R i l l ~ ais lloh- lind Holz als Roh- und Werkstoff 4{I (1982) 293-301 _l_ ll._ll,...yilIL~ t.~It, rksi.ll 9 Springer-Verlag 1982 Pine Tannin Adhesives for Pariicleboard A. Pizzi National Timber Research inslilute. Council for Scientific and Industrial Researu'h. Pretoria, P, epublic o[ Soulh Africa Pine lannill-bascd adhesive formulalions suilablc [or the industrial nlallUfaciui-e of exterior gra(le particleboard are discussed. The formulations dcscribed are a conlbination o[ substantial amounts of pine tannin extract with nmlarnine-l'ormaldehydc, phenol- formaldehyde and diisocvanai.e wood adhesi\'es. The pine tannin extraci/diisocyanatc { M DII formulation appears to be particularly sllitaMe Ibr industrial application. The results obtained al laboratory level with the latter fornltllalion are cxcellenl. The elimillation of prob]ell/S inherenl in lhc chemicul lliiltlrc o[ pille lal]llill extr;/cl'~ \\ah oblaiilcd b} alrcad\ tlY, gd Jll(Jtl'~{l'ial cllld lal~iHalnl) "he]xirulr Ctl)plicalion" ivcimiquc~,. !lie I'ornluhlliot> 4nd apt~lic~llion techni cities presented ;tp['lCLtl' Io bC suitable I],r li/o~l ~q' the tllt)lC \\ idch di>,iribuled pine spccic~ ,,ucll a ~, i>inti,~ paltila. P radklia. P. taccia. P. c/liolii alld olhcr,,. I{iefernlaniiin-llhldenliliel Iiir .';pali!ilallt, il I ", ~crdcn I';indcmillr Htifdol (ilundlagc \<,il Kicli'rn- [tllllllll f{h' clic il/dtl',ll'lcdlc I I/r ,,Ol/ '\ui~,cnsp;irll)141h.'n I)~_,- schricbr I)ic Rc/r ",lclh'n lille I,.oiniHnaticm HiP, I~r li,:hcn .k, lcn~cn [<icic:rt:lnlllllc\ir;ikt Mc[:illiili F<Hlllcilclciiyd-. Pilu- nc)14 ,unlaliMn, d- tiiltl /)ii>,,>c)amitbilidclmllc'hi tl,ii [)It_' ~iclu'l'll tannJncxtrakl-r)Jist,csHnctlf\ll)ll-I,~C/el~iHl cl-,cllcml l{il dic in,lu sl~iellu ,\n~\cndune :l[s he'>uncle:is gr [)iv c!clin:ll,, h',l I clb~>t lllttlJy;lab ci'/ivllun I i~cl-iillY, C Mild ~,ehr gut I)ic l/c,,v'lligttng \nil Pioblemcn. dic liiil dcr chcnii,,chcn N4;il[ll" \nil kJclern{anuili c~,{luk[ zusal/Hilcnh{inir v, urdcll ,.hin.h iihIichc indu>llJcllc und LM~orl<.chnikcn eltcichl, liii dic ~eschildcilcrl I,?,C/Cl'dUrCll Clil<l .\n\\ci!t!lllis hl],l[t)~ica Cl's I'{]r" I tliLIl,{C ilia, (iC!i IIICI,[CII 7v~kShnlMIcn Kic!ciilcillc!i \\it" / I{ Pillti< !x!ltll4. [> !;idi;tlcl. P. IHt.'da. [>. c!liulii tl ~i., gcci,',2'nr I lnlrndilelion The tl<<C el lallllill adhc'd\'cx flu lilt Ill;llltll'{ICllllc" i'll wood- bcised ghled products such ax particlebo:ud, pl>\\o,.~d <ind ghilam ha:-, been gaming il~ci-c';liill,4 industrial anti lechnical 4cccplancc durin, 4 the M~I decade. All Ihc lo~ nltil:.itiOl/> li:,ecl industriall.,, ;.ll-C, hox~cver, based on tI~e use oi ir colldcIlscd lanniils, such as \~ atllelminlu~a cxlract t)iCOmlncrce. Acacia illeallsii, dc Wilch) and quebracho ISchinopsis Iorcntzii) or on partial substitution of plienol in PP resms ~ith h) dro- lizable tallllins sl.icl] as chestnut (Pizzi 19801. A ...... ,,0: .{@2 I HIJN A ~U. I A V A \ V n V V V XOH ',, 7,'2",7 ,Y v "oH ', I(Ahl ,'1 '. / \x / \, OH."