IJCPE Vol.5 No. 3 (2007) Iraqi Journal of Chemical and Petroleum Engineering Vol.10 No.3 (September 2009) 57-63 ISSN: 1997-4884 Methanol Effect on color stability and shelf life of phenolic Resin compound under acidic conditions Ammar Waadallah Ahmed * * bio chemical engineering department – Al Khwarizmi College of engineering- University of Baghdad – Iraq Abstract The object of this work is to investigate the effect of the addition of methanol on the shelf life and color characteristics of novolak resin. Different percentages were added and two mechanisms were suggested for the addition. High ortho structure (1, 2-3) novolak resin was prepared and used in the above investigation. Experimental determination using FT-IR and UV-spectroscopy showed that on the addition of 30% of methanol and according to the second mechanism of addition novolak shelf life increased to 12 months without obvious decomposition and color change. It is suggested that methanol plays an important role in the inhabitation of the reactive sites on the resi n that are responsible for the oxidation of the polymer when exposed to atmospheric or storage conditions. Introduction Phenol, formaldehyde resin is considered to be one of the most important polymers in the molding industry. The first commercially available resin is indeed phenol formaldehyde resin developed by Leo M. Backland in 1907 based on earlier discovery by A. Von Bayer in 1872. Phenolic resins (high ortho figure (1)) are produced by the reaction of formaldehyde with excess phenol under acidic condition (pH = 1 to 3) with typical formaldehyde to phenol ratios are between 0.8 and 0.85. The most common industrial catalysts are oxalic, hydrochloric, sulfuric, phosphoric, and sulfuric acids. Fig. 1 Random and High ortho novolak structures University of Baghdad College of Engineering Iraqi Journal of Chemical and Petroleum Engineering Methanol Effect on color stability and shelf life of phenolic Resin compound under acidic conditions 58 Vol.10 No.3 (September 2009) Color change Before(20) use this resin in molding to produce any composite material some properties were changed during storage starting from oxidation to color instability which affect the final composite properties The main reason for color change of novolak is the existence of un-reacted phenol that is not removed completely from final product that undergoes decomposition reaction (20, 21, and 22). This compound is considered responsible for the color change from colorless to reddish. The above compound known as Quinones root (1, 5, and 22), attacks the polymer chain and causes decomposition by breaking the polymeric chain at these sites. The following mechanism of attack is proposed: It is also possible that uneven distribution of reactive site on the polymer may lead to oxidation and consequent decomposition of the final polymer structure. Modified resins Polymers are considered to be photo-resistant and stable, if they resist the influence of oxidation in an inert atmosphere without changing in their properties significantly. The following methods are suitable to improve the oxidative resistance of phenolic resins [1] 1. Etherification or Estrification of phenolic hydroxyl group. 2. Complex formation with polyvalent elements (Ca, Mg,Zn,Cd,…). 3. Replacement of the methylene linking group by heteroatoms (O,S,N,Si,…). The most important general modification reactions in phenolic polymer chemistry are the etherification and C- alkylation (Friedel-Crafts) reaction (1). Both reactions are commonly used to enhance flexibility and compatibility with polymers and solvent to reactivity and performance. Etherification reaction The hydroxymethyl group in phenol prepolymers can easily be etherified (A) with alcohol because of their tendency to form hydroxybenzylcarbonium ions. High hudroxymethylated phenols and an excess of alcohol are used to avoid the self-condensation reaction. In general the reaction is performed with monoalcohols like methanol, butanol and isobutanol. On the other hand, the etherification of the phenolic hydroxyl group (O-alkylation (B)) leads to improved alkali resistance. Better flexibility, light fastness and with allyl compounds, enhanced air drying properties are also obtained. Experimental Work The reaction of phenol with formaldehyde in acid