全 文 ：№.4　　　　　　　　　　　　　　　 　　　　陕西科技大学学报　　　　　　　　　　　　　　　　　　Aug.2008
Vo l.26　　　　　　JOURNAL OF SHAANXI UNIVERSITY OF SCIENCE & TECHNOLOGY　　　　　　·5·
＊　文章编号:1000-5811(2008)04-0005-06
EFFECT OF MODIFICATION BY PHENOLATIONON STRUCTURES
OF WHEAT STRAW SODA LIGNIN AND PROPERTIES OF
LIGNIN-BASED PHENOL FORMALDEHYDE ADHESIVE
LIU Gang-yong1 , 2 , QIU Xue-qing2 , YANG Dong-jie2
(1.Depar tment o f Cosmetics Science , Guangdong Food and Drug Vocational Co llege , Guang zhou 510520 , Chi-
na;2.Schoo l of Chemistry and Chemical Enginee ring , South China University o f Technology , Guangzhou
510640 , Guangdong , China)
Abstract:The changes in chem ical st ructures of w heat st raw soda lignin (WSSL)af ter the
modif ication of WSSL by phenolat ion in alkaline medium , including functional groups and
molecular average w eight , studied by chemical analyses , Fourier transform inf rared , carbon-
13 nuclear magnet ic resonance spect roscopy (13 C-NMR), gel pe rmeation chromato graphy
(GPC), and the properties of pheno lated and non-phenolated LPF adhesives w ere dete r-
mined.The resul t show s that af ter the modif icat ion , content of methoxyl g roup of WSSL de-
crease f rom 11.04 % to 8.72 %, and the content of phenolic hydro xy l increase from 2.64 %
to 4.20 %, resulting in increased nonvolati le solids and adhesive st reng th o f LPF.After the
modif ication , the weight-average molecular weight of WSSL decrease f rom 1 902 to 1 473 ,
the number-ave rage molecular weight decrease f rom 1 737 to 934 , these results in decreased
visco sity and increased sto rage stabili ty o f LPF adhesive.Therefore , the modif icat ion of
WSSL by phenolation increases it s reactivity and further improves the perfo rmance of lignin-
based pheno l-formaldehyde adhesive.
Key words:wheat st raw soda lignin;pheno lation;chemical modification;adhesive
CLC Number:TS79;O636.2　　　　Document Code:A
0　Introduction
Phenol fo rmaldehyde (PF)resin , due its st rong adhesive ability , good weathe r-resistant and w ater-
proof characteristics , i s an ideal thermose tt ing binder to prepare manufactured boards and panels , but
phenol derives from non-renew able pe trochemical indust rial products.Therefore , it is necessary to sub-
stitute the cheap renewed ma terials to for phenol in preparing PF adhesive.As a by-product o f pulping
indust ry , lig nin is an abundant and renew ed substance w ith the similar st ructure to PF resin[ 1] , so the
use of various lignin , including soda o r kraf t lignin , lig no sulfonate and organosolv lignin and so on , as a
substitute for PF resin[ 2 , 3] was extensively studied.The lignin is alw ays modif ied by chemical methods
befo re being used because of i ts low reactivi ty.The common chemical modi ficat ions include methy lola-
tion
[ 2] , demethy lation[ 3] and phenolation[ 4] .Of them , the phenolat ion is the most promising modification
for lignosulfonate[ 5] , which can g reat ly improve the reactivity of lig no sulfonate.Generally , the modifi-
＊ 收稿日期:2008-04-18
作者简介:刘纲勇(1974-),男 ,江西省莲花市人 ,博士 ,研究方向:精细化工
基金项目:广东省科技攻关计划项目(2007B010600042)
陕西科技大学学报 第 26 卷
cat ion of ligno sulfonate by phenolat ion is carried out in an acidic medium , but soda lignin can only dis-
so lve in alkaline so lution and the lignin-based phenol-fo rmaldehyde (LPF)adhesive is prepared in an al-
kaline solution to o.So , it is necessary to study the modif icat ion of soda lignin by pheno lation in the al-
kali medium.To the best of our know ledge , the re are few reports on effect of modification by phenola-
tion on st ructures of soda lignin and proper ties o f lignin-based phenol fo rmaldehyde adhesive.
In this paper , the change s in chem ical st ructure of w heat st raw soda lignin(WSSL)af ter the modi-
fication by phenolat ion in alkaline medium , including functional g roups and molecular average w eight ,
were studied by chemical analyse s , Fourie r t ransfo rm inf rared(FTIR), carbon-13 nuclear magnet ic res-
onance spect roscopy (13C-NMR), gel permeat ion chromatog raphy (GPC).Furthermore , the propert ies
of PF adhesive , phenolated and non-pheno lated LPF adhesive w ere compared.
