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A TECHNICAL AND ECONOMIC ASSESSMENT

Pe te r Vajda, President Colmhia Engineering International Ltd.

Vancower , Canada

Abstract

%is paper sumMlrizes the history and technology of structural flakeboard IMnufacture and the currently ongoing research work aimed a t bpmving and/or reducing the axt of the presently marketed products. tive emnanics of the product, or its a m p t i - tive position against softwood plywocd are dis- u s e d and evaluated. It is concluded that structural flakebards present a good opportu- nity to supplement the diminishing softwood plywood supply in the housing construction and saw industrial markets.

!Ihe basic mqara

Firs t , let m make an attempt to clear up SOE uncertainties as to the terminology of "structural grade particleboards" or " f l a k e boards".

Structural grade particleboards are called by saw sources "particleboards" by others "flakeboards" and still by sm others as "waferbard" or " s t r a n M " . A l l these t e r m s refer mainly to the types or kinds of particles which are being used i n the manufacture of an exterior grade reoonstituted wood panel product. We w i l l therefore have t o agree on terminology before atknpk-ing to analyze the technology and emanics of manufacturing these products.

In the follming paper, I propose to use the follming terns:

particles are used as a generic term for any kind of wccd particles be they randan or of specific length, width, thickness parallel to the grain or at right angles to the grain

flakes are particles which are cut parallel to the grain (that is, t k cutting knife is parallel to the grain)

"semi-flakes" or "chip flakes" are flakes cut fran pulp chips by a ring type flakec s i n e the pulp &ips are essent ia l ly cut across the grain, the resulting flakes w i l l also have a cross-grain feature

randcm particles are particles cut fran shavings, sawdust and other m i l l residue, or even chips, by a hamwrmill or hog type macfiine

"wafers ' ' are large, square flakes as used in "waferboard"

"strands" are flakes hose length is a t least 3 to 4 t ines greater than their width (the slenderness ra t io is essen- t ial for orientation)

S a w sources refer t o structural particleboards as s t n l c t u r a l flakeboards mainly because the use of flake-type particles is thought to be essential for the manufacture of an exterior structural grade product. The term structural particleboard is used by those who do not wish to pre-judge the n e d for a specific kind of particle in order to acfiieve structural properties.

As the term "particleboard" is closely associated with the industrial gra& and underlayrnent grade particleboards manufactured at present by the industry wit!! uF resins, for interior applications, for the purposes of differentiation 1 w i l l use in this paper the t e r m structural flakeboards as designating a product which is made w i t h exterior grade resins (PF or other) and having properties suitable for structural and exterior applica- ticms. exclude the possibility that structural properties may be achieved by using ei ther "semi- flakes" or even "randm particles" in say the axe of a structural grade panel.

This terminology is not intended t o

History

Structural grade flakeboard or the idea of structural grade flakeboard has been m u n d for a long time.

A l m o s t a l l the original particleboards i n E u r o p in the late Forties and ear ly Fif t ies w e r e made w i t h flakes and were aired at optimizing bending strength and stiffness. They w e r e hawever manufactured w i t h urea resins and w e r e therefore interior rather than exterior grade products. flakes or randan particles or semi-flakes and the enphasis on surface cfiaracteristics and 3ntemal bond properties cam a t a later date, probably a f te r 1960.

The use of smller

I n North America, one of the f i r s t particleboards introduced was "Novoply" which used flakes i n the surface layers of the board and had potentially structural properties w i t h the exception that it w a s again made w i t h urea resins.

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In the early Fif t ies , Dale Turner working a t the Forest Products Laboratory in Madison, W i s c o n s i n , explored the effect of flake amfiguration cm board properties and shaed that structural or plymod-like properties are adievable w i t h suitable flake canfiguraticm. His paper published in 1954 is probably one of the classics i n N o r t h Amrican particleboard literature.

In 1954, Jim d'Arcy C l a r k e presented a paper to an the concept of a "waferboard" product and a w a f e r b o a r d plant. mrk on this project w a s carried out a t Washin- State University Wood Products Laboratory at Pull.", Washingbn and, by 1958, a waferbard plant w a s i n operation at Sand- point, Idaho.

mseting i n Seattle introducing

The research and p i lo t plant

The introduction of a waferboard or structural flake!xard product in 1958, haever, w a s not t imly. supply of law cost peeler logs and sheathing grade p l y w d . ?he cost advantage of waferboard against sheathing grade plywood was marginal, especially sine the Sandpoint plant w a s located i n the northwest region along w i t h a l l the plymod plants. As a result, the Sandpint plant did not succeed in p e t r a t i n g the structural sheathing grade plywlooa market and the pmduct w a s sold mainly for deaxative end uses.

North An-erica had an abundant

The late Fif t ies and early Sixties also saw the experinentation and p i lo t plant work carried out by Armin Elmendorf, a t t a p t i n g to work out a process fo r the manufacture of oriented flakeboard or, as it is n w called "Oriented S t r a n M " . John Talbot a t Washington State University also carried out s m investigations on flake orientation and the properties of such an oriented flakeboard product.

I n 1963, another waferboard plant w a s bu i l t in Hudson Bay, Saskatchewan, based on Jim C l a r k e ' s process and concept. This venture also failed under its i n i t i a l m e r s h i p and management. It w a s f i r s t taken over by the Govenwnt of Saskatchewan and eventually sold to Madillan B l c e d e l Ltd. of Vanmver, B.C. Under MacMillan B l o e d e l ' s m a g m n t and sales effor ts , the wafertx>ard prcduct found its way into the structural sheathing grade markets in ccanpetition with plywood, mainly based on its freight advantage against West C o a s t plywoOa in Canada' s mi&estern Prairie markets.

The f i r s t applications penetrated by waferkmard in the Prairies were i n the construction and rermdelling of farm buildings, fences and other general u t i l i t y applications. In these applications, the pmduct proved itself to be satisfactory as an exterior grade parel. As a result, it received Cock

approval in the construction of haws and 2 S t o r y apartment buildings. '

In 1969, MaMillan Bloedel doubled its capacity at Hudson Bay, Saskatchewan. 1971 to 1974 period, four mre w a f e r b a r d plants =re built i n Canada - three in

In the

B a y , Ontario and one at Ti.", Ont.

A t the present, waferboard in Canada is produced at a rate of about 500 to 550 PMsf 3/8" per annun rate. duction is sold i n Canada while half is exported to the northeastern and northcentral U n i t e d States. w a f e r b o a r d is about 12% to 13% of Canadian softwood plywood consmption.

About half this pro-

The Canadian mnsmption of

The developent of a structural flakeboard, or a substitute for plywoodr proceeded i n the united States a t a much slaver pace than i n Canada, i n spite of the fact tha t the expansion potential of the U.S. plyklwa industry in tenus of available sof-twood peeler log supply i n the U.S. is mu& mre limited and is probably approaching its ultimate level.

