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Discoloration

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Discoloration

    Discoloration

    JournalofHarbinInstituteofTechnology(NewSeries),Vo1.13,No.6,2006 Discolorationandcolor'sreversionofScotpineveneers

    byresin-eliminatedtreatment

    GUOng?hui,SONGKui?yan,FANGMin

    郭明辉,宋魁彦,房敏

    (KeylaboratoryofBio-basedMaterialScienceandTechnology,NortheastForestryUniversity,Harbin150040,China)

    Abstract:ThediscolorationofScotpine(Pinussylvestrisvar.Mongolica)veneerscausedbyr

    eliminated esin

    treatmentandthereversionofthecolorwerestudied.Theresultshowedthatthecoloroftheveneerschanged

    frombufftoyellowishbrownafterthetreatmentofresineliminationandthediscolorationofheartwoodwasmore

    severethanthatofsapwood;thedegreeofdiscolorationwassignificantlypositivelycorrelatedwiththemedica

    mentstrength.temperatureandresin.eliminatedduration.Thevarianceanalysisshowedtheeffectsofthose

    threefactorsonthediscolorationweresignificant.Withhydrogenperoxide(HO,)ascolorreversionmedica.

    mentandinorganiccompoundasmediumofthereaction.thereversionofthecolorofheartwoodwasmoreinac

    cessiblethanthatofsapwood:thedegreeofthecolor'sreversionwaspositivelycorrelatedwiththeH,O,

    strength.temperatureandu'eatingtime:theH,O,concentrationhassignificanteffectsonthediscoloration.In

    ordertoreducediscolorationofScotpineveneers.medicamentofresin

eliminatedusedhavetobeatsomelow

    concentration.andtheoptimalconcentrationofH,0,is0.35%duringtheprocessofcolor'srev

    ersion.

    Keywords:Scotpineveneerresineliminationdescoloration CLCnumber:s781Doeumentcode:AArticleID:loo5_9113(2006)06-0723-04

    Scotpine(Pinussylvestrisvar.Mongolica)is mainlydistributedinNorthemEuropeandtheSiberian area.Beingofstraightgrainandsymmetricalstructure, Scotpineisoneofthemainimportwoodspeciesin China.However,theapplicationofScotpine'slumber hasadrawbackduetoitsoverabundantresin.The

    resineliminatedtreatmentofScotpinelumberisanim

    perative.

    Thepopularresin.eliminationtreatmentusesalye processonthepinelumber,butduringthatprocess, thecolorofpinelumberchanges.Thecolorchangeof somekindsofpinestimbercouldbecontrolledbyalka. 1inetreatment.butthattreatmentcannotcompletelye

    liminatethediscolorationl.JunHuangandZejun Chenresearchedthecolor'sreversionofresin.elimina

    tedMassonpinerespectively.Buttherehasbeennore

    portaboutresineliminatedtreatmentandcolor'Srever. sionofScotpineindomesticareasoroverseas. Inordertofindtheinexpensiveandconvenient processofcolor'sreversion.thediscolorationofScot pine'stimberwithalkalinetreatmentwasstudiedin thispaper.

    1ExperimentalMaterialandMethods

    1.1MaterialandInstruments

sizeofveneers:100mm×5Omm×0.7mm

    Initialmoisturecontent:9%.

    Medicaments:Sodiumhydroxide,Sodiumcarbon

    ate,Oxalicacid,hydrogenperoxide.

    Instruments:NumericalAlbedoApparatus,Reac

    tionContainer,Constanttemperaturebox.etc. 1.2Methods

    (1)SpecimensGrouping:

    Heartwood,1000samples;sapwood,1000sam

    ples.

    Boththeheartwoodandsapwoodwererandomly dividedinto10groups.

    (2)AlbedoVclueMeasurement:

    Duringthreedifferentphases(unsettled,afteral

    kalinetreatmentandaftercolor'sreversion,respec

    tively).thealbedooftheveneerswasmeasuredwith thenumerica1albedoapparatusunderthesamemois

    turecontentlevel(Tab.1).Thedifferentpositionon everyboardweremeasured,andtheaveragevaluewas calculated.

