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Kazakov Farkhot Farmonovich, Assistant of the Department "Technology and equipment of Light Industry" Bukhara engineering-technological institute, Republic of Uzbekistan E-mail: [email protected] Kodirov Tulkin Jumaevich, Technical sciences associate, professor, Tashkent institute of Chemical Technology, Republic of Uzbekistan
TANNING OF ASTRAKHAN SKINS MODIFIED BY CARBOAMID OF ORMALDEHYDE RESIN
Abstract: It is synthesized carbamide-formaldehyde resin modified with acrylic acid. The tanning action of the modified carbamide of formaldehyde resin on astrakhan skins is investigated. The tanning action is determined by temperature of a welding of comparable samples of astrakhan fur by processing of the modified carbamide-formaldehyde resin.
Keywords: Synthesis, carbamide-formaldehyde resin, modification, acrylic acid, fur, astrakhan fur, tanning, filling.
Researches of the last years and experience of the industry demonstrates prospects of application for improvement different types quality of skin which water-soluble synthetic polymers and especially amino resin.
Being products ofpolycondensation of nitrogen-containing organic compounds (urea, melamine, dicyandiamide or their derivatives) with formaldehyde, amino resins possess not only filling, but also with the tanning actions [1]. The most available of the amino resins applied in various industries around the world and including in the Republic of Uzbekistan, is carbamide-formaldehyde resin.
The standard technique of production of skin for a bottom of footwear provides filling of a semi-finished product a carbamide by formaldehyde resin (medicine KMU). As a result of such filling of skin gain a number of valuable properties [2].
However, a lack of such skin are characterized by the increased content of the substances which are washed away by water, the insufficient elasticity increased by a soakage and some other negative properties though in general on values of the corresponding indicators of skin meet requirements of state standard specification (SSS). The reason of these shortcomings, according to us introduction to a semi-finished products with resin of a significant amount of free urea which has hydrophobic effect on collagen, another is weakens communication of tannin and synthetic tannin with collagen. Besides, the applied resins are characterized by the increased hygroscopic.
By early researches it was established [3] that carbamide-formaldehyde- croton the aldehyde oligomer modified with acrylic acid improves physical, chemical and mechanical properties of skin and by that giving them high fullness. It was a prerequisite to development of a method which synthesis of resins on the basis of urea, formaldehyde and acrylic acid in lack of croton aldehyde for the purpose of application of filling a semi-finished product of astrakhan fur.
In this regard carbamide-formaldehyde resin modified with acrylic acid is synthesized by us. In this case formaldehyde wasn't applied until formaldehyde is formed in the course of interaction on a carbamide by sulfuric acid.
Acrylic acid is chosen as the modifier with the fact that for receiving the amino- aldehyde of resins only always for the beginning of reaction (initiation) and hardening various acids or sour salts are used.
In this research the modified is carbamide-formaldehyde resines (MCFR) at various consumption of acrylic acid are synthesized. For receiving MCFR the carbamide (99,8%) - 100, urotropin (99,4%) -50, sulfuric acid (100%) - 32, acrylic acid 98,2) - 10 is used; 30; 50 and water - 250 (in masses. h). As a control sample the modifier acrylic acid isn't used.
Synthesis was carried out at a natural temperature by introduction to water solution of small portions of a carbamide, urotropin and sulfuric acid, during the 2 hours. At continuous hashing in solution filled in with small portions sulfuric acid, without allowing temperature increase of reactionary mix 55 °C are above. Then entered acrylic acid into solution without raising pH 6,7. Residual content of acid was determined with use of the indicator of a phenolphthalein. Consumption of acrylic acid to a molar ratio carbamide: acrylic acid, equal 1,0:0,5; 1,0:0,1; 1,0:0,3; 1,0:0,5. Duration of synthesis is 2 hours.
Use of urotropin is more preferable as from the point of view the quality of received product, and sanitary and hygienic conditions of its preparation.
The received resin light - brown color, soluble in water, ethyl alcohol, is besieged in acetone, with a density of 1,42 g/cm 3. The exit made 82,6%. The dry rest is 26%.
Moreover, it is well-known [4] that acrylic acid is capable to copolymerization with various monomers which at the increased temperature in the course of formation a product of a sopolyconden-sation can initiate process and by that can react with disclosure of double communication. And its trailer carboxyl group can block further the allocated free formic aldehyde and react with active amino groups of a collagen of the skin protein tissue of fur.
The interaction of various is studied with protein of derma by the nature of tannin. Despite it, changes of properties of a derma as a result of processing by the bonds having the tanning properties occurs in one direction. In the course of tanning fastening by
particles of the tanning substance of interfacing protein molecules in thin structure of a collagen is reached.
The most typical implications of effect of tanning consider [5]: temperature increase of a welding of a collagen; rising of durability at stretching of the flooded derma and decrease of moisture capacity at a swelling in water; decrease of the general orderliness of thin structure of a collagen, etc.
Tanning is characterized not by the separate listed changes, but their set. Obligatory sign of tanning is irreversibility of process.
Temperature increase of a welding of a collagen as a result of interaction with the tanning substances continues to remain the most important proof of correctness of formation ideas of transversal communications between molecular chains when tanning [6]. The conducted researches [7] showed that polycondensation the
methylol of derivatives of urea in the conditions of chromic tanning leads to formation of chrome-urea- formaldehyde resin (CUFR).