In the early Seventies, Potlatch Forests Inc. b u i l t a p i lo t plant to prove the technical and marketing feasibi l i ty of Oriented S t r a n d w a d based on the Elmendorf process. Using this technology, Potlatch opted for the manufacture of a cross-oriented core board for use in the "facture of a ccmposite flakeboard/plywcod product n m d Plystran. A l s o i n the early Seventies, Blandin Paper a t Grand R a p i d s , Minnesota bu i l t a waferboard plant based on the Clarke process. had considerable start-up diff icul t ies but is now reported t o be i n f u l l production and is marketing the product successfully.

This plant

Time and spa= do not permit the e n w r - a t i o n here of a l l the research and p i lo t plant work that has been carried out in relation to structural board during the past 10 years by various institutions i n N o r t h Amrica. A l l of these mncepts hmever would require considerable additional work i n order to be jumed as fully practical and qel-ational. view of the expected increase i n North Ameri- can dernand for structural grade wood p-1 prcducts coupled w i t h the impending shortage of softwood peeler log supplied i n the U.S. r

the demnd for structural flakebard products in the U.S. should accelerate in the next 5 years resulting in increased plant con~tru* tion and the introdudion of ww structrual products and prcduct variations into the U.S. markets.

In

The Properties and Technology of C-cially Produced Structural Flakeboards

Just what dc we mean by structural flakeboard? In sinple terms, vie are aiming a t a

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prdducrt which a u l d replace exterior sheathing grade (mnstruction grade) plywoOa or the standard CDX grade plywWa marketed i n the U.S. Other applications and end uses are possible, even probable, but in all Likelihood the initial market penetration w i l l have to be made sinply as plywood r e p l a m t .

here the significant praperties of "CDX" plymod. In general and sa"t dpp&tt? terms these are: - modulus of rupture (bending strength) - along the grain 8,000 psi , across the grain 4,000 psi; along the grain 1,200,000 psi , across the grain 500,000 psi; linear expansion (30% to 90% relative hmidity) - along the grain .lo%, across the grain .14%.

It is of interest therefore to s"rize

rrociulus of e las t ic i ty

These are the ge=ral properties of "ax" plywood although it is seldan expressed in this m r . concerned with the quality and efficiency of the glue l ine in terms of glue vs. wood failure in the standard tests. In addition, they are also aimed a t m t r o l l i n g veneer quality in relation to the various plywood grades.

The p l m specifications are mainTy

Using "C" and "D" grade veneers and a standard glue l ine and gluing procedures, as in the CDX grade ( f i r veneer) product, we w i l l get properties sawhat similar to those given above. W e w i l l also get a panel which retains about 60% to 70% of its original strength under severe long term exposure to weather or under tests which sirmlate such exposure.

One should also note that these propr t i e s are achieved a t a panel density of 36 lbs/ft3 or .58 specific gravity.

Can we achieve or approximate these properties w i t h the present structural flakeboards?

The "waferboard" product as it is mufac - tured today does approximate plywood's "acmss the grain" properties. Since it is a product using large, almost square, flakes ("wafers" ) f o m d in a random manner, the product has no "grain" and the properties are the s m in both p a r d directions.

" e r c i a l l y produced waferboard has an m. 0.r. of about 2,500 psi, an m.0.e. of 450,000 psi and a linear expansion of about -15% i n both panel directions. Its strength retention is w e l l over 50% af te r the standard 6 cycle weathering test and f ie ld experience w i t h the product i n exterior applications is excellent. ?he density is 42 Ibs/ft3 or .65 sp g.

Both the Canadian and U.S. Building Codes approved waferboard for use in roof decking and subflooring, but it has to be 1/16" to 1/8" thicker than plywood i n the sane use depending on support spacing.

It should be mted here that waferboard as it is produced a t the present has a powdered phenolic resin content of about 2.5% to 3.0%. A sliFpltly higher resin m t e n t (3.5%) pawder- ed resin or 6% resin solids in liquid form wuld improve all strength properties by a t least 20%. The product hmever has performxl and sold w e l l i n its present f o p and the mufacturers did not see any need to umrade or improve. Probably the market accepted the waferboard prcduct - i n spite of 1mr physical properties -- because it is mre uniform and has less surface defects than plymod made with "C" or I'D" grade vc-rs.

T h e other strucbxal flakebcard product which is nearing introduction i n North Amrica is " S t r w " . It is made with elongated flakes, called "strands" , which are oriented (mchanically) i n the fonning operation. The faces are oriented along the panel direct ion and the core across the width. a developrent of Elrnendorf Research Inc. Potlatch Forests has a semi-production type pi lo t plant operating a t k w i s t o n , Idaho.

The product is

%e ?roperties of "Strandwood" (as achieved in the p i lo t plant and using 5.5 to 6.0% resin solids i n liquid form) are mch closer to plywoOa; along the grain an m.0.r . of 8,000 psi , m.0.e. of 1,000,000 psi and linear expansion of 0.11%; across the grain m.0 . r . of 2,500 psi , m.0.e. 35G,OOO ps i and linear expansion abaut 0.16%. The market aqxrience w i t h the product is limited but it appears to have great pranise.

Aqain, the above properties relate to a density of 42 lbs/ft3 (.65 specific gravity) when using softmods or lm density hardwoods.

We may conclude fm the above that the technolcqy for the manufacture of a semi- structural grade flakeboard, namely "waferboard", exists and is proven by 7 operating plants. Furthemre, the product has been -11 ac(Xpted by both Canadian and U.S. markets. fully structural product inasmuch as it has lmer strength and stiffness properties than CDX plywood. flakeboard Process d e s hmever yield a product whose praperties nearly or fully equal the strength and stiffness properties of plywood. The technology in th i s regard exists, it is similar to the one used i n the manufacture of waferboard and is also proven out i n the p i lo t plant operation of Potlatch a t Lewiston.

Admittedly, waferboard is not a

The strandwood or oriented

It is to be noted here that a l l presently manufactured waferboards are made €ram aspen roundwcd. O t h e r species have been tried i n laboratories and pi lot plants with varying degrees of success. especially heavier density hardwoods, in the manufacture of waferboard therefore cannot be

The use of other Species,

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called a t the present fully operational.

Potlatch at -ism is using "maxi--dlipsll or large &ips made frcm western softmod species A the manufacture of its cmss-oriented OOZ. S E E C ~ S and sare law density hardwood species would be suitable for the mufacture of wafer board or oriented strandwood when using true flakes, wafers or strands which are c u t f run mundwood. 'Ihe sui tabi l i ty of semi-flakes made f run chips or maxi-chips is questionable at the present, especially as it affects dirrrensional stability. A t the pnxient state of tedmology, true flakes (wafers or strands) w i l l have to be used a t least in the surface layers of a structural panel in order to achieve satisfactory strength and dimensional s tab i l i ty properties.

In all probability, all softwood

The Manufacturing Technique of Waferbmrd

Waferboard is mufactuyed by a process which is dlmost identical to the one used for the manufacm of industrial grade flakeboards &nly i n Eurape but also by the early North Amrican flakeboard or particleboard plants.

