TAP CHi KHOA HOC DHSP TPHCM ^S B&c Giang va tgk
CAT MACH OXI HOA CAO SU THIEN NHIEN DEPROTEIN HOA BANG HYDROPEROXIT VA NATRI NITRIT
l e DU-C GIANG", DINH MONG T H A O " , H O A N G T H | HUdNG"
TOM TAT
Cao su thien nhiin long co nhom hydroxyl cudi mgch da dugc diiu che bdng phdn img cat mgch oxi hoa cao su thien nhien deprotein hoa trong hdn hgp toluen vd nudc a 6CfC trong 24 gid. chdt ddng thi tetrahidrofuran (THF) vd chdt khai mao hydroproxit/natri nitrit. Phuang phdp sic ki thdm thdu gel (GPC) dd xdc dinh dugc khoi lugng phdn tic trung binh sd. khdi lugng phdn tit trung binh khdi vd dd phdn bd khdi lugng phdn tir ciia CSTNL ldn lugt la 4,836>^10' g/mol, 11,31 /xlO' g/mol vd 2,34. Cdu true hda hoc cua CSTNL dugc khdng dinh bdng phuang phdp phd hdng ngogi vd cgng hudng tic hat nhdn 'H vd "C. Trong cong trinh ndy, chiing Idi cUng da di xudt ca chi phdn ling cdt mgch vd hydroxyl hoa cgo su thien nhien tgo thdnh CSTNL tren ca sdphdn tich cdc dU lieu vli cdc cdng trinh dd cdng bd.
Tir khoa: cao su thien nhien deprotein hda, cao su thien nhien ldng cd nhom hydroxyl culi mach, cat mach oxi hda cao su thien nhiSn, phan hiiy oxi hda.
ABSTRACT
Oxidative depolymerization of deproteinized natural rubber using hydrogen peroxide and sodium nitrite as reagents
Hydroxyl terminated liquid natural rubber (HTLNR) was prepared by the depolymerization of deproteinized natural rubber (DPNR) in mixture of toluene and water at 6(fC for 24 hours in the presence of hydrogen peroxide and sodium nitrite gs an initiator and tetrahydrofurgn (THF) as a homogenizing agent. GPC analysis revealed that the number-average molecular weight (MJ and weight-average moleculgr weight (M„,} of HTLNR were found to be 4.831x10^ g/mol and 11.317^10^ g/mol, respectively, with polydispersili index (PDl) of 2.34. The chemical structure of HTLNR was determined by FTIR and H-NMR and C-NMR spectroscopic analysis. Based on the analytical data the mechanism of depolymerization and hydroxylation of NR lo form HTNR was also suggested.
Keywords: Deproteinized natural rubber (DPNR), hydroxyl terminated liquid natural rubber (HTLNR), depolymerization of natural rabber, oxidative degradation.
1. Mo-dau
Cao su thien nhien ldng (CSTNL) la cao su thien nhign (CSTN) biln tinh vdi cd khdi lugng phan tir khoang 2000-20.000 dvC. CSTNL dugc sir dung lam nguyen lieu de che tao keo dan, son, chat hda deo trong cdng nghigp cao su, vat lieu chdng rung va
_PGS TS, Tm'dng Oai hgc Vinh; Email: leducgiang@gmail com
" SV, Trufrng Bai hoc Vinh
TAP CHi KHOA HOC OHSP TPHCM Sd 3(81) nam 2016
chat chdng thim. DJc biet, CSTNL voi nhdm chiic cudi mach dugc sii dung lam chit tuong hgp, chit biln tinh cho cac polyme blend va dimg de tdng hgp cac copolyme khdi. [6, 10,11]
CSTNL dugc tdng hgp bing phuang phap cit mach CSTN nhu cit mach nhiet, ca hpc, oxi hda va quang hda. Trong dd, phuong phap cit mach oxi hda va quang hda dugc sir dung de tdng hgp CSTNL cd chiia cac nhdm chile d cudi mach [6]. Cac tac nhan oxi hda nhu phenylhydra2in-FeCl2 [9], phenylhydrazin-oxi khdng khi, axit periodic [5], kali persunfat va propanal [1] da dugc sflr dung dl tdng hgp CSTNL va cao su thita nhien ldng epoxy hda tir latex ciia CSTN. Ravindran va cgng su [10] da tdng hgp dugc CSTNL cd chua nhdm hydroxyl cudi mach bing phugng phap phan hiiy quang hda dung dich CSTN trong toluen d nhiet do phdng vdi su cd mat ciia hydro peroxit, tac nhan ddng thl la metanol va tetrahydroiiiran (THF). Gin day, Pham Hiiu Li va cdng su da tdng hgp dugc CSTNL cd nhdm hydroxyl cudi mach bang phugng phap cit m^ch CSTN bdi tac nhan Fenton va Fenton quang hda. [7]
Trong cdng trinh nay, chiing tdi da tdng hgp dugc CSTNL cd nhdm hydroxyl d cudi mach bing phuang phap cit mach oxi hda CSTN da tach loai protein bing hydro peroxit va natri nitrit; ciu tnie hda hpc cua CSTNL da dugc khao sat bing phd hdng ngoai va phd cgng hudng tir hat nhan; khdi lugng phan tii va dp phan bd Ididi lugng phan tli dugc xac dinh bang phuang phap sac ki tham thiu gel (GPC) va da de nghi ca che ciia phan iing cat mach va hydroxyl hda tao thanh CSTNL cd nhdm hydroxyl cudi mach.