    (3)AlkalineTreatment:

    Theexperimentwastakenwiththreefactorsand threelevelsinmindfTab.2).Purewatertreatmentwas carriedouttobeasacontrast.Itsconditionsare:the temperatureis90oC.durationis3Ominutes. First.themedicamentswerecompoundedand heatedupfollowingthespecifiedtemperature(Tab. 2),andthenthecompoundedmedicamentswereemit- Received2OO4l215.

    SponsoredbytheScienceFundofHarbinCity(GrantNo.2005AA6CN080)andScienceFou

ndofHeilongjiangProvince(GrantNo.GB06B3033)?

    ?

    723?

JournalofHarbinInstituteofTechnology(NewSeries),Vo1.13,No.6,2006

    tedintothereactioncontainerinwhichthespecimens hadbeenput.

    Second,thecontainerwasputintotheconstant temperatureboxandheatedwiththespecifiedtempera- tureandtime(Tab.2).

    Atlast.thespecimensweretakenoutofthecon. tainerandweredried.

    !.1Thealbedovalue8tdifferentphases

    Tab.2Factorsandlevelsofexperiment

    (4)Color'sReversion:everyresineliminated

    veneersgroups(110)wasdividedinto10differents

    smallgroups(ix)again.Themethodsisasshownin

    Tab.3.

    Tab.3Theorthogonaltestofcolor'sreversion 2ResultandDiscussion

    Alongwiththeincreasedconcentrationofsodium hydroxide,elevatedtemperature,andprolongeddura. tionoftheprocessofalkalinedegreasing,thecolorof theveneerschangedfrombufftoyellowishbrown.and thealbedovaluebecame1ower.ThisexperimentPr0. metheanusedthemethodofoneorthogonaltestadded toanotherorthogonaltesttodiscussthediscoloration ?

    724-

    influenceandcolor'sreversion.

2.1TheDiscoloration

    kalineDegreasing

    DuringtheProcessofAl-

    Thealbedovaluedecreasedwhenthesubstanceof chromogenicgroupsinchemicalcomponentofwoodin

    creasedorthemicroscopicstructureoftimberisde. structed.And,itiscorrelatedtothecolorofwood's surfaceandextractivesextractedbycoldandhotwa. ter

    .ThediscolorationofScotpineveneersarethe resultofbothofthesetwodifferenteffects. (1)Thedifferenceofdiscolorationsbetweenhear. twoodandsapwood

    Thecoloroftimberismainlydecidedbythelig ninsinwoodandtheextractivesinthecellcavitiesand cel1walls.Withalkalinecondition.thechromogenic groupsandauxochromicgroupsinthelignin(carboxyl group,unsaturateddupletbond,eta1)aresynthe. sized.Theinteriorextractives_seepedtothesurface oflumber.andthendecreasedthealbedovalue.The ligninsandtheextractivesofheartwoodmust1)ehigher thanthatofsapwood,sothealbedovalueofheartwood is1owerthanthatofsapwoodwiththesametreatment. (Tab.1),thesetwokindsofveneerhadobviousdiffer

    ences(Tab.41.

    Tab.4Varianceanalysisofalbedovaluebetweenheart. woodandsapwood

    (2)Thecolorvariationwithdifferenttreatment conditions

    Theinfluencesofsodiumhydroxide.temperature

    andtreatmenttimeontheveneercolorweresignifi. cant.Increasingconcentrationofsodiumhydroxide couldacceleratetheoxidationandthecondensationof thephenol,andthencausedthewooddegeneration. Elevatingtemperatureurgedthespeedofchemicalre. actions,andchangedwoodchemicalcomposition. whichalsocausedthefa11ofthealbedovalue.Astime prolonged,thealbedovaluealsodecreased(Tab.5). Tab.5Varianceanalysisofalbedovaluebetweenunsettled anddegreasedveneers

    Whiletheconcentrationofsodiumhydroxidein.

JournalofHarbinInstituteofTechnology(NewSeries),Vo1.13,No.6,2006

    creased.thetemperatureelevatedandtheduration timeprolonged,therateofdegreasingalsoincreased, andthesolubleresin(includingtheauxochromic groupssuchashydroxy1)proportioninthesolutionin- creasedaccordingly.Thiscanaugmenttheprobability ofthesecoloredextractives(piganents,thetannin,the resin.eta1)stickingonthesurfaceoftheveneers.It isfoundthatthealbedovalueoftreatedveneerishigh

    erthanthatofuntreatedveneers.