In this work data on studying of the tanning action of MCFR which is formed immediately in structure of a derma are stated. Formation of MCFR in a derma was reached by introduction of a dimetilolurea (DMU) and not modified CFR and a formic aldehyde. Polycondensation was carried out at the expense of acid of the tanning chrome bonds. Concentration of DMM made 3,0 g/l, chrome bonds (including on Cr2O3) 1,0 g/l, fluid coefficient (FC) =8,0, temperature of 35 °C.
The tanning action was determined by temperature of a welding of comparable samples of astrakhan fur by processing (M)CFR and formaldehyde with the subsequent tanning by compound of chrome (fig. 1).
Figure 1. Temperature of a welding of an astrakhan semi-finished product after tanning: 1 - MCFR; 2 - CFR and 3 - formaldehyde
It is apparently from fig.1. joint processing of astrakhan fur meti- Stronger fastening of molecular chains of MCFR collagen,
lol derivatives ofurea and compounds of chrome gives to a semi-fin- formed in structure terms in the conditions of the carried-out tan-
ished product more high temperature of a welding that demonstrates ning is the reason of it, than when tanning formaldehyde. stronger tanning ability of MCFR.
Figure 2. Change of hydrothermal destruction of an astrakhan semi-finished product when tanning: 1 - MChCFR (FC = 0,8); 2 - MChCFR (FC = 10,0); and 3 - Cr2O3 (FC = 10,0)
The maximum temperature of a welding is reached at initial value pH 5,5. The reason of it is that the tanning MCFR particle in these conditions becomes more reactive, than formaldehyde, due to emergence in its structure of additional active groups as a result of interaction with metilol derivatives of urea.
Increase in acidity of the tanning solutions (a curve 2) is followed by weakening of their tanning action. It is explained by
speed increase of polycondensation over diffusion and the fact that the bulk of MCFR is fixed only in blankets terms or remains in the processing solution; on the other hand, the condensed MCFR support smaller the number of reactive groups, than low-molecular products of condensation.
Decrease in acidity (a curve 2) is also followed by weakening of the tanning effect of solutions as with increase in basicity of the sizes of chromic complexes with the subsequent chromic tanning increase. It complicates diffusion of tannin in thin structure of collagen and weakens the tanning ability [8].
The weakening of the tanning action is more considerably shown for formaldehyde solutions (fig. 1, a curve 3) that also con-
firms stronger «sewing together» of structural elements terms with MCFR.
The kinetics of tanning (M)CFR and formaldehyde was studied on change of temperature of a welding of astrakhan fur in the processing solutions.
Tanning was carried out by two options:
1. option. An expense (M)CFR of 3,0% (on the dry rest), compounds of chrome, considering on Cr2O3, NaCl of 50 g/l, FC=8,0, temperature of 35 °C.
2. option. The same as it is stated above but at FC = 10,0.
Control samples tanned formaldehyde.
The research is showed (rice 2, 3, 4) that introduction to solution of compounds of chrome the metilol of derivatives of urea — (M)ChFR promotes faster penetration of the tanning connections in an astrakhan fur term.
Process of the combined tanning is reduced in comparison with chromic. Increase in concentration of the tanning connections (without change of their general expense) intensifies tanning process.
Figure 3. Absorption metilol of derivatives of urea astrakhan fur when tanning: 1 - Cr2O3 (FC = 10,0); 2 - MChCFR (FC = 10,0) and 3 - MChCFR (FC = 0,8)
From figure 4. it is visible that chromic tanning and tanning of MKFS leads to change of provision of the reflex (at a diffraction angle 20 = 4,0 o) corresponding to an interval between axes of protofibrils
Radiographic researches of a collagen defined the major inter-planar distances corresponding about 0,29; 0,45 and 1,10 nanometers. By authors it is taped [9; 10] that the distance 0,29 is a projection to an axis of a spiral of one amino-acid rest in the main chain, 0,45 nanometers - diameter of a round of the main chain, and distance of 1,10 nanometers correspond to distance between axes of three-spiral particles.
For a research the following is chosen: a collagen the tanned MKFS; a collagen of chromic tanning with MKFS (a mechanical admixture); collagen of chromic tanning; not tanned collagen.
Roentgenograms of a mechanical admixture and collagen of chromic tanning in some interval coincide. Emergence of a new reflex (at 20 = 1,10 o) for a mechanical admixture is explained by MCFR additive.
It demonstrates that MCFR isn't just postponed for surfaces of structural elements of a derma, and has the tanning effect. Tanning of MCFR leads to essential changes in thin structure of a collagen.
These changes affected physic mechanical properties of a skin.
Thus, generalizing results of researches it is possible to conclude that, joint processing of astrakhan fur metilol derivatives ofurea and bonds of chrome gives to a semi-finished product more high temperature of a welding that testifies about stronger the formaldehyde resin modified Carbamide tanning abilities. It is defined that introduction to solution of bonds of chrome the metilol of derivatives of urea — the formaldehyde resin modified chrome Carbamide promotes more intensive penetration of the tanning bonds into an astrakhan fur derma. Radiographic researches of a collagen not tanned, tanned the modified carboamide formaldehyde resin, chromic tanning with the modified carboamide formaldehyde resin of a mechanical admixture and chromic tanning defined the major inter-planar distances. It is established that a Carbamide-formic aldehyde-croton the aldehyde oligomer modified with acrylic acid improves physical and chemical and mechanical properties of astrakhan skins, at the same time filling.
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