2. Phirong phap nghien cihi va thi^c nghidm 2.1. Nguyen iieu va hoa chdt
Latex cao su thien nhien vdi ham lugng cao su khd 30% ve khdi lugng (iK, - 7,8x10' g/mol, pH - 9,8) dugc dn dinh bing amoniac dugc cung cip bdi Cdng ti TNHH Diu tu va Phat triin Ddng Duong (Viet Nam).
Toluen, tetrahydrofuran (THF), natri dodexyl sunfat (SDS; 99%), metanol (Sigma-Aldrich, USA), hydroquinon, hydro peroxit, natri nitrit, ure, axit formic (Merck, Germany).
2.2. Chi tao CSTN deprotein hoa va CSTNL co nhom hydroxyl cudi mgch CSTN deprotein hda dugc chi tao bing phuong phap xil li latex CSTN vdi 0,2%
ure va 1,0% natri dodexyl sunfat d 30°C trong 60 phiit theo quy trinh ciia Kawahara va cdng su [4]. Sau dd, latex cao su dugc ddng tu bing metanol, rua sach san phim nhilu lin bing nudc cit va siy khd trong tu siy chan khdng din khdi lugng khdng ddi.
Hda tan 5,0 g CSTN deprotein hda frong 100ml toluen frong 5 ngay. Cho 100 ml dung dich do vao binh ciu day trdn, 3 cd, dung tich 250ml, dugc lip dng sinh ban hdi luu, nhiet kl va dat frto may khuiy tir. Sau dd, 20 ml THF, dung dich hydro peroxit
TAP CHi KHOA HOC BHSP TPHCM i « ^"''^ ^'""S "«tgk
(O,lmol), natri nifrit (O,lmol) va 20ml dung dich axit foraiic 5% lan lugt dugc cho vao binh ciu. Hdn hgp dugc khuiy bing may khuiy tir d 60°C frong 24 gid. Sau dd, them 2 ml dung dich hydroquinon 0,5% vao dl tit mach phan ung. Hdn hgp dugc phan thanh hai ldp, tach ldp toluen d frto va kit tiia.bing metanol thu dugc cliat long nhdt. San phim dugc rita nhilu lin bing nudc cit va siy khd d 70°C trong tu siy chan khdng din khdi lugng khdng ddi.
2.3. Phirang phdp nghien ciru
c i u tnic hda hgc ciia CSTNL cd nhdm hydroxyl cudi mach dugc khao sat bing phd hdng ngoai va phd cdng hudng tit h?t nhan. Phd hdng ngoai dugc do tren may Shimadzu Irprestige-21 (Nhat Ban) tai Khoa Hda hgc, Trudng Dai hgc Su pham Ha Ngi; phd cdng hudng tir hat nhan 'H-NMR va "C-NIWR dugc do frong dung mdi CDCI3 tren may ADVANCE 125 MHz va ADVANCE 500 MHz (Bruker, Dire) tai Vien Hda hpc, Vifn Han Itai Khoa hpc va Cdng nghe Vidt Nam.
Khdi lugng phan hi trung binh sd, khdi lugng phan tit trung binh khdi va dd phan bd khdi lugng phan tir ciia CSTNL cd nhdm hydroxyl cuoi mach dugc xac dinh bing phuang phap sic ki tham thau gel (GPC) vdi detector khiic xa ke vi sai RID-lOA (Shimadzu, Nh^t Ban) tai Khoa Hda hgc, Trudng Dai hpc BUioa hpc Tu nhien, DHQG Ha Ndi. Cac phep do dugc thuc hien d SO^C su dung THF lam dung mdi vdi tdc dp l,Oml/phut, chat chuan la polystiren vdi khoi lugng phan tii khoang tir 2,95^10^ g/mol din 4,22x10" g/mol.