    2.2TheInnuenceoftheTreatmentConditionson Color'sReversion

    (1)Thedifferenceofthecolor'sreversionbe. tweenheartwoodandsapwood50%oftheveneersre

    versedorevenexceededtheirinitialalbedovaluesafter thetreatmentofcolor'sreversion,whiletheamountof heartwoodis40%andtheamountofsapwoodis60%. (Figs.1and2).

Untraate,'

    .

    

    <

    /Afterreversion

    sf1Pimens/PPP

    Fig.1SapwoodAlbedoofuntreatedandreversedveneers 50

    40

    =

    j30

    {2O

    {10

    0

    lOl20l30l40l

    thereversion(Tab.7).Ithasdecidedtheconditions ofchemicalreactionbalancesystem.Withtheright temperature,theeffectiveoxygencanfullyactitsfunc

    tions.However,thehightemperaturewouldintensify thedecompositionofH,O,.

    (4)Theinfluenceofthedurationtothecolor's reversion

    Prolongingdurationcanmakethealbedovalueel- evated,buttheeffectisnotsignificant(Tab.6). Tab.6Varianceanalysisofalbedovalueaftertheprocess ofcolor'sreversion(Group2)

    Tab.7Theinfluenceoftreatmentconditionsonthe color'sreversion

    speimns/f1ieP——

    Fig.2Albedoheartwoodofuntreatedandreversedwe-3Conclusions

neerS

    (2)TheinfluenceofH,O,concentrationonthe color'sreversion

    TheconcentrationofH,O,alsohassignificantin

    fluenceonthecolor'sreversion(Tab.6).Inacertain limitation.theincreasedconcentrationofH,07inthe medicamentcancausethesharpriseofthealbedoval

    ue(Tab.7).Thehighcontent,effectiveoxygenof H2Ocandestroythechromogenicgroups(C=C,C= O)thataYefoundonthebranchedchainsofthelig

    nins,sothecolorofveneercanreverse.However,the concentrationofHO,cannotexceedthelimitationin 0rdertoavoidthemassivedestructionofthelignins. f3)Theinfluenceofthetemperatureoncolor's reversion

    Theinfluenceofthetemperatureoncolor'srever

    si0nislowerthanthatofH,O,concentration's(Tab. 6).butitalsohasadirectcorrelationontheeffectof 1)Theeffectofalkalinityconcentration.tempera- tureanddurationonthealbedovalueweresignificant. Whilethealkalinityconcentrationincreased,thetem- peratureelevatedandthedurationprolonged,thealbe

    dovaluewasreduced.Thediscolorationofheartwood andsapwoodisdifferentwiththealkalineconditions. Inordertoavoidthemorediscolorationoftheveneers, thesuggestionisgiventousethealkaliatalowcon

    centration.

    2)TheeffectofH,O,onthecolor'Sreversionof theveneerswassignificant.Withtheconditionsofthe experimentthealbedovalueoftheveneersreversedef-

fectively.Thealbedovalueincreasedalongwiththein

    creasedconcentration.TheH2O2hasdestructiveeffects ontheveneer.sotheconcentrationwouldbeatalow levelintheprocessofcolor'sreversion,andthesuit

    ableconcentrationis0.35%.

    3)Elevatedtemperaturehasabettereffectonthe ?

    725-

    \=TI!0Il

JournalofHarbinInstituteofTechnology(NewSeries),Vo1.13,No.6,2006

    reversionofthecolor,buttheactivityofH2O2hasto beheldonto.

    4)Prolongingdurationhasabettereffectonthe reversion.However,theeffectflattenedafterthecoin

    pletedecompositionofH2O2.

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    726-

    ForestryUniversity.2003.4:6972.

    [3]HUANGJun.Newtechnologystudyforthedegreaseand colourretainingofmassonpine'Swoodblanksandsquares [J].WoodProcessingMachinery,1999,3:1014.

    41CHENZcjun.Degreaseandcolor'srevels{onofmasson pineandmainequipmentdesign[J].HunanForestrySci- ence&Technology,1999.6:18.

    5]FANGGuizhen.Woodchemistrycompositionanalysesof2O differentspecies[J].ChinaPulp&Paper,2002,6:79

    8O.

    6]ZHENGZhifeng.HowdoesthelumbercoloriSproduced [J].YunnanForestry,2005,26(2):1315.

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