JP2002265664A - Method for recovering material from molded rubber product and recovered material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering a material from a rubber molded product by which a high-molecular weight rubber and/or carbon black directly usable as a rubber raw material from vulcanized or unvulcanized rubbers such as rubber wastes, etc., of once molded tires or scrap rubbers can readily and surely be recovered and to obtain a recovered material. SOLUTION: This method for recovering the material comprises (1) applying heat treatment for enabling the rubber molded product containing carbon black and rubber to substantially retain an outer shape before heating at 220-400 deg.C temperature under atmospheric pressure, then (2) extracting the resultant rubber molded product with an organic solvent and separating the molded product into a solvent extract component and an extraction residue, (3) removing the solvent from the separated solvent extract component and thereby covering a liquid rubber and (4) (i) pyrolyzing the separated extraction residue at >=500 deg.C temperature or (ii) dissolving the extraction residue in a rubber solubilizing agent, degrading the rubber component and recovering the carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a material for recovering material from a rubber molded product, and more particularly to a method for recovering rubber waste such as tires and rubber tubes and vulcanized or unvulcanized rubber molded products such as rubber waste. As a reusable material,
The present invention relates to a method for recovering a high molecular weight rubber component and / or carbon black, and a material for recovering the same.

[0002]

2. Description of the Related Art In recent years, waste treatment, particularly recovery and reuse of raw materials from industrial waste, has become an important social issue. For rubber waste materials such as tires with high emissions, it is desirable to recover and reuse raw materials.However, recover rubber and carbon black, etc. of possible quality that can be reused as raw materials from vulcanized and stabilized rubber waste materials. Is not easy and most of them are incinerated directly as fuel. For example, when trying to recover raw materials from rubber waste,
High temperature (typically above 500 ° C.) or high pressure (typically above 20 bar) decomposition is common. Various catalysts, solvents and the like for use in such high temperature or pressure decomposition have been proposed (US Pat. Nos. 3,704,108 and 3,996,022, European Patent 71789).
And JP-A-60-40193 and JP-A-7-310076.

In the above-mentioned high-temperature or high-pressure cracking method, the rubber component can be recovered as a gaseous low-molecular hydrocarbon or oil, but it is difficult to recover it with a high-molecular-weight rubber that can be used as it is as a rubber raw material. is there. In addition, regarding carbon black, it is generally difficult to recover carbon black of the same quality as the raw material carbon black after high-temperature decomposition. It is said that carbon black is substantially difficult to reuse because it can be obtained in a mixed state with a decomposed crosslinked rubber).

[0004]

SUMMARY OF THE INVENTION The present invention has been made under the above-mentioned circumstances, and is particularly intended to effectively reuse tires, rubber wastes such as rubber scraps, and the like. A method for recovering material from molded articles, which can easily and easily recover a high-molecular-weight rubber component and / or carbon black that can be used as a rubber raw material from vulcanized or unvulcanized rubber, and a method for recovering these materials, It is intended to provide a rubber composition containing the material.

[0005]

Even when a rubber molded article such as a tire is heated at a temperature lower than the temperature conventionally used for pyrolysis (for example, about 300 ° C.), its shape does not substantially change. Can not confirm the decomposition. It is well known that vulcanized bulk rubber does not substantially change or swell even when immersed in an organic solvent. However, while the present inventors have studied for the purpose of recovering both rubber and carbon black from a rubber molded product such as waste material in a reusable state, conventional studies on the conventional industrial treatment of rubber waste material have been conducted. Unexpectedly high purity and high molecular weight rubber can be recovered in high yield by extracting with organic solvent after preheating at low temperature, which is not possible, and high quality carbon black is recovered I found out what could be done.

The present inventors have further specifically studied the preheating / extraction method based on the above findings. For example, it has been found that a conventional thermal decomposition method can be obtained from a vulcanized molded product of a standard rubber compounded tire. Average molecular weight (Mw) 15 which was difficult
A high purity liquid isoprene of about 000 can be recovered at a high recovery rate of 80% with respect to the raw material rubber, and a rubber having a higher molecular weight can be recovered depending on selection conditions within the above preheating temperature range. It has been found that it is possible and is a commercially useful method capable of easily and reliably recovering a high-molecular-weight liquid rubber. In addition, the residue from solvent extraction can be easily recovered as carbon black that can be reused as a high quality material by decomposing the rubber component by high-temperature pyrolysis or dissolving the rubber component using a specific rubber dissolving agent. The inventors have found that the present invention can be performed, and have completed the present invention.

