WO2009064215A1

WO2009064215A1 - Method for liquefying rubbers and rubber-containing waste materials

Info

Publication number: WO2009064215A1
Application number: PCT/RU2008/000369
Authority: WO
Inventors: Konstantin Alexandrovich Dubkov; Sergey Vladimirovich Semikolenov; Dmitry Petrovich Ivanov; Dmitry Eduardovich Babushkin; Valentin Nikolaevich Parmon; Gennady Ivanovich Panov
Original assignee: Institut Kataliza Imeni G.K. Boreskova Sibirskogo Otdeleniya Rossiiskoi Akademii Nauk
Priority date: 2007-11-15
Filing date: 2008-06-10
Publication date: 2009-05-22
Also published as: RU2362795C1; RU2007142266A

Abstract

The invention relates to recycling conventional and specific polydiene rubbers (types of) and rubber-containing waste materials based on said rubbers, in particular tyre rubber and waste tyres. The inventive method involves liquefying rubber and rubber-containing waste by bringing them into contact with nitrogen oxide N2O in such a way that viscous-flow or liquid products are formed. The process is carried out at a temperature of 100-500°C and the nitrogen oxide pressure of 1-200 atm. For a contact process, nitrogen oxide can be substituted for a mixture of N2O with diluting gases in the form of inert gases, C1-C4 alkanes or mixtures thereof.

Description

The method of liquefaction of rubber and rubber waste

The invention relates to a method for processing rubbers for various purposes based on polydiene rubbers (polyisoprene, polybutadiene, natural, styrene butadiene, nitrile butadiene, etc.), as well as rubber-containing waste made from such rubbers, in particular tire rubbers and used car tires .

In recent years, in many countries considerable attention has been paid to the problem of the disposal of rubber waste. The most urgent problem is the use of used car tires, which are one of the largest polymer-containing waste. Thus, according to [US 2007/0004812, Al, C08L 1/04, B01D11 / 02, B29B 17/02, 01/04/2007] about 15 million tons of retired tires are accumulated annually in the world (about 1 billion units). Limited reserves of natural hydrocarbon raw materials require a more rational use of these secondary resources. Therefore, the processing and recycling of rubber waste, including waste tires, is of great economic and environmental importance.

Known methods of processing used tires can be divided into two main groups. The first group includes methods in which rubber does not undergo significant physico-chemical changes and basically retains its structure. These methods make it possible to grind rubber-containing waste and obtain rubber crumb of various dispersion. The most widespread practical application is found in technology involving simple mechanical grinding of used tires. This method has several disadvantages. Thus, when tires are processed mechanically, oxidative processes are intensified due to the occurrence of high temperatures during grinding, the properties of the starting material change, which leads to a decrease in the quality of the resulting rubber crumb and excludes the possibility of its use in high-tech rubber industries. The method does not make it possible to completely separate the rubber crumb from the remnants of textiles and metal cord, which leads to a decrease in the quality of the resulting product and to increased wear of the equipment due to the presence of metal inclusions. Due to dust and high temperatures arising from the grinding of rubber, as well as active chemical emissions into the atmosphere, this production belongs to the category of environmentally hazardous. However, this technology is widely used to produce rubber crumbs of various dispersion. At present, rubber crumb is the main and affordable type of product obtained as a result of tire processing. It can be used, for example, as an additive in the manufacture of new tires and rubber products, as an additive to road bitumen [US 5385401, 01/31/1995; RU 2164927, 10/04/2001], for the production of bitumen materials [US 4609696, 09/02/1986; WO 95/20623, 08/03/1995; RU 2286998, 12.24.2004, etc.]. In the latter case, rubber crumb is mixed with heavy oil fractions and subjected to heat treatment at temperatures above 170 ⁰ C.

A known method of producing rubber crumb by mechanical grinding of tires in the presence of ozone [RU 97115873, 03.20.1999; EP 1016508, Al, 07/05/2000]. This method consists in creating mechanical deforming loads on a car tire placed in a chamber into which ozone-containing gas is supplied. The method allows to reduce energy consumption for grinding used tires, however, after treatment with ozone, the rubber changes its initial properties.

A known method of producing rubber crumb by grinding tires at cryogenic temperatures using liquid nitrogen [GB 1438278, 07/11/1973]. According to this method, car tires are frozen with liquid nitrogen to a state of brittleness and then crushed, followed by separation of the metal cord and textile. The cryogenic method allows to reduce the cost of crushing, to improve the separation of metal and textile from rubber. However, the complexity of delivering liquid nitrogen, the problem of its storage, high cost and high energy costs for its production are the main reasons that hinder the use of this technology.

