JP2011153272A - Method for decomposing and recovering vulcanized rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for decomposing and recovering a vulcanized rubber, the method exhibiting a low reaction temperature and a high energy efficiency and being excellent in reactivity and in recycle recovery of a decomposition reactant. <P>SOLUTION: In the method for decomposing and recovering a vulcanized rubber, divalent iron ion is used as a reaction initiator; a vulcanized rubber including a filler is decomposed by a lipid peroxidation reaction of linoleic acid, or the like; a decomposed rubber component is dissolved in an organic solvent; and the lipid is eliminated by reprecipitating the rubber component in an alcohol including an alkali added thereto, thus recovering the rubber component. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for decomposing and recovering vulcanized rubber. More specifically, the present invention relates to a method for decomposing and recovering vulcanized rubber. More specifically, the decomposition reaction temperature is low, the energy efficiency is high, the decomposition rate is high, and the decomposition reaction product is easily decomposed. The present invention relates to a method for decomposing and recovering vulcanized rubber.

  Rubber products are difficult to reuse together with plastic products, and are often used as fuel mainly in cement factories. However, with increasing interest in environmental issues in recent years, instead of burning rubber products as fuel, there is a need to develop energy-saving methods that decompose at low temperatures, such as compost, and material recycling methods that reuse decomposed materials. ing.

  Conventionally, desulfurization reaction is known as a technology for recycling vulcanized rubber, but there is a problem that energy efficiency is poor because of high reaction temperature. Moreover, microbial decomposition is known as a recycling technique with a low reaction temperature, but there is a problem that the decomposition rate is slow.

  Under such circumstances, for example, Patent Document 1 discloses a method for decomposing a vulcanized rubber in which the vulcanized rubber is decomposed in a specific organic solvent in the presence of a specific acid. Non-Patent Documents 1 and 2 disclose a method for decomposing polyisoprene rubber or the like using a microbial enzyme component or the like.

JP 2006-70127 A

Macromolecular Bioscience Volume 2003 Issue 3 Pages 668-674 (2003) Biomacromolecules Vol. 4, No. 2, pp. 314-320 (2003)

  However, in recent vulcanized rubber recycling technology, it is necessary not only to have a low decomposition reaction temperature and excellent energy efficiency, but also to have a high decomposition rate and to obtain a decomposition product that can be easily recycled and recovered. While there is a need for vulcanized rubber recycling technology that is superior not only in efficiency but also in decomposition speed and ease of recovery, energy efficiency and decomposition speed are compatible in the above vulcanized rubber recycling technology. It is a situation that cannot be done. For example, if the energy efficiency is excellent, such as microbial decomposition, the decomposition rate is slow. On the other hand, if the decomposition rate is fast, such as a desulfurization reaction, the energy efficiency is poor, and vulcanization that achieves both energy efficiency and decomposition rate is achieved. There is still room for improvement in rubber recycling technology. Furthermore, there is still room for improvement with respect to the technology for recycling vulcanized rubber, which is compatible with the technology for obtaining a decomposition product that can be easily recycled.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for decomposing and recovering vulcanized rubber that has a low decomposition reaction temperature, is excellent in energy efficiency, has a high decomposition rate, and can yield a decomposition product that can be easily recycled and recovered.

  The inventor has intensively studied to solve the above problems, and has found a method for decomposing and recovering vulcanized rubber by a specific decomposition reaction process and a process recovery process, and has completed the present invention.

  That is, the method for decomposing and recovering vulcanized rubber according to the present invention comprises a step of decomposing vulcanized rubber by a lipid peroxidation reaction, decomposing the vulcanized rubber, dissolving the decomposed rubber component in an organic solvent, The method further comprises a step of removing the lipid by reprecipitation of the rubber component in the alcohol added with the step of recovering the rubber component.