Accordingly, in the method for recovering material from a rubber molded product according to the present invention, the process of recovering a rubber component as a material in the rubber molded product is a first mode, and the process of recovering carbon black is a second mode. A process for recovering both the rubber component and the carbon black is provided as a third embodiment. That is, in the present invention,
(1) A rubber molded article containing carbon black and rubber is subjected to a heat treatment capable of substantially maintaining the outer shape before heating at a temperature of 220 to 400 ° C., and (2) extraction with an organic solvent to extract the solvent And (3) removing the solvent from the separated solvent extract to recover the liquid rubber, thereby providing a method for recovering material from a rubber molded product.

[0008] In the present invention, (1) the rubber molded product, 220
After applying a heat treatment capable of substantially maintaining the outer shape before heating at a temperature of up to 400 ° C., (2) extraction with an organic solvent separates a solvent extraction component and an extraction residue, and then (4) separates The rubber extract is decomposed by (i) heating the solvent extraction residue at a temperature of 500 ° C. or higher, or (ii) dissolving it in a rubber dissolving agent containing 0.01 to 50% of a peroxide, A method for recovering material from a rubber molded article for recovering carbon black is also provided.

The method for recovering material from a rubber molded product according to the present invention may be a mode in which (4) is performed in addition to (1) to (3), that is, (1) carbon black and rubber are contained. After applying a heat treatment to the rubber molded article at a temperature of 220 to 400 ° C., which can substantially retain the outer shape before heating,
(2) organic solvent extraction to separate the solvent extractables and extraction residue; (3) removal of the solvent from the separated solvent extractables to recover the liquid rubber; and (4) separation of the solvent extractables. The residue is (i) heated at a temperature of 500 ° C. or higher, or (ii) dissolved in a rubber dissolving agent containing 0.01 to 50% of peroxide to decompose a rubber component and convert carbon black. The collecting mode may be adopted.

In the above (1), when processing a rubber molded product made of isoprene rubber raw material, the preheating temperature is preferably from 220 to 300 ° C. (temperature under normal pressure). In the case of treating a rubber molded product made of a butyl rubber raw material, the preheating temperature is desirably 300 to 380 ° C (temperature under normal pressure). In the above (2), the organic solvent extraction is performed by subjecting the rubber molded article heat-treated in the above (1) to:
It can be performed by immersing in toluene at 0 to 40 ° C.

[0011] In the above (4), the solvent extraction residue is used for (i)
If the rubber component is decomposed into gaseous hydrocarbons by heating at a temperature of 500 ° C. or higher, carbon black can be easily collected as a decomposition residue. The rubber dissolving agent used in the step (ii) of the above (4) is benzoyl peroxide in 0.1 g.
Preferably, it is toluene containing from 01 to 50%.

In the present invention, rubber or carbon black is also provided as the material recovered above. For example, a liquid rubber having an average molecular weight (Mw) of 15,000 or more can be provided, and preferably a high molecular weight liquid rubber having a molecular weight of 50,000 or more can be provided. This rubber is usually isoprene rubber or butyl rubber. The recovered carbon black provided in the present invention can be reused as a high quality material. The present invention also provides a rubber composition containing at least one of the above rubber or carbon black as a recovery material.

[0013] In order to identify the rubber component, several methods for extracting the rubber component from the bulk rubber have been proposed. For example, DW Carlson et al. (Analytical Chemistry, 4).
2,1278 (1970)) has proposed a method of heating at 200 ° C. and extracting with carbon disulfide. Some other methods using reflux with an organic solvent such as o-dichlorobenzene and nitrobenzene have been proposed. The heating temperature is about 200 ° C. or about 210 ° C. if refluxed with nitrobenzene, in order to identify the rubber component.
Therefore, it can be said that these analysis methods suggest that vulcanized rubber does not mean that no rubber component can be taken out. However, although these methods can be said to be sufficient treatment methods from the viewpoint of rubber component identification, the amount of extracted rubber is small and has not been generally regarded as a method applicable to rubber recovery. Therefore, conventionally, extraction with an organic solvent is not usually considered as a method for recovering rubber that can be industrially performed. Also, it cannot be said that the recovery of high quality carbon black from waste rubber has been substantially studied.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a method for recovering material from a rubber molded product, a material in the rubber molded product recovered by the recovery method, and a rubber composition containing the recovered material. Hereinafter, the present invention will be specifically described with reference to a process flow schematically shown in FIG. In the method for recovering material from a rubber molded product according to the present invention, the rubber and / or
Alternatively, it is possible to recover carbon black, but in the following, a process for recovering rubber for convenience is the first embodiment,
The process of recovering carbon black is referred to as a second embodiment, and the process of recovering both rubber and carbon black is referred to as a third embodiment. In any of the embodiments, first, the rubber molded article is subjected to (1) a step of preheating at a specific temperature, and (2) an organic solvent extraction step.