1　Materials and Methods
1.1　Materials
Commercial g rade phenol of 99%puri ty , fo rmaldehyde so lution (37 w t % aqueous solutions)and
sodium hydroxide of 96 %purity w ere used.The WSS L powder separated f rom soda-AQ pulping black
liquor of w heat st raw by acid precipi tation w as supplied by Shandong T ralin Paper Co.Ltd.
1.2　Samples preparat ion
1.2.1　Preparation of phenola ted WSS L
WSSL , phenol , NaOH and w ate r wi th mass ratio o f 1.0∶1.0∶0.2∶1.8 w ere first added to a
four-neck f lask equipped w ith a condense r and a thermometer successively.Then , the mix ture w as heat-
ed on the heater w ith st irrer and refluxing at 100±2 ℃fo r 1 h.After the reaction product coo ling down
to the ro om tempe rature , it w as acidif ied to pH =2.5 w ith HCl and centrifug alized.The precipi tate w as
w ashed tho roughly w ith ether and dried unde r vacuum.Finally , the test sample w as obtained.
1.2.2　Purification o f WSS L and phenolated WSSL
Both WSS L and phenolated WSS L used for the chemical or spectral analy ses w ere purified acco rding
to the procedure of Lundquist
[ 6] .
1.2.3　Preparation of the phenolated LPF adhesives
LPF adhesive w as prepared in tw o stage s:phenolation of lignin and the preparation o f LPF adhesive
(i.e., polycondensation stag).In the first stag , 30 g o f phenol , 70 g of WSS L , 15.8 g of N aOH and
120 g o f wa ter w ere pour into a f lask equipped wi th a st irrer , the rmometer and ref lux condenser.The
mixture w as then sti rred fo r 10 minutes , and the temperature w as raised up to 100±2 ℃ fo r pheno lation
reaction and maintained for 1 h.In the second stag , 42 g of formaldehyde w as added fo r poly condensation
reaction and held fo r 30 min at 50 ℃.Then temperature w as raised up to 80 ℃ at a rate of 0.5 ℃/min
and maintained fo r 1 h.Finally , 28 g of formaldehyde w as added dropwise in 5 min , and the temperature
w as maintained fo r 1 h , the reactant w as then coo led down and discharged.
1.2.4　Preparation of the non-phenolated LPF adhesives
The process of non-phenolated LPF adhesives is like that of phenolated LPF adhesive except the
phenolated stag .
1.2.5　Preparation of PF adhesive
The PF adhe sive is prepa red wi th the ratio of phenol to formaldehyde 2.0 , the catalyst of alkaline ,
and tw o po lycondensation stag s.
1.2.6　Plyw ood panels manufacture
Plyw ood panels w ere prepared by pressing w hite bassw ood veneers wi th a thickness of 12 mm ,
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第 4 期 刘纲勇等:酚化改性对麦草碱木素结构及 LPF 树脂性能的影响
moisture content of 8 w t % at a certain tempe ra ture.The glue-spread of the LPF adhe sives w as
125 g/m2 .The hot-press condi tions:pressure , temperature and t ime w ere respectively cho sen as 1.0
MPa , 150 ℃ and 216 seconds.
1.3　A nalysis and test
Phenolic hydro xyl and carboxy l g roups w ere determinated by conductometric tit rimetry
[ 7] .The me-
tho xy l content w as measured by modif ied Ziesel method.
The GPC g raphs w ere acquired on the Water-515 ult raviolet GPC equipped w i th ul trahydrogel 250
column made by Waters Co.Ltd.NaNO 3 solution(pH =10)was used as eluent w ith a f low rate 1.0
mL/min at 25 ℃.A UV-pho tometer w as used to determine the concentrat ion of lignin wi th maximum
abso rbance in the neighborhood of 280 nm.
The FT IR spectra of WSSL and phenolated one w ere carried out on a Vector 33 FTIR spect ropho-
tometer made by Bruker Co .l td.
13C-NMR spectra w ere obtained on Brucke r ARX-400 MHz.The lignin samples w ere acety lated by
being dissolved in solution of acetic anhydride and acetone wi th volume rat io o f 2∶1 , at the ro om tem-
perature fo r 48 h , and then purified by ethe r and dried under vacuum.T he ace tyla ted lignin samples
w ere disso lved in dimethyl sulfoxide D6(DMSO-d6)fo r 13C-NMR analy sis.
