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1Givi Papava, Professor, Doctor, Petre Melikishvili Institute of Physical and Organic Chemistry of Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia, ORCIDID: https://orcid.org/0000-0002-8837-4909
Marina Gurgenishvili, Doctor, Petre Melikishvili Institute of Physical and Organic Chemistry of Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia, ORCID ID: https://orcid.org/0000-0002-2272-8380
Ia Chitrekashvili, Doctor, Petre Melikishvili Institute of Physical and Organic Chemistry of Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia, ORCID ID: https://orcid.org/0000-0002-6673-191X
Eter Gavashelidze, Doctor, Petre Melikishvili Institute of Physical and Organic Chemistry of Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia, ORCID ID: https://orcid.org/0000-0002-0479-5782
Nora Dokhturishvili, Doctor, Petre Melikishvili Institute of Physical and Organic Chemistry of Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia, ORCID ID: https://orcid.org/0000-0002-6021-1120
DOI: https://doi.org/10.31435/rsglobal_ws/30092020/7207
CHEMISTRY
SYNTHESIS OF NOVOLAC TYPE PHENOL FORMALDEHYDE OLIGOMERS
ARTICLE INFO
Received: 08 July 2020 Accepted: 20 August 2020 Published: 30 September 2020
KEYWORDS
oligomer, polymer, polymerization, paraform, oxibenzene, formaldehyde, novolac, melt.
ABSTRACT
Mixed novolac-type oligomers are synthesized in the melt on the base of oxibenzene and its alkilsubstituted. The content of dioxibenzene changes in the range of 0,1 - 0,5 mol. The influence of temperature and duration of the reaction of initial components, transformation has been studied.
Citation: Givi Papava, Marina Gurgenishvili, Ia Chitrekashvili, Eter Gavashelidze, Nora Dokhturishvili. (2020) Synthesis of Novolac Type Phenol Formaldehyde Oligomers. World Science. 7(59). doi: 10.3143 5/rsglobal_ws/30092020/7207
Copyright: © 2020 Givi Papava, Marina Gurgenishvili, Ia Chitrekashvili, Eter Gavashelidze, Nora Dokhturishvili. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
For the synthesis of oligomers of the novolac type, oxybenzene and its alkyl derivatives are used as starting components. Formaldehyde is used as the second component. A technology has been developed for obtaining oligomers in a melt, in which there is no wash water. The resulting oligomer contains a minimum amount of unreacted oxybenzene.
To obtain mixed oligomers, along with oxybenzene, its alkyl-substituted derivatives were used. The presence of alkyl groups in the oligomer has a plasticizing effect, which is important during the processing of plastics.
When carrying out the synthesis reaction of the oligomer in the melt, paraform is used as the second component, which depolymerizes when heated and releases formaldehyde. Formaldehyde, when formed, immediately reacts with oxybenzene and its alkyl-substituted derivatives and forms methylol derivatives:
+ CH2O
OH
HOH2C ^pH3
CH2OH
H3
+ CH2O
H
OH ^—C
+ CH2O CH3
CH2OH
CH2OH
CH2OH
CH
CH3
CH
CH2OH
In the production of novolac, the reaction is carried out in the presence of an excess of hydroxy derivatives of benzene. The reaction temperature and catalyst concentration affect the reaction rate, while the duration affects the average molecular weight of the oligomer.
In the synthesis of mixed oligomers, as the second component, together with oxybenzene, we used 1-hydroxy-2-methyl-, 1-hydroxy-3-methyl- and 1-hydroxy-4-methylbenzene.
Since the oxybenzene derivative is used in excess, and, besides, the rate of the condensation reaction is higher than the rate of the addition reaction, the oligomers practically do not contain methylol groups, which is confirmed by a spectroscopic study.
The intensity of the absorption bands characteristic of methylol groups in the region of 1030 cm-1 first appears, and then gradually decreases and by the end completely disappears.