(1) Preheating Step First, a heat treatment at a temperature of 220 to 400 ° C. is applied to the rubber molded product. The rubber molded product subjected to the recovery treatment in the present invention is:
It is sufficient that the rubber is formed once, and the shape is not limited at all, and the components other than the rubber are not particularly limited. Further, the rubber molded product is not limited to vulcanized rubber, and may be unvulcanized, partially vulcanized rubber, a mixture of vulcanized rubber and unvulcanized rubber, and the like. May be a composite with the constituent material.

Examples of the raw rubber for forming such a rubber molded product include natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), butyl rubber (IIR), and chloroprene. Rubber (CR) and the like can be mentioned.

The rubber composition may contain a filler, and examples of the filler include those known as fillers such as carbon black, silica, zinc oxide, and calcium carbonate without particular limitation. . Note that the rubber molded product subjected to rubber recovery in the first embodiment may or may not contain carbon black, but in the second and third embodiments described later, a rubber containing at least carbon black is used. A molded article is used.

Examples of the rubber molded product include non-elemental sulfur vulcanizing agents such as sulfur, tetramethylthiuram disulfide, tetraethylthiuram disulfide, bismorpholine disulfide, dipentamethylene thiuram tetrasulfide, organic peroxides, quinone dioxime, phenol Formaldehyde resin, nitroso compound and diisocyanate mixture, zinc oxide, magnesium oxide, zinc peroxide, triethylenetetramine, methylenedianiline, diphenylguanidine, hexamethylenediaminecarbamate, ethylenediaminecarbamate, bis-p-aminocyclohexylmethanecarbamate, stearin acid,
It may be vulcanized by a vulcanization system such as oleic acid (vulcanizing agent, vulcanization accelerator, vulcanization aid, etc.).

The rubber molded article may contain two or more components of rubber, vulcanization system, and filler. In addition to these, known resins, other elastomers, various compounding agents, rubber additives, etc. May contain a wide range of materials, such as activators, vulcanization retarders, softeners, plasticizers, adhesives, tackifiers, curing agents, foaming agents, foaming aids, reinforcing agents, antioxidants, coloring Agent,
It may contain pigments, flame retardants, release agents, and the like. Also, as the composite material, steel materials such as steel cord,
Fibers such as polyester carcass cord and the like are included. The amount of each component contained in the rubber molded product is not particularly limited. For example, when the rubber molded product is a tire, usually, about 50 parts by weight of carbon black is added to 100 parts by weight of the rubber, and other components are added. The agent contains about 10 parts by weight in total.

Specific examples of the above rubber molded articles include rubber parts for automobiles such as natural rubber tires, synthetic rubber tires, bladders and liners, rubber products such as cables, belts, hoses, sheets and packings, and smelting wastes.
Examples include molded waste rubber such as processing waste. These rubber molded articles do not necessarily have to be used, but are desirably rubber waste materials. For example, unused rubber waste materials include rubber vulcanized materials that have been vulcanized early in the kneading and molding processes during the manufacture of rubber products such as tires and vulcanization unevenness (burn, scorch).
Defective rubber products that have caused so-called dripping in the vulcanization process, those with mixed vulcanized and unvulcanized parts, those with a low degree of cross-linking overall, steel, organic fibers, and other members Various forms of shavings, such as those that are attached, can be mentioned. Among them, the tire or its molded waste rubber is a waste rubber material capable of recovering natural rubber and isoprene with high purity, and is preferable. Also preferred are butyl rubber raw materials for automobile rubber parts and the like. It is preferable that the rubber molded product is cut into small pieces and provided for improving thermal efficiency and extraction efficiency.

In the present invention, the above rubber molded product may have 220-4
A heat treatment at 00 ° C. is performed, and the heat treatment is performed so that the outer shape before heating can be substantially maintained. In this specification, substantially retaining the outer shape before heating means that no apparent decomposition deformation occurs. For example, a cubic rubber molded product retains a substantially cubic shape even after heat treatment. I have. On the other hand, when a solid material is broken down by liquefaction or gasification such as thermal decomposition or dissolution in a solvent so that at least a part thereof does not retain the original shape, it is called decomposition of a molded article.

As the heating device, an oven, a tube furnace, or the like can be used. The heating may be performed in an inert atmosphere such as in air or nitrogen gas, but is preferably performed in an inert atmosphere if it is necessary to avoid denaturation (oxidation) of the rubber. It is difficult to confirm the decomposition in appearance even when heating is continued in the above temperature range, but when heated in air, the recovered rubber is slightly oxidized. This oxidation can be confirmed by IR spectrum,
There is almost no problem in practical use. When preheating is performed in air, rubber having a low average molecular weight (Mw) tends to be recovered in the post-process (3), as compared with the case where heating is performed in an inert atmosphere. They tend to have a molecular weight distribution. If necessary, for example, a high molecular weight component can be separated.