-m"- Resorcino[ic A-ring Phloroglucinnlic A ring Wattle Tannin Pine Tannin However, the considerably more abundant and diffuse poleniial reservoir of condensed tannins, of phloroglucinolic type, such as those derived from the vast majority of pine trce species (Pinus) has not been commercially exploited. The main reasons have been of a technical nalure snch as thc low solubility of the l?me tannins, their high molecular weight, high viscosiW and especially their uncontrcdlably fast reactivily with form'll dehvdc leading Io very short gitic mix pot4ivcs. ]here have been rcportod tiso~, o[ pine t;.lllilill CXll-aCts tar \toed ,_ldhosivc:s. Hm~,cxel. all dlcsc upprc~ache~, have ,qllt~2rcd Iio111 iillpOlICillt Icchnical or oconomical t]av, s. I I is iml~Orlaill Io revic\~ bricllv and crilically these dc\elopnl0nl>: I. Ph,\4ood ;alllcsivc~ of ;icccpt:.iblc l'~Cl-lOllllLInt:e have appar0ntly beoil plnduccd by using the lanllin eXll-aCt of the bclr], o] Pilltls b!tl[ia IA\'la aud l~tnanles\4arall 198(1t Fills Mud} \~a ~, cairicd otll al iab~wcilory ic\r I here i-, 1~o doubt Ihclt thoxc adhcsi\r ha\o polential add ~lrc prnbal~ly el ;luucpl;ihlr st;lnd;ird lhc i];i\k in lids case i~, liui ill the gated or bad i]ctl~.)ri/iHilcc hi lho (;ninil] ;Mhcsitc. hut in II/c I;ililliI1 exlrcicl clscd, t:ilst. Pinun brutia is hal widely distributed otib- sid<." a Few cotlntrics: this diminishes, ;it legist I;,>r the present tilnc, ils eCollOllliCtll importm~ce as a source ot'lgll]nin for wood adhesi\cs Second. and l\lr i/lOll_" import',inl [lom a IcchlHcal poinl iH\ ie\\, i~, lhc fact thai Pinu,, bruti;l :lppc'<irs h> produce {l bHFk cx{r;.lcl \\hich 5;r lo bc Its-4 reucli~c tmvards l'orlnaldchvdc (Ayla cilkl [>ar'<inic<,\'~cir:.ln lg.,RI)). Lh-tll 1he ianilin oPs4mlc of 1he iYi<)lC \\ idch dislribuled pine q~ccie>, l hu<,, Ibis rant]in uppcal s io t)c ,;oiTicwlml c:.micr it, handle, till hidnshial appiicatim~, Ih:.lll Ihc lanliiliS <)1 lllOle cliffu~c pine >pecies I I~.<,s',oti\\ 19771. To \\ hal lhi> bcha\ intN is chic t~ll] {11. this :-,tHgo bc el!l\ t/ <,nb.ivc/ c~l>tlu'cul;ition. II could bc due to ;i higher C<ll/{,2ill O[ icsnrcinolic-t~pc L,\-Fing) Ila\<m~,id~ in Ph/ti,, txtllia ihHli in t,lheF spccica ,,l h~ dilli:rcllccs in its a\ClX_ls lnolcctil;.il wd,_,ht clithougl-i 1iOllC of lhis is imirlcdialclv c,, iclenl !roitl the data a\'ailahIv Lip It, no\\, (\Vei:~snlai/ :tilt] A\ILI IcJSI)). (~oiliiciolls and piric t;inllin species corit;tinin.g higher itlllOtllliS or resorcinolici(ypo l]:.ivomdds (I)ouglas Iir and Pin us pohderosa have aheady been reported (Boyetie 1978) and Pinus brutia might well be a similar case. The differ- ences quoted are, however, evident from the gelation-time values reported for the reaction of Pinus brutia with fc)rlnal- dehyde (Ayla and Parameswaran 19801. In l::ig. 1, the gelation-times with formaldehyde, under silnilar conditions, of the tannin extracts of wattle (Acacia mearnsii), Pmus brutia and Pinus radiata are reported. It is then noticeable that Ihe Pinus brutia tannin gel-time is some- what half-way between that of a predominantly resorcmolic (A-rings) rennin such as wattle and that of a totally phloro-