3. Ket qua va thao luan
3.1. Cau triic hoa hpc cda cao su thien nhiSn long
Trong phd hdng ngoai cua CSTNL (Hinh 1) cho thiy cac dinh dac trung eho ciu tnic ciia ci>l,4-isopren trong CSTN nhu: Dao ddng hda fri cua lien kit C-H d 2920cm'', dao ddng biln djng ciia lien kit C-H d 1446cm''; dac biet eac dinh phd d 1662 cm' va d 833 cm' ISn lugt dac trung cho dao ddng hda fri ciia lien kit ddi C=C va dao ddng biln d ^ g ciia liSn kit =C-H. Ben cpih dd, cdn xuit hien dai phd hi 3200-3500cm'' dac tnmg cho dao ddng hda tri cua nhdm hydroxyl va dinh phd d 1373 cm'' dac trung cho dao ddng hda fri cua lien kit C-OH. Dilu dd cho thiy ring da cd su xuit hien eiia nhdm hydroxyl b^c 1 trong CSTNL.
TAP CHi KHOA HQC DHSP TPHCM S6 3(81) nam 2016
;nO 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 400 l/cm
Hinh 1. Pho hdng ngogi cua cao su thien nhien long
Trong pho cpng hudng tir hat nhan 'H ciia CSTNL (Hinh 2) xuat hign cac pic dgc trung cho cau tnic c/5-l,4-isopren ciia cao su thien nhien, dd la cac pic d 5 = 1, 65ppm, 2,05ppm va 5,12ppm lan luat la dp chuyen dich hda hoc ciia proton frong nhdm metil is, 3H), metilen {brs, 4H) va nhdm metin khdng no (m, IH).
JIX.
11
Hinh 2. Pho 'H-NMR cua CSTNL Hinh 3. Pho "C-NMR cua CSTNL
TAP CHi KHOA HOC DHSP TPHCM ^^ ^"''^ ^'""S ^ tgk
Tir phd cdng hudng tir hat nhan '^C cua CSTNL (Hinh 3) cho thiy cac pic djc trung cua 5 nguyen tu cacbon trong ciu triic c«-l,4-isopren ciia CSTN: Cl (32,22 ppm), C2 (134,23 ppm), C3 (124,45 ppm), C, (26,34 ppm) va C5 (23,34 ppm). Ngoai ra, cac pic vdi dp chuyin dich hda hpc d 78,39 ppm, 76,98 ppm va 75,57 ppm la cila cac proton frong dung mdi CDCI3 chua deuteri hda.
Nhu vay, cac du lieu phi hdng ngoai va phd cpng hudng tir hat nhan ( H-NMR va
"C-NMR) ciia CSTISIL cho thiy CSTNL dilu chi dugc cd chua nhdm hydroxyl cudi mach va cd cau tnic c/j-l,4-isopren ciia CSTN.
3.2. Khoi lu^ng phan tuvd dpphdn bd khii luang phan tir
Khdi lugng phan til trung binh sd (M„), khdi lupng phan til trung binh khdi (M„) va dp phan bd khdi luang phan tli cua CSTNL cd nhdm hydroxyl cudi mach dugc xac dinh bing phuang phap sic ki thim thiu gel (GPC) vdi detector khiic xa ke vi sai RID- lOA (Shimadzu, Nhat Ban). Kit qua phan tich cho thiy khdi lugng phan tir trung binh sd va khdi lugng phan tit trung binh khdi cua CSTNL tdng hgp dugc lan lugt la 4,836x10' g/mol va 11,317x10' g/mol, vdi ddphan bd khdi lugng la 2,34 (Bang 1).
Bdng 1. Khoi lugng phdn tir vd do phdn bd khoi lugng phdn tic ciia CSTNL Khoi lugng phan tit
trung binh so (g/mol) 4,836x10^
BChoi lugng phan tu trung binh khoi (g/raol)
11,317x103
Do phan bo kh6i lugng phan tir
2,34 3.3. Cff che phan dngcStm^ch vd hydroj^l hda
Trong phan tu CSTN, do clu true d^ng cis va mach cacbon r^t dai nen lien kk a giGa cac nhom metilen (Uen kit C1-C4) kem b^n, dl hi dut duai tac dung cua Iuc ca hgc, nhiet d6, goc tu do hoac biic xa.
1 ^ = CH,
, / "
c.
\ 4CH;
1 - ^ H . ^
4 C H , - . .
= ^ \ H
Day chinh la ca sd cua phan img c5t mach lam giam khdi lugng phan hi ciia CSTN de tao thanh CSTNL da dugc thao Iuan trong nhilu cdng trinh nghien cim trudc day [7, 10].
Trgn CO sd phan ling tao thanh gdc hydroxyl tir phan img cua hydro peroxit vdi nafri nifrit trong mdi tnrdiig axit [2, 5] va phan irng cit mach CSTN bdi cac tac nhto khac [7, 10], chung tdi dl nghi co chi phan ung cit mach CSTN deprotein hda bdi hydro peroxit va nafri nifrit trong mdi tnrdng axit tao thanh CSTNL cd nhdm hydroxyl cudi mach nhu sau:
TAP CHi KHOA HOC DHSP TPHCM So 3(81) nam 2016
H2O2 -I- NO2' - ONOQ- + H+
ONOOH
- ONOO' -I- H2O
^ ONOOH OH' i- NO2 CH3 /H
\ 2 3 /
^=C.