The heating conditions vary depending on the heating raw material (rubber molded product), the treatment atmosphere and the like, but are appropriately selected within the temperature range of 220 to 400 ° C. depending on the desired molecular weight and yield of the recovered rubber. The molecular weight and yield of the recovered rubber is
There is a tendency to be affected by temperature rather than heating time. Specifically, even in the above temperature range, a higher molecular weight rubber can be recovered on the lower temperature side, but the yield decreases, and on the high temperature side, the yield is high. However, the molecular weight tends to decrease.

The above preheating temperature is a temperature under normal pressure. Preheating is usually performed under normal pressure, but when preheating is performed under pressure conditions other than normal pressure, a temperature corresponding to the heating temperature under normal pressure under the selected pressure is selected. . The heating time depends on the heating environment, but may be generally about 10 minutes, and preferably about 15 minutes. Even if heated for a long time, the rubber recovery rate does not increase significantly, and the rubber molecular weight tends to decrease. Therefore, the heating time is at most 4
It is about 0 minutes, preferably up to about 30 minutes.

When the preformed rubber molded product is made of butyl rubber as a raw material, the temperature is desirably 300 to 380 ° C., preferably 300 to 350 ° C., and particularly preferably 330 to 380 ° C. in the above heating temperature range. 350 ° C. When the preformed rubber molded article is made of isoprene rubber as a raw material, the heating temperature is preferably 220 to 300 ° C. within the above heating temperature range. Average molecular weight (Mw)
High molecular weight rubber of 15,000 or more can be extracted and recovered. The preheating temperature of the isoprene rubber molded product is preferably from 220 to 280 ° C, more preferably from 220 to 250 ° C.
° C. At this preferred temperature, ultimately Mw of 30,000 or more, preferably 50,000 or more even in air, and a higher molecular weight rubber can be easily recovered in an inert gas atmosphere.

More specifically, for the isoprene rubber molded article, for example, using a tubular furnace (heat-resistant tube),
7 to 15 kg / mm square vulcanized rubber (standard tire)
When heated for 15 minutes in a nitrogen stream with a filling amount of m ³ , 2
In the case of heating at 50 ° C. for 15 minutes, isoprene having Mw of about 84000 was recovered at a recovery rate of 30% or more, and Mw of
About 6000 isoprene can be obtained with a recovery of 70% or more. The recovery rate is a value obtained as a recovery rate with respect to the amount of rubber in the rubber molded article when a rubber molded article (vulcanized) having a known composition is provided as a raw material for the recovery processing.

(2) Organic Solvent Extraction Step The rubber molded article preheated as described above is then subjected to solvent extraction (dissolution). Specifically, the rubber molded article heat-treated in the above (1) is usually immersed in an organic solvent to extract a dissolved component. At this time, the organic solvent may be heated, but from the viewpoint of work cost, room temperature (normally about 0 to 40 ° C.)
Is preferably immersed in an organic solvent. The immersion time is
10 hours or more is desirable, usually overnight. The organic solvent is desirably used in such an amount that the solid rubber molded product can be sufficiently immersed. Usually, 1 kg of the rubber molded product is immersed in about 8 to 10 liters of the organic solvent.

Here, as the organic solvent, a saturated or unsaturated hydrocarbon can be used, and the hydrocarbon is not particularly limited to aromatic, aliphatic, alicyclic and the like. For example, benzene, toluene, xylene, hexane, decalin (decahydronaphthalene), tetralin (tetrahydronaphthalene), cyclohexane and the like can be used. These may be used in combination. Of these, hexane, toluene, xylene and the like are preferably used. Next, the solvent extraction component and the extraction residue (insoluble component) are separated by general-purpose separation means such as centrifugation and filtration.

(3) Rubber recovery step In the first embodiment of the method for recovering material from a rubber molded product according to the present invention, rubber is recovered by removing an organic solvent from the solvent extract separated as described above. Organic solvents can be removed, for example, by distillation. By the above, high molecular weight rubber can be recovered. Although it depends on the heating conditions in the preheating step (1), for example, from an isoprene rubber molded article, an average molecular weight (Mw) of 15,000 or more, preferably 50,000 or more, more preferably 70,000 by preheating at 220 to 300 ° C. The high molecular weight liquid rubber can be recovered. If necessary, it is possible to extract and recover a rubber having a high molecular weight of 90,000 or more. From the butyl rubber molded product, liquid rubber having a Mw of 30,000 or more, preferably 50,000 or more can be recovered at a high recovery rate by preheating at a preferable temperature of 300 to 350 ° C. With regard to the molecular weight, a liquid rubber having a high molecular weight of 100,000 or more can be recovered. The recovered rubber of the present invention does not cause any problem even if it contains a vulcanizing agent such as sulfur contained in the raw rubber molded product. The recovered rubber can be further purified with methanol or water. The recovered rubber can be reused as a usual raw material for rubber products, and since the rubber has a high molecular weight, it is useful as a raw material for rubber products. The average molecular weight (Mw) of the rubber can be measured by gel permeation chromatography (GPC) according to a standard method.