The adhesive strength w as tested on Inst ron 5566 Universal Materials Te sting Machine w i th a
crosshead speed o f 3 mm/min according to GB/T 9846-2004.The visco sity of the adhesive w as measured
according to GB/T 14074-93 on a Brookf ield DV III rheome ter at 25 ℃.The nonvolati le content w as e-
valuated acco rding to GB/ T 14074-93.The storage stability w as estimated acco rding to GB/T 9846-
2004.
Tab.1　Functional group of WSSL and phenolate-
d WSSL
lignin me thoxy l
g roup/ % pheno lic hydr-oxy l g r oup/ % carboxy lg roup/ %
WSS L 11.04 2.64 4.03
phenola ted WSSL 8.72 4.20 3.64
Tab.2　Average molecular weight of WSSL
　 　　and phenolated WSSL
Lignin Mw Mn Mw/Mn
WSSL 1 902 1 737 1.10
Phenolated WSS L 1 473 934 1.58
2　Results and Discussion
2.1　Change in st ructure o f WSSL af ter phenola-
tion
In o rder to disclose the ef fect of modification
by pheno lation on st ructure s o f WSS L , WSSL and
phenolated WSSL w ere studied by chemical analy-
ses , GPC , FTIR and 13C-NMR spect ra.
2.1.1　Chemical analy ses
Table 1 show s that , af ter the modification by
phenolation , the content o f methoxyl g roup o f WSSL decreases f rom 11.04 % to 8.72 %.Meanwhile ,
the content of pheno lic hydro xyl increases from 2.64 % to 4.20 %.As the phenolic hydroxyl and me-
tho xy l g roups are the act ive and de-active g roups respectively , the modif icat ion of WSS L by pheno lation
can improve its reactivi ty.The table also show s that the content of carboxyl group decreases f rom 4.03
% to 3.64 %, resulting in the increase in the w ater resistance of WSSL , which may leads to higher w a-
ter resistance o f LPF adhesive.
2.1.2　G PC analy sis
The number-average molecular w eight(Mn), weight-average molecular w eight (Mw)and po lydis-
per sities(Mw/Mn)of pheno lated WSSL and WSS L are listed in Tab.2.And the molecular weight dist ri-
but ion of pheno lated WSS L and WSSL is plo t ted in Fig.1.Tab.2 and Fig.1 show that , af ter the modifi-
cat ion , the dist ribution of mo lecula r w eight increases , the WSSL has a molecular w eight o f 830 to 4 200 ,
and the phenolated one is 200 to 4 720.Tab.2 also show s that , af ter the modification , the Mw of WSSL
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陕西科技大学学报 第 26 卷
Fig.1 　Molecular weight distribu-
tions of WSSL and pheno-
lated WSSL
decreases f rom 1 902 to 1 473 , and the Mn decreases f rom 1 737 to
934.Besides , Fig.1 show s that mo lecular w eight of a fraction of
phenolated WSSL is higher than that of the WSS L , indicating the
condensation of WSSL w ith pheno l in the pheno lation reaction.
A s is known , the larg e molecular w eight material cannot pen-
et rate into the cell w alls of the wood to form an adhesive continu-
um between contiguous w ood particles[ 3] .Compared wi th PF res-
in , lig nin has higher mo lecular weight , which w ill reduce the per-
formance of LPF adhesive.Howeve r , the modification by pheno-
lat ion can reduce the molecular w eight of WSS L evident ly , which
Fig.2　FTIR spectra of WSSL and phenolated
WSSL
will improve the performance of LPF adhesive.
2.1.3　FTIR analysis
The FT IR spect ra of WSSL and phenolated WSSL
are show n in Fig.2 , f rom which i t is seen that the spec-
t ra of both WSSL and phenolated one are similar and can
be characterized by the presence o f a broad band vibra-
tions at 3 400 cm-1(OH), 2 927 cm-1(CH), 1 605 and
1 514 (aromatic skele tal vibrations), 1 426 cm -1(CH)
corresponding to ring stretching CH in-plane defo rma-
tion.Also , there are some bands vary.Assuming that
the aromat ic st ructures do no t degrade under t reatment , the absorption band of 1 514 cm-1 co rrespond-
ing to the skeleton modes in the aromat ic ring is selected as an internal reference
[ 8] .T he band 1 710
cm
-1 , co rresponding to ester carbony l vibration of phenolated WSSL is reduced , indicating that most of
the ether groups of WSSL are cleaved.This leads to the reduct ion of molecular mass o f lignin structure.