medium proceeds as follows: 2C6H5OH + CH2 O C6H4OHCH2 C6H4OH + H2O Novolak was prepared by reacting formaldehyde with excess phenol under acidic conditions; hydrochloric acid was used as a catalyst. The reaction was carried out in stainless steel batch reactor as shown in figure (2). High ortho novolak resin was prepared using the following well known ratios (2, 3):- F/P = 0.8, A/P = 0.01 and W/F = 2..5577 or OH . O O . Environment effect Ammar Waadallah Ahmed 59 Vol.10 No.3 (September 2009) Fig. 2 Equipments used in the production of novolak resin The reaction was carried out for about 4 hours at an operating temperature of 80oC and pH of 1.5 in a 3 liter stainless steel jacketed reactor. A provision was made for mechanical stirrers to be immersed into the reactor. Other previous were made for a condenser, reactant input, and temperature and pressure control instrument. Products are withdrawn from the bottom of the reactor. Different percentages of methanol added and two mechanisms were suggested for the addition .Methanol ratio was added according to formaldehyde concentration. First Mechanism of Addition Reactants were added to the reactor according to the molar ratio mentioned earlier (2, 3) and then methanol (20% of the total amount of reactants at 20oC) was added to the reactants at a mixing speed of 500 rpm then, the temperature was raised up to 80oC gradually. Reaction was continued for about 4 hours and novolak resin was formed. Heating was halted and two layers were observed. i.e. water at the top of the novolak was formed. In order to get rid of the water formed as a by-product, the reactor was heated up to 120oC for 2 hours with mixing under 0.1 bar vacuum. To remove about 90% of the formed water. Second Mechanism of Addition The same procedure above was carried out; however, methanol was added after completion of polymerization i.e. when the two layers of by-product and novolak were formed. Then the mixing and vacuum process was continued until about 90% of the residual water was removed. The same procedure was carried out several times using different percentage of methanol in order to determine the optimum value. The following ratios were suggested (15, 30, 45 and 60%) based on total volume. Electronic spectrophotometer measurements were conducted by Schimadzu UV-214 A (UV-Visible Spectrophotometer) using MEK (Methyl Ethyl Keton) as a solvent and a quartz cell of 1.0 cm path length. Samples for that purpose were prepared as shown in table (1). A comparison was made between samples with methanol added against this with no methanol added using FT-IR. Table (1): Design parameter for the experimental work RRuunn NNoo.. MMiixxttuurree vvoolluummee mmll.. MMeetthhaannooll vvoolluummee mmll.. TToottaall vvoolluummee mmll.. PPeerrcceennttaaggee ooff MMeetthhaannooll %% 11 6600 00 6600 00%% 22 6600 1100..66 7700..66 1155%% 33 6600 2255..77 8855..77 3300%% 44 6600 4499 110099 4455%% 55 6600 9900 115500 6600%% Results and Discussion SSaammpplleess were left for a period of about 12 month under ordinary storage at atmospheric conditions and monthly tests were carried out using UV-Spectroscopy and finally FT-IR instruments. Color change was observed by naked eye. The following results are obtained and showed in the table (2). Short shelf life and color change were observed for samples that were not treated with methanol. A decomposition of its structure is expected due to activity of reactive sites. Methanol was suggested as an additive for two main reasons. 1. Its structural composition is similar to that of formaldehyde. 2. Cheap and readily available. According to the experimental results the second mechanism of addition was in favor of the first i.e. addition of methanol is suggested to be added after the polymerization step of water mixing and vacuum application for water withdrawal. It could be seen that sample (3) at 30% methanol did not suffer structural and no color change, as shown in table (2) and figure (3). Methanol Effect on color stability and shelf life of phenolic Resin compound under acidic conditions 60 Vol.10 No.3 (September 2009) First month: All samples absorbed the light at (λ = 343 nm) with no color change as shown in data table (2). Second to 12th month: First sample changed into reddish brown color with (λ = 363 nm ±5) as