(4) Carbon Black Recovery Step In the above step (2), the solvent extraction residue separated from the solvent extraction component is either (i) thermally decomposed at a temperature of 500 ° C. or higher, or (ii) peroxide. By dissolving the substance in a rubber dissolving agent containing 0.01 to 50%, the rubber component is decomposed and carbon black can be recovered.

In the thermal decomposition of the solvent extraction residue (i) at a temperature of 500 ° C. or more, the amount of the organic component (mainly a rubber component) on the surface due to heating is reduced by the amount of the organic compound on the surface of the raw material (virgin) carbon black. It is desirable to carry out until the amount becomes equal to or less than the component amount. The rubber component can be decomposed into gaseous hydrocarbons and / or oil by thermal decomposition in this step. If the rubber component is decomposed into gaseous hydrocarbons, carbon black can be recovered as it is as a decomposition residue, which is preferable. Specifically, the residue of the solvent extraction is usually added in a non-oxidizing atmosphere at a temperature of 500 ° C to 15 ° C.
00 ° C, preferably 500 ° C to 1000 ° C, for 30 seconds or more, preferably 5 minutes to 120 minutes, more preferably 7 minutes to 6 minutes.
Heat for 0 minutes. With such a heating temperature, the rubber component can be removed without carbonizing the carbon black to be recovered. Further, the toluene extraction residue is preferably finely divided so that it can be heated homogeneously, and it is also desirable to reduce the filling rate in the furnace and improve the heat treatment efficiency. For example, using a tubular furnace (heat-resistant tube), a 2 mm square vulcanized rubber (standard tire)
It is preferable to carry out in a nitrogen stream at a filling amount of 15 kg / m ³ .

The amount of an organic component such as a rubber component on the surface of the carbon black is evaluated by a thermal analysis method of thermogravimetry (TGA) by a weight change at 20 ° C. to 700 ° C. in a non-oxidizing atmosphere. be able to. The amount of organic components on the surface of virgin carbon black is usually 2
Assuming that the weight of the sample at 0 ° C is 100%,
The weight loss of the sample at a temperature of 20 ° C to 700 ° C is the same as that of the virgin carbon black. It is preferably 2.5% or less, and more preferably 1% to 2%.

The carbon black recovered as described above can sufficiently withstand reuse. When this recovered carbon black is used, the tensile stress and loss tangent of a rubber composition containing ordinary carbon black are reduced. An equivalent or high tensile stress and low loss tangent can be obtained. Although the reason for this is not clear at present, the present inventors believe that the organic component does not adhere to the surface of the carbon black, or that the organic component does not adhere to the carbon black in a very small amount.

As described above, if (i) pyrolysis is performed through (1) and (2), high-quality carbon black, which was difficult to recover by conventional pyrolysis, can be recovered.
This recovered carbon black can be reused for applications similar to virgin carbon black.

In the present invention, as the carbon black recovery step (4), (ii) dissolution of the solvent extraction residue with a rubber dissolving agent can be carried out. The rubber dissolving agent used in the present invention contains peroxide in an amount of 0.01 to 50%, preferably 0.1 to 1%.
The organic solvent is more preferably contained at a concentration of 0% to 0.5% to 2%. As the peroxide, known organic peroxides can be widely used, and specifically, benzoyl peroxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, p-methane hydroperoxide, cumene An organic peroxide such as hydroperoxide can be used. Further, it may contain a radical generator such as azobisisobutyronitrile and the like. The peroxide may contain water or the like to prevent explosion.

The organic solvent is liquid at normal pressure and normal temperature,
Known materials can be widely used as long as they can dissolve the peroxide. Specific examples include hydrocarbons and alcohols, and the hydrocarbons may be saturated or unsaturated, and are not particularly limited to aromatics, aliphatics, alicyclics, and the like. Examples of such an organic solvent include benzene, toluene, xylene, hexane, decalin (decahydronaphthalene), methanol, ethanol, tetralin (tetrahydronaphthalene), and cyclohexane. The alcohols may contain water like a commercial product, or may be further diluted with water. Among them, those capable of swelling the rubber at room temperature are preferable, and aromatic hydrocarbons such as toluene, benzene, and xylene are preferably used.