The reduction of abso rbing intensity af ter modification at 1 120 cm -1 , corresponding to methoxy l group ,
show s the cleavage of methoxy l g roups.In the FTIR spect rum of phenolated WSSL , a new band at 755
cm-1 i s found , which coincides w ith the modif icat ion of ligno sulfonate by phenolation in acid medium ,
which arises f rom the reaction be tw een pheno l in or tho- o r para-posi tion and α-hydro xy l groups in the
side chain of lignin
[ 5] .These resul ts fur ther pro ve that condensation take place betw een WSSL and phe-
nol in the pheno lation reaction.
Fig.3　13C-NMR spectra of WSSL and phenolated WSSL
2.1.4　13C-NMR analy sis
The
13
C-NMR spect ra of WSSL and demethy lated WSSL are show n in Fig.3.The chem ical shif t of
171.5 to 171.9 ppm and 167.7 to 169.8 ppm are respect ively assigned to aromatic and aliphat ic ace tates
w hich ref lect the concentration o f phenolic and alcoho lic g roups in lignin.The fact that the a romatic ace-
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第 4 期 刘纲勇等:酚化改性对麦草碱木素结构及 LPF 树脂性能的影响
tate signals of pheno lated WSSL are larg er than that o f WSSL confirm s that the phenolated WSS L has
more f ree pheno lic hydro xy l groups than WSSL .T he signals of aroma tic carbons of lignin range f rom
100 to 160 ppm.The most intense signals in this region are the C3/C5 and C2/C6 signals o f syringy l uni ts
and guaiacy l uni ts.This confirm s that the WSSL is of GS type[ 2] .
Sy ringy l uni ts are characterized by the presence of the chemical shif t s of 103.8 to 104.8 ppm.The
w eaker signals of sy ringyl units of phenolated WSS L in contrast to that of WSSL indicate the deg rada-
tion of sy ringyl uni ts.Typical signal for β-O-4 st ructural units(63.6 ppm)in the spect rum of phenolated
WSSL is a li t tle weaker compared w ith to that of WSS L , indicating that par tial β-O-4 st ructural units are
deg raded af ter the modi fica tion.The chemical shif t s of 35.8 to 40.8 and 19.8 to 20.9 ppm are assigned
to DMSO and methy l g roup in acety l respectively.A ssuming that the signals o f methy l group in acety l
do not change under t reatment , typical signals of methoxy l g roups in the phenolated WSS L (55.8 ～
56.7 ppm)are w eaker than tho se in WSS L , demonst rating that the methoxy l g roups of w ere cleaved af-
ter the modification by phenolation , which are consistent w ith the results of chemical analy ses and F TIR
spectra.
2.2　Change in propert ie s o f LPF adhesive af ter phenolat ion
From the above results , i t i s concluded tha t the modif icat ion o f WSSL by pheno lation increases i ts
reactivity and decreases it s average molecular.In orde r to investig ate the ef fect of the modif icat ion of
WSSL by pheno lation on the properties of LPF adhesive , we prepared the phenolated LPF adhesive at 70
%WSSL substitution and non-phenolated LPF at 70 %WSSL substitution.Also , a t raditional PF ad-
hesive w as also prepared and its propert ies w ere dete rmined fo r comparison.The results are li sted in
Tab.3. 　Tab.3　Properties of PF and phenolated and non-phenolated
adhesives
proper ty PF adhesive
non-phenolated
LPF adhesive
phenolated
LPF adhe siv e
adhesiv e strength/M Pa 2.12 1.21 1.93
nonvolatile so lids/ % 44.0 42.5 43.4
visco sity/ mPa· s 410 1 950 858
sto rage stability/ h 5 7 9
　　Tab.3 show s that the adhe-
sive st reng th o f pheno lated LPF adhe-
sive is nearly equal to the adhesive
st reng th o f the PF adhesive , and much
higher than the adhesive st reng th o f
non-phenolated LPF adhesive , demon-
strat ing that the modification of WSSL
by pheno lation improves it s react ivity ;the nonvo latile solids of non-pheno lated LPF is low er than the
nonvolati le solids of the phenolated LPF adhesive due to the fact that the modification of WSSL improves
it s reactivi ty , and further raises the resin y ield o f LPF adhesive;the viscosity of phenolated LPF adhe-
sive is much low er than that of non-pheno lated LPF.This is because the molecular w eight of WSS L de-
creases af ter the modifica tion by phenolation , and the lignin contributes the visco sity of LPF adhesive
g reat ly
[ 9] ;and the sto rage stabili ty of phenola ted LPF adhesive is higher that o f non-phenolated LPF ad-
hesive , which is caused by the low er viscosity of pheno lated LPF adhesive.Therefore , the modification
of WSS L by phenolation increases the reactivity of WSS L and furthe r improve the perfo rmance o f LPF
adhesive.