\ ' i>.
+ OH"
^H
CH2-
H
„ 3 / " " " - ' ^ ^ 3 / ™ ^ - -
CH,
\ .
1 ^ = \ 4 .
— C H 2 CH2
5
™N. 3 / "
• 1 / = = \ .
CH, CH,—OH Sff do 1. Ca ehe phdn ung eat mgch vd hydroxyl hoa CSTN
4. Ket luan
Bang phuang phap cat mach CSTN deprotein hoa trong dung dich toluen, voi tac nhan oxi hoa la hydro peroxit va natri nitrit trong moi truang axit, da dieu ch8 dugc CSTNL CO nhom hydroxyl cu6i mach vai Mn - 4,836x10^ g/mol, M„~ 11,317x10^
g/mol va do phan bo khoi lugng phan tu ~ 2,34. Phan ung dugc thuc hien 6 60°C trong 24 gia vol chat dong the la tetrahydrofuran. Cau true hoa hgc cua CSTNL da dugc khao sat biing pho hong ngoai va pho cgng huang tiJ hat nhan 'H va '"'C. Cac dfi lieu phan tich thu dugc xac nhan da xay ra phan ung cat mach oxi hoa CSTN tao thanh CSTNL CO nhom hydroxyl cuoi mach. Ca che phan ung cat mach va hydrxyl hoa da dugc de nghi tren ca sa cac ket qua nghien cuu da cong bo.
TAP CHl KHOA HOC DHSP TPHCM LS Birc Giang vd tgk
TAI LIEU THAM KHAO
L Chaikumpollert 0., Sae-Heng K., Wakisaka O., Mase A., Yamamoto Y, Kawahara S.
(2011), "Low temperature degradation and characterization of natural rubber", Polym.
Degrad Stab, 96, pp. 1989-1995.
2. Kennett B.C., Davies M.J. (2007), "Degradation of matrix glycosaminoglycans by peroxynifrite/peroxynifrous acid: Evidence for a hydroxyl-radical-like mechanism".
Free Radio. Biol Med 42, pp. 1278-1289.
3. Kodama S., Nishi K., Furukawa M. (2003), "Preparation of low molecular weight natural rubber by ozonolysis of high ammonia latex". J. Rubb. Res., 6, pp. 153-163.
4. Kawahara S, Klinklai W, Kuroda H, Isono Y (2004), "Removal of proteins from natural rubber with urea", Po/vmv4rfv7ec/z«D/., 15 , pp. 181-184.
5. Lehnig M. (1999), "Radical mechanisms of the decomposition of peroxynitrite and the peroxynitrite-COa adduct and of reactions with L-tirosine and related compounds as studied by 15N chemically induced dynamic nuclear polarization". Arch. Biochem.
Biophys. 368, pp. 303-318.
6. Nor H.M., Ebdon J.R. (1998), "Telechelic liquid natural rubber: A review". Prog Polym. Sci, 23,pp.U2-m.
7. Pham H.L, Do B. T, Pham T S., Le D. G. (2013), "Synthesis and characterisation of hydroxyl-terminated liquid natural rubber by photo-Fenton reaction", ASEAN J. Sci.
Technol. Dev, 30, pp.29-36.
8. Phinyocheep P., Phetphaisit C.W., Derouet D., Campistron, I., Brosse, J.C. (2005),
"Chemical degradation of epoxidized natural rubber using periodic acid: Preparation of epoxidized liquid natural rubber", J. Appl. Polym. Sci, 95, pp.6-15.
9. Huy H.T, Nga, N.T, Hong L.Q., Chu P.N.S. (1996), "Depolymerization of natural mbber latex using phenylhydrazine-FeCl, system". Pure Appl Chem, 33, pp 1923- 1930.
10. Ravindran, T., Nayar M.R.G, Francis D.J. (1988), "Production of hydroxyl-terminated liquid nahiral mbber—Mechanism of photochemical depolymerization and hydroxylation", J. Appl Polym. Sci,3S,pp.l227-l239.
11. Zainol I., Ahmad M.I., Zakaria EA., Ramli, A., Marzuki, H.F.A., Aziz, A.A. (2006),
"Modification ofepoxy resin using liquid natural mbber", Mjter.Sci Forum 517 pp.
272-274.
(Ngiy na sosn nh0n auoo bil: 03-12-2015: ngiy phin biSn dinh gii: 06-3-2016- ngiy chip nh$n ding: 17-3-2016)
