The method of stabilization of butyl rubber

 

(57) Abstract:

The main problem in how to obtain unsaturated rubbers, such as butyl rubber, is the selection and introduction to the process of obtaining rubber antioxidants, allowing to obtain a colorless rubber, resistant to storage and processing. To solve this problem, a method of stabilizing butyl rubber, including the introduction of the stabilizer on the stage of degassing, which is used bottled product of the interaction of para-cresol with Dicyclopentadiene (Wangsta-L) with a molecular weight of 550-750 in amount of 0.2-1.5 kg/t, mixed with the salt of a fatty acid and a metal of the 2nd group of the Periodic table with respect Wangsta-L: salt of the fatty acid, is 0,015-0.3, and possible supply of salts of fatty acids into crumb rubber to introducing the antioxidant. 1 C.p. f-crystals, 1 table.

The invention relates to the field of stabilizing nanosystem polymers, more specifically to the field of stabilization of butyl rubber.

The main problem with the stabilization of the butyl rubber is the selection of antioxidant, not coloring the rubber and at the same time ensuring the stability of the polymer to degradation at the stage of selection and storage.

The chemical which when selected, that creates additional requirements applicable antioxidant and features a butyl rubber from other malonarushennykh polymers.

There is a method of stabilization of butyl rubber, in which the first by the copolymerization of isobutylene with isoprene in the tubular reactor of the type in which the temperature is about -100oWith the help of liquid ethylene. Dispersion of butyl rubber containing 14-18% polymer, 5-7% of the monomers and methyl chloride, superseded supplied by the charge removed from polymerizate in water degasser, where it vaporizes the main part of methyl chloride and neproreagirovavshikh monomers and rubber in the form of crumb goes into the water. From the first crystallizer slurry of rubber in water is fed into the second vacuum degasser, where to eliminate residual monomers and methyl chloride. Pumping of crumb rubber from the first crystallizer in the second it is dosed stabilizer in suspension in the water. Out of vacuum degasser rubber water is directed to the separation, drying and packaging. The resulting rubber is stable, because all the available antioxidants, allowing to produce white butyl rubber, does not provide stability in the allocation.

If you use a mixture of antioxidantscience rubber, Ed. by I. C. Garmonov, L.: Chemistry, 1983, pp. 544-546].

Well roll butyl rubber in its allocation of the antioxidant 2,2'-Methylenebis(4-methyl, 6-tert-butylphenol)(Agidol-2) gives the rubber yellow [P. A. Kirpichnikov, in. A. Beresnev, L. M. Popova. Album technological schemes the main production of the synthetic rubber industry, publishing house "Chemistry, Leningrad branch, 1976, pp. 71-72). Colorless treatment stabilizer-pentaerithrityl [3,(3,5 ditretbutyl-hydroxyphenyl) propionate (Irganox-1010) leads to the loss of Mooney viscosity of butyl rubber crumbs in the allocation system, especially in the case when averaging rubber experiencing the allocation of hydrogen chloride by hydrolysis of the remaining crumb rubber catalyst is aluminum chloride.

The closest is the method of stabilization of butyl rubber using as a synergistic antioxidant mixture of 2,2'-Methylenebis(4-methyl, 6-tertbutylphenol) (Agidol-2) to three(3,5-ditertbutyl) postitem (Stator-24) in the ratio of 2-4: 1 [RF Patent N 2156263, C 08 F 210/12, p. 20.09.2000].

When using the mixture obtained butyl rubber has a white color and stability during storage and processing. However, when preparing suspended conditions causes difficulties because of the different dispersive ability of the pigment of these antioxidants in the water. As a result, when certain weight load percentage of antioxidants in the rubber may be different, which will affect the quality of the finished polymer or in the appearance of the painting, or the loss of stability in the allocation. In addition, when using the mixture of antioxidants there is a noticeable drop in tensile strength of rubber vulcanizates after accelerated aging, which indicates insufficient protective function of the stabilizer during storage and processing of rubber.

The objective of the invention is to develop a method of stabilizing butyl rubber antioxidant, combining the functions colorless treatment and stabilizing agent for maintaining the strength of the rubber and in the allocation and processing.

The problem is solved in that the stabilizer is butyl rubber use bottled reaction product of para-cresol with Dicyclopentadiene General formula

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with a molecular weight in the range 550-750 units (commercial product Bingley-L) in an amount of 0.2-1.5 kg/ton of rubber, mixed with the salt of a fatty acid and a metal of group 2 in the ratio of 0.015-0.3. And possible supply of salts of fatty acids and metal 2 groups in crumb rubber before weedie - fragments of Dicyclopentadiene, and salt of the fatty acid binds impurities, destabilizing the operation of the antioxidant. Antioxidant Wangsta-L is introduced into the supply line of the crumb rubber to vacuum degassing in the form of 1-3% suspension in water in the amount of 0.2-1.5 kg/ton of rubber, with the particle size of the suspension of the proposed antioxidant plays no role; salt of the fatty acid is administered either in the same pipeline to supply antioxidant, or directly into water degasser, which scheme is preceded by a vacuum, in the form of 2-5% suspension in water.

When compared to known the inventive method of stabilizing the butyl rubber is specially selected mixture of stabilizer that includes bottled reaction product of paracresol with Dicyclopentadiene with a molecular weight of 550-750 in amount of 0.2-1.5 kg/ton of rubber and salt of fatty acid and metal 2 groups in the ratio of 0.015 to 0.3, combining fragments of an inhibitor of destruction and sitosterolemia.

