JP7343929B1 - Waste treatment method - Google Patents

Abstract

An object of the present invention is to provide a waste processing method in which hardly soluble rubber of waste rubber products such as waste rubber tires and waste seismic isolation rubber units is dissolved, and rubber and metal can be easily recycled separately. [Solution] In the waste treatment method of the present invention, waste rubber products are immersed and held in a solvent containing fatty acid methyl ester as a main component, and the solvent is desirably heated to a liquid temperature of 200° C. or higher and below the ignition point. The present invention is characterized by having a dissolution treatment procedure of dissolving the rubber of the waste rubber product by heating and holding it. Another waste treatment method of the present invention is that in the waste treatment method of the present invention, before the dissolution treatment, the waste rubber product is immersed in a pretreatment liquid containing propyl bromide as a main component. The present invention is characterized by further comprising a pretreatment step of maintaining the pretreatment liquid at room temperature. As a result, the rubber of the waste rubber product can be dissolved and liquefied, and the rubber and metal of the waste rubber product can be easily separated. [Selection diagram] None

Description

The present invention relates to a waste disposal method for dissolving waste products (hereinafter referred to as waste rubber products) containing rubber members, such as rubber tires and seismic isolation rubber units, and in particular, the present invention relates to a waste disposal method for dissolving and processing waste products containing rubber members such as rubber tires and seismic isolation rubber units. The present invention relates to a processing method and a processing solvent that selectively dissolve.

Discarded rubber tires (waste rubber tires) are generally treated by combustion or shredded into chips or powder and recycled as fuel. In addition to recycling as a fuel, for example, a technique has been proposed in which the above-mentioned powder is kneaded with a polymer and recycled as a new rubber material (see Patent Document 1). Furthermore, for example, a technique has been proposed in which a waste rubber tire is devulcanized and the devulcanized substance is recovered and used as a rubber material (see Patent Document 2).

As a treatment for discarded styrene foam, there is a technique in which the volume is significantly reduced by liquefying it using a solvent liquid such as limonene (see, for example, Patent Document 3). Styrofoam is mainly used as a cushioning material, so chemical resistance is not thought to be given much consideration, but the rubber components used in rubber tires have high chemical resistance and are difficult to use due to the purpose and function of rubber tires. It is a soluble rubber.

Japanese Patent Application Publication No. 10-202658 Japanese Patent Application Publication No. 2005-023225 JP2012-251120A

In the above-mentioned conventional technology, when waste rubber products are subjected to combustion treatment, not only is it impossible to recycle the rubber members, but also exhaust gas containing greenhouse gases and other pollutants is released into the atmosphere. In addition, in shredding processing, metal members and fiber members constituting a rubber tire are included in rubber chips and rubber powder, and the purity of the obtained rubber material does not become high. Furthermore, if the waste rubber product is a seismic isolation rubber unit, it is difficult to burn or shred it.

Many waste rubber products are composites with metal parts, and ideally, it would be desirable to be able to cleanly separate the rubber parts and metal parts. If the metal member can be separated from the rubber member, it is easy to recycle the metal. Furthermore, if the rubber member can be separated from the metal member, the possibility of recycling the rubber and the range of purposes can be expanded.

As described above, in the above-mentioned conventional technology, the main processing method for waste rubber products such as rubber tires is combustion treatment or shredding processing, so it is difficult to separate rubber parts and metal parts and obtain them separately. .

The present invention solves such conventional problems by melting the hardly soluble rubber of waste rubber products such as waste rubber tires and waste seismic isolation rubber units, and separating rubber and metal easily and separately. The purpose of this project is to provide a recyclable waste treatment method.

In order to solve the above problems, the waste treatment method of the present invention includes a dissolution treatment step in which a waste rubber product is immersed and held in a solvent containing fatty acid methyl ester as a main component, and the rubber of the waste rubber product is dissolved. It is characterized by having the following.