The second group includes recycling methods that lead to deep irreversible changes in the structure of rubbers and polymers in their composition, associated with the destruction of the spatial grid of rubber and rubber chains at high temperatures.

One of the currently most common methods for such disposal is the pyrolysis processing of car tires [US 5087436, C09C1 / 48, 02/11/1992; GB 1481353, B29B17 / 00, 02/06/1975; RU 2269415, B29B17 / 00, 10/10/2005; RU 2139187, B29B17 / 00, 10/04/2001]. These methods make it possible to obtain a number of useful intermediates and energy carriers. Car tire pyrolysis is carried out in a vacuum or in a reducing or inert atmosphere. The pyrolysis temperature in various hardware options is from 500 to 1000 C. As a result of pyrolysis from car tires, three types of products are obtained: hydrocarbon gas, pyrolysis liquid and solid carbon residue.

Known methods for the disposal of tire rubbers by thermooxidative air treatment [US 4588477, ClO 539/07, C09 C 1/48, 05/13/1986; RU 2062284, ClO B 49/04, 06/20/1996]. In accordance with these methods, the mixture of pieces of tires is treated with air, passing through the heating, pyrolysis, coking, combustion zones and the cooling zone in series. A solid residue is discharged from the reactor and the target processing products are removed: combustible gas and aerosol containing vapors and small drops of pyrolysis resins. The maximum temperature in the combustion zone is 800-1700 ⁰ C.

A known method of disposal of automobile tires using catalytic cracking [US 4175211, C10B53 / 07, 11.20.19791]. In accordance with this method, rubber-containing waste is heated in a hydrogen atmosphere at a temperature of 65-37O ⁰ C in a mixture with mineral oils until completely dissolved and a homogeneous mass is obtained. The resulting liquid, similar to crude oil, is subjected to catalytic cracking to produce gasoline and distillates. The common disadvantages of these methods are high energy consumption, complex hardware design of the process, and, therefore, the high cost of the products obtained.

The present invention describes a new method for processing rubbers and rubber waste.

According to the proposed method, the processing of rubber and rubber waste is carried out by contacting with nitrous oxide (N ₂ O) or with N ₂ O-containing gas at elevated temperature and pressure. As a result, depending on the conditions and intensity of the process, the method allows to obtain viscous-fluid or liquid products from rubbers.

For processing by the proposed method, rubbers of various purposes are used based on polydiene rubbers (polyisoprene, polybutadiene, natural, styrene butadiene, nitrile butadiene, etc.), as well as rubber-containing waste made from such rubbers. In particular, this method is applicable for the processing of tire rubbers and used car tires. In this case, not only rubber crumb of various sizes, which are widely available raw materials, but also large pieces of tires can be used as feedstock.

According to the proposed method, the contacting of rubber and rubber waste with nitrous oxide or with an NgO-containing gas is carried out at a temperature of 100-500 ⁰ C and a pressure of N ₂ O from 1 to 200 ATM.

The viscous-fluid or liquid products resulting from this process can be used for subsequent secondary processing either without separation or after fractionation. An important advantage of the proposed method is the ability to easily separate products obtained by liquefying tire rubbers and waste tires, from the remnants of textiles and metal cord. Liquefaction of rubbers and rubber-containing wastes by contacting them with nitrous oxide can be carried out without solvents.

However, it is preferable to carry out the process using solvents. Nitrous oxide is known to be able to form flammable mixtures with organic compounds [G. Rapater, A. Sicagd, V Sumrosium on Combustiop, 1955, p. 620]. In accordance with this invention, in order to increase the explosion safety of the process, an inert gas that does not react with N ₂ O, for example, nitrogen, argon, helium, carbon dioxide, etc., or their mixture. The role of an inert diluent gas can also play the exhaust gases of the reaction containing molecular nitrogen.

C ₁ -C ₄ alkanes or mixtures thereof can also be used as a diluent gas. In addition, a mixture of C ₁ -C ₄ alkanes with inert gases containing from 1 to 50% inert gas can be used as a diluent gas. The concentration of the diluent gas in the mixture with N ₂ O is selected so that it is from 1 to 90% of the concentration of N ₂ O. To reduce the risk of explosion, combustion inhibitors such as trifluorobromomethane, difluorochlorobromomethane, dibromotetrafluoroethane, etc. can also be added to the reaction mixture.

The proposed method does not require high purity nitrous oxide, which can be used both in pure form and with impurities of various gases, the presence of which can be associated with the method of its production. For example, flue gases in the production of adipic acid can be used as a source of nitrous oxide [A.K. Ugarte Stud. Suf. Sсi. Catal., 2000, v. 130, p. 743].

The proposed process can be carried out in a wide range of conditions, both in a static and in a flow reactor, which can be made of steel, titanium or other suitable material.