Previously stabilizer constructed according to this principle, to protect the butyl rubber was not used. The presence of these significant signs according the proposed method the basis of patentability "novelty" and priorie the proposed method allows to obtain a colorless butyl rubber, to prevent degradation of the polymer during its passage through push the car, save the tensile strength of the finished polymer during aging, the concentration of the antioxidant in the polymer always corresponds to a given, that it is difficult to sustain when using the mixture of antioxidants because of their different dispersive ability of the pigment.

"Industrial primenimosti" method is confirmed by the following examples.

Example 1. The copolymerization of isobutylene with isoprene is carried out in the tubular reactor type at a temperature of -100oSince, in the environment of methyl chloride, the feed mixture in the reactor 14 t/h, the concentration of isobutylene in the charge 21 wt.%, dosage of isoprene based on the isobutylene 2.6 wt.%. The catalyst was fed into the reactor in the form of 0.08 wt.% solution of aluminum chloride in chlormethine in the amount of 0.1 wt. % AlCl3based on the isobutylene in the charge. When the conversion reached 70% is obtained suspension containing ~ 15 wt.% polymer in chlormethine. The suspension is fed into the crystallizer, where the degassing chlormethyl by supplying hot water and steam. At the outlet of the degasser get crumb rubber in water with a concentration of 3 wt.% 70 t/h Suspension antioxidant Agidol-2 in water is prepared in a separate apparatusfor it served the suspension of the antioxidant in the amount at the rate of 1 kg Agidol-2 1 t rubber. After that babe goes to vacuum degassing, and then averaging, drying and briquetting. Samples of rubber from briquette analyzed physico-mechanical properties, viscosity Mooney, fall Mooney viscosity in terms of thermo-mechanical treatment by passing through an extruder within 1.2 minutes at a temperature of 220oWith the content of the antioxidant by means of UV-spectroscopy, as well as visually the color after aging in a week.

Example 2 (the prototype). The experience carried out as described in example 1, except that the suspension of antioxidants prepared from a mixture of Agidol-2 and Stator-24, taken in the ratio of 3:1 with a particle size of 10 μm. The total dosage of antioxidants is 1 kg/ton of polymer.

Example 3. The experience carried out as described in example 1, except that the suspension of the antioxidant is prepared by mixing Bingley-L with water. Molecular weight antioxidant-600, dosage of 1.0 kg/ton of rubber.

Example 4. The experience carried out as in example 3, except that in the pipeline before filing a suspension of Winglee-L dispense a 3% suspension of calcium stearate in water in an amount of 10 kg stearate 1 ton of rubber.

Examples 5-8. The experiments of osushestvlyaetsya. And dosage salts of fatty acids are changed so that the ratio of antioxidant : salt of the fatty acid was 0.1.

Examples 9-12. Experiments carried out as described in example 4, except that the molecular weight of the antioxidant is 460, 550, 750, 850.

Examples 13-16. Experiments carried out as in example 4, except that the weight ratio dosing of Winglee-L and salts of fatty acid is 0.01, 0.015 g, 0,3, 0,35.

Example 17-18. The experiments were carried out as in example 4 except that as the salt of the fatty acid used palmiet calcium stearate and zinc.

Example 19. The experience carried out as in example 4, except that a suspension of a salt of a fatty acid is metered in crumb rubber after submission to it of the suspension of Winglee-L.

Data analysis of the rubber obtained in accordance with examples 1-19 shown in the table.

From the table it follows that the use of bottled product of the interaction of para-cresol with Dicyclopentadiene (Wangsta-L) in optimal quantities and the optimal molecular weight of the mixture with the salt of a fatty acid and a metal of group 2, taken in the optimal ratio, allows you to create a concentration of the Academy of Sciences of the x-oxidants. If this turns out to be a good stabilizing effect, which is manifested in the preservation of the Mooney viscosity of the polymer as it passes through the extruder and maintaining strength at break after accelerated aging.

The optimal dosage Wangsta-L is 0.2 to 1.5 kg/ton of rubber. When the reduction of the dosage is reduced below 0.2 inhibitory effect of antioxidant, which is manifested in the fall of Mooney viscosity with the passage through the extruder and the decrease in strength during aging. With increasing dosages above 1.5 kg/t no further amplification inhibitory effect and therefore it is impractical.

The optimum molecular weight Wangsta-L, depending on the content Dicyclopentadiene fragments in the molecule of the reagent for stabilization tasks butyl rubber is an interval of 550-750. The decrease of molecular weight below 550, which means reducing the number Dicyclopentadiene links reduces colour of stabilization and the appearance of color in rubber. The increase of molecular weight above 750 means an increase in the number cyclopentadiene links and, consequently, a decline in the share of bottled parts of cresol in the molecule antioxidant, which reduces ing the position of strength after aging. The optimal ratio of antioxidant : salt of fatty acid is the ratio of 0.015-0.3. Decreasing this ratio deteriorates the rate of tensile strength before and after aging due to an excess of salts of fatty acid in the rubber. Increasing this ratio decreases the actual dosage of the antioxidant in the rubber, apparently due to its decomposition in the presence of impurities. At a dose of salts of fatty acids after the filing of an antioxidant also reduced its actual concentration for the same reason.

1. The method of stabilization of the butyl rubber in the suspension, including the introduction of the stabilizer on the stage of degassing in the form of a suspension in water, characterized in that the stabilizer is used bottled reaction product of para-cresol with Dicyclopentadiene General formula

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molecular weight of 550-750 in amount of 0.2-1.5 kg/ton of rubber in the mixture with the salt of a fatty acid and a metal of group 2 of the Periodic table in relation to the equal of 0.015 to 0.3.

2. The method of stabilization under item 1, characterized in that the salt of a fatty acid and a metal of group 2 of the Periodic table is metered into the crumb rubber to feed her butylated reaction product of para-cresol with Dicyclopentadiene.

 

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