The w a f e r s or large flakes are made on either clisc or drum type flakers. flaking, the mundwood is put through a thaw pond or mdi t ion ing chamber partially to thaw the mod during the m l d winter mnths i n the mrthem U. S. and Canada but also to soften the wood for better flaking. A l l presently operating waferboard plants debark their wood prior to flaking.

P r i o r to

Most operating wafe-d plants use a disc flaker made by CAE i n Vancouver, B.C. notably G r e a t Lakes Pulp & Paper in Thunder Bay and Waferboard Ltd. i n T h n h s , Ontario use a drum flaker made by Betmer. "Z" type drum flaker would perfom the sarfe function.

S a w ,

The H&ak

D i s c flakers are thought to produce more accurate flakes or wafers and gemrate less fines than drum flakers. ever that the logs be slashed to a fa i r ly accurate 2' length. This slashing operation is very cun-bersane and generates a relatively high peroentage of s m a l l " l i l y pads'' which cannot he used in the flaking operation and are was ted .

length but also accept logs down to 3' or 34' lengths. slashing operation and a mini" reject factor i n snall " l i l y pads". Adnittedly, drun flakers do produce a higher percentage of fines. This -ever is balanced by a mu& lesser percentage of l i l y pad rejects. D r m flakers also have a m& higher output capacity than disc flakers and are therefore mnsidered to be a mre practical machine for actual plant operations.

They do require hm-

flakers can use logs up to 54" in

This results i n a less cmrrbersm

The H a n b a k YJ" type flakers capable of, accepting tree length logs for flaking are an interesting alternative for the mufac tu re of flakes or "wafers" . These machines are used extensively in Eurape but have not been selec- ted by North Amrican waferboard or s t r a n M plants to date.

The flakes are dried i n ODnVentional particleboard dryers of the 3 pass or single pass drcnn type (Hei l , ME€, Guaranty Perfor - mance). Up to the present, these dryers have been f i red by natural gas or oil. N m , mt plants are rapidly converting to the f i r ing of t r im w a s t e and fines w i t h the resultant and w e l l knm misture aontml, f i r e hazard and emission control problems.

'

The binning of dry or w e t flakes or w a f e r s must be given specid attention since the flakes or w a f e r s bind or bridge'in bins to a mudl greater extent that particles. Hofft H type bins, or similar Units, have proven to be the mt satisfactory an3 least troublesm in the b-g and feeding of flakes, wafers and s t r a d s .

Miller

A l l w a f e r i x w d plants use a large, s l w l y rotating drum for the blending operatian, par t ia l ly i n order to prevent an excessive breaking cr splitting of the flakes and/or wafers. The manufacture of w a f e r b a d does require that the large wafers "sin as intact as possible throughout the manufacturing operation, par t ia l ly to E t a i n the typical wafertxwrd-like appearance of the product for reasons of marketability but also i n order to " i z e resin consuption. smll blenders used i n the manufacture of particleboards are thought to cause excessive wafer spl i t t ing and higher resin r e q u i m t s . Unquestionalby, high speed blenders do cause wafer breakup. The contention that as a result of this , resin consumption would increase significantly is however questionable.

The high speed

Potiat& a t m i s t o n in the mufac ture of the mss-Orimted board does use high speed blenders of the Keyston type in connection with liquid phenol resin. Here, the breakup of the larger flakes into strands is desirable. It is r e p r t e d that the fines and short strands generated by this high speed blender are presently higher than intended. %sin amsunption hawever is a highly acceptable 54 to 6% solids.

The f i r s t waferboard plants used a fo&g machine specially designed by Jim Clarke for the forming of w a f e r s . B l c e d e l and Weldwood of Canada installed a s d a t mre conventional f o m r designed a d manufactured by D u r a in Vanmuver, B.C. The G r e a t Lakes Paper plant at Thunder my and Waferboard Ltd. a t Tirmcins use a sawwhat modified Wurtex forming machine from Germany-

Later, Ma&iillan

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' A W t any of the European forming md-hes (Wurtex, Schenck, Bism, Fahrni) are thought to be suitable for the forming of w a f e r s , flakes or strands since they were originally designed fo r the fonning of relatively large flakes. Some a d j u s m t s and modifications i n these formers waild hme to be inplemntea to handle the different flake sizes. Potlatch uses a specially designed noss-orienter and f o m r for the manufacture of their mss-oriented axe board. strandmod or oriented flakeboard, all of the above n a n d forming machines wwld be suitable i f equipped with an orienting device.

For the forming of oriented

A t the present, three basic orienters are available. orienter designed and patented by ElnEndorf and currently manufactured by Bison in Germany. The second is an electrical orienter manufac tured and supplied by Voltage Systems Inc. of Portland, Oxegon. been successfully tested i n p i lo t plant operations although neither has been proven in actual cnmercial plant operations. The third orienting device is the cross-orienter designed by Potlatch and cun-ently manufactured ard supplied by Ledcenby of Seattle, Washington. This is the mly orienter i n actual 24 hours/ day plant operation in North America.

The f i r s t one is a mchanical type

Both these orienters have

It should be noted h m that the electrical orienter supplied by Voltage S y s t m s is repop ted to have been installed in 2 operating plants in Europe and is sucocssfully orienting industrial grade flakeboard made with urea resin.

The m a t handling and pressing operation of waferbard and strandmod is m o r n 4 by the ccnventional caul system coupled w i t h the nulti-apening press, loader and unloader unit. Specific press pressures required are i n the order of 500 to 600 psi. of waferhard using powdered phenolic resin, press tenperatures i n excess of 4009 are mcessary for the achievcmmt of satisfactory board properties and acu=ptable curing tin?? cycles. I", when using liquid phenols, 1-r press temperatures (say 350 to 3750F) a

For the mufacture

The swing e q u i p n t used by waferbard or s t r a " d plants is similar to that used i n the manufacture of industrial particleboard. Presently operating waferbard plants do not have sanders as the pressing operations are sufficiently accurate to yield an unsanded product within the required and acceptable thickness toleranas. that i n the future structural flakeboards, waferbard or strandwood products w i l l find their way into applications where thickness variations m y have to be keptwithin closer limits. Caxeqwntly, future plants may have to install sanders.

It is highly probable

The above w i l l serve to hi@li*t the manufacturing techniques applied i n the pro - ductim of w a f a b o a r d , especially inasmuch as they differ fran the mventional particleboard manufacturing tedmiques.

current D e V e l O ~ t s

A t the present, a substantial m u n t of research is being carried out dealing w i t h the mdifications of and hpmvarents to the basic structural flakeboard mept. Investigations are being carried out w i t h regard to the use of different mod species, various board mnstruction and configuration, new mthods of flaking and the use of new and different resins and resin extenders. of this author, the mt significant work of rather M a t e interest includes the following:

To the knowledge

1. The use of semi-flakes made from whole tree &ips or chipped forestry w a s t e and logging slash in the mufac ture of structural board products. This is an extensive project carried out by the Forest Products laboratory a t Madison, Wisconsin.

2. Mike H u n t ' s project a t Pixdue University in Indiana dealing with the ccnceptual design of a 1-1/8" thick roof deck product made fran red oak flakes.

