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0KINETICS STUDY AND MECHANISM CELLULOSE CROSSING REACTIONS
Sativaldiev Aziz Kahramanovich
PhD., Associate Professor Andijan Mechanical Engineering Institute https://doi.org/10.5281/zenodo.10968492
Abstract. The study of reaction kinetics makes it possible to understand the mechanism of chemical interaction, determine the order and rate constant, activation energy, and also more accurately assess the activity of catalysts.
Keywords: catalyst, activation, cellulose, reaction, cross-linking, mechanism, kinetics.
INTRODUCTION
Finishing fabrics in the presence of catalysts consisting of organic acid and inorganic salt allows one to reduce the heat treatment temperature, but this consumes a large amount of finishing agent and catalyst. During the finishing process, acid is formed, which not only accelerates the process of cellulose cross-linking with sizing reagents, but also leads to the destruction of cellulose. However, the use of effective catalysts leads to improved quality of fabrics with less consumption of sizing reagents. [1].
When studying a particular reaction that occurs under certain conditions, an important place is occupied by the study of the kinetics of the reaction, which makes it possible to determine its optimal temperature-time parameters. The study of reaction kinetics makes it possible to understand the mechanism of chemical interaction, determine the order and rate constant, activation energy [2], and also more accurately assess the activity of catalysts.
MATERIALS AND METHODS
The kinetics of the cellulose crosslinking reaction was studied in the presence of 180 g/l [50%] DMEM and EPA and NH4Cl catalysts at heat treatment temperatures of 900C from 5 minutes to 60 minutes. In this case, the processing temperature was chosen as close as possible to the drying temperature of fabrics under production conditions. Fabric samples were subjected to heat treatment according to 2 options:
1. Impregnated fabrics were heat treated immediately after pulsing.
2. The pulsed fabrics were dried at room temperature and then subjected to heat treatment.
The rate of reaction of cellulose with DMEM was determined by changes in the content of
bound nitrogen, formaldehyde and an increase in the crease resistance angle.
Figure 1 shows the dependence of the change in the content of bound nitrogen on the time of heat treatment at different temperatures, for the EPA and NH4Cl catalyst according to option 1 and in Figure 2 for option 2. When using the EPA catalyst, the reaction rate is higher than with NH4CL As can be seen from Figures 1 and 2, when modifying tissues in the presence of the EPA catalyst, a lower temperature is required to achieve the required content of bound nitrogen, and a higher temperature for NH4Cl. When modifying tissues in the presence of NH4.Cl at a temperature of 500 C, it was impossible to determine the presence of bound nitrogen due to its insignificant amount in the tissues.
RESULTS
Studies have shown that when modifying ti s sues in the presence of EPA and DMEM, the formation of cross-links containing 0.85-0.95% of bound nitrogen is sufficient, when the crease resistance angle of the modified tissues is 209-230°.
Based on the maximum value of bound nitrogen, formaldehyde and crease resistance angle during heat treatment at 1400 C for 5 to 6 minutes, a graph of Ig (Amax-A) versus reaction time was plotted [5].
Figure 1. Dependence of changes in the content of bound nitrogen on the time of heat
treatment at different temperatures
Figure 2 Dependence of bound nitrogen content on heat treatment time for EPA (curve 1-6) and NH4Cl (curve 7-11) catalysts at different temperatures
SO i/o
Fig.4. II-option
Dependence of 1g (Amak-A) on heat treatment time for EPA catalysts (curves 1-6) and NH4C1 (curves 7-11) at different temperatures.
Atah - maximum nitrogen content (formaldehyde) and an increase in the crease resistance angle during heat treatment at 140 0C.
A-nitrogen content (formaldehyde) and increase in the angle of persistence at time -t. Figures 3 and 4 show the indicated dependence for EPA and NH4Q catalysts for both options. DISCUSSION
The straightness of the graph shows that the reaction of cellulose with DMEM is quite well described by the first-order reaction equation. The average value of the rate constant calculated
using the first-order reaction formula agrees well with the values found from the tangent of the straight line in coordinates Ig (Amax-A) from t.
Table 1 shows the values of the rate constants calculated for various pairs of A and t values for EPA and NH4CI catalysts at a heat treatment temperature of 700C. The obtained values coincide within the scatter with the experimental points. Thus, after modifying tissues in the presence of the EPA catalyst at 700C, the tangent of the straight line is 0.0077, which gives a rate constant value of 1.8*10-2 min-1.
Of greatest interest is the study of the kinetics of the cross-linking reaction of cellulose with DMEM according to the first 1st option. Since when modifying fabrics under production conditions, fabrics are subjected to temperature treatments immediately after pulsing.
When modifying tissues according to option 1, the rate of the cross-linking reaction in the presence of EPA at temperatures of 70-900 0C is respectively 17.6 and 4 times higher than in the presence of NH4C1.
It was established that when modifying tissues in the presence of EPA and NH4C1 at temperatures of 50, 70, 900 0C, the reaction rate constants were in 1 variant, respectively: in the presence of EPA 1.07 * 10-2, 1.76 x 10-2, 5.64 x 10- 2.
I n the presence of NH4C1; 1.0 x 10-3 (700C), 1.4 x 10-2 (900C). After modification according to option 2 in the presence of EPA: 7.4 x 10-3, 1.9 x 10-1, 3, 4 x 10-2.
Table 1.
Change in the reaction rate of DMEM with cellulose at a temperature of 700C in the presence
of EPA and NH4C1 depending on time
Time, For EPA catalyst For NH4C1catalyst
min Nitrogen content, % K EPA Nitrogen content, % C NH4C1
5 0,763 0,021 0,410 0,030
10 0,851 0,021 0,515 0,028
20 0,970 0,018 0,680 0,026
30 1,089 0,018 0,750 0,022
40 1,175 0,018 0,810 0,019
50 1,242 0,017 0,870 0,018
60 1,316 0,018 0,920 0,017
As studies have shown, an environment with t ie required pH can be created by intro
the EPA catalyst into the sizing solution; the pH of the sizing solution in the presence of the EPA catalyst at 50 0C is 6.0, and in the presence of NH4C1-7.0 and MgCh -8.5.
CONCLUSIONS
In conclusion, a study of the kinetics of the cellulose crosslinking reaction with DMEM showed that when modifying tissues in the presence of the EPA catalyst, the reaction begins at 500C, and in the presence of NH4Cl at 700C and higher temperatures.
Based on the results obtained, we propose the following mechanism for crosslinking cellulose with DMEM in the presence of EPA.
When the H+ proton attaches to the oxygen of the methylal group, the process of enolization occurs:
The addition of the H proton occurs predominantly to the carbonyl group of the DMEM molecule and, at a sufficient H concentration, the proton also attaches to the oxygen of the methylal group:
As established in the sizing solution, the components of the EPA catalyst consist of monosubstituted phosphates [3,4] and upon hydrolysis, phosphoric acid is formed:
Unlike known catalysts, when modifying tissues in the presence of an EPA catalyst, although an acidic environment is formed, the EPA components maintain the required pH environment and, due to the subsequent reaction, the reaction environment does not become strongly acidic.
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