The process of interaction of oxybenzene and its methyl-substituted derivatives with formaldehyde was studied. The results are shown in Figure 1. The molar ratio of oxybenzene and its methyl derivative in the mixture was 0.5: 0.5, the reaction temperature was 40-100 °C. The molar ratio of the mixture of oxybenzene and its methyl derivative to formaldehyde was 1.15: 1, respectively.
As can be seen from the data in the figure, the course of the reaction is influenced by both the temperature and the duration of the reaction. With increasing reaction time and temperature, the conversion increases. For example, in the interaction of oxybenzene and 1-hydroxy-2-methylbenzene with formaldehyde at 40 ° C, after 20 minutes the degree of conversion is 58.8%, at 60 °C - 67.3, at 80 °C it increases to 82, and at 100 °C it reaches 87%.
,CH2OH HOH2C
\
■ HO
CH2-O-H2Cn
-CH2O
CH2S
CH2OH HN +
CH7
In the course of the reaction, formaldehyde can interact with the already formed methylol derivative, or with the oligomer. In parallel, methylol derivatives interact with each other, or with hydroxy derivatives of benzene, or with oligomers. During this interaction, along with the addition reactions,
3
+
-H2O
98 7(59), September 2020
RS Global
polycondensation reactions proceed in parallel. The addition in the molecule of the oxy derivative occurs with the participation of active hydrogen atoms in the ortho and para positions to the hydroxyl.
Reaction duration, hours
Fig.1. Change in the degree of conversion of oxy- and 1-hydroxy-2-methylbenzene (a), oxy- and 1-hydroxy-3-methylbenzene (b) and oxy- and 1-hydroxy-4-methylbenzene (d) with formaldehyde in the melt.
In the case of oxybenzene and 1-hydroxy-3-methylbenzene, the conversion degree increases in the following sequence: 55.1> 64.3> 79.3> 83.6%; in the case of oxybenzene and 1-hydroxy-4-methylbenzene - 59.8> 69.4> 84.0> 88.8%.
Schematically, the condensation process in an acidic medium can generally be expressed as
follows:
( x + 1 ) [ C6H5OH + C6H4CH3OH ] + xCH2O ^ x H2O + H [ - ( C6H3OH ) - CH2 - ( C6H2( CH3)OH ) -CH2 - ]- C6H3(CH3 )OH , where x = 10 - 14
The degree of polymerization of the novolac oligomers obtained in the melt is 10-14. As can be seen, at the increase of the process duration, the amount of formaldehyde that doesn't enter the reaction decreases. The intensity of the decrease is higher in the initial stage. For example, if during the course of the reaction at 40 0C in the case of oxybenzene and 1 -hydroxy-2-methylbenzene, after 2 minutes the amount of formaldehyde not reacted is 91.1%, after 5 minutes it decreases to 74.7, after 10 minutes - 59.5, after 15 minutes -48.9, and after 20 minutes to 41.1%; at 600C, respectively 77.6> 60.7> 43.4> 39.5> 32.7%; at 80 0C - 71.0> 49.2> 32.9> 23.2> 18.0%; and at 100 0C - 57.7> 36.7> 20.9> 15.5> 12.3%. A similar trend is observed in the case of other oxides.
Mixed oligomers dissolve in alcohol, acetone, dimethylformamide, tricresol, etc. When interacting with hexamethylenetetramine at 180-200 0C, they are structured and turn into resite, which have a spatial structure. At the same time, they completely lose solubility in the above solvents and do not melt.
REFERENCES
1. A.M. Toroptseva, K.V. Belogorodskaya, V.M. Bondarenko. Laboratory practicum in chemistry and technology of high molecular compounds. Leningrad, "Khimia" 1972, p. 199
2. Technology of plastic masses (under the editorship of V.V. Korshak). Moscow, "Khimia", 1985, pp.25
3. G.Sh. Papava, N.S. Gelashvili, Z.P. Molodinashvili, K.R. Papava, N.Z. Khotenashvili, I.A. Chitrekashvili. Obtaining of novolac type phenol formaldehyde oligomer in the melt. Azerbaijanian Journal of Chemistry, 2005, № 4, p.33-35.