shown in table (2). Third to 12th month: All samples showed decomposition and color change except sample (3) with 30% methanol addition as shown in table (2). The value of λ was 345 nm ±2 during the above periods. The effect of methanol addition on the polymer can be explained as follows: Assists in the withdrawal of by-product water formed in reaction which considered being a physical process (16, 17, 18, and 22). Inhibit reactive sites of –CH2 groups i.e. that exist on the high ortho novolak which is considered to be a chemical process (11, 16, 17, and 19). The effect of methanol addition on the un-reacted chemical can be explained as follows: 1. Complete the phenol – formaldehyde reaction and obtain further novolak which is a chemical process (11, 19, and 20). 2. Get ride of un-reacted phenol from reaction mixture which is considered responsible for the decomposition of novolak structure during storage and hence reducing the shelf life (10, 11, 12, and 15). FT-IR test made for samples (1) and (3) indicated the fact that methanol addition according to the second mechanism was of physical meaning and was not chemically oriented since no structural changes were observed as shown in figures (4, 5 and 6). Fig.3 The change in color for sample (1) and (3) after 12 month of novolak resin Table (2): UV-visible results for each sample with the methanol percentage deferent during 12 month SSaammpplleess mmoonntthh ppeerriioodd MMeetthhaannooll %% λλ CCoolloorr cchhaannggee 11 11 00 334433 NNoo cchhaannggee 22 11 1155 334433 NNoo cchhaannggee 33 11 3300 334433 NNoo cchhaannggee 44 11 4455 334433 NNoo cchhaannggee 55 11 6600 334433 NNoo cchhaannggee SSaammpplleess mmoonntthh ppeerriioodd MMeetthhaannooll %% λλ CCoolloorr cchhaannggee 11 22 00 334433 cchhaannggee 22 22 1155 334433 NNoo cchhaannggee 33 22 3300 334433 NNoo cchhaannggee 44 22 4455 334433 NNoo cchhaannggee 55 22 6600 334433 NNoo cchhaannggee SSaammpplleess mmoonntthh ppeerriioodd MMeetthhaannooll %% λλ CCoolloorr cchhaannggee 11 33 00 334433 cchhaannggee 22 33 1155 334433 cchhaannggee 33 33 3300 334433 NNoo cchhaannggee 44 33 4455 334433 cchhaannggee 55 33 6600 334433 cchhaannggee SSaammpplleess mmoonntthh ppeerriioodd MMeetthhaannooll %% λλ CCoolloorr cchhaannggee 11 1122 00 334433 SSttrroonngg cchhaannggee 22 1122 1155 334433 SSttrroonngg cchhaannggee 33 1122 3300 334433 NNoo cchhaannggee 44 1122 4455 334433 SSttrroonngg cchhaannggee 55 1122 6600 334433 SSttrroonngg cchhaannggee Ammar Waadallah Ahmed 61 Vol.10 No.3 (September 2009) FFiigg..44FFTT--IIRR SSttaannddaarrdd PPlloott ooff OOrrtthhoo NNoovvoollaakk RReessiinn wwiitthhoouutt DDeeccoommppoossiittiioonn FFiigg..55 FFTT--IIRR PPlloott ooff OOrrtthhoo NNoovvoollaakk RReessiinn wwiitthhoouutt MMeetthhaannooll aaddddiittiioonn SSaammppllee ((11)).. Methanol Effect on color stability and shelf life of phenolic Resin compound under acidic conditions 62 Vol.10 No.3 (September 2009) FFiigg..66 FFTT--IIRR PPlloott ooff OOrrtthhoo NNoovvoollaakk RReessiinn wwiitthh MMeetthhaannooll aaddddiittiioonn SSaammppllee ((33)).. Conclusions 1. Experimental determination using FT-IR and UV- Spectroscopy showed that on the addition of 30% of methanol and according to the second mechanism of addition, lead to the increase of shelf life to 12 months without obvious decomposition and color change. 2. It is suggested that methanol plays an important role in the inhabitation of the reactive sites on the resin which are responsible for the oxidation of the polymer when exposed to atmospheric or storage condition. Nomenclature A moles of Catalyst F moles of Formaldehyde P moles of Phenol W moles of Water λ Absorbed light of UV-Spectroscope References 11.. Knopf A. and Scheib W. (1979) Chemistry and Application of Phenolic Resins, Springer – Verlag Publishing Com., NY. 22.. Van Oss J.F. (1973), Journal of Material and Technology, Vol. 6, 586. 33.. Kirk – Othmer (1984), Encyclopedia of Chemical Technology, Vol. 10, 335, John Wiley & Sons, Inc. 44.. Francis A., Carey (1996), Organic Chemistry, McGraw-Hill companies, Third Edition. 55.. Kirk – Othmer (1984) “Encyclopedia of Chemical Technology” Vol. 17, 384, John Wiley & Sons, Inc.. 66.. Linjie Zhi, Tong Zhao (2003) Preparation of Phenolic Resin/Silver Nanocomposites via in-situ Reduction, Chinese Chemical Letters Vol. 14, No. 4, pp 426 – 428. 