Another waste treatment method of the present invention is that in the waste treatment method of the present invention, before the dissolution treatment, the waste rubber product is immersed in a pretreatment liquid containing propyl bromide as a main component. The present invention is characterized in that it further includes a pretreatment step of maintaining the pretreatment liquid at room temperature.

According to the present invention, by immersing and holding the waste rubber product in a solvent containing fatty acid methyl ester as a main component, the rubber of the waste rubber product can be dissolved and liquefied, and the rubber and metal of the waste rubber product can be separated. Since they can be easily separated, each member can be recycled individually, and rubber can be recycled for multiple purposes using waste rubber liquid.

In the present invention, waste rubber products such as waste rubber tires, waste seismic isolation rubber units, waste rubber crawlers, waste rubber road wheels, and waste high-pressure rubber hoses are melted using fatty acid methyl ester (FAME) as the main component. By immersing and holding the rubber member in a solvent (hereinafter referred to as solvent D), the rubber member among the constituent members of the waste rubber product is dissolved in the solvent D and liquefied. Here, "waste" such as waste rubber tires means those that have been used or have failed inspection and are discarded.

The above-mentioned rubber member dissolves in solvent D even at room temperature, but by immersing it in solvent D and maintaining it under heat, the dissolution rate becomes faster. The heating temperature (liquid temperature of solvent D) at this time is desirably 200° C. or higher and needs to be lower than the ignition point. Therefore, the temperature of the solvent D in the dissolution process is set within a range of room temperature or higher and lower than the ignition point. Further, the dissolution treatment using the solvent D can be carried out not only in the open atmosphere but also under pressure control using a closed container or the like, or in an oxygen-deficient atmosphere. Note that the concentration of fatty acid methyl ester in solvent D is preferably 80% by weight or more.

Furthermore, as a pre-treatment for the above-mentioned dissolution treatment, the above-mentioned waste rubber product is immersed in a pre-treatment liquid (hereinafter referred to as pre-treatment liquid E) containing propyl bromide (1-bromopropane) as a main component, and kept at room temperature. By doing so, the pretreatment liquid E is allowed to penetrate into the rubber member of the waste rubber product, and the dissolution rate of the rubber member in the subsequent dissolution treatment is increased. Note that the concentration of propyl bromide in the pretreatment liquid E is preferably 80% by weight or more.

Fatty acid methyl ester, which is the main component of solvent D, has excellent permeability to the natural rubber component, especially among the rubber components of waste rubber products, and has the property of being able to dissolve the entire rubber member of waste rubber products. This fatty acid methyl ester has been used as a biodiesel fuel for some time, but it was not known that it could dissolve rubber. Fatty acid methyl ester can dissolve rubber in waste rubber products even at room temperature, but the rate of penetration and dissolution increase when heated. In other words, the fatty acid methyl ester is a treatment liquid that not only penetrates into rubber and swells it, but also dissolves into the inside of the rubber. Note that fatty acid methyl ester is a water-insoluble liquid at a temperature ranging from room temperature to below the ignition point, and has a flash point of 180° C. or lower. Furthermore, the ignition point of fatty acid methyl ester varies depending on the atmospheric pressure, oxygen concentration, etc., but is said to be 290° C. or higher.

Propyl bromide, which is the main component of pretreatment liquid E, has excellent permeability to the rubber members of waste rubber products at room temperature, swells the rubber components, and accelerates the dissolution treatment of rubber by solvent D (dissolution rate (to raise) fulfill one's role. This propyl bromide has been used as a plating remover for some time, and has the property of not damaging metals, especially aluminum. In other words, propyl bromide is a treatment liquid that penetrates into rubber and causes it to swell, making it easier to dissolve in solvent D, and leaving metals such as aluminum intact without damaging them. Note that propyl bromide is a colorless and transparent liquid at room temperature.

