RU2061710C1 - Method for reclaiming of rubber - Google Patents

Abstract

FIELD: reclaiming of rubber from general- purpose rubber for manufacture of tier industry products, industrial rubber goods and bituminous-rubber cement for hydraulic insulation materials and anticorrosion automobile mastic. SUBSTANCE: rubber crumb sizing up to 10 mm is treated with plasticizer and activator. Plasticizer is used in form of mixture of residual oil with solvent in form of kerosene, o-xylene or white spirit. Activator is used in form of tin tetrachloride and/or its crystal hydrate in the amount of 4-7 mas.% of crumb mass. Preliminarily introduced into activator is calcium oxide in the amount of 2.4-4.2 mas.% of crumb mass. Mixture treated with plasticizer and activator is held for 40-60 min at the temperature of 140-180 C. Characteristics of the reclaimed product: content of nonvolatile substance in bituminous-rubber composition in film 300 plus-minus 10 mcm thick is 65-75%; resistance of film to water effect at 20 C more than 70 days; resistance to 9% NaCl solution is 60 days. EFFECT: provision of treatment of crumb sizing up to 10 mm, extended assortment of treated materials - used rubber. 1 tbl

Description

 The invention relates to a technology for the regeneration of rubber from general-purpose rubbers (natural rubber, SKI isoprene, SKDdivinyl, BSK-butadiene, BC butyl rubber) and can be used for the manufacture of rubber products for various purposes in the tire industry, the production of rubber goods and rubber mastics, based on which waterproofing materials used in construction (roofing mastics, pipe insulation, road surfaces, etc.), as well as for the manufacture of anti-corrosion automotive mastic.

At present, rubber regeneration methods are widely known and used in industry: water-neutral (neutral), thermomechanical (riclemerator process), steam and its modifications, high-temperature steam and steam [1] The vast majority of methods for regenerating "old" rubber (mainly worn tires and chambers, waste products manufactured by rubber goods, etc.) is based on two sequential processes:
1. Initially, waste rubber products or worn tires and chambers are subjected to mechanical grinding into crumbs;
2. Regenerate is obtained from crumbs by processing it in a softener and activator. A regenerate is a mixture of gel and sol fractions, where the gel fraction consists of fragments of a vulcanization network, and the sol fraction consists of fragments of rubber chains of a linear and branched structure.

A common disadvantage of these methods are:
1. Significant energy consumption during grinding and processing;
2. The regeneration process requires the use of metal-intensive equipment (mixers, extruders, rollers, etc.);
3. The final product is a regenerate, the further vulcanization of which allows the production of rubbers with obviously inferior physical and mechanical properties than rubber-based rubbers;
4. The regeneration process is accompanied by the release into the environment of vapors and fumes containing, in particular, sulfur.

A known method of regeneration of rubber, including the processing of crumb rubber in a medium of halogen-containing activators [2] In this method, as a halogen-containing activator take dechlor C ₁₀ CI ₁₀ in an amount of 2-3 wt.h. per 100 wt. including the recovered mixture and treated for 1 hour in air at 180 ^o C. This method partially eliminates the above disadvantages of the known methods, however, its possibilities are limited in that it provides only rubber based on butyl rubber at a relatively low productivity.

 The closest invention is a method of regenerating rubber, comprising treating rubber crumb in an activator softener [3] According to this invention, rubber crumb with a size of 0.4-0.8 mm is treated in a softener comprising dipentene, tall oil and aromatic oil, the treatment being carried out in a mixer at 2000 m / min, the ends of the mixer, followed by the addition of a phenylhydrazine activator with porous iron.

 This method provides a regenerate with a lower degree of degradation, as a result of which the mixtures containing it are more “dry”, less sticky and have a slightly higher viscosity compared to regenerates obtained by known thermomechanical methods. The main characteristics of such a regenerate are: acetone extract 22-30 chloroform extract 2-4 Mooney viscosity 50-80 units [1, p. 81] This method has found widespread use in industry and is known as the method of the company Trelleborg.