77.. Leite, J. L.; Pires, A. T. N.; Souza, S. M. A. G. Ulson de (April - June 2004) Characterization of a Phenolic resin and sugar cane pulp composite, Brazilian Journal of Chemical Engineering, Vol. 21, No. 02 pp. 253 – 260. http://www.scielo.br/cgi-bin/wxis.exe/iah/?IsisScript=iah/iah.xis&base=article%5Edlibrary&format=iso.pft&lang=i&nextAction=lnk&indexSearch=AU&exprSearch=LEITE,+J.+L. http://www.scielo.br/cgi-bin/wxis.exe/iah/?IsisScript=iah/iah.xis&base=article%5Edlibrary&format=iso.pft&lang=i&nextAction=lnk&indexSearch=AU&exprSearch=PIRES,+A.+T.+N. http://www.scielo.br/cgi-bin/wxis.exe/iah/?IsisScript=iah/iah.xis&base=article%5Edlibrary&format=iso.pft&lang=i&nextAction=lnk&indexSearch=AU&exprSearch=SOUZA,+S.+M.+A.+G.+ULSON+DE http://www.scielo.br/cgi-bin/wxis.exe/iah/?IsisScript=iah/iah.xis&base=article%5Edlibrary&format=iso.pft&lang=i&nextAction=lnk&indexSearch=AU&exprSearch=SOUZA,+S.+M.+A.+G.+ULSON+DE Ammar Waadallah Ahmed 63 Vol.10 No.3 (September 2009) 88.. E. Fossum and K. Matyjaszewski, (1997), Morphology of Polystyrene-block-poly (methylphenylsilylene). Journal of Macromolecules, 30 (6), pp 1765–1767. 99.. Julia A. King, Michael D. Via, Jason M. Keith (2009), Effects of Carbon Fillers on Rheology of Polypropylene-based Resins. Journal of Composite Materials, Vol. 43. 1100.. H. Liu, X. Ge, Y. Ni, Q. Ye, Z. Zhang, (2001), Preparation and characterization of ZnS / poly (acrylamide-co-acrylic acid) dendritical nanocomposites by γ-irradiation. Radiat. Phys. Chem, 61, 89. 1111.. D. Kumlutas and I. H. Tavman, (2006), A Numerical and Experimental Study on Thermal Conductivity of Particle Filled Polymer Composites. Journal of Thermoplastic Composite Materials, 19(4): 441 - 455. 1122.. Chin-Lung Chiang, Chen-Chim. MA,1 Dai-Lin WU,1 HSU-Chiang Kuani, (2008), Preparation, Characterization, and Properties of Novolac- Type Phenolic/SiO2 Hybrid Organic–Inorganic Nanocomposite Materials by Sol–Gel Method, Journal of Frontiers of Chemical Engineering in China, Volume 2, Number 3. 1133.. D. Mangaiyarkarsai, K. Kamada, N. Saito, S. Ichikawa, T. Akai, K. Kadono and T. Yazawa, (2005), large area multi-color changes induced by femtosecond laser pulses in soda-lime silicate glass embedded with Ag nanoparticles. Journal of Non- Crystalline Solids, Volume 351, Pages 3156-3159. 1144.. John J. Stolfo (nov. 6, 1979) Production of novel modified novolak resin and there use in pressure sensitive papers, United State patent (4,173,684). 1155.. Maynard H. Olson, John C. Chang, Imelda A. Muggli (apr. 18, 1989) Process for providing polyamide materials with stain resistance with sulfonated novolak resin and polymethacrylic acd, United State patent (4,822,373). 1166.. Medhat A. Toukhy, Leo Klawansky (mar. 22, 1983) Positive novolak photo resist compositions, United State patent (4,377,631). 1177.. Kazuto Kunita (may 21, 2002) Photosensitive resin composition image recording material and planographic printing plate using the same, United State patent (6,391,519). 1188.. Zoilo Cheng Ho Tan (aug. 22, 2000) Photoresist developer and method, United State patent (6,107,009). 1199.. Yoshiaki Kurimoto, Katsuhiro Maruyama, Akira Yoshitomo, Satoru Yoshida, Satoru Kitano (Jun. 5, 2001) Novolak type phenol resin, United State patent (6,242,533). 2200.. Edwin S. Smith (Nov. 12, 1968) Phenol- formaldehyde novolak-phenol-formaldehyde resole molding surface for a reinforced matrix base sheet, United State patent (3,410,718). 2211.. NPCS Board of Consultants & Engineers, (08 Jun 2009) Phenolic Resins Technology Handbook, Niir Project Consultancy Services. 2222.. Richard M. Lazarus, Randall Kautz, Sunit S. Dixit (apr. 24, 1990) High contrast high thermal stability positive Photoresist with mixed cresol and hydroxybenzaldehyde prepared novolak and photosensitive diazoquinone. United State patent (4,920,028). 2233.. Yoshitomo Nakano, Masumi Kada (oct. 24, 1989) High molecular weight ortho cresol-novolak resins and process for the preparation thereof using alcoholic or acidic organic solvent, United State patent (4,876,324). http://www.springerlink.com/content/120534/?p=880589b4bdbf422e91846c9ddb8a673a&pi=0 http://www.springerlink.com/content/120534/?p=880589b4bdbf422e91846c9ddb8a673a&pi=0 http://www.springerlink.com/content/120534/?p=880589b4bdbf422e91846c9ddb8a673a&pi=0