3. ?he manufacture of flakes by mans of a shaping lathe carried aut by Pe te r Koch of the Forest SeMce i n Louisiana.

The use of isocyanate resins in the mufacture of a structural exterior grade flakeboard products. This work is being carried out by a nuher of researders in a nuher of Laboratories.

4 .

5. The use of dried and powdered coniferous foliage as an extender to phenolic resins in the manufacture of w a f e r board (and plywood) carried out by Suezone Chw at the Western Forest Pmducts Laboratory in Vancouver, B.C.

Progress reports have been received on a l l of these projects a t various FPRS m t i n g s and a t the Particleboard Symposium a t Pullman. lhey are of significance because they are at-ting to achieve substantial savings i n either wood casts or resin costs i n the m u - facture of structural flak- products and would also resul t in the greater utilization of the existing North

Space does not pennit a detailed evalua-

forest resource

tion of these projects. reader is referred to the reports published in the FPFS Journals and the proceedings of the Pullman Particleboard Symposium.

For detail , the

431

The author did however prepare conceptual plant designs and capital cost estimates for plants turning out a structural grade flakeboard product as determined by the investigations of the Forest products Laboratory a t Madison. therefore to report here i n sunmary form on the results of th i s study.

It is ansidered to be appropriate

Conceptual Plant Designs for the Manufacture of Structural Flakeboards as Devekped by the Forest Products Labaratory - Madison, Wisconsin

The essential finding of the Madison resear& work w a s that a structural grade flakeboard of acceptable properties my be mufactured by using semi-flakes ma& f m whole tree &ips or chipped f o r e s t q w a s t e in the axe of the board and true flakes made f m ra"d i n the face. In other words, it was found that the use of "chip flakes" or "Semi- flakes" in the mre would e t i n an insig- nificant deterioration of strength ard dimensional s tab i l i ty praperties when measured against similar properties of a baard made entirely f r a n true xomciwcod flakes.

Based on this finding, a board construction w a s devised mnsisting of 60% "chip flakes" to be plaaed i n the core of the board and 40% true flakes to be used in the face layers of the board. As a resul t , the raw material supply oonditions set out for the plant design were as follows:

1. 40% of raw material demand in the form of tree length logs; 60% of the demand i n the form of whole tree chips

2. 40% of the demand in true flakes fran a shaping lathe operaticm; 60% of the demand i n who le tree chips

The plants w e r e designed for 4 differing output capacities:

50 m f 3/8" per a"

0100 W f 3/8" per annum

0150 mf 3/8" per annum

0 200 MMsf 3/8" per annum

(about 35,000 O.D. tons/year)




A nutber of suitable press sizes were t o be ms ide red for ea& plant Output.

Later, i n the course of the study, it w a s decided to include a wood supply situation consisting of 100% true flakes resulting from a shaping lathe operation for the smallest output capacity plants.

I n order to deal w i t h the great n m r of variables, the plant w a s broken dam into

'

apprapriate sections su& as the raw material handling and flaking section, the wing and blending section and the fonning and pressing section. The raw material handling and flaking sectim was designed to handle and/or flake each raw material form such as shaping lathe flakes, whole tree logs and whole tree or forestry chips. Each handling and flaking section was designed to handle and flake the various raw materials at the designakd plant capacities. Similarly, the drying an3 blending section w a s designed to handle the material flow a t the designated plant capacities. The forming and pressing sectim w a s also designed for the designated plant outputs a t a number of press sizes and configur- ations.

Figures 1, 2 and 3 shcw the basic section flow sheets for the handling and/or flaking of shaping lathe flakes, whole tree logs and whole tree &ips or forestry chips, respectively.

Figures 4 and 5 show the basic section flw sheets for the drying ad blending of the raw materials. The drying and blending section flow sheet DB1 refers to the use of 100% shaping lathe flakes a t the 50 MMsf 3/8" per annum output capacity. refers to the raw material inpt andi t ions of 40% flakes in the face (either fran whole tree logs or lathe flakes) and 60% chip flakes in the axe. and the size of the bins and blenders are varied depsnding on p h t output. Similarly, the nupnber of ring flakers i n Figure 3 ('I* WF3) is also varied deperdhg on plant output (one flaker a t the lmest output and 4 flakers at the highest output).

Flow sheet DE32

The nurtber of dryers and screens

In the case of the whole tree length log supply and drum flaking (Figure 21, the smallest available drum flaker oonsidered ta be of practical use in an operating plant had sufficient capacity to handle the output of the largest unit. ?is a result, the s m flow sheet and the sarne nunher of flak- apply to all plant outputs; only the size of the soaking ponds or anditioning chanbers is varied d e w g on plant output.

In the case of the shaping lathe flake supply andi t ion, no flakers are ~ a e s s a r y . It is ass& here that the flakes w i l l be prepared by adjacent aperations "Ufacturing hardwood cants or possibly peeling veneer a d the shaping lathe flakes are a by-product of these operations to be delivered by truck to the board plant.

Figure 6 shows the forming and pressing f low sheet which is applicable to al l plant capacities and press amfigurations as only

432

‘ &e size of unit is varied dependjng on pmss amfiguration and output capacity.

Using these basic section flw sheets, a total plant f l w sheet may be devised for all mod supply amditions and at all plant outqut capacities. Figures 7, 8 and 9.

the plants (ba& fines and board trim) would be used as the fuel for the dqers and the boiler. About 50% to 60% of the fuel -?3=- inents are self-generated. requirerents is made up by purchased bark or hog fuel. Alternately, coal a x l d be used for making up the shorhge i n the fuel demand of the boiler. The flow sheets related to the plant waste util ization as fuel in the dryers and the boiler an= alsoshawnin Figmxi 7 , 8 and 9 .

Examples of these are shm i n

It was ass& that the w a s t e genzraed by

The shortage in fuel.

Capi ta l Costs

Based on the plant design and flw sheets described abave, plant designs =re prepand and equipmt msts, building 00s- and plant amstruction costs were estimated.

Table 1 s h m the s u “ r y of capital msts at t h various output capacities and press amfigurations. northern and southern locations, taking into “sideration @ p e n t and building require- mts suited to northern and southern climtes.

Each plant w a s designed for

Table 2 s h m the s a capital costs on a per uni t of output basis for the purpose of cxxnparison.

The Tables shw that the use of lathe flakes results in considerable savings i n capital mts a t all plant capacities against the use of tree length logs for the manufacture of true flakes. Since lathe flakes arrive a t the plant prepared, ready for drying, their use w i l l also resul t in significant savings in processing and manufacturing axts.

The availability of lathe flakes i n ade- quate quantities and in any given location may be questioned. or foresee the cost of such lathe flakes to a prcposed board plant or, i n other wrds, the price which may be acoeptable to a mufac- turer producing the lathe flakes as a by- product. A t any rate, it was assumed that by providing a use for such a w a s t e product of a hardwood lumber or furniture CQnPonent manufacbxer such operations would be en- raged and rendered emnanical. of lathe flakes fmn softwoods was not con- sidered to be an eoonanical alternative since the saw material could also be turned into pulp chips for which a pulp m i l l would normally pay a nu& higher price than the board plant.