The constituent parts of a rubber tire are classified into a tread part, a sidewall part, a bead part, a belt part, a carcass part, etc. The tread and sidewalls are mainly made of vulcanized rubber, which is a mixture of natural rubber and synthetic rubber.The bead and belt parts are made of metals such as high carbon steel and steel cord. consists of fibers. In such rubber tires, the rubber in the tread portion is the most difficult to dissolve.

The seismic isolation rubber unit is a rubber-metal composite with a structure in which a rubber body is sandwiched between two metal bodies. Also, a plurality of metal bodies are embedded inside the rubber body. The joint between rubber and metal is extremely strong, making it difficult to separate the rubber body and metal body. Furthermore, the rubber body is extremely dense and strong, manufactured under several thousand tons of pressure, and it is difficult to shred or cut it, and it is also difficult to burn it. Therefore, the seismic isolation rubber unit is a waste rubber product that is difficult to recycle.

Crawler units (infinite track mechanisms) are used in heavy machinery such as bulldozers and agricultural machinery such as combines, and consist of crawlers, starting wheels, rolling wheels, guide wheels, etc. Some crawlers and wheels are made of rubber. A rubber crawler is a belt having a structure in which a metal member for connection is embedded in a rubber belt component. Rubber wheels are a composite product of rubber and metal, with a rubber member bonded to the circumferential surface of a metal wheel, and some have the metal wheels made of aluminum. Unvulcanized rubber is generally used for rubber crawlers and rubber wheels.

A high-pressure rubber hose is a rubber-metal composite product with a structure in which the outer circumferential surface of a metal pipe is covered with a rubber layer. The outer rubber layer of a high-pressure hose generally has a vulcanized surface.

The procedure for processing waste rubber products according to the present invention will be explained below. A waste rubber product as waste to be treated, a solvent D, and a pretreatment liquid E are prepared. Examples of waste rubber products include rubber tires, seismic isolation rubber units, rubber crawlers, rubber wheels, and high-pressure rubber hoses. Out of the waste rubber products, if possible, cut them into predetermined sizes or make cuts at predetermined intervals. As a result, the permeation speed of the solvent D and the pretreatment liquid E can be increased, and the degree of freedom in selecting usable processing containers can be increased. For example, it becomes possible to process waste rubber products using containers too small to fit them as they are.

First, a waste rubber product is immersed in pretreatment liquid E and kept at room temperature for a predetermined period of time. At this time, the immersion retention time is set depending on the characteristics, size, thickness, etc. of the rubber member of the waste rubber product, and is set to, for example, 12 to 48 hours. As a result, the pretreatment liquid E penetrates into the rubber member of the waste rubber product, and the rubber member swells in advance, so that the subsequent dissolution treatment can be facilitated. It should be noted that the effect of increasing the speed of dissolution by this pretreatment liquid E increases as the immersion holding time increases, and the increasing tendency becomes more gradual after 24 hours.

Next, the waste rubber product is taken out from the pretreatment liquid E and immersed in the solvent D, and the solvent D is brought to a preset liquid temperature and held as such for a predetermined period of time. At this time, the liquid temperature of the solvent D and the immersion holding time are set according to the characteristics, size, thickness, etc. of the rubber member of the waste rubber product. The liquid temperature is, for example, 200 to 280° C. under open air. Further, the immersion holding time is, for example, 0.5 to 12 hours. Note that the effect of increasing the speed of dissolution by heating the solvent D (heat dissolution treatment) becomes remarkable when the liquid temperature is 200° C. or higher. Furthermore, depending on the type of waste rubber product, it is also possible to perform dissolution treatment with solvent D without pretreatment with pretreatment liquid E.

The inventors of the present invention have found through experiments that fatty acid methyl ester has the property of dissolving rubber (particularly natural rubber), and that the rate of dissolution is increased by heating. Furthermore, it was found that natural rubber, synthetic rubber, composite rubber of natural rubber and synthetic rubber, vulcanized rubber, and unvulcanized rubber can all be dissolved. It has long been known that fatty acid methyl esters penetrate rubber and cause it to swell. The same applies to propyl bromide. In addition to these, there are also known liquid substances that swell rubber. However, it was unknown that fatty acid methyl ester dissolves rubber members such as tires and seismic isolation rubber units.