3　Conclusions
Afte r the modi fica tion of WSSL by pheno lation , chemical analy ses show that the content of me thox-
yl g roup o f WSSL decreases , and the content of pheno lic hydroxy l increase;the result of GPC show that
the average mo lecular w eight o f WSS L decreases and the dist ribution of molecular w eight increases;the
FTIR spect ra prove that WSSL is pheno lated , w ith methoxy l g roups cleaved;13C-NMR analy sis show s
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陕西科技大学学报 第 26 卷
that methoxy l g roups and β-O-4 st ructural units cleaved.
The determination of the propert ie s o f phenolated and non-phenolated LPF adhesives show that the
adhesive st reng th , nonvolatile solids , and sto rag e ability of LPF adhesive increase , and the viscosity of
LPF adhesive decrease.
In summary , the modification o f WSSL by phenolation in alkaline medium can improve i ts reactivity
and reduce its complexi ty of molecular st ructure , resulting in the improvement o f the perfo rmance of
LPF adhesive , whereas the mechanism of modification of WSS L by pheno lation in alkaline condit ion is to
be fur ther studied.
References
[ 1] Lin Q J , Liu J H , Yang G D , et al.Preparat ion of w ood ad hesive f rom sulfate pulping black liquid [ J] .T ran saction s of China Pulp
and Paper , 2005 , 20(1):106-120.
[ 2] Alonso M V , Oliet M , Rodrí uez F , et al.Modification of ammonium lign osulfonate by phenolation for u se in phen olic resin s [ J] .
Bio resource Techn ology , 2005 , 96(9):1 013-1 018.
[ 3] Wu S B , Zhan H Y.Characteris tics of demethylated w heat s t raw soda lignin and i t s ut ilization in lig nin-b ased phenolic fo rm aldehyde
resins [ J] .Cellulos e Chemist ry and T ech nology , 2001 , 35(3-4):253-262.
[ 4] Allan G G , Dalan J A , Foster N C.Modificat ion of lignins for use in ph enolic resins [ A] .Hemingw ay R W., Conner A H ., Bran-
h am S J.Adhesive f rom renewable resource-ACS symposium series 385[ C] .Washing ton , DC:American Chemical S ociety , 1989:
55-76.
[ 5] Liu H W , Yu J L , Chen J X.Determination of p hen olic hyd roxy l and carboxyl groups in lignin w ith conductomet ric tit ration in or-
ganic s olvent [ J] .C hina Pulp and Paper , 1990 , 9(1):55-58.
[ 6] M cVay T M ., Baxter G F., Dup re J., et a l.React ive phenolic resin modifier [ P] .US:5 866 642 , 1999-2-2.
[ 7] Skrebets T .E., Bogolit syn K.G., Kosyakov D.S., et al.An IR study of organosolvent lignin [ J] .Russian Journal of Applied
C hemist ry , 2004 , 77(9):1 536-1 539.
[ 8] Ysbrandy R E , Sanderson R D , Geris cher G ER.Adhesives f rom autohydrolysi s bagasse lignin , a renew able res ou rce.part 1.the
physical properties of laminates made w ith phen olated lignin n ovalacs [ J] .H olzforchu ng , 1992 , 46(3):249-252.
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酚化改性对麦草碱木素结构
及 LPF树脂性能的影响
刘纲勇1 , 2 , 邱学青2 , 杨东杰2
(1.广东食品药品职业学院化妆品科学系 , 广东 广州　510520;2.华南理工大学化学与化工学院 , 广东广州
　510640)
摘　要:用化学分析 、红外光谱(FTIR)、核磁共振碳谱(13 C-NMR)、凝胶渗透色谱(GPC)等方
法分析了麦草碱木素在碱性条件下酚化改性前后的官能团 、分子量等化学结构的变化 ,并测试
了酚化的末改性 LPF 胶粘剂的性能.结果表明 ,麦草碱木素在改性后甲氧基含量由11.04%降
低至 8.92 %,酚羟基含量由 2.64 %升高至 4.20 %,导致 LPF 胶的固体含量和胶粘强度升
高;麦草碱木素在改性后平均相对分子质量降低 ,重均相对分子质量(Mw)由 1 737降为 934 ,
数均相对分子质量(Mn)由 1 902降为 1 473 ,导致 LPF 胶的粘度降低 ,储存稳定性增加.因此 ,
酚化改性可以提高麦草碱木素的活性 ,并进一步提高木质素酚醛树脂胶粘剂的性能.
关键词:麦草碱木素;酚化;化学改性;胶粘剂
中图分类号:TS79;O636.2　　　　文献标识码:A
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