I t is also d i f f icu l t to project

The mufac ture

For the sam reasons, i n a southern lcca- tion any kind of structural flakeboard plant is unlikely to be supplied w i t h sofbmcd raw material. mis t s mainly of Southern pine and mixed ha&mods. util ized for the manufa- of l-, plywood and pulp. m i l l s and plyvJooa plants are also likely to be pur- by pulp m i l l s at a prioe much in e x ~ s s of the e m a n i d l y feasible l i m i t s of a structural flakeboard plant. scm of the softwood bgying and folEstrry waste (slash, bran-, txps, etc.) may be available in chip form to flakebo& plants. The high bark content of t h i s r a w m a t e r i a l w i l l mder it urdesirable fo r pulp manufacture - a t least in the near term. In al l probability, ways w i l l be found to separate the bark frun the wood in these types of chips and pulp mills w i l l be foraed to u t i l i ze this softcllood raw ma te r i a l as w e l l .

The farest resource in the south

The pire tinher is likely to be

The chips generated by saw-

In the long term therefore, structural flakebard plants in the South w i l l have to f a l l back on the hardwood resource. the unutilized hardwood in the South is of the high aenSity species such as cak and hickory. w i l l be required to prove the feasibi l i ty of manufacturing a structural flak- of acceptable propertieS and density frcm this high density raw material.

mst of

Substantial munts of resear& work

The manufacturing msts and earnings projections for the various plants described earlier and as surac\arized in Tables 1 and 2 have been analyzed and prepared by mans of a ccmputer program developed for this special purpose by the Forest Products Laboratory at Madison. !the projections are prepared for a great n- of potential plant locations and e available from the lab a t Madison.

It is understood that the ccarputer program is available for analyzing and preparing data for any -ired plant location and raw material condition and is th re fo re suitable for the accurate analysis of specific cases. paper proposes tm deal w i t h the overall and basic cxxpetitive position of structural flakeboard against softwood plywood in the u.S. or North Amrica i n general.

This

In the f inal analysis, structural flakeboard is mt to ccmplesnent the softwood supply in the U.S. markets and, as a result, w i l l have to ccmpete w i t h softmcd plywood. It is true that , potentially, structural flakeboard does have s a w properties and charactertistics which are superior to sheathing grade softwax3 plywood (surface properties, panel size, etc.) and could therefoxe eventually find special a d specific

433

-et applications avoiding direct ompetition with the_ softklood plymcd product, sheathing grade or sanded eade. S t i l l , i n i t i a l ly as

w i l l have to carpete w i t h the standard CDX sheathing grade softvllood plywood i n the am- wntional larye vlolune housing mnstruction markets such as the roof decking, floor decking and w a l l sheathing applications. The oost conrpetitive position of structural flakeboard against UIX plywood is th&ore of vital hportane in assessing the long term e m d c and financial viabi l i ty of the flakeboard industry i n the U.S. and i n North &erica.

Table 3 shm a amprison of softwood plywood (CDX) vs. structural flakeboard mts. The oost figures sham in Table 1 are meant to represent the average range of mts experie~ad by presently operating plymod plants against presently aperating waferbard plants.

The costs of other types of structural

w11 as in the long run, structural flakeboard

boards, such as oriented flakeboard plants or flakeboard plants using raw materials other than aspen roundmod, are l ikely to be in the same range as the ones sham i n Table 3 under structural board mts - scm spcial locations and mod supply ccxlditions excepted.

The costs sham in Table 3 are roeant to be typical and to be used in a cmparative sense. They refer to plant cutput capacities ranging f m about 100 to 160 W f 3/8" per annum. W y do not include sane cost factors such as interest msts and Oorporate overhead msts s i n e these iterns are d i f f icu l t to ampaxe as they vary fran plant to plant or corporation to corporatian.

?he amversion aosts of the two products

PlywaA has higher labor costs are fa i r ly similar except for chemical and labor msts. while structural board has higher M c a l oosts. Prior to 1974, these two factors were reasonably balanced so that the total m n v e r sion a s t s e r e also about equal. The sharp increase i n resin prices which toak place i n 1974 have hurt structural board a great deal mre than plywood. board's cost disadvantage i n chemicals is greater than the advantage in labor axits. On the whole and under present and foreseeable future mditims, the direct amversion oosts of structural board w i l l be, on the average, $7 e0 possibly $14 per Msf 3/8" higher than those of CDX plymcxl.

W IXJISL amversicm costs including depreciation (taken cm a 15 year, straight line basis) w i l l also be about $12 to $15 higher for structural board than for plywood.

It should be mted here that these cost ocnparisons are fo r newly bui l t plants against

As a result, structural

newly built plants. huiever that newly bu i l t structural board ' plants would have to axpete against plywoOa plants Wkicfi were bu i l t 5 to 10 years ago a t a substantially 1-r than present capital oost and w h i c h are laryely depreciated. In reali ty therefore, the advantaw of plywood in total conversion oosts would be mre in the order of $15 to $20 per Msf 3/8". This is a real and significant advantage for plyw.m-3 i n soft markets as they are in a p i t i o n to lmr prices without suffering actual cash losses. A t the sane pricz level, nekl structural board plants woad not be able to met their financial charges such as interest and principal paylnents on outstanding loans.

s m h t di f f icu l t to

The fact of the matter is

The wood msts of the two products are

Strandwood requires about .75 O.D. tons of wood per Msf 3/8" output. are easy to calculate. per O.D. tm delivered log cost, the wood msts of a structural board plant muld be in the order of $22 to $23 per Msf 3/8". instances, when using forestry drips in the a r e of the board, the fines generation would be higher than i n presently operating waferboard plants and therefore wood reqUiranents may be mre in the order of .8 to .85 O.D. tons per Msf 3/8". may be used as fuel i n the dxyers and i n the boiler and, a t the presently applicable fuel r e p l a m n t values, this would result in significant reduction i n fuel purchase require- mnts.

H e r e , wood msts For instance, a t $30

In SOE

The rejected fines hmever

Tbe wood casts given for structural board i n Table 3 represent the l w and the high range applicable under present circurnstanes. Elost Canadian w a f e m plants pay about $32 to $35 per O.D. ton for aspen rwndwood. In s ~ m e i n s t anes such log msts are d m to $25 per O.D. ton. It is unreasonable to e-ct that wood in any form may be pur&& for less than $25 per O.D. trm delivered to the plant. This figure therefore represents the law end of the range while the $35 per O.D. ton figure would, a t present, be representa- t ive of the high end of the wood cost range.