Rubber products such as rubber tires, rubber crawlers (rubber tracks) of crawler units, and rubber wheels are designed to have extremely high resistance to chemical dissolution due to their uses and functions, and use poorly soluble rubber. Swelling and dissolution of rubber are two different phenomena, and conventional waste rubber treatment is not carried out on the premise that even if rubber products swell, it is difficult to dissolve them. was. Furthermore, it is difficult to shred a waste seismic isolation rubber unit, and the entire unit is melted at once by being put into a metal melting furnace, for example.

In the present invention, solvent D can dissolve rubber that is considered to be poorly soluble. In addition to natural rubber, the types of rubber that can be dissolved include synthetic rubbers such as butyl rubber, ethylene/propylene rubber, acrylic rubber, and fluorine rubber, as well as mixed rubbers of multiple types of these synthetic rubbers, as well as natural rubber and these synthetic rubbers. It is a mixed rubber with. However, as for silicone rubber, it is possible to dissolve it when mixed with other synthetic rubbers or natural rubber, but it is difficult to dissolve it when silicone rubber alone is used. Regarding the liquid temperature of solvent D, the dissolution rate increases as the temperature increases from room temperature to high temperature, and the dissolution rate rapidly increases when the temperature reaches 200° C. or higher. Furthermore, by performing pretreatment with pretreatment liquid E, the dissolution rate becomes faster when compared under the same dissolution treatment conditions, and the rubber can be peeled off and dissolved without damaging the metal.

By melting the waste rubber into a liquid, the rubber and metal of the waste rubber product can be separated and obtained separately, so a versatile recycling method can be used for each of the waste rubber and waste metal. In addition, waste rubber liquid is more convenient than solid rubber for recycling into, for example, asphalt materials, rubber sheeting materials, and soundproofing materials. In order to construct a playground using asphalt, the asphalt must have a certain degree of elasticity. By mixing waste rubber liquid with buffing powder from rubber such as rubber tires, the elasticity of asphalt can be easily controlled.

As described above, according to the embodiment of the present invention, the waste rubber product is immersed in the solvent D containing fatty acid methyl ester as a main component and maintained at a liquid temperature above room temperature and below the ignition point. In addition to being able to melt and liquefy rubber parts, it is also possible to easily separate the rubber and metal of waste rubber products, making it possible to recycle each part individually and making it possible to recycle rubber for multiple purposes using waste rubber liquid. . Note that the present invention is not limited to what has been described in the embodiments, and various changes can be made without departing from the spirit thereof.

An example of melting treatment of waste rubber tires will be explained below. The waste rubber tires used were previously cut into 5-10 cm squares. First, the cut waste rubber tire piece was immersed in pretreatment liquid E and held at room temperature for 24 hours, then immersed in solvent D and heated and held at a liquid temperature of 230 to 250°C for 5 hours. As a result, the rubber of the waste rubber tire piece was dissolved in the solvent D and liquefied, and remained liquid even after returning to room temperature. Further, the above waste rubber tire piece was immersed in pre-treatment liquid E, held at room temperature for 24 hours, immersed in solvent D, heated and held at a liquid temperature of 180 to 230°C for 1 hour, and further heated to the liquid temperature of solvent D. The temperature was raised to 230-270°C and kept heated for 6 hours. As a result, the rubber of the waste rubber tire was dissolved in the solvent D. Note that the popping sound continued from the beginning to just before the end of the one hour period in which the liquid temperature was maintained at 180 to 230°C. Furthermore, the above waste rubber tire piece was immersed in solvent D without being immersed in pretreatment liquid E (without pretreatment), and heated and held at a liquid temperature of 230 to 270°C for 12 hours. As a result, the waste rubber tire rubber was dissolved in the solvent D.

