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9CHEMIA | ХИМИЧЕСКИЕ НАУКИ
OLIGOMERS EPIBROGIDR WITH BENZTRIAZOLYL MODIFIER AND RUBBER
Ismailov Alisher Israilovich,
Senior Research Fellow-Competitor, faculty «Oil and Gas»
ABSTRACT
As a result of spontaneous oligomerization of epibromohydrin (EBG) with benzotriazole (BTZ) in polar solvents form soluble oligomers containing reactive functional groups. Kinetic studies determined the reaction order for components, the activation energy. Spectroscopic studies found the chemical structure of the resulting oligomer-based EBG with BTZ. It is found that oligomeric quaternary ammonium compounds can be used as modifiers for rubbers and rubber.
Key words: epibromohydrin, benzotriazole, oligomer, oligomerization, rubber, gum elastic modification.
Introduction
It is known that epihalohydrin-based oligomers are widely used in the manufacture of synthetic rubbers, stabilizers for polymeric materials, epoxy resins, ion exchange resins and others. Therefore, the synthesis of new oligomers based epibromohydrin with predetermined properties are of great theoretical and practical importance. In this regard, by obtaining promising oligomers are oligomerization epihalohydrin to secondary and tertiary aminami1,2.
It should be noted that the development of efficient methods for the preparation of oligomeric compounds, study of their properties and finding ways to practical use is a major concern today. In recent years, there is a tendency to expand the research work in the field of synthesis, properties, and finding ways of using oligomers in the different sectors of the economy. As follows from the above epihalohydrin becomes the object of numerous studies, as it is used to obtain near nitrogenous compounds. However, a systematic study of the processes of synthesis of oligomers based on EGG with nitrogen-containing compounds are not available.
Therefore, the synthesis of oligomers based epibromohydrin, the study of their physic-chemical properties and applications, the study of the kinetics of the respective oligomerization process is very aktualnym3-5.
Experimental
Methods spontaneous polymerization EBG with BTZ studied the dilatometric method (as well as the gravimetric method to study the kinetics of formation of oligomers at high degrees of conversion), by allowing the selection of the reaction mixture during the oligomerization determine the yield of the polymer.
The conversion of monomers in the oligomer q (proportion in weight %) was calculated by the formula
Q=AV/V0.K'
wherein V0- initial volume of the reaction mixture at predetermined temperature oligomerization ml; AV- change in volume of the reaction mixture over period ml; K'-contraction ratio determining the degree of change in volume of the monomer mixture at this t emperature after complete conversion of the monomers into the oligomer.
The coefficient of contraction depends on the density of the monomer and oligomer and is calculated by the formula:
1
1
K' =
Pm Pn 1
Pn
where p , p - density respectively monomer and oligomer, g/sm3.
Before setting up systematic experiment in all cases carried out the pre-test reproducibility. The final product obtained was dissolved in ethanol and precipitated with diethyl ether to remove non reagiration monomers. Thereafter, the oligomer was dried in a vacuum oven at room temperature to constant weight.
IR-spectra of the monomers and the oligomers removed spectrophotometer «Spekord - 75UR» in the wavelength range 500-4000 sm-1. Samples were prepared by compression into tablets with KBr.
PMR-spectra were recorded on the device SXP-5-100 firm «Bruker» (Germany) in a solution of heavy water at a frequency of 94,1 MHz.
Results and Discussion
We have found that the interaction EBG with BTZ spontaneous oligomerization process takes place in the absence of initiators at moderate temperatures (room and above). Studying the process of spontaneous oligomerization flowing in interaction with nitrogen-containing heterocyclic EBG is scientific and practical interest.
The study of kinetics of spontaneous oligomerization EBG with BTZ initial stage conversion with different molar ratios of components showed that the highest yield of the oligomer is achieved with an equimolar ratio of starting monomers.
In order to find optimal conditions for obtaining the oligomer based EBG with BTZ oligomerization was conducted in solvents with different dielectric constants (ethanol, tetrahydrofuran and water). Established experimentally that the rate of spontaneous oligomerization flowing in the interaction the EBG with BTZ depends on the environment occurs rather easily in water and in polar organic media. Increasing the polarity of the medium to accelerate the process of spontaneous oligomerization, and in all cases, the greatest velocity is observed in the aqueous medium. Increasing the speed of spontaneous oligomerization
with increasing polarity of the medium in the interaction EBG with BTZ, apparently, can be explained by the acceleration of the reaction Menschutkina, is the limiting stage of the process of spontaneous oligomerization. The interaction EBG with BTZ due to the high reactivity of the bromine atom EBG and nucleophilicity of the nitrogen-containing compounds have the quaternization of the amino compounds in the intermediate product which enhances the activity of the functional groups, which in turn increases the rate of spontaneous oligomerization occurs at the interaction EBG with BTZ.
In order to clarify the dependence of the rate of spontaneous oligomerization flowing in the interaction EBG with BTZ temperature, series of experiments in ethanol at 298-313 K, the rate of conversion of the starting monomers in the oligomer increases with increasing temperature and its dependence on the return value of the temperature in the range of 298-313K obeys the Arrhenius equation. The overall activation energy determined from the slope of the curve defined in the Arrhenius coordinates in ethanol is 30,1 kDj/mol, which is close to the activation energy of reactions Menshutkin. It should be noted that during the spontaneous oligomerization EBG with BTZ at 313K output oligomer equivalent ratio of the initial components reached 75-76%.