The rubber dissolving agent may contain two or more kinds of organic solvents and / or peroxides, and may contain other components as needed as long as the object of the present invention is not impaired. You may. Among these, a benzoyl peroxide / toluene solution is particularly preferably used.

By immersing the solvent extraction residue in the rubber dissolving agent, the solvent extraction residue is dissolved and decomposed to obtain a suspension of the liquefied rubber component and carbon black. The rubber dissolving agent is used in such an amount that the solvent extraction residue can be sufficiently decomposed, and the treatment is preferably carried out with stirring. The treatment may be performed at normal temperature (usually 40 ° C. or lower), and need not be performed at a high temperature. For example, when a 1% benzoyl peroxide / toluene solution is used, the treatment may be performed at room temperature for about 40 to 50 hours, preferably for about 60 to 70 hours.

As described above, the solvent extraction residue is dissolved and decomposed by the rubber dissolving agent, and the decomposition mixture is obtained as a free-flowing suspension. When the suspension is allowed to stand, the insoluble portion mainly containing carbon black sediments. This is centrifuged, membrane separated,
Separation by conventional means such as decantation and filtration makes it possible to easily separate the sedimentation section from the transparent solution containing the rubber decomposition component.

The recovered sediment usually contains a small amount of a rubber component together with the main component carbon black (which can be confirmed by gas chromatography and TGA analysis).
0: about 20. These can be used as carbon black without separation. When the recovered carbon black is used in the same manner as ordinary carbon black, a rubber composition having excellent damping performance can be formed. Therefore, it is useful for compounding seismic isolation rubber and tires.

On the other hand, the solution mainly contains a liquid rubber whose molecular chains have been cut, and contains a vulcanizing agent such as a small amount of peroxide, a decomposition product of peroxide, and sulfur contained in the rubber dissolving agent. May be. The organic solvent is removed from this solution in the same manner as in the above (3), and the precipitated peroxide and the decomposition product of the peroxide are treated with methanol, water, and the like, and the insoluble matter is recovered. The rubber having a molecular weight of about 10,000 or less can be easily recovered although the molecular weight is lower than that of the rubber recovered in the step (1).

When the rubber molded article of the present invention is a composite of different kinds of vulcanized rubbers, it is possible to separate them by utilizing a difference in solubility in a rubber dissolving agent. For example, in a laminate of a natural rubber vulcanizate and a butyl rubber (IIR) liner, natural rubber has higher solubility in a rubber dissolving agent than butyl rubber, and a rubber dissolving agent phase and an insoluble phase (butyl rubber is substantially a solid). (As a liner). The method using (ii) a rubber dissolving agent as described above has an advantage that energy consumption during recovery of carbon black is low.

In the present invention, the method for recovering rubber by the steps (1) to (3) and the method for recovering carbon black by performing (1) to (2) and (4) are separately described. Alternatively, (1) to (4) may be performed to recover rubber and carbon black. The rubber and carbon black recovered above can be reused as raw materials, and the present invention can also provide a rubber composition containing one or both of the recovered rubber and carbon black. In the rubber composition containing these recovered materials, at least a part of the rubber component in the rubber composition may be the recovered rubber, and the mixing ratio between the recovered rubber and the virgin rubber is appropriately selected according to the purpose and the like. And may be entirely recovered rubber. Similarly, at least a portion of the carbon black in the rubber composition may be the recovered carbon black, and the mixing ratio between the recovered carbon black and the virgin carbon black can be appropriately selected depending on the intended purpose. All may be recovered carbon black.

[0044]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. (Example 1) <Rubber molded article> 100 parts by weight of NR (natural rubber), 50 parts by weight of carbon black (ASTM code N118), 5 parts by weight of zinc oxide, 3 parts by weight of stearic acid, antioxidant 1
Parts by weight, vulcanization accelerator 1.2 parts by weight, and sulfur 1.8
A decomposition test was performed using a vulcanized rubber obtained by heating a rubber compound consisting of parts by weight at 148 ° C. for 10 minutes.

(1) The vulcanized rubber obtained above was cut into 2 mm square to obtain a die-shaped rubber molded product, which was filled with 7 to 15 mg per 1 cm ³ of a heat-resistant tube. Using a quartz glass tubular furnace, under a nitrogen atmosphere, 220 ° C., 250 ° C.,
280 ° C, 300 ° C for 15 minutes, 25 minutes, 3
Each was preheated for 5 minutes. (2) 30 g of the die-shaped rubber molded article heated above was immersed in 270 ml of toluene, stirred slowly at room temperature for 24 hours, and then centrifuged to separate a toluene extract and an extract residue. (3) For toluene extract, toluene was removed by an evaporator, and rubber was recovered. (4) The extraction residue was heat-treated at 600 ° C. for 30 minutes in a nitrogen atmosphere to recover carbon black.