An example of dissolving a waste seismic isolation rubber unit will be explained below. First, the waste seismic isolation rubber unit was immersed as it was in pretreatment liquid E, and kept at room temperature for 24 hours. Next, the waste seismic isolation rubber unit was taken out from the pretreatment liquid E, immersed in solvent D, and heated and held at a liquid temperature of 280°C for 12 hours. As a result, the metal body was peeled off from the rubber body of the waste seismic isolation rubber unit, and the rubber body began to melt.

An example of the dissolution treatment of waste rubber crawlers will be explained below. The waste rubber crawler used was cut in advance to a length of 10 to 15 cm. The above waste rubber crawler piece was immersed in pretreatment liquid E and kept at room temperature for 24 hours. Next, the waste rubber crawler pieces were taken out from the pretreatment liquid E, immersed in solvent D, and heated at 250° C. for 3 hours. This made it possible to separate the metal from the rubber of the waste rubber crawler piece. Furthermore, the immersion of the waste rubber crawler piece in the solvent D was continued, and the liquid temperature was maintained at 250° C. for 6 hours. As a result, the rubber of the waste rubber crawler pieces was completely dissolved in the solvent D.

An example of the dissolution treatment of waste rubber wheels will be described below. The waste rubber roller was immersed in pretreatment liquid E and held at room temperature for 12 hours, then immersed in solvent D, and heated and held at a liquid temperature of 250°C for 3 hours. As a result, the rubber of the waste rubber wheel was peeled off from the metal wheel and began to melt. Further, another waste rubber wheel was immersed in pretreatment liquid E and held at room temperature for 24 hours, then immersed in solvent D, and heated and held at a liquid temperature of 250°C for 1 hour. As a result, the rubber of the waste rubber wheel was peeled off from the metal wheel and began to melt. Furthermore, another waste rubber roller was immersed in pretreatment liquid E and held at room temperature for 48 hours, then immersed in solvent D, and heated and held at a liquid temperature of 250°C for 30 minutes. As a result, the rubber of the waste rubber wheel was peeled off from the metal wheel and began to melt.

An example of dissolution treatment of waste high pressure rubber hose will be explained below. Three types of waste high-pressure rubber hoses from manufacturers A, B, and C were prepared as waste rubber products to be treated. A waste high-pressure rubber hose from manufacturer A was immersed in solvent D without using pretreatment liquid E, and heated and held at a liquid temperature of 250°C for 4 hours. As a result, the rubber jacket of Manufacturer A's hose could be peeled off from the metal pipe and dissolved. Further, a waste high-pressure rubber hose from Manufacturer B was immersed in pretreatment liquid E and held at room temperature for 12 hours, then immersed in solvent D, and heated and held at a liquid temperature of 250°C for 4 hours. As a result, Manufacturer B's outer covering rubber could be peeled off from the metal pipe and dissolved. In addition, by immersing a waste high-pressure rubber hose from manufacturer C in solvent D without using pretreatment liquid E and heating and holding it at a liquid temperature of 280°C for 4 hours, the outer covering rubber was peeled off from the metal pipe and dissolved. did it.

A, B, C high pressure hose manufacturer, D solvent, E pre-treatment liquid.

Claims (3)

A pretreatment procedure in which a waste rubber product is immersed in a pretreatment liquid containing propyl bromide as a main component and the pretreatment liquid is maintained at room temperature;
a dissolution treatment step in which the pretreated waste rubber product is immersed and held in a solvent containing fatty acid methyl ester as a main component to dissolve the rubber of the waste rubber product ;
A waste treatment method characterized by having the following. 2. The waste treatment method according to claim 1, wherein the dissolution treatment includes heating and maintaining the solvent at a liquid temperature of 200° C. or higher and lower than the ignition point. 3. The waste treatment method according to claim 1 , further comprising the step of mixing rubber buff powder into the waste rubber liquid obtained by the dissolution treatment .