In the mufacture of p l w , akuut 45% to 47% of the log ends up as veneer or eventually as plywoOa. About 37% to 38% of the wood v01u-1~ is in the fonn of pulp chips or lumber manufactured from the axe. Assdmg for the m n t that dl1 of th i s ends up i n chips, these &ips are saleable a t a reasonable price to the pulp industry -- although saw pulp mills dislike veneer chips and prefer sawmill &ips or chips made fran round- wood. w i l l be forced to use this chip form so that chips generated by the plywood aperation do represent a substantial inaxe to the plywood

In the long run however, pulp mills

434

plant. shrinkage (in the Wing operation) and as w a s t e (dry trim). fuel, a t the present a t a $20 to $25 per O.D. ton fuel r e p l a m t value.

The rest of the woo3 v o l m ends up i n

The latter may be used as

For the purposes of (zu'pXing plyWOd costs w i t h structural board costs, the wood 03Sts of plywood mus t be calcula&d on a net basis, that is, log casts less chip sales. In the normal plymod prof i t and loss statemnt, chip sales are sham as in" and all wood 00s- are debited against plycod costs. lhis could be hi-y misleading for purposes of canparison.

w i l l depend on actual delivered log cost to the m i l l , less the &ip price obtainable FOB plywoOa plant in any given location. figures may vary widely depending on the log supply situation of a given mill as w11 as its relative location to pulp mills or to a chip export loading faci l i ty . Furth-re, log costs w i l l also vary widely depending on whether the m i l l is operating wholly or partially on self-awned tinker or on public, Forest Serviae m e d t i n h e r supply.

The net wood aosts of plywooa therefore

These

'&e wood cost range shm for plywood in Table 3 represents to the best of the author's h l e d g e the net wood axts experienced by

sheathing grade plywood industry a t the present. "he low range would represent a oondition wherein log costs are relatively l c w and am= ampled w i t h relatively high chip sales values. 3/8" w a d be valid i f log costs are relative- l y high and chip sale values are on the lcw side. Sam plywmd plants may experienoe lmr than the $30 per Msf net mod oosts while others may be in excess of the $50 per Msf 3/8" range. As an industry average hwever, the net wood mst range sham in Table 3 is believed to be fa i r ly representative.

representative of the structural board and plywood industries are fair ly similar. xange of both costs should apply to larger outplt plants (about 150 W f 3/8") enjoying favorable wood supply corditions while the high range wuld apply to less favorable wood supply conditions at a laer plant output (about 100 MMsf 3/8" pei annum). hcwever tha t existing plywcod plants would still enjq a $5 to $10 per Msf 3/8" advantage against newly bu i l t structural board plants due t o t h e i r l a e r plant costs and resulting lcw depreciation charyes.

'Ihe high range of $50 per Msf

On the whole, the total cost ranges,

The law

It is to be not&

A t the present, structural board or mnwrcially produced wafexboard has a further disadvantage against plpccd. As nentioned earlier, waferboard is accepted i n the housing industry at greater thicknesses (1/16") i n the

load bearing application as plywood. In

reality therefore, 7/16" wa€erbcard is sold against 3/8" plymcd a t the sam price. I n the same application therefore (and at the pEsent) waferboard costs would be an addi- ticmal $12 to $17 per Msf 3/8" higher than that of the thinner coapetitive a x plywood producrt.

This oost disadvantage may be overam in the future if oriented structural flake board is proven to have similar strength properties to plywood and is appmved by the codes thick- mss for thickness w i t h the plywood product. The inpartanoe of achieving strength and therefore thickness parity with plywood in the markets is thereby anply damnstrat&.

coin. factured in the eastern Wted States, close to the large eastern markets and ut i l iz ing the mixed hamhod resource still plentiful in t ? eastern regions. In such locations, structural board would enjoy the sam freight advantages relative to local markets and against plywood originating fmn the W e s t Coast as presently enjqed by the southern plywoOa plants " f ac tu r ing plywood from Scuthern pine and sell ing the output i n the S o u t h , Mihst and N o r t h e a s t .

There is haever another side of the cost structural flakeboards may be mu-

A t the present, about *thirds of the U.S. plymod supply originates in the West and about one-third i n the South. supply situation may change sxwhat in the future in favor of the South. It is unlikely that plywood production in the South w i l l ex& the 8 Bsf 3/8" level or roughly 40% of the present total U.S. demand for plywood.

Against this supply picture, about 40% of the U.S. pl- supply is consum& i n the South, about 40% in the northcentral and northeastern regions and about 20% i n theWest. It is therefore reasonable to expect that southem plywood production w i l l essentially be m n s m d i n the South while structural board is likely to find its greatest success i f manufactured 5n the northcentral and northeastern regions, supplemnting and ccmpeting w i t h westem plywcod i n the Midwest a d North- east m k e t s . In these locations (and i f properly located) structural board a u l d enjoy a $30 to $35 per Msf 3/8" freight advantage against western plywad wh ich would largely ove ram the basic a d earlier demon- s t r a k d cost disadvantages. structural board which wuld be acepted by the Codes on a thickness parity basis with plywood, the cost advantage against western plybod on a delivered axst basis to specific markets would be real and significant.

This

For an oriented

In the southem location, a structural flakeboard plant would have to ampte direc- t l y with southem plywcd in the southern

435

markets. This would appear to be a d i f f icu l t task and, unless southern &nand for plywoOa e x d the s w l y i n the south, a relatively high risk venture.

structural flakebard to the W e t s , the northcentral or northeastern lccatim m a r s to be mn= advantageous. The "facture of structural board in the mth is likely to entail a lesser degxee of financial risk after the product has been we11 established and accepted by the general housing mtruc t i on and possibly S ~ I E industrial markets.

"hem is a further interesting point which may be deduced from Table 3. for the use of a structural flakeboard type panel include its application as core mater ia l i n a oonpositicm type panel having "er faoes and a structural board are. is nand "Can-ply", or "plystran'a as manufa- tured by Potlatch a t Lewiston. product, the structural board sirrply replaces core veneer i n a plymcd-like panel. interest to ccmpare the aost of manufacturing structural board against veneer manufacturing msts.

For this xeascm and at least in the initial stages of introducing

Current prcposdLs

The product

In this

It is of

Table 3 shms that the approximate average mt of manufacturing structural flakeboard is in the order c,f $90 per Msf 3/8" or $30 per M s f Y8". m a t e price range of f i r core veneer an a 1/8" basis as guoted an the wst Coast. ast of a veneer, and especially axe veneer, to plywood manufacturers is prdMbly s w t less. On this basis; the substitution of vemer w i t h structural flakeboard does not seem to offer significant advantages. A substantid tightening of the oore veneer supply both in the West and in the South and a consequent increase in the cost and price of veneer w i l l have to take place before such substitution may be wnsidered eoonanical.

This is fairly close to the approxi-

The actual

Conclusions

Fmn the foregoing analyses, we may mnclude the follcrwing.

flakeboard product carmercially manufactued a t the present, has found a strong acceptance in both the Canadian and U.S. markets. present price levels, these plants are gmeratixq attractive earnings, i n spite of the fact that waf-ard must be sold 1/16" thicker than plywad in the same load bearing application.