The molecular weight of the rubber recovered in the above (3) is determined by GP
C was measured. It is shown in Table 1. The I of each sample collected
By measuring the R spectrum, it was confirmed that the rubber was an isoprene rubber. Of these, sample number 1 in Table 1
The IR spectrum of-is shown in FIG.

[0047]

[Table 1] (Example 2) The heating conditions in (1) of Example 1 are shown in Table 2.
The rubber was recovered in the same manner as in Example 1 except that the heating was performed in the air in place of the heating time and temperature shown in (1). Table 2 shows the results. In GPC of the recovered rubber, 2 or 3 molecular weight distribution peaks were confirmed on the low temperature side of the preheating treatment. The Mw and the weight ratio of each peak are shown outside of Table 2. Also, by measuring the IR spectrum of each collected sample,
It was confirmed that it was isoprene rubber. FIG. 3 shows an IR spectrum of Sample No. 2- in Table 2.

[Table 2]

Example 3 and Reference Example 1 <Recovered Rubber Composition> The recovered rubber (Mw 84) obtained in Example 1 under No. 1- (preheating temperature 250 ° C. × 15 minutes)
000) and number 1- (preheating temperature 300 ° C. × 1)
(5 minutes), a rubber composition was formed using the recovered rubber (Mw 26000) obtained to obtain a vulcanized rubber. That is, in the <rubber molded product> of Example 1, the number 1 was used instead of the NR.
The rubber composition of Example 1 was vulcanized from the same rubber composition as in Example 1, except that the rubber of No. or the rubber of No. 1 was changed to 100 parts by weight of NR (virgin rubber) and the mixed rubber component in the ratios shown in Table 3. I got the rubber. Using the vulcanized rubber obtained above and the vulcanized rubber obtained in <Rubber molded article> of Example 1 as Reference Example 1, their stress-strain (SS) characteristics and loss tangent (tan δ) were determined. It was measured as follows. FIG. 4 shows an SS curve, and FIG. 5 shows a temperature-tangent loss (tan δ) characteristic.
Further, 300% modulus (M ₃₀₀ ), breaking strength (TB), breaking elongation (EB), E
Table 3 shows NG and tan δ values at each temperature.

<Stress-Strain (SS) Characteristics> Dumbbell-shaped test pieces (JIS No. 3) having a thickness of 1 mm were cut out and subjected to JIS.
According to K 6251, a 300% modulus (M ₃₀₀
/ MPa), breaking strength (TB / MPa), elongation at break (E
B /%) and energy (ENG / MPa) corresponding to the area determined from the SS curve.

<Measurement of Loss Tangent (tan δ)> Width 5 m
m, a length of 100 mm, and a thickness of 1 mm.
%, Amplitude ± 2%, frequency 20 Hz).
The loss tangent (tan δ) at 0 ° C. and 60 ° C. was measured.

[0051]

[Table 3]

Example 4 and Reference Example 2 <Composition of Recovered Carbon Black> Step (4) (i) 600 ° C. × 30
For 1 minute, and carbon black was recovered. The extraction residue obtained by performing the pre-heating step at 250 ° C. × 15 minutes in the first stage, and the extraction residue obtained by performing the pre-heating step at 280 ° C. × 15 minutes were thermally decomposed as UFA-1. The residue obtained by thermal decomposition of the extraction residue was converted to UFA-2.
And The operations of other steps (1) to (3) were performed in the same manner as in Example 1. A vulcanized rubber was molded in the same manner as in <Rubber molded article> of Example 1, except that the obtained carbon blacks UFA-1 and UFA-2 were used. A rubber molded product using virgin carbon black (N118) is shown in Table 4 as Reference Example 2. The SS characteristic and the temperature-tan δ characteristic were measured in the same manner as in Example 3. The results are shown in FIG. 6 (SS curve), FIG. 7 (temperature-tan δ characteristic) and Table 4.

[Table 4]

(Example 5) As a rubber molded product, a vulcanized bladder for molding tires for passenger cars (raw rubber: II of Mw 450,000)
R) was used to recover butyl rubber. In (1) of Example 1, the symmetrical material was replaced with the above-mentioned butyl rubber molded product, and the heating conditions were as shown in Table 5 for the heating time (300 ° C., 330 ° C.).
(350 ° C., 380 ° C.) for 15 minutes, except that the rubber was recovered in the same manner as in steps (1) to (3) of Example 1. (4) The extraction residue was heat-treated at 600 ° C. for 30 minutes in a nitrogen atmosphere to recover carbon black.