In the case of a static variant of the process, for example, rubber crumb and a solvent are loaded into the autoclave reactor at room temperature. Then nitrous oxide or its mixture with diluent gas is fed into the reactor. The amount of nitrous oxide is selected so that its pressure at the reaction temperature is 1-200 atm. After that, the reactor is closed and heated to a reaction temperature in the region of 100-500 ⁰ C. The reaction time is from several minutes to several tens of hours, depending on the conditions of its implementation. After completion of the reaction, the reactor is cooled to room temperature, the pressure is slowly released and the resulting solution is discharged. This solution, in addition to soluble components, also contains a finely divided carbon filler (carbon black or carbon black), which, as a rule, is in suspension and cannot be removed by filtration. The resulting solution, if necessary, is filtered to remove residues of textile fiber and metal cord, or these components are removed by any other known method.

Then the solvent is distilled off from the solution and the product is isolated, which is a homogeneous mixture, which as the main components contains a low molecular weight polymer and a fine carbon filler (carbon black or carbon black). Depending on the process conditions, this product is viscous flowing or liquid. The distilled solvent can be reused for rubber processing by the proposed method.

Obtained according to the proposed method, the product may have wide applications. For example, it can be reused in the production of rubber and various rubber products, as an additive to bitumen and asphalt, as well as hydrocarbon fuel, for example, for the complete or partial replacement of fuel oil in power plants.

In addition, the resulting product by any known method, in particular by filtration in a suitable solvent, can be divided into two main fractions. The first fraction is a low molecular weight polymer (liquid rubber), which may have a consistency from a flowing polymer to a viscous liquid. The second fraction is a pasty product containing carbon filler (carbon black or carbon black).

The resulting liquid rubber can be further used, for example, to obtain sealants, adhesives, as additives to composite materials, etc. A paste-like product containing carbon filler can be used, for example, as fuel, a component for the preparation of non-essential rubber products, bitumen, etc. The invention is illustrated by the following examples.

Example 1

In the example, liquefied nitrous oxide rubber crumb obtained by mechanical grinding used truck tires. This crumb mainly contains rubber based on polyisoprene rubber and in a small amount contains rubbers prepared using styrene butadiene and styrene butadiene rubbers. In a stainless steel reactor with a volume of 2000 cm ³ (Parr company), 200 g of rubber crumb with a particle size of 2-3 mm and 1000 cm of benzene as a solvent are charged. Air is removed from the reactor by evacuation with a vacuum pump and then nitrous oxide is injected to an initial pressure of 20 atm. The reactor is hermetically sealed, heated to 230 ⁰ C and maintained at this temperature for 6 hours.

At the end of the experiment, 190 g of a product having the consistency of a viscous liquid was isolated from a solution. After dividing the product into two fractions, 90 g of liquid rubber was obtained having a number average molecular weight of M _n = HOO and a narrow molecular weight distribution (M _w / M _n = 2.1), as well as 98 g of a soft paste-like product, mainly containing a carbon filler. Example 2

This example is similar to example 1, with the difference that 100 g of large pieces of tire with a size of up to 10 cm are loaded into the reactor, and toluene is used as a solvent. The initial pressure of N ₂ O is 7 atm. The process is carried out at 280 ° C for 2 hours. As a result of the experiment, 98 g of a viscous-fluid product, a product having the consistency of a viscous liquid, are isolated from a solution. After its separation into two fractions, 45 g of liquid rubber having a molecular weight of M _n = 4800 (M _w / M _n = 2.3) and 50 g of a soft pasty product, mainly containing a carbon filler, were obtained. Example 3

This example is similar to example 1, with the difference that pieces of rubber with a size of 2-3 cm prepared on the basis of SKD-ND butadiene rubber are loaded into the reactor, and the solvent used is cyclohexane. The initial pressure of N ₂ O is 10 atm. The process is carried out at 200 ⁰ C for 24 hours

As a result of the experiment, 94 g of a viscous flowing product were isolated from the solution. After its separation into two fractions, 42 g of liquid rubber having a molecular weight of M _n = 8100 (M _w / M _n = 2.2) and 50 g of a soft pasty product, mainly containing a carbon filler, were obtained.

Examples 4-6 show the possibility of carrying out the process using nitrous oxide diluted with alkanes and other diluent gases. Example 4

Similar to example 1, with the difference that 100 g of rubber crumb is loaded into the reactor. For contact, instead of pure nitrous oxide, a mixture of nitrous oxide with ethane of the composition: 68% N ₂ O, 32% C ₂ H _{6 is used} , which corresponds to the maximum N ₂ O content in this mixture to ensure complete explosion safety of the reaction mixture. The solvent used is mesitylene. The initial pressure of the mixture is 20 atm. The initial pressure of N ₂ O is 10 atm. The process is carried out at 200 ⁰ C for 10 hours

As a result of the experiment, 96 g of a viscous flowing product were isolated from the solution. After separation of the product into two fractions, 44 g of liquid rubber having a molecular weight of M _n = 6200 (M _w / M _n = 2.0) and 51 g of a soft pasty product, mainly containing a carbon filler, were obtained.