The results of the " e n t l y ongoing researdl work indicae that oriented structural flakeboard aould easily adtieve strength parity with plywood and aould be sold th~ckness for thickness against plywcod i n the amstruction markets. Plants manufacturing sudl a product

W a f e K b O a r d , the only s t r u e a l grade

A t

would have a reasonably s-g cmpst i t ive. position against CDX ply"CX3 i f located in the northcentral ard northeastern regicms of the united Stat32s.

considering the diminishing supply of

against the projected expansion of the markets for plywood or plywood-like products, st=ruc tural flakeboards present a good apportunity to supplement this diminishing supply while uti l izing a hithem unused fo-t resour~e.

softmod peeler 1- i n the united sta*s

The eventual mufacture of strudmral flakebard products for market wlicatims other than those presently occupied by softmod plymcd is a good, long range possibility.

The dewlopent of l m e r oost and more effective resins and resin extenders is also a gocd possibility. strengthen the q t i t i v e positicm of structural flakeboards against plywood products.

This would further

436

c

TABLE 1

U.S.O.A. Forest Products Laboratory Wadi son , W i sconsin

SIIFWIRY OF CAPITAL COSTS

STRUCTURAL PARTI CLEBOARO

W A C 1 TY/Y R 40% LATHE FLAKES- 40% TREE LENGTH LOGS- MMsf 3/8" LOCATION PRESS SIZE 100% LATHE FLAKES 60% CHIPS 60% CHIPS

50 SOUTH Continuous f 7,100.000 f 8.200.000 f 9,950,000

4'~16'-12 opg $ 8.100,OOO f 9.200,OOO f 10.800.000

50 NORTH Continuous f 7,450,000 f 8,550,000 f 10.400.000 4 ' ~ 8'-24 opg f 7.560,000 f 8.670.000 f 10,500,000

f 9.600.000 f 11,600,000 4'~16'-12 opg f 8.550.000

100 SOUTH 4'~16'-24 opg f 11,700.000 f 13,550,000

NORTH 4'~16'-24 opg f 12,300.000 f 14.600.000

4 ' ~ 8'-24 opg $ 7,100.000 f 8,200,000 f 9,900,000

150 U)mH 4'~24'-24 OQg 8'~24'-12 ow f 14.900,OOO

f 17,000.000 f 17,000.000 f 19.200.000

150 NORTH 4Ix24l-24 opg 8'~24'-12 opg

f 15,800,000 f 18.000,OOO

200 SOUTH 8'~24'-16 opg

NORTH 8'~24'-16 opg

~~

f 20,000,000

f 21.500.000

f 18,700,000 f 21.000.000

f 22,400.000

f 24.500.000

..... TABLE 2

U.S.O.A. Forest Products Laboratory k d i s o n . Wisconsin STRUCTURAL PARTICLEBOARD

SUMMARY OF CAPITAL COSTS PER UNIT OF OUTPUT ($ PER Msf 3/8") CAPAC I T Y / Y R 40% LATHE FLAKES 40% TREE LENGTH LOGS

60% CHIPS msf 3/8 LOCATION PRESS S I Z E 100% LATHE FLAKES 60% CHIPS

50 SOUTH Continuous $142 -00 4 ' ~ 8'-24 opg 142 .OO 4'~16'-12 opg 162.00

$164.00 164.00 184.00

5199.00 -198.60 216.00

50 NORTH Continuous 149.00 4 ' ~ 8'-24 Opg 151.00 4'~16'-12 opg 170.00

171.00 173.00 192.00

208.00 210.00 232.00

100 SOUTH 4'~16'-24 Opg 117.00 135.00

100 NORTH 4'~16'-24 opg 123.00 146 .OO

150 SOUTH 4'~24'-24 opg 8'~24'-12 opg

99.00 113.00

113.00 128.00

150 NORTH 4'~24'-24 opg 8'~24'-12 opg

105.00 120.00

124.00 140.00

200 SOUTH 8'~24'-16 opg 100.00 112.00

200 NORTH 8'~24'-16 opg 107.00 122.00

437

TABLE 3

COMPARISON OF PLYWOOD (CDX) vs. STRUCTURAL BOARD COSTS

PLVWWD STRUCTURAL BOARD

CHEMICALS POWER STEAM 8 FUEL

SUPPLIES LABOR

A D M I N ~ S T R A T ~ V E S A L A R I E S 8

TAXES 8 INSURANCE

DIRECT CONVERSION COSTS

DEPRECIATION (15 YEAR STRAIGHT

EXPENSES

LINE)

TOTAL CONVERSION COSTS

WOOD COSTS

LESS CHIP SALES a S25/O.D. TON a t35/O.D. TON

TOTAL COSTS

$/MSF 3/0"

8.00 - 10.00 3.00 - 5.00 1.00 - 3.00 18.00 - 24.00 5.00 - 7.00

4.00 - 5.m 2.00 - 3.00

41.00 - 57.00

9.00 - 11.00

50.00 - 68.00

30.00 - 50.00

80.00 - 118.00

25.00 - 28.00 4.00 - 7.00 1-00 - 3.00 12.00 - 15.00 6.00 - 8.00

4.00 - 5.00 3.00 - 4.00

55.00 - 70.00

10.00 - 13.00

65.00 - 83.00

19.00 28.00

84.00 - 111.00

ii TCUCC

DUMP 1

I DRY E. 9, M ETECI NG-

--

TO DCY_E--

Fig. 1 -- &sic sec t ion f l m h e t . and flaking sect ion. Lathe flake handling.

wood yard Type WF 1 and WF la.

Fig. 2 -- Basic sect ion f lwshee t . wood yard and flaking section. Type WF-2. log flaking.

T r e e length

I--- I---I---I

Fig. 3 -- Basic sect ion f l m sheet. yard and f laking section. Type WF 3. &p handling flaking.

wood

438

IFACE 1 4CAL€ -1 , P-. SCALE.

Fig. 4 -- Basic section f l m h e e t . Drying and blending section. T y p DB-1.

Fig. 5 -- Basic section flaisheet. Drying and blending section. ?Lpe DB-2.

439

I

?*" : L -

1 - . - - ' I = ' -

i

Pig. 7 -- Basic p lan t f l o w sheet. i.nput conditions:

P l a n t output capacity: 50 M.M.S.F., 3/8" per y e a . k b d

100 % shaping late flakes.

. . *

1 TYPE D O - Z

c

.-

Fig. 8 -- Basic plant flm sheet. Plant output capacity: 100 M.M.S.F. 3/8" per yc.,rr- Wad input mnditions: 40% lathe flakes and 60 % chips.

441

ADHESIVES FROM SOUTHERN P I N E BARK- A REVLE?; GP PAST AND CURRENT A P P R O A C H E S TO RESIN F o m u L ~ , n o ; , PROBLEMS

R i c h a r d W . Hemingway P r i n c i p a l Wood S c i e n t i s t

S o u t h e n ? F o v e s t Expe r imen t S t a t . i on u . S. F o r e s t S e r v i c e

P i n e v i l l e , L o u i s i a n a

A b s t r a c t

B a s i c p r o p e r t i e s of c o n i f e r b a r k p o l y f l a v o n o i d s and v a r i o u s a p p r o a c h e s t o t h e i r u s e i n wood a d h e s i v e s are r e v i e w e d . The o b j e c t i s t o f o c u s on t h e i m p o r t a n t problems which m u s t be overcome i f t h e s e abundan t and renewa- b l e p h e n o l s a re t o b e u t i l i z e d i!? wood adhe s i vc f o r m u l a t i o n s .