The molecular weight of the rubber recovered in the above (3) was determined by GP
C was measured. The results are shown in Table 5 together with the recovery. The extract obtained when the unvulcanized rubber prepared using the above raw rubber was extracted according to the step (2) had an Mw of 420,000.
Further, by measuring the IR spectrum of each of the collected samples, it was confirmed that the sample was butyl rubber. FIG. 8 shows the IR spectrum of Sample No. 5- in Table 5.

[Table 5]

[0055]

According to the present invention as described above, rubber and carbon black useful as rubber raw materials can be reliably recovered from rubber molded products, particularly from rubber waste such as waste tires, rubber scraps, and wire-covered rubber waste. can do.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a process flow of the present invention.

FIG. 2 is a view showing an IR spectrum of the isoprene rubber obtained in Example 1.

FIG. 3 is a view showing an IR spectrum of the isoprene rubber obtained in Example 2.

FIG. 4 is a diagram showing an SS curve of a vulcanized rubber using recovered rubber.

FIG. 5: Temperature-tan δ of vulcanized rubber using recovered rubber
It is a figure showing a characteristic.

[Fig. 6] S of vulcanized rubber using recovered carbon black
It is a figure which shows a -S curve.

FIG. 7 is a graph showing a temperature-tan δ characteristic of a vulcanized rubber using recovered carbon black.

FIG. 8 is a view showing an IR spectrum of the butyl rubber obtained in Example 5.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Susumu Ashizawa 2-1 Oiwake, Hiratsuka-shi, Kanagawa Prefecture Yokohama Rubber Co. Hiratsuka Works F-term (reference) 4F301 AA03 AB02 CA04 CA09 CA12 CA25 CA72

Claims (13)

[Claims] (1) A rubber molded article is subjected to a heat treatment at 220 to 400 ° C. capable of substantially maintaining the outer shape before heating, and (2) extraction with an organic solvent to obtain a solvent-extracted component. (3) A method for recovering a material from a rubber molded product, wherein the rubber is recovered by removing a solvent from the separated solvent extractables by separating an extraction residue. 2. A rubber molded article containing carbon black and rubber is subjected to a heat treatment at 220 to 400.degree. C. capable of substantially retaining the shape before heating, and (2) extraction with an organic solvent. (4) heating the separated extraction residue at (i) a temperature of 500 ° C. or higher, or (ii) removing the peroxide from 0.01 to 50%
A method for recovering material from a rubber molded product, in which a rubber component is decomposed and carbon black is recovered by dissolving in a rubber dissolving agent. 3. A rubber molded article containing carbon black and rubber is subjected to a heat treatment at 220 to 400.degree. C. capable of substantially retaining the shape before heating, and (2) extraction with an organic solvent. (3) The rubber is recovered by removing the solvent from the separated solvent extract, and (4) the separated extract residue is (i) 500 ° C. Heating at the above temperature or (ii) 0.01-50% of peroxide
A method for recovering material from a rubber molded product, in which a rubber component is decomposed and carbon black is recovered by dissolving in a rubber dissolving agent. 4. The method according to claim 1, wherein in the step (2), the solvent extraction is immersion of the heat-treated rubber molded article in toluene at 0 to 40 ° C. Material recovery method. 5. The method according to (4), wherein the extraction residue is (i)
The material recovery method according to claim 2, wherein the rubber component is decomposed into a gaseous hydrocarbon by heating at a temperature of 500 ° C or higher, and carbon black is recovered as a decomposition residue. 6. The method according to claim 2, wherein the rubber dissolving agent used in the step (ii) of the step (4) is toluene containing 0.01 to 50% of benzoyl peroxide. 7. The method according to claim 1, wherein in the step (1), a rubber molded product made of a raw material of isoprene rubber is preheated at a temperature of 220 to 300 ° C. 8. The method according to claim 1, wherein in the step (1), a rubber molded product made of a butyl rubber raw material is preheated at a temperature of 300 to 380 ° C. 9. A liquid, having an average molecular weight (Mw) of 5 which is recovered by the recovery method according to claim 1 or 3 and is liquid.
More than ten thousand rubber. 10. The rubber of claim 9 wherein said rubber is isoprene rubber.
The rubber described in the above. 11. The rubber according to claim 9, wherein said rubber is butyl rubber. 12. A carbon black recovered by the recovery method according to claim 2. 13. A rubber composition containing at least one of the rubber or carbon black according to claim 9 as a material recovered from a rubber molded product.