Moreover, it is desirable to use linoleic acid as the lipid, and it is desirable to use divalent iron ions as the reaction initiator.
The vulcanized rubber is preferably a diene rubber.
The vulcanized rubber preferably contains a filler, and more preferably, the filler is at least one selected from silica and carbon black.
Moreover, it is desirable to extract the anti-aging agent in the vulcanized rubber with an organic solvent.
Moreover, after dissolving in the organic solvent, it is desirable to filter the insoluble matter, and it is desirable to centrifuge the insoluble matter.

  According to the method for decomposing and recovering vulcanized rubber of the present invention, there is provided a method for decomposing and recovering vulcanized rubber, which has a low decomposition reaction temperature, is excellent in energy efficiency, has a high decomposition rate, and is capable of obtaining a decomposition product that is easy to recycle. can do. As described above, the method for decomposing and recovering vulcanized rubber according to the present invention is sufficient for not only industrial profitability but also recent vulcanized rubber recycling treatment in which environmental considerations such as energy saving and recyclability are being emphasized. This is a possible method.

Hereinafter, the present invention will be described in detail.
The method for decomposing and recovering vulcanized rubber according to the present invention comprises a step of decomposing vulcanized rubber by a lipid peroxidation reaction, decomposing vulcanized rubber by the method of decomposing vulcanized rubber, It is characterized in that it comprises a step of removing the lipid by reprecipitation of the rubber component in alcohol added with alkali and recovering the rubber component.

[Disassembly process]
The decomposition step of the present invention is a step of generating radicals by a lipid peroxidation reaction and decomposing the double bond site of the vulcanized rubber.

[Subject: Vulcanized rubber]
The vulcanized rubber to be decomposed is formed by vulcanizing a rubber composition containing at least a rubber component and a vulcanizing agent. Examples of the decomposable rubber component include natural rubber, synthetic polyisoprene rubber, butadiene rubber, and SBR. Examples of the vulcanizing agent include soluble sulfur; elemental sulfur (free sulfur); sulfur-donating vulcanizing agents such as organosilane polysulfides, amine disulfides, polysulfides, or sulfur olefin adducts, and insoluble polymer sulfur. . In addition, activators, retarders, vulcanization accelerators, processing aids such as oil, resins containing tackifying resins, plasticizers, pigments, additional fillers, fatty acids, zinc oxide, waxes, antioxidants, ozone Any vulcanized rubber containing various commonly used additives such as a deterioration inhibitor and a peptizer, preferably a diene rubber, can be used as an object. The vulcanized rubber preferably contains a filler, more preferably at least one selected from silica and carbon black. Specific examples of the object include various industrial products and household products manufactured using vulcanized rubber, or wastes thereof, or processed products obtained by pretreating the industrial products and wastes. Examples of industrial products include tires, mats, hoses, belts, golf balls, seismic isolation bearing materials, various seals and packing materials, cable covering materials, various cushions, gloves, rubber bands, adhesives, and the like.

[Preprocessing]
Specific examples of the pretreatment include a process of pulverizing an object such as an industrial product with a shredder, a heat treatment, a heating / humidification treatment, and the like. Furthermore, it is preferable to perform a pretreatment for extracting the anti-aging agent with an organic solvent.

[Decomposition reaction]
The decomposition reaction is a reaction that generates radicals by a lipid peroxidation reaction and decomposes the double bond site of the vulcanized rubber. As the lipid peroxidation reaction, a step of decomposing vulcanized rubber in the presence of a Fenton reagent and an unsaturated fatty acid is suitable.