The results of the analysis of the PMR spectrum of the reaction product EBG with BTZ shows the formation of new proton signals are absent in the spectrum of the starting materials. Benzene ring produces signals in the 8,0-8,2 m.f. in 5,01 m.f. singlet proton signal of a methylene group N+CH2, while in the region of 3,9 m.f. signals appear OCH2, groups. The PMR spectrum of the oligomer EBG with BTZ signals BTZ
iiCH- CH - c
o
y
Hp
I + II
proton in 8,2-8,5 m.f., signals of active hydrogen functional NH group shown at 6,1-6,4 m.f.
For qualitative characteristics of reactions was used as the method of infrared spectroscopy. Spectral analysis of the starting materials were subjected to a reaction product thereof and a time at room temperature. It should be noted that the results of the PMR spectroscopy fully confirmed by comparison of the IR spectra and EBG oligomer obtained from them.
The IR spectrum of the oligomer has an absorption band in 1665 sm-1 due to bending vibrations of OH groups, 1630 sm-1 are assigned to the stretching vibrations of C=N communications, 1600-1500 sm-1 due to stretching vibrations of the aromatic ring. Stretching vibrations of C-Br communication (720-750 sm-1) belonging to the group CH2Br EBG and bending vibration NH group (1545 sm-1) completely disappear due to the formation of new quaternary ammonium groups in the region of 22002500 sm-1. It also formed a new strong absorption bands in the 1050-1100 sm-1 related to the asymmetric stretching vibrations of ether (-C-O-C-) connection by opening the epoxy groups (1260, 930-855 sm-1) in the EBG spontaneous oligomerization process.
Experimentally found that conventional radical polymerization inhibitors (difenilpikrilgidrazin
2,2,6,6-tetramethylpiperidyl-1-oxyl, hydroquinone and oxygen from the air) on spontaneous oligomerization process EBG with BTZ no significant effect, indicating the nature of non-radical oligomerization process.
On the basis of kinetic and spectroscopic studies of the reaction of epibromohydrin with benzotriazole and reception on their basis of the oligomer can be represented as follows:
— CH2- CH - o —
©
I
CH
I
NH Br
O
NH
il
J-N
It should be noted that the flow of information about the oligomeric antioxidants for rubbers and rubbers, showing their particular effectiveness and protective action kauchukah6. In this connection, practical interest is the modification of some synthetic rubbers synthesized by us on the basis of oligomeric compounds EBG with BTZ to produce on their basis rubbers with improved physical and mechanical properties.
Addition of oligomeric compounds in an amount of 0,6 phr isoprene rubber stamps in SKI-3 together with the other
ingredients of rubber compositions were prepared. When using the compounds synthesized in rubber compounds found that oligomer EBG with BTZ is effective rubber accelerators and contributes to obtaining rubbers with improved physical and mechanical properties. Test vulcanizates showed that when using the compounds synthesized oligomer resistance to tearing increased compared to vulcanizate of standard rubber composition (tab.).
Table.
Indicators oligomer EBG with BTZ Standard rubber compound The modified rubber mixture
Tensile strength, MPa 26,0 28,5
Relative extension, % 841 903
Relative residual deformation after break,% 13 11
The coefficient of thermal aging at 373 K on the tensile strength 0,72 0,90
The coefficient of elongation 0,77 0,78
Thermal aging rubbers based on isoprene rubber stamps SKI-3 was carried out at 373 K for 72 hours. As can be seen from the table, thermal aging results in lower initial physical-mechanical properties of the vulcanizate modified to a lesser extent than standard vulcanizate. Thermal aging is especially dramatically affects the vulcanizate derived from a standard rubber composition. Tear resistance changes at a greater rate than the elongation. The change of physical and mechanical properties of the vulcanizate of the modified during aging as compared to standard because oligomers based on the EBG with BTZ introduced in the rubber composition to inhibit the chain reactions of oxidation.
Increased resistance to thermal aging of rubber is caused by binding of accelerators and antioxidants in the polymer chain, which contributes to a uniform distribution of the rubber composition.
The use of synthesized oligomers EBG with BTZ as rubber vulcanization accelerators (optimum vulcanization is reduced by 15 minutes - the optimum curing the mixture to a standard - 45 minutes, and for the modified rubber oligomer EBG with BTZ - 30 minutes) and antioxidant rubbers based on isoprene rubber stamp SKI- 3 while preventing undesirable effects such as migration, extraction solvent hardener, improves certain physical and mechanical properties.
Conclusion
It was found that the interaction EBG with BTZ is the process of spontaneous polymerization. The result of these reactions is the formation of soluble ammonium oligomers of regular structure.
It is shown that the introduction of an oligomeric additive based on the reaction product of EBG with BTZ in the rubber mixtures based on isoprene rubber improves flexibility, strength, elongation, kalandriruemost reduces the rate of aging of rubber.
Acknowledgmants. I offer my gratitude for the financial support of the research fund innovative projects of the State Committee for Science and Technology Development of Uzbekistan (grant number I0T-07-25-2015).
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