vnotl," 1). 2 0 . X e w Torli, Pitman ,(.'(lr[,,, 1942. I
Plastic.- ICtiryclopedia Charta,
Proctor, P. B., C'hemui.gir P a p e r s . 1946, No. fi,517. TirnhPrmun, 49, x o . :3.40 (19481 I h i d . , p. 41. I h i d . , p.42. Wall-Lundberg Co., Portland agelit foi, Agicide Laboratories, I n c . , Los .ingele.;. Calif. Wood, A . D., and Linn, T. G . . "Plj-woods. Their Development, Manufacture, and .ipplication," p . 79, Brooklyn, S . Y . , Chemical Pub. C o . , 1943.