[Initiator]
The reaction proceeds faster when divalent iron ions, known as Fenton reagents, are used as starting materials. The Fenton reagent is an oxidation color reagent in which hydrogen peroxide (H ₂ O ₂ ) and iron (II) salt are mixed.
As the Fenton reagent, a mixture of hydrogen peroxide (H ₂ O ₂ ) and iron (II) salt can be used. Examples of the iron (II) salt include iron (II) sulfate (FeSO ₄ ), ferrous fumarate, ferrous oxalate, ferrous chloride, sodium ferrous citrate, ferrous gluconate, Ferrous citrate, ferrous orotate, ferrous acetate, and the like can be used, and preferably, iron (II) sulfate (FeSO ₄ ) can be used.
The concentration of the iron (II) salt as a constituent of the Fenton reagent (1 ml) is, for example, preferably 0.1 to 50 mM, more preferably 0.3 to 10 mM, and even more preferably 0.5 to 3 mM. . The concentration of hydrogen peroxide as a constituent element of the Fenton reagent is, for example, preferably 0.001 to 5 mM, more preferably 0.03 to 1 mM, and still more preferably 0.05 to 0.3 mM.

[Reaction mechanism]
This reaction is called the Fenton reaction. Oxidation mechanism of Fenton reagent is believed to generate radicals hydroxide (OH ^·) by the following reaction.
^{_{H 2 O 2 + Fe 2+ →}} Fe 3+ + HO - + OH ·
Hydroxyl radicals (OH ^· ) generated by the Fenton reaction are useful active oxygen species for rapid oxidative decomposition of organic chemical substances.

Radical hydroxide (OH ^·) is, to the work of the initiator. Lipid (L-H), hydrogen abstraction, changes in lipid radical (L ^·). Further, by going through the oxidation reaction or the like, lipid radicals ^{(L ·, LO ·, LOO} ·) becomes. The lipid radical is unstable, it reacts rapidly with oxygen in the atmosphere, the lipid peroxy radicals (LOO ^·). The lipid peroxy radical abstracts hydrogen and becomes lipid peroxide (LOOH). The peroxide bonds (O-O bonds) are readily cleaved to generate two radicals hydroxide (OH ^·) and lipid alkoxy radicals (LO ^·), sharply increases the radical concentration. These lipid radicals radicalize vulcanized rubber (R—H) (R ^· ). Lipid alkoxy radical (LO ^·) has a large hydrogen abstraction rate than lipid peroxy radicals (LOO ^·) and hydroxyl radicals (OH ^·), occupies a central position of the reaction. For this reason, vulcanized rubber is radicalized mainly by lipid radicals.

Vulcanized rubber radicals can be oxidized vulcanized rubber peroxy radicals (ROO ^·), through the vulcanized rubber alkoxy radicals (RO ^·), a portion thereof, beta - causing cleavage. In this way, the vulcanized rubber is reduced in molecular weight by the oxidation radical reaction, and the decomposition reaction proceeds.
OH ^· + L−H → H ₂ O + L ^·
L ^・ , LO ^・ , LOO ^・ + RH → L−H, LOH, LOOH + R ^・
R ^· + O ₂ → ROO ^· → RO ^· → beta-cleavage
The double bond site of vulcanized rubber is decomposed by beta-cleavage under the attack of lipid radicals.
R ₁ R ₂ = O ^· → R ₁ ^· + R ₂ = O

  Ordinarily recycled vulcanized rubber contains antioxidants and antioxidants as additive components. A vulcanized rubber is kneaded with a phenolic type inhibitor that directly captures radicals, a phosphoric acid type inhibitor that decomposes peroxide and prevents radical growth, and the like. For this reason, normally recycled vulcanized rubber has high resistance to lipid peroxidation, mainly radical chain reaction, and slows the degradation rate. For this reason, it is preferable to perform the pretreatment which extracts an anti-aging agent with an organic solvent.

[Lipid]
A lipid is used for the lipid peroxidation reaction. The lipid is preferably an unsaturated fatty acid. It is particularly preferred to use linoleic acid as the unsaturated fatty acid. As unsaturated fatty acids other than linoleic acid, for example, linolenic acid, arachidonic acid and oleic acid can be used. For example, the concentration of the unsaturated fatty acid is preferably from 0.1 mM to 100 mM, more preferably from 1 mM to 20 mM, and even more preferably from 3 mM to 10 mM.