 However, this method also has the disadvantages of thermomechanical processing of rubbers. As is known, during thermomechanical processing, a local heating of the treated mass occurs, which can lead to ignition of the mixture. From the above characteristics of the regenerate it can be seen that reduces the physicomechanical characteristics of the relatively low content of sol fraction. Moreover, the method provides for the regeneration of fine crumb rubber that does not contain impurities, in particular cord fibers, which limits the possibilities of the method in terms of processed raw materials. This method is most effective for the production of regenerate from driving chambers based on butyl rubber, vulcanized with sulfur and is not effective in the processing of worn tires, since the use of rubber crumb with particle sizes less than 0.5 mm is not economically feasible when regenerating rubbers (see [1 ] p. 60).

 The technical result, the solution of which the present invention is directed, is to improve the quality of the regenerate and expand the range of processed raw materials.

The problem, which consists in the method according to the invention, is achieved by the fact that in the method of rubber regeneration, which includes treating rubber crumb in an activator softener, a mixture of fuel oil with a solvent selected from the group: kerosene, o-xylene, white spirit, in tin tetrachloride and / or its crystalline hydrate are used as activator, while 2.4-4.2 wt. calcium oxide by weight of the processed chips, and the activator take 4-7 wt. by weight of the processed chips, and after mixing the latter with a softener and activator, the resulting mixture is kept at 140-180 ^o C for 40-60 minutes

New in the method of regeneration is the processing of crumb rubber in the presence of tin tetrachloride and / or its crystalline hydrate (SnCl ₄ • 5H ₂ O) [4]
An additional introduction to the activator of calcium oxide (quicklime) provides the rubber devulcanization due to the destruction of sulfide bonds and eliminates the emission of hydrogen chloride into the atmosphere. It was found that as a result of chemical transformation during the regeneration process, calcium chloride is formed, which ensures the destruction of cord fibers at a process temperature of 140-180 ^o С, which makes it possible to use raw materials with a significant mass fraction (up to 15 wt.) Of cord fibers. The resulting regenerate used for the production of anticorrosion mastics prevents the penetration of moisture to the protected surface.

It was experimentally found that the content of calcium oxide in the activator is directly dependent on the amount of tin tetrachloride and / or its crystalline hydrate, excluding the release of gaseous hydrogen chloride during the interaction of the activator with crumb rubber and ensuring the destruction of cord fibers. These conditions are provided when the ratio of calcium oxide and activator is found and is 0.6 1, i.e. should be 2.4-4.2 wt. by weight of the processed rubber crumb. As experiments showed, a decrease in calcium oxide supplementation of less than 2.4 wt. leads to abundant gas evolution of Hcl and the presence in the regenerate of undamaged cord fibers that reduce the quality of the regenerate. The increase in the content of calcium oxide more than 4.2% wt. impractical, since the specified upper limit, providing complete absorption of hydrogen chloride, allows you to destroy the maximum number of cord yarns that make up 12-15 wt. Technological features of the method make it possible to use cheap and affordable raw materials (fuel oil, diesel fuel, hot bitumen, etc.) as a softener mixed with various solvents (o-xylene, white spirit, kerosene, etc.). In the case of using hot bitumen (softening temperature 50 ^o С GOST 22245-76), the final product of the process is rubber-bitumen compositions, which can later be used to obtain waterproofing materials in construction and transport. The optimum temperature range in which the rubber crumb is devulcanized is 140-180 ^o С. Worn tires and chambers, as well as rubber waste made on the basis of general purpose rubbers (NK, SKI, SKD, BSK) vulcanized, can be used as feedstock. sulfur and phenol-formaldehyde resins, while the size of the chips can be 2-10 mm, optimally 3-4 mm.

 The essence of the method is illustrated by the following examples of specific performance.