Example 5

Similar to example 4 with the difference that instead of pure nitrous oxide, a mixture with inert gas, argon, in which the concentration of N ₂ O is 60%, is used for contacting. The initial pressure in the reactor is set equal to 40 atm. The process is carried out at a temperature of 18O ⁰ C for 15 hours

As a result of the experiment, 95 g of a bitumen-like product were isolated from the solution. After its separation into two fractions, 35 g of liquid rubber with a molecular weight of M _n = 25600 (M _w / M _n = 2.3), having the consistency of a flowing polymer, and 58 g of a pasty product, mainly containing a carbon filler, were obtained. Example 6

It is similar to example 3, with the difference that pieces of rubber prepared on the basis of nitrile butadiene rubber BNKS-28AMH with a content of 28 moles of nitrile units are loaded into the reactor. % For contact, instead of pure nitrous oxide, its mixture with butane and nitrogen containing 50% nitrogen is used. For this, a mixture of the composition is fed into the reactor: 66% N ₂ O, 17% butane, 17% nitrogen. The initial pressure in the reactor is set equal to 45 atm. The process is carried out at 150 ⁰ C for 35 hours

As a result of the experiment, 94 g of a viscous flowing product were isolated from the solution. After its separation into two fractions, 30 g of liquid rubber with a molecular weight of M _p = 32000 (M _w / M _n = 2.3), having the consistency of a flowing polymer, and 62 g of a pasty product, mainly containing a carbon filler, were obtained.

Thus, in examples 1-6, the possibility of liquefying rubbers and rubber-containing waste obtained on the basis of different types of polydiene rubbers by contacting them with N ₂ O or nitrous oxide in the presence of a diluent gas is shown.

Claims

Claim

1. A method for liquefying rubbers for various purposes based on polydiene rubbers, as well as rubber-containing waste made from such rubbers, by contacting them with nitrous oxide (N ₂ O).

2. The method according to p. 1, characterized in that the contacting is carried out at a temperature of 100-500 ⁰ C and a pressure of nitrous oxide of 1 to 200 ATM.

3. A method according to any one of claims 1-2, characterized in that rubbers and rubber-containing wastes based on polyisoprene, natural, polybutadiene, styrene-butadiene-rubber, butadiene-nitrile rubbers are used for contacting.

4. The method according to any one of paragraphs. 1-2, characterized in that for contacting tire rubbers and rubber-containing waste obtained from used automobile tires, for example, rubber crumb and pieces of tires.

5. The method according to any one of paragraphs. 1-2, characterized in that the resulting product is divided into two fractions, one of which is a low molecular weight polymer (liquid rubber), and the second contains a carbon filler.

6. A method for liquefying rubbers for various purposes based on polydiene rubbers, as well as rubber-containing waste made from such rubbers, by contacting them with nitrous oxide (N ₂ O) in the presence of a diluent gas.

7. The method according to p. 6, characterized in that the contacting is carried out at a temperature of 100-500 ⁰ C and a pressure of nitrous oxide from 1 to 200 ATM.

8. A method according to any one of claims 6-7, characterized in that rubbers and rubber-containing wastes based on polyisoprene, natural, polybutadiene, styrene-butadiene-rubber, butadiene-nitrile rubbers are used for contacting.

9. The method according to any one of paragraphs. 6-7, characterized in that for contacting use rubber tires and rubber waste derived from used car tires, for example, rubber crumb and pieces of tires.

10. The method according to any one of paragraphs. 6-7, characterized in that the resulting product is divided into two fractions, one of which is a low molecular weight polymer (liquid rubber), and the second contains a carbon filler.

11. The method according to any one of p. 6-7, characterized in that as a diluent gas use alkanes C ₁ -C ₄ or any mixture thereof.

12. The method according to any one of p. 6-7, characterized in that inert gases, for example nitrogen, argon, helium, carbon dioxide or any mixture thereof, are used as a diluent gas.

13. The method according to any one of p. 6-7, characterized in that as a diluent gas use a mixture of C ₁ -C ₄ alkanes with an inert gas, for example, nitrogen, argon, helium, carbon dioxide containing 1 to 50 % inert gas.

14. The method according to any one of p. 6-7, characterized in that the content of diluent gas in a mixture with nitrous oxide is 1 - 90% of the nitrous oxide content.