[Reaction system]
The reaction system can be prepared by, for example, mixing other components such as Fenton reagent, unsaturated fatty acid, and surfactant in an appropriate buffer. When the target object is brought into contact with the prepared reaction system, the target object may be simply immersed in the reaction system, or may be stirred while the target object is immersed in the reaction system. Furthermore, you may make a target object contact a reaction system, ventilating.

[Reaction conditions]
The temperature of the reaction system is preferably maintained in the range of 15 to 50 ° C, more preferably in the range of 25 to 45 ° C, and still more preferably in the range of 35 to 40 ° C. The pH of the reaction system is preferably maintained in the range of 5-9, more preferably in the range of 6-8, and even more preferably in the range of 6.5-7.5. . Furthermore, 0.1-10 g / L is preferable and, as for the ratio of the target object contained in a reaction system, it is more preferable to maintain at 0.5-5 g / L. The reaction time is preferably 1 to 240 hours, more preferably 6 to 48 hours. It is preferable to stop the reaction by adding a reaction terminator such as BHT.

[Recovery process]
In this process, the decomposed rubber component is dissolved in an organic solvent, and the rubber component is reprecipitated in an alcohol to which an alkali is added to remove the lipid and recover the rubber component.
In general, vulcanized rubber is insoluble in any organic solvent, but becomes soluble in an organic solvent by the decomposition method of the present invention. As the organic solvent, one in which unvulcanized raw rubber such as toluene, tetrahydrofuran, cyclohexane and chloroform is soluble is selected. However, the recovery method differs depending on whether or not a filler such as carbon black is blended in the sample before decomposition.

When no filler is blended, the decomposition product becomes liquid, so that separation from the reaction solution is not mixed with water such as chloroform, and an organic solvent that dissolves rubber is added to the reaction solution, and the rubber component is liquid- Liquid extraction is required.
When a filler such as carbon black is blended, the reaction solution and decomposed rubber can be easily separated by filtration or decantation using filter paper, etc., but the decomposed rubber component is filled. Therefore, when the decomposition product is dissolved in an organic solvent, carbon black, inorganic fillers such as silica and zinc oxide remain as insoluble components, and these are removed by filtration or centrifugation.

[Removal of lipid]
Next, a lipid removal process is performed. In the organic solvent in which the rubber component decomposed by the above treatment is dissolved, the unsaturated fatty acid used in the lipid peroxidation reaction is mixed. Thus, as a result of intensive studies, the inventors have found that unsaturated fatty acids and rubber can be efficiently separated by reprecipitation of a rubber decomposition product in an alcohol to which an alkali is added. Here, examples of the alkali include potassium hydroxide, sodium hydroxide, calcium hydroxide, and magnesium hydroxide, but a potassium hydroxide aqueous solution is preferable. The alkali concentration is preferably 0.1 to 5N, and more preferably 0.2 to 2N. Examples of the alcohol include methanol, ethanol, propanol and the like, but ethanol is preferable.

[Separation process]
When the rubber decomposed by the above treatment is taken out, the rubber becomes soluble in an organic solvent. For this reason, not only can it be easily recovered, but it has a structure similar to that of the raw rubber and can be recovered in a state where it can be easily used for material recycling.

[Evaluation methods]
The recovered rubber was dried and weighed. For molecular weight measurement, a sample was dissolved in tetrahydrofuran at a concentration of 0.1%, filtered through a 0.45 μ filter, and 100 μl was injected into the GPC apparatus. The column used was TSK-GMH, and the detector used was a differential refractive index detector. In addition, in this specification, a weight average molecular weight (Mw) means the value calculated | required by polystyrene conversion measured by GPC.