I n t r o d u c t i o n

Along w i t h t h e u r g e n t n e c e s s i t y -f s h i f t i n g from p e t r o l e u m t o a l t e r - n a t e s o u r c e s o f e n e r g y , i t i s a l s o e s s e n t i a l t o d e v e l o p new s o u r c e s o f i n d u s t r i a l c h e m i c a l s from r e n e w a b l e r e s o u r c e s . O i l s u p p l i e s c a n b e e x p e c t e d t o b e i n c r e a s i n g l y d i v e r t e d from e n e r g y t o t h e p r o d u c t i o n of p e t r o - c h e m i c a l s , b u t t h e r e i s no a s s u r a n c e of t h e l o n g t e r m s u p p l y of t h e u s u a l a r r a y o f i n e x p e n s i v e b a s e c h e m i c a l s , D e s p i t e deba te o v e r i t s t i m i n g , t h e r e l a t i v e c o s t of c h e m i c a l s d e r i v e d f rom o i l m u s t e v e n t u a l l y c l i m b d i s - p r o p o r t i o n a t e l y t o t h e i n c r e a s e i n c o s t of r e n e w a b l e r e s o u r c e s s u c h as f o r e s t p r o d u c t s ,

Of p a r t i c u l a r c o n c e r n tc t h e for- e s t product,^ i n d u s t r y i s t h e l o n g t e rm s u p p l y and c o s t o f c h e m i c a l s for t h e s y n t h e s i s of a d h e s i v e s which w i l l b e r e q u i r e d i n i n e r e a s i n @ amcunts a5 ma te r i a l s s u c h as e x t e r i o r f l a k e b o a r d s a r e made from f o r e s t r e s o u r c e s o f d i m i n i s h i n g q u a l i t y . For t h e p a s t 25 y e a r s , p a r t i c u l a r l y i n p e t r o l e u m d e f i c i e n t c o u n t r i e s , a c o n c e r t e d e f f o r t h a s been made t o r e p l a c e sub- s t a i i t i a l amounts of p h e n o l and r e s o r - c i n o l w i t h t r e e b a r k s or t h e i r e x t r a c t s f o r t h e p r e p a r a t i o n o f wood a d h e s i v e s , A r e s u r g e n n e o f i n t e r e s t i n t h i s p o s s i b i l i t y has a l s o o c c u r r e d i n t h e U n i t e d S t a t e s b e c a u s e o f t h e changed ecoJiomic c l i m a t e r e l a t i v e t o p e t r o l e u m . However, d e s p i t e c o n s i d e r a b l e r e s e a r c h and deve lopmen t , w i t h t h e e x c e p t i o n of t h e u s e o f w a t t l e t a n n i n s i n l i m i t e d amourits , t h e s e a d h e s i v e s have n o t been w i d e l y a p p l i e d by i n d u s t r y . The l a c k of thteir . a c c e p t a n c e h a s been t h e result 0 1 ' b o t h a r e l a t i v e l y low c o s t o f ~ I I C J ! C 1 ~ J I the past and t e c h n o i o g i c a l pr.ob1 ems e n c o u n t e r e d when u s i n g t h e s e

--_ ----__

a d h e s i v e s unde r i n d u s t r i a l c o n d i t i o n s . I n t h i s p a p e r , some o f t h e proper2-

t i e s of c o n i f e r b a r k p o l y f l a v o n o i d s and v a r i o u s a p p r o a c h e s t o t h e i r u s e i n wood a d h e s i v e s a r e r e v i e w e d . The i n t e n t i s t o f o c u s on some o f t h e i m p o r t a n t p r o p e r t i e s and p rob lems which m u s t b e d e a l t w i t h if t h e s e a- bundant and r e n e w a b l e p h e n o l s a r e t(; be u t i l i z e d in wood a d h e s i v e s .

P o l v f l a v o n o i d s --

St r u c t w e __- ____

The mater ia ls i n c o n i f e r b a r k s which a r e t h e a c t i v e c o n s t i t u e n t s used i n a d h e s i v e f o r m u l a t i o n a r e po lymers b u i l t up o f f l a v o n o i d u n i t s . These po lymers are c l a s s i f i e d on t h e bas i s of t h e i r s o l u b i l i t y i n t o g r o u p s s u c h as t h e condensed t a n n i n s ( s o l u b l e i n a l c o h o l and w a t e r ) , t h e p h l o b a p h e n e s ( s o l u b l e i n a l c o h o l b u t n o t w a t e r ) , and t h e p h e n o l i c a c i d s ( i n s o l u b l e i n n e u t r a l s o l v e n t s b u t s o l u b l e i n a l k a l i n e s o l u t i o n s ) (1). When a t t e m p t i n g t o u s e t h e s e po lymers I n wood a d h e s i v e f o r m u l a t i o n s , i t i s i m p o r t a n t t o have d e v e l o p e d a r e a l i s t i c c o n c e p t u a l model of t h e i r s t r u c t u r e t o a s s i s t i n making d e c i s - i o n s a s t o how t o a c c e n t u a t e o r min imize p r o p e r t i e s o f t hese p o l y m e r s . D e s p i t e t h e e f f o r t s of many n o t e d c h e m i s t s , t h e s t r u c t u r e and p r o p e r t i e s of p o l y f l a v o n o i d s f rom c o n i f e r b a r k s r e m a i n p o o r l y u n d e r s t o o d .

C o n s i d e r a b l e p r o g r e s s has been made, however , on t h e c h e m i s t r y o f t h e p r o a n t h o c y a n i d i n s ( d i m e r i c and t r i m e r i c f l a v o n o i d s ) by t h e r e s e a r c h g r o u p s o f Roux (2), Haslam ( 3 ) , and Weinges (4). Recent work by Haslam e t al. ( 5 ) s u g g e s t s t h a t t h e p rocyan- i d i n s ( D r o a n t h o c y a n i d i n s which g i v e c:qayii d i n chloride on t r e a t m e n t w i t h HC1) a r c forined from a f l a v e n e i n t e r n t r d i a t e ( T ) hhich i s held b y a n enzyme t o p e r m i t s t e r e o s p e c i f i c f o r m a t i o n o f e i t h e r a c a r b o c a t i o n (T!) o r a f lavaf i -3-01 (JlI) and tha t t h e p r o c v a n i d i n s a r e t h e n formed noti- e n z y m a t i c a l l y b y condensa t io r i of' t k l l

c a r b o r a t i o n (C -11 ) w i t h t h e n u c l e o - p h i l l i c s i t e s (C-8 nr C-6) o f t l i e

f l a v a n - i-(11s , C q i i t i t i u e d concleri:,nt, i o i

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