 Example 1

Crystalline hydrate of tin tetrachloride 21 g and 12.6 g of calcium oxide (7 wt. And 4.2 wt. Respectively) are introduced into a reactor with a softener (30 g of 10 wt. Mazut and 270 g of 90 wt. Of kerosene), based on the weight of the processed rubber crumb 300 g , mix and fall asleep crumb rubber from worn tires based on SKI-3 sulfuric vulcanization (GOST 14929-75) with particle sizes of 3-4 mm The reactor is closed, the mixture is stirred and maintained at a temperature of 180 ^° C. for 40 minutes. Then, a solvent of kerosene 1000 g is fed into the reactor and the mixture is treated at a temperature of 180 ^{° C.} for 60 minutes. At the end of the process, kerosene is removed by boiling, and its residues in the regenerate are distilled off in a vacuum dryer.

 The properties of rubber compounds containing the known and obtained by this method devulcanizates in various softeners and activators are given in table. 2.

 Example 15

A softener (3O g of fuel oil and 270g of white spirit) is poured into the reactor, tin tetrachloride 12 g and 7.2 g of calcium oxide (4 wt. And 2.4 wt., Respectively) from 300 g of processed rubber crumbs. The mixture is mixed, the rubber is poured crumb from chamber rubber based on butyl rubber vulcanized with phenol-formaldehyde resins, particle size 8-10 mm. The reactor is closed, the mixture swells at 160 ^o C for 60 minutes. Then, 14,000 g of molten bitumen are introduced into the reactor and the mixture is stirred and treated at a temperature of 180 ^{° C.} for 60 minutes. A rubber-bituminous fuel oil composition is obtained.

The final product is homogeneous in composition, the glass transition temperature of the rubber-bitumen-fuel oil composition 55 ^o C, the softening temperature +55 ^o C. When testing the film composition with a thickness of 300 ± 10 μm, the following was established: the content of non-volatile substances according to GOST 17537-72 70 ± 5% duration drying according to GOST 19007-73 at 20 ± 2 ^o C, hours to the degree of 1-48, at 105 ± 5 ^o C, min, to the degree of 1-30, peeling of the film from the substrate (according to GOST 15140-78) is not observed, film resistance to water at 20 ± 2 ^o С (according to GOST 9.403-90) for more than 70 days, film resistance to 3 NaCl solutions for 60 days.

 To assess the conditional strength and the relative elongation of the regenerate vulcanizates, a standard technique is used [1, p. 94], which involves the manufacture of samples from a mixture (see table 1).

Removing the mixture from the rollers after 10 minutes, vulcanization conditions 143 ^o C, 15 minutes.

As the table illustrates 2, increasing the content of activator (see example 6) to 8 wt. with the addition of CaO 4.2 wt. does not lead to an increase in the mechanical properties of the test sample, while the possibilities of implementing the method are limited by a sharp increase in the gas evolution of Hcl. The same is observed with a decrease in CaO addition of less than 2.4 (see example 8). The most optimal conditions for obtaining high-quality regenerate is to carry out the process in the presence of an activator 6-7 and calcium oxide 3.6-4.2 by weight of the processed chips at a temperature of 140-180 ^o C.

 Technological features of the method, in comparison with the prototype, provide a regenerate from recycled materials based on general rubbers vulcanized with sulfur and phenol-formaldehyde resins, i.e. the range of processed raw materials is expanding. At the same time, it is possible to process larger rubber crumb (8-10 mm), optimally 3-4 mm, while in a known case the size of the crumb does not exceed 0.4-0.8 mm. As tests of the regenerate samples obtained by the proposed method show, an increase in the conditional tensile strength by 12-15 is achieved with an increase in the relative elongation by 11-13 TTT1 TTT2 TTT3 TTT4

Claims (1)

A method of regenerating rubber, comprising treating rubber crumb in an emollient and activator, characterized in that the emollient is a mixture of fuel oil and a solvent selected from the group consisting of kerosene, o-xylene, white spirit, tin tetrachloride and / or are used as an activator its crystalline hydrate, while additionally introducing into it 2.4 4.2% of calcium oxide by weight of the processed chips, and the activator take in the amount of 4 7% of the mass of processed chips, and after mixing the latter with a softener and activator obtained the mixture was kept at 140-180 ^° C for 40-60 minutes.

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