  As described above, the method for decomposing and recovering a vulcanized rubber according to the present invention not only has a low reaction temperature and high energy efficiency, but also has an excellent reaction rate and excellent recyclability of decomposition products. Therefore, the method for decomposing and recovering vulcanized rubber of the present invention can be suitably used for material recycling, and more specifically, it is very useful as an additive for rubber products and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

Example 1
In a 100 ml reaction solution having a composition of 0.2 mM hydrogen peroxide, 1 mM ferrous sulfate (iron (II) sulfate [FeSO ₄ ]), 5 mM linoleic acid, 15 mM buffer, and 0.01 mM nonionic surfactant. While stirring at 37 ° C. for 24 hours, 0.1 g of latex glove rubber was decomposed. To this reaction solution, 50 ml of chloroform containing 10 mM BHT was added, and the rubber component was subjected to liquid-liquid extraction. After the chloroform solution was separated from the reaction solution, the chloroform solution was added dropwise to ethanol to which 1N potassium hydroxide had been added to recover the rubber component. The recovered rubber amount was 0.06 g, and the weight average molecular weight was 13,500.

(Example 2)
With the same composition as in Example 1, 0.1 g of a carbon-containing vulcanized natural rubber whose composition was shown in Table 1 was recovered by decomposition. 0.03 g of a vulcanized rubber decomposition product was recovered as a liquid rubber having a weight average molecular weight of 9550.

(Comparative Example 1)
Even when the same treatment as in Example 1 was performed with the reaction solution obtained by removing ferrous sulfate from the reaction solution in Example 1, the glove rubber was not decomposed.

  It can be seen from Example 1 that the vulcanized rubber can be easily decomposed by this method and can be suitably recovered as a liquid rubber. It can also be seen from Example 2 that a liquid rubber can be obtained from a vulcanized rubber compounded with carbon.

  According to the present invention, after the vulcanized rubber is decomposed by a lipid peroxidation reaction, the decomposed rubber component is dissolved in an organic solvent, and the rubber component is reprecipitated in an alcohol to which an alkali is added to remove the lipid, and the rubber A method of recovering minutes was provided. Since the method of the present invention is a decomposition and recovery method using a chemical reaction under conditions close to normal temperature and pressure, there is an advantage that the energy consumption is small, the environmental load such as carbon dioxide emission is small, and the cost is low, Furthermore, since the recovered rubber component is easy to use, it is considered that it greatly contributes to the reuse of used vulcanized rubber such as waste tires.

Claims (9)

  A step of decomposing vulcanized rubber by a lipid peroxidation reaction, and after decomposing the vulcanized rubber, by dissolving the decomposed rubber component in an organic solvent and reprecipitating the rubber component in alcohol to which alkali is added. A method for decomposing and recovering vulcanized rubber, comprising a step of removing lipids and recovering rubber.   The method for decomposing and recovering a vulcanized rubber of a vulcanized rubber according to claim 1, wherein the lipid peroxidation reaction is performed using linoleic acid as a lipid.   The method for decomposing and recovering vulcanized rubber according to claim 1 or 2, wherein divalent iron ions are used as a reaction initiator for the lipid peroxidation reaction.   The method for decomposing and recovering a vulcanized rubber according to any one of claims 1 to 3, wherein the vulcanized rubber contains a diene rubber.   The method for decomposing and recovering vulcanized rubber according to any one of claims 1 to 4, wherein the vulcanized rubber contains a filler.   6. The method for decomposing and recovering vulcanized rubber according to claim 5, wherein the filler is at least one selected from silica and carbon black.   The method for decomposing and recovering vulcanized rubber according to any one of claims 1 to 6, wherein the vulcanized rubber contains an anti-aging agent, and the anti-aging agent is extracted with an organic solvent.   The method for decomposing and recovering vulcanized rubber according to any one of claims 1 to 7, wherein insoluble matter is filtered after dissolving in the organic solvent.   The method for decomposing and recovering vulcanized rubber according to any one of claims 1 to 8, wherein the insoluble matter is centrifuged after